- ID:
- ivo://CDS.VizieR/J/MNRAS/449/2937
- Title:
- HST BVI catalogue of star clusters in 5 HCGs
- Short Name:
- J/MNRAS/449/2937
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric catalogue of star cluster candidates in Hickson compact groups (HCGs) 7, 31, 42, 59, and 92, based on observations with the Advanced Camera for Surveys and the Wide Field Camera 3 on the Hubble Space Telescope. The catalogue contains precise cluster positions (right ascension and declination), magnitudes, and colours in the BVI filters. The number of detected sources ranges from 2200 to 5600 per group, from which we construct the high-confidence sample by applying a number of criteria designed to reduce foreground and background contaminants. Furthermore, the high-confidence cluster candidates for each of the 16 galaxies in our sample are split into two subpopulations: one that may contain young star clusters and one that is dominated by globular older clusters. The ratio of young star cluster to globular cluster candidates varies from group to group, from equal numbers to the extreme of HCG 31 which has a ratio of 8 to 1, due to a recent starburst induced by interactions in the group. We find that the number of blue clusters with M_V_<-9 correlates well with the current star formation rate in an individual galaxy, while the number of globular cluster candidates with M_V_<-7.8 correlates well (though with large scatter) with the stellar mass. Analyses of the high-confidence sample presented in this paper show that star clusters can be successfully used to infer the gross star formation history of the host groups and therefore determine their placement in a proposed evolutionary sequence for compact galaxy groups.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/122/1330
- Title:
- HST BVI photometry of M 81 star clusters
- Short Name:
- J/AJ/122/1330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the discovery of 114 compact star clusters in the nearby spiral galaxy M81 from B-, V-, and I-band Hubble Space Telescope Wide Field Planetary Camera 2 imaging in eight fields, covering a total area of ~40arcmin^2^. The fields sample a variety of environments (both spiral and interarm regions), as well as a range of projected galactocentric distances from 2 to 12kpc. The sample is complete to V~22, deeper by ~1mag than any previous cluster survey in M81. We present details of the separation of clusters from both stellar sources and background galaxies, which has been based solely on structural parameters and morphology and not using any color cuts, as is necessary for ground-based surveys. We present magnitudes and colors of detected clusters. Surface brightness profiles are compared with single-mass King models, giving a range of core radii for the clusters in our sample between 0.2 and 7pc.
- ID:
- ivo://CDS.VizieR/J/ApJS/248/31
- Title:
- HST & Chandra obs. of elliptical galaxies
- Short Name:
- J/ApJS/248/31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate X-ray binary (XRB) luminosity function (XLF) scaling relations for Chandra-detected populations of low-mass XRBs (LMXBs) within the footprints of 24 early-type galaxies. Our sample includes Chandra and Hubble Space Telescope observed galaxies at D<~25Mpc that have estimates of the globular cluster (GC) specific frequency (S_N_) reported in the literature. As such, we are able to directly classify X-ray-detected sources as being coincident with unrelated background/foreground objects, GCs, or sources that are within the fields of the galaxy targets. We model the GC and field LMXB population XLFs for all galaxies separately and then construct global models characterizing how the LMXB XLFs vary with galaxy stellar mass and S_N_. We find that our field LMXB XLF models require a component that scales with S_N_ and has a shape consistent with that found for the GC LMXB XLF. We take this to indicate that GCs are "seeding" the galactic field LMXB population, through the ejection of GC LMXBs and/or the diffusion of the GCs in the galactic fields themselves. However, we also find that an important LMXB XLF component is required for all galaxies that scales with stellar mass, implying that a substantial population of LMXBs are formed "in situ," which dominates the LMXB population emission for galaxies with S_N_<~2. For the first time, we provide a framework quantifying how directly associated GC LMXBs, GC-seeded LMXBs, and in situ LMXBs contribute to LMXB XLFs in the broader early-type galaxy population.
- ID:
- ivo://mast.stsci/siap/hst.cosmos
- Title:
- HST Cosmic Evolution Survey
- Short Name:
- HST.COSMOS
- Date:
- 23 Jul 2020 19:35:16
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- COSMOS (P.I. Nicholas Scoville, California Institute of Technology, USA/CA) is an HST Treasury Program to survey a 2 square degree equatorial field, centered on RA=10:00:28.6 and DEC=+02:12:21.0 with the ACS in the I band of the VIMOS equatorial field. Parallel observations with WFPC2 and NICMOS were also obtained.
