VERY LARGE ARRAY OBSERVATIONS OF AMMONIA IN INFRARED-DARK CLOUDS. II. INTERNAL KINEMATICS

Journal Article · Mon Feb 20 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/746/2/174· OSTI ID:22011679

Ragan, Sarah E; Bergin, Edwin A ^[1]; Heitsch, Fabian ^[2]; Wilner, David ^[3]

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1. Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States)
2. Department of Physics and Astronomy, University of North Carolina-Chapel Hill, CB 3255 Phillips Hall, Chapel Hill, NC 27599 (United States)
3. Smithsonian Center for Astrophysics, Mail Stop 42, 60 Garden Street, Cambridge, MA 02138 (United States)

Infrared-dark clouds (IRDCs) are believed to be the birthplaces of rich clusters and thus contain the earliest phases of high-mass star formation. We use the Green Bank Telescope and Very Large Array maps of ammonia (NH{sub 3}) in six IRDCs to measure their column density and temperature structure (Paper 1), and here, we investigate the kinematic structure and energy content. We find that IRDCs overall display organized velocity fields, with only localized disruptions due to embedded star formation. The local effects seen in NH{sub 3} emission are not high-velocity outflows but rather moderate (few km s{sup -1}) increases in the linewidth that exhibit maxima near or coincident with the mid-infrared emission tracing protostars. These linewidth enhancements could be the result of infall or (hidden in NH{sub 3} emission) outflow. Not only is the kinetic energy content insufficient to support the IRDCs against collapse, but also the spatial energy distribution is inconsistent with a scenario of turbulent cloud support. We conclude that the velocity signatures of the IRDCs in our sample are due to active collapse and fragmentation, in some cases augmented by local feedback from stars.

• OSTI ID: 22011679
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 746; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AMMONIA
ENERGY SPECTRA
GALAXIES
KINETIC ENERGY
MASS
PROTOSTARS
STARS
TELESCOPES