118539059
THE CHANDRA HRC VIEW OF THE SUBARCSECOND STRUCTURES IN THE NUCLEAR REGION OF NGC 1068
We have obtained a high spatial resolution X-ray image of the nucleus of NGC 1068 using the High Resolution Camera (HRC-I) on board the Chandra X-ray Observatory, which provides an unprecedented view of the innermost 1 arcsec radius region of this galaxy. The HRC image resolves the narrow-line region into X-ray emission clumps matching bright emission-line clouds in the HST [OIII] λ5007 images and allows comparison with subarcsecond-scale radio jet for the first time. Two distinct X-ray knots are revealed at 1.3-1.4 arcsec northeast and southwest of the nucleus. Based on the combined X-ray, [O III], and radio continuum morphology, we identify the locations of intense radio jet-cloud interaction. The [O III] to soft X-ray ratios show that some of these clouds are strongly affected by shock heating, whereas in other locations the jet simply thrusts through with no signs of strong interaction. This is further strengthened by the presence of a kT ~ 1 keV collisionally ionized component in the ACIS spectrum of a shock-heated cloud HST-G. We estimate that the kinematic luminosity of the jet-driven shocks is 6 × 1038 erg s–1, a negligible fraction (10–4) of the estimated total jet power.
54883621
The X-ray reflector in NGC 4945: a time- and space-resolved portrait
We present a time, spectral and imaging analysis of the X-ray reflector in NGC 4945, which reveals its geometrical and physical structure with unprecedented detail. NGC 4945 hosts one of the brightest AGN in the sky above 10 keV, but it is only visible through its reflected/scattered emission below 10 keV, due to absorption by a column density of ∼4 × 10 24 cm −2 .An ew Suzaku campaign of five observations spanning ∼6 months, together with past XMM–Newton and Chandra observations, shows a remarkable constancy (within <10 per cent) of the reflected component. Instead, Swift-BAT reveals strong intrinsic variability on time-scales longer than 1 yr. Modelling the circumnuclear gas as a thin cylinder with the axis on the plane of the sky, we show that the reflector is at a distance ≥30–50 pc, well within the imaging capabilities of Chandra at the distance of NGC 4945 (1 arcsec ∼18 pc). Accordingly, the Chandra imaging reveals a resolved, flattened, ∼150 pc long clumpy structure, whose spectrum is fully due to cold reflection of the primary AGN emission. The clumpiness may explain the small covering factor derived from the spectral and variability properties.
119242318
A DEEP CHANDRA ACIS STUDY OF NGC 4151. II. THE INNERMOST EMISSION LINE REGION AND STRONG EVIDENCE FOR RADIO JET–NLR CLOUD COLLISION
We have studied the X-ray emission within the inner {approx}150 pc radius of NGC 4151 by constructing high spatial resolution emission line images of blended O VII, O VIII, and Ne IX. These maps show extended structures that are spatially correlated with the radio outflow and optical [O III] emission. We find strong evidence for jet-gas cloud interaction, including morphological correspondences with regions of X-ray enhancement, peaks of near-infrared [Fe II] emission, and optical clouds. In these regions, moreover, we find evidence of elevated Ne IX/O VII ratios; the X-ray emission of these regions also exceeds that expected from nuclear photoionization. Spectral fitting reveals the presence of a collisionally ionized component. The thermal energy of the hot gas suggests that {approx}> 0.1% of the estimated jet power is deposited into the host interstellar medium through interaction between the radio jet and the dense medium of the circumnuclear region. We find possible pressure equilibrium between the collisionally ionized hot gas and the photoionized line-emitting cool clouds. We also obtain constraints on the extended iron and silicon fluorescent emission. Both lines are spatially unresolved. The upper limit on the contribution of an extended emission region to the Fe K{alpha} emission is {approx}<more » 5% of the total, in disagreement with a previous claim that 65% of the Fe K{alpha} emission originates in the extended narrow line region.« less
119249190
A Deep Chandra ACIS Study of NGC 4151. III. The Line Emission and Spectral Analysis of the Ionization Cone
