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X-Ray Emitting GHz-Peaked Spectrum Galaxies: Testing a Dynamical-Radiative Model with Broad-Band Spectra

Description: In a dynamical-radiative model we recently developed to describe the physics of compact, GHz-Peaked-Spectrum (GPS) sources, the relativistic jets propagate across the inner, kpc-sized region of the host galaxy, while the electron population of the expanding lobes evolves and emits synchrotron and inverse-Compton (IC) radiation. Interstellar-medium gas clouds engulfed by the expanding lobes, and photoionized by the active nucleus, are responsible for the radio spectral turnover through free-free… more
Date: June 7, 2010
Creator: Ostorero, L.; Moderski, R.; Stawarz, L.; Diaferio, A.; Kowalska, I.; Cheung, C. C. et al.
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Partner: UNT Libraries Government Documents Department
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Sources of the Radio Background Considered

Description: We investigate possible origins of the extragalactic radio background reported by the ARCADE 2 collaboration. The surface brightness of the background is several times higher than that which would result from currently observed radio sources. We consider contributions to the background from diffuse synchrotron emission from clusters and the intergalactic medium, previously unrecognized flux from low surface brightness regions of radio sources, and faint point sources below the flux limit of exi… more
Date: August 22, 2011
Creator: Singal, J.; Stawarz, L.; Lawrence, A. & Petrosian, V.
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Partner: UNT Libraries Government Documents Department
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Chandra Reveals Twin X-ray Jets in the Powerful FR-II Radio Galaxy 3C353

Description: We report X-ray imaging of the powerful FR II radio galaxy 3C 353 using the Chandra X-ray Observatory. 3C 353's two 4-inch wide and 2-feet long jets allow us to study in detail the internal structure of the large-scale relativistic outflows at both radio and X-ray photon energies with the sub-arcsecond spatial resolution provided by the VLA and Chandra instruments. In a 90 ks Chandra observation, we have detected X-ray emission from most radio structures in 3C 353, including the nucleus, the je… more
Date: June 13, 2008
Creator: Kataoka, J.; Stawarz, L.; Harris, D.E.; Siemiginowska, A.; Ostrowski, M.; Swain, M.R. et al.
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Partner: UNT Libraries Government Documents Department
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The Highest Redshift Relativistic Jets

Description: We describe our efforts to understand large-scale (10's-100's kpc) relativistic jet systems through observations of the highest-redshift quasars. Results from a VLA survey search for radio jets in {approx} 30 z > 3.4 quasars are described along with new Chandra observations of 4 selected targets.
Date: December 18, 2007
Creator: Cheung, C.C.; Stawarz, L.; Siemiginowska, A.; Harris, D.E; Schwartz, D.A.; Wardle, J.F.C. et al.
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Partner: UNT Libraries Government Documents Department
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On the Evolution of and High-Energy Emission from GHz-Peaked-Spectrum Sources

Description: Here we discuss evolution and broad-band emission of compact (< kpc) lobes in young radio sources. We propose a simple dynamical description for these objects, consisting of a relativistic jet propagating into a uniform gaseous medium in the central parts of an elliptical host. In the framework of the proposed model, we follow the evolution of ultrarelativistic electrons injected from a terminal hotspot of a jet to expanding lobes, taking into account their adiabatic energy losses as well as… more
Date: December 18, 2007
Creator: Stawarz, L.; Ostorero, L.; Begelman, M. C.; Moderski, R.; Kataoka, J. & Wagner, S.
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Partner: UNT Libraries Government Documents Department
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Intermittent Jet Activity in the Radio Galaxy 4C29.30?

Description: We present radio observations at frequencies ranging from 240 to 8460 MHz of the radio galaxy 4C29.30 (J0840+2949) using the Giant Metrewave Radio Telescope (GMRT), the Very Large Array (VLA) and the Effelsberg telescope. We report the existence of weak extended emission with an angular size of {approx} 520 arcsec (639 kpc) within which a compact edge-brightened double-lobed source with a size of 29 arcsec (36 kpc) is embedded. We determine the spectrum of the inner double from 240 to 8460 MHz … more
Date: April 2, 2007
Creator: Jamrozy, M.; Konar, C.; Saikia, D. J.; Stawarz, L.; Mack, K. -H. & Siemiginowska, A.
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Partner: UNT Libraries Government Documents Department
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Electron Energy Distributions at Relativistic Shock Sites: Observational Constraints from the Cygnus A Hotspots

