2020ApJ...904...18J -
Astrophys. J., 904, 18-18 (2020/November-3)
Characterizing [C II] line emission in massive star-forming clumps.
JACKSON J.M., ALLINGHAM D., KILLERBY-SMITH N., WHITAKER J.S., SMITH H.A., CONTRERAS Y., GUZMAN A.E., HOGGE T., SANHUEZA P. and STEPHENS I.W.
Abstract (from CDS):
Because the 157.74 µm [C II] line is the dominant coolant of star-forming regions, it is often used to infer the global star formation rates of galaxies. By characterizing the [C II] and far-infrared emission from nearby Galactic star-forming molecular clumps, it is possible to determine whether extragalactic [C II] emission arises from a large ensemble of such clumps, and whether [C II] is indeed a robust indicator of global star formation. We describe [C II] and far-infrared observations using the FIFI-LS instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) airborne observatory toward four dense, high-mass, Milky Way clumps. Despite similar far-infrared luminosities, the [C II] to far-infrared luminosity ratio, L[CII]/LFIR, varies by a factor of at least 140 among these four clumps. In particular, for AGAL313.576+0.324, no [C II] line emission is detected despite a FIR luminosity of 24,000 L☉. AGAL313.576+0.324 lies a factor of more than 100 below the empirical correlation curve between L[CII]/LFIR and Sν(63µm)/Sν(158µm) found for galaxies. AGAL313.576+0.324 may be in an early evolutionary "protostellar" phase with insufficient ultraviolet flux to ionize carbon, or in a deeply embedded "'hypercompact" HII region phase where dust attenuation of UV flux limits the region of ionized carbon to undetectably small volumes. Alternatively, its apparent lack of [C II] emission may arise from deep absorption of the [C II] line against the 158 µm continuum, or self-absorption of brighter line emission by foreground material, which might cancel or diminish any emission within the FIFI-LS instrument's broad spectral resolution element (ΔV∼250 km s–1).
Abstract Copyright:
© 2020. The American Astronomical Society. All rights reserved.
Journal keyword(s):
Molecular clouds - H II regions - Star-forming regions
Simbad objects:
11
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