Star formation associated with the infrared dust bubble N68

Abstract

We investigated the environment of the infrared dust bubble N68 and searched for evidence of triggered star formation in its surroundings. We performed a multiwavelength study of the nebula with data taken from several large-scale surveys: GLIMPSE, MIPSGAL, IRAS, NVSS, GRS and JCMT. We analyzed the spectral profile and the distribution of the molecular gas (13CO J = 1 − 0 and J = 3 − 2), and the dust in the environment of N68. The position-velocity diagram clearly shows that N68 may be expanding outward. We used two three-color images of the mid-infrared emission to explore the physical environment, and one color-color diagram to investigate the distribution of young stellar objects (YSOs). We found that the 24 μm emission is surrounded by the 8.0 μm emission. Morphologically, the 1.4 GHz continuum strongly correlates with the 24 μm emission, and the 13CO J = 1 − 0 and J = 3 − 2 emissions correlate well with the 8.0 μm emission. We investigated two compact cores located in the shell of N68. The spectral intensity ratios of 13CO J = 3 − 2 to J = 1 − 0 range from 5 to 0.3. In addition, YSOs, masers, IRAS and UC HII regions are distributed in the shell of the bubble. The active region may be triggered by the expansion of the bubble N68.