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Radio Synchrotron Emission: Electron Energy Spectrum, Supernovae, Microquasars, Active Nuclei, Cluster Relics and Halos; X-Ray Halos

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Radio Synchrotron Emission: Electron Energy Spectrum, Supernovae, Microquasars, Active Nuclei, Cluster Relics and Halos; X-Ray Halos Radio synchrotron emission: electron energy spectrum, supernovae, microquasars, active nuclei, cluster relics and halos; X-ray halos Nimisha G. Kantharia Tata Institute of Fundamental Research Post Bag 3, Ganeshkhind, Pune-411007, India Email: [email protected] URL: https://sites.google.com/view/ngkresearch/home April 2019 Abstract energy imparted per particle, the light particles can acquire extremely high velocities. In this paper, transient high energy events and their hosts are discussed with focus on signatures of ra- • The prompt radio synchrotron emission detected dio synchrotron emission. There are numerous out- soon after a supernova explosion is from light standing questions ranging from the origin of the two plasma composed of positrons and electrons phases of radio emission in supernovae to the forma- which should escape the explosion site soon after tion of conical jets launched at relativistic velocities the neutrinos and radiate in the ambient circum- in active nuclei to the formation of radio hotspots stellar magnetic field. The delayed radio emis- in FR II sources to the formation of radio relics and sion from supernova remnants can be explained halos in clusters of galaxies to the origin of the rela- by synchrotron emission from the relativistic tivistic electron population and its energy spectrum proton-electron plasma mixed with and radiat- which is responsible for the synchrotron emission to ing in the magnetic field frozen in the ejected the composition of the radio synchrotron-emitting thermal plasma. All matter has to be energised plasma in these sources. Observations have helped to escape velocities or more before expulsion. build an empirical model of active nuclei but the ori- The main source of energy in both type I and II gin of the narrow line regions, broad line regions, supernovae has to be a thermonuclear explosion dust, accretion disk in active nuclei and their connec- and the ejected matter will consist of relativistic tion to radio jets and lobes remains largely unknown. neutrinos, relativistic positron-electron plasma, This paper attempts to understand and resolve the non-thermal proton-electron plasma and ther- above outstanding issues. The summary of a few in- mal ionized plasma. Neutrinos and positrons can ferences presented in the paper is: be generated in the thermonuclear reactions. • The matter before being ejected in a transient • The observable structure of an accreting rotat- explosive event like a supernova has to be rapidly ing black hole has to consist of a quasi-spherical accelerated in situ to at least the escape veloc- pseudosurface made of infalling matter which ity. The energy distribution of the ejected cos- has been compressed to degenerate matter den- mic rays including electrons has to be a normal sities near the event horizon, a broad line region arXiv:1904.02446v1 [astro-ph.HE] 4 Apr 2019 distribution since the energising process will be (BLR) accreted on the non-polar regions of the statistical in nature. The peak of the normal pseudosurface and accreted matter on the polar distribution has to be at or beyond the energy regions of the pseudosurface which is enriched equivalent of the escape velocity for protons for a and episodically ejected due to energy injection large fraction of matter to escape. This explains from a thermonuclear outburst which should oc- the ubiquitous curved+power law nature of the cur when favourable physical conditions in the observed radio synchrotron spectra and the cos- accreted matter are achieved. The ejected mat- mic ray energy spectra which peaks near 1 GeV. ter from the poles is observed as synchrotron jets The dispersion of the E/m i.e. energy/mass dis- and thermal narrow line region (NLR). Dust is tribution for each species of particles will be dif- generated in the metal-rich clumps formed in the ferent and will determine the range in their ran- NLR. An accretion disk is formed in the non- dom velocity component so that for a constant polar regions from the excess matter that col- Radio synchrotron emission Kantharia lects beyond the BLR due to latitude-dependent permassive black hole in the central galaxy dur- accretion rates on a rotating black hole which ing its active phase and which has since diffused are minimum for the equatorial regions. The ob- over a large region. The relics can indicate the served spectral lines appear at a redshift which orientation of the