Oral Presentation
ALMA Observations of Spiral Accretion Flows towards Class 0 source VLA1623A with a Keplerian disk
Presenter: Shih-Ping Lai (National Tsing Hua University)
Studying the accretion flows toward Class 0 sources is an important step for understanding how the protostars are assembled in the early stage of star formation. Here we investigate the accretion flows in an extremely young Class 0 protostar VLA1623A with a Keplerian disk likely just formed (Murillo et al. 2013). The accretion flows are commonly seen in the MHD numerical simulations (Li et al. 2014, Seifried et al. 2015); however, it is rarely observed in Class 0 sources. Here we report our discovery of ~5000 AU long accretion flows toward VLA1623 in C18O emission with ALMA observations. ‘Dendrogram’ algorithm (Goodman et al. 2009) are used to identify the accretion flows, and we find the three brightest ‘branches’ and their associated ‘leaves’ likely correspond to the spiral structure flowing toward the central young cluster. The fourth brightest branch may correspond to an outflow associated with VLA1623W. We further compare the PV diagrams of the three accretion flows to the CMU model (Ulrich 1976; Cassen & Moosman 1981) which describe the velocity structure of the gas accreting to the central protostar with constant angular momentum, and we find that our identified branch structures well match with the CMU model.
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