A summary of where most of my time goes
My research focuses on galaxy formation and evolution in the early universe as well as the processes that lead to the shutdown of star formation in massive galaxies at later times. Jump directly to a more detailed research overview .
I am the U.S. lead principal investigator of ALPINE, a 70-hour ALMA program to study the gas and dust properties of 122 main-sequence galaxies in the early Universe (z>4). All data are taken and we are busy with publishing the first papers! Learn more about ALPINE here and see below for more collaborations
Most of my time is spent as part of IPAC's brand-new Joint Survey Processing and Tech-Initiative team. We are building a science platform that provides to the community a user-friendly and fast access to and analysis of the high-volume datasets produced by missions during the next decade(s). On a technical level, I manage the Keck spectroscopic database for the COSMOS survey.
It is very exciting to be part of the (hopefully) the next generation of space missions! I am part of the science team for CASTOR, a Canada-led ultra-violet space telescope. See here for more information.
I am a full member of several large collaborations with high impact over the next decades:
What physical processes shape the interior of galaxies in the early Universe? Why are their properties so different compared to today's galaxies?
I study the ISM properties of high redshift galaxies by using the Hubble Space Telescope, the Keck telescopes, and the Atacama Large (Sub) Millimeter Array (ALMA). Furthermore, I study in detail resolved local analogs of high redshift galaxies to predict and explain the unresolved observations of high redshift galaxies. This led to the first observation based prediction of an increasing escape fraction of ionizing radiation in early galaxies. It suggests that galaxies in the early Universe have a different setup of H2 molecular regions in connection with a harder radiation from vigurous star formation. I am currently investigating the gas and dust distribution, infrared properies, and dust temperatures of redshift z=4-6 galaxies with ALMA observations and infrared detected low redshift analogs. Specifically, I am the US lead PI of ALPINE, a 70h program with ALMA to study the gas and dust properties of 118 galaxies in this redshift range. I am getting ready for observations with JWST that will be important to reveal in more detail what causes the differences in the physical properties compared to today's galaxies.
The predicted escape fraction of ionizing radiation as a function of redshift derived from local analogs of high redshift galaxies. This is indicative of different ISM properties and setup of molecular clouds in high redshift galaxies as well strengthens our picture that these galaxies are responsible for reionizing the Universe at z>6. Figure taken from Faisst 2016c.
How do massive galaxies in the early Universe form and grow?
I am using Spitzer mid-infrared colors and large samples of spectrospic redshifts to study the emission line properties of massive galaxies at redshifts z > 3, which indicate the recent star formation history in these galaxies. Furthermore, I am using measurements of UV absorption lines obtained by the Keck telescope to estimate the gas-phase metallicities of galaxies at z = 5. The results suggest a fast and chaotic growth of these galaxies with mass doubling timescales of only a couple 100 million years. I will use these results as well as machine learning techniques to provide an ideal sample for the efficient follow-up with JWST to test these predictions in detail.
The average specific star formation rate (sSFR) derived from Spitzer colors out to z>6 (orange) shows that these galaxies double their stellar masses on very short timescales (a couple of 100 million years). Figure taken from Faisst et al. 2016a.
What stops the formation of stars in massive galaxies? How does this process (quenching) change the structure of these galaxies?
I use an empirical model to describe the evolution of star-formation, stellar mass, and size of star forming massive galaxies and apply different processes that stop the formation of stars. By comparing this model to the observed stellar mass vs. size relation of quiescent galaxies I find that a central starburst (maybe triggered by a merger event) with a fast consumption of gas (the fuel for star-formation) fits best for very massive galaxies. Furthermore subsequent individual growth of the galaxies via mergers is necessary to meet the observations.
Faisst et al. 2017a
The comparison of the size evolution of massive (logM > 11.4) star-forming and quiescent galaxies since z=2 encapsulates hints on the processes that stop the formation of stars at high masses. Figure taken from Faisst et al. 2017a.
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