Cardamone, Carolin - Mid-infrared properties and color-selection for X-ray detected AGN
Georganopoulos, Markos - Multiwavelength constraints on the large scale jets of quasars.
Yaji, Yuichi - Discovery non-thermal X-ray from radio lobe of Cygnus A
Carolin Cardamone (Yale University) , Maaike Damen (Leiden), Marijn Franx (Leiden), Eric Gawiser (Rutgers), Ivo Labbe (Carnegie), Ezequiel Treister (ESO) , C. Megan Urry (Yale) , P. van Dokkum (Yale), and Shanil N. Virani (Yale)
We present the mid-infrared colors of X-ray-detected AGN and explore mid-infrared selection criteria. Using a statistical matching technique, the likelihood ratio, 921 IRAC counterparts were identified with the 1017 published X-ray sources in the Chandra Deep Field South and Extended Chandra Deep Field South. Although most X-ray selected sources have mid-infrared spectral shapes consistent with power-law slopes,
, they display a wide range of colors in the four observed infrared wavelengths (
making color selection challenging without longer wavelength coverage.
Markos Georganopoulos (University of Maryland, Baltimore County and NASA/GSFC) , Demosthenes Kazanas (NASA/GSFC), Eric Perlman (Florida Institute of Technology)
We present global and model-specific constraints that the radio to X-ray multiwavelength spectra and morphologies pose on our understanding of quasar large scale jets.
Barbara Mattson (UMD/Goddard Space Flight Center/ADNET) , Kimberly Weaver (NASA/GSFC), Christopher Reynolds (UMD)
We report results of a systematic X-ray spectral variability study of bright Seyfert galaxies observed by the Rossi X-Ray Timing Explorer (RXTE). The RXTE public archive contains data for 40 Seyfert galaxies spanning timescales from weeks to years. We have developed a data pipeline to automate the data reduction. The pipeline produces a series of time-resolved spectra for each source. The sample consists of 450 time-resolved spectra from 20 Seyfert 1/1.2 and 190 spectra from 13 Seyfert 1.9/2.0 galaxies. Each spectrum is fitted to a model with an intrinsic powerlaw X-ray spectrum produced close to the central black hole that is reprocessed and absorbed by material around the black hole. To test the robustness of our results, we performed Monte Carlo simulations of the spectral sample. For the Seyfert 1 galaxies, we find a complex relationship between the iron line equivalent width (EW) and the underlying powerlaw index, which may be driven by dilution of a disk spectrum (which includes the narrow iron line) by a beamed jet component and, hence, could be used as a diagnostic of jet-dominance.
Kushal Mehta (University of Maryland, Baltimore County) , Markos Georganopoulos (UMBC-NASA/GSFC), Eric Perlman (FIT), Alex Padgett (UMBC-NASA/GSFC), George Chartas (PSU), Demosthenes Kazanas (NASA/GSFC)
We present new NICMOS and ACS HST observations of the jet in PKS 0637-752 that result to the most complete spectral coverage of the jet to date. We also discuss the implications of these observations in the context of models for the jet X-ray emission.
Monika Moscibrodzka (UNLV) , Daniel Proga (UNLV), Bozena Czerny (N. Copernicus Astronomical Center),Aneta Siemiginowska (CfA)
Numerical simulations of MHD accretion flows in the vicinity of a supermasssive black hole provide useful insights in to the problem of why and how systems - such as the Galactic center - are underluminous and variable. In particular, the simulations indicate that low angular-momentum accretion flow is highly variable both quantitatively and qualitatively. This variability and a relatively low mass-accretion rate are caused by interplay between a rotationally supported torus, its outflow, and a nearly non-rotating inflow. To investigate the applicability of such flows to real objects, we examine the dynamical MHD studies with computations of the time-dependent radiation spectra predicted by the simulations. We calculated the synthetic broadband spectra of accretion flows using Monte Carlo techniques. We applied this method to calculating spectra predicted by the time-dependent model of an axisymmetic MHD flow accreting onto a black hole presented by Proga and Begelman (2003). Our calculations show that variability in an accretion flow is not always reflected in the corresponding spectra, at least not in all wavelengths. We find no one-to-one correspondence between the accretion state and the predicted spectrum. For example, we find that two states with different properties - such as the geometry and accretion rate - could have relatively similar spectra. However, we also find two very different states with very different spectra. The existence of nonthermal radiation may be needed to explain X-ray flaring because thermal bremsstrahlung, dominates X-ray emission, is produced at relatively large radii where the flow changes are small and slow.
