Description:

Astrophysics abounds with precision measurement problems, for example when we search for exoplanets, map the dark matter in our Galaxy, or test the cosmological model. Because astronomy is observational, not experimental, no measurement is clean; we always have to model many auxiliary components (instrument calibration, foregrounds, and backgrounds) in addition to the component we most care about. I'll argue that getting data with good or rich causal structure is key to component separation. I will highlight the roles of classical statistics (especially the likelihood principle) and machine learning in making good measurements. When deployed correctly (but counterintuitively), machine-learning methods can be used to make precision measurements and discoveries more conservative and more believable. I will give examples from recent work in exoplanets, dark matter, and cosmology.

Speaker: David Hogg, New York University, Center for Computational Astrophysics

Host: Adam Miller

Description:

JWST has transformed our ability to understand the properties of the first stars and galaxies that formed in the universe following the Big Bang. These objects are important because they provide the first ionizing radiation in the universe. As this radiation permeates from the galaxies into the intergalactic medium it ionizes the surrounding gas. This process is called “reionization”, and it corresponds to the last major phase transition in cosmology whereby all the intergalactic medium is fully ionized, where it has remained to the present day.

I will provide a brief history of our understanding of reionization in the universe. I will discuss how we have come to understand the evolving properties of galaxies, and how this connects to the reionization process. I will discuss observations from JWST that provide measurements of the physical conditions and formation histories of galaxies that exist during the epoch of reionization. These observations show the galaxies produce copious amounts of ionizing radiation, exceeding predictions based on stellar populations in galaxies that form later in the universe.  I will also discuss analyses of JWST data that constrain how much of this radiation escapes from galaxies.  I will also discuss JWST observations that constrain the physical properties of these early galaxies and how they may differ from galaxies that form later in the universe. 

Speaker: Casey Papovich, Texas A&M University

Host: Allison Strom

Description:

TBA

Speaker: Kishalay De, Columbia University

Host: Adam Miller

Description:

CIERA Colloquia feature distinguished external visiting researchers, and are a regularly occurring colloquia series held throughout the Fall, Winter, and Spring academic quarters. Colloquium speakers are invited to spend several days at CIERA.

Description:

TBA

Speaker: Anna-Christina Eilers, MIT

Host: Claude-André Faucher-Giguére