Dense molecular shocks and accretion onto protostellar disks

Details Dense molecular shocks and accretion onto protostellar disks Dense molecular shocks and accretion onto protostellar disks

Jun 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...428..170n&link_type=abstract

Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 428, no. 1, p. 170-185

Astronomy and Astrophysics

Astrophysics

71

Accretion Disks, Interstellar Matter, Molecular Gases, Protostars, Shock Wave Propagation, Star Formation Rate, Stellar Mass Accretion, Carbon Monoxide, Granular Materials, Hydroxyl Emission, Water Vapor

Scientific paper

We have examined the physical and chemical processes which accompany the propagation of a J-type shock through molecular astrophysical gas of density 107.5 - 1012 H nuclei per cu cm. Our study is primarily relevant to the high-density accretion shocks which are associated with the supersonic infall of material during the collapse of a molecular cloud core to form a protostar. We have carried out a general parameter study to determine the characteristic infrared emission spectrum of dense molecular shocks and the extent of grain destruction within such shocks as a function of relevant shock parameters. Accretion shocks with mass accretion rates approximately greater than 10-5 solar masses per y are plausible sources of the CO v = 2-0 vibrational band emission observed in many protostars, at least for sources of moderate CO v = 2-0 luminosity (approximately less than few x 1023 W). Rovibrational emissions from H2O and OH are also predicted to be luminous in dense molecular accretion shocks. Vaporization is the dominant mechanism of grain destruction within dense molecular shocks, leading to the efficient removal of those grains which are heated to their vaporization temperature by the combined effects of radiative heating, drag heating, and thermal heating by the hot postshock gas. The criteria for grain vaporization are obtained for grains composed of several different materials: metallic iron, silicate, troilite, refractory organic materials, volatile organic materials, and water ice.

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