Wine and Cheese Spring 2021

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.

01 February

Vadim Burwitz (MPE)

The eROSITA X-ray Telescope Onboard the Spektr-RG Observatory: First Results
In my talk I will describe the eROSITA X-ray telescope onboard the Russian-German mission Spektr-RG that was launched in July 2019 from Baikonur. After an inflight calibration and performance verification phase the all sky survey commenced in December 2019. Since then two all sky surveys have been completed. Work is ongoing to analyse the rich yield of data. I will also present an overview of the first exiting scientific results that have been obtained over the last year (from stars, x-ray binaries to AGN, Clusters as well as diffuse X-ray emission).

08 February

Xinfeng Xu (JHU)

Extreme Outflows in Quasars: Most Energetic & Largest Accelerated Outflows
Supermassive black holes (SMBHs) are believed to exist in the center of almost all massive galaxies, and the active ones are named “active galactic nuclei” (AGN). Quasars are among the most luminous AGNs and show ubiquitous outflows, where blue-shifted absorption and emission lines are attributed to sub-relativistic (~1000 - 10,000 km/s) mass ejection. Outflows could be the prime candidates for producing various AGN feedback processes in galactic-scale: curtailing the growth of the host galaxy, explaining the relationship between the masses of the central black hole and the galaxy’s bulge, and chemical enrichment of the surrounding environment (ICM and IGM). In this talk, I will present my research progress on discovering quasar outflows with extreme physical properties (energies and accelerations), where our data was collected by the Hubble Space Telescope.

Renata Cumbee (UMCP/GSFC)

Astrophysical Charge eXchange: From the Laboratory to the Cosmos
Comets, planets, star-forming galaxies, supernova remnants, and galaxy clusters can all produce rich X-ray emission spectra. Disentangling the individual emission lines and processes that form them teaches us about the formation of these objects. The X-ray spectrum resulting from charge exchange (CX) - which involves a collision between an ion and a neutral atom or molecule - varies strongly based on the present ions, atoms or molecules, and the velocity of the collision. With a reliable CX model, this process can be used as a diagnostic tool for understanding neutral and ion density distributions, ion temperatures, elemental abundances, and ion charge state distributions in these environments. A reliable CX model requires a set of accurate, velocity-dependent cross-sections for a wide range of collision velocities and any relevant ions and neutrals that might be observed astrophysically. Theoretical methods used for calculating these cross-sections are often only relevant for a subset of these parameters, and these calculations must be benchmarked against experiments when possible. I introduce the process for preparing and testing the reliability of a CX model and provide examples of spectra in which this process is of particular importance.

15 February

Cicero Lu (JHU)

Constraining the Role of Collisions in the beta Pictoris Debris Disk
Debris disks provide exciting opportunities to study planet formation through their compositions and architectures. My current project examines an archetypal debris disk, beta Pictoris (βPic), with the Spitzer Infrared Spectrograph (IRS). The βPic disk is one of the few systems that can be spatially-resolved, providing extra-solar spatial distribution of mineralogy for comparison with that of the solar system. I aim to (1) examine silicate distribution in the βPic disk as a function of stello-centric distance, and (2) constrain the origin of the CO gas concentration at 65 AU (~3’’) in the southwest side of the disk (Dent et al. 2014). By performing an Advanced Optimal Extraction (Lebouteiller et al. 2010), I discovered pronounced 19 and 23 μm forsterite emission bands for the first time. My preliminary spectral modeling results indicate that the 18 μm band is well-fitted by a 98.9 percent Mg-rich forsterite, consistent with the stoichiometry of the 69 μms forsterite feature with Herschel Photodetector Array Camera and Spectrometer (PACS) (De Vries et al. 2012). Such Mg-rich silicates grain composition shows that the parent bodies - planetesimals - are primitive and unprocessed, similar to the comets seen in the Kuiper belt in the solar system. I also found that the 18 μm band is fitted well by a model with two rings of forsterite grains at 300 K and 100 K, indicating a spatial gradient in crystalline grains. I have also explored a range of grain shape distributions, including spherical grains calculated from Mie theory and continuous distribution of ellipsoids. The fitting results show that the true shape distribution is a mixture of the two and the relative ratio needs to be further explored with MCMC and particle swarm optimization. For the second task, my preliminary result shows no evidence of small grains; the spatially-resolved spectrum lacks triangle-shaped silicate emission features produced by sub-μm sized dust. For future work, I will measure the grain size distribution and compare it quantitatively with the blowout size of the system.

