Extended X‐ray emission from the BL Lac object PKS 0521‐365

Models that seek to unify BL Lacs and low-power radio galaxies predict that the two types of object should show similar isotropically emitted X-ray emission. Testing this is usually limited by difficulties in separating strong X-ray emission from a BL Lac nucleus and surrounding low-surface brightness emission. In this paper we report ROSAT HRI observations of the z = 0.055 BL Lac object PKS 0521 365. We are able to separate a luminous extended X-ray component from the bright nucleus. Using a new radio map, we show that it is unlikely that the extended emission is due to inverseCompton scattering of photons from the active nucleus, and instead interpret it as thermal emission from dense, rapidly cooling gas. This is a more extreme environment than is found in typical FRI radio galaxies, and may pose a problem for unified models.

[1]  G. Hasinger,et al.  Spatial corrections of ROSAT HRI observations , 1998, astro-ph/9811121.

[2]  C. Lawrence,et al.  Extended and Compact X-Ray Emission from the Powerful Radio Galaxy 3C 220.1 , 1998, astro-ph/9804102.

[3]  M. Birkinshaw,et al.  Dynamics of the radio galaxy 3C 449 , 1998, astro-ph/9802175.

[4]  R. Sambruna.  Soft X-Ray Properties of Flat-Spectrum Radio Quasars , 1997 .

[5]  M. Birkinshaw,et al.  Magnetic field strengths in the hotspots of 3C 33 and 111 , 1997 .

[6]  J. Stocke,et al.  The Canada-France-Hawaii Telescope Imaging Survey of BL Lacertae Objects. II. Clustering Environments , 1997 .

[7]  R. Falomo.  Host galaxy and close environment of BL Lacertae objects , 1996 .

[8]  Dayton L. Jones,et al.  VLBI observations of southern EGRET identifications .1. PKS 0208-512, PKS 0521-365, and PKS 0537-441 , 1996 .

[9]  E. Pian,et al.  The Broadband Energy Distribution of the Misaligned Gamma-Ray Blazar PKS 0521-365 , 1996 .

[10]  John T. Stocke,et al.  The Canada-France-Hawaii Telescope Imaging Survey of BL Lacertae Objects. I. Properties of the Host Galaxies , 1996 .

[11]  C. Urry,et al.  On the spectral energy distributions of blazars , 1996 .

[12]  J. E. Pesce,et al.  Environmental Properties of BL LAC Objects , 1995 .

[13]  P. Padovani,et al.  UNIFIED SCHEMES FOR RADIO-LOUD ACTIVE GALACTIC NUCLEI , 1995, astro-ph/9506063.

[14]  B. Dingus,et al.  EGRET observations of the BL Lacertae objects 0716+714 and 0521-365 , 1995 .

[15]  E. Feigelson,et al.  Discovery of Inverse-Compton X-Rays in Radio Lobes , 1995 .

[16]  Eric P. Smith,et al.  The megaparsec-scale environments of BL Lacertae objects , 1995 .

[17]  P. Giommi,et al.  THE X-RAY SPECTRA OF BLAZARS OBSERVED WITH EXOSAT , 1994 .

[18]  E. Perlman,et al.  New very large array maps of highly core-dominated BL Lacs: Testing unified schemes , 1994 .

[19]  M. Bersanelli,et al.  Optical Spectrophotometry of Blazars , 1994 .

[20]  J. Morse.  A METHOD FOR CORRECTING ASPECT SOLUTION ERRORS IN ROSAT HRI OBSERVATIONS OF COMPACT SOURCES , 1994 .

[21]  M. Birkinshaw,et al.  Multiple X-ray emission components in low-power radio galaxies , 1994 .

[22]  C. Carilli,et al.  X-ray emission from the radio hotspots of Cygnus A , 1993, Nature.

[23]  J. Cepa,et al.  STATISTICS AND PROPERTIES OF H-II REGIONS IN NGC-6814 , 1993 .

[24]  E. Perlman,et al.  The radio structure source of X-ray-selected BL Lacertae objects , 1993 .

[25]  D. H. Roberts,et al.  Radio Constraints on the Nature of BL Lacertae Objects and their Parent Population , 1992 .

[26]  C. Carilli,et al.  Multifrequency radio observations of Cygnus A - Spectral aging in powerful radio galaxies , 1991 .

[27]  C. Crawford,et al.  Optical imaging of BL Lac host galaxies. , 1991 .

[28]  B. Wilkes,et al.  X-ray spectra of compact extragalactic radio sources , 1990 .

[29]  Cesare Barbieri,et al.  First Results from the Faint Object Camera: Observations of PKS 0521-36 , 1990 .

[30]  Belinda J. Wilkes,et al.  Accurate galactic N(H) values towards quasars and AGN , 1989 .

[31]  A. S. Monk,et al.  A complete sample of radio galaxies – I. The radio data , 1989 .

[32]  C. Sarazin.  X-Ray Emission from Clusters of Galaxies , 1988 .

[33]  G. Neugebauer,et al.  Energy distributions of blazars , 1988 .

[34]  W. Keel.  The jet of PKS 0521 - 36 - an aging counterpart of M87? , 1986 .

[35]  R. Antonucci,et al.  Extended radio emission and the nature of blazars , 1985 .

[36]  J. Angel,et al.  The radio morphology of blazars and relationships to optical polarization and to normal radio galaxies. , 1984 .

[37]  I. Browne.  Is it possible to turn an elliptical radio galaxy into a BL Lac object , 1983 .

[38]  M. Longair,et al.  The clustering of galaxies about extragalactic radio sources , 1979 .

[39]  J. Riley,et al.  The Morphology of Extragalactic Radio Sources of High and Low Luminosity , 1974 .

[40]  W. Keel,et al.  Optical Spectroscopy of Radio Galaxies in Abell Clusters II. BL Lacs and FR I Unification , 1996 .

[41]  M. Ulrich,et al.  BL Lac objects. , 1989 .

[42]  J. Peacock,et al.  The cluster environments of powerful radio galaxies , 1988 .