Chandra's First Decade of Discovery

AGN Jets

Probing the variability of the warm absorber in Mrk 279

Jacobo Ebrero, SRON - Netherlands Institute for Space Research
E. Costantini (SRON), J. S. Kaastra (SRON), R. G. Detmers (SRON), N. Arav (Virginia Tech), G. A. Kriss (STSi)

We present here the results on the detailed modeling of the complex absorption spectrum of the Seyfert 1 galaxy Mrk 279. The source was observed three times by XMM-Newton RGS for a total exposure time of ~150 ks spread over three satellite orbits. The data are modeled in terms of two warm absorber components with different ionization parameters and blue-shifted with respect to the rest frame of the source. We find no significant response of the absorbing gas to the smooth (~25%) continuum variation of the source during the observations. We also investigate possible long term (~2 years) variations of the absorber by comparing XMM-Newton observations with previous Chandra observations, therefore putting important constraints on the distance of the absorber to the ionizing source as well as studying the possible relationships between the spectral components on long term timescales.

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Radio and X-ray Emission in MOJAVE Blazars: The Case of 0106+013

Preeti Kharb, Rochester Institute of Technology
Herman Marshall (MIT), Matthew Lister (Purdue Univ)

The kiloparsec-scale radio emission in the MOJAVE sample selected on the basis of relativistically boosted parsec-scale flux density, does not reveal a clear divide between quasars and BL Lac objects. The strong correlation observed between the kpc-scale lobe emission and parsec-scale apparent jet speeds highlights the crucial role played by the jet speed in determining the source radio power and thereby their Fanaroff-Riley classification, in the framework of the radio-loud unification scheme. Of the MOJAVE blazars with significant extended radio emission, nearly 80% have X-ray jets, indicative of the relevance of relativistic bulk motion in producing nonthermal X-ray emission. We present the primary findings of the kpc-scale radio study of MOJAVE blazars and discuss the preliminary results on some newly discovered X-ray jets in them, with special emphasis on the quasar 0106+013.

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Parsec-scale Radio Imaging of the nearby X-ray bright Seyfert NGC6764

Preeti Kharb, Rochester Institute of Technology
Ananda Hota (ASIAA), Judith Croston (Univ.Hertfordshire), Martin Hardcastle (Univ.Hertfordshire), Ralph Kraft (CfA), David Axon (Univ.Sussex), Andrew Robinson (RIT)

NGC6764 is a nearby Seyfert 2/LINER galaxy with signatures of recent massive star formation. It is one of the few Seyfert galaxies with large (kpc-) scale radio bubbles in them. The ROSAT X-ray Observatory detected a highly variable X-ray source in NGC6764, which was suggestive of the presence of a compact AGN. However our recent Chandra observations failed to reveal a strong X-ray nucleus. The Chandra observations however did reveal kpc-scale diffuse X-ray emission coincident with the radio bubbles (Croston et al., 2008). Spectral fitting indicated that the X-ray emission was emanating from hot thermal gas, possibly excited by an AGN outflow. Here we present results from our recent parsec-scale radio imaging of NGC6764 with the Very Long Baseline Array (VLBA) at 1.6 and 4.9 GHz, which detected a faint jet-like structure, almost perpendicular to the kpc-scale radio/X-ray bubbles. We discuss the implications of this finding in the light of the conclusions drawn from our Chandra study on NGC6764.