Description: We report new detections of the hotspots in Cygnus A at 4.5 and 8.0 microns with the Spitzer Space Telescope. Together with detailed published radio observations and synchrotron self-Compton modeling of previous X-ray detections, we reconstruct the underlying electron energy spectra of the two brightest hotspots (A and D). The low-energy portion of the electron distributions have flat power-law slopes (s {approx} 1.5) up to the break energy which corresponds almost exactly to the mass ratio bet… more
Date: October 15, 2007
Creator: Cheung, C.C.Teddy; Stawarz, L.; Harris, D.E. & Ostrowski, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Electron Energy Distribution in Hotspots of Cygnus A:Filling the Gap with Spitzer Space Telescope

Description: Here we present Spitzer Space Telescope imaging of Cyg A with the Infrared Array Camera at 4.5 {micro}m and 8.0 {micro}m, resulting in the detection of the high-energy tails or cut-offs in the synchrotron spectra for all four hotspots of this archetype radio galaxy. When combined with the other data collected (and re-analyzed) from the literature, our observations allow for detailed modeling of the broad-band (radio-to-X-ray) emission for the brightest spots A and D. We confirm that the X-ray f… more
Date: March 6, 2007
Creator: Stawarz, L.; Cheung, C.C.; Harris, D.E. & Ostrowski, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Detailed Structure of the X-Ray Jet in 4C 19.44 (=PKS1354+195)

Description: We investigate the variations of the magnetic field, Doppler factor, and relativistic particle density along the jet of a quasar at z=0.72. We chose 4C 19.44 for this study because of its length and straight morphology. The 18 arcsec length of the jet provides many independent resolution elements in the Chandra X-ray image. The straightness suggests that geometry factors, although uncertain, are almost constant along the jet. We assume the X-ray emission is from inverse Compton scattering of th… more
Date: October 31, 2006
Creator: Schwartz, Daniel A.; Harris, D. E.; Landt, H.; Siemiginowska, A.; Perlman, E. S.; Cheung, C. C. et al.
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Partner: UNT Libraries Government Documents Department
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Direct And Reprocessed Gamma-Ray Emission of Kpc-Scale Jets in FR I Radio Galaxies

Description: We discuss the contribution of kiloparsec-scale jets in FR I radio galaxies to the diffuse {gamma}-ray background radiation. The analyzed {gamma}-ray emission comes from inverse-Compton scattering of starlight photon fields by the ultrarelativistic electrons whose synchrotron radiation is detected from such sources at radio, optical and X-ray energies. We find that these objects, under the minimum-power hypothesis (corresponding to a magnetic field of 300 {micro}G in the brightest knots of thes… more
Date: October 9, 2007
Creator: Stawarz, L.; Kneiske, T. M. & Kataoka, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Epsiodic Activity in Radio Galaxies

Description: One of the interesting issues in our understanding of active galactic nuclei is the duration of their active phase and whether such activity is episodic. In this paper we summarize our recent results on episodic activity in radio galaxies obtained with the GMRT and the VLA.
Date: October 15, 2007
Creator: Saikia, D.J.; Konar, C.; /NCRA, Ganeshkhind; Jamrozy, M.; Machalski, J.; U., /Jagiellonian et al.
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Partner: UNT Libraries Government Documents Department
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Radio Loudness of AGNs: Host Galaxy Morphology and the Spin Paradigm

Description: We investigate how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass. We find that AGNs form two distinct and well separated sequences on the radio-loudness -- Eddington-ratio plane. We argue that these sequences mark the real upper bounds of radio-loudness of two distinct populations of AGNs: those hosted respectively by elliptical and disk galaxies. Both sequences show the same dependence of the radio-loudness on the … more
Date: October 15, 2007
Creator: Stawarz, L.; Sikora, M. & Lasota, J.-P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Multiwavelength Observations of the Powerful Gamma-ray Quasar PKS 1510-089: Clues on the Jet Composition

