Craig L. Sarazin

University of Virginia, Charlottesville, Virginia, United States

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Publications (322)1126.37 Total impact

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    ABSTRACT: We report the results of a deep XMM-Newton observation of the radio-faint γ-ray pulsar J1741–2054 and its nebula together with the analysis of five years of Fermi Large Area Telescope (LAT) data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. The nebular emission is consistent with that of a synchrotron pulsar wind nebula, with hints of spatial spectral variation. We extended the available Fermi LAT ephemeris and folded the γ-ray and X-ray data. We detected X-ray pulsations from the neutron star: both the thermal and non-thermal components are ~35%-40% pulsed, with phase-aligned maxima. A sinusoid fits the thermal-folded profile well. A 10 bin phase-resolved analysis of the X-ray emission shows softening of the non-thermal spectrum during the on-pulse phases. The radio, X-ray, and γ-ray light curves are single-peaked, not phase-aligned, with the X-ray peak trailing the γ-ray peak by more than half a rotation. Spectral considerations suggest that the most probable pulsar distance is in the 0.3-1.0 kpc range, in agreement with the radio dispersion measure.
    The Astrophysical Journal 07/2014; 790(1):51. · 6.73 Impact Factor
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    ABSTRACT: We report the results of a deep XMM-Newton observation of the radio-faint $\gamma$-ray pulsar J1741-2054 and its nebula together with the analysis of 5 years of Fermi LAT data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. The nebular emission is consistent with that of a synchrotron pulsar wind nebula, with hints of spatial spectral variation. We extended the available Fermi LAT ephemeris and folded the $\gamma$-ray and X-ray data. We detected X-ray pulsations from the neutron star: both the thermal and non-thermal components are about 35-40% pulsed, with phase-aligned maxima. A sinusoid fits the thermal folded profile well. A 10-bin phase-resolved analysis shows softening of the non-thermal spectrum during the on-pulse phases. The radio, X-ray and $\gamma$-ray light curves are single-peaked, not phase-aligned, with the X-ray peak trailing the $\gamma$-ray peak by over half a rotation. Spectral considerations suggest that the most probable pulsar distance is in the 0.3-1.0 kpc range.
    04/2014;
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    ABSTRACT: Scaling properties of galaxy cluster observables with mass provide central insights into the processes shaping clusters. Calibrating proxies for cluster mass will be crucial to cluster cosmology with upcoming surveys like eROSITA and Euclid. The recent Planck results led to suggestions that X-ray masses might be biased low by $\sim\!40$ %, more than previously considered. We extend the direct calibration of the weak lensing -- X-ray mass scaling towards lower masses (as low as $1\!\times\!10^{14}\,\mathrm{M}_{\odot}$) in a sample representative of the $z\!\sim\!0.4$--$0.5$ population. We investigate the scaling of MMT/Megacam weak lensing (WL) masses for $8$ clusters at $0.39\!\leq\!z\!\leq\!0.80$ as part of the \emph{400d} WL programme with hydrostatic \textit{Chandra} X-ray masses as well as those based on the proxies, e.g. $Y_{\mathrm{X}}\!=\!T_{\mathrm{X}}M_{\mathrm{gas}}$. Overall, we find good agreement between WL and X-ray masses, with different mass bias estimators all consistent with zero. Subdividing the sample, we find the high-mass subsample to show no significant mass bias while for the low-mass subsample, there is a bias towards overestimated X-ray masses at the $\sim\!2\sigma$ level for some mass proxies. The overall scatter in the mass-mass scaling relations is surprisingly low. Neither observation can be traced back to the parameter settings in the WL analysis. We do not find evidence for a strong ($\sim\!40$ %) underestimate in the X-ray masses, as suggested to reconcile Planck cluster counts and cosmological constraints. For high-mass clusters, our measurements are consistent with studies in the literature. The mass dependent bias, significant at $\sim\!2\sigma$, may hint at a physically different cluster population (less relaxed clusters with more substructure and mergers); or it may be due to small number statistics.
