Bulletin of the American Physical Society
APS April Meeting 2018
Volume 63, Number 4
Saturday–Tuesday, April 14–17, 2018; Columbus, Ohio
Session S16: Active Galaxies |
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Sponsoring Units: DAP Chair: Jeremy Perkins, NASA Room: B232-233 |
Monday, April 16, 2018 1:30PM - 1:42PM |
S16.00001: Halo Occupation of Quasars: AGN Unification From a Cosmological Perspective Kaustav Mitra, Suchetana Chatterjee, Michael DiPompeo, Adam Myers, Zheng Zheng We use the angular two-point correlation function (2PCF) of obscured and unobscured quasars selected using the Wide-field Infrared Survey Explorer (WISE), at a median redshift of z $\sim$ 1. Our theoretical framework, a five-parameter Halo Occupation Distribution (HOD) model, derived from a cosmological hydrodynamic simulation by Chatterjee et al. (2012), was previously used to model the 2PCF of optically selected quasars and X-ray bright active galactic nuclei (AGN). The current work shows that a single HOD parametrization can be used to model the population of different kinds of AGN in dark matter halos suggesting the universality of the relationship between AGN and their host halos. Our results show that the median dark matter halo mass of central quasar hosts and the projected satellite fractions tend to increase from unobscured to obscured quasars, and hence tend to disfavor a simple `orientation only' theory of AGN unification. We show that future measurements of the small-scale clustering of obscured quasars can put constraints on the current theories of AGN - supermassive black hole co-evolution, where quasars evolve from an IR-bright obscured phase to the optically bright unobscured phase. [Preview Abstract] |
Monday, April 16, 2018 1:42PM - 1:54PM |
S16.00002: Connecting the kinetic flux of X-ray jets to a spinning, super-massive black hole. Dan Schwartz We model the X-ray emission of large scale quasar jets as due to inverse Compton scattering off the cosmic microwave background. This allows an estimate the kinetic flux of the jet to be made based on direct measurements of the jet itself! We use this model to estimate the kinetic fluxes carried by 31 quasar jets detected in a survey by Marshall et al. (2005, 2011, 2018). Massive black holes greater than 10$^8$ solar mass with spin parameters greater than 0.3, can provide this energy for millions of years via the Blanford/Znajek (1977) effect. Equating the kinetic flux to the energy flux emitted from the vicinity of the black hole, and assuming the latter is initially a pure Poynting flux, we can estimate the magnetic field strength at the gravitational radius of the hole, and find it comparable to strengths deduced for magnetically arrested disks (Narayan+ 2003). Since the Poynting vector carries both the energy and the angular momentum lost by the black hole, we can derive constraints on the magnetic field as a function of jet radius. [Preview Abstract] |
Monday, April 16, 2018 1:54PM - 2:06PM |
S16.00003: HAWC Search for Extreme TeV Flares from Blazars Thomas Weisgarber We present a search for hour-scale extreme TeV flares from 187 blazars monitored by the HAWC observatory. HAWC is a ground-based gamma-ray survey instrument operating in the TeV energy band. With its wide field of view of $\sim$2 sr, HAWC facilitates searches for rapid variability at TeV energies. In this presentation, we describe the HAWC real-time flare monitor and report on the detection of several rapid flares in data collected over a period of more than three years. We discuss the prospects for future multiwavelength studies of extreme flares detected by the real-time flare monitor to provide clues into the mechanisms powering the blazar jets and probe the particles and fields in intergalactic space. [Preview Abstract] |
(Author Not Attending)
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S16.00004: Statistical Detection of TeV Blazars with the HAWC Real-Time Flare Monitor Stefan Westerhoff, Michael Scott, Thomas Weisgarber The HAWC observatory is a ground-based gamma-ray detector with sensitivity in the TeV energy band. We present a search for TeV blazars using triggers from the HAWC real-time flare monitor that fall below the standard threshold criterion for detection. This search enables us to detect blazars statistically via the different distribution of triggers that their low level of VHE emission produces. We interpret these results as a limit on the rate of extreme TeV blazar flares. [Preview Abstract] |
Monday, April 16, 2018 2:18PM - 2:30PM |
