Wine and Cheese Fall 2019

This page records the schedule, titles and abstracts of the JHU/STScI CAS Astrophysics Wine & Cheese Series in Fall 2019.

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.

9 September

Speaker (TDB)

Title
Abstract

16 September

Joshua Kable (JHU)

Using CMB Consistency Checks to Understand Tensions
In recent years tensions have arisen between cosmological measurements. The most serious involves the Hubble constant, but there are other tensions as well. In light of these tensions, consistency checks provide valuable checks of the presence of underestimated or unidentified systematic errors and may provide insights into potential extensions to LCDM to resolve tensions. Toward this end, we derived a new analytic method for calculating the correlations between correlated data sub-sets that can assess the consistency of parameter constraints from various CMB power spectra. We applied this method to the most recent SPTpol data set and conclude that these correlations need to be accounted for when performing internal TT vs TE vs EE consistency checks in future CMB experiments. In addition, I will discuss the degeneracy between H0 and the matter density across several current CMB experiments showing that the degeneracy directions are consistent with LCDM predictions (Kable et al. 2019).

Yajing Huang (JHU)

Accounting for Correlations When Fitting Extra Cosmological Parameters
Current cosmological tensions motivate investigating extensions to the standard $\Lambda$CDM model. Additional model parameters are typically varied one or two at a time, in a series of separate tests. The purpose of this paper is to highlight that information is lost by not also examining the correlations between these additional parameters, which arise when their effects on model predictions are similar, even if the parameters are not varied simultaneously. We show how these correlations can be quantified with simulations and Markov Chain Monte Carlo (MCMC) methods. As an example, we assume that $\Lambda$CDM is the true underlying model, and calculate the correlations expected between the phenomenological lensing amplitude parameter, $A_L$, the running of the spectral index, $n_{\rm run}$, and the primordial helium mass fraction, $Y_P$, when these parameters are varied one at a time along with the $\Lambda$CDM parameters in fits to the $\textit{Planck}$ 2015 temperature power spectrum. These correlations are not small, ranging from 0.31 ($A_L-n_{\rm run}$) to $-0.93$ ($n_{\rm run}-Y_P$). We find that the values of these three parameters from the $\textit{Planck}$ data are consistent with $\Lambda$CDM expectations within $0.9\sigma$ when the correlations are accounted for. This does not explain the 1.8-2.7$\sigma$ $\textit{Planck}$ preference for $A_L>1$, but provides an additional $\Lambda$CDM consistency test. For example, if $A_L>1$ was a symptom of an underlying systematic error or some real but unknown physical effect that also produced spurious correlations with $n_{\rm run}$ or $Y_P$ our test might have revealed this. We recommend that future cosmological analyses examine correlations between additional model parameters in addition to investigating them separately, one a time.

Sumit Dahal (JHU)

The Cosmology Larger Angular Scale Surveyor (CLASS) Detector Design and Performance
The Cosmology Large Angular Scale Surveyor (CLASS) aims to detect and characterize the primordial B-mode signal, and make a cosmic variance limited measurement of the optical depth to reionization. CLASS is a ground-based multi-frequency microwave polarimeter that surveys 70% of the microwave sky from the Atacama Desert. CLASS uses a unique combination of large sky coverage, control of systematic errors, and high sensitivity detectors to measure or place upper limits on the tensor-to-scalar ratio at a level of r = 0.01. In June 2019, CLASS fielded a 150/220 GHz dichroic detector array alongside the existing 40 and 90 GHz instruments. In this talk, I will focus on the design and performance of the CLASS detectors, and update on the current status of CLASS telescopes.

23 September

Henrique Reggiani (JHU)

Metal-poor Stars in the Inner Halo: Hints on Galaxy Formation and Chemical Evolution
We studied the Formation and early Chemical Evolution of the inner Galactic halo via precise chemical abundances of the metal-poor stellar component, via a sample of high-resolution, and high S/N spectra, analyzed with the line-by-line differential abundance technique. We see evidence that the inner halo was formed by one major merger event, and we use our abundance patterns to constrain a chemical evolution model. As byproduct of our analysis, we studied binary stellar evolution and nucleosynthesis in AGB stars using two Blue Stragglers. I will also show the results of a study focused on a pair of binary stars with further implications on the formation of the inner halo and the use of chemical tagging to constrain the birth environment of stars, and implications of possible planetary formation in metal-poor stars. At last, the outcome of atomic modeling for a non-LTE analysis of potassium line formation, and the study of the chemical evolution of potassium through cosmic history.

Andrei Vayner (JHU)

Quasar Host Galaxies and their Environments with Multi-Wavelength 3D Spectroscopy
I will present results from a multi-wavelength survey of distant (1.3 < z < 2.6) luminous quasars host galaxies. The data was obtained using the Keck integral field spectrograph (IFS) OSIRIS and laser guide star adaptive optics (LGS-AO) system, ALMA, HST, and VLA. Studying distant quasar host galaxies is essential for understanding the role of active galactic nuclei (AGN) feedback on the interstellar medium (ISM), and its capability of regulating the growth of massive galaxies and their supermassive black holes (SMBH). The combination of LGS-AO and OSIRIS affords the necessary spatial resolution and contrast to disentangle the bright quasar emission from that of its faint host galaxy. We resolve the nebular emission lines Hβ, [OIII], [NII], Hα and [SII] at a sub-kiloparsec resolution to study the distribution, kinematics, and dynamics of the warm-ionized ISM in each quasar host galaxy. The goal of the survey was to search for ionized outflows and relate their spatial extent and energetics to the star-forming properties of the host galaxy. Combining ALMA and OSIRIS, we directly test whether outflows detected with OSIRIS are affecting the molecular ISM. I will discuss the origins of outflows in these quasar host galaxies and their role in depleting the gas reservoir and the implication for massive galaxy formation and evolution. We are now obtaining detailed observations of the circumgalactic medium (CGM) of these systems with the newly commissioned Keck Cosmic Web Imager (KCWI). The gas in the CGM may play an essential role in the evolution of these galaxies. I will show preliminary results from deep observation on several sources taken over the last year.