Arcsecond-resolution submillimeter HCN imaging of the binary protostar IRAS 16293-2422

Shigehisa Takakuwa, Nagayoshi Ohashi, Tyler L. Bourke, Naomi Hirano, T. P.Ho Paul, Jes K. Jørgensen, Y. I.Jehng Kuan, David J. Wilner, Sherry C.C. Yeh

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Abstract

With the Submillimeter Array (SMA) we have made high angular resolution (∼1″ = 160 AU ) observations of the protobinary system IRAS 16293-2422 in the HCN (4-3), HC15N (4-3), and 354.5 GHz continuum emission. The HCN (4-3) line was also observed using the JCMT to supply missing short-spacing information. The submillimeter continuum emission is detected from the individual binary components of source A in the southeast and source B in the northwest, with a separation of ∼5″. The optically thin HC 15N (4-3) emission taken with the SMA has revealed a compact (∼500 AU) flattened structure (P.A. = -16°) at source A. This compact structure shows a velocity gradient along the projected minor axis, which can be interpreted as an infalling gas motion. Our HCN image including the short-spacing information shows an extended (∼3000 AU ) circumbinary envelope, as well as the compact structure at source A. A toy model consisting of a flattened structure with radial infall toward a 1 M central star reproduces the HCN/HC15N position-velocity diagram along the minor axis of the HC15N emission. In the extended envelope there is also a northeast (blue) to southwest (red) velocity gradient across the binary alignment, which is likely to reflect gas motion in the swept-up dense gas associated with the molecular outflow from source A. Only a weak and narrow (∼2 km s-1) compact HC15N emission is associated with source B, where no clear molecular outflow is identified, suggesting the different evolutionary starges between sources A and B. Our study demonstrates the importance of adding short-spacing data to interferometer data in order to probe the detailed structure and kinematics of low-mass protostellar envelopes.

Original languageEnglish
Pages (from-to)431-442
Number of pages12
JournalAstrophysical Journal
Volume662
Issue number1 I
DOIs
Publication statusPublished - 2007 Jun 10

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Keywords

  • ISM: individual (IRAS 16293-2422)
  • ISM: molecules
  • Stars: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Takakuwa, S., Ohashi, N., Bourke, T. L., Hirano, N., Paul, T. P. H., Jørgensen, J. K., Kuan, Y. I. J., Wilner, D. J., & Yeh, S. C. C. (2007). Arcsecond-resolution submillimeter HCN imaging of the binary protostar IRAS 16293-2422. Astrophysical Journal, 662(1 I), 431-442. https://doi.org/10.1086/513589