COLORS AND KINEMATICS OF L DWARFS FROM THE SLOAN DIGITAL SKY SURVEY

We present a sample of 484 L dwarfs, 210 of which are newly discovered from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic database. We combine this sample with known L dwarfs to investigate their izJHKS colors. Our spectroscopically selected sample has ~0.1 mag bluer median J – KS color at a given spectral type (for L0-L4) than previously known L dwarfs, which reflects a bias toward redder L dwarfs in past selection criteria. We present photometric distance relations based on i – z and i – J colors and derive distances to our L dwarf sample. We combine the distances with SDSS/2MASS proper motions in order to examine the tangential velocities. For the majority of our spectroscopic sample, we measured radial velocities and present three-dimensional kinematics. We also provide Hα detections for the fraction of our sample with sufficient quality spectra. Comparison of the velocities of our L dwarf sample to a kinematic model shows evidence for both cold and hot dynamical populations, consistent with young and old disk components. The dispersions of these components are similar to those found for M dwarfs. We also show that J – KS color is correlated with velocity dispersion, confirming a relationship between J – KS color and age.

[1]  et al,et al.  Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: The Effects of Temperature, Clouds, and Gravity , 2004, astro-ph/0402451.

[2]  A. A. Henden,et al.  Astrometry and photometry for cool dwarfs and brown dwarfs , 2002 .

[3]  et al,et al.  Toward Spectral Classification of L and T Dwarfs: Infrared and Optical Spectroscopy and Analysis , 2001, astro-ph/0108443.

[4]  Meeting the Cool Neighbors. X. Ultracool Dwarfs from the 2MASS All-Sky Data Release , 2008 .

[5]  T. Barman,et al.  A Sample of Very Young Field L Dwarfs and Implications for the Brown Dwarf “Lithium Test” at Early Ages , 2008, 0808.3153.

[6]  B. Burningham,et al.  Ultra-cool dwarfs: new discoveries, proper motions, and improved spectral typing from SDSS and 2MASS photometric colors , 2009, 0902.2798.

[7]  John E. Gizis,et al.  Brown Dwarfs and the TW Hydrae Association , 2002, astro-ph/0204342.

[8]  I. Reid,et al.  Trigonometric parallaxes and the HR diagram at the bottom of the main sequence , 1995 .

[9]  The First Direct Measurements of Surface Magnetic Fields on Very Low Mass Stars , 2006, astro-ph/0610365.

[10]  K. Covey,et al.  Spectroscopic Properties of Cool Stars in the SDSS , 2004 .

[11]  J. Brinkmann,et al.  Spectroscopic Properties of Cool Stars in the Sloan Digital Sky Survey: An Analysis of Magnetic Activity and a Search for Subdwarfs , 2004, astro-ph/0403486.

[12]  M. Giampapa,et al.  Stellar coronae at the end of the main sequence: A Rosat survey of the late M dwarfs , 1993 .

[13]  M. E. Muller,et al.  A Note on the Generation of Random Normal Deviates , 1958 .

[14]  D. Marquardt.  An Algorithm for Least-Squares Estimation of Nonlinear Parameters , 1963 .

[15]  David R. Soderblom,et al.  Calculating Galactic Space Velocities and Their Uncertainties, with an Application to the Ursa Major Group , 1987 .

[16]  T. Roellig,et al.  Discovery of Two Nearby Peculiar L Dwarfs from the 2MASS Proper-Motion Survey: Young or Metal-Rich? , 2008, 0806.1059.

[17]  Four Nearby L Dwarfs , 1999, astro-ph/9909336.

[18]  Alexander S. Szalay,et al.  Sloan digital sky survey: Early data release , 2002 .

[19]  M. Shara,et al.  THE BROWN DWARF KINEMATICS PROJECT I. PROPER MOTIONS AND TANGENTIAL VELOCITIES FOR A LARGE SAMPLE OF LATE-TYPE M, L, AND T DWARFS , 2008, 0809.3008.

