Wine and Cheese Spring 2022

This page records the schedule, titles and abstracts of the JHU/STScI CAS Astrophysics Wine & Cheese Series in Spring 2021.

Wine and Cheese sessions with one speaker 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.

7 February

Ari Cukierman (Stanford)

The Oscillating Sky: BICEP as an axion direct-detection experiment
I will describe how a CMB telescope can function as a direct-detection experiment for axion-like dark matter, and I will present first demonstrations with data from the BICEP series of experiments. A local axion field induces all-sky oscillations in CMB polarization. For axion masses between 1e-23 and 1e-18 eV, the oscillation periods are on the order of hours to years. As CMB scan strategies typically involve repeated observations over many years, we can set limits on the axion-photon coupling constant by searching for time variability in CMB polarization with data that have already been gathered. The expected sensitivity of current-generation CMB experiments is at the level of the leading axion limits in this mass range, and the search will continue with next-generation instruments.

14 February

Lara Cullinane (JHU)

The Magellanic Edges Survey (MagES)
I’m a new JHU astronomy postdoc, working with Karrie Gilbert on M33/M31. However, in this talk, I’ll discuss my previous thesis work on the Magellanic Edges Survey, or MagES, which kinematically maps the extremely low-surface-brightness periphery of the Magellanic Clouds. We use a combination of Gaia astrometry and spectroscopically-derived radial velocities, obtained with 2dF+AAOmega on the Anglo-Australian Telescope, to determine the first 3D kinematics for a wealth of stellar substructure extending to distances beyond 23 degrees from the Clouds’ centres. Our initial results focus on the LMC. We reveal a large northern substructure that, due to its discrepant kinematics relative to the LMC disk, was likely formed in ancient interactions with the SMC, and subsequently strongly influenced during a recent interaction with the Milky Way; and several structures in the southwestern LMC that new dynamical models reveal were likely formed in interactions with the SMC 400+Myr ago. These are the first kinematic constraints on the dynamical history of the Clouds prior to their most recent close passage, and represent an enormous step forward in understanding their complex interactions.

21 February

Kedron Silsbee (MPE)

Cosmic Rays in the Context of Star Formation: Effects and Propagation
Cosmic rays alter the chemistry and dynamics of the molecular gas that collapses to form young stellar systems. Despite this, their abundance, particularly in denser regions, remains uncertain. Although cosmic rays in distant locations are not directly observable, we can infer their presence in molecular clouds from chemical tracers of gas ionization, gamma ray and synchrotron emission and enhanced gas temperature.  These suggest that while cosmic rays above approximately 1 GeV propagate freely into clouds, lower energy cosmic rays are excluded from the denser gas. This is qualitatively in agreement with predictions from theoretical models of cosmic ray attenuation. However, depending on the physics that dominates the propagation, the degree of attenuation varies significantly, and current data is insufficient to distinguish between the models. In this talk I will give an overview of the different transport regimes thought to play a role (diffusion, free propagation, and self-modulation), and what predictions these make for the variation of the ionization rate with gas density.  The propagation of cosmic rays is influenced by the properties of small-scale turbulence in the interstellar medium.  I will then also discuss some recent related work I’ve done on the damping of MHD turbulence due to radiative cooling.