Accepted Cycle 20 Theory Proposals

Proposal Number	Subject Category	PI Name	Title
20200552	STARS AND WD	Cecilia Garraffo	MODELING CHANDRA OBSERVATIONS OF DISK-STAR INTERACTION
20400027	BH AND NS BINARIES	Davide Lazzati	The afterglows of binary neutron star mergers: telling a jet from a balloon
20500580	SN, SNR AND ISOLATED NS	Guo-Xin Chen	The Atomic Physics of Fe XVII X-ray Line Emission: Towards Accurate Diagnostics for Supernova Remnants
20700378	ACTIVE GALAXIES AND QUASARS	Mislav Balokovic	Modeling X-ray Reprocessing in AGN at High Spatial and Spectral Resolution
20700638	ACTIVE GALAXIES AND QUASARS	Mackenzie Jones	A physical model connecting black hole growth to the cosmic X-ray background.
20800431	CLUSTERS OF GALAXIES	August Evrard	Calibrating Optical Cluster Samples with X-rays: Simulation Modeling to Support DES-redMaPPer Analysis
20800555	CLUSTERS OF GALAXIES	Shy Genel	Understanding what sets the metallicity distribution in the atmospheres of groups and clusters
20900304	EXTRAGALACTIC DIFFUSE EMISSION AND SURVEYS	Anastasia Fialkov	The Nature of the First X-ray Sources: Signatures in the X-ray Band and at 21 cm
20910134	GALACTIC DIFFUSE EMISSION AND SURVEYS	Aigen Li	Interstellar X-Ray Absorption and Scattering

Subject Category: STARS AND WD

Proposal Number: 20200552

Title: MODELING CHANDRA OBSERVATIONS OF DISK-STAR INTERACTION

PI Name: Cecilia Garraffo

We propose to implement a Keplerian disk in the state-of-the-art BATS-R-US global 3D MagnetoHydroDynamics (MHD) code in order to study Classical T Tauri Stars (CTTS) and their X-ray observations. The end result will be the next generation modeling framework for CTTS and a unique standard tool to study and disentangle the complicated multi-physical processes both fluid and kinetic in the global dynamics of these systems. Such code will allow us to understand the influence of the stellar wind on the protoplanetary disk and the impact of the disk on the activity of the star.

Subject Category: BH AND NS BINARIES

Proposal Number: 20400027

Title: The afterglows of binary neutron star mergers: telling a jet from a balloon

PI Name: Davide Lazzati

The almost simultaneous observation of gravitational waves and gamma-rays from GW170817 proved that binary neutron star mergers are associated with short gamma-ray bursts. However, it is still unclear wheter GW170817 was a misaligned short GRB or a weak, spherical outflow. Chandra observations and a detailed modeling of the afterglow are key to pinning down the nature of GW170817. We propose to develop a code to study the key characteristics of afterglows from binary neutron star mergers, including the polar structure of the jet, radial stratification of the ejecta, and a high energy cutoff in the electrons' distribution. The code will produce images, spectra, polarization, and light curves that will be fundamental in interpreting Chandra data of GW170817 and other LIGO mergers.

Subject Category: SN, SNR AND ISOLATED NS

Proposal Number: 20500580

Title: The Atomic Physics of Fe XVII X-ray Line Emission: Towards Accurate Diagnostics for Supernova Remnants

PI Name: Guo-Xin Chen

We propose to study strong Fe XVII X-ray line emission produced by supernova remnant 1987A and other compact SNR. Our calculations of 2 lines 3C at 15.01 and 3D at 15.26 Angstroms demonstrate that we can reproduce the measured line intensity ratio at lab. The calculation of three 3s lines near 17 Angstroms is not straightforward because the effects of resonances near threshold, recombination, cascades from highlying levels, and electron distributions can all be more important than direct excitation. Recombination to the 3s levels is important for non-equilibrium ionization (NEI) plasmas, making 3s/3d line ratio a good diagnostic. Using the new atomic data, we will compute 3s/3d by the APEC code under conditions of both equilibrium and NEI, and disseminate the results to the community.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 20700378

Title: Modeling X-ray Reprocessing in AGN at High Spatial and Spectral Resolution

PI Name: Mislav Balokovic

The principal objective of the proposed project is the calculation of spectra formed via X-ray reprocessing in the AGN torus and the innermost regions of AGN host galaxies. Recent Chandra observations found that reprocessed emission, typically assumed to be due to the compact AGN torus, can be extended up to kpc scales in some nearby AGN. Models with a higher degree of realism than those currently available are needed to self-consistently interpret those observations. With modest modification of our existing radiative transfer code, we aim to provide tabulated libraries of spectral templates to the community in the form useful for spectral analysis of X-ray data from Chandra in particular, but also NuSTAR, and future X-ray telescopes.