- ID:
- ivo://CDS.VizieR/J/ApJS/240/15
- Title:
- HST/COS UV obs. of low-z SDSS galaxy groups
- Short Name:
- J/ApJS/240/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A small survey of the UV-absorbing gas in 12 low-z galaxy groups has been conducted using the Cosmic Origins Spectrograph on board the Hubble Space Telescope. Targets were selected from a large, homogeneously selected sample of groups found in the Sloan Digital Sky Survey. A critical selection criterion excluded sight lines that pass close (<1.5 virial radii) to a group galaxy, to ensure absorber association with the group as a whole. Deeper galaxy redshift observations are used both to search for closer galaxies and also to characterize these 10^13.5^-10^14.5^M_{sun}_ groups, the most massive of which are highly virialized with numerous early-type galaxies (ETGs). This sample also includes two spiral-rich groups, not yet fully virialized. At group-centric impact parameters of 0.3-2Mpc, these signal-to-noise ratios = 15-30 spectra detected HI absorption in 7 of 12 groups; high (OVI) and low (SiIII) ion metal lines are present in two-thirds of the absorption components. None of the three most highly virialized, ETG-dominated groups are detected in absorption. Covering fractions >~50% are seen at all impact parameters probed, but do not require large filling factors despite an enormous extent. Unlike halo clouds in individual galaxies, group absorbers have radial velocities that are too low to escape the group potential well without doubt. This suggests that these groups are "closed boxes" for galactic evolution in the current epoch. Evidence is presented that the cool and warm group absorbers are not a pervasive intra-group medium (IGrM), requiring a hotter (T~10^6^-10^7^K) IGrM to be present to close the baryon accounting.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/75
- Title:
- HST-COS UV spectra observations of AGNs
- Short Name:
- J/ApJ/794/75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ionizing fluxes from quasars and other active galactic nuclei (AGNs) are critical for interpreting their emission-line spectra and for photoionizing and heating the intergalactic medium. Using far-ultraviolet (FUV) spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), we directly measure the rest-frame ionizing continua and emission lines for 159 AGNs at redshifts 0.001<z_AGN_<1.476 and construct a composite spectrum from 475 to 1875 {AA}. We identify the underlying AGN continuum and strong extreme ultraviolet (EUV) emission lines from ions of oxygen, neon, and nitrogen after masking out absorption lines from the H I Ly{alpha} forest, 7 Lyman-limit systems (N_HI_>=10^17.2^/cm2) and 214 partial Lyman-limit systems (14.5<logN_HI_<17.2). The 159 AGNs exhibit a wide range of FUV/EUV spectral shapes, F_v_{propto}{nu}^{alpha}_{nu}_^, typically with -2<={alpha}_{nu}_<=0 and no discernible continuum edges at 912 {AA} (H I) or 504 {AA} (He I). The composite rest-frame continuum shows a gradual break at {lambda}_br_{approx} 1000 {AA}, with mean spectral index {alpha}_{nu}_=-0.83+/-0.09 in the FUV (1200-2000 {AA}) steepening to {alpha}_{nu}_=-1.41+/-0.15 in the EUV (500-1000 {AA}). We discuss the implications of the UV flux turnovers and lack of continuum edges for the structure of accretion disks, AGN mass inflow rates, and luminosities relative to Eddington values.
