A Survey of Optical and Near-Infrared Jets in Taurus Embedded Sources

GOMEZ, M., WHITNEY, B. A., KENYON, S. J.

ASTRONOMICAL JOURNAL

IOP PUBLISHING LTD

Lugar: Londres; Año: 1997 p. 1138 - 1153

0004-6256

We describe optical ([S II], 6732 Å) and near-infrared (H_2<, 2.122 μm) imaging observations of 22 embedded protostars in the Taurus-Auriga molecular cloud. Our survey identifies 4 new [S II] emission sources and 4 new H_2 sources. We detect three emission knots in both [S II] and H_2; one object with H_2< emission has no [S II] emission. These results increase the number of class I sources with optical or near-IR outflows to 13. We also detect [S II] emission in two additional class II sources, ZZ Tau IRS and IC 2087 IRS. When combined with previous results, the frequency of optical outflows among class H sources, ?10%, is much smaller than the frequency among class I sources, 60%. The large difference in the frequency of optical and molecular outflows indicates that outflow activity decreases with age among pre-main-sequence stars. The jets in the Taurus-Auriga protostars are poorly collimated, with multiple knots indicative of large opening angles, ?10°-40°. The image morphologies are complex and suggest a time dependence in the direction of ejection. A simple precessing jet can account for the sinusoidal chain of [S II] knots-HH 31-associated with 04248+2612. The precessing jets, together with the good alignment between the axes of the jets, molecular outflows, and reflection nebulae, support current models where jets produce molecular outflows and bipolar cavities in the dense infalling cloud cores surrounding class I sources.