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Astron. Astrophys. 325, 542-550 (1997)

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1. Introduction

Herbig-Haro (HH) objects are shocks which trace bipolar supersonic outflows from young stars in the process of building up their masses through accretion. They are ubiquitous in star forming molecular clouds, and their presence signals a recent nearby star birth.

Most HH driving energy sources are deeply embedded in placental material. In an earlier paper, Reipurth et al. (1993a, hereafter Paper I) obtained 1300 µm photometry of 59 HH energy sources, and demonstrated that they are surrounded by considerable amounts of cold (36K) circumstellar material, typically in the range from a few tenths to several solar masses. It was concluded that HH energy sources, as a class, are among the youngest stellar objects known.

With the advent of sensitive array detectors on large radio telescopes it has become feasible to map the structure and environment of large numbers of newborn stars in the mm radio continuum. Interferometer maps are less ideal for this, partly because of practical time constraints, but also because extended emission tends to be filtered out. In this paper we discuss the structure of the massive dust envelopes of HH energy sources based on detailed 1300 µm maps of 20 of the sources we detected in Paper I.

The large areas covered by our maps have permitted us to additionally search for hitherto unknown protostellar sources in the neighborhood of the central HH energy sources. Because star formation tends to occur in groups, we believe that the most effective way of finding such protostars is to survey the cloud regions immediately around very young stars, and this search strategy has been borne out by the discovery of several protostellar candidates in our recent surveys (Chini et al. 1993, Reipurth et al. 1996).

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998