    02/2014;
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    ABSTRACT: High-resolution GBT+MUSTANG observations of the Sunyaev-Zel'dovich Effect (SZE) at 90GHz have revealed complex substructure in the hot intra-cluster medium (ICM) of several massive galaxy clusters. The SZE is a nearly redshift-independent, complementary probe of the ICM to X-ray emission and combined analyses of both data sets provide a better understanding of astrophysical phenomena such as shocks, cold fronts, and sloshing of the gas within a cluster's dark matter potential. Understanding how substructure, especially in merging clusters, affects the scaling between SZE flux and total cluster mass is essential to placing tight constraints on cosmological parameters with SZE surveys. First, I will present recent results from MUSTANG observations of the SZE in MACS J0647.7+7015 and MACS J1206.2-0847. In order to better characterize the cluster dynamics, a number of models are jointly fit in the map domain using a least squares fitting routine. We compare our data to the best-fit generalized Navarro, Frenk, and White (gNFW) profiles from Bolocam and find evidence for a steeper central slope in both clusters than had previously been determined. Furthermore, MUSTANG detects significant features near the core of both clusters that are suggestive of substructure. High-resolution SZE measurements out to larger angular scales will be necessary to better understand the nature of features like these. With this in mind, we are building MUSTANG-1.5, a new bolometer camera which offers many advantages over MUSTANG and unlocks SZE's true potential as an independent tool to understand the ICM on a broad range of angular scales and with a noise level better than any current instrument. I will present a status report on the progress of the receiver, which we aim to install on the Green Bank Telescope (GBT) for first light this season. The improvement in sensitivity and much larger field-of-view (3.5' compared to 35" for MUSTANG) will enable us to pursue a far more comprehensive observing program including the first ever detection of X-ray cavities via the SZE and high-resolution measurements of the ICM out to unprecedented radii.
    01/2014;
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    ABSTRACT: Diffuse radio emission permeating the cluster gravitational potential reveals the widespread presence of relativistic particles and magnetic fields in the intracluster medium (ICM). This emission is observed in numerous clusters which are dynamically complex. The radio emission is observationally classified as halo or relic. Additional low frequency ICM emission is detected from cluster-center radio galaxies which are important for energy feedack into the ICM. I will present recent low frequency radio (VLA and GMRT) data and Chandra X-ray results on several cluster systems. The recently discovered ultra-steep spectrum source in Abell 2443 may be a member of the relatively rare class of adiabatically compressed radio relics. Chandra observations reveal the presence of two surface brightness edges in the ICM and new GMRT observations provide additional details of the spectral index distribution in the ICM. Upcoming improvements in radio instruments will be crucial for expanding our understanding of the relativistic particle and magnetic field content of the ICM. I will briefly discuss a new exploratory concept (LOBO or LOw Band Observatory) which could enable low band (<500 MHz) observing using the new NRL/NRAO Low Band receivers in parallel with all high frequency VLA observing programs.
