Cyganowski, C. J.Brogan, C. L.Hunter, TuckerGraninger, DawnOberg, KarinVasyunin, A.Zhang, QiyuFriesen, R.Schnee, S.2016-01-212014Cyganowski, C. J., C. L. Brogan, T. R. Hunter, D. Graninger, K. I. Öberg, A. Vasyunin, Q. Zhang, R. Friesen, and S. Schnee. 2014. “G11.92–0.61-MM2: A bonafide massive prestellar core?” The Astrophysical Journal 796 (1) (October 31): L2. doi:10.1088/2041-8205/796/1/l2.2041-8213http://nrs.harvard.edu/urn-3:HUL.InstRepos:24816624Core 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 Submillimeter Array (SMA) 1.3 mm, 1.1 mm, and 0.88 mm and Very Large Array 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 α = 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 of MM2 is best fit with a dust temperature of ~17-19 K and luminosity of ~5-7 L ⊙. The combined physical properties of MM2, as inferred from its dust continuum emission, are extreme: M >~ 30 M ⊙ within a radius <1000 AU, N_H_2>1025 cm-2 and n_H_2 >109 cm-3. Comparison of the molecular abundance limits derived from our SMA observations with gas-grain chemical models indicates that extremely dense (n(H) Gt 108 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.en-USJournal Article2016-01-09Cyganowski, C.J., Brogan, C.L., Hunter, T.R., Graninger, D., Oberg, K.I., Vasyunin, A., Zhang, Q., Friesen, R., Schnee, S.2016-01-2110.1088/2041-8205/796/1/L2