EPoS Contribution
EPoS Contribution
Constraining the Infalling Envelope Models of Embedded Protostars: BHR 71 and its Hot Corino

Yao-Lun Yang
RIKEN/UVa, Charlottesville, US
The collapse of the protostellar envelope results in the growth of the protostar and the development of a protoplanetary disk, playing a critical role during the early stages of star formation. Characterizing the gas infall in the envelope constrains the dynamical models of star formation. We present unambiguous signatures of infall, probed by the red-shifted absorption against continuum from optically thick molecular lines, toward an isolated embedded protostar, BHR 71 IRS1. The three dimensional radiative transfer calculations indicate that a slowly rotating infalling envelope model following the ``inside-out'' collapse reproduces the observations of both HCO+ J=4-3 and CS J=7-6 lines, and the low velocity emission of the HCN J=4-3 line. The envelope has a model-derived age of 12000+/-3000 years after the initial collapse. The synthetic position-velocity diagrams have a more symmetric morphology compared to the observations, suggesting a higher rotation at the inner 100 au than that of our model. Our ALMA observations serendipitously discover the emission of complex organic molecules (COMs) concentrated within a radius of 100 au, indicating that BHR 71 IRS1 harbors a hot corino. Eight species of COMs are identified, including methanol, methyl formate, and ethanol. The emission of methyl formate and 13C-methanol shows a clear velocity gradient within a radius of 50 au, hinting at an unresolved Keplerian rotating disk. Our modeling demonstrates that a simple "inside-out" collapsing envelope sufficiently reproduces the observed infall signature but underestimates the rotation at the disk-forming region. I will also describe our scheduled follow-up ALMA program that aims to empirically measure the infall velocity as a function of radius using multiple transitions of HCO+ at high frequency.
Caption: The line profiles (top row) and position-velocity diagrams (bottom row) of the HCO+ J=4-3, HCN J=4-3, and CS J=7-6 lines (left to right). The observed spectra are shown in blue, while the synthetic line profiles are shown in orange. Typical infall signatures are detected at the HCO+ and HCN lines. At the bottom row, the observed PV diagrams are shown in magenta contours, while the synthetic observations are shown as the colored images. The white cross incidates the spectral and spatial resolutions of the observations.
Collaborators:
N. Evans, UT-Austin, US
A. Smith, MIT, US
J.-E. Lee, KyungHee U., KR
J. Tobin, NRAO, US
S. Terebey, Cal State LA, US
H. Calcutt, Chalmers, SE
J. Jorgensen, U Copenhagen, DK
Key publication

Suggested Session: Cores2Disks