Emissions from Shells Associated with Dying Radio Sources Hirotaka Ito YITP, Kyoto University Collabolators Motoki Kino NAOJ Nozomu Kawakatu Tsukuba University ＠Workshop on East-Asian Collaboration for the SKA 2011 12/2 Shocked Shell Radio lobe shell Forward shock Jet Energy dissipation Lobe Shell Comparable energy is deposited in the lobe and shell Shell = shocked ambient gas X-ray observation of shell Centausus A Croston + (2009) Chandra Non-thermal synchrotron emission (S∝ν-α ) Shell γe ~ 108 (B/10μＧ) -1/2 Shocked shells offer sites for particle accelerations e.g., Fujita+(2007, 2011), Berezhko (2008), Ito+(2011) - lobe and shell are site of particle acceleration - comparable energy is deposited in the lobe and shell - prominent radio emission from lobe is confirmed in large number of sources - no radio emission is detected in shell （few nearby sources are detected X-ray） e.g., Carilli et al. 1998 Lobe emission dominated over the shell emissions Shells in dying radio sources The fraction （~15-30%） of young compact radio sources （R<few kpc） in the flux-limited catalogues is much larger than that expected from their age (~0.01%) significant fraction of young sources may be short-lived e.g., Gugliucci + 2005, Kunert-Bajaszewska+2005, 2006, Orienti+2008,2010 Emission from sources after the jet injection has ceased Lobe emission fades rapidly (fader) fresh electrons are no longer supplied e.g, Reynolds+ 1997, Mocz+2010, Nath 2010 Shell emissions only show gradual decrease electrons are continuously supplied from the bow shock Shell emission becomes dominant Present Study Evolution of emissions from lobe and shell of dying radio sources Lobe-dominated jet Jet active phase shell-dominated Fading phase Dynamics thin shell approximation Assumptions (e. g., Ostriker & McKee 1988) ・spherical symmetry ・ambient density profile tj ：duration of jet injection Lj ：jet power (I) blast wave with continuous energy injection (II) blast wave of instant energy (Sedov-Taylor expansion) Non-thermal electrons (shell) ・ cooling Adiabatic cooling ・ injection Maximum energy Synchrotron Inverse Compton （IC） Seed photons Normalization factor - UV emission (accretion disc) - IR emission (dusty torus) - NIR emission (host galaxy) - Radio emission (Lobe) - CMB compression of ISM magnetic field Non-thermal electrons (shell) ・ cooling Adiabatic cooling ・ injection Maximum energy Synchrotron Inverse Compton （IC） Seed photons Normalization factor No emission from core - NIR emission (host galaxy) - Radio emission (Lobe) - CMB compression of ISM magnetic field Non-thermal electrons (lobe) ・ cooling Adiabatic cooling ・ injection Maximum energy Synchrotron Inverse Compton （IC） Seed photons Normalization factor - UV emission (accretion disc) - IR emission (dusty torus) - NIR emission (host galaxy) - Radio emission (Lobe) - CMB 10% of the equipartition value Non-thermal electrons (lobe) ・ cooling Adiabatic cooling Synchrotron Inverse Compton （IC） Seed photons No emission from core - NIR emission (host galaxy) - Radio emission (Lobe) - CMB ・ injection No injection Evolution of energy distribution of non-thermal electrons SHELL LOBE Radiative cooling t=10^5 yr (R~1.5kpc) t=5×10^5 yr (R~5kpc) t=10^6 yr (R~8kpc) t=10^7 yr (R~30kpc) High energy electrons within the lobe depletes due to the absence of injection Evolution of emission spectrum after the jet injection has ceased emission is dominted by the shell Detectection prospects D=1Gpc candidates for unID radio sources good target for SKA Summary Using simple dynamical model, we evaluated the emissions from dying young radio sources - Shell emissions becomes dominant after the jet injection has ceased due to the rapid decrease of lobe emissions - Emissions from the shell is essential for studying the properties of dying radio sources - Some of the unidentified radio sources may be attributed by the shell emissions - Target for SKA
© Copyright 2024 Paperzz
