Radio Spectral Indices of the Powering Sources of Outflows

Abstract

Eight regions containing molecular or HH out—ows (Mon R2E, S287, L1654, L483, PV Cephei, L1203, L1251A, and CB 247) have been observed with the VLA at 6 cm, and total of 55 sources have been detected above 5 p level. By combining our observations at 6 cm with previous data obtained at 3.6 cm, we estimate the spectral indices of the sources in the —elds. For 32 of the sources we discriminate the sign of the spectral index and thus, we obtain information about the nature of the emission. For seven out—ows (Mon R2E, S287-B, L1654, L483, PV Cephei, L1203, and L1251A) we found at least central source with an spectral index consistent with thermal free-free emission from thermal radio jets. Multiple sources, separated D10A, are found near the center of the Mon R2E, S287-B, L1654, and L1251A out—ows. In the case of S287-B we found two sources that are valid candidates to drive the S287-B molecular out—ow and could be related to the out—ow excitation. Under the assumption that the observed emission arises from thermal radio jets, we discuss the mechanism responsible for the ionization and the constraints that introduces on their physical parameters, and we estimate that the —ow of ionized material has to originate at few AU from the exciting star. Most of the remaining, noncentral, sources are characterized by negative spectral indices ( a [0.1) and are probably nonthermal background objects unrelated to the studied star-forming regions.