[20]  Wm. A. Wheaton,et al.  2MASS All Sky Catalog of point sources. , 2003 .

[21]  J. A. Smith,et al.  SDSS data management and photometric quality assessment , 2004 .

[22]  Suzanne L. Hawley,et al.  The Palomar/MSU Nearby Star Spectroscopic Survey. IV. The Luminosity Function in the Solar Neighborhood and M Dwarf Kinematics , 2002 .

[23]  K. Abazajian,et al.  THE SEVENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY , 2008, 0812.0649.

[24]  Johns Hopkins University,et al.  Characterization of M, L, and T Dwarfs in the Sloan Digital Sky Survey , 2002, astro-ph/0204065.

[25]  R. J. Wainscoat,et al.  Space Velocities of L- and T-Type Dwarfs , 2007, 0706.0784.

[26]  et al,et al.  The Sloan Digital Sky Survey Photometric Camera , 1998, astro-ph/9809085.

[27]  et al,et al.  L Dwarfs Found in Sloan Digital Sky Survey Commissioning Imaging Data , 2000 .

[28]  Ansgar Reiners,et al.  Chromospheric Activity, Rotation, and Rotational Braking in M and L Dwarfs , 2008, 0805.1059.

[29]  Andrew A. West,et al.  Stellar SEDs from 0.3 to 2.5 μm: Tracing the Stellar Locus and Searching for Color Outliers in the SDSS and 2MASS , 2007, 0707.4473.

[30]  M. Cushing,et al.  AN INFRARED HIGH PROPER MOTION SURVEY USING THE 2MASS AND SDSS : DISCOVERY OF M, L, AND T DWARFS , 2008, 0809.0697.

[31]  S. Seager,et al.  Clouds and chemistry: Ultracool dwarf atmospheric properties from optical and infrared colors , 2002 .

[32]  Walter A. Siegmund,et al.  The Second Data Release of the Sloan Digital Sky Survey , 2004 .

[33]  David G. Monet,et al.  U.S. Naval Observatory CCD parallaxes of faint stars. I - Program description and first results , 1992 .

[34]  S. Schmidt,et al.  Activity and Kinematics of Ultracool Dwarfs, Including an Amazing Flare Observation , 2007, astro-ph/0701055.

[35]  Walter Dehnen,et al.  Local stellar kinematics from Hipparcos data , 1997 .

[36]  G. Bruce Berriman,et al.  A Cross-Match of 2MASS and SDSS: Newly Found L and T Dwarfs and an Estimate of the Space Density of T Dwarfs , 2007, 0710.4157.

[37]  M. Fukugita,et al.  The Sloan Digital Sky Survey Photometric System , 1996 .

[38]  Russel J. White,et al.  Multiepoch Radial Velocity Observations of L Dwarfs , 2007, 0705.3901.

[39]  Spectroscopic rotation velocities of L dwarfs from VLT/UVES and their comparison with periods from photometric monitoring , 2004, astro-ph/0403013.

[40]  Discovery of a nearby L–T transition object in the Southern Galactic plane , 2007, astro-ph/0703808.

[41]  Dagny L. Looper,et al.  Clouds, Gravity, and Metallicity in Blue L Dwarfs: The Case of 2MASS J11263991–5003550 , 2007, 0710.1123.

[42]  J. Bochanski,et al.  CONSTRAINING THE AGE–ACTIVITY RELATION FOR COOL STARS: THE SLOAN DIGITAL SKY SURVEY DATA RELEASE 5 LOW-MASS STAR SPECTROSCOPIC SAMPLE , 2007, 0712.1590.

[43]  J. Gizis.  A pr 2 00 2 Brown Dwarfs and the TW Hya Association , 2002 .

[44]  David A. Golimowski,et al.  A Unified Near-Infrared Spectral Classification Scheme for T Dwarfs , 2006 .

