We present radial entropy profiles of the intracluster medium (ICM) for a collection of 239 clusters taken from the Chandra X-ray Observatory's Data Archive. Entropy is of great interest because it controls ICM global properties and records the thermal history of a cluster. Entropy is therefore a useful quantity for studying the effects of feedback on the cluster environment and investigating any breakdown of cluster self-similarity. We find that most ICM entropy profiles are well-fit by a model which is a power-law at large radii and approaches a constant value at small radii: K(r) = K 0 + K 100 (r/100 kpc) α , where K 0 quantifies the typical excess of core entropy above the best fitting power-law found at larger radii. We also show that the K 0 distributions of both the full archival sample and the primary HIFLUGCS sample of Reiprich (2001) are bimodal with a distinct gap between K 0 ≈ 30 − 50 keV cm 2 and population peaks at K 0 ∼ 15 keV cm 2 and K 0 ∼ 150 keV cm 2 . The effects of PSF smearing and angular resolution on best-fit K 0 values are investigated using mock Chandra observations and degraded entropy profiles, respectively. We find that neither of these effects is sufficient to explain the entropy-profile flattening we measure at small radii. The influence of profile curvature and number of radial bins on best-fit K 0 is also considered, and we find no indication K 0 is significantly impacted by either. For completeness, we include previously unpublished optical spectroscopy of Hα and [N II] emission lines discussed in Cavagnolo et al. (2008a). All data and results associated with this work are publicly available via the project web site.Abell 119 (z = 0.0442): This is a highly diffuse cluster without a prominent cool core. The large core region and slowly varying surface brightness made deprojection highly unstable. We have excluded a small source at the very center of the BCG. The exclusion region for the source is ≈ 2.2 ′′ in radius which at the redshift of the cluster is ∼ 2 kpc. This cluster required a double β-model.Abell 160 (z = 0.0447): The highly asymmetric, low surface brightness of this cluster resulted in a noisy surface brightness profile that could not be deprojected. This cluster required a double β-model. The BCG hosts a compact X-ray source. The exclusion region for the compact source has a radius of ∼ 5 ′′ or ∼ 4.3 kpc. The BCG for this cluster is not coincident with the X-ray centroid and hence is not at the zero-point of our radial analysis.Abell 193 (z = 0.0485): This cluster has an azimuthally symmetric and a very diffuse ICM centered on a BCG which is interacting with a companion galaxy. In Fig. 1 one can see that the central three bins of this cluster's surface brightness profile are highly discrepant from the best-fit β-model. This is a result of the BCG being coincident with a bright, compact X-ray source. As we have concluded in 3.5, compact X-ray sources are excluded from our analysis as they are not the focus of our study here. Hence we have used the best-fit β-model in d...

Using Chandra X-ray and VLA radio data, we investigate the scaling relationship between jet power, P jet , and synchrotron luminosity, P radio . We expand the sample presented in Bîrzan et al. (2008) to lower radio power by incorporating measurements for 21 gEs to determine if the Bîrzan et al. (2008) P jet -P radio scaling relations are continuous in form and scatter from giant elliptical galaxies (gEs) up to brightest cluster galaxies (BCGs). We find a mean scaling relation of P jet ≈ 5.8 × 10 43 (P radio /10 40 ) 0.70 erg s −1 which is continuous over ∼ 6 − 8 decades in P jet and P radio with a scatter of ≈ 0.7 dex. Our mean scaling relationship is consistent with the model presented in Willott et al. (1999) if the typical fraction of lobe energy in non-radiating particles to that in relativistic electrons is > ∼ 100. We identify several gEs whose radio luminosities are unusually large for their jet powers and have radio sources which extend well beyond the densest parts of their X-ray halos. We suggest that these radio sources are unusually luminous because they were unable to entrain appreciable amounts of gas.

Our Chandra X-Ray Observatory archival study of intracluster entropy in a sample of 222 galaxy clusters shows that Ha and radio emission from the brightest cluster galaxy are much more pronounced when the cluster's core gas entropy is Շ30 keV cm 2 . The prevalence of Ha emission below this threshold indicates that it marks a dichotomy between clusters that can harbor multiphase gas and star formation in their cores and those that cannot. The fact that strong central radio emission also appears below this boundary suggests that AGN feedback turns on when the intracluster medium starts to condense, strengthening the case for AGN feedback as the mechanism that limits star formation in the universe's most luminous galaxies.

