This program investigates the star formation process by exploiting the rich synergy of recent Galactic Plane Surveys that trace various phases and conditions of interstellar gas and dust. The main focus is to synthesize the information resident within these collective survey data sets to provide the most complete observational constraints to the physics of star formation in the inner disk of the Galaxy. In particular, physical processes within a giant molecular cloud responsible for the development of massive clumps from which clusters and OB stars condense are investigated.
The data sets include the FCRAO (Five College Radio Astronomy Observatory) surveys of 12CO and 13CO emission, the Bolocam Galactic Plane Survey (BGPS), the Very Large Array (VLA) Galactic Plane Survey, and the Spitzer Legacy program Multiband Imaging Photometer for Spitzer Inner Galactic Plane Survey (MIPSGAL). By linking sources identified within the millimeter, dust, and radio continuum surveys to velocities of 13CO emission, one obtains measures of the star formation activity within giant molecular clouds over varying environments and locations in the Galaxy.
Such measures include the fraction of cloud mass residing within massive clumps, star formation rates derived from infrared luminosity, and a census of Lyman-alpha continuum photons from the radio luminosity. These properties are compared to the dynamical state and velocity structure of the parent molecular cloud derived from 13CO emission. This collective information is used to evaluate the role of shocks driven by interstellar turbulence and expanding ionization fronts on regulating star formation.
Part of this project is to calibrate the coefficient of the size-velocity dispersion relationship for a set of clouds whose distances have been determined to better than 10% by trigonometric parallax measurements. This calibration then establishes a new distance measure for giant molecular clouds in the Milky Way that can complement or improve upon kinematic distances derived from the Galactic rotation curve.
The establishment of a new distance measure in the Galaxy significantly aids studies of Galactic structure and investigations of individual star forming regions. A compilation of star forming regions is made available on the web during the project. The multi-wavelength, multi-dimensional character of these data sets requires the development and use of generalized multi-variate methods that could be applied to other astronomical data. This project is the basis of a doctoral thesis; it will fully engage the funded graduate student and therefore contribute to the training of the next generation of scientists.
