SCUBA Image of the L1551 Starburst Region

Doug Johnstone - Herzberg Institute of Astrophysics, National Research Council of Canada>
Gerald Moriarty Schieven - Joint Astronomy Centre/National Research Council of Canada
& John Bally - University of Colorado

SII image of the L1551 region with contours of 850µm emission overlaid.

The Taurus molecular cloud complex, one of the closest star-forming regions at 140pc, is well-known for its low star-formation efficiency, and sparce low-mass stars. The exception is the L1551 dark cloud which is the nearest, one of the best-known, and well studied region of low mass star formation. This 40 M_sol dark molecular cloud contains at least one class 0/I protostar (L1551 NE), the archetypical class I outflow source (L1551 IRS5), several T Tauri (class II) stars including HL/XZ Tau, and weak T Tauri (class III) stars including UX Tau. Indeed, X-ray observations have identified at least 38 young stars in the L1551 cloud.. The large number of young protostars in a small region is more reminiscent of a starburst cloud like the ρ Ophiuchi complex, than the rest of the Taurus cloud complex.

Many of these young protostars are very active. Three (or possibly four) bipolar molecular outflows are known, including the archetypical L1551 IRS5 flow, at least two jets emanate from the cluster around HL Tau, and strings of Herbig Haro objects have been determined (through proper motion studies) to originate from several sources.

Nevertheless, this extemely active and well-studied region has not been the subject of a large-scale SCUBA study. We have mapped a 20'x20' centered on IRS5. In addition, because IRS5 is often used as a pointing source and HL Tau is one of our secondary calibrator sources, we used data mining to extract all SCUBA data of this region ever taken from the archive and included those in our data reduction. Image reconstruction was done using the matrix inversion method described by Johnstone et al (2000, ApJS, 131, 505), and large-scale (and probably unreal) ripple was removed using unsharp masking.

The amount of structure visible in the image is remarkable. Above left is a close-up of the L1551 IRS5 region (full size click here. The two continuum peaks are L1551 IRS5 (right) and L1551 NE (left). The IRS5 outflow also shows up in 850µm in select regions, particularly at a strong bow shock. To the right is a close-up of the HL/XZ Tau region.

Analysis of these data is in progress, and a paper is in preparation.

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