Mid-infrared images of the massive star forming region W75 N

¹ Istituto Astrofisica Spaziale e Fisica Cosmica, INAF, via fosso del cavaliere 100, 00133 Roma, Italy e-mail: persi@rm.iasf.cnr.it
² Instituto de Astronomía, UNAM, Apartado Postal 877, 22830 Ensenada, BC Mexico
³ Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Received: 15 April 2005
Accepted: 22 August 2005

Abstract

An infrared study that includes ground-based mid-infrared images between 8.7 and 18.7 μm and IRAC images at 3.6, 4.5, 5.8 and 8.0 μm of the W75 N massive star forming region is presented. The 12.5 μm image shows the presence of four mid-infrared sources in the region W75 N(B), three of which have bright near-infrared counterparts, IRS 1, IRS 2 and IRS 3, all with significant excess emission at m. IRS 2 has a steep energy distribution and the computed infrared luminosity is consistent with the presence of a young B3 star. The observed IRAC colors of IRS 3 indicate that this source is a Class II intermediate mass young star, consistent with its infrared energy distribution and luminosity. The fourth, newly discovered, mid-infrared source appears coincident with the ultracompact HII region VLA 3, and is located within the millimeter core MM 1. We derived a luminosity of ∼ and a visual extinction for this source. From the IRAC images, we detected 75 sources in an area of centered in W75 N. At least 25 of these sources are associated with the molecular cloud and form a young stellar cluster as shown in the IRAC two-color and the versus diagrams.