- Camilla Pacifici, CSA instrument scientist - cpacifici@stsci.edu, Muller office S307
- Project duration: 1yr rotation with potential for thesis project
- Project abstract:
While galaxies evolve, they are subject to merger events, structural transformations, and feedback processes. These mechanisms regulate how galaxy activity changes between star-forming and quiescent phases. We propose to measure the time galaxies spend on the main sequence of star formation (which is the tight correlation between stellar mass and star formation rate) during their lifetime. We propose to explore trends between such timescales and stellar mass, structural parameters, and environment to assess which mechanisms dominate. We can do this by using our physically motivated models of the spectral energy distribution (SED) of galaxies to simultaneously interpret photometric and spectroscopic observations from a large sample of galaxies of all shapes and colors at z<2.5. The combination of HST photometry and spectroscopy will allow us to break the degeneracies between star-formation history and dust attenuation that often complicate the interpretation of galaxy SEDs, and will push the analysis of galaxy stellar populations to higher and higher redshifts. Photometric catalogs, grism spectra, and measurements of structural parameters are already in hand, but we need a sophisticated joint analysis with state-of-the-art modeling to properly measure how galaxies evolve.
Caption: We measure the time galaxies spend on the star-formation main sequence. From fits to the photometry and spectroscopy, we derive for each galaxy a best-estimate SFH and its uncertainty (left-hand side). On the U V J diagram, this galaxy would move in the star-forming region (center; we simply assume that as the metal enrichment increases, the dust increases). On the right-hand side, we show the (simplified) star-formation main sequence at increasing redshifts (thus increasing SSFR). As the galaxy evolves, the mass increases and the SFR fluctuates. From this, we measure the time the galaxy spends on the main sequence (non-shaded areas). - Role of the student: The student would be leading the paper showing the results of the analysis. All measurements and almost all fits to the photometry are already in hand. The student would spend time understanding the correlations between the different quantities, running the fits including the spectroscopic data, using statistics to infer well-justified results, and writing up the results.
