X-Rays & Γ-Rays from Relativistic Jets in Quasars
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Polarimetric Properties of Blazars Caught by the WEBT
galaxies Review Polarimetric Properties of Blazars Caught by the WEBT Claudia M. Raiteri * and Massimo Villata INAF, Osservatorio Astrofisico di Torino, via Osservatorio 20, I-10025 Pino Torinese, Italy; [email protected] * Correspondence: [email protected] Abstract: Active galactic nuclei come in many varieties. A minority of them are radio-loud, and exhibit two opposite prominent plasma jets extending from the proximity of the supermassive black hole up to megaparsec distances. When one of the relativistic jets is oriented closely to the line of sight, its emission is Doppler beamed and these objects show extreme variability properties at all wavelengths. These are called “blazars”. The unpredictable blazar variability, occurring on a continuous range of time-scales, from minutes to years, is most effectively investigated in a multi-wavelength context. Ground-based and space observations together contribute to give us a comprehensive picture of the blazar emission properties from the radio to the g-ray band. Moreover, in recent years, a lot of effort has been devoted to the observation and analysis of the blazar polarimetric radio and optical behaviour, showing strong variability of both the polarisation degree and angle. The Whole Earth Blazar Telescope (WEBT) Collaboration, involving many tens of astronomers all around the globe, has been monitoring several blazars since 1997. The results of the corresponding data analysis have contributed to the understanding of the blazar phenomenon, particularly stressing the viability of a geometrical interpretation of the blazar variability. We review here the most significant polarimetric results achieved in the WEBT studies. Keywords: active galactic nuclei; blazars; jets; polarimetry Citation: Raiteri, C.M.; Villata, M. -
Quantum Detection of Wormholes Carlos Sabín
www.nature.com/scientificreports OPEN Quantum detection of wormholes Carlos Sabín We show how to use quantum metrology to detect a wormhole. A coherent state of the electromagnetic field experiences a phase shift with a slight dependence on the throat radius of a possible distant wormhole. We show that this tiny correction is, in principle, detectable by homodyne measurements Received: 16 February 2017 after long propagation lengths for a wide range of throat radii and distances to the wormhole, even if the detection takes place very far away from the throat, where the spacetime is very close to a flat Accepted: 15 March 2017 geometry. We use realistic parameters from state-of-the-art long-baseline laser interferometry, both Published: xx xx xxxx Earth-based and space-borne. The scheme is, in principle, robust to optical losses and initial mixedness. We have not observed any wormhole in our Universe, although observational-based bounds on their abundance have been established1. The motivation of the search of these objects is twofold. On one hand, the theoretical implications of the existence of topological spacetime shortcuts would entail a challenge to our understanding of deep physical principles such as causality2–5. On the other hand, typical phenomena attributed to black holes can be mimicked by wormholes. Therefore, if wormholes exist the identity of the objects in the center of the galaxies might be questioned6 as well as the origin of the already observed gravitational waves7, 8. For these reasons, there is a renewed interest in the characterization of wormholes9–11 and in their detection by classical means such as gravitational lensing12, 13, among others14. -
Active Galactic Nuclei: a Brief Introduction
