SELECTING M GIANTS WITH INFRARED PHOTOMETRY: DISTANCES, METALLICITIES, AND THE SAGITTARIUS STREAM
| Autor: | Jing Zhong, Zhengyi Shao, Hao Tian, Emma Small, Chao Liu, Linlin Li, Jeffrey L. Carlin, Jinliang Hou, Jing Li, Martin C. Smith, Heidi Jo Newberg, Li Chen |
|---|---|
| Přispěvatelé: | Kapteyn Astronomical Institute |
| Rok vydání: | 2016 |
| Předmět: |
stars: abundances
Metallicity FOS: Physical sciences Astrophysics::Cosmology and Extragalactic Astrophysics Astrophysics Sagittarius Stream 01 natural sciences Photometry (optics) Galactic halo 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics 010306 general physics Galaxy: structure 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Physics galaxies: individual: Sagittarius Star formation stars: late-type Galactic anticenter Astronomy and Astrophysics Quasar Giant star Astrophysics - Astrophysics of Galaxies Galaxy: halo Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) stars: distances Astrophysics::Earth and Planetary Astrophysics |
| Zdroj: | The Astrophysical Journal, 823(1):59. IOP PUBLISHING LTD |
| ISSN: | 1538-4357 0004-637X |
| Popis: | Using a spectroscopically confirmed sample of M-giants, M-dwarfs and quasars from the LAMOST survey, we assess how well WISE $\&$ 2MASS color-cuts can be used to select M-giant stars. The WISE bands are very efficient at separating M-giants from M-dwarfs and we present a simple classification that can produce a clean and relatively complete sample of M-giants. We derive a new photometric relation to estimate the metallicity for M-giants, calibrated using data from the APOGEE survey. We find a strong correlation between the $(W1-W2)$ color and $\rm [M/H]$, where almost all of the scatter is due to photometric uncertainties. We show that previous photometric distance relations, which are mostly based on stellar models, may be biased and devise a new empirical distance relation, investigating trends with metallicity and star formation history. Given these relations, we investigate the properties of M-giants in the Sagittarius stream. The offset in the orbital plane between the leading and trailing tails is reproduced and, by identifying distant M-giants in the direction of the Galactic anti-center, we confirm that the previously detected debris in the outer halo is the apocenter of the trailing tail. We also find tentative evidence supporting an existing overdensity near the leading tail in the Northern Galactic hemisphere, possibly an extension to the trailing tail (so-called Branch C). We have measured the metallicity distribution along the stream, finding a clear metallicity offset between the leading and trailing tails, in agreement with models for the stream formation. We include an online table of M-giants to facilitate further studies. 15 pages, 13 figures, accepted by ApJ. Minor issue fixed with Fig 12 and Section 5.3 |
| Databáze: | OpenAIRE |
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