jet axis of the black hole dur- is some combination of gravitational redshift, ing its active phase indicating that a fraction of Doppler shift and galaxy redshift. the plasma still retains its forward-directed mo- tion. The formation of relics can be explained by • The accreting black hole in all jetted sources is radiation pressure exerted back on the plasmas rotating and hosts an accretion disk in the equa- by pair annihilation photons formed beyond the torial regions. extent of the thermal X-ray halo. • Observations support a positron-electron com- position for the fast radio jets launched from the Contents polar regions of microquasars and active nuclei. The light plasma will radiate in the magnetic 1 Introduction 3 field that is frozen in the ejected thermal gas i.e. 1.1 Recap from Kantharia (2016a, 2017) . 3 in the narrow line region. 1.1.1 Formation of a pseudosurface . 3 1.1.2 Origin of relativistic particles . 4 • The fast positron-electron jet is launched from 1.1.3 Clump and dust formation . 4 near the event horizon of a fast spinning black 1.1.4 Formation of accretion disk hole and hence requires relativistic escape ve- and bipolar outflow . 4 locities. This explains the relativistic bulk ex- 1.2 Known Emission Processes . 5 pansion velocities observed for radio jets and 1.2.1 Synchrotron emission . 5 their ballistic nature which persists upto long 1.2.2 The Compton processes . 6 distances. The radial ejection of jet plasma is 1.3 This work . 7 from the polar region of the quasi-spherical pseu- dosurface which is not influenced by the cen- 2 Cosmic rays 7 trifugal potential i.e. is devoid of a broad line 2.1 Background on particle acceleration . 7 region and this region will be small in extent for 2.2 Observed cosmic ray energy spectrum 8 a fast spinning black hole. This readily explains 2.3 Normal distribution of cosmic ray en- the observed range of jet opening angles, conical ergies or universal spectrum . 9 shapes of jets and their high collimation. The 2.4 Observed radio synchrotron spectrum 11 central black holes in FR II radio sources have to be the fastest spinning objects in the universe 3 Supernovae and supernova remnants 12 that we know. 3.1 Summary of observed features . 12 3.2 A comprehensive explanation . 14 • The positron-electron plasma has to emit an- nihilation line photons near 511 keV along the 3.3 Case Studies . 18 entire length of the jet. Compton scattering of 3.3.1 Type II SNR: Cas A in Milky these soft γ−ray photons to X-ray energies can Way . 18 explain the formation of the thick X-ray beams 3.3.2 Type II SN: SN1986J in NGC detected along radio jets in several radio galaxies 891 . 21 (e.g. Cygnus A, Pictor A). The annihilation pho- 3.3.3 Type II SN: SN1987A in LMC 23 tons can also explain the formation of hotspots 3.3.4 Type II SN: SN1993J in M 81 27 and backflow lobes in FR II sources due to the 3.3.5 Summary . 29 radiation pressure they exert back on the plas- 4 Accreting rotating black holes 29 mas when the annihilation happens beyond the 4.1 Microquasars . 30 observable jet i.e. beyond the periphery of ther- 4.1.1 Summary of observed features . 31 mal gas. When the lobes flow back to the core in FR II sources, the large accretion disk around 4.1.2 A comprehensive explanation . 33 the black hole will deflect them by ∼ 90◦ which 4.1.3 Case Studies . 35 explains the formation of winged radio structure. 4.1.3.1 SS 433 in Milky Way 35 4.1.3.2 GRB 170817A in • The radio plasma in cluster radio halos and relics NGC 4993 . 38 is commensurate with the relativistic positron- 4.2 Active Galaxies . 40 electron plasma which was ejected from the su- 4.2.1 Summary of observed features . 42 2 Radio synchrotron emission Kantharia 4.2.2 A comprehensive explanation . 50 not know all the sources of energy in active nuclei 4.2.2.1 Recap: Quasar model 51 the launch-site of jets, the origin of the relativistic 4.2.2.2 Model for active plasma responsible for the radio synchrotron emis- galaxies . 52 sion, the connection between the prompt short-lived 4.2.2.3 Summary . 76 radio emission from supernovae and long-lived radio 4.2.3 Case Studies . 80 emission from supernova remnants, the origin of ra- 4.2.3.1 FR II quasar - 3C 273 82 dio halos and relics in clusters, the reason for spec- 4.2.3.2 FR II galaxy - tral curvature at low radio frequencies in most radio Cygnus A . 84 sources and so on. Aiming to resolve these within the 4.2.3.3 FR I galaxy - Virgo A 89 realm of known physics and respecting multiband ob- 4.2.3.4 Seyfert 1.5 - NGC 4151 92 servational results as inviolable boundary conditions, 4.2.4 A short summary . 96 we research these problems in detail. The results of 4.3 Radio relics and halos in galaxy clusters 97 this effort are presented in the paper.
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