Active Galactic Nuclei: a brief introduction Manel Errando Washington University in St. Louis The discovery of quasars 3C 273: The first AGN z=0.158 2 <latexit sha1_base64="4D0JDPO4VKf1BWj0/SwyHGTHSAM=">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</latexit> <latexit sha1_base64="H7Rv+ZHksM7/70841dw/vasasCQ=">AAACQHicbVDLSgMxFM34tr6qLt0Ei+BCy0TEx0IoPsBlBWuFTlsyaVqDSWZI7ghlmE9z4ye4c+3GhSJuXZmxFXxdCDk599zk5ISxFBZ8/8EbGR0bn5icmi7MzM7NLxQXly5slBjGayySkbkMqeVSaF4DAZJfxoZTFUpeD6+P8n79hhsrIn0O/Zg3Fe1p0RWMgqPaxXpwzCVQfNIOFIUro1KdMJnhA+yXfX832FCsteVOOzgAobjFxG+lhGTBxpe+HrBOBNjiwd5rpZsky9rFUn5BXvgvIENQQsOqtov3QSdiieIamKTWNogfQzOlBgSTPCsEieUxZde0xxsOaurMNNPPADK85pgO7kbGLQ34k/0+kVJlbV+FTpm7tr97Oflfr5FAd6+ZCh0nwDUbPNRNJIYI52nijjCcgew7QJkRzitmV9RQBi7zgguB/P7yX3CxVSbb5f2z7VLlcBjHFFpBq2gdEbSLKugUVVENMXSLHtEzevHuvCfv1XsbSEe84cwy+lHe+wdR361Q</latexit> The power source of quasars • The luminosity (L) of quasars, i.e. how bright they are, can be as high as Lquasar ~ 1012 Lsun ~ 1040 W. • The energy source of quasars is accretion power: - Nuclear fusion: 2 11 1 ∆E =0.007 mc =6 10 W s g− -
A Multimessenger View of Galaxies and Quasars from Now to Mid-Century M
A multimessenger view of galaxies and quasars from now to mid-century M. D’Onofrio 1;∗, P. Marziani 2;∗ 1 Department of Physics & Astronomy, University of Padova, Padova, Italia 2 National Institute for Astrophysics (INAF), Padua Astronomical Observatory, Italy Correspondence*: Mauro D’Onofrio [email protected] ABSTRACT In the next 30 years, a new generation of space and ground-based telescopes will permit to obtain multi-frequency observations of faint sources and, for the first time in human history, to achieve a deep, almost synoptical monitoring of the whole sky. Gravitational wave observatories will detect a Universe of unseen black holes in the merging process over a broad spectrum of mass. Computing facilities will permit new high-resolution simulations with a deeper physical analysis of the main phenomena occurring at different scales. Given these development lines, we first sketch a panorama of the main instrumental developments expected in the next thirty years, dealing not only with electromagnetic radiation, but also from a multi-messenger perspective that includes gravitational waves, neutrinos, and cosmic rays. We then present how the new instrumentation will make it possible to foster advances in our present understanding of galaxies and quasars. We focus on selected scientific themes that are hotly debated today, in some cases advancing conjectures on the solution of major problems that may become solved in the next 30 years. Keywords: galaxy evolution – quasars – cosmology – supermassive black holes – black hole physics 1 INTRODUCTION: TOWARD MULTIMESSENGER ASTRONOMY The development of astronomy in the second half of the XXth century followed two major lines of improvement: the increase in light gathering power (i.e., the ability to detect fainter objects), and the extension of the frequency domain in the electromagnetic spectrum beyond the traditional optical domain. -
A Supernova Origin for Dust in a High-Redshift Quasar
A SUPERNOVA ORIGIN FOR DUST IN A HIGH-REDSHIFT QUASAR R. Maiolino ∗, R. Schneider †∗, E. Oliva ‡∗, S. Bianchi §, A. Ferrara ¶, F. Mannucci§, M. Pedani‡, M. Roca Sogorb k ∗ INAF - Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy † “Enrico Fermi” Center, Via Panisperna 89/A, 00184 Roma, Italy ‡ Telescopio Nazionale Galileo, C. Alvarez de Abreu, 70, 38700 S.ta Cruz de La Palma, Spain § CNR-IRA, Sezione di Firenze, Largo Enrico Fermi 5, 50125 Firenze, Italy ¶ SISSA/International School for Advanced Studies, Via Beirut 4, 34100 Trieste, Italy k Astrofisico Fco. S`anchez, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain Interstellar dust plays a crucial role in the evolution of the Universe by assisting the formation of molecules1, by triggering the formation of the first low-mass stars2, and by absorbing stellar ultraviolet-optical light and subsequently re-emitting it at infrared/millimetre wavelengths. Dust is thought to be produced predominantly in the envelopes of evolved (age >1 Gyr), low-mass stars3. This picture has, however, recently been brought into question by the discovery of large masses of dust in the host galaxies of quasars4,5 at redshift z > 6, when the age of the Universe was less than 1 Gyr. Theoretical studies6,7,8, corroborated by observations of nearby supernova remnants9,10,11, have suggested that supernovae provide a fast and efficient dust formation environment in the early Universe. Here we report infrared observations of a quasar at redshift 6.2, which are used to obtain directly its dust extinction curve. We then show that such a curve is in excellent agreement with supernova dust models. -
