Exploring the age-dependent properties of M and L dwarfs using Gaia and SDSS. (2019)
Keywords :
stars activity - stars: kinematics and dynamics - stars: low-mass
Abstract:We present a sample of 74216 M and L dwarfs constructed from two existing catalogs of cool dwarfs spectroscopically identified in the Sloan Digital Sky Survey (SDSS). We cross-matched the SDSS catalog with Gaia DR2 (Cat. I/345) to obtain parallaxes and proper motions and modified the quality cuts suggested by the Gaia Collaboration to make them suitable for late-M and L dwarfs. We also provide relations between Gaia colors and absolute magnitudes with spectral type and conclude that (G-G_RP_) has the tightest relation to spectral type for M and L dwarfs. In addition, we study magnetic activity as a function of position on the color-magnitude diagram, finding that H{alpha} magnetically active stars have, on average, redder colors and/or brighter magnitudes than inactive stars. This effect
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In this paper, we present the MLSDSS-GaiaDR2 sample of M and L dwarfs
including spectral types, H{alpha} measurements, survey photometry,
and Galactic kinematics. The compilation of the MLSDSS-GaiaDR2 sample
was accomplished in two parts: assembling the base sample, dubbed the
"MLSDSS" sample, and then cross-matching it with the Gaia Data Release 2
(DR2; Gaia Collaboration et al. 2018, Cat. I/345). The MLSDSS sample
is based on data from the SDSS Data Releases 7, 10, and 12 (DR7; DR10;
DR12; Abazajian et al. 2009, Cat. II/294; Ahn et al. 2014ApJS..211....1H;
Alam et al. 2015, Cat. V/147) and the SDSS-III Baryon Oscillation
Spectroscopic Survey (BOSS; Eisenstein et al. 2011AJ....142...72E;
Dawson et al. 2013AJ....145...10D).
We cross-matched the MLSDSS sample with Gaia DR2 to obtain precise
proper motions and parallaxes. First, we propagated the positions from
the SDSS epoch (ranging from 1999 to 2007) to the Gaia DR2 epoch (2015.5)
using the proper motions in MLSDSS. Second, we queried the Gaia Archive
(http://gea.esac.esa.int/archive/) and selected all the objects within
a radius of 5" of the 2015.5 position. We found that 98% (73003 stars)
of MLSDSS stars have at least one match in Gaia DR2. Of these, 8269 have
between two and five matches within a 5" radius. To find a single best
match, we propagated the position of each match back to the SDSS epoch
using the Gaia DR2 proper motion and kept only the closest match between
the Gaia position at the SDSS epoch and the SDSS position.
- VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
- II/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)
- V/147 : The SDSS Photometric Catalogue, Release 12 (Alam+, 2015)
- I/345 : Gaia DR2 (Gaia Collaboration, 2018)
- J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002)
- J/AJ/131/2722 : New L and T dwarfs from the SDSS (Chiu+, 2006)
- J/ApJ/676/1281 : L and T dwarfs in 2MASS/SDSS (Metchev+, 2008)
- J/AJ/139/1808 : Colors and kinematics of SDSS L dwarfs (Schmidt+, 2010)
- J/AJ/141/97 : SDSS DR7 M dwarfs (West+, 2011)
- J/AJ/149/158 : The BUD sample. I. L dwarf activity sample (Schmidt+, 2015)
- J/ApJ/810/158 : M,L,T dwarfs fundamental parameters and SEDs
- J/AJ/154/112 : NIR spectroscopy of new L and T dwarf candidates