- ID:
- ivo://CDS.VizieR/J/AJ/159/119
- Title:
- HST emission line survey of Andromeda. I. Be stars
- Short Name:
- J/AJ/159/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a two epoch Hubble Space Telescope H{alpha} emission line survey of the Andromeda galaxy that overlaps the footprint of the Panchromatic Hubble Andromeda Treasury (PHAT) survey. We found 552 (542) classical Be stars and 8429 (8556) normal B-type stars in epoch 1 (epoch 2), yielding an overall fractional Be content of 6.15%{+/-}0.26% (5.96%{+/-}0.25%). The fractional Be content decreased with spectral subtype from ~23.6%{+/-}2.0% (~23.9%{+/-}2.0%) for B0-type stars to ~3.1%{+/-}0.34% (~3.4%{+/-}0.35%) for B8-type stars in epoch 1 (epoch 2). We observed a clear population of cluster Be stars at early fractional main-sequence lifetimes, indicating that a subset of Be stars emerge onto the zero-age main sequence as rapid rotators. Be stars are 2.8x rarer in M31 for the earliest subtypes compared to the Small Magellanic Cloud, confirming that the fractional Be content decreases in significantly more metal-rich environments (like the Milky Way and M31). However, M31 does not follow a clear trend of Be fraction decreasing with metallicity compared to the Milky Way, which may reflect that the Be phenomenon is enhanced with evolutionary age. The rate of disk-loss or disk-regeneration episodes we observed, 22%{+/-}2%/yr, is similar to that observed for seven other Galactic clusters reported in the literature, assuming these latter transient fractions scale by a linear rate. The similar number of disk-loss events (57) as disk-renewal events (43) was unexpected since disk dissipation timescales can be ~2x the typical timescales for disk build-up phases.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/152
- Title:
- HST FGS-1r parallaxes for 8 metal-poor stars
- Short Name:
- J/ApJ/835/152
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hubble Space Telescope (HST) fine guidance sensor observations were used to obtain parallaxes of eight metal-poor ([Fe/H]< -1.4) stars. The parallaxes of these stars determined by the new Hipparcos reduction average 17% accuracy, in contrast to our new HST parallaxes, which average 1% accuracy and have errors on the individual parallaxes ranging from 85 to 144{mu}as. These parallax data were combined with HST Advanced Camera for Surveys photometry in the F606W and F814W filters to obtain the absolute magnitudes of the stars with an accuracy of 0.02-0.03 mag. Six of these stars are on the main sequence (MS) (with -2.7<[Fe/H]< -1.8) and are suitable for testing metal-poor stellar evolution models and determining the distances to metal-poor globular clusters (GCs). Using the abundances obtained by O'Malley+ (2017ApJ...838...90O), we find that standard stellar models using the VandenBerg & Clem (2003AJ....126..778V) color transformation do a reasonable job of matching five of the MS stars, with HD 54639 ([Fe/H]=-2.5) being anomalous in its location in the color-magnitude diagram. Stellar models and isochrones were generated using a Monte Carlo analysis to take into account uncertainties in the models. Isochrones that fit the parallax stars were used to determine the distances and ages of nine GCs (with -2.4{<=}[Fe/H]{<=}-1.9). Averaging together the age of all nine clusters led to an absolute age of the oldest, most metal-poor GCs of 12.7+/-1.0Gyr, where the quoted uncertainty takes into account the known uncertainties in the stellar models and isochrones, along with the uncertainty in the distance and reddening of the clusters.
1639. HST Hubble Deep Field
- ID:
- ivo://mast.stsci/siap/hst.hdf
- Title:
- HST Hubble Deep Field
- Short Name:
- HST.HDF
- Date:
- 23 Jul 2020 19:35:54
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- The Hubble Deep Field (HDF) is a Director's Discretionary program on HST in Cycle 5 to image a typical field at high galactic latitude in four wavelength passbands as deeply as reasonably possible. In order to optimize observing in the time available, a field in the northern continuous viewing zone (CVZ) was selected and images were taken for 10 consecutive days, or approximately 150 orbits. Shorter 1-orbit images were also obtained of the fields immediately adjacent to the primary HDF in order to facilitate spectroscopic follow-up by ground-based telescopes. The observations were carried out from 18-30 December 1995, and the data are available to the community for study.
- ID:
- ivo://mast.stsci/siap/hst.hdf_south
- Title:
- HST Hubble Deep Field South
- Short Name:
- HST.HDF_SOUTH
- Date:
- 23 Jul 2020 19:36:18
- Publisher:
- Space Telescope Science Institute Archive
- Description:
- A second Hubble Deep Field campaign was carried out between late September and October of 1998. The raw, pipeline calibrated and reprocessed data were released to the community on November 23, 1998. The rationale for undertaking a second deep field campaign followed from the wealth of information that has come out of HDF-N, and from the desire to provide a point of focus for similar studies of the distant universe from southern-hemisphere facilities. Simultaneous, parallel observations were made with the three HST instruments STIS, WFPC2 and NICMOS of separate, neighboring fields. As was the case for HDF-N, approximately 150 consecutive orbits were devoted to a single telescope pointing.