Arxiv:2010.11303V2 [Astro-Ph.GA] 23 Feb 2021
DRAFT VERSION FEBRUARY 24, 2021 Preprint typeset using LATEX style emulateapj v. 01/23/15 RECONCILING EHT AND GAS DYNAMICS MEASUREMENTS IN M87: IS THE JET MISALIGNED AT PARSEC SCALES? BRITTON JETER1,2,3 ,AVERY E. BRODERICK1,2,3 , 1 Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada 2 Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, ON N2L 2Y5, Canada 3 Waterloo Centre for Astrophysics, University of Waterloo, Waterloo, ON N2L 3G1, Canada Draft version February 24, 2021 ABSTRACT The Event Horizon Telescope mass estimate for M87* is consistent with the stellar dynamics mass estimate and inconsistent with the gas-dynamics mass estimates by up to 2σ. We have previously explored a new gas-dynamics model that incorporated sub-Keplerian gas velocities and could, in principle, explain the discrepancy in the stellar and gas-dynamics mass estimate. In this paper, we extend this gas-dynamical model to also include non-trivial disk heights, which may also resolve the mass discrepancy independent of sub-Keplerian velocity components. By combining the existing velocity measurements and the Event Horizon Telescope mass estimate, we place con- straints on the gas disk inclination and sub-Keplerian fraction. These constraints require the parsec-scale ionized gas disk to be misaligned with the milliarcsecond radio jet by at least 11◦, and more typically 27◦. Modifications to the gas-dynamics model either by introducing sub-Keplerian velocities or thick disks produce further misalign- ment with the radio jet. If the jet is produced in a Blandford–Znajek-type process, the angular momentum of the black hole is decoupled with the angular momentum of the large-scale gas feeding M87*. -
Active Galactic Nuclei
Active Galactic Nuclei • Optical spectra, distance, line width • Varieties of AGN and unified scheme • Variability and lifetime • Black hole mass and growth • Geometry: disk, BLR, NLR • Reverberation mapping • Jets and blazars • AGN spectra Optical spectrum of an AGN • Variety of different emission lines • Each line has centroid, area, width • There is also continuum emission Emission lines • Shift of line centroid gives recession velocity v/c = Δλ/λ. • The width is usually characterized by the “Full Width at Half Maximum”. For a Gaussian FHWM = 2.35σ. • The line width is determined by the velocity distribution of the line emitting gas, Δv/c = σ/λ. • Area is proportional to the number of detected line photons or the line flux. • Usually characterized by “equivalent width” or range in wavelength over which integration of the continuum produces the same flux as the line. Early observations of AGN • Very wide emission lines have been known since 1908. • In 1959, Woltjer noted that if the profiles are due to Doppler motion and the gas is gravitationally bound then v2 ~ GM/r. For v ~ 2000 km/s, we have 10 r M ≥10 ( 100 pc ) M Sun • So AGN, known at the time as Seyfert galaxies, must either have a very compact and luminous nucleus or be very massive. Quasars • Early radio telescopes found radio emission from stars, nebulae, and some galaxies. • There were also point-like, or star-like, radio sources which varied rapidly these are the `quasi-stellar’ radio sources or quasars. • In visible light quasars appear as points, like stars. Quasar optical spectra Redshift of 3C273 is 0.16. -
Powerful Jets from Radiatively Efficient Disks, a Decades-Old Unresolved Problem in High Energy Astrophysics