    01/2014;
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    ABSTRACT: We present the analysis of a deep Chandra observation of a ~2 L * late-type galaxy, ESO 137-002, in the closest rich cluster A3627. The Chandra data reveal a long (gsim40 kpc) and narrow tail with a nearly constant width (~3 kpc) to the southeast of the galaxy, and a leading edge ~1.5 kpc from the galaxy center on the upstream side of the tail. The tail is most likely caused by the nearly edge-on stripping of ESO 137-002's interstellar medium (ISM) by ram pressure, compared to the nearly face-on stripping of ESO 137-001 discussed in our previous work. Spectral analysis of individual regions along the tail shows that the gas throughout it has a rather constant temperature, ~1 keV, very close to the temperature of the tails of ESO 137-001, if the same atomic database is used. The derived gas abundance is low (~0.2 solar with the single-kT model), an indication of the multiphase nature of the gas in the tail. The mass of the X-ray tail is only a small fraction (<5%) of the initial ISM mass of the galaxy, suggesting that the stripping is most likely at an early stage. However, with any of the single-kT, double-kT, and multi-kT models we tried, the tail is always "over-pressured" relative to the surrounding intracluster medium (ICM), which could be due to the uncertainties in the abundance, thermal versus non-thermal X-ray emission, or magnetic support in the ICM. The Hα data from the Southern Observatory for Astrophysical Research show a ~21 kpc tail spatially coincident with the X-ray tail, as well as a secondary tail (~12 kpc long) to the east of the main tail diverging at an angle of ~23° and starting at a distance of ~7.5 kpc from the nucleus. At the position of the secondary Hα tail, the X-ray emission is also enhanced at the ~2σ level. We compare the tails of ESO 137-001 and ESO 137-002, and also compare the tails to simulations. Both the similarities and differences of the tails pose challenges to the simulations. Several implications are briefly discussed. Based on observations made with the Chandra X-Ray Observatory and the Southern Observatory for Astrophysical Research (SOAR) telescope.
    The Astrophysical Journal 11/2013; 777(2):122-. · 6.73 Impact Factor
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    ABSTRACT: We present multi-frequency observations of the radio galaxy Hydra-A (3C218) located in the core of a massive, X-ray luminous galaxy cluster. IFU spectroscopy is used to trace the kinematics of the ionised and warm molecular hydrogen which are consistent with a ~ 5 kpc rotating disc. Broad, double-peaked lines of CO(2-1), [CII]157 $\mu$m and [OI]63 $\mu$m are detected. We estimate the mass of the cold gas within the disc to be M$_{gas}$ = 2.3 $\pm$ 0.3 x 10$^9$ M$_{\odot}$. These observations demonstrate that the complex line profiles found in the cold atomic and molecular gas are related to the rotating disc or ring of gas. Finally, an HST image of the galaxy shows that this gas disc contains a substantial mass of dust. The large gas mass, SFR and kinematics are consistent with the levels of gas cooling from the ICM. We conclude that the cold gas originates from the continual quiescent accumulation of cooled ICM gas. The rotation is in a plane perpendicular to the projected orientation of the radio jets and ICM cavities hinting at a possible connection between the kpc-scale cooling gas and the accretion of material onto the black hole. We discuss the implications of these observations for models of cold accretion, AGN feedback and cooling flows.
    Monthly Notices of the Royal Astronomical Society 10/2013; 437(1). · 5.52 Impact Factor
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    ABSTRACT: We present the analysis of a deep Chandra observation of a ~2L_* late-type galaxy, ESO 137-002, in the closest rich cluster A3627. The Chandra data reveal a long (>40 kpc) and narrow tail with a nearly constant width (~3 kpc) to the southeast of the galaxy, and a leading edge ~1.5 kpc from the galaxy center on the upstream side of the tail. The tail is most likely caused by the nearly edge-on stripping of ESO 137-002's ISM by ram pressure, compared to the nearly face-on stripping of ESO 137-001 discussed in our previous work. Spectral analysis of individual regions along the tail shows that the gas throughout it has a rather constant temperature, ~1 keV, very close to the temperature of the tails of ESO 137-001, if the same atomic database is used. The derived gas abundance is low (~0.2 solar with the single-kT model), an indication of the multiphase nature of the gas in the tail. The mass of the X-ray tail is only a small fraction (<5%) of the initial ISM mass of the galaxy, suggesting that the stripping is most likely at an early stage. However, with any of the single-kT, double-kT and multi-kT models we tried, the tail is always "over-pressured" relative to the surrounding ICM, which could be due to the uncertainties in the abundance, thermal vs. non-thermal X-ray emission, or magnetic support in the ICM. The H-alpha data from SOAR show a ~21 kpc tail spatially coincident with the X-ray tail, as well as a secondary tail (~12 kpc long) to the east of the main tail diverging at an angle of ~23 degrees and starting at a distance of ~7.5 kpc from the nucleus. At the position of the secondary H-alpha tail, the X-ray emission is also enhanced at the ~2 sigma level. We compare the tails of ESO 137-001 and ESO 137-002, and also compare the tails to simulations. Both the similarities and differences of the tails pose challenges to the simulations. Several implications are briefly discussed.
