- ID:
- ivo://CDS.VizieR/J/ApJ/497/188
- Title:
- A103, A118 and A114 morphological studies
- Short Name:
- J/ApJ/497/188
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a program to study the detailed morphologies of galaxies in intermediate-redshift clusters and hence understand the physical origin of the enhanced star formation seen in the environments at earlier epochs. Deep, high-resolution imagery has been obtained of three rich clusters, AC 103, AC 118 and AC 114 at z=0.31, through the R (F702W) filter of the Wide Field Planetary Camera (WFPC2) of the Hubble Space Telescope (HST).
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- ID:
- ivo://CDS.VizieR/J/AJ/117/247
- Title:
- Ages for globular clusters in the halo
- Short Name:
- J/AJ/117/247
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Wide Field Planetary Camera 2 on the Hubble Space Telescope to obtain photometry of the outer halo globular clusters Palomar 3, Palomar 4, and Eridanus. These three are classic examples of the "second-parameter" anomaly because of their red horizontal-branch morphologies in combination with their low-to-intermediate metallicities. Our color-magnitude diagrams (CMDs) in V, V - I reach V_lim_ {=~} 27.0, clearly delineating the subgiant and turnoff regions and about 3 mag of the unevolved main sequences.
- ID:
- ivo://CDS.VizieR/J/A+A/324/915
- Title:
- Blue stragglers in M3
- Short Name:
- J/A+A/324/915
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The core of the Galactic Globular Cluster M 3 (NGC 5272) has been observed with the WFPC2 through the filters F255W, F336W, F555W, and F814W. Using these observations along with a thorough reanalysis of earlier catalogs, we have produced a catalog of blue straggler stars (BSS) spanning the cluster. Earlier studies and the fainter part of our sample suffer severe selection biases. Our analysis is based on a more reliable bright global sample of 122 BSS. We confirm earlier suggestions that the radial BSS distribution in M 3 is bimodal. It is strongly peaked in the center, has a clear dip 100-200" from the center, and rises again at larger radii. The observed distribution agrees with the dynamical model of Sigurdsson et al. (1994ApJ...431L.115S) which takes into account both star collisions and merging of primordial binaries for the origin of BSS. The observed luminosity functions of BSS in the inner and outer parts of the cluster are different. Interpreting these using the models of Bailyn & Pinsonneault (1995ApJ...439..705B), we suggest that the BSS in the inner cluster are formed by stellar collisions and those in the outer cluster from merging primordial binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/522/802
- Title:
- Cepheid calibration of SN 1989B in NGC 3627
- Short Name:
- J/ApJ/522/802
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Repeated imaging observations have been made of NGC 3627 with the Hubble Space Telescope in 1997 - 1998 over an interval of 58 days. Images were obtained on 12 epochs in the F555W band and on five epochs in the F814W band. The galaxy hosted the prototypical, "Branch normal," type Ia supernova SN 1989B. A total of 83 variables have been found, of which 68 are definite Cepheid variables with periods ranging from 75 to 3.85 days. The dereddened distance modulus is determined to be (m-M)_o_=30.22{+/-}0.12 (internal uncertainty) using a subset of the Cepheid data whose reddening and error parameters are secure.
- ID:
- ivo://CDS.VizieR/J/ApJ/475/469
- Title:
- Composite HST Spectrum of Quasars
- Short Name:
- J/ApJ/475/469
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We construct a composite quasar spectrum from 284 HST FOS spectra of 101 quasars with redshifts z>0.33. The spectrum covers the wavelengths between 350 and 3000A in the rest frame, with a peak S/N level of ~130 per A at ~1200A. Since ~90% of the sample quasars have redshift z<1.5, the spectrum is suitable for studying the wavelength region shortward of Ly{alpha} without large effects from intervening Ly{alpha} forest absorption. Data in the waveband between 350 and 600A are mainly from the spectra of z>1.5 quasars, for which significant corrections for the accumulated Lyman-series line and continuum absorption have been applied. There is a significant steepening of the continuum slope around 1050A. The continuum between 1050 and 2200A can be modeled as a power law f_{nu} proportional to {nu}_{alpha}_ with {alpha}=-0.99+/-0.05. For the full sample the power-law index in the extreme ultraviolet (EUV) between 350 and 1050A is {alpha}=-1.96+/-0.15. For the radio-loud subsample (60 objects), the EUV spectral index is {alpha}~=-2.2, while for the radio-quiet subsample (41 objects) it is {alpha}~=-1.8. The continuum flux in the wavelengths near the Lyman limit shows a depression of ~10%. The break in the power-law index and the slight depression of the continuum near the Lyman limit are features expected in Comptonized accretion-disk spectra. Comptonization produces a power-law tail in the wavelength band shortward of 1000A and smears out the Lyman-limit edge of the intrinsic accretion-disk spectrum. In the EUV waveband, we detect several possible emission features, including one around 690A that may be O III + N III produced by the Bowen fluorescence effect. Comparing our composite spectrum with one made at higher redshifts by Francis et al. (1991ApJ...373..465F), we find that the equivalent widths of Ly{alpha} and high-ionization emission lines are larger in our sample, reflecting a known luminosity dependence. The equivalent widths of low-ionization lines do not exhibit such a dependence, suggesting that the quasar EUV continuum above ~50eV is steeper at higher luminosity. Radio-quiet quasars appear to show a slightly harder continuum and lower ionization levels in their emission lines.
- ID:
- ivo://CDS.VizieR/J/AJ/118/2071
- Title:
- ESO 565-11 UBVI(c) photometry
- Short Name:
- J/AJ/118/2071
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multiband Wide Field Planetary Camera 2 images of the central regions of ESO 565-11, a peculiar southern barred galaxy recently shown to have the largest known example of a circumnuclear starburst ring. We also present ground-based near-infrared H-band imaging and photometry of the galaxy. The results provide an interesting picture of the star-forming ring and its environment.
- ID:
- ivo://CDS.VizieR/J/AJ/118/1671
- Title:
- Fornax cluster 4 VI photometry
- Short Name:
- J/AJ/118/1671
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using observations from the Hubble Space Telescope archive, color-magnitude diagrams (CMDs) have been constructed for globular cluster 4 in the Fornax dwarf spheroidal galaxy and its surrounding field.
- ID:
- ivo://CDS.VizieR/J/ApJ/504/113
- Title:
- F175W and F275W photometry of M31 and M32
- Short Name:
- J/ApJ/504/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Faint Object Camera (FOC) ultraviolet images of the central 14"x14" of Messier 31 and Messier 32. The hot stellar populations detected in the composite UV spectra of these nearby galaxies are partially resolved into individual stars, and their individual colors and apparent magnitudes are measured. We detect 433 stars in M31 and 138 stars in M32, down to detection limits m_F275W_=25.5mag and m_F175W_=24.5mag.
- ID:
- ivo://CDS.VizieR/J/AJ/112/359
- Title:
- Galaxies in the Hubble Deep Field
- Short Name:
- J/AJ/112/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of morphological and color data for galaxies with 21<I_814<25mag in the Hubble Deep Field (Williams et al. 1996, in Science with the Hubble Space Telescope II). Galaxies have been inspected and (when possible) independently visually classified on the MDS and DDO systems. Measurements of central concentration and asymmetry are also included in the catalog. The fraction of interacting and merging objects is seen to be significantly higher in the Hubble Deep Field than it is among nearby galaxies. Barred spirals are essentially absent from the deep sample. The fraction of early-type galaxies in the Hubble Deep Field is similar to the fraction of early-types in the Shapley-Ames Catalog, but the fraction of galaxies resembling archetypal grand-design late-type spiral galaxies is dramatically lower in the distant HDF sample.
10. Globulars in M31
- ID:
- ivo://CDS.VizieR/J/AJ/114/1488
- Title:
- Globulars in M31
- Short Name:
- J/AJ/114/1488
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep (V=~27) V- and I-band stellar photometry of G302 and G312, two globular star clusters in the halo of M31. These data were obtained using the Hubble Space Telescope's Wide Field/Planetary Camera 2. We find iron abundances of [Fe/H]=-1.85+/-0.12 for G302 and [Fe/H]=-0.56+/-0.03 for G312, consistent with spectroscopic measurements. The color-magnitude diagrams for each cluster show no evidence for an intermediate-aged population of stars, or a second parameter effect in the morphology of the horizontal branch. G302 shows no evidence for a color gradient but the inner regions of G312 are bluer than the outer regions. G312 shows no evidence of ellipticity or an extended halo of stars. G302 has a projected ellipticity of {epsilon}=0.195+/-0.012 with the projected major axis oriented towards the center of M31. G302 also shows evidence of an extended asymmetric stellar halo extending to at least twice the fitted Michie-King tidal radius. The amount of mass beyond the tidal radius of G302 is consistent with the stellar escape rates which have been predicted by N-body simulations of globular clusters in the Galactic tidal field. (c) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/VII/246
- Title:
- GOODS Morphological Catalog
- Short Name:
- VII/246
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present below the morphological catalogs of galaxies in the GOODS North and South fields, as determined visually by R. S. Ellis with a magnitude limit from HST/ACS imaging of z<22.5 (AB).
- ID:
- ivo://CDS.VizieR/J/ApJ/551/111
- Title:
- HDF early-type and spiral galaxies
- Short Name:
- J/ApJ/551/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the internal optical colors of a complete sample of I_814_<24mag early-type and spiral galaxies from the northern and southern Hubble Deep Fields (HDF). The subset of galaxies in the HDF-North are also investigated in the near-infrared using NICMOS photometry. We compare the central (inner 5% radius) colors of those spirals with clearly visible bulges with the integrated colors of ellipticals in our sample.
- ID:
- ivo://CDS.VizieR/J/A+A/364/517
- Title:
- HDF-N spiral and irregular galaxies
- Short Name:
- J/A+A/364/517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze a morphologically-selected complete sample of 52 late-type (spiral and irregular) galaxies in the Hubble Deep Field North with total K-magnitudes brighter than K=20.47 and typical redshifts z~0.5 to 1.4. This sample exploits in particular the ultimate imaging quality achieved by HST in this field, allowing us to clearly disentangle the early- from late-type galaxy morphologies, based on accurate profiles of the surface brightness distributions.
- ID:
- ivo://CDS.VizieR/J/ApJ/513/34
- Title:
- HDF photometric redshifts catalog
- Short Name:
- J/ApJ/513/34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the newly available infrared images of the Hubble Deep Field in the J, H, and K bands and an optimal photometric method, we have refined a technique to estimate the redshifts of 1067 galaxies. A detailed comparison of our results with the spectroscopic redshifts in those cases where the latter are available shows that this technique gives very good results for bright enough objects [AB(814nm)<26.0]. From a study of the distribution of residuals [{Delta}z_rms_/(1+z)~0.1 at all redshifts], we conclude that the observed errors are mainly due to cosmic variance. This very important result allows for the assessment of errors in quantities to be directly or indirectly measured from the catalog. We present some of the statistical properties of the ensemble of galaxies in the catalog, and we finish by presenting a list of bright high-redshift (z~5) candidates extracted from our catalog together with recent spectroscopic redshift determinations confirming that two of them are at z=5.34 and z=5.60.
