17406200
EVOLUTION OF GASEOUS DISK VISCOSITY DRIVEN BY SUPERNOVA EXPLOSIONS IN STAR-FORMING GALAXIES AT HIGH REDSHIFT
Motivated by Genzel et al.'s observations of high-redshift star-forming galaxies, containing clumpy and turbulent rings or disks, we build a set of equations describing the dynamical evolution of gaseous disks with inclusion of star formation and its feedback. Transport of angular momentum is due to "turbulent" viscosity induced by supernova explosions in the star formation region. Analytical solutions of the equations are found for the initial cases of a gaseous ring and the integrated form for a gaseous disk, respectively. For a ring with enough low viscosity, it evolves in a slow process of gaseous diffusion and star formation near the initial radius. For a high viscosity, the ring rapidly diffuses in the early phase. The diffusion drives the ring into a region with a low viscosity and starts the second phase undergoing pile-up of gas at a radius following the decreased viscosity torque. The third is a sharply decreasing phase because of star formation consumption of gas and efficient transportation of gas inward forming a stellar disk. We apply the model to two z similar to 2 galaxies BX 482 and BzK 6004, and find that they are undergoing a decline in their star formation activity.
118825166
INTEGRAL and Swift/XRT observations of IGR J18179−1621
IGR J18179-1621 is a hard X-ray binary transient discovered recently by INTEGRAL. Here we report on detailed timing and spectral analysis of IGR J18179-1621 in X-rays based on available INTEGRAL and Swift data. From the INTEGRAL analysis, IGR J18179-1621 is detected with a significance of 21.6s in the 1840 keV band by ISGRI and 15.3s in the 325 keV band by JEM-X, between 2012 February 29 and 2012 March 1. We analyse two quasi-simultaneous Swift ToO observations. A clear 11.82-s pulsation is detected above the white noise at a confidence level larger than 99.99 per cent. The pulse fraction is estimated as 22 +/- 8 per cent at 0.210 keV. No sign of pulsation is detected by INTEGRAL/ISGRI in the 1840 keV band. With Swift and INTEGRAL spectra combined in soft and hard X-rays, IGR J18179-1621 could be fitted by an absorbed power law with a high-energy cut-off plus a Gaussian absorption line centred at 21.5 keV. An additional absorption intrinsic to the source is found, while the absorption line is evidence for a most probable origin from cyclotron resonant scattering and suggests a magnetic field in the emitting region of 2.4 x 1012 G.
14133011
The Unified Model of Active Galactic Nuclei. I. Non-Hidden Broad-Line Region Seyfert 2 and Narrow-Line Seyfert 1 Galaxies
The unified model of Seyfert galaxies suggests that there are hidden broad-line regions (HBLRs) in Seyfert 2 galaxies (S2s). However, there is increasing evidence for the appearance of a subclass of S2s lacking HBLRs (non-HBLR S2s). An interesting issue arises as to the relations of non-HBLR S2s with other types of Seyfert galaxies and whether or not they can be included in the unified model. We assemble two subsamples consisting of 42 non-HBLR S2s and 44 narrow-line Seyfert 1 galaxies (NLS1s) with redshift z ? 0.05 from published literatures to explore this issue. We compare black hole masses in the galactic centers, accretion rates, and infrared color ratio (f60 ?m/f25 ?m) as a potential indicator of the dusty torus orientation, [O III] ?5007, radio, and far-infrared luminosities. We find that non-HBLR S2s and NLS1s have (1) similar distributions of black hole masses [ ? 107 M?] and Eddington ratios (LBol/LEdd ~ 1); (2) significantly different distributions of f60 ?m/f25 ?m ratios; and (3) similar distributions of bulge magnitudes and luminosities of [O III], radio, and far-infrared emission. The similarities and differences can be understood naturally if they are intrinsically the same, but non-HBLR S2s are viewed at larger angles of the observer's sight than NLS1s. We thus suggest that non-HBLR S2s only have narrower broad-line regions and that they are the counterparts of NLS1s viewed at high inclination angles. The absence of the polarized emission line in non-HBLR S2s is caused by the less massive black holes and high accretion rate similar to NLS1s. The implications of the unification scheme of non-HBLR S2s and NLS1s are discussed.