    09/2013;
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    JOSHUA C. KEMPNER, CRAIG L. SARAZIN
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    ABSTRACT: We have undertaken a systematic search for diffuse radio halos and relics in all of the Abell clusters that are visible in the Westerbork Northern Sky Survey (WENSS). In this survey we found 18 candidates, 11 of which are already known from the literature, and 7 for which we provide the first evidence of diffuse radio emission. All the clusters in this sample show other evidence for a recent or ongoing merger. We also investigate the correlation between cluster X-ray luminosity and radio power of halos. We develop a very simple model for merger shocks that reproduces the sense of this correlation, although it i s probably not as steep as the correlation in the data. We discuss the implications of X-ray-radio correlations for f uture detections of radio halos.
    The Astrophysical Journal 07/2013; · 6.73 Impact Factor
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    ABSTRACT: We present a new Chandra X-ray observation of the intracluster medium in the galaxy cluster Abell 2443, hosting an ultra-steep spectrum radio source. The data reveal that the intracluster medium is highly disturbed. The thermal gas in the core is elongated along a northwest to southeast axis and there is a cool tail to the north. We also detect two X-ray surface brightness edges near the cluster core. The edges appear to be consistent with an inner cold front to the northeast of the core and an outer shock front to the southeast of the core. The southeastern edge is coincident with the location of the radio relic as expected for shock (re)acceleration or adiabatic compression of fossil relativistic electrons.
    The Astrophysical Journal 06/2013; 772(2). · 6.73 Impact Factor
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    ABSTRACT: We have identified a merging galaxy cluster with evidence of two distinct sub-clusters. The X-ray and optical data suggest that the subclusters are moving away from each other after closest approach. This cluster merger was discovered from observations of the well localized short-duration gamma-ray burst (GRB), GRB 050509B. The Swift/Burst Alert Telescope (BAT) source position is coincident with a cluster of galaxies ZwCl 1234.0+02916. The subsequent Swift/X-Ray Telescope (XRT) localization of the X-ray afterglow found the GRB coincident with 2MASX J12361286+2858580, a giant red elliptical galaxy in the cluster. Deep multi-epoch optical images were obtained to constrain the evolution of the GRB afterglow, including a 27480s exposure in the F814W band with Hubble Space Telescope Advanced Camera for Surveys (ACS), among the deepest imaging ever obtained towards a known galaxy cluster in a single passband. We perform a weak gravitational lensing analysis, including mapping the total mass distribution of the merger system. Combined with Chandra X-ray Observatory and Swift/XRT observations, we investigate the dynamical state of the merger to probe the nature of the dark matter component. Our weak gravitational lensing measurements reveal a separation of the X-ray centroid of the western subcluster from the center of the mass and galaxy light distributions, similar to that of the famous "Bullet cluster". We conclude that the "Burst cluster" is another candidate merger system for determining the nature of dark matter and for studying the environment of short GRBs. We discuss connections between the cluster dynamical state and/or matter composition and compact object mergers, the leading model for the origin of short GRBs. Finally, we present results from a weak lensing survey based on archival Very Large Telescope (VLT) images in the areas of 5 other short GRBs.
