Backflows by active galactic nuclei jets: global properties and influence on supermassive black hole accretion

NASA Astrophysics Data System (ADS)

Cielo, S.; Antonuccio-Delogu, V.; Silk, J.; Romeo, A. D.

2017-06-01

Jets from active galactic nuclei (AGN) inflate large cavities in the hot gas environment around galaxies and galaxy clusters. The large-scale gas circulation promoted within such cavities by the jet itself gives rise to backflows that propagate back to the centre of the jet-cocoon system, spanning all the physical scales relevant for the AGN. Using an adaptive mesh refinement code, we study these backflows through a series of numerical experiments, aiming at understanding how their global properties depend on jet parameters. We are able to characterize their mass flux down to a scale of a few kiloparsecs to about 0.5 M⊙ yr-1 for as long as 15 or 20 Myr, depending on jet power. We find that backflows are both spatially coherent and temporally intermittent, independently of jet power in the range 1043-1045 erg s-1. Using the mass flux thus measured, we model analytically the effect of backflows on the central accretion region, where a magnetically arrested disc lies at the centre of a thin circumnuclear disc. Backflow accretion on to the disc modifies its density profile, producing a flat core and tail. We use this analytic model to predict how accretion beyond the black hole magnetopause is modified, and thus how the jet power is temporally modulated. Under the assumption that the magnetic flux stays frozen in the accreting matter, and that the jets are always launched via the Blandford-Znajek mechanism, we find that backflows are capable of boosting the jet power up to tenfold during relatively short time episodes (a few Myr).

HI Clouds Near the Galactic Center: Possible Tracers of the Nuclear Wind

NASA Astrophysics Data System (ADS)

Lockman, Felix J.; McClure-Griffiths, Naomi; DiTeodoro, Enrico

2017-01-01

We have used the Green Bank Telescope to discover more than one hundred neutral hydrogen clouds that appear to be embedded in the Fermi Bubble -- the Milky Way’s nuclear wind. With the other members of this population that were previously found with the Australia Telescope Compact Array, we now have a sample of about 200 such clouds. They are identified by their peculiar velocities. The cloud kinematics show no trace of Galactic rotation or association with the Galactic bar. Near longitude zero the clouds can have values of VLSR = +-200 km/s. No clouds have been detected with |VLSR| > 350 km/s. The clouds are concentrated toward the Galactic plane, but some are still found to |b|=10 degrees, or z > 1 kpc at the Galactic Center, where the current surveys end. These clouds are important tracers of conditions in the nuclear wind of the Milky Way.

The Spatially Uniform Spectrum of the Fermi Bubbles: The Leptonic Active Galactic Nucleus Jet Scenario

NASA Astrophysics Data System (ADS)

Yang, H.-Y. K.; Ruszkowski, M.

2017-11-01

The Fermi bubbles are among the most important findings of the Fermi Gamma-ray Space Telescope; however, their origin is still elusive. One of the unique features of the bubbles is that their gamma-ray spectrum, including a high-energy cutoff at ˜110 GeV and the overall shape of the spectrum, is nearly spatially uniform. The high-energy spectral cutoff is suggestive of a leptonic origin due to synchrotron and inverse-Compton cooling of cosmic-ray (CR) electrons; however, even for a leptonic model, it is not obvious why the spectrum should be spatially uniform. In this work, we investigate the bubble formation in the leptonic active galactic nucleus (AGN) jet scenario using a new CRSPEC module in FLASH that allows us to track the evolution of a CR spectrum during the simulations. We show that the high-energy cutoff is caused by fast electron cooling near the Galactic center (GC) when the jets were launched. Afterwards, the dynamical timescale becomes the shortest among all relevant timescales, and therefore the spectrum is essentially advected with only mild cooling losses. This could explain why the bubble spectrum is nearly spatially uniform: the CRs from different parts of the bubbles as seen today all share the same origin near the GC at an early stage of the bubble expansion. We find that the predicted CR spatial and spectral distribution can simultaneously match the normalization, spectral shape, and high-energy cutoff of the observed gamma-ray spectrum and their spatial uniformity, suggesting that past AGN jet activity is a likely mechanism for the formation of the Fermi bubbles.

The Highest Resolution Chandra View of Photoionization and Jet-Cloud Interaction in the Nuclear Region of NGC 4151

NASA Astrophysics Data System (ADS)

Wang, Junfeng; Fabbiano, G.; Karovska, M.; Elvis, M.; Risaliti, G.; Zezas, A.; Mundell, C. G.

2009-10-01

We report high resolution imaging of the nucleus of the Seyfert 1 galaxy NGC 4151 obtained with a 50 ks Chandra High Resolution Camera (HRC) observation. The HRC image resolves the emission on spatial scales of 0farcs5, ~30 pc, showing an extended X-ray morphology overall consistent with the narrow-line region (NLR) seen in optical line emission. Removal of the bright point-like nuclear source and image deconvolution techniques both reveal X-ray enhancements that closely match the substructures seen in the Hubble Space Telescope [O III] image and prominent knots in the radio jet. We find that most of the NLR clouds in NGC 4151 have [O III]/soft X-ray ratio ~10, despite the distance of the clouds from the nucleus. This ratio is 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 decreasing as r -2 as expected for a nuclear wind scenario. The [O III]/X-ray ratios at the location of radio knots show an excess of X-ray emission, suggesting shock heating in addition to photoionization. We examine various mechanisms for the X-ray emission and find that, in contrast to jet-related X-ray emission in more powerful active galactic nucleus, the observed jet parameters in NGC 4151 are inconsistent with synchrotron emission, synchrotron self-Compton, inverse Compton of cosmic microwave background photons or galaxy optical light. Instead, our results favor thermal emission from the interaction between radio outflow and NLR gas clouds as the origin for the X-ray emission associated with the jet. This supports previous claims that frequent jet-interstellar medium interaction may explain why jets in Seyfert galaxies appear small, slow, and thermally dominated, distinct from those kpc-scale jets in the radio galaxies.

The inner jet of an active galactic nucleus as revealed by a radio-to-gamma-ray outburst.

PubMed

Marscher, Alan P; Jorstad, Svetlana G; D'Arcangelo, Francesca D; Smith, Paul S; Williams, G Grant; Larionov, Valeri M; Oh, Haruki; Olmstead, Alice R; Aller, Margo F; Aller, Hugh D; McHardy, Ian M; Lähteenmäki, Anne; Tornikoski, Merja; Valtaoja, Esko; Hagen-Thorn, Vladimir A; Kopatskaya, Eugenia N; Gear, Walter K; Tosti, Gino; Kurtanidze, Omar; Nikolashvili, Maria; Sigua, Lorand; Miller, H Richard; Ryle, Wesley T

2008-04-24

Blazars are the most extreme active galactic nuclei. They possess oppositely directed plasma jets emanating at near light speeds from accreting supermassive black holes. According to theoretical models, such jets are propelled by magnetic fields twisted by differential rotation of the black hole's accretion disk or inertial-frame-dragging ergosphere. The flow velocity increases outward along the jet in an acceleration and collimation zone containing a coiled magnetic field. Detailed observations of outbursts of electromagnetic radiation, for which blazars are famous, can potentially probe the zone. It has hitherto not been possible to either specify the location of the outbursts or verify the general picture of jet formation. Here we report sequences of high-resolution radio images and optical polarization measurements of the blazar BL Lacertae. The data reveal a bright feature in the jet that causes a double flare of radiation from optical frequencies to TeV gamma-ray energies, as well as a delayed outburst at radio wavelengths. We conclude that the event starts in a region with a helical magnetic field that we identify with the acceleration and collimation zone predicted by the theories. The feature brightens again when it crosses a standing shock wave corresponding to the bright 'core' seen on the images.

An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system

NASA Astrophysics Data System (ADS)

Gandhi, P.; Bachetti, M.; Dhillon, V. S.; Fender, R. P.; Hardy, L. K.; Harrison, F. A.; Littlefair, S. P.; Malzac, J.; Markoff, S.; Marsh, T. R.; Mooley, K.; Stern, D.; Tomsick, J. A.; Walton, D. J.; Casella, P.; Vincentelli, F.; Altamirano, D.; Casares, J.; Ceccobello, C.; Charles, P. A.; Ferrigno, C.; Hynes, R. I.; Knigge, C.; Kuulkers, E.; Pahari, M.; Rahoui, F.; Russell, D. M.; Shaw, A. W.

2017-12-01

Relativistic plasma jets are observed in many systems that host accreting black holes. According to theory, coiled magnetic fields close to the black hole accelerate and collimate the plasma, leading to a jet being launched1-3. Isolating emission from this acceleration and collimation zone is key to measuring its size and understanding jet formation physics. But this is challenging because emission from the jet base cannot easily be disentangled from other accreting components. Here, we show that rapid optical flux variations from an accreting Galactic black-hole binary are delayed with respect to X-rays radiated from close to the black hole by about 0.1 seconds, and that this delayed signal appears together with a brightening radio jet. The origin of these subsecond optical variations has hitherto been controversial4-8. Not only does our work strongly support a jet origin for the optical variations but it also sets a characteristic elevation of ≲103 Schwarzschild radii for the main inner optical emission zone above the black hole9, constraining both internal shock10 and magnetohydrodynamic11 models. Similarities with blazars12,13 suggest that jet structure and launching physics could potentially be unified under mass-invariant models. Two of the best-studied jetted black-hole binaries show very similar optical lags8,14,15, so this size scale may be a defining feature of such systems.

Cosmic jets

NASA Technical Reports Server (NTRS)

Rees, M. J.

1986-01-01

The evidence that active galactic nuclei produce collimated plasma jets is summarised. The strongest radio galaxies are probably energised by relativistic plasma jets generated by spinning black holes interacting with magnetic fields attached to infalling matter. Such objects can produce e(+)-e(-) plasma, and may be relevant to the acceleration of the highest-energy cosmic ray primaries. Small-scale counterparts of the jet phenomenon within our own galaxy are briefly reviewed.

Examining the High-energy Radiation Mechanisms of Knots and Hotspots in Active Galactic Nucleus Jets

NASA Astrophysics Data System (ADS)

Zhang, Jin; Du, Shen-shi; Guo, Sheng-Chu; Zhang, Hai-Ming; Chen, Liang; Liang, En-Wei; Zhang, Shuang-Nan

2018-05-01

We compile the radio–optical–X-ray spectral energy distributions (SEDs) of 65 knots and 29 hotspots in 41 active galactic nucleus jets to examine their high-energy radiation mechanisms. Their SEDs can be fitted with the single-zone leptonic models, except for the hotspot of Pictor A and six knots of 3C 273. The X-ray emission of 1 hotspot and 22 knots is well explained as synchrotron radiation under the equipartition condition; they usually have lower X-ray and radio luminosities than the others, which may be due to a lower beaming factor. An inverse Compton (IC) process is involved for explaining the X-ray emission of the other SEDs. Without considering the equipartition condition, their X-ray emission can be attributed to the synchrotron-self-Compton process, but the derived jet powers (P jet) are not correlated with L k and most of them are larger than L k, with more than three orders of magnitude, where L k is the jet kinetic power estimated with their radio emission. Under the equipartition condition, the X-ray emission is well interpreted with the IC process for the cosmic microwave background photons (IC/CMB). In this scenario, the derived P jet of knots and hotspots are correlated with and comparable to L k. These results suggest that the IC/CMB model may be a promising interpretation of the X-ray emission. In addition, a tentative knot–hotspot sequence in the synchrotron peak-energy–peak-luminosity plane is observed, similar to the blazar sequence, which may be attributed to the different cooling mechanisms of electrons.

Radiation from Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Mizuno, Y.; Hardee, P.; Sol, H.; Medvedev, M.; Zhang, B.; Nordlund, A.; Frederiksen, J. T.; Fishman, G. J.; Preece, R.

2008-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the presence of relativistic jets, instabilities such as the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability create collisionless shocks, which are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The 'jitter' radiation from deflected electrons in small-scale magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation, a case of diffusive synchrotron radiation, may be important to understand the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Spectral Energy Distribution Models for Low-Luminosity Active Galactic Nuclei in LINERs

NASA Technical Reports Server (NTRS)

Nemmen, Rodrigo S.; Storchi-Bergmann, Thaisa; Eracleous, Michael

2012-01-01

Low-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN population in the present-day universe and they trace the low-level accreting supermassive black holes. In order to probe the accretion and jet physical properties in LLAGNs as a class, we model the broadband radio to X-rays spectral energy distributions (SEDs) of 21 LLAGNs in low-ionization nuclear emission-line regions (LINERs) with a coupled accretion-jet model. The accretion flow is modeled as an inner ADAF outside of which there is a truncated standard thin disk. We find that the radio emission is severely underpredicted by ADAF models and is explained by the relativistic jet. The origin of the X-ray radiation in most sources can be explained by three distinct scenarios: the X-rays can be dominated by emission from the ADAF, or the jet, or the X-rays can arise from a jet-ADAF combination in which both components contribute to the emission with similar importance. For 3 objects both the jet and ADAF fit equally well the X-ray spectrum and can be the dominant source of X-rays whereas for 11 LLAGNs a jet-dominated model accounts better than the ADAF-dominated model for the data. The individual and average SED models that we computed can be useful for different studies of the nuclear emission of LLAGNs. From the model fits, we estimate important parameters of the central engine powering LLAGNs in LINERs, such as the mass accretion rate and the mass-loss rate in the jet and the jet power - relevant for studies of the kinetic feedback from jets.

Galactic bulge preferred over dark matter for the Galactic centre gamma-ray excess

NASA Astrophysics Data System (ADS)

Macias, Oscar; Gordon, Chris; Crocker, Roland M.; Coleman, Brendan; Paterson, Dylan; Horiuchi, Shunsaku; Pohl, Martin

2018-05-01

An anomalous gamma-ray excess emission has been found in the Fermi Large Area Telescope data1 covering the centre of the Galaxy2,3. Several theories have been proposed for this `Galactic centre excess'. They include self-annihilation of dark-matter particles4, an unresolved population of millisecond pulsars5, an unresolved population of young pulsars6, or a series of burst events7. Here, we report on an analysis that exploits hydrodynamical modelling to register the position of interstellar gas associated with diffuse Galactic gamma-ray emission. We find evidence that the Galactic centre excess gamma rays are statistically better described by the stellar over-density in the Galactic bulge and the nuclear stellar bulge, rather than a spherical excess. Given its non-spherical nature, we argue that the Galactic centre excess is not a dark-matter phenomenon but rather associated with the stellar population of the Galactic bulge and the nuclear bulge.

Evidence for a nuclear radio jet and its structure down to ≲100 Schwarzschild radii in the center of the Sombrero galaxy (M 104, NGC 4594)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hada, Kazuhiro; Giroletti, Marcello; Giovannini, Gabriele

2013-12-10

The Sombrero galaxy (M 104, NGC 4594) is associated with one of the nearest low-luminosity active galactic nuclei (AGNs). We investigated the detailed radio structure of the Sombrero nucleus using high-resolution, quasi-simultaneous, multi-frequency, phase-referencing Very Long Baseline Array observations. We obtained high-quality images of this nucleus at seven frequencies, where those at 15, 24, and 43 GHz are the first clear very long baseline interferometry detections. At 43 GHz, the nuclear structure was imaged on a linear scale under 0.01 pc or 100 Schwarzschild radii, revealing a compact, high-brightness-temperature (≳ 3 × 10{sup 9} K) radio core. We discovered themore » presence of the extended structure emanating from the core on two sides in the northwest and southeast directions. The nuclear radio spectra show a clear spatial gradient, which is similar to that seen in more luminous AGNs with powerful relativistic jets. Moreover, the size and position of the core tend to be frequency dependent. These findings provide evidence that the central engine of the Sombrero is powering radio jets and the jets are overwhelming the emission from the underlying radiatively inefficient accretion flow over the observed frequencies. Based on these radio characteristics, we constrained the following physical parameters for the M 104 jets: (1) the northern side is approaching, whereas the southern one is receding; (2) the jet viewing angle is relatively close to our line-of-sight (≲ 25°); and (3) the intrinsic jet velocity is highly sub-relativistic (≲ 0.2c). The derived pole-on nature of the M 104 jets is consistent with the previous argument that this nucleus contains a true type II AGN, i.e., the broad line region is actually absent or intrinsically weak if the plane of the circumnuclear torus is perpendicular to the jet axis.« less

Microscopic Processes in Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Nordlund, A.; Fredricksen, J.; Sol, H.; Niemiec, J.; Lyubarsky, Y.;

The Disk-Jet Connection in Radio-Loud AGN: The X-Ray Perspective

NASA Technical Reports Server (NTRS)

Sambruna, Rita

2008-01-01

Unification schemes assume that radio-loud active galactic nuclei (AGN) contain an accretion disk and a relativistic jet perpendicular to the disk, and an obscuring molecular torus. The jet dominance decreases with larger viewing angles from blazars to Broad-Line and Narrow-Line Radio Galaxies. A fundamental question is how accretion and ejecta are related. The X-rays provide a convenient window to study these issues, as they originate in the innermost nuclear regions and penetrate large obscuring columns. I review the data, using observations by Chandra but also from other currently operating high-energy experiments. Synergy with the upcoming GLAST mission will also be highlighted.

Pondermotive acceleration of charged particles along the relativistic jets of an accreting blackhole

NASA Astrophysics Data System (ADS)

Ebisuzaki, T.; Tajima, T.

2014-05-01

Accreting blackholes such as miniquasars and active galactic nuclei can contribute to the highest energy components of intra- (˜1015 eV) galactic and extra-galactic components (˜1020 eV) of cosmic rays. Alfven wave pulses which are excited in the accretion disk around blackholes propagate in relativistic jets. Because of their highly non-linear nature of the waves, charged particles (protons, ions, and electrons) can be accelerated to high energies in relativistic jets in accreting blackhole systems, the central engine of miniquasars and active galactic nuclei.

Reprint of: Reaction measurements with the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target

NASA Astrophysics Data System (ADS)

Chipps, K. A.

2018-01-01

Explosive stellar environments are sometimes driven by nuclear reactions on short-lived, radioactive nuclei. These reactions often drive the stellar explosion, alter the observable light curves produced, and dictate the final abundances of the isotopes created. Unfortunately, many reaction rates at stellar temperatures cannot be directly measured in the laboratory, due to the physical limitations of ultra-low cross sections and high background rates. An additional complication arises because many of the important reactions involve radioactive nuclei which have lifetimes too short to be made into a target. As such, direct reactions require very intense and pure beams of exotic nuclei. Indirect approaches with both stable and radioactive beams can, however, provide crucial information on the nuclei involved in these astrophysical reactions. A major development toward both direct and indirect studies of nuclear reactions rates is the commissioning of the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) supersonic gas jet target. The JENSA system provides a pure, homogeneous, highly localized, dense, and robust gaseous target for radioactive ion beam studies. Charged-particle reactions measurements made with gas jet targets can be cleaner and display better resolution than with traditional targets. With the availability of pure and localized gas jet targets in combination with developments in exotic radioactive ion beams and next-generation detector systems, the range of reaction studies that are experimentally possible is vastly expanded. Various representative cases will be discussed.

AGN feedback compared: jets versus radiation

NASA Astrophysics Data System (ADS)

Cielo, Salvatore; Bieri, Rebekka; Volonteri, Marta; Wagner, Alexander Y.; Dubois, Yohan

2018-06-01

Feedback by active galactic nuclei (AGNs) is often divided into quasar and radio mode, powered by radiation or radio jets, respectively. Both are fundamental in galaxy evolution, especially in late-type galaxies, as shown by cosmological simulations and observations of jet-ISM (interstellar medium) interactions in these systems. We compare AGN feedback by radiation and by collimated jets through a suite of simulations, in which a central AGN interacts with a clumpy, fractal galactic disc. We test AGNs of 1043 and 1046 erg s-1, considering jets perpendicular or parallel to the disc. Mechanical jets drive the more powerful outflows, exhibiting stronger mass and momentum coupling with the dense gas, while radiation heats and rarefies the gas more. Radiation and perpendicular jets evolve to be quite similar in outflow properties and effect on the cold ISM, while inclined jets interact more efficiently with all the disc gas, removing the densest 20 {per cent} in 20 Myr, and thereby reducing the amount of cold gas available for star formation. All simulations show small-scale inflows of 0.01-0.1 M⊙ yr-1, which can easily reach down to the Bondi radius of the central supermassive black hole (especially for radiation and perpendicular jets), implying that AGNs modulate their own duty cycle in a feedback/feeding cycle.

The Jet-driven Outflow in the Radio Galaxy SDSS J1517+3353: Implications for Double-peaked Narrow-line Active Galactic Nucleus

NASA Astrophysics Data System (ADS)

Rosario, D. J.; Shields, G. A.; Taylor, G. B.; Salviander, S.; Smith, K. L.

2010-06-01

We report on the study of an intriguing active galaxy that was selected as a potential multiple supermassive black hole merger in the early-type host SDSS J151709.20+335324.7 (z = 0.135) from a complete search for double-peaked [O III] lines from the SDSS spectroscopic quasi-stellar object (QSO) database. Ground-based SDSS imaging reveals two blue structures on either side of the photometric center of the host galaxy, separated from each other by about 5.7 kpc. From a combination of SDSS fiber and Keck/HIRES long-slit spectroscopy, it is demonstrated that, in addition to these two features, a third distinct structure surrounds the nucleus of the host galaxy. All three structures exhibit highly ionized line emission with line ratios characteristic of Seyfert II active galactic nuclei. The analysis of spatially resolved emission-line profiles from the HIRES spectrum reveal three distinct kinematic subcomponents, one at rest and the other two moving at -350 km s-1 and 500 km s-1 with respect to the systemic velocity of the host galaxy. A comparison of imaging and spectral data confirm a strong association between the kinematic components and the spatial knots, which implies a highly disturbed and complex active region in this object. A comparative analysis of the broadband positions, colors, kinematics, and spectral properties of the knots in this system lead to two plausible explanations: (1) a multiple active galactic nucleus (AGN) produced due to a massive dry merger, or (2) a very powerful radio jet-driven outflow. Subsequent VLA radio imaging reveals a clear jet aligned with the emission-line gas, confirming the latter explanation. We use the broadband radio measurements to examine the impact of the jet on the interstellar medium of the host galaxy, and find that the energy in the radio lobes can heat a significant fraction of the gas to the virial temperature. Finally, we discuss tests that may help future surveys distinguish between jet-driven kinematics and

Accretion Disk Spectra of the Ultra-luminous X-ray Sources in Nearby Spiral Galaxies and Galactic Superluminal Jet Sources

NASA Technical Reports Server (NTRS)

White, Nicholas E. (Technical Monitor); Ebisawa, Ken; Zycki, Piotr; Kubota, Aya; Mizuno, Tsunefumi; Watarai, Ken-ya

2003-01-01

Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and Galactic superluminal jet sources share the common spectral characteristic that they have unusually high disk temperatures which cannot be explained in the framework of the standard optically thick accretion disk in the Schwarzschild metric. On the other hand, the standard accretion disk around the Kerr black hole might explain the observed high disk temperature, as the inner radius of the Kerr disk gets smaller and the disk temperature can be consequently higher. However, we point out that the observable Kerr disk spectra becomes significantly harder than Schwarzschild disk spectra only when the disk is highly inclined. This is because the emission from the innermost part of the accretion disk is Doppler-boosted for an edge-on Kerr disk, while hardly seen for a face-on disk. The Galactic superluminal jet sources are known to be highly inclined systems, thus their energy spectra may be explained with the standard Kerr disk with known black hole masses. For ULXs, on the other hand, the standard Kerr disk model seems implausible, since it is highly unlikely that their accretion disks are preferentially inclined, and, if edge-on Kerr disk model is applied, the black hole mass becomes unreasonably large (greater than or approximately equal to 300 Solar Mass). Instead, the slim disk (advection dominated optically thick disk) model is likely to explain the observed super- Eddington luminosities, hard energy spectra, and spectral variations of ULXs. We suggest that ULXs are accreting black holes with a few tens of solar mass, which is not unexpected from the standard stellar evolution scenario, and their X-ray emission is from the slim disk shining at super-Eddington luminosities.

Blowing in the Milky Way Wind: Neutral Hydrogen Clouds Tracing the Galactic Nuclear Outflow

NASA Astrophysics Data System (ADS)

Di Teodoro, Enrico M.; McClure-Griffiths, N. M.; Lockman, Felix J.; Denbo, Sara R.; Endsley, Ryan; Ford, H. Alyson; Harrington, Kevin

2018-03-01

We present the results of a new sensitive survey of neutral hydrogen above and below the Galactic Center with the Green Bank Telescope. The observations extend up to Galactic latitude | b| < 10^\\circ with an effective angular resolution of 9.‧5 and an average rms brightness temperature noise of 40 mK in a 1 {km} {{{s}}}-1 channel. The survey reveals the existence of a population of anomalous high-velocity clouds extending up to heights of about 1.5 kpc from the Galactic plane and showing no signature of Galactic rotation. These clouds have local standard of rest velocities | {V}LSR}| ≲ 360 {km} {{{s}}}-1, and assuming a Galactic Center origin, they have sizes of a few tens of parsec and neutral hydrogen masses spanning 10{--}{10}5 {M}ȯ . Accounting for selection effects, the cloud population is symmetric in longitude, latitude, and V LSR. We model the cloud kinematics in terms of an outflow expanding from the Galactic Center and find the population consistent with being material moving with radial velocity {V}{{w}}≃ 330 {km} {{{s}}}-1 distributed throughout a bicone with opening angle α > 140^\\circ . This simple model implies an outflow luminosity {L}{{w}}> 3× {10}40 erg s‑1 over the past 10 Myr, consistent with star formation feedback in the inner region of the Milky Way, with a cold gas mass-loss rate ≲ 0.1 {{M}ȯ {yr}}-1. These clouds may represent the cold gas component accelerated in the nuclear wind driven by our Galaxy, although some of the derived properties challenge current theoretical models of the entrainment process.

MOJAVE - XIV. Shapes and opening angles of AGN jets

NASA Astrophysics Data System (ADS)

Pushkarev, A. B.; Kovalev, Y. Y.; Lister, M. L.; Savolainen, T.

2017-07-01

We present 15 GHz stacked VLBA images of 373 jets associated with active galactic nuclei (AGNs) having at least five observing epochs within a 20 yr time interval 1994-2015 from the Monitoring Of Jets in Active galactic nuclei with VLBA Experiments (MOJAVE) programme and/or its precursor, the 2-cm VLBA Survey. These data are supplemented by 1.4 GHz single-epoch VLBA observations of 135 MOJAVE AGNs to probe larger scale jet structures. The typical jet geometry is found to be close to conical on scales from hundreds to thousands of parsecs, while a number of galaxies show quasi-parabolic streamlines on smaller scales. A true jet geometry in a considerable fraction of AGNs appears only after stacking epochs over several years. The jets with significant radial accelerated motion undergo more active collimation. We have analysed total intensity jet profiles transverse to the local jet ridgeline and derived both apparent and intrinsic opening angles of the flows, with medians of 21.5° and 1.3°, respectively. The Fermi LAT-detected gamma-ray AGNs in our sample have, on average, wider apparent and narrower intrinsic opening angle, and smaller viewing angle than non-LAT-detected AGNs. We have established a highly significant correlation between the apparent opening angle and gamma-ray luminosity, driven by Doppler beaming and projection effects.

Radio jet refraction in galactic atmospheres with static pressure gradients

NASA Technical Reports Server (NTRS)

Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

1981-01-01

A theory based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy, is proposed for double radio sources with a Z or S morphology. The model describes a collimated jet of supersonic material that bends self-consistently under the influence of external static pressure gradients, and may alternatively be seen as a continuous-jet version of the buoyancy model proposed by Gull (1973). Emphasis is placed on (1) S-shaped radio sources identified with isolated galaxies, such as 3C 293, whose radio structures should be free of distortions resulting from motion relative to a cluster medium, and (2) small-scale, galaxy-dominated rather than environment-dominated S-shaped sources such as the inner jet structure of Fornax A.

Radiative Processes in Jets

NASA Astrophysics Data System (ADS)

Vila, Gabriela S.

Relativistic jets and collimated outflows are ubiquitous phenomena in astrophysical settings, from young stellar objects up to Active Galactic Nuclei. The observed emission from some of these jets can cover the whole electromagnetic spectrum, from radio to gamma-rays. The relevant features of the spectral energy distributions depend on the nature of the source and on the characteristics of the surrounding environment. Here the author reviews the main physical processes that command the interactions between populations of relativistic particles locally accelerated in the jets, with matter, radiation and magnetic fields. Special attention is given to the conditions that lead to the dominance of the different radiative mechanisms. Examples from various types of sources are used to illustrate these effects.

Probing transverse momentum broadening via jet-related angular correlations in relativistic nuclear collisions

NASA Astrophysics Data System (ADS)

Chen, Lin; Qin, Guang-You; Wei, Shu-Yi; Xiao, Bo-Wen; Zhang, Han-Zhong

2017-11-01

Jet-related correlations have been regarded as important tools for studying jet-medium interaction and jet quenching in relativistic heavy-ion collisions at RHIC and the LHC. Here we present our recent work [L. Chen, G.-Y. Qin, S.-Y. Wei, B.-W. Xiao, H.-Z. Zhang, Probing Transverse Momentum Broadening via Dihadron and Hadron-jet Angular Correlations in Relativistic Heavy-ion Collisions, arxiv:arXiv:1607.01932] and show that the back-to-back angular correlations in dijet, dihadron and hadron-jet measurements can be utilized as a quantitative tool to probe the medium-induced transverse momentum broadening and to extract jet quenching parameter q̂. By comparing with the dihadron and hadron-jet angular correlation data at RHIC, we obtain the medium-induced transverse momentum broadening, averaged over different jet paths, 〈 p⊥2 〉 ∼ 13 GeV2 for a quark jet in most central Au-Au collisions at 200A GeV. Future experiments with statistically improved data on jet-related (angular) correlations will allow us to obtain more precise knowledge of jet quenching parameter and parton-medium interaction in high-energy nuclear collisions.

Microscopic Processes On Radiation from Accelerated Particles in Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P. E.; Mizuno, Y.; Medvedev, M.; Zhang, B.; Sol, H.; Niemiec, J.; Pohl, M.; Nordlund, A.; Fredriksen, J.;

PREFACE: Astronomy at High Angular Resolution 2011: The central kiloparsec in galactic nuclei

NASA Astrophysics Data System (ADS)

Iserlohe, Christof; Karas, Vladimir; Krips, Melanie; Eckart, Andreas; Britzen, Silke; Fischer, Sebastian

2012-07-01

We are pleased to present the proceedings from the Astronomy at High Angular Resolution 2011: The central kiloparsec in galactic nuclei conference. The conference took place in the Physikzentrum of the Deutsche Physikalische Gesellschaft (DPG), Bad Honnef, Germany, from 28 August to 2 September 2011. It was the second conference of this kind, following the Astronomy at High Angular Resolution conference held in Bad Honnef, three years earlier in 2008. The main objective of the conference was to frame the discussion of the broad range of physical processes that occur in the central 100pc of galactic nuclei. In most cases, this domain is difficult to probe through observations. This is mainly because of the lack of angular resolution, the brightness of the central engine and possible obscurations through dust and gas, which play together in the central regions of host galaxies of galactic nuclei within a broad range of activity. The presence of large amounts of molecular and atomic (both neutral and ionized) gas, dust and central engines with outflows and jets implies that the conditions for star formation in these regions are very special, and probably different from those in the disks of host galaxies. Numerous presentations covering a broad range of topics, both theoretical and experimental, those related to research on Active Galactic Nuclei and on a wide range of observed wavelengths were submitted to the Scientific Organizing Committee. Presentations have been grouped into six sessions: The nuclei of active galaxies The Galactic Center The immediate environment of Super Massive Black Holes The physics of nuclear jets and the interaction of the interstellar medium The central 100pc of the nuclear environment Star formation in that region The editors thank all participants of the AHAR 2011 conference for their enthusiasm and their numerous and vivid contributions to this conference. We would especially like to thank John Hugh Seiradakis from the Aristotle

Probing the formation history of the nuclear star cluster at the Galactic Centre with millisecond pulsars

NASA Astrophysics Data System (ADS)

Abbate, F.; Mastrobuono-Battisti, A.; Colpi, M.; Possenti, A.; Sippel, A. C.; Dotti, M.

2018-01-01

The origin of the nuclear star cluster in the centre of our Galaxy is still unknown. One possibility is that it formed after the disruption of stellar clusters that spiralled into the Galactic Centre due to dynamical friction. We trace the formation of the nuclear star cluster around the central black hole, using state-of-the-art N-body simulations, and follow the dynamics of the neutron stars born in the clusters. We then estimate the number of millisecond pulsars (MSPs) that are released in the nuclear star cluster during its formation. The assembly and tidal dismemberment of globular clusters lead to a population of MSPs distributed over a radius of about 20 pc, with a peak near 3 pc. No clustering is found on the subparsec scale. We simulate the detectability of this population with future radio telescopes like the MeerKAT radio telescope and SKA1, and find that about an order of 10 MSPs can be observed over this large volume, with a paucity of MSPs within the central parsec. This helps discriminating this scenario from the in situ formation model for the nuclear star cluster that would predict an overabundance of MSPs closer to the black hole. We then discuss the potential contribution of our MSP population to the gamma-ray excess at the Galactic Centre.

Gamma ray constraints on the Galactic supernova rate

NASA Technical Reports Server (NTRS)

Hartmann, D.; The, L.-S.; Clayton, Donald D.; Leising, M.; Mathews, G.; Woosley, S. E.

1991-01-01

We perform Monte Carlo simulations of the expected gamma ray signatures of Galactic supernovae of all types to estimate the significance of the lack of a gamma ray signal due to supernovae occurring during the last millenium. Using recent estimates of the nuclear yields, we determine mean Galactic supernova rates consistent with the historic supernova record and the gamma ray limits. Another objective of these calculations of Galactic supernova histories is their application to surveys of diffuse Galactic gamma ray line emission.

Gamma ray constraints on the galactic supernova rate

NASA Technical Reports Server (NTRS)

Hartmann, D.; The, L.-S.; Clayton, D. D.; Leising, M.; Mathews, G.; Woosley, S. E.

1992-01-01

Monte Carlo simulations of the expected gamma-ray signatures of galactic supernovae of all types are performed in order to estimate the significance of the lack of a gamma-ray signal due to supernovae occurring during the last millenium. Using recent estimates of nuclear yields, we determine galactic supernova rates consistent with the historic supernova record and the gamma-ray limits. Another objective of these calculations of galactic supernova histories is their application to surveys of diffuse galactic gamma-ray line emission.

Accretion in active galactic nuclei and disk-jet coupling

NASA Astrophysics Data System (ADS)

Czerny, B.; You, B.

2016-02-01

We review the current state of understanding how accretion onto a black hole proceeds and what the key elements needed to form relativistic jets are. Theoretical progress is severely undermined by the lack of thorough understanding of the microphysics involved in accretion discs and in the formation of jets, particularly in the presence of strong magnetic fields. Therefore, all proposed solutions are still models that need to be validated by observational constraints.

How Space Radiation Risk from Galactic Cosmic Rays at the International Space Station Relates to Nuclear Cross Sections

NASA Technical Reports Server (NTRS)

Lin, Zi-Wei; Adams, J. H., Jr.

2005-01-01

Space radiation risk to astronauts is a major obstacle for long term human space explorations. Space radiation transport codes have thus been developed to evaluate radiation effects at the International Space Station (ISS) and in missions to the Moon or Mars. We study how nuclear fragmentation processes in such radiation transport affect predictions on the radiation risk from galactic cosmic rays. Taking into account effects of the geomagnetic field on the cosmic ray spectra, we investigate the effects of fragmentation cross sections at different energies on the radiation risk (represented by dose-equivalent) from galactic cosmic rays behind typical spacecraft materials. These results tell us how the radiation risk at the ISS is related to nuclear cross sections at different energies, and consequently how to most efficiently reduce the physical uncertainty in our predictions on the radiation risk at the ISS.

Nuclear processes in the jets of SS 433

NASA Technical Reports Server (NTRS)

Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

1984-01-01

The very narrow gamma-ray lines observed at 1.495 and 6.695 MeV from SS 433 which are blueshifted 1.369 and 6.129 emissions from deexcitations of (24)Mg-asterisk and (16)O-asterisk in grains moving with the jets and inelastically excited by interactions with the ambient medium are discussed. Energetic particle interactions in grains produce very narrow gamma ray lines from deexcitation of nuclear levels whose lifetimes are long enough that the excited nuclei stop before deexcitation. The presence of grains in the jets resolves hitherto discussed difficulties of inelastic excitation models for gamma ray production in SS 433, the very narrow widths of the observed lines and the absence of other strong lines, expected from abundant elements. A model is proposed which could be distinguished from a previously proposed fusion model by gamma ray line observations.

Nuclear processes in the jets of SS433

NASA Technical Reports Server (NTRS)

Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

1984-01-01

The very narrow gamma-ray lines observed at 1.495 and 6.695 MeV from SS433 which are blueshifted 1.369 and 6.129 emissions from deexcitations of (24)Mg* and (16)O* in grains moving with the jets and inelastically excited by interactions with the ambient medium are discussed. Energetic particle interactions in grains produce very narrow gamma ray lines from deexcitation of nuclear levels whose lifetimes are long enough that the excited nuclei stop before deexcitation. The presence of grains in the jets resolves hitherto discussed difficulties of inelastic excitation models for gamma ray production in SS433, the very narrow widths of the observed lines and the absence of other strong lines, expected from abundant elements. A model is proposed which could be distinguished from a previously proposed fusion model by gamma ray line observations.

The remarkable AGN jets

NASA Astrophysics Data System (ADS)

Komissarov, Serguei

The jets from active galactic nuclei exhibit stability which seems to be far superior compared to that of terrestrial and laboratory jets. They manage to propagate over distances up to a billion of initial jet radii. Yet this may not be an indication of some exotic physics but mainly a reflection of the specific environment these jets propagate through. The key property of this environment is a rapid decline of density and pressure along the jet, which promotes its rapid expansion. Such an expansion can suppress global instabilities, which require communication across the jet, and hence ensure its survival over huge distances. At kpc scales, some AGN jets do show signs of strong instabilities and even turn into plumes. This could be a result of the flattening of the external pressure distribution in their host galaxies or inside the radio lobes. In this regard, we discuss the possible connection between the stability issue and the Fanaroff-Riley classification of extragalactic radio sources. The observations of AGN jets on sub-kpc scale do not seem to support their supposed lack of causal connectivity. When interpreted using simple kinematic models, they reveal a rather perplexing picture with more questions than answers on the jets dynamics.

The Invariant Twist of Magnetic Fields in the Relativistic Jets of Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes; Gabuzda, Denise C.

2009-01-01

The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in Active Galactic Nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1 %. This lends support to the hypothesis that the Universe is seeded by B fields that are generated in AGN via this mechanism

QUASI-STAR JETS AS UNIDENTIFIED GAMMA-RAY SOURCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Czerny, Bozena; Sikora, Marek; Janiuk, Agnieszka

2012-08-10

Gamma-ray catalogs contain a considerable amount of unidentified sources. Many of these are located out of the Galactic plane and therefore may have extragalactic origin. Here we assume that the formation of massive black holes in galactic nuclei proceeds through a quasi-star stage and consider the possibility of jet production by such objects. Those jets would be the sources of collimated synchrotron and Compton emission, extending from radio to gamma rays. The expected lifetimes of quasi-stars are of the order of million of years while the jet luminosities, somewhat smaller than that of quasar jets, are sufficient to account formore » the unidentified gamma-ray sources. The jet emission dominates over the thermal emission of a quasi-star in all energy bands, except when the jet is not directed toward an observer. The predicted synchrotron emission peaks in the IR band, with the flux close to the limits of the available IR all sky surveys. The ratio of the gamma-ray flux to the IR flux is found to be very large ({approx}60), much larger than in BL Lac objects but reached by some radio-loud quasars. On the other hand, radio-loud quasars show broad emission lines while no such lines are expected from quasi-stars. Therefore, the differentiation between various scenarios accounting for the unidentified gamma-ray sources will be possible at the basis of the photometry and spectroscopy of the IR/optical counterparts.« less

76 FR 37798 - DOE Response to Recommendation 2010-2 of the Defense Nuclear Facilities Safety Board, Pulse Jet...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-28

... Safety Board, Pulse Jet Mixing at the Waste Treatment and Immobilization Plant AGENCY: Department of... their Recommendation 2010-2, concerning Pulse Jet Mixing at the Waste Treatment and Immobilization Plant... Nuclear Facilities Safety Board (Board) Recommendation 2010-2, Pulse Jet Mixing (PJM) at the Waste...

Particle Acceleration, Magnetic Field Generation, and Associated Emission in Collisionless Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.

2007-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron)jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

Particle Acceleration, Magnetic Field Generation and Associated Emission in Collisionless Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K. I.; Ramirez-Ruiz, E.; Hardee, P.; Mizuno, Y.; Fishman. G. J.

2007-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

76 FR 13397 - DOE Response to Recommendation 2010-2 of the Defense Nuclear Facilities Safety Board, Pulse Jet...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-11

... Safety Board, Pulse Jet Mixing at the Waste Treatment and Immobilization Plant AGENCY: Department of..., concerning Pulse Jet Mixing at the Waste Treatment and Immobilization Plant was published in the Federal... Defense Nuclear Facilities Safety Board (Board) Recommendation 2010-2, Pulse Jet Mixing at the Waste...

Star formation inside a galactic outflow.

PubMed

Maiolino, R; Russell, H R; Fabian, A C; Carniani, S; Gallagher, R; Cazzoli, S; Arribas, S; Belfiore, F; Bellocchi, E; Colina, L; Cresci, G; Ishibashi, W; Marconi, A; Mannucci, F; Oliva, E; Sturm, E

2017-04-13

Recent observations have revealed massive galactic molecular outflows that may have the physical conditions (high gas densities) required to form stars. Indeed, several recent models predict that such massive outflows may ignite star formation within the outflow itself. This star-formation mode, in which stars form with high radial velocities, could contribute to the morphological evolution of galaxies, to the evolution in size and velocity dispersion of the spheroidal component of galaxies, and would contribute to the population of high-velocity stars, which could even escape the galaxy. Such star formation could provide in situ chemical enrichment of the circumgalactic and intergalactic medium (through supernova explosions of young stars on large orbits), and some models also predict it to contribute substantially to the star-formation rate observed in distant galaxies. Although there exists observational evidence for star formation triggered by outflows or jets into their host galaxy, as a consequence of gas compression, evidence for star formation occurring within galactic outflows is still missing. Here we report spectroscopic observations that unambiguously reveal star formation occurring in a galactic outflow at a redshift of 0.0448. The inferred star-formation rate in the outflow is larger than 15 solar masses per year. Star formation may also be occurring in other galactic outflows, but may have been missed by previous observations owing to the lack of adequate diagnostics.

NEW CLASS OF VERY HIGH ENERGY {gamma}-RAY EMITTERS: RADIO-DARK MINI SHELLS SURROUNDING ACTIVE GALACTIC NUCLEUS JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kino, Motoki; Ito, Hirotaka; Kawakatu, Nozomu

We explore non-thermal emission from a shocked interstellar medium, which is identified as an expanding shell, driven by a relativistic jet in active galactic nuclei (AGNs). In this work, we particularly focus on parsec-scale size mini shells surrounding mini radio lobes. From the radio to X-ray band, the mini radio lobe emission dominates the faint emission from the mini shell. On the other hand, we find that inverse-Compton (IC) emission from the shell can overwhelm the associated lobe emission at the very high energy (VHE; E > 100 GeV) {gamma}-ray range, because energy densities of synchrotron photons from the lobemore » and/or soft photons from the AGN nucleus are large and IC scattering works effectively. The predicted IC emission from nearby mini shells can be detected with the Cherenkov Telescope Array and they are potentially a new class of VHE {gamma}-ray emitters.« less

Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

2006-01-01

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration' is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different spectral properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

Wiggles and knots in radio jets

NASA Astrophysics Data System (ADS)

Trussoni, E.; Ferrari, A.; Zaninetti, L.

Dynamical effects in binary nuclei inside parent galactic cores, gravitational interactions with companion galaxies, and Kelvin-Helmholtz instabilities in the flow propagation have been proposed as mechanism responsible for the formation of the low amplitude morphologies, wiggles and knots, observed in radio jets. Here the basic characteristics and implications of these models are discussed with reference to the limited sample of existing data. In conclusion it will be shown that present observations cannot discriminate definitely these theories; conversely, different mechanisms may be at work together in any jet at the same time.

Formation of Relativistic Jets : Magnetohydrodynamics and Synchrotron Radiation

NASA Astrophysics Data System (ADS)

Porth, Oliver J. G.

2011-11-01

In this thesis, the formation of relativistic jets is investigated by means of special relativistic magnetohydrodynamic simulations and synchrotron radiative transfer. Our results show that the magnetohydrodynamic jet self-collimation paradigm can also be applied to the relativistic case. In the first part, jets launched from rotating hot accretion disk coronae are explored, leading to well collimated, but only mildly relativistic flows. Beyond the light-cylinder, the electric charge separation force balances the classical trans-field Lorentz force almost entirely, resulting in a decreased efficiency of acceleration and collimation in comparison to non-relativistic disk winds. In the second part, we examine Poynting dominated flows of various electric current distributions. By following the outflow for over 3000 Schwarzschild radii, highly relativistic jets of Lorentz factor 8 and half-opening angles below 1 degree are obtained, providing dynamical models for the parsec scale jets of active galactic nuclei. Applying the magnetohydrodynamic structure of the quasi-stationary simulation models, we solve the relativistically beamed synchrotron radiation transport. This yields synthetic radiation maps and polarization patterns that can be used to confront high resolution radio and (sub-) mm observations of nearby active galactic nuclei. Relativistic motion together with the helical magnetic fields of the jet formation site imprint a clear signature on the observed polarization and Faraday rotation. In particular, asymmetries in the polarization direction across the jet can disclose the handedness of the magnetic helix and thus the spin direction of the central engine. Finally, we show first results from fully three-dimensional, high resolution adaptive mesh refinement simulations of jet formation from a rotating magnetosphere and examine the jet stability. Relativistic field-line rotation leads to an electric charge separation force that opposes the magnetic Lorentz

Analysis of Material Sample Heated by Impinging Hot Hydrogen Jet in a Non-Nuclear Tester

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Foote, John; Litchford, Ron

2006-01-01

A computational conjugate heat transfer methodology was developed and anchored with data obtained from a hot-hydrogen jet heated, non-nuclear materials tester, as a first step towards developing an efficient and accurate multiphysics, thermo-fluid computational methodology to predict environments for hypothetical solid-core, nuclear thermal engine thrust chamber. The computational methodology is based on a multidimensional, finite-volume, turbulent, chemically reacting, thermally radiating, unstructured-grid, and pressure-based formulation. The multiphysics invoked in this study include hydrogen dissociation kinetics and thermodynamics, turbulent flow, convective and thermal radiative, and conjugate heat transfers. Predicted hot hydrogen jet and material surface temperatures were compared with those of measurement. Predicted solid temperatures were compared with those obtained with a standard heat transfer code. The interrogation of physics revealed that reactions of hydrogen dissociation and recombination are highly correlated with local temperature and are necessary for accurate prediction of the hot-hydrogen jet temperature.

Origin of superluminal radio jets in microquasars

NASA Astrophysics Data System (ADS)

Yadav, J. S.; Bhandare, R. S.

In Microquasars, superluminal radio jets are seen at large distances from few hundred AU to 5000 AU with very high radio luminosity. We suggest that these superluminal jets are due to internal shocks which form in the previously generated slowly moving wind (from the accretion disk or the companion star) with beta < 0.01 as the fast moving discrete jet with beta sim 1 catches up and interacts with it. The black hole X-ray binaries with transient radio emission (mostly LMXBs) produce superluminal jets with beta_app > 1 when the accretion rate is high and the bolometric luminosity, L_bol approaches the Eddington Luminosity, L_Edd. On the other hand, the black hole X-ray binaries with persistent radio emission (mostly HMXBs) produce superluminal jets with beta_app < 1 at relatively low accretion rate. Our work here brings Galactic microquasars closer to extragalactic AGNs and quasars as the environment plays an important role in the formation of superluminal jets.

Gamma-ray and X-ray emission from the Galactic centre: hints on the nuclear star cluster formation history

NASA Astrophysics Data System (ADS)

Arca-Sedda, Manuel; Kocsis, Bence; Brandt, Timothy D.

2018-06-01

The Milky Way centre exhibits an intense flux in the gamma and X-ray bands, whose origin is partly ascribed to the possible presence of a large population of millisecond pulsars (MSPs) and cataclysmic variables (CVs), respectively. However, the number of sources required to generate such an excess is much larger than what is expected from in situ star formation and evolution, opening a series of questions about the formation history of the Galactic nucleus. In this paper we make use of direct N-body simulations to investigate whether these sources could have been brought to the Galactic centre by a population of star clusters that underwent orbital decay and formed the Galactic nuclear star cluster (NSC). Our results suggest that the gamma ray emission is compatible with a population of MSPs that were mass segregated in their parent clusters, while the X-ray emission is consistent with a population of CVs born via dynamical interactions in dense star clusters. Combining observations with our modelling, we explore how the observed γ ray flux can be related to different NSC formation scenarios. Finally, we show that the high-energy emission coming from the galactic central regions can be used to detect black holes heavier than 105M⊙ in nearby dwarf galaxies.

Hydrodynamic Simulations of the Central Molecular Zone with a Realistic Galactic Potential

NASA Astrophysics Data System (ADS)

Shin, Jihye; Kim, Sungsoo S.; Baba, Junichi; Saitoh, Takayuki R.; Hwang, Jeong-Sun; Chun, Kyungwon; Hozumi, Shunsuke

2017-06-01

We present hydrodynamic simulations of gas clouds inflowing from the disk to a few hundred parsec region of the Milky Way. A gravitational potential is generated to include realistic Galactic structures by using thousands of multipole expansions (MEs) that describe 6.4 million stellar particles of a self-consistent Galaxy simulation. We find that a hybrid ME model, with two different basis sets and a thick-disk correction, accurately reproduces the overall structures of the Milky Way. Through non-axisymmetric Galactic structures of an elongated bar and spiral arms, gas clouds in the disk inflow to the nuclear region and form a central molecular zone-like nuclear ring. We find that the size of the nuclear ring evolves into ˜ 240 {pc} at T˜ 1500 {Myr}, regardless of the initial size. For most simulation runs, the rate of gas inflow to the nuclear region is equilibrated to ˜ 0.02 {M}⊙ {{yr}}-1. The nuclear ring is off-centered, relative to the Galactic center, by the lopsided central mass distribution of the Galaxy model, and thus an asymmetric mass distribution of the nuclear ring arises accordingly. The vertical asymmetry of the Galaxy model also causes the nuclear ring to be tilted along the Galactic plane. During the first ˜100 Myr, the vertical frequency of the gas motion is twice that of the orbital frequency, thus the projected nuclear ring shows a twisted, ∞ -like shape.

Nuclear Thermal Rocket - Arc Jet Integrated System Model

NASA Technical Reports Server (NTRS)

Taylor, Brian D.; Emrich, William

2016-01-01

In the post-shuttle era, space exploration is moving into a new regime. Commercial space flight is in development and is planned to take on much of the low earth orbit space flight missions. With the development of a heavy lift launch vehicle, the Space Launch, System, NASA has become focused on deep space exploration. Exploration into deep space has traditionally been done with robotic probes. More ambitious missions such as manned missions to asteroids and Mars will require significant technology development. Propulsion system performance is tied to the achievability of these missions and the requirements of other developing technologies that will be required. Nuclear thermal propulsion offers a significant improvement over chemical propulsion while still achieving high levels of thrust. Opportunities exist; however, to build upon what would be considered a standard nuclear thermal engine to attain improved performance, thus further enabling deep space missions. This paper discuss the modeling of a nuclear thermal system integrated with an arc jet to further augment performance. The performance predictions and systems impacts are discussed.

Coupling hydrodynamics and radiation calculations for star-jet interactions in active galactic nuclei

NASA Astrophysics Data System (ADS)

de la Cita, V. M.; Bosch-Ramon, V.; Paredes-Fortuny, X.; Khangulyan, D.; Perucho, M.

2016-06-01

Context. Stars and their winds can contribute to the non-thermal emission in extragalactic jets. Because of the complexity of jet-star interactions, the properties of the resulting emission are closely linked to those of the emitting flows. Aims: We simulate the interaction between a stellar wind and a relativistic extragalactic jet and use the hydrodynamic results to compute the non-thermal emission under different conditions. Methods: We performed relativistic axisymmetric hydrodynamical simulations of a relativistic jet interacting with a supersonic, non-relativistic stellar wind. We computed the corresponding streamlines out of the simulation results and calculated the injection, evolution, and emission of non-thermal particles accelerated in the jet shock, focusing on electrons or e±-pairs. Several cases were explored, considering different jet-star interaction locations, magnetic fields, and observer lines of sight. The jet luminosity and star properties were fixed, but the results are easily scalable when these parameters are changed. Results: Individual jet-star interactions produce synchrotron and inverse Compton emission that peaks from X-rays to MeV energies (depending on the magnetic field), and at ~100-1000 GeV (depending on the stellar type), respectively. The radiation spectrum is hard in the scenarios explored here as a result of non-radiative cooling dominance, as low-energy electrons are efficiently advected even under relatively high magnetic fields. Interactions of jets with cold stars lead to an even harder inverse Compton spectrum because of the Klein-Nishina effect in the cross section. Doppler boosting has a strong effect on the observer luminosity. Conclusions: The emission levels for individual interactions found here are in the line of previous, more approximate, estimates, strengthening the hypothesis that collective jet-star interactions could significantly contribute at high energies under efficient particle acceleration.

Measurements of photo-nuclear jet production in Pb + Pb collisions with ATLAS

DOE PAGES

Angerami, Aaron

2017-09-25

Ultra-peripheral heavy ion collisions provide a unique opportunity to study the parton distributions in the colliding nuclei via the measurement of photo-nuclear jet production. An analysis of jet production in ultra-peripheral Pb+Pb collisions at √ sNN = 5.02 TeV performed using data collected with the ATLAS detector in 2015 is described. The data set corresponds to a total Pb+Pb integrated luminosity of 0.38 nb -1. The ultra-peripheral collisions are selected using a combination of forward neutron and rapidity gap requirements. The cross-sections, not unfolded for detector response, are compared to results from Pythia Monte Carlo simulations re-weighted to match amore » photon spectrum obtained from the STARlight model. As a result, qualitative agreement between data and these simulations is observed over a broad kinematic range suggesting that using these collisions to measure nuclear parton distributions is experimentally realisable.« less

The age of the Galactic disk - Inflow, chemical evolution, astration, and radioactivity

NASA Technical Reports Server (NTRS)

Clayton, Donald D.

1989-01-01

Theoretical models of Galactic evolution and observational data on the age of the Galaxy are compared, with a focus on recent results. Topics addressed include the infall of material and its effects on the age-metallicity relation, the distribution of metallicity, the present gas fraction and metallicity, and the age spectrum of interstellar nuclei; the chemical evolution of the solar neighborhood; the key results of nuclear cosmochronology; and astration effects on Galactic age. It is found that both nuclear cosmochronology and detailed stellar and Galactic evolution models tend to support an age of 12-16 Gyr.

Submerged jet mixing in nuclear waste tanks: a correlation for jet velocity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daas, M.; Srivastava, R.; Roelant, D.

2007-07-01

Experimental studies were carried out in jet-stirred slurry tanks to correlate the influence of nozzle diameter, initial jet flow velocity, submerged depth of jet, tank diameter and slurry properties on the jet axial velocity. The tanks used in the experimental work had diameters of 0.3 m (1-ft) and 2.13 m (7-ft). The fluids emerged from nozzles of 0.003 m and 0.01 m in diameter, 1/8-inch and 3/8-inch respectively. The examined slurries were non-Newtonian and contained 5 weight percent total insoluble solids. The axial velocities along the centerline of a submerged jet stream were measured at different jet flow rates andmore » at various distances from the nozzle orifice (16 to 200 nozzle diameters) utilizing electromagnetic velocity meter. A new simplified correlation was developed to describe the jet axial velocity in submerged jet stirred tanks utilizing more than 350 data points. The Buckingham Pi theorem and non-linear regression method of multivariate approximation, in conjunction with the Gauss-Jordan elimination method, were used to develop the new correlation. The new correlation agreed well with the experimental data obtained from the current study. Good agreement was also possible with literature data except at large distances from the nozzle as the model slightly overestimated the jet axial velocity. The proposed correlation incorporates the contributions of system geometry, fluid properties, and external forces. Furthermore, it provides reasonable estimates of jet axial velocity. (authors)« less

Initial state nuclear effects for jet production measured in s=200GeV d+Au collisions by STAR

NASA Astrophysics Data System (ADS)

STAR Collaboration; Kapitán, Jan; STAR Collaboration

2009-11-01

Full jet reconstruction in heavy-ion collisions is a promising tool for quantitative study of properties of the dense medium produced at RHIC. Measurements of d+Au collisions are important to disentangle initial state nuclear effects from medium-induced k broadening and jet quenching. We report measurements of mid-rapidity (|η|<0.4|) di-jet correlations in d+Au using high-statistics run 8 RHIC data at s=200GeV.

3-D RPIC simulations of relativistic jets: Particle acceleration, magnetic field generation, and emission

NASA Technical Reports Server (NTRS)

Nishikawa, K.-I.

2006-01-01

Nonthermal radiation observed from astrophysical systems containing (relativistic) jets and shocks, e.g., supernova remnants, active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the .shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. We will review recent PIC simulations which show particle acceleration in jets.

Signatures of Relativistic Helical Motion in the Rotation Measures of Active Galactic Nucleus Jets

NASA Astrophysics Data System (ADS)

Broderick, Avery E.; Loeb, Abraham

2009-10-01

Polarization has proven to be an invaluable tool for probing magnetic fields in relativistic jets. Maps of the intrinsic polarization vectors have provided the best evidence to date for uniform, toroidally dominated magnetic fields within jets. More recently, maps of the rotation measure (RM) in jets have for the first time probed the field geometry of the cool, moderately relativistic surrounding material. In most cases, clear signatures of the toroidal magnetic field are detected, corresponding to gradients in RM profiles transverse to the jet. However, in many objects, these profiles also display marked asymmetries that are difficult to explain in simple helical jet models. Furthermore, in some cases, the RM profiles are strongly frequency and/or time dependent. Here we show that these features may be naturally accounted for by including relativistic helical motion in the jet model. In particular, we are able to reproduce bent RM profiles observed in a variety of jets, frequency-dependent RM profile morphologies, and even the time dependence of the RM profiles of knots in 3C 273. Finally, we predict that some sources may show reversals in their RM profiles at sufficiently high frequencies, depending upon the ratio of the components of jet sheath velocity transverse and parallel to the jet. Thus, multi-frequency RM maps promise a novel way in which to probe the velocity structure of relativistic outflows.

