We present a catalog of compact double radio galaxies (hereafter COMP2CAT) listing 43 edge-brightened radio sources whose projected linear size does not exceed 60 kpc, the typical size of their host ...galaxies. This is the fifth in a series of radio source catalogs recently created, namely: FRICAT, FRIICAT, FR0CAT, and WATCAT, each of which focuses on a different class of radio galaxies. The main aim of our analysis is to attain a better understanding of sources with intermediate morphologies between FR IIs and FR 0s. COMP2CAT sources were selected from an existing catalog of radio sources based on NVSS, FIRST and SDSS observations because they have (i) edge-brightened morphologies typical of FR IIs, (ii) redshifts z < 0.15, and (iii) projected linear sizes smaller than 60 kpc. With radio luminosities at 1.4 GHz 1038 ≲ L1.4 ≲ 1041 erg s−1, COMP2CAT sources appear as the low radio luminosity tail of FR IIs. However, their host galaxies are indistinguishable from those of large-scale radio sources: they are luminous (−21 ≳ Mr ≳ −24), red, early-type galaxies with black hole masses in the range 107.5 ≲ MBH ≲ 109.5 M⊙. Moreover, all but one of the COMP2CAT sources are optically classifiable as low-excitation radio galaxies, in agreement with being the low radio luminosity tail of FR Is and FR IIs. This catalog of compact double sources, which is ∼47% complete at z < 0.15, can potentially be used to clarify the role of compact double sources in the general evolutionary scheme of radio galaxies.
We investigate the contribution of the beamed jet component to the high-energy emission in young and compact extragalactic radio sources, focusing for the first time on the gamma -ray band. We derive ...predictions on the gamma -ray luminosities associated with the relativistic jet assuming a leptonic radiative model. The high-energy emission is produced via Compton scattering by the relativistic electrons in a spherical region at the considered scales (lap 10 kpc). Simulations show a wide range of gamma -ray luminosities, with intensities up to ~10 super(46)-10 super(48) erg s super(-1) depending on the assumed jet parameters. We find a highly linear relation between the simulated X-ray and gamma -ray luminosities that can be used to select candidates for gamma -ray detection. We compare the simulated luminosity distributions in the radio, X-ray, and gamma -ray regimes with observations for the largest sample of X-ray-detected young radio quasars. Our analysis of ~4-yr Fermi Large Area Telescope (LAT) data does not yield any statistically significant detections. However, the majority of the model-predicted gamma -ray fluxes for the sample are near or below the current Fermi-LAT flux threshold and compatible with the derived upper limits. Our study gives constraints on the minimum jet power (L sub(jet,kin)/L sub(disk) > 0.01 ) of a potential jet contribution to the X-ray emission in the most compact sources (<, ~ 1 kpc) and on the particle-to-magnetic field energy density ratio that are in broad agreement with equipartition assumptions.
We present Chandra X-ray and Very Large Array radio observations of the radio galaxy 3C305. The X-ray observations reveal the details of the previously known extended X-ray halo around the radio ...galaxy. We show using X-ray spectroscopy that the X-ray emission is consistent with being shock-heated material and can be modelled with standard collisional-ionization models, rather than being photoionized by the active nucleus. On this basis, we can make a self-consistent model in which the X-ray-emitting plasma is responsible for the depolarization of some regions of the radio emission from the jets and hotspots, and to place lower and upper limits on the magnetic field strength in the depolarizing medium. On the assumption that the X-ray-emitting material, together with the previously known extended emission-line region and the outflow in neutral hydrogen, is all being driven out of the centre of the galaxy by an interaction with the jets, we derive a detailed energy budget for the radio galaxy, showing that the X-ray-emitting gas dominates the other phases in terms of its energy content. The power supplied by the jets must be 1043ergs-1. PUBLICATION ABSTRACT
Context. This paper presents the X-ray properties of a flux- and volume-limited complete sample of 16 giga-hertz peaked spectrum (GPS) galaxies. Aims. This study addresses three basic questions in ...our understanding of the nature and evolution of GPS sources: a) What is the physical origin of the X-ray emission in GPS galaxies? b) Which physical system is associated with the X-ray obscuration? c) What is the “endpoint” of the evolution of compact radio sources? Methods. We discuss in this paper the results of the X-ray spectral analysis, and compare the X-ray properties of the sample sources with radio observables. Results. We obtain a 100% (94%) detection fraction in the 0.5–2 keV (0.5–10 keV) energy band. GPS galaxy X-ray spectra are typically highly obscured ($\langle N_{\rm H}^{{\rm GPS}} \rangle = 3 \times 10^{22}$ cm-2; $\sigma_{N_{\rm H}} \simeq 0.5$ dex). The X-ray column density is larger than the HI column density measured in the radio by a factor 10 to 100. GPS galaxies lie well on the extrapolation to high radio powers of the correlation between radio and X-ray luminosity known in low-luminosity FR I radio galaxies. On the other hand, GPS galaxies exhibit a comparable X-ray luminosity to FR II radio galaxies, notwithstanding their much larger radio luminosity. Conclusions. The X-ray to radio luminosity ratio distribution in our sample is consistent with the bulk of the high-energy emission being produced by the accretion disk, as well as with dynamical models of GPS evolution where X-rays are produced by Compton upscattering of ambient photons. Further support to the former scenario comes from the location of GPS galaxies in the X-ray to Oiii luminosity ratio versus NH plane. We propose that GPS galaxies are young radio sources, which would reach their full maturity as classical FR II radio galaxies. However, column densities $\gtrsim $1022 cm-2 could lead to a significant underestimate of dynamical age determinations based on the hotspot recession velocity measurements.
