- ID:
- ivo://CDS.VizieR/J/AJ/135/1858
- Title:
- Old globular clusters in dwarf irregular galaxies
- Short Name:
- J/AJ/135/1858
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a search for old globular clusters (GCs) using archival F606W and F814W Hubble Space Telescope/Advanced Camera for Surveys images of 19 Magellanic-type dwarf Irregular (dIrr) galaxies. Those dIrrs reside in nearby (2-8Mpc) associations of dwarf galaxies only. All dIrrs have absolute magnitudes fainter than or equal to that of the SMC (M_V_=-16.2mag). We detect in total 50 GC candidates in 13 dIrrs, of which 37 have (V-I) colors consistent with "blue" (old, metal-poor) GCs (bGCs). The luminosity function (LF) of the bGC candidates in our sample shows a turnover magnitude of M_V_=-7.41+/-0.22mag, consistent with other galaxy types.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/634/861
- Title:
- Old passively evolving galaxies at z=1
- Short Name:
- J/ApJ/634/861
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We obtained the number counts and the rest-frame B-band luminosity function of color-selected old passively evolving galaxies (OPEGs) at z=1 with very high statistical accuracy using a large and homogeneous sample of about 4000 such objects with z'<25 detected in an area of 1.03deg^2^ in the Subaru/XMM-Newton Deep Survey (SXDS) field. Our selection criteria are defined on the i'-z' and R-z' color-magnitude plane so that OPEGs at z=0.9-1.1 with formation redshift z_f_=2-10 are properly sampled with minimum contamination by other populations. The limiting magnitude corresponds to the luminosity of galaxies with M*+3 at z=0 (where M* is the characteristic absolute magnitude of the Schechter galaxy luminosity function). We made pilot redshift observations for 99 OPEG candidates with 19<z'<22 and found that at least 78% (73 of 93) of the entire sample, or 95% (73 of 77) of those whose redshifts were obtained, indeed lie between z=0.87 and 1.12, and most of their spectra show a continuum break and strong Ca H and K lines, indicating that these objects are indeed dominated by the old stellar populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/805/160
- Title:
- Old star clusters in M101 from HST
- Short Name:
- J/ApJ/805/160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new photometric catalog of 326 candidate globular clusters (GCs) in the nearby spiral galaxy M101, selected from B, V, and I Hubble Space Telescope Advanced Camera for Surveys images. The luminosity function (LF) of these clusters has an unusually large number of faint sources compared with GCLFs in many other spiral galaxies. Accordingly, we separate and compare the properties of "bright" (M_v_<-6.5) versus "faint" (M_v_>-6.5; one magnitude fainter than the expected GC peak) clusters within our sample. The LF of the bright clusters is well fit by a peaked distribution similar to those observed in the Milky Way (MW) and other galaxies. These bright clusters also have similar size (r_eff_) and spatial distributions as MW GCs. The LF of the faint clusters, on the other hand, is well described by a power law, dN(L_v_)/dL_v_{propto}L_v_^{alpha}^ with {alpha}=2.6+/-0.3, similar to those observed for young and intermediate-age cluster systems in star forming galaxies. We find that the faint clusters have larger typical r_eff_ than the bright clusters, and have a flatter surface density profile, being more evenly distributed, as we would expect for clusters associated with the disk. We use the shape of the LF and predictions for mass-loss driven by two-body relaxation to constrain the ages of the faint clusters. Our results are consistent with two populations of old star clusters in M101: a bright population of halo clusters and a fainter, possibly younger, population of old disk clusters.
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJS/116/1
- Title:
- Old Stellar Populations. VI. Absorption-Line
- Short Name:
- J/ApJS/116/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present absorption-line strengths on the Lick/IDS line-strength system of 381 galaxies and 38 globular clusters in the 4000--6400 angstrom region. All galaxies were observed at Lick Observatory between 1972 and 1984 with the Cassegrain Image Dissector Scanner spectrograph, making this study one of the largest homogeneous collections of galaxy spectral line data to date. We also present a catalogue of nuclear velocity dispersions used to correct the absorption-line strengths onto the stellar Lick/IDS system. Extensive discussion of both random and systematic errors of the Lick/IDS system is provided. Indices are seen to fall into three families: alpha-element-like indices (including CN, Mg, Na D, and TiO2) that correlate positively with velocity dispersion; Fe-like indices (including Ca, the G band, TiO1, and all Fe indices) that correlate only weakly with velocity dispersion and the alpha indices; and Hbeta which anti-correlates with both velocity dispersion and the alpha indices. C2 4668 seems to be intermediate between the alpha and Fe groups. These groupings probably represent different element abundance families with different nucleosynthesis histories.
