A Search for Optical Outflows from Brown Dwarfs in the Chamaeleon I Molecular Cloud

Abstract

A deep and wide-field HH object survey has been carried out towardthe Chamaeleon I (Cha I) molecular cloud with a sky coverage of 1degrees x 2 degrees, which embraces the entire Cha I molecular cloud.In total, 18 HH objects have been detected, including the previouslyknown objects HH 48-51. The newly discovered HH objects are namedHH 905-918. The possible exciting sources of the detected HH objectsare discussed based on the morphology and locations of the HH objectsand on results of previous surveys. Although more than 40 brown dwarfsor brown dwarf candidates have been detected in Cha I, no compellingevidence for optical outflows from brown dwarfs has been found inour images at the detection limit of 2.3 x 10(-20) W m(-2) arcsec(-2)(3 sigma) in the {[}S II] lambda lambda 6717, 6731 emission. Thetypical peak brightness of HH objects in Cha I is about 20 timesabove our detection limit. We conclude that the brightness of opticaloutflows from substellar objects should be about 20 times lower thanthat of outflows from young solar-type stars if all the HH objectsdetected in Cha I are driven by young stars. In three cases - i.e.,HH 51, 908, and 909 - however, there are hints of a connection betweenHH objects and the nearby brown dwarfs or very low mass stars.