The Origin of High Energy Emission in the Young Radio Source PKS 1718-649

Abstract

We present a model for the broadband radio-to-$\gamma$-ray spectral energy distribution of the compact radio source, PKS 1718-649. Because of its young age (100 years) and proximity ($z=0.014$), PKS 1718-649 offers a unique opportunity to study nuclear conditions and the jet/host galaxy feedback process at the time of an initial radio jet expansion. PKS 1718-649 is one of a handful of young radio jets with $\gamma$-ray emission confirmed with the Fermi/LAT detector. We show that this $\gamma$-ray emission can be successfully explained by Inverse Compton scattering of the ultraviolet photons, presumably from an accretion flow, off non-thermal electrons in the expanding radio lobes. The origin of the X-ray emission in PKS 1718-649 is more elusive. While Inverse Compton scattering of the infrared photons emitted by a cold gas in the vicinity of the expanding radio lobes contributes significantly to the X-ray band, the data require that an additional X-ray emission mechanism is at work, e.g. a weak X-ray corona or a radiatively inefficient accretion flow, expected from a LINER type nucleus such as that of PKS 1718-649. We find that the jet in PKS 1718-649 has low power, $L_j\simeq 2.2\times 10^{42}$ erg s${}^{-1}$, and expands in an environment with density $n_0\simeq 20$ cm${}^{-3}$. The inferred mass accretion rate and gas mass reservoir within 50-100 pc are consistent with estimates from the literature obtained by tracing molecular gas in the innermost region of the host galaxy with SINFONI and ALMA.

10 pages, 2 figures, published in ApJ

References in corpus (25)

• CRATES: An All-Sky Survey of Flat-Spectrum Radio Sources
• Compact steep-spectrum and peaked-spectrum radio sources
• The Dynamic Evolution of Young Extragalactic Radio Sources
• High-energy particle acceleration at the radio-lobe shock of Centaurus A
• The Black Hole Mass-Bulge Luminosity Relationship for Active Galactic Nuclei from Reverberation Mapping and Hubble Space Telescope Imaging
• An XMM-Newton study of the environments, particle content and impact of low-power radio galaxies
• The Wilkinson Microwave Anisotropy Probe (WMAP) Source Catalog
• On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources
• The properties of extragalactic radio sources selected at 20 GHz
• The Australia Telescope 20 GHz (AT20G) Survey: The Bright Source Sample
• A representative survey of the dynamics and energetics of FRII radio galaxies
• High-ionization mid-infrared lines as black hole mass and bolometric luminosity indicators in active galactic nuclei
• Are young radio sources in equipartition?
• Blind and non-blind source detection in WMAP 5-year maps
• On the BL Lacertae objects/radio quasars and the FRI/II dichotomy
• Spitzer mid-infrared spectroscopy of compact symmetric objects: What powers radio-loud active galactic nuclei?
• What triggers a radio AGN? The intriguing case of PKSB 1718-649
• The Spectral Variability of the GHz-Peaked Spectrum Radio Source PKS 1718-649 and a Comparison of Absorption Models
• On the dynamical evolution of hot spots in powerful radio loud AGNs
• NGC 3894: a young radio galaxy seen by Fermi-LAT
• TXS 0128+554: A Young Gamma-Ray Emitting AGN With Episodic Jet Activity
• Gamma-rays from young radio galaxies and quasars
• Gamma-ray emission in radio galaxies under the VLBI scope -- I. Parsec-scale kinematics and high-energy properties of $\gamma$-ray detected TANAMI radio galaxies
• X-ray emission from GPS and CSS sources
• The MHz-peaked radio spectrum of the unusual gamma-ray source PMN J1603-4904

Cited by in corpus (2)

• The extremely X-ray luminous radio-loud quasar CFHQS J142952+544717 at $z=6.18$ under Chandra high-angular resolution lens
• A plausible link between dynamically unsettled molecular gas and the radio jet in NGC 6328