[Previous] | [Session 3] | [Next]
D. A. Golimowski (JHU), X. Fan (Princeton), T. R. Geballe (NOAO/Gemini), J. E. Gunn (Princeton), T. J. Henry (JHU), G. R. Knapp (Princeton), S. K. Leggett (JACH/UKIRT), R. H. Lupton, A. McDaniel (Princeton), E. Peng (JHU), D. P. Schneider (Penn State), M. A. Strauss (Princeton), Z. I. Tsvetanov, A. Uomoto, W. Zheng (JHU), Sloan Digital Sky Survey Collaboration
Since the inceptions of the DEep Near-Infrared Survey (DENIS), the Two Micron All Sky Survey (2MASS), and the Sloan Digital Sky Survey (SDSS), the known population of dwarfs with spectral types later than M has increased from 2 to over 100. These very cool dwarfs have fallen into two categories: ``L dwarfs,'' whose near-IR spectra feature carbon exclusively in the form of CO, and even cooler ``methane dwarfs'' (or ``T dwarfs''), whose near-IR spectra show carbon exclusively in CH4. No examples of dwarfs exhibiting the transition of carbon from CO to CH4 have heretofore been known. We have recently identified from SDSS imaging data three such transition dwarfs whose optical and near-IR colors span the gap between the known L and T dwarfs (see abstract by Geballe et al., this meeting). One of these dwarfs was detected in both the SDSS i' and z' bands. The two others were detected only in z', but were matched with second detections in 2MASS or subsequent SDSS images. All of the objects have SDSS i'-z' colors as red as those of previously detected Gl 229B-like methane dwarfs, but have near-IR colors between those of L dwarfs (J-K ~ 1.5) and cooler T dwarfs (J-K ~ 0). A preliminary estimate shows that the detection rate of transition dwarfs is similar to those of warmer L dwarfs and cooler T dwarfs.