* Astronomy

Title: A Virialised Filamentary Infrared Dark Cloud
Authors: Audra K. Hernandez (1), Jonathan C. Tan (2), Jouni Kainulainen (3), Paola Caselli (4), Michael J. Butler (5), Izaskun Jimenez-Serra (6), Francesco Fontani (7) ((1) Department of Astronomy, University of Wisconsin-Madison, (2) Departments of Astronomy & Physics, University of Florida, (3) Max-Planck-Institute for Astronomy (4) School of Physics & Astronomy, University of Leeds (5) Department of Astronomy, University of Florida, (6) Harvard-Smithsonian Center for Astrophysics, (7) INAF - Osservatorio Astrofisico di Arcetri)

The initial conditions of massive star and star cluster formation are expected to be cold, dense and high column density regions of the interstellar medium, which can reveal themselves via near, mid and even far-infrared absorption as Infrared Dark Clouds (IRDCs). Elucidating the dynamical state of IRDCs thus constrains theoretical models of these complex processes. In particular, it is important to assess whether IRDCs have reached virial equilibrium, where the internal pressure balances that due to the self-gravitating weight of the cloud plus the pressure of the external environmental. We study this question for the filamentary IRDC G035.39-00.33 by deriving mass from combined NIR & MIR extinction maps and velocity dispersion from C18O (1-0) & (2-1) line emission. In contrast to our previous moderately super-virial results based on 13CO emission and MIR-only extinction mapping, with improved mass measurements we now find that the filament is consistent with being in virial equilibrium, at least in its central parsec-wide region where ~1000 solar masses snakes along several parsecs. This equilibrium state does not require large-scale net support or confinement by magnetic fields.

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Ed ~ The filament IRDC G035.39--00.33 is in the W48 molecular complex