    The Astrophysical Journal 05/2013; 772(1). · 6.73 Impact Factor
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    ABSTRACT: We report the results of a multi-wavelength study of the nearby galaxy group, Abell 3581 (z=0.0218). This system hosts the most luminous cool core of any nearby group and exhibits active radio mode feedback from the super-massive black hole in its brightest group galaxy, IC 4374. The brightest galaxy has suffered multiple active galactic nucleus outbursts, blowing bubbles into the surrounding hot gas, which have resulted in the uplift of cool ionised gas into the surrounding hot intragroup medium. High velocities, indicative of an outflow, are observed close to the nucleus and coincident with the radio jet. Thin dusty filaments accompany the uplifted, ionised gas. No extended star formation is observed, however, a young cluster is detected just north of the nucleus. The direction of rise of the bubbles has changed between outbursts. This directional change is likely due to sloshing motions of the intragroup medium. These sloshing motions also appear to be actively stripping the X-ray cool core, as indicated by a spiraling cold front of high metallicity, low temperature, low entropy gas.
    Monthly Notices of the Royal Astronomical Society 04/2013; 435(2). · 5.52 Impact Factor
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    ABSTRACT: We report striking changes in the broadband spectrum of the compact jet of the black hole transient MAXI J1836–194 over state transitions during its discovery outburst in 2011. A fading of the optical-infrared (IR) flux occurred as the source entered the hard-intermediate state, followed by a brightening as it returned to the hard state. The optical-IR spectrum was consistent with a power law from optically thin synchrotron emission, except when the X-ray spectrum was softest. By fitting the radio to optical spectra with a broken power law, we constrain the frequency and flux of the optically thick/thin break in the jet synchrotron spectrum. The break gradually shifted to higher frequencies as the source hardened at X-ray energies, from ~1011 to ~4 × 1013 Hz. The radiative jet luminosity integrated over the spectrum appeared to be greatest when the source entered the hard state during the outburst decay (although this is dependent on the high-energy cooling break, which is not seen directly), even though the radio flux was fading at the time. The physical process responsible for suppressing and reactivating the jet (neither of which are instantaneous but occur on timescales of weeks) is uncertain, but could arise from the varying inner accretion disk radius regulating the fraction of accreting matter that is channeled into the jet. This provides an unprecedented insight into the connection between inflow and outflow, and has implications for the conditions required for jets to be produced, and hence their launching process.
    The Astrophysical Journal Letters 04/2013; 768(2):L35. · 6.35 Impact Factor
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    ABSTRACT: We present a spectral investigation of X-ray binaries in NGC 5128 (Cen A), using six 100 ks Chandra observations taken over two months in 2007. We divide our sample into thermally and non-thermally dominated states based on the behavior of the fitted absorption column, and present the spectral parameters of sources with L >2x10^37 erg/s. The majority of sources are consistent with being neutron star low mass X-ray binaries (NS LMXBs) and we identify three transient black hole (BH) LMXB candidates coincident with the dust lane, which is the remnant of a small late-type galaxy. Our results also provide tentative support for the apparent `gap' in the mass distribution of compact objects between ~2-5 Msol. We propose that BH LMXBs are preferentially found in the dust lane, and suggest this is because of the younger stellar population. The majority (~70-80%) of potential Roche-lobe filling donors in the Cen A halo are >12 Gyr old, while BH LMXBs require donors >1 Msol to produce the observed peak luminosities. This requirement for more massive donors may also explain recent results that claim a steepening of the X-ray luminosity function with age at Lx >= 5x10^38 erg/s for the XB population of early-type galaxies; for older stellar populations, there are fewer stars >1 Msol, which are required to form the more luminous sources.
