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Confirmation of the VeLLO L1148−IRS: star formation at very low (column) density
Kauffmann, J.,Bertoldi, F.,Bourke, T. L.,Myers, P. C.,Lee, C. W.,Huard, T. L. Blackwell Publishing Ltd 2011 Monthly notices of the Royal Astronomical Society Vol.416 No.3
<P><B>ABSTRACT</B></P><P>We report the detection of a compact (∼5 arcsec; about 1800 au projected size) CO outflow from L1148−IRS. This confirms that this <I>Spitzer</I> source is physically associated with the nearby (≈325 pc) L1148 dense core. Radiative transfer modelling suggests an internal luminosity of 0.08 to 0.13 L<SUB>⊙</SUB>. This validates L1148−IRS as a Very Low Luminosity Object (VeLLO; <I>L</I>≤ 0.1 L<SUB>⊙</SUB>). The L1148 dense core has unusually low densities and column densities for a star‐forming core. It is difficult to understand how L1148−IRS might have formed under these conditions. Independent of the exact final mass of this VeLLO (which is likely <0.24 M<SUB>⊙</SUB>), L1148−IRS and similar VeLLOs might hold some clues about the isolated formation of brown dwarfs.</P>
Kim, Hyo Jeong,Evans II, Neal J.,Dunham, Michael M.,Chen, Jo-Hsin,Lee, Jeong-Eun,Bourke, Tyler L.,Huard, Tracy L.,Shirley, Yancy L.,De Vries, Christopher IOP Publishing 2011 The Astrophysical journal Vol.729 No.2
<P>We present new observations of the CB130 region composed of three separate cores. Using the Spitzer Space Telescope, we detected a Class 0 and a Class II object in one of these, CB130-1. The observed photometric data from Spitzer and ground-based telescopes are used to establish the physical parameters of the Class 0 object. Spectral energy distribution fitting with a radiative transfer model shows that the luminosity of the Class 0 object is 0.14-0.16 L-circle dot, which is low for a protostellar object. In order to constrain the chemical characteristics of the core having the low-luminosity object, we compare our molecular line observations to models of lines including abundance variations. We tested both ad hoc step function abundance models and a series of self-consistent chemical evolution models. In the chemical evolution models, we consider a continuous accretion model and an episodic accretion model to explore how variable luminosity affects the chemistry. The step function abundance models can match observed lines reasonably well. The best-fitting chemical evolution model requires episodic accretion and the formation of CO2 ice from CO ice during the low-luminosity periods. This process removes C from the gas phase, providing a much improved fit to the observed gas-phase molecular lines and the CO2 ice absorption feature. Based on the chemical model result, the low luminosity of CB130-1 is explained better as a quiescent stage between episodic accretion bursts rather than being at the first hydrostatic core stage.</P>