We present a multiwavelength study of IC 1531 (z = 0.02564), an extragalactic radio source associated with the γ-ray object 3FGL J0009.9 − 3206 and classified as a blazar of uncertain type in the ...Third Fermi-Large Area Telescope AGN catalog (3LAC). A core-jet structure, visible in radio and X-rays, is enclosed within a ∼220 kpc wide radio structure. The morphology and spectral characteristics of the kiloparsec jet in radio and X-rays are typical of Fanaroff–Riley type I galaxies. The analysis of the radio data and optical spectrum and different diagnostic methods based on the optical, infrared, and γ-ray luminosities also support a classification as a low-power RG seen at moderate angles (θ = 10°–20°). In the framework of leptonic models, the high-energy peak of the non-thermal nuclear spectral energy distribution can be explained in terms of synchrotron-self-Compton emission from a jet seen at θ ∼ 15°. Similarly to other misaligned AGNs detected by Fermi, the required bulk motion is lower (Γ_bulk = 4) than the values inferred in BL Lac objects, confirming that, because of the de-boosting of emission from the highly relativistic blazar region, these nearby systems are valuable targets to probe the existence of multiple sites of production of the most energetic emission in the jets.
We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z = 0.263). CSS sources are thought to be young radio objects at the beginning of ...their evolution and can potentially test the cluster heating process. 1321+045 is a relatively low-luminosity source and its morphology consists of two radio lobes on the opposite sides of a radio core with no evidence for jets or hotspots. The optical emission line ratios are consistent with an interstellar medium dominated by active galactic nucleus photoionization with a small contribution from star formation, and no contributions from shocks. Based on these ratios, we classify 1321+045 as a low excitation galaxy (LEG) and suggest that its radioactivity is in a coasting phase. The X-ray emission associated with the radio source is detected with 36.1 + or - 8.3 counts, but the origin of this emission is highly uncertain. The current X-ray image of the cluster does not show any signatures of a radio source impact on the cluster medium. Chandra detects the cluster emission at >3sigma level out to ~60" (240 kpc). We obtain the best-fit beta model parameters of the surface brightness profile of beta = 0.58 + or - 0.2 and a core radius of (ProQuest: Formulae and/or non-USASCII text omitted) arcsec. The average temperature of the cluster is equal to kT = (ProQuest: Formulae and/or non-USASCII text omitted) keV, with a temperature and cooling profile indicative of a cooling core. We measure the cluster luminosity L sub((0.5-2 keV)) = 3 x 10 super(44) erg s super(-1) and mass 1.5 x 10 super(14) M sub(middot in circle).
Here we present the analysis of multifrequency data gathered for the Fanaroff-Riley type-II (FR II) radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy in the center of A1836. Based on ...analysis of new Chandra and XMM Newton X-ray observations and archival radio data, and assuming the well-established model for the evolution of FR II radio galaxies, we derive the preferred range for the jet kinetic luminosity L sub(j) ~ (1-6) x 10 super(-3) L sub(Edd) ~ (0.5-3) x 10 super(45) erg s super(-1). This is above the values implied by various scaling relations proposed for radio sources in galaxy clusters, being instead very close to the maximum jet power allowed for the given accretion rate. In this context, we speculate on a possible bias against detecting stronger jet-driven shocks in poorer environments, resulting from inefficient electron heating at the shock front, combined with a relatively long electron-ion temperature equilibration timescale.
We report the discovery of a one-sided 3".6 (24 kpc, projected) long jet in the high-redshift, z = 4.72, quasar GB 1428+4217 in new Chandra X-ray and Very Large Array (VLA) radio observations. This ...is the highest redshift kiloparsec-scale X-ray/radio jet known. Analysis of archival very long baseline interferometry 2.3 and 8.6 GHz data reveal a faint one-sided jet extending out to ~200 pc and aligned to within ~30degrees of the Chandra/VLA emission. The 3".6 distant knot is not detected in an archival Hubble Space Telescope image, and its broadband spectral energy distribution is consistent with an origin from inverse Compton scattering of cosmic microwave background photons for the X-rays. Assuming also equipartition between the radiating particles and magnetic field, the implied jet Lorentz factor is approximate5. This is similar to the other two known z ~ 4 kpc scale X-ray jet cases and smaller than typically inferred in lower-redshift cases. Although there are still but a few such very high redshift quasar X-ray jets known, for an inverse Compton origin, the present data suggest that they are less relativistic on large scales than their lower-redshift counterparts.
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