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Chandra observation of 3C 288

Dharam Vir Lal, Harvard-Smithsonian Center for Astrophysics
R.P. Kraft (Harvard-Smithsonian Center for Astrophysics), D.A. Evans (MIT Kavli Institute for Astrophysics and Space Research), M.J. Hardcastle (University of Hertfordshire), J.H. Croston (University of Hertfordshire), W.R. Forman (Harvard-Smithsonian Center for Astrophysics), Christine Jones (Harvard-Smithsonian Center for Astrophysics), J.C. Lee (Harvard-Smithsonian Center for Astrophysics)

We present preliminary results from a 40-ks Chandra/ACIS-S observation of the cluster gas associated with the transitional FRI/FRII radio galaxy 3C 288 at z = 0.246. We measure the total energy of the current outburst to be ~1060 ergs. We find multiple surface brightness discontinuities in the gas indicative of either supersonic heating by the inflation of the radio lobe or a recent merger event. The X-ray isophotes do not appear to be centered on the central galaxy, demonstrating the presence of non-hydrostatic gas motions on scales of kpcs. Additionally, we find a significant soft (<0.5 keV) excess X-ray emission above that predicted from the 3 keV cluster gas temperature. This excess is clearly present in archival ROSAT observations of this cluster. The origin of this emission is unclear, but implies either massive cooling if thermal, or the presence of a population of ultra-relativistic electrons with a total energy far in excess of the energy of the current nuclear outburst.

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Constraining the Outburst Properties of the SMBH in Fornax A through X-ray, Infrared, and Radio Observations

Lauranne Lanz, Harvard University
Christine Jones (SAO), William R. Forman (SAO), Matthew L.N. Ashby (SAO), Ralph Kraft (SAO), Ryan C. Hickox (SAO)

Combined Chandra, Spitzer, XMM-Newton, and VLA observations of the giant radio galaxy NGC 1316 (Fornax A) show features indicative of an AGN outburst likely triggered by a merger with a galaxy with a stellar mass of 0.9-7.8 x 1010 solar masses about 0.4 Gyr ago. X-ray cavities in the Chandra and XMM-Newton images likely result from the radio jet and the expansion of the radio lobes. The dust emission seen at wavelengths longer than 4.5 microns is strongest in the regions with little or no radio emission, suggesting that the expanding radio plasma removes or destroys the dust as well as the hot gas. These results constrain properties of the outburst and the merger galaxy. The size of the X-ray cavities implies a minimum outburst energy of 1.2 x 1058 ergs. The present size of the radio lobes implies that the outburst is at least 0.4 Gyr old. The inferred dust mass implies that the merger galaxy was a late-type spiral with a stellar mass of 0.9-7.8 x 1010 solar masses and a gas mass of 0.4-4.4 x 1010 solar masses.

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Observing circumnuclear photoionized gas in high resolution spectra of Seyfert 1 Galaxies.

Anna Lia Longinotti, MIT Kavli Institute
A. Nucita (ESAC, Madrid), M. Guainazzi (ESAC, Madrid), M. Santos-Lleo (ESAC, Madrid), E. Costantini (SRON, Utrecht)

I will present XMM-Newton-RGS observations of the Seyfert 1 Galaxies Mrk 335 and NGC 4051 that unveiled an emission line-rich spectrum during a low flux state of the AGN continuum.Line ratio diagnostics from H-like and He-like ions indicate that the emission lines arise in X-ray photoionized plasma. The physical properties of the line emitting material were derived using the CLOUDY photoionization code. Although the properties of the plasma cannot be uniquely determined, we found that the density of the X-ray photoionized gas in Mrk 335 is constrained at 99% c.l. to 109-1011 cm-3, placing the gas within the inner edge of the optical Broad Line Region. For NGC 4051, the density and the location of the plasma are instead consistent with outer region of the AGN. I will briefly present other Seyfert 1 sources where X-ray photoionized emission lines possibly arise in the Broad Line Region and I will review the implication of these findings in a broader context.

