- 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.
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- 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/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/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/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.
