Wine and Cheese Fall 2020

This page records the schedule, titles and abstracts of the JHU/STScI CAS Astrophysics Wine & Cheese Series in Fall 2020.

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.

21 September

Jose Luis Bernal Mera (JHU)

Cosmology with Large-Scale Structure Clustering and Implications for Early Dark Energy Models
During the last decade, measurements of the galaxy clustering have become one of the cornerstones for our understanding of the Universe. With next-generation galaxy surveys and the promise of line-intensity mapping experiments, observations will be more precise will probe regimes that have been unexplored so far. In this talk we will review the cosmological information encoded in large-scale structure clustering and discuss the validity and reach of standard measurements. We also will review recent claims of galaxy clustering ruling out early dark energy models as a solution for the Hubble constant tension: although we agree with the results of the analyses performed, we reckon that such results are driven by the choice of prior and potential tensions between different observables, hence concluding that early dark energy is still a viable model and potential solution for the Hubble constant tension.

David Nataf (JHU)

Recent developments in the study of the distance and extinction to the Large and Small Magellanic Cloud
The Small and in particular the Large Magellanic Clouds (LMC) remain important anchors both to the extragalactic distance scale and to stellar astrophysics in general. As virtually all classes of variable stars and all classes of distance indicators have been studied in the LMC, it is possible and necessary to evaluate if these are consistent. I will begin my talk by first reviewing a surprising recent development. There is a 0.18 mag in the zero-point of the V-band extinction to the LMC, which vastly exceeds the quoted errors of virtually all prior studies of the matter. I will then discuss how our recent paper (https://arxiv.org/abs/2006.03603) resolved this issue, concurrently with another independent effort (https://arxiv.org/abs/2006.02448), using four different calibrations: stellar isochrones, RR Lyrae stars, Cepheids, and the SFD extinction maps. The resulting error is decreased to <~ 0.04 mag.

28 September

D'Arcy Kenworthy (JHU)

Next-Generation Standardization of Type Ia Supernovae for Cosmology
Type Ia supernova luminosities, after standardization using a light curve model, are an excellent probe of the luminosity distance - redshift relation. This allows measurement of cosmological parameters of interest such as the equation of state of dark energy and the Hubble constant. Meeting the science goals of next generation projects such as the Vera Rubin Observatory and the Roman Space Telescope requires improvements in systematic uncertainties in type Ia light curve modeling. In contrast, measurement of the Hubble constant is statistics-limited by the small number of nearby type Ia SNe, whose precision can be improved by the use of near-infrared data. I will present an overview of a new Python-based code to train supernova light curve models to achieve better standardization across these domains.

Sihao Cheng (JHU)

A New Vocabulary for Patterns and its Cosmological Application
I will present a new tool to characterize patterns in datasets, called the "scattering transform”. It borrows ideas from convolutional neural nets, but it is much more interpretable and controllable. I will also show its application to weak lensing data for constraining cosmological parameters, and compare its performance with classic statistical estimators and neural nets.

Cyril Creque-Sarbinowski (JHU)

TBD

5 October

Ben Mazin (UCSB)

Large Satellite Constellations and their Impact on Astronomy
I will discuss recent work to quantify the impact of large satellite constellations, such as SpaceX Starlink and OneWeb constellations that are currently in construction, on astronomical observations across the electromagnetic spectrum. In the process, I will also discuss the economics and other potential issues raised by these constellations.

12 October

Philip Kaaret (U Iowa)

A Clumpy Disc-Dominated Circumgalactic Medium of the Milky Way Seen in X-ray Emission
The Milky Way galaxy is surrounded by a circumgalactic medium (CGM) that may play a key role in galaxy evolution as the source of gas for star formation and a repository of metals and energy produced by star formation and nuclear activity. The CGM may also be a repository for baryons seen in the early universe, but undetected locally. The CGM has an ionized component at temperatures near 2 MK studied primarily in the soft X-ray band. Here we report a survey of the southern Galactic sky with a CubeSat-based soft X-ray spectrometer optimized to study diffuse soft X-ray emission. The X-ray emission is best fit with a disc-like model based on the radial profile of the surface density of molecular hydrogen, a tracer of star formation, suggesting that the X-ray emission is predominantly from hot plasma produced via stellar feedback. Strong variations in the X-ray emission on angular scales of 10°� indicate that the CGM is clumpy. Addition of an extended, and possibly massive, halo component is needed to match the halo density inferred from other observations.