The Circumstellar Structure of the Class I Protostar TMC-1 (IRAS 04381+2540) from Hubble Space Telescope NICMOS Data

Details The Circumstellar Structure of the Class I Protostar TMC-1 (IRAS 04381+2540) from Hubble Space Telescope NICMOS Data The Circumstellar Structure of the Class I Protostar TMC-1 (IRAS 04381+2540) from Hubble Space Telescope NICMOS Data

Feb 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006apj...637..811t&link_type=abstract

The Astrophysical Journal, Volume 637, Issue 2, pp. 811-822.

Astronomy and Astrophysics

Astronomy

11

Stars: Circumstellar Matter, Ism: Jets And Outflows, Stars: Formation, Stars: Individual (Tmc-1), Stars: Individual (Iras 04381+2540)

Scientific paper

The class I protostar TMC-1 (IRAS 04381+2540) is oriented favorably for determining the properties of its circumstellar envelope and outflow cavity. Deep, high spatial resolution Hubble Space Telescope (HST) NICMOS images at 1.6 μm exhibit both a narrow jet and a wide-angle conical outflow cavity. Model images of the scattered-light distribution fit the data well, reproducing the intensity level, cavity width, and observed limb brightening. The best-fit geometry for TMC-1 has a 45deg+/-5deg source inclination and an 80deg+/-5deg deprojected wind opening angle (full width). The age, normally a poorly known quantity, is well constrained; the protostar age, i.e., time since the onset of cloud collapse, is 1×105 yr to within a factor of 2. We offer a possible resolution to the well-known luminosity problem. By considering the efficiency of infall onto the protostar, we find that plausible parameters can give an efficiency, and hence accretion luminosity, as low as 10% of the value derived from the collapsing cloud core. The efficiency, together with a luminosity constraint, leads to a mass estimate that ranges from about 0.1 Msolar for high efficiency to 0.2 Msolar for low accretion efficiency onto the protostar. Similarly, the estimated mass accretion rate onto the protostar ranges over roughly (0.9-1.4)×10-6 Msolar yr-1, which is smaller than the (1.6-3.5)×10-6 Msolar yr-1 infall rate of the cloud. If low efficiency rates are prevalent for protostars, one important consequence is that it will take longer to assemble the central star than the time t=Min/M˙in, a time that assumes all of the infalling material lands on the protostar.

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