High resolution observations of the hot core in G29.96–0.02

¹ University of Puerto Rico, Physics Department, PO Box 23343 University Station, San Juan, PR 00931-3343, USA
² Istituto di Radio Astronomia, CNR Sezione di Firenze, Largo E. Fermi 5, 50125 Firenze, Italy
³ Osservatorio Astrofisico di Arcetri, INAF, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: cesa@arcetri.astro.it; walmsley@arcetri.astro.it
⁴ Arecibo Observatory, Cornell University, HC3 Box 53995, Arecibo, PR 00612, USA e-mail: hofner@naic.edu
⁵ Instituto de Astronomia, Universidad Nacional Autónoma de México, Apdo. Postal 3-72, C.P. 58090, Morelia, Michoacán, Mexico e-mail: s.kurtz@astrosmo.unam.mx
⁶ Washburn Observatory, University of Wisconsin-Madison, 475 North Charter Street, Madison, WI 53706, USA e-mail: ebc@astro.wisc.edu

Corresponding author: L. Olmi, olmi@naic.edu

Received: 12 February 2003
Accepted: 21 May 2003

Abstract

We present high angular resolution observations obtained with the Owens Valley and the IRAM Plateau de Bure millimeter-wave interferometers toward the hot core in G29.96–0.02. We observed the ground state (6–5), (6–5), vibrationally excited () (6–5), and the (1–0) rotational transitions, as well as the 2.7 mm continuum emission. Our continuum maps show evidence of a compact source barely resolved whose diameter we estimate to be about 0.06 pc and whose emission mechanism is dominated by thermal emission from warm dust. Both the ground state and the  methyl cyanide lines, as well as other serendipituosly detected molecular transitions, arise from a compact source at the same position as the 2.7 mm continuum emission. The  observations sample the structure and kinematics of the molecular surroundings of the hot core and from the  data we estimate a gas mass of about   in a region with a diameter of 0.32 pc, corresponding to an average number density of about 10⁶ cm^-3. Our data show evidence of both a temperature and density gradient in the hot core and its molecular surroundings. The density gradient, in particular, is consistent with the infalling scenario suggested by the presence of an East-West oriented velocity gradient, which is however of opposite sign in  and . We tentatively interpret the  velocity gradient as associated with infall, whereas the  gradient, consistent with that measured in  by Cesaroni et al. ([CITE]), is likely to trace a massive rotating disk.