VLA and ALMA Imaging of the Massive Prestellar Core G11.92-0.61 MM2

¹ NRAO Charlottesville, VA, USA
² University of St. Andrews, UK

Abstract

We have obtained new Jansky Very Large Array (VLA) observations at X, K, and Ka bands (3 cm, 1.3 cm, and 0.9 cm) which have resolved the continuum emission from the most promising candidate for a massive pre-stellar core discovered to date: G11.92–0.61 MM2. As described in Cyganowski et al. ([1]), this bright dust continuum source (190 mJy at 1.1 mm) exhibits no spectral line emission in sub-arcsecond-resolution Submillimeter Array (SMA) images across 24 GHz of bandwidth, including the typical tracers CO, HCN, HCO⁺, and N₂H⁺. Astrochemical models require high density (> 10⁹ cm⁻³) and low temperature (< 20 K) to explain the rare chemistry of this massive (M ≥ 30 M_⊙) object, which may exist in a fleeting evolutionary state. This source is well detected and elongated in VLA Ka-band (9 mm) continuum image with a 0.25′′ beam (800 AU), is marginally detected in poorer resolution (1) K-band (1.3 cm) data, and is undetected at X-band (3 cm) with 0.25′′ resolution. In combination with existing SMA millimeter wavelength data, our results provide an accurate spectral energy distribution of this source, constraining the dust grain emissivity index to 1.0–1.6 and the luminosity to 3–37 L_⊙. Preliminary results from ALMA Band 7 images confirm that the dust emission from MM2 is resolved in an east-west direction.