Multiwaveband Polarimetric Observations of 15 Active Galactic Nuclei at High Frequencies: Correlated Polarization Behavior

NASA Astrophysics Data System (ADS)

Jorstad, Svetlana G.; Marscher, Alan P.; Stevens, Jason A.; Smith, Paul S.; Forster, James R.; Gear, Walter K.; Cawthorne, Timothy V.; Lister, Matthew L.; Stirling, Alastair M.; Gómez, José L.; Greaves, Jane S.; Robson, E. Ian

2007-08-01

We report on multifrequency linear polarization monitoring of 15 active galactic nuclei containing highly relativistic jets with apparent speeds from ~4c to >40c. The measurements were obtained at optical, 1 mm, and 3 mm wavelengths, and at 7 mm with the Very Long Baseline Array. The data show a wide range in degree of linear polarization among the sources, from <1% to >30%, and interday polarization variability in individual sources. The polarization properties suggest separation of the sample into three groups with low, intermediate, and high variability of polarization in the core at 7 mm (LVP, IVP, and HVP, respectively). The groups are partially associated with the common classification of active galactic nuclei as radio galaxies and quasars with low optical polarization (LVP), BL Lacertae objects (IVP), and highly optically polarized quasars (HVP). Our study investigates correlations between total flux, fractional polarization, and polarization position angle at the different wavelengths. We interpret the polarization properties of the sources in the sample through models in which weak shocks compress turbulent plasma in the jet. The differences in the orientation of sources with respect to the observer, jet kinematics, and abundance of thermal matter external to the jet near the core can account for the diversity in the polarization properties. The results provide strong evidence that the optical polarized emission originates in shocks, most likely situated between the 3 and 7 mm VLBI cores. They also support the idea that the 1 mm core lies at the edge of the transition zone between electromagnetically dominated and turbulent hydrodynamic sections of the jet.

Measurement of inclusive jet production and nuclear modifications in pPb collisions at √{s_{_NN}} =5.02 TeV

NASA Astrophysics Data System (ADS)

Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Asilar, E.; Bergauer, T.; Brandstetter, J.; Brondolin, E.; Dragicevic, M.; Erö, J.; Flechl, M.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hartl, C.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Knünz, V.; König, A.; Krammer, M.; Krätschmer, I.; Liko, D.; Matsushita, T.; Mikulec, I.; Rabady, D.; Rad, N.; Rahbaran, B.; Rohringer, H.; Schieck, J.; Schöfbeck, R.; Strauss, J.; Treberer-Treberspurg, W.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Suarez Gonzalez, J.; Alderweireldt, S.; Cornelis, T.; De Wolf, E. A.; Janssen, X.; Knutsson, A.; Lauwers, J.; Luyckx, S.; Van De Klundert, M.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Abu Zeid, S.; Blekman, F.; D'Hondt, J.; Daci, N.; De Bruyn, I.; Deroover, K.; Heracleous, N.; Keaveney, J.; Lowette, S.; Moreels, L.; Olbrechts, A.; Python, Q.; Strom, D.; Tavernier, S.; Van Doninck, W.; Van Mulders, P.; Van Onsem, G. P.; Van Parijs, I.; Barria, P.; Brun, H.; Caillol, C.; Clerbaux, B.; De Lentdecker, G.; Fang, W.; Fasanella, G.; Favart, L.; Goldouzian, R.; Grebenyuk, A.; Karapostoli, G.; Lenzi, T.; Léonard, A.; Maerschalk, T.; Marinov, A.; Perniè, L.; Randle-conde, A.; Seva, T.; Vander Velde, C.; Vanlaer, P.; Yonamine, R.; Zenoni, F.; Zhang, F.; Beernaert, K.; Benucci, L.; Cimmino, A.; Crucy, S.; Dobur, D.; Fagot, A.; Garcia, G.; Gul, M.; Mccartin, J.; Ocampo Rios, A. A.; Poyraz, D.; Ryckbosch, D.; Salva, S.; Sigamani, M.; Tytgat, M.; Van Driessche, W.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Beluffi, C.; Bondu, O.; Brochet, S.; Bruno, G.; Caudron, A.; Ceard, L.; Delaere, C.; Delcourt, M.; Favart, D.; Forthomme, L.; Giammanco, A.; Jafari, A.; Jez, P.; Komm, M.; Lemaitre, V.; Mertens, A.; Musich, M.; Nuttens, C.; Perrini, L.; Piotrzkowski, K.; Popov, A.; Quertenmont, L.; Selvaggi, M.; Vidal Marono, M.; Beliy, N.; Hammad, G. H.; Aldá Júnior, W. L.; Alves, F. L.; Alves, G. A.; Brito, L.; Correa Martins Junior, M.; Hamer, M.; Hensel, C.; Moraes, A.; Pol, M. E.; Rebello Teles, P.; Belchior Batista Das Chagas, E.; Carvalho, W.; Chinellato, J.; Custódio, A.; Da Costa, E. M.; De Jesus Damiao, D.; De Oliveira Martins, C.; Fonseca De Souza, S.; Huertas Guativa, L. M.; Malbouisson, H.; Matos Figueiredo, D.; Mora Herrera, C.; Mundim, L.; Nogima, H.; Prado Da Silva, W. L.; Santoro, A.; Sznajder, A.; Tonelli Manganote, E. J.; Vilela Pereira, A.; Ahuja, S.; Bernardes, C. A.; De Souza Santos, A.; Dogra, S.; Fernandez Perez Tomei, T. R.; Gregores, E. M.; Mercadante, P. G.; Moon, C. S.; Novaes, S. F.; Padula, Sandra S.; Romero Abad, D.; Ruiz Vargas, J. C.; Aleksandrov, A.; Hadjiiska, R.; Iaydjiev, P.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Vutova, M.; Dimitrov, A.; Glushkov, I.; Litov, L.; Pavlov, B.; Petkov, P.; Ahmad, M.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Chen, M.; Cheng, T.; Du, R.; Jiang, C. H.; Leggat, D.; Plestina, R.; Romeo, F.; Shaheen, S. M.; Spiezia, A.; Tao, J.; Wang, C.; Wang, Z.; Zhang, H.; Asawatangtrakuldee, C.; Ban, Y.; Li, Q.; Liu, S.; Mao, Y.; Qian, S. J.; Wang, D.; Xu, Z.; Avila, C.; Cabrera, A.; Chaparro Sierra, L. F.; Florez, C.; Gomez, J. P.; Gomez Moreno, B.; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Puljak, I.; Ribeiro Cipriano, P. M.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Kadija, K.; Luetic, J.; Micanovic, S.; Sudic, L.; Attikis, A.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Rykaczewski, H.; Bodlak, M.; Finger, M.; Finger, M.; Abdelalim, A. A.; Awad, A.; Mahrous, A.; Radi, A.; Calpas, B.; Kadastik, M.; Murumaa, M.; Raidal, M.; Tiko, A.; Veelken, C.; Eerola, P.; Pekkanen, J.; Voutilainen, M.; Härkönen, J.; Karimäki, V.; Kinnunen, R.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Peltola, T.; Tuominiemi, J.; Tuovinen, E.; Wendland, L.; Talvitie, J.; Tuuva, T.; Besancon, M.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Favaro, C.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; Hamel de Monchenault, G.; Jarry, P.; Locci, E.; Machet, M.; Malcles, J.; Rander, J.; Rosowsky, A.; Titov, M.; Zghiche, A.; Abdulsalam, A.; Antropov, I.; Baffioni, S.; Beaudette, F.; Busson, P.; Cadamuro, L.; Chapon, E.; Charlot, C.; Davignon, O.; Filipovic, N.; Granier de Cassagnac, R.; Jo, M.; Lisniak, S.; Mastrolorenzo, L.; Miné, P.; Naranjo, I. N.; Nguyen, M.; Ochando, C.; Ortona, G.; Paganini, P.; Pigard, P.; Regnard, S.; Salerno, R.; Sauvan, J. B.; Sirois, Y.; Strebler, T.; Yilmaz, Y.; Zabi, A.; Agram, J.-L.; Andrea, J.; Aubin, A.; Bloch, D.; Brom, J.-M.; Buttignol, M.; Chabert, E. C.; Chanon, N.; Collard, C.; Conte, E.; Coubez, X.; Fontaine, J.-C.; Gelé, D.; Goerlach, U.; Goetzmann, C.; Le Bihan, A.-C.; Merlin, J. A.; Skovpen, K.; Van Hove, P.; Gadrat, S.; Beauceron, S.; Bernet, C.; Boudoul, G.; Bouvier, E.; Carrillo Montoya, C. A.; Chierici, R.; Contardo, D.; Courbon, B.; Depasse, P.; El Mamouni, H.; Fan, J.; Fay, J.; Gascon, S.; Gouzevitch, M.; Ille, B.; Lagarde, F.; Laktineh, I. B.; Lethuillier, M.; Mirabito, L.; Pequegnot, A. L.; Perries, S.; Ruiz Alvarez, J. D.; Sabes, D.; Sordini, V.; Vander Donckt, M.; Verdier, P.; Viret, S.; Toriashvili, T.; Tsamalaidze, Z.; Autermann, C.; Beranek, S.; Feld, L.; Heister, A.; Kiesel, M. K.; Klein, K.; Lipinski, M.; Ostapchuk, A.; Preuten, M.; Raupach, F.; Schael, S.; Schulte, J. F.; Verlage, T.; Weber, H.; Zhukov, V.; Ata, M.; Brodski, M.; Dietz-Laursonn, E.; Duchardt, D.; Endres, M.; Erdmann, M.; Erdweg, S.; Esch, T.; Fischer, R.; Güth, A.; Hebbeker, T.; Heidemann, C.; Hoepfner, K.; Knutzen, S.; Kreuzer, P.; Merschmeyer, M.; Meyer, A.; Millet, P.; Mukherjee, S.; Olschewski, M.; Padeken, K.; Papacz, P.; Pook, T.; Radziej, M.; Reithler, H.; Rieger, M.; Scheuch, F.; Sonnenschein, L.; Teyssier, D.; Thüer, S.; Cherepanov, V.; Erdogan, Y.; Flügge, G.; Geenen, H.; Geisler, M.; Hoehle, F.; Kargoll, B.; Kress, T.; Künsken, A.; Lingemann, J.; Nehrkorn, A.; Nowack, A.; Nugent, I. M.; Pistone, C.; Pooth, O.; Stahl, A.; Aldaya Martin, M.; Asin, I.; Bartosik, N.; Behnke, O.; Behrens, U.; Borras, K.; Burgmeier, A.; Campbell, A.; Contreras-Campana, C.; Costanza, F.; Diez Pardos, C.; Dolinska, G.; Dooling, S.; Dorland, T.; Eckerlin, G.; Eckstein, D.; Eichhorn, T.; Flucke, G.; Gallo, E.; Garcia, J. Garay; Geiser, A.; Gizhko, A.; Gunnellini, P.; Hauk, J.; Hempel, M.; Jung, H.; Kalogeropoulos, A.; Karacheban, O.; Kasemann, M.; Katsas, P.; Kieseler, J.; Kleinwort, C.; Korol, I.; Lange, W.; Leonard, J.; Lipka, K.; Lobanov, A.; Lohmann, W.; Mankel, R.; Melzer-Pellmann, I.-A.; Meyer, A. B.; Mittag, G.; Mnich, J.; Mussgiller, A.; Naumann-Emme, S.; Nayak, A.; Ntomari, E.; Perrey, H.; Pitzl, D.; Placakyte, R.; Raspereza, A.; Roland, B.; Sahin, M. Ö.; Saxena, P.; Schoerner-Sadenius, T.; Seitz, C.; Spannagel, S.; Stefaniuk, N.; Trippkewitz, K. D.; Walsh, R.; Wissing, C.; Blobel, V.; Centis Vignali, M.; Draeger, A. R.; Erfle, J.; Garutti, E.; Goebel, K.; Gonzalez, D.; Görner, M.; Haller, J.; Hoffmann, M.; Höing, R. S.; Junkes, A.; Klanner, R.; Kogler, R.; Kovalchuk, N.; Lapsien, T.; Lenz, T.; Marchesini, I.; Marconi, D.; Meyer, M.; Nowatschin, D.; Ott, J.; Pantaleo, F.; Peiffer, T.; Perieanu, A.; Pietsch, N.; Poehlsen, J.; Rathjens, D.; Sander, C.; Scharf, C.; Schleper, P.; Schlieckau, E.; Schmidt, A.; Schumann, S.; Schwandt, J.; Sola, V.; Stadie, H.; Steinbrück, G.; Stober, F. M.; Tholen, H.; Troendle, D.; Usai, E.; Vanelderen, L.; Vanhoefer, A.; Vormwald, B.; Barth, C.; Baus, C.; Berger, J.; Böser, C.; Butz, E.; Chwalek, T.; Colombo, F.; De Boer, W.; Descroix, A.; Dierlamm, A.; Fink, S.; Frensch, F.; Friese, R.; Giffels, M.; Gilbert, A.; Haitz, D.; Hartmann, F.; Heindl, S. M.; Husemann, U.; Katkov, I.; Kornmayer, A.; Lobelle Pardo, P.; Maier, B.; Mildner, H.; Mozer, M. U.; Müller, T.; Müller, Th.; Plagge, M.; Quast, G.; Rabbertz, K.; Röcker, S.; Roscher, F.; Schröder, M.; Sieber, G.; Simonis, H. J.; Ulrich, R.; Wagner-Kuhr, J.; Wayand, S.; Weber, M.; Weiler, T.; Williamson, S.; Wöhrmann, C.; Wolf, R.; Anagnostou, G.; Daskalakis, G.; Geralis, T.; Giakoumopoulou, V. A.; Kyriakis, A.; Loukas, D.; Psallidas, A.; Topsis-Giotis, I.; Agapitos, A.; Kesisoglou, S.; Panagiotou, A.; Saoulidou, N.; Tziaferi, E.; Evangelou, I.; Flouris, G.; Foudas, C.; Kokkas, P.; Loukas, N.; Manthos, N.; Papadopoulos, I.; Paradas, E.; Strologas, J.; Bencze, G.; Hajdu, C.; Hazi, A.; Hidas, P.; Horvath, D.; Sikler, F.; Veszpremi, V.; Vesztergombi, G.; Zsigmond, A. J.; Beni, N.; Czellar, S.; Karancsi, J.; Molnar, J.; Szillasi, Z.; Bartók, M.; Makovec, A.; Raics, P.; Trocsanyi, Z. L.; Ujvari, B.; Choudhury, S.; Mal, P.; Mandal, K.; Sahoo, D. K.; Sahoo, N.; Swain, S. K.; Bansal, S.; Beri, S. B.; Bhatnagar, V.; Chawla, R.; Gupta, R.; Bhawandeep, U.; Kalsi, A. K.; Kaur, A.; Kaur, M.; Kumar, R.; Mehta, A.; Mittal, M.; Singh, J. B.; Walia, G.; Kumar, Ashok; Bhardwaj, A.; Choudhary, B. C.; Garg, R. B.; Malhotra, S.; Naimuddin, M.; Nishu, N.; Ranjan, K.; Sharma, R.; Sharma, V.; Bhattacharya, S.; Chatterjee, K.; Dey, S.; Dutta, S.; Majumdar, N.; Modak, A.; Mondal, K.; Mukhopadhyay, S.; Roy, A.; Roy, D.; Roy Chowdhury, S.; Sarkar, S.; Sharan, M.; Chudasama, R.; Dutta, D.; Jha, V.; Kumar, V.; Mohanty, A. K.; Pant, L. M.; Shukla, P.; Topkar, A.; Aziz, T.; Banerjee, S.; Bhowmik, S.; Chatterjee, R. M.; Dewanjee, R. K.; Dugad, S.; Ganguly, S.; Ghosh, S.; Guchait, M.; Gurtu, A.; Jain, Sa.; Kole, G.; Kumar, S.; Mahakud, B.; Maity, M.; Majumder, G.; Mazumdar, K.; Mitra, S.; Mohanty, G. B.; Parida, B.; Sarkar, T.; Sur, N.; Sutar, B.; Wickramage, N.; Chauhan, S.; Dube, S.; Kapoor, A.; Kothekar, K.; Sharma, S.; Bakhshiansohi, H.; Behnamian, H.; Etesami, S. M.; Fahim, A.; Khakzad, M.; Mohammadi Najafabadi, M.; Naseri, M.; Paktinat Mehdiabadi, S.; Rezaei Hosseinabadi, F.; Safarzadeh, B.; Zeinali, M.; Felcini, M.; Grunewald, M.; Abbrescia, M.; Calabria, C.; Caputo, C.; Colaleo, A.; Creanza, D.; Cristella, L.; De Filippis, N.; De Palma, M.; Fiore, L.; Iaselli, G.; Maggi, G.; Maggi, M.; Miniello, G.; My, S.; Nuzzo, S.; Pompili, A.; Pugliese, G.; Radogna, R.; Ranieri, A.; Selvaggi, G.; Silvestris, L.; Venditti, R.; Abbiendi, G.; Battilana, C.; Bonacorsi, D.; Braibant-Giacomelli, S.; Brigliadori, L.; Campanini, R.; Capiluppi, P.; Castro, A.; Cavallo, F. R.; Chhibra, S. S.; Codispoti, G.; Cuffiani, M.; Dallavalle, G. M.; Fabbri, F.; Fanfani, A.; Fasanella, D.; Giacomelli, P.; Grandi, C.; Guiducci, L.; Marcellini, S.; Masetti, G.; Montanari, A.; Navarria, F. L.; Perrotta, A.; Rossi, A. M.; Rovelli, T.; Siroli, G. P.; Tosi, N.; Cappello, G.; Chiorboli, M.; Costa, S.; Di Mattia, A.; Giordano, F.; Potenza, R.; Tricomi, A.; Tuve, C.; Barbagli, G.; Ciulli, V.; Civinini, C.; D'Alessandro, R.; Focardi, E.; Gori, V.; Lenzi, P.; Meschini, M.; Paoletti, S.; Sguazzoni, G.; Viliani, L.; Benussi, L.; Bianco, S.; Fabbri, F.; Piccolo, D.; Primavera, F.; Calvelli, V.; Ferro, F.; Lo Vetere, M.; Monge, M. R.; Robutti, E.; Tosi, S.; Brianza, L.; Dinardo, M. E.; Fiorendi, S.; Gennai, S.; Gerosa, R.; Ghezzi, A.; Govoni, P.; Malvezzi, S.; Manzoni, R. A.; Marzocchi, B.; Menasce, D.; Moroni, L.; Paganoni, M.; Pedrini, D.; Ragazzi, S.; Redaelli, N.; Tabarelli de Fatis, T.; Buontempo, S.; Cavallo, N.; Di Guida, S.; Esposito, M.; Fabozzi, F.; Iorio, A. O. M.; Lanza, G.; Lista, L.; Meola, S.; Merola, M.; Paolucci, P.; Sciacca, C.; Thyssen, F.; Azzi, P.; Bacchetta, N.; Benato, L.; Bisello, D.; Boletti, A.; Branca, A.; Carlin, R.; Checchia, P.; Dall'Osso, M.; Dorigo, T.; Dosselli, U.; Fanzago, F.; Gasparini, F.; Gasparini, U.; Gozzelino, A.; Kanishchev, K.; Lacaprara, S.; Margoni, M.; Meneguzzo, A. T.; Pazzini, J.; Pozzobon, N.; Ronchese, P.; Simonetto, F.; Torassa, E.; Tosi, M.; Zanetti, M.; Zotto, P.; Zucchetta, A.; Zumerle, G.; Braghieri, A.; Magnani, A.; Montagna, P.; Ratti, S. P.; Re, V.; Riccardi, C.; Salvini, P.; Vai, I.; Vitulo, P.; Alunni Solestizi, L.; Bilei, G. M.; Ciangottini, D.; Fanò, L.; Lariccia, P.; Mantovani, G.; Menichelli, M.; Saha, A.; Santocchia, A.; Androsov, K.; Azzurri, P.; Bagliesi, G.; Bernardini, J.; Boccali, T.; Castaldi, R.; Ciocci, M. A.; Dell'Orso, R.; Donato, S.; Fedi, G.; Foà, L.; Giassi, A.; Grippo, M. T.; Ligabue, F.; Lomtadze, T.; Martini, L.; Messineo, A.; Palla, F.; Rizzi, A.; Savoy-Navarro, A.; Serban, A. T.; Spagnolo, P.; Tenchini, R.; Tonelli, G.; Venturi, A.; Verdini, P. G.; Barone, L.; Cavallari, F.; D'imperio, G.; Del Re, D.; Diemoz, M.; Gelli, S.; Jorda, C.; Longo, E.; Margaroli, F.; Meridiani, P.; Organtini, G.; Paramatti, R.; Preiato, F.; Rahatlou, S.; Rovelli, C.; Santanastasio, F.; Traczyk, P.; Amapane, N.; Arcidiacono, R.; Argiro, S.; Arneodo, M.; Bellan, R.; Biino, C.; Cartiglia, N.; Costa, M.; Covarelli, R.; Degano, A.; Demaria, N.; Finco, L.; Kiani, B.; Mariotti, C.; Maselli, S.; Migliore, E.; Monaco, V.; Monteil, E.; Obertino, M. M.; Pacher, L.; Pastrone, N.; Pelliccioni, M.; Pinna Angioni, G. L.; Ravera, F.; Romero, A.; Ruspa, M.; Sacchi, R.; Solano, A.; Staiano, A.; Belforte, S.; Candelise, V.; Casarsa, M.; Cossutti, F.; Della Ricca, G.; Gobbo, B.; La Licata, C.; Marone, M.; Schizzi, A.; Zanetti, A.; Kropivnitskaya, A.; Nam, S. K.; Kim, D. H.; Kim, G. N.; Kim, M. S.; Kong, D. J.; Lee, S.; Oh, Y. D.; Sakharov, A.; Son, D. C.; Brochero Cifuentes, J. A.; Kim, H.; Kim, T. J.; Song, S.; Cho, S.; Choi, S.; Go, Y.; Gyun, D.; Hong, B.; Kim, H.; Kim, Y.; Lee, B.; Lee, K.; Lee, K. S.; Lee, S.; Lim, J.; Park, S. K.; Roh, Y.; Yoo, H. D.; Choi, M.; Kim, H.; Kim, J. H.; Lee, J. S. H.; Park, I. C.; Ryu, G.; Ryu, M. S.; Choi, Y.; Goh, J.; Kim, D.; Kwon, E.; Lee, J.; Yu, I.; Dudenas, V.; Juodagalvis, A.; Vaitkus, J.; Ahmed, I.; Ibrahim, Z. A.; Komaragiri, J. R.; Md Ali, M. A. B.; Mohamad Idris, F.; Wan Abdullah, W. A. T.; Yusli, M. N.; Zolkapli, Z.; Casimiro Linares, E.; Castilla-Valdez, H.; De La Cruz-Burelo, E.; Heredia-De La Cruz, I.; Hernandez-Almada, A.; Lopez-Fernandez, R.; Mejia Guisao, J.; Sanchez-Hernandez, A.; Carrillo Moreno, S.; Vazquez Valencia, F.; Pedraza, I.; Salazar Ibarguen, H. A.; Morelos Pineda, A.; Krofcheck, D.; Butler, P. H.; Ahmad, A.; Ahmad, M.; Hassan, Q.; Hoorani, H. R.; Khan, W. A.; Khurshid, T.; Shoaib, M.; Waqas, M.; Bialkowska, H.; Bluj, M.; Boimska, B.; Frueboes, T.; Górski, M.; Kazana, M.; Nawrocki, K.; Romanowska-Rybinska, K.; Szleper, M.; Zalewski, P.; Brona, G.; Bunkowski, K.; Byszuk, A.; Doroba, K.; Kalinowski, A.; Konecki, M.; Krolikowski, J.; Misiura, M.; Olszewski, M.; Walczak, M.; Bargassa, P.; Da Cruz E Silva, C. Beirão; Di Francesco, A.; Faccioli, P.; Parracho, P. G. Ferreira; Gallinaro, M.; Hollar, J.; Leonardo, N.; Lloret Iglesias, L.; Nguyen, F.; Rodrigues Antunes, J.; Seixas, J.; Toldaiev, O.; Vadruccio, D.; Varela, J.; Vischia, P.; Afanasiev, S.; Bunin, P.; Gavrilenko, M.; Golutvin, I.; Gorbunov, I.; Kamenev, A.; Karjavin, V.; Lanev, A.; Malakhov, A.; Matveev, V.; Moisenz, P.; Palichik, V.; Perelygin, V.; Shmatov, S.; Shulha, S.; Skatchkov, N.; Smirnov, V.; Zarubin, A.; Golovtsov, V.; Ivanov, Y.; Kim, V.; Kuznetsova, E.; Levchenko, P.; Murzin, V.; Oreshkin, V.; Smirnov, I.; Sulimov, V.; Uvarov, L.; Vavilov, S.; Vorobyev, A.; Andreev, Yu.; Dermenev, A.; Gninenko, S.; Golubev, N.; Karneyeu, A.; Kirsanov, M.; Krasnikov, N.; Pashenkov, A.; Tlisov, D.; Toropin, A.; Epshteyn, V.; Gavrilov, V.; Lychkovskaya, N.; Popov, V.; Pozdnyakov, l.; Safronov, G.; Spiridonov, A.; Vlasov, E.; Zhokin, A.; Chadeeva, M.; Chistov, R.; Danilov, M.; Rusinov, V.; Tarkovskii, E.; Andreev, V.; Azarkin, M.; Dremin, I.; Kirakosyan, M.; Leonidov, A.; Mesyats, G.; Rusakov, S. V.; Baskakov, A.; Belyaev, A.; Boos, E.; Ershov, A.; Gribushin, A.; Kaminskiy, A.; Kodolova, O.; Korotkikh, V.; Lokhtin, I.; Miagkov, I.; Obraztsov, S.; Petrushanko, S.; Savrin, V.; Snigirev, A.; Vardanyan, I.; Azhgirey, I.; Bayshev, I.; Bitioukov, S.; Kachanov, V.; Kalinin, A.; Konstantinov, D.; Krychkine, V.; Petrov, V.; Ryutin, R.; Sobol, A.; Tourtchanovitch, L.; Troshin, S.; Tyurin, N.; Uzunian, A.; Volkov, A.; Adzic, P.; Cirkovic, P.; Devetak, D.; Milosevic, J.; Rekovic, V.; Alcaraz Maestre, J.; Calvo, E.; Cerrada, M.; Chamizo Llatas, M.; Colino, N.; De La Cruz, B.; Delgado Peris, A.; Escalante Del Valle, A.; Fernandez Bedoya, C.; Ramos, J. P. Fernández; Flix, J.; Fouz, M. C.; Garcia-Abia, P.; Gonzalez Lopez, O.; Goy Lopez, S.; Hernandez, J. M.; Josa, M. I.; Navarro De Martino, E.; Yzquierdo, A. Pérez-Calero; Puerta Pelayo, J.; Quintario Olmeda, A.; Redondo, I.; Romero, L.; Soares, M. S.; Albajar, C.; de Trocóniz, J. F.; Missiroli, M.; Moran, D.; Cuevas, J.; Fernandez Menendez, J.; Folgueras, S.; Gonzalez Caballero, I.; Palencia Cortezon, E.; Vizan Garcia, J. M.; Cabrillo, I. J.; Calderon, A.; Castiñeiras De Saa, J. R.; Curras, E.; De Castro Manzano, P.; Fernandez, M.; Garcia-Ferrero, J.; Gomez, G.; Lopez Virto, A.; Marco, J.; Marco, R.; Martinez Rivero, C.; Matorras, F.; Piedra Gomez, J.; Rodrigo, T.; Rodríguez-Marrero, A. Y.; Ruiz-Jimeno, A.; Scodellaro, L.; Trevisani, N.; Vila, I.; Vilar Cortabitarte, R.; Abbaneo, D.; Auffray, E.; Auzinger, G.; Bachtis, M.; Baillon, P.; Ball, A. H.; Barney, D.; Benaglia, A.; Bendavid, J.; Benhabib, L.; Berruti, G. M.; Bloch, P.; Bocci, A.; Bonato, A.; Botta, C.; Breuker, H.; Camporesi, T.; Castello, R.; Cepeda, M.; Cerminara, G.; D'Alfonso, M.; d'Enterria, D.; Dabrowski, A.; Daponte, V.; David, A.; De Gruttola, M.; De Guio, F.; De Roeck, A.; De Visscher, S.; Di Marco, E.; Dobson, M.; Dordevic, M.; Dorney, B.; du Pree, T.; Duggan, D.; Dünser, M.; Dupont, N.; Elliott-Peisert, A.; Franzoni, G.; Fulcher, J.; Funk, W.; Gigi, D.; Gill, K.; Giordano, D.; Girone, M.; Glege, F.; Guida, R.; Gundacker, S.; Guthoff, M.; Hammer, J.; Harris, P.; Hegeman, J.; Innocente, V.; Janot, P.; Kirschenmann, H.; Kortelainen, M. J.; Kousouris, K.; Krajczar, K.; Lecoq, P.; Lourenço, C.; Lucchini, M. T.; Magini, N.; Malgeri, L.; Mannelli, M.; Martelli, A.; Masetti, L.; Meijers, F.; Mersi, S.; Meschi, E.; Moortgat, F.; Morovic, S.; Mulders, M.; Nemallapudi, M. 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M.; Maruyama, S.; Mason, D.; McBride, P.; Merkel, P.; Mrenna, S.; Nahn, S.; Newman-Holmes, C.; O'Dell, V.; Pedro, K.; Prokofyev, O.; Rakness, G.; Sexton-Kennedy, E.; Soha, A.; Spalding, W. J.; Spiegel, L.; Stoynev, S.; Strobbe, N.; Taylor, L.; Tkaczyk, S.; Tran, N. V.; Uplegger, L.; Vaandering, E. W.; Vernieri, C.; Verzocchi, M.; Vidal, R.; Wang, M.; Weber, H. A.; Whitbeck, A.; Acosta, D.; Avery, P.; Bortignon, P.; Bourilkov, D.; Brinkerhoff, A.; Carnes, A.; Carver, M.; Curry, D.; Das, S.; Field, R. D.; Furic, I. K.; Konigsberg, J.; Korytov, A.; Kotov, K.; Ma, P.; Matchev, K.; Mei, H.; Milenovic, P.; Mitselmakher, G.; Rank, D.; Rossin, R.; Shchutska, L.; Snowball, M.; Sperka, D.; Terentyev, N.; Thomas, L.; Wang, J.; Wang, S.; Yelton, J.; Hewamanage, S.; Linn, S.; Markowitz, P.; Martinez, G.; Rodriguez, J. L.; Ackert, A.; Adams, J. R.; Adams, T.; Askew, A.; Bein, S.; Bochenek, J.; Diamond, B.; Haas, J.; Hagopian, S.; Hagopian, V.; Johnson, K. F.; Khatiwada, A.; Prosper, H.; Weinberg, M.; Baarmand, M. M.; Bhopatkar, V.; Colafranceschi, S.; Hohlmann, M.; Kalakhety, H.; Noonan, D.; Roy, T.; Yumiceva, F.; Adams, M. R.; Apanasevich, L.; Berry, D.; Betts, R. R.; Bucinskaite, I.; Cavanaugh, R.; Evdokimov, O.; Gauthier, L.; Gerber, C. E.; Hofman, D. J.; Kurt, P.; O'Brien, C.; Sandoval Gonzalez, l. D.; Turner, P.; Varelas, N.; Wu, Z.; Zakaria, M.; Zhang, J.; Bilki, B.; Clarida, W.; Dilsiz, K.; Durgut, S.; Gandrajula, R. P.; Haytmyradov, M.; Khristenko, V.; Merlo, J.-P.; Mermerkaya, H.; Mestvirishvili, A.; Moeller, A.; Nachtman, J.; Ogul, H.; Onel, Y.; Ozok, F.; Penzo, A.; Snyder, C.; Tiras, E.; Wetzel, J.; Yi, K.; Anderson, I.; Barnett, B. A.; Blumenfeld, B.; Cocoros, A.; Eminizer, N.; Fehling, D.; Feng, L.; Gritsan, A. V.; Maksimovic, P.; Osherson, M.; Roskes, J.; Sarica, U.; Swartz, M.; Xiao, M.; Xin, Y.; You, C.; Baringer, P.; Bean, A.; Bruner, C.; Kenny, R. P.; Majumder, D.; Malek, M.; Mcbrayer, W.; Murray, M.; Sanders, S.; Stringer, R.; Wang, Q.; Ivanov, A.; Kaadze, K.; Khalil, S.; Makouski, M.; Maravin, Y.; Mohammadi, A.; Saini, L. K.; Skhirtladze, N.; Toda, S.; Lange, D.; Rebassoo, F.; Wright, D.; Anelli, C.; Baden, A.; Baron, O.; Belloni, A.; Calvert, B.; Eno, S. C.; Ferraioli, C.; Gomez, J. A.; Hadley, N. J.; Jabeen, S.; Kellogg, R. G.; Kolberg, T.; Kunkle, J.; Lu, Y.; Mignerey, A. C.; Shin, Y. H.; Skuja, A.; Tonjes, M. B.; Tonwar, S. C.; Apyan, A.; Barbieri, R.; Baty, A.; Bi, R.; Bierwagen, K.; Brandt, S.; Busza, W.; Cali, I. A.; Demiragli, Z.; Di Matteo, L.; Gomez Ceballos, G.; Goncharov, M.; Gulhan, D.; Iiyama, Y.; Innocenti, G. M.; Klute, M.; Kovalskyi, D.; Lai, Y. S.; Lee, Y.-J.; Levin, A.; Luckey, P. D.; Marini, A. C.; Mcginn, C.; Mironov, C.; Narayanan, S.; Niu, X.; Paus, C.; Roland, C.; Roland, G.; Salfeld-Nebgen, J.; Stephans, G. S. F.; Sumorok, K.; Tatar, K.; Varma, M.; Velicanu, D.; Veverka, J.; Wang, J.; Wang, T. W.; Wyslouch, B.; Yang, M.; Zhukova, V.; Benvenuti, A. C.; Dahmes, B.; Evans, A.; Finkel, A.; Gude, A.; Hansen, P.; Kalafut, S.; Kao, S. C.; Klapoetke, K.; Kubota, Y.; Lesko, Z.; Mans, J.; Nourbakhsh, S.; Ruckstuhl, N.; Rusack, R.; Tambe, N.; Turkewitz, J.; Acosta, J. G.; Oliveros, S.; Avdeeva, E.; Bartek, R.; Bloom, K.; Bose, S.; Claes, D. R.; Dominguez, A.; Fangmeier, C.; Gonzalez Suarez, R.; Kamalieddin, R.; Knowlton, D.; Kravchenko, I.; Meier, F.; Monroy, J.; Ratnikov, F.; Siado, J. E.; Snow, G. R.; Alyari, M.; Dolen, J.; George, J.; Godshalk, A.; Harrington, C.; Iashvili, I.; Kaisen, J.; Kharchilava, A.; Kumar, A.; Rappoccio, S.; Roozbahani, B.; Alverson, G.; Barberis, E.; Baumgartel, D.; Chasco, M.; Hortiangtham, A.; Massironi, A.; Morse, D. M.; Nash, D.; Orimoto, T.; Teixeira De Lima, R.; Trocino, D.; Wang, R.-J.; Wood, D.; Zhang, J.; Bhattacharya, S.; Hahn, K. A.; Kubik, A.; Low, J. F.; Mucia, N.; Odell, N.; Pollack, B.; Schmitt, M.; Sung, K.; Trovato, M.; Velasco, M.; Dev, N.; Hildreth, M.; Jessop, C.; Karmgard, D. J.; Kellams, N.; Lannon, K.; Marinelli, N.; Meng, F.; Mueller, C.; Musienko, Y.; Planer, M.; Reinsvold, A.; Ruchti, R.; Smith, G.; Taroni, S.; Valls, N.; Wayne, M.; Wolf, M.; Woodard, A.; Antonelli, L.; Brinson, J.; Bylsma, B.; Durkin, L. S.; Flowers, S.; Hart, A.; Hill, C.; Hughes, R.; Ji, W.; Ling, T. Y.; Liu, B.; Luo, W.; Puigh, D.; Rodenburg, M.; Winer, B. L.; Wulsin, H. W.; Driga, O.; Elmer, P.; Hardenbrook, J.; Hebda, P.; Koay, S. A.; Lujan, P.; Marlow, D.; Medvedeva, T.; Mooney, M.; Olsen, J.; Palmer, C.; Piroué, P.; Stickland, D.; Tully, C.; Zuranski, A.; Malik, S.; Barker, A.; Barnes, V. E.; Benedetti, D.; Bortoletto, D.; Gutay, L.; Jha, M. K.; Jones, M.; Jung, A. W.; Jung, K.; Kumar, A.; Miller, D. H.; Neumeister, N.; Radburn-Smith, B. C.; Shi, X.; Shipsey, I.; Silvers, D.; Sun, J.; Svyatkovskiy, A.; Wang, F.; Xie, W.; Xu, L.; Parashar, N.; Stupak, J.; Adair, A.; Akgun, B.; Chen, Z.; Ecklund, K. M.; Geurts, F. J. M.; Guilbaud, M.; Li, W.; Michlin, B.; Northup, M.; Padley, B. P.; Redjimi, R.; Roberts, J.; Rorie, J.; Tu, Z.; Zabel, J.; Betchart, B.; Bodek, A.; de Barbaro, P.; Demina, R.; Eshaq, Y.; Ferbel, T.; Galanti, M.; Garcia-Bellido, A.; Han, J.; Hindrichs, O.; Khukhunaishvili, A.; Lo, K. H.; Tan, P.; Verzetti, M.; Chou, J. P.; Contreras-Campana, E.; Ferencek, D.; Gershtein, Y.; Halkiadakis, E.; Heindl, M.; Hidas, D.; Hughes, E.; Kaplan, S.; Kunnawalkam Elayavalli, R.; Lath, A.; Nash, K.; Saka, H.; Salur, S.; Schnetzer, S.; Sheffield, D.; Somalwar, S.; Stone, R.; Thomas, S.; Thomassen, P.; Walker, M.; Foerster, M.; Riley, G.; Rose, K.; Spanier, S.; Thapa, K.; Bouhali, O.; Castaneda Hernandez, A.; Celik, A.; Dalchenko, M.; De Mattia, M.; Delgado, A.; Dildick, S.; Eusebi, R.; Gilmore, J.; Huang, T.; Kamon, T.; Krutelyov, V.; Mueller, R.; Osipenkov, I.; Pakhotin, Y.; Patel, R.; Perloff, A.; Rose, A.; Safonov, A.; Tatarinov, A.; Ulmer, K. A.; Akchurin, N.; Cowden, C.; Damgov, J.; Dragoiu, C.; Dudero, P. R.; Faulkner, J.; Kunori, S.; Lamichhane, K.; Lee, S. W.; Libeiro, T.; Undleeb, S.; Volobouev, I.; Appelt, E.; Delannoy, A. G.; Greene, S.; Gurrola, A.; Janjam, R.; Johns, W.; Maguire, C.; Mao, Y.; Melo, A.; Ni, H.; Sheldon, P.; Tuo, S.; Velkovska, J.; Xu, Q.; Arenton, M. W.; Cox, B.; Francis, B.; Goodell, J.; Hirosky, R.; Ledovskoy, A.; Li, H.; Lin, C.; Neu, C.; Sinthuprasith, T.; Sun, X.; Wang, Y.; Wolfe, E.; Wood, J.; Xia, F.; Clarke, C.; Harr, R.; Karchin, P. E.; Kottachchi Kankanamge Don, C.; Lamichhane, P.; Sturdy, J.; Belknap, D. A.; Carlsmith, D.; Dasu, S.; Dodd, L.; Duric, S.; Gomber, B.; Grothe, M.; Herndon, M.; Hervé, A.; Klabbers, P.; Lanaro, A.; Levine, A.; Long, K.; Loveless, R.; Mohapatra, A.; Ojalvo, I.; Perry, T.; Pierro, G. A.; Polese, G.; Ruggles, T.; Sarangi, T.; Savin, A.; Sharma, A.; Smith, N.; Smith, W. H.; Taylor, D.; Verwilligen, P.; Woods, N.; CMS Collaboration

2016-07-01

Inclusive jet production in pPb collisions at a nucleon-nucleon (NN) center-of-mass energy of √{s_{_NN}} =5.02 TeV is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 30.1 nb^{-1} is analyzed. The jet transverse momentum spectra are studied in seven pseudorapidity intervals covering the range -2.0<η _{CM}< 1.5 in the NN center-of-mass frame. The jet production yields at forward and backward pseudorapidity are compared and no significant asymmetry about η _{CM} = 0 is observed in the measured kinematic range. The measurements in the pPb system are compared to reference jet spectra obtained by extrapolation from previous measurements in pp collisions at √{s}=7 TeV . In all pseudorapidity ranges, nuclear modifications in inclusive jet production are found to be small, as predicted by next-to-leading order perturbative QCD calculations that incorporate nuclear effects in the parton distribution functions.

Proto-jet configurations in RADs orbiting a Kerr SMBH: symmetries and limiting surfaces

NASA Astrophysics Data System (ADS)

Pugliese, D.; Stuchlík, Z.

2018-05-01

Ringed accretion disks (RADs) are agglomerations of perfect-fluid tori orbiting around a single central attractor that could arise during complex matter inflows in active galactic nuclei. We focus our analysis to axi-symmetric accretion tori orbiting in the equatorial plane of a supermassive Kerr black hole; equilibrium configurations, possible instabilities, and evolutionary sequences of RADs were discussed in our previous works. In the present work we discuss special instabilities related to open equipotential surfaces governing the material funnels emerging at various regions of the RADs, being located between two or more individual toroidal configurations of the agglomerate. These open structures could be associated to proto-jets. Boundary limiting surfaces are highlighted, connecting the emergency of the jet-like instabilities with the black hole dimensionless spin. These instabilities are observationally significant for active galactic nuclei, being related to outflows of matter in jets emerging from more than one torus of RADs orbiting around supermassive black holes.

Linear Polarization Properties of Parsec-Scale AGN Jets

NASA Astrophysics Data System (ADS)

Pushkarev, Alexander; Kovalev, Yuri; Lister, Matthew; Savolainen, Tuomas; Aller, Margo; Aller, Hugh; Hodge, Mary

2017-12-01

We used 15 GHz multi-epoch Very Long Baseline Array (VLBA) polarization sensitive observations of 484 sources within a time interval 1996--2016 from the MOJAVE program, and also from the NRAO data archive. We have analyzed the linear polarization characteristics of the compact core features and regions downstream, and their changes along and across the parsec-scale active galactic nuclei (AGN) jets. We detected a significant increase of fractional polarization with distance from the radio core along the jet as well as towards the jet edges. Compared to quasars, BL Lacs have a higher degree of polarization and exhibit more stable electric vector position angles (EVPAs) in their core features and a better alignment of the EVPAs with the local jet direction. The latter is accompanied by a higher degree of linear polarization, suggesting that compact bright jet features might be strong transverse shocks, which enhance magnetic field regularity by compression.

MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VIII. Faraday Rotation in Parsec-scale AGN Jets

NASA Astrophysics Data System (ADS)

Hovatta, Talvikki; Lister, Matthew L.; Aller, Margo F.; Aller, Hugh D.; Homan, Daniel C.; Kovalev, Yuri Y.; Pushkarev, Alexander B.; Savolainen, Tuomas

2012-10-01

We report observations of Faraday rotation measures for a sample of 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array observations were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. We detect parsec-scale Faraday rotation measures in 149 sources and find the quasars to have larger rotation measures on average than BL Lac objects. The median core rotation measures are significantly higher than in the jet components. This is especially true for quasars where we detect a significant negative correlation between the magnitude of the rotation measure and the de-projected distance from the core. We perform detailed simulations of the observational errors of total intensity, polarization, and Faraday rotation, and concentrate on the errors of transverse Faraday rotation measure gradients in unresolved jets. Our simulations show that the finite image restoring beam size has a significant effect on the observed rotation measure gradients, and spurious gradients can occur due to noise in the data if the jet is less than two beams wide in polarization. We detect significant transverse rotation measure gradients in four sources (0923+392, 1226+023, 2230+114, and 2251+158). In 1226+023 the rotation measure is for the first time seen to change sign from positive to negative over the transverse cuts, which supports the presence of a helical magnetic field in the jet. In this source we also detect variations in the jet rotation measure over a timescale of three months, which are difficult to explain with external Faraday screens and suggest internal Faraday rotation. By comparing fractional polarization changes in jet components between the four frequency bands to depolarization models, we find that an external purely random Faraday screen viewed through only a few lines of sight can explain most of our polarization observations, but in some sources, such as 1226+023 and 2251+158, internal

MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. VIII. FARADAY ROTATION IN PARSEC-SCALE AGN JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hovatta, Talvikki; Lister, Matthew L.; Aller, Margo F.

2012-10-01

We report observations of Faraday rotation measures for a sample of 191 extragalactic radio jets observed within the MOJAVE program. Multifrequency Very Long Baseline Array observations were carried out over 12 epochs in 2006 at four frequencies between 8 and 15 GHz. We detect parsec-scale Faraday rotation measures in 149 sources and find the quasars to have larger rotation measures on average than BL Lac objects. The median core rotation measures are significantly higher than in the jet components. This is especially true for quasars where we detect a significant negative correlation between the magnitude of the rotation measure andmore » the de-projected distance from the core. We perform detailed simulations of the observational errors of total intensity, polarization, and Faraday rotation, and concentrate on the errors of transverse Faraday rotation measure gradients in unresolved jets. Our simulations show that the finite image restoring beam size has a significant effect on the observed rotation measure gradients, and spurious gradients can occur due to noise in the data if the jet is less than two beams wide in polarization. We detect significant transverse rotation measure gradients in four sources (0923+392, 1226+023, 2230+114, and 2251+158). In 1226+023 the rotation measure is for the first time seen to change sign from positive to negative over the transverse cuts, which supports the presence of a helical magnetic field in the jet. In this source we also detect variations in the jet rotation measure over a timescale of three months, which are difficult to explain with external Faraday screens and suggest internal Faraday rotation. By comparing fractional polarization changes in jet components between the four frequency bands to depolarization models, we find that an external purely random Faraday screen viewed through only a few lines of sight can explain most of our polarization observations, but in some sources, such as 1226+023 and 2251

Simulations of Astrophysical Jets in Dense Environments

NASA Astrophysics Data System (ADS)

Krause, Martin; Gaibler, Volker; Camenzind, Max

We have simulated the interaction of jets with a galactic wind at high resolution using the magnetohydrodynamics code NIRVANA on the NEC SX-6 at the HLRS. This setup may describe a typical situation for the starbursting radio galaxies of the early universe. The results show a clear resolution dependence in the expected way, but the formed clumps are denser than expected from linear extrapolation. We also report our recent progress in the adaptation of the magnetic part of NIRVANA to the SX-6. The code is now fully tuned to the machine and reached more than 3 Gflops. We plan to use this new code version to extend our study of magnetized jets down to very low jet densities. This should be especially applicable to the conditions in the young universe.

AGN jets under the microscope: A divide? Doctoral Thesis Award Lecture 2011

NASA Astrophysics Data System (ADS)

Karouzos, M.; Britzen, S.; Witzel, A.; Zensus, A. J.; Eckart, A.

2012-06-01

A new paradigm for active galactic jet kinematics has emerged through detailed investigations of BL Lac objects using very long baseline radio interferometry. In this new scheme, most, if not all, jet components appear to remain stationary with respect to the core but show significant non-radial motions. This paper presents results from our kinematic investigation of the jets of a statistically complete sample of radio-loud flat-spectrum active galaxies, focusing on the comparison between the jet kinematic properties of BL Lacs and flat-spectrum radio-quasars. It is shown that there is a statistically significant difference between the kinematics of the two AGN classes, with BL Lacs showing more bent jets, that are wider and show slower movement along the jet axis, compared to flat-spectrum radio-quasars. This is interpreted as evidence for helically structured jets.

On the internal structure of relativistic jets collimated by ambient gas pressure

NASA Astrophysics Data System (ADS)

Beskin, V. S.; Chernoglazov, A. V.; Kiselev, A. M.; Nokhrina, E. E.

2017-12-01

Recent progress in very long baseline interferometry (VLBI) observations of relativistic jets outflowing from active galactic nuclei gives us direct information about jet width rjet(l) dependence on the distance l from the 'central engine'. Being the missing link in previous works, this relation opens the possibility of determining the internal structure of a jet. In this article, we consider a relativistic jet submerged in an external medium with finite gas pressure Pext. Neither an external magnetic field nor an infinitely thin current sheet will be assumed. This approach allows us to construct a reasonable solution in which both the magnetic field and the flow velocity vanish at the jet boundary r = rjet. In particular, the connection between external gas pressure and internal structure of a relativistic jet is determined.

Measurement of charged jet production cross sections and nuclear modification in p-Pb collisions at √{sNN} = 5.02 TeV

NASA Astrophysics Data System (ADS)

Adam, J.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahn, S. U.; Aimo, I.; Aiola, S.; Ajaz, M.; Akindinov, A.; Alam, S. N.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altinpinar, S.; Altsybeev, I.; Alves Garcia Prado, C.; Andrei, C.; Andronic, A.; Anguelov, V.; Anielski, J.; Antičić, T.; Antinori, F.; Antonioli, P.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Armesto, N.; Arnaldi, R.; Aronsson, T.; Arsene, I. C.; Arslandok, M.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Bach, M.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Baldisseri, A.; Baltasar Dos Santos Pedrosa, F.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Belmont, R.; Belmont-Moreno, E.; Belyaev, V.; Bencedi, G.; Beole, S.; Berceanu, I.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biswas, S.; Bjelogrlic, S.; Blanco, F.; Blau, D.; Blume, C.; Bock, F.; Bogdanov, A.; Bøggild, H.; Boldizsár, L.; Bombara, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Bossú, F.; Botje, M.; Botta, E.; Böttger, S.; Braun-Munzinger, P.; Bregant, M.; Breitner, T.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buncic, P.; Busch, O.; Buthelezi, Z.; Buxton, J. T.; Caffarri, D.; Cai, X.; Caines, H.; Calero Diaz, L.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Carena, F.; Carena, W.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Cavicchioli, C.; Ceballos Sanchez, C.; Cepila, J.; Cerello, P.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chelnokov, V.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Chunhui, Z.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Conesa Balbastre, G.; Conesa del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Crochet, P.; Cruz Albino, R.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; De, S.; De Caro, A.; de Cataldo, G.; de Cuveland, J.; De Falco, A.; De Gruttola, D.; De Marco, N.; De Pasquale, S.; Deisting, A.; Deloff, A.; Dénes, E.; D'Erasmo, G.; Di Bari, D.; Di Mauro, A.; Di Nezza, P.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Dobrowolski, T.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Engel, H.; Erazmus, B.; Erhardt, F.; Eschweiler, D.; Espagnon, B.; Estienne, M.; Esumi, S.; Eum, J.; Evans, D.; Evdokimov, S.; Eyyubova, G.; Fabbietti, L.; Fabris, D.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Felea, D.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Fleck, M. G.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Frankenfeld, U.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gallio, M.; Gangadharan, D. R.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Gargiulo, C.; Gasik, P.; Germain, M.; Gheata, A.; Gheata, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Gomez Ramirez, A.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Graczykowski, L. K.; Grelli, A.; Grigoras, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grinyov, B.; Grion, N.; Grosse-Oetringhaus, J. F.; Grossiord, J.-Y.; Grosso, R.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gulkanyan, H.; Gunji, T.; Gupta, A.; Gupta, R.; Haake, R.; Haaland, Ø.; Hadjidakis, C.; Haiduc, M.; Hamagaki, H.; Hamar, G.; Hanratty, L. D.; Hansen, A.; Harris, J. W.; Hartmann, H.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Heide, M.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Hess, B. A.; Hetland, K. F.; Hilden, T. E.; Hillemanns, H.; Hippolyte, B.; Hristov, P.; Huang, M.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Ilkiv, I.; Inaba, M.; Ionita, C.; Ippolitov, M.; Irfan, M.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jacobs, P. M.; Jahnke, C.; Jang, H. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jimenez Bustamante, R. T.; Jones, P. G.; Jung, H.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kamin, J.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Khan, K. H.; Khan, M. M.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Kileng, B.; Kim, B.; Kim, D. W.; Kim, D. J.; Kim, H.; Kim, J. S.; Kim, M.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobayashi, T.; Kobdaj, C.; Kofarago, M.; Köhler, M. K.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kouzinopoulos, C.; Kovalenko, O.; Kovalenko, V.; Kowalski, M.; Kox, S.; Koyithatta Meethaleveedu, G.; Kral, J.; Králik, I.; Kravčáková, A.; Krelina, M.; Kretz, M.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kugathasan, T.; Kuhn, C.; Kuijer, P. G.; Kulakov, I.; Kumar, J.; Kumar, L.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kushpil, S.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lea, R.; Leardini, L.; Lee, G. R.; Lee, S.; Legrand, I.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; Leoncino, M.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Ljunggren, H. M.; Lodato, D. F.; Loenne, P. I.; Loggins, V. R.; Loginov, V.; Loizides, C.; Lopez, X.; López Torres, E.; Lowe, A.; Luettig, P.; Lunardon, M.; Luparello, G.; Luz, P. H. F. N. D.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manceau, L.; Manko, V.; Manso, F.; Manzari, V.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martin, N. A.; Martin Blanco, J.; Martinengo, P.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Martynov, Y.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Massacrier, L.; Mastroserio, A.; Masui, H.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzoni, M. A.; Mcdonald, D.; Meddi, F.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Miake, Y.; Mieskolainen, M. M.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Minervini, L. M.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Molnar, L.; Montaño Zetina, L.; Montes, E.; Morando, M.; Moreira De Godoy, D. A.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Müller, H.; Mulligan, J. D.; Munhoz, M. G.; Murray, S.; Musa, L.; Musinsky, J.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Nattrass, C.; Nayak, K.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Nellen, L.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Oh, S. K.; Ohlson, A.; Okatan, A.; Okubo, T.; Olah, L.; Oleniacz, J.; Oliveira Da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Ozdemir, M.; Pachmayer, Y.; Pagano, P.; Paić, G.; Pajares, C.; Pal, S. K.; Pan, J.; Pandey, A. K.; Pant, D.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, W. J.; Parmar, S.; Passfeld, A.; Paticchio, V.; Paul, B.; Peitzmann, T.; Pereira Da Costa, H.; Pereira De Oliveira Filho, E.; Peresunko, D.; Pérez Lara, C. E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Piano, S.; Pikna, M.; Pillot, P.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Read, K. F.; Real, J. S.; Redlich, K.; Reed, R. J.; Rehman, A.; Reichelt, P.; Reicher, M.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Rettig, F.; Revol, J.-P.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rivetti, A.; Rocco, E.; Rodríguez Cahuantzi, M.; Rodriguez Manso, A.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Romita, R.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rui, R.; Russo, R.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Sadovsky, S.; Šafařík, K.; Sahlmuller, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salgado, C. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Sanchez Castro, X.; Šándor, L.; Sandoval, A.; Sano, M.; Santagati, G.; Sarkar, D.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schuchmann, S.; Schukraft, J.; Schulc, M.; Schuster, T.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Seeder, K. S.; Seger, J. E.; Sekiguchi, Y.; Selyuzhenkov, I.; Senosi, K.; Seo, J.; Serradilla, E.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, N.; Shigaki, K.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singha, S.; Singhal, V.; Sinha, B. C.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Søgaard, C.; Soltz, R.; Song, J.; Song, M.; Song, Z.; Soramel, F.; Sorensen, S.; Spacek, M.; Spiriti, E.; Sputowska, I.; Spyropoulou-Stassinaki, M.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stefanek, G.; Steinpreis, M.; Stenlund, E.; Steyn, G.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Sultanov, R.; Šumbera, M.; Symons, T. J. M.; Szabo, A.; Szanto de Toledo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Takahashi, J.; Tanaka, N.; Tangaro, M. A.; Tapia Takaki, J. D.; Tarantola Peloni, A.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thäder, J.; Thomas, D.; Tieulent, R.; Timmins, A. R.; Toia, A.; Trogolo, S.; Trubnikov, V.; Trzaska, W. H.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vajzer, M.; Vala, M.; Valencia Palomo, L.; Vallero, S.; Van Der Maarel, J.; Van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vechernin, V.; Veen, A. M.; Veldhoen, M.; Velure, A.; Venaruzzo, M.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Verweij, M.; Vickovic, L.; Viesti, G.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Vinogradov, A.; Vinogradov, L.; Vinogradov, Y.; Virgili, T.; Vislavicius, V.; Viyogi, Y. P.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Vranic, D.; Vrláková, J.; Vulpescu, B.; Vyushin, A.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Wang, Y.; Watanabe, D.; Weber, M.; Weber, S. G.; Wessels, J. P.; Westerhoff, U.; Wiechula, J.; Wikne, J.; Wilde, M.; Wilk, G.; Wilkinson, J.; Williams, M. C. S.; Windelband, B.; Winn, M.; Yaldo, C. G.; Yamaguchi, Y.; Yang, H.; Yang, P.; Yano, S.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yurchenko, V.; Yushmanov, I.; Zaborowska, A.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zaporozhets, S.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zgura, I. S.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zinovjev, G.; Zyzak, M.

2015-10-01

Charged jet production cross sections in p-Pb collisions at √{sNN} = 5.02 TeV measured with the ALICE detector at the LHC are presented. Using the anti-kT algorithm, jets have been reconstructed in the central rapidity region from charged particles with resolution parameters R = 0.2 and R = 0.4. The reconstructed jets have been corrected for detector effects and the underlying event background. To calculate the nuclear modification factor, RpPb, of charged jets in p-Pb collisions, a pp reference was constructed by scaling previously measured charged jet spectra at √{ s} = 7 TeV. In the transverse momentum range 20 ≤p T , ch jet ≤ 120 GeV / c, RpPb is found to be consistent with unity, indicating the absence of strong nuclear matter effects on jet production. Major modifications to the radial jet structure are probed via the ratio of jet production cross sections reconstructed with the two different resolution parameters. This ratio is found to be similar to the measurement in pp collisions at √{ s} = 7 TeV and to the expectations from PYTHIA pp simulations and NLO pQCD calculations at √{sNN} = 5.02 TeV.

Measurement of charged jet production cross sections and nuclear modification in p–Pb collisions at s NN = 5.02  TeV

DOE PAGES

Adam, J.

2015-07-26

Charged jet production cross sections in p-Pb collisions at √s(NN) = 5.02 TeV measured with the ALICE detector at the LHC are presented. Using the anti-k T algorithm, jets have been reconstructed in the central rapidity region from charged particles with resolution parameters R = 0.2 and R = 0.4. The reconstructed jets have been corrected for detector effects and the underlying event background. To calculate the nuclear modification factor, R- pPb, of charged jets in p-Pb collisions, a pp reference was constructed by scaling previously measured charged jet spectra at √s = 7 TeV. In the transverse momentum rangemore » 20 ≤ p T, ch jet ≤ 120 GeV/c, R- pPb is found to be consistent with unity, indicating the absence of strong nuclear matter effects on jet production. Major modifications to the radial jet structure are probed via the ratio of jet production cross sections reconstructed with the two different resolution parameters. In conclusion, this ratio is found to be similar to the measurement in pp collisions at √s = 7 TeV and to the expectations from PYTHIA pp simulations and NLO pQCD calculations at √s(NN) = 5.02 TeV.« less

Evaluating Galactic Cosmic Ray Environment Models Using RaD-X Flight Data

NASA Technical Reports Server (NTRS)

Norman, R. B.; Mertens, C. J.; Slaba, T. C.

2016-01-01

Galactic cosmic rays enter Earth's atmosphere after interacting with the geomagnetic field. The primary galactic cosmic rays spectrum is fundamentally changed as it interacts with Earth's atmosphere through nuclear and atomic interactions. At points deeper in the atmosphere, such as at airline altitudes, the radiation environment is a combination of the primary galactic cosmic rays and the secondary particles produced through nuclear interactions. The RaD-X balloon experiment measured the atmospheric radiation environment above 20 km during 2 days in September 2015. These experimental measurements were used to validate and quantify uncertainty in physics-based models used to calculate exposure levels for commercial aviation. In this paper, the Badhwar-O'Neill 2014, the International Organization for Standardization 15390, and the German Aerospace Company galactic cosmic ray environment models are used as input into the same radiation transport code to predict and compare dosimetric quantities to RaD-X measurements. In general, the various model results match the measured tissue equivalent dose well, with results generated by the German Aerospace Center galactic cosmic ray environment model providing the best comparison. For dose equivalent and dose measured in silicon, however, the models were compared less favorably to the measurements.