This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy of the Seyfert 1 galaxy NGC 4151, devoted to study its complex circumnuclear X-ray emission. Emission features in the soft X-ray spectrum of the bright extended emission (L{sub 0.3-2{sub keV}} {approx} 10{sup 40} erg s{sup -1}) at r > 130 pc (2'') are consistent with blended brighter O VII, O VIII, and Ne IX lines seen in the Chandra HETGS and XMM-Newton RGS spectra below 2 keV. We construct emission line images of these features and find good morphological correlations with the narrow-line region clouds mapped in [O III] {lambda}5007. Self-consistent photoionization models provide good descriptions of the spectra of the large-scale emission, as well as resolved structures, supporting the dominant role of nuclear photoionization, although displacement of optical and X-ray features implies a more complex medium. Collisionally ionized emission is estimated to be {approx}<12% of the extended emission. Presence of both low- and high-ionization spectral components and extended emission in the X-ray image perpendicular to the bicone indicates leakage of nuclear ionization, likely filtered through warm absorbers, instead of being blocked by a continuous obscuring torus. The ratios of [O III]/soft X-raymore » flux are approximately constant ({approx}15) for the 1.5 kpc radius spanned by these measurements, indicating similar relative contributions from the low- and high-ionization gas phases at different radial distances from the nucleus. If the [O III] and X-ray emission arise from a single photoionized medium, this further implies an outflow with a wind-like density profile. Using spatially resolved X-ray features, we estimate that the mass outflow rate in NGC 4151 is {approx}2 M{sub Sun} yr{sup -1} at 130 pc and the kinematic power of the ionized outflow is 1.7 Multiplication-Sign 10{sup 41} erg s{sup -1}, approximately 0.3% of the bolometric luminosity of the active nucleus in NGC 4151.« less
18395747
IMAGING THE CIRCUMNUCLEAR REGION OF NGC 1365 WITH CHANDRA
We present the first Chandra/ACIS imaging study of the circumnuclear region of the nearby Seyfert galaxy NGC 1365. The X-ray emission is resolved into pointlike sources and complex, extended emission. The X-ray morphology of the extended emission shows a biconical soft X-ray-emission region extending ~5 kpc in projection from the nucleus, coincident with the high-excitation outflow cones seen in optical emission lines particularly to the northwest. Harder X-ray emission is detected from a kpc-diameter circumnuclear ring, coincident with the star-forming ring prominent in the Spitzer mid-infrared (IR) images; this X-ray emission is partially obscured by the central dust lane of NGC 1365. Spectral fitting of spatially separated components indicates a thermal plasma origin for the soft extended X-ray emission (kT = 0.57 keV). Only a small amount of this emission can be due to photoionization by the nuclear source. Detailed comparison with [O III]λ5007 observations shows that the hot interstellar medium (ISM) is spatially anticorrelated with the [O III]-emitting clouds and has thermal pressures comparable to those of the [O III] media, suggesting that the hot ISM acts as a confining medium for the cooler photoionized clouds. The abundance ratios of the hot ISM are fully consistent with the theoretical values for enrichment from Type II supernovae, suggesting that the hot ISM is a wind from the starburst circumnuclear ring. X-ray emission from a ~450 pc long nuclear radio jet is also detected to the southeast.
119266124
A DEEP CHANDRA ACIS STUDY OF NGC 4151. I. THE X-RAY MORPHOLOGY OF THE 3 kpc DIAMETER CIRCUM-NUCLEAR REGION AND RELATION TO THE COLD INTERSTELLAR MEDIUM
We report on the imaging analysis of ~200 ks sub-arcsecond resolution Chandra Advanced CCD Imaging Spectrometer (ACIS-S) observations of the nearby Seyfert 1 galaxy NGC 4151. Bright, structured soft X-ray emission is observed to extend from 30 pc to 1.3 kpc in the southwest from the nucleus, much farther than seen in earlier X-ray studies. The terminus of the northeastern X-ray emission is spatially coincident with a CO gas lane, where the outflow likely encounters dense gas in the host galactic disk. X-ray emission is also detected outside the boundaries of the ionization cone, which indicates that the gas there is not completely shielded from the nuclear continuum, as would be the case for a molecular torus collimating the bicone. In the central r < 200 pc region, the subpixel processing of the ACIS data recovers the morphological details on scales of <30 pc (<05) first discovered in Chandra High Resolution Camera images. The X-ray emission is more absorbed toward the boundaries of the ionization cone, as well as perpendicular to the bicone along the direction of a putative torus in NGC 4151. The innermost region where X-ray emission shows the highest hardness ratio is spatially coincident with the near-infrared-resolved H2 emission and dusty spirals we find in an Hubble Space Telescope V – H color image. The agreement between the observed H2 line flux and the value predicted from X-ray-irradiated molecular cloud models supports photo-excitation by X-rays from the active nucleus as the origin of the H2 line, although contribution from UV fluorescence or collisional excitation cannot be ruled out with current data. The discrepancy between the mass of cold molecular gas inferred from recent CO and near-infrared H2 observations may be explained by the anomalous CO abundance in this X-ray-dominated region. The total H2 mass derived from the X-ray observation agrees with the recent measurement by Storchi-Bergmann et al.