Description: We present the results from a multiwavelength campaign conducted in August 2006 of the powerful {gamma}-ray quasar PKS 1510--089 (z = 0.361). This campaign commenced with a deep Suzaku observation lasting three days for a total exposure time of 120 ks, and continued with Swift monitoring over 18 days. Besides Swift observations, which sampled the optical/UV flux in all 6 UVOT filters as well as the X-ray spectrum in the 0.3--10 keV energy range, the campaign included ground-based optical and ra… more
Date: September 28, 2007
Creator: Kataoka, J.; Madejski, G.; Sikora, M.; Roming, P.; Chester, M. M.; Grupe, D. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Confronting X-Ray Emission Models with theHighest-Redshift Kiloparsec-Scale Jets: The z = 3.89 Jet in Quasar 1745+624

Description: A newly identified kiloparsec-scale X-ray jet in the high-redshift z=3.89 quasar 1745+624 is studied with multi-frequency Very Large Array, Hubble Space Telescope, and Chandra X-ray imaging data. This is only the third large-scale X-ray jet beyond z > 3 known and is further distinguished as being the most luminous relativistic jet observed at any redshift, exceeding 10{sup 45} erg/s in both the radio and X-ray bands. Apart from the jet's extreme redshift, luminosity, and high inferred equipa… more
Date: June 28, 2006
Creator: Cheung, C.C.; /KIPAC, Menlo Park; Stawarz, L.; Observ., /Heidelberg; Siemiginowska, A. & Astrophys., /Harvard-Smithsonian Ctr.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Broad Line Radio Galaxies Observed with Fermi-LAT: The Origin of the GeV Gamma-Ray Emission

Description: We report on a detailed investigation of the {gamma}-ray emission from 18 broad line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope (LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed {gamma}-ray emission reveals in addition possible flux variability in both sources. No statistically significant {gamma}-ray detection of the other BLRGs was however f… more
Date: June 7, 2012
Creator: Kataoka, J.; Stawarz, L.; Takahashi, Y.; Cheung, C. C.; Hayashida, M.; Grandi, P. et al.
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Partner: UNT Libraries Government Documents Department
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An Experiment to Locate the Site of TeV Flaring in M87

Description: We describe a Chandra X-ray target-of-opportunity project designed to isolate the site of TeV flaring in the radio galaxy M87. To date, we have triggered the Chandra observations only once (2010 April) and by the time of the first of our nine observations, the TeV flare had ended. However, we found that the X-ray intensity of the unresolved nucleus was at an elevated level for our first observation. Of the more than 60 Chandra observations we have made of the M87 jet covering nine years, the nu… more
Date: May 18, 2012
Creator: Harris, D. E.; Massaro, F.; Cheung, C. C.; Horns, D.; Raue, M.; Stawarz, L. et al.
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Partner: UNT Libraries Government Documents Department
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On the Radio and Optical Luminosity Evolution of Quasars

Description: We calculate simultaneously the radio and optical luminosity evolutions of quasars, and the distribution in radio loudness R defined as the ratio of radio and optical luminosities, using a flux limited data set containing 636 quasars with radio and optical fluxes from White et al. We first note that when dealing with multivariate data it is imperative to first determine the true correlations among the variables, not those introduced by the observational selection effects, before obtaining the i… more
Date: May 20, 2011
Creator: Singal, J.; Petrosian, V.; Lawrence, A. & Stawarz, L.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B

Description: CentaurusB is a nearby radio galaxy positioned in the Southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months accumulation of Fermi-LAT data and of newly acquired Suzaku X-ray data for Centaurus B. The source is detected at GeV photon energies, although we cannot completely exclude the possibility that it is an artifact due to incorrect modeling of the bright Galactic diffuse emission in the region. The LAT image provides a weak hint of a spatial … more
Date: August 17, 2012
Creator: Katsuta, Junichiro; Tanaka, Y. T.; Stawarz, L.; O'Sullivan, S. P.; Cheung, C. C.; Kataoka, J. et al.
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Partner: UNT Libraries Government Documents Department
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The Radio and Optical Luminosity Evolution of Quasars II - The SDSS Sample

Description: We determine the radio and optical luminosity evolutions and the true distribution of the radio loudness parameter R, defined as the ratio of the radio to optical luminosity, for a set of more than 5000 quasars combining SDSS optical and FIRST radio data. We apply the method of Efron and Petrosian to access the intrinsic distribution parameters, taking into account the truncations and correlations inherent in the data. We find that the population exhibits strong positive evolution with redshift… more
Date: December 28, 2012
Creator: Singal, J.; Petrosian, V.; Stawarz, L. & Lawrence, A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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