Bulletin of the American Physical Society
Mid-Atlantic Section 2022 Meeting
Volume 67, Number 20
Friday–Sunday, December 2–4, 2022; University Park, PA, Pennsylvania State University
Session G02: Astrophysics II |
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Chair: Frank Schroeder, University of Delaware Room: Pennsylvania State University Osmond 104 |
Sunday, December 4, 2022 9:00AM - 9:35AM |
G02.00001: Particle Acceleration in Multimessenger & MeV Blazars Invited Speaker: Tiffany R Lewis The acceleration mechanisms in blazars jets are currently uncertain. In order to study particle acceleration in this environment, we have to filter through the additional uncertainty in the high-energy emission processes. What has become clear regardless is that to understand either requires simulating both acceleration and cooling processes accurately in the particle population. The advent of new data types, like high-energy polarization and coincident neutrinos point toward shock acceleration and leptohadronic composition for at least some blazars. Thus, I present some theoretical models that treat these cases for a sample of MeV bright and Multimessenger blazars relevant for the AMEGO-X mission concept and future MeV missions in the context of a future vision for a balanced multimessenger and multiwavelength approach to programatic planning. |
Sunday, December 4, 2022 9:35AM - 9:47AM |
G02.00002: The Nature of the X-ray Emission and Innermost Accretion Regions of Typical Radio-Loud Quasars William N Brandt, Shifu Zhu, John Timlin Radio-loud quasars (RLQs) are typically more X-ray luminous, by a factor of 2-20, than matched radio-quiet quasars (RQQs). This excess X-ray emission has generally been attributed to small-scale jets. To determine the nature of this excess X-ray emission, we have constructed a large, uniform sample of 729 optically selected RLQs and investigate correlations between X-ray, optical/UV, and radio luminosities. Strikingly, we find that steep-spectrum RLQs (SSRQs) follow a quantitatively similar relation between X-ray vs. optical luminosities as RQQs, suggesting a common accretion-disk corona origin for the X-ray emission of both classes. Formal statistical model selection supports these conclusions, as does consideration of analogies with black-hole X-ray binaries. However, the relation's intercept for SSRQs is larger than that for RQQs and increases with radio loudness, suggesting a connection between the radio jets and the accretion-flow configuration. Spectral measurements of X-ray continuum shapes and (average) reflection signatures confirm these conclusions, as do measurements of weeks-years X-ray variability. The observed corona-jet connection implies that small-scale processes in the vicinity of black holes, probably associated with the magnetic flux/topology instead of black-hole spin, are controlling quasar radio loudness. |
Sunday, December 4, 2022 9:47AM - 9:59AM |
G02.00003: Constraining the Temperature Evolution of the Cosmic Microwave Background Using the Sunyaev-Zeldovich Effect with SPT-3G Milo Korman, Srinivasan Raghunathan, Riccardo Gualtieri The adiabatic temperature evolution of the Cosmic Microwave Background (CMB) is a fundamental prediction of the standard model of cosmology. Deviations from adiabatic temperature evolution would leave a characteristic signature in the Sunyaev-Zeldovich Effect (SZE). The SZE is caused by inverse Compton scattering of CMB photons off of hot electrons in galaxy clusters, and if the CMB temperature evolves adiabatically the SZE is independent of redshift. However, deviations from adiabatic temperature evolution lead to a redshift dependence in the SZE. In this talk, I will present results from an ongoing work to look for deviations from adiabatic CMB temperature evolution parameterized as T(z)=(1+z)(1-α). This work uses maps from SPT-3G, the third-generation camera on the South Pole Telescope, along with previously cataloged galaxy clusters detected by SPT-SZ to obtain new constraints on deviations from α=0, the value predicted by standard cosmology. |
Sunday, December 4, 2022 9:59AM - 10:11AM |
G02.00004: Revising the Rotational Period of NGC 1624-2 Shaquann S Seadrow, Véronique Petit, Gregg Wade, Alexandre David-Uraz, David Bohlender, Jesús Maíz Apellániz It has been found that approximately one in ten massive stars unexpectedly have large-scale surface magnetic fields. Considerable research effort has been aimed at understanding the origins of these fields, their characteristics, and their overall impact on massive star astrophysics. Among this subpopulation, NGC 1642-2 hosts the strongest magnetic field ever measured on an O-star (20 kG polar), which is ten times stronger than that of the 2nd in rank. We measure a new rotational period for NGC 1642-2 after finding that the previously adopted 157.99 ± 0.94 d period does not accurately phase-fold recent observations. We assemble a multi-epoch, multi-instrument, collection of spectroscopic and spectropolarimetric observations and analyze the variations of several optical spectral lines with Lomb Scargle and Phase Dispersion Minimization periodograms. We report a rotational period of 153.57 days, and report on the implications of this revised period for previous observational studies of this important star. |
Sunday, December 4, 2022 10:11AM - 10:23AM |
G02.00005: Identification and Characterization of a Large Sample of Distant Active Dwarf Galaxies in XMM-SERVS Fan Zou, William N Brandt Active dwarf galaxies are important because they contribute to the evolution of dwarf galaxies and can reveal their hosted massive black holes. However, the sample size of such sources is still highly limited, especially beyond the local universe. In this work, we search for active dwarf galaxies in the recently completed XMM-SERVS survey, which is currently the largest medium-depth X-ray survey. After considering several factors that may lead to misidentifications, we identify 87 active dwarf galaxies at z < 1.2, which constitutes the current largest sample beyond the local universe. Our sources are generally less obscured than the prediction based on the massive-AGN (active galactic nucleus) X-ray luminosity function. Their Eddington ratios and X-ray bolometric corrections also significantly deviate from the expected relation. We find that our sources reside in similar environments as for inactive dwarf galaxies. We further quantify the accretion distribution of the dwarf-galaxy population after considering various selection effects and then analyze the dependence of the active fraction on stellar mass, redshift, and luminosity. Throughout this work, we highlight several fundamental problems in reliably measuring some basic parameters for distant active dwarf galaxies. |
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