Subject Category: ACTIVE GALAXIES AND QUASARS

Proposal Number: 20700638

Title: A physical model connecting black hole growth to the cosmic X-ray background.

PI Name: Mackenzie Jones

Chandra has revolutionized our understanding of black hole growth, resolving up to 80% of the cosmic X-ray background (CXB) emission at 2-8 keV. However, important questions remain: At the peak energy of the CXB (~30 keV) a large fraction (~40%) is unaccounted for by Chandra sources, and the physical conditions under which the CXB is produced (e.g., Eddington ratios, halo masses, galaxy properties) remain unclear. This project aims to use a simple but powerful physical model of the AGN and galaxy populations resolved by Chandra to investigate the origin of the CXB. This model will allow us to investigate the black hole, galaxy, and dark matter properties of the missing 20-40% of the CXB that Chandra is unable to resolve and enable predictions for the next generation of X-ray observatories.

Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 20800431

Title: Calibrating Optical Cluster Samples with X-rays: Simulation Modeling to Support DES-redMaPPer Analysis

PI Name: August Evrard

This proposal seeks to develop a simulation and modeling workflow to support accurate interpretation of X-ray studies for Dark Energy Survey redMaPPer-selected cluster samples. The work addresses more careful treatments of systematic uncertainties, especially those related to poorly known property covariance, and a better understanding of selection biases. We will address these issues by developing a simulation-based framework for joint X-ray and optical analysis designed specifically to support interpretation of X-ray follow-up studies of DES RM samples. Selection functions --- mapping derived properties from synthetic observations to input ``truth'' --- along with the covariance among X-ray and optical properties at fixed halo mass, are important factors in this work.

Subject Category: CLUSTERS OF GALAXIES

Proposal Number: 20800555

Title: Understanding what sets the metallicity distribution in the atmospheres of groups and clusters

PI Name: Shy Genel

The distribution of metals in cluster atmospheres probes multiple processes occurring both in proto-cluster environments and inside clusters themselves. Chandra observations, generally indicating significant core metallicity dispersions and relative outskirts uniformity, therefore provide constraints to theoretical models. We propose to interpret these observations using the IllustrisTNG simulation - a (300Mpc)^3 cosmological volume with a full model of galaxy formation, where hundreds of 10^(14-15)Msun halos are resolved with 10^7Msun baryonic resolution elements. We will perform mock observations and compare simulated to observed clusters, follow the flow of metals from their production sites into and within the clusters, and determine when, where, and which processes are most important.

Subject Category: EXTRAGALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 20900304

Title: The Nature of the First X-ray Sources: Signatures in the X-ray Band and at 21 cm

PI Name: Anastasia Fialkov

In this theory proposal we develop synergy between large-scale X-ray and radio observations. Such synergy has never been developed in full detail and will become important in future with experiments such as Lynx (X-rays) and HERA (21-cm) coming online. Here we propose to explore properties of cross-correlation between the 21-cm signal and the unresolved cosmic X-ray background as a way to probe both the character of the high-redshift X-ray population and the big picture of the evolution of the Universe.

Subject Category: GALACTIC DIFFUSE EMISSION AND SURVEYS

Proposal Number: 20910134

Title: Interstellar X-Ray Absorption and Scattering

PI Name: Aigen Li

Accurate estimates of the absorption of X-rays by interstellar gas and dust are crucial for the analysis and interpretation of almost all astronomical soft X-ray observations. Presently, the interstellar X-ray absorption data extensively used by the X-ray community were that of Wilms et al. (2000). However, their results were computed based on a subsolar interstellar abundance. Also, they used the self-shielding approximation to estimate the X-ray absorption of dust which ignores scattering. Therefore, the X-ray absorption of Wilms et al. could have been substantially underestimated. We propose to update the interstellar X-ray absorption and scattering by making use of updated atomic data, updated abundances, and realistic X-ray dust physics. A Fortran code will be provided for XSPEC.