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 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 2004AJ....127.3034M), the radial velocities (measured by Bochanski et
al., 2007AJ....134.2418B 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:
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FileName Lrecl Records Explanations
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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
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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
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Bytes Format Units Label Explanations
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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
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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 2004AJ....127.3034M)
Note (3): Radial Velocities computed using Bochanski et al.
(2007AJ....133..531B 2007AJ....133..531B) templates
Note (4): Photometric distance calculated using r-z colors from Covey et al.
(2008arXiv0807.2452C 2008arXiv0807.2452C)
Note (5): Galactic extinction from Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S)
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Acknowledgements:
Andrew West, aaw(at)mit.edu
(End) Andrew A. West [MIT, USA], Patricia Vannier [CDS] 09-Sep-2008