- ID:
- ivo://CDS.VizieR/J/A+AS/145/111
- Title:
- HDF-South catalogue of galaxies
- Short Name:
- J/A+AS/145/111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of galaxies in the HDF-S, created using the public version 1 images of the WFPC2 data. We created a catalogue with 4 pass-band (I(814), V(606), B(450), U(300). In V(606), B(450), U(300) and I(814), for each galaxy the catalogue gives photometric parameters. For the I(814), we estimated also the colours and for I(814)<26, the petrosian radius, the mean surface brightness within the petrosian radius, light concentration indexes, that is C_eta_ and C_abr_, and the asymmetry index as computed by Abraham software.
- ID:
- ivo://CDS.VizieR/J/ApJ/538/493
- Title:
- HDF-South NICMOS field
- Short Name:
- J/ApJ/538/493
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of photometry and photometric redshifts of 335 faint objects in the Hubble Deep Field South (HDF-S) near-infrared camera and multiobject spectrograph (NICMOS) field. The analysis is based on (1) infrared images obtained with the Hubble Space Telescope (HST) using the NICMOS with the F110W, F160W, and F222M filters; (2) an optical image obtained with HST using the Space Telescope Imaging Spectrograph with no filter; and (3) optical images obtained with the European Southern Observatory Very Large Telescope with U, B, V, R, and I filters. The primary utility of the catalog of photometric redshifts is as a survey of faint galaxies detected in the NICMOS F160W and F222M images. The sensitivity of the survey varies significantly with position, reaching a limiting depth of AB(1.6{mu}m)~28.7 and covering 1.01arcmin^2^ to AB(1.6{mu}m)=27 and 1.05arcmin^2^ to AB(1.6{mu}m)=26.5. The catalog of photometric redshifts identifies 21 galaxies (or 6% of the total) of redshift z>5, eight galaxies (or 2% of the total) of redshift z>10, and 11 galaxies (or 3% of the total) of best-fit spectral type E/S0, of which five galaxies (or 1% of the total) are of redshift z>1.
- ID:
- ivo://CDS.VizieR/J/AJ/120/2747
- Title:
- HDF-South WFPC2 observations
- Short Name:
- J/AJ/120/2747
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Deep Field South (HDF-S) observations targeted a high Galactic latitude field near QSO J2233-606. We present Wide Field Planetary Camera 2 observations of the field in four wide bandpasses centered at roughly 300, 450, 606, and 814 nm. Observations, data reduction procedures, and noise properties of the final images are discussed in detail. A catalog of sources is presented, and the number counts and color distributions of the galaxies are compared with a new catalog of the original Hubble Deep Field (HDF-N) that has been constructed in an identical manner. The two fields are qualitatively similar, with the galaxy number counts for the two fields agreeing to within 20%. The HDF-S has more candidate Lyman break galaxies at z>2 than the HDF-N. The star formation rate per unit volume computed from the HDF-S, based on the UV luminosity of high-redshift candidates, is a factor of 1.9 higher than from the HDF-N at z~2.7, and a factor of 1.3 higher at z~4.
- ID:
- ivo://CDS.VizieR/J/AJ/119/486
- Title:
- HDF-S: STIS imaging
- Short Name:
- J/AJ/119/486
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the imaging observations made with the Space Telescope Imaging Spectrograph (STIS) of the Hubble Deep Field South. The field was imaged in four bandpasses: a clear CCD bandpass for 156ks, a long-pass filter for 22-25ks/pix typical exposure, a near-UV bandpass for 23ks, and a far-UV bandpass for 52ks. The clear, visible image is the deepest observation ever made in the UV-optical wavelength region, reaching a 10{sigma}AB magnitude of 29.4 for an object of area 0.2arcsec^2^. The field contains QSO J2233-606, the target of the STIS spectroscopy, and extends 50"x50" for the visible images, and 25"x25" for the ultraviolet images. We present the images, catalog of objects, and galaxy counts obtained in the field.
- ID:
- ivo://CDS.VizieR/J/ApJS/166/549
- Title:
- HST/ACS observations of NGC 346
- Short Name:
- J/ApJS/166/549
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric study of the star-forming region NGC 346 and its surrounding field in the Small Magellanic Cloud, using data taken with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). The data set contains both short and long exposures for increased dynamic range, and photometry was performed using the ACS module of the stellar photometry package DOLPHOT. We detected almost 100,000 stars over a magnitude range of V~11 to V~28 mag, including all stellar types from the most massive young stars to faint lower main-sequence and pre-main-sequence stars. We find that this region, which is characterized by a plethora of stellar systems and interesting objects, is an outstanding example of mixed stellar populations. We take into account different features of the color-magnitude diagram of all the detected stars to distinguish the two dominant stellar systems: the stellar association NGC 346 and the old spherical star cluster BS 90. These observations provide a complete stellar sample of a field about 5'x5' around the most active star-forming region in this galaxy. Considering the importance of these data for various investigations in the area, we provide the full stellar catalog from our photometry. This paper is the first part of an ongoing study to investigate in detail the two dominant stellar systems in the area and their surrounding field.
- ID:
- ivo://CDS.VizieR/B/hst
- Title:
- HST Archived Exposures Catalog
- Short Name:
- B/hst
- Date:
- 20 Feb 2022 06:00:52
- Publisher:
- CDS
- Description:
- This catalogue is a copy of the Archived Exposures Catalog (AEC) compiled from the Hubble Space Telescope Data Archive database, with an indication about the existence of scientific images or spectra. It provides a summary of completed HST science observations. This catalogue contains also WFPC2 observations stacked into associations which usage is recommended for a large fraction of the WFPC2 images (see details in the "WFPC2 Associations" section below).
- ID:
- ivo://CDS.VizieR/J/ApJ/499/112
- Title:
- HST CFRS and LDSS redshift surveys. I.
- Short Name:
- J/ApJ/499/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze Hubble Space Telescope images of a complete sample of 341 galaxies drawn from the Canada-France Redhsift Survey (CFRS) and Low-Dispersion Survey Spectrograph (LDSS) ground-based redshift surveys. In this, the first paper in the series, each galaxy has been morphologically classified according to a scheme similar to that developed for the Medium Deep Survey. We discuss the reproducibility of these classifications and quantify possible biases that may arise from various redshift-dependent effects. We then discuss automated classifications of the sample and conclude, from several tests, that we can expect an apparent migration with redshift to later Hubble types that corresponds to a misclassification in our adopted machine classification system of ~24%+/-11 of the true "spirals" as "peculiars" at a redshift z~=0.9. After allowing for such biases, the redshift distribution for normal spirals, together with their luminosity function derived as a function of redshift, indicates approximately 1mag of luminosity evolution in B_AB_ by z~=1. The elliptical sample is too small for precise evolutionary constraints. However, we find a substantial increase in the proportion of galaxies with irregular morphology at large redshift from 9%+/-3% for 0.3<=z<=0.5 to 32%+/-12% for 0.7<=z<=0.9. These galaxies also appear to be the dominant cause of the rapid rise with redshift in the blue luminosity density identified in the redshift surveys. Although galaxies with irregular morphology may well comprise a mixture of different physical systems and might not correspond to present-day irregulars, it is clear that the apparently declining abundance and luminosities of our distant "irregulars" holds an important key to understanding recent evolution in the star formation history of normal galaxies.
- ID:
- ivo://CDS.VizieR/J/AJ/117/2244
- Title:
- HST color-magnitude diagrams of the LMC
- Short Name:
- J/AJ/117/2244
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results on the analysis of background field stars found in Hubble Space Telescope Wide Field Planetary Camera 2 observations of six of the old globular clusters of the Large Magellanic Cloud. Treated as contaminants by the globular cluster analysts, we produce (V-I, V) color-magnitude diagrams (CMDs) of the field stars and use them to explore the LMC's star formation history. The photometry approaches V {~} 26, well below the turnoff of an ancient ({~} 14 Gyr) LMC population of stars. The field star CMDs are generally characterized by an upper main sequence broadened by stellar evolution, an old red giant branch, a prominent red clump, and an unevolved lower main sequence. The CMDs also contain a few visual differences, the most obvious of which is the smeared appearance of the NGC 1916 field caused by heavy differential reddening. More subtly, the base of the subgiant branch near the old turnoff appears extended in V, and the red giant branch appears broad in V-I in four of the fields but not in the NGC 1754 field.
- ID:
- ivo://CDS.VizieR/J/ApJS/140/143
- Title:
- HST FOS spectral atlas
- Short Name:
- J/ApJS/140/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyzed the absorption line spectra of all quasars observed with the high-resolution gratings of the Faint Object Spectrograph on board the Hubble Space Telescope. We examined 788 spectra for 334 quasars and present line lists and identifications of absorption lines in the spectra of 271 of them. Analysis of the statistics of the Ly{alpha} and metal absorption systems are presented in companion papers. The data and several analysis products are available on the authors' Web site, http://lithops.as.arizona.edu/~jill/QuasarSpectra .
- ID:
- ivo://CDS.VizieR/J/ApJ/513/168
- Title:
- HST observations of carbon in spiral galaxies
- Short Name:
- J/ApJ/513/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the gas-phase abundance ratio C/O in six H II regions in the spiral galaxies M101 and NGC 2403, based on ultraviolet spectroscopy using the Faint Object Spectrograph on the Hubble Space Telescope. The ratios of C to O increase systematically with O/H in both galaxies, from log(C/O){~=}-0.8 at log(O/H){~=}-4.0 to log(C/O){~=}-0.1 at log(O/H){~=}-3.4. C/N shows no correlation with O/H. The rate of increase of C/O is somewhat uncertain because of uncertainty as to the appropriate UV reddening law and uncertainty in the metallicity dependence on grain depletions. However, the trend of increasing C/O with O/H is clear, confirming and extending the trend in C/O indicated previously from observations of irregular galaxies. Our data indicate that the radial gradients in C/H across spiral galaxies are steeper than the gradients in O/H. Comparing the data to chemical-evolution models for spiral galaxies shows that models in which the massive star yields do not vary with metallicity predict radial C/O gradients that are much flatter than the observed gradients.
- ID:
- ivo://CDS.VizieR/J/AJ/117/1700
- Title:
- HST observations of clusters in NGC 3597
- Short Name:
- J/AJ/117/1700
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analyzed HST/WFPC2 images of NGC 3597 and find {=~}700 compact objects surrounding the galaxy with an average (B-R)_0_ {=~}0.6. We propose that the majority of these objects are young globular clusters. They have a spread in colors that is consistent with that expected for a population of young clusters with a common age and spread induced by photometric errors and reddening within NGC 3597.
