Particle acceleration in low-power hotspots: modelling the broad-band spectral energy distribution

Abstract

The acceleration and radiative processes active in low-power radio hotspots are investigated by means of new deep near-infrared (NIR) and optical VLT observations, complemented with archival, high-sensitivity VLT, radio VLA and X-ray Chandra data. For the three studied radio galaxies (3C 105, 3C 195 and 3C 227), we confirm the detection of NIR/optical counterparts of the observed radio hotspots. We resolve multiple components in 3C 227 West and in 3C 105 South and characterize the diffuse NIR/optical emission of the latter. We show that the linear size of this component ($\gtrsim$4 kpc) makes 3C 105 South a compelling case for particles' re-acceleration in the post-shock region. Modeling of the radio-to-X-ray spectral energy distribution (SED) of 3C 195 South and 3C 227 W1 gives clues on the origin of the detected X-ray emission. In the context of inverse Compton models, the peculiarly steep synchrotron curve of 3C 195 South sets constraints on the shape of the radiating particles' spectrum that are testable with better knowledge of the SED shape at low ($\lesssim$GHz) radio frequencies and in X-rays. The X-ray emission of 3C 227 W1 can be explained with an additional synchrotron component originating in compact ($<$100 pc) regions, such those revealed by radio observations at 22 GHz, provided that efficient particle acceleration ($\gamma \gtrsim$10${}^7$) is ongoing. The emerging picture is that of systems in which different acceleration and radiative processes coexist.

arXiv comment16 pages, 10 figures, accepted for publication in MNRAS

References in corpus (44)

• The Large Area Telescope on the Fermi Gamma-ray Space Telescope Mission
• LOFAR: The LOw-Frequency ARray
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• HI4PI: A full-sky HI survey based on EBHIS and GASS
• The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
• The GMRT 150 MHz All-sky Radio Survey: First Alternative Data Release TGSS ADR1
• Automated data reduction workflows for astronomy
• The LOFAR Two-metre Sky Survey - II. First data release
• Sherpa: a Mission-Independent Data Analysis Application
• Deep Galaxy Counts, Extragalactic Background Light, and the Stellar Baryon Budget
• X-ray Emission Properties of Large Scale Jets, Hotspots and Lobes in Active Galactic Nuclei
• The origins of X-ray emission from the hotspots of FRII radio sources
• Proper Motions in Compact Symmetric Objects
• PPM-Extended (PPMX) - a catalogue of positions and proper motions
• A Particle Module for the PLUTO code: II - Hybrid Framework for Modeling Non-thermal emission from Relativistic Magnetized flows
• Chandra X-Ray Detection of the Radio Hotspots of 3C295
• Deep Chandra observations of Pictor A
• The Electron Energy Distribution in the Hotspots of Cygnus A: Filling the Gap with the Spitzer Space Telescope
• VLBI observations of 10 CSO candidates: expansion velocities of hot spots
• Bayesian inference of jet bulk-flow speeds in FRII radio sources
• A Chandra study of particle acceleration in the multiple hotspots of nearby radio galaxies
• LOFAR imaging of Cygnus A -- Direct detection of a turnover in the hotspot radio spectra
• Witnessing the gradual slow-down of powerful extragalactic jets: The X-ray -- optical -- radio connection
• FR II radio galaxies at low frequencies I: morphology, magnetic field strength and energetics
• Large Scale Extragalactic Jets in the Chandra era I: data reduction and analysis
• In-Situ Particle Acceleration in Extragalactic Radio Hot Spots: Observations Meet Expectations
• A high resolution view of the jet termination shock in a hot spot of the nearby radio galaxy Pictor A: implications for X-ray models of radio galaxy hot spots
• FR-II radio galaxies at low frequencies II: spectral ageing and source dynamics
• Chandra Detection of Hotspot and Knots of 3C 303
• A Multi-Wavelength Study of the High Surface Brightness Hotspot in PKS1421-490
• The Kinematic and Spectral Ages of the Compact Radio Source CTD 93
• Cygnus A: A Long Wavelength Resolution of the Hot Spots
• Spitzer Observations of Hotspots in Radio Lobes
• Particle Accelerators in the Hot Spots of the Radio Galaxy 3C445 Imaged With the VLT
• Chandra Observations of the Radio Galaxy 3C 445 and the Hotspot X-ray Emission Mechanism
• An X-ray survey of the 2Jy sample. II: X-ray emission from extended structures
• Complex particle acceleration processes in the hotspots of 3C105 and 3C445
• NIR/Optical Counterparts of Hotspots in Radio Galaxies
• Discovery of Optical Emission in the Hotspots of Three 3CR Quasars: High-Energy Particle Acceleration in Powerful Radio Hotspots
• Examining High Energy Radiation Mechanisms of Knots and Hotspots in Active Galactic Nucleus Jets
• Two types of shock in the hotspot of the giant quasar 4C74.26: a high-resolution comparison from Chandra, Gemini & MERLIN
• ALMA polarization observations of the particle accelerators in the hot spot of the radio galaxy 3C 445
• LOFAR Measures the Hotspot Advance Speed of the High-Redshift Blazar S5 0836+710
• Jansky VLA observations of synchrotron emitting optical hotspots of 3C 227 and 3C 445 radio galaxies

Cited by in corpus (9)

• Simulating the dynamics and non-thermal emission of relativistic magnetised jets I. Dynamics
• Simulating the dynamics and synchrotron emission from relativistic jets II. Evolution of non-thermal electrons
• Connecting steady emission and Very High Energy flaring states in blazars: the case of Mrk 421
• Long-term FRII jet evolution in dense environments
• Extended X-ray emission around FR II radio galaxies: hotspots, lobes and galaxy clusters
• X-ray Spectral Analysis of the Jet Termination Shock in Pictor A on Sub-Arcsecond Scales with Chandra
• Multiwavelength study of radio galaxy Pictor A: detection of western hotspot in far-UV and possible origin of high energy emissions
• A high-resolution radio morphology and polarization of the kpc-scale X-ray jet of PKS 1127-145
• NuSTAR discovery of the hard X-ray emission and a wide-band X-ray spectrum from the Pictor A western hot spot