- ID:
- ivo://CDS.VizieR/J/A+A/467/1025
- Title:
- JHK photometry of Fornax red giant branch
- Short Name:
- J/A+A/467/1025
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the evolved stellar populations in the dwarf spheroidal galaxy Fornax based on wide-area near-infrared observations, aimed at obtaining new independent estimates of its distance and metallicity distribution. Assessing the reliability of near-infrared methods is most important in view of future space- and ground-based deep near-infrared imaging of resolved stellar systems.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/573/A84
- Title:
- JHK photometry of IC 1613 AGB stars
- Short Name:
- J/A+A/573/A84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A member of the Local Group, IC 1613 is a gas rich irregular dwarf galaxy that appears to have formed stars continuously over the last 10Gyr and is relatively independent of external influences from other galaxies. This paper aims to study the spatial distribution of the asymptotic giant branch (AGB) population in IC 1613 and its metallicity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/404/1475
- Title:
- JHK photometry of Leo I AGB and red giants
- Short Name:
- J/MNRAS/404/1475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A near-infrared imaging study of the evolved stellar populations in the dwarf spheroidal galaxy Leo I is presented. Based on JHK observations obtained with the WFCAM wide-field array at the United Kingdom Infrared Telescope, we build a near-infrared photometric catalogue of red giant branch (RGB) and asymptotic giant branch (AGB) stars in Leo I over a 13.5arcmin^2^ area. The V-K colours of RGB stars, obtained by combining the new data with existing optical observations, allow us to derive a distribution of global metallicity [M/H] with average [M/H]=-1.51 (uncorrected) or [M/H]=-1.24+/-.05(int)+/-0.15(syst) after correction for the mean age of Leo I stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/385/1045
- Title:
- JHKsIc photometry of AGB in Phoenix dwarf gal.
- Short Name:
- J/MNRAS/385/1045
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- JHKs near-infrared photometry of stars in the Phoenix dwarf galaxy is presented and discussed. Combining these data with the optical photometry of Massey et al. (2007, Cat. <J/AJ/133/2393>) allows a rather clean separation of field stars from Phoenix members. The discovery of a Mira variable (P=425d), which is almost certainly a carbon star, leads to an estimate of the distance modulus of 23.10+/-0.18 that is consistent with other estimates and indicates the existence of a significant population of age ~2Gyr. The two carbon stars of Da Costa have Mbol=-3.8 and are consistent with belonging to a population of similar age; some other possible members of such a population are identified. A Da Costa non-carbon star is {Delta}Ks~0.3mag brighter than these two carbon stars. It may be an asymptotic giant branch star of the dominant old population. The nature of other stars lying close to it in the Ks, (J-Ks) diagram needs studying.
- ID:
- ivo://CDS.VizieR/J/MNRAS/428/2216
- Title:
- JHKs photometry of AGB stars in NGC 6822
- Short Name:
- J/MNRAS/428/2216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- JHKs photometry is presented from a 3.5yr survey of the central regions of the irregular galaxy NGC 6822. The morphology of the colour-magnitude and colour-colour diagrams is discussed with particular reference to M-, S- and C-type asymptotic giant branch (AGB) stars and to M supergiants. Mean JHKs magnitudes and periods are given for 11 O-rich and 50 presumed C-rich Miras. Data are also listed for 27 large-amplitude AGB stars without periods and for 69 small-amplitude AGB variables. The slope of the bolometric period-luminosity relation for the C-rich Miras is in good agreement with that in the Large Magellanic Cloud. Distance moduli derived from the C- and O-rich Miras are in agreement with other estimates. The period distribution of C-rich Miras in NGC 6822 is similar to that in the Magellanic Clouds, but differs from that in the dwarf spheroidals in the Local Group. In the latter there is a significant proportion of large-amplitude, short-period variables indicating a population producing old carbon-rich AGB stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/388/1185
- Title:
- JHKs photometry of LeoII dSph giants
- Short Name:
- J/MNRAS/388/1185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the evolved stellar populations in the dwarf spheroidal galaxy Leo II, based on JHKs observations obtained with the near-infrared array WFCAM at the UKIRT telescope. Combining the new data with optical data, we derived photometric estimates of the distribution of global metallicity [M/H] of individual red giant stars from their V-Ks colours. Our results are consistent with the metallicities of red giant branch (RGB) stars obtained from CaII triplet spectroscopy, once the age effects are considered.
