arXiv subjects

M. D. Smith

Publications and source records attributed to M. D. Smith.

38 records · Page 3Linked to original sources

arXiv2003

Far-infrared photometry of deeply embedded outflow sources

We present far-infrared maps and spectroscopy for a number of deeply embedded protostellar objects (CepE, HH211-MM, IC1396W, L1157, L1211, and RNO15FIR) from data that we acquired with the ISO instruments PHOT and LWS. Several previously undetected deeply embedded sources are found in the vicinity of our targets. We determine temperatures and luminosities of seven objects and locate them on a Lbol-Tbol diagram - the equivalent to a Hertzsprung-Russell diagram for protostars. Their masses and ages, according to their location on tracks taken from our evolutionary model, are derived. L1211 and CepE appear to be intermediate mass objects which will reach final masses of about 3Mo, while the other sources are in or below the solar mass range. The derived ages of 15000 to 30000yr are consistent with their current Class0 state. A comparison of the luminosity of the associated outflows in the 1-0S(1) line of molecular hydrogen with the source properties (bolometric luminosity, bolometric temperature, and envelope mass) of 16 Class0 sources shows no statistically significant correlations. Nevertheless, the data are consistent with a scheme in which the outflow strength and protostar evolve simultaneously. We show that the relationship is partially disguised, however, by the local properties of the surrounding material, the extinction, and short-term flux variability.

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arXiv2003

Multi-wavelength spectroscopy of the bipolar outflow from Cepheus E

Cepheus E is the site of an exceptional example of a protostellar outflow with a very young dynamical age and extremely high near infrared luminosity. We combine molecular spectroscopic data from the submillimeter to the near infrared in order to interpret the rotational excitation of CO and the ro-vibrational excitation of H2. We conclude that C-type shocks with a paraboloidal bow shock geometry can simultaneously explain all the molecular excitations. Extinction accounts for the deviation of the column densities from local thermodynamic equilibrium. A difference in the extinction between the red and blue-shifted outflow lobes may account for the measured flux difference. The outflow is deeply embedded in a clump of density 10^5cm^-3, yet a good fraction of atomic hydrogen, about 40%, is required to explain the excitation and statistical equilibrium. We propose that this atomic component arises, self-consistently, from the dissociated gas at the apex of the leading bow shocks and the relatively long molecule reformation time. At least 20 bow shocks are required in each lobe, although these may be sub-divided into smaller bows and turbulent shocked regions. The total outflow mechanical power and cooling amounts to over 30L_\odot, almost half the source's bolometric luminosity. Nevertheless, only about 6% of the clump mass has been set in outward motion by the outflow, allowing a collapse to continue.

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