X-ray spectral analyses of the M87 jet

Francesco Massaro, Smithsonian Astrophysical Observatory
D. E. Harris (Harvard, Smithsonian Astrophysical Observatory), C. C. Cheung, (NASA Goddard Space Flight Center), E. S. Perlman (Florida Institute of Technology), W. Sparks (Space Telescope Science Institute), L. Stawarz (Kavli Institute for Particle Astrophysics and Cosmology, Stanford University)

We present X-ray spectral analyses of the jet in the giant radiogalaxy M87. We derive spectral parameters of the X-ray emission between the radio knots from the various long observations in the Chandra archive. In addition we use the 60 monitoring observations(5ks each, spanning the last 7 years) to evaluate the X-ray spectral variability of the three brightest knots, HST-1, D, and A. This project is one component of a broader investigation of the spectral energy distribution for all parts of the entire jet. The work at SAO was supported by NASA grants GO8-9116X and GO9-0108X.

XJET: X-ray Emission from Extragalactic Radio Jets

Francesco Massaro, Harvard - Smithsonian Astrophysical Observatory
C. C. Cheung (NASA Goddard Space Flight Center), D. E. Harris (Harvard - Smithsonian Astrophysical Observatory)

For several years we have been collecting basic parameters for extragalactic jets detected in the X-rays. There are now about 90 sources for which X-ray detections of knots and hotspots have been published. In 2009 we have been adding a suite of fits files for each source consisting of flux maps in 3 X-ray energy bands together with an event file which has had pixel randomization removed and also been registered so that the nuclear emission is aligned with the radio nucleus to within approximately 0.1 arcsec. We also provide the radio map used for registration. In this poster, we show how users can obtain X-ray flux values for any region in the images and give some basic statistics of the sample. The XJET website (http://hea-www.harvard.edu/XJET/) is partially supported by NASA grant AR6-7013X.

A Detection of an X-ray Wind and an Ionized Disk in the Chandra HETGS Observation of the Seyfert 2 Galaxy IRAS 18325-5926

Philip Mocz, Harvard College
Julia C. Lee (Harvard University and Harvard-Smithsonian Center for Astrophysics), Kazushi Iwasawa (Institute of Astronomy, Cambridge), Claude R. Canizares (Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology)

We present the first high-resolution spectroscopic X-ray observation of the Seyfert 2 galaxy IRAS 18325-5926 taken by the Chandra High Energy Transmission Grating Spectrometer (HETGS). IRAS 18325-5926 is a unique source because it displays many Seyfert 1 characteristics despite being classified as a type 2 Seyfert. We detect a blueshifted ionized absorber in the X-ray spectrum, which may be an X-ray wind originating in the obscuring torus around the black hole. We explore whether the associated ejected mass flux plays a a significant role in affecting the large scale-environment of the host galaxy. We find a broad Fe XXV emission that is consistent with previous (e.g. XMM-Newton) results showing an origin in an ionized disk. With Chandra we place constraints on the narrow core. The X-ray results confirm the dual Seyfert 1 and Seyfert 2 properties of IRAS 18325-5926. Because we are able to view both the obscuring gas and the accretion disk of IRAS 18325-5926, it may be that the surrounding gas of the black hole is patchy, or that we are viewing the system at an angle just grazing the obscuring torus.

The physical properties of X-ray absorbers in AGNs

Guido Risaliti, SAO

We present time-resolved X-ray spectroscopy of several bright AGNs, performed with Chandra, XMM-Newton and Suzaku, showing that absorption variability on time scales of hours to days is common among AGNs. An analysis of the observational properties of these occultation events strongly support a scenario where the clumpy X-ray absorber and the Broad Emission Line (BEL) clouds are one and the same. Therefore, X-ray spectroscopy can be a powerful way to determine the physical parameters (density, size, shape, ionization state) of BEL clouds.