Jet pump-drive system for heat removal

NASA Technical Reports Server (NTRS)

French, James R. (Inventor)

1987-01-01

The invention does away with the necessity of moving parts such as a check valve in a nuclear reactor cooling system. Instead, a jet pump, in combination with a TEMP, is employed to assure safe cooling of a nuclear reactor after shutdown. A main flow exists for a reactor coolant. A point of withdrawal is provided for a secondary flow. A TEMP, responsive to the heat from said coolant in the secondary flow path, automatically pumps said withdrawn coolant to a higher pressure and thus higher velocity compared to the main flow. The high velocity coolant is applied as a driver flow for the jet pump which has a main flow chamber located in the main flow circulation pump. Upon nuclear shutdown and loss of power for the main reactor pumping system, the TEMP/jet pump combination continues to boost the coolant flow in the direction it is already circulating. During the decay time for the nuclear reactor, the jet pump keeps running until the coolant temperature drops to a lower and safe temperature where the heat is no longer a problem. At this lower temperature, the TEMP/jet pump combination ceases its circulation boosting operation. When the nuclear reactor is restarted and the coolant again exceeds the lower temperature setting, the TEMP/jet pump automatically resumes operation. The TEMP/jet pump combination is thus automatic, self-regulating and provides an emergency pumping system free of moving parts.

Jet pump-drive system for heat removal

NASA Technical Reports Server (NTRS)

French, J. R. (Inventor)

1985-01-01

A jet pump, in combination with a TEMP, is employed to assure safe cooling of a nuclear reactor after shutdown. A TEMP, responsive to the heat from the coolant in the secondary flow path, automatically pumps the withdrawn coolant to a higher pressure and thus higher velocity compared to the main flow. The high velocity coolant is applied as a driver flow for the jet pump which has a main flow chamber located in the main flow circulation pump. Upon nuclear shutdown and loss of power for the main reactor pumping system, the TEMP/jet pump combination continues to boost the coolant flow in the direction it is already circulating. During the decay time for the nuclear reactor, the jet pump keeps running until the coolant temperature drops to a lower and safe temperature. At this lower temperature, the TEMP/jet jump combination ceases its circulation boosting operation. The TEMP/jet pump combination is automatic, self-regulating and provides an emergency pumping system free of moving parts.

A High Resolution View of Galactic Centers: Arp 220 and M31

NASA Astrophysics Data System (ADS)

Lockhart, Kelly E.

The centers of galaxy are small in size and yet incredibly complex. They play host to supermassive black holes and nuclear star clusters (NSCs) and are subject to large gas inows, nuclear starbursts, and active galactic nuclear (AGN) activity. They can also be the launching site for large-scale galactic outows. However, though these systems are quite important to galactic evolution, observations are quite difficult due to their small size. Using high spatial resolution narrowband imaging with HST/WFC3 of Arp 220, a latestage galaxy merger, I discover an ionized gas bubble feature ( r = 600 pc) just off the nucleus. The bubble is aligned with both the western nucleus and with the large-scale galactic outflow. Using energetics arguments, I link the bubble with a young, obscured AGN or with an intense nuclear starburst. Given its alignment along the large-scale outflow axis, I argue that the bubble presents evidence for a link between the galactic center and the large-scale outflow. I also present new observations of the NSC in M31, the closest large spiral galaxy to our own. Using the OSIRIS near-infrared integral field spectrograph (IFS) on Keck, I map the kinematics of the old stellar population in the eccentric disk of the NSC. I compare the observations to models to derive a precession speed of the disk of 0+/-5 km s-1 pc-1 , and hence confirm that winds from the old stellar population may be the source of gas needed to form the young stellar population in the NSC. Studies of galactic centers are dependent on high spatial resolution observations. In particular, IFSs are ideal instruments for these studies as they provide two-dimensional spectroscopy of the field of view, enabling 2D kinematic studies. I report on work to characterize and improve the data reduction pipeline of the OSIRIS IFS, and discuss implications for future generations of IFS instrumentation.

A Universal Scaling for the Energetics of Relativistic Jets From Black Hole Systems

NASA Technical Reports Server (NTRS)

Nemmen, R. S.; Georganopoulos, M.; Guiriec, S.; Meyer, E. T.; Gehrels, N.; Sambruna, R. M.

2013-01-01

Black holes generate collimated, relativistic jets which have been observed in gamma-ray bursts (GRBs), microquasars, and at the center of some galaxies (active galactic nuclei; AGN). How jet physics scales from stellar black holes in GRBs to the supermassive ones in AGNs is still unknown. Here we show that jets produced by AGNs and GRBs exhibit the same correlation between the kinetic power carried by accelerated particles and the gamma-ray luminosity, with AGNs and GRBs lying at the low and high-luminosity ends, respectively, of the correlation. This result implies that the efficiency of energy dissipation in jets produced in black hole systems is similar over 10 orders of magnitude in jet power, establishing a physical analogy between AGN and GRBs.

A universal scaling for the energetics of relativistic jets from black hole systems.

PubMed

Nemmen, R S; Georganopoulos, M; Guiriec, S; Meyer, E T; Gehrels, N; Sambruna, R M

2012-12-14

Black holes generate collimated, relativistic jets, which have been observed in gamma-ray bursts (GRBs), microquasars, and at the center of some galaxies [active galactic nuclei (AGN)]. How jet physics scales from stellar black holes in GRBs to the supermassive ones in AGN is still unknown. Here, we show that jets produced by AGN and GRBs exhibit the same correlation between the kinetic power carried by accelerated particles and the gamma-ray luminosity, with AGN and GRBs lying at the low- and high-luminosity ends, respectively, of the correlation. This result implies that the efficiency of energy dissipation in jets produced in black hole systems is similar over 10 orders of magnitude in jet power, establishing a physical analogy between AGN and GRBs.

Magnetic field, reconnection, and particle acceleration in extragalactic jets

NASA Technical Reports Server (NTRS)

Romanova, M. M.; Lovelace, R. V. E.

1992-01-01

Extra-galactic radio jets are investigated theoretically taking into account that the jet magnetic field is dragged out from the central rotating source by the jet flow. Thus, magnetohydrodynamic models of jets are considered with zero net poloidal current and flux, and consequently a predominantly toroidal magnetic field. The magnetic field naturally has a cylindrical neutral layer. Collisionless reconnection of the magnetic field in the vicinity of the neutral layer acts to generate a non-axisymmetric radial magnetic field. In turn, axial shear-stretching of reconnected toroidal field gives rise to a significant axial magnetic field if the flow energy-density is larger than the energy-density of the magnetic field. This can lead to jets with an apparent longitudinal magnetic field as observed in the Fanaroff-Riley class II jets. In the opposite limit, where the field energy-density is large, the field remains mainly toroidal as observed in Fanaroff-Riley class I jets. Driven collisionless reconnection at neutral layers may lead to acceleration of electrons to relativistic energies in the weak electrostatic field of the neutral layer. A simple model is discussed for particle acceleration at neutral layers in electron/positron and electron/proton plasmas.

A Three Dimensional Picture of Galactic Center Mass Flows From Kiloparsec to Subparsec Scales

NASA Astrophysics Data System (ADS)

Mills, Elisabeth A.

2018-06-01

The centers of galaxies host extreme and energetic phenomena, from the amassing of incredibly dense reservoirs of gas to nuclear starbursts producing tens to hundreds of solar masses per year to accreting supermassive black holes launching jets. All of these are found on compact scales from hundreds of parsecs to less than a microparsec. The nearest laboratory for examining these processes is the center of our own Milky Way Galaxy. Although the black hole is not currently active and the star formation rate is relatively low, it is still our best opportunity for detailed insight into the processes that regulate the growth of the central supermassive black hole. By providing access to mid and far infrared wavelengths, SOFIA plays a unique role in connecting large and small scales in the Galactic center and studying the cycling of gas through this region. In this talk I will highlight several key open questions and outline the role that SOFIA continues to play in answering them.

Self-similar semi-analytical RMHD jet model: first steps towards a more comprehensive jet modelling for data fitting

NASA Astrophysics Data System (ADS)

Markoff, Sera; Ceccobello, Chiara; Heemskerk, Martin; Cavecchi, Yuri; Polko, Peter; Meier, David

2017-08-01

Jets are ubiquitous and reveal themselves at different scales and redshifts, showing an extreme diversity in energetics, shapes and emission. Indeed jets are found to be characteristic features of black hole systems, such as X-ray binaries (XRBs) and active galactic nuclei (AGN), as well as of young stellar objects (YSOs) and gamma-ray bursts (GRBs). Observations suggest that jets are an energetically important component of the system that hosts them, because the jet power appears to be comparable to the accretion power. Significant evidence has been found of the impact of jets not only in the immediate proximity of the central object, but as well on their surrounding environment, where they deposit the energy extracted from the accretion flow. Moreover, the inflow/outflow system produces radiation over the entire electromagnetic spectrum, from radio to X-rays. Therefore it is a compelling problem to be solved and deeply understood. I present a new integration scheme to solve radial self-similar, stationary, axisymmetric relativistic magneto-hydro-dynamics (MHD) equations describing collimated, relativistic outflows crossing smoothly all the singular points (the Alfvén point and the modified slow/fast points). For the first time, the integration can be performed all the way from the disk mid-plane to downstream of the modified fast point. I will discuss an ensemble of jet solutions showing diverse jet dynamics (jet Lorentz factor ~ 1-10) and geometric properties (i.e. shock height ~ 103 - 107 gravitational radii), which makes our model suitable for application to many different systems where a relativistic jet is launched.

Luminous Infrared Galaxies. III. Multiple Merger, Extended Massive Star Formation, Galactic Wind, and Nuclear Inflow in NGC 3256

NASA Astrophysics Data System (ADS)

Lípari, S.; Díaz, R.; Taniguchi, Y.; Terlevich, R.; Dottori, H.; Carranza, G.

2000-08-01

ouflow axis (at P.A.~160deg). We analyze in detail the physical conditions in the giant H II regions located in the asymmetric spiral arms, the two main optical nuclei, and the outflow component (using long-slit spectroscopy, plus standard models of photoionization, shocks, and starbursts). We present four detailed emission-line ratios (N II/Hα, S II/Hα, S II/S II), and FWHM (Hα) maps for the central region (30''×30'' rmax~22''~4 kpc), with a spatial resolution of 1". In the central region (r~5-6 kpc) we detected that the nuclear starburst and the extended giant H II regions (in the spiral arms) have very similar properties, i.e., high metallicity and low-ionization spectra, with Teff=35,000 K, solar abundance, a range of Te~6000-7000 K, and Ne~100-1000 cm-3. The nuclear and extended outflow shows properties typical of galactic wind/shocks, associated with the nuclear starburst. We suggest that the interaction between dynamical effects, the galactic wind (outflow), low-energy cosmic rays, and the molecular+ionized gas (probably in the inflow phase) could be the possible mechanism that generate the ``similar extended properties in the massive star formation, at a scale of 5-6 kpc!'' We have also studied the presence of the close merger/interacting systems NGC 3256C (at ~150 kpc, ΔV=-100 km s-1) and the possible association between the NGC 3256 and 3263 groups of galaxies. In conclusion, these results suggest that NGC 3256 is the product of a multiple merger, which generated an extended massive star formation process with an associated galactic wind plus a nuclear inflow. Therefore, NGC 3256 is another example in which the relation between mergers and extreme starburst (and the powerful galactic wind, ``multiple'' Type II supernova explosions) play an important role in the evolution of galaxies (the hypothesis of Rieke et al., Joseph et al., Terlevich et al., Heckman et al., and Lípari et al.). Based on observations obtained at the Hubble Space Telescope (HST; Wide

Broadband High-Energy Observations of the Superluminal Jet Source GRO J1655-40 During an Outburst

NASA Technical Reports Server (NTRS)

Zhang, S. N.; Ebisawa, K.; Sunyaev, R.; Ueda, Y.; Harmon, B. A.; Sazonov, S.; Fishman, G. J.; Inoue, H.; Paciesas, W. S.; Takahash, T.

1997-01-01

The X-ray/radio transient superluminal jet source GRO J1655-40 was recently suggested to contain a black hole from optical observations. Because it is a relatively close-by system (d approximately 3.2 kpc), it can likely provide us with rich information about the physics operating in both Galactic and extragalactic jet sources. We present the first simultaneous broadband high-energy observations of GRO J1655-40 during the 1995 July-August outburst by three instruments: ASCA, WATCH/Granat, and BATSE/CGRO, in the energy band from 1 keV to 2 MeV. Our observations strengthen the interpretation that GRO J1655-40 contains a black hole. We detected a two-component energy spectrum, commonly seen from other Galactic black hole binaries, but never detected from a neutron star system. Combining our results with the mass limits derived from optical radial velocity and orbital period measurements, we further constrain the mass of the central object to be between 3.3 and 5.8 solar mass, above the well-established mass upper limit of 3.2 solar mass for a neutron star (the optical mass function for GRO J1655-40 is 3.16 + 0.2 solar mass). This system is therefore the first Galactic superluminal jet source for which there is strong evidence that the system contains a stellar mass black hole. The inclination angle of the binary system is constrained to be between 76 deg and 87 deg, consistent with estimates obtained from optical light curves and radio jet kinematics.

Magnetically driven relativistic jets and winds: Exact solutions

NASA Technical Reports Server (NTRS)

Contopoulos, J.

1994-01-01

We present self-consistent solutions of the full set of ideal MHD equations which describe steady-state relativistic cold outflows from thin accretion disks. The magnetic field forms a spiral which is anchored in the disk, rotates with it, and accelerates the flow out of the disk plane. The collimation at large distances depends on the total amount of electric current that flows along the jet. We considered various distributions of electric current and derived the result that in straight jets which extend to infinite distances, a strong electric current flows along their axis of symmetry. The asymptotic flow velocities are of the order of the initial rotational velocity at the base of the flow (a few tenths of the speed of light). The solutions are applied to both galactic (small-scale) and extragalactic (large-scale) jets.

Uncorrelated Far Active Galactic Nuclei Flaring with Their Delayed Ultra High Energy Cosmic Rays Events

NASA Astrophysics Data System (ADS)

Fargion, Daniele; Oliva, Pietro; De Sanctis Lucentini, Pier Giorgio

The most distant Active Galactic Nuclei (AGN), within the allowed Greisen-Zatsepin-Kuzmin (GZK) cut-off radius ( ≲ 100 Mpc), have been recently candidate by many authors as the best location for the observed Ultra High Energy Cosmic Rays (UHECR) origination. Indeed, the apparent homogeneity and isotropy of recent UHECR signals seems to require a far cosmic isotropic and homogeneous scenario, involving a proton UHECR courier: our galaxy or nearest local group or super galactic plane (ruled by the Virgo cluster) are too near and apparently too anisotropic to be in agreement with the (Pierre Auger Observatory (PAO) and Telescope Array (TA) almost-homogeneous data sample. However, the few and mild UHECR observed clustering, the so called North and South Hot Spots, are smeared in wide (±18°) solid angles. Their consequent random walk flight from most far GZK UHECR sources, nearly at 100 Mpc, must be delayed — withrespect to a straight AGN photon gamma flaring arrival trajectory — at least by a million years. During this time, the AGN jet blazing signal, its probable axis deflection (such as the helical jet in Mrk 501), its miss alignment or even its almost certain exhaust activity, may lead to a complete misleading correlation between present UHECR events and a much earlier active AGN ejection. UHECR maps may be anyway related to galactic or nearest (Cen A, M82) AGN extragalactic UHECR sources shining in twin Hot Spot. Therefore we defend our (quite different) scenario where UHECR are mostly made by lightest UHECR nuclei originated by nearby AGN sources, or few galactic sources, whose delayed signals are reaching us within few thousand years in the observed smeared sky areas.

Measurement of inclusive jet production and nuclear modifications in pPb collisions at $$\\sqrt{s_{_\\mathrm {NN}}} =5.02\\,\\mathrm{TeV} $$

DOE PAGES

Khachatryan, Vardan

2016-07-04

In this study, inclusive jet production in pPb collisions at a nucleon–nucleon (NN) center-of-mass energy of √ sNN = 5.02 TeV is studied with the CMS detector at the LHC. A data sample corresponding to an integrated luminosity of 30.1 nb -1 is analyzed. The jet transverse momentum spectra are studied in seven pseudorapidity intervals covering the range -2.0 < η CM < 1.5 in the NN center-of-mass frame. The jet production yields at forward and backward pseudorapidity are compared and no significant asymmetry about ηCM=0 is observed in the measured kinematic range. The measurements in the pPb system aremore » compared to reference jet spectra obtained by extrapolation from previous measurements in pp collisions at √s = 7 TeV. In all pseudorapidity ranges, nuclear modifications in inclusive jet production are found to be small, as predicted by next-to-leading order perturbative QCD calculations that incorporate nuclear effects in the parton distribution functions.« less

DISCOVERY OF A PSEUDOBULGE GALAXY LAUNCHING POWERFUL RELATIVISTIC JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotilainen, Jari K.; Olguín-Iglesias, Alejandro; León-Tavares, Jonathan

Supermassive black holes launching plasma jets at close to the speed of light, producing gamma-rays, have ubiquitously been found to be hosted by massive elliptical galaxies. Since elliptical galaxies are generally believed to be built through galaxy mergers, active galactic nuclei (AGN) launching relativistic jets are associated with the latest stages of galaxy evolution. We have discovered a pseudobulge morphology in the host galaxy of the gamma-ray AGN PKS 2004-447. This is the first gamma-ray emitter radio-loud AGN found to have been launched from a system where both the black hole and host galaxy have been actively growing via secularmore » processes. This is evidence of an alternative black hole–galaxy co-evolutionary path to develop powerful relativistic jets, which is not merger driven.« less

RELATIVISTIC DOPPLER BEAMING AND MISALIGNMENTS IN AGN JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singal, Ashok K., E-mail: asingal@prl.res.in

Radio maps of active galactic nuclei often show linear features, called jets, on both parsec and kiloparsec scales. These jets supposedly possess relativistic motion and are oriented close to the line of sight of the observer, and accordingly the relativistic Doppler beaming makes them look much brighter than they really are in their respective rest frames. The flux boosting due to the relativistic beaming is a very sensitive function of the jet orientation angle, as seen by the observer. Sometimes, large bends are seen in these jets, with misalignments being 90° or more, which might imply a change in themore » orientation angle that should cause a large change in the relativistic beaming factor. Hence, if relativistic beaming does play an important role in these jets such large bends should usually show high contrast in the brightness of the jets before and after the bend. It needs to be kept in mind that sometimes a small intrinsic change in the jet angle might appear as a much larger misalignment due to the effects of geometrical projection, especially when seen close to the line of sight. What really matters are the initial and final orientation angles of the jet with respect to the observer’s line of sight. Taking the geometrical projection effects properly into account, we calculate the consequences of the presumed relativistic beaming and demonstrate that there ought to be large brightness ratios in jets before and after the observed misalignments.« less

Relativistic Doppler Beaming and Misalignments in AGN Jets

NASA Astrophysics Data System (ADS)

Singal, Ashok K.

2016-08-01

Radio maps of active galactic nuclei often show linear features, called jets, on both parsec and kiloparsec scales. These jets supposedly possess relativistic motion and are oriented close to the line of sight of the observer, and accordingly the relativistic Doppler beaming makes them look much brighter than they really are in their respective rest frames. The flux boosting due to the relativistic beaming is a very sensitive function of the jet orientation angle, as seen by the observer. Sometimes, large bends are seen in these jets, with misalignments being 90° or more, which might imply a change in the orientation angle that should cause a large change in the relativistic beaming factor. Hence, if relativistic beaming does play an important role in these jets such large bends should usually show high contrast in the brightness of the jets before and after the bend. It needs to be kept in mind that sometimes a small intrinsic change in the jet angle might appear as a much larger misalignment due to the effects of geometrical projection, especially when seen close to the line of sight. What really matters are the initial and final orientation angles of the jet with respect to the observer’s line of sight. Taking the geometrical projection effects properly into account, we calculate the consequences of the presumed relativistic beaming and demonstrate that there ought to be large brightness ratios in jets before and after the observed misalignments.

Introducing CGOLS: The Cholla Galactic Outflow Simulation Suite

NASA Astrophysics Data System (ADS)

Schneider, Evan E.; Robertson, Brant E.

2018-06-01

We present the Cholla Galactic OutfLow Simulations (CGOLS) suite, a set of extremely high resolution global simulations of isolated disk galaxies designed to clarify the nature of multiphase structure in galactic winds. Using the GPU-based code Cholla, we achieve unprecedented resolution in these simulations, modeling galaxies over a 20 kpc region at a constant resolution of 5 pc. The simulations include a feedback model designed to test the effects of different mass- and energy-loading factors on galactic outflows over kiloparsec scales. In addition to describing the simulation methodology in detail, we also present the results from an adiabatic simulation that tests the frequently adopted analytic galactic wind model of Chevalier & Clegg. Our results indicate that the Chevalier & Clegg model is a good fit to nuclear starburst winds in the nonradiative region of parameter space. Finally, we investigate the role of resolution and convergence in large-scale simulations of multiphase galactic winds. While our largest-scale simulations show convergence of observable features like soft X-ray emission, our tests demonstrate that simulations of this kind with resolutions greater than 10 pc are not yet converged, confirming the need for extreme resolution in order to study the structure of winds and their effects on the circumgalactic medium.

Elusive active galactic nuclei

NASA Astrophysics Data System (ADS)

Maiolino, R.; Comastri, A.; Gilli, R.; Nagar, N. M.; Bianchi, S.; Böker, T.; Colbert, E.; Krabbe, A.; Marconi, A.; Matt, G.; Salvati, M.

2003-10-01

A fraction of active galactic nuclei do not show the classical Seyfert-type signatures in their optical spectra, i.e. they are optically `elusive'. X-ray observations are an optimal tool to identify this class of objects. We combine new Chandra observations with archival X-ray data in order to obtain a first estimate of the fraction of elusive active galactic nuclei (AGN) in local galaxies and to constrain their nature. Our results suggest that elusive AGN have a local density comparable to or even higher than optically classified Seyfert nuclei. Most elusive AGN are heavily absorbed in the X-rays, with gas column densities exceeding 1024 cm-2, suggesting that their peculiar nature is associated with obscuration. It is likely that in elusive AGN the nuclear UV source is completely embedded and the ionizing photons cannot escape, which prevents the formation of a classical narrow-line region. Elusive AGN may contribute significantly to the 30-keV bump of the X-ray background.

Exploratory investigation of the HIPPO gas-jet target fluid dynamic properties

NASA Astrophysics Data System (ADS)

Meisel, Zach; Shi, Ke; Jemcov, Aleksandar; Couder, Manoel

2016-08-01

In order to optimize the performance of gas-jet targets for future nuclear reaction measurements, a detailed understanding of the dependence of the gas-jet properties on experiment design parameters is required. Common methods of gas-jet characterization rely on measuring the effective thickness using nuclear elastic scattering and energy loss techniques; however, these tests are time intensive and limit the range of design modifications which can be explored to improve the properties of the jet as a nuclear reaction target. Thus, a more rapid jet-characterization method is desired. We performed the first steps towards characterizing the gas-jet density distribution of the HIPPO gas-jet target at the University of Notre Dame's Nuclear Science Laboratory by reproducing results from 20Ne(α,α)20Ne elastic scattering measurements with computational fluid dynamics (CFD) simulations performed with the state-of-the-art CFD software ANSYS Fluent. We find a strong sensitivity to experimental design parameters of the gas-jet target, such as the jet nozzle geometry and ambient pressure of the target chamber. We argue that improved predictive power will require moving to three-dimensional simulations and additional benchmarking with experimental data.

A STUDY OF RADIO POLARIZATION IN PROTOSTELLAR JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cécere, Mariana; Velázquez, Pablo F.; De Colle, Fabio

2016-01-10

Synchrotron radiation is commonly observed in connection with shocks of different velocities, ranging from relativistic shocks associated with active galactic nuclei, gamma-ray bursts, or microquasars, to weakly or non-relativistic flows such as those observed in supernova remnants. Recent observations of synchrotron emission in protostellar jets are important not only because they extend the range over which the acceleration process works, but also because they allow us to determine the jet and/or interstellar magnetic field structure, thus giving insights into the jet ejection and collimation mechanisms. In this paper, we compute for the first time polarized (synchrotron) and non-polarized (thermal X-ray)more » synthetic emission maps from axisymmetrical simulations of magnetized protostellar jets. We consider models with different jet velocities and variability, as well as a toroidal or helical magnetic field. Our simulations show that variable, low-density jets with velocities of ∼1000 km s{sup −1} and ∼10 times lighter than the environment can produce internal knots with significant synchrotron emission and thermal X-rays in the shocked region of the leading bow shock moving in a dense medium. While models with a purely toroidal magnetic field show a very large degree of polarization, models with a helical magnetic field show lower values and a decrease of the degree of polarization, in agreement with observations of protostellar jets.« less

Milky Way scattering properties and intrinsic sizes of active galactic nuclei cores probed by very long baseline interferometry surveys of compact extragalactic radio sources

NASA Astrophysics Data System (ADS)

Pushkarev, A. B.; Kovalev, Y. Y.

2015-10-01

We have measured the angular sizes of radio cores of active galactic nuclei (AGNs) and analysed their sky distributions and frequency dependences to study synchrotron opacity in AGN jets and the strength of angular broadening in the interstellar medium. We have used archival very long baseline interferometry (VLBI) data of more than 3000 compact extragalactic radio sources observed at frequencies, ν, from 2 to 43 GHz to measure the observed angular size of VLBI cores. We have found a significant increase in the angular sizes of the extragalactic sources seen through the Galactic plane (|b| ≲ 10°) at 2, 5 and 8 GHz, about one-third of which show significant scattering. These sources are mainly detected in directions to the Galactic bar, the Cygnus region and a region with galactic longitudes 220° ≲ l ≲ 260° (the Fitzgerald window). The strength of interstellar scattering of the AGNs is found to correlate with the Galactic Hα intensity, free-electron density and Galactic rotation measure. The dependence of scattering strengths on source redshift is insignificant, suggesting that the dominant scattering screens are located in our Galaxy. The observed angular size of Sgr A* is found to be the largest among thousands of AGNs observed over the sky; we discuss possible reasons for this strange result. Excluding extragalactic radio sources with significant scattering, we find that the angular size of opaque cores in AGNs scales typically as ν-1, confirming predictions of a conical synchrotron jet model with equipartition.

An XMM-Newton Observation of 4U1755-33 in Quiescence: Evidence for a Fossil X-Ray Jet

NASA Technical Reports Server (NTRS)

Angelini, Lorella; White, Nicholas E.

2003-01-01

We report an XMM-Newton observation of the Low mass X-ray Binary (LMXB) and black hole candidate 4U1755-33. This source had been a bright persistent source for at least 25 yrs, but in 1995 entered an extended quiescent phase. 4U1755-33 was not detected with an upper limit to the 2-10 keV luminosity of 5 x 10(exp 31) d(sup 2) (sub 4kpc) ergs per second (where d(sub 4kpc) is the distance in units of 4 kpc) - consistent with the luminosity of other black hole candidates in a quiescent state. An unexpected result is the discovery of a narrow 7 arc min long X-ray jet centered on the position of 4Ul755-33. The spectrum of the jet is similar to that of jets observed from other galactic and extragalactic sources, and may have been ejected from 4Ul755-33 when it was bright. Jets are a feature of accreting black holes, and the detection of a fossil jet provides additional evidence supporting the black hole candidacy of 4U1755-33. The spectral properties of three bright serendipitous sources in the field are reported and it is suggested these are background active galactic nuclei sources.

Simulations of AGN jets: magnetic kink instability versus conical shocks

NASA Astrophysics Data System (ADS)

Barniol Duran, Rodolfo; Tchekhovskoy, Alexander; Giannios, Dimitrios

2017-08-01

Relativistic jets in active galactic nuclei (AGN) convert as much as half of their energy into radiation. To explore the poorly understood processes that are responsible for this conversion, we carry out fully 3D magnetohydrodynamic (MHD) simulations of relativistic magnetized jets. Unlike the standard approach of injecting the jets at large radii, our simulated jets self-consistently form at the source and propagate and accelerate outwards for several orders of magnitude in distance before they interact with the ambient medium. We find that this interaction can trigger strong energy dissipation of two kinds inside the jets, depending on the properties of the ambient medium. Those jets that form in a new outburst and drill a fresh hole through the ambient medium fall victim to a 3D magnetic kink instability and dissipate their energy primarily through magnetic reconnection in the current sheets formed by the instability. On the other hand, those jets that form during repeated cycles of AGN activity and escape through a pre-existing hole in the ambient medium maintain their stability and dissipate their energy primarily at MHD recollimation shocks. In both cases, the dissipation region can be associated with a change in the density profile of the ambient gas. The Bondi radius in AGN jets serves as such a location.

Numerical Study of AGN Jet Propagation with Two Dimensional Relativistic Hydrodynamic Code

NASA Astrophysics Data System (ADS)

Mizuta, Akira; Yamada, Shoichi; Takabe, Hideaki

2001-12-01

We investigate the morphology of Active Galactic Nuclei(AGN) jets. AGN jets propagate over kpc ~ Mpc and their beam velocities are close to the speed of light. The reason why many jets propagate over so long a distance and sustain a very collimated structure is not well understood. It is argued taht some dimensionless parameters, the density and the pressure ratio of the jet beam and the ambient gas, the Mach number of the beam, and relative speed of the beam compared to the speed of light, are very useful to understand the morphology of jets namely, bow shocks, cocoons, nodes etc. The role of each parameters has been studied by numerical simulations. But more research is necessary to understand it systematically. We have developed 2D relativistic hydrodynamic code to analyze relativistic jets. We pay attention to the propagation velocity which is derived from 1D momentum balance in the frame of the working surface. We show some of our models and discuss the dependence of the morphology of jets on the parameter.

THE INTERNAL STRUCTURE OF OVERPRESSURED, MAGNETIZED, RELATIVISTIC JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martí, J. M.; Perucho, M.; Gómez, J. L.

This work presents the first characterization of the internal structure of overpressured, steady superfast-magnetosonic relativistic jets in connection with their dominant type of energy. To this aim, relativistic magnetohydrodynamic simulations of different jet models threaded by a helical magnetic field have been analyzed covering a wide region in the magnetosonic Mach number–specific internal energy plane. The merit of this plane is that models dominated by different types of energy (internal energy: hot jets; rest-mass energy: kinetically dominated jets; magnetic energy: Poynting-flux-dominated jets) occupy well-separated regions. The analyzed models also cover a wide range of magnetizations. Models dominated by the internalmore » energy (i.e., hot models, or Poynting-flux-dominated jets with magnetizations larger than but close to one) have a rich internal structure characterized by a series of recollimation shocks and present the largest variations in the flow Lorentz factor (and internal energy density). Conversely, in kinetically dominated models, there is not much internal or magnetic energy to be converted into kinetic, and the jets are featureless with small variations in the flow Lorentz factor. The presence of a significant toroidal magnetic field threading the jet produces large gradients in the transversal profile of the internal energy density. Poynting-flux-dominated models with high magnetization (≈10 or larger) are prone to be unstable against magnetic pinch modes, which sets limits on the expected magnetization in parsec-scale active galactic nucleus jets or constrains their magnetic field configuration.« less

Relativistic jet models for the BL Lacertae object Mrk 421 during three epochs of observation

NASA Technical Reports Server (NTRS)

Mufson, S. L.; Hutter, D. J.; Kondo, Y.; Wisniewski, W. Z.

1988-01-01

Coordinated observation of the nearby BL Lacertae object Mrk 421 obtained during May 1980, January 1984, and March 1984 are described. These observations give a time-frozen picture of the continuous spectrum of Mrk 421 at X-ray, ultraviolet, optical, and radio wavelengths. The observed spectra have been fitted to an inhomogeneous relativistic jet model. In general, the models reproduce the data well. Many of the observed differences during the three epochs can be attributed to variations in the opening angle of the jet and in the angle that the jet makes to the line of sight. The jet models obtained here are compared with the homogeneous, spherically symmetric, synchrotron self-Compton models for this source. The models are also compared with the relativistic jet models obtained for other active galactic nuclei.

Mapping jet-ISM interactions in X-ray binaries with ALMA: a GRS 1915+105 case study

NASA Astrophysics Data System (ADS)

Tetarenko, A. J.; Freeman, P.; Rosolowsky, E. W.; Miller-Jones, J. C. A.; Sivakoff, G. R.

2018-03-01

We present Atacama Large Millimetre/Sub-Millimetre Array (ALMA) observations of IRAS 19132+1035, a candidate jet-interstellar medium (ISM) interaction zone near the black hole X-ray binary (BHXB) GRS 1915+105. With these ALMA observations (combining data from the 12 m array and the Atacama Compact Array), we map the molecular line emission across the IRAS 19132+1035 region. We detect emission from the 12CO [J = 2 - 1], 13CO [ν = 0, J = 2 - 1], C18O [J = 2 - 1], H2CO [J = 30, 3 - 20, 2], H2CO [J = 32, 2 - 22, 1], H2CO [J = 32, 1 - 22, 0], SiO [ν = 0, J = 5 - 4], CH3OH [J = 42, 2 - 31, 2], and CS [ν = 0, J = 5 - 4] transitions. Given the morphological, spectral, and kinematic properties of this molecular emission, we present several lines of evidence that support the presence of a jet-ISM interaction at this site, including a jet-blown cavity in the molecular gas. This compelling new evidence identifies this site as a jet-ISM interaction zone, making GRS 1915+105, the third Galactic BHXB with at least one conclusive jet-ISM interaction zone. However, we find that this interaction occurs on much smaller scales than was postulated by previous work, where the BHXB jet does not appear to be dominantly powering the entire IRAS 19132+1035 region. Using estimates of the ISM conditions in the region, we utilize the detected cavity as a calorimeter to estimate the time-averaged power carried in the GRS 1915+105 jets of (8.4^{+7.7}_{-8.1})× 10^{32} erg s^{-1}. Overall, our analysis demonstrates that molecular lines are excellent diagnostic tools to identify and probe jet-ISM interaction zones near Galactic BHXBs.

Real-time evolution of a large-scale relativistic jet

NASA Astrophysics Data System (ADS)

Martí, Josep; Luque-Escamilla, Pedro L.; Romero, Gustavo E.; Sánchez-Sutil, Juan R.; Muñoz-Arjonilla, Álvaro J.

2015-06-01

Context. Astrophysical jets are ubiquitous in the Universe on all scales, but their large-scale dynamics and evolution in time are hard to observe since they usually develop at a very slow pace. Aims: We aim to obtain the first observational proof of the expected large-scale evolution and interaction with the environment in an astrophysical jet. Only jets from microquasars offer a chance to witness the real-time, full-jet evolution within a human lifetime, since they combine a "short", few parsec length with relativistic velocities. Methods: The methodology of this work is based on a systematic recalibraton of interferometric radio observations of microquasars available in public archives. In particular, radio observations of the microquasar GRS 1758-258 over less than two decades have provided the most striking results. Results: Significant morphological variations in the extended jet structure of GRS 1758-258 are reported here that were previously missed. Its northern radio lobe underwent a major morphological variation that rendered the hotspot undetectable in 2001 and reappeared again in the following years. The reported changes confirm the Galactic nature of the source. We tentatively interpret them in terms of the growth of instabilities in the jet flow. There is also evidence of surrounding cocoon. These results can provide a testbed for models accounting for the evolution of jets and their interaction with the environment.

Light ion components of the galactic cosmic rays: Nuclear interactions and transport theory

NASA Technical Reports Server (NTRS)

Cucinotta, F. A.; Townsend, L. W.; Wilson, J. W.; Shinn, J. L.; Badhwar, G. D.; Dubey, R. R.

1996-01-01

Light nuclei are present in the primary galactic cosmic rays (GCR) and are produced in thick targets due to projectile or target fragmentation from both nucleon and heavy induced reactions. In the primary GCR, He-4 is the most abundant nucleus after H-1. However, there are also a substantial fluxes of H-2 and He-3. In this paper we describe theoretical models based on quantum multiple scattering theory for the description of light ion nuclear interactions. The energy dependence of the light ion fragmentation cross section is considered with comparisons of inclusive yields and secondary momentum distributions to experiments described. We also analyze the importance of a fast component of lights ions from proton and neutron induced target fragementation. These theoretical models have been incorporated into the cosmic ray transport code HZETRN and will be used to analyze the role of shielding materials in modulating the production and the energy spectrum of light ions.

A dynamical model for gas flows, star formation and nuclear winds in galactic centres

NASA Astrophysics Data System (ADS)

Krumholz, Mark R.; Kruijssen, J. M. Diederik; Crocker, Roland M.

2017-04-01

We present a dynamical model for gas transport, star formation and winds in the nuclear regions of galaxies, focusing on the Milky Way's Central Molecular Zone (CMZ). In our model angular momentum and mass are transported by a combination of gravitational and bar-driven acoustic instabilities. In gravitationally unstable regions the gas can form stars, and the resulting feedback drives both turbulence and a wind that ejects mass from the CMZ. We show that the CMZ is in a quasi-steady state where mass deposited at large radii by the bar is transported inwards to a star-forming, ring-shaped region at ˜100 pc from the Galactic Centre, where the shear reaches a minimum. This ring undergoes episodic starbursts, with bursts lasting ˜5-10 Myr occurring at ˜20-40 Myr intervals. During quiescence the gas in the ring is not fully cleared, but is driven out of a self-gravitating state by the momentum injected by expanding supernova remnants. Starbursts also drive a wind off the star-forming ring, with a time-averaged mass flux comparable to the star formation rate. We show that our model agrees well with the observed properties of the CMZ, and places it near a star formation minimum within the evolutionary cycle. We argue that such cycles of bursty star formation and winds should be ubiquitous in the nuclei of barred spiral galaxies, and show that the resulting distribution of galactic nuclei on the Kennicutt-Schmidt relation is in good agreement with that observed in nearby galaxies.

Probing medium-induced jet splitting and energy loss in heavy-ion collisions

NASA Astrophysics Data System (ADS)

Chang, Ning-Bo; Cao, Shanshan; Qin, Guang-You

2018-06-01

The nuclear modification of jet splitting in relativistic heavy-ion collisions at RHIC and the LHC energies is studied based on the higher twist formalism. Assuming coherent energy loss for the two splitted subjets, a non-monotonic jet energy dependence is found for the nuclear modification of jet splitting function: strongest modification at intermediate jet energies whereas weaker modification for larger or smaller jet energies. Combined with the smaller size and lower density of the QGP medium at RHIC than at the LHC, this helps to understand the groomed jet measurements from CMS and STAR Collaborations: strong modification of the momentum sharing zg distribution at the LHC and no obvious modification of zg distribution at RHIC. In addition, the observed nuclear modification pattern of the groomed jet zg distribution cannot be explained solely by independent energy loss of the two subjets. Our result may be tested in future measurements of groomed jets with lower jet energies at the LHC and larger jet energies at RHIC, for different angular separations between the two subjets.

Rapid variability of the arcsec-scale X-ray jets of SS 433

NASA Astrophysics Data System (ADS)

Migliari, S.; Fender, R. P.; Blundell, K. M.; Méndez, M.; van der Klis, M.

2005-04-01

We present X-ray images of all the available Chandra observations of the galactic jet source SS 433. We have studied the morphology of the X-ray images and inspected the evolution of the arcsec X-ray jets, recently found to be manifestations of in situ reheating of the relativistic gas downstream in the jets. The Chandra images reveal that the arcsec X-ray jets are not steady long-term structures; the structure varies, indicating that the reheating processes have no preference for a particular precession phase or distance from the binary core. Three observations made within about five days in 2001 May, and a 60-ks observation made in 2003 July, show that the variability of the jets can be very rapid, from time-scales of days to (possibly) hours. The three 2001 May images show two resolved knots in the east jet getting brighter one after the other, suggesting that a common phenomenon might be at the origin of the sequential reheatings of the knots. We discuss possible scenarios and propose a model to interpret these brightenings in terms of a propagating shock wave, revealing a second, faster outflow in the jet.

Connections Between Jet Formation and Multiwavelength Spectral Evolution in Black Hole Transients

NASA Technical Reports Server (NTRS)

Kakemci, Emrah; Chun, Yoon-Young; Dincer, Tolga; Buxton, Michelle; Tomsick, John A.; Corbel, Stephane; Kaaret, Philip

2011-01-01

Multiwavelength observations are the key to understand conditions of jet formation in Galactic black hole transient (GBHT) systems. By studying radio and optical-infrared evolution of such systems during outburst decays, the compact jet formation can be traced. Comparing this with X-ray spectral and timing evolution we can obtain physical and geometrical conditions for jet formation, and study the contribution of jets to X-ray emission. In this work, first X-ray evolution - jet relation for XTE J1752-223 will be discussed. This source had very good coverage in X-rays, optical, infrared and radio. A long exposure with INTEGRAL also allowed us to study gamma-ray behavior after the jet turns on. We will also show results from the analysis of data from GX 339-4 in the hard state with SUZAKU at low flux levels. The fits to iron line fluorescence emission show that the inner disk radius increases by a factor of greater than 27 with respect to radii in bright states. This result, along with other disk radius measurements in the hard state will be discussed within the context of conditions for launching and sustaining jets.

Unusual Metals in Galactic Center Stars

NASA Astrophysics Data System (ADS)

Hensley, Kerry

2018-03-01

Far from the galactic suburbs where the Sun resides, a cluster of stars in the nucleus of the Milky Way orbits a supermassive black hole. Can chemical abundance measurements help us understand the formation history of the galactic center nuclear star cluster?Studying Stellar PopulationsMetallicity distributions for stars in the inner two degrees of the Milky Way (blue) and the central parsec (orange). [Do et al. 2018]While many galaxies host nuclear star clusters, most are too distant for us to study in detail; only in the Milky Way can we resolve individual stars within one parsec of a supermassive black hole. The nucleus of our galaxy is an exotic and dangerous place, and its not yet clear how these stars came to be where they are were they siphoned off from other parts of the galaxy, or did they form in place, in an environment rocked by tidal forces?Studying the chemical abundances of stars provides a way to separate distinct stellar populations and discern when and where these stars formed. Previous studies using medium-resolution spectroscopy have revealed that many stars within the central parsec of our galaxy have very high metallicities possibly higher than any other region of the Milky Way. Can high-resolution spectroscopy tell us more about this unusual population of stars?Spectral Lines on DisplayTuan Do (University of California, Los Angeles, Galactic Center Group) and collaborators performed high-resolution spectroscopic observations of two late-type giant starslocated half a parsec from the Milky Ways supermassive black hole.Comparison of the observed spectra of the two galactic center stars (black) with synthetic spectra with low (blue) and high (orange) [Sc/Fe] values. Click to enlarge. [Do et al. 2018]In order to constrain the metallicities of these stars, Do and collaborators compared the observed spectra to a grid of synthetic spectra and used a spectral synthesis technique to determine the abundances of individual elements. They found that

A swirling jet in the quasar 1308+326

NASA Astrophysics Data System (ADS)

Britzen, S.; Qian, S.-J.; Steffen, W.; Kun, E.; Karouzos, M.; Gergely, L.; Schmidt, J.; Aller, M.; Aller, H.; Krause, M.; Fendt, C.; Böttcher, M.; Witzel, A.; Eckart, A.; Moser, L.

2017-06-01

Context. Despite numerous and detailed studies of the jets of active galactic nuclei (AGN) on pc-scales, many questions are still debated. The physical nature of the jet components is one of the most prominent unsolved problems, as is the launching mechanism of jets in AGN. The quasar 1308+326 (z = 0.997) allows us to study the overall properties of its jet in detail and to derive a more physical understanding of the nature and origin of jets in general. The long-term data provided by the Monitoring Of Jets in Active galactic nuclei with Very Long Baseline Array (VLBA) experiments (MOJAVE) survey permit us to trace out the structural changes in 1308+326 that we present here. The long-lived jet features in this source can be followed for about two decades. Aims: We investigate the very long baseline interferomety (VLBI) morphology and kinematics of the jet of 1308+326 to understand the physical nature of this jet and jets in general, the role of magnetic fields, and the causal connection between jet features and the launching process. Methods: Fifty VLBA observations performed at 15 GHz from the MOJAVE survey were re-modeled with Gaussian components and re-analyzed (the time covered: 20 Jan. 1995-25 Jan. 2014). The analysis was supplemented by multi-wavelength radio-data (UMRAO, at 4.8, 8.0, and 14.5 GHz) in polarization and total intensity. We fit the apparent motion of the jet features with the help of a model of a precessing nozzle. Results: The jet features seem to be emitted with varying viewing angles and launched into an ejection cone. Tracing the component paths yields evidence for rotational motion. Radio flux-density variability can be explained as a consequence of enhanced Doppler boosting corresponding to the motion of the jet relative to the line of sight. Based on the presented kinematics and other indicators, such as electric-vector polarization position-angle (EVPA) rotation, we conclude that the jet of 1308+326 has a helical structure, meaning that

Galactic wind shells and high redshift radio galaxies. On the nature of associated absorbers

NASA Astrophysics Data System (ADS)

Krause, M.

2005-06-01

A jet is simulated on the background of a galactic wind headed by a radiative bow shock. The wind shell, which is due to the radiative bow shock, is effectively destroyed by the impact of the jet cocoon, thanks to Rayleigh-Taylor instabilities. Associated strong HI absorption, and possibly also molecular emission, in high redshift radio galaxies which is observed preferentially in the smaller ones may be explained by that model, which is an improvement of an earlier radiative bow shock model. The model requires temperatures of ≈106 K in the proto-clusters hosting these objects, and may be tested by high resolution spectroscopy of the Lyα line. The simulations show that - before destruction - the jet cocoon fills the wind shell entirely for a considerable time with intact absorption system. Therefore, radio imaging of sources smaller than the critical size should reveal the round central bubbles, if the model is correct.

The Fossil Nuclear Outflow in the Central 30 pc of the Galactic Center

NASA Astrophysics Data System (ADS)

Hsieh, Pei-Ying; Ho, Paul T. P.; Hwang, Chorng-Yuan; Shimajiri, Yoshito; Matsushita, Satoki; Koch, Patrick M.; Iono, Daisuke

2016-11-01

We report a new 1 pc (30″) resolution CS(J=2-1) line map of the central 30 pc of the Galactic center (GC), made with the Nobeyama 45 m telescope. We revisit our previous study of an extraplanar feature called the polar arc (PA), which is a molecular cloud located above SgrA*, with a velocity gradient perpendicular to the galactic plane. We find that the PA can be traced back to the galactic disk. This provides clues to the launching point of the PA, roughly 6 × 106 years ago. Implications of the dynamical timescale of the PA might be related to the Galactic center lobe at parsec scale. Our results suggest that, in the central 30 pc of the GC, the feedback from past explosions could alter the orbital path of molecular gas down to the central tenth of a parsec. In the follow-up work of our new CS(J=2-1) map, we also find that, near systemic velocity, the molecular gas shows an extraplanar hourglass-shaped feature (HG-feature) with a size of ˜13 pc. The latitude-velocity diagrams show that the eastern edge of the HG-feature is associated with an expanding bubble B1, ˜7 pc away from SgrA*. The dynamical timescale of this bubble is ˜3 × 105 years. This bubble is interacting with the 50 km s-1 cloud. Part of the molecular gas from the 50 km s-1 cloud was swept away by the bubble to b=-0\\buildrel{\\circ}\\over{.} 2. The western edge of the HG-feature seems to be molecular gas entrained from the 20 km s-1 cloud toward the north of the galactic disk. Our results suggest a fossil explosion in the central 30 pc of the GC, a few 105 years ago.

Interstellar Matters: Neutral Hydrogen and the Galactic Magnetic Field

NASA Astrophysics Data System (ADS)

Verschuur, Gerrit; Schmelz, Joan T.; Asgari-Targhi asgari-Targhi, M.

2018-01-01

The physics of the interstellar medium was revolutionized by the observations of the Galactic Arecibo L-Band Feed Array (GALFA) HI survey done at the Arecibo Observatory. The high-resolution, high-sensitivity, high-dynamic- range images show complex, tangled, extended filaments, and reveal that the fabric of the neutral interstellar medium is deeply tied to the structure of the ambient magnetic field. This discovery prompts an obvious question – how exactly is the interstellar {\\it neutral} hydrogen being affected by the galactic magnetic field? We look into this question by examining a set of GALFA-HI data in great detail. We have chosen a long, straight filament in the southern galactic sky. This structure is both close by and isolated in velocity space. Gaussian analysis of profiles both along and across the filament reveal internal structure – braided strands that can be traced through the simplest part, but become tangled in more complex segments. These braids do not resemble in any way the old spherical HI clouds and rudimentary pressure balance models that were used to explain the pre-GALFA- HI interstellar medium. It is clear that these structures are created, constrained, and dominated by magnetic fields. Like many subfields of astronomy before it, e.g., physics of the solar coronal, extragalactic radio jets, and pulsar environment, scientists are confronted with observations that simply cannot be explained by simple hydrodynamics and are forced to consider magneto-hydrodynamics.

Misaligned Accretion and Jet Production

NASA Astrophysics Data System (ADS)

King, Andrew; Nixon, Chris

2018-04-01

Disk accretion onto a black hole is often misaligned from its spin axis. If the disk maintains a significant magnetic field normal to its local plane, we show that dipole radiation from Lense–Thirring precessing disk annuli can extract a significant fraction of the accretion energy, sharply peaked toward small disk radii R (as R ‑17/2 for fields with constant equipartition ratio). This low-frequency emission is immediately absorbed by surrounding matter or refracted toward the regions of lowest density. The resultant mechanical pressure, dipole angular pattern, and much lower matter density toward the rotational poles create a strong tendency to drive jets along the black hole spin axis, similar to the spin-axis jets of radio pulsars, also strong dipole emitters. The coherent primary emission may explain the high brightness temperatures seen in jets. The intrinsic disk emission is modulated at Lense–Thirring frequencies near the inner edge, providing a physical mechanism for low-frequency quasi-periodic oscillations (QPOs). Dipole emission requires nonzero hole spin, but uses only disk accretion energy. No spin energy is extracted, unlike the Blandford–Znajek process. Magnetohydrodynamic/general-relativistic magnetohydrodynamic (MHD/GRMHD) formulations do not directly give radiation fields, but can be checked post-process for dipole emission and therefore self-consistency, given sufficient resolution. Jets driven by dipole radiation should be more common in active galactic nuclei (AGN) than in X-ray binaries, and in low accretion-rate states than high, agreeing with observation. In non-black hole accretion, misaligned disk annuli precess because of the accretor’s mass quadrupole moment, similarly producing jets and QPOs.

Galactic gamma-ray observations and galactic structure

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1975-01-01

Recent observations of gamma-rays originating in the galactic disk together with radio observations, support an emerging picture of the overall structure of our galaxy with higher interstellar gas densities and star formation rates in a region which corresponds to that of the inner arms. The emerging picture is one where molecular clouds make up the dominant constituent of the interstellar gas in the inner galaxy and play a key role in accounting for the gamma-rays and phenomena associated with the production of young stars and other population 1 objects. In this picture, cosmic rays are associated with supernovae and are primarily of galactic origin. These newly observed phenomena can be understood as consequences of the density wave theories of spiral structure. Based on these new developments, the suggestion is made that a new galactic population class, Population O, be added to the standard Populations 1 and 2 in order to recognize important differences in dynamics and distribution between diffuse galactic H1 and interstellar molecular clouds.

Fourier plane modeling of the jet in the galaxy M81

NASA Astrophysics Data System (ADS)

Ramessur, Arvind; Bietenholz, Michael F.; Leeuw, Lerothodi L.; Bartel, Norbert

2015-03-01

The nearby spiral galaxy M81 has a low-luminosity Active Galactic Nucleus in its center with a core and a one-sided curved jet, dubbed M81*, that is barely resolved with VLBI. To derive basic parameters such as the length of the jet, its orientation and curvature, the usual method of model-fitting with point sources and elliptical Gaussians may not always be the most appropriate one. We are developing Fourier-plane models for such sources, in particular an asymmetric triangle model to fit the extensive set of VLBI data of M81* in the u-v plane. This method may have an advantage over conventional ones in extracting information close to the resolution limit to provide us with a more comprehensive picture of the structure and evolution of the jet. We report on preliminary results.

Particle Acceleration in Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Miller, James A.

1997-01-01

The high efficiency of energy generation inferred from radio observations of quasars and X-ray observations of Seyfert active galactic nuclei (AGNs) is apparently achieved only by the gravitational conversion of the rest mass energy of accreting matter onto supermassive black holes. Evidence for the acceleration of particles to high energies by a central engine is also inferred from observations of apparent superluminal motion in flat spectrum, core-dominated radio sources. This phenomenon is widely attributed to the ejection of relativistic bulk plasma from the nuclei of active galaxies, and accounts for the existence of large scale radio jets and lobes at large distances from the central regions of radio galaxies. Reports of radio jets and superluminal motion from galactic black hole candidate X-ray sources indicate that similar processes are operating in these sources. Observations of luminous, rapidly variable high-energy radiation from active galactic nuclei (AGNs) with the Compton Gamma Ray Observatory show directly that particles are accelerated to high energies in a compact environment. The mechanisms which transform the gravitational potential energy of the infalling matter into nonthermal particle energy in galactic black hole candidates and AGNs are not conclusively identified, although several have been proposed. These include direct acceleration by static electric fields (resulting from, for example, magnetic reconnection), shock acceleration, and energy extraction from the rotational energy of Kerr black holes. The dominant acceleration mechanism(s) operating in the black hole environment can only be determined, of course, by a comparison of model predictions with observations. The purpose of the work proposed for this grant was to investigate stochastic particle acceleration through resonant interactions with plasma waves that populate the magnetosphere surrounding an accreting black hole. Stochastic acceleration has been successfully applied to the

Jets, arcs, and shocks: NGC 5195 at radio wavelengths

NASA Astrophysics Data System (ADS)

Rampadarath, H.; Soria, R.; Urquhart, R.; Argo, M. K.; Brightman, M.; Lacey, C. K.; Schlegel, E. M.; Beswick, R. J.; Baldi, R. D.; Muxlow, T. W. B.; McHardy, I. M.; Williams, D. R. A.; Dumas, G.

2018-05-01

We studied the nearby, interacting galaxy NGC 5195 (M 51b) in the radio, optical and X-ray bands. We mapped the extended, low-surface-brightness features of its radio-continuum emission; determined the energy content of its complex structure of shock-ionized gas; constrained the current activity level of its supermassive nuclear black hole. In particular, we combined data from the European Very Long Baseline Interferometry Network (˜1-pc scale), from our new e-MERLIN observations (˜10-pc scale), and from the Very Large Array (˜100-1000-pc scale), to obtain a global picture of energy injection in this galaxy. We put an upper limit to the luminosity of the (undetected) flat-spectrum radio core. We find steep-spectrum, extended emission within 10 pc of the nuclear position, consistent with optically thin synchrotron emission from nuclear star formation or from an outflow powered by an active galactic nucleus (AGN). A linear spur of radio emission juts out of the nuclear source towards the kpc-scale arcs (detected in radio, Hα and X-ray bands). From the size, shock velocity, and Balmer line luminosity of the kpc-scale bubble, we estimate that it was inflated by a long-term-average mechanical power ˜3-6 × 1041 erg s-1 over the last 3-6 Myr. This is an order of magnitude more power than can be provided by the current level of star formation, and by the current accretion power of the supermassive black hole. We argue that a jet-inflated bubble scenario associated with previous episodes of AGN activity is the most likely explanation for the kpc-scale structures.

DISCOVERY OF NUCLEAR WATER MASER EMISSION IN CENTAURUS A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ott, Juergen; Meier, David S.; Walter, Fabian

2013-07-10

We report the detection of a 22 GHz water maser line in the nearest (D {approx} 3.8 Mpc) radio galaxy Centaurus A (Cen A) using the Australia Telescope Compact Array (ATCA). The line is centered at a velocity of {approx}960 km s{sup -1}, which is redshifted by about 415 km s{sup -1} from the systemic velocity. Such an offset, as well as the width of {approx}120 km s{sup -1}, could be consistent with either a nuclear maser arising from an accretion disk of the central supermassive black hole (SMBH), or with a jet maser that is emitted from the materialmore » that is shocked near the base of the jet in Cen A. The best spatial resolution of our ATCA data constrains the origin of the maser feature within <3 pc of the SMBH. The maser exhibits an isotropic luminosity of {approx}1 L{sub Sun }, which classifies it as a kilomaser, and appears to be variable on timescales of months. A kilomaser can also be emitted by shocked gas in star-forming regions. Given the small projected distance from the core, the large offset from systemic velocity, and the smoothness of the line feature, we conclude that a jet maser line emitted by shocked gas around the base of the active galactic nucleus is the most likely explanation. For this scenario we can infer a minimum density of the radio jet of {approx}> 10 cm{sup -3}, which indicates substantial mass entrainment of surrounding gas into the propagating jet material.« less

The study of the plasma jets of lead and silver simulating spent nuclear fuel components

NASA Astrophysics Data System (ADS)

Antonov, N. N.; Gavrikov, A. V.; Smirnov, V. P.; Liziakin, G. D.; Usmanov, R. A.; Vorona, N. A.; Timirkhanov, R. A.

2018-01-01

One of the tasks that must be solved to develop a spent nuclear fuel (SNF) plasma separation method is a creation of plasma source of substances simulating SNF components. Plasma of the diffuse arc discharge in a magnetic field with an incandescent cathode was considered in this paper, as such source. The discharge was initiated in a model substances vapor (lead and silver). Evaporation was carried out by crucible induction heating. Current- voltage characteristics of the discharge were obtained. Spectral analysis of the plasma jets radiation and double probe characteristics measurements in the area behind the anode were carried out. The minimum potential difference between the anode and cathode reached a value of about 7 V at current of about 1 A. When the potential difference in the discharge gap was close to 30 V (4.5 A) and 10 V (5.2 A) electron temperature in the plasma jet was 5-7 eV and 1-3 eV, respectively. Plasma density in jets took the value from 1011 cm-3 to 1012 cm-3. The obtained results indicate the possibility of using this type of discharge for the SNF plasma separation method approbation.

The Spectacular Radio-Near-IR-X-Ray Jet of 3C 111: the X-Ray Emission Mechanism and Jet Kinematics

NASA Technical Reports Server (NTRS)

Clautice, Devon; Perlman, Eric S.; Georganopoulos, Markos; Lister, Matthew L.; Tombesi, Francesco; Cara, Mihai; Marshall, Herman L.; Hogan, Brandon M.; Kazanas, Demos

2016-01-01

Relativistic jets are the most energetic manifestation of the active galactic nucleus (AGN) phenomenon. AGN jets are observed from the radio through gamma-rays and carry copious amounts of matter and energy from the subparsec central regions out to the kiloparsec and often megaparsec scale galaxy and cluster environs. While most spatially resolved jets are seen in the radio, an increasing number have been discovered to emit in the optical/near- IR and/or X-ray bands. Here we discuss a spectacular example of this class, the 3C 111 jet, housed in one of the nearest, double-lobed FR II radio galaxies known. We discuss new, deep Chandra and Hubble Space Telescope (HST) observations that reveal both near-IR and X-ray emission from several components of the 3C 111 jet, as well as both the northern and southern hotspots. Important differences are seen between the morphologies in the radio, X-ray, and near-IR bands. The long (over 100 kpc on each side), straight nature of this jet makes it an excellent prototype for future, deep observations, as it is one of the longest such features seen in the radio, near-IR/optical, and X-ray bands. Several independent lines of evidence, including the X-ray and broadband spectral shape as well as the implied velocity of the approaching hotspot, lead us to strongly disfavor the EC/CMB model and instead favor a two-component synchrotron model to explain the observed X-ray emission for several jet components. Future observations with NuSTAR, HST, and Chandra will allow us to further constrain the emission mechanisms.

