DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA

Abstract

We have conducted a 4030-square-deg near-infrared proper motion survey using\nmulti-epoch data from the Two Micron All-Sky Survey (2MASS). We find 2778\nproper motion candidates, 647 of which are not listed in SIMBAD. After\ncomparison to DSS images, we find that 107 of our proper motion candidates lack\ncounterparts at B-, R-, and I-bands and are thus 2MASS-only detections. We\npresent results of spectroscopic follow-up of 188 targets that include the\ninfrared-only sources along with selected optical-counterpart sources with\nfaint reduced proper motions or interesting colors. We also establish a set of\nnear-infrared spectroscopic standards with which to anchor near-infrared\nclassifications for our objects. Among the discoveries are six young field\nbrown dwarfs, five "red L" dwarfs, three L-type subdwarfs, twelve M-type\nsubdwarfs, eight "blue L" dwarfs, and several T dwarfs. We further refine the\ndefinitions of these exotic classes to aid future identification of similar\nobjects. We examine their kinematics and find that both the "blue L" and "red\nL" dwarfs appear to be drawn from a relatively old population. This survey\nprovides a glimpse of the kinds of research that will be possible through\ntime-domain infrared projects such as the UKIDSS Large Area Survey, various\nVISTA surveys, and WISE, and also through z- or y-band enabled, multi-epoch\nsurveys such as Pan-STARRS and LSST.\n