[45]  David G. Monet,et al.  67 Additional L Dwarfs Discovered by the Two Micron All Sky Survey , 2000, astro-ph/0003317.

[46]  David G. Monet,et al.  Dwarfs Cooler than “M”: The Definition of Spectral Type “L” Using Discoveries from the 2-Micron All-Sky Survey (2MASS) , 1999 .

[47]  J. Bochanski,et al.  DISCOVERY OF AN UNUSUALLY BLUE L DWARF WITHIN 10 pc OF THE SUN , 2009, 0912.3565.

[48]  B. Yanny,et al.  The Sloan Digital Sky Survey monitor telescope pipeline , 2006 .

[49]  D. A. Golimowski,et al.  Preliminary Parallaxes of 40 L and T Dwarfs from the US Naval Observatory Infrared Astrometry Program , 2004 .

[50]  Bhasker K. Moorthy,et al.  The First Data Release of the Sloan Digital Sky Survey , 2003, astro-ph/0305492.

[51]  Kenneth Levenberg.  A METHOD FOR THE SOLUTION OF CERTAIN NON – LINEAR PROBLEMS IN LEAST SQUARES , 1944 .

[52]  James Liebert,et al.  Meeting the Cool Neighbors. V. A 2MASS-Selected Sample of Ultracool Dwarfs , 2003, astro-ph/0307429.

[53]  A. Burgasser,et al.  YOUNG L DWARFS IDENTIFIED IN THE FIELD: A PRELIMINARY LOW-GRAVITY, OPTICAL SPECTRAL SEQUENCE FROM L0 TO L5 , 2008, 0812.0364.

[54]  M. Osorio,et al.  Two T dwarfs from the UKIDSS early data release , 2007, astro-ph/0702534.

[55]  J. Bochanski,et al.  Exploring the Local Milky Way: M Dwarfs as Tracers of Galactic Populations , 2006, 0708.0044.

[56]  Pennsylvania State University,et al.  Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey , 2006, astro-ph/0601089.

[57]  E. al.,et al.  The Sloan Digital Sky Survey: Technical summary , 2000, astro-ph/0006396.

[58]  Dagny L. Looper,et al.  Discovery of 11 New T Dwarfs in the Two Micron All Sky Survey, Including a Possible L/T Transition Binary , 2007, 0706.1601.

[59]  D. York,et al.  L Dwarfs Found in Sloan Digital Sky Survey Commissioning Data. II. Hobby-Eberly Telescope Observations , 2001, astro-ph/0110273.

[60]  E. Berger,et al.  PERIODIC RADIO AND Hα EMISSION FROM THE L DWARF BINARY 2MASSW J0746425+200032: EXPLORING THE MAGNETIC FIELD TOPOLOGY AND RADIUS OF AN L DWARF , 2008, 0809.0001.

[61]  J. Gunn,et al.  A Photometricity and Extinction Monitor at the Apache Point Observatory , 2001, astro-ph/0106511.

[62]  A. Burrows,et al.  The Spectra of T Dwarfs. II. Red Optical Data , 2003, astro-ph/0305139.

[63]  Thierry Forveille,et al.  Spectroscopic Classification of Late-M and L Field Dwarfs , 1999 .

[64]  A. Upgren,et al.  An analysis of parallaxes determined in two coordinates , 1980 .

[65]  New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence , 2000, astro-ph/0004361.

[66]  R. Lupton,et al.  Astrometric Calibration of the Sloan Digital Sky Survey , 2002, astro-ph/0211375.

[67]  James Liebert,et al.  Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field , 2006, astro-ph/0609648.

[68]  Michael C. Liu,et al.  SDSS J141624.08+134826.7: A NEARBY BLUE L DWARF FROM THE SLOAN DIGITAL SKY SURVEY , 2009, 0912.3796.

[69]  G. Basri,et al.  Rotation and Activity in Mid-M to L Field Dwarfs , 2002, astro-ph/0201455.