Wine and Cheese Spring 2018

This page records the schedule, titles and abstracts of the JHU/STScI CAS Astrophysics Wine & Cheese Series in Fall 2017.

Wine and Cheese sessions with one talk will have a 50 minute talk with 10 minutes for questions. Sessions with two speakers will have two 25 minute talks, each with 5 minutes for questions. Sessions in the Graduate Student Series will have three 15 minute talks, each with 5 minutes for questions.

February 5th (Graduate Student Series)

Katie Harrington

Variable-delay Polarization Modulators for the CLASS Telescopes
The search for inflationary primordial gravitational waves and the optical depth to reionization, both through their imprint on the large angular scale correlations in the polarization of the cosmic microwave background (CMB), has created the need for high sensitivity measurements of polarization across large fractions of the sky at millimeter wavelengths. These measurements are subjected to instrumental and atmospheric 1/f noise, which has motivated the development of polarization modulators to facilitate the rejection of these large systematic effects.

Variable-delay polarization modulators (VPMs) are used in the Cosmology Large Angular Scale Surveyor (CLASS) telescopes as the first element in the optical chain to rapidly modulate the incoming polarization. VPMs consist of a linearly polarizing wire grid in front of a moveable flat mirror; varying the distance between the grid and the mirror produces a changing phase shift between polarization states parallel and perpendicular to the grid which modulates Stokes U (linear polarization at 45°) and Stokes V (circular polarization). The reflective and scalable nature of the VPM enables its placement as the first optical element in a reflecting telescope. This simultaneously allows a lock-in style polarization measurement and the separation of sky polarization from any instrumental polarization farther along in the optical chain.

Erini Lambrides

Running Up The Gas Bill, The Cost of Leaving Your AGN On: Warm Molecular Gas and Dust in Active Galaxies
We analyze 2015 mid-infrared spectra of active and star-forming galaxies to determine if and how accreting, super-massive black holes at the center of galaxies impact the interstellar medium of their hosts. We assess the AGN's impact on the gas and dust of their host galaxies by compiling the largest sample of extragalactic objects with mid-infrared spectroscopic data, and performing a suite of diagnostics and statistical tests. We provide a large census of rotational molecular hydrogen emission in the context mid-infrared star-formation and AGN activity diagnostics. We find a statistically significant positive correlation between excess molecular hydrogen emission and the relative contribution of the AGN to the IR emission. We find a 200K difference between the excitation temperatures of the higher pure rotational molecular hydrogen transitions in AGN dominated and non-AGN dominated spectra. We interpret our findings as evidence of distinct differences in the star-forming molecular gas in AGN host galaxies, and interpret our molecular hydrogen temperature differences as evidence of AGN host galaxies having a warmer or more dense warm molecular hydrogen component. Thus we find evidence of a distinctly different population of molecular hydrogen gas that exists in AGN host galaxies.

David Ely

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February 12th

== Amiel Sternberg (Tel Aviv University, Israel Max Planck Institute for Extraterrestrial Physics, Germany Flatiron Institute, Simons Foundation, USA) == The Atomic to Molecular (HI-to-H2) Transition in Galaxy Star-Forming Regions
The atomic to molecular hydrogen (HI-to-H2) phase transition is of fundamental importance for star-formation and the emergence of chemical complexity in the interstellar medium of galaxies. I will present an overview, and discuss recent theoretical studies, numerical and analytic, of the HI-to-H2 transition in irradiated systems, with applications to the multi-scale behavior observed in star-forming galaxy disks from low- to high-redshift.

February 19th

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February 26th

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March 5th

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March 12th (Graduate Student Series)

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March 19th

Spring Break

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March 26th

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April 2nd

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April 9th

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April 16th

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April 23rd (Graduate Student Series)

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