    The Astrophysical Journal 04/2013; 766(2):88. · 6.73 Impact Factor
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    ABSTRACT: Based on Suzaku X-ray observations, we study the hot gas around the NGC4839 group of galaxies and the radio relic in the outskirts of the Coma cluster. We find a gradual decline in the gas temperature from 5 keV around NGC4839 to 3.6 keV at the radio relic, across which there is a further, steeper drop down to 1.5 keV. This drop as well as the observed surface brightness profile are consistent with a shock with Mach number M = 2.2 pm 0.5 and velocity vs = (1410 pm 110) km s^-1. A lower limit of B > 0.33 mu G is derived on the magnetic field strength around the relic from upper limits to inverse Compton X-ray emission. Although this suggests that the non-thermal electrons responsible for the relic are generated by diffusive shock acceleration (DSA), the relation between the measured Mach number and the electron spectrum inferred from radio observations are inconsistent with that expected from the simplest, test-particle theory of DSA. Nevertheless, DSA is still viable if it is initiated by the injection of a pre-existing population of non-thermal electrons. Combined with previous measurements, the temperature profile of Coma in the southwest direction is shallower outside NGC4839 and also slightly shallower in the outermost region. The metal abundance around NGC4839 is confirmed to be higher than in its vicinity, implying a significant peak in the abundance profile that decreases to 0.2 solar toward the outskirts. We interpret these facts as due to ram pressure stripping of metal-enriched gas from NGC4839 as it falls into Coma. The relic shock may result from the combined interaction of pre-existing intracluster gas, gas associated with NGC 4839, and cooler gas flowing in from the large-scale structure filament in the southwest.
    Publications- Astronomical Society of Japan 02/2013; · 2.44 Impact Factor
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    ABSTRACT: Chandra X-ray observations of nearby galaxies continue to resolve tens to hundreds of low-mass X-ray binaries (LMXBs) per galaxy. Ongoing studies have brought up issues with the behavior of this population of stellar corpses, in particular the connection between LMXBs and globular clusters (GCs) and the nature of the LMXB luminosity function (LF). We present 195 LMXB candidates detected from Chandra images of of three S0 galaxies, NGC1380, NGC2768, and NGC4477. 16 sources in NGC1380 were matched with globular clusters identified from the ACS Fornax Cluster Survey done by Hubble. We show that the results of spectral fitting and hardness ratio analysis indicate the population of LMXBs are consistent with Galactic absorption and a power-law X-ray spectrum. We discuss the asymmetric distribution of sources in NGC4477 and the new observation of NGC 1380-ULX1. We compare the population of LMXBs in the sample S0 galaxies to other populations in elliptical galaxies.
    01/2013;
  • Taylor Hogge, C. L. Sarazin, D. R. Wik
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    ABSTRACT: Abell 2061 is a galaxy cluster in the north-central region of the Corona Borealis supercluster (z ~ 0.07). We observed this cluster with the Chandra X-ray Observatory. We have detected a likely shock in its central NE region. This shock is probably associated with the same merger that produced a cool "Plume'' further to the NE, and the shock may be material from the Plume which is falling into the cluster center. Many of the X-ray features of the cluster are reproduced by a numerical model of an offset, unequal mass merger after first core passage, taken from the SLAM library of simulations. This merger is also the likely source of the peripheral radio relic and central radio halo/relic in the cluster. Our Chandra spectra of the shock region have confirmed the expected temperature enhancement. We discuss the merger dynamics of the cluster in more detail.
    01/2013;
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    Craig L. Sarazin, Alexis Finoguenov, Daniel R. Wik
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    ABSTRACT: We present new XMM-Newton observations of the northwest (NW) radio relic region in the cluster Abell 3667. We detect a jump in the X-ray surface brightness and X-ray temperature at the sharp outer edge of the radio relic which indicate that this is the location of a merger shock with a Mach number of about 2. Comparing the radio emission to the shock properties implies that approximately 0.2% of the dissipated shock kinetic energy goes into accelerating relativistic electrons. This is an order of magnitude smaller than the efficiency of shock acceleration in many Galactic supernova remnants, which may be due to the lower Mach numbers of cluster merger shocks. The X-ray and radio properties indicate that the magnetic field strength in the radio relic is >= 3 muG, which is a very large field at a projected distance of ~2.2 Mpc from the center of a cluster. The radio spectrum is relatively flat at the shock, and steepens dramatically with distance behind the shock. This is consistent with radiative losses by the electrons and the post-shock speed determined from the X-ray properties. The Cygnus A radio source is located in a merging cluster of galaxies. This appears to be an early-stage merger. Our recent Suzaku observation confirm the presence of a hot region between the two subclusters which agrees with the predicted shocked region. The high spectral resolution of the CCDs on Suzaku allowed us to measure the radial component of the merger velocity, Delta v_r \approx 2650 km/s.
