- ID:
- ivo://CDS.VizieR/J/ApJS/227/12
- Title:
- NGVS XXV. Virgo globular clusters photometry
- Short Name:
- J/ApJS/227/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The central region of the Virgo cluster of galaxies contains thousands of globular clusters (GCs), an order of magnitude more than the numbers found in the Local Group. Relics of early star formation epochs in the universe, these GCs also provide ideal targets to test our understanding of the Spectral Energy Distributions (SEDs) of old stellar populations. Based on photometric data from the Next Generation Virgo cluster Survey (NGVS) and its near-infrared counterpart NGVS-IR, we select a robust sample of ~2000 GCs with excellent photometry and spanning the full range of colors present in the Virgo core. The selection exploits the well defined locus of GCs in the uiK diagram and the fact that the globular clusters are marginally resolved in the images. We show that the GCs define a narrow sequence in 5-dimensional color space, with limited but real dispersion around the mean sequence. The comparison of these SEDs with the predictions of eleven widely used population synthesis models highlights differences between models, and also shows that no single model adequately matches the data in all colors. We discuss possible causes for some of these discrepancies. Forthcoming papers of this series will examine how best to estimate photometric metallicities in this context, and compare the Virgo globular cluster colors with those in other environments.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/160/220
- Title:
- NIR light curve of 234 RR Lyrae in Messier 3
- Short Name:
- J/AJ/160/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new near-infrared (NIR), JHKs, time-series observations of RR-Lyrae variables in the Messier-3 (NGC5272) globular cluster using the WIRCam instrument at the 3.6m Canada-France-Hawaii Telescope. Our observations cover a sky area of ~21'x21' around the cluster center and provide an average of 20 epochs of homogeneous JHKs-band photometry. New homogeneous photometry is used to estimate robust mean magnitudes for 175 fundamental-mode (RRab), 47 overtone-mode (RRc), and 11 mixed-mode (RRd) variables. Our sample of 233 RR-Lyrae variables is the largest thus far obtained in a single cluster with time-resolved, multiband NIR photometry. NIR-to-optical amplitude ratios for RR-Lyrae in Messier-3 exhibit a systematic increase moving from RRc to short-period (P<0.6day) and long-period (P>~0.6day) RRab variables. We derive JHKs-band period-luminosity relations for RRab, RRc, and the combined sample of variables. Absolute calibrations based on the theoretically predicted period-luminosity-metallicity relations for RR Lyrae stars yield a distance modulus, {mu}=15.041{+/-}0.017(statistical){+/-}0.036(systematic)mag, to Messier-3. When anchored to trigonometric parallaxes for nearby RR-Lyrae stars from the Hubble Space Telescope and the Gaia mission, our distance estimates are consistent with those resulting from the theoretical calibrations, albeit with relatively larger systematic uncertainties.
- ID:
- ivo://CDS.VizieR/J/A+A/308/733
- Title:
- NTT VI photometry in Terzan 5
- Short Name:
- J/A+A/308/733
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the metal-rich bulge globular cluster Terzan 5 by means of VI colour-magnitude diagrams, with images obtained under exceptional seeing conditions (0.34"-0.50"). Differential reddening is important across the cluster. We derive a reddening of E(B-V)=2.49 and a distance from the Sun d_{sun}_=5.6kpc, closer than previous estimates. Based on the red giant branch curvature, we derive a metallicity somewhat higher than that of NGC 6553, probably solar.
- ID:
- ivo://CDS.VizieR/J/MNRAS/411/1744
- Title:
- Observations of RR Lyr stars in M5
- Short Name:
- J/MNRAS/411/1744
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The period changes of 86 M5 RR Lyrae stars have been investigated on a 100-yr time base. The published observations have been supplemented by archival Asiago, Konkoly and Las Campanas photographic observations obtained between 1952 and 1993.
- ID:
- ivo://CDS.VizieR/J/AJ/101/1352
- Title:
- Observations of variable stars in M9
- Short Name:
- J/AJ/101/1352
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of RR Lyrae variables near the transition between fundamental and first-overtone mode in the Oosterhoff type II (Oo II) globular clusters M80, M9, and NGC 2298 have been analyzed in a search for double-mode pulsators (RRd stars). These three clusters were selected because they have metal abundances that are intermediate between those of the Oo II clusters and the Oo I clusters that are known to have RRd stars. Any RRd stars identified in these three clusters would be useful for verification of a mass-metallicity relation. The analysis was based on published observations for all three clusters, and in addition, 44 CCD frames of M9 and 32 photographs of NGC 2298, all obtained with the University of Toronto telescope at Las Campanas. No new RRd stars were discovered. It is noted that the only globular clusters known to have RRd stars are the most metal poor Oo I clusters and metal poor Oo II clusters. Published observations of the RRd stars in M15 have been analyzed in order to determine accurate periods and period ratios for stars whose periods were previously considered to be uncertain.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A123
- Title:
- OGLE IV and Gaia EDR3 data for RR Lyrae stars
- Short Name:
- J/A+A/657/A123
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- RR Lyrae stars are useful standard candles allowing one to derive accurate distances for old star clusters. Based on the recent catalogues from OGLE-IV and Gaia Early Data Release 3 (EDR3), the distances can be improved for a few bulge globular clusters. The aim of this work is to derive an accurate distance for the following six moderately metal-poor, relatively high-reddening bulge globular clusters: NGC 6266, NGC 6441, NGC 6626, NGC 6638, NGC 6642, and NGC 6717. We combined newly available OGLE-IV catalogues of variable stars containing mean I magnitudes, with Clement's previous catalogues containing mean V magnitudes, and with precise proper motions from Gaia EDR3. Astrometric membership probabilities were computed for each RR Lyrae, in order to select those compatible with the cluster proper motions. Applying luminosity-metallicity relations derived from BaSTI alpha-enhanced models (He-enhanced for NGC 6441 and canonical He for the other clusters), we updated the distances with relatively low uncertainties. Distances were derived with the I and V bands, with a 5-8% precision. We obtained 6.6kpc, 13.1kpc, 5.6 kpc, 9.6kpc, 8.2kpc, and 7.3kpc for NGC 6266, NGC 6441, NGC 6626, NGC 6638, NGC 6642, and NGC 6717, respectively. The results are in excellent agreement with the literature for all sample clusters, considering the uncertainties. The present method of distance derivation, based on recent data of member RR Lyrae stars, updated BaSTI models, and robust statistical methods, proved to be consistent. A larger sample of clusters will be investigated in a future work.
- ID:
- ivo://CDS.VizieR/J/A+AS/125/343
- Title:
- OGLE RR Lyr stars in omega Cen
- Short Name:
- J/A+AS/125/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 lists light curve parameters and rectangular coordinates for variables OGLEGC 71-211. Table 2 contains equatorial coordinates of variables OGLEGC 71-211. Tables (table3 to 203) contain V-band light curves for variables OGLEGC71-211.
- 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.
- 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.