THE SPECTACULAR RADIO-NEAR-IR-X-RAY JET OF 3C 111: THE X-RAY EMISSION MECHANISM AND JET KINEMATICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clautice, Devon; Perlman, Eric S.; Georganopoulos, Markos

2016-08-01

Relativistic jets are the most energetic manifestation of the active galactic nucleus (AGN) phenomenon. AGN jets are observed from the radio through gamma-rays and carry copious amounts of matter and energy from the sub-parsec central regions out to the kiloparsec and often megaparsec scale galaxy and cluster environs. While most spatially resolved jets are seen in the radio, an increasing number have been discovered to emit in the optical/near-IR and/or X-ray bands. Here we discuss a spectacular example of this class, the 3C 111 jet, housed in one of the nearest, double-lobed FR II radio galaxies known. We discuss new,more » deep Chandra and Hubble Space Telescope ( HST ) observations that reveal both near-IR and X-ray emission from several components of the 3C 111 jet, as well as both the northern and southern hotspots. Important differences are seen between the morphologies in the radio, X-ray, and near-IR bands. The long (over 100 kpc on each side), straight nature of this jet makes it an excellent prototype for future, deep observations, as it is one of the longest such features seen in the radio, near-IR/optical, and X-ray bands. Several independent lines of evidence, including the X-ray and broadband spectral shape as well as the implied velocity of the approaching hotspot, lead us to strongly disfavor the EC/CMB model and instead favor a two-component synchrotron model to explain the observed X-ray emission for several jet components. Future observations with NuSTAR , HST , and Chandra will allow us to further constrain the emission mechanisms.« less

The sixteen to forty micron spectroscopy from the NASA Lear jet

NASA Technical Reports Server (NTRS)

Houck, J. R.

1982-01-01

Two cryogenically cooled infrared grating spectrometers were designed, fabricated and used on the NASA Lear Jet Observatory. The first spectrometer was used to measure continuum sources such as dust in H II regions, the galactic center and the thermal emission from Mars, Jupiter, Saturn, and Venus over the 16 to 40 micron spectral range. The second spectrometer had higher resolution and was used to measure ionic spectral lines in H II regions (S III at 18.7 microns). It was later used extensively on NASA C-141 Observatory to make observations of numerous objects including H II regions, planetary nebulae, stars with circumstellar shells, the galactic center and extragalactic objects. The spectrometers are described including the major innovations and a list of the scientific contributions.

Physics of liquid jets

NASA Astrophysics Data System (ADS)

Eggers, Jens; Villermaux, Emmanuel

2008-03-01

Jets, i.e. collimated streams of matter, occur from the microscale up to the large-scale structure of the universe. Our focus will be mostly on surface tension effects, which result from the cohesive properties of liquids. Paradoxically, cohesive forces promote the breakup of jets, widely encountered in nature, technology and basic science, for example in nuclear fission, DNA sampling, medical diagnostics, sprays, agricultural irrigation and jet engine technology. Liquid jets thus serve as a paradigm for free-surface motion, hydrodynamic instability and singularity formation leading to drop breakup. In addition to their practical usefulness, jets are an ideal probe for liquid properties, such as surface tension, viscosity or non-Newtonian rheology. They also arise from the last but one topology change of liquid masses bursting into sprays. Jet dynamics are sensitive to the turbulent or thermal excitation of the fluid, as well as to the surrounding gas or fluid medium. The aim of this review is to provide a unified description of the fundamental and the technological aspects of these subjects.

Jetting Through the Primordial Universe

NASA Astrophysics Data System (ADS)

Kunnawalkam Elayavalli, Raghav

Collisions of heavy ion nuclei at relativistic speeds (close to the speed of light), sometimes referred to as the "little bang", can recreate conditions similar to the early universe. This high temperature and very dense form of matter, now known to consist of de-confined quarks and gluons is named the quark gluon plasma (QGP). An early signature of the QGP, both theorized and seen in experiments, was the aspect of "jet quenching" and understanding that phenomenon will be the main focus of this thesis. The concept behind quenching is that a high energetic quark or gluon jet undergoes significant energy loss due to the overall structure modifications related to its fragmentation and radiation patterns as it traverses the medium. The term jet, parameterized by a fixed lateral size or the jet radius, represents the collimated spray of particles arising from an initial parton. In this thesis, Run1 experimental data from pp and heavy ion collisions at the CERN LHC is analyzed with the CMS detector. Analysis steps involved in the measurement of the inclusive jet cross section in pp, pPb and PbPb systems are outlined in detail. The pp jet cross section is compared with next to leading order theoretical calculations supplemented with non perturbative corrections for three different jet radii highlighting better comparisons for larger radii jets. Measurement of the jet yield followed by the nuclear modification factors in proton-lead at 5.02 TeV and lead-lead collisions at 2.76 TeV are presented. Since pp data at 5.02 TeV was not available in Run1, an extrapolation method is performed to derive a reference pp spectra. A new data driven technique is introduced to estimate and correct for the fake jet contribution in PbPb for low transverse momenta jets. The nuclear modification factors studied in this thesis show jet quenching to be attributed to final state effects, have a strong correlation to the event centrality, a weak inverse correlation to the jet transverse momenta

Jets from Young Stars in Cygnus-X

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-03-01

How do you spot very young, newly formed stars? One giveaway is the presence of jets and outflows that interact with the stars environments. In a new study, scientists have now discovered an unprecedented number of these outflows in a nearby star-forming region of our galaxy.Young Stars Hard at WorkCO map of the Cygnus-X region of the galactic plane, with the grid showing the UWISH2 coverage and the black triangles showing the positions of the detected outflows. [Makin Froebrich 2018]The birth and evolution of young stars is a dynamic, energetic process. As new stars form, material falls inward from the accretion disks surrounding young stellar objects, or YSOs. This material can power collimated streams of gas and dust that flow out along the stars rotation axes, plowing through the surrounding material. Where the outflows collide with the outside environment, shocks form that can be spotted in near-infrared hydrogen emission.Though weve learned a lot about these outflows, there remain a number of open questions. What factors govern their properties, such as their lengths, luminosities, and orientations? What is the origin of the emission features we see within the jets, known as knots? What roles do the driving sources and the environments play in the behavior and appearance of the jets?A selection of previously unknown outflows discovered as a result of this survey. Click for a closer look. [Makin Froebrich 2018]To answer these questions, we need to build a large, unbiased statistical sample of YSOs from across the galactic plane. Now, a large infrared survey known as the UKIRT Widefield Infrared Survey for H2 (UWISH2) is working toward that goal.Jackpot in Cygnus-XIn a recent publication, Sally Makin and Dirk Froebrich (University of Kent, UK), present results from UWISH2s latest release: a survey segment targeting a 42-square-degree region in the galactic plane known as the Cygnus-X star-forming region.The teams search for shock-excited emission in Cygnus

Jet-torus connection in radio galaxies. Relativistic hydrodynamics and synthetic emission

NASA Astrophysics Data System (ADS)

Fromm, C. M.; Perucho, M.; Porth, O.; Younsi, Z.; Ros, E.; Mizuno, Y.; Zensus, J. A.; Rezzolla, L.

2018-01-01

Context. High resolution very long baseline interferometry observations of active galactic nuclei have revealed asymmetric structures in the jets of radio galaxies. These asymmetric structures may be due to internal asymmetries in the jets or they may be induced by the different conditions in the surrounding ambient medium, including the obscuring torus, or a combination of the two. Aims: In this paper we investigate the influence of the ambient medium, including the obscuring torus, on the observed properties of jets from radio galaxies. Methods: We performed special-relativistic hydrodynamic (SRHD) simulations of over-pressured and pressure-matched jets using the special-relativistic hydrodynamics code Ratpenat, which is based on a second-order accurate finite-volume method and an approximate Riemann solver. Using a newly developed radiative transfer code to compute the electromagnetic radiation, we modelled several jets embedded in various ambient medium and torus configurations and subsequently computed the non-thermal emission produced by the jet and thermal absorption from the torus. To better compare the emission simulations with observations we produced synthetic radio maps, taking into account the properties of the observatory. Results: The detailed analysis of our simulations shows that the observed properties such as core shift could be used to distinguish between over-pressured and pressure matched jets. In addition to the properties of the jets, insights into the extent and density of the obscuring torus can be obtained from analyses of the single-dish spectrum and spectral index maps.

DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEI. II. THE CASE OF EQUAL PEAKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, K. L.; Shields, G. A.; Salviander, S.

Active galactic nuclei (AGNs) with double-peaked narrow lines (DPAGNs) may be caused by kiloparsec-scale binary AGNs, bipolar outflows, or rotating gaseous disks. We examine the class of DPAGNs in which the two narrow-line components have closely similar intensity as being especially likely to involve disks or jets. Two spectroscopic indicators support this likelihood. For DPAGNs from Smith et al., the 'equal-peaked' objects (EPAGNs) have [Ne V]/[O III]ratios lower than for a control sample of non-double-peaked AGNs. This is unexpected for a pair of normal AGNs in a galactic merger, but may be consistent with [O III] emission from a rotatingmore » ring with relatively little gas at small radii. Also, [O III]/H{beta} ratios of the redshifted and blueshifted systems in the EPAGN are more similar to each other than in a control sample, suggestive of a single ionizing source and inconsistent with the binary interpretation.« less

Dual-Frequency VLBI Study of Centaurus A on Sub-Parsec Scales: The Highest-Resolution View of an Extragalactic Jet

NASA Technical Reports Server (NTRS)

Mueller, C.; Kadler, M.; Ojha, R.; Wilms, J.; Boeck, M.; Edwards, P.; Fromm, C. M.; Hase, H.; Horiuchi, S.; Katz, U.;

Detection of helicoidal motion in the optical jet of PKS 0521-365

NASA Astrophysics Data System (ADS)

Jiménez-Andrade, E. F.; Chavushyan, V.; León-Tavares, J.; Patiño-Álvarez, V. M.; Olguín-Iglesias, A.; Kotilainen, J.; Falomo, R.; Hyvönen, T.

2017-09-01

The jet activity of active galactic nuclei (AGNs), and its interaction with the interstellar medium, may play a pivotal role in the processes that regulate the growth and star formation of its host galaxy. Observational evidence that pinpoints the conditions of such interaction is paramount to unveil the physical processes involved. We report on the discovery of extended emission-line regions exhibiting an S-shaped morphology along the optical jet of the radio-loud AGN PKS 0521-365 (z = 0.055), by using long-slit spectroscopic observations obtained with FOcal Reducer/low dispersion Spectrograph 2 on the Very Large Telescope. The velocity pattern derived from the [O II] λ3727 Å, H β λ4861 Å and [O III] λλ4959, 5007 Å emission lines is well fitted by a sinusoidal function of the form: v(r) = αr1/2sin(βr1/2 + γ), suggesting helicoidal motions along the jet up to distances of 20 kpc. We estimate a lower limit for the mass of the outflowing ionized gas along the jet of ˜104 M⊙. Helical magnetic fields and jet precession have been proposed to explain helicoidal paths along the jet at pc scales; nevertheless, it is not clear yet whether these hypotheses may hold at kpc scales.

Galactic plane gamma-radiation

NASA Technical Reports Server (NTRS)

Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Fichtel, C. E.; Ogelman, H. B.; Tumer, T.; Ozel, M. E.

1979-01-01

Analysis of the SAS 2 data together with the COS B results shows that the distribution of galactic gamma-radiation has several similarities to that of other large-scale tracers of galactic structure. The radiation is primarily confined to a thin disc which exhibits offsets from b = 0 degrees similar to warping at radio frequencies. The principal distinction of the gamma-radiation is a stronger contrast in intensity between the region from 310 to 45 degrees in longitude and the regions away from the center that can be attributed to a variation in cosmic-ray density as a function of position in Galaxy. The diffuse galactic gamma-ray energy spectrum shows no significant variation in direction, and the spectrum seen along the plane is the same as that for the galactic component of the gamma-radiation at high altitudes. The uniformity of the galactic gamma-ray spectrum, the smooth decrease in intensity as a function of altitude, and the absence of any galactic gamma-ray sources at high altitudes indicate a diffuse origin for bulk of the galactic gamma-radiation rather than a collection of localized sources.

A (likely) X-ray jet from NGC6217 observed by XMM-Newton

NASA Astrophysics Data System (ADS)

Falocco, Serena; Larsson, Josefin; Nandi, Sumana

2017-12-01

NGC6217 is a nearby spiral galaxy with a starburst region near its centre. Evidence for a low-luminosity Active Galactic Nucleus (AGN) in its core has also been found in optical spectra. Intriguingly, X-ray observations by ROSAT revealed three knots aligned with the galaxy centre, resembling a jet structure. This paper presents a study of XMM-Newton observations made to assess the hypothesis of a jet emitted from the centre of NGC6217. The XMM data confirm the knots found with ROSAT and our spectral analysis shows that they have similar spectral properties with a hard photon index Γ ∼ 1.7. The core of NGC6217 is well fitted by a model with an AGN and a starburst component, where the AGN contributes at most 46 per cent of the total flux. The candidate jet has an apparent length ∼15 kpc and a luminosity of ∼5 × 1038 erg s- 1. It stands out by being hosted by a spiral galaxy, since jets are more widely associated with ellipticals. To explain the jet launching mechanism we consider the hypothesis of an advection dominated accretion flow with a low accretion rate. The candidate jet emitted from NGC6217 is intriguing since it represents a challenge to the current knowledge of the connection between AGN, jets and host galaxies.

The Stability of Radiatively Cooling Jets I. Linear Analysis

NASA Technical Reports Server (NTRS)

Hardee, Philip E.; Stone, James M.

1997-01-01

The results of a spatial stability analysis of a two-dimensional slab jet, in which optically thin radiative cooling is dynamically important, are presented. We study both magnetized and unmagnetized jets at external Mach numbers of 5 and 20. We model the cooling rate by using two different cooling curves: one appropriate to interstellar gas, and the other to photoionized gas of reduced metallicity. Thus, our results will be applicable to both protostellar (Herbig-Haro) jets and optical jets from active galactic nuclei. We present analytical solutions to the dispersion relations in useful limits and solve the dispersion relations numerically over a broad range of perturbation frequencies. We find that the growth rates and wavelengths of the unstable Kelvin-Helmholtz (K-H) modes are significantly different from the adiabatic limit, and that the form of the cooling function strongly affects the results. In particular, if the cooling curve is a steep function of temperature in the neighborhood of the equilibrium state, then the growth of K-H modes is reduced relative to the adiabatic jet. On the other hand, if the cooling curve is a shallow function of temperature, then the growth of K-H modes can be enhanced relative to the adiabatic jet by the increase in cooling relative to heating in overdense regions. Inclusion of a dynamically important magnetic field does not strongly modify the important differences between an adiabatic jet and a cooling jet, provided the jet is highly supermagnetosonic and not magnetic pressure-dominated. In the latter case, the unstable modes behave more like the transmagnetosonic magnetic pressure-dominated adiabatic limit. We also plot fluid displacement surfaces associated with the various waves in a cooling jet in order to predict the structures that might arise in the nonlinear regime. This analysis predicts that low-frequency surface waves and the lowest order body modes will be the most effective at producing observable features in

Galaxy interactions and the stimulation of nuclear activity

NASA Technical Reports Server (NTRS)

Heckman, Timothy M.

1990-01-01

The author discusses the idea that interactions between galaxies can lead to enhanced galactic activity. He discusses whether, apart from the observational evidence, there is a strong theoretical or heuristic motivation for investigating galaxy interactions as stimulators of nuclear activity in galaxies. Galactic interactions as mechanisms for triggering nuclear starbursts are covered.

The power of relativistic jets is larger than the luminosity of their accretion disks.

PubMed

Ghisellini, G; Tavecchio, F; Maraschi, L; Celotti, A; Sbarrato, T

2014-11-20

Theoretical models for the production of relativistic jets from active galactic nuclei predict that jet power arises from the spin and mass of the central supermassive black hole, as well as from the magnetic field near the event horizon. The physical mechanism underlying the contribution from the magnetic field is the torque exerted on the rotating black hole by the field amplified by the accreting material. If the squared magnetic field is proportional to the accretion rate, then there will be a correlation between jet power and accretion luminosity. There is evidence for such a correlation, but inadequate knowledge of the accretion luminosity of the limited and inhomogeneous samples used prevented a firm conclusion. Here we report an analysis of archival observations of a sample of blazars (quasars whose jets point towards Earth) that overcomes previous limitations. We find a clear correlation between jet power, as measured through the γ-ray luminosity, and accretion luminosity, as measured by the broad emission lines, with the jet power dominating the disk luminosity, in agreement with numerical simulations. This implies that the magnetic field threading the black hole horizon reaches the maximum value sustainable by the accreting matter.

Measurements of the nuclear modification factor for jets in Pb + Pb collisions at s NN = 2.76 TeV with the ATLAS detector

DOE PAGES

Aad, G.

2015-02-20

The measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √ sNN = 2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14 nb -1, respectively. The jets are identified with the anti-kt algorithm with R = 0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32T<500 GeV and absolute rapidity |y|<2.1 and as a function of collision centrality. The nuclear modification factor R AA is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions comparedmore » to pp collisions. The R AA shows a slight increase with p T and no significant variation with rapidity.« less

Benchmark studies of thermal jet mixing in SFRs using a two-jet model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omotowa, O. A.; Skifton, R.; Tokuhiro, A.

To guide the modeling, simulations and design of Sodium Fast Reactors (SFRs), we explore and compare the predictive capabilities of two numerical solvers COMSOL and OpenFOAM in the thermal jet mixing of two buoyant jets typical of the outlet flow from a SFR tube bundle. This process will help optimize on-going experimental efforts at obtaining high resolution data for V and V of CFD codes as anticipated in next generation nuclear systems. Using the k-{epsilon} turbulence models of both codes as reference, their ability to simulate the turbulence behavior in similar environments was first validated for single jet experimental datamore » reported in literature. This study investigates the thermal mixing of two parallel jets having a temperature difference (hot-to-cold) {Delta}T{sub hc}= 5 deg. C, 10 deg. C and velocity ratios U{sub c}/U{sub h} = 0.5, 1. Results of the computed turbulent quantities due to convective mixing and the variations in flow field along the axial position are presented. In addition, this study also evaluates the effect of spacing ratio between jets in predicting the flow field and jet behavior in near and far fields. (authors)« less

Arrhenius reconsidered: astrophysical jets and the spread of spores

NASA Astrophysics Data System (ADS)

Sheldon, Malkah I.; Sheldon, Robert B.

2015-09-01

In 1871, Lord Kelvin suggested that the fossil record could be an account of bacterial arrivals on comets. In 1903, Svante Arrhenius suggested that spores could be transported on stellar winds without comets. In 1984, Sir Fred Hoyle claimed to see the infrared signature of vast clouds of dried bacteria and diatoms. In 2012, the Polonnaruwa carbonaceous chondrite revealed fossilized diatoms apparently living on a comet. However, Arrhenius' spores were thought to perish in the long transit between stars. Those calculations, however, assume that maximum velocities are limited by solar winds to ~5 km/s. Herbig-Haro objects and T-Tauri stars, however, are young stars with jets of several 100 km/s that might provide the necessary propulsion. The central engine of bipolar astrophysical jets is not presently understood, but we argue it is a kinetic plasma instability of a charged central magnetic body. We show how to make a bipolar jet in a belljar. The instability is non-linear, and thus very robust to scaling laws that map from microquasars to active galactic nuclei. We scale up to stellar sizes and recalculate the viability/transit-time for spores carried by supersonic jets, to show the viability of the Arrhenius mechanism.

Hydrodynamic stability of jets produced by mass accreting systems

NASA Technical Reports Server (NTRS)

Hardee, P. E.

1982-01-01

The existing model for pulsed X-ray emission from the source Hercules X-1 is reviewed. A necessary part of this model is a processing accretion disk which turns the source on and off with 35 day cycle. It is usually assumed that precession of the primary star in this binary system, Hz Hercules, slaves the disk to its precession rate. This model can account for the system behavior in a qualitative manner. Precession of Hz Hercules with 35 day period requires precession of the binary orbit. Pulse arrival times from Herc X-1 have been analyzed for orbital precession. The inclusion of precession does not significantly improve the results obtained assuming a non-precessing orbit. The fluid dynamical stability of extra-galactic jets and the possible consequences of Kelvin-Helmholtz instability at the jet surface external medium interface are considered.

Diffuse γ-ray emission from misaligned active galactic nuclei

DOE PAGES

Di Mauro, M.; Calore, F.; Donato, F.; ...

2013-12-20

Active galactic nuclei (AGNs) with jets seen at small viewing angles are the most luminous and abundant objects in the γ-ray sky. AGNs with jets misaligned along the line of sight appear fainter in the sky but are more numerous than the brighter blazars. Here, we calculate the diffuse γ-ray emission due to the population of misaligned AGNs (MAGNs) unresolved by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). Furthermore, a correlation between the γ-ray luminosity and the radio-core luminosity is established and demonstrated to be physical by statistical tests, as well as compatible with uppermore » limits based on Fermi-LAT data for a large sample of radio-loud MAGNs. We constrain the derived γ-ray luminosity function by means of the source-count distribution of the radio galaxies detected by the Fermi-LAT. We finally calculate the diffuse γ-ray flux due to the whole MAGN population. These results demonstrate that MAGNs can contribute from 10% up to nearly the entire measured isotropic gamma-ray background. We evaluate a theoretical uncertainty on the flux of almost an order of magnitude.« less

A Three Parsec-Scale Jet-Driven Outflow from Sgr A

NASA Technical Reports Server (NTRS)

Yusef-Zadeh, F.; Arendt, R.; Bushouse, H.; Cotton, W.; Haggard, D.; Pound, M. W.; Roberts, D. A.; Royster, M.; Wardle, M.

2012-01-01

The compact radio source Sgr A* is coincident with a 4x 10(exp 6) solar Mass black hole at the dynamical center of the Galaxy and is surrounded by dense orbiting ionized and molecular gas. We present high resolution radio continuum images of the central 3' and report a faint continuous linear structure centered on Sgr A*. This feature is rotated by 28 deg in PA with respect to the Galactic plane. A number of weak blobs of radio emission with X-ray counterparts are detected along the axis of the linear structure. In addition, the continuous linear feature appears to be terminated symmetrically by two linearly polarized structures at 8.4 GHz, approx 75" from Sgr A*. The linear structure is best characterized by a mildly relativistic jet-driven outflow from Sgr A*, and an outflow rate 10(exp 6) solar M / yr. The near and far-sides of the jet are interacting with orbiting ionized and molecular gas over the last 1-3 hundred years and are responsible for the origin of a 2" hole, the "minicavity", where disturbed kinematics, enhanced FeII/III line emission, and diffuse X-ray gas have been detected. The estimated kinetic luminosity of the outflow is approx 1.2 X 10(exp 41) erg/s which can produce the Galactic center X-ray flash that has recently been identified

Accretion disk winds as the jet suppression mechanism in the microquasar GRS 1915+105.

PubMed

Neilsen, Joseph; Lee, Julia C

2009-03-26

Stellar-mass black holes with relativistic jets, also known as microquasars, mimic the behaviour of quasars and active galactic nuclei. Because timescales around stellar-mass black holes are orders of magnitude smaller than those around more distant supermassive black holes, microquasars are ideal nearby 'laboratories' for studying the evolution of accretion disks and jet formation in black-hole systems. Whereas studies of black holes have revealed a complex array of accretion activity, the mechanisms that trigger and suppress jet formation remain a mystery. Here we report the presence of a broad emission line in the faint, hard states and narrow absorption lines in the bright, soft states of the microquasar GRS 1915+105. ('Hard' and 'soft' denote the character of the emitted X-rays.) Because the hard states exhibit prominent radio jets, we argue that the broad emission line arises when the jet illuminates the inner accretion disk. The jet is weak or absent during the soft states, and we show that the absorption lines originate when the powerful radiation field around the black hole drives a hot wind off the accretion disk. Our analysis shows that this wind carries enough mass away from the disk to halt the flow of matter into the radio jet.

Carbon-13 and proton nuclear magnetic resonance analysis of shale-derived refinery products and jet fuels and of experimental referee broadened-specification jet fuels

NASA Technical Reports Server (NTRS)

Dalling, D. K.; Bailey, B. K.; Pugmire, R. J.

1984-01-01

A proton and carbon-13 nuclear magnetic resonance (NMR) study was conducted of Ashland shale oil refinery products, experimental referee broadened-specification jet fuels, and of related isoprenoid model compounds. Supercritical fluid chromatography techniques using carbon dioxide were developed on a preparative scale, so that samples could be quantitatively separated into saturates and aromatic fractions for study by NMR. An optimized average parameter treatment was developed, and the NMR results were analyzed in terms of the resulting average parameters; formulation of model mixtures was demonstrated. Application of novel spectroscopic techniques to fuel samples was investigated.

`Zwicky's Nonet': a compact merging ensemble of nine galaxies and 4C 35.06, a peculiar radio galaxy with dancing radio jets

NASA Astrophysics Data System (ADS)

Biju, K. G.; Bagchi, Joydeep; Ishwara-Chandra, C. H.; Pandey-Pommier, M.; Jacob, Joe; Patil, M. K.; Kumar, P. Sunil; Pandge, Mahadev; Dabhade, Pratik; Gaikwad, Madhuri; Dhurde, Samir; Abraham, Sheelu; Vivek, M.; Mahabal, Ashish A.; Djorgovski, S. G.

2017-10-01

We report the results of our radio, optical and infrared studies of a peculiar radio source 4C 35.06, an extended radio-loud active galactic nucleus (AGN) at the centre of galaxy cluster Abell 407 (z = 0.047). The central region of this cluster hosts a remarkably tight ensemble of nine galaxies, the spectra of which resemble those of passive red ellipticals, embedded within a diffuse stellar halo of ˜1 arcmin size. This system (named 'Zwicky's Nonet') provides unique and compelling evidence for a multiple-nucleus cD galaxy precursor. Multifrequency radio observations of 4C 35.06 with the Giant Meterwave Radio Telescope (GMRT) at 610, 235 and 150 MHz reveal a system of 400-kpc scale helically twisted and kinked radio jets and outer diffuse lobes. The outer extremities of jets contain extremely steep-spectrum (spectral index -1.7 to -2.5) relic/fossil radio plasma with a spectral age of a few ×(107-108) yr. Such ultra-steep spectrum relic radio lobes without definitive hotspots are rare and they provide an opportunity to understand the life cycle of relativistic jets and physics of black hole mergers in dense environments. We interpret our observations of this radio source in the context of growth of its central black hole, triggering of its AGN activity and jet precession, all possibly caused by galaxy mergers in this dense galactic system. A slow conical precession of the jet axis due to gravitational perturbation between interacting black holes is invoked to explain the unusual jet morphology.

The Possible Submillimeter Bump and Accretion-jet in the Central Supermassive Black Hole of NGC 4993

NASA Astrophysics Data System (ADS)

Wu, Qingwen; Feng, Jianchao; Fan, Xuliang

2018-03-01

NGC 4993, as a host galaxy of the electromagnetic counterpart of the first gravitational-wave detection of a binary neutron-star merger, was observed by many powerful telescopes from radio to γ-ray wavebands. The weak nuclear activities of NGC 4993 suggest that it is a low-luminosity active galactic nuclei (LLAGNs). We build the multiwaveband spectral energy distributions (SEDs) of NGC 4993 from the literature. We find that the radio spectrum at ∼100–300 GHz is much steeper than that of the low-frequency waveband (e.g., 6–100 GHz), where this break was also found in the supermassive black holes (SMBHs) in our galaxy center (Sgr A*), and in some other nearby AGNs. The radio emission above and below this break may have different physical origins, which provide an opportunity to probe the accretion and jet properties. We model the multiwaveband SEDs of NGC 4993 with an advection-dominated accretion flow (ADAF) jet model. We find that the high-frequency steep radio emission at the millimeter waveband is consistent with the prediction of the ADAF, while the low-frequency flat radio spectrum is better fitted by the jet. Furthermore, the X-ray emission can also be simultaneously explained by the ADAF model. From the model fits, we estimate important parameters of the central engine (e.g., the accretion rate near the horizon of the black hole and the mass-loss rate in the jet) for NGC 4993. This result strengthens the theory that the millimeter, submillimeter, and deep X-ray observations are crucial to understanding the weak or quiescent activities in SMBH systems. Further simultaneous millimeter and X-ray monitoring of this kind of LLAGN will help us to better understand the physical origin of multiwaveband emission.

Symmetry in the Changing Jets of SS 433 and Its True Distance from Us

NASA Astrophysics Data System (ADS)

Blundell, Katherine M.; Bowler, Michael G.

2004-12-01

We present the deepest yet radio image of the Galactic jet source SS 433, which reveals over two full precession cycles (>2×163 days) of the jet axis. Systematic and identifiable deviations from the traditional kinematical model for the jets are found: variations in jet speed, lasting for as long as tens of days, are necessary to match the detailed structure of each jet. It is remarkable that these variations are equal and opposite, matching the two jets simultaneously. This explains certain features of the correlated redshift residuals found in fits to the kinematic model of SS 433 reported in the literature. Asymmetries in the image caused by light-travel time enabled us to measure the jet speeds of particular points to be within a range from 0.24c to 0.28c, consistent with, yet determined independently from, the speeds derived from the famous moving optical emission lines. Taken together with the angular periodicity of the zigzag/corkscrew structure projected on the plane of the sky (produced by the precession of the jet axis), these measurements determine beyond all reasonable doubt the distance to SS 433 to be 5.5+/-0.2 kpc, significantly different from the distance most recently inferred using neutral hydrogen measurements together with the current rotation model for the Galaxy.

Galactic Winds

NASA Astrophysics Data System (ADS)

Veilleux, Sylvain

Galactic winds have become arguably one of the hottest topics in extragalactic astronomy. This enthusiasm for galactic winds is due in part to the detection of winds in many, if not most, high-redshift galaxies. Galactic winds have also been invoked by theorists to (1) suppress the number of visible dwarf galaxies and avoid the "cooling catastrophe" at high redshift that results in the overproduction of massive luminous galaxies, (2) remove material with low specific angular momentum early on and help enlarge gas disks in CDM + baryons simulations, (3) reduce the dark mass concentrations in galaxies, (4) explain the mass-metallicity relation of galaxies from selective loss of metal-enriched gas from smaller galaxies, (5) enrich and "preheat" the ICM, (6) enrich the IGM without disturbing the Lyαforest significantly, and (7) inhibit cooling flows in galaxy clusters with active cD galaxies. The present paper highlights a few key aspects of galactic winds taken from a recent ARAA review by Veilleux, Cecil, &Bland-Hawthorn (2005; herafter VCBH). Readers interested in a more detailed discussion of this topic are encouraged to refer to the original ARAA article.

Jet Propagation Through Irregular Media and the Impact of Lobes on Galaxy Formation

NASA Astrophysics Data System (ADS)

Wiita, Paul J.

2004-09-01

We review results of two- and three-dimensional simulations of jets striking clouds with a view toward determining the conditions under which extragalactic jets might stably survive such collisions, and thereby produce “dog-leg” or wide-angle-tail morphologies. Under most circumstances, the jet either destroys the cloud and has its stability little affected or it stalls and is rapidly destabilized by the impact. But there does appear to be a limited range in parameter space where jets can be deflected by clouds but still survive for an extended period. Some of the effects of radio lobes on protogalactic clouds are also considered. At redshifts above 2, the number of radio galaxies (RGs) is much larger than it is in the local universe, and their lobes may well have filled a large fraction of the web of baryonic matter that is still forming galaxies at that epoch. The overpressures in those lobes can trigger extensive star formation on galactic scales and also may have major implications for the spreading of magnetic fields and metals through the intergalactic medium.

Measurements of the Nuclear Modification Factor for Jets in Pb +Pb Collisions at √{sNN}=2.76 TeV with the ATLAS Detector

NASA Astrophysics Data System (ADS)

Aad, G.; Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; Abouzeid, O. S.; Abramowicz, H.; Abreu, H.; Abreu, R.; Abulaiti, Y.; Acharya, B. S.; Adamczyk, L.; Adams, D. L.; Adelman, J.; Adomeit, S.; Adye, T.; Agatonovic-Jovin, T.; Aguilar-Saavedra, J. A.; Agustoni, M.; Ahlen, S. P.; Ahmadov, F.; Aielli, G.; Akerstedt, H. Å.; Kesson, T. P. A.; Akimoto, G.; Akimov, A. V.; Alberghi, G. L.; Albert, J.; Albrand, S.; Alconada Verzini, M. J.; Aleksa, M.; Aleksandrov, I. N.; Alexa, C.; Alexander, G.; Alexandre, G.; Alexopoulos, T.; Alhroob, M.; Alimonti, G.; Alio, L.; Alison, J.; Allbrooke, B. M. M.; Allison, L. J.; Allport, P. P.; Almond, J.; Aloisio, A.; Alonso, A.; Alonso, F.; Alpigiani, C.; Altheimer, A.; Alvarez Gonzalez, B.; Alviggi, M. G.; Amako, K.; Amaral Coutinho, Y.; Amelung, C.; Amidei, D.; Amor Dos Santos, S. P.; Amorim, A.; Amoroso, S.; Amram, N.; Amundsen, G.; Anastopoulos, C.; Ancu, L. S.; Andari, N.; Andeen, T.; Anders, C. F.; Anders, G.; Anderson, K. J.; Andreazza, A.; Andrei, V.; Anduaga, X. S.; Angelidakis, S.; Angelozzi, I.; Anger, P.; Angerami, A.; Anghinolfi, F.; Anisenkov, A. V.; Anjos, N.; Annovi, A.; Antonaki, A.; Antonelli, M.; Antonov, A.; Antos, J.; Anulli, F.; Aoki, M.; Aperio Bella, L.; Apolle, R.; Arabidze, G.; Aracena, I.; Arai, Y.; Araque, J. P.; Arce, A. T. H.; Arguin, J.-F.; Argyropoulos, S.; Arik, M.; Armbruster, A. J.; Arnaez, O.; Arnal, V.; Arnold, H.; Arratia, M.; Arslan, O.; Artamonov, A.; Artoni, G.; Asai, S.; Asbah, N.; Ashkenazi, A.; Åsman, B.; Asquith, L.; Assamagan, K.; Astalos, R.; Atkinson, M.; Atlay, N. B.; Auerbach, B.; Augsten, K.; Aurousseau, M.; Avolio, G.; Azuelos, G.; Azuma, Y.; Baak, M. A.; Baas, A. E.; Bacci, C.; Bachacou, H.; Bachas, K.; Backes, M.; Backhaus, M.; Backus Mayes, J.; Badescu, E.; Bagiacchi, P.; Bagnaia, P.; Bai, Y.; Bain, T.; Baines, J. T.; Baker, O. K.; Balek, P.; Balli, F.; Banas, E.; Banerjee, Sw.; Bannoura, A. A. E.; Bansal, V.; Bansil, H. S.; Barak, L.; Baranov, S. P.; Barberio, E. L.; Barberis, D.; Barbero, M.; Barillari, T.; Barisonzi, M.; Barklow, T.; Barlow, N.; Barnett, B. M.; Barnett, R. M.; Barnovska, Z.; Baroncelli, A.; Barone, G.; Barr, A. J.; Barreiro, F.; Barreiro Guimarães da Costa, J.; Bartoldus, R.; Barton, A. E.; Bartos, P.; Bartsch, V.; Bassalat, A.; Basye, A.; Bates, R. L.; Batley, J. R.; Battaglia, M.; Battistin, M.; Bauer, F.; Bawa, H. S.; Beattie, M. D.; Beau, T.; Beauchemin, P. H.; Beccherle, R.; Bechtle, P.; Beck, H. P.; Becker, K.; Becker, S.; Beckingham, M.; Becot, C.; Beddall, A. J.; Beddall, A.; Bedikian, S.; Bednyakov, V. A.; Bee, C. P.; Beemster, L. J.; Beermann, T. A.; Begel, M.; Behr, K.; Belanger-Champagne, C.; Bell, P. J.; Bell, W. H.; Bella, G.; Bellagamba, L.; Bellerive, A.; Bellomo, M.; Belotskiy, K.; Beltramello, O.; Benary, O.; Benchekroun, D.; Bendtz, K.; Benekos, N.; Benhammou, Y.; Benhar Noccioli, E.; Benitez Garcia, J. A.; Benjamin, D. P.; Bensinger, J. R.; Benslama, K.; Bentvelsen, S.; Berge, D.; Bergeaas Kuutmann, E.; Berger, N.; Berghaus, F.; Beringer, J.; Bernard, C.; Bernat, P.; Bernius, C.; Bernlochner, F. U.; Berry, T.; Berta, P.; Bertella, C.; Bertoli, G.; Bertolucci, F.; Bertsche, C.; Bertsche, D.; Besana, M. I.; Besjes, G. J.; Bessidskaia Bylund, O.; Bessner, M.; Besson, N.; Betancourt, C.; Bethke, S.; Bhimji, W.; Bianchi, R. M.; Bianchini, L.; Bianco, M.; Biebel, O.; Bieniek, S. P.; Bierwagen, K.; Biesiada, J.; Biglietti, M.; Bilbao de Mendizabal, J.; Bilokon, H.; Bindi, M.; Binet, S.; Bingul, A.; Bini, C.; Black, C. W.; Black, J. E.; Black, K. M.; Blackburn, D.; Blair, R. E.; Blanchard, J.-B.; Blazek, T.; Bloch, I.; Blocker, C.; Blum, W.; Blumenschein, U.; Bobbink, G. J.; Bobrovnikov, V. S.; Bocchetta, S. S.; Bocci, A.; Bock, C.; Boddy, C. R.; Boehler, M.; Boek, T. T.; Bogaerts, J. A.; Bogdanchikov, A. G.; Bogouch, A.; Bohm, C.; Bohm, J.; Boisvert, V.; Bold, T.; Boldea, V.; Boldyrev, A. S.; Bomben, M.; Bona, M.; Boonekamp, M.; Borisov, A.; Borissov, G.; Borri, M.; Borroni, S.; Bortfeldt, J.; Bortolotto, V.; Bos, K.; Boscherini, D.; Bosman, M.; Boterenbrood, H.; Boudreau, J.; Bouffard, J.; Bouhova-Thacker, E. V.; Boumediene, D.; Bourdarios, C.; Bousson, N.; Boutouil, S.; Boveia, A.; Boyd, J.; Boyko, I. R.; Bracinik, J.; Brandt, A.; Brandt, G.; Brandt, O.; Bratzler, U.; Brau, B.; Brau, J. E.; Braun, H. M.; Brazzale, S. F.; Brelier, B.; Brendlinger, K.; Brennan, A. J.; Brenner, R.; Bressler, S.; Bristow, K.; Bristow, T. M.; Britton, D.; Brochu, F. M.; Brock, I.; Brock, R.; Bromberg, C.; Bronner, J.; Brooijmans, G.; Brooks, T.; Brooks, W. K.; Brosamer, J.; Brost, E.; Brown, J.; Bruckman de Renstrom, P. A.; Bruncko, D.; Bruneliere, R.; Brunet, S.; Bruni, A.; Bruni, G.; Bruschi, M.; Bryngemark, L.; Buanes, T.; Buat, Q.; Bucci, F.; Buchholz, P.; Buckingham, R. M.; Buckley, A. G.; Buda, S. I.; Budagov, I. A.; Buehrer, F.; Bugge, L.; Bugge, M. K.; Bulekov, O.; Bundock, A. C.; Burckhart, H.; Burdin, S.; Burghgrave, B.; Burke, S.; Burmeister, I.; Busato, E.; Büscher, D.; Büscher, V.; Bussey, P.; Buszello, C. P.; Butler, B.; Butler, J. M.; Butt, A. I.; Buttar, C. M.; Butterworth, J. M.; Butti, P.; Buttinger, W.; Buzatu, A.; Byszewski, M.; Cabrera Urbán, S.; Caforio, D.; Cakir, O.; Calafiura, P.; Calandri, A.; Calderini, G.; Calfayan, P.; Calkins, R.; Caloba, L. P.; Calvet, D.; Calvet, S.; Camacho Toro, R.; Camarda, S.; Cameron, D.; Caminada, L. M.; Caminal Armadans, R.; Campana, S.; Campanelli, M.; Campoverde, A.; Canale, V.; Canepa, A.; Cano Bret, M.; Cantero, J.; Cantrill, R.; Cao, T.; Capeans Garrido, M. D. M.; Caprini, I.; Caprini, M.; Capua, M.; Caputo, R.; Cardarelli, R.; Carli, T.; Carlino, G.; Carminati, L.; Caron, S.; Carquin, E.; Carrillo-Montoya, G. D.; Carter, J. R.; Carvalho, J.; Casadei, D.; Casado, M. P.; Casolino, M.; Castaneda-Miranda, E.; Castelli, A.; Castillo Gimenez, V.; Castro, N. F.; Catastini, P.; Catinaccio, A.; Catmore, J. R.; Cattai, A.; Cattani, G.; Caughron, S.; Cavaliere, V.; Cavalli, D.; Cavalli-Sforza, M.; Cavasinni, V.; Ceradini, F.; Cerio, B. C.; Cerny, K.; Cerqueira, A. S.; Cerri, A.; Cerrito, L.; Cerutti, F.; Cerv, M.; Cervelli, A.; Cetin, S. A.; Chafaq, A.; Chakraborty, D.; Chalupkova, I.; Chang, P.; Chapleau, B.; Chapman, J. D.; Charfeddine, D.; Charlton, D. G.; Chau, C. C.; Chavez Barajas, C. A.; Cheatham, S.; Chegwidden, A.; Chekanov, S.; Chekulaev, S. V.; Chelkov, G. A.; Chelstowska, M. A.; Chen, C.; Chen, H.; Chen, K.; Chen, L.; Chen, S.; Chen, X.; Chen, Y.; Chen, Y.; Cheng, H. C.; Cheng, Y.; Cheplakov, A.; Cherkaoui El Moursli, R.; Chernyatin, V.; Cheu, E.; Chevalier, L.; Chiarella, V.; Chiefari, G.; Childers, J. T.; Chilingarov, A.; Chiodini, G.; Chisholm, A. S.; Chislett, R. T.; Chitan, A.; Chizhov, M. V.; Chouridou, S.; Chow, B. K. B.; Chromek-Burckhart, D.; Chu, M. L.; Chudoba, J.; Chwastowski, J. J.; Chytka, L.; Ciapetti, G.; Ciftci, A. K.; Ciftci, R.; Cinca, D.; Cindro, V.; Ciocio, A.; Cirkovic, P.; Citron, Z. H.; Citterio, M.; Ciubancan, M.; Clark, A.; Clark, P. J.; Clarke, R. N.; Cleland, W.; Clemens, J. C.; Clement, C.; Coadou, Y.; Cobal, M.; Coccaro, A.; Cochran, J.; Coffey, L.; Cogan, J. G.; Coggeshall, J.; Cole, B.; Cole, S.; Colijn, A. P.; Collot, J.; Colombo, T.; Colon, G.; Compostella, G.; Conde Muiño, P.; Coniavitis, E.; Conidi, M. C.; Connell, S. H.; Connelly, I. A.; Consonni, S. M.; Consorti, V.; Constantinescu, S.; Conta, C.; Conti, G.; Conventi, F.; Cooke, M.; Cooper, B. D.; Cooper-Sarkar, A. M.; Cooper-Smith, N. J.; Copic, K.; Cornelissen, T.; Corradi, M.; Corriveau, F.; Corso-Radu, A.; Cortes-Gonzalez, A.; Cortiana, G.; Costa, G.; Costa, M. J.; Costanzo, D.; Côté, D.; Cottin, G.; Cowan, G.; Cox, B. E.; Cranmer, K.; Cree, G.; Crépé-Renaudin, S.; Crescioli, F.; Cribbs, W. A.; Crispin Ortuzar, M.; Cristinziani, M.; Croft, V.; Crosetti, G.; Cuciuc, C.-M.; Cuhadar Donszelmann, T.; Cummings, J.; Curatolo, M.; Cuthbert, C.; Czirr, H.; Czodrowski, P.; Czyczula, Z.; D'Auria, S.; D'Onofrio, M.; da Cunha Sargedas de Sousa, M. J.; da Via, C.; Dabrowski, W.; Dafinca, A.; Dai, T.; Dale, O.; Dallaire, F.; Dallapiccola, C.; Dam, M.; Daniells, A. C.; Dano Hoffmann, M.; Dao, V.; Darbo, G.; Darmora, S.; Dassoulas, J. A.; Dattagupta, A.; Davey, W.; David, C.; Davidek, T.; Davies, E.; Davies, M.; Davignon, O.; Davison, A. R.; Davison, P.; Davygora, Y.; Dawe, E.; Dawson, I.; Daya-Ishmukhametova, R. K.; de, K.; de Asmundis, R.; de Castro, S.; de Cecco, S.; de Groot, N.; de Jong, P.; de la Torre, H.; de Lorenzi, F.; de Nooij, L.; de Pedis, D.; de Salvo, A.; de Sanctis, U.; de Santo, A.; de Vivie de Regie, J. B.; Dearnaley, W. J.; Debbe, R.; Debenedetti, C.; Dechenaux, B.; Dedovich, D. V.; Deigaard, I.; Del Peso, J.; Del Prete, T.; Deliot, F.; Delitzsch, C. M.; Deliyergiyev, M.; Dell'Acqua, A.; Dell'Asta, L.; Dell'Orso, M.; Della Pietra, M.; Della Volpe, D.; Delmastro, M.; Delsart, P. A.; Deluca, C.; Demers, S.; Demichev, M.; Demilly, A.; Denisov, S. P.; Derendarz, D.; Derkaoui, J. E.; Derue, F.; Dervan, P.; Desch, K.; Deterre, C.; Deviveiros, P. O.; Dewhurst, A.; Dhaliwal, S.; di Ciaccio, A.; di Ciaccio, L.; di Domenico, A.; di Donato, C.; di Girolamo, A.; di Girolamo, B.; di Mattia, A.; di Micco, B.; di Nardo, R.; di Simone, A.; di Sipio, R.; di Valentino, D.; Dias, F. A.; Diaz, M. A.; Diehl, E. B.; Dietrich, J.; Dietzsch, T. A.; Diglio, S.; Dimitrievska, A.; Dingfelder, J.; Dionisi, C.; Dita, P.; Dita, S.; Dittus, F.; Djama, F.; Djobava, T.; Do Vale, M. A. B.; Do Valle Wemans, A.; Doan, T. K. O.; Dobos, D.; Doglioni, C.; Doherty, T.; Dohmae, T.; Dolejsi, J.; Dolezal, Z.; Dolgoshein, B. A.; Donadelli, M.; Donati, S.; Dondero, P.; Donini, J.; Dopke, J.; Doria, A.; Dova, M. T.; Doyle, A. T.; Dris, M.; Dubbert, J.; Dube, S.; Dubreuil, E.; Duchovni, E.; Duckeck, G.; Ducu, O. A.; Duda, D.; Dudarev, A.; Dudziak, F.; Duflot, L.; Duguid, L.; Dührssen, M.; Dunford, M.; Duran Yildiz, H.; Düren, M.; Durglishvili, A.; Dwuznik, M.; Dyndal, M.; Ebke, J.; Edson, W.; Edwards, N. C.; Ehrenfeld, W.; Eifert, T.; Eigen, G.; Einsweiler, K.; Ekelof, T.; El Kacimi, M.; Ellert, M.; Elles, S.; Ellinghaus, F.; Ellis, N.; Elmsheuser, J.; Elsing, M.; Emeliyanov, D.; Enari, Y.; Endner, O. C.; Endo, M.; Engelmann, R.; Erdmann, J.; Ereditato, A.; Eriksson, D.; Ernis, G.; Ernst, J.; Ernst, M.; Ernwein, J.; Errede, D.; Errede, S.; Ertel, E.; Escalier, M.; Esch, H.; Escobar, C.; Esposito, B.; Etienvre, A. I.; Etzion, E.; Evans, H.; Ezhilov, A.; Fabbri, L.; Facini, G.; Fakhrutdinov, R. M.; Falciano, S.; Falla, R. J.; Faltova, J.; Fang, Y.; Fanti, M.; Farbin, A.; Farilla, A.; Farooque, T.; Farrell, S.; Farrington, S. M.; Farthouat, P.; Fassi, F.; Fassnacht, P.; Fassouliotis, D.; Favareto, A.; Fayard, L.; Federic, P.; Fedin, O. L.; Fedorko, W.; Fehling-Kaschek, M.; Feigl, S.; Feligioni, L.; Feng, C.; Feng, E. J.; Feng, H.; Fenyuk, A. B.; Fernandez Perez, S.; Ferrag, S.; Ferrando, J.; Ferrari, A.; Ferrari, P.; Ferrari, R.; Ferreira de Lima, D. E.; Ferrer, A.; Ferrere, D.; Ferretti, C.; Ferretto Parodi, A.; Fiascaris, M.; Fiedler, F.; Filipčič, A.; Filipuzzi, M.; Filthaut, F.; Fincke-Keeler, M.; Finelli, K. D.; Fiolhais, M. C. N.; Fiorini, L.; Firan, A.; Fischer, A.; Fischer, J.; Fisher, W. C.; Fitzgerald, E. A.; Flechl, M.; Fleck, I.; Fleischmann, P.; Fleischmann, S.; Fletcher, G. T.; Fletcher, G.; Flick, T.; Floderus, A.; Flores Castillo, L. R.; Florez Bustos, A. C.; Flowerdew, M. J.; Formica, A.; Forti, A.; Fortin, D.; Fournier, D.; Fox, H.; Fracchia, S.; Francavilla, P.; Franchini, M.; Franchino, S.; Francis, D.; Franconi, L.; Franklin, M.; Franz, S.; Fraternali, M.; French, S. T.; Friedrich, C.; Friedrich, F.; Froidevaux, D.; Frost, J. A.; Fukunaga, C.; Fullana Torregrosa, E.; Fulsom, B. G.; Fuster, J.; Gabaldon, C.; Gabizon, O.; Gabrielli, A.; Gabrielli, A.; Gadatsch, S.; Gadomski, S.; Gagliardi, G.; Gagnon, P.; Galea, C.; Galhardo, B.; Gallas, E. J.; Gallo, V.; Gallop, B. J.; Gallus, P.; Galster, G.; Gan, K. K.; Gandrajula, R. P.; Gao, J.; Gao, Y. S.; Garay Walls, F. M.; Garberson, F.; García, C.; García Navarro, J. E.; Garcia-Sciveres, M.; Gardner, R. W.; Garelli, N.; Garonne, V.; Gatti, C.; Gaudio, G.; Gaur, B.; Gauthier, L.; Gauzzi, P.; Gavrilenko, I. L.; Gay, C.; Gaycken, G.; Gazis, E. N.; Ge, P.; Gecse, Z.; Gee, C. N. P.; Geerts, D. A. A.; Geich-Gimbel, Ch.; Gellerstedt, K.; Gemme, C.; Gemmell, A.; Genest, M. H.; Gentile, S.; George, M.; George, S.; Gerbaudo, D.; Gershon, A.; Ghazlane, H.; Ghodbane, N.; Giacobbe, B.; Giagu, S.; Giangiobbe, V.; Giannetti, P.; Gianotti, F.; Gibbard, B.; Gibson, S. M.; Gilchriese, M.; Gillam, T. P. S.; Gillberg, D.; Gilles, G.; Gingrich, D. M.; Giokaris, N.; Giordani, M. P.; Giordano, R.; Giorgi, F. M.; Giorgi, F. M.; Giraud, P. F.; Giugni, D.; Giuliani, C.; Giulini, M.; Gjelsten, B. K.; Gkaitatzis, S.; Gkialas, I.; Gladilin, L. K.; Glasman, C.; Glatzer, J.; Glaysher, P. C. F.; Glazov, A.; Glonti, G. L.; Goblirsch-Kolb, M.; Goddard, J. R.; Godfrey, J.; Godlewski, J.; Goeringer, C.; Goldfarb, S.; Golling, T.; Golubkov, D.; Gomes, A.; Gomez Fajardo, L. S.; Gonçalo, R.; Goncalves Pinto Firmino da Costa, J.; Gonella, L.; González de La Hoz, S.; Gonzalez Parra, G.; Gonzalez-Sevilla, S.; Goossens, L.; Gorbounov, P. A.; Gordon, H. A.; Gorelov, I.; Gorini, B.; Gorini, E.; Gorišek, A.; Gornicki, E.; Goshaw, A. T.; Gössling, C.; Gostkin, M. I.; Gouighri, M.; Goujdami, D.; Goulette, M. P.; Goussiou, A. G.; Goy, C.; Gozpinar, S.; Grabas, H. M. X.; Graber, L.; Grabowska-Bold, I.; Grafström, P.; Grahn, K.-J.; Gramling, J.; Gramstad, E.; Grancagnolo, S.; Grassi, V.; Gratchev, V.; Gray, H. M.; Graziani, E.; Grebenyuk, O. G.; Greenwood, Z. D.; Gregersen, K.; Gregor, I. M.; Grenier, P.; Griffiths, J.; Grillo, A. A.; Grimm, K.; Grinstein, S.; Gris, Ph.; Grishkevich, Y. V.; Grivaz, J.-F.; Grohs, J. P.; Grohsjean, A.; Gross, E.; Grosse-Knetter, J.; Grossi, G. C.; Groth-Jensen, J.; Grout, Z. J.; Guan, L.; Guescini, F.; Guest, D.; Gueta, O.; Guicheney, C.; Guido, E.; Guillemin, T.; Guindon, S.; Gul, U.; Gumpert, C.; Gunther, J.; Guo, J.; Gupta, S.; Gutierrez, P.; Gutierrez Ortiz, N. G.; Gutschow, C.; Guttman, N.; Guyot, C.; Gwenlan, C.; Gwilliam, C. B.; Haas, A.; Haber, C.; Hadavand, H. K.; Haddad, N.; Haefner, P.; Hageböck, S.; Hajduk, Z.; Hakobyan, H.; Haleem, M.; Hall, D.; Halladjian, G.; Hamacher, K.; Hamal, P.; Hamano, K.; Hamer, M.; Hamilton, A.; Hamilton, S.; Hamity, G. N.; Hamnett, P. G.; Han, L.; Hanagaki, K.; Hanawa, K.; Hance, M.; Hanke, P.; Hanna, R.; Hansen, J. B.; Hansen, J. D.; Hansen, P. H.; Hara, K.; Hard, A. S.; Harenberg, T.; Hariri, F.; Harkusha, S.; Harper, D.; Harrington, R. D.; Harris, O. M.; Harrison, P. F.; Hartjes, F.; Hasegawa, M.; Hasegawa, S.; Hasegawa, Y.; Hasib, A.; Hassani, S.; Haug, S.; Hauschild, M.; Hauser, R.; Havranek, M.; Hawkes, C. M.; Hawkings, R. J.; Hawkins, A. D.; Hayashi, T.; Hayden, D.; Hays, C. P.; Hayward, H. S.; Haywood, S. J.; Head, S. J.; Heck, T.; Hedberg, V.; Heelan, L.; Heim, S.; Heim, T.; Heinemann, B.; Heinrich, L.; Hejbal, J.; Helary, L.; Heller, C.; Heller, M.; Hellman, S.; Hellmich, D.; Helsens, C.; Henderson, J.; Henderson, R. C. W.; Heng, Y.; Hengler, C.; Henrichs, A.; Henriques Correia, A. M.; Henrot-Versille, S.; Hensel, C.; Herbert, G. H.; Hernández Jiménez, Y.; Herrberg-Schubert, R.; Herten, G.; Hertenberger, R.; Hervas, L.; Hesketh, G. G.; Hessey, N. P.; Hickling, R.; Higón-Rodriguez, E.; Hill, E.; Hill, J. C.; Hiller, K. H.; Hillert, S.; Hillier, S. J.; Hinchliffe, I.; Hines, E.; Hirose, M.; Hirschbuehl, D.; Hobbs, J.; Hod, N.; Hodgkinson, M. C.; Hodgson, P.; Hoecker, A.; Hoeferkamp, M. R.; Hoenig, F.; Hoffman, J.; Hoffmann, D.; Hofmann, J. I.; Hohlfeld, M.; Holmes, T. R.; Hong, T. M.; Hooft van Huysduynen, L.; Hostachy, J.-Y.; Hou, S.; Hoummada, A.; Howard, J.; Howarth, J.; Hrabovsky, M.; Hristova, I.; Hrivnac, J.; Hryn'ova, T.; Hsu, C.; Hsu, P. J.; Hsu, S.-C.; Hu, D.; Hu, X.; Huang, Y.; Hubacek, Z.; Hubaut, F.; Huegging, F.; Huffman, T. B.; Hughes, E. W.; Hughes, G.; Huhtinen, M.; Hülsing, T. A.; Hurwitz, M.; Huseynov, N.; Huston, J.; Huth, J.; Iacobucci, G.; Iakovidis, G.; Ibragimov, I.; Iconomidou-Fayard, L.; Ideal, E.; Iengo, P.; Igonkina, O.; Iizawa, T.; Ikegami, Y.; Ikematsu, K.; Ikeno, M.; Ilchenko, Y.; Iliadis, D.; Ilic, N.; Inamaru, Y.; Ince, T.; Ioannou, P.; Iodice, M.; Iordanidou, K.; Ippolito, V.; Irles Quiles, A.; Isaksson, C.; Ishino, M.; Ishitsuka, M.; Ishmukhametov, R.; Issever, C.; Istin, S.; Iturbe Ponce, J. 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C.; Sansoni, A.; Santoni, C.; Santonico, R.; Santos, H.; Santoyo Castillo, I.; Sapp, K.; Sapronov, A.; Saraiva, J. G.; Sarrazin, B.; Sartisohn, G.; Sasaki, O.; Sasaki, Y.; Sauvage, G.; Sauvan, E.; Savard, P.; Savu, D. O.; Sawyer, C.; Sawyer, L.; Saxon, D. H.; Saxon, J.; Sbarra, C.; Sbrizzi, A.; Scanlon, T.; Scannicchio, D. A.; Scarcella, M.; Scarfone, V.; Schaarschmidt, J.; Schacht, P.; Schaefer, D.; Schaefer, R.; Schaepe, S.; Schaetzel, S.; Schäfer, U.; Schaffer, A. C.; Schaile, D.; Schamberger, R. D.; Scharf, V.; Schegelsky, V. A.; Scheirich, D.; Schernau, M.; Scherzer, M. I.; Schiavi, C.; Schieck, J.; Schillo, C.; Schioppa, M.; Schlenker, S.; Schmidt, E.; Schmieden, K.; Schmitt, C.; Schmitt, S.; Schneider, B.; Schnellbach, Y. J.; Schnoor, U.; Schoeffel, L.; Schoening, A.; Schoenrock, B. D.; Schorlemmer, A. L. S.; Schott, M.; Schouten, D.; Schovancova, J.; Schramm, S.; Schreyer, M.; Schroeder, C.; Schuh, N.; Schultens, M. J.; Schultz-Coulon, H.-C.; Schulz, H.; Schumacher, M.; Schumm, B. A.; Schune, Ph.; Schwanenberger, C.; Schwartzman, A.; Schwegler, Ph.; Schwemling, Ph.; Schwienhorst, R.; Schwindling, J.; Schwindt, T.; Schwoerer, M.; Sciacca, F. G.; Scifo, E.; Sciolla, G.; Scott, W. G.; Scuri, F.; Scutti, F.; Searcy, J.; Sedov, G.; Sedykh, E.; Seidel, S. C.; Seiden, A.; Seifert, F.; Seixas, J. M.; Sekhniaidze, G.; Sekula, S. J.; Selbach, K. E.; Seliverstov, D. M.; Sellers, G.; Semprini-Cesari, N.; Serfon, C.; Serin, L.; Serkin, L.; Serre, T.; Seuster, R.; Severini, H.; Sfiligoj, T.; Sforza, F.; Sfyrla, A.; Shabalina, E.; Shamim, M.; Shan, L. Y.; Shang, R.; Shank, J. T.; Shapiro, M.; Shatalov, P. B.; Shaw, K.; Shehu, C. Y.; Sherwood, P.; Shi, L.; Shimizu, S.; Shimmin, C. O.; Shimojima, M.; Shiyakova, M.; Shmeleva, A.; Shochet, M. J.; Short, D.; Shrestha, S.; Shulga, E.; Shupe, M. A.; Shushkevich, S.; Sicho, P.; Sidiropoulou, O.; Sidorov, D.; Sidoti, A.; Siegert, F.; Sijacki, Dj.; Silva, J.; Silver, Y.; Silverstein, D.; Silverstein, S. B.; Simak, V.; Simard, O.; Simic, Lj.; Simion, S.; Simioni, E.; Simmons, B.; Simoniello, R.; Simonyan, M.; Sinervo, P.; Sinev, N. B.; Sipica, V.; Siragusa, G.; Sircar, A.; Sisakyan, A. N.; Sivoklokov, S. Yu.; Sjölin, J.; Sjursen, T. B.; Skottowe, H. P.; Skovpen, K. Yu.; Skubic, P.; Slater, M.; Slavicek, T.; Sliwa, K.; Smakhtin, V.; Smart, B. H.; Smestad, L.; Smirnov, S. Yu.; Smirnov, Y.; Smirnova, L. N.; Smirnova, O.; Smith, K. M.; Smizanska, M.; Smolek, K.; Snesarev, A. A.; Snidero, G.; Snyder, S.; Sobie, R.; Socher, F.; Soffer, A.; Soh, D. A.; Solans, C. A.; Solar, M.; Solc, J.; Soldatov, E. Yu.; Soldevila, U.; Solodkov, A. A.; Soloshenko, A.; Solovyanov, O. V.; Solovyev, V.; Sommer, P.; Song, H. Y.; Soni, N.; Sood, A.; Sopczak, A.; Sopko, B.; Sopko, V.; Sorin, V.; Sosebee, M.; Soualah, R.; Soueid, P.; Soukharev, A. M.; South, D.; Spagnolo, S.; Spanò, F.; Spearman, W. R.; Spettel, F.; Spighi, R.; Spigo, G.; Spiller, L. A.; Spousta, M.; Spreitzer, T.; Spurlock, B.; St. Denis, R. D.; Staerz, S.; Stahlman, J.; Stamen, R.; Stamm, S.; Stanecka, E.; Stanek, R. W.; Stanescu, C.; Stanescu-Bellu, M.; Stanitzki, M. M.; Stapnes, S.; Starchenko, E. A.; Stark, J.; Staroba, P.; Starovoitov, P.; Staszewski, R.; Stavina, P.; Steinberg, P.; Stelzer, B.; Stelzer, H. J.; Stelzer-Chilton, O.; Stenzel, H.; Stern, S.; Stewart, G. A.; Stillings, J. A.; Stockton, M. C.; Stoebe, M.; Stoicea, G.; Stolte, P.; Stonjek, S.; Stradling, A. R.; Straessner, A.; Stramaglia, M. E.; Strandberg, J.; Strandberg, S.; Strandlie, A.; Strauss, E.; Strauss, M.; Strizenec, P.; Ströhmer, R.; Strom, D. M.; Stroynowski, R.; Stucci, S. A.; Stugu, B.; Styles, N. A.; Su, D.; Su, J.; Subramaniam, R.; Succurro, A.; Sugaya, Y.; Suhr, C.; Suk, M.; Sulin, V. V.; Sultansoy, S.; Sumida, T.; Sun, S.; Sun, X.; Sundermann, J. E.; Suruliz, K.; Susinno, G.; Sutton, M. R.; Suzuki, Y.; Svatos, M.; Swedish, S.; Swiatlowski, M.; Sykora, I.; Sykora, T.; Ta, D.; Taccini, C.; Tackmann, K.; Taenzer, J.; Taffard, A.; Tafirout, R.; Taiblum, N.; Takai, H.; Takashima, R.; Takeda, H.; Takeshita, T.; Takubo, Y.; Talby, M.; Talyshev, A. A.; Tam, J. Y. C.; Tan, K. G.; Tanaka, J.; Tanaka, R.; Tanaka, S.; Tanaka, S.; Tanasijczuk, A. J.; Tannenwald, B. B.; Tannoury, N.; Tapprogge, S.; Tarem, S.; Tarrade, F.; Tartarelli, G. F.; Tas, P.; Tasevsky, M.; Tashiro, T.; Tassi, E.; Tavares Delgado, A.; Tayalati, Y.; Taylor, F. E.; Taylor, G. N.; Taylor, W.; Teischinger, F. A.; Teixeira Dias Castanheira, M.; Teixeira-Dias, P.; Temming, K. K.; Ten Kate, H.; Teng, P. K.; Teoh, J. J.; Terada, S.; Terashi, K.; Terron, J.; Terzo, S.; Testa, M.; Teuscher, R. J.; Therhaag, J.; Theveneaux-Pelzer, T.; Thomas, J. P.; Thomas-Wilsker, J.; Thompson, E. N.; Thompson, P. D.; Thompson, P. D.; Thompson, R. J.; Thompson, A. S.; Thomsen, L. A.; Thomson, E.; Thomson, M.; Thong, W. M.; Thun, R. P.; Tian, F.; Tibbetts, M. J.; Tikhomirov, V. O.; Tikhonov, Yu. A.; Timoshenko, S.; Tiouchichine, E.; Tipton, P.; Tisserant, S.; Todorov, T.; Todorova-Nova, S.; Toggerson, B.; Tojo, J.; Tokár, S.; Tokushuku, K.; Tollefson, K.; Tomlinson, L.; Tomoto, M.; Tompkins, L.; Toms, K.; Topilin, N. D.; Torrence, E.; Torres, H.; Torró Pastor, E.; Toth, J.; Touchard, F.; Tovey, D. R.; Tran, H. L.; Trefzger, T.; Tremblet, L.; Tricoli, A.; Trigger, I. M.; Trincaz-Duvoid, S.; Tripiana, M. F.; Trischuk, W.; Trocmé, B.; Troncon, C.; Trottier-McDonald, M.; Trovatelli, M.; True, P.; Trzebinski, M.; Trzupek, A.; Tsarouchas, C.; Tseng, J. C.-L.; Tsiareshka, P. V.; Tsionou, D.; Tsipolitis, G.; Tsirintanis, N.; Tsiskaridze, S.; Tsiskaridze, V.; Tskhadadze, E. G.; Tsukerman, I. I.; Tsulaia, V.; Tsuno, S.; Tsybychev, D.; Tudorache, A.; Tudorache, V.; Tuna, A. N.; Tupputi, S. A.; Turchikhin, S.; Turecek, D.; Turk Cakir, I.; Turra, R.; Tuts, P. M.; Tykhonov, A.; Tylmad, M.; Tyndel, M.; Uchida, K.; Ueda, I.; Ueno, R.; Ughetto, M.; Ugland, M.; Uhlenbrock, M.; Ukegawa, F.; Unal, G.; Undrus, A.; Unel, G.; Ungaro, F. C.; Unno, Y.; Unverdorben, C.; Urbaniec, D.; Urquijo, P.; Usai, G.; Usanova, A.; Vacavant, L.; Vacek, V.; Vachon, B.; Valencic, N.; Valentinetti, S.; Valero, A.; Valery, L.; Valkar, S.; Valladolid Gallego, E.; Vallecorsa, S.; Valls Ferrer, J. A.; van den Wollenberg, W.; van der Deijl, P. C.; van der Geer, R.; van der Graaf, H.; van der Leeuw, R.; van der Ster, D.; van Eldik, N.; van Gemmeren, P.; van Nieuwkoop, J.; van Vulpen, I.; van Woerden, M. C.; Vanadia, M.; Vandelli, W.; Vanguri, R.; Vaniachine, A.; Vankov, P.; Vannucci, F.; Vardanyan, G.; Vari, R.; Varnes, E. W.; Varol, T.; Varouchas, D.; Vartapetian, A.; Varvell, K. E.; Vazeille, F.; Vazquez Schroeder, T.; Veatch, J.; Veloso, F.; Veneziano, S.; Ventura, A.; Ventura, D.; Venturi, M.; Venturi, N.; Venturini, A.; Vercesi, V.; Verducci, M.; Verkerke, W.; Vermeulen, J. C.; Vest, A.; Vetterli, M. C.; Viazlo, O.; Vichou, I.; Vickey, T.; Vickey Boeriu, O. E.; Viehhauser, G. H. A.; Viel, S.; Vigne, R.; Villa, M.; Villaplana Perez, M.; Vilucchi, E.; Vincter, M. G.; Vinogradov, V. B.; Virzi, J.; Vivarelli, I.; Vives Vaque, F.; Vlachos, S.; Vladoiu, D.; Vlasak, M.; Vogel, A.; Vogel, M.; Vokac, P.; Volpi, G.; Volpi, M.; von der Schmitt, H.; von Radziewski, H.; von Toerne, E.; Vorobel, V.; Vorobev, K.; Vos, M.; Voss, R.; Vossebeld, J. H.; Vranjes, N.; Vranjes Milosavljevic, M.; Vrba, V.; Vreeswijk, M.; Vu Anh, T.; Vuillermet, R.; Vukotic, I.; Vykydal, Z.; Wagner, P.; Wagner, W.; Wahlberg, H.; Wahrmund, S.; Wakabayashi, J.; Walder, J.; Walker, R.; Walkowiak, W.; Wall, R.; Waller, P.; Walsh, B.; Wang, C.; Wang, C.; Wang, F.; Wang, H.; Wang, H.; Wang, J.; Wang, J.; Wang, K.; Wang, R.; Wang, S. M.; Wang, T.; Wang, X.; Wanotayaroj, C.; Warburton, A.; Ward, C. P.; Wardrope, D. R.; Warsinsky, M.; Washbrook, A.; Wasicki, C.; Watkins, P. M.; Watson, A. T.; Watson, I. J.; Watson, M. F.; Watts, G.; Watts, S.; Waugh, B. M.; Webb, S.; Weber, M. S.; Weber, S. W.; Webster, J. S.; Weidberg, A. R.; Weigell, P.; Weinert, B.; Weingarten, J.; Weiser, C.; Weits, H.; Wells, P. S.; Wenaus, T.; Wendland, D.; Weng, Z.; Wengler, T.; Wenig, S.; Wermes, N.; Werner, M.; Werner, P.; Wessels, M.; Wetter, J.; Whalen, K.; White, A.; White, M. J.; White, R.; White, S.; Whiteson, D.; Wicke, D.; Wickens, F. J.; Wiedenmann, W.; Wielers, M.; Wienemann, P.; Wiglesworth, C.; Wiik-Fuchs, L. A. M.; Wijeratne, P. A.; Wildauer, A.; Wildt, M. A.; Wilkens, H. G.; Will, J. Z.; Williams, H. H.; Williams, S.; Willis, C.; Willocq, S.; Wilson, A.; Wilson, J. A.; Wingerter-Seez, I.; Winklmeier, F.; Winter, B. T.; Wittgen, M.; Wittig, T.; Wittkowski, J.; Wollstadt, S. J.; Wolter, M. W.; Wolters, H.; Wosiek, B. K.; Wotschack, J.; Woudstra, M. J.; Wozniak, K. W.; Wright, M.; Wu, M.; Wu, S. L.; Wu, X.; Wu, Y.; Wulf, E.; Wyatt, T. R.; Wynne, B. M.; Xella, S.; Xiao, M.; Xu, D.; Xu, L.; Yabsley, B.; Yacoob, S.; Yakabe, R.; Yamada, M.; Yamaguchi, H.; Yamaguchi, Y.; Yamamoto, A.; Yamamoto, K.; Yamamoto, S.; Yamamura, T.; Yamanaka, T.; Yamauchi, K.; Yamazaki, Y.; Yan, Z.; Yang, H.; Yang, H.; Yang, U. K.; Yang, Y.; Yanush, S.; Yao, L.; Yao, W.-M.; Yasu, Y.; Yatsenko, E.; Yau Wong, K. H.; Ye, J.; Ye, S.; Yeletskikh, I.; Yen, A. L.; Yildirim, E.; Yilmaz, M.; Yoosoofmiya, R.; Yorita, K.; Yoshida, R.; Yoshihara, K.; Young, C.; Young, C. J. S.; Youssef, S.; Yu, D. R.; Yu, J.; Yu, J. M.; Yu, J.; Yuan, L.; Yurkewicz, A.; Yusuff, I.; Zabinski, B.; Zaidan, R.; Zaitsev, A. M.; Zaman, A.; Zambito, S.; Zanello, L.; Zanzi, D.; Zeitnitz, C.; Zeman, M.; Zemla, A.; Zengel, K.; Zenin, O.; Ženiš, T.; Zerwas, D.; Zevi Della Porta, G.; Zhang, D.; Zhang, F.; Zhang, H.; Zhang, J.; Zhang, L.; Zhang, X.; Zhang, Z.; Zhao, Z.; Zhemchugov, A.; Zhong, J.; Zhou, B.; Zhou, L.; Zhou, N.; Zhu, C. G.; Zhu, H.; Zhu, J.; Zhu, Y.; Zhuang, X.; Zhukov, K.; Zibell, A.; Zieminska, D.; Zimine, N. I.; Zimmermann, C.; Zimmermann, R.; Zimmermann, S.; Zimmermann, S.; Zinonos, Z.; Ziolkowski, M.; Zobernig, G.; Zoccoli, A.; Zur Nedden, M.; Zurzolo, G.; Zutshi, V.; Zwalinski, L.; Atlas Collaboration

