We present images from five observations of the quasar 3C 273 with the Chandra X-Ray Observatory. The jet has at least four distinct features that are not resolved in previous observations. The first knot in the jet (A1) is very bright in X-rays. Its X-ray spectrum is well fitted with a power law with (where a p 0.60 ‫ע‬ 0.05 ). Combining this measurement with lower frequency data shows that a pure synchrotron model can fit Ϫa S ∝ n n the spectrum of this knot from 1.647 GHz to 5 keV (over nine decades in energy) with , similar a p 0.76 ‫ע‬ 0.02 to the X-ray spectral slope. Thus, we place a lower limit on the total power radiated by this knot of 1.5 # ergs s Ϫ1 ; substantially more power may be emitted in the hard X-ray and g-ray bands. Knot A2 is also 43 10 detected and is somewhat blended with knot B1. Synchrotron emission may also explain the X-ray emission, but a spectral bend is required near the optical band. For knots A1 and B1, the X-ray flux dominates the emitted energy. For the remaining optical knots (C through H), localized X-ray enhancements that might correspond to the optical features are not clearly resolved. The position angle of the jet ridge line follows the optical shape with distinct, aperiodic excursions of ‫1ע‬Њ from a median value of Ϫ138Њ .0. Finally, we find X-ray emission from the "inner jet" between 5Љ and 10Љ from the core.

We present results from two Chandra/ACIS-I observations and one XMM-Newton observation of X-ray emission from the ISM and the inner radio lobes of the nearby radio galaxy Centaurus A. The ISM has an average radial surface brightness profile that is well described by a β-model profile with index β=0.40±0.04 and a temperature of k B T ISM ∼0.29 keV beyond 2 kpc from the nucleus. We find that diffuse X-ray emission is coincident with the outer half of the southwest radio lobe, and a bright X-ray enhancement is detected along the edge of the lobe. On the basis of energetic and lifetime arguments, we reject a nonthermal explanation for this emission. We model this emission as a thin, hot shell or cap of X-ray emitting plasma surrounding the radio lobe that was created by the supersonic inflation of the lobe. This plasma shell is both hotter than (k B T SH ∼2.9 keV) and greatly overpressurized relative to the ambient ISM indicating supersonic expansion. We estimate that the lobe is expanding into the ISM at approximately Mach 8.5 or 2400 km s −1 . We are not directly observing the bow shock, but rather the cooler, denser material that is accumulating ahead of the contact discontinuity. The thermal energy in the shell is a significant fraction of the thermal energy of the hot ISM, demonstrating the possibility that the hot ISM of early galaxies can be re-energized by outflows from nuclear activity.

We present high angular resolution X-ray images and spectra from two Chandra AXAF CCD Imaging Spectrometer (ACIS-I) observations of the X-ray jet in the nearby radio galaxy Cen A. We find that the X-ray emission from the jet is composed of a low surface brightness diffuse component extending continuously from within at least 60 pc of the active nucleus into the northeast radio lobe 4 kpc from the nucleus, along with 31 discrete compact knots, most of which are extended at the resolution of our observation. We find that there are small but significant differences between the X-ray and radio morphologies of the inner jet at the arcsecond level, making it unlikely that a single, spatially coincident population of ultrarelativistic electrons is responsible for the emission in both energy regimes. We suggest that the X-ray knots of the inner jet are indeed the sites of particle acceleration and shocks and that the X-ray and radio knot offsets are caused by a combination of particle diffusion and energy loss. These offsets may be a common feature of all jets in radio galaxies, or at least jets in FR I galaxies, and may be fundamental to the physics of such jets. They are best observed in Cen A because the source is so close. Even though the X-ray and radio knots are offset in position and there are variations of more than a factor of 3 in the ratio of X-ray to radio flux density in the inner jet, the radio to X-ray two-point spectral indices at the X-ray knots are not unusually flat and are consistent with those observed in other X-ray jets seen in FR I galaxies such as M87 and 3C 66B. We find the width of the jet in the X-ray bandpass to be narrower than that measured in the radio along most of its length. The X-ray spectra of several regions of the jet are well fitted by absorbed power-law models with photon indices $2.2-2.5, although the spectrum of one bright knot located $1 kpc from the nucleus (knot B) is harder (photon index = 2.0).

The surveys of Sneden et al. (1997Sneden et al. ( , 2000 found star-to-star abundance scatter of the light elements and the neutroncapture elements in M15 Red Giant Branch (RGB) stars. Further examination of three select RGB tip stars revealed a distinct r-process nucleosynthetic signature (consistent with a scaled solar system r-process abundance distribution). As part of a general survey of metal-poor red horizontal branch (RHB) stars, Preston et al. (2006) observed six RHB members of M15. They detected some star-to-star abundance scatter in both the light and n-capture elements. Notably, Preston et al. found that the mean metallicity of these stars was significant lower (by roughly 0.2 dex) than their RGB counterparts. We present a new comparative abundance derivation for three RGB and six RHB stars of the globular cluster M15. We make a considerable effort to understand the apparent discrepancy in the metallicity of RGB and RHB stars. We then perform a detailed examination of the n-capture elements. We will discuss the abundance results and consider the chemical inhomogeneity of M15.

We present results from a 49.4 ks Chandra/ACIS-S observation of the nearby (z=0.059) X-shaped FRII radio galaxy 3C 403. This is the first Chandra observation of an X-shaped radio galaxy, and one of the goals of this pioneering study is to determine the relationship between the X-ray emitting gas and the X-shaped radio morphology. We find that the X-ray isophotes of the hot gas within ∼3.5 ′′ of the central galaxy are highly elliptical (eccentricity∼0.57) and co-aligned with the elliptical optical isophotes. This supports the hypothesis that X-shaped radio sources are created by propagation of jets through asymmetric density distributions. Within large uncertainties, there is no evidence that the lobes or wings are overpressurized relative to the ISM, supporting the scenario in which the wings are the result of strong backflow of material from the jet head and subsequent buoyant evolution. We have detected X-ray emission from several of the radio knots to the E of the active nucleus, and diffuse emission from the radio lobe to the W. The X-ray emission from the eastern knots cannot be explained by an inverse Compton model unless they are far from equipartition. Using archival HST data, optical emission is detected from two knots, and the radio/optical/Xray spectra are well fitted by simple synchrotron models. This is one of the