- ID:
- ivo://CDS.VizieR/J/ApJ/541/977
- Title:
- HST observations of low-mass stars in IC 348
- Short Name:
- J/ApJ/541/977
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the low-mass population of the young cluster IC 348 down to the deuterium-burning limit, a fiducial boundary between brown dwarf and planetary mass objects, using a new and innovative method for the spectral classification of late-type objects. Using photometric indices, constructed from HST/NICMOS narrowband imaging, that measure the strength of the 1.9{mu}m water band, we determine the spectral type and reddening for every M-type star in the field, thereby separating cluster members from the interloper population. Due to the efficiency of our spectral classification technique, our study is complete from ~0.7 to 0.015M_{sun}_. The mass function derived for the cluster in this interval, dN/dlogM{prop.to}M^0.5^, is similar to that obtained for the Pleiades, but appears significantly more abundant in brown dwarfs than the mass function for companions to nearby Sunlike stars. This provides compelling observational evidence for different formation and evolutionary histories for substellar objects formed in isolation versus as companions. Because our determination of the IMF is complete to very low masses, we can place interesting constraints on the role of physical processes such as fragmentation in the star and planet formation process and the fraction of dark matter in the Galactic halo that resides in substellar objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/527/199
- Title:
- HST observations of old clusters in the LMC
- Short Name:
- J/ApJ/527/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present V, V-I color-magnitude diagrams (CMDs) for three old star clusters in the Large Magellanic Cloud (LMC): NGC 1466, NGC 2257, and Hodge 11. Our data extend {~}3 mag below the main-sequence turnoff, allowing us to determine accurate relative ages and the blue straggler frequencies. Based on a differential comparison of the CMDs, any age difference between the three LMC clusters is less than 1.5 Gyr. Comparing their CMDs to those of M92 and M3, the LMC clusters, unless their published metallicities are significantly in error, are the same age as the old Galactic globulars. The similar ages to Galactic globulars are shown to be consistent with hierarchical clustering models of galaxy formation. The blue straggler frequencies are also similar to those of Galactic globular clusters. We derive a true distance modulus to the LMC of (m - M)_0_ = 18.46 {+/-} 0.09 [assuming (m - M)_0_ = 14.61 for M92] using these three LMC clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/347/841
- Title:
- HST Observations of SMC N88A
- Short Name:
- J/A+A/347/841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- High-resolution Hubble Space Telescope images have allowed us for the first time to resolve the compact SMC ionized ``blob'' N88A (diameter ~3.5arcsec or 1pc). This very young HII, region, which is hatching from its natal molecular cloud, is heavily affected by absorbing dust associated with the cloud. The interstellar reddening towards N88A is on average A_v_~1.5mag and strikingly rises to more than 3.5mag in a narrow dust band crossing the core of the HII region. Such a high extinction is unprecedented for an HII region in the metal-poor SMC. We present the photometry of some 70 stars lying towards the OB association at the center of which lies N88A. The exciting star(s) of N88A is not detected, due to the heavy extinction. The chronology of star formation is discussed for the whole region.
- ID:
- ivo://CDS.VizieR/J/A+A/391/945
- Title:
- HST photometry of 74 galactic globular clusters
- Short Name:
- J/A+A/391/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the complete photometric database and the color-magnitude diagrams for 74 Galactic globular clusters observed with the HST/WFPC2 camera in the F439W and F555W bands. A detailed discussion of the various reduction steps is also presented, and of the procedures to transform instrumental magnitudes into both the HST F439W and F555W flight system and the standard Johnson B and V systems. We also describe the artificial star experiments which have been performed to derive the star count completeness in all the relevant branches of the color magnitude diagram. The entire photometric database and the completeness function will be made available on the Web immediately after the publication of the present paper.
- ID:
- ivo://CDS.VizieR/J/ApJS/120/265
- Title:
- HST photometry of M4
- Short Name:
- J/ApJS/120/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents a detailed description of the acquisition and processing of a large body of imaging data for three fields in the globular cluster M4 taken with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. Analysis with the ALLFRAME package yielded the deepest photometry yet obtained for this cluster. The resulting data set for 4708 stars (positions and calibrated photometry in V, I, and, in two fields, U) spanning approximately six cluster core radii is presented. The scientific analysis is deferred to three companion papers, which investigate the significant white dwarf population discovered and the main-sequence population.
- ID:
- ivo://CDS.VizieR/J/ApJS/128/99
- Title:
- HST photometry of 4 Virgo LSB galaxies
- Short Name:
- J/ApJS/128/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Utilizing the F814W and F300W filters, Hubble Space Telescope Wide Field Planetary Camera-2 (WFPC2) images were taken of four low surface brightness galaxies in the direction of the Virgo Cluster - V7L3, V2L8, V1L4, and Malin 1. The high resolution of the WFPC2 combined with the extremely diffuse nature of the four galaxies makes them essentially transparent, allowing for the serendipitous discovery of 139 background galaxies visible through both the disks and nuclei of the foreground galaxies. Surface photometry was done on the newly discovered galaxies through the F814W (I-band) filter. The detected galaxies have both r1/4 and exponential-type profiles with radii (to the {mu}_F814W_=25.0mag/arcsec^2^ limit) less than 5.0". Their total magnitudes range from 18.9 through the survey cutoff at 25.0 in the F814W filter.
- ID:
- ivo://CDS.VizieR/J/ApJS/97/1
- Title:
- HST Quasar Absorption Line Key Project. X.
- Short Name:
- J/ApJS/97/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sensitive H I 21cm emission line spectra have been measured for the directions to 143 quasars and AGNs chosen from the observing lists for the HST Quasar Absorption Line Key Project. Narrow-band and wide-band data were obtained with the NRAO 43m radio telescope for each object. The narrow-band data have a velocity resolution of 1km/s, extend from -220 to +170km/s, and are corrected for stray 21cm radiation. The wide-band data have a resolution of 4km/s and extend from -1000 to +1000km/s. The data are important for the interpretation of ultraviolet absorption lines near zero redshift in Key Project spectra. Twenty-two percent of the quasars lie behind Galactic high-velocity H I clouds with |VLSR|>100km/s whose presence can increase the equivalent width of interstellar absorption lines significantly. This paper contains the emission spectra and measures of the H I velocities and column densities along the sight line to each quasar. We discuss how the measurements can be used to estimate the visual and ultraviolet extinction toward each quasar and to predict the approximate strength of the strong ultraviolet resonance lines of neutral gas species in the HST Key Project spectra.
- ID:
- ivo://CDS.VizieR/J/ApJS/122/81
- Title:
- HST snapshot survey of 3CR radio sources
- Short Name:
- J/ApJS/122/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and describe optical counterparts to 46 3CR radio galaxies of redshifts less than 0.1 that were imaged with the Hubble Space Telescope's (HST) WFPC2 camera through the broadband F702W filter as part of the 3CR Snapshot Survey. This is the fifth and last such paper describing the 252 radio galaxies of this R-band survey. At the 0.1'' resolution of the images, a wealth of detail is visible. Approximately 89% of the galaxies are ellipticals, and nearly all reside in groups or clusters of galaxies of various richness and compactness. Nearby elliptical companions of slightly smaller size and mass are common. Dust is prevalent in the cores of the 3C hosts; nearly half of the galaxies possess some type of dust structure, such as irregular dust lanes, filaments, or disks. Besides the well-known dust disks of 3C 264 and 3C 270, we have found five new candidates in 3C 31, 3C 40, 3C 296, 3C 449, and 3C 465, as well as in the central regions of the nearby neighbors of 3C 31 and 3C 465. Our sample includes six confirmed optical synchrotron jets in 3C 15, 3C 66B, 3C 78, 3C 264, 3C 274, and 3C 371, or approximately 13% of the sample. Unresolved nuclei, consistent with the point spread function of WFPC2, are found in 43%-54% of the galaxies and in the majority of galaxies with dust disks and optical jets.
- ID:
- ivo://CDS.VizieR/J/ApJ/521/577
- Title:
- HST studies of the WLM globular cluster
- Short Name:
- J/ApJ/521/577
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained V and I images of the lone globular cluster that belongs to the dwarf Local Group irregular galaxy known as WLM. The color-magnitude diagram of the cluster shows that it is a normal old globular cluster with a well-defined giant branch reaching to M_V_=-2.5, a horizontal branch at M_V_=+0.5, and a subgiant branch extending to our photometry limit of M_V_=+2.0. A best fit to theoretical isochrones indicates that this cluster has a metallicity of [Fe/H]=-1.52{+/-}0.08 and an age of 14.8{+/-}0.6 Gyr, thus indicating that it is similar to normal old halo globulars in our Galaxy. From the fit we also find that the distance modulus of the cluster is 24.73{+/-}0.07 and the extinction is A_V_=0.07{+/-}0.06, both values that agree within the errors with data obtained for the galaxy itself by others.
- ID:
- ivo://CDS.VizieR/J/MNRAS/300/665
- Title:
- HST VI Photometry of Six LMC Old Globular Clusters
- Short Name:
- J/MNRAS/300/665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The following tables contain the results of photometry performed on Hubble Space Telescope WFPC2 images of the Large Magellanic Cloud globular clusters NGC 1754, 1835, 1898, 1916, 2005, and 2019. The magnitudes reported here were measured from Planetary Camera F555W and F814W images using DoPHOT (Schechter, Mateo, & Saha 1993) and afterwards transformed to Johnson V/Kron-Cousins I using equation 9 of Holtzman et al. (1995PASP..107.1065H). We carried out photometry on both long (1500 sec combined in F555W, 1800 sec in F814W) and short (40 sec combined in F555W, 60 sec in F814W) exposures. Where the short exposure photometry produced smaller errors, we report those magnitudes in place of those measured from the long exposures. For each star, we give an integer identifier, its x and y pixel position as measured in the F555W PC image, its V and I magnitude, the photometric errors reported by DoPHOT, both the V and I DoPHOT object types (multiplied by 10 if the reported magnitude was measured in the short exposure frame), and a flag if the star was removed during our procedure for statistical field star subtraction. Summary of data reduction and assessment of photometric accuracy: Cosmic ray rejection, correction for the y-dependent CTE effect (Holtzman et al. 1995a), geometric distortion correction, and bad pixel flagging were applied to the images before performing photometry. For the photometry, we used version 2.5 of DoPHOT, modified by Eric Deutsch to handle floating-point images. We found that there were insufficient numbers of bright, isolated stars in the PC frames for producing aperture corrections. Aperture corrections as a function of position in the frame were instead derived using WFPC2 point spread functions kindly provided by Peter Stetson. As these artificially generated aperture corrections agree well with ones derived from isolated stars in the WF chips, we trust that they are reliable to better than 0.05 mag. In agreement with the report of Whitmore & Heyer (1997), we found an offset in mean magnitudes between the short- and long-exposure photometry. We corrected for this effect by adjusting the short-exposure magnitudes to match, on average, those of the long exposures. Finally, we merged the short- and long- exposure lists of photometry as described above and transformed the magnitudes from the WFPC2 system to Johnson V/Kron-Cousins I, applying the Holtzman et al. (1995PASP..107.1065H) zero points. Statistical field star subtraction was performed using color-magnitude diagrams of the field stars produced from the combined WF frames. Completeness and random and systematic errors in the photometry were extensively modelled through artificial star tests. Crowding causes the completeness to be a strong function of position in the frame, with detection being most difficult near the cluster centers. In addition, we found that crowding introduces systematic errors in the photometry, generally <0.05 mag, that depend on the V-I and V of the star. Fortunately, these errors are well-understood. However, unknown errors in the zero points may persist at the ~0.05 mag level.
