- ID:
- ivo://CDS.VizieR/J/ApJ/844/164
- Title:
- HST astro-photometric analysis of NGC5139. III.
- Short Name:
- J/ApJ/844/164
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We take advantage of the exquisite quality of the Hubble Space Telescope 26-filter astro-photometric catalog of the core of {omega}Cen presented in the first paper of this series and the empirical differential-reddening correction presented in the second paper in order to distill the main sequence into its constituent populations. To this end, we restrict ourselves to the five most useful filters: the magic "trio" of F275W, F336W, and F438W, along with F606W and F814W. We develop a strategy for identifying color systems where different populations stand out most distinctly, then we isolate those populations and examine them in other filters where their subpopulations also come to light. In this way, we have identified at least 15 subpopulations, each of which has a distinctive fiducial curve through our five-dimensional photometric space. We confirm the MSa to be split into two subcomponents, and find that both the bMS and the rMS are split into three subcomponents. Moreover, we have discovered two additional MS groups: the MSd (which has three subcomponents) shares similar properties with the bMS, and the MSe (which has four subcomponents) has properties more similar to those of the rMS. We examine the fiducial curves together and use synthetic spectra to infer relative heavy-element, light-element, and helium abundances for the populations. Our findings show that the stellar populations and star formation history of {omega} Cen are even more complex than inferred previously. Finally, we provide as a supplement to the original catalog a list that identifies for each star which population it is most likely associated with.
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/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/ApJ/707/1347
- Title:
- HST F160W photometry in RMC 136
- Short Name:
- J/ApJ/707/1347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep Hubble Space Telescope NICMOS 2 F160W band observations of the central 56"x57" (14pcx14.25pc) region around R136 in the starburst cluster 30 Dor (NGC 2070) located in the Large Magellanic Cloud. Our aim is to derive the stellar initial mass function (IMF) down to ~1M_{sun}_ in order to test whether the IMF in a massive metal-poor cluster is similar to that observed in nearby young clusters and the field in our Galaxy. We estimate the mean age of the cluster to be 3Myr by combining our F160W photometry with previously obtained HST WFPC2 optical F555W and F814W band photometry and comparing the stellar locus in the color-magnitude diagram with main sequence and pre-main sequence isochrones. The color-magnitude diagrams show the presence of differential extinction and possibly an age spread of a few megayear. We convert the magnitudes into masses adopting both a single mean age of 3Myr isochrone and a constant star formation history from 2 to 4Myr. We derive the IMF after correcting for incompleteness due to crowding. The faintest stars detected have a mass of 0.5M_{sun}_ and the data are more than 50% complete outside a radius of 5pc down to a mass limit of 1.1M_{sun}_ for 3Myr old objects.
- 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/853/86
- Title:
- HST large programme on {omega} Centauri. II.
- Short Name:
- J/ApJ/853/86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this second installment of the series, we look at the internal kinematics of the multiple stellar populations of the globular cluster {omega} Centauri in one of the parallel Hubble Space Telescope (HST) fields, located at about 3.5 half-light radii from the center of the cluster. Thanks to the over 15yr long baseline and the exquisite astrometric precision of the HST cameras, well-measured stars in our proper-motion catalog have errors as low as ~10{mu}as/yr, and the catalog itself extends to near the hydrogen-burning limit of the cluster. We show that second-generation (2G) stars are significantly more radially anisotropic than first-generation (1G) stars. The latter are instead consistent with an isotropic velocity distribution. In addition, 1G stars have excess systemic rotation in the plane of the sky with respect to 2G stars. We show that the six populations below the main-sequence (MS) knee identified in our first paper are associated with the five main population groups recently isolated on the upper MS in the core of cluster. Furthermore, we find both 1G and 2G stars in the field to be far from being in energy equipartition, with {eta}_1G_=-0.007+/-0.026 for the former and {eta}_2G_=0.074+/-0.029 for the latter, where {eta} is defined so that the velocity dispersion {sigma}_{mu}_ scales with stellar mass as {sigma}_{mu}_{propto}m^-{eta}^. The kinematical differences reported here can help constrain the formation mechanisms for the multiple stellar populations in {omega} Centauri and other globular clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/106/154
- Title:
- HST Observations in inner region of M15
- Short Name:
- J/AJ/106/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A set of high resolution images of the core of the Galactic Globular Cluster M15 (NGC 7078) were obtained for the first time with the Faint Object Camera on Hubble Space Telescope through the f/48-F140W, f/48-F220W and f/96-F342W ultraviolet filters. Two UV-Color-Magnitude Diagrams are presented for the ~3000 objects measured in the 22"x22" field centered on the core covered by our observations. Out of these, 19 are variables discovered from the rms frame-to-frame scatter of the F220W images, 14 of which are probably RR Lyrae. The existence of the gap on the Horizontal Branch (HB) separating the bulk of the HB stars from the Blue Tail already known for the outer parts of the cluster, is confirmed for the core regions. The temperature and the mass distribution of the HB stars is derived from the ultraviolet color-color diagram. We also detect a well developed Blue Straggler sequence. At least two of the brighter blue stragglers reside within the sharp core.
- 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/ApJS/85/293
- Title:
- HST Observations of core of 47 Tuc
- Short Name:
- J/ApJS/85/293
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/ApJ/746/88
- Title:
- HST observations of GCs in NGC 1399
- Short Name:
- J/ApJ/746/88
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We combine new Wide Field Camera 3 IR Channel (WFC3/IR) F160W (H_160_) imaging data for NGC 1399, the central galaxy in the Fornax cluster, with archival F475W (g_475_), F606W (V_606_), F814W (I_814_), and F850LP (z _850_) optical data from the Advanced Camera for Surveys (ACS). The purely optical g_475_-I_814_, V_606_-I_814_, and g_475_-z_850_colors of NGC 1399's rich globular cluster (GC) system exhibit clear bimodality, at least for magnitudes I_814_>21.5. The optical-IR I_814_-H_160_ color distribution appears unimodal, and this impression is confirmed by mixture modeling analysis. The V_606_-H_160_ colors show marginal evidence for bimodality, consistent with bimodality in V_606_-I_814_ and unimodality in I_814_-H_160_.
