- 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.
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Search Results
- 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/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/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/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/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.
