Chandra Imaging of the Western Hotspot in the Radio Galaxy Pictor A: Image Deconvolution and Variability Analysis

Abstract

Here we present an analysis of the X-ray morphology and flux variability of the particularly bright and extended Western hotspot in the nearest powerful (FR II-type) radio galaxy, Pictor A, based on data obtained with the Chandra X-ray Observatory. The hotspot marks the position where the relativistic jet, that originates in the active nucleus of the system, interacts with the intergalactic medium, at hundreds-of-kiloparsec distances from the host galaxy, forming a termination shock that converts jet bulk kinetic energy to internal energy of the plasma. The hotspot is bright in X-rays due to the synchrotron emission of electrons accelerated to ultra-relativistic energies at the shock front. In our analysis, we make use of several Chandra observations targeting the hotspot over the last decades with various exposures and off-axis angles. For each pointing, we study in detail the PSF, which allows us to perform the image deconvolution, and to resolve the hotspot structure. In particular, the brightest segment of the X-ray hotspot is observed to be extended in the direction perpendicular to the jet, forming a thin, $\sim$3 kpc-long, feature that we identify with the front of the reverse shock. The position of this feature agrees well with the position of the optical intensity peak of the hotspot, but is clearly off-set from the position of the radio intensity peak, located $\sim$1 kpc further downstream. In addition, we measure the net count rate on the deconvolved images, finding a gradual flux decrease by about 30% over the 15-year timescale of the monitoring.

arXiv commentrevised version, accepted for publication in the Astrophysical Journal

References in corpus (26)

• The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
• Sherpa: a Mission-Independent Data Analysis Application
• The origins of X-ray emission from the hotspots of FRII radio sources
• Chandra X-ray Observations of Pictor A: High Energy Cosmic Rays in a Radio Galaxy?
• Relativistic and slowing down: the flow in the hotspots of powerful radio galaxies and quasars
• Deep Chandra observations of Pictor A
• The Electron Energy Distribution in the Hotspots of Cygnus A: Filling the Gap with the Spitzer Space Telescope
• Accurate Redshifts and Classifications for 110 Radio-Loud AGNs
• On Multiwavelength Emission of Large-Scale Quasar Jets
• Constraints on the energetics and plasma composition of relativistic jets in FR II sources
• 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
• Propagation and Dynamics of Relativistic Jets
• Accounting for Calibration Uncertainties in X-ray Analysis: Effective Areas in Spectral Fitting
• Complex shock structure in the western hot-spot of Pictor A
• Spitzer Observations of Hotspots in Radio Lobes
• Cygnus A super-resolved via convex optimisation from VLA data
• Particle Accelerators in the Hot Spots of the Radio Galaxy 3C445 Imaged With the VLT
• Optical structure and polarization of the western hot spot of Pictor A
• The Complicated Evolution of the ACIS Contamination Layer over the Mission Life of the Chandra X-ray Observatory
• Complex particle acceleration processes in the hotspots of 3C105 and 3C445
• Novel Analysis of the Multiwavelength Structure of Relativistic Jet in Quasar 3C 273
• Evidence that the maximum electron energy in hotspots of FR II galaxies is not determined by synchrotron cooling
• Two types of shock in the hotspot of the giant quasar 4C74.26: a high-resolution comparison from Chandra, Gemini & MERLIN
• Mid-infrared excess from the west hot spot of the radio galaxy Pictor A unveiled by WISE
• ALMA polarization observations of the particle accelerators in the hot spot of the radio galaxy 3C 445

Cited by in corpus (8)

• Richardson-Lucy deconvolution with a spatially Variant point-spread function of Chandra: Supernova Remnant Cassiopeia A as an Example
• Kinematics of Supernova Remnants Using Multiepoch Maximum Likelihood Estimation: Chandra Observation of Cassiopeia A as an Example
• Variability of extragalactic X-ray jets on kiloparsec scales
• X-ray Spectral Analysis of the Jet Termination Shock in Pictor A on Sub-Arcsecond Scales with Chandra
• Prospects for Time-Domain and Multi-Messenger Science with eXTP
• Arcsecond-Scale X-ray Imaging and Spectroscopy of SS 433 with Chandra HETG
• Complex Structure of the Eastern Lobe of the Pictor A Radio Galaxy: Spectral Analysis and X-ray/Radio Correlations
• NuSTAR discovery of the hard X-ray emission and a wide-band X-ray spectrum from the Pictor A western hot spot