- ID:
- ivo://CDS.VizieR/J/MNRAS/459/610
- Title:
- 47 Tuc sub-giant branch chemical abundances
- Short Name:
- J/MNRAS/459/610
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The globular cluster 47 Tuc exhibits a complex sub-giant branch (SGB) with a faint-SGB comprising only about the 10 per cent of the cluster mass and a bright-SGB hosting at least two distinct populations. We present a spectroscopic analysis of 62 SGB stars including 21 faint-SGB stars. We thus provide the first chemical analysis of the intriguing faint-SGB population and compare its abundances with those of the dominant populations. We have inferred abundances of Fe, representative light elements C, N, Na, and Al, {alpha} elements Mg and Si for individual stars. Oxygen has been obtained by co-adding spectra of stars on different sequences. In addition, we have analysed 12 stars along the two main RGBs of 47 Tuc. Our principal results are (i) star-to-star variations in C/N/Na among RGB and bright-SGB stars; (ii) substantial N and Na enhancements for the minor population corresponding to the faint-SGB; (iii) no high enrichment in C+N+O for faint-SGB stars. Specifically, the C+N+O of the faint-SGB is a factor of 1.1 higher than the bright-SGB, which, considering random (+/-1.3) plus systematic errors (+/-0.3), means that their C+N+O is consistent within observational uncertainties. However, a small C+N+O enrichment for the faint-SGB, similar to what predicted on theoretical ground, cannot be excluded. The N and Na enrichment of the faint-SGB qualitatively agrees with this population possibly being He-enhanced, as suggested by theory. The iron abundance of the bright and faint-SGB is the same to a level of ~0.10dex, and no other significant difference for the analysed elements has been detected.
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882. Type II Cepheids
- ID:
- ivo://CDS.VizieR/J/AJ/114/341
- Title:
- Type II Cepheids
- Short Name:
- J/AJ/114/341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined the photospheric compositions of five luminous F-G variables in globular clusters: V11 in M2, V42 in M5, V84 in M5, V2 in M10, and V17 in M28, three of which are classified as RV Tau variable stars. Unlike the recent findings that the photospheres of field RV Tau variables have been altered by a gas-dust separation process, none of these stars, except possibly V2 in M10, show such signs. We suggest that either a smaller carbon abundance in the photosphere of a globular cluster RV Tau star (compared to its field analogues) might be a factor in the gas-dust separation process due to the lack of sufficient carbon grain formation, or the stellar winds and their efficacy as dust-grain separators is influenced by the metallicity of the stellar envelope which, unlike the photosphere, is never subject to alteration by a dust-gas separation. Our analysis is most complete for V84, for which we have estimated the abundances of 19 chemical elements. Compared to the other giants in M5, this star displays a very large excess of Na and a deficit of O. This finding is consistent with a recently proposed mechanism of Na production in the ON-cycling region of metal-poor RGB stars. The value of [Al/Fe] for V84 is also high (also consistent with ON-cycling), but a comparison with the other cluster giants cannot be performed until Al is measured in their spectra. The s-process elements are not significantly enhanced in the atmosphere of V84 relative to the other cluster members. (c) 1997 American Astronomical Society.
- ID:
- ivo://CDS.VizieR/J/MNRAS/345/949
- Title:
- UBRI photometry of NGC 3379 globular clusters
- Short Name:
- J/MNRAS/345/949
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wide-area UBRI photometry for globular clusters around the Leo group galaxy NGC 3379. Globular cluster candidates are selected from their B-band magnitudes and their (U-B)_0_ versus (B-I)_0_ colours. A colour-colour selection region was defined from photometry of the Milky Way and M31 globular cluster systems. We detect 133 globular cluster candidates, which supports previous claims of a low specific frequency for NGC 3379.
- ID:
- ivo://CDS.VizieR/J/AJ/121/935
- Title:
- UBV and proper motions of Palomar 13
- Short Name:
- J/AJ/121/935
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a proper-motion, CCD photometric study of stars in the distant halo globular cluster Palomar 13. The absolute proper motion of Pal 13 with respect to the background galaxies, derived from moderate-scale photographic plates separated by a 40 year baseline, is (pmRAcosDE, pmDE)=(2.30, 0.27)+/-(0.26, 0.25)mas/yr.
- ID:
- ivo://CDS.VizieR/II/37
- Title:
- UBV HR Diagrams of Globular Clusters
- Short Name:
- II/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- UBV observations of over 37,000 stars have been compiled from the literature to yield 165 color-magnitude diagrams. There is a list of bibliographic references for each cluster diagram.