119278481
The X-ray nature of the nucleus in Seyfert 2 galaxy NGC 7590
We present the results of the Chandra high-resolution observation of the Seyfert 2 galaxy NGC 7590. This object was reported to show no X-ray absorption in the low-spatial resolution ASCA data. The XMM-Newton observations show that the X-ray emission of NGC 7590 is dominated by an off-nuclear ultra-luminous X-ray source (ULX) and extended emissions from the host galaxy, and the nucleus is rather weak, likely hosting a Compton-thick AGN. Our recent Chandra observation of NGC 7590 enables us to effectively remove the X-ray contamination from the ULX and the extended component. The nuclear source remains undetected at the flux level of ~ 4 × 10 −15 erg cm −2 s −1 . Although not detected, the Chandra data give a 2–10 keV flux upper limit of ~ 6.1 × 10 −15 erg cm −2 s −1 (at a 3σ level), a factor of three less than the XMM-Newton value, strongly supporting the Compton-thick nature of the nucleus. In addition, we detected five off-nuclear X-ray point sources within the galaxy’s D 25 ellipse, all with 2 – 10 keV luminosity above 2 × 10 38 erg s −1 (assuming the distance of NGC 7590). In particular, the ULX previously identified by ROSAT data is resolved by Chandr a into two distinct X-ray sources. Our analysis highlights the importance of high spatial resolution images in discovering and studying ULXs.
32357992
Charmonium Decays of Y(4260), psi(4160), and psi(4040).
Using data collected with the CLEO detector operating at the CESR e+e- collider at sqrt[s]=3.97-4.26 GeV, we investigate 15 charmonium decay modes of the psi(4040), psi(4160), and Y(4260) resonances. We confirm, at 11 sigma significance, the BABAR Y(4260)-->pi+pi- J/psi discovery, make the first observation of Y(4260)--> pi(0)pi(0) J/psi (5.1 sigma), and find the first evidence for Y(4260)-->K+K- J/psi(3.7 sigma). We measure e+e- cross sections at sqrt[s]=4.26 GeV as sigma(pi+pi- J/psi)=58(+12)(-10)+/-4 pb, sigma(pi(0)pi(0) J/psi)=23(+12)(-8)+/-1 pb, and sigma(K+K- J/psi)=9(+9)(-5)+/-1 pb, in which the uncertainties are statistical and systematic, respectively. Upper limits are placed on other decay rates from all three resonances.
109931424
Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC
Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H --> gamma-gamma, H --> ZZ* --> 4 leptons and H --> WW --> 2 leptons + 2 neutrinos. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of about 25/fb. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson.
1018474
RF breakdown studies in copper electron linac structures
The authors present a summary of RF breakdown-limited electric fields observed in experimental linac structures at SLAC (Stanford Linear Accelerator Center) and a discussion of how these experiments can be interpreted against the background of existing, yet incomplete, theories. The motivation of these studies, begun in 1984, is to determine the maximum accelerating field gradients that can be used safely in future e/sup +or-/ colliders, to contribute to the basic understanding of the RF breakdown mechanism, and to discover whether a special surface treatment can make it possible to supersede the field limits presently attainable room-temperature copper structures.<<ETX>>
11298079
An X-Ray Census of Young Stars in the Massive Southern Star-forming Complex NGC 6357
We present the first high spatial resolution X-ray study of the massive star-forming region NGC 6357, obtained in a 38 ks Chandra/ACIS observation. Inside the brightest constituent of this large H II region complex is the massive open cluster Pismis 24. It contains two of the brightest and bluest stars known, yet remains poorly studied; only a handful of optically bright stellar members have been identified. We investigate the cluster extent and initial mass function and detect ~800 X-ray sources with a limiting sensitivity of ~1030 ergs s-1; this provides the first reliable probe of the rich intermediate-mass and low-mass population of this massive cluster, increasing the number of known members from optical study by a factor of ~50. The high-luminosity end (log Lh[2-8 keV] ≥ 30.3 ergs s-1) of the observed X-ray luminosity function in NGC 6357 is clearly consistent with a power-law relation as seen in the Orion Nebula Cluster and Cepheus B, yielding the first estimate of NGC 6357's total cluster population, a few times the known Orion population. We investigate the structure of the cluster, finding small-scale substructures superposed on a spherical cluster with 6 pc extent, and discuss its relationship to the nebular morphology. The long-standing LX - 10-7Lbol correlation for O stars is confirmed. Twenty-four candidate O stars and one possible new obscured massive YSO or Wolf-Rayet star are presented. Many cluster members are estimated to be intermediate-mass stars from available infrared photometry (assuming an age of ~1 Myr), but only a few exhibit K-band excess. We report the first detection of X-ray emission from an evaporating gaseous globule at the tip of a molecular pillar; this source is likely a B0-B2 protostar.