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

P. Persi; M. Tapia; H. A. Smith

doi:doi:10.1051/0004-6361:20053251

Free access

Issue		A&A Volume 445, Number 3, January III 2006


Page(s)		971 - 978
Section		Interstellar and circumstellar matter
DOI		http://dx.doi.org/10.1051/0004-6361:20053251

A&A 445, 971-978 (2006)
DOI: 10.1051/0004-6361:20053251

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

P. Persi¹, M. Tapia² and H. A. Smith³

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 $\mu$ m and IRAC images at 3.6, 4.5, 5.8 and 8.0 $\mu$ m of the W75 N massive star forming region is presented. The 12.5 $\mu$ 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 $\lambda > 2.0 ~\mu$ 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 $\sim$ $750~L_\odot$ and a visual extinction $A_{\rm V} \simeq 90$ for this source. From the IRAC images, we detected 75 sources in an area of $120'' \times 120 ''$ 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 $H-K_{\rm s}$ versus $K_{\rm s}-[3.6]$ diagrams.

Key words: stars: formation -- infrared: stars -- ISM: clouds -- ISM: HII regions

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