galaxies Article Powerful Jets from Radiatively Efficient Disks, a Decades-Old Unresolved Problem in High Energy Astrophysics Chandra B. Singh 1,*,†, David Garofalo 2,† and Benjamin Lang 3 1 South-Western Institute for Astronomy Research, Yunnan University, University Town, Chenggong, Kunming 650500, China 2 Department of Physics, Kennesaw State University, Marietta, GA 30060, USA; [email protected] 3 Department of Physics & Astronomy, California State University, Northridge, CA 91330, USA; [email protected] * Correspondence: [email protected] † These authors contributed equally to this work. Abstract: The discovery of 3C 273 in 1963, and the emergence of the Kerr solution shortly thereafter, precipitated the current era in astrophysics focused on using black holes to explain active galactic nuclei (AGN). But while partial success was achieved in separately explaining the bright nuclei of some AGN via thin disks, as well as powerful jets with thick disks, the combination of both powerful jets in an AGN with a bright nucleus, such as in 3C 273, remained elusive. Although numerical simulations have taken center stage in the last 25 years, they have struggled to produce the conditions that explain them. This is because radiatively efficient disks have proved a challenge to simulate. Radio quasars have thus been the least understood objects in high energy astrophysics. But recent simulations have begun to change this. We explore this milestone in light of scale-invariance and show that transitory jets, possibly related to the jets seen in these recent simulations, as some have proposed, cannot explain radio quasars. We then provide a road map for a resolution. -
Pos(MQW7)111 Ce
Long-term optical activity of the microquasar V4641 Sgr PoS(MQW7)111 Vojtechˇ Šimon Astronomical Institute, Academy of Sciences of the Czech Republic, 25165 Ondˇrejov, Czech Republic E-mail: [email protected] Arne Henden AAVSO, 49 Bay State Road, Cambridge, MA 02138, USA E-mail: [email protected] We present an analysis of the optical activity of the microquasar V4641 Sgr using the visual and photographic data. We analyze four smaller (echo) outbursts that followed the main outburst (1999). Their mean recurrence time TC is 377 days, with a trend of a decrease. We interpret the characteristic features of the recent activity of V4641 Sgr (the narrow outbursts separated by a long quiescence, a clear trend in the evolution of their TC) as the thermal instability of the accre- tion disk operating in dwarf novae and soft X-ray transients. We argue that the luminosity of four echo outbursts is too high to be explained by the thermal emission of the accretion disk. We inter- pret them as due to the thermal instability, in which the outburst gives rise to a jet radiating also in the optical. This supports the finding by Uemura et al., PASJ 54, L79 (2002). The pre-outburst observations (1964–1967) reveal ongoing activity of the system. It displays low-amplitude fluc- tuations on the timescale of several weeks, independent on the orbital phase. In addition, a larger brightening which lasted for several tens of days and occurred from the level of brightness higher than in other years can be resolved. VII Microquasar Workshop: Microquasars and Beyond September 1 - 5, 2008 Foca, Izmir, Turkey c Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. -
HUBBLE SPACE TELESCOPE ULTRAVIOLET SPECTROSCOPY of 14 LOW-REDSHIFT QUASARS1 Rajib Ganguly,2 Michael S
A The Astronomical Journal, 133:479Y486, 2007 February # 2007. The American Astronomical Society. All rights reserved. Printed in U.S.A. HUBBLE SPACE TELESCOPE ULTRAVIOLET SPECTROSCOPY OF 14 LOW-REDSHIFT QUASARS1 Rajib Ganguly,2 Michael S. Brotherton,2 Nahum Arav,3 Sara R. Heap,4 Lutz Wisotzki,5 Thomas L. Aldcroft,6 Danielle Alloin,7,8 Ehud Behar,9 Gabriela Canalizo,10 D. Michael Crenshaw,11 Martijn de Kool,12 Kenneth Chambers,13 Gerald Cecil,14 Eleni Chatzichristou,15 John Everett,16,17 Jack Gabel,3 C. Martin Gaskell,18 Emmanuel Galliano,19 Richard F. Green,20 Patrick B. Hall,21 Dean C. Hines,22 Vesa T. Junkkarinen,23 Jelle S. Kaastra,24 Mary Elizabeth Kaiser,25 Demosthenes Kazanas,4 Arieh Konigl,26 Kirk T. Korista,27 Gerard A. Kriss,28 Ari Laor,9 Karen M. Leighly,29 Smita Mathur,30 Patrick Ogle,31 Daniel Proga,32 Bassem Sabra,33 Ran Sivron,34 Stephanie Snedden,35 Randal Telfer,36 and Marianne Vestergaard37 Received 2006 June 27; accepted 2006 October 4 ABSTRACT We present low-resolution ultraviolet spectra of 14 low-redshift (zem P 0:8) quasars observed with the Hubble Space Telescope STIS as part of a Snapshot project to understand the relationship between quasar outflows and luminosity. By design, all observations cover the C iv emission line. Ten of the quasars are from the Hamburg-ESO catalog, three are from the Palomar-Green catalog, and one is from the Parkes catalog. The sample contains a few interesting quasars, including two broad absorption line (BAL) quasars (HE 0143À3535 and HE 0436À2614), one quasar with a mini-BAL (HE 1105À0746), and one quasar with associated narrow absorption (HE 0409À5004). -