16064481
The central engines of radio-loud quasars
We have assembled a sample of 37 radio-loud quasars that have been imaged with the Hubble Space Telescopein order to investigate their black hole masses, accretion rates, and the structure of their accretion disks. The black hole masses were estimated from the luminosities of the host galaxies, and the accretion powers were extrapolated from the emission-line luminosities. The majority of the quasars have masses in the range MBH 10 8 10 9 M. Their accretion rates, ˙ M 0:01 1 times the Eddington rate, suggest that most of the objects possess standard optically thick, geometrically thin accretion disks, in some cases perhaps accompanied by an optically thin advection-dominated component. The coexistence of strong radio emission and a standard disk conflicts with recent models for jet formation. We discuss modifications of the standard model that can resolve this discrepancy. We find there is a strong correlation between the accretion rate and the extended radio luminosity. This lends support to the idea that the extended radio emission is somehow linked to the accretion disk. Lastly, we combine the present sample of radio-loud quasars with the sample of BL Lac objects studied by Wang et al. (2002) to reevaluate the unification picture for radio-loud active galactic nuclei. Consistent with current ideas for the unification of radio-loud sources, we find that flat-spectrum radio quasars and FR II radio galaxies indeed seem to belong to the same population, as do BL Lac objects and FR I radio galaxies on the opposite end of the luminosity spectrum. However, some members of the low frequency- peaked BL Lac objects may be more closely associated with FR II rather than FR I radio galaxies. We describe how the various subclasses of radio-loud sources can be viewed as a continuous sequence of varying accretion rate.
15715110
Suppressed star formation in circumnuclear regions in seyfert galaxies
Feedback from black hole activity is widely believed to play a key role in regulating star formation and black hole growth. A long-standing issue is the relation between star formation and the fueling of the supermassive black holes in active galactic nuclei (AGNs). We compile a sample of 57 Seyfert galaxies to tackle this issue. We estimate the surface densities of gas and star formation rates in circumnuclear regions (CNRs). Comparing them with the well-known Kennicutt-Schmidt (K-S) law, we find that the star formation rates (SFRs) in the CNRs of most Seyfert galaxies are suppressed in this sample. Feedback is suggested to explain the suppressed SFRs.
119247847
THE HARD X-RAY BEHAVIOR OF AQL X-1 DURING TYPE-I BURSTS
We report the discovery of an anti-correlation between the soft and hard X-ray light curves of the X-ray binary Aql X-1 when bursting. This behavior may indicate that the corona is cooled by the soft X-ray shower fed by the type-I X-ray bursts, and that this process happens within a few seconds. Stacking the Aql X-1 light curves of type-I bursts, we find a shortage in the 40-50 keV band, delayed by 4.5 ± 1.4 s with respect to the soft X-rays. The photospheric radius expansion bursts are different in that neither a shortage nor an excess shows up in the hard X-ray light curve.
51768280
Evidence for gluon interference in hadronic Z decays
We present evidence for soft gluon interference, as required by QCD. This interference is expected to manifest itself in an angular ordering of the gluons radiated within a jet. Using hadronic decays of the Z boson in the L3 detector at LEP, we compare variables sensitive to such an angular ordering, namely the energy-energy correlation asymmetry and the newly introduced particle-particle correlation asymmetry, with the predictions of various parton shower models. Only those models which incorporate the expected interference agree with the data.
118415484
UNVEILING THE PHYSICAL PROPERTIES AND KINEMATICS OF MOLECULAR GAS IN THE ANTENNAE GALAXIES (NGC 4038/9) THROUGH HIGH-RESOLUTION CO (J=3-2) OBSERVATIONS
We present a similar to 1 '' (100 pc) resolution (CO)-C-12 (3-2) map of the nearby intermediate-stage interacting galaxy pair NGC 4038/9 (the Antennae galaxies) obtained with the Submillimeter Array. We find that half the CO (3-2) emission originates in the overlap region where most of the tidally induced star formation had been previously found in shorter wavelength images, with the rest being centered on each of the nuclei. The gross distribution is consistent with lower resolution single-dish images, but we show for the first time the detailed distribution of the warm and dense molecular gas across this galaxy pair at resolutions comparable to the size of a typical giant molecular complex. While we find that 58% (33/57) of the spatially resolved Giant Molecular Associations (a few x 100 pc) are located in the overlap region, only <= 30% spatially coincides with the optically detected star clusters, suggesting that the bulk of the CO (3-2) emission traces the regions with very recent or near future star formation activity. The spatial distribution of the CO (3-2)/CO (1-0) integrated brightness temperature ratios mainly ranges between 0.3 and 0.6, which suggests that on average the CO (3-2) line in the Antennae is not completely thermalized and similar to the average values of nearby spirals. A higher ratio is seen in both nuclei and the southern complexes in the overlap region. A higher radiation field associated with intense star formation can account for the nucleus of NGC 4038 and the overlap region, but the nuclear region of NGC 4039 shows relatively little star formation or active galactic nucleus activity and cannot be easily explained. We show kinematical evidence that the high line ratio in NGC 4039 is possibly caused by gas inflow into the counter-rotating central disk.
