Pizza Lunch: Sarah Kovac
Oct 2 @ 12:30 pm – 1:30 pm
Pizza Lunch: Sarah Kovac @ AY 119

The Citizen Cate Project

Colloquium: David Nataf (Host: Jason Jackiewicz)
Oct 5 @ 3:15 pm – 4:15 pm
Colloquium: David Nataf (Host: Jason Jackiewicz) @ BX102

Clues to Globular Cluster Formation

David Nataf, Johns Hopkins University

Globular clusters are now well-established to host “Second-generation” stars, which show anomalous abundances in some or all of He, C, N, O, Na, Al, Mg, etc.  The simplest explanations for these phenomena typically require the globular clusters to have been ~20x more massive at birth, and to have been enriched by processes which are not consistent with the theoretical predictions of massive star chemical synthesis models. The library of observations is now a vast one, yet there has been comparatively little progress in understanding how globular clusters could have formed and evolved. In this talk I discuss two new insights into the matter. First, I report on a meta-analysis of globular cluster abundances that combined APOGEE and literature data for 28 globular clusters, new trends with globular cluster mass are identified. I discuss the chemical properties of former globular cluster stars that are now part of the field population, and what can be learned.

Public Talk: Janna Levin: Black Hole Blues
Mar 5 @ 7:30 pm – 8:45 pm
Colloquium: Elise Boera (Host: Kristian Finlator)
Dec 6 @ 3:15 pm – 4:15 pm
Colloquium: Elise Boera (Host: Kristian Finlator) @ BX102

Revealing reionization with the thermal history of the intergalactic medium

Elisa Boera, SISSA Trieste

During hydrogen reionization the UV radiation from the first luminous sources injected vast amount of energy into the intergalactic medium, photo-heating the gas to tens of thousands of degree Kelvin. This increase in temperature has left measurable `imprints’ in the thermal history of the cosmic gas: a peak in the temperature evolution at the mean density and a smoothing out of the gas in the physical space by the increased gas pressure following reionization (i.e. Jeans smoothing effect). The structures of the HI Lyman-alpha forest at high redshift are sensitive to both these effects and therefore represent a powerful tool to understand when and how reionization happened. I will present the most recent constraints on the thermal history of the intergalactic medium obtained using the Lyman-alpha forest flux power spectrum at z>5. I will show how these results can be used to obtain information on the timing and the sources of the reionization process and I will discuss their consistency with different possible reionization scenarios.