Wine and Cheese Fall 2018

This page records the schedule, titles and abstracts of the JHU/STScI CAS Astrophysics Wine & Cheese Series in Fall 2018.

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.

10 September

Zaven Arazoumian (GSFC)

A NICER View: Astrophysics and Exploration from the International Space Station
Neutron stars are extraordinary in nearly every way. They are the densest objects in the universe, their gravity is immense, and they are the most powerful magnets known. Some -- those we call "pulsars" -- sweep narrow beams of radiation through space as they spin, sometimes as fast as blender blades, appearing to flash with unrivaled regularity like cosmic timepieces. Launched in June 2017, NASA's dual-purpose Neutron star Interior Composition Explorer (NICER) mission aims to answer longstanding questions about the physics and astrophysics of neutron stars, with a telescope on the International Space Station designed to investigate their X-ray emissions and precisely time their pulsations. The mission's second purpose is a first-ever demonstration of autonomous spacecraft navigation using pulsars as beacons in a "Galactic Positioning System." This presentation provides an overview of the NICER mission, its SEXTANT navigation demonstration, and the insights that NICER is delivering about neutron stars, black holes, and the high-energy processes that they drive.

17 September

Kathryn Johnston (Columbia)

Physical Manifestations of Evolution, Regularity and Chaos In and Around Our Galaxy
Our Galaxy is thought to be dynamically young with a fairly smooth potential dominated by a nearly spherical dark matter halo that has evolved little in the last several billion years. These attributes broadly suggest that potential evolution and dynamical chaos should have negligible influences on the orbits of its constituent stars, as well as on the stellar structures they collectively support. This talk reviews some recent results which point to signatures of Galactic evolution and the chaotic nature of stellar orbits that can be (and have been) observed.

24 September (GSS)

Alexander de la Vega (JHU)

Resolved Star Formation Trends in Massive Galaxies at z~1
Critical to our understanding of galaxy evolution is how galaxies stop forming stars and evolve from blue, star-forming disks to red, centrally concentrated spheroids. The processes that suppress star formation become important from redshift z ~ 1 to today, when red galaxies significantly increase in number density. Analyzing where stars form in different kinds of galaxies in this cosmic epoch can hint at the physics of star formation quenching. I present preliminary results of star formation radial profiles of ~1600 massive (>= 10^10 M_sun) galaxies in the CANDELS HST survey at 0.4 < z < 1.5. At z ~ 1, galaxies in transition between blue and red galaxies show central star formation rates consistent with the centers of blue galaxies. Star formation in the outskirts of these transition galaxies is lower by an order of magnitude and is more consistent with the outer parts of red galaxies. I juxtapose these trends with models of star formation quenching and discuss possible scenarios.

Hsiang-Chih Hwang (JHU)

Gas Accretion Caught in the Act
Gas accretion plays a crucial role in galaxy formation and evolution. Indeed, the growth in the stellar masses of galaxies over cosmic time occurs mainly through the accretion of gas from the environment, and no local star-forming galaxies can continue forming stars without replenishing their gas. As the inflow brings metal-poor gas into a galaxy, it lowers the metallicity in the local ISM, meaning that the metallicity distribution is a signpost to recent gas accretion. Therefore, we searched for regions with anomalously low metallicity in the IFU survey MaNGA. I will present how such regions are distributed within mergers, close pairs, and isolated galaxies, and how gas accretion happens in these systems. I will also discuss the lifetime of such regions, the balance between gas accretion and star formation rates, and the implication for galaxy evolution.

Weichan Wang (JHU)

Galaxy Inclinations and the Dust Attenuation Law at z~1.5
Measuring how fast galaxies form stars is the key step to understand galaxy formation at high redshift. The measurement is usually based on galaxy UV luminosity. However, high-redshift galaxies can be substantially obscured by dust in the UV and a proper correction for dust is needed. The correction is quantified by the infrared-to-UV luminosity ratio, IRX=L(IR)/L(UV). And IRX is usually inferred from the slope of galaxy UV spectrum, beta. We present the discovery that the relation between IRX and beta varies systematically with galaxy inclination. This applies to massive and star-forming disk galaxies (above 10^10 solar mass) at z~1.5. Such inclination dependence is consistent with a two-component model of dust distribution inside galaxies. Dust and stars are spatially mixed in the diffuse interstellar medium, and young stars are additionally surrounded by dust cocoons near their H II regions. Interestingly, for less massive galaxies at this epoch, we do not find evidence for a similar inclination dependence. This is likely because low-mass galaxies are more prolate and have disturbed gas kinematics.

1 October

Andrew Youdin (UC Berkeley)

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Yuan-Sen Ting ()

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8 October

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Paz Beniammini (GWU)

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15 October

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Alice Pisani (Princeton)

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22 October (GSS)

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29 Kevin France (Colorado)

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5 November

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12 November =

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26 November (GSS)

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3 December

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