Superluminal Motion of Gamma-Ray Blazars
High Energy Blazar Astronomy ASP Conference Series, Vol. 299, 2003 L.O. Takalo and E. Valtaoja Superluminal Motion of Gamma-Ray Blazars S.G. Jorstad Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215-1401 Astronomical Institute of St. Petersburg State University, Universitetskij pr. 28, 198504 St. Petersburg, Russia A.P. Marscher Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215-1401 Abstract. We have completed a program of monitoring of a sample of γ-ray blazars with the VLBA at 22 and 43 GHz. Analysis of the data allows us to conclude that the population of bright γ-ray blazars can be classified as highly superluminal, with apparent speeds as high as ∼40c. However, many of the blazars exhibit a wide range of apparent speeds from ∼4c to ∼20c in the same source. Comparison of brightness and polarization parameters with the jet velocities of moving components does not show significant correlation between these parameters. Intensive multifrequency VLBI monitoring is needed to reveal any patterns that might exist in the distribution of apparent speeds observed in the same object. 1. Introduction Apparent speed is one of the most important parameters for determining the physics of radio jets. The largest class of identified γ-ray sources (Hartman et al. 1999) consists of violently variable AGNs (blazars) characterized by one-sided superluminal radio jets. A popular model for the production of high-energy radiation in AGNs involves inverse-Compton scattering of low-energy photons by highly relativistic electrons in the jet. However, the seed photons for this process are uncertain: they might be from the accretion disk and/or nearby region (ECS-model; Sikora et al. -
OJ 287: NEW TESTING GROUND for GENERAL RELATIVITY and BEYOND C Sivaram Indian Institute of Astrophysics, Bangalore
OJ 287: NEW TESTING GROUND FOR GENERAL RELATIVITY AND BEYOND C Sivaram Indian Institute of Astrophysics, Bangalore Abstract: The supermassive short period black hole binary OJ287 is discussed as a new precision testing ground for general relativity and alternate gravity theories. Like in the case of binary pulsars, the relativistic gravity effects are considerably larger than in the solar system. For instance the observed orbital precession is forty degrees per period. The gravitational radiation energy losses are comparable to typical blazar electromagnetic radiation emission and it is about ten orders larger than that of the binary pulsar with significant orbit shrinking already apparent in the light curves. This already tests Einstein gravity to a few percent for objects at cosmological distances. Constraints on alternate gravity theories as well as possible detection of long term effects of dark matter and dark energy on this system are described. 1 For more than fifty years after Einstein proposed the general theory of relativity in 1915, observational tests to verify some of the predictions were confined to within the solar system; where the effects are quite small. This situation changed with the discovery of the binary pulsar in 1975 where the relativistic periastron shift was more than four degrees per year, a whopping thirty thousand times more than the paltry well known correction of 43 arc seconds/century for mercury.1, 2 The recently discovered 2.4 hour period binary pulsar has a periastron shift of sixteen degrees per year!3 Other relativistic effects like the time delay of the signals and time dilation and frequency shifts are also much larger for these binary systems.