Discovery of a Jet-Like Structure at the High Redshift QSO CXOMP J084128.3+131107

The Chandra Multiwavelength Project (ChaMP) has discovered a jet-like structure associated with a newly recognized QSO at redshift z=1.866. The system was 9.4 arcmin off-axis during an observation of 3C 207. Although significantly distorted by the mirror PSF, we use both a raytrace and a nearby bright point source to show that the X-ray image must arise from some combination of point and extended sources, or else from a minimum of three distinct point sources. We favor the former situation, as three unrelated sources would have a small probability of occurring by chance in such a close alignment. We show that interpretation as a jet emitting X-rays via inverse Compton (IC) scattering on the cosmic microwave background (CMB) is plausible. This would be a surprising and unique discovery of a radio-quiet QSO with an X-ray jet, since we have obtained upper limits of 100 microJy on the QSO emission at 8.46 GHz, and limits of 200 microJy for emission from the putative jet.Comment: 12 pages including 4 figures. Accepted for publication by ApJ Letter

Discovery of an optical bow-shock around pulsar B0740-28

We report the discovery of a faint H-alpha pulsar wind nebula (PWN) powered by the radio pulsar B0740-28. The characteristic bow-shock morphology of the PWN implies a direction of motion consistent with the previously measured velocity vector for the pulsar. The PWN has a flux density more than an order of magnitude lower than for the PWNe seen around other pulsars, but, for a distance 2 kpc, it is consistent with propagation through a medium of atomic density n_H ~ 0.25 cm^{-3}, and neutral fraction of 1%. The morphology of the PWN in the area close to the pulsar is distinct from that in downstream regions, as is also seen for the PWN powered by PSR B2224+65. In particular, the PWN associated with PSR B0740-28 appears to close at its rear, suggesting that the pulsar has recently passed through a transition from low density to high density ambient gas. The faintness of this source underscores that deep searches are needed to find further examples of optical pulsar nebulae.Comment: 5 pages, 1 figure, to appear in Astronomy & Astrophysics Letter

Chandra Multiwavelength Project: Normal Galaxies at Intermediate Redshift

(abridged) We have investigated 136 Chandra extragalactic sources without broad optical emission lines, including 93 galaxies with narrow emission lines (NELG) and 43 with only absorption lines (ALG). Based on fx/fo, Lx, X-ray spectral hardness and optical emission line diagnostics, we have conservatively classified 36 normal galaxies (20 spirals and 16 ellipticals) and 71 AGNs. We found no statistically significant evolution in Lx/LB, within the limited z range. We have built log(N)-log(S), after correcting for completeness based on a series of simulations. The best-fit slope is -1.5 for both S and B energy bands, which is considerably steeper than that of the AGN-dominated cosmic background sources, but slightly flatter than the previous estimate, indicating normal galaxies will not exceed the AGN population until fx ~ 2 x 10-18 erg s-1 cm-2 (a factor of ~5 lower than the previous estimate). A group of NELGs appear to be heavily obscured in X-rays, i.e., a typical type 2 AGN. After correcting for intrinsic absorption, their X-ray luminosities could be Lx > 10^44 erg s-1, making them type 2 quasar candidates. While most X-ray luminous ALGs (XBONG - X-ray bright, optically normal galaxy candidates) do not appear to be significantly absorbed, we found two heavily obscured objects, which could be as luminous as an unobscured broad-line quasar. Among 43 ALGs, we found two E+A galaxy candidates with strong Balmer absorption lines, but no [OII] line. The X-ray spectra of both galaxies are soft and one of them has a nearby close companion galaxy, supporting the merger/interaction scenario rather than the dusty starburst hypothesis.Comment: 31 pages, 9 figures, accepted for publication in ApJ (20 June 2006, v644), replaced with minor correction

The 300 kpc Long X-ray Jet in PKS 1127-145, z=1.18 Quasar: Constraining X-ray Emission Models

We present a ~100 ksec Chandra X-ray observation and new VLA radio data of the large scale, 300 kpc long X-ray jet in PKS1127-145, a radio loud quasar at redshift z=1.18. With this deep X-ray observation we now clearly discern the complex X-ray jet morphology and see substructure within the knots. The X-ray and radio jet intensity profiles are seen to be strikingly different with the radio emission peaking strongly at the two outer knots while the X-ray emission is strongest in the inner jet region. The jet X-ray surface brightness gradually decreases by an order of magnitude going out from the core. The new X-ray data contain sufficient counts to do spectral analysis of the key jet features. The X-ray energy index of the inner jet is relatively flat with alpha_X = 0.66 +/-0.15 and steep in the outer jet with alpha_X = 1.0 +/-0.2. We discuss the constraints implied by the new data on the X-ray emission models and conclude that ``one-zone'' models fail and at least a two component model is needed to explain the jet's broad-band emission. We propose that the X-ray emission originates in the jet proper while the bulk of the radio emission comes from a surrounding jet sheath. We also consider intermittent jet activity as a possible cause of the observed jet morphology

AGN Feedback and Evolution of Radio Sources: Discovery of an X-ray Cluster Associated with z=1 Quasar

We report the first significant detection of an X-ray cluster associated with a powerful (L(bol) ~1e47 erg/sec) radio-loud quasar at high redshift (z=1.06). Diffuse X-ray emission is detected out to ~120 kpc from the CSS quasar 3C 186. A strong Fe-line emission at the z(rest)=1.06 confirms its thermal nature. We find that the CSS radio source is highly overpressured with respect to the thermal cluster medium by ~2-3 orders of magnitude. This provides direct observational evidence that the radio source is not thermally confined as posited in the ``frustrated'' scenario for CSS sources. Instead, the radio source may be young and at an early stage of its evolution. This source provides the first detection of the AGN in outburst in the center of a cooling flow cluster. Powerful radio sources are thought to be triggered by the cooling flows. The evidence for the AGN activity and intermittent outbursts comes from the X-ray morphology of low redshift clusters, which usually do not harbour quasars. 3C186 is a young active radio source which can supply the energy into the cluster and potentially prevent its cooling. We discuss energetics related to the quasar activity and the cluster cooling flow, and possible feedback between the evolving radio source and the cluster.Comment: 5 pages, 3 figures, to appear in Proc. "The X-ray Universe 2005", San Lorenzo de El Escorial, Spain, September 200

Chandra Discovery of a 300 kpc X-ray Jet in the GPS Quasar PKS1127-145

We have discovered an X-ray jet with Chandra imaging of the z=1.187 radio-loud quasar PKS1127-145. In this paper we present the Chandra X-ray data, follow-up VLA observations, and optical imaging using the HST WFPC2. The X-ray jet contains 273+/-5 net counts in 27ksec and extends ~30 arcsec, from the quasar core, corresponding to a minimum projected linear size of ~330/h_50 kpc. The evaluation of the X-ray emission processes is complicated by the observed offsets between X-ray and radio brightness peaks. We discuss the problems posed by these observations to jet models. In addition, PKS1127-145 is a Giga-Hertz Peaked Spectrum radio source, a member of the class of radio sources suspected to be young or ``frustrated'' versions of FRI radio galaxies. However the discovery of an X-ray and radio jet extending well outside the host galaxy of PKS1127-145 suggests that activity in this and other GPS sources may be long-lived and complex.Comment: 22 pages, 11 ps figures, 1 figure in a JPG file, 3 tables. AASTEX. Accepted by The Astrophysical Journa