IRAS 18511+0146: a proto Herbig Ae/Be cluster?^*

¹ INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: sarita@arcetri.astro.it
² ESO, Karl Schwarzschild str. 2, 85748 Garching, Germany
³ INAF – Istituto di Fisica dello Spazio Interplanetario, Via Fosso del Cavaliere, 00133 Roma, Italy
⁴ Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125, USA

Received: 2 April 2007
Accepted: 18 May 2007

Abstract

Context.The evolution of a young protocluster depends on the relative spatial distribution and dynamics of both stars and gas.

Aims.We study the distribution and properties of the gas and stars surrounding the luminous (10⁴ ) protocluster IRAS 18511+0146.

Methods.IRAS 18511+0146 and the cluster associated with it has been investigated using the sub-millimetre (JCMT-SCUBA), infrared (Spitzer-MIPSGAL, Spitzer-GLIMPSE, Palomar) and radio (VLA) continuum data. Cluster simulations have been carried out in order to understand the properties of clusters as well as to compare with the observations.

Results.The central most obscured part of the protocluster coincident with the compact sub-millimetre source found with SCUBA is responsible for at least 2/3 of the total luminosity. A number of cluster members have been identified which are bright in mid infrared and show rising (near to mid infrared) spectral energy distributions suggesting that these are very young stellar sources. In the mid infrared 8.0 μm image, a number of filamentary structures and clumps are detected in the vicinity of IRAS 18511+0146.

Conclusions.Based on the luminosity and cluster size as well as on the evolutionary stages of the cluster members, IRAS 18511+0146 is likely to be protocluster with the most massive object being a precursor to a Herbig type star.