- ID:
- ivo://CDS.VizieR/J/AJ/123/1411
- Title:
- UBVIHalpha photometry of NGC 4314 star clusters
- Short Name:
- J/AJ/123/1411
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Hubble Space Telescope (HST) WFPC2 images, we have obtained U, B, V, I, and H{alpha} photometry for 76 star clusters in the nuclear star-forming ring of the barred spiral galaxy NGC 4314. These clusters are likely associated with an inner inner Lindblad resonance (IILR). The blue colors and H{alpha} emission for most of these clusters imply very young ages of 115 Myr. Age estimates based on several reddening-free parameters indicate that the present epoch of star formation has lasted at least 30Myr. By estimating the masses of stars in the clusters and comparing with the H{alpha} luminosity, we conclude that a significant fraction of ongoing star formation in the nuclear ring of NGC 4314 occurs in clusters. The cluster masses identify these as young open clusters, not young globular clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/641/763
- Title:
- UBVI photometry for Arp 220 star clusters
- Short Name:
- J/ApJ/641/763
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new optical observations of young massive star clusters in Arp 220, the nearest ultraluminous infrared galaxy, taken in UBVI with the Hubble Space Telescope ACS HRC camera. We find a total of 206 probable clusters whose spatial distribution is centrally concentrated toward the nucleus of Arp 220. We use model star cluster tracks to determine ages, luminosities, and masses for 14 clusters with complete UBVI indices or previously published near-infrared data. We estimate rough masses for 24 additional clusters with I<24mag from BVI indices alone.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A70
- Title:
- UBVI photometry in 3 globular clusters
- Short Name:
- J/A+A/573/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the photometric analysis of the external regions of three Galactic Globular Clusters: NGC 6121, NGC 6397 and NGC 6752. The main goal is the characterization of the multiple stellar populations along the main sequence (MS) and the study of the radial trend of the different populations hosted by the target clusters. The data have been collected using FORS2 mounted at the ESO/VLT@UT1 telescope in UBVI filters. From these data sets we extracted high-accuracy photometry and constructed color-magnitude diagrams. We exploit appropriate combination of colors and magnitudes which are powerful tools to identify multiple stellar populations, like B versus U-B and V versus c_U,B,I_=(U-B)-(B-I) CMDs. We confirm previous findings of a split MS in NGC 6752 and NGC 6121. Apart from the extreme case of omega Centauri, this is the first detection of multiple MS from ground-based photometry. For NGC 6752 and NGC 6121 we compare the number ratio of the blue MS to the red MS in the cluster outskirts with the fraction of first and second generation stars measured in the central regions. There is no evidence for significant radial trend. The MS of NGC 6397 is consistent with a simple stellar population. We propose that the lack of multiple sequences is due both to observational errors and to the limited sensitivity of U,B,V,I photometry to multiple stellar populations in metal-poor GCs. Finally, we compute the helium abundance for the stellar populations hosted by NGC 6121 and NGC 6752, finding a mild ({Delta}Y~0.02) difference between stars in the two sequences.
- ID:
- ivo://CDS.VizieR/J/ApJ/783/56
- Title:
- UBVI photometry in NGC 6752
- Short Name:
- J/ApJ/783/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper is devoted to photometric study of the Galactic globular cluster (GGC) NGC 6752 in UBVI, focusing on the multiplicity of its stellar population. We emphasize that our U passband is (1) narrower than the standard one due to its smaller extension blueward and (2) redshifted by ~300{AA} relative to its counterparts, such as the HST F336W filter. Accordingly, both the spectral features encompassed by it and photometric effects of the multiplicity revealed in our study are somewhat different than in recent studies of NGC 6752. Main sequence stars bluer in U-B are less centrally concentrated, as red giants are. We find a statistically significant increasing luminosity of the red giant branch (RGB) bump of {Delta}U{approx}0.2mag toward the cluster outskirts with no so obvious effect in V. The photometric results are correlated with spectroscopic data: the bluer RGB stars in U-B have lower nitrogen abundances. We draw attention to a larger width of the RGB than the blue horizontal branch (BHB) in U-B. This seems to agree with the effects predicted to be caused by molecular bands produced by nitrogen-containing molecules. We find that brighter BHB stars, especially the brightest ones, are more centrally concentrated. This implies that red giants that are redder in U - B, i.e., more nitrogen enriched and centrally concentrated, are the main progenitors of the brighter BHB stars. However, such a progenitor-progeny relationship disagrees with theoretical predictions and with the results on the elemental abundances in horizontal branch stars. We isolated the asymptotic giant branch clump and estimated the parameter {Delta}V_ZAHB_^clump^=0.98+/-0.12.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/40
- Title:
- UBVI photometry of GCs in the Fornax galaxy cluster
- Short Name:
- J/ApJ/763/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wide-field multiband photometry of globular cluster (GC) systems in NGC 1399, NGC 1404, and NGC 1387 located in the central region of the Fornax galaxy cluster. Observation was carried out through U, B, V, and I bands, which marks one of the widest and deepest U-band studies on extragalactic GC systems. The present U-band photometry enables us to significantly reduce the contamination by a factor of two for faint sources (V_0_~23.5). The main results based on some 2000 GC candidates around NGC 1399, NGC 1404, and NGC 1387 are as follows: (1) the GC system in each galaxy exhibits bimodal color distributions in all colors examined, but the shape of color histograms varies systematically depending on colors; (2) NGC 1399 shows that the mean colors of both blue and red GCs become bluer with increasing galactocentric radius; (3) NGC 1399 shows overabundance of GCs in the directions of NGC 1404 and NGC 1387, indicating their ongoing interactions; and (4) NGC 1399 also exhibits a ~0.'5 offset between the center of the inner GC distribution and the galaxy's optical center, suggesting that NGC 1399 is not yet dynamically relaxed and may be undergoing merger events.
