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

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 7mu;m 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 λ > 2.0 μm. 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 ∼ 750 L⊙ and a visual extinction Av ≃ 90 for this source. From the IRAC images, we detected 75 sources in an area of 120″ × 120″ 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 H - Ks versus Ks - [3.6] diagrams. © ESO 2006.