Velocity resolved spectroscopy of the Brackett gamma line emission of CRL 490 and M17 IRS 1

Abstract

High-resolution spectra of the Br-gamma lines of CRL 490 and M17 IRS 1 are presented, which give evidence for strong gas flows in the ionized regions associated with the objects. The Br-gamma line of CRL 490 is about 150 km/s wide at half-power, and is blueshifted by about 30 km/s with respect to the CO velocity of the surrounding molecular cloud. The Br-gamma line of M17 IRS 1 is about 135 km/s wide at half-power, and is blueshifted by about 24 km/s with respect to its molecular cloud. Mass loss rates appear to exceed 10 to the -7th solar mass per year, and modeling of the profiles shows that the Br-gamma lines are probably optically thick, which implies that estimates of the dust extinction to these objects on the basis of nebular recombination theory are invalid.