Astronomy & Astrophysics

Free access article

Issue		A&A Volume 407, Number 2, August IV 2003
Page(s)		503 - 513
Section		Galactic structure and dynamics
DOI		10.1051/0004-6361:20030751

A&A 407, 503-513 (2003)
DOI: 10.1051/0004-6361:20030751

Chandra observations of the X-ray environment of BL Lacs

D. Donato¹, M. Gliozzi², R. M. Sambruna^{1, 2} and J. E. Pesce^{2, 3}

¹ George Mason University, School of Computational Sciences, 4400 University Drive, Fairfax, VA 22030, USA
² George Mason University, Dept. of Physics & Astronomy, MS 3F3, 4400 University Drive, Fairfax, VA 22030, USA
³ Eureka Scientific

(Received 17 February 2003 / Accepted 13 May 2003)

Abstract
We present Chandra observations of the X-ray environment of a sample of 6 BL Lacertae objects. The improved sensitivity of the ACIS experiment allows us to separate the core X-ray emission from the contribution of diffuse emission from the host galaxy/cluster scales. Within the short (2-6 ks) ACIS exposures, we find evidence for diffuse X-ray emission in 3 sources (BL Lac, PKS 0548-322, and PKS 2005-489). The diffuse emission can be modeled with a King profile with $\beta \sim 0.3{-}0.6$ , core radii $r_{\rm c} \sim 15{-}28$ kpc, and 0.4-5 keV luminosities in the range 10⁴¹-10⁴² erg s ^-1. In the remaining 3 sources, one (3C 371) has a radial profile entirely consistent with an unresolved source, while two (1ES 2344+514 and 1ES 2321+419) show evidence for weak diffuse emission on kpc scales. These results support current models for radio-loud AGN unifying BL Lacs and FRI radio galaxies through the orientation of their jets. In PKS 0548-322 and PKS 2005-489, we also find evidence for diffuse emission on cluster scales, although the spatial properties of this emission are not constrained. The temperature ( $kT \sim 3{-}5$ keV) and luminosity ( $L_{0.4-5~{\rm keV}} \sim 10^$ erg s ^-1) of the cluster gas are typical of normal clusters. Interestingly, these are the two brightest sources of the sample, suggesting a link between environment and nuclear activity.

Key words: galaxies: active -- galaxies: fundamental parameters -- galaxies: nuclei -- X-rays: galaxies

Offprint request: D. Donato, davide@physics.gmu.edu

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