School of Astronomy

Abstract:

We are studying the impact of HII regions on star formation in their associated molecular clouds in a sample of 10 HII regions. We use James Clerk Maxwell Telescope (JCMT) to make 7x7 arcmin maps in 12CO(2-1), which we use to investigate the structure of the cloud and to identify the individual clumps and the dense cores within each clump. We make single point observations in 13CO(2-1) and CS(5-4) at the brightest 12CO(2-1) peak within each clump in order to measure the physical properties of the gas. We calculate and measure densities, temperatures, clump masses, peak velocities and line width.

We have identified two condensed regions (A and B) associated with S175 HII region.

S175A is adjacent to the ionized gas fronts and expected to be affected by the HII region while S175B is too distant to be disturbed. We compare the structure and gas properties of these two regions to investigate how the molecular gas has been affected by the HII region. Noticeably S175A has a narrow structure and is highly fragmented. S175B seems to be more uniform and identified clumps within this region lie on an extended uniform CO emission. S175B contains a very active sub-region with strong evidence of outflow. We discuss various factors that cause such differences within the observed regions.