Exteremely High Velocity Outflows

Abstract

Extremely high velocity (EHV) wings, with full widths of 72 to 140 km/s, are seen on the CO J=3-2 lines toward W3 IRS 5, GL 490, NGC 2071, W28 A2, GL 2591, S140, and Cepheus A. The results of our survey suggest that EHV wings are common around infrared sources of moderate to high luminosity (500 to 4x10^5 Lsun) in dense regions. Line ratios imply that the EHV gas is usually optically thin and warm. Characteristic velocities range from 20 to 40 km/s, yielding timescales of 1600-4200 yr. Since most sources in this study are producing some ionizing photons, these short timescales suggest that neutral winds coexist with ionizing photons. We examined two possible sources for the EHV CO emission: a neutral stellar wind; and swept-up or entrained molecular gas. Neither can be ruled out. If the high-velocity (HV) gas is swept up by a momentum-conserving stellar wind traced by the extremely high velocity CO emission, most of the C in the winds from luminous objects cannot be in CO. If the EHV and HV forces are equal, the fraction of C in a form other than CO increases with source luminosity and with the production rate of ionizing photons.