Wednesday, March 16, 2011, 11:00 am, Pratt Conference Room
The Contribution of Evolved Stars to the Near-IR Luminosities of Galaxies:
Implications for Stellar Mass Estimates of High Redshift Galaxies
Dr. Jason Melbourne (Caltech)
| Stellar mass estimate of galaxies are typically made by measuring the luminosity of a galaxy and modeling the mass/light ratio. Because near-IR (NIR) luminosities are less affected by dust obscuration and less driven by current star formation than optical wavelengths, they have been employed extensively to estimate the stellar masses of galaxies, especially at high redshift using Spitzer imaging. However, certain phases of late-stage stellar evolution have been shown to contribute dramatically to the NIR luminosity of galaxy while contributing negligible mass. Unless these phases are well calibrated, stellar mass estimates of galaxies can be systematically wrong by large fractions. Using resolved stellar populations of local galaxies from HST WFC3, we demonstrate that current stellar populations synthesis codes over-predict the numbers of asymptotic giant branch branch stars, for the measured star formation history. Simultaneously, these codes tend to under-predict the numbers and luminosities of luminous red helium burning stars. We explore the implications of these two results for stellar mass estimates of galaxies at high redshift. |