- ID:
- ivo://CDS.VizieR/J/A+A/420/173
- Title:
- JK photometry of Omega Cen red giants
- Short Name:
- J/A+A/420/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The IR catalogue of omega Cen is based on ground-based observations using SOFI (Infrared Spectrograph and Imaging Camera on the NTT telescope at ESO, La Silla) and contains about 73000 stars covering an area of 13"x13" around the center of the cluster. The limiting magnitude is K<=17.5m and the positional accuracy is better than 0.2"
- ID:
- ivo://CDS.VizieR/J/AJ/160/12
- Title:
- J, Ks, NUV emission of 133 red giant stars
- Short Name:
- J/AJ/160/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Main-sequence stars exhibit a clear rotation-activity relationship, in which rapidly rotating stars drive strong chromospheric/coronal ultraviolet and X-ray emission. While the vast majority of red giant stars are inactive, a few percent exhibit strong ultraviolet emission. Here we use a sample of 133 red giant stars observed by Sloan Digital Sky Survey APOGEE and Galaxy Evolution Explorer to demonstrate an empirical relationship between near-UV (NUV) excess and rotational velocity (vsini). Beyond this simple relationship, we find that NUV excess also correlates with rotation period and with Rossby number in a manner that shares broadly similar trends to those found in M dwarfs, including activity saturation among rapid rotators. Our data also suggest that the most extremely rapidly rotating giants may exhibit so-called supersaturation, which could be caused by centrifugal stripping of these stars rotating at a high fraction of breakup speed. As an example application of our empirical rotation-activity relation, we demonstrate that the NUV emission observed from a recently reported system comprising a red giant with a black hole companion is fully consistent with arising from the rapidly rotating red giant in that system. Most fundamentally, our findings suggest a common origin of chromospheric activity in rotation and convection for cool stars from main sequence to red giant stages of evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/809/143
- Title:
- K-band spectra of stars within central 1pc of the MW
- Short Name:
- J/ApJ/809/143
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a metallicity analysis of 83 late-type giants within the central 1pc of the Milky Way. K-band spectroscopy of these stars was obtained with the medium spectral resolution integral-field spectrograph NIFS on Gemini North using laser-guided star adaptive optics. Using spectral template fitting with the MARCS synthetic spectral grid, we find that there is a large variation in the metallicity, with stars ranging from [M/H]<-1.0 to above solar metallicity. About 6% of the stars have [M/H]<-0.5. This result is in contrast to previous observations with smaller samples that show stars at the Galactic center having approximately solar metallicity with only small variations. Our current measurement uncertainties are dominated by systematics in the model, especially at [M/H]>0, where there are stellar lines not represented in the model. However, the conclusion that there are low-metallicity stars, as well as large variations in metallicity, is robust. The metallicity may be an indicator of the origin of these stars. The low-metallicity population is consistent with that of globular clusters in the Milky Way, but their small fraction likely means that globular cluster infall is not the dominant mechanism for forming the Milky Way nuclear star cluster. The majority of stars are at or above solar metallicity, which suggests they were formed closer to the Galactic center or from the disk. In addition, our results indicate that it will be important for star formation history analyses using red giants at the Galactic center to consider the effect of varying metallicity.
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/2652
- Title:
- Keck Aperture Masking Experiment. Red giants
- Short Name:
- J/MNRAS/426/2652
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- While the importance of dusty asymptotic giant branch (AGB) stars to galactic chemical enrichment is widely recognized, a sophisticated understanding of the dust formation and wind-driving mechanisms has proven elusive due in part to the difficulty in spatially resolving the dust-formation regions themselves. We have observed 20 dust-enshrouded AGB stars as part of the Keck Aperture Masking Experiment, resolving all of them in multiple near-infrared bands between 1.5 and 3.1um.
