by Nathan Goldbaum | May 18, 2011 | Daily Paper Summaries
Title: The History of Star Formation in Galaxy Disks in the Local Volume as Measured by the ACS Nearby Galaxy Survey Treasury Authors: Benjamin F. Williams et al. Affiliation: Department of Astronomy, University of Washington The star formation history of the universe is an area of active research. As galaxies consume their gas into stars, newborn massive stars emit copious amounts of ionizing radiation and explode in powerful core-collapse supernovae. Both of these radiative and mechanical feedback mechanisms can significantly affect the development of galaxies, resulting in the galaxy populations we see today. Deep photometry from space and ground-based observatories have allowed astronomers to directly measure the in situ star formation history of the universe by counting the number of star forming galaxies we see at earlier epochs of the universe’s evolution. One could alternatively observe the age and mass of resolved stellar populations in nearby galaxies to infer the star formation history of these systems. These two disparate measurements should agree, except for departures due to cosmic variance. In this paper, the authors use deep Hubble observations of a volume-limited sample (the ACS Neaby Galaxy Treasury Survey, ANGST for short) of nearby galaxies to measure the star formation using stellar population synthesis modeling.Measuring the star formation history of a resolved stellar population requires detailed models for the positions of stars in a color-magnitude diagram (CMD for short). A CMD is just an observer’s version of the more commonly discussed Hertzprung-Russell diagram. Models of stellar evolution and synthetic spectral modeling of the model stars are sufficiently advanced that the luminosity and color of practically any star can be predicted...
