- 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.
Number of results to display per page
Search Results
- 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://CDS.VizieR/J/MNRAS/459/1626
- Title:
- HST Frontier Fields Herschel sources
- Short Name:
- J/MNRAS/459/1626
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a complete census of all Herschel-detected sources within the six massive lensing clusters of the HST Frontier Fields (HFF). We provide a robust legacy catalogue of 263 sources with Herschel fluxes, primarily based on imaging from the Herschel Lensing Survey and PEP/HerMES Key Programmes. We optimally combine Herschel, Spitzer and WISE infrared (IR) photometry with data from HST, VLA and ground-based observatories, identifying counterparts to gain source redshifts. For each Herschel-detected source we also present magnification factor ({mu}), intrinsic IR luminosity and characteristic dust temperature, providing a comprehensive view of dust-obscured star formation within the HFF. We demonstrate the utility of our catalogues through an exploratory overview of the magnified population, including more than 20 background sub-LIRGs unreachable by Herschel without the assistance gravitational lensing.
- ID:
- ivo://CDS.VizieR/J/ApJ/840/30
- Title:
- HST/Gemini proper motions for Pyxis
- Short Name:
- J/ApJ/840/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a proper motion measurement for the halo globular cluster Pyxis, using Hubble Space Telescope/ACS data as the first epoch and GeMS/GSAOI Adaptive Optics data as the second, separated by a baseline of ~5 years. This is both the first measurement of the proper motion of Pyxis and the first calibration and use of Multi-Conjugate Adaptive Optics data to measure an absolute proper motion for a faint, distant halo object. Consequently, we present our analysis of the Adaptive Optics data in detail. We obtain a proper motion of {mu}_{alpha}_cos({delta})=1.09+/-0.31mas/yr and {mu}_{delta}_=0.68+/-0.29mas/yr. From the proper motion and line-of-sight velocity, we find that the orbit of Pyxis is rather eccentric, with its apocenter at more than 100kpc and its pericenter at about 30kpc. We also investigate two literature-proposed associations for Pyxis with the recently discovered ATLAS stream and the Magellanic system. Combining our measurements with dynamical modeling and cosmological numerical simulations, we find it unlikely Pyxis is associated with either system. We examine other Milky Way satellites for possible association using the orbit, eccentricity, metallicity, and age as constraints and find no likely matches in satellites down to the mass of Leo II. We propose that Pyxis probably originated in an unknown galaxy, which today is fully disrupted. Assuming that Pyxis is bound and not on a first approach, we derive a 68% lower limit on the mass of the Milky Way of 0.95x10^12^M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/ApJ/586/765
- Title:
- HST K-selected extremely red galaxies
- Short Name:
- J/ApJ/586/765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We selected 115 extremely red objects (EROs) from deep Hubble Space Telescope (HST) WFPC2 archive data combined with ground-based K-band images, with (F814W-Ks)>=4, K-band signal-to-noise ratio >=5, and a median limiting Ks magnitude of ~18.7, over a corresponding area of 228 arcmin2, for a morphological study of the ERO galaxy population. The survey covered a total of ~409-arcmin^2^ over 77 separate WFPC2 fields. This is the first complete sample of bright EROs with high-resolution HST morphologies.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/712
- Title:
- HST light curves of six SNe and Union2
- Short Name:
- J/ApJ/716/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise Hubble Space Telescope data, and spectra of six SNe Ia that were discovered during 2001, are presented. Additionally, for the two SNe with z>1, we present ground-based J-band photometry from Gemini and the Very Large Telescope. These are among the most distant SNe Ia for which ground-based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation. We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 SNe, the Union2 compilation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/330/1
- Title:
- HST observations of Extremely Red Objects
- Short Name:
- J/MNRAS/330/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey for extremely red objects (EROs) undertaken in the fields of 10 massive galaxy cluster lenses at z~0.2, combining sensitive, high-resolution Hubble Space Telescope imaging with deep, half-arcsecond K-band imaging from UKIRT. We detect 60 EROs with (R-K)>=5.3, of which 26 have (R-K)>=6.0 in a total image-plane survey area of 49arcmin2 down to K=20.6, including one multiply imaged ERO.
- 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/886/99
- Title:
- HST obs. in the region of 3 young LMC SNIa remnants
- Short Name:
- J/ApJ/886/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used two methods to search for surviving companions of Type Ia supernova progenitors in three Balmer-dominated supernova remnants in the Large Magellanic Cloud: 0519-69.0, 0505-67.9 (DEM L71), and 0548-70.4. In the first method, we use the Hubble Space Telescope photometric measurements of stars to construct color-magnitude diagrams (CMDs) and compare positions of stars in the CMDs with those expected from theoretical post-impact evolution of surviving main-sequence or helium star companions. No obvious candidates of surviving companions are identified in this photometric search. Future models for surviving red giant companions or with different explosion mechanisms are needed for thorough comparisons with these observations in order to make more definitive conclusions. In the second method, we use Multi Unit Spectroscopic Explorer observations of 0519-69.0 and DEM L71 to carry out spectroscopic analyses of stars in order to use large peculiar radial velocities as diagnostics of surviving companions. We find a star in 0519-69.0 and a star in DEM L71 moving at radial velocities of 182+/-0km/s and 213+/-0km/s, respectively, more than 2.5{sigma} from the mean radial velocity of the underlying stellar population, 264 and 270km/s, respectively. These stars need higher-quality spectra to investigate their abundances and rotation velocities to determine whether they are indeed surviving companions of the supernova progenitors.
- ID:
- ivo://CDS.VizieR/J/ApJ/857/67
- Title:
- HST obs. of Mira candidates in NGC 4258
- Short Name:
- J/ApJ/857/67
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present year-long, near-infrared (NIR) Hubble Space Telescope (HST) WFC3 observations of Mira variables in the water megamaser host galaxy NGC 4258. Miras are asymptotic giant branch variables that can be divided into oxygen- (O-) and carbon- (C-) rich subclasses. Oxygen-rich Miras follow a tight (scatter ~0.14mag) period-luminosity relation (PLR) in the NIR and can be used to measure extragalactic distances. The water megamaser in NGC 4258 gives a geometric distance to the galaxy accurate to 2.6% that can serve to calibrate the Mira PLR. We develop criteria for detecting and classifying O-rich Miras with optical and NIR data as well as NIR data alone. In total, we discover 438 Mira candidates that we classify with high confidence as O-rich. Our most stringent criteria produce a sample of 139 Mira candidates that we use to measure a PLR. We use the OGLE-III sample of O-rich Miras in the Large Magellanic Cloud to obtain a relative distance modulus, {mu}_4258_-{mu}_LMC_=10.95+/-0.01 (statistical) +/-0.06 (systematic) mag, that is statistically consistent with the relative distance determined using Cepheids. These results demonstrate the feasibility of discovering and characterizing Miras using the NIR with the HST and the upcoming James Webb Space Telescope and using those Miras to measure extragalactic distances and determine the Hubble constant.