- ID:
- ivo://CDS.VizieR/J/AJ/116/2081
- Title:
- Hubble Deep Field catalog of color-based redshift
- Short Name:
- J/AJ/116/2081
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We derive simple empirical color-redshift relations for z<~4 galaxies in the Hubble Deep Field (HDF) using a linear function of three photometric colors (U-B, B-V, V-I). The dispersion between the estimated redshifts and the spectroscopically observed ones is small for relations derived in several separate color regimes; the dispersions range from {sigma}_z_~=0.03 to 0.1 for z<~2 galaxies, and from {sigma}_z_~=0.14 to 0.25 for z>~2 galaxies. We apply the color-redshift relations to the HDF photometric catalog and obtain estimated redshifts that are consistent with those derived from spectral template fitting methods. The advantage of these color-redshift relations is that they are simple and easy to use and do not depend on the assumption of any particular spectral templates; they provide model independent redshift estimates for z<~4 galaxies using only multiband photometry, and they apply to about 90% of all galaxies. We provide a color-based estimated redshift catalog of HDF galaxies to z<~4. We use the estimated redshifts to investigate the redshift distribution of galaxies in the HDF; we find peaks in the redshift distribution that suggest large-scale clustering of galaxies to at least z~1 and that are consistent with those identified in spectroscopic probes of the HDF.
- ID:
- ivo://CDS.VizieR/J/AJ/117/17
- Title:
- Hubble Deep Field near-IR obs.
- Short Name:
- J/AJ/117/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents data obtained during the NICMOS Guaranteed Time Observations of a portion of the Hubble Deep Field. The data are in a catalog format similar to the publication of the original WFPC2 Hubble Deep Field program (Williams et al., 1996, Cat. <J/AJ/112/1335>). The catalog contains 342 objects in a 49.1"x48.4" subfield of the total observed field, 235 of which are considered coincident with objects in the WFPC2 catalog. The 3{sigma} signal-to-noise ratio level is at an aperture AB magnitude of approximately 28.8 at 1.6{mu}m. The catalog sources, listed in order of right ascension, are selected to satisfy a limiting signal-to-noise ratio criterion of greater than or equal to 2.5. This introduces a few false detections into the catalog, and users should take careful note of the completeness and reliability levels for the catalog discussed in sections 9 and 10. The catalog also contains a test parameter indicating the results of half-catalog tests and the degree of coincidence with the original WFPC2 catalog.
- ID:
- ivo://CDS.VizieR/J/AJ/112/1335
- Title:
- Hubble Deep Field observations
- Short Name:
- J/AJ/112/1335
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Deep Field (HDF) is a Director's Discretionary program on HST in Cycle 5 to image an undistinguished field at high Galactic latitude in four passbands as deeply as reasonably possible. These images provide the most detailed view to date of distant field galaxies and are likely to be important for a wide range of studies in galaxy evolution and cosmology. In order to optimize observing in the time available, a field in the northern continuous viewing zone was selected and images were taken for ten consecutive days, or approximately 150 orbits. Shorter 1-2 orbit images were obtained of the fields immediately adjacent to the primary HDF in order to facilitate spectroscopic follow-up by ground- based telescopes. The observations were made from 1995 December 18-30, and both raw and reduced data have been put in the public domain as a community service. We present a summary of the criteria for selecting the field, the rationale behind the filter selection and observing times in each band, and the strategies for planning the observations to maximize the exposure time while avoiding Earth-scattered light. Data reduction procedures are outlined, and images of the combined frames in each band are presented. Objects detected in these images are listed in a catalog with their basic photometric parameters.
- ID:
- ivo://CDS.VizieR/J/A+AS/129/583
- Title:
- Hubble Deep Field surface photometry
- Short Name:
- J/A+AS/129/583
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The detailed surface photometry of a sample of early-type galaxies in the Hubble Deep Field is presented as part of a long-term project aimed to settle strong observational constraints to the theories modelling the evolution of elliptical galaxies from the early stages. The sample has been extracted, in the V_606_ band, from the database provided by the ESO-STECF-HDF Group (Couch, 1996, <http://ecf.hq.eso.org>). The selection criteria involve the total magnitude, the number of pixels detected above the background level and an automatic star/galaxy classifier. Moreover, form visual inspection of the frames, we excluded the galaxies showing unambiguous late-type morphology. The analysis of the luminosity and geometrical profiles, carried out on the 162 candidates obeying our selection criteria, resulted in a list of 99 'bona fide' early-type galaxies, for which accurate total magnitudes and effective radii were computed on the basis of the equivalent luminosity profiles. The comparison with the magnitudes given by Williams et al. (1996, Cat. <J/AJ/112/1335>) indicates that the automated photometry tends to underestimate the total luminosity of the ellipticals. The luminosity profiles of most of galaxies in our sample follow fairly well the de~Vaucouleurs law ('Normal' profiles). However, a relevant fraction of galaxies, even following the r^1/4^ law in the main body light distribution, exhibit in the inner region a flattening of the luminosity profile not attributable to the PSF (`Flat' profiles) or, in some cases, a complex (multi-nucleus) structure (`Merger' profiles). A statistically significant correlation is found between the shapes of the luminosity profiles and the ellipticity distribution. In particular, the average ellipticity of galaxies belonging to the `Flat' and `Merger' classes is significantly higher than that of the `Normal' galaxies. Finally, even taken into account the relevant uncertainty of the outer position angle profiles, the amount of isophotal twisting of HDF ellipticals turns out to be significantly larger with respect to that of the local samples.
- ID:
- ivo://CDS.VizieR/II/258
- Title:
- Hubble Ultra Deep Field Catalog (UDF)
- Short Name:
- II/258
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Ultra Deep Field (PI: Steven V. W. Beckwith) is a 400-orbit Cycle 12 program to image a single field of the Wide Field Camera (WFC) of the Advanced Camera for Surveys (ACS) in four filters: F435W (B), F606W (V), F775W (i), and F850LP (z). The observations took place over 4 months from September 2003 to January 2004 under two program IDs: 9978 and 10086. The observations consist of half-orbit exposures, cycling through each of the filters in a 4-point dither pattern to provide sub-pixel sampling, as well as a larger-scale 3-point line pattern to cover the 2 second of arc gap between the two ACS/WFC chips. The total exposure times are summarized below, with typical exposure times of 1200s for individual images. The AB magnitude zero-points for ACS are current as of March 2004. --------------------------------------------------------------- Number of Number of Total Exp. AB mag. Orbits Exposures Time (s) zero-point --------------------------------------------------------------- B (F435W): 56 112 134880 25.673 V (F606W): 56 112 135320 26.486 i (F775W): 144 288 347110 25.654 z (F850LP): 144 288 346620 24.862 --------------------------------------------------------------- More details are found in the "intro.txt" file, or from the UDF home page.
- ID:
- ivo://CDS.VizieR/J/ApJ/591/53
- Title:
- I photometry of Cl 0024+16
- Short Name:
- J/ApJ/591/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe a new wide-field Hubble Space Telescope survey of the galaxy cluster Cl 0024+16 (z~0.4) consisting of a sparsely sampled mosaic of 39 Wide Field Planetary Camera 2 images that extends to a cluster radius of ~5Mpc. Together with extensive ground-based spectroscopy taken from the literature, augmented with over a hundred newly determined redshifts, this unique data set enables us to examine environmental influences on the properties of cluster members from the inner core to well beyond the virial radius (~1.7Mpc). We catalog photometric measures for 22000 objects to I>~25 and assign morphological types for 2181 to I=22.5, of which 195 are spectroscopically confirmed cluster members.
- ID:
- ivo://CDS.VizieR/J/ApJ/596/748
- Title:
- IR Observations in HDF-North
- Short Name:
- J/ApJ/596/748
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The original analysis of the star formation history in the NICMOS deep images of the northern Hubble Deep Field (NHDF) is extended to the entire NHDF utilizing NICMOS and WFPC2 archival data. The roughly constant star formation rate from redshifts 16 found in this study is consistent with the original results. Star formation rates from this study, Lyman break galaxies, and submillimeter observations are now in concordance. The spike of star formation at redshift 2 due to two ultraluminous IR galaxies in the small deep NICMOS field is smoothed out in the larger area results presented here. The larger source base of this study allows comparison with predictions from hierarchical galaxy formation models. In general, the observation are consistent with the predictions. The observed luminosity functions at redshifts 16 are presented for future comparisons with theoretical galaxy evolution calculations. Mid- and far-infrared properties of the sources are also calculated and compared with observations. A candidate for the VLA source VLA 3651+1221 is discussed.
- ID:
- ivo://CDS.VizieR/J/ApJ/540/1016
- Title:
- K-band & NICMOS photometry of Trapezium Cluster
- Short Name:
- J/ApJ/540/1016
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained images of the Trapezium Cluster (140"x140"; 0.3pc x 0.3pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R=800) and existing spectral types and photometry, we have constructed an H-R diagram and used it and other arguments to infer masses and ages.
- ID:
- ivo://CDS.VizieR/J/AJ/117/206
- Title:
- LMC far-ultraviolet imaging
- Short Name:
- J/AJ/117/206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the deepest pure UV observations with the highest angular resolution ever performed, a set of 12 exposures with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 and F160BW filter obtained in parallel observing mode, which covers ~12arcmin^2^ in the Large Magellanic Cloud (LMC), north of the bar, and in the "general field" regime of the LMC. The 341 independent measurements of 198 objects represent an accumulated exposure of >=2x10^4^s and reveal stars as faint as m_UV_~=22mag. The observations show that about two-thirds of the UV emission from the LMC is emitted by our HST-detected UV stars in the field, that is, not in clusters or associations. We identified optical counterparts in the Royal Observatory Edinburgh/Naval Research Laboratory photometric catalog for about one-third of the objects.