The s-process should occur in all but the lower mass progenitor stars of planetary nebulae, and this should be reflected in the chemical composition of the gas that is expelled to create the current planetary nebula shell. Weak forbidden emission lines are expected from several s-process elements in these shells and have been searched for and in some cases detected in previous investigations. Here we extend these studies by combining very high signal-to-noise ratio echelle spectra of a sample of PNe with a critical analysis of the identification of the emission lines of Z > 30 ions. Emission lines of Br, Kr, Xe, Rb, Ba, and Pb are detected with a reasonable degree of certainty in at least some of the objects studied here, and we also tentatively identify lines from Te and I, each in one object. The strengths of these lines indicate enhancement of s-process elements in the central star progenitors, and we determine the abundances of Br, Kr, and Xe, elements for which atomic data relevant for abundance determination have recently become available. As representative elements of the ''light'' and ''heavy''s-process peaks, Kr and Xe exhibit similar enhancements over solar values, suggesting that PN progenitors experience substantial neutron exposure.

The X-ray properties of a relaxed cluster of galaxies are determined primarily by its gravitational potential well and the entropy distribution of its intracluster gas. That entropy distribution reflects both the accretion history of the cluster and the feedback processes that limit the condensation of intracluster gas. Here we present Chandra observations of the core entropy profiles of nine classic ''cooling flow'' clusters that appear relatively relaxed (at least outside the central 10-20 kpc) and contain intracluster gas with a cooling time less than a Hubble time. We show that those entropy profiles are remarkably similar, despite the fact that the clusters range over a factor of 3 in temperature. They typically have an entropy level of %130 keV cm 2 at 100 kpc that declines to a plateau $10 keV cm 2 at P10 kpc. Between these radii, the entropy profiles are /r with % 1:0 1:3. The nonzero central entropy levels in these clusters correspond to a cooling time $10 8 yr, suggesting that episodic heating on this timescale maintains the central entropy profile in a quasi-steady state. We show in an appendix that although disturbances and bubbles are visible in the central regions of these clusters, these phenomena do not strongly bias our entropy estimates.

Current models of galaxy evolution suggest that feedback from active galactic nuclei is needed to explain the high-luminosity cutoff in the galaxy luminosity function. Exactly how an AGN outflow couples with the ambient medium and suppresses star formation remains poorly understood. However, we have recently uncovered an important clue to how that coupling might work. Observations of Ha emission and blue light from the universe's most luminous galaxies, which occupy the centers of galaxy clusters, show that star formation happens only if the minimum specific entropy of the intracluster gas is Շ30 keV cm 2 . Here we suggest that this threshold for star formation is set by the physics of electron thermal conduction, implying that conduction is critical for channeling AGN energy input toward incipient star-forming regions and limiting the progress of star formation.

We present an analysis of the spatial distribution of metal-rich gas in ten galaxy clusters using deep observations from the Chandra X-ray Observatory. The brightest cluster galaxies have experienced recent AGN activity in the forms of bright radio emission, cavities, and shock fronts embedded in the hot atmospheres. The heavy elements are distributed anisotropically and are aligned with the largescale radio and cavity axes. They are apparently being transported from the halo of the brightest cluster galaxy into the intracluster medium along large-scale outflows driven by the radio jets. The radial ranges of the metal-enriched outflows are found to scale with jet power as R Fe ∝ P 0.42 jet , with a scatter of only 0.5 dex. The heavy elements are transported beyond the extent of the inner cavities in all clusters, suggesting this is a long lasting effect sustained over multiple generations of outbursts. Black holes in BCGs will likely have difficulty ejecting metal enriched gas beyond 1 Mpc unless their masses substantially exceed 10 9 M ⊙ .

We explore the band dependence of the inferred X-ray temperature of the intracluster medium (ICM ) for 192 wellobserved galaxy clusters selected from the Chandra Data Archive. If the hot ICM is nearly isothermal in the projected region of interest, the X-ray temperature inferred from a broadband (0.7Y7.0 keV ) spectrum should be identical to the X-ray temperature inferred from a hard-band (2.0Y7.0 keV ) spectrum. However, if unresolved cool lumps of gas are contributing soft X-ray emission, the temperature of a best-fit single-component thermal model will be cooler for the broadband spectrum than for the hard-band spectrum. Using this difference as a diagnostic, the ratio of best-fitting hard-band and broadband temperatures may indicate the presence of cooler gas even when the X-ray spectrum itself may not have sufficient signal-to-noise ratio (S/ N ) to resolve multiple temperature components. To test this possible diagnostic, we extract X-ray spectra from core-excised annular regions for each cluster in our archival sample. We compare the X-ray temperatures inferred from single-temperature fits when the energy range of the fit is 0.7Y7.0 keV (broad) and when the energy range is 2:0/(1 þ z)Y7.0 keV (hard). We find that the hard-band temperature is significantly higher, on average, than the broadband temperature. On further exploration, we find this temperature ratio is enhanced preferentially for clusters which are known merging systems. In addition, cool-core clusters tend to have best-fit hard-band temperatures that are in closer agreement with their best-fit broadband temperatures. We show, using simulated spectra, that this diagnostic is sensitive to secondary cool components (T X ¼ 0:5Y3.0 keV ) with emission measures !10Y30% of the primary hot component.