The M dwarf problem in the Galaxy
Abstract
We present evidence that there is an M dwarf problem similar to the previously identified G dwarf and K dwarf problems: the number of low-metallicity M dwarfs is not sufficient to match simple closed-box models of local Galactic chemical evolution. We estimated the metallicity of 4141 M dwarf stars with spectra from the Sloan Digital Sky Survey (SDSS) using a molecular band strength versus metallicity calibration developed using high resolution spectra of nearby M dwarfs. Using a sample of M dwarfs with measured magnitudes, parallaxes and metallicities, we derived a relation that describes the absolute magnitude variation as a function of metallicity. When we examined the metallicity distribution of SDSS stars, after correcting for the different volumes sampled by the magnitude-limited survey, we found that there is an M dwarf problem, with the number of M dwarfs at [Fe/H] ∼-0.5 less than 1 per cent the number at [Fe/H] = 0, where a Simple model of Galactic chemical evolution predicts a more gradual drop in star numbers with decreasing metallicity.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2012
- DOI:
- 10.1111/j.1365-2966.2012.20722.x
- arXiv:
- arXiv:1202.3078
- Bibcode:
- 2012MNRAS.422.1489W
- Keywords:
-
- stars: abundances;
- stars: late-type;
- stars: statistics;
- Galaxy: abundances;
- Galaxy: evolution;
- Galaxy: stellar content;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- To be published in Monthly Notices of the RAS by the Royal Astronomical Society and Blackwell Publishing. 7 pages, 3 figures