- ID:
- ivo://CDS.VizieR/J/A+A/288/413
- Title:
- Massive stars in I Zw 36
- Short Name:
- J/A+A/288/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed the blue dwarf galaxy I Zw 36 with the f/96 relay of the HST Faint Object Camera and have for the first time resolved massive stars, using the broad band filters F175W, F342W, F430W and F480LP. We have measured the fluxes of 143 of these objects and studied their characteristics in color-magnitude diagrams. A few stars may be red supergiants but their contribution to the integrated light is less than 5% in the F430W filter. The F175W-F430W color of the integrated stellar population is redder than expected from the current burst of star formation, suggesting therefore the presence of an older and unresolved underlying population. The ultraviolet measurements combined with synthetic photometry calculations allow us to place the massive stars in a bolometric magnitude vs. temperature diagram. In this diagram, the stars are compared to evolutionary tracks for different stellar masses. The current burst probably has an age less than 12Myr. We infer an Initial Mass Function, with a power-law slope in the range -1.7 to -2.6 for masses M>=20M_{sun}_. This is consistent with most of the values reported for sites of star formation in the Galaxy and the Magellanic Clouds and does not support the view of an IMF flattening at low metallicity.
46. M101 Cepheids
- ID:
- ivo://CDS.VizieR/J/ApJ/508/491
- Title:
- M101 Cepheids
- Short Name:
- J/ApJ/508/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the identification of 255 candidate variable stars in a field located some 1.7' from the center of the late-type spiral galaxy M101 = NGC 5457, based on observations made with the Wide Field and Planetary Camera 2 on board the Hubble Space Telescope. Photometric measurements in the F555W and F814W filters - analyzed independently with the DAOPHOT/ALLFRAME and DoPHOT software suites - have been transformed to the Johnson V and Kron-Cousins I standard magnitude systems. Periods and intensity-averaged mean magnitudes for 61 carefully selected candidate Cepheid variables with periods in the range 10-48 days indicate a reddening-corrected mean distance modulus (m-M)_0_=29.05+/-0.14 (if the true modulus of the Large Magellanic Cloud is 18.50+/-0.10, and if there is no dependence of the period-luminosity relation on metal abundance); results consistent with this are obtained whether or not the sample is expanded to include a larger fraction of the candidates. Applying a metallicity-dependent correction of +0.16+/-0.10mag would increase this estimate to (m-M)_0_= 29.21+/-0.17mag.
- ID:
- ivo://CDS.VizieR/J/ApJS/110/213
- Title:
- Morphological Types in 10 Distant Rich Clusters
- Short Name:
- J/ApJS/110/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present catalogs of objects detected in deep images of 11 fields in 10 distant clusters obtained using WFPC-2 on board the Hubble Space Telescope. The clusters span the redshift range z=0.37-0.56 and are the subject of a detailed ground- and space-based study to investigate the evolution of galaxies as a function of environment and epoch. The data presented here include positions, photometry and basic morphological information on ~9000 objects in the fields of the 10 clusters. For a brighter subset of 1857 objects in these areas, we provide more detailed morphological information.
- ID:
- ivo://CDS.VizieR/J/ApJS/107/1
- Title:
- Morphologies of distant galaxies II
- Short Name:
- J/ApJS/107/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The morphological properties of high-redshift galaxies are investigated using a sample of 507 objects (I<22.0mag) from the Hubble Space Telescope (HST) Medium Deep Survey. Independent visual morphological classifications for each galaxy are used to quantify the statistical uncertainties in the galaxy classifications. Visual classifications are found to agree well for I<21mag. Fainter than I=21mag significant disagreements are seen in the independent visual classifications of late-type systems with T>7, merging systems, and peculiar galaxies. The classifications of these systems are shown to be somewhat subjective. Objective classifications based upon measurements of central concentration and asymmetry for the Medium Deep Survey sample are presented. These classifications are calibrated using measurements of structural parameters for an artificially redshifted sample of local objects. Morphologically segregated number counts using both sets of visual classifications and objective classifications support the conclusion that the observed galaxy counts agree with no-evolution predictions for the elliptical and spiral populations, as reported in Glazebrook et al. (1995MNRAS.275L..19G). A major conclusion is that the large overdensity of merging/ peculiar/ irregular galaxies relative to the predictions of no-evolution models (reported by Glazebrook et al. 1995MNRAS.275L..19G) is confirmed. However, the shape of the faint-end (I>21.0mag) number count relation for peculiar objects is sensitive to the large systematic uncertainties inherent in the visual classification of these objects. Despite this caveat, the frequency of objects showing clear evidence for tidal interactions (e.g., tidal tails) in the HST sample is at least 50% larger than it is among nearby galaxies, at the 2{sigma} level. Relatively few "chain galaxies" are seen among the sample of peculiar objects, suggesting that these systems do not form a large component of the peculiar galaxy population at I<22mag.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1757
- Title:
- M30 UBV photometry
- Short Name:
- J/AJ/116/1757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present F555W (V), F439W (B), and F336W (U) photometry of 9507 stars in the central 2' of the dense, post-core-collapse cluster M30 (NGC 7099) derived from Hubble Space Telescope Wide Field Planetary Camera 2 images. These data are used to study the mix of stellar populations in the central region of the cluster. Forty-eight blue straggler stars are identified; they are found to be strongly concentrated toward the cluster center. The specific frequency of blue stragglers, F_BSS_=N(BSS)/N(V<V_HB_+2), is 0.25+/-0.05 in the inner region of M30 (r<20"), significantly higher than the frequency found in other clusters: F_BSS_=0.05-0.15. The shape of M30's blue straggler luminosity function resembles the prediction of the collisional formation model, and is inconsistent with the binary merger model of Bailyn & Pinsonneault (1995ApJ...439..705B). An unusually blue star (B=18.6, B-V=-0.97), possibly a cataclysmic variable based on its color, is found about 1.2" from the crowded cluster center; the photometric uncertainty for this star is large, however, because of the presence of a very close neighbor. Bright red giant stars (B<16.6) appear to be depleted by a factor of 2-3 in the inner r<10" relative to fainter giants, subgiants, and main-sequence turnoff stars (95% significance). We confirm that there is a radial gradient in the color of the overall cluster light, going from B-V~0.82 at r~1' to B-V~0.45 in the central 10". The central depletion of the bright red giants is responsible for about half of the observed color gradient; the rest of the gradient is caused by the relative underabundance of faint red main-sequence stars near the cluster center (presumably a result of mass segregation). The luminosity function of M30's evolved stars does not match the luminosity function shape derived from standard stellar evolutionary models: the ratio of the number of bright giants to the number of turnoff stars in the cluster is 30% higher than predicted by the model (3.8{sigma} effect), roughly independent of red giant brightness over the range M_V_=-2 to +2.
- ID:
- ivo://CDS.VizieR/J/AJ/121/3048
- Title:
- Multicolor photometry in NGC 1512 and NGC 5248
- Short Name:
- J/AJ/121/3048
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present broadband (U, V, I, and H) and narrowband (H{alpha}+[N II] and Pa{alpha}) images of the circumnuclear starburst rings in two nearby spiral galaxies, NGC 1512 and NGC 5248, obtained with the WFPC2 and NICMOS cameras on HST. Combined with previously published ultraviolet (UV) HST images at 2300{AA} these data provide a particularly wide wavelength range with which to study the properties of the stellar populations, the gas, and the dust in the rings.
- ID:
- ivo://CDS.VizieR/J/ApJ/524/536
- Title:
- Nearby Ly{alpha} quasar absorbers
- Short Name:
- J/ApJ/524/536
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectroscopy of 10 quasars obtained with the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) is presented. In the 10 sight lines, we detect 357 absorption lines above a significance level of 3{sigma} and 272 lines above a significance level of 4.5{sigma}. Automated software is used to detect and identify the lines, almost all of which are unresolved at the GHRS G140L resolution of 200km/s. After identifying Galactic lines, intervening metal lines, and higher order Lyman lines, we are left with 139 Ly{alpha} absorbers in the redshift range 0<z<0.22 (lines within 900km/s of geocoronal Ly{alpha} are not selected). These diffuse hydrogen absorbers have column densities that are mostly in the range 10^13^-10^15^cm^-2^ for an assumed Doppler parameter of 30km/s. The number density of lines above a rest equivalent width of 0.24{AA}, dN/dz=38.3{+/-}5.3, agrees well with the measurement from the Quasar Absorption-Line Key Project. There is marginal evidence for cosmic variance in the number of absorbers detected among the 10 sight lines.
- ID:
- ivo://CDS.VizieR/J/PASP/110/1012
- Title:
- New double stars from HST
- Short Name:
- J/PASP/110/1012
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data from the Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) interferometers, covering 22 months of guide-star acquisition operations, have been analyzed for evidence of stellar duplicity. The data comprise a survey of observed guide stars, all of which are taken from the HST Guide Star Catalog, ranging in magnitude from 9 to 14. The survey results cover a parameter space for the newly found doubles, for the fainter stars, which are of smaller limiting angular separations than in any previous surveys. The normal HST engineering telemetry data from 13,979 acquisitions on 4882 stars have been processed. The FGS guidance data can reveal duplicity with separations ranging from approximately 30mas, for the brighter stars, with small magnitude differences, up to the neighborhood of 500mas, and in some cases to 1000mas. The fraction of guide stars indicating duplicity is a function of the statistical criteria used but is over 5% at a very high level of confidence. It is possible that if some of the brighter and closer pairs could be identified as nearby, then their orbital motions would be rapid enough to allow a mass and distance determination on a timescale of a decade if followed with ground-based interferometric and spectroscopic instruments. A brief catalog of doubles is given, nearly all of which are of certain duplicity. Information for accessing on-line catalogs of large numbers of stars with lesser, but nevertheless strong, probabilities of duplicity and also for the solutions for duplicity from all acquisitions is provided.
- ID:
- ivo://CDS.VizieR/J/AJ/117/1708
- Title:
- NGC 1741 HST photometry
- Short Name:
- J/AJ/117/1708
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Hubble Space Telescope (HST) Faint Object Camera (FOC) ultraviolet (UV) and WFPC2 optical images in conjunction with UV spectroscopic observations taken with the Goddard High Resolution Spectrograph to examine the star formation history and properties of the interacting galaxy system NGC 1741 in the Hickson Compact Group 31. The high spatial resolution afforded by HST has allowed us to identify a large number of starburst knots, or "superstar clusters" (SSCs), in the starburst regions of this system. Photometry of these SSCs in the UV and optical bands indicates that most of these objects have ages of a few Myr, with a few up to ~100Myr, and masses between 10^4^ and 10^6^M_{sun}_. The estimated age is confirmed by a spectral synthesis analysis of one knot for which we have obtained a UV spectrum. The V-band luminosity function of the SSCs is well represented by a power law {Phi}(L)~L^-{alpha}^ with an index of -1.85, with no evidence of a turnover brighter than the completeness limit. These properties are in good agreement with those found for SSCs in other starburst galaxies. Our results support the suggestion that some of these SSCs may be extremely young globular clusters formed in a relatively recent starburst episode that has been triggered by a merger event.