    Astronomische Nachrichten 11/2012; · 1.40 Impact Factor
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    ABSTRACT: Here, we present the final stacked ``coadded'' analysed in the paper. The data set consists of observations of eight fields centred on galaxy clusters selected from the 400d survey (Burenin et al., 2007, Cat. J/ApJS/172/561, Vikhlinin et al. 2009ApJ...692.1033V). All of these clusters have been observed with the Megacam wide-field imager, then located at the 6.5m MMT telescope at Fred Lawrence Whipple Observatory (files MMT*). The galaxy shapes analysed in our article were drawn from the r' band images (*_r.fits), consistently. For four of the clusters, auxiliary bands (g', i') could be observed and taken into account for galaxy selection. Note that the r' band of CL 0030+2618 and the g' and r' bands were taken in non-photometric conditions, while the rest of the data is of photometric quality. We also include observations obtained with the CFHT MegaCam/MegaPrime imager (files CFHT*) for CL 1701+6414 in the g'r'i'z' filters, which we analysed for comparison. Note that the exposure time of these images in accessible in the fits headers via the TEXPTIME keyword, not via EXPTIME. For all images, we also include the weight and flag images used in our analysis, giving the pixel-to-pixel quality variation in the main files and regions excluded from the analysis, respectively. (2 data files).
    VizieR Online Data Catalog. 10/2012;
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    ABSTRACT: In a number of nearby clusters of galaxies, recent X-ray observations have revealed the detailed interaction of AGN radio jets and lobes with the intracluster medium. These AGN provide feedback to their host galaxies and surrounding clusters, and significantly affect their evolution. Sloshing of cluster cores, related to off-axis cluster or group mergers, may distort the AGN's radio lobes, sometimes resulting in a "bent" shape. I will discuss detailed, nearby AGN/cluster interactions as well as describe a high-redshift cluster survey being conducted in the optical and IR using distorted radio sources as signposts. This sample will yield hundreds of high-z clusters with central, active galaxies allowing us to study feedback in distant systems.
    09/2012;

Publication Stats

6k Citations
1,126.37 Total Impact Points

Institutions

  • 1992–2014
    • University of Virginia
      • Department of Astronomy
      Charlottesville, Virginia, United States
  • 2009–2013
    • University of Bristol
      • School of Physics
      Bristol, England, United Kingdom
    • University of Bonn
      • Argelander-Institute of Astronomy
      Bonn, North Rhine-Westphalia, Germany
  • 2012
    • University of Pennsylvania
      • Department of Physics and Astronomy
      Philadelphia, Pennsylvania, United States
  • 2010
    • Boston University
      • Institute for Astrophysical Research
      Boston, MA, United States
  • 2008
    • Washington State University
      • Department of Physics and Astronomy
      Pullman, WA, United States
  • 2007
    • Pontifical Catholic University of Chile
      • Departamento de Anatomía
      CiudadSantiago, Santiago, Chile
  • 2005
    • University of Leicester
      • Department of Physics and Astronomy
      Leicester, ENG, United Kingdom
    • Ohio University
      • Astrophysical Institute
      Athens, OH, United States
  • 2004
    • The Graduate University for Advanced Studies
      • Department of Astronomical Science
      Миура, Kanagawa, Japan
  • 2002
    • Yamagata University
      • Department of Physics
      Ямагата, Yamagata, Japan
  • 2001
    • University of Alabama
      Tuscaloosa, Alabama, United States
  • 2000
    • National Radio Astronomy Observatory
      Charlottesville, Virginia, United States
  • 1998
    • National Optical Astronomy Observatory
      Tucson, Arizona, United States
  • 1997
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States