2015-02-01

Measurements of inclusive jet production are performed in p p and Pb +Pb collisions at √{sNN}=2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14 nb-1 , respectively. The jets are identified with the anti-kt algorithm with R =0.4 , and the spectra are measured over the kinematic range of jet transverse momentum 32 nuclear modification factor RAA is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to p p collisions. The RAA shows a slight increase with pT and no significant variation with rapidity.

On the Importance of Very Light Internally Subsonic AGN Jets in Radio-mode AGN Feedback

NASA Astrophysics Data System (ADS)

Guo, Fulai

2016-07-01

Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light (η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonic jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations by internally subsonic and internally supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.

Jets, hotspots and lobes: what X-ray observations tell us about extra-galactic radio sources.

PubMed

Hardcastle, Martin J

2005-12-15

The brightest and most numerous discrete radio sources in the sky, radio galaxies and quasars, are powered by twin jets of plasma which emerge at relativistic speeds from very small regions at the centre of large elliptical galaxies, powered by mass infall on to supermassive black holes. The jets can carry material out to very large distances (millions of light years) where it forms balloon-like lobes. Until recently it has been impossible to make definite statements about the energy or the nature of the matter supplied by the jets, or the dynamics of the lobes as they expand into the external medium. This has meant that crucial questions about the generation of radio sources and their effect on their environment have gone unanswered. The situation has been revolutionized by the launch at the start of this decade of a new generation of X-ray observatories, Chandra and XMM-Newton. In this article, I explain why observations with these instruments have made such a difference, what we have learned as a result and why the community remains divided on some important features of the interpretation of the data.

Disc-jet quenching of the galactic black hole Swift J1753.5-0127

NASA Astrophysics Data System (ADS)

Rushton, A. P.; Shaw, A. W.; Fender, R. P.; Altamirano, D.; Gandhi, P.; Uttley, P.; Charles, P. A.; Kolehmainen, M.; Anderson, G. E.; Rumsey, C.; Titterington, D. J.

2016-11-01

We report on radio and X-ray monitoring observations of the BHC Swift J1753.5-0127 taken over a ˜10 yr period. Presented are daily radio observations at 15 GHz with the Arcminute Microkelvin Imager Large Array (AMI-LA) and X-ray data from Swift X-ray Telescope and Burst Alert Telescope. Also presented is a deep 2 h JVLA observation taken in an unusually low-luminosity soft-state (with a low disc temperature). We show that although the source has remained relatively radio-quiet compared to XRBs with a similar X-ray luminosity in the hard-state, the power-law relationship scales as ζ = 0.96 ± 0.06, I.e. slightly closer to what has been considered for radiatively inefficient accretion discs. We also place the most stringent limit to date on the radio-jet quenching in an XRB soft-state, showing the connection of the jet quenching to the X-ray power-law component; the radio flux in the soft-state was found to be < 21 μJy, which is a quenching factor of ≳ 25.

A study of (OI) 63.2 and 145.5 micron emission from M17 and SGR A from the Lear jet

NASA Technical Reports Server (NTRS)

Melnick, G. G.

1986-01-01

The Lear Jet Observatory was used to observe the 157.7 micron (C II) line from the galactic H II regions W3 and W51. These measurements established a lower limit in the 157.7 micron line for solar luminosity of 360 from W3, assuming adistance of 2 kpc, and a solar luminosity of 4100 from W51, assuming a distance of 7 kpc. The data indicated that the CII/far infrared continuum ratio for both W3 and W51 were within the range found for other galactic H II regions.

Measurements of the charm jet cross section and nuclear modification factor in pPb collisions at s NN = 5.02   TeV

DOE PAGES

Sirunyan, A. M.; Tumasyan, A.; Adam, W.; ...

2017-06-23

The CMS Collaboration presents the first measurement of the differential cross section of jets from charm quarks produced in proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy ofmore » $$\\sqrt{s{NN}}$$ = 5.02 TeV, as well as results from charm quark jets in proton-proton (pp) collisions at $$\\sqrt{s}$$= 2.76 and 5.02 TeV. By comparing the yields of the pPb and pp collision systems at the same energy, a nuclear modification factor for charm jets in pPb collisions at $$\\sqrt{s{NN}}$$ = 5.02 TeV of $$R_{pA}$$ = 0.92 +/- 0.07 (stat) +/- 0.11 (syst) is obtained. This is consistent with an absence of final-state energy loss for charm quarks in pPb collisions. In addition, the fraction of jets coming from charm quarks is found to be consistent with that predicted by PYTHIA 6 for pp collisions at $$\\sqrt{s}$$= 2.76 and 5.02 TeV, and is independent of the jet transverse momentum from 55 to 400 GeV.« less

Radio jets in NGC 4151: where eMERLIN meets HST

NASA Astrophysics Data System (ADS)

Williams, D. R. A.; McHardy, I. M.; Baldi, R. D.; Beswick, R. J.; Argo, M. K.; Dullo, B. T.; Knapen, J. H.; Brinks, E.; Fenech, D. M.; Mundell, C. G.; Muxlow, T. W. B.; Panessa, F.; Rampadarath, H.; Westcott, J.

2017-12-01

We present high-sensitivity eMERLIN radio images of the Seyfert galaxy NGC 4151 at 1.51 GHz. We compare the new eMERLIN images to those from archival MERLIN observations in 1993 to determine the change in jet morphology in the 22 yr between observations. We report an increase by almost a factor of 2 in the peak flux density of the central core component, C4, thought to host the black hole, but a probable decrease in some other components, possibly due to adiabatic expansion. The core flux increase indicates an active galactic nucleus (AGN) that is currently active and feeding the jet. We detect no significant motion in 22 yr between C4 and the component C3, which is unresolved in the eMERLIN image. We present a spectral index image made within the 512 MHz band of the 1.51 GHz observations. The spectrum of the core, C4, is flatter than that of other components further out in the jet. We use HST emission-line images (H α, [O III] and [O II]) to study the connection between the jet and the emission-line region. Based on the changing emission-line ratios away from the core and comparison with the eMERLIN radio jet, we conclude that photoionization from the central AGN is responsible for the observed emission-line properties further than 4 arcsec (360 pc) from the core, C4. Within this region, a body of evidence (radio-line co-spatiality, low [O III]/H α and estimated fast shocks) suggests additional ionization from the jet.

The prototype nuclear Compton telescope: Observations of the Galactic Anticenter region

NASA Astrophysics Data System (ADS)

Bowen, Jason Dione

Observations of the Galactic Anticenter region and atmospheric 511 keV positron annihilation emission have been performed with a prototype of the Nuclear Compton Telescope (NCT) during a high altitude balloon flight on June 1, 2005 from Ft. Sumner, NM. NCT is a balloon-borne soft gamma-ray (0.2 MeV to 10 MeV) germanium Compton telescope (GCT) designed to study astrophysical sources of nuclear line emission and polarization through spectroscopy and imaging. A prototype instrument was successfully launched from Ft. Sumner, NM on June 1, 2005. The NCT prototype consists of two 3D position-sensitive high purity germanium strip detectors (GeDs). The compact design and new technologies allow NCT to achieve high efficiencies with excellent spectral resolution and background reduction. The GeDs are custom 15 mm thick cross-strip detectors each with an active area of 54 cm 2 and are enclosed in an aluminum cryostat capable of supporting up to 12 detectors. Here is presented a detailed study of approximately 8 hours of background measurements made from 890 g/cm 2 (1265 m ) to an average float altitude of 3.0 g/cm 2 (40 km ), with particular emphasis on float observations. A total of 6 hr 9 min of observation time was acquired at float, while the duration of the ascent portion of the flight included in this study was 2 hr. The expected contributions to the background are discussed, especially in light of detailed Monte Carlo simulations modeling the entire flight and incorporating complete depth dependent environmental inputs, including 4 cosmic components (protons, photons, electrons, and positrons) and 8 atmospheric components (photons, atmospheric 511 keV emission, neutrons, protons, electrons, positrons, and muons). The results of these investigations include the component makeup of the total background as a function of atmospheric depth, and the contribution of delayed emission due to neutron and proton activation of passive materials. At 1 MeV photons emitted following

Intrinsic Brightness Temperatures of AGN Jets

NASA Astrophysics Data System (ADS)

Homan, D. C.; Kovalev, Y. Y.; Lister, M. L.; Ros, E.; Kellermann, K. I.; Cohen, M. H.; Vermeulen, R. C.; Zensus, J. A.; Kadler, M.

2006-05-01

We present a new method for studying the intrinsic brightness temperatures of the parsec-scale jet cores of active galactic nuclei (AGNs). Our method uses observed superluminal motions and observed brightness temperatures for a large sample of AGNs to constrain the characteristic intrinsic brightness temperature of the sample as a whole. To study changes in intrinsic brightness temperature, we assume that the Doppler factors of individual jets are constant in time, as justified by their relatively small changes in observed flux density. We find that in their median-low brightness temperature state, the sources in our sample have a narrow range of intrinsic brightness temperatures centered on a characteristic temperature, Tint~=3×1010 K, which is close to the value expected for equipartition, when the energy in the radiating particles equals the energy stored in the magnetic fields. However, in their maximum brightness state, we find that sources in our sample have a characteristic intrinsic brightness temperature greater than 2×1011 K, which is well in excess of the equipartition temperature. In this state, we estimate that the energy in radiating particles exceeds the energy in the magnetic field by a factor of ~105. We suggest that the excess of particle energy when sources are in their maximum brightness state is due to injection or acceleration of particles at the base of the jet. Our results suggest that the common method of estimating jet Doppler factors by using a single measurement of observed brightness temperature, the assumption of equipartition, or both may lead to large scatter or systematic errors in the derived values.

On Three-dimensional Structures in Relativistic Hydrodynamic Jets

NASA Astrophysics Data System (ADS)

Hardee, Philip E.

2000-04-01

the helical surface mode winds around the jet. Higher order surface modes and first body modes produce less variation. Angular variation in the flow direction associated with the helical mode appears consistent with precessing jet models that have been proposed to explain the variability in 3C 273 and BL Lac object AO 0235+164. In particular, cyclic angular variation in the flow direction produced by the normal modes could produce the activity seen in BL Lac object OJ 287. Jet precession provides a mechanism for triggering the helical modes on multiple length scales, e.g., the galactic superluminal GRO J1655-40.

A highly magnetized twin-jet base pinpoints a supermassive black hole

NASA Astrophysics Data System (ADS)

Baczko, A.-K.; Schulz, R.; Kadler, M.; Ros, E.; Perucho, M.; Krichbaum, T. P.; Böck, M.; Bremer, M.; Grossberger, C.; Lindqvist, M.; Lobanov, A. P.; Mannheim, K.; Martí-Vidal, I.; Müller, C.; Wilms, J.; Zensus, J. A.

2016-09-01

Supermassive black holes (SMBH) are essential for the production of jets in radio-loud active galactic nuclei (AGN). Theoretical models based on (Blandford & Znajek 1977, MNRAS, 179, 433) extract the rotational energy from a Kerr black hole, which could be the case for NGC 1052, to launch these jets. This requires magnetic fields on the order of 103G to 104G. We imaged the vicinity of the SMBH of the AGN NGC 1052 with the Global Millimetre VLBI Array and found a bright and compact central feature that is smaller than 1.9 light days (100 Schwarzschild radii) in radius. Interpreting this as a blend of the unresolved jet bases, we derive the magnetic field at 1 Schwarzschild radius to lie between 200 G and ~ 8.3 × 104 G consistent with Blandford & Znajek models. The VLBI images shown in Figs. 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A47

ON THE IMPORTANCE OF VERY LIGHT INTERNALLY SUBSONIC AGN JETS IN RADIO-MODE AGN FEEDBACK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Fulai, E-mail: fulai@shao.ac.cn

Radio-mode active galactic nucleus (AGN) feedback plays a key role in the evolution of galaxy groups and clusters. Its physical origin lies in the kiloparsec-scale interaction of AGN jets with the intracluster medium. Large-scale jet simulations often initiate light internally supersonic jets with density contrast 0.01 < η < 1. Here we argue for the first time for the importance of very light ( η < 0.01) internally subsonic jets. We investigated the shapes of young X-ray cavities produced in a suite of hydrodynamic simulations, and found that bottom-wide cavities are always produced by internally subsonic jets, while internally supersonicmore » jets inflate cylindrical, center-wide, or top-wide cavities. We found examples of real cavities with shapes analogous to those inflated in our simulations by internally subsonic and internally supersonic jets, suggesting a dichotomy of AGN jets according to their internal Mach numbers. We further studied the long-term cavity evolution, and found that old cavities resulted from light jets spread along the jet direction, while those produced by very light jets are significantly elongated along the perpendicular direction. The northwestern ghost cavity in Perseus is pancake shaped, providing tentative evidence for the existence of very light jets. Our simulations show that very light internally subsonic jets decelerate faster and rise much slower in the intracluster medium than light internally supersonic jets, possibly depositing a larger fraction of jet energy to cluster cores and alleviating the problem of low coupling efficiencies found previously. The internal Mach number points to the jet’s energy content, and internally subsonic jets are energetically dominated by non-kinetic energy, such as thermal energy, cosmic rays, or magnetic fields.« less

The jets of AGN as giant coaxial cables

NASA Astrophysics Data System (ADS)

Gabuzda, Denise C.; Nagle, Matt; Roche, Naomi

2018-04-01

Context. The currents carried by the jets of active galactic nuclei (AGNs) can be probed using maps of the Faraday rotation measure (RM), since a jet current will be accompanied by a toroidal magnetic field, which will give rise to a systematic change in the RM across the jet. Aims: The aim of this study is to identify new AGNs displaying statistically significant transverse RM gradients across their parsec-scale jets, in order to determine how often helical magnetic fields occur in AGN jets, and to look for overall patterns in the implied directions for the toroidal field components and jet currents. Methods: We have carried out new analyses of Faraday RM maps derived from previously published 8.1, 8.4, 12.1 and 15.3 GHz data obtained in 2006 on the NRAO Very Long Baseline Array (VLBA). In a number of key ways, our procedures were identical to those of the original authors, but the new imaging and analysis differs from the original methods in several ways: the technique used to match the resolutions at the different frequencies, limits on the widths spanned by the RM gradients analyzed, treatment of core-region RM gradients, approach to estimation of the significances of the gradients analyzed, and inclusion of a supplementary analysis using circular beams with areas equal to those of the corresponding elliptical naturally weighted beams. Results: This new analysis has substantially increased the number of AGNs known to display transverse RM gradients that may reflect the presence of a toroidal magnetic-field component. The collected data on parsec and kiloparsec scales indicate that the current typically flows inward along the jet axis and outward in a more extended region surrounding the jet, typical to the current structure of a co-axial cable, accompanied by a self-consistent system of nested helical magnetic fields, whose toroidal components give rise to the observed transverse Faraday rotation gradients. Conclusions: The new results presented here make it

Implosive accretion and outbursts of active galactic nuclei

NASA Technical Reports Server (NTRS)

Lovelace, R. V. E.; Romanova, M. M.; Newman, W. I.

1994-01-01

A model and simulation code have been developed for time-dependent axisymmetric disk accretion onto a compact object including for the first time the influence of an ordered magnetic field. The accretion rate and radiative luminosity of the disk are naturally coupled to the rate of outflow of energy and angular momentum in magnetically driven (+/- z) winds. The magnetic field of the wind is treated in a phenomenological way suggested by self-consistent wind solutions. The radial accretion speed u(r, t) of the disk matter is shown to be the sum of the usual viscous contribution and a magnetic contribution proportional to r(exp 3/2)(B(sub p exp 2))/sigma, where B(sub p)(r,t) is the poloidal field threading the disk and sigma(r,t) is the disk's surface mass density. An enhancement or variation in B(sub p) at a large radial distance leads to the formation of a soliton-like structure in the disk density, temperature, and B-field which propagates implosively inward. The implosion gives a burst in the power output in winds or jets and a simultaneous burst in the disk radiation. The model is pertinent to the formation of discrete fast-moving components in jets observed by very long baseline interferometry. These components appear to originate at times of optical outbursts of the active galactic nucleus.

Probing the Relativistic Jets of Active Galactic Nuclei with Multiwavelength Monitoring

NASA Technical Reports Server (NTRS)

Marscher, Alan P.; Jorstad, Svetlana G.; Aller, Margo

2005-01-01

The work completed includes the analysis of observations obtained during Cycle 7 (March 2002-February 2003) of the Rossi X-ray Timing Explorer (RXTE). The project was part of a longer-term, continuing program to study the X-ray emission process in blazars and radio galaxies in collaboration with Dr. Ian McHardy (U. of Southampton, UK) and Prof. Thomas Balonek (Colgate U.). The goals of the program are to study the X-ray emission mechanism in blazars and radio galaxies and the relation of the X-ray emission to changes in the relativistic jet. The program includes contemporaneous brightness and linear polarization monitoring at radio and optical wavelengths, total and polarized intensity imaging at at 43 GHz with a resolution of 0.1 milliarcseconds with the VLBA, and well-sampled X-ray light curves obtained from a series of approved RXTE programs. The objects studied in the time period covered by the grant were 3C 120, 3C 279, PKS 1510-089, and 3C 273, all with radio jets containing bright knots that appear to move at superluminal speeds. During RXTE Cycle 7, the project was awarded RXTE time to monitor PKS 1510-089 two times per week, 3C 273 and 3C 279 three times per week, and 3C 120 four times per week. In addition, 3C273 and 3C 279 were observed several times per day during a ten-day period in April 2002. The X-ray data, including those from earlier cycles, were compared with radio measurements obtained in the centimeter-wave band by the monitoring program of Drs. Margo and Hugh Aller at the University of Michigan Radio Astronomy Observatory, monthly imaging observations with the VLBA at 43 GHz, and optical observations obtained at several telescopes around the world.

A galactic microquasar mimicking winged radio galaxies.

PubMed

Martí, Josep; Luque-Escamilla, Pedro L; Bosch-Ramon, Valentí; Paredes, Josep M

2017-11-24

A subclass of extragalactic radio sources known as winged radio galaxies has puzzled astronomers for many years. The wing features are detected at radio wavelengths as low-surface-brightness radio lobes that are clearly misaligned with respect to the main lobe axis. Different models compete to account for these peculiar structures. Here, we report observational evidence that the parsec-scale radio jets in the Galactic microquasar GRS 1758-258 give rise to a Z-shaped radio emission strongly reminiscent of the X and Z-shaped morphologies found in winged radio galaxies. This is the first time that such extended emission features are observed in a microquasar, providing a new analogy for its extragalactic relatives. From our observations, we can clearly favour the hydrodynamic backflow interpretation against other possible wing formation scenarios. Assuming that physical processes are similar, we can extrapolate this conclusion and suggest that this mechanism could also be at work in many extragalactic cases.

Galactic Bulge Giants: Probing Stellar and Galactic Evolution. 1. Catalogue of Spitzer IRAC and MIPS Sources (PREPRINT)

NASA Technical Reports Server (NTRS)

Uttenthaler, Stefan; Stute, Matthias; Sahai, Raghvendra; Blommaert, Joris A.; Schultheis, Mathias; Kraemer, Kathleen E.; Groenewegen, Martin A.; Price, Stephan D.

2010-01-01

Aims. We aim at measuring mass-loss rates and the luminosities of a statistically large sample of Galactic bulge stars at several galactocentric radii. The sensitivity of previous infrared surveys of the bulge has been rather limited, thus fundamental questions for late stellar evolution, such as the stage at which substantial mass-loss begins on the red giant branch and its dependence on fundamental stellar properties, remain unanswered. We aim at providing evidence and answers to these questions. Methods. To this end, we observed seven 15 15 arcmin2 fields in the nuclear bulge and its vicinity with unprecedented sensitivity using the IRAC and MIPS imaging instruments on-board the Spitzer Space Telescope. In each of the fields, tens of thousands of point sources were detected. Results. In the first paper based on this data set, we present the observations, data reduction, the final catalogue of sources, and a detailed comparison to previous mid-IR surveys of the Galactic bulge, as well as to theoretical isochrones. We find in general good agreement with other surveys and the isochrones, supporting the high quality of our catalogue.

The Jet Heated X-Ray Filament in the Centaurus A Northern Middle Radio Lobe

NASA Astrophysics Data System (ADS)

Kraft, R. P.; Forman, W. R.; Hardcastle, M. J.; Birkinshaw, M.; Croston, J. H.; Jones, C.; Nulsen, P. E. J.; Worrall, D. M.; Murray, S. S.

2009-06-01

We present results from a 40 ks XMM-Newton observation of the X-ray filament coincident with the southeast edge of the Centaurus A Northern Middle Radio Lobe (NML). We find that the X-ray filament consists of five spatially resolved X-ray knots embedded in a continuous diffuse bridge. The spectrum of each knot is well fitted by a thermal model with temperatures ranging from 0.3 to 0.7 keV and subsolar elemental abundances. In four of the five knots, nonthermal models are a poor fit to the spectra, conclusively ruling out synchrotron or IC/CMB mechanisms for their emission. The internal pressures of the knots exceed that of the ambient interstellar medium or the equipartition pressure of the NML by more than an order of magnitude, demonstrating that they must be short lived (~3 × 106 yr). Based on energetic arguments, it is implausible that these knots have been ionized by the beamed flux from the active galactic nucleus of Cen A or that they have been shock heated by supersonic inflation of the NML. In our view, the most viable scenario for the origin of the X-ray knots is that they are the result of cold gas shock heated by a direct interaction with the jet. The most plausible model of the NML is that it is a bubble from a previous nuclear outburst that is being re-energized by the current outburst. The northeast inner lobe and the large-scale jet are lossless channels through which the jet material rapidly travels to the NML in this scenario. We also report the discovery of a large-scale (at least 35 kpc radius) gas halo around Cen A.

Constraining high-energy neutrino emission from choked jets in stripped-envelope supernovae

NASA Astrophysics Data System (ADS)

Senno, Nicholas; Murase, Kohta; Mészáros, Peter

2018-01-01

There are indications that γ-ray dark objects such as supernovae (SNe) with choked jets, and the cores of active galactic nuclei may contribute to the diffuse flux of astrophysical neutrinos measured by the IceCube observatory. In particular, stripped-envelope SNe have received much attention since they are capable of producing relativistic jets and could explain the diversity in observations of collapsar explosions (e.g., gamma-ray bursts (GRBs), low-luminosity GRBs, and Type Ibc SNe). We use an unbinned maximum likelihood method to search for spatial and temporal coincidences between Type Ibc core-collapse SNe, which may harbor a choked jet, and muon neutrinos from a sample of IceCube up-going track-like events measured from May 2011–May 2012. In this stacking analysis, we find no significant deviation from a background-only hypothesis using one year of data, and are able to place upper limits on the total amount of isotropic equivalent energy that choked jet core-collapse SNe deposit in cosmic rays Script Ecr and the fraction of core-collapse SNe which have a jet pointed towards Earth fjet. This analysis can be extended with yet to be made public IceCube data, and the increased amount of optically detected core-collapse SNe discovered by wide field-of-view surveys such as the Palomar Transient Factory and All-Sky Automated Survey for Supernovae. The choked jet SNe/high-energy cosmic neutrino connection can be more tightly constrained in the near future.

Active galactic nuclei

PubMed Central

Fabian, Andrew C.

1999-01-01

Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated. PMID:10220363

How AGN Jets Heat the Intracluster Medium—Insights from Hydrodynamic Simulations

NASA Astrophysics Data System (ADS)

Yang, H.-Y. Karen; Reynolds, Christopher S.

2016-10-01

Feedback from active galactic nuclei (AGNs) is believed to prevent catastrophic cooling in galaxy clusters. However, how the feedback energy is transformed into heat, and how the AGN jets heat the intracluster medium (ICM) isotropically, still remain elusive. In this work, we gain insights into the relative importance of different heating mechanisms using three-dimensional hydrodynamic simulations including cold gas accretion and momentum-driven jet feedback, which are the most successful models to date in terms of reproducing the properties of cool cores. We find that there is net heating within two “jet cones” (within ∼30° from the axis of jet precession) where the ICM gains entropy by shock heating and mixing with the hot thermal gas within bubbles. Outside the jet cones, the ambient gas is heated by weak shocks, but not enough to overcome radiative cooling, therefore, forming a “reduced” cooling flow. Consequently, the cluster core is in a process of “gentle circulation” over billions of years. Within the jet cones, there is significant adiabatic cooling as the gas is uplifted by buoyantly rising bubbles; outside the cones, energy is supplied by the inflow of already-heated gas from the jet cones as well as adiabatic compression as the gas moves toward the center. In other words, the fluid dynamics self-adjusts such that it compensates and transports the heat provided by the AGN, and hence no fine-tuning of the heating profile of any process is necessary. Throughout the cluster evolution, turbulent energy is only at the percent level compared to gas thermal energy, and thus turbulent heating is not the main source of heating in our simulation.

HIREGS observations of the Galactic center and Galactic plane: Separation of the diffuse Galactic hard X-ray continuum from the point source spectra

NASA Technical Reports Server (NTRS)

Boggs, S. E.; Lin, R. P.; Coburn, W.; Feffer, P.; Pelling, R. M.; Schroeder, P.; Slassi-Sennou, S.

1997-01-01

The balloon-borne high resolution gamma ray and X-ray germanium spectrometer (HIREGS) was used to observe the Galactic center and two positions along the Galactic plane from Antarctica in January 1995. For its flight, the collimators were configured to measure the Galactic diffuse hard X-ray continuum between 20 and 200 keV by directly measuring the point source contributions to the wide field of view flux for subtraction. The hard X-ray spectra of GX 1+4 and GRO J1655-40 were measured with the diffuse continuum subtracted off. The analysis technique for source separation is discussed and the preliminary separated spectra for these point sources and the Galactic diffuse emission are presented.

Star-disc interaction in galactic nuclei: formation of a central stellar disc

NASA Astrophysics Data System (ADS)

Panamarev, Taras; Shukirgaliyev, Bekdaulet; Meiron, Yohai; Berczik, Peter; Just, Andreas; Spurzem, Rainer; Omarov, Chingis; Vilkoviskij, Emmanuil

2018-05-01

We perform high-resolution direct N-body simulations to study the effect of an accretion disc on stellar dynamics in an active galactic nucleus (AGN). We show that the interaction of the nuclear stellar cluster (NSC) with the gaseous accretion disc (AD) leads to formation of a stellar disc in the central part of the NSC. The accretion of stars from the stellar disc on to the super-massive black hole is balanced by the capture of stars from the NSC into the stellar disc, yielding a stationary density profile. We derive the migration time through the AD to be 3 per cent of the half-mass relaxation time of the NSC. The mass and size of the stellar disc are 0.7 per cent of the mass and 5 per cent of the influence radius of the super-massive black hole. An AD lifetime shorter than the migration time would result in a less massive nuclear stellar disc. The detection of such a stellar disc could point to past activity of the hosting galactic nucleus.

75 FR 81250 - Pulse Jet Mixing at the Waste Treatment and Immobilization Plant

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-27

... DEFENSE NUCLEAR FACILITIES SAFETY BOARD [Recommendation 2010-2] Pulse Jet Mixing at the Waste... Board has made a recommendation to the Secretary of Energy concerning the use of pulse jet mixing at the..., 2010. Peter S. Winokur, Chairman. Recommendation 2010-2 to the Secretary of Energy Pulse Jet Mixing at...

Measurements of the Nuclear Modification Factor for Jets in Pb+Pb Collisions at √(s)NN]=2.76  TeV with the ATLAS detector.

PubMed

Aad, G; Abbott, B; Abdallah, J; Abdel Khalek, S; Abdinov, O; Aben, R; Abi, B; Abolins, M; AbouZeid, O S; Abramowicz, H; Abreu, H; Abreu, R; Abulaiti, Y; Acharya, B S; Adamczyk, L; Adams, D L; Adelman, J; Adomeit, S; Adye, T; Agatonovic-Jovin, T; Aguilar-Saavedra, J A; Agustoni, M; Ahlen, S P; Ahmadov, F; Aielli, G; Akerstedt, H; Åkesson, T P A; Akimoto, G; Akimov, A V; Alberghi, G L; Albert, J; Albrand, S; Alconada Verzini, M J; Aleksa, M; Aleksandrov, I N; Alexa, C; Alexander, G; Alexandre, G; Alexopoulos, T; Alhroob, M; Alimonti, G; Alio, L; Alison, J; Allbrooke, B M M; Allison, L J; Allport, P P; Almond, J; Aloisio, A; Alonso, A; Alonso, F; Alpigiani, C; Altheimer, A; Alvarez Gonzalez, B; Alviggi, M G; Amako, K; Amaral Coutinho, Y; Amelung, C; Amidei, D; Amor Dos Santos, S P; Amorim, A; Amoroso, S; Amram, N; Amundsen, G; Anastopoulos, C; Ancu, L S; Andari, N; Andeen, T; Anders, C F; Anders, G; Anderson, K J; Andreazza, A; Andrei, V; Anduaga, X S; Angelidakis, S; Angelozzi, I; Anger, P; 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2015-02-20

Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √(s)NN=2.76  TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14  nb(-1), respectively. The jets are identified with the anti-k(t) algorithm with R=0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32nuclear modification factor R(AA) is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to pp collisions. The R(AA) shows a slight increase with p(T) and no significant variation with rapidity.

X-ray Variability In Extragalactic Jets as Seen by Chandra

NASA Astrophysics Data System (ADS)

Trevor, Max; Meyer, Eileen; Georganopoulos, Markos; Aubin, Sam; Hewitt, Jennifer; DeNigris, Natalie; Whitley, Kevin

2018-01-01

The unrivaled spatial resolution of Chandra has lead to the detection of over 100 extragalactic jetsemitting X-rays on kiloparsec scales, far from the central AGN. These jets are understood to be powerful redistributors of energy on galactic and extragalactic scales, with important effects on galaxy evolution and cluster heating. However, we lack an understanding of many important jet properties, including the particle makeup, particle acceleration characteristics, and total energy content, and even how fast the jet is at kpc scales. In the most powerful jets, a persistently open question is the nature of the emission mechanism for the Chandra-observed X-rays. While inverse Compton upscattering of CMB photons (IC/CMB) by a still-relativistic jet is widely adopted, our group has very recently ruled it out in several cases, suggesting that the X-rays from powerful sources, like the low-power jets, have a synchrotron origin, albeit one with unknown origins, requiring in-situ lepton acceleration at least up to 100 TeV. A very efficient way to extend this result to many more sources is to check for variability of the large scale jet X-ray emission, something that is definitively not expected in the case of IC/CMB due to the extremely long cooling times of the electrons responsible for the emission, but it is plausible if the X-rays are of synchrotron nature. Based on previously published observations of X-ray variability in the jets of M87 and Pictor A, as well as preliminary results suggesting variability in two more powerful jets, we have examined archival observations of over 40 jets which have been imaged twice or more with Chandra for variability, with timescales of a few to nearly 14 years. This analysis has two main goals, namely (i) to confirm a synchrotron origin for the X-rays in powerful sources, as variability is inconsistent with the competing IC/CMB model and (ii) to use the timescales and characteristics (e.g., spectral changes) of any detected X

Dichotomy of Solar Coronal Jets: Standard Jets and Blowout Jets

NASA Technical Reports Server (NTRS)

Moore, R. L.; Cirtain, J. W.; Sterling, A. C.; Falconer, D. A.

2010-01-01

By examining many X-ray jets in Hinode/XRT coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H alpha macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major CMEs. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jets that were also caught in He II 304 Angstrom snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T 10(exp 4) - 10(exp 5) K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.

HOW AGN JETS HEAT THE INTRACLUSTER MEDIUM—INSIGHTS FROM HYDRODYNAMIC SIMULATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karen Yang, H.-Y.; Reynolds, Christopher S., E-mail: hsyang@astro.umd.edu

Feedback from active galactic nuclei (AGNs) is believed to prevent catastrophic cooling in galaxy clusters. However, how the feedback energy is transformed into heat, and how the AGN jets heat the intracluster medium (ICM) isotropically, still remain elusive. In this work, we gain insights into the relative importance of different heating mechanisms using three-dimensional hydrodynamic simulations including cold gas accretion and momentum-driven jet feedback, which are the most successful models to date in terms of reproducing the properties of cool cores. We find that there is net heating within two “jet cones” (within ∼30° from the axis of jet precession)more » where the ICM gains entropy by shock heating and mixing with the hot thermal gas within bubbles. Outside the jet cones, the ambient gas is heated by weak shocks, but not enough to overcome radiative cooling, therefore, forming a “reduced” cooling flow. Consequently, the cluster core is in a process of “gentle circulation” over billions of years. Within the jet cones, there is significant adiabatic cooling as the gas is uplifted by buoyantly rising bubbles; outside the cones, energy is supplied by the inflow of already-heated gas from the jet cones as well as adiabatic compression as the gas moves toward the center. In other words, the fluid dynamics self-adjusts such that it compensates and transports the heat provided by the AGN, and hence no fine-tuning of the heating profile of any process is necessary. Throughout the cluster evolution, turbulent energy is only at the percent level compared to gas thermal energy, and thus turbulent heating is not the main source of heating in our simulation.« less

Resolved, expanding jets in the Galactic black hole candidate XTE J1908+094

NASA Astrophysics Data System (ADS)

Rushton, A. P.; Miller-Jones, J. C. A.; Curran, P. A.; Sivakoff, G. R.; Rupen, M. P.; Paragi, Z.; Spencer, R. E.; Yang, J.; Altamirano, D.; Belloni, T.; Fender, R. P.; Krimm, H. A.; Maitra, D.; Migliari, S.; Russell, D. M.; Russell, T. D.; Soria, R.; Tudose, V.

2017-07-01

Black hole X-ray binaries undergo occasional outbursts caused by changing inner accretion flows. Here we report high angular resolution radio observations of the 2013 outburst of the black hole candidate X-ray binary system XTE J1908+094, using data from the Very Long Baseline Array and European VLBI Network. We show that following a hard-to-soft state transition, we detect moving jet knots that appear asymmetric in morphology and brightness, and expand to become laterally resolved as they move away from the core, along an axis aligned approximately -11° east of north. We initially see only the southern component, whose evolution gives rise to a 15-mJy radio flare and generates the observed radio polarization. This fades and becomes resolved out after 4 days, after which a second component appears to the north, moving in the opposite direction. From the timing of the appearance of the knots relative to the X-ray state transition, a 90° swing of the inferred magnetic field orientation, the asymmetric appearance of the knots, their complex and evolving morphology, and their low speeds, we interpret the knots as working surfaces where the jets impact the surrounding medium. This would imply a substantially denser environment surrounding XTE J1908+094 than has been inferred to exist around the microquasar sources GRS 1915+105 and GRO J1655-40.

Intermittent behavior of galactic dynamo activities

NASA Technical Reports Server (NTRS)

Ko, C. M.; Parker, E. N.

1989-01-01

Recent observations by Beck and Golla of far-infrared and radio continuum emission from nearby spiral galaxies suggest that the galactic magnetic field strength is connected to the current star formation rate. The role of star formation on the generation of large-scale galactic magnetic field is studied in this paper. Using a simple galactic model, it is shown how the galactic dynamo depends strongly on the turbulent velocity of the interstellar medium. When the star formation efficiency is high, the ISM is churned which in turn amplifies the galactic magnetic field. Between active star formation epochs, the magnetic field is in dormant state and decays at a negligible rate. If density waves trigger star formation, then they also turn on the otherwise dormant dynamo.

Jet axes and universal transverse-momentum-dependent fragmentation

NASA Astrophysics Data System (ADS)

Neill, Duff; Scimemi, Ignazio; Waalewijn, Wouter J.

2017-04-01

We study the transverse momentum spectrum of hadrons in jets. By measuring the transverse momentum with respect to a judiciously chosen axis, we find that this observable is insensitive to (the recoil of) soft radiation. Furthermore, for small transverse momenta we show that the effects of the jet boundary factorize, leading to a new transverse-momentum-dependent (TMD) fragmentation function. In contrast to the usual TMD fragmentation functions, it does not involve rapidity divergences and is universal in the sense that it is independent of the type of process and number of jets. These results directly apply to sub-jets instead of hadrons. We discuss potential applications, which include studying nuclear modification effects in heavy-ion collisions and identifying boosted heavy resonances.

Search for EeV protons of galactic origin

NASA Astrophysics Data System (ADS)

Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashi, M.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kishigami, S.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lubsandorzhiev, B.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, K.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Onogi, R.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Saito, K.; Saito, Y.; Sakaki, N.; Sakurai, N.; Scott, L. M.; Sekino, K.; Shah, P. D.; Shibata, T.; Shibata, F.; Shimodaira, H.; Shin, B. K.; Shin, H. S.; Smith, J. D.; Sokolsky, P.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takahashi, Y.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, M.; Tanaka, K.; Tanaka, H.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tirone, A. H.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

2017-01-01

Cosmic rays in the energy range 1018.0-1018.5 eV are thought to have a light, probably protonic, composition. To study their origin one can search for anisotropy in their arrival directions. Extragalactic cosmic rays should be isotropic, but galactic cosmic rays of this type should be seen mostly along the galactic plane, and there should be a shortage of events coming from directions near the galactic anticenter. This is due to the fact that, under the influence of the galactic magnetic field, the transition from ballistic to diffusive behavior is well advanced, and this qualitative picture persists over the whole energy range. Guided by models of the galactic magnetic field that indicate that the enhancement along the galactic plane should have a standard deviation of about 20° in galactic latitude, and the deficit in the galactic anticenter direction should have a standard deviation of about 50° in galactic longitude, we use the data of the Telescope Array surface detector in 1018.0 to 1018.5 eV energy range to search for these effects. The data are isotropic. Neither an enhancement along the galactic plane nor a deficit in the galactic anticenter direction is found. Using these data we place an upper limit on the fraction of EeV cosmic rays of galactic origin at 1.3% at 95% confidence level.

Possible Accretion Disk Origin of the Emission Variability of a Blazar Jet

NASA Astrophysics Data System (ADS)

Chatterjee, Ritaban; Roychowdhury, Agniva; Chandra, Sunil; Sinha, Atreyee

2018-06-01

We analyze X-ray light curves of the blazar Mrk 421 obtained from the Soft X-ray Imaging Telescope (SXT) and the Large Area X-ray Proportional Counter (LAXPC) instrument on board the Indian space telescope AstroSat and archival observations from Swift. We show that the X-ray power spectral density (PSD) is a piece-wise power-law with a break; i.e., the index becomes more negative below a characteristic “break timescale.” Galactic black hole (BH) X-ray binaries and Seyfert galaxies exhibit a similar characteristic timescale in their X-ray variability that is proportional to their respective BH mass. X-rays in these objects are produced in the accretion disk or corona. Hence, such a timescale is believed to be linked to the properties of the accretion flow. Any relation observed between events in the accretion disk and those in the jet can be used to characterize the disk–jet connection. However, evidence of such a link has been scarce and indirect. Mrk 421 is a BL Lac object that has a prominent jet pointed toward us and a weak disk emission, and it is assumed that most of its X-rays are generated in the jet. Hence, the existence of the break in its X-ray PSD may indicate that changes in the accretion disk, which may be the source of the break timescale, are translating into the jet where the X-rays are produced.

DICHOTOMY OF SOLAR CORONAL JETS: STANDARD JETS AND BLOWOUT JETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.

2010-09-01

By examining many X-ray jets in Hinode/X-Ray Telescope coronal X-ray movies of the polar coronal holes, we found that there is a dichotomy of polar X-ray jets. About two thirds fit the standard reconnection picture for coronal jets, and about one third are another type. We present observations indicating that the non-standard jets are counterparts of erupting-loop H{alpha} macrospicules, jets in which the jet-base magnetic arch undergoes a miniature version of the blowout eruptions that produce major coronal mass ejections. From the coronal X-ray movies we present in detail two typical standard X-ray jets and two typical blowout X-ray jetsmore » that were also caught in He II 304 A snapshots from STEREO/EUVI. The distinguishing features of blowout X-ray jets are (1) X-ray brightening inside the base arch in addition to the outside bright point that standard jets have, (2) blowout eruption of the base arch's core field, often carrying a filament of cool (T {approx} 10{sup 4} - 10{sup 5} K) plasma, and (3) an extra jet-spire strand rooted close to the bright point. We present cartoons showing how reconnection during blowout eruption of the base arch could produce the observed features of blowout X-ray jets. We infer that (1) the standard-jet/blowout-jet dichotomy of coronal jets results from the dichotomy of base arches that do not have and base arches that do have enough shear and twist to erupt open, and (2) there is a large class of spicules that are standard jets and a comparably large class of spicules that are blowout jets.« less

Probing stochastic inter-galactic magnetic fields using blazar-induced gamma ray halo morphology

NASA Astrophysics Data System (ADS)

Duplessis, Francis; Vachaspati, Tanmay

2017-05-01

Inter-galactic magnetic fields can imprint their structure on the morphology of blazar-induced gamma ray halos. We show that the halo morphology arises through the interplay of the source's jet and a two-dimensional surface dictated by the magnetic field. Through extensive numerical simulations, we generate mock halos created by stochastic magnetic fields with and without helicity, and study the dependence of the halo features on the properties of the magnetic field. We propose a sharper version of the Q-statistics and demonstrate its sensitivity to the magnetic field strength, the coherence scale, and the handedness of the helicity. We also identify and explain a new feature of the Q-statistics that can further enhance its power.

Nuclear planetology: understanding habitable planets as Galactic bulge stellar remnants (black dwarfs) in a Hertzsprung-Russell (HR) diagram

NASA Astrophysics Data System (ADS)

Roller, Goetz

2016-04-01

model constraining the evolution of a rocky planet like Earth or Mercury from a stellar precursor of the oldest population to a Fe-C BLD, shifting through different spectral classes in a HR diagram after massive decompression and tremendous energy losses. In the light of WD/BLD cosmochronology [1], solar system bodies like Earth, Mercury and Moon are regarded as captured interlopers from the Galactic bulge, Earth and Moon possibly representing remnants of an old binary system. Such a preliminary scenario is supported by similar ages obtained from WD's for the Galactic halo [1] and, independently, by means of 187Re-232Th-238U nuclear geochronometry [2, 4, 5], together with recent observations extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way [6]. This might be further elucidated in the near future by Th/U cosmochronometry based upon a nuclear production ratio Th/U = 0.96 [5] and additionally by means of a newly developed nucleogeochronometric age dating method for stellar spectroscopy, which will be presented in a forthcoming paper. The model shall stimulate geochemical data interpretation from a different perspective to constrain the (thermal) evolution of a habitable planet as to its geo-, bio-, hydro- and atmosphere. [1] Fontaine et al. (2001), Public. Astron. Soc. of the Pacific 113, 409-435. [2] Roller (2015), Abstract T34B-0407, AGU Spring Meeting 2015. [3] Arevalo et al. (2010), Chem. Geol. 271, 70-85. [4] Roller (2015), Geophys. Res. Abstr. 17, EGU2015-2399. [5] Roller (2015), 78th Annu. Meeting Met. Soc., Abstract #5041. [6] Howes et al. (2015), Nature 527, 484-487.

Radio-Loud Narrow-Line Seyfert 1 as a New Class of Gamma-Ray Active Galactic Nuclei

DOE PAGES

Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

2009-12-04

In this work, we report the discovery with Fermi/LAT of γ-ray emission from three radio-loud narrow-line Seyfert 1 galaxies: PKS 1502+036 (z = 0.409), 1H 0323+342 (z = 0.061), and PKS 2004 – 447 (z = 0.24). In addition to PMN J0948+0022 (z = 0.585), the first source of this type to be detected in γ rays, they may form an emerging new class of γ-ray active galactic nuclei (AGNs). Lastly, these findings can have strong implications on our knowledge about relativistic jets and the unified model of the AGN.

Jet in jet in M87

NASA Astrophysics Data System (ADS)

Sob'yanin, Denis Nikolaevich

2017-11-01

New high-resolution Very Long Baseline Interferometer observations of the prominent jet in the M87 radio galaxy show a persistent triple-ridge structure of the transverse 15-GHz profile with a previously unobserved ultra-narrow central ridge. This radio structure can reflect the intrinsic structure of the jet, so that the jet as a whole consists of two embedded coaxial jets. A relativistic magnetohydrodynamic model is considered in which an inner jet is placed inside a hollow outer jet and the electromagnetic fields, pressures and other physical quantities are found. The entire jet is connected to the central engine that plays the role of a unipolar inductor generating voltage between the jets and providing opposite electric currents, and the charge neutrality and current closure together with the electromagnetic fields between the jets can contribute to the jet stabilization. The constant voltage is responsible for the similar widening laws observed for the inner and outer jets. This jet-in-jet structure can indicate simultaneous operation of two different jet-launching mechanisms, one relating to the central supermassive black hole and the other to the surrounding accretion disc. An inferred magnetic field of 80 G at the base is sufficient to provide the observed jet luminosity.

Gas Cloud Accretion onto the SMBH SgrA* and Formation of Jet 4

NASA Astrophysics Data System (ADS)

Nishiyama, Shogo

2015-06-01

A dense gas cloud was detected to be rapidly approaching the Galactic supermassive black hole (SMBH) Sgr A*, and was 1,600 Schwarzschild radii from the SMBH at the pericenter of its eccentric orbit in Mar 2014. Ongoing tidal disruption has been observed, and cloud fragments are expected to accrete onto the SMBH on dynamical timescales, suggesting a jet formation in the following years. So we are carrying out daily monitoring observations of Sgr A* in near-infrared and radio wavelengths, and we propose quick follow-up observations with Subaru/Gemini. Br-gamma line emission maps obtained with Gemini/NIFS will be used to fine tune our 3D simulation to estimate how much mass accretes, and when the fragments accrete onto the SMBH. Polarimetric and astrometric signals from a jet taken with Subaru/HiCIAO and KaVA will be compared with the finely tuned simulation to understand the timescale of jet formation, and to investigate the correlation between the accreted mass of the cloud fragments and a luminosity of the newly-formed jet. Spectroscopic and imaging observations from 1.6 - 11 mum (Subaru/IRCS, COMICS) will also be conducted to understand processes responsible for near to mid-infrared emission during the accretion event.