- ID:
- ivo://CDS.VizieR/J/ApJ/546/694
- Title:
- NICMOS star formation history
- Short Name:
- J/ApJ/546/694
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an extensive analysis of the star formation rates determined from the NICMOS deep images of the northern Hubble Deep Field. We use SED template fitting photometric techniques to determine both the redshift and the extinction for each galaxy in our field. Measurement of the individual extinctions provides a correction for star formation hidden by dust obscuration. We determine star formation rates for each galaxy based on the 1500{AA} UV flux and add the rates in redshift bins of width 1.0 centered on integer redshift values.
- ID:
- ivo://CDS.VizieR/J/ApJ/562/303
- Title:
- Old Stellar Populations of the SMC
- Short Name:
- J/ApJ/562/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry is given for six data sets of SMC photometry, all in the V and I bands. Field names in the file summary below are the names used in the STScI archive for the WFPC2 observations. WFPC2 observations of NGC 121 and the SMC fields reach limiting magnitudes of V=26 and I=25.5; ground-based observations cover a square region of 14.5 arcmin on a side and reach V=25.5 and I=24.5.
56. Orion HST survey
- ID:
- ivo://CDS.VizieR/J/AJ/111/846
- Title:
- Orion HST survey
- Short Name:
- J/AJ/111/846
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on a survey of the brightest portions of the Orion Nebula made with the Wide Field Planetary Camera 2 of the Hubble Space Telescope. Fifteen paintings were made, each employing interference filters isolating the principal emission lines of HI, [NII], and [OIII] and another isolating an interval similar to the V bandpass. A careful survey of compact objects of stellar and nearly stellar appearance was made and astrometric solutions for individual fields were used to determine positions accurate to about 0.1". 344 stars were measured, down to about V=22. In addition to structures in several of the previously known Herbig-Haro objects, 145 compact sources that can be classified as proplyds were found. Proplyds are young stars surrounded by circumstellar material which is rendered visible by being in or near an HII region. In the central region, where detection of proplyds is easiest, almost all of the low-mass pre-main-sequence stars have obvious circumstellar material. The fraction falls as one views areas away from the dominant photoionizing star {theta}^1^C Ori. Six new dark disk proplyds are found, bringing the total to seven. These are objects showing only in silhouette against the bright background of the HII region. Most of these are elliptical in form, indicating that they are circumstellar disks. In addition to these compact sources, the new images allow detection of numerous large structures previously unreported from ground-based observations. These include shells and shocks apparently related to Herbig-Haro objects and high velocity outflows from young stellar objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/468/633
- Title:
- Photometry in the M31 OB association NGC 206
- Short Name:
- J/ApJ/468/633
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our effort to determine what affects the star formation process by looking at the products of that process, we have obtained broadband Hubble Space Telescope images of the large OB association NGC 206 in the nearby spiral galaxy M31. Our images cover approximately the southern half of the association. We have detected stars down to an F555W magnitude of 25.5 and measure stars on the main sequence in NGC 206 to an M_F555W,0_ of -1 or a mass of ~6M_{sun}_. From a comparison with isochrones, ages up to about 8Myr are plausible, and we adopt an age of 6Myr. For stellar masses 6-15M_{sun}_, we determine an initial mass function slope of -1.4+/-0.5. This is close to the value for a Salpeter mass function, although the uncertainty is large. The uncertainty in the slope represents disagreement among the individual mass bins. In terms of intermediate-mass stars (6-15M_{sun}_) the NGC 206 star formation event appears to be typical of star formation processes in other nearby galaxies, and it is part of a growing number of studies ,that are finding similarities in the products of the star formation processes in a wide variety of star formation events and galactic environments. Nevertheless, the density of stars formed in NGC 206 is much lower than that in giant H II regions such as NGC 604 in M33 or 30 Doradus in the LMC and in typical OB associations.
- ID:
- ivo://CDS.VizieR/J/ApJS/122/355
- Title:
- Properties of low z QSO absorption systems
- Short Name:
- J/ApJS/122/355
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (Partial): We examine the clustering properties of low-redshift Ly{alpha} and heavy-element QSO absorption line systems seen in the spectra of 13 QSOs at the Galactic poles. This is the densest sample of ~1 degree separated QSOs observed spectroscopically with the Hubble Space Telescope to date. At the median redshift of the Ly{alpha} sample (z{=~}0.7), the QSO lines of sight are separated on transverse scales from about 15 to 200h^-1^Mpc (q_0_=0.5, H=100h.km/s/Mpc), allowing the three-dimensional clustering of the absorbers to be examined on those scales. The Galactic poles are also regions where relatively deep and wide-field galaxy redshift surveys have taken place, so the distributions of galaxies and Ly{alpha} systems can be compared within the same volume of space. There are 545 total absorption lines detected in the complete sample from 13 QSOs. We identify 307 Ly{alpha} systems, of which 18 contain heavy-element lines. We confirm the relatively slow redshift number density evolution for Ly systems at z{<=}1. There are also five likely C IV doublets in our sample, for which the Ly{alpha} line is not accessible.
- ID:
- ivo://CDS.VizieR/J/ApJ/566/993
- Title:
- rho Ophiuchus (Lynds 1688) cluster NICMOS imaging
- Short Name:
- J/ApJ/566/993
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of near-infrared photometry of young stars associated with the Ophiuchus molecular cloud based on observations made with the Hubble Space Telescope NICMOS3 camera at 1.1 and 1.6{mu}m. Our survey covers 0.02deg^2^ centered on the dense molecular cores in Lynds 1688. We detect 165 sources at 1.6{mu}m and 65 sources at 1.1{mu}m within our estimated completeness limits of 21.0 and 21.5mag, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/480/568
- Title:
- RK photometry in 3C 336 field
- Short Name:
- J/ApJ/480/568
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present very deep WFPC2 images and FOS spectroscopy from the Hubble Space Telescope (HST) together with numerous supporting ground-based observations of the field of the quasar 3C 336 (z_em_=0.927). The observations are designed to investigate the nature of galaxies producing metal-line absorption systems in the spectrum of the QSO. Along a single line of sight, we find at least six metal-line absorption systems (of which three are newly discovered) ranging in redshift from 0.317 to 0.892. Through an extensive program of optical and IR imaging, QSO spectroscopy, and faint galaxy spectroscopy, we have identified five of the six metal-line absorption systems with luminous (L_K_>=0.1L^*^_K_) galaxies. These have morphologies ranging from very late-type spiral to S0, and they exhibit a wide range of inclination and position angles with respect to the QSO sight line. The only unidentified absorber, despite our intensive search, is a damped Lyman-{alpha} system at z_abs_=0.656. Analysis of the absorption spectrum suggests that the metal abundances ([Fe/H]=-1.2) in this system are similar to those in damped systems at z~2 and to the two other damped systems for which abundances have been determined at z<1. The absorption line system must either be associated with an underluminous, late-type spiral galaxy, which we find at a projected disk impact parameter of ~120h^-1^kpc, or with an as yet unseen, extremely faint galaxy (L<0.05L^*^_K_) near the QSO sight line that eludes detection despite our deep HST and high-resolution ground-based near-IR images. We have found no examples of intrinsically faint galaxies (L<0.1L^*^) at small impact parameters that might have been missed as absorber candidates in our previous ground-based imaging and spectroscopic programs on Mg II absorbing galaxies. We have, however, identified several intrinsically faint galaxies within ~50h^-1^kpc of the QSO sight line that do not produce detectable metal-line absorption. There are no bright galaxies (L>0.1L_K_) within 50h^-1^kpc that do not produce detectable metal lines (of Mg II {lambda}{lambda}2796, 2803 and/or C IV {lambda}{lambda}1548, 1550) in the QSO spectrum. All of these results generally support the inferences we have previously reached from a larger survey for absorption-selected galaxies at z<1. There are several other galaxies with redshifts near that of 3C 336, suggesting that the QSO is situated in an overdense region, perhaps a galaxy cluster. Previously published reports of a cluster around 3C 336 were largely misled by the presence of many foreground galaxies seen in projection near the QSO. It is possible that a reported measurement of weak shear gravitational lensing in this field may be produced by the QSO cluster itself, since there appear to be no other groups or clusters in the foreground. We find no evidence for a normal, bright QSO host galaxy, although there are several faint objects very close to the quasar and at similar redshift that might either be companions or part of a disorganized QSO host.
- ID:
- ivo://CDS.VizieR/J/ApJS/122/431
- Title:
- Star Clusters in M33
- Short Name:
- J/ApJS/122/431
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present the discovery of 60 star clusters in 20 multiband Hubble Space Telescope (HST) WFPC2 fields in M33. The fields sample a variety of environments, from outer regions to spiral arms and central regions, as well as a range of galactocentric distances. The HST spatial resolution allowed us to penetrate the crowded, spiral arm regions of M33 yielding the first unbiased, representative sample of star clusters for this galaxy. We discuss the separation of clusters from stellar sources, and from other extended sources such as star-forming regions, H II regions, and supernova remnants. For the clusters we present multiband images and discuss morphology, location, and integrated photometry. Measured cluster colors and magnitudes are presented. The cluster density in our sample as a function of galactocentric distance yields an estimate of 690 total clusters in M33.
- ID:
- ivo://CDS.VizieR/J/AJ/113/669
- Title:
- Stars in M13 core
- Short Name:
- J/AJ/113/669
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the dense core of the globular cluster Messier 13 (NGC 6205) using pre-refurbishment Planetary Camera-I images obtained with the Hubble Space Telescope. Short exposures (60s) through the F555W and F785LP filters (similar to Johnson V and I, respectively) have been used to obtain V and I photometry of 2877 stars brighter than V~20 in a 1.25arcmin^2^ region of the cluster including its core and extending out to r~66arcsec (2.3pc) from its center. The sample is complete to V~=18.3 (the main sequence turnoff) and the 1{sigma} photometric error is about 0.1mag. We find 15 blue straggler star candidates and 10 other possible blue stragglers in this region of M13. Their specific frequency is in the range F_(BSS)=0.04-0.07, comparable to what is observed near the centers of other dense clusters. A comparison between M13's observed V band stellar luminosity function and a theoretical model (Bergbusch & Vandenberg, 1992ApJS...81..163B) for the luminosity function of an old, metal-poor cluster shows that the model predicts too few of the brightest red giants (V~12.5-15) by a factor of two relative to subgiants/turnoff stars (>6{sigma} effect). The radial distributions of red giants, blue stragglers, and subgiants are consistent with one another, and are well fit by a King profile of core radius r_(core)_=38+/-6arcsec (90% confidence limits) or 1.3pc. Stars in the blue horizontal branch of M13, however, appear to be centrally depleted relative to other stellar types. We combine data from three dense ``King model clusters,'' M13, M3, and 47 Tuc, and two post core collapse clusters, M30 and M15, and compare the distributions of various stellar types as a function of (r/r_(half light)_) and (r/r_(core)_). The horizontal branch stars in the combined sample appear to be centrally depleted relative to the giants (97% significance), this depletion is only a 1-2{sigma} effect in each of the clusters taken individually. The blue stragglers in the combined sample are centrally concentrated relative to the giants. (Copyright) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/J/ApJS/146/209
- Title:
- STIS emission-line galaxies observations
- Short Name:
- J/ApJS/146/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the first 3 years of operation the Space Telescope Imaging Spectrograph (STIS) obtained slitless spectra of ~2500 fields in parallel to prime Hubble Space Telescope (HST) observations as part of the STIS parallel survey (SPS). The archive contains ~300 fields at high Galactic latitude (|b|>30{deg}) with spectroscopic exposure times greater than 3000s. This sample contains 219 fields (excluding special regions and requiring a consistent grating angle) observed between 1997 June 6 and 2000 September 21, with a total survey area of ~160-arcmin^2^. At this depth, the SPS detects an average of one emission-line galaxy per three fields. We present the analysis of these data and the identification of 131 low- to intermediate-redshift galaxies detected by optical emission lines. The sample contains 78 objects with emission lines that we infer to be redshifted [O II] {lambda}3727 emission at 0.43<z<1.7. The comoving number density of these objects is comparable to that of H{alpha}-emitting galaxies in the NICMOS parallel observations. One quasar and three probable Seyfert galaxies are detected. Many of the emission-line objects show morphologies suggestive of mergers or interactions. The reduced data are available upon request from the authors.
