- ID:
- ivo://CDS.VizieR/J/AJ/143/52
- Title:
- Old star clusters in NGC 4449 from HST imaging
- Short Name:
- J/AJ/143/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Hubble Space Telescope imaging to show that the nearby dwarf starburst galaxy NGC 4449 (=UGC 7592) has an unusual abundance of luminous red star clusters. Joint constraints from integrated photometry, low-resolution spectroscopy, dynamical mass-to-light ratios, and resolved color-magnitude diagrams provide evidence that some of these clusters are old globular clusters (GCs). Spectroscopic data for two massive clusters suggest intermediate metallicities ([Fe/H]~-1) and subsolar Mg enhancement ([Mg/Fe]~-0.1 to -0.2). One of these clusters may be the nucleus of a tidally disrupting dwarf galaxy; the other is very massive (~3*10^6^M_{sun}_). We have also identified a population of remote halo GCs. NGC 4449 is consistent with an emerging picture of the ubiquity of stellar halos among dwarf galaxies, and study of its GCs may help distinguish between accretion and in situ scenarios for such halos.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/409/1281
- Title:
- Old star clusters in the FSR catalogue
- Short Name:
- J/MNRAS/409/1281
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the old star clusters in the sample of cluster candidates from the Froebrich, Scholz & Raftery (FSR, 2007, Cat. J/MNRAS/374/399) list. Based on photometry from the Two-Micron All-Sky Survey, we generated decontaminated colour-magnitude and colour-colour diagrams to select a sample of 269 old stellar clusters. This sample contains 63 known globular clusters, 174 known open clusters and 32 so far unclassified objects. Isochrone fitting has been used to homogeneously calculate the age, distance and reddening to all clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/389/1924
- Title:
- Old stellar systems (globulars to ellipticals)
- Short Name:
- J/MNRAS/389/1924
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Elliptical galaxies and globular clusters (GCs) have traditionally been regarded as physically distinct entities due to their discontinuous distribution in key scaling diagrams involving size, luminosity and velocity dispersion. Recently this distinctness has been challenged by the discovery of stellar systems with mass intermediate between those of GCs and dwarf ellipticals (such as ultracompact dwarfs and dwarf galaxy transition objects). Here we examine the relationship between the virial and stellar mass for a range of old stellar systems, from GCs to giant ellipticals, and including such intermediate-mass objects (IMOs). Improvements on previous work in this area include the use of (i) near-infrared magnitudes from the Two Micron All Sky Survey (2MASS), (ii) aperture corrections to velocity dispersions, (iii) homogeneous half-light radii and (iv) accounting for the effects of non-homology in galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A76
- Title:
- Omega Cen candidates RAVE-selected
- Short Name:
- J/A+A/583/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using six-dimensional phase-space information from the Fourth Data release of the RAdial Velocity Experiment (RAVE) over the range of Galactic longitude 240{deg}<l<360{deg} and VLSR<-239km/s, we computed orbits for 329 RAVE stars that were originally selected as chemically and kinematically related to Omega Centauri. The orbits were integrated in a Milky-Way-like axisymmetric Galactic potential, ignoring the effects of the dynamical evolution of Omega Centauri due to the tidal effects of the Galaxy disk on the cluster along time. We also ignored secular changes in the Milky Way potential over time. In a Monte Carlo scheme, and under the assumption that the stars may have been ejected with velocities greater than the escape velocity (V_rel_>V_esc,0_) from the cluster, we identified 15 stars as having close encounters with Omega Centauri: (i) 8 stars with relative velocities V_rel_<200km/s may have been ejected ~200Myr ago from Centauri; (ii) another group of 7 stars were identified with high relative velocity V_rel_>200km/s during close encounters, and it seems unlikely that they were ejected from Omega Centauri. We also confirm the link between J131340.4-484714 as a potential member of Omega Centauri, and probably ejected ~2.0Myr ago, with a relative velocity V_rel_~80km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/604/A120
- Title:
- omega Cen RR Lyrae and SX Phoenicis stars
- Short Name:
- J/A+A/604/A120
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The globular cluster {omega} Centauri (NGC 5139) hosts hundreds of pulsating variable stars of different types, thus representing a treasure trove for studies of their corresponding period-luminosity (PL) relations. Our goal in this study is to obtain the PL relations for RR Lyrae and SX Phoenicis stars in the field of the cluster, based on high-quality, well-sampled light curves in the near-infrared (IR). Observations were carried out using the VISTA InfraRed CAMera (VIRCAM) mounted on the Visible and Infrared Survey Telescope for Astronomy (VISTA). A total of 42 epochs in J and 100 epochs in K_S_ were obtained, spanning 352 days. Point-spread function photometry was performed using DoPhot and DAOPHOT crowded-field photometry packages in the outer and inner regions of the cluster, respectively. Based on the comprehensive catalog of near-IR light curves thus secured, PL relations were obtained for the different types of pulsators in the cluster, both in the J and K_S_ bands. This includes the first PL relations in the near-IR for fundamental-mode SX Phoenicis stars. The near-IR magnitudes and periods of Type II Cepheids and RR Lyrae stars were used to derive an updated true distance modulus to the cluster, with a resulting value of (m-M)_0_=13.708+/-0.035+/-0.10mag, where the error bars correspond to the adopted statistical and systematic errors, respectively. Adding the errors in quadrature, this is equivalent to a heliocentric distance of 5.52+/-0.27kpc.
