Joel Leja Assistant Professor of Astronomy and Astrophysics 515 Davey Lab University Park, PA 16802 Phone: +1 814-863-6039 Fax: Email: joel.leja@psu.edu Personal webpage

My research interests focus on understanding the processes of galaxy formation across cosmic time. I am an observer, in the sense that I work with data. I primarily build models to interpret data from surveys of galaxies in the distant universe: these models range from understanding data on the pixel-by-pixel level, to complex models of the stellar populations in galaxies, to analytical models for the evolution of the galaxy population as a whole.

In particular, I specialize in fitting flexible models to galaxy photometry and spectra, in building and exploring analytical and theoretical models of galaxy evolution, and in learning about and applying astrostatistics. I’ve harnessed millions of hours of supercomputer time running specialized code to build a more complete picture of how galaxies form and evolve. I’ve collaborated on a wide range of projects ranging from understanding the stellar origins of kilonova explosions to developing new methods for wide-field IR surveys.

My most recent publication was constructing a multi-level Bayesian model for the growth of the galaxy stellar mass function across 0.2 < z < 3, covering a span of 9 billion years. I am currently involved working hard to prepare for the launch of the James Webb Space Telescope, to better understand the structure of the galaxy star-forming sequence, and to build better tools to analyze the spatial structure of high-redshift galaxies.