X-ray jets and Evolution of Radio Sources

Aneta Siemiginowska, SAO

Chandra X-ray observations revealed powerful relativistic outflows associated with the AGN activity. Large scale X-ray jets extend to more than 100 kpc distances from the nucleus of the host galaxy. They indicate a long-term evolution of a powerful radio source and the importance of jets and radio source interactions with the environment on many different physical scales. They also show that the feedback process linked to a radio mode activity of a central black hole happens at all redshifts. I discuss results of X-ray studies of a sample of compact radio sources. These sources can represent the first stage of the radio source growth. They are contained within their host galaxy and interact strongly with the dense ISM. Although, X-rays can provide information about the source interactions with the ISM and feedback process they could not be observed in X-ray due to limited sensitivity of the earlier missions. We have observed a complete sample of very compact radio sources in X-rays for the first time using the XMM-Newton and Chandra. I discuss X-ray properties of these sources, emission processes and possible evolution into FRI/FRII large scale radio source.

The Highest Resolution X-ray View of the Nuclear Region of NGC 4151

Junfeng Wang, SAO
G. Fabbiano, M. Karovska, M. Elvis, G. Risaliti, A. Zezas (CfA/SAO) and C. G. Mundell (Liverpool John Moores University, UK)

We report high resolution imaging of the nucleus of the Seyfert 1 galaxy NGC 4151 obtained with a 50 ks Chandra HRC observation. The HRC image resolves the emission on spatial scales of 0.5 arcsec (30 pc), showing an extended X-ray morphology overall consistent with the narrow line region seen in optical line emission. Removal of the bright point-like nuclear source and image deconvolution technique both reveal X-ray enhancements that closely match the substructures seen in the HST [OIII] image and prominent knots in the radio jet. We find that most of the NLR clouds in NGC 4151 have [OIII] to soft X-ray ratio consistent with the values observed in NLRs of some Seyfert 2 galaxies, which indicates a uniform ionization parameter even at large radii and a density dependence ∝ r-2 as expected in the disk wind scenario. We examine various X-ray emission mechanisms of the radio jet and consider thermal emission from interaction between radio outflow and the NLR clouds the most probable origin for the X-ray emission associated with the jet.

Orientation Effects in the X-ray Properties of High-z, 3CRR Quasars

Belinda Wilkes, SAO
Joanna Kuraszkiewicz (SAO), Martin Haas (Bochum), S.P. Willner (SAO), Matt Ashby (SAO), Margaret Yellen (SAO), Christian Leipski (UCSB), R. Antonucci (UCSB), P. Barthel Kapteyn Institute), Mark Birkinshaw (Bristol), Rolf Chini (Bochum), G.G. Fazio (SAO), F. Heymann (ESO), C. R. Lawrence (JPL), P. Ogle (Spitzer, Science Center), Bernhard Schulz (IPAC), D.M. Worrall (Bristol)

A critical problem in understanding active galaxies is separation of intrinsic physical differences from observed differences due to orientation. Relativistic motion in powerful radio sources produces a significant level of anisotropic emission at all but the lowest frequencies. Obscuration is also anisotropic and strongly frequency-dependent. Combined, these two effects result in complex selection effects for observations in most wavebands, and there are few ways to select a sample that is sufficiently unbiased to test orientation effects as predicted by unification models. Low-frequency radio emission is one way to select an orientation-unbiased sample, albeit limited to the minority of AGN with strong radio emission. Chandra observations of a complete, flux-limited sample of 38 high-redshift 3CRR sources, 1<z<2 with Chandra. Of these, 21 are quasars and 17 galaxies. According to unification models, the galaxies are viewed edge-on while the quasars are relatively face-on. The quasars have soft X-ray hardness ratios, high radio core-dominance and high X-ray to radio luminosity ratios. These are all indicators of relatively low obscuration, as expected for their relatively face-on orientation in unification models. The galaxies have a wide range of X-ray hardness ratio, lower core dominance and lower luminosity ratios, again consistent with unification. A subset of galaxies have soft X-ray emission, suggestive that these sources are Compton thick with purely scattered AGN light visible in X-rays (as in NGC1068). A few sources have contradictory properties inconsistent with straight-forward classification, as has been observed in many previous studies. These sources offer the potential to explore physical reason(s) for the transition between the various AGN classes.