Carrie Filion (JHU)

Constraining the Low-Mass Stellar Initial Mass Function of the Boötes I Ultra-Faint Dwarf Galaxy
The stellar initial mass function (IMF) describes the mass distribution of (single) stars formed in any one star formation event. The IMF plays a crucial role in the evolution of stellar populations and underpins the interpretation of observations across a wide range of topics and scales, from cosmic reionization to stellar feedback in simulations of galaxy formation. Empirical evidence from different age and metallicity populations in the Milky Way, such as the old, metal-poor stellar halo and the young, metal-rich local disk, reveal an IMF that is consistent with being invariant. It is unclear, however, if the IMF of other galaxies is the same as that of the Milky Way. The low-mass end of the IMF, below one solar mass, is particularly uncertain and can be constrained in nearby populations, where individual low-mass stars can be resolved, via star-count analysis. In this talk, I discuss my on-going analysis of the low-mass IMF of the Boötes I ultra-faint dwarf galaxy.

Mario Aguilar Faúndez (JHU)

Does H0LiCOW’s Hubble Constant Correlation with Lens Redshift Offer a Clue to the Hubble Tension?
We study late time phenomenological model deviations from the flat LCDM cosmology in their capacity to reduce the descending trend of the Hubble constant H0 with lens redshift reported by the H0LiCOW collaboration. We consider a low redshift (z<2.3) cosmological dataset comprising strong-lensing time delay (SLTD) data and type Ia SNe. The model modifications of the flat LCDM scenario under study include a linear reparametrization in redshift of the Hubble constant H0, linear and quadratic perturbations in redshift, or a Cubic Spline model reconstruction of the late time expansion history. Doing so, we find that for some models is possible to achieve a relief of this internal tension when fitting the SLTD data alone, but a low redshift model departure from a LCDM cosmology is extremely unlikely to mitigate the measured H0–lens redshift correlation when Type SNe Ia data is included.

22 February

Sarah Millholland (Princeton)

Tidal Sculpting of Short-Period Exoplanets
Multiple-planet systems composed of close-in super-Earth/sub-Neptune-sized planets are ubiquitous, representing the dominant outcome of planet formation. This population exhibits predictable hallmarks of architectural regularity and uniformity, such as low eccentricities and inclinations, similar orbital spacings, and intra-system correlations in planetary masses and radii. On top of this first-order structure, however, these systems also exhibit surprising anomalies that require explanation. Examples include (1) ultra-short period planets, whose extremely-irradiated orbits have been separated off from the rest of their systems; (2) planets piled up wide of mean-motion resonances; and (3) a subset of Neptune-sized planets that show signs of radius inflation. In this talk, I will propose that tidal dynamics can account for these specific anomalies and more. Specifically, I will discuss the critical role of enhanced tidal dissipation due to non-zero planetary axial tilts (obliquities), which arise by way of prevalent dynamical resonances. I will highlight strategies for testing these tidal theories and observing obliquities directly in the future.

1 March

Kirk Barrow (KIPAC)

Using High-Cadence Synthetic Observations to Unlock a New Era in Astrophysics
As astronomers near the commissioning of the extremely large telescopes, the Rubin Observatory, as well as new space-based observatories like the Roman Space Telescope and JWST to peer more deeply into our Universe, our community is challenged to develop a theoretical and modeling framework to characterize and study what will be humanity's greatest astronomical discoveries. My research addresses this need by generating detailed, state-of-the-art synthetic observations from hydrodynamic cosmological simulations. By calculating all the processes that photons undergo as they travel across the Universe from the surface of a distant star to a telescope’s detector, my collaborators and I have been able to disentangle perplexing trends in observed galactic spectra as well as make predictions for what we might unveil in the near future. Topics we have investigated in prior work include massive black hole formation, the first stars and galaxies, and the intricate interplay between nebular emission lines and the escape fraction of ionizing radiation. Looking forward, I propose to create the largest and most detailed database of synthetic observational tools and predictions at a time that will come to define astronomy for generations.

8 March

Jennifer Marshall (Texas A&M)

The Future of Massively Multiplexed Spectroscopy: the Maunakea Spectroscopic Explorer
The Maunakea Spectroscopic Explorer (MSE) is a planned next generation massively multiplexed spectroscopic facility that is completely dedicated to optical and near-Infrared spectroscopy of samples of thousands to millions of astrophysical objects at resolutions from R~3,000 to R~40,000. With science goals spanning all of astronomy, from detailed chemical abundance studies of nearby stars to investigating the cosmology of the early Universe, MSE will provide key next-generation science capabilities that will revolutionize the field. In this talk I will review the current status of the project and provide an overview of MSE's wide range of scientific capabilities.

