Ammonia Images near Objects with Class 0 Spectral Energy Distributions

Details Ammonia Images near Objects with Class 0 Spectral Energy Distributions Ammonia Images near Objects with Class 0 Spectral Energy Distributions

Feb 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995ap%26ss.224...43w&link_type=abstract

Astrophysics and Space Science, Volume 224, Issue 1-2, pp. 43-46

Astronomy and Astrophysics

Astrophysics

3

Star Formation, Protostars, Circumstellar Matter, Class 0, Ammonia

Scientific paper

A shroud of cold dust shapes the ‘Class 0’ spectral distribution of the youngest stars. We have imaged a number of these objects in the inversion lines of ammonia to investigate the molecular circumstellar environment on thousand AU scales. Although the dust spectra of these objects resemble one another, a variety of physical characteristics occur in the sample. In some circumstellar environments, NGC1333IRAS4A and S106FIR, ammonia bearing gas clearly traces outflowing warm gas and a dense warm elongated structure immediately surrounding the young star. More commonly ammonia bearing gas shows only a weak association with any structure in immediate contact with the dusty near-stellar environment (NGC1333IRAS4B, IRAS4C, IRAS16293-2422 A and B) and in some cases no evidence can be found that ammonia occurs in the near-stellar environment in association with the dust at all (VLA1623, SM-2). The ammonia abundance in all objects must lie two orders of magnitude or so below its value in more extended cloud regions. The high molecular excitation conditions which mark the spectra of other molecules, such as formaldehyde, are invisible in ammonia spectra taken with beamsizes of projected diameters of ˜1000 AU.

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