Chandra's First Decade of Discovery

Session 12: Resolved AGN Jet Structures

Resolved Jet Structures

Dan Schwartz, SAO

The half arcsecond resolution of the Chandra X-ray observatory has enabled an entire field of study: X-ray jets.The very first target of the Chandra observatory, intended for use in focusing the telescope, surprisingly revealed a rich jet structure on a scale of ten arcsec. X-ray jets are seen in a wide variety of astronomical systems, including stars, neutron star pulsars, black hole binaries, radio galaxies spanning the full range of radio power, and quasars. Especially notable are radio sources in clusters of galaxies, whose jets reverse the cooling flows of the hot intracluster gas, and quasars, whose jets maintain relativistic velocities up to a Mpc away from the quasar core. The latter offer the intriguing possibility of revealing the most distant supermassive black holes via the interaction of the jet with the cosmic microwave background.

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Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068

Daniel Evans, MIT
Patrick M. Ogle (Caltech), Herman L. Marshall (MIT), Michael A. Nowak (MIT), Kim Weaver (GSFC), Stefano Bianchi (Roma Tre University, Italy), Matteo Guainazzi (ESAC, Spain), Anna Lia Longinotti (MIT), Claude R. Canizares (MIT)

We present results from a new 440-ks Chandra HETG GTO observation of the canonical Seyfert 2 galaxy NGC 1068. The proximity of NGC 1068, together with Chandra's superb spatial and spectral resolution, allow an unprecedented view of its nucleus and circumnuclear NLR. We perform the first spatially resolved high-resolution X-ray spectroscopy of the “ionization cone” in any AGN, and use the sensitive line diagnostics offered by the HETG to measure the ionization state, density, and temperature at discrete points along the ionized NLR. We argue that the NLR takes the form of outflowing photoionized gas, rather than gas that has been collisionally ionized by the small-scale radio jet in NGC 1068. We investigate evidence for any velocity gradients in the outflow, and describe our next steps in modeling the NLR as a multiphase biconical outflow. Our results have key implications for the nature of the nuclei and circumnuclear environments in AGN, together with the connection between galactic-scale outflows in AGN as moderators of galaxy evolution.

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The HETGS View of the Microquasar GRS 1915+105: Fast Spectral Variability and the Disk-Jet Connection

Joseph Neilsen, Harvard University, CfA
Julia C. Lee (Harvard/CfA), Ron Remillard (MIT)

Over the last decade, Chandra has observed the enigmatic microquasar GRS 1915+105 eleven times at high time resolution using the high spectral resolution of the HETGS. We will present the results of both long-term and fast spectral variability studies of these observations, which provide new and powerful probes of the connection between relativistic jets and the accretion disk around this stellar-mass black hole. Our study of the long-term spectral variability of GRS 1915+105 shows that spectrally hard states (known for their production of optically thick jets) exhibit broad iron emission lines, while softer states produce an accretion disk wind. We use this gradient in behavior to argue that Comptonization mediates the disk-jet interaction in GRS 1915+105. Our fast timing and spectral analysis of the same observations is designed to identify the geometry of the Comptonizing medium and its role in photoionization of the accretion flow. We show how strong absorption lines from highly ionized iron appear and disappear on timescales of 5 seconds or less, and relate this evolution to changes in the broadband X-ray continuum. These results underscore Chandra's phenomenal capabilities and show that the HETGS can compete with RXTE in timing analysis of bright X-ray sources.

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Centaurus A: Interaction of a Radio Source with its Environment

Paul Nulsen, Harvard-Smithsonian Center for Astrophysics
RP Kraft (CfA), D Stark (CfA), JH Croston (Southampton), MJ Hardcastle (Hertfordshire), M Birkinshaw (Bristol), DM Worrall (Bristol), GR Sivakoff (Virginia), A Jordan (Ohio State), NJ Brassington (CfA), DA Evans (MIT), WR Forman (CfA), M Gilfanov (MPE), JL Goodger (Hertfordshire), C Jones (CfA), WE Harris (McMaster), AM Juett (GSFC), SS Murray (CfA), S Raychaudhury (Birmingham), CL Sarazin (Virginia), R Voss (MPE), KA Woodley (McMaster)

Deep Chandra observations have been used to investigate the impact of Centaurus A, the nearest extragalactic radio source, on its environment. The southwest radio lobe drives a shock into the interstellar medium. In low density regions where the shock is strong, X-ray emission from the shocked gas is predominantly synchrotron radiation. The radio jet to the northeast also shows significant X-ray synchrotron emission. A simple flow model for the jet requires significant dissipation within the jet, most likely due to the entrainment of mass lost by stars lying in the path of the jet. Some implications will be discussed.

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Exploring the kingdom of an AGN: Chandra and XMM-Newton observations of Mrk279

Elisa Costantini, SRON, Netherland Institute for Space Research
J. Kaastra (SRON), N. Arav (Virginia Tech), J. Kriss (STSci), J. Ebrero (SRON)

The X-ray emission and absorption spectrum of AGN carry the signature of different regions of the black hole environment. Here we present a detailed analysis of long XMM-Newton and Chandra observations of Mrk279.The spectrum displays absorption by ionized gas and a variety of emission lines. In particular, broad emission structures are seen around OVIII Ly-alpha and OVII triplet as well as around the iron K-alpha line. Using simultaneous HST and FUSE line-measurement, we successfully explain the oxygen features as arising from a Broad Line Region. For the first time we also quantified, by mean of the LOC (Locally Optimally emitting Cloud) model, widely used to model the optical/UV lines of the BLR, the modest contribution of the BLR to the ironK-alpha line, which shows a complex structure in the XMM-Newton spectrum.

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