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J/AJ/135/785        SDSS-DR5 low-mass star spectroscopic sample    (West+, 2008)

Constraining the age-activity relation for cool stars: the Sloan Digital Sky Survey Data Release 5 low-mass star spectroscopic sample. West A.A., Hawley S.L., Bochanski J.J., Covey K.R., Reid I.N., Dhital S., Hilton E.J., Masuda M. <Astron. J., 135, 785-795 (2008)> =2008AJ....135..785W
ADC_Keywords: Stars, late-type ; Stars, M-type ; Spectral types ; Radial velocities ; Proper motions ; Photometry, ugriz ; Photometry, SDSS ; Photometry, infrared Keywords: solar neighborhood - Galaxy: kinematics and dynamics - Galaxy: structure - stars: activity - stars: late-type - stars: low-mass, brown dwarfs Abstract: We present a spectroscopic analysis of over 38000 low-mass stars from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Analysis of this unprecedentedly large sample confirms the previously detected decrease in the fraction of magnetically active stars (as traced by Hα emission) as a function of vertical distance from the Galactic Plane. The magnitude and slope of this effect varies as a function of spectral type. Using simple 1-D dynamical models, we demonstrate that the drop in activity fraction can be explained by thin disk dynamical heating and a rapid decrease in magnetic activity. The timescale for this rapid activity decrease changes according to the spectral type. By comparing our data to the simulations, we calibrate the age-activity relation at each M dwarf spectral type. We also present evidence for a possible decrease in the metallicity as a function of height above the Galactic Plane. In addition to our activity analysis, we provide line measurements, molecular band indices, colors, radial velocities, 3-D space motions and mean properties as a function of spectral type for the SDSS DR5 low-mass star sample. Description: Photometric and Spectroscopic parameters for 44084 M and L dwarfs from the Sloan Digital Sky Survey Data Release 5. We include the positions (equatorial, and Galactic), SDSS and 2MASS photometry (when available), the proper motions (as measured by Munn et al., 2004AJ....127.3034M), the radial velocities (measured by Bochanski et al., 2007AJ....134.2418B), a variety of spectroscopic indices (including H-alpha, TiO5, CaH1 etc.), the distance (from the Sun and from the Galactic plane), and full space motions (where available). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars1.dat 331 22000 Spectroscopic and Photometric parameters for 22000 M and L dwarfs in SDSS DR5 stars2.dat 331 22084 Spectroscopic and Photometric parameters for 22084 M and L dwarfs in SDSS DR5
See also: II/276 : The SDSS Photometric Catalog, Release 5 (Adelman-McCarthy+, 2007) http://www.sdss.org/ : SDSS Home Page J/AJ/123/3409 : SDSS M, L, and T dwarfs (Hawley+, 2002) J/AJ/128/426 : Subdwarfs in the SDSS (West+, 2004) Byte-by-byte Description of file: stars?.dat
Bytes Format Units Label Explanations
1- 4 I4 --- Plate SDSS plate 6- 10 I5 d MJD Modified Julian date of observation 12- 14 I3 --- Fiber Fiber number 16- 25 F10.6 deg RAdeg Right ascension (J2000) 27- 35 F9.5 deg DEdeg Declination (J2000) 37- 38 I2 --- SpT [0/10] Spectral M-type code (1) 40- 46 F7.1 mas/yr pmRA ?=-9999.0 Proper motion along right ascension (2) 48- 54 F7.1 mas/yr pmDE ?=-9999.0 Proper motion along declination (2) 56- 60 F5.1 mas/yr e_pmRA Proper motion along RA error (2) 62- 66 F5.1 mas/yr e_pmDE Proper motion along DE error (2) 68- 75 F8.1 km/s RV Radial velocity (3) 77- 85 F9.1 pc Dist Photometric distance (4) 87- 91 F5.2 mag umag SDSS u-band psf magnitude 93- 97 F5.2 mag gmag SDSS g-band psf magnitude 99-103 F5.2 mag rmag SDSS r-band psf magnitude 105-109 F5.2 mag imag SDSS i-band psf magnitude 111-115 F5.2 mag zmag SDSS z-band psf magnitude 117-121 F5.2 mag Jmag ?=0.00 2MASS J-band psf magnitude 123-127 F5.2 mag Hmag ?=0.00 2MASS H-band psf magnitude 129-133 F5.2 mag Kmag ?=0.00 2MASS K-band psf magnitude 135-139 F5.2 mag e_umag SDSS u-band psf magnitude error 141-146 F6.2 mag e_gmag SDSS g-band psf magnitude error 148-153 F6.2 mag e_rmag SDSS r-band psf magnitude error 155-158 F4.2 mag e_imag SDSS i-band psf magnitude error 160-163 F4.2 mag e_zmag SDSS z-band psf magnitude error 165-170 F6.2 mag e_Jmag ?=999.99 2MASS J-band psf magnitude error 172-177 F6.2 mag e_Hmag ?=999.99 2MASS H-band psf magnitude error 179-184 F6.2 mag e_Kmag ?=999.99 2MASS K-band psf magnitude error 186-189 F4.2 mag Au u-band Galactic extinction (5) 191-194 F4.2 mag Ag g-band Galactic extinction (5) 196-199 F4.2 mag Ar r-band Galactic extinction (5) 201-204 F4.2 mag Ai i-band Galactic extinction (5) 206-209 F4.2 mag Az z-band Galactic extinction (5) 211-217 F7.2 0.1nm EWHa Hα equivalent width 219-224 F6.2 0.1nm e_EWHa Hα equivalent width error 226-231 F6.2 --- TiO5 TiO5 bandhead 233-238 F6.2 --- CaH1 ?=* CaH1 bandhead 240-245 F6.2 --- CaH2 CaH2 bandhead 247-252 F6.2 --- CaH3 CaH3 bandhead 254-259 F6.2 --- TiO8 ?=* TiO8 bandhead 261 A1 --- Ac [mnwy] Activity indicator (y=active, n=no, m=marginally, w=weakly) 263-271 F9.1 pc zDist Vertical distance from the Galactic plane 273-282 F10.6 deg GLON Galactic longitude 284-293 F10.6 deg GLAT Galactic latitude 295-302 F8.1 km/s UVel U space motion (positive toward Galactic center) 304-312 F9.1 km/s VVel V space motion 314-322 F9.1 km/s WVel W space motion 324-331 F8.3 --- SNR Signal-to-noise ratio near Hα
Note (1): Spectral types are defined as M0=0, M1=1 . . . L0=10 Note (2): Matched to SDSS by Munn et al. (2004AJ....127.3034M) Note (3): Radial Velocities computed using Bochanski et al. (2007AJ....133..531B) templates Note (4): Photometric distance calculated using r-z colors from Covey et al. (2008arXiv0807.2452C) Note (5): Galactic extinction from Schlegel et al. (1998ApJ...500..525S)
Acknowledgements: Andrew West, aaw(at)mit.edu
(End) Andrew A. West [MIT, USA], Patricia Vannier [CDS] 09-Sep-2008
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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