TY - JOUR

T1 - Arcsecond-resolution submillimeter HCN imaging of the binary protostar IRAS 16293-2422

AU - Takakuwa, Shigehisa

AU - Ohashi, Nagayoshi

AU - Bourke, Tyler L.

AU - Hirano, Naomi

AU - Paul, T. P.Ho

AU - Jørgensen, Jes K.

AU - Kuan, Y. I.Jehng

AU - Wilner, David J.

AU - Yeh, Sherry C.C.

PY - 2007/6/10

Y1 - 2007/6/10

N2 - 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.

AB - 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.

KW - ISM: individual (IRAS 16293-2422)

KW - ISM: molecules

KW - Stars: formation

UR - http://www.scopus.com/inward/record.url?scp=34347239286&partnerID=8YFLogxK

U2 - 10.1086/513589

DO - 10.1086/513589

M3 - Journal article

AN - SCOPUS:34347239286

VL - 662

SP - 431

EP - 442

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1 I

ER -