Images of star-forming regions. II - The circumstellar environment of L1551 IRS 5

Abstract

The purpose of this investigation is to extend the understanding of the detailed wavelength-dependent morphology of L1551 IRS 5, by making use of high-resolution optical imaging and image-enhancement techniques. The authors compare the optical structures and positions with those observed or inferred at other wavelengths, and find that there is a marked displacement between the optical and radio centroids. This result is consistent with a conclusion that scattering dominates the observed emission associated with "IRS 5" from visible wavelengths out to at least 2 μm. The authors also find evidence for a marked bend in outflow direction in the inner few arcseconds, and they examine and speculate on two possible explanations for that effect: jet-nozzle precession of a dynamically decoupled inner disk, and/or a dependence in collimating mechanism on distance from the core source. In addition, the authors have detected proper motion of the most prominent Hα knot in the IRS 5 jet at ≡1arcsec/yr, which leads to a tangential velocity of order 700 km/s. Finally, the IRAS source L1551-NE has been detected as an optical pointlike source at 8000 Å.