The W Band Survey: Searching for Water-bearing Young Brown Dwarfs in the Rho Oph Molecular Cloud Complex

Tanvi Sharma^1*, Wen Ping Chen¹, W Band team membes²

¹Institute of Astronomy, National Central University, 300 Zhongda Road, Zhongli, Taoyuan, Taiwan
²W band team, UK

* Presenter:Tanvi Sharma, email:stanvi406@gmail.com

Brown dwarfs unlike stars have masses too low to sustain hydrogen fusion in their cores. It is still an open question whether brown dwarfs, like stars, form by gravitational contraction of molecular clouds or, like exoplanets, by condensation within young circumstellar disks. The cool atmospheres (< 2800 K) of brown dwarfs are characterized by molecullar bands, such as due to water or methane in their spectra. Here we present our effort to identify brown dwarf candidates in star-forming regions, i.e., when these objects are in infancy and hence are relatively hot and bright. By imaging photometry on-and-off the water absorption band near 1.45 microns, using a custom-made spectral (W) filter adapted to the CFHT/WIRCam, together with data taken at J and H bands, we are able to distinguish water-bearing brown dwarfs against reddened field stars. We report here the list of brown dwarf candidates in the Rho Oph cloud thus identified. Once spectroscopically confirmed, our brown dwarf sample will be valuable to compare with the known young stars in the same region to shed light on the formation processes and early evolution in the broad stellar to substellar mass ramge. We also present additional diagnosis of young brown dwarf membership against field contamination via kinematics. The proper motion is measured with deep multi-epoch CFHT/WIRCam images which span some 12 year in time and reach much fainter than Gaia does. The confirmed substellar population serves as the critical first step to quantify early evolution (1—2 Myr) of cool atmospheres (e.g., dust condensation).

Keywords: substellar objects, brown dwarfs, W-Band, reddening insensitive index