A cross-match of 2MASS and SDSS. II. Peculiar l dwarfs, unresolved binaries, and the space density of T dwarf secondaries.
GEISSLER K., METCHEV S., KIRKPATRICK J.D., BERRIMAN G.B. and LOOPER D.
Abstract (from CDS):
We present the completion of a program to cross-correlate the Sloan Digital Sky Survey Data Release 1 (SDSS DR1) and Two-Micron All-Sky Survey (2MASS) Point Source Catalog in search for extremely red L and T dwarfs. The program was initiated by Metchev and collaborators, who presented the findings on all newly identified T dwarfs in SDSS DR1 and estimated the space density of isolated T0-T8 dwarfs in the solar neighborhood. In the current work, we present most of the L dwarf discoveries. Our red-sensitive (z - J ≥ 2.75 mag) cross-match proves to be efficient in detecting peculiarly red L dwarfs, adding two new ones, including one of the reddest known L dwarfs. Our search also nets a new peculiarly blue L7 dwarf and, surprisingly, two M8 dwarfs. We further broaden our analysis to detect unresolved binary L or T dwarfs through spectral template fitting to all L and T dwarfs presented here and in the earlier work by Metchev and collaborators. We identify nine probable binaries, six of which are new and eight harbor likely T dwarf secondaries. We combine this result with current knowledge of the mass ratio distribution and frequency of substellar companions to estimate an overall space density of 0.005-0.05/pc3 for individual T0-T8 dwarfs.