Linking Galactic and Extragalactic Star Formation

West Virginia University Research Corporation, Morgantown WV

Investigators

Abstract

It is surprising how little we know about global star formation in our Milky Way Galaxy compared to other galaxies in the Universe. This is because the Sun lies in the flat Milky Way disk and because nearly all star formation occurs within this disk. Looking at the sky, the disk appears as a relatively thin band, with stars at all distances found within this band. This project will disentangle this band of light into a three-dimensional map with the aim of understanding the global star formation in our Galaxy. This map will allow us to differentiate between the brightness of regions (an observed property) with their luminosities (an intrinsic property). The team will create the three-dimensional map by measuring the brightness of all known massive star formation regions at infrared and radio wavelengths, and will use radio observations to turn the infrared and radio brightnesses into luminosities. Local high school students will assist in the observations, providing vital research opportunities for the students of West Virginia. The PI and his students will compare the distribution of derived luminosities with that of other galaxies to determine the type of galaxy we live in. They will also estimate how many stars our Galaxy is forming. These results will help us to better understand star formation in our Galactic home. There is a severe lack of communication between Galactic and extragalactic astronomers because there is no complete sample of Galactic star forming regions that can be compared to those of external galaxies. The team will solve this problem by creating a catalog of all Galactic HII regions ionized by single O-stars using radio recombination line observations. Local high school students will help with the observations, providing vital science opportunities for the students of West Virginia. These observations will allow us to compute kinematic distances from the observed radial velocities using a rotation curve model. The team will supplement the distances by locating clusters of HII regions that have similar radial velocities, and presumably similar distances, and will adjust for catalog biases using a population synthesis model. The PI and his students will derive HII region fluxes at wavelengths from 8 micron to 21 cm and turn these fluxes into luminosities using the catalog distances. They will investigate three extragalactic results found in studies of the HII region luminosity function (LF): the break in the Galactic LF seen in some galaxies, the finding that ''clustered'' and ''distributed'' HII-region LFs have different shapes, and the correlation between the galaxy's LF shape and its Hubble type. The total Milky Way luminosity can then be computed by summing the luminosities of all catalog HII regions. The total Milky Way luminosities will then be converted into star formation rates using extragalactic star formation rate calibrations.