Martin Mueller (KIPAC/SLAC) , Dan Schwartz (Harvard-CfA)
We re-analyze the Chandra X-ray spectrum of the kpc-scale jet in PKS 0637-752 to investigate the possible low energy cut-off in the relativistic electron spectrum producing the non-thermal radiation in the scenario of inverse Compton emission off the cosmic microwave background. The soft X-ray band is the most promising to detect the effects of this cut-off, as the corresponding radio band at which the synchrotron spectrum starts to show deviations from power law shape is usually too low in frequency to permit observations. PKS 0637-752 was among the first objects targeted by the Chandra Observatory and gives a unique opportunity to study the low energy X-ray emission free of contamination. The power law index of the X-ray spectrum is consistent with that of the synchrotron component, but there is evidence for a broad excess of emission below 1 keV. Under the assumption that this soft excess is unrelated to the electron population responsible for the power law emission, the absence of any low energy turn-over in the X-ray spectrum implies a minimum Lorentz factor of the electron distribution of no higher than 75. In addition, the observed optical flux can be used to place a lower limit on ; the constraint is not very strong, but does suggest that must be higher than 1 to avoid overproducing the optical emission. An alternative phenomenological description of the soft excess is offered, where the low-energy end of the electron distribution is modified to account for the excess; a possible interpretation is that we are seeing the high-energy tail of the IC/CMB spectrum produced by the mildly relativistic bulk shocked electrons in the jet.
Ken-Ichi Nishikawa (NSSTC/UAH) , P. Hardee (UA), Y. Mizuno (NASA/NSSTC), G.J. Fishman (NASA/MSFC), D. Hartmann (Clemson Univ.), M. Medvedev (Univ. Kansas).
We studied collisionless shocks and their associated emissions in an effort to model the X-ray hot spots observed in the jet of M87. In collisionless shocks, the Weibel instability is responsible for particle acceleration and magnetic field generation. Particle In Cell (PIC) simulations of relativistic, collisionless shocks show that particle acceleration is provided in situ by the Weibel instability, which produces current filaments and associated magnetic fields. Particles develop a velocity distribution with higher energy a tail due to the acceleration in small-scale, highly non-uniform, amplified magnetic fields. The resulting jitter radiation from electrons in these non-uniform fields can have very different spectral properties than synchrotron radiation. We report recent results of our PIC simulations and relate them to X-ray observations with Chandra.
Cristian Saez (PSU) , C. Saez (PSU), G. Chartas (PSU), W. N. Brandt (PSU), B. D. Lehmer (PSU), F. E. Bauer (Columbia), X. Dai (OSU), and G. P. Garmire (PSU).
We present results from a statistical analysis of 173 bright radio-quiet AGNs selected from the Chandra Deep Field-North and Chandra Deep Field-South surveys (hereafter, CDFs) in the redshift range of 0.1<z<4. We find that the X-ray power-law photon index of radio-quiet AGNs is correlated with their 2–10 keV rest-frame X-ray luminosity at the > 99.5 onfidence level in two redshift bins, 0.3<z<0.96, and 1.5<z<3.3 and slightly less significant in the redshift bin 0.96<z<1.5. The X-ray spectral slope steepens as the X-ray luminosity increases for AGNs in the luminosity range 10^42 to 10^45 erg s^-1. Combining our results from the CDFs with those from previous studies in the redshift range 1.5<z<3.3, we find that he Gamma−Lx correlation has a null-hypothesis probability of 1.6×10^-9. We investigate the redshift evolution of the correlation between the power-law photon index (Gamma) and the hard X-ray luminosity (LX) and find that the slope and offset of a linear fit to the correlation changes significantly (at the > 99.9 onfidence level) between redshift bins with 0.3<z<0.96 and 1.5<z <3.3. We explore possible physical scenarios explaining the origin of this correlation and its possible evolution with redshift in the context of steady corona models focusing on its dependency on variations of the properties of the hot corona with redshift.
Yuichi Yaji (Department Physics, Saitama University) , H. Seta (Saitama University), M. Tashiro (Saitama University), N. Isobe (RIKEN), M. Kino (JAXA), K. Asada (JAXA), H. Nagai (NAOJ), M. Kusunose (Kwansei Gakuin University)
Lobes of radio galaxies are enormous storages of large amount of non-thermal electrons and magnetic fields, both of which are thought to be transferred by jets from active galactic nuclei. Their energies can be comparable to those of thermal energies of intra-cluster medium (ICM), and resultant X-ray "cavities" in ICM are observed from several clusters. Observation of the inverse-Compton (IC) X-ray emission from non-thermal electrons in lobes is crucial to measure the electron and magnetic energy densities. However, it is difficult to precisely measure the IC X-ray from the lobes of radio galaxies located in clusters, because they are often contaminated by the thermal X-rays from ICM. In order to avoid the contamination, spatial resolution is the key. We analysed all the available archival data of the bright FR II radio galaxy Cygnus A (9 pointing in total). After the standard data screening, we obtained 230 ks of good exposure has been obtained. We carefully subtracted the ambient ICM emission, and have succeeded to detect a hard X-ray emission associated with the radio lobes. The spectra of the east and the west lobes are well described by power-law models with energy indices of 
), we regard that the hard X-ray emission from the lobes is produced via IC process by the synchrotron electron in the lobes. Comparison of the determined X-ray flux and radio flux indicates that the electron energy highly dominates that of the magnetic field in the lobes. Comparison of the derived non-thermal pressure with that of ICM will also discussed in the paper.