S16.00005: Tidal Stream Circularization by Schwarzschild Black Holes Michael Kesden, Juan Servin A star that wanders within the tidal radius $r_t \simeq R_\star (M_\bullet/M_\star)^{1/3}$ of a supermassive black hole (SMBH) will be torn apart by the tidal field of the SMBH. Approximately $50\%$ of the tidal debris will become gravitationally bound to the black hole and evolve into a tidal stream with a distribution of specific binding energies of width $\Delta\epsilon \simeq GM_\bullet R_\star/r_t^2$. This tidal stream must dissipate substantial energy [increasing its specific binding energy to $E_c \simeq (\Delta\epsilon/4)( M_\bullet/M_\star)^{1/3}$] if it is to form a quasi-circular accretion disk at the circularization radius $r_c \simeq 2r_t$ from which gas can be accreted onto the SMBH, powering a luminous tidal disruption event (TDE). This energy dissipation may occur in an inelastic collision when the stream intersects with itself. The timing and efficiency of energy dissipation at this collision point depends crucially on the kinematics of the tidal stream including relativistic apsidal precession. We calculate the energy dissipated at the collision point as a function of SMBH mass and stellar penetration factor $\beta = r_t/r_p$ and the resulting delays to disk circularization. [Preview Abstract] |
Monday, April 16, 2018 2:30PM - 2:42PM |
S16.00006: The nature of the soft X-ray emission of tidal disruption events Katie Auchettl, James Guillochon, Enrico Ramirez-Ruiz If a star passes within the tidal radius of a supermassive black hole, it will be disrupted, and subsequently accreted, producing a luminous X-ray flare. Over the last few decades, a significant number of tidal disruption events (TDEs) have been discovered, however for only a handful of these events has the X-ray emission from these source been studied in detail. In this talk, I will present the results of a comprehensive, systematic study of the soft X-ray emission from arising from TDEs, while highlighting observationally how the X-ray emission from these events differ from those of AGN. In particular, I will show that the X-ray emission of a TDE evolves significantly with time and decays with power-law indices that are much shallower than the canonical $-$5/3. In addition, I will show that the long lifetimes of TDEs are consistent with what one would expect from a main sequence star being disrupted by a viscously slowed BH with mass $<10^{7}\,M_{\odot}$, while the isotropic luminosities of jetted and non-jetted events are separated by a "reprocessing valley", which we suggest is naturally populated by optical/UV TDEs whose X-ray emission is being reprocessed into lower energies. [Preview Abstract] |
Monday, April 16, 2018 2:42PM - 2:54PM |
S16.00007: Cosmology with the WFIRST High Latitude Survey Ami Choi, Chris Hirata, Michael Troxel The Wide Field Infrared Survey Telescope (WFIRST) is an upcoming NASA observatory that will investigate dark energy, exoplanets, and infrared astrophysics. The first of these areas, dark energy, continues to be one of the most enigmatic cosmological discoveries. With the goal of shedding light on the nature of the origin of cosmic acceleration, the WFIRST High Latitude Survey (HLS) will deliver a dataset with the statistical power to make extremely precise measurements of cosmic expansion and structure growth. This talk will give an overview of ongoing activities within the Science Investigation Team tasked with designing and implementing the cosmology program of the HLS and will highlight recent results from these studies. [Preview Abstract] |
Monday, April 16, 2018 2:54PM - 3:06PM |
S16.00008: Two Armed Spiral And Two Armed Barred Spiral Galaxy Forms Are Universal Patterns In Nature Appearing A Cup of Instant Coffee On A Small Scale And In Space On A Grand Scale Stewart Brekke After putting a teaspoonfull of old powdered coffee creamer into a cup of recently prepared instant coffee I stirred and first the powdered coffee creamer formed a number of pairs of short concentric longitudinal sections which orbited the rim of the coffee cup as the instant coffee swirled around the cup. As the instant coffee and concentric longitudinal coffee creamer sections slowed down in the coffee cup, the orbits of the concentric creamer strands decayed and tangentially accreted in their fore sections forming a set of perfect two armed spiral and two armed barred spiral coffee creamer galaxies which after formation began to rotate. The rotation was due to the transformation of the orbital angular momentum of the pre formed coffee creamer galactic arms into the rotational motion of the newly formed perfect two armed spiral and two armed barred spiral galaxies. The equation for this origin of rotation and galactic rotation is $I\omega_{new galaxy} = I\omega_{arm1} + I\omega_{arm2}$ : if $I\omega_{arm}$ is the orbital angular momentum of each of the pre galactic arms and $I\omega_{new galaxy}$ is the rotational angular momentum of the newly formed coffee creamer galaxy.It appears that the two armed and two armed barred spiral galaxy forms are universal patterns in nature. [Preview Abstract] |
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