Making Sense of Black Holes: Modeling the Galactic Center and Other Low-power AGN

NASA Astrophysics Data System (ADS)

Falcke, Heino; Moscibrodzka, Monika

2018-06-01

The Galactic center host a well-known flat-spectrum radio source, Sgr A*, that is akin to the radio nuclei of quasars and radio galaxies. It is the main target of the Event Horizon Telescope to image the shadow of the black hole. There is, however, still considerable discussion on where the near-horizon emission originates from. Does it come from an accretion flow or is it produced in a relativistic jet-like outflow? Using advanced three-dimensional general relativistic magnetohydrodynamics simulations coupled to general relativistic ray tracing simulations, we now model the dynamics and emission of the plasma around starving black holes in great detail out to several thousand Schwarzschild radii. Jets appear almost naturally in theses simulations. A crucial parameter is the heating of radiating electrons and we argue that electron-proton coupling is low in the accretion flow and high in the magnetized region of the jets, making the jet an important ingredient for the overall appearance of the source. This comprehensive model is able to predict the radio size and appearance, the spectral energy distribution from radio to X-rays, the variability, and the time lags of Sgr A* surprisingly well. Interestingly, the same model can be easily generalized to other low-power AGN like M87, suggesting that GRMHD models for AGN are finally becoming predictive. With upcoming submm-VLBI experiment on the ground and in space, we will be able to further test these models in great detail and see black holes in action.

Collectivity and manifestations of minimum-bias jets in high-energy nuclear collisions

NASA Astrophysics Data System (ADS)

Trainor, Thomas A.

2018-01-01

Collectivity, as interpreted to mean flow of a dense medium in high-energy A-A collisions described by hydrodynamics, has been attributed to smaller collision systems - p-A and even p-p collisions - based on recent analysis of LHC data. However, alternative methods reveal that some data features attributed to flows are actually manifestations of minimum-bias (MB) jets. In this presentation I review the differential structure of single-particle pt spectra from SPS to LHC energies in the context of a two-component (soft + hard) model (TCM) of hadron production. I relate the spectrum hard component to measured properties of isolated jets. I use the spectrum TCM to predict accurately the systematics of ensemble-mean p̅t in p-p, p-A and A-A collision systems over a large energy interval. Detailed comparisons of the TCM with spectrum and correlation data suggest that MB jets play a dominant role in hadron production near midrapidity. Claimed flow phenomena are better explained as jet manifestations agreeing quantitatively with measured jet properties.

The annihilation of galactic positrons

NASA Technical Reports Server (NTRS)

Bussard, R.; Rematy, R.

1978-01-01

The probabilities of various channels of galactic positron annihilation were evaluated and the spectrum of the resulting radiation was calculated. The narrow width (FWHM less than 3.2 keV) of the 0.511 MeV line observed from the galactic center implies that a large fraction of positrons should annihilate in a medium of temperature less than 100,000 K and ionization fraction greater than 0.05. HII regions at the galactic center could be possible sites of annihilation.

Disc-jet Coupling in the 2009 Outburst of the Black Hole Candidate H1743-322

NASA Technical Reports Server (NTRS)

Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; Coriat, M.; Corbel, S.; Dhawan, V.; Krimm, H. A.; Remillard, R. A.; Rupen, M. P.; Russell, D. M.;

Research Opportunities on board Virgin Galactic's SpaceShipTwo

NASA Astrophysics Data System (ADS)

Attenborough, S.; Pomerantz, W.; Stephens, K.

2013-09-01

Virgin Galactic is building the world's first commercial spaceline. Our suborbital spaceflight system, pictured in Figure 1, consists of two vehicles: WhiteKnightTwo (WK2) and SpaceShipTwo (SS2). WhiteKnightTwo is a four-engine, dual-fuselage jet aircraft capable of high-altitude heavy lift missions, including, but not limited to fulfilling its role as a mothership for SpaceShipTwo, an air-launched, suborbital spaceplane capable of routinely reaching an apogee up to 110 kilometers. In conjunction, these two vehicles allow access to space and to regions of the atmosphere ranging from the troposphere to the thermosphere; additionally, they provide extended periods of microgravity in a reliable and affordable way. SpaceShipTwo, with a payload capacity of up to 1,300 lbs. (~600 kg), features payload mounting interfaces that are compatible with standard architectures such as NASA Space Shuttle Middeck Lockers, Cargo Transfer Bags, and server racks, in addition to custom structures. With the standard interface, payloads are allowed access to the large 17 inch diameter cabin windows for external observations. Each dedicated research flight will be accompanied by a Virgin Galactic Flight Test Engineer, providing an opportunity for limited in-flight interaction. In addition, tended payloads - a flight that includes the researcher and his or her payload - are also an option. At a price point that is highly competitive with parabolic aircraft and sounding rockets and significantly cheaper than orbital flights, SpaceShipTwo is a unique platform that can provide frequent and repeatable research opportunities. Suborbital flights on SpaceShipTwo offer researchers several minutes of microgravity time and views of the external environment in the upper atmosphere and in outer space. In addition to serving as an important research platform in and of itself, SpaceShipTwo also offers researchers a means to test, iterate, and calibrate experiments designed for orbital platforms

Multiwavelength observations of Active Galactic Nuclei from the radio to the hard X-rays

NASA Astrophysics Data System (ADS)

Beuchert, Tobias

2017-07-01

Active Galaxies form a peculiar type of galaxies. Their cores, the so-called "Active Galactic Nuclei" (AGN), are the most persistent luminous objects in the universe. Accretion of several solar masses per year onto black holes of Millions to Billions of solar masses drive the immense energy output of these systems, which can exceed that of the entire galaxy. The compact energy source, however, only measures about one over a Billion times that of the entire galaxy. Subject of my thesis are observations of the two main channels of energy release of selected AGN systems, both of which are encompassed by profound and yet unanswered questions. These channels are on the one hand the pronounced X-ray emission of the hot and compact accreting environment in close vicinity of the black hole, and on the other hand the radio synchrotron emission of magnetically collimated jets that are fed by portions of the accreted matter. These jets also function as effective accelerators and drive the injected matter deep into the intergalactic medium. As the circumnuclear environment of AGN is too compact to be spatially resolved in the X-rays, I show how X-ray spectroscopy can be used to: (1) understand the effects of strong gravity to trace the geometry and physics of the X-ray source and (2) more consistently quantify matter that surrounds and dynamically absorbs our direct line of sight towards the X-ray source. Second, I unveil the valuable information contained in the polarized radio light being emitted from magnetized jet outflows. In contrast to the X-ray emitting region, I am able to spatially resolve the inner parts of the jet of a prominent galaxy with help of the Very Long Baseline Array, a large network of radio telescopes. The resulting polarization maps turn out to be exceptionally promising in answering fundamental questions related to jet physics.

Photon-tagged and B-meson-tagged b-jet production at the LHC

DOE PAGES

Huang, Jinrui; Kang, Zhong -Bo; Vitev, Ivan; ...

2015-09-18

Tagged jet measurements in high energy hadronic and nuclear reactions provide constraints on the energy and parton flavor origin of the parton shower that recoils against the tagging particle. Such additional insight can be especially beneficial in illuminating the mechanisms of heavy flavor production in proton–proton collisions at the LHC and their modification in the heavy ion environment, which are not fully understood. With this motivation, we present theoretical results for isolated-photon-tagged and B-meson-tagged b-jet production at √s NN = 5.1 TeV for comparison to the upcoming lead–lead data. We find that photon-tagged b-jets exhibit smaller momentum imbalance shift inmore » nuclear matter, and correspondingly smaller energy loss, than photon-tagged light flavor jets. Our results show that B-meson tagging is most effective in ensuring that the dominant fraction of recoiling jets originate from prompt b-quarks. Furthermore, in this channel the large suppression of the cross section is not accompanied by a significant momentum imbalance shift.« less

Coupling of jet and accretion activity in the active galaxy NGC 1052

NASA Astrophysics Data System (ADS)

Boeck, Moritz; Kadler, Matthias; Ros, Eduardo; Weaver, Kimberly; Wilms, Joern; Brenneman, Laura; Angelakis, Emmanouil

The radio loud galaxy NGC 1052 has been monitored for the past fifteen years with Very Long Baseline Interferometry (VLBI) observations and has been the target of an intense multiwave-length monitoring campaign since 2005. This provides an excellent dataset for analyzing the relationship between properties of the relativistic jet and the accretion disk in active galactic nuclei. Components in the jet are tracked and the ejection times of new components are deter-mined. The analysis of the radio variability is complemented by the study of X-ray observations allowing us to draw conclusions on the accretion activity. The X-ray variability on weekly and monthly time scales is monitored with the Rossi X-ray Timing Explorer, whereas deep XMM-Newton and Suzaku observations provide spectra showing a broad Fe Kα line, whose variability can provide a particularly valuable probe of the inner accretion flow.

Dynamical Processes Near the Super Massive Black Hole at the Galactic Center

NASA Astrophysics Data System (ADS)

Antonini, Fabio

2011-01-01

Observations of the stellar environment near the Galactic center provide the strongest empirical evidence for the existence of massive black holes in the Universe. Theoretical models of the Milky Way nuclear star cluster fail to explain numerous properties of such environment, including the presence of very young stars close to the super massive black hole (SMBH) and the more recent discovery of a parsec-scale core in the central distribution of the bright late-type (old) stars. In this thesis we present a theoretical study of dynamical processes near the Galactic center, strongly related to these issues. Using different numerical techniques we explore the close environment of a SMBH as catalyst for stellar collisions and mergers. We study binary stars that remain bound for several revolutions around the SMBH, finding that in the case of highly inclined binaries the Kozai resonance can lead to large periodic oscillations in the internal binary eccentricity and inclination. Collisions and mergers of the binary elements are found to increase significantly for multiple orbits around the SMBH. In collisions involving a low-mass and a high-mass star, the merger product acquires a high core hydrogen abundance from the smaller star, effectively resetting the nuclear evolution clock to a younger age. This process could serve as an important source of young stars at the Galactic center. We then show that a core in the old stars can be naturally explained in a scenario in which the Milky Way nuclear star cluster (NSC) is formed via repeated inspiral of globular clusters into the Galactic center. We present results from a set of N -body simulations of this process, which show that the fundamental properties of the NSC, including its mass, outer density profile and velocity structure, are also reproduced. Chandrasekhar's dynamical friction formula predicts no frictional force on a test body in a low-density core, regardless of its density, due to the absence of stars moving

The correlation between the total magnetic flux and the total jet power

NASA Astrophysics Data System (ADS)

Nokhrina, Elena E.

2017-12-01

Magnetic field threading a black hole ergosphere is believed to play the key role in both driving the powerful relativistic jets observed in active galactic nuclei and extracting the rotational energy from a black hole via Blandford-Znajek process. The magnitude of magnetic field and the magnetic flux in the vicinity of a central black hole is predicted by theoretical models. On the other hand, the magnetic field in a jet can be estimated through measurements of either the core shift effect or the brightness temperature. In both cases the obtained magnetic field is in the radiating domain, so its direct application to the calculation of the magnetic flux needs some theoretical assumptions. In this paper we address the issue of estimating the magnetic flux contained in a jet using the measurements of a core shift effect and of a brightness temperature for the jets, directed almost at the observer. The accurate account for the jet transversal structure allow us to express the magnetic flux through the observed values and an unknown rotation rate of magnetic surfaces. If we assume the sources are in a magnetically arrested disk state, the lower limit for the rotation rate can be obtained. On the other hand, the flux estimate may be tested against the total jet power predicted by the electromagnetic energy extraction model. The resultant expression for power depends logarithmically weakly on an unknown rotation rate. We show that the total jet power estimated through the magnetic flux is in good agreement with the observed power. We also obtain the extremely slow rotation rates, which may be an indication that the majority of the sources considered are not in the magnetically arrested disk state.

Finding Distant Galactic HII Regions

NASA Astrophysics Data System (ADS)

Anderson, L. D.; Armentrout, W. P.; Johnstone, B. M.; Bania, T. M.; Balser, Dana S.; Wenger, Trey V.; Cunningham, V.

2015-12-01

The WISE Catalog of Galactic H ii Regions contains ˜2000 H ii region candidates lacking ionized gas spectroscopic observations. All candidates have the characteristic H ii region mid-infrared morphology of WISE 12 μ {{m}} emission surrounding 22 μ {{m}} emission, and additionally have detected radio continuum emission. We here report Green Bank Telescope hydrogen radio recombination line and radio continuum detections in the X-band (9 GHz; 3 cm) of 302 WISE H ii region candidates (out of 324 targets observed) in the zone 225^\\circ ≥slant {\\ell }≥slant -20^\\circ , | {\\text{}}b| ≤slant 6^\\circ . Here we extend the sky coverage of our H ii region Discovery Survey, which now contains nearly 800 H ii regions distributed across the entire northern sky. We provide LSR velocities for the 302 detections and kinematic distances for 131 of these. Of the 302 new detections, 5 have ({\\ell },{\\text{}}b,v) coordinates consistent with the Outer Scutum-Centaurus Arm (OSC), the most distant molecular spiral arm of the Milky Way. Due to the Galactic warp, these nebulae are found at Galactic latitudes >1° in the first Galactic quadrant, and therefore were missed in previous surveys of the Galactic plane. One additional region has a longitude and velocity consistent with the OSC but lies at a negative Galactic latitude (G039.183-01.422 -54.9 {km} {{{s}}}-1). With Heliocentric distances >22 kpc and Galactocentric distances >16 kpc, the OSC H ii regions are the most distant known in the Galaxy. We detect an additional three H ii regions near {\\ell }≃ 150^\\circ whose LSR velocities place them at Galactocentric radii >19 kpc. If their distances are correct, these nebulae may represent the limit to Galactic massive star formation.

AGN jet power, formation of X-ray cavities, and FR I/II dichotomy in galaxy clusters

NASA Astrophysics Data System (ADS)

Fujita, Yutaka; Kawakatu, Nozomu; Shlosman, Isaac

2016-04-01

We investigate the ability of jets in active galactic nuclei to break out of the ambient gas with sufficiently large advance velocities. Using observationally estimated jet power, we analyze 28 bright elliptical galaxies in nearby galaxy clusters. Because the gas density profiles in the innermost regions of galaxies have not been resolved so far, we consider two extreme cases for temperature and density profiles. We also follow two types of evolution for the jet cocoons: being driven by the pressure inside the cocoon [Fanaroff-Riley (FR) type I], and being driven by the jet momentum (FR type II). Our main result is that regardless of the assumed form of the density profiles, jets with observed powers of ≲1044 erg s-1 are not powerful enough to evolve as FR II sources. Instead, they evolve as FR I sources and appear to be decelerated below the buoyant velocities of the cocoons when jets were propagating through the central dense regions of the host galaxies. This explains why FR I sources are more frequent than FR II sources in clusters. Furthermore, we predict the sizes of X-ray cavities from the observed jet powers and compare them with the observed ones-they are consistent within a factor of two if the FR I type evolution is realized. Finally, we find that the jets with a power ≳1044 erg s-1 are less affected by the ambient medium, and some of them, but not all, could serve as precursors of the FR II sources.

Kiloparsec Jet Properties of Hybrid, Low-, and High-Synchrotron-Peaked Blazars

NASA Astrophysics Data System (ADS)

Stanley, Ethan C.

Blazars are a rare class of active galactic nucleus (AGN) with relativistic jets closely aligned with the line of sight. Many aspects of the environments and kiloparsec-scale jet structure are not fully understood. Hybrid and high synchrotron peaked (HSP) blazars are two types of blazar that provide unique opportunities to study these jets. Hybrid blazars appear to have jets of differing morphology on each side of their core, suggesting that external factors shape their jet morphology. Three hybrid sources were investigated in radio, optical, and X-ray wavelengths: 8C 1849+670, PKS 2216-038, and PKS 1045-188. For all three, X-ray emission was detected only from the approaching jet. All three had jet radio flux densities and emission mechanisms similar to higher-power FR II sources, but two had approaching jets similar to lower-power FR I sources. None of the three showed definitive signs of asymmetry in their external environments. These results agree with previous multiwavelength studies of hybrid sources that show a dominance of FR I approaching jets and FR II emission mechanisms. With the addition of these three hybrid sources, 13 have been studied in total. Eleven have FR I approaching jets, and eight of those have FR II emission mechanisms. These trends may be due to small number statistics, or they may indicate other factors are creating hybrid-like appearances. High synchrotron peaked blazars are defined by the frequency of the peak of their jet synchrotron emission. Some have shown extreme variability which would imply incredibly-powerful and well-aligned jets, but VLBA observations have measured only modest jet speeds. A radio survey was performed to measure the extended radio luminosity of a large sample of HSP sources. These sources were compared to the complete radio flux density limited MOJAVE 1.5 Jy sample. Flat spectrum radio quasars (FSRQs) showed significant overlap with low synchrotron peaked (LSP) BL Lacs in multiple parameters, which may suggest

Observing the Next Galactic Supernova

NASA Astrophysics Data System (ADS)

Adams, Scott M.; Kochanek, C. S.; Beacom, John F.; Vagins, Mark R.; Stanek, K. Z.

2013-12-01

No supernova (SN) in the Milky Way has been observed since the invention of the optical telescope, instruments for other wavelengths, neutrino detectors, or gravitational wave observatories. It would be a tragedy to miss the opportunity to fully characterize the next one. To aid preparations for its observations, we model the distance, extinction, and magnitude probability distributions of a successful Galactic core-collapse supernova (ccSN), its shock breakout radiation, and its massive star progenitor. We find, at very high probability (sime 100%), that the next Galactic SN will easily be detectable in the near-IR and that near-IR photometry of the progenitor star very likely (sime 92%) already exists in the Two Micron All Sky Survey. Most ccSNe (98%) will be easily observed in the optical, but a significant fraction (43%) will lack observations of the progenitor due to a combination of survey sensitivity and confusion. If neutrino detection experiments can quickly disseminate a likely position (~3°), we show that a modestly priced IR camera system can probably detect the shock breakout radiation pulse even in daytime (64% for the cheapest design). Neutrino experiments should seriously consider adding such systems, both for their scientific return and as an added and internal layer of protection against false triggers. We find that shock breakouts from failed ccSNe of red supergiants may be more observable than those of successful SNe due to their lower radiation temperatures. We review the process by which neutrinos from a Galactic ccSN would be detected and announced. We provide new information on the EGADS system and its potential for providing instant neutrino alerts. We also discuss the distance, extinction, and magnitude probability distributions for the next Galactic Type Ia supernova (SN Ia). Based on our modeled observability, we find a Galactic ccSN rate of 3.2^{+7.3}_{-2.6} per century and a Galactic SN Ia rate of 1.4^{+1.4}_{-0.8} per century for a

RELATIVISTIC MHD SIMULATIONS OF COLLISION-INDUCED MAGNETIC DISSIPATION IN POYNTING-FLUX-DOMINATED JETS/OUTFLOWS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Wei; Zhang, Bing; Li, Hui

We perform 3D relativistic ideal magnetohydrodynamics (MHD) simulations to study the collisions between high-σ (Poynting-flux-dominated (PFD)) blobs which contain both poloidal and toroidal magnetic field components. This is meant to mimic the interactions inside a highly variable PFD jet. We discover a significant electromagnetic field (EMF) energy dissipation with an Alfvénic rate with the efficiency around 35%. Detailed analyses show that this dissipation is mostly facilitated by the collision-induced magnetic reconnection. Additional resolution and parameter studies show a robust result that the relative EMF energy dissipation efficiency is nearly independent of the numerical resolution or most physical parameters in themore » relevant parameter range. The reconnection outflows in our simulation can potentially form the multi-orientation relativistic mini jets as needed for several analytical models. We also find a linear relationship between the σ values before and after the major EMF energy dissipation process. Our results give support to the proposed astrophysical models that invoke significant magnetic energy dissipation in PFD jets, such as the internal collision-induced magnetic reconnection and turbulence model for gamma-ray bursts, and reconnection triggered mini jets model for active galactic nuclei. The simulation movies are shown in http://www.physics.unlv.edu/∼deng/simulation1.html.« less

Strong-coupling jet energy loss from AdS/CFT

NASA Astrophysics Data System (ADS)

Morad, R.; Horowitz, W. A.

2014-11-01

We propose a novel definition of a holographic light hadron jet and consider the phenomenological consequences, including the very first fully self-consistent, completely strong-coupling calculation of the jet nuclear modification factor R AA, which we find compares surprisingly well with recent preliminary data from LHC. We show that the thermalization distance for light parton jets is an extremely sensitive function of the a priori unspecified string initial conditions and that worldsheets corresponding to non-asymptotic energy jets are not well approximated by a collection of null geodesics. Our new string jet prescription, which is defined by a separation of scales from plasma to jet, leads to the re-emergence of the late-time Bragg peak in the instantaneous jet energy loss rate; unlike heavy quarks, the energy loss rate is unusually sensitive to the very definition of the string theory object itself. A straightforward application of the new jet definition leads to significant jet quenching, even in the absence of plasma. By renormalizing the in-medium suppression by that in the vacuum we find qualitative agreement with preliminary CMS RAAjet >( p T) data in our simple plasma brick model. We close with comments on our results and an outlook on future work.

Radio observations of active galactic nuclei with mm-VLBI

NASA Astrophysics Data System (ADS)

Boccardi, B.; Krichbaum, T. P.; Ros, E.; Zensus, J. A.

2017-11-01

Over the past few decades, our knowledge of jets produced by active galactic nuclei (AGN) has greatly progressed thanks to the development of very-long-baseline interferometry (VLBI). Nevertheless, the crucial mechanisms involved in the formation of the plasma flow, as well as those driving its exceptional radiative output up to TeV energies, remain to be clarified. Most likely, these physical processes take place at short separations from the supermassive black hole, on scales which are inaccessible to VLBI observations at centimeter wavelengths. Due to their high synchrotron opacity, the dense and highly magnetized regions in the vicinity of the central engine can only be penetrated when observing at shorter wavelengths, in the millimeter and sub-millimeter regimes. While this was recognized already in the early days of VLBI, it was not until the very recent years that sensitive VLBI imaging at high frequencies has become possible. Ongoing technical development and wide band observing now provide adequate imaging fidelity to carry out more detailed analyses. In this article, we overview some open questions concerning the physics of AGN jets, and we discuss the impact of mm-VLBI studies. Among the rich set of results produced so far in this frequency regime, we particularly focus on studies performed at 43 GHz (7 mm) and at 86 GHz (3 mm). Some of the first findings at 230 GHz (1 mm) obtained with the Event Horizon Telescope are also presented.

Flavors in the soup: An overview of heavy-flavored jet energy loss at CMS

NASA Astrophysics Data System (ADS)

Jung, Kurt E.

The energy loss of jets in heavy-ion collisions is expected to depend on the flavor of the fragmenting parton. Thus, measurements of jet quenching as a function of flavor place powerful constraints on the thermodynamical and transport properties of the hot and dense medium. Measurements of the nuclear modification factors of the heavy flavor tagged jets from charm and bottom quarks in both PbPb and pPb collisions can quantify such energy loss effects. Specifically, pPb measurements provide crucial insights into the behavior of the cold nuclear matter effect, which is required to fully understand the hot and dense medium effects on jets in PbPb collisions. This dissertation presents the energy modification of b-jets in PbPb at √sNN = 2.76 TeV and pPb collisions at √sNN = 5.02 TeV, along with the first ever measurements of charm jets in pPb collisions at √s NN =5.02 TeV and in pp collisions at √s = 2.76 TeV. Measurements of b-jet and c-jet spectra are compared to pp data at √s = 2.76 TeV and to PYTHIA predictions at both 2.76 and 5.02 TeV. We observe a centrality-dependent suppression for b-jets in PbPb and a result that is consistent with PYTHIA for both charm and bottom jets in pPb collisions.

Limb-brightened jet of 3C 84 revealed by the 43 GHz very-long-baseline-array observation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagai, H.; Hada, K.; Haga, T.

2014-04-10

We present a study of the sub-parsec scale radio structure of the radio galaxy 3C 84/NGC 1275 based on the Very Long Baseline Array data at 43 GHz. We discover a limb brightening in the 'restarted' jet that is associated with the 2005 radio outburst. In the 1990s, the jet structure was ridge brightening rather than limb brightening, despite the observations being done with similar angular resolutions. This indicates that the transverse jet structure has recently changed. This change in the morphology reveals an interesting agreement with the γ-ray flux increase, i.e., the γ-ray flux in the 1990s was atmore » least seven times lower than the current one. One plausible explanation for the limb brightening is that the velocity structure of the jet is in the context of the stratified jet, which is a successful scenario that explains the γ-ray emission in some active galactic nuclei. If this is the case, then the change in apparent transverse structure might be caused by the change in the transverse velocity structure. We argue that the transition from ridge brightening to limb brightening is related to the γ-ray time variability on the timescale of decades. We also discuss the collimation profile of the jet.« less

A Study of the Unstable Modes in High Mach Number Gaseous Jets and Shear Layers

NASA Astrophysics Data System (ADS)

Bassett, Gene Marcel

1993-01-01

Instabilities affecting the propagation of supersonic gaseous jets have been studied using high resolution computer simulations with the Piecewise-Parabolic-Method (PPM). These results are discussed in relation to jets from galactic nuclei. These studies involve a detailed treatment of a single section of a very long jet, approximating the dynamics by using periodic boundary conditions. Shear layer simulations have explored the effects of shear layers on the growth of nonlinear instabilities. Convergence of the numerical approximations has been tested by comparing jet simulations with different grid resolutions. The effects of initial conditions and geometry on the dominant disruptive instabilities have also been explored. Simulations of shear layers with a variety of thicknesses, Mach numbers and densities perturbed by incident sound waves imply that the time for the excited kink modes to grow large in amplitude and disrupt the shear layer is taug = (546 +/- 24) (M/4)^{1.7 } (Apert/0.02) ^{-0.4} delta/c, where M is the jet Mach number, delta is the half-width of the shear layer, and A_ {pert} is the perturbation amplitude. For simulations of periodic jets, the initial velocity perturbations set up zig-zag shock patterns inside the jet. In each case a single zig-zag shock pattern (an odd mode) or a double zig-zag shock pattern (an even mode) grows to dominate the flow. The dominant kink instability responsible for these shock patterns moves approximately at the linear resonance velocity, nu_ {mode} = cextnu_ {relative}/(cjet + c_ {ext}). For high resolution simulations (those with 150 or more computational zones across the jet width), the even mode dominates if the even penetration is higher in amplitude initially than the odd perturbation. For low resolution simulations, the odd mode dominates even for a stronger even mode perturbation. In high resolution simulations the jet boundary rolls up and large amounts of external gas are entrained into the jet. In low

Open star clusters and Galactic structure

NASA Astrophysics Data System (ADS)

Joshi, Yogesh C.

2018-04-01

In order to understand the Galactic structure, we perform a statistical analysis of the distribution of various cluster parameters based on an almost complete sample of Galactic open clusters yet available. The geometrical and physical characteristics of a large number of open clusters given in the MWSC catalogue are used to study the spatial distribution of clusters in the Galaxy and determine the scale height, solar offset, local mass density and distribution of reddening material in the solar neighbourhood. We also explored the mass-radius and mass-age relations in the Galactic open star clusters. We find that the estimated parameters of the Galactic disk are largely influenced by the choice of cluster sample.

Probing stochastic inter-galactic magnetic fields using blazar-induced gamma ray halo morphology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duplessis, Francis; Vachaspati, Tanmay, E-mail: fdupless@asu.edu, E-mail: tvachasp@asu.edu

Inter-galactic magnetic fields can imprint their structure on the morphology of blazar-induced gamma ray halos. We show that the halo morphology arises through the interplay of the source's jet and a two-dimensional surface dictated by the magnetic field. Through extensive numerical simulations, we generate mock halos created by stochastic magnetic fields with and without helicity, and study the dependence of the halo features on the properties of the magnetic field. We propose a sharper version of the Q-statistics and demonstrate its sensitivity to the magnetic field strength, the coherence scale, and the handedness of the helicity. We also identify andmore » explain a new feature of the Q-statistics that can further enhance its power.« less

TENTATIVE EVIDENCE FOR RELATIVISTIC ELECTRONS GENERATED BY THE JET OF THE YOUNG SUN-LIKE STAR DG Tau

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ainsworth, Rachael E.; Ray, Tom P.; Taylor, Andrew M.

2014-09-01

Synchrotron emission has recently been detected in the jet of a massive protostar, providing further evidence that certain jet formation characteristics for young stars are similar to those found for highly relativistic jets from active galactic nuclei. We present data at 325 and 610 MHz taken with the Giant Metrewave Radio Telescope of the young, low-mass star DG Tau, an analog of the Sun soon after its birth. This is the first investigation of a low-mass young stellar object at such low frequencies. We detect emission with a synchrotron spectral index in the proximity of the DG Tau jet and interpretmore » this emission as a prominent bow shock associated with this outflow. This result provides tentative evidence for the acceleration of particles to relativistic energies due to the shock impact of this otherwise very low-power jet against the ambient medium. We calculate the equipartition magnetic field strength B {sub min} ≈ 0.11 mG and particle energy E {sub min} ≈ 4 × 10{sup 40} erg, which are the minimum requirements to account for the synchrotron emission of the DG Tau bow shock. These results suggest the possibility of low energy cosmic rays being generated by young Sun-like stars.« less

Afterglow model for the radio emission from the jetted tidal disruption candidate Swift J1644+57

NASA Astrophysics Data System (ADS)

Metzger, Brian D.; Giannios, Dimitrios; Mimica, Petar

2012-03-01

The recent transient event Swift J1644+57 has been interpreted as emission from a collimated relativistic jet, powered by the sudden onset of accretion on to a supermassive black hole following the tidal disruption of a star. Here we model the radio-microwave emission as synchrotron radiation produced by the shock interaction between the jet and the gaseous circumnuclear medium (CNM). At early times after the onset of the jet (t≲ 5-10 d) a reverse shock propagates through and decelerates the ejecta, while at later times the outflow approaches the Blandford-McKee self-similar evolution (possibly modified by additional late energy injection). The achromatic break in the radio light curve of Swift J1644+57 is naturally explained as the transition between these phases. We show that the temporal indices of the pre- and post-break light curve are consistent with those predicted if the CNM has a wind-type radial density profile n∝r-2. The observed synchrotron frequencies and self-absorbed flux constrain the fraction of the post-shock thermal energy in relativistic electrons ɛe≈ 0.03-0.1, the CNM density at 1018 cm n18≈ 1-10 cm-3 and the initial Lorentz factor Γj≈ 10-20 and opening angle ? of the jet. Radio modelling thus provides robust independent evidence for a narrowly collimated outflow. Extending our model to the future evolution of Swift J1644+57, we predict that the radio flux at low frequencies (ν≲ few GHz) will begin to brighten more rapidly once the characteristic frequency νm crosses below the radio band after it decreases below the self-absorption frequency on a time-scale of months (indeed, such a transition may already have begun). Our results demonstrate that relativistic outflows from tidal disruption events provide a unique probe of the conditions in distant, previously inactive galactic nuclei, complementing studies of normal active galactic nuclei.

Plasma jet takes off.

PubMed Central

Frazer, L

1999-01-01

Thanks to a series of joint research projects by Los Alamos National Laboratory, Beta Squared of Allen, Texas, and the University of California at Los Angeles, there is now a more environmentally sound method for cleaning semiconductor chips that may also be effective in cleaning up chemical, bacterial, and nuclear contaminants. The Atmospheric Pressure Plasma Jet uses a type of ionized gas called plasma to clean up contaminants by binding to them and lifting them away. In contrast to the corrosive acids and chemical solvents traditionally used to clean semiconductor chips, the jet oxidizes contaminants, producing only benign gaseous by-products such as oxygen and carbon dioxide. The new technology is also easy to transport, cleans thoroughly and quickly, and presents no hazards to its operators. PMID:10417375

Galactic cosmic ray composition

NASA Technical Reports Server (NTRS)

Meyer, J. P.

1986-01-01

An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

Enhancement of Feedback Efficiency by Active Galactic Nucleus Outflows via the Magnetic Tension Force in the Inhomogeneous Interstellar Medium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asahina, Yuta; Ohsuga, Ken; Nomura, Mariko, E-mail: asahina@cfca.jp

By performing three-dimensional magnetohydrodynamics simulations of subrelativistic jets and disk winds propagating into the magnetized inhomogeneous interstellar medium (ISM), we investigate the magnetic effects on the active galactic nucleus feedback. Our simulations reveal that the magnetic tension force promotes the acceleration of the dense gas clouds, since the magnetic field lines, which are initially straight, bend around the gas clouds. In the jet models, the velocity dispersion of the clouds increases with an increase in the initial magnetic fields. The increment of the kinetic energy of the clouds is proportional to the initial magnetic fields, implying that the magnetic tensionmore » force increases the energy conversion efficiency from the jet to the gas clouds. Through simulations of the mildly collimated disk wind and the funnel-shaped disk wind, we confirm that such an enhancement of the energy conversion efficiency via the magnetic fields appears even if the energy is injected via the disk winds. The enhancement of the acceleration of the dense part of the magnetized ISM via the magnetic tension force will occur wherever the magnetized inhomogeneous matter is blown away.« less

Multiphase environment of compact galactic nuclei: the role of the nuclear star cluster

NASA Astrophysics Data System (ADS)

Różańska, A.; Kunneriath, D.; Czerny, B.; Adhikari, T. P.; Karas, V.

2017-01-01

We study the conditions for the onset of thermal instability in the innermost regions of compact galactic nuclei, where the properties of the interstellar environment are governed by the interplay of quasi-spherical accretion on to a supermassive black hole (SMBH) and the heating/cooling processes of gas in a dense nuclear star cluster (NSC). Stellar winds are the source of material for radiatively inefficient (quasi-spherical, non-magnetized) inflow/outflow on to the central SMBH, where a stagnation point develops within the Bondi-type accretion. We study the local thermal equilibrium to determine the parameter space that allows cold and hot phases in mutual contact to co-exist. We include the effects of mechanical heating by stellar winds and radiative cooling/heating by the ambient field of the dense star cluster. We consider two examples: the NSC in the Milky Way central region (including the gaseous mini-spiral of Sgr A*), and the ultracompact dwarf galaxy M60-UCD1. We find that the two systems behave in different ways because they are placed in different areas of parameter space in the instability diagram: gas temperature versus dynamical ionization parameter. In the case of Sgr A*, stellar heating prevents the spontaneous formation of cold clouds. The plasma from stellar winds joins the hot X-ray emitting phase and forms an outflow. In M60-UCD1, our model predicts spontaneous formation of cold clouds in the inner part of the galaxy. These cold clouds may survive since the cooling time-scale is shorter than the inflow/outflow time-scale.

A wide and collimated radio jet in 3C84 on the scale of a few hundred gravitational radii

NASA Astrophysics Data System (ADS)

Giovannini, G.; Savolainen, T.; Orienti, M.; Nakamura, M.; Nagai, H.; Kino, M.; Giroletti, M.; Hada, K.; Bruni, G.; Kovalev, Y. Y.; Anderson, J. M.; D'Ammando, F.; Hodgson, J.; Honma, M.; Krichbaum, T. P.; Lee, S.-S.; Lico, R.; Lisakov, M. M.; Lobanov, A. P.; Petrov, L.; Sohn, B. W.; Sokolovsky, K. V.; Voitsik, P. A.; Zensus, J. A.; Tingay, S.

2018-06-01

Understanding the formation of relativistic jets in active galactic nuclei remains an elusive problem1. This is partly because observational tests of jet formation models suffer from the limited angular resolution of ground-based very-long-baseline interferometry that has thus far been able to probe the structure of the jet acceleration and collimation region in only two sources2,3. Here, we report observations of 3C84 (NGC 1275)—the central galaxy of the Perseus cluster—made with an interferometric array including the orbiting radio telescope of the RadioAstron4 mission. The data transversely resolve the edge-brightened jet in 3C84 only 30 μas from the core, which is ten times closer to the central engine than was possible in previous ground-based observations5 and allows us to measure the jet collimation profile from 102 to 104 gravitational radii (rg) from the black hole. The previously found5, almost cylindrical jet profile on scales larger than a few thousand rg is seen to continue at least down to a few hundred rg from the black hole, and we find a broad jet with a transverse radius of ≳250 rg at only 350 rg from the core. This implies that either the bright outer jet layer goes through a very rapid lateral expansion on scales ≲102 rg or it is launched from the accretion disk.

A wide and collimated radio jet in 3C84 on the scale of a few hundred gravitational radii

NASA Astrophysics Data System (ADS)

Giovannini, G.; Savolainen, T.; Orienti, M.; Nakamura, M.; Nagai, H.; Kino, M.; Giroletti, M.; Hada, K.; Bruni, G.; Kovalev, Y. Y.; Anderson, J. M.; D'Ammando, F.; Hodgson, J.; Honma, M.; Krichbaum, T. P.; Lee, S.-S.; Lico, R.; Lisakov, M. M.; Lobanov, A. P.; Petrov, L.; Sohn, B. W.; Sokolovsky, K. V.; Voitsik, P. A.; Zensus, J. A.; Tingay, S.

2018-04-01

Understanding the formation of relativistic jets in active galactic nuclei remains an elusive problem1. This is partly because observational tests of jet formation models suffer from the limited angular resolution of ground-based very-long-baseline interferometry that has thus far been able to probe the structure of the jet acceleration and collimation region in only two sources2,3. Here, we report observations of 3C84 (NGC 1275)—the central galaxy of the Perseus cluster—made with an interferometric array including the orbiting radio telescope of the RadioAstron4 mission. The data transversely resolve the edge-brightened jet in 3C84 only 30 μas from the core, which is ten times closer to the central engine than was possible in previous ground-based observations5 and allows us to measure the jet collimation profile from 102 to 104 gravitational radii (rg) from the black hole. The previously found5, almost cylindrical jet profile on scales larger than a few thousand rg is seen to continue at least down to a few hundred rg from the black hole, and we find a broad jet with a transverse radius of ≳250 rg at only 350 rg from the core. This implies that either the bright outer jet layer goes through a very rapid lateral expansion on scales ≲102 rg or it is launched from the accretion disk.

Anisotropy and corotation of galactic cosmic rays.

PubMed

Amenomori, M; Ayabe, S; Bi, X J; Chen, D; Cui, S W; Danzengluobu; Ding, L K; Ding, X H; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gao, X Y; Geng, Q X; Guo, H W; He, H H; He, M; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Huang, Q; Jia, H Y; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, J Y; Lou, Y-Q; Lu, H; Lu, S L; Meng, X R; Mizutani, K; Mu, J; Munakata, K; Nagai, A; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ouchi, T; Ozawa, S; Ren, J R; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Sasaki, T; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, B; Wang, H; Wang, X; Wang, Y G; Wu, H R; Xue, L; Yamamoto, Y; Yan, C T; Yang, X C; Yasue, S; Ye, Z H; Yu, G C; Yuan, A F; Yuda, T; Zhang, H M; Zhang, J L; Zhang, N J; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhaxisangzhu; Zhou, X X

2006-10-20

The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.

Measurement of jet suppression in central Pb–Pb collisions at s NN = 2.76 TeV

DOE PAGES

Adam, J.

2015-04-22

Here, the transverse momentum (p T) spectrum and nuclear modification factor (R AA) of reconstructed jets in 0–10% and 10–30% central Pb–Pb collisions at √s NN = 2.76 TeV were measured. Jets were reconstructed using the anti-k T jet algorithm with a resolution parameter of R=0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet p T spectra are reported in the pseudorapidity interval of |η jet| < 0.5 for 40 < pT,jet < 120 GeV/c in 0–10% and for 30 < pT,jet < 100 GeV/c in 10–30% collisions. Reconstructed jets were requiredmore » to contain a leading charged particle with p T > 5 GeV/c to suppress jets constructed from the combinatorial background in Pb–Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb–Pb collisions had a negligible effect on the R AA. The nuclear modification factor R AA was found to be 0.28 ± 0.04 in 0–10% and 0.35 ± 0.04 in 10–30% collisions, independent of p T,jet within the uncertainties of the measurement. The observed suppression is in fair agreement with expectations from two model calculations with different approaches to jet quenching.« less

GOT C+: Galactic Plane Survey of the 1.9 THz [CII] Line

NASA Astrophysics Data System (ADS)

Langer, William

2012-01-01

The ionized carbon [CII] 1.9 THz fine structure line is a major gas coolant in the interstellar medium (ISM) and controls the thermal conditions in diffuse gas clouds and Photodissociation Regions (PDRs). The [CII] line is also an important tracer of the atomic gas and atomic to molecular transition in diffuse clouds throughout the Galaxy. I will review some of the results from the recently completed Galactic Observations of Terahertz C+ (GOT C+) survey. This Herschel Open Time Key Project is a sparse, but uniform volume sample survey of [CII] line emission throughout the Galactic disk using the HIFI heterodyne receiver. HIFI observations, with their high spectral resolution, isolate and locate individual clouds in the Galaxy and provide excitation information on the gas. I will present [CII] position-velocity maps that reveal the distribution and motion of the clouds in the inner Galaxy and discuss results on the physical properties of the gas using spectral observations of [CII] and ancillary HI and 12CO, 13CO, and C18O J=1-0 data. The [CII] emission is also a useful tracer of the "Dark H2 Gas", and I will discuss its distribution in a sample of interstellar clouds. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

High Energy Neutrinos Produced in the Accretion Disks by Neutrons from Nuclei Disintegrated in the AGN Jets

NASA Astrophysics Data System (ADS)

Bednarek, W.

2016-12-01

We investigate the consequences of acceleration of nuclei in jets of active galaxies not far from the surface of an accretion disk. The nuclei can be accelerated in the re-connection regions in the jet and/or at the jet boundary, between the relativistic jet and its cocoon. It is shown that the relativistic nuclei can efficiently fragment onto specific nucleons in collisions with the disk radiation. Neutrons, directed toward the accretion disk, take a significant part of energy from the relativistic nuclei. These neutrons develop a cascade in the dense accretion disk. We calculate the neutrino spectra produced in such a hadronic cascade within the accretion disk. We propose that the neutrinos produced in such a scenario, from the whole population of super-massive black holes in active galaxies, can explain the extragalactic neutrino background recently measured by the IceCube neutrino detector, provided that a 5% fraction of galaxies have an active galactic nucleus and a few percent of neutrons reach the accretion disk. We predict that the neutrino signals in the present neutrino detectors, produced in terms of such a model, will not be detectable even from the nearby radio galaxies similar to M87.

Suzaku View of the Swift/BAT Active Galactic Nuclei. V. Torus Structure of Two Luminous Radio-Loud Active Galactic Nuclei (3C 206 and PKS 0707-35)

NASA Technical Reports Server (NTRS)

Tazaki, Fumie; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.; Tombesi, Francesco

2013-01-01

We present the results from broadband X-ray spectral analysis of 3C 206 and PKS 0707-35 with Suzaku and Swift/BAT, two of the most luminous unobscured and obscured radio-loud active galactic nuclei (AGNs) with hard X-ray luminosities of 10(sup 45.5) erg per second and 10(sup 44.9) erg per second (14-195 keV), respectively. Based on the radio core luminosity, we estimate that the X-ray spectrum of 3C 206 contains a significant (60% in the 14-195 keV band) contribution from the jet, while it is negligible in PKS 0707-35.We can successfully model the spectra with the jet component (for 3C 206), the transmitted emission, and two reflection components from the torus and the accretion disk. The reflection strengths from the torus are found to be R(sub torus)(=Omega/2pi) = 0.29 +/- 0.18 and 0.41 +/- 0.18 for 3C 206 and PKS 0707-35, respectively, which are smaller than those in typical Seyfert galaxies. Utilizing the torus model by Ikeda et al., we quantify the relation between the half-opening angle of a torus (theta(sub oa)) and the equivalent width of an iron-K line. The observed equivalent width of 3C 206, less than 71 eV, constrains the column density in the equatorial plane to N(sup eq)(sub H) lesst han 10(sup 23) per square centimeter, or the half-opening angle to theta(sub oa) greater than 80 deg. if N(sup eq)(sub H) = 10(sup 24) per square centimeter is assumed. That of PKS 0707-35, 72 +/- 36 eV, is consistent with N(sup eq)(sub H) 10(sup 23) per square centimeter. Our results suggest that the tori in luminous radio-loud AGNs are only poorly developed. The trend is similar to that seen in radio-quiet AGNs, implying that the torus structure is not different between AGNs with jets and without jets.

Testing Galactic Cosmic Ray Models

NASA Technical Reports Server (NTRS)

Adams, James H., Jr.

2009-01-01

Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The existing models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

Testing Galactic Cosmic Ray Models

NASA Technical Reports Server (NTRS)

Adams, James H., Jr.

2010-01-01

Models of the Galactic Cosmic Ray Environment are used for designing and planning space missions. The exising models will be reviewed. Spectral representations from these models will be compared with measurements of galactic cosmic ray spectra made on balloon flights and satellite flights over a period of more than 50 years.

Plasma Jet Interaction with Thomson Scattering Probe Laser

NASA Astrophysics Data System (ADS)

Byvank, Tom; Banasek, Jacob; Potter, William; Kusse, Bruce

2016-10-01

Thomson scattering systems can diagnose plasma temperatures and velocities. When probing a plasma jet with the Thomson scattering laser, we observe a laser-plasma interaction that inputs energy into the plasma jet. The absorbed energy causes a bubble of low density ( 5*1017 cm-2) in the jet (unperturbed 1018 cm-2). A pulsed power machine (1 MA peak current, 100 ns rise time) with a radial foil (15 μm thick Al) configuration generates the plasma jet. We compare the effects of using 10 J and 1 J laser energies, for which the 10 J laser is a larger perturbation. We discuss how the interaction affects the Thomson scattering temperature and velocity measurements. Work supported by National Nuclear Security Administration (NNSA) Stewardship Sciences Academic Programs under Department of Energy (DOE) Cooperative Agreement DE-NA0001836 and National Science Foundation (NSF) Grant PHY-1102471.

Twin Jet

NASA Technical Reports Server (NTRS)

Henderson, Brenda; Bozak, Rick

2010-01-01

Many subsonic and supersonic vehicles in the current fleet have multiple engines mounted near one another. Some future vehicle concepts may use innovative propulsion systems such as distributed propulsion which will result in multiple jets mounted in close proximity. Engine configurations with multiple jets have the ability to exploit jet-by-jet shielding which may significantly reduce noise. Jet-by-jet shielding is the ability of one jet to shield noise that is emitted by another jet. The sensitivity of jet-by-jet shielding to jet spacing and simulated flight stream Mach number are not well understood. The current experiment investigates the impact of jet spacing, jet operating condition, and flight stream Mach number on the noise radiated from subsonic and supersonic twin jets.

DISCOVERY OF RR LYRAE STARS IN THE NUCLEAR BULGE OF THE MILKY WAY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minniti, Dante; Ramos, Rodrigo Contreras; Zoccali, Manuela

Galactic nuclei, such as that of the Milky Way, are extreme regions with high stellar densities, and in most cases, the hosts of a supermassive black hole. One of the scenarios proposed for the formation of the Galactic nucleus is merging of primordial globular clusters. An implication of this model is that this region should host stars that are characteristically found in old Milky Way globular clusters. RR Lyrae stars are primary distance indicators, well known representatives of old and metal-poor stellar populations, and therefore are regularly found in globular clusters. Here we report the discovery of a dozen RRmore » Lyrae type ab stars in the vicinity of the Galactic center, i.e., in the so-called nuclear stellar bulge of the Milky Way. This discovery provides the first direct observational evidence that the Galactic nuclear stellar bulge contains ancient stars (>10 Gyr old). Based on this we conclude that merging globular clusters likely contributed to the build-up of the high stellar density in the nuclear stellar bulge of the Milky Way.« less

Comparison of ejection events in the jet and accretion disc outflows in 3C 111

NASA Astrophysics Data System (ADS)

Tombesi, F.; Sambruna, R. M.; Marscher, A. P.; Jorstad, S. G.; Reynolds, C. S.; Markowitz, A.

2012-07-01

We present a comparison of the parameters of accretion disc outflows and the jet of the broad-line radio galaxy 3C 111 on subparsec (sub-pc) scales. We make use of published X-ray observations of ultra-fast outflows (UFOs) and new 43-GHz Very Long Baseline Array images to track the jet knot ejection. We find that the superluminal jet coexists with the mildly relativistic outflows on sub-pc scales, possibly indicating a transverse stratification of a global flow. The two are roughly in pressure equilibrium, with the UFOs potentially providing additional support for the initial jet collimation. The UFOs are much more massive than the jet, but their kinetic power is probably about an order of magnitude lower, at least for the observations considered here. However, their momentum flux is equivalent and both of them are powerful enough to exert a concurrent feedback impact on the surrounding environment. A link between these components is naturally predicted in the context of magnetohydrodynamic models for jet/outflow formation. However, given the high radiation throughput of active galactic nuclei, radiation pressure should also be taken into account. From the comparison with the long-term 2-10 keV Rossi X-ray Timing Explorer light curve, we find that the UFOs are preferentially detected during periods of increasing flux. We also find the possibility to place the UFOs within the known X-ray dips-jet ejection cycles, which has been shown to be a strong proof of the disc-jet connection, in analogue with stellar mass black holes. However, given the limited number of observations presently available, these relations are only tentative and additional spectral monitoring is needed to test them conclusively.

Black-hole model of galactic nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norman, C.A.; ter Haar, D.

1973-04-01

It is shown that the observed large infrared emission from some galactic nuclei finds a natural explanation, if one takes plasma turbulence into account in Lynden-Bell and Rees' blackhole model of galactic nuclei. (auth)

Particle content, radio-galaxy morphology, and jet power: all radio-loud AGN are not equal

NASA Astrophysics Data System (ADS)

Croston, J. H.; Ineson, J.; Hardcastle, M. J.

2018-05-01

Ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (AGNs) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. A crucial and long-standing problem is the composition of the radio-lobe plasma that traces AGN jet activity. In this paper, we carry out a systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies to demonstrate conclusively that their internal composition is systematically different. This difference is best explained by the presence of an energetically dominant proton population in the FRI, but not the FRII radio galaxies. We show that, as expected from this systematic difference in particle content, radio morphology also affects the jet-power/radio-luminosity relationship, with FRII radio galaxies having a significantly lower ratio of jet power to radio luminosity than the FRI cluster radio sources used to derive jet-power scaling relations via X-ray cavity measurements. Finally, we also demonstrate conclusively that lobe composition is unconnected to accretion mode (optical excitation class): the internal conditions of low- and high-excitation FRII radio lobes are indistinguishable. We conclude that inferences of population-wide AGN impact require careful assessment of the contribution of different jet subclasses, particularly given the increased diversity of jet evolutionary states expected to be present in deep, low-frequency radio surveys such as the LOFAR Two-Metre Sky Survey.

Galactic politics

NASA Image and Video Library

2015-12-07

Only rarely does an astronomical object have a political association. However, the spiral galaxy NGC 7252 acquired exactly that when it was given an unusual nickname. In December 1953, the US President Dwight D. Eisenhower gave a speech advocating the use of nuclear power for peaceful purposes. This  “Atoms for Peace” speech was significant for the scientific community, as it brought nuclear research into the public domain, and NGC 7252, which has a superficial resemblance to an atomic nucleus surrounded by the loops of electronic orbits, was dubbed the Atoms for Peace galaxy in honour of this. These loops are well visible in a wider field of view image. This nickname is quite ironic, as the galaxy’s past was anything but peaceful. Its peculiar appearance is the result of a collision between two galaxies that took place about a billion years ago, which ripped both galaxies apart. The loop-like outer structures, likely made up of dust and stars flung outwards by the crash, but recalling orbiting electrons in an atom, are partly responsible for the galaxy’s nickname. This NASA/ESA Hubble Space Telescope image shows the inner parts of the galaxy, revealing a pinwheel-shaped disc that is rotating in a direction opposite to the rest of the galaxy. This disc resembles a spiral galaxy like our own galaxy, the Milky Way, but is only about 10 000 light-years across — about a tenth of the size of the Milky Way. It is believed that this whirling structure is a remnant of the galactic collision. It will most likely have vanished in a few billion years’ time, when NGC 7252 will have completed its merging process.

Spatially Resolved Imaging and Spectroscopy of Candidate Dual Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

McGurk, R. C.; Max, C. E.; Medling, A. M.; Shields, G. A.; Comerford, J. M.

2015-09-01

When galaxies merge, both central supermassive black holes are immersed in a dense and chaotic environment. If there is sufficient gas in the nuclear regions, one expects to see close pairs of active galactic nuclei (AGNs), or dual AGNs, in a fraction of galaxy mergers. However, finding them remains a challenge. The presence of double-peaked [O iii] emission lines has been proposed as a technique to select dual AGNs efficiently. We studied a sample of double-peaked narrow [O iii] emitting AGNs from Sloan Digital Sky Survey (SDSS) DR7. By obtaining new and archival high spatial resolution images taken with the Keck II Laser Guide Star Adaptive Optics system and the near-infrared camera NIRC2, we show that 30% of 140 double-peaked [O iii] emission line SDSS AGNs have two spatial components within a 3″ radius. However, spatially resolved spectroscopy or X-ray observations are needed to confirm these galaxy pairs as systems containing two AGNs. We followed up three spatially double candidate dual AGNs with integral field spectroscopy from Keck OSIRIS and 10 candidates with long-slit spectroscopy from the Shane Kast Double Spectrograph at Lick Observatory. We find that the double-peaked emission lines in our sample of 12 candidates are caused by: one dual AGN (SDSS J114642.47+511029.6), one confirmed outflow and four likely outflows, two pairs of star-forming galaxies, one candidate indeterminate due to sky line interference, and three AGNs with spatially coincident double [O iii] peaks, likely due to unresolved complex narrow line kinematics, outflows, binary AGN, or small-scale jets.

A Connection Between Corona and Jet

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-03-01

The structure immediately around a supermassive black hole at the heart of an active galaxy can tell us about how material flows in and out of these monsters but this region is hard to observe! A new study provides us with clues of what might be going on in these active and energetic cores of galaxies.In- and OutflowsIn active galactic nuclei (AGN), matter flows both in and out. As material flows toward the black hole via its surrounding accretion disk, much of this gas and dust can then be expelled from the vicinity via highly collimated jets.Top: The fraction of X-rays that is reflected decreases as jet power increases. Bottom: the distance between the corona and the reflecting part of the disk increases as jet power increases. [Adapted from King et al. 2017]To better understand this symbiosis between accretion and outflows, we examine whats known as the corona the hot, X-ray-emitting gas thats located in the closest regions around the black hole. But because the active centers of galaxies are generally obscured by surrounding gas and dust, its difficult for us to learn about the structure of these inner regions near the black hole.Where are the X-rays of the corona produced: in the inner accretion flow, or at the base of the jet? How far away is this corona from the disk? And how does the coronas behavior relate to that of the jet?Reflected ObservationsTo address some of these questions, a group of scientists led by Ashley King (Einstein Fellow at Stanford University) has analyzed X-ray observations from NuSTAR and XMM-Newton of over 40 AGN. The team examined the reflections of the X-rays off of the accretion disk and used two measurements to learn about the structure around the black hole:the fraction of the coronas X-rays that are reflected by the disk, andthe time lag between the original and reflected X-rays, which reveals the distance from the corona to the reflecting part of the disk.A visualization of the authors model for an AGN. The accretion disk is

Pinpointing the base of the AGN jets through general relativistic X-ray reverberation studies

NASA Astrophysics Data System (ADS)

Emmanoulopoulos, D.

2015-03-01

Many theoretical models of Active Galactic Nuclei (AGN) predict that the X-ray corona, lying above the black hole, constitutes the base of the X-ray jet. Thus, by studying the exact geometry of the close black hole environment, we can pinpoint the launching site of the jet. Detection of negative X-ray reverberation time delays (i.e. soft band X-ray variations lagging behind the corresponding hard band X-ray variations) can yield significant information about the geometrical properties of the AGN, such as the location of the X-ray source, as well as the physical properties of the the black hole, such as its mass and spin. In the frame-work of the lamp-post geometry, I present the first systematic X-ray time-lag modelling results of an ensemble of 12 AGN, using a fully general relativistic (GR) ray tracing approach for the estimation of the systems' response functions. By combing these state-of-the art GR response models with statistically innovative fitting routines, I derive the geometrical layout of the close BH environment for each source, unveiling the position of the AGN jet-base.

Effects of Nuclear Cross Sections at Different Energies on Space Radiation Exposure from Galactic Cosmic Rays

NASA Technical Reports Server (NTRS)

Li, Zi-Wei; Adams, James H., Jr.

2007-01-01

Space radiation from galactic cosmic rays (GCR) is a major hazard to space crews, especially in long duration human space explorations. For this reason, they will be protected by radiation shielding that fragments the GCR heavy ions. Here we investigate how sensitive the crew's radiation exposure is to nuclear fragmentation cross sections at different energies. We find that in deep space cross sections between about 0.2 and 1.2 GeV/u have the strongest effect on dose equivalent behind shielding in solar minimum GCR environments, and cross sections between about 0.6 and 1.7 GeV/u are the most important at solar maximum'. On the other hand, at the location of the International Space Station, cross sections at_higher -energies, between about 0.6 and 1.7 GeV /u at solar minimum and between about 1.7 and 3.4 GeV/u'at,solar maximum, are the most important This is. due-to the average geomagnetic cutoff for the ISS orbit. We also show the effect of uncertainties in the fragmentation cross sections on the elemental energy spectra behind shielding. These results help to focus the studies of fragmentation cross sections on the proper energy range in order to improve our predictions of crew exposures.

Accretion States of the Galactic Micro Quasar GRS 1758-258

NASA Technical Reports Server (NTRS)

Soria, Roberto; Mehdipour, Missagh; Broderick, Jess W.; Hao, JingFang; Hannikainen, Diana C.; Pottschmidt, Katja; Zhang, Shuang-Nan

2011-01-01

We present the results of a radio and X-ray study of the Galactic micro quasar GRS 1758-258, using unpublished archival data and new observations. We focus in particular on the 2000-2002 state transitions, and on its more quiet behaviour in 2008-2009. Our spectral and timing analysis of the XMM-Newton data shows that the source was in the canonical intermediate, soft and hard states in 2000 September 19,2001 March 22 and 2002 September 28, respectively. We estimate the disk size, luminosity and temperature, which are consistent with a black hole mass approx.10 Solar Mass, There is much overlap between the range of total X-ray luminosities (on average approx. 0.02L(sub Edd)) in the hard and soft states, and probably between the corresponding mass accretion rates; in fact, the hard state is often more luminous. The extended radio lobes seen in 1992 and 1997 are still present in 2008-2009. The 5-GHz radio core flux density has shown variability between approx. 0.1-0.5 mJy over the last two decades. This firmly places GRS 1758-258 in the radio-quiet sequence of Galactic black holes, in the radio/X-ray plane. We note that this dichotomy is similar to the dichotomy between the radio/X-ray sequences of Seyfert and radio galaxies. We propose that the different radio efficiency of the two sequences is due to relativistic electron/positron jets in radio-loud black holes, and sub-relativistic, thermally dominated outflows in radio-quiet sources.

Poynting Robertson Battery and the Chiral Magnetic Fields of AGN Jets

NASA Technical Reports Server (NTRS)

Kazanas, Demosthenes

2010-01-01

We propose that the magnetic fields in the accretion disks of active galactic nuclei (AGNs) are generated by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with the AGN photons (the Poynting Robertson battery). This process provides a unique relation between the polarity of the poloidal B field to the angular velocity Omega of the accretion disk (B is parallel to Omega), a relation absent in the more popular dynamo B-field generation. This then leads to a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry comes about by chance being approx.0.06 %. This lends support to the hypothesis that the universe is seeded by B fields that are generated in AGNs via this mechanism and subsequently injected into intergalactic space by the jet outflows.