119214676
THE PROGRESSION OF STAR FORMATION IN THE ROSETTE MOLECULAR CLOUD
Using Spitzer Space Telescope and Chandra X-Ray Observatory data, we identify young stellar objects (YSOs) in the Rosette Molecular Cloud (RMC). By being able to select cluster members and classify them into YSO types, we are able to track the progression of star formation locally within the cluster environments and globally within the cloud. We employ the nearest neighbor method analysis to explore the density structure of the clusters and YSO ratio mapping to study age progressions in the cloud. We find a relationship between the YSO ratios and extinction that suggests star formation occurs preferentially in the densest parts of the cloud and that the column density of gas rapidly decreases as the region evolves. This suggests rapid removal of gas may account for the low star formation efficiencies observed in molecular clouds. We find that the overall age spread across the RMC is small. Our analysis suggests that star formation started throughout the complex around the same time. Age gradients in the cloud appear to be localized and any effect the H II region has on the star formation history is secondary to that of the primordial collapse of the cloud.
29354902
Measurement of differential cross sections for the production of a pair of isolated photons in pp collisions at $$\sqrt{s}=7\,\text {TeV} $$s=7TeV
A measurement of differential cross sections for the production of a pair of isolated photons in proton–proton collisions at $$\sqrt{s}=7\,\text {TeV} $$s=7TeV is presented. The data sample corresponds to an integrated luminosity of 5.0$$\,\text {fb}^{-1}$$fb-1 collected with the CMS detector. A data-driven isolation template method is used to extract the prompt diphoton yield. The measured cross section for two isolated photons, with transverse energy above 40 and 25$$\,\text {GeV}$$GeV respectively, in the pseudorapidity range $$|\eta |<2.5$$|η|<2.5, $$|\eta |\notin [1.44,1.57]$$|η|∉[1.44,1.57] and with an angular separation $$\Delta R > 0.45$$ΔR>0.45, is $$17.2 \pm 0.2\,\text {(stat)} \pm 1.9\,\text {(syst)} \pm 0.4\,\text {(lumi)} $$17.2±0.2(stat)±1.9(syst)±0.4(lumi)$$\text {\,pb}$$\,pb. Differential cross sections are measured as a function of the diphoton invariant mass, the diphoton transverse momentum, the azimuthal angle difference between the two photons, and the cosine of the polar angle in the Collins–Soper reference frame of the diphoton system. The results are compared to theoretical predictions at leading, next-to-leading, and next-to-next-to-leading order in quantum chromodynamics.
119232894
Search for heavy quarks decaying into a top quark and a W or Z boson using lepton + jets events in pp collisions at $ \sqrt{s}=7 $ TeV
A bstractResults are presented from a search for the pair-production of heavy quarks, $ \mathrm{Q}\overline{\mathrm{Q}} $, that decay exclusively into a top quark and a W or Z boson. The search is performed using a sample of proton-proton collisions at $ \sqrt{s}=7 $ TeV corresponding to an integrated luminosity of 5.0 fb−1, collected by the Compact Muon Solenoid experiment. The signal region is defined using a sample of events containing one electron or muon, missing transverse momentum, and at least four jets with large transverse momenta, where one jet is likely to originate from the decay of a bottom quark. No significant excess of events is observed with respect to the standard model expectations. Assuming a strong pair-production mechanism, quark masses below 675 (625) GeV decaying into tW (tZ) are excluded at the 95 % confidence level.