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G11.92-0.61-MM2: A Bonafide Massive Prestellar Core? | | C. J. Cyganowski
; C. L. Brogan
; T. R. Hunter
; D. Graninger
; K. I. Öberg
; A. Vasyunin
; Q. Zhang
; R. Friesen
; S. Schnee
; | | Date: |
9 Oct 2014 | | Abstract: | Core accretion models of massive star formation require the existence of
stable massive starless cores, but robust observational examples of such
objects have proven elusive. We report subarcsecond-resolution SMA 1.3 mm, 1.1
mm, and 0.88 mm and VLA 1.3 cm observations of an excellent massive starless
core candidate, G11.92-0.61-MM2, initially identified in the course of studies
of GLIMPSE Extended Green Objects (EGOs). Separated by ~7.2" from the nearby
MM1 protostellar hot core, MM2 is a strong, compact dust continuum source
(submillimeter spectral index alpha=2.6+/-0.1), but is devoid of star formation
indicators. In contrast to MM1, MM2 has no masers, no centimeter continuum, and
no (sub)millimeter wavelength line emission in ~24 GHz of bandwidth observed
with the SMA, including N2H+(3-2), HCO+(3-2), and HCN(3-2). Additionally, there
is no evidence for an outflow driven by MM2. The (sub)millimeter spectral
energy distribution (SED) of MM2 is best fit with a dust temperature of ~17-19
K and luminosity of ~5-7 L_sun. The combined physical properties of MM2, as
inferred from its dust continuum emission, are extreme: M>30 M_sun within a
radius<1000 AU, N(H2)>10^25 cm^-2 and n(H2)>10^9 cm^-3. Comparison of the
molecular abundance limits derived from our SMA observations with gas-grain
chemical models indicates that extremely dense (n(H)>>10^8 cm^-3), cold (<20 K)
conditions are required to explain the lack of observed (sub)millimeter line
emission, consistent with the dust continuum results. Our data suggest that
G11.92-0.61-MM2 is the best candidate for a bonafide massive prestellar core
found to date, and a promising target for future, higher-sensitivity
observations. | | Source: | arXiv, 1410.2605 | | Services: | Forum | Review | PDF | Favorites | |
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