2003ApJ...592..176M

Observations of the environment of the star-forming region NGC 7129 obtained with an angular resolution of 1' in the 21 cm line of H I are described. Two features of the image are extensively discussed: (1) a ring of H I emission about 30' in extent and (2) a relatively dense concentration of H I with unusually wide line profiles positionally coincident with the B star BD +65°1638. The H I ring is consistent with photodissociation of H₂by the interstellar UV radiation field at the surface of an extended molecular cloud in which both BD +65°1638 and NGC 7129 are situated. We further show that BD +65°1638 appears to be an unusual example of a ``dissociating star'' surrounded by an extensive region of photodissociated H₂and accompanied by a small H II region. The derived spectral type (B2.5) and the absolute magnitude for BD +65°1638 further suggest that the latter is very close to the birthline. The very young stellar age implied by the parameters of the H I region, considerably less than 10⁴ yr, is discussed, and the properties of the H I region are compared with those of the prototype for this rare class of objects. We discuss both aspects within the context of star formation in NGC 7129.