July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 1 Discovery of Brown Dwarfs With Virtual Observatories : Why Get Excited Over One Brown Dwarf? G. Bruce Berriman (IPAC, Caltech) J. Davy Kirkpatrick (IPAC, Caltech) Robert Hanisch (STScI) Alex Szalay (JHU) Roy Williams (CACR, Caltech)

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 2 Science Driver for Brown Dwarf Search Purpose of pilot study –Cross-match 2MASS & SDSS to find candidate brown dwarfs that are cooler and more distant (>12pc) than either survey alone can reliably find. History –2MASS and SDSS have revolutionized our knowledge of the coolest “stellar” spectral types, L and T. Mid-T dwarfs detected out to ~12pc. –Beyond these limits, SDSS-detected T dwarfs become z’-only detections. Most z’-only detections from SDSS are unreliable (Fan et al. 2001). –Similarly, cooler T dwarfs are expected to become J- only detections in 2MASS. Most J-only detections from 2MASS are unreliable (Burgasser 2001).

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 3 As a T dwarf becomes cooler (i.e., methane and water absorptions increase) or more distant… –SDSS detects it only at z’ band –2MASS detects it only at J band

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 4 What is the Best Way to Cross-Match Large Catalogs? Cross-matching is I/O intensive  performance is severely bandwidth limited Cross-matching best performed by replicating remote data sets at one site cf. Cross-matching over a network. –10,225,897 SDSS EDR sources & 454,516 2MASS 2IDR sources –90 seconds locally vs. 13,500 seconds over 100 Mbits/second network

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 5 Cross-Match Statistics 326,020 cross-matched candidate pairs in the 2MASS IDR2 and SDSS EDR overlap (~150 sq deg; ~0.4% of sky) 2889 objects with z-J>2.75  late-L to T dwarf candidates with separations of <3” Nine with separations of 1.0. –Two are known brown dwarfs –Four were likely spurious detections –Three are new candidate brown dwarfs

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 6 Brown Dwarfs & Candidates ObjectTypeJJ-K S z-J 2MASSI J Known L MASSI J Known T MASSI J NEW NEW L MASSI J Suspected L MASSI J Suspected L/T

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 7 2MASS KSKS J The Wee Broon Beastie H

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 8 Keck LRIS Spectrum of 2MASSI J

July 17 & 18, 2003 JD08: Large Telescopes and Virtual Observatories 9 The Next Step: Sloan DR1 vs. 2MASS All Sky DR1 covers 2099 square degrees 53,000, 000 objects Sloan DR1 - Imaging Sky Coverage Both Surveys publicly released Spring 2003 Larger area gives us much better chance of finding cooler objects, not just more distant ones