- ID:
- ivo://CDS.VizieR/J/A+A/644/A95
- Title:
- omega Cen RR Lyrae and Type II Cepheids
- Short Name:
- J/A+A/644/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The separation between RR Lyrae (RRLs) and type II Cepheid (T2Cs) variables based on their period is debated. Both types of variable stars are distance indicators, and we aim to promote the use of T2Cs as distance indicators in synergy with RRLs. We adopted new and existing optical and Near-Infrared (NIR) photometry of omega Cen to investigate several diagnostics (colour-magnitude diagram, Bailey diagram, Fourier decomposition of the light curve, amplitude ratios) for the empirical separation between Type II Cepheids (T2Cs) and RR Lyrae (RRLs). We also derived NIR period-luminosity relations and found a distance modulus of 13.65+/-0.07 (err.)+/-0.01 (sigma) mag, in agreement with the recent literature. We also found that RRLs and T2Cs obey the same PL relations in the NIR.
- ID:
- ivo://CDS.VizieR/J/AJ/135/1395
- Title:
- omega Cen Spitzer photometry
- Short Name:
- J/AJ/135/1395
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Spitzer Space Telescope imaging survey of the most massive Galactic globular cluster, {omega} Centauri, and investigate stellar mass loss at low metallicity and the intracluster medium (ICM). The survey covers approximately 3.2x the cluster half-mass radius at 3.6, 4.5, 5.8, 8, and 24um, resulting in a catalog of over 40000 point sources in the cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/722/1373
- Title:
- {omega} Centauri giants abundances
- Short Name:
- J/ApJ/722/1373
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present elemental abundances for 855 red giant branch (RGB) stars in the globular cluster Omega Centauri ({omega} Cen) from spectra obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. The sample includes nearly all RGB stars brighter than V=13.5 and spans {omega} Cen's full metallicity range. The heavy {alpha} elements (Si, Ca, and Ti) are generally enhanced by +/-0.3 dex and exhibit a metallicity-dependent morphology that may be attributed to mass and metallicity-dependent Type II supernova (SN) yields. The heavy {alpha} and Fe-peak abundances suggest minimal contributions from Type Ia SNe. The light elements (O, Na, and Al) exhibit >0.5 dex abundance dispersions at all metallicities, and a majority of stars with [Fe/H]>-1.6 have [O/Fe], [Na/Fe], and [Al/Fe] abundances similar to those in monometallic globular clusters, as well as O-Na, O-Al anticorrelations and the Na-Al correlation in all but the most metal-rich stars. A combination of pollution from intermediate-mass asymptotic giant branch stars and in situ mixing may explain the light element abundance patterns. A large fraction (27%) of {omega} Cen stars are O-poor ([O/Fe]<0) and are preferentially located within 5'-10' of the cluster center. The O-poor giants are spatially similar, located in the same metallicity range, and are present in nearly equal proportions to blue main-sequence stars. This suggests that the O-poor giants and blue main-sequence stars may share a common origin. [La/Fe] increases sharply at [Fe/H]>~-1.6, and the [La/Eu] ratios indicate that the increase is due to almost pure s-process production.
- ID:
- ivo://CDS.VizieR/J/A+A/400/521
- Title:
- Omega Cen XMM observations
- Short Name:
- J/A+A/400/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed the globular cluster Omega Cen (NGC 5139) with XMM-Newton on August 13th, 2001. The observation lasted 37ks and was performed with a medium filter. These tables list all the detected sources, and the spectral properties of selected sources within the field of view. For each source, we indicate its position, count rate, correlation with previous X-ray observation, and associated errors. For selected sources we also indicate its flux.
- ID:
- ivo://CDS.VizieR/J/A+A/335/510
- Title:
- Optical spectra of 7 hot UV bright stars in GC
- Short Name:
- J/A+A/335/510
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained medium-resolution spectra of seven UV-bright stars discovered on images of four southern globular clusters obtained with the Ultraviolet Imaging Telescope (UIT). Effective temperatures, surface gravities and helium abundances are derived from LTE and non-LTE model atmosphere fits. Three of the stars have sdO spectra, including M4-Y453 (T_eff_=58800K, logg=5.15), NGC 6723-III60 (T_eff_=40600K, logg=4.46) and NGC 6752-B2004 (T_eff_=37000K, logg=5.25). All seven stars lie along either post-extended horizontal branch (EHB) or post-early AGB evolutionary tracks. The post-early AGB stars show solar helium abundances, while the post-EHB stars are helium deficient, similar to their EHB progenitors. Based on observations collected at the European Southern Observatory (ESO No 57.E-0101)
