The HII region KR 140: Spontaneous formation of a high-mass star

We have used a multiwavelength data set from the Canadian Galactic Plane Su rvey (CGPS) to study the Galactic H II region KR 140, both on the scale of the nebula itself and in the context of the star-forming activity in the ne arby W3/W4/51r5 complex of molecular clouds and H II regions. From both rad io and infrared data we have found a covering factor of about 0.5 for KR 14 0, and we interpret the nebula as a bowl-shaped region viewed close to face on. Extinction measurements place the region on the near side of its paren t molecular cloud. The nebula is kept ionized by one 08.5 V(e) star, VES 73 5, which is less than a few million years old. CO data show that VES 735 ha s disrupted much of the original molecular cloud for which the estimated ma ss and density are about 5000 M. and 100 cm(-3) respectively. KR 140 is iso lated from the nearest star-forming activity, in W3. Our data suggest that KR 140 is an example of spontaneous (i.e., nontriggered) formation of, unus ually, a high-mass star.