- 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/581/A41
- Title:
- OmegaWINGS BV photometry of galaxy clusters
- Short Name:
- J/A+A/581/A41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The WIde-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field and multiwavelength survey of 76 galaxy clusters in the local Universe. The sample consists of all clusters at 0.04<z<0.07 in both hemispheres at Galactic latitude |b|>20 selected from the ROSAT X-ray-Brightest Abell-type Cluster Sample, the Brightest Cluster Sample, and its extension. The original WINGS survey is based on B and V imaging for the 76 clusters over a 34 by 34 arcminute field of view taken with the Wide Field Cameras on the INT and the 2.2m MPG/ESO telescopes. With the aim to cover the virial region and extend out into the infall region, we have obtained GTO OmegaCAM imaging in the B, and V bands over 1 by 1 degree for 45 fields covering 46 WINGS clusters. We present the Johnson B- and V-band OmegaCAM photometry of 46 WINGS clusters. With a median seeing of 1 arcsecond in both B- and V-bands, our 25-minutes exposures in each band typically reach the 50% completeness level at V=23.1mag.
- ID:
- ivo://CDS.VizieR/J/ApJS/254/30
- Title:
- One-side head-tail (OHT) galaxies from FIRST & SDSS
- Short Name:
- J/ApJS/254/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One-side head-tail (OHT) galaxies are radio galaxies with a peculiar shape. They usually appear in galaxy clusters, but they have never been cataloged systematically. We design an automatic procedure to search for them in the Faint Images of the Radio Sky at Twenty-Centimeters source catalog and compile a sample with 115 HT candidates. After cross-checking with the Sloan Digital Sky Survey photometric data and catalogs of galaxy clusters, we find that 69 of them are possible OHT galaxies. Most of them are close to the center of galaxy clusters. The lengths of their tails do not correlate with the projection distance to the center of the nearest galaxy clusters, but show weak anticorrelation with the cluster richness, and are inversely proportional to the radial velocity differences between clusters and host galaxies. Our catalog provides a unique sample to study this special type of radio galaxies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/481/2458
- Title:
- On the nature of small galaxy systems
- Short Name:
- J/MNRAS/481/2458
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim at defining homogeneous selection criteria of small galaxy systems in order to build catalogues suitable to compare main properties of pairs, triplets, and groups with four or more members. To this end we use spectroscopic and photometric Sloan Digital Sky Survey (SDSS) data to identify systems with a low number of members. We study global properties of these systems and the properties of their member galaxies finding that galaxies in groups are systematically redder and with lower star formation activity indicators than galaxies in pairs which have a higher fraction of star-forming galaxies. Triplet galaxies present intermediate trends between pairs and groups. We also find an enhancement of star formation activity for galaxies in small systems with companions closer than 100kpc, irrespective of the number of members. We have tested these analyses on SDSS mock catalogues derived from the Millennium simulation, finding as conservative thresholds 76 per cent completeness and a contamination of 23 per cent in small galaxy systems, when considering an extreme case of incompleteness due to fiber collisions. Nevertheless, we also found that the results obtained are not likely affected by projection effects. Our studies suggest that an extra galaxy in a system modify the properties of the member galaxies. In pairs, galaxy-galaxy interactions increase gas density and trigger starbursts. However, repeated interactions in triplets and groups can generate gas stripping, turbulence, and shocks quenching the star formation in these systems.
- ID:
- ivo://CDS.VizieR/J/A+A/583/A124
- Title:
- Ophiuchus r'g'z' photometry and redshifts
- Short Name:
- J/A+A/583/A124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Ophiuchus cluster, at a redshift z=0.0296, is known from X-rays to be one of the most massive nearby clusters, but due to its very low Galactic latitude its optical properties have not been investigated in detail. Aims. We discuss the optical properties of the galaxies in the Ophiuchus cluster, in particular with the aim of understanding better its dynamical properties. We have obtained deep optical imaging in several bands with various telescopes, and applied a sophisticated method to model and subtract the contributions of stars in order to measure galaxy magnitudes as accurately as possible. The colour-magnitude relations obtained show that there are hardly any blue galaxies in Ophiuchus (at least brighter than r'<=19.5), and this is confirmed by the fact that we only detect two galaxies in H{alpha}. We also obtained a number of spectra with ESO-FORS2, that we combined with previously available redshifts. Altogether, we have 152 galaxies with spectroscopic redshifts in the 0.02<=z<=0.04 range, and 89 galaxies with both a redshift within the cluster redshift range and a measured r' band magnitude (limited to the Megacam 1x1deg^2^ field).