Hot ammonia in NGC 6334I & I(N) ^*

¹ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: beuther@mpia.de
² James Cook University, Townsville, QLD 4811, Australia e-mail: Andrew.Walsh@jcu.edu.au
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: sthorwirth@mpifr-bonn.mpg.de
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA e-mail: zhang@cfa.harvard.edu
⁵ NRAO, 520 Edgemont Rd, Charlottesville, VA 22903, USA e-mail: thunter@nrao.edu
⁶ Ritter Observatory, Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606-3390, USA e-mail: megeath@astro1.panet.utoledo.edu


Received: 23 November 2006
Accepted: 23 January 2007

Abstract

Aims.The massive twin cores NGC 6334I and I(N) are in different evolutionary stages and hence ideal targets to study evolutionary variations within the same larger-scale environment. Here, we study the warm, compact gas components.

Methods.We imaged the two regions with the Australia Telescope Compact Array (ATCA) at high angular resolution in the NH₃(3, 3) to (6, 6) inversion lines.

Results.Compact emission is detected toward both regions in all observed inversion lines with energy levels up to 407 K above ground. This is particularly surprising for NGC 6334I(N) since it lacks bright infrared emission and is considered a massive cold core at an early evolutionary stage. High optical depth and multiply-peaked line profiles complicate rotation temperature estimates, and we can only conclude that gas components with temperatures >100 K are present in both regions. Toward NGC 6334I, we confirm previous reports of NH₃(3, 3) maser emission toward the outflow bow-shocks. Furthermore, we report the first detection of an NH₃(6, 6) maser toward the central region of NGC 6334I. This maser is centered on the second millimeter (mm) peak and elongated along the outflow axis, indicating that this mm continuum core harbors the driving source of the molecular outflow. Toward the main mm peak in NGC 6334I(N), we detect a double-horn line profile in the NH₃(6, 6) transition. The current data do not allow us to differentiate whether this double-horn profile is produced by multiple gas components along the line of sight, or whether it may trace a potential underlying massive accretion disk.