16335111
X-RAY STAR CLUSTERS IN THE CARINA COMPLEX
The distribution of young stars found in the Chandra Carina Complex Project (CCCP) is examined for clustering structure. X-ray surveys are advantageous for identifying young stellar populations compared to optical and infrared surveys in suffering less contamination from nebular emission and Galactic field stars. The analysis is based on smoothed maps of a spatially complete subsample of ~3000 brighter X-ray sources classified as Carina members and ~10,000 stars from the full CCCP sample. The principal known clusters are recovered, and some additional smaller groups are identified. No rich embedded clusters are present, although a number of sparse groups are found. The CCCP reveals considerable complexity in clustering properties. The Trumpler 14 and 15 clusters have rich stellar populations in unimodal, centrally concentrated structures several parsecs across. Non-spherical internal structure is seen, and large-scale low surface density distributions surround these rich clusters. Trumpler 16, in contrast, is comprised of several smaller clusters within a circular boundary. Collinder 228 is a third type of cluster which extends over tens of parsecs with many sparse compact groups likely arising from triggered star formation processes. A widely dispersed, but highly populous, distribution of X-ray stars across the ~50 pc CCCP mosaic supports a model of past generations of star formation in the region. Collinder 234, a group of massive stars without an associated cluster of pre-main-sequence stars, may be part of this dispersed population.
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.
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
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.
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
17930160
DAMPING EFFECT STUDIES FOR X-BAND NORMAL CONDUCTING HIGH GRADIENT STANDING WAVE STRUCTURES*
The Multi-TeV colliders should have the capability to accelerate low emittance beam with high rf efficiency, X-band normal conducting high gradient accelerating structure is one of the promising candidate. However, the long range transverse wake field which can cause beam emittance dilution is one of the critical issues. We examined effectiveness of dipole mode damping in three kinds of X-band, {pi}-mode standing wave structures at 11.424GHz with no detuning considered. They represent three damping schemes: damping with cylindrical iris slot, damping with choke cavity and damping with waveguide coupler. We try to reduce external Q factor below 20 in the first two dipole bands, which usually have very high (R{sub T}/Q){sub T}. The effect of damping on the acceleration mode is also discussed.
119035074
X-Ray Properties of the Point Source Population in the Spiral Galaxy NGC 5055 （M63） with Chandra
Using Chandra ACIS S3 data we studied the X-ray properties of low-and high-mass X-ray binary populations in the nearby spiral galaxy NGC 5055. A total of 43 X-ray point sources were detected within two effective radii, with 31 sources located on the disk and the rest 12 sources in the bulge. The resolved point sources dominate the X-ray emission of the galaxy, accounting for about 80% of the total counts in 0.3–10 keV. From spectral fittings we calculated the 0.3–10.0 keV luminosities of all the detected X-ray point sources and found that they span a wide range from a few times 1037 erg s−1 to over 1039 erg s−1. After compensating for incompleteness at the low luminosity end, we found that the corrected XLF of the bulge population is well fitted with a broken power-law with a break at 1.57+0.21−0.20×1038 erg s−1, while the profile of the disk population's XLF agrees with a single power-law distribution of slope 0.93+0.07−0.06. The disk population is significantly richer at 2×1038 erg s−1 than the bulge population, indicating that the disk may have undergone relatively recent, strong starbursts that significantly increased the HMXB population, although ongoing starbursts are also observed in the nuclear region. Similar XLF profiles of the bulge and disk populations were found in M81. However, in most other spiral galaxies different patterns of spatial variation of the XLF profiles from the bulge to the disk have been observed, indicating that the star formation and evolution history may be more complex than we have expected.
215597188
Electron reconstruction and identification efficiency measurements with the ATLAS detector using the 2011 LHC proton–proton collision data
Many of the interesting physics processes to be measured at the LHC have a signature involving one or more isolated electrons. The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton–proton collision data collected in 2011 at $$\sqrt{s}= 7$$s=7 TeV and corresponding to an integrated luminosity of 4.7 fb$$^{-1}$$-1. Tag-and-probe methods using events with leptonic decays of $$W$$W and $$Z$$Z bosons and $$J/\psi $$J/ψ mesons are employed to benchmark these performance parameters. The combination of all measurements results in identification efficiencies determined with an accuracy at the few per mil level for electron transverse energy greater than 30 GeV.
118515683
CHANDRA OBSERVATION OF A WEAK SHOCK IN THE GALAXY CLUSTER A2556
Based on a 21.5 ks Chandra observation of A2556, we identify an edge on the surface brightness profile at about 160 h(71)(-1) kpc northeast of the cluster center, and it corresponds to a shock front whose Mach number M is calculated to be 1.25(-0.03)(+0.02). No prominent substructure, such as sub-cluster, is found in either the optical or X-ray band that can be associated with the edge, suggesting that the conventional supersonic motion mechanism may not work in this case. As an alternative solution, we propose that the nonlinear steepening of an acoustic wave, which is induced by the turbulence of the intracluster medium at the core of the cluster, can be used to explain the origin of the shock front. Although nonlinear steepening weak shock is expected to occur frequently in clusters, why it is rarely observed still remains a question that requires further investigation, including both deeper X-ray observation and extensive theoretical studies.
7814576
MINIMIZATION OF TRANSVERSE WAKEFIELDS IN THE NLC ACCELERATOR STRUCTURES
The progress of a multiple bunches of electrons through several thousand accelerator structures results in a wakefield which if left unchecked will kick successive bunches off the axis of the accelerator and can at the very least dilute the final luminosity of the final colliding beams, or at worst can lead to a BBU (Beam Break Up) instability. In order to damp the wakefields to acceptable levels for travelling wave structures we detune the frequencies of the cells and we couple out the field to four adjacent manifolds. Optimizing the manifold-cell coupling for several hundred cells and changing the bandwidth parameters of the distribution has in previous structures been achieved by a process of trial and error. Here, we report on an optimized Fortran code that has been specifically written with the aim minimizing the sum of the squares of the RMS and standard deviation of the sum wakefield. Sparse matrix techniques are employed to reduce the computational time required for each frequency step. The wakefield is minimized while ensuring that no significant local surface heating occurs due to slots cuts into the accelerator cells to couple out the wakefield.