29 March

Ani Thakar & Jordan Raddick (JHU)

SciServer - a Science Platform for SDSS and Beyond

SciServer (www.sciserver.org) is an online science platform developed by IDIES (idies.jhu.edu) that offers instant browser-based access to Petabytes of scientific data in astronomy and other sciences. This includes the Sloan Digital Sky Survey (SDSS) datasets. In fact SciServer is the official science platform for the SDSS catalog data, and will continue to host the data for the SDSS-V mappers as well.

When you sign up for a free SciServer account, you gain access to our virtual computing resources, including 10 GB of personal, backed-up storage space and nearly unlimited shared space for temporary data products. In addition to the stalwart SDSS science portals, SkyServer and CasJobs, SciServer provides many new server-side science capabilities. You can analyze, visualize, and publish all available datasets along with your own, using Python or R scripts in Jupyter notebooks. There is a new spectrum analysis tool that can be used in standalone mode or within a Jupyter notebook.

With easy data and resource sharing features and no required setup, SciServer makes an excellent resource for collaborative research and for teaching undergraduate courses.

In this live interactive demo session, learn how to access images, spectra, and catalog data from SDSS (including MaNGA/Marvin) and HEASARC, along with catalog parameters and flat files from the Indra and Millennium Simulations. To save time during the demo, please register for a SciServer account beforehand. You will learn about the 20+ sample Jupyter notebooks that you can adapt for your own research and teaching.

05 April

Daniel Zucker (Macquarie)

The Southern Stellar Stream Spectroscopic Survey (S5)
Over a dozen new stellar streams in the halo of the Milky Way have been discovered in the southern hemisphere with the Dark Energy Survey (DES) in recent years, with other datasets yielding additional stellar substructure. To study these we have embarked on an ongoing spectroscopic program, S5, which has been mapping these southern streams with 2df+AAOmega on the AAT. An international collaboration, S5 is the first systematic program pursuing a complete census of known streams in the southern hemisphere. The radial velocities and stellar metallicities from S5 - together with proper motions from Gaia - provide us with a unique dataset for understanding the stellar populations of the Milky Way's halo, the progenitors and formation processes of the streams, the mass and overall morphology of the Milky Way's gravitational potential, and ultimately potential clues to the nature of dark matter. I will give an overview of the S5 program, including target selection, observation, and data analysis, present early science results from S5 data and follow-up observations, and discuss some of the implications of these results for the study of Milky Way streams and satellites in the context of current and future major astronomical surveys.

12 April

Ryan Trainor (F&M)

Galaxy Formation in Lyman-alpha or: How I Learned to Stop Worrying and Love Scattered Light
Lyman-alpha emission is produced ubiquitously by excited hydrogen, so it is a powerful tracer of the interactions among gas, stars, and AGN that shape galaxy formation. However, the resonant scattering of this emission line makes its interpretation complex. In this talk, I will describe three spectroscopic surveys of >1000 galaxies at z~2-3 that make use of Lyman-alpha emission: the Keck Baryonic Structure Survey (KBSS), the KBSS-Lya, and the Keck Lyman Continuum Survey (KCLS). By understanding when and where Lya escapes galaxies, we can characterize galaxy feedback, supermassive black hole growth, and the nature of cosmic reionization. In each of these efforts, the scattered nature of Lyman-alpha emission can be a tool as well as a challenge.

26 April

Roberto Cotesta (JHU)

Enriching the Symphony of Gravitational Waves from Binary Black Holes by Tuning Higher Harmonics
Accurate models of gravitational waveforms are necessary to take full advantage of the increase in sensitivity of current and future gravitational wave detectors. In this talk, I will show the impact of more accurate waveform models for binary black holes (BBH), which include the effect of spin-precession and higher harmonics, on the precision and accuracy of the inferred parameters of these sources. I will first focus on the role of these waveform models in the source characterisation of the stellar-mass BBHs detected during the third LIGO and Virgo observing run (O3). I will then explain how the same waveform models can be used for the parameter estimation of massive BBH observable with the space-based interferometer LISA, and describe their impact on the characterisation

of these sources.