LAUNCHING AND QUENCHING OF BLACK HOLE RELATIVISTIC JETS AT LOW ACCRETION RATE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pu, Hung-Yi; Chang, Hsiang-Kuang; Hirotani, Kouichi

2012-10-20

Relativistic jets are launched from black hole (BH) X-ray binaries and active galactic nuclei when the disk accretion rate is below a certain limit (i.e., when the ratio of the accretion rate to the Eddingtion accretion rate, m-dot , is below about 0.01) but quenched when above. We propose a new paradigm to explain this observed coupling between the jet and the accretion disk by investigating the extraction of the rotational energy of a BH when it is surrounded by different types of accretion disk. At low accretion rates (e.g., when m-dot {approx}<0.1), the accretion near the event horizon ismore » quasi-spherical. The accreting plasmas fall onto the event horizon in a wide range of latitudes, breaking down the force-free approximation near the horizon. To incorporate the plasma inertia effect, we consider the magnetohydrodynamical (MHD) extraction of the rotational energy from BHs by the accreting MHD fluid, as described by the MHD Penrose process. It is found that the energy extraction operates, and hence a relativistic jet is launched, preferentially when the accretion disk consists of an outer Shakura-Sunyaev disk (SSD) and an inner advection-dominated accretion flow. When the entire accretion disk type changes into an SSD, the jet is quenched because the plasmas bring more rest-mass energy than what is extracted from the hole electromagnetically to stop the extraction. Several other issues related to observed BH disk-jet couplings, such as why the radio luminosity increases with increasing X-ray luminosity until the radio emission drops, are also explained.« less

The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342

NASA Astrophysics Data System (ADS)

Kynoch, Daniel; Landt, Hermine; Ward, Martin J.; Done, Chris; Gardner, Emma; Boisson, Catherine; Arrieta-Lobo, Maialen; Zech, Andreas; Steenbrugge, Katrien; Pereira Santaella, Miguel

2018-03-01

The detection of several radio-loud narrow-line Seyfert 1 (NLS1) galaxies by the Fermi Gamma-Ray Space Telescope hints at the existence of a rare, new class of γ-ray emitting active galactic nuclei with low black hole masses. Like flat spectrum radio quasars (FSRQs), their γ-ray emission is thought to be produced via the external Compton mechanism whereby relativistic jet electrons upscatter a photon field external to the jet, e.g. from the accretion disc, broad line region (BLR), and dusty torus, to higher energies. Here we study the origin of the γ-ray emission in the lowest-redshift candidate among the currently known γ-ray emitting NLS1s, 1H 0323+342, and take a new approach. We observationally constrain the external photon field using quasi-simultaneous near-infrared, optical, and X-ray spectroscopy. Applying a one-zone leptonic jet model, we simulate the range of jet parameters for which this photon field, when Compton scattered to higher energies, can explain the γ-ray emission. We find that the site of the γ-ray emission lies well within the BLR and that the seed photons mainly originate from the accretion disc. The jet power that we determine, 1.0 × 1045 erg s-1, is approximately half the accretion disc luminosity. We show that this object is not simply a low-mass FSRQ, its jet is intrinsically less powerful than predicted by scaling a typical FSRQ jet by black hole mass and accretion rate. That γ-ray-emitting NLS1s appear to host underpowered jets may go some way to explaining why so few have been detected to date.

Exposure to galactic cosmic radiation and solar energetic particles.

PubMed

O'Sullivan, D

2007-01-01

Several investigations of the radiation field at aircraft altitudes have been undertaken during solar cycle 23 which occurred in the period 1993-2003. The radiation field is produced by the passage of galactic cosmic rays and their nuclear reaction products as well as solar energetic particles through the Earth's atmosphere. Galactic cosmic rays reach a maximum intensity when the sun is least active and are at minimum intensity during solar maximum period. During solar maximum an increased number of coronal mass ejections and solar flares produce high energy solar particles which can also penetrate down to aircraft altitudes. It is found that the very complicated field resulting from these processes varies with altitude, latitude and stage of solar cycle. By employing several active and passive detectors, the whole range of radiation types and energies were encompassed. In-flight data was obtained with the co-operation of many airlines and NASA. The EURADOS Aircraft Crew in-flight data base was used for comparison with the predictions of various computer codes. A brief outline of some recent studies of exposure to radiation in Earth orbit will conclude this contribution.

Internal absorption of gamma-rays in relativistic blobs of active galactic nuclei

NASA Astrophysics Data System (ADS)

Sitarek, Julian; Bednarek, Wlodek

2007-06-01

We investigate the production of gamma-rays in the inverse Compton (IC) scattering process by leptons accelerated inside relativistic blobs in jets of active galactic nuclei. Leptons are injected homogeneously inside the spherical blob and initiate IC e ± pair cascade in the synchrotron radiation (produced by the same population of leptons, SSC model), provided that the optical depth for gamma-rays is larger than unity. It is shown that for likely parameters internal absorption of gamma-rays has to be important. We suggest that new type of blazars might be discovered by the future simultaneous X-ray and γ-ray observations, showing peak emissions in the hard X-rays, and in the GeV γ-rays. Moreover, the considered scenario might be also responsible for the orphan X-ray flares recently reported from BL Lac type active galaxies.

Ultra-high-energy cosmic rays from low-luminosity active galactic nuclei

NASA Astrophysics Data System (ADS)

Duţan, Ioana; Caramete, Laurenţiu I.

2015-03-01

We investigate the production of ultra-high-energy cosmic ray (UHECR) in relativistic jets from low-luminosity active galactic nuclei (LLAGN). We start by proposing a model for the UHECR contribution from the black holes (BHs) in LLAGN, which present a jet power Pj ⩽1046 erg s-1. This is in contrast to the opinion that only high-luminosity AGN can accelerate particles to energies ⩾ 50 EeV. We rewrite the equations which describe the synchrotron self-absorbed emission of a non-thermal particle distribution to obtain the observed radio flux density from sources with a flat-spectrum core and its relationship to the jet power. We found that the UHECR flux is dependent on the observed radio flux density, the distance to the AGN, and the BH mass, where the particle acceleration regions can be sustained by the magnetic energy extraction from the BH at the center of the AGN. We use a complete sample of 29 radio sources with a total flux density at 5 GHz greater than 0.5 Jy to make predictions for the maximum particle energy, luminosity, and flux of the UHECRs from nearby AGN. These predictions are then used in a semi-analytical code developed in Mathematica (SAM code) as inputs for the Monte-Carlo simulations to obtain the distribution of the arrival direction at the Earth and the energy spectrum of the UHECRs, taking into account their deflection in the intergalactic magnetic fields. For comparison, we also use the CRPropa code with the same initial conditions as for the SAM code. Importantly, to calculate the energy spectrum we also include the weighting of the UHECR flux per each UHECR source. Next, we compare the energy spectrum of the UHECRs with that obtained by the Pierre Auger Observatory.

The Structure of Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Kriss, Gerard A.

1997-01-01

We are continuing our systematic investigation of the nuclear structure of nearby active galactic nuclei (AGN). Upon completion, our study will characterize hypothetical constructs such as narrow-line clouds, obscuring tori, nuclear gas disks. and central black holes with physical measurements for a complete sample of nearby AGN. The major scientific goals of our program are: (1) the morphology of the NLR; (2) the physical conditions and dynamics of individual clouds in the NLR; (3) the structure and physical conditions of the warm reflecting gas; (4) the structure of the obscuring torus; (5) the population and morphology of nuclear disks/tori in AGN; (6) the physical conditions in nuclear disks; and (7) the masses of central black holes in AGN. We will use the Hubble Space Telescope (HST) to obtain high-resolution images and spatially resolved spectra. Far-UV spectroscopy of emission and absorption in the nuclear regions using HST/FOS and the Hopkins Ultraviolet Telescope (HUT) will help establish physical conditions in the absorbing and emitting gas. By correlating the dynamics and physical conditions of the gas with the morphology revealed through our imaging program, we will be able to examine mechanisms for fueling the central engine and transporting angular momentum. The kinematics of the nuclear gas disks may enable us to measure the mass of the central black hole. Contemporaneous X-ray observations using ASCA will further constrain the ionization structure of any absorbing material. Monitoring of variability in the UV and X-ray absorption will be used to determine the location of the absorbing gas, possibly in the outflowing warm reflecting gas, or the broad-line region, or the atmosphere of the obscuring torus. Supporting ground-based observations in the optical, near-IR, imaging polarimetry, and the radio will complete our picture of the nuclear structures. With a comprehensive survey of these characteristics in a complete sample of nearby AGN, our

Jet angularity measurements for single inclusive jet production

NASA Astrophysics Data System (ADS)

Kang, Zhong-Bo; Lee, Kyle; Ringer, Felix

2018-04-01

We study jet angularity measurements for single-inclusive jet production at the LHC. Jet angularities depend on a continuous parameter a allowing for a smooth interpolation between different traditional jet shape observables. We establish a factorization theorem within Soft Collinear Effective Theory (SCET) where we consistently take into account in- and out-of-jet radiation by making use of semi-inclusive jet functions. For comparison, we elaborate on the differences to jet angularities measured on an exclusive jet sample. All the necessary ingredients for the resummation at next-to-leading logarithmic (NLL) accuracy are presented within the effective field theory framework. We expect semiinclusive jet angularity measurements to be feasible at the LHC and we present theoretical predictions for the relevant kinematic range. In addition, we investigate the potential impact of jet angularities for quark-gluon discrimination.

Interferometric analysis of laboratory photoionized plasmas utilizing supersonic gas jet targets.

NASA Astrophysics Data System (ADS)

Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

2018-06-01

Photoionized plasmas are an important component of active galactic nuclei, x-ray binary systems and other astrophysical objects. Laboratory produced photoionized plasmas have mainly been studied at large scale facilities, due to the need for high intensity broadband x-ray flux. Using supersonic gas jets as targets has allowed university scale pulsed power generators to begin similar research. The two main advantages of this approach with supersonic gas jets include: possibility of a closer location to the x-ray source and no attenuation related to material used for containment and or tamping. Due to these factors, this experimental platform creates a laboratory environment that more closely resembles astrophysical environments. This system was developed at the Nevada Terawatt Facility using the 1 MA pulsed power generator Zebra. Neon, argon, and nitrogen supersonic gas jets are produced approximately 7-8mm from the z-pinch axis. The high intensity broadband x-ray flux produced by the collapse of the z-pinch wire array implosion irradiates the gas jet. Cylindrical wire arrays are made with 4 and 8 gold 10µm thick wire. The z-pinch radiates approximately 12-16kj of x-ray energy, with x-ray photons under 1Kev in energy. The photoionized plasma is measured via x-ray absorption spectroscopy and interferometry. A Mach-Zehnder interferometer is used to the measure neutral density of the jet prior to the zebra shot at a wavelength of 266 nm. A dual channel air-wedge shearing interferometer is used to measure electron density of the ionized gas jet during the shot, at wavelengths of 532nm and 266nm. Using a newly developed interferometric analysis tool, average ionization state maps of the plasma can be calculated. Interferometry for nitrogen and argon show an average ionization state in the range of 3-8. Preliminary x-ray absorption spectroscopy collected show neon absorption lines. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.

Storage Rings in the Sky: Gamma Ray Bursts and Galactic Gravitational Collapse Stored Energy

NASA Astrophysics Data System (ADS)

Greyber, H. D.

2004-05-01

The recent discovery of almost 100% polarization of the prompt gamma ray emission from GRB021206, (1), confirms my 44 year old ``Strong" Magnetic Field" model (SMF) for galactic dynamics. In SMF, Storage Ring particles were accelerated long ago during the original gravitational collapse of the pregalactic/prequasar plasma cloud that is permeated by an almost uniform primordial magnetic field (2,3) The enormous, intense, slender, relativistic, stable, completely coherent Storage Ring stores a very small fraction of the huge galactic gravitational collapse energy in an almost radiationless state, unless disturbed. The concept of an Astrophysical Storage Ring was introduced by me in l961. At first it was to explain galactic structure, but soon it proved useful to explain active galactic nuclei (AGN) and the dynamics of quasar/AGN jets. AGN and galactic morphology, energetics and dynamics vary as the ratio of magnetic energy to rotational energy in the particular object. Gamma ray bursts (GRB) are due simply to a ``rock". i.e. a white dwarf, ordinary star, neutron sstar, asteroid, planet, etc. falling rapidly through the Storage Ring and being almost instantly vaporized into a hot plasma fireball, causing an electromagnetic shower (2) Then the fireball speeds into the huge organized magnetic field surrounding the current ring, thus generating very highly polarized prompt gamma ray emission (as seen in GRB021206) from the synchrotron radiation process. The timing fits the GRB observations nicely. For instance, a ``rock" racing at 1000 kilometers per second across a 20,000 km. path in the beam would produce a twenty second burst. Other times, a target might track across a short chord for a short burst. Space missions have shown that often typical currents in space plasmas are made up of slender filaments. Thus the puzzling less than one millisecond spikes observed in some GRB are simply describing the structure of that particular ring current at that particular time. 1

Inclusive jet production in ultrarelativistic proton-nucleus collisions

NASA Astrophysics Data System (ADS)

Perepelitsa, Dennis V.

High-pT processes in proton- and deuteron-nucleus collisions at TeV energies are the best presently available way to study the partonic structure of the nucleus in a high-density regime. Jet production over a wide range of phase space can significantly constrain the current knowledge of nuclear parton distribution functions (nPDFs), which are substantially less well understood than the corresponding PDFs in protons and which have only recently begun to be treated in a spatially-dependent way. An accurate knowledge of nPDFs is crucial for a definitive control of perturbative processes in a cold nuclear environment, since high-pT probes are used to quantitatively investigate the hot QCD matter created in ultrarelativistic nucleus-nucleus collisions. Furthermore, jets from low Bjorken-x partons can probe the transition from the dilute to saturated nuclear regimes. Jet production is investigated in d+Au collisions at √s = 200 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC), and in p+Pb collisions at √s = 5.02 TeV with the ATLAS detector at the Large Hadron Collider (LHC). The measurements shown here utilize ∫Ldt = 23 nb-1 and 0.2 pb-1 of 200 GeV d+Au and pp data, respectively, recorded in 2007-8 at RHIC and ∫Ldt = 31 nb -1 and 4.1 pb-1 of 5.02 TeV p+Pb and 2.76 TeV pp data, respectively, recorded in 2013 at the LHC. Jets are reconstructed using the sigma=0.3 Gaussian filter and R=0.4, 0.6 anti-kT algorithms. Inclusive, centrality-dependent jet yields within |eta| < 0.35 and 10 GeV < p T < 40 GeV in 200 GeV d+Au and pp collisions are presented. The jet yield in d+Au collisions relative to the geometric expectation is found to be slightly suppressed (≍0.9) in central events and moderately enhanced (≍1.3) in peripheral events, with no modification when averaged over all d+Au events. Separately, inclusive, centrality-dependent jet yields within |y *| < 4.4 and 25 GeV < pT < 800 GeV in 5.02 TeV p+Pb and 2.76 TeV pp collisions are

ARCADE 2 Observations of Galactic Radio Emission

NASA Technical Reports Server (NTRS)

Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Mirel, P.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.;

Active galaxies. A strong magnetic field in the jet base of a supermassive black hole.

PubMed

Martí-Vidal, Ivan; Muller, Sébastien; Vlemmings, Wouter; Horellou, Cathy; Aalto, Susanne

2015-04-17

Active galactic nuclei (AGN) host some of the most energetic phenomena in the universe. AGN are thought to be powered by accretion of matter onto a rotating disk that surrounds a supermassive black hole. Jet streams can be boosted in energy near the event horizon of the black hole and then flow outward along the rotation axis of the disk. The mechanism that forms such a jet and guides it over scales from a few light-days up to millions of light-years remains uncertain, but magnetic fields are thought to play a critical role. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have detected a polarization signal (Faraday rotation) related to the strong magnetic field at the jet base of a distant AGN, PKS 1830-211. The amount of Faraday rotation (rotation measure) is proportional to the integral of the magnetic field strength along the line of sight times the density of electrons. The high rotation measures derived suggest magnetic fields of at least tens of Gauss (and possibly considerably higher) on scales of the order of light-days (0.01 parsec) from the black hole. Copyright © 2015, American Association for the Advancement of Science.

The physics of galactic winds driven by active galactic nuclei

NASA Astrophysics Data System (ADS)

Faucher-Giguère, Claude-André; Quataert, Eliot

2012-09-01

Active galactic nuclei (AGN) drive fast winds in the interstellar medium of their host galaxies. It is commonly assumed that the high ambient densities and intense radiation fields in galactic nuclei imply short cooling times, thus making the outflows momentum conserving. We show that cooling of high-velocity shocked winds in AGN is in fact inefficient in a wide range of circumstances, including conditions relevant to ultraluminous infrared galaxies (ULIRGs), resulting in energy-conserving outflows. We further show that fast energy-conserving outflows can tolerate a large amount of mixing with cooler gas before radiative losses become important. For winds with initial velocity vin ≳ 10 000 km s-1, as observed in ultraviolet and X-ray absorption, the shocked wind develops a two-temperature structure. While most of the thermal pressure support is provided by the protons, the cooling processes operate directly only on the electrons. This significantly slows down inverse Compton cooling, while free-free cooling is negligible. Slower winds with vin ˜ 1000 km s-1, such as may be driven by radiation pressure on dust, can also experience energy-conserving phases but under more restrictive conditions. During the energy-conserving phase, the momentum flux of an outflow is boosted by a factor ˜vin/2vs by work done by the hot post-shock gas, where vs is the velocity of the swept-up material. Energy-conserving outflows driven by fast AGN winds (vin ˜ 0.1c) may therefore explain the momentum fluxes Ṗ≫LAGN/c of galaxy-scale outflows recently measured in luminous quasars and ULIRGs. Shocked wind bubbles expanding normal to galactic discs may also explain the large-scale bipolar structures observed in some systems, including around the Galactic Centre, and can produce significant radio, X-ray and γ-ray emission. The analytic solutions presented here will inform implementations of AGN feedback in numerical simulations, which typically do not include all the important

Deflection of jets induced by jet-cloud and jet-galaxy interactions

NASA Astrophysics Data System (ADS)

Mendoza, S.; Longair, M. S.

2001-06-01

The model first introduced by Raga & Cantó in which astrophysical jets are deflected on passing through an isothermal high-density region is generalized by taking into account gravitational effects on the motion of the jet as it crosses the high-density cloud. The problem is also generalized for relativistic jets in which gravitational effects induced by the cloud are neglected. Two further cases, classical and relativistic, are discussed for the cases in which the jet is deflected on passing through the interstellar gas of a galaxy in which a dark matter halo dominates the gravitational potential. The criteria for the stability of jets due to the formation of internal shocks are also discussed.

Acceleration of petaelectronvolt protons in the Galactic Centre

NASA Astrophysics Data System (ADS)

HESS Collaboration; Abramowski, A.; Aharonian, F.; Benkhali, F. Ait; Akhperjanian, A. G.; Angüner, E. O.; Backes, M.; Balzer, A.; Becherini, Y.; Tjus, J. Becker; Berge, D.; Bernhard, S.; Bernlöhr, K.; Birsin, E.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Carr, J.; Casanova, S.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Cui, Y.; Davids, I. D.; Degrange, B.; Deil, C.; Dewilt, P.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Grudzińska, M.; Hadasch, D.; Häffner, S.; Hahn, J.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kerszberg, D.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lefaucheur, J.; Lefranc, V.; Lemiére, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Lui, R.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Menzler, U.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Morå, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niemiec, J.; Oakes, L.; Odaka, H.; Öttl, S.; Ohm, S.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Arribas, M. Paz; Pekeur, N. W.; Pelletier, G.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reichardt, I.; Reimer, A.; Reimer, O.; Renaud, M.; de Los Reyes, R.; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seyffert, A. S.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Tuffs, R.; Valerius, K.; van der Walt, J.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Żywucka, N.

2016-03-01

Galactic cosmic rays reach energies of at least a few petaelectronvolts (of the order of 1015 electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators (‘PeVatrons’), but all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies. Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 1013 electronvolts) were inferred from recent γ-ray observations. However, none of the currently known accelerators—not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays—has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of γ-rays extending without a cut-off or a spectral break to tens of teraelectronvolts. Here we report deep γ-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outburstsand an outflow from the Galactic Centre. Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 106-107 years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays.

Constraints on Jet Formation Mechanisms with the Most Energetic Giant Outbursts in MS 0735+7421

NASA Astrophysics Data System (ADS)

Li, Shuang-Liang; Cao, Xinwu

2012-07-01

Giant X-ray cavities lie in some active galactic nuclei (AGNs) locating in central galaxies of clusters, which are estimated to have stored 1055-1062 erg of energy. Most of these cavities are thought to be inflated by jets of AGNs on a timescale of >~ 107 years. The jets can be either powered by rotating black holes or the accretion disks surrounding black holes, or both. The observations of giant X-ray cavities can therefore be used to constrain jet formation mechanisms. In this work, we choose the most energetic cavity, MS 0735+7421, with stored energy ~1062 erg, to constrain the jet formation mechanisms and the evolution of the central massive black hole in this source. The bolometric luminosity of the AGN in this cavity is ~10-5 L Edd, however, the mean power of the jet required to inflate the cavity is estimated as ~0.02L Edd, which implies that the source has previously experienced strong outbursts. During outbursts, the jet power and the mass accretion rate should be significantly higher than its present values. We construct an accretion disk model in which the angular momentum and energy carried away by jets are properly included to calculate the spin and mass evolution of the massive black hole. In our calculations, different jet formation mechanisms are employed, and we find that the jets generated with the Blandford-Znajek (BZ) mechanism are unable to produce the giant cavity with ~1062 erg in this source. Only the jets accelerated with a combination of the Blandford-Payne and BZ mechanisms can successfully inflate such a giant cavity if the magnetic pressure is close to equipartition with the total (radiation+gas) pressure of the accretion disk. For a dynamo-generated magnetic field in the disk, such an energetic giant cavity can be inflated by the magnetically driven jets only if the initial black hole spin parameter a 0 >~ 0.95. Our calculations show that the final spin parameter a of the black hole is always ~0.9-0.998 for all the computational

Ultrafast Outflows: Galaxy-scale Active Galactic Nucleus Feedback

NASA Astrophysics Data System (ADS)

Wagner, A. Y.; Umemura, M.; Bicknell, G. V.

2013-01-01

We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.

ULTRAFAST OUTFLOWS: GALAXY-SCALE ACTIVE GALACTIC NUCLEUS FEEDBACK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, A. Y.; Umemura, M.; Bicknell, G. V., E-mail: ayw@ccs.tsukuba.ac.jp

We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves inmore » the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.« less

Blazar spectral variability as explained by a twisted inhomogeneous jet.

PubMed

Raiteri, C M; Villata, M; Acosta-Pulido, J A; Agudo, I; Arkharov, A A; Bachev, R; Baida, G V; Benítez, E; Borman, G A; Boschin, W; Bozhilov, V; Butuzova, M S; Calcidese, P; Carnerero, M I; Carosati, D; Casadio, C; Castro-Segura, N; Chen, W-P; Damljanovic, G; D'Ammando, F; Di Paola, A; Echevarría, J; Efimova, N V; Ehgamberdiev, Sh A; Espinosa, C; Fuentes, A; Giunta, A; Gómez, J L; Grishina, T S; Gurwell, M A; Hiriart, D; Jermak, H; Jordan, B; Jorstad, S G; Joshi, M; Kopatskaya, E N; Kuratov, K; Kurtanidze, O M; Kurtanidze, S O; Lähteenmäki, A; Larionov, V M; Larionova, E G; Larionova, L V; Lázaro, C; Lin, C S; Malmrose, M P; Marscher, A P; Matsumoto, K; McBreen, B; Michel, R; Mihov, B; Minev, M; Mirzaqulov, D O; Mokrushina, A A; Molina, S N; Moody, J W; Morozova, D A; Nazarov, S V; Nikolashvili, M G; Ohlert, J M; Okhmat, D N; Ovcharov, E; Pinna, F; Polakis, T A; Protasio, C; Pursimo, T; Redondo-Lorenzo, F J; Rizzi, N; Rodriguez-Coira, G; Sadakane, K; Sadun, A C; Samal, M R; Savchenko, S S; Semkov, E; Skiff, B A; Slavcheva-Mihova, L; Smith, P S; Steele, I A; Strigachev, A; Tammi, J; Thum, C; Tornikoski, M; Troitskaya, Yu V; Troitsky, I S; Vasilyev, A A; Vince, O

2017-12-21

Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions-such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution-can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016-2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing angle

Blazar spectral variability as explained by a twisted inhomogeneous jet

NASA Astrophysics Data System (ADS)

Raiteri, C. M.; Villata, M.; Acosta-Pulido, J. A.; Agudo, I.; Arkharov, A. A.; Bachev, R.; Baida, G. V.; Benítez, E.; Borman, G. A.; Boschin, W.; Bozhilov, V.; Butuzova, M. S.; Calcidese, P.; Carnerero, M. I.; Carosati, D.; Casadio, C.; Castro-Segura, N.; Chen, W.-P.; Damljanovic, G.; D'Ammando, F.; di Paola, A.; Echevarría, J.; Efimova, N. V.; Ehgamberdiev, Sh. A.; Espinosa, C.; Fuentes, A.; Giunta, A.; Gómez, J. L.; Grishina, T. S.; Gurwell, M. A.; Hiriart, D.; Jermak, H.; Jordan, B.; Jorstad, S. G.; Joshi, M.; Kopatskaya, E. N.; Kuratov, K.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lähteenmäki, A.; Larionov, V. M.; Larionova, E. G.; Larionova, L. V.; Lázaro, C.; Lin, C. S.; Malmrose, M. P.; Marscher, A. P.; Matsumoto, K.; McBreen, B.; Michel, R.; Mihov, B.; Minev, M.; Mirzaqulov, D. O.; Mokrushina, A. A.; Molina, S. N.; Moody, J. W.; Morozova, D. A.; Nazarov, S. V.; Nikolashvili, M. G.; Ohlert, J. M.; Okhmat, D. N.; Ovcharov, E.; Pinna, F.; Polakis, T. A.; Protasio, C.; Pursimo, T.; Redondo-Lorenzo, F. J.; Rizzi, N.; Rodriguez-Coira, G.; Sadakane, K.; Sadun, A. C.; Samal, M. R.; Savchenko, S. S.; Semkov, E.; Skiff, B. A.; Slavcheva-Mihova, L.; Smith, P. S.; Steele, I. A.; Strigachev, A.; Tammi, J.; Thum, C.; Tornikoski, M.; Troitskaya, Yu. V.; Troitsky, I. S.; Vasilyev, A. A.; Vince, O.

2017-12-01

Blazars are active galactic nuclei, which are powerful sources of radiation whose central engine is located in the core of the host galaxy. Blazar emission is dominated by non-thermal radiation from a jet that moves relativistically towards us, and therefore undergoes Doppler beaming. This beaming causes flux enhancement and contraction of the variability timescales, so that most blazars appear as luminous sources characterized by noticeable and fast changes in brightness at all frequencies. The mechanism that produces this unpredictable variability is under debate, but proposed mechanisms include injection, acceleration and cooling of particles, with possible intervention of shock waves or turbulence. Changes in the viewing angle of the observed emitting knots or jet regions have also been suggested as an explanation of flaring events and can also explain specific properties of blazar emission, such as intra-day variability, quasi-periodicity and the delay of radio flux variations relative to optical changes. Such a geometric interpretation, however, is not universally accepted because alternative explanations based on changes in physical conditions—such as the size and speed of the emitting zone, the magnetic field, the number of emitting particles and their energy distribution—can explain snapshots of the spectral behaviour of blazars in many cases. Here we report the results of optical-to-radio-wavelength monitoring of the blazar CTA 102 and show that the observed long-term trends of the flux and spectral variability are best explained by an inhomogeneous, curved jet that undergoes changes in orientation over time. We propose that magnetohydrodynamic instabilities or rotation of the twisted jet cause different jet regions to change their orientation and hence their relative Doppler factors. In particular, the extreme optical outburst of 2016–2017 (brightness increase of six magnitudes) occurred when the corresponding emitting region had a small viewing

Galactic Train Wrecks

NASA Image and Video Library

2011-05-25

This montage combines observations from NASA Spitzer Space Telescope and NASA Galaxy Evolution Explorer GALEX spacecraft showing three examples of colliding galaxies from a new photo atlas of galactic train wrecks.

The Evolving Polarized Jet of Black Hole Candidate Swift J1745-26

NASA Technical Reports Server (NTRS)

Curran, P. A.; Coriat, M.; Miller-Jones, J. C. A.; Armstrong, R. P.; Edwards, P. G.; Sivakoff, G. R.; Woudt, P.; Altamirano, D.; Belloni, T. M.; Corbel, S.;

Observational Signatures of Mass-loading in Jets Launched by Rotating Black Holes

NASA Astrophysics Data System (ADS)

O’ Riordan, Michael; Pe’er, Asaf; McKinney, Jonathan C.

2018-01-01

It is widely believed that relativistic jets in X-ray binaries (XRBs) and active-galactic nuclei are powered by the rotational energy of black holes. This idea is supported by general-relativistic magnetohydrodynamic (GRMHD) simulations of accreting black holes, which demonstrate efficient energy extraction via the Blandford–Znajek mechanism. However, due to uncertainties in the physics of mass loading, and the failure of GRMHD numerical schemes in the highly magnetized funnel region, the matter content of the jet remains poorly constrained. We investigate the observational signatures of mass loading in the funnel by performing general-relativistic radiative transfer calculations on a range of 3D GRMHD simulations of accreting black holes. We find significant observational differences between cases in which the funnel is empty and cases where the funnel is filled with plasma, particularly in the optical and X-ray bands. In the context of Sgr A*, current spectral data constrains the jet filling only if the black hole is rapidly rotating with a ≳ 0.9. In this case, the limits on the infrared flux disfavor a strong contribution from material in the funnel. We comment on the implications of our models for interpreting future Event Horizon Telescope observations. We also scale our models to stellar-mass black holes, and discuss their applicability to the low-luminosity state in XRBs.

Galactic Winds and the Role Played by Massive Stars

NASA Astrophysics Data System (ADS)

Heckman, Timothy M.; Thompson, Todd A.

Galactic winds from star-forming galaxies play at key role in the evolution of galaxies and the intergalactic medium. They transport metals out of galaxies, chemically enriching the intergalactic medium and modifying the chemical evolution of galaxies. They affect the surrounding interstellar and circumgalactic media, thereby influencing the growth of galaxies though gas accretion and star formation. In this contribution we first summarize the physical mechanisms by which the momentum and energy output from a population of massive stars and associated supernovae can drive galactic winds. We use the prototypical example of M 82 to illustrate the multiphase nature of galactic winds. We then describe how the basic properties of galactic winds are derived from the data, and summarize how the properties of galactic winds vary systematically with the properties of the galaxies that launch them. We conclude with a brief discussion of the broad implications of galactic winds.

The galactic contribution to IceCube's astrophysical neutrino flux

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denton, Peter B.; Marfatia, Danny; Weiler, Thomas J., E-mail: peterbd1@gmail.com, E-mail: dmarf8@hawaii.edu, E-mail: tom.weiler@vanderbilt.edu

2017-08-01

High energy neutrinos have been detected by IceCube, but their origin remains a mystery. Determining the sources of this flux is a crucial first step towards multi-messenger studies. In this work we systematically compare two classes of sources with the data: galactic and extragalactic. We assume that the neutrino sources are distributed according to a class of Galactic models. We build a likelihood function on an event by event basis including energy, event topology, absorption, and direction information. We present the probability that each high energy event with deposited energy E {sub dep}>60 TeV in the HESE sample is Galactic,more » extragalactic, or background. For Galactic models considered the Galactic fraction of the astrophysical flux has a best fit value of 1.3% and is <9.5% at 90% CL. A zero Galactic flux is allowed at <1σ.« less

AGN jet-driven stochastic cold accretion in cluster cores

NASA Astrophysics Data System (ADS)

Prasad, Deovrat; Sharma, Prateek; Babul, Arif

2017-10-01

Several arguments suggest that stochastic condensation of cold gas and its accretion on to the central supermassive black hole (SMBH) is essential for active galactic nuclei (AGNs) feedback to work in the most massive galaxies that lie at the centres of galaxy clusters. Our 3-D hydrodynamic AGN jet-ICM (intracluster medium) simulations, looking at the detailed angular momentum distribution of cold gas and its time variability for the first time, show that the angular momentum of the cold gas crossing ≲1 kpc is essentially isotropic. With almost equal mass in clockwise and counterclockwise orientations, we expect a cancellation of the angular momentum on roughly the dynamical time. This means that a compact accretion flow with a short viscous time ought to form, through which enough accretion power can be channeled into jet mechanical energy sufficiently quickly to prevent a cooling flow. The inherent stochasticity, expected in feedback cycles driven by cold gas condensation, gives rise to a large variation in the cold gas mass at the centres of galaxy clusters, for similar cluster and SMBH masses, in agreement with the observations. Such correlations are expected to be much tighter for the smoother hot/Bondi accretion. The weak correlation between cavity power and Bondi power obtained from our simulations also matches observations.

Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

NASA Astrophysics Data System (ADS)

Hsieh, Pei-Ying; Koch, Patrick M.; Ho, Paul T. P.; Kim, Woong-Tae; Tang, Ya-Wen; Wang, Hsiang-Hsu; Yen, Hsi-Wei; Hwang, Chorng-Yuan

2017-09-01

The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2 pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides a unique opportunity to study SMBH accretion at subparsec scales. Our new wide-field CS(J = 2 - 1) map toward the Galactic center (GC) reveals multiple dense molecular streamers that originated from the ambient clouds 20 pc further out, and that are connected to the central 2 pc of the CND. These dense gas streamers appear to carry gas directly toward the nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up corotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei.

Galactic nuclei evolution with spinning black holes: method and implementation

NASA Astrophysics Data System (ADS)

Fiacconi, Davide; Sijacki, Debora; Pringle, J. E.

2018-04-01

Supermassive black holes at the centre of galactic nuclei mostly grow in mass through gas accretion over cosmic time. This process also modifies the angular momentum (or spin) of black holes, both in magnitude and in orientation. Despite being often neglected in galaxy formation simulations, spin plays a crucial role in modulating accretion power, driving jet feedback, and determining recoil velocity of coalescing black hole binaries. We present a new accretion model for the moving-mesh code AREPO that incorporates (i) mass accretion through a thin α-disc, and (ii) spin evolution through the Bardeen-Petterson effect. We use a diverse suite of idealised simulations to explore the physical connection between spin evolution and larger scale environment. We find that black holes with mass ≲ 107 M⊙ experience quick alignment with the accretion disc. This favours prolonged phases of spin-up, and the spin direction evolves according to the gas inflow on timescales as short as ≲ 100 Myr, which might explain the observed jet direction distribution in Seyfert galaxies. Heavier black holes (≳ 108 M⊙) are instead more sensitive to the local gas kinematic. Here we find a wider distribution in spin magnitudes: spin-ups are favoured if gas inflow maintains a preferential direction, and spin-downs occur for nearly isotropic infall, while the spin direction does not change much over short timescales ˜100 Myr. We therefore conclude that supermassive black holes with masses ≳ 5 × 108 M⊙ may be the ideal testbed to determine the main mode of black hole fuelling over cosmic time.

Global dynamics and diffusion in triaxial galactic models

NASA Astrophysics Data System (ADS)

Papaphilippou, Y.

We apply the Frequency Map Analysis method to the 3--dimensional logarithmic galactic potential in order to clarify the dynamical behaviour of triaxial power--law galactic models. All the fine dynamical details are displayed in the complete frequency map, a direct representation of the system's Arnol'd web. The influence of resonant lines and the extent of the chaotic zones are directly associated with the physical space of the system. Some new results related with the diffusion of galactic orbits are also discussed. This approach reveals many unknown dynamical features of triaxial galactic potentials and provides strong indications that chaos should be an innate characteristic of triaxial configurations.

The Planck Catalogue of Galactic Cold Clumps : PGCC

NASA Astrophysics Data System (ADS)

Montier, L.

The Planck satellite has provided an unprecedented view of the submm sky, allowing us to search for the dust emission of Galactic cold sources. Combining Planck-HFI all-sky maps in the high frequency channels with the IRAS map at 100um, we built the Planck catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results. XXVIII), counting 13188 sources distributed over the whole sky, and following mainly the Galactic structures at low and intermediate latitudes. This is the first all-sky catalogue of Galactic cold sources obtained with a single instrument at this resolution and sensitivity, which opens a new window on star-formation processes in our Galaxy.

Galactic-scale Feedback Observed in the 3C 298 Quasar Host Galaxy

NASA Astrophysics Data System (ADS)

Vayner, Andrey; Wright, Shelley A.; Murray, Norman; Armus, Lee; Larkin, James E.; Mieda, Etsuko

2017-12-01

We present high angular resolution multiwavelength data of the 3C 298 radio-loud quasar host galaxy (z = 1.439) taken using the W.M. Keck Observatory OSIRIS integral field spectrograph (IFS) with adaptive optics, the Atacama Large Millimeter/submillimeter Array (ALMA), the Hubble Space Telescope (HST) WFC3, and the Very Large Array (VLA). Extended emission is detected in the rest-frame optical nebular emission lines Hβ, [O III], Hα, [N II], and [S II], as well as in the molecular lines CO (J = 3‑2) and (J = 5‑4). Along the path of the relativistic jets of 3C 298, we detect conical outflows in ionized gas emission with velocities of up to 1700 {km} {{{s}}}-1 and an outflow rate of 450–1500 {M}ȯ {{yr}}-1 extended over 12 kpc. Near the spatial center of the conical outflow, CO (J = 3‑2) emission shows a molecular gas disk with a rotational velocity of ±150 {km} {{{s}}}-1 and total molecular mass ({M}{{{H}}2}) of 6.6+/- 0.36× {10}9 {M}ȯ . On the blueshifted side of the molecular disk, we observe broad extended emission that is due to a molecular outflow with a rate of 2300 {M}ȯ {{yr}}-1 and depletion timescale of 3 Myr. We detect no narrow Hα emission in the outflow regions, suggesting a limit on star formation of 0.3 {M}ȯ {{yr}}-1 {{kpc}}-2. Quasar-driven winds are evacuating the molecular gas reservoir, thereby directly impacting star formation in the host galaxy. The observed mass of the supermassive black hole is {10}9.37{--9.56} {M}ȯ , and we determine a dynamical bulge mass of {M}{bulge}=1{--}1.7× {10}10\\tfrac{R}{1.6 {kpc}} {M}ȯ . The bulge mass of 3C 298 lies 2–2.5 orders of magnitude below the expected value from the local galactic bulge—supermassive black hole mass ({M}{bulge}{--}{M}{BH}) relationship. A second galactic disk observed in nebular emission is offset from the quasar by 9 kpc, suggesting that the system is an intermediate-stage merger. These results show that galactic-scale negative feedback is occurring early in the merger

Proper Motion of the Compact, Nonthermal Radio Source in the Galactic Center, Sagittarius A*

NASA Astrophysics Data System (ADS)

Backer, D. C.; Sramek, R. A.

1999-10-01

Proper motions and radial velocities of luminous infrared stars in the Galactic center have provided strong evidence for a dark mass of 2.5×106 Msolar in the central 0.05 pc of the Galaxy. The leading hypothesis for this mass is a black hole. High angular resolution measurements at radio wavelengths find a compact radio source, Sagittarius (Sgr) A*, that is either the faint glow from a small amount of material accreting onto the hole with low radiative efficiency or a miniature active galactic nucleus (AGN) core-jet system. This paper provides a full report on the first program that has measured the apparent proper motion of Sgr A* with respect to background extragalactic reference frame. Our current result isμl,*=[-6.18+/-0.19] mas yr-1 μb,*=[-0.65+/-0.17] mas yr-1 . The observations were obtained with the NRAO Very Large Array at 4.9 GHz over 16 yr. The proper motion of Sgr A* provides an estimate of its mass based on equipartition of kinetic energy between the hole and the surrounding stars. The measured motion is largest in galactic longitude. This component of the motion is consistent with the secular parallax that results from the rotation of the solar system about the center, which is a global measure of the difference between Oort's constants (A-B), with no additional peculiar motion of Sgr A*. The current uncertainty in Oort's galactic rotation constants limits the use of this component of the proper motion for a mass inference. In latitude, we find a small, and weakly significant, peculiar motion of Sgr A*, -19+/-7 km s-1 after correction for the motion of the solar system with respect to the local standard of rest. We consider sources of peculiar motion of Sgr A* ranging from unstable radio wave propagation through intervening turbulent plasma to the effects of asymmetric masses in the center. These fail to account for a significant peculiar motion. One can appeal to an m=1 dynamical instability that numerical simulations have revealed. However, the

Pitch angle of galactic spiral arms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michikoshi, Shugo; Kokubo, Eiichiro, E-mail: michiko@mail.doshisha.ac.jp, E-mail: kokubo@th.nao.ac.jp

2014-06-01

One of the key parameters that characterizes spiral arms in disk galaxies is a pitch angle that measures the inclination of a spiral arm to the direction of galactic rotation. The pitch angle differs from galaxy to galaxy, which suggests that the rotation law of galactic disks determines it. In order to investigate the relation between the pitch angle of spiral arms and the shear rate of galactic differential rotation, we perform local N-body simulations of pure stellar disks. We find that the pitch angle increases with the epicycle frequency and decreases with the shear rate and obtain the fittingmore » formula. This dependence is explained by the swing amplification mechanism.« less

The distances of the Galactic Novae

NASA Astrophysics Data System (ADS)

Ozdonmez, Aykut; Guver, Tolga; Cabrera-Lavers, Antonio; Ak, Tansel

2016-07-01

Using location of the RC stars on the CMDs obtained from the UKIDSS, VISTA and 2MASS photometry, we have derived the reddening-distance relations towards each Galactic nova for which at least one independent reddening measurement exists. We were able to determine the distances of 72 Galactic novae and set lower limits on the distances of 45 systems. The reddening curves of the systems are presented. These curves can be also used to estimate reddening or the distance of any source, whose location is close to the position of the nova in our sample. The distance measurement method in our study can be easily applicable to any source, especially for ones that concentrated along the Galactic plane.

Nonradial and nonpolytropic astrophysical outflows. X. Relativistic MHD rotating spine jets in Kerr metric

NASA Astrophysics Data System (ADS)

Chantry, L.; Cayatte, V.; Sauty, C.; Vlahakis, N.; Tsinganos, K.

2018-04-01

Context. High-resolution radio imaging of active galactic nuclei (AGN) has revealed that the jets of some sources present superluminal knots and transverse stratification. Recent observational projects, such as ALMA and γ-ray telescopes, such as HESS and HESS2 have provided new observational constraints on the central regions of rotating black holes in AGN, suggesting that there is an inner- or spine-jet surrounded by a disk wind. This relativistic spine-jet is likely to be composed of electron-positron pairs extracting energy from the black hole and will be explored by the future γ-ray telescope CTA. Aims: In this article we present an extension to and generalization of relativistic jets in Kerr metric of the Newtonian meridional self-similar mechanism. We aim at modeling the inner spine-jet of AGN as a relativistic light outflow emerging from a spherical corona surrounding a Kerr black hole and its inner accretion disk. Methods: The model is built by expanding the metric and the forces with colatitude to first order in the magnetic flux function. As a result of the expansion, all colatitudinal variations of the physical quantities are quantified by a unique parameter. Unlike previous models, effects of the light cylinder are not neglected. Results: Solutions with high Lorentz factors are obtained and provide spine-jet models up to the polar axis. As in previous publications, we calculate the magnetic collimation efficiency parameter, which measures the variation of the available energy across the field lines. This collimation efficiency is an integral part of the model, generalizing the classical magnetic rotator efficiency criterion to Kerr metric. We study the variation of the magnetic efficiency and acceleration with the spin of the black hole and show their high sensitivity to this integral. Conclusions: These new solutions model collimated or radial, relativistic or ultra-relativistic outflows in AGN or γ-ray bursts. In particular, we discuss the

Hydrodynamic Stability Analysis of Multi-jet Effects in Swirling Jet Combustors

NASA Astrophysics Data System (ADS)

Emerson, Benjamin; Lieuwen, Tim

2016-11-01

Many practical combustion devices use multiple swirling jets to stabilize flames. However, much of the understanding of swirling jet dynamics has been generated from experimental and computational studies of single reacting, swirling jets. A smaller body of literature has begun to explore the effects of multi-jet systems and the role of jet-jet interactions on the macro-system dynamics. This work uses local temporal and spatio-temporal stability analyses to isolate the hydrodynamic interactions of multiple reacting, swirling jets, characterized by jet diameter, D, and spacing, L. The results first identify the familiar helical modes in the single jet. Comparison to the multi-jet configuration reveals these same familiar modes simultaneously oscillating in each of the jets. Jet-jet interaction is mostly limited to a spatial synchronization of each jet's oscillations at the jet spacing values analyzed here (L/D =3.5). The presence of multiple jets vs a single jet has little influence on the temporal and absolute growth rates. The biggest difference between the single and multi-jet configurations is the presence of nearly degenerate pairs of hydrodynamic modes in the multi-jet case, with one mode dominated by oscillations in the inner jet, and the other in the outer jets. The close similarity between the single and multi-jet hydrodynamics lends insight into experiments from our group.

The Galactic Club or Galactic Cliques? Exploring the limits of interstellar hegemony and the Zoo Hypothesis

NASA Astrophysics Data System (ADS)

Forgan, Duncan H.

2017-10-01

The Zoo solution to Fermi's Paradox proposes that extraterrestrial intelligences (ETIs) have agreed to not contact the Earth. The strength of this solution depends on the ability for ETIs to come to agreement, and establish/police treaties as part of a so-called `Galactic Club'. These activities are principally limited by the causal connectivity of a civilization to its neighbours at its inception, i.e. whether it comes to prominence being aware of other ETIs and any treaties or agreements in place. If even one civilization is not causally connected to the other members of a treaty, then they are free to operate beyond it and contact the Earth if wished, which makes the Zoo solution `soft'. We should therefore consider how likely this scenario is, as this will give us a sense of the Zoo solution's softness, or general validity. We implement a simple toy model of ETIs arising in a Galactic Habitable Zone, and calculate the properties of the groups of culturally connected civilizations established therein. We show that for most choices of civilization parameters, the number of culturally connected groups is >1, meaning that the Galaxy is composed of multiple Galactic Cliques rather than a single Galactic Club. We find in our models for a single Galactic Club to establish interstellar hegemony, the number of civilizations must be relatively large, the mean civilization lifetime must be several millions of years, and the inter-arrival time between civilizations must be a few million years or less.

The Formation of Galactic Bulges

NASA Astrophysics Data System (ADS)

Carollo, C. Marcella; Ferguson, Henry C.; Wyse, Rosemary F. G.

2000-03-01

Part I. Introduction: What are galactic bulges?; Part II. The Epoch of Bulge Formation: Origin of bulges; Deep sub-mm surveys: High-z ULIRGs and the formation of spheroids; Ages and metallicities for stars in the galactic bulge; Integrated stellar populations of bulges: First results; HST-NICMOS observations of galactic bulges: Ages and dust; Inside-out bulge formation and the origin of the Hubble sequence; Part III. The Timescales of Bulge Formation: Constraints on the bulge formation timescale from stellar populations; Bulge building with mergers and winds; Role of winds, starbursts, and activity in bulge formation; Dynamical timescales of bulge formation; Part IV. Physical Processes in Bulge Formation: the role of bars for secular bulge formation; Bars and boxy/peanut-shaped bulges: an observational point of view; Boxy- and peanut-shaped bulges; A new class of bulges; The role of secondary bars in bulge formation; Radial transport of molecular gas to the nuclei of spiral galaxies; Dynamical evolution of bulge shapes; Two-component stellar systems: Phase-space constraints; Central NGC 2146 - a firehose-type bending instability?; Bulge formation: the role of the multi-phase ISM; Global evolution of a self-gravitating multi-phase ISM in the central kpc region of galaxies; Part V. Bulge Phenomenology: Bulge-disk decomposition of spiral galaxies in the near-infrared; The triaxial bulge of NGC 1371; The bulge-disk orthogonal decoupling in galaxies: NGC 4698 and NGC 4672; The kinematics and the origin of the ionized gas in NGC 4036; Optically thin thermal plasma in the galactic bulge; X-ray properties of bulges; The host galaxies of radio-loud AGN; The centers of radio-loud early-type galaxies with HST; Central UV spikes in two galactic spheroids; Conference summary: where do we stand?

First measurement of jet mass in Pb-Pb and p-Pb collisions at the LHC

NASA Astrophysics Data System (ADS)

Acharya, S.; Adamová, D.; Aggarwal, M. M.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, N.; Ahn, S. U.; Aiola, S.; Akindinov, A.; Alam, S. N.; Albuquerque, D. S. D.; Aleksandrov, D.; Alessandro, B.; Alexandre, D.; Alfaro Molina, R.; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Altsybeev, I.; Alves Garcia Prado, C.; An, M.; Andrei, C.; Andrews, H. A.; Andronic, A.; Anguelov, V.; Anson, C.; Antičić, T.; Antinori, F.; Antonioli, P.; Anwar, R.; Aphecetche, L.; Appelshäuser, H.; Arcelli, S.; Arnaldi, R.; Arnold, O. W.; Arsene, I. C.; Arslandok, M.; Audurier, B.; Augustinus, A.; Averbeck, R.; Azmi, M. D.; Badalà, A.; Baek, Y. W.; Bagnasco, S.; Bailhache, R.; Bala, R.; Baldisseri, A.; Ball, M.; Baral, R. C.; Barbano, A. M.; Barbera, R.; Barile, F.; Barioglio, L.; Barnaföldi, G. G.; Barnby, L. S.; Barret, V.; Bartalini, P.; Barth, K.; Bartke, J.; Bartsch, E.; Basile, M.; Bastid, N.; Basu, S.; Bathen, B.; Batigne, G.; Batista Camejo, A.; Batyunya, B.; Batzing, P. C.; Bearden, I. G.; Beck, H.; Bedda, C.; Behera, N. K.; Belikov, I.; Bellini, F.; Bello Martinez, H.; Bellwied, R.; Beltran, L. G. E.; Belyaev, V.; Bencedi, G.; Beole, S.; Bercuci, A.; Berdnikov, Y.; Berenyi, D.; Bertens, R. A.; Berzano, D.; Betev, L.; Bhasin, A.; Bhat, I. R.; Bhati, A. K.; Bhattacharjee, B.; Bhom, J.; Bianchi, L.; Bianchi, N.; Bianchin, C.; Bielčík, J.; Bielčíková, J.; Bilandzic, A.; Biro, G.; Biswas, R.; Biswas, S.; Blair, J. T.; Blau, D.; Blume, C.; Boca, G.; Bock, F.; Bogdanov, A.; Boldizsár, L.; Bombara, M.; Bonomi, G.; Bonora, M.; Book, J.; Borel, H.; Borissov, A.; Borri, M.; Botta, E.; Bourjau, C.; Braun-Munzinger, P.; Bregant, M.; Broker, T. A.; Browning, T. A.; Broz, M.; Brucken, E. J.; Bruna, E.; Bruno, G. E.; Budnikov, D.; Buesching, H.; Bufalino, S.; Buhler, P.; Buitron, S. A. I.; Buncic, P.; Busch, O.; Buthelezi, Z.; Butt, J. B.; Buxton, J. T.; Cabala, J.; Caffarri, D.; Caines, H.; Caliva, A.; Calvo Villar, E.; Camerini, P.; Capon, A. A.; Carena, F.; Carena, W.; Carnesecchi, F.; Castillo Castellanos, J.; Castro, A. J.; Casula, E. A. R.; Ceballos Sanchez, C.; Cerello, P.; Chang, B.; Chapeland, S.; Chartier, M.; Charvet, J. L.; Chattopadhyay, S.; Chattopadhyay, S.; Chauvin, A.; Cherney, M.; Cheshkov, C.; Cheynis, B.; Chibante Barroso, V.; Chinellato, D. D.; Cho, S.; Chochula, P.; Choi, K.; Chojnacki, M.; Choudhury, S.; Christakoglou, P.; Christensen, C. H.; Christiansen, P.; Chujo, T.; Chung, S. U.; Cicalo, C.; Cifarelli, L.; Cindolo, F.; Cleymans, J.; Colamaria, F.; Colella, D.; Collu, A.; Colocci, M.; Concas, M.; Conesa Balbastre, G.; Conesa Del Valle, Z.; Connors, M. E.; Contreras, J. G.; Cormier, T. M.; Corrales Morales, Y.; Cortés Maldonado, I.; Cortese, P.; Cosentino, M. R.; Costa, F.; Costanza, S.; Crkovská, J.; Crochet, P.; Cuautle, E.; Cunqueiro, L.; Dahms, T.; Dainese, A.; Danisch, M. C.; Danu, A.; Das, D.; Das, I.; Das, S.; Dash, A.; Dash, S.; de, S.; de Caro, A.; de Cataldo, G.; de Conti, C.; de Cuveland, J.; de Falco, A.; de Gruttola, D.; De Marco, N.; de Pasquale, S.; de Souza, R. D.; Degenhardt, H. F.; Deisting, A.; Deloff, A.; Deplano, C.; Dhankher, P.; di Bari, D.; di Mauro, A.; di Nezza, P.; di Ruzza, B.; Diaz Corchero, M. A.; Dietel, T.; Dillenseger, P.; Divià, R.; Djuvsland, Ø.; Dobrin, A.; Domenicis Gimenez, D.; Dönigus, B.; Dordic, O.; Drozhzhova, T.; Dubey, A. K.; Dubla, A.; Ducroux, L.; Duggal, A. K.; Dupieux, P.; Ehlers, R. J.; Elia, D.; Endress, E.; Engel, H.; Epple, E.; Erazmus, B.; Erhardt, F.; Espagnon, B.; Esumi, S.; Eulisse, G.; Eum, J.; Evans, D.; Evdokimov, S.; Fabbietti, L.; Faivre, J.; Fantoni, A.; Fasel, M.; Feldkamp, L.; Feliciello, A.; Feofilov, G.; Ferencei, J.; Fernández Téllez, A.; Ferreiro, E. G.; Ferretti, A.; Festanti, A.; Feuillard, V. J. G.; Figiel, J.; Figueredo, M. A. S.; Filchagin, S.; Finogeev, D.; Fionda, F. M.; Fiore, E. M.; Floris, M.; Foertsch, S.; Foka, P.; Fokin, S.; Fragiacomo, E.; Francescon, A.; Francisco, A.; Frankenfeld, U.; Fronze, G. G.; Fuchs, U.; Furget, C.; Furs, A.; Fusco Girard, M.; Gaardhøje, J. J.; Gagliardi, M.; Gago, A. M.; Gajdosova, K.; Gallio, M.; Galvan, C. D.; Ganoti, P.; Gao, C.; Garabatos, C.; Garcia-Solis, E.; Garg, K.; Garg, P.; Gargiulo, C.; Gasik, P.; Gauger, E. F.; Gay Ducati, M. B.; Germain, M.; Ghosh, P.; Ghosh, S. K.; Gianotti, P.; Giubellino, P.; Giubilato, P.; Gladysz-Dziadus, E.; Glässel, P.; Goméz Coral, D. M.; Gomez Ramirez, A.; Gonzalez, A. S.; Gonzalez, V.; González-Zamora, P.; Gorbunov, S.; Görlich, L.; Gotovac, S.; Grabski, V.; Graczykowski, L. K.; Graham, K. L.; Greiner, L.; Grelli, A.; Grigoras, C.; Grigoriev, V.; Grigoryan, A.; Grigoryan, S.; Grion, N.; Gronefeld, J. M.; Grosa, F.; Grosse-Oetringhaus, J. F.; Grosso, R.; Gruber, L.; Grull, F. R.; Guber, F.; Guernane, R.; Guerzoni, B.; Gulbrandsen, K.; Gunji, T.; Gupta, A.; Gupta, R.; Guzman, I. B.; Haake, R.; Hadjidakis, C.; Hamagaki, H.; Hamar, G.; Hamon, J. C.; Harris, J. W.; Harton, A.; Hatzifotiadou, D.; Hayashi, S.; Heckel, S. T.; Hellbär, E.; Helstrup, H.; Herghelegiu, A.; Herrera Corral, G.; Herrmann, F.; Hess, B. A.; Hetland, K. F.; Hillemanns, H.; Hippolyte, B.; Hladky, J.; Hohlweger, B.; Horak, D.; Hornung, S.; Hosokawa, R.; Hristov, P.; Hughes, C.; Humanic, T. J.; Hussain, N.; Hussain, T.; Hutter, D.; Hwang, D. S.; Ilkaev, R.; Inaba, M.; Ippolitov, M.; Irfan, M.; Isakov, V.; Ivanov, M.; Ivanov, V.; Izucheev, V.; Jacak, B.; Jacazio, N.; Jacobs, P. M.; Jadhav, M. B.; Jadlovska, S.; Jadlovsky, J.; Jaelani, S.; Jahnke, C.; Jakubowska, M. J.; Janik, M. A.; Jayarathna, P. H. S. Y.; Jena, C.; Jena, S.; Jercic, M.; Jimenez Bustamante, R. T.; Jones, P. G.; Jusko, A.; Kalinak, P.; Kalweit, A.; Kang, J. H.; Kaplin, V.; Kar, S.; Karasu Uysal, A.; Karavichev, O.; Karavicheva, T.; Karayan, L.; Karpechev, E.; Kebschull, U.; Keidel, R.; Keijdener, D. L. D.; Keil, M.; Ketzer, B.; Khan, P.; Khan, S. A.; Khanzadeev, A.; Kharlov, Y.; Khatun, A.; Khuntia, A.; Kielbowicz, M. M.; Kileng, B.; Kim, D.; Kim, D. W.; Kim, D. J.; Kim, H.; Kim, J. S.; Kim, J.; Kim, M.; Kim, M.; Kim, S.; Kim, T.; Kirsch, S.; Kisel, I.; Kiselev, S.; Kisiel, A.; Kiss, G.; Klay, J. L.; Klein, C.; Klein, J.; Klein-Bösing, C.; Klewin, S.; Kluge, A.; Knichel, M. L.; Knospe, A. G.; Kobdaj, C.; Kofarago, M.; Kollegger, T.; Kolojvari, A.; Kondratiev, V.; Kondratyeva, N.; Kondratyuk, E.; Konevskikh, A.; Kopcik, M.; Kour, M.; Kouzinopoulos, C.; Kovalenko, O.; Kovalenko, V.; Kowalski, M.; Koyithatta Meethaleveedu, G.; Králik, I.; Kravčáková, A.; Krivda, M.; Krizek, F.; Kryshen, E.; Krzewicki, M.; Kubera, A. M.; Kučera, V.; Kuhn, C.; Kuijer, P. G.; Kumar, A.; Kumar, J.; Kumar, L.; Kumar, S.; Kundu, S.; Kurashvili, P.; Kurepin, A.; Kurepin, A. B.; Kuryakin, A.; Kushpil, S.; Kweon, M. J.; Kwon, Y.; La Pointe, S. L.; La Rocca, P.; Lagana Fernandes, C.; Lakomov, I.; Langoy, R.; Lapidus, K.; Lara, C.; Lardeux, A.; Lattuca, A.; Laudi, E.; Lavicka, R.; Lazaridis, L.; Lea, R.; Leardini, L.; Lee, S.; Lehas, F.; Lehner, S.; Lehrbach, J.; Lemmon, R. C.; Lenti, V.; Leogrande, E.; León Monzón, I.; Lévai, P.; Li, S.; Li, X.; Lien, J.; Lietava, R.; Lindal, S.; Lindenstruth, V.; Lippmann, C.; Lisa, M. A.; Litichevskyi, V.; Ljunggren, H. M.; Llope, W. J.; Lodato, D. F.; Loenne, P. I.; Loginov, V.; Loizides, C.; Loncar, P.; Lopez, X.; López Torres, E.; Lowe, A.; Luettig, P.; Lunardon, M.; Luparello, G.; Lupi, M.; Lutz, T. H.; Maevskaya, A.; Mager, M.; Mahajan, S.; Mahmood, S. M.; Maire, A.; Majka, R. D.; Malaev, M.; Maldonado Cervantes, I.; Malinina, L.; Mal'Kevich, D.; Malzacher, P.; Mamonov, A.; Manko, V.; Manso, F.; Manzari, V.; Mao, Y.; Marchisone, M.; Mareš, J.; Margagliotti, G. V.; Margotti, A.; Margutti, J.; Marín, A.; Markert, C.; Marquard, M.; Martin, N. A.; Martinengo, P.; Martinez, J. A. L.; Martínez, M. I.; Martínez García, G.; Martinez Pedreira, M.; Mas, A.; Masciocchi, S.; Masera, M.; Masoni, A.; Mastroserio, A.; Mathis, A. M.; Matyja, A.; Mayer, C.; Mazer, J.; Mazzilli, M.; Mazzoni, M. A.; Meddi, F.; Melikyan, Y.; Menchaca-Rocha, A.; Meninno, E.; Mercado Pérez, J.; Meres, M.; Mhlanga, S.; Miake, Y.; Mieskolainen, M. M.; Mihaylov, D. L.; Mikhaylov, K.; Milano, L.; Milosevic, J.; Mischke, A.; Mishra, A. N.; Miśkowiec, D.; Mitra, J.; Mitu, C. M.; Mohammadi, N.; Mohanty, B.; Mohisin Khan, M.; Montes, E.; Moreira de Godoy, D. A.; Moreno, L. A. P.; Moretto, S.; Morreale, A.; Morsch, A.; Muccifora, V.; Mudnic, E.; Mühlheim, D.; Muhuri, S.; Mukherjee, M.; Mulligan, J. D.; Munhoz, M. G.; Münning, K.; Munzer, R. H.; Murakami, H.; Murray, S.; Musa, L.; Musinsky, J.; Myers, C. J.; Naik, B.; Nair, R.; Nandi, B. K.; Nania, R.; Nappi, E.; Naru, M. U.; Natal da Luz, H.; Nattrass, C.; Navarro, S. R.; Nayak, K.; Nayak, R.; Nayak, T. K.; Nazarenko, S.; Nedosekin, A.; Negrao de Oliveira, R. A.; Nellen, L.; Nesbo, S. V.; Ng, F.; Nicassio, M.; Niculescu, M.; Niedziela, J.; Nielsen, B. S.; Nikolaev, S.; Nikulin, S.; Nikulin, V.; Noferini, F.; Nomokonov, P.; Nooren, G.; Noris, J. C. C.; Norman, J.; Nyanin, A.; Nystrand, J.; Oeschler, H.; Oh, S.; Ohlson, A.; Okubo, T.; Olah, L.; Oleniacz, J.; Oliveira da Silva, A. C.; Oliver, M. H.; Onderwaater, J.; Oppedisano, C.; Orava, R.; Oravec, M.; Ortiz Velasquez, A.; Oskarsson, A.; Otwinowski, J.; Oyama, K.; Pachmayer, Y.; Pacik, V.; Pagano, D.; Pagano, P.; Paić, G.; Palni, P.; Pan, J.; Pandey, A. K.; Panebianco, S.; Papikyan, V.; Pappalardo, G. S.; Pareek, P.; Park, J.; Park, W. J.; Parmar, S.; Passfeld, A.; Pathak, S. P.; Paticchio, V.; Patra, R. N.; Paul, B.; Pei, H.; Peitzmann, T.; Peng, X.; Pereira, L. G.; Pereira da Costa, H.; Peresunko, D.; Perez Lezama, E.; Peskov, V.; Pestov, Y.; Petráček, V.; Petrov, V.; Petrovici, M.; Petta, C.; Pezzi, R. P.; Piano, S.; Pikna, M.; Pillot, P.; Pimentel, L. O. D. L.; Pinazza, O.; Pinsky, L.; Piyarathna, D. B.; Płoskoń, M.; Planinic, M.; Pluta, J.; Pochybova, S.; Podesta-Lerma, P. L. M.; Poghosyan, M. G.; Polichtchouk, B.; Poljak, N.; Poonsawat, W.; Pop, A.; Poppenborg, H.; Porteboeuf-Houssais, S.; Porter, J.; Pospisil, J.; Pozdniakov, V.; Prasad, S. K.; Preghenella, R.; Prino, F.; Pruneau, C. A.; Pshenichnov, I.; Puccio, M.; Puddu, G.; Pujahari, P.; Punin, V.; Putschke, J.; Qvigstad, H.; Rachevski, A.; Raha, S.; Rajput, S.; Rak, J.; Rakotozafindrabe, A.; Ramello, L.; Rami, F.; Rana, D. B.; Raniwala, R.; Raniwala, S.; Räsänen, S. S.; Rascanu, B. T.; Rathee, D.; Ratza, V.; Ravasenga, I.; Read, K. F.; Redlich, K.; Rehman, A.; Reichelt, P.; Reidt, F.; Ren, X.; Renfordt, R.; Reolon, A. R.; Reshetin, A.; Reygers, K.; Riabov, V.; Ricci, R. A.; Richert, T.; Richter, M.; Riedler, P.; Riegler, W.; Riggi, F.; Ristea, C.; Rodríguez Cahuantzi, M.; Røed, K.; Rogochaya, E.; Rohr, D.; Röhrich, D.; Rokita, P. S.; Ronchetti, F.; Ronflette, L.; Rosnet, P.; Rossi, A.; Rotondi, A.; Roukoutakis, F.; Roy, A.; Roy, C.; Roy, P.; Rubio Montero, A. J.; Rueda, O. V.; Rui, R.; Russo, R.; Rustamov, A.; Ryabinkin, E.; Ryabov, Y.; Rybicki, A.; Saarinen, S.; Sadhu, S.; Sadovsky, S.; Šafařík, K.; Saha, S. K.; Sahlmuller, B.; Sahoo, B.; Sahoo, P.; Sahoo, R.; Sahoo, S.; Sahu, P. K.; Saini, J.; Sakai, S.; Saleh, M. A.; Salzwedel, J.; Sambyal, S.; Samsonov, V.; Sandoval, A.; Sarkar, D.; Sarkar, N.; Sarma, P.; Sas, M. H. P.; Scapparone, E.; Scarlassara, F.; Scharenberg, R. P.; Scheid, H. S.; Schiaua, C.; Schicker, R.; Schmidt, C.; Schmidt, H. R.; Schmidt, M. O.; Schmidt, M.; Schuchmann, S.; Schukraft, J.; Schutz, Y.; Schwarz, K.; Schweda, K.; Scioli, G.; Scomparin, E.; Scott, R.; Šefčík, M.; Seger, J. E.; Sekiguchi, Y.; Sekihata, D.; Selyuzhenkov, I.; Senosi, K.; Senyukov, S.; Serradilla, E.; Sett, P.; Sevcenco, A.; Shabanov, A.; Shabetai, A.; Shadura, O.; Shahoyan, R.; Shangaraev, A.; Sharma, A.; Sharma, A.; Sharma, M.; Sharma, M.; Sharma, N.; Sheikh, A. I.; Shigaki, K.; Shou, Q.; Shtejer, K.; Sibiriak, Y.; Siddhanta, S.; Sielewicz, K. M.; Siemiarczuk, T.; Silvermyr, D.; Silvestre, C.; Simatovic, G.; Simonetti, G.; Singaraju, R.; Singh, R.; Singhal, V.; Sinha, T.; Sitar, B.; Sitta, M.; Skaali, T. B.; Slupecki, M.; Smirnov, N.; Snellings, R. J. M.; Snellman, T. W.; Song, J.; Song, M.; Soramel, F.; Sorensen, S.; Sozzi, F.; Spiriti, E.; Sputowska, I.; Srivastava, B. K.; Stachel, J.; Stan, I.; Stankus, P.; Stenlund, E.; Stiller, J. H.; Stocco, D.; Strmen, P.; Suaide, A. A. P.; Sugitate, T.; Suire, C.; Suleymanov, M.; Suljic, M.; Sultanov, R.; Šumbera, M.; Sumowidagdo, S.; Suzuki, K.; Swain, S.; Szabo, A.; Szarka, I.; Szczepankiewicz, A.; Szymanski, M.; Tabassam, U.; Takahashi, J.; Tambave, G. J.; Tanaka, N.; Tarhini, M.; Tariq, M.; Tarzila, M. G.; Tauro, A.; Tejeda Muñoz, G.; Telesca, A.; Terasaki, K.; Terrevoli, C.; Teyssier, B.; Thakur, D.; Thakur, S.; Thomas, D.; Tieulent, R.; Tikhonov, A.; Timmins, A. R.; Toia, A.; Tripathy, S.; Trogolo, S.; Trombetta, G.; Trubnikov, V.; Trzaska, W. H.; Trzeciak, B. A.; Tsuji, T.; Tumkin, A.; Turrisi, R.; Tveter, T. S.; Ullaland, K.; Umaka, E. N.; Uras, A.; Usai, G. L.; Utrobicic, A.; Vala, M.; van der Maarel, J.; van Hoorne, J. W.; van Leeuwen, M.; Vanat, T.; Vande Vyvre, P.; Varga, D.; Vargas, A.; Vargyas, M.; Varma, R.; Vasileiou, M.; Vasiliev, A.; Vauthier, A.; Vázquez Doce, O.; Vechernin, V.; Veen, A. M.; Velure, A.; Vercellin, E.; Vergara Limón, S.; Vernet, R.; Vértesi, R.; Verweij, M.; Vickovic, L.; Vigolo, S.; Viinikainen, J.; Vilakazi, Z.; Villalobos Baillie, O.; Villatoro Tello, A.; Vinogradov, A.; Vinogradov, L.; Virgili, T.; Vislavicius, V.; Vodopyanov, A.; Völkl, M. A.; Voloshin, K.; Voloshin, S. A.; Volpe, G.; von Haller, B.; Vorobyev, I.; Voscek, D.; Vranic, D.; Vrláková, J.; Wagner, B.; Wagner, J.; Wang, H.; Wang, M.; Watanabe, D.; Watanabe, Y.; Weber, M.; Weber, S. G.; Weiser, D. F.; Wessels, J. P.; Westerhoff, U.; Whitehead, A. M.; Wiechula, J.; Wikne, J.; Wilk, G.; Wilkinson, J.; Willems, G. A.; Williams, M. C. S.; Windelband, B.; Witt, W. E.; Yalcin, S.; Yang, P.; Yano, S.; Yin, Z.; Yokoyama, H.; Yoo, I.-K.; Yoon, J. H.; Yurchenko, V.; Zaccolo, V.; Zaman, A.; Zampolli, C.; Zanoli, H. J. C.; Zardoshti, N.; Zarochentsev, A.; Závada, P.; Zaviyalov, N.; Zbroszczyk, H.; Zhalov, M.; Zhang, H.; Zhang, X.; Zhang, Y.; Zhang, C.; Zhang, Z.; Zhao, C.; Zhigareva, N.; Zhou, D.; Zhou, Y.; Zhou, Z.; Zhu, H.; Zhu, J.; Zhu, X.; Zichichi, A.; Zimmermann, A.; Zimmermann, M. B.; Zimmermann, S.; Zinovjev, G.; Zmeskal, J.; Alice Collaboration