64. The Carina Dwarf
- ID:
- ivo://CDS.VizieR/J/AJ/114/1458
- Title:
- The Carina Dwarf
- Short Name:
- J/AJ/114/1458
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our analysis of Hubble Space Telescope Wide Field Planetary Camera 2 observations in F555W (~V) and F814W (~I) of the Carina dwarf spheroidal galaxy. The resulting V vs V-I color-magnitude diagrams reach V~27.1mag. The reddening of Carina is estimated to be E(V-I)=0.08+/-0.02 mag. A new estimate of the distance modulus of Carina, (m-M)0=19.87+/-0.11mag, has been derived primarily from existing photometry in the literature. The apparent distance moduli in V and I were determined to be (m-M)V=20.05+/-0.11mag and (m-M)I=19.98+/-0.12mag, respectively. These determinations assumed that Carina has a metallicity of [Fe/H]=-1.9+/-0.2dex. This space-based observation, when combined with previous ground-based observations, is consistent with (but does not necessarily prove) the following star formation scenario. The Carina dwarf spheroidal galaxy formed its old stellar population in a short burst (<~3Gyr) at about the same time the Milky Way formed its globular clusters. The dominant burst of intermediate-age star formation then began in the central region of the galaxy where stars formed for several billion years before the process of star formation became efficient enough in the outer regions of the galaxy to allow for the formation of large numbers of stars. There has been negligible star formation during the last few billion years. This observation provides evidence that at least some dwarf galaxies can have complex global star formation histories with local variations of the rate of star formation as a function of time and position within the galaxy. (c) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/J/AJ/116/146
- Title:
- UGC 6456 HST photometry
- Short Name:
- J/AJ/116/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry on the UVI system has been performed on the resolved stellar content of the blue compact dwarf galaxy UGC 6456 using Wide Field Planetary Camera 2 (WFPC2) images obtained with the Hubble Space Telescope. The resulting color-magnitude diagram (CMD) goes to about V=27.5 and reveals not only a young population of blue main-sequence stars and blue and red supergiants, but also an older evolved population of red giants and a fairly well represented asymptotic giant branch. The distance to the galaxy is estimated from the tip of the red giant branch to be 4.5Mpc, placing it about 1.5Mpc farther away than the major members of the M81 Group, with which it is usually associated. The youngest stars are generally associated with H ii regions shown on our Halpha image and are largely confined to the 745pc field of our PC images. A comparison of their distribution in the CMD with theoretical isochrones suggests ages from 4 to 10Myr. The population of older stars is found throughout all WFPC2 camera fields and seems to show an elliptical distribution with an aspect ratio of about 2.4 and an exponential falloff in surface density with distance from a center of symmetry that is not far from the centroid of the youngest stars. Theoretical modeling of the CMD at a metallicity of Z=0.001 suggests star formation in the age interval 1-2Gyr, a strong burst in the interval 600-800Myr, and a lower rate of star formation up to the present. The evidence is compatible with a scenario beginning with the formation of a population of low-metallicity stars, enriching a major residual of prestellar material that subsequently fueled an active episode of star formation. That burst of star formation must have been particularly spectacular and may be related to the activity we now see in the distant blue dwarf galaxies revealed in deep imaging.
- ID:
- ivo://CDS.VizieR/J/ApJS/107/215
- Title:
- UV Images of Nearby Galaxies
- Short Name:
- J/ApJS/107/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The accompanying tables are part of a pictorial atlas of UV (2300A) images, obtained with the Hubble Space Telescope (HST) Faint Object Camera, of the central 22"x22" of 110 galaxies. The observed galaxies are an unbiased selection constituting about one half of a complete sample of all large (D>6') and nearby (V< 2000 km/s) galaxies. This is the first extensive UV imaging survey of normal galaxies. The data are useful for studying star formation, low-level nuclear activity, and UV emission by evolved stellar populations in galaxies. At the HST resolution (0.05"), the images display an assortment of morphologies and UV brightnesses. These include bright nuclear point sources, compact young star clusters scattered in the field or arranged in circumnuclear rings, centrally-peaked diffuse light distributions, and galaxies with weak or undetected UV emission. We measure the integrated 2300A flux in each image, and classify the UV morphology. The UV and optical parameters are given in the tables.
- ID:
- ivo://CDS.VizieR/J/A+A/287/769
- Title:
- UV photometry of NGC 6397
- Short Name:
- J/A+A/287/769
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The core of the nearby and very concentrated globular cluster NGC 6397 has been imaged through the f/96-F140W, f/48-F140W, f/96-F210M and f/48-F220W ultraviolet filters of the Faint Object Camera on board the Hubble Space Telescope down to an ultraviolet limiting magnitude of ~19. The most interesting objects in the field of view are six very bright centrally concentrated, blue stragglers observed for the first time in the UV. Using these and other data from ground-based observations, we have been able to deduce from a comparison with Kurucz's atmosphere models, temperatures of ~10000K and masses of ~1.6M_{sun}_ for the four brightest ones, which is remarkably close to twice the turn-off mass of NGC 6397. This finding supports the idea that two-star mechanisms (collisions, mergers) are at the origin of the blue stragglers in the core of NGC 6397. Since the central density is very high, collisions between main sequence stars are frequent, therefore providing the best formation mechanism. We have computed the number of such collisions in the core of NGC 6397 and found it to be of the same order as the number of bright blue stragglers observed there. Thanks to the HST resolution, we have also been able to resolve one object, previously classified as a yellow straggler, into a blend of a blue straggler and three redder stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/529/723
- Title:
- VI photometry of Cepheids
- Short Name:
- J/ApJ/529/723
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Cepheid-based distances to seven Type Ia supernovae (SNe) host galaxies have been derived using the standard Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale pipeline. For the first time, this allows for a transparent comparison of data accumulated as part of three different HST projects: the Key Project, the Sandage et al. Type Ia supernovae (SNe) program, and the Tanvir et al. Leo I Group study. Reanalyzing the Tanvir et al. galaxy and six Sandage et al. galaxies, we find a mean (weighted) offset in true distance moduli of 0.12+/-0.07mag; i.e., 6% in linear distance, in the sense of reducing the distance scale or increasing H_0_. Adopting the reddening-corrected Hubble relations of Suntzeff et al. tied to a zero point based on SNe 1990N, 1981B, 1998bu, 1989B, 1972E, and 1960F and the photometric calibration of Hill et al. leads to a Hubble constant of H_0_=68+/-2(random)+/-5(systematic)km/s/Mpc. Adopting the Kennicutt et al. Cepheid period-luminosity-metallicity dependency decreases the inferred H_0_ by 4%. The H0 result from Type Ia SNe is now in good agreement, to within their respective uncertainties, with that from the Tully-Fisher and surface brightness fluctuation relations.
- ID:
- ivo://CDS.VizieR/J/ApJ/463/26
- Title:
- VI photometry of 29 Cepheids in M101.
- Short Name:
- J/ApJ/463/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the discovery of 29 Cepheid variables in the galaxy M101 using the original Wide Field Camera (WFC) and the new Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope. We observed a field in M101 at 17 independent epochs in V (F555W), five epochs in I (F785LP/F814W), and one epoch in B (F439W), with a time interval baseline of 381 days. We have found Cepheids with periods ranging from 10 to 60 days. The data have been calibrated using WFPC2 observations with zero points derived from Omega Cen, Pal 4, and NGC 2419 observations. This calibration has been verified by using the Medium Deep Survey (MDS) WFC photometric zero points, and ground-based secondary standards in V and I. The V calibrations agree to +/-0.06mag, and the I calibrations agree to +/-0.4mag. We have constructed V and I period-luminosity (PL) relations and have derived apparent distance moduli based on a distance modulus for the Large Magellanic Cloud (LMC) of 18.50mag and a reddening of E(B-V)=0.10mag to the LMC Cepheids. Period-residual minimization was used to minimize the effects of Malmquist bias on the period-luminosity relation fitting process. Using a Galactic extinction law and the apparent V and I distance moduli, we have found a mean reddening for the M101 sample of E(B-V)=0.03mag and a true distance modulus to M101 of 29.34+/-0.17mag, corresponding to a distance of 7.4+/-0.6Mpc. The sources of error have been rigorously tracked through an error budget; systematic and random errors contribute roughly equally to the quoted error. The mean gas-phase metal abundances in the LMC and in the M101 outer field are similar so we expect metallicity effects to be minimal. These Cepheids will be used in conjunction with results from a Key Project search for Cepheids in an inner field, where the metallicity is larger by a factor of 5, to probe the effects of abundance on the Cepheid period-luminosity relation.
- ID:
- ivo://CDS.VizieR/J/ApJ/453/48
- Title:
- VI photometry of HST faint field galaxies
- Short Name:
- J/ApJ/453/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a complete morphologically classified sample of 144 faint field galaxies from the HST Medium Deep Survey with 20.0=<Imag<22.0mag. We compare the global properties of the ellipticals and early- and late-type spirals and find a non-negligible fraction (13/144) of compact blue [(V-I)<1.0mag] systems with r^1/4^ profiles. We give the differential galaxy number counts for ellipticals and early-type spirals independently and find that the data are consistent with no-evolution predictions based on conventional flat Schechter luminosity functions (LFs) and a standard cosmology. Conversely, late-type/irregulars show a steeply rising differential number count with slope ({delta}logN/{delta}m)=0.64+/-0.1. No-evolution models based on the Loveday et al. (1992ApJ...390..338L) and Marzke et al. (1994AJ....108..437M & 1994ApJ...428...43M) local luminosity functions underpredict the late-type/irregular counts by 1.0 and 0.5dex, respectively, at Imag=21.75mag. Examination of the irregulars alone shows that ~50% appear inert and the remainder have multiple cores. If the inert galaxies represent a non-evolving late-type population, then a Loveday-like LF ({alpha}=~-1.0) is ruled out for these types, and an LF with a steep faint end ({alpha}=~-1.5) is suggested. If multiple core structure indicates recent star formation, then the observed excess of faint blue field galaxies is likely a result of et evolutionary processes acting on a steep field LF for late-type/irregulars. The evolutionary mechanism is unclear, but 60% of the multiple-core irregulars show close companions. To reconcile a Marzke-like LF with the faint redshift surveys, this evolution must be preferentially occurring in the brightest late-type galaxies with z>=0.5 at m_I_=21.75mag.
