Sep 20, 2018

Matt Povich, California State Polytechnic University

"The Balance of Power in Galactic Massive Star-Forming Regions"

The star formation rate (SFR) is a fundamental parameter in theoretical models of galaxy evolution and governs the observed properties of galaxies. The most widely-used empirical measurements of the SFR in both the Milky Way and external galaxies rely on indirect observational tracers sensitive to only the most massive 1% of stars. Hence state-of-the-art astrophysical methods for diagnosing galactic star-formation activity are analogous to using only the tax returns and investment portfolios of the richest 1% of earners to diagnose U.S. economic activity.

I will present recent work to model the 3.6 micron through 10 mm spectral energy distributions (SEDs) for a sample of 28 young Galactic massive star-forming regions. We performed large-aperture photometry on archival imaging data obtained using an armada of space-based observatories: Spitzer, MSX, IRAS, Herschel, and Planck and fit the resulting SEDs with multicomponent dust, blackbody, and power-law continuum models. Because the massive stellar content in the majority of these regions has been spectroscopically cataloged, we balance the "energy budgets" in each region by comparing the luminosity input by stars to that emerging in the SEDs.we find that ∼34% of Lyman continuum photons emitted by massive stars are absorbed by dust before contributing to the ionization of H II regions, while ∼68% of the stellar bolometric luminosity is absorbed and reprocessed by dust in the H II regions and surrounding photodissociation regions. We calibrate infrared and radio diagnostics of obscured SFRs to the known ionizing stellar populations. Widely-employed extragalactic SFR calibrations based on 24 micron luminosity agree with our calibrations to within 30%, while analogous extragalactic calibrations based on 70 micron luminosity must be corrected for the smaller physical size of individual Galactic regions.

Looking ahead, we plan to apply our new SFR calibrations to the upcoming catalog of ~4000 Galactic star-forming regions produced by citizen scientists for the Milky Way Project to map the SFR distribution in our home Galaxy.

Event Details

Date:
Sep 20, 2018

Time:
3:30–5pm

Location:
4421 Stering Hall

Notes:
Coffee served at 3:30pm; talk starts at 3:45pm

Speaker Host:
Robert Benjamin UW - Milwaukee

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