- ID:
- ivo://CDS.VizieR/J/A+A/366/498
- Title:
- VI photometry of M33 star clusters
- Short Name:
- J/A+A/366/498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have detected 102 star clusters in M 33, from 35 deep Hubble Space Telescope (HST) WFPC2 fields taken from our program and from the HST archive. Twenty-eight fields have V and I band imaging, and an additional seven fields are imaged in a single V filter. Eighty-two of the clusters were previously unknown. Integrated photometry reveals that 25 clusters have (V-I) colors typical of those found in Galactic globular clusters (only ten of these objects were previously known). Our discovery of 15 new globular cluster candidates increases previous estimates of the old cluster population in M 33 by ~60%. An additional eleven objects (only two were previously known) have colors expected for intermediate age clusters. The new clusters have a range of ages from 6 million years to >15Gyrs, and masses between 10^2^M_{sun}_-10^6^M_{sun}_, although these parameters are estimated from only one color.
- ID:
- ivo://CDS.VizieR/J/ApJ/523/540
- Title:
- VI photometry of new Cepheids in NGC 3319
- Short Name:
- J/ApJ/523/540
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distance to NGC 3319 has been determined from Cepheid variable stars as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen and four epochs of observations, using filters F555W (V) and F814W (I), respectively, were made with the Wide Field Planetary Camera 2. Thirty-three Cepheid variables between periods of 8 and 47 days were discovered. Adopting a Large Magellanic Cloud distance modulus of 18.50{+/-}0.10 mag and extinction of E(V-I)=0.13 mag, a true reddening-corrected distance modulus (based on an analysis employing the ALLFRAME software package) of 30.78 {+/-}0.14 (random) {+/-}0.10 (systematic) mag and the extinction of E(V-I)=0.06 mag were determined for NGC 3319. This galaxy is the last galaxy observed for the HST H_o_ Key Project.
- ID:
- ivo://CDS.VizieR/J/ApJ/514/614
- Title:
- VI photometry of new Cepheids in NGC 3198
- Short Name:
- J/ApJ/514/614
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of Cepheid variable stars and a new distance to the Sc spiral NGC 3198. NGC 3198 is one of 25 galaxies that have been observed with the WFPC2 of the Hubble Space Telescope (HST) for the purpose of measuring Cepheid distances. Eighteen of these galaxies were targeted by the HST Key Project on the Extragalactic Distance Scale, whose objective is to calibrate a variety of secondary distant indicators and determine the Hubble constant to an accuracy of 10%. NGC 3198 was selected as part of this sample because its type and orientation make it very suitable as a Tully-Fisher calibrator. The WFPC2 data are comprised of 13 epochs in F555W ({~}V) and five epochs in F814W ({~}I). Two different crowded-field photometry packages (DAOPHOT/ALLFRAME and DoPHOT) were used. The magnitudes derived from these two packages agree to within a few percent. We identified 78 Cepheid candidates in the period range from eight to >50 days, of which 52 were selected for establishing the distance modulus. Period-luminosity relations were constructed in Johnson V and Kron-Cousins I by transforming the F555W and F814W to the standard system. We adopted a distance modulus of {mu}_o_=18.50{+/-}0.10 mag and mean reddening of E(B-V)=0.10 mag to the Large Magellanic Cloud Cepheids and found a true distance modulus to NGC 3198 of {mu}_o_=30.80{+/-}0.16 (random) {+/-}0.12 (systematic) mag. This modulus corresponds to a distance of 14.5 Mpc, with random and systematic errors of {+/-}1.2 and {+/-}0.9 Mpc, respectively.
- ID:
- ivo://CDS.VizieR/J/ApJ/507/655
- Title:
- VI photometry of new Cepheids in NGC 2541
- Short Name:
- J/ApJ/507/655
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of Cepheids and a new distance to the spiral galaxy NGC 2541, based on data obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope (HST). A total of 25 exposures (divided into 13 epochs) were obtained using the F555W filter (transformed to Johnson V), and nine exposures were obtained (divided into five epochs) using the F814W filter (transformed to Cousins I). Photometric reduction of the data is performed using two independent packages, DoPHOT and DAOPHOT II/ALLFRAME, which give very good agreement in the measured magnitudes. A total of 34 bona fide Cepheids, with periods ranging from 12 to over 60 days, are identified based on both sets of photometry. By fitting V and I period-luminosity relations, apparent distance moduli are derived assuming a Large Magellanic Cloud distance modulus and mean color excess of {mu}_LMC_=18.50+/-0.10mag and E(B-V)=0.10mag, respectively. Adopting A(V)/E(V-I)=2.45, we obtain a true distance modulus to NGC 2541 of {mu}_0_=30.47+/-0.11 (random) +/-0.12 (systematic) mag (D=12.4+/-0.6 [random] +/-0.7 [systematic] Mpc), and a total (Galactic plus internal) mean color excess E(B-V)=0.08+/-0.05 (internal error) mag.
- ID:
- ivo://CDS.VizieR/J/ApJ/512/48
- Title:
- VI photometry of new Cepheids in NGC 4725
- Short Name:
- J/ApJ/512/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The distance to NGC 4725 has been derived from Cepheid variables as part of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale. Thirteen F555W (V) and four F814W (I) epochs of cosmic-ray-split Wide Field and Planetary Camera 2 observations were obtained. Twenty Cepheids were discovered, with periods ranging from 12 to 49 days. Adopting a Large Magellanic Cloud distance modulus and extinction of 18.50{+/-}0.10 mag and E(V-I)=0.13 mag, respectively, a true reddening-corrected distance modulus (based on an analysis employing the ALLFRAME software package) of 30.50{+/-}0.16 (random) {+/-}0.17 (systematic) mag was determined for NGC 4725. The corresponding of distance of 12.6{+/-}1.0 (random) {+/-}1.0 (systematic) Mpc is in excellent agreement with that found with an independent analysis based upon the DoPHOT photometry package. With a foreground reddening of only E(V-I)=0.02, the inferred intrinsic reddening of this field in NGC 4725, E(V-I)=0.19, makes it one of the most highly reddened fields encountered by the HST Key Project to date.
- ID:
- ivo://CDS.VizieR/J/AJ/115/592
- Title:
- VI photometry of NGC 2157
- Short Name:
- J/AJ/115/592
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out Wide Field Planetary Camera 2 V- and I-band imaging of the young LMC cluster NGC 2157. Construction of a color-magnitude diagram and isochrone fitting yield an age of {tau}=10^8^yr, a reddening E(B-V)=0.1, and a distance modulus of 18.4mag. Our data cover the mass range 0.75M_{sun}_<=m<=5.1M_{sun}_. We find that the cluster mass function changes significantly from the inner regions to the outer regions, becoming steeper (larger number of low-mass stars relative to high-mass stars) at larger radii. The age of NGC 2157 is comparable to its two-body relaxation timescale only in the cluster core. The observed steepening of the mass function at larger radii is therefore most likely an initial condition of the cluster stars. Such initial conditions are predicted in models of cluster star formation in which dissipative processes act more strongly upon more massive stars.
- ID:
- ivo://CDS.VizieR/J/AJ/119/1748
- Title:
- WFPC 2 imaging of young LMC clusters
- Short Name:
- J/AJ/119/1748
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out Wide Field Planetary Camera 2 (WFPC2) F160BW, F555W, and F656N imaging of four young populous clusters: NGC 330, in the Small Magellanic Cloud, and NGC 1818, 2004, and 2100, in the Large Magellanic Cloud. We report photometric results for these four clusters, including identification using photometric colors of the cluster Be star population. We present theoretical WFPC2 and broadband colors and bolometric corrections for LMC and SMC metallicities. The use of the far-UV F160BW filter enables accurate determination of the effective temperatures for stars in the vicinity of the main-sequence turnoff and on the unevolved main sequence.
- ID:
- ivo://CDS.VizieR/J/AJ/109/960
- Title:
- Young star clusters in The Antennae
- Short Name:
- J/AJ/109/960
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New high-resolution images of the disks of NGC 4038/4039 obtained with the Wide Field Camera of the Hubble Space Telescope (HST) are presented. NGC 4038/4039, nicknamed "The Antennae," is a prototypical example of a pair of colliding galaxies believed to be at an early stage of a merger. Down to the limiting magnitude of V~23mag, the HST images reveal a population of over 700 blue pointlike objects within the disks. The mean absolute magnitude of these objects is M_V_=-11mag, with the brightest objects reaching M_V_~-15. Their mean apparent color indices are U-V=-0.7mag and V-I=0.8mag on the Johnson UVI passband system, while their mean indices corrected for internal reddening are (U-V)_0_=-1.0mag and (V-I)_0_=0.5. Their mean effective radius, determined from slightly resolved images, is 18pc (for H0=50km/s/Mpc). Based on their luminosities and resolution, most of these objects cannot be individual stars, but are likely young compact star clusters. The brighter ones are similar to the objects found in NGC 1275 and NGC 7252, which appear to be young globular clusters formed during recent galaxy mergers. Based on their U-V and V-I colors, the brightest, bluest clusters of NGC 4038/4039 appear to be less than 10Myr old. Most of these bright clusters are relatively tightly clustered themselves, with typically a dozen individual clusters belonging to a complex identified as a giant H II region from ground-based observations. The cluster luminosity function (LF) is approximately a power law, {Phi}(L)dL is proportional to L^(-1.78+/-0.05)^dL, with no hint of a turnover at fainter magnitudes. This power-law shape agrees with the LF of Magellanic Cloud clusters and Galactic open clusters, but differs from the LF of old globular cluster systems that is typically Gaussian with a FWHM of ~3mag. Possible explanations for this apparent difference include: (1) We have not observed faint enough to see the turnover, (2) the initial LF of star clusters is a power law but the fainter objects dissolve with time, (3) conditions at the present epoch favor the formation of a wide range of cluster masses while conditions at earlier epochs favored the formation of massive clusters, and (4) the NGC 4038/4039 clusters may not evolve into normal globular clusters. Besides the blue clusters, we also find about a dozen extremely red objects with V-I>3.0. The highest number density of these red objects is found in the SE quadrant, where star formation appears to be most recent. We propose that these objects may be very young star clusters still embedded in their placental dust cocoons.