2018-01-01

This letter presents the first measurement of jet mass in Pb-Pb and p-Pb collisions at √{sNN } = 2.76 TeV and √{sNN } = 5.02 TeV, respectively. Both the jet energy and the jet mass are expected to be sensitive to jet quenching in the hot Quantum Chromodynamics (QCD) matter created in nuclear collisions at collider energies. Jets are reconstructed from charged particles using the anti-kT jet algorithm and resolution parameter R = 0.4. The jets are measured in the pseudorapidity range |ηjet | < 0.5 and in three intervals of transverse momentum between 60 GeV/c and 120 GeV/c. The measurement of the jet mass in central Pb-Pb collisions is compared to the jet mass as measured in p-Pb reference collisions, to vacuum event generators, and to models including jet quenching. It is observed that the jet mass in central Pb-Pb collisions is consistent within uncertainties with p-Pb reference measurements. Furthermore, the measured jet mass in Pb-Pb collisions is not reproduced by the quenching models considered in this letter and is found to be consistent with PYTHIA expectations within systematic uncertainties.

TANAMI: Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry. II. Additional sources

NASA Astrophysics Data System (ADS)

Müller, C.; Kadler, M.; Ojha, R.; Schulz, R.; Trüstedt, J.; Edwards, P. G.; Ros, E.; Carpenter, B.; Angioni, R.; Blanchard, J.; Böck, M.; Burd, P. R.; Dörr, M.; Dutka, M. S.; Eberl, T.; Gulyaev, S.; Hase, H.; Horiuchi, S.; Katz, U.; Krauß, F.; Lovell, J. E. J.; Natusch, T.; Nesci, R.; Phillips, C.; Plötz, C.; Pursimo, T.; Quick, J. F. H.; Stevens, J.; Thompson, D. J.; Tingay, S. J.; Tzioumis, A. K.; Weston, S.; Wilms, J.; Zensus, J. A.

2018-02-01

Context. TANAMI is a multiwavelength program monitoring active galactic nuclei (AGN) south of - 30° declination including high-resolution very long baseline interferometry (VLBI) imaging, radio, optical/UV, X-ray, and γ-ray studies. We have previously published first-epoch8.4 GHz VLBI images of the parsec-scale structure of the initial sample. In this paper, we present images of 39 additional sources. The full sample comprises most of the radio- and γ-ray brightest AGN in the southern quarter of the sky, overlapping with the region from which high-energy (> 100 TeV) neutrino events have been found. Aims: We characterize the parsec-scale radio properties of the jets and compare them with the quasi-simultaneous Fermi/LAT γ-ray data. Furthermore, we study the jet properties of sources which are in positional coincidence with high-energy neutrino events compared to the full sample. We test the positional agreement of high-energy neutrino events with various AGN samples. Methods: TANAMI VLBI observations at 8.4 GHz are made with southern hemisphere radio telescopes located in Australia, Antarctica, Chile, New Zealand, and South Africa. Results: Our observations yield the first images of many jets below - 30° declination at milliarcsecond resolution. We find that γ-ray loud TANAMI sources tend to be more compact on parsec-scales and have higher core brightness temperatures than γ-ray faint jets, indicating higher Doppler factors. No significant structural difference is found between sources in positional coincidence with high-energy neutrino events and other TANAMI jets. The 22 γ-ray brightest AGN in the TANAMI sky show only a weak positional agreement with high-energy neutrinos demonstrating that the > 100 TeV IceCube signal is not simply dominated by a small number of the γ-ray brightest blazars. Instead, a larger number of sources have to contribute to the signal with each individual source having only a small Poisson probability for producing an event in

NUCLEAR FLASH TYPE STEAM GENERATOR

DOEpatents

Johns, F.L.; Gronemeyer, E.C.; Dusbabek, M.R.

1962-09-01

A nuclear steam generating apparatus is designed so that steam may be generated from water heated directly by the nuclear heat source. The apparatus comprises a pair of pressure vessels mounted one within the other, the inner vessel containing a nuclear reactor heat source in the lower portion thereof to which water is pumped. A series of small ports are disposed in the upper portion of the inner vessel for jetting heated water under pressure outwardly into the atmosphere within the interior of the outer vessel, at which time part of the jetted water flashes into steam. The invention eliminates the necessity of any intermediate heat transfer medium and components ordinarily required for handling that medium. (AEC)

Galactic Sources Detected in the NuSTAR Serendipitous Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomsick, John A.; Clavel, Maïca; Chiu, Jeng-Lun

The Nuclear Spectroscopic Telescope Array (NuSTAR) provides an improvement in sensitivity at energies above 10 keV by two orders of magnitude over non-focusing satellites, making it possible to probe deeper into the Galaxy and universe. Lansbury and collaborators recently completed a catalog of 497 sources serendipitously detected in the 3–24 keV band using 13 deg{sup 2} of NuSTAR coverage. Here, we report on an optical and X-ray study of 16 Galactic sources in the catalog. We identify 8 of them as stars (but some or all could have binary companions), and use information from Gaia to report distances and X-ray luminositiesmore » for 3 of them. There are 4 CVs or CV candidates, and we argue that NuSTAR J233426–2343.9 is a relatively strong CV candidate based partly on an X-ray spectrum from XMM-Newton . NuSTAR J092418–3142.2, which is the brightest serendipitous source in the Lansbury catalog, and NuSTAR J073959–3147.8 are low-mass X-ray binary candidates, but it is also possible that these 2 sources are CVs. One of the sources is a known high-mass X-ray binary (HMXB), and NuSTAR J105008–5958.8 is a new HMXB candidate that has strong Balmer emission lines in its optical spectrum and a hard X-ray spectrum. We discuss the implications of finding these HMXBs for the surface density (log N –log S ) and luminosity function of Galactic HMXBs. We conclude that with the large fraction of unclassified sources in the Galactic plane detected by NuSTAR in the 8–24 keV band, there could be a significant population of low-luminosity HMXBs.« less

Vector-boson-tagged jet production in heavy ion collisions at energies available at the CERN Large Hadron Collider [Vector boson-tagged jet production in heavy ion collisions at the LHC

DOE PAGES

Kang, Zhong -Bo; Vitev, Ivan Mateev; Xing, Hongxi

2017-07-25

Here, vector-boson-tagged jet production in collisions of heavy nuclei opens new opportunities to study parton shower formation and propagation in strongly interacting matter. It has been argued to provide a golden channel that can constrain the energy loss of jets in the quark-gluon plasma created in heavy ion reactions. We present theoretical results for isolated-photon-tagged and Z 0-boson-tagged jet production in Pb + Pb collisions with √s NN = 5.02TeV at the LHC. Specifically, we evaluate the transverse momentum imbalance x JV distribution and nuclear modification factor I AA of tagged jets and compare our theoretical calculations to recent experimentalmore » measurements by ATLAS and CMS collaborations. Our analysis, which includes both collisional and radiative energy losses, sheds light on their relative importance versus the strength of jet-medium interactions and helps quantify the amount of out-of-cone radiation of predominantly prompt quark-initiated jets.« less

Propagation of nuclear data uncertainties for fusion power measurements

NASA Astrophysics Data System (ADS)

Sjöstrand, Henrik; Conroy, Sean; Helgesson, Petter; Hernandez, Solis Augusto; Koning, Arjan; Pomp, Stephan; Rochman, Dimitri

2017-09-01

Neutron measurements using neutron activation systems are an essential part of the diagnostic system at large fusion machines such as JET and ITER. Nuclear data is used to infer the neutron yield. Consequently, high-quality nuclear data is essential for the proper determination of the neutron yield and fusion power. However, uncertainties due to nuclear data are not fully taken into account in uncertainty analysis for neutron yield calibrations using activation foils. This paper investigates the neutron yield uncertainty due to nuclear data using the so-called Total Monte Carlo Method. The work is performed using a detailed MCNP model of the JET fusion machine; the uncertainties due to the cross-sections and angular distributions in JET structural materials, as well as the activation cross-sections in the activation foils, are analysed. It is found that a significant contribution to the neutron yield uncertainty can come from uncertainties in the nuclear data.

Fuzzy jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mackey, Lester; Nachman, Benjamin; Schwartzman, Ariel

Collimated streams of particles produced in high energy physics experiments are organized using clustering algorithms to form jets . To construct jets, the experimental collaborations based at the Large Hadron Collider (LHC) primarily use agglomerative hierarchical clustering schemes known as sequential recombination. We propose a new class of algorithms for clustering jets that use infrared and collinear safe mixture models. These new algorithms, known as fuzzy jets , are clustered using maximum likelihood techniques and can dynamically determine various properties of jets like their size. We show that the fuzzy jet size adds additional information to conventional jet tagging variablesmore » in boosted topologies. Furthermore, we study the impact of pileup and show that with some slight modifications to the algorithm, fuzzy jets can be stable up to high pileup interaction multiplicities.« less

Fuzzy jets

DOE PAGES

Mackey, Lester; Nachman, Benjamin; Schwartzman, Ariel; ...

2016-06-01

Collimated streams of particles produced in high energy physics experiments are organized using clustering algorithms to form jets . To construct jets, the experimental collaborations based at the Large Hadron Collider (LHC) primarily use agglomerative hierarchical clustering schemes known as sequential recombination. We propose a new class of algorithms for clustering jets that use infrared and collinear safe mixture models. These new algorithms, known as fuzzy jets , are clustered using maximum likelihood techniques and can dynamically determine various properties of jets like their size. We show that the fuzzy jet size adds additional information to conventional jet tagging variablesmore » in boosted topologies. Furthermore, we study the impact of pileup and show that with some slight modifications to the algorithm, fuzzy jets can be stable up to high pileup interaction multiplicities.« less

Galactic Haze seen by Planck and Galactic Bubbles seen by Fermi

NASA Image and Video Library

2012-02-13

This all-sky image shows the distribution of the galactic haze seen by ESA Planck mission at microwave frequencies superimposed over the high-energy sky, as seen by NASA Fermi Gamma-ray Space Telescope.

Galactic bulge population II Cepheids in the VVV survey: period-luminosity relations and a distance to the Galactic centre

NASA Astrophysics Data System (ADS)

Bhardwaj, A.; Rejkuba, M.; Minniti, D.; Surot, F.; Valenti, E.; Zoccali, M.; Gonzalez, O. A.; Romaniello, M.; Kanbur, S. M.; Singh, H. P.

2017-09-01

Context. Multiple stellar populations of different ages and metallicities reside in the Galactic bulge that trace its structure and provide clues to its formation and evolution. Aims: We present the near-infrared observations of population II Cepheids in the Galactic bulge from VISTA Variables in the Vía Láctea (VVV) survey. The JHKs photometry together with optical data from Optical Gravitational Lensing Experiment (OGLE) survey provide an independent estimate of the distance to the Galactic centre. The old, metal-poor and low-mass population II Cepheids are also investigated as useful tracers for the structure of the Galactic bulge. Methods: We identify 340 population II Cepheids in the VVV survey Galactic bulge catalogue based on their match with the OGLE-III Catalogue. The single-epoch JH and multi-epoch Ks observations complement the accurate periods and optical (VI) mean-magnitudes from OGLE. The sample consisting of BL Herculis and W Virginis subtypes is used to derive period-luminosity relations after correcting mean-magnitudes for the extinction. Our Ks-band period-luminosity relation, Ks = -2.189(0.056) [log (P)-1] + 11.187(0.032), is consistent with published work for BL Herculis and W Virginis variables in the Large Magellanic Cloud. Results: We present a combined OGLE-III and VVV catalogue with periods, classification, mean magnitudes, and extinction for 264 Galactic bulge population II Cepheids that have good-quality Ks-band light curves. The absolute magnitudes for population II Cepheids and RR Lyraes calibrated using Gaia and Hubble Space Telescope parallaxes, together with calibrated magnitudes for Large Magellanic Cloud population II Cepheids, are used to obtain a distance to the Galactic centre, R0 = 8.34 ± 0.03(stat.) ± 0.41(syst.), which changes by with different extinction laws. While noting the limitation of small number statistics, we find that the present sample of population II Cepheids in the Galactic bulge shows a nearly spheroidal

Energy distribution of relativistic electrons in the kiloparsec scale jet of M 87 with Chandra

NASA Astrophysics Data System (ADS)

Sun, Xiao-Na; Yang, Rui-Zhi; Rieger, Frank M.; Liu, Ruo-Yu; Aharonian, Felix

2018-05-01

The X-ray emission from the jets in active galactic nuclei (AGN) carries important information on the distributions of relativistic electrons and magnetic fields on large scales. We reanalysed archival Chandra observations on the jet of M 87 from 2000 to 2016 with a total exposure of 1460 kiloseconds to explore the X-ray emission characteristics along the jet. We investigated the variability behaviours of the nucleus and the inner jet component HST-1, and confirm indications for day-scale X-ray variability in the nucleus contemporaneous to the 2010 high TeV γ-ray state. HST-1 shows a general decline in X-ray flux over the last few years consistent with its synchrotron interpretation. We extracted the X-ray spectra for the nucleus and all knots in the jet, showing that they are compatible with a single power law within the X-ray band. There are indications that the resultant X-ray photon index exhibit a trend, with slight but significant index variations ranging from ≃ 2.2 (e.g. in knot D) to ≃ 2.4-2.6 (in the outer knots F, A, and B). When viewed in a multiwavelength context, a more complex situation can be seen. Fitting the radio to X-ray spectral energy distributions (SEDs) assuming a synchrotron origin, we show that a broken power-law electron spectrum with break energy Eb around 1 (300 μG/B)1/2 TeV allows a satisfactory description of the multiband SEDs for most of the knots. However, in the case of knots B, C, and D we find indications that an additional high-energy component is needed to adequately reproduce the broad-band SEDs. We discuss the implications and suggest that a stratified jet model may account for the differences.

NuSTAR results from the Galactic Center - diffuse emission

NASA Astrophysics Data System (ADS)

Hailey, Charles

2016-03-01

The Nuclear Spectroscopic Telescope Array (NuSTAR) was launched in June 2012. It carried the first true, hard X-ray (>~10 keV-79 keV) focusing telescopes into orbit. Its twin telescopes provide 10 times better angular resolution and 100 times better sensitivity than previously obtainable in the hard X-ray band. Consequently NuSTAR is able to resolve faint diffuse structures whose hard X-rays offer insight into some of the most energetic processes in the Galactic Center. One of the surprising discoveries that NuSTAR made in the Galactic Center is the central hard X-ray emission (CHXE). The CHXE is a diffuse emission detected from ~10 keV to beyond 50 keV in X-ray energy, and extending spatially over a region ~8 parsecs x ~4 parsecs in and out of the plane of the galaxy respectively, and centered on the supermassive black hole Sgr A*. The CHXE was speculated to be due to a large population of unresolved black hole X-ray binaries, millisecond pulsars (MSP), a class of highly magnetized white dwarf binaries called intermediate polars, or to particle outflows from Sgr A*. The presence of an unexpectedly large population of MSP in the Galactic Center would be particularly interesting, since MSP emitting at higher energies and over a much larger region have been posited to be the origin of the gamma-ray emission that is also ascribed to dark matter annihilation in the galaxy. In addition, the connection of the CHXE to the ~9000 unidentified X-ray sources in the central the the ~100 pc detected by the Chandra Observatory, to the soft X-ray emission detected by the Chandra and XMM/Newton observatories in the Galactic Center, and to the hard X-ray emission detected by both the RXTE and INTEGRAL observatories in the Galactic Ridge, is unclear. I review these results and present recent NuSTAR observations that potentially resolve the origin of the CHXE and point to a unified origin for all these X-ray emissions. Two other noteworthy classes of diffuse structures in the

Laser interferometry of radiation driven gas jets

NASA Astrophysics Data System (ADS)

Swanson, Kyle James; Ivanov, Vladimir; Mancini, Roberto; Mayes, Daniel C.

2017-06-01

In a series of experiments performed at the 1MA Zebra pulsed power accelerator of the Nevada Terawatt Facility nitrogen gas jets were driven with the broadband x-ray flux produced during the collapse of a wire-array z-pinch implosion. The wire arrays were comprised of 4 and 8, 10μm-thick gold wires and 17μm-thick nickel wires, 2cm and 3cm tall, and 0.3cm in diameter. They radiated 12kJ to 16kJ of x-ray energy, most of it in soft x-ray photons of less than 1keV of energy, in a time interval of 30ns. This x-ray flux was used to drive a nitrogen gas jet located at 0.8cm from the axis of the z-pinch radiation source and produced with a supersonic nozzle. The x-ray flux ionizes the nitrogen gas thus turning it into a photoionized plasma. We used laser interferometry to probe the ionization of the plasma. To this end, a Mach-Zehnder interferometer at the wavelength of 266 nm was set up to extract the atom number density profile of the gas jet just before the Zebra shot, and air-wedge interferometers at 266 and 532 nm were used to determine the electron number density of the plasma right during the Zebra shot. The ratio of electron to atom number densities gives the distribution of average ionization state of the plasma. A python code was developed to perform the image data processing, extract phase shift spatial maps, and obtain the atom and electron number densities via Abel inversion. Preliminary results from the experiment are promising and do show that a plasma has been created in the gas jet driven by the x-ray flux, thus demonstrating the feasibility of a new experimental platform to study photoionized plasmas in the laboratory. These plasmas are found in astrophysical scenarios including x-ray binaries, active galactic nuclei, and the accretion disks surrounding black holes1. This work was sponsored in part by DOE Office of Science Grant DE-SC0014451.1R. C. Mancini et al, Phys. Plasmas 16, 041001 (2009)

STABILITY OF GAS CLOUDS IN GALACTIC NUCLEI: AN EXTENDED VIRIAL THEOREM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xian; Cuadra, Jorge; Amaro-Seoane, Pau, E-mail: xchen@astro.puc.cl, E-mail: jcuadra@astro.puc.cl, E-mail: Pau.Amaro-Seoane@aei.mpg.de

2016-03-10

Cold gas entering the central 1–10{sup 2} pc of a galaxy fragments and condenses into clouds. The stability of the clouds determines whether they will be turned into stars or can be delivered to the central supermassive black hole (SMBH) to turn on an active galactic nucleus (AGN). The conventional criteria to assess the stability of these clouds, such as the Jeans criterion and Roche (or tidal) limit, are insufficient here, because they assume the dominance of self-gravity in binding a cloud, and neglect external agents, such as pressure and tidal forces, which are common in galactic nuclei. We formulatemore » a new scheme for judging this stability. We first revisit the conventional Virial theorem, taking into account an external pressure, to identify the correct range of masses that lead to stable clouds. We then extend the theorem to further include an external tidal field, which is equally crucial for the stability in the region of our interest—in dense star clusters, around SMBHs. We apply our extended Virial theorem to find new solutions to controversial problems, namely, the stability of the gas clumps in AGN tori, the circum-nuclear disk in the Galactic Center, and the central molecular zone of the Milky Way. The masses we derive for these structures are orders of magnitude smaller than the commonly used Virial masses (equivalent to the Jeans mass). Moreover, we prove that these clumps are stable, contrary to what one would naively deduce from the Roche (tidal) limit.« less

Star formation around active galactic nuclei

NASA Technical Reports Server (NTRS)

Keel, William C.

1987-01-01

Active galactic nuclei (Seyfert nuclei and their relatives) and intense star formation can both deliver substantial amounts of energy to the vicinity of a galactic nucleus. Many luminous nuclei have energetics dominated by one of these mechanisms, but detailed observations show that some have a mixture. Seeing both phenomena at once raises several interesting questions: (1) Is this a general property of some kinds of nuclei? How many AGNs have surround starbursts, and vice versa? (2) As in 1, how many undiscovered AGNs or starbursts are hidden by a more luminous instance of the other? (3) Does one cause the other, and by what means, or do both reflect common influences such as potential well shape or level of gas flow? (4) Can surrounding star formation tell us anything about the central active nuclei, such as lifetimes, kinetic energy output, or mechanical disturbance of the ISM? These are important points in the understanding of activity and star formation in galactic nuclei. Unfortunately, the observational ways of addressing them are as yet not well formulated. Some preliminary studies are reported, aimed at clarifying the issues involved in study of the relationships between stellar and nonstellar excitement in galactic nuclei.

Induced starburst and nuclear activity: Faith, facts, and theory

NASA Technical Reports Server (NTRS)

Shlosman, Isaac

1990-01-01

The problem of the origin of starburst and nuclear (nonstellar) activity in galaxies is reviewed. A physical understanding of the mechanism(s) that induce both types of activity requires one to address the following issues: (1) what is the source of fuel that powers starbursts and active galactic nuclei; and (2) how is it channeled towards the central regions of host galaxies? As a possible clue, the author examines the role of non-axisymmetric perturbations of galactic disks and analyzes their potential triggers. Global gravitational instabilities in the gas on scales approx. 100 pc appear to be crucial for fueling the active galactic nuclei.

Jet measurements in heavy ion physics

NASA Astrophysics Data System (ADS)

Connors, Megan; Nattrass, Christine; Reed, Rosi; Salur, Sevil

2018-04-01

A hot, dense medium called a quark gluon plasma (QGP) is created in ultrarelativistic heavy ion collisions. Early in the collision, hard parton scatterings generate high momentum partons that traverse the medium, which then fragment into sprays of particles called jets. Understanding how these partons interact with the QGP and fragment into final state particles provides critical insight into quantum chromodynamics. Experimental measurements from high momentum hadrons, two particle correlations, and full jet reconstruction at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) continue to improve our understanding of energy loss in the QGP. Run 2 at the LHC recently began and there is a jet detector at RHIC under development. Now is the perfect time to reflect on what the experimental measurements have taught us so far, the limitations of the techniques used for studying jets, how the techniques can be improved, and how to move forward with the wealth of experimental data such that a complete description of energy loss in the QGP can be achieved. Measurements of jets to date clearly indicate that hard partons lose energy. Detailed comparisons of the nuclear modification factor between data and model calculations led to quantitative constraints on the opacity of the medium to hard probes. However, while there is substantial evidence for softening and broadening jets through medium interactions, the difficulties comparing measurements to theoretical calculations limit further quantitative constraints on energy loss mechanisms. Since jets are algorithmic descriptions of the initial parton, the same jet definitions must be used, including the treatment of the underlying heavy ion background, when making data and theory comparisons. An agreement is called for between theorists and experimentalists on the appropriate treatment of the background, Monte Carlo generators that enable experimental algorithms to be applied to theoretical calculations

Molecular diagnostics of Galactic star-formation regions

NASA Astrophysics Data System (ADS)

Loenen, Edo; Baan, Willem; Spaans, Marco

2007-10-01

We propose a sensitive spectral survey of Galactic star-formation regions. Using the broadband correlator at two different frequencies, we expect to detect the (1-0) transition of CO, CN, HNC, HCN, HCO+, and HCO and various of their isotopes lines, as well as the (12-11) and (10-9) transitions of HC3N. The purpose of these observations is to create a consistent (public) database of molecular emission from galactic star-formation regions. The data will be interpreted using extensive physical and chemical modeling of the whole ensemble of lines, in order to get an accurate description of the molecular environment of these regions. In particular, this diagnostic approach will describe the optical depths, the densities, and the radiation fields in the medium and will allow the establishment of dominant temperature gradients. These observations are part of a program to study molecular emission on all scales, going from individual Galactic star-formation regions, through resolved nearby galaxies, to unresolved extra-galactic emission.

Parameters of Six Selected Galactic Potential Models

NASA Astrophysics Data System (ADS)

Bajkova, Anisa; Bobylev, Vadim

2017-11-01

This paper is devoted to the refinement of the parameters of the six three-component (bulge, disk, halo) axisymmetric Galactic gravitational potential models on the basis of modern data on circular velocities of Galactic objects located at distances up to 200 kpc from the Galactic center. In all models the bulge and disk are described by the Miyamoto-Nagai expressions. To describe the halo, the models of Allen-Santillán (I), Wilkinson-Evans (II), Navarro- Frenk-White (III), Binney (IV), Plummer (V), and Hernquist (VI) are used. The sought-for parameters of potential models are determined by fitting the model rotation curves to the measured velocities, taking into account restrictions on the local dynamical matter density p⊙ - 0.1M⊙ pc-3 and the vertical force |Kz=1.1|/2πG = 77M⊙ pc-2. A comparative analysis of the refined potential models is made and for each of the models the estimates of a number of the Galactic characteristics are presented.

T Pyxidis: The First Cataclysmic Variable with a Collimated Jet

NASA Technical Reports Server (NTRS)

Shahbaz, T.; Livio, M.; Southwell, K. A.; Charles, P. A.

1997-01-01

We present the first observational evidence for a collimated jet in a cataclysmic variable system; the recurrent nova T Pyxidis. Optical spectra show bipolar components of H(alpha) with velocities approx. 1400 km/s, very similar to those observed in the supersoft X-ray sources and in SS 433. We argue that a key ingredient of the formation of jets in the supersoft X-ray sources and T Pyx (in addition to an accretion disk threaded by a vertical magnetic field), is the presence of nuclear burning on the surface of the white dwarf.

IRAS 18113-2503: THE WATER FOUNTAIN WITH THE FASTEST JET?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gomez, Jose F.; Guerrero, MartIn A.; Ricardo Rizzo, J.

2011-09-20

We present Expanded Very Large Array water maser observations at 22 GHz toward the source IRAS 18113-2503. Maser components span over a very high velocity range of {approx_equal} 500 km s{sup -1}, the second largest found in a Galactic maser, only surpassed by the high-mass star-forming region W49N. Maser components are grouped into a blueshifted and a redshifted cluster, separated by 0.''12. Further mid-IR and radio data suggest that IRAS 18113-2503 is a post-asymptotic giant branch star, thus a new bona fide member of the rare class of 'water fountains' (WFs). It is the evolved object with the largest totalmore » velocity spread in its water masers and with the highest velocity dispersion within its redshifted and blueshifted lobes ({approx_equal} 170 km s{sup -1}). The large total velocity range of emission probably indicates that IRAS 18113-2503 has the fastest jet among the known WF stars. On the other hand, the remarkably high velocity dispersion within each lobe may be interpreted in terms of shocks produced by an episode of mass ejection whose velocity increased up to very high values or, alternatively, by projection effects in a jet with a large opening angle and/or precessing motions.« less

First measurement of jet mass in Pb–Pb and p–Pb collisions at the LHC

DOE PAGES

Acharya, S.; Adamová, D.; Aggarwal, M. M.; ...

2017-11-23

This letter presents the first measurement of jet mass in Pb–Pb and p–Pb collisions atmore » $$\\sqrt{s}$$$_ {NN}$$ =2.76 TeV and $$\\sqrt{s}$$$_ {NN}$$ =5.02 TeV, respectively. Both the jet energy and the jet mass are expected to be sensitive to jet quenching in the hot Quantum Chromodynamics (QCD) matter created in nuclear collisions at collider energies. Jets are reconstructed from charged particles using the anti-k T jet algorithm and resolution parameter R=0.4. The jets are measured in the pseudorapidity range |η jet| < 0.5 and in three intervals of transverse momentum between 60 GeV/c and 120 GeV/c. The measurement of the jet mass in central Pb–Pb collisions is compared to the jet mass as measured in p–Pb reference collisions, to vacuum event generators, and to models including jet quenching. It is observed that the jet mass in central Pb–Pb collisions is consistent within uncertainties with p–Pb reference measurements. Furthermore, the measured jet mass in Pb–Pb collisions is not reproduced by the quenching models considered here and is found to be consistent with PYTHIA expectations within systematic uncertainties.« less

First measurement of jet mass in Pb–Pb and p–Pb collisions at the LHC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Acharya, S.; Adamová, D.; Aggarwal, M. M.

This letter presents the first measurement of jet mass in Pb–Pb and p–Pb collisions atmore » $$\\sqrt{s}$$$_ {NN}$$ =2.76 TeV and $$\\sqrt{s}$$$_ {NN}$$ =5.02 TeV, respectively. Both the jet energy and the jet mass are expected to be sensitive to jet quenching in the hot Quantum Chromodynamics (QCD) matter created in nuclear collisions at collider energies. Jets are reconstructed from charged particles using the anti-k T jet algorithm and resolution parameter R=0.4. The jets are measured in the pseudorapidity range |η jet| < 0.5 and in three intervals of transverse momentum between 60 GeV/c and 120 GeV/c. The measurement of the jet mass in central Pb–Pb collisions is compared to the jet mass as measured in p–Pb reference collisions, to vacuum event generators, and to models including jet quenching. It is observed that the jet mass in central Pb–Pb collisions is consistent within uncertainties with p–Pb reference measurements. Furthermore, the measured jet mass in Pb–Pb collisions is not reproduced by the quenching models considered here and is found to be consistent with PYTHIA expectations within systematic uncertainties.« less

Dielectronic Recombination In Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Lukic, D. V.; Schnell, M.; Savin, D. W.; Altun, Z.; Badnell, N.; Brandau, C.; Schmidt, E. W.; Mueller, A.; Schippers, S.; Sprenger, F.;

Galaxy gas as obscurer - II. Separating the galaxy-scale and nuclear obscurers of active galactic nuclei

NASA Astrophysics Data System (ADS)

Buchner, Johannes; Bauer, Franz E.

2017-03-01

The 'torus' obscurer of active galactic nuclei (AGN) is poorly understood in terms of its density, sub-structure and physical mechanisms. Large X-ray surveys provide model boundary constraints, for both Compton-thin and Compton-thick levels of obscuration, as obscured fractions are mean covering factors fcov. However, a major remaining uncertainty is host-galaxy obscuration. In Paper I, we discovered a relation of {NH} ∝ M_{star }^{1/3} for the obscuration of galaxy-scale gas. Here, we apply this observational relation to the AGN population, and find that galaxy-scale gas is responsible for a luminosity-independent fraction of Compton-thin AGN, but does not produce Compton-thick columns. With the host-galaxy obscuration understood, we present a model of the remaining nuclear obscurer, which is consistent with a range of observations. Our radiation-lifted torus model consists of a Compton-thick component (fcov ∼ 35 per cent) and a Compton-thin component (fcov ∼ 40 per cent), which depends on both black hole mass and luminosity. This provides a useful summary of observational constraints for torus modellers who attempt to reproduce this behaviour. It can also be employed as a sub-grid recipe in cosmological simulations that do not resolve the torus. We also investigate host-galaxy X-ray obscuration inside cosmological, hydrodynamic simulations (Evolution and Assembly of Galaxies and their Environment; Illustris). The obscuration from ray-traced galaxy gas can agree with observations, but is highly sensitive to the chosen feedback assumptions.

Monte-Carlo Event Generators for Jet Modification in d(p)-A and A-A Collisions

NASA Astrophysics Data System (ADS)

Kordell, Michael C., III

This work outlines methods to use jet simulations to study both initial and final state nuclear effects in heavy-ion collisions. To study the initial state of heavy-ion collisions, the production of jets and high momentum hadrons from jets, produced in deuteron (d)-Au collisions at the relativistic heavy-ion collider (RHIC) and proton (p)- Pb collisions at the large hadron collider (LHC) are studied as a function of centrality, a measure of the impact parameter of the collision. A modified version of the event generator PYTHIA, widely used to simulate p-p collisions, is used in conjunction with a nuclear Monte-Carlo event generator which simulates the locations of the nucleons within a large nucleus. It is demonstrated how events with a hard jet may be simulated, in such a way that the parton distribution function of the projectile is frozen during its interaction with the extended nucleus. Using this approach, it is demonstrated that the puzzling enhancement seen in peripheral events at RHIC and the LHC, as well as the suppression seen in central events at the LHC are mainly due to mis-binning of central and semi-central events, containing a jet, as peripheral events. This occurs due to the suppression of soft particle production away from the jet, caused by the depletion of energy available in a nucleon of the deuteron (in d-Au at RHIC) or in the proton (in p-Pb at LHC), after the production of a hard jet. In conclusion, partonic correlations built out of simple energy conservation are responsible for such an effect, though these are sampled at the hard scale of jet production and, as such, represent smaller states. To study final state nuclear effects, the modification of hard jets in the Quark Gluon Plasma (QGP) is simulated using the MATTER event generator. Based on the higher twist formalism of energy loss, the MATTER event generator simulates the evolution of highly virtual partons through a medium. These partons sampled from an underlying PYTHIA kernel

Calculated performance of a mercury-compressor-jet powered airplane using a nuclear reactor as an energy source

NASA Technical Reports Server (NTRS)

Doyle, R B

1951-01-01

An analysis was made at a flight Mach number of 1.5, an altitude of 45,000 feet, a turbine-inlet temperature of 1460 degrees R, of a mercury compressor-jet powered airplane using a nuclear reactor as an energy source. The calculations covered a range of turbine-exhaust and turbine-inlet pressures and condenser-inlet Mach numbers. For a turbine--inlet pressure of 40 pounds per square inch absolute, a turbine-exhaust pressure of 14 pounds per square inch absolute, and a condenser-inlet Mach number of 0.23 the calculated airplane gross weight required to carry a 20,000 pound payload was 322000 pounds and the reactor heat release per unit volume was 8.9 kilowatts per cubic inch. These do not represent optimum operating conditions.

Galactic Observations of Terahertz C+ (GOT C+): Inner Galaxy Survey

NASA Astrophysics Data System (ADS)

Yorke, Harold; Langer, William; Velusamy, T.; Pineda, J. L.; Goldsmith, P. F.; Li, D.

To understand the lifecycle of the interstellar gas and star formation we need detailed information about the diffuse atomic and diffuse molecular gas cloud properties. The ionized carbon [CII] 1.9 THz fine structure line is an important tracer of the atomic gas in the diffuse regions and the interface regions of atomic gas to molecular clouds. Furthermore, C+ is a major ISM coolant and among the Galaxy's strongest far-IR emission lines, and thus controls the thermal conditions throughout large parts of the Galaxy. Until now our knowledge of interstellar gas has been limited to the diffuse atomic phase traced by HI and to the dense molecular H2 phase traced by CO. However, we are missing an important phase of the ISM, called "dark gas" in which there is no or little, HI, and mostly molecular hydrogen but with insufficient shielding of UV to allow CO to form. C+ emission and absorption lines at 1.9 THz have the potential to trace such cloud transitions and evolution. Galactic Observations of the Terahertz C+ Line (GOT C+) is a Herschel Space Observatory Open Time Key Program to study the diffuse interstellar medium by sampling [CII] 1.9 THz line emission throughout the Galactic disk. We discuss the broader perspective of this survey and the first results of GOT C+ obtained during the Science Demonstration Phase (SDP) and Priority Science Phase (PSP) of HIFI, which focus on approximately 100 lines of sight in the inner galaxy. These observations are being carried out with the Herschel Space Observatory, which is an ESA cornerstone mission, with contributions from NASA. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration. JLP is a Caltech-JPL Postdoctoral Associate.

Fluid sampling system for a nuclear reactor

DOEpatents

Lau, Louis K.; Alper, Naum I.

1994-01-01

A system of extracting fluid samples, either liquid or gas, from the interior of a nuclear reactor containment utilizes a jet pump. To extract the sample fluid, a nonradioactive motive fluid is forced through the inlet and discharge ports of a jet pump located outside the containment, creating a suction that draws the sample fluid from the containment through a sample conduit connected to the pump suction port. The mixture of motive fluid and sample fluid is discharged through a return conduit to the interior of the containment. The jet pump and means for removing a portion of the sample fluid from the sample conduit can be located in a shielded sample grab station located next to the containment. A non-nuclear grade active pump can be located outside the grab sampling station and the containment to pump the nonradioactive motive fluid through the jet pump.

Fluid sampling system for a nuclear reactor

DOEpatents

Lau, L.K.; Alper, N.I.

1994-11-22

A system of extracting fluid samples, either liquid or gas, from the interior of a nuclear reactor containment utilizes a jet pump. To extract the sample fluid, a nonradioactive motive fluid is forced through the inlet and discharge ports of a jet pump located outside the containment, creating a suction that draws the sample fluid from the containment through a sample conduit connected to the pump suction port. The mixture of motive fluid and sample fluid is discharged through a return conduit to the interior of the containment. The jet pump and means for removing a portion of the sample fluid from the sample conduit can be located in a shielded sample grab station located next to the containment. A non-nuclear grade active pump can be located outside the grab sampling station and the containment to pump the nonradioactive motive fluid through the jet pump. 1 fig.

Astrophysical ZeV acceleration in the relativistic jet from an accreting supermassive blackhole

NASA Astrophysics Data System (ADS)

Ebisuzaki, Toshikazu; Tajima, Toshiki

2014-04-01

An accreting supermassive blackhole, the central engine of active galactic nucleus (AGN), is capable of exciting extreme amplitude Alfven waves whose wavelength (wave packet) size is characterized by its clumpiness. The pondermotive force and wakefield are driven by these Alfven waves propagating in the AGN (blazar) jet, and accelerate protons/nuclei to extreme energies beyond Zetta-electron volt (ZeV=1021 eV). Such acceleration is prompt, localized, and does not suffer from the multiple scattering/bending enveloped in the Fermi acceleration that causes excessive synchrotron radiation loss beyond 1019 eV. The production rate of ZeV cosmic rays is found to be consistent with the observed gamma-ray luminosity function of blazars and their time variabilities.

Q2122-444: A NAKED ACTIVE GALACTIC NUCLEUS FULLY DRESSED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gliozzi, M.; Satyapal, S.; Panessa, F.

Based on previous spectral and temporal optical studies, Q2122-444 has been classified as a naked active galactic nucleus (AGN) or true type 2 AGN, that is, an AGN that genuinely lacks a broad-line region (BLR). Its optical spectrum seemed to possess only narrow forbidden emission lines that are typical of type 2 (obscured) AGNs, but the long-term optical light curve, obtained from a monitoring campaign over more than two decades, showed strong variability, apparently ruling out the presence of heavy obscuration. Here we present the results from a {approx}40 ks XMM-Newton observation of Q2122-444 carried out to shed light onmore » the energetics of this enigmatic AGN. The X-ray analysis was complemented with Australia Telescope Compact Array radio data to assess the possible presence of a jet, and with new NTT/EFOSC2 optical spectroscopic data to verify the actual absence of a BLR. The higher-quality optical data revealed the presence of strong and broad Balmer lines that are at odds with the previous spectral classification of this AGN. The lack of detection of radio emission rules out the presence of a jet. The X-ray data combined with simultaneous UV observations carried out by the Optical Monitor (OM) aboard XMM-Newton confirm that Q2122-444 is a typical type 1 AGN without any significant intrinsic absorption. New estimates of the black hole mass independently obtained from the broad Balmer lines and from a new scaling technique based on X-ray spectral data suggest that Q2122-444 is accreting at a relatively high rate in Eddington units.« less

Molecular Gas Feeding the Circumnuclear Disk of the Galactic Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, Pei-Ying; Koch, Patrick M.; Ho, Paul T. P.

The interaction between a supermassive black hole (SMBH) and the surrounding material is of primary importance in modern astrophysics. The detection of the molecular 2 pc circumnuclear disk (CND) immediately around the Milky Way SMBH, SgrA*, provides a unique opportunity to study SMBH accretion at subparsec scales. Our new wide-field CS( J = 2 − 1) map toward the Galactic center (GC) reveals multiple dense molecular streamers that originated from the ambient clouds 20 pc further out, and that are connected to the central 2 pc of the CND. These dense gas streamers appear to carry gas directly toward themore » nuclear region and might be captured by the central potential. Our phase-plot analysis indicates that these streamers show a signature of rotation and inward radial motion with progressively higher velocities as the gas approaches the CND and finally ends up corotating with the CND. Our results might suggest a possible mechanism of gas feeding the CND from 20 pc around 2 pc in the GC. In this paper, we discuss the morphology and the kinematics of these streamers. As the nearest observable Galactic nucleus, this feeding process may have implications for understanding the processes in extragalactic nuclei.« less

Galactic-scale civilization

NASA Technical Reports Server (NTRS)

Kuiper, T. B. H.

1980-01-01

Evolutionary arguments are presented in favor of the existence of civilization on a galactic scale. Patterns of physical, chemical, biological, social and cultural evolution leading to increasing levels of complexity are pointed out and explained thermodynamically in terms of the maximization of free energy dissipation in the environment of the organized system. The possibility of the evolution of a global and then a galactic human civilization is considered, and probabilities that the galaxy is presently in its colonization state and that life could have evolved to its present state on earth are discussed. Fermi's paradox of the absence of extraterrestrials in light of the probability of their existence is noted, and a variety of possible explanations is indicated. Finally, it is argued that although mankind may be the first occurrence of intelligence in the galaxy, it is unjustified to presume that this is so.

Optical monitoring of Active Galactic Nuclei from ARIES

NASA Astrophysics Data System (ADS)

Gopal-Krishna; Wiita, Paul Joseph

2018-04-01

This overview provides a historical perspective highlighting the pioneering role which the fairly modest observational facilities of ARIES have played since the 1990s in systematically characterizing the optical variability on hour-like time scale (intra-night optical variability, or INOV) of several major types of high-luminosity Active Galactic Nuclei (AGN). Such information was previously available only for blazars. Similar studies have since been initiated in at least a dozen countries, giving a boost to AGN variability research. Our work has, in particular, provided strong indication that mild INOV occurs in radio-quiet QSOs (amplitude up to 3 – 5 % and duty cycle 10%) and, moreover, has demonstrated that similarly mild INOV is exhibited even by the vast majority of radio-loud quasars which possess powerful relativistic jets (even including many that are beamed towards us). The solitary outliers are blazars, the tiny strongly polarized subset of powerful AGN, which frequently exhibit a pronounced INOV. Among the blazars, BL Lac objects often show a bluer-when-brighter chromatic behavior, while the flat spectrum radio quasars seem not to. Quantifying any differences of INOV among the major subclasses of non-blazar type AGNs will require dedicated monitoring programs using 2 - 3 metre class telescopes.

Evidence of 9Be  +  p nuclear reactions during 2ω CH and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas

NASA Astrophysics Data System (ADS)

Krasilnikov, A. V.; Kiptily, V.; Lerche, E.; Van Eester, D.; Afanasyev, V. I.; Giroud, C.; Goloborodko, V.; Hellesen, C.; Popovichev, S. V.; Mironov, M. I.; contributors, JET

2018-02-01

The intensity of 9Be  +  p nuclear fusion reactions was experimentally studied during second harmonic (2ω CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to 9Be  +  p interaction, were observed with fast ion loss detectors, γ-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using 9Be(p, d)2α and 9Be(p, α)6Li nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.

Evolution of the Oort Cloud under Galactic Perturbations

NASA Astrophysics Data System (ADS)

Higuchi, A.; Kokubo, E.; Mukai, T.

2005-08-01

The Oort cloud is a spherical comet reservoir surrounding the solar system. There is general agreement that the Oort cloud comets are the residual planetesimals of planet formation. The standard scenario of the Oort cloud formation consists of two dynamical stages: (1) giant planets raise the aphelia of planetesimals to the outer region of the solar system and (2) the galactic tide, passing stars, and giant molecular clouds pull up their perihelia out of the planetary region and randomize their inclinations. Here we show the orbital evolution of planetesimals due to the galactic tide. Planetesimals with large aphelion distances change their perihelion distances toward the outside of the planetary region by the galactic tide and become members of the Oort cloud. We consider only the vertical component of the galactic tide because it is dominant compared to other components. Then, under such an axi-symmetric assumption, some planetesimals may show the librations around ω (argument of perihelion)=π /2 or 3π /2 (the Kozai mechanism). The alternate increases of eccentricity and inclination of the Kozai mechanism are effective to form the Oort cloud. Using the secular perturbation theory, we can understand the motion of the planetesimals analytically. We applied the Kozai mechanism to the galactic tide and found that the galactic tide raise perihelia and randomize inclinations of planetesimals with semimajor axes larger than ˜ 103 AU in 5Gyr. We take into account time evolution of the local galactic density, which is thought to be denser in the early stage of the sun than the current one. This work was supported by the 21st Century COE Program Origin and Evolution of Planetary Systems of the Ministry of Education, Culture, Sports, Science, and Technology, Japan, and JSPS Research Fellowship for Young Scientists.

Benchmark solutions for the galactic heavy-ion transport equations with energy and spatial coupling

NASA Technical Reports Server (NTRS)

Ganapol, Barry D.; Townsend, Lawrence W.; Lamkin, Stanley L.; Wilson, John W.

1991-01-01

Nontrivial benchmark solutions are developed for the galactic heavy ion transport equations in the straightahead approximation with energy and spatial coupling. Analytical representations of the ion fluxes are obtained for a variety of sources with the assumption that the nuclear interaction parameters are energy independent. The method utilizes an analytical LaPlace transform inversion to yield a closed form representation that is computationally efficient. The flux profiles are then used to predict ion dose profiles, which are important for shield design studies.

Polarization of the diffuse galactic light.

NASA Technical Reports Server (NTRS)

Sparrow, J. G.; Ney, E. P.

1972-01-01

Polarization measurements made from the satellite OSO-5 show that the polarized intensity in the direction of the Scutum arm of the Galaxy is different in intensity and direction of the polarization from that observed due to the zodiacal light. The observations are consistent with polarized diffuse galactic light superposed on the zodiacal light. The results are interpreted in terms of a model in which the galactic starlight is scattered by interstellar dust.

The Galactic Magnetic Field and its lensing of Ultrahigh Energy and Galactic Cosmic Rays

NASA Astrophysics Data System (ADS)

Farrar, Glennys

2015-08-01

It has long been recognized that magnetic fields play an important role in many astrophysical environments, but the magnetic field strength and structure has only been quantitatively determined for relatively few systems beyond our solar system.Our understanding of the Galactic magnetic field (GMF) has improved tremendously in recent years. The Jansson-Farrar (2012) (JF12) GMF model is the most realistic and comprehensive model available. It was constrained by fitting all-sky Faraday Rotation Measures of ~40k extragalactic sources, simultaneously with WMAP polarized (Q,U) and total synchrotron emission maps - together providing a total of more than 10,000 independent datapoints, each with measured astrophysical variance. In addition to disk and toroidal halo components, a previously overlooked coherent poloidal halo field proves to be necessary to account for the RM, Q and U data. Moreover a “striated” random component is needed in addition to a fully random component, in both disk and halo.The talk will give a concise review of the JF12 model and its derivation, with emphasis on which features of the GMF are well or poorly established. I will show that the data unambiguously demand a large scale coherent component to the halo field which is a diverging-spiral centered on the Galactic center, with field lines running from Southern to Northern hemispheres. The puzzles posed by the large scale coherent halo and disk magnetic fields, and their possible origins, will be discussed.Having a good model of the Galactic magnetic field is crucial for determining the sources of UHECRs, for modeling the transport of Galactic CRs (the halo field provides a heretofore-overlooked escape route for by diffusion along its field lines), and for calculating the background to dark matter and CMB-cosmology studies. I will present new results on the lensing effect of the GMF on UHECRs, which produces multiple images and dramatic magnification and demagnification that varies with

YSO jets in the Galactic plane from UWISH2 - V. Jets and outflows in M17

NASA Astrophysics Data System (ADS)

Samal, M. R.; Chen, W. P.; Takami, M.; Jose, J.; Froebrich, D.

2018-07-01

Jets and outflows are the first signposts of stellar birth. Emission in the H2 1-0 S(1) line at 2.122- μm is a powerful tracer of shock excitation in these objects. Here we present the analysis of 2.0 × 0.8 deg2 data from the UK Wide-field Infrared Survey for H2 (UWISH2) in the 1-0 S(1) line to identify and characterize the outflows of the M17 complex. We uncover 48 probable outflows, of which 93 per cent are new discoveries. We identified driving source candidates for 60 per cent of outflows. Among the driving source candidate young stellar objects (YSOs), 90 per cent are protostars and the remaining 10 per cent are Class II YSOs. In comparison with results from other surveys, we suggest that H2 emission fades very quickly as the objects evolve from protostars to pre-main-sequence stars. We fit spectral energy distribution (SED) models to 14 candidate outflow-driving sources and conclude that the outflows of our sample are mostly driven by moderate-mass YSOs that are still actively accreting from their protoplanetary disc. We examined the spatial distribution of the outflows with the gas and dust distribution of the complex and observed that the filamentary dark cloud M17SWex, located on the south-western side of the complex, is associated with a greater number of outflows. We find that our results corroborate previous suggestions that, in the M17 complex, M17SWex is the most active site of star formation. Several of our newly identified outflow candidates are excellent targets for follow-up studies to understand better the very early phase of protostellar evolution.

Reconstruction and attributes of jets observed in center of mass energy = 200 GeV proton-proton and deuteron-gold collisions at STAR

NASA Astrophysics Data System (ADS)

Henry, Thomas William

The STAR collaboration recorded s = 200 GeV per nucleon d+Au and p+p collision events during the year 2003 RHIC run. In the p+p and the d+Au data samples, it is possible to reconstruct jets and make comparisons between them. This dissertation describes the reconstructed jet sample from the p+p events, the measurements of the jet jT distribution which quantifies the shape of the jet perpendicular to the jet direction, the jet fragmentation function (z), which quantifies the fraction of jet momentum carried by the jet particles, and the width of the parton momentum broadening distribution (kT). This dissertation also describes the comparison of these results to the reconstructed jet sample from d+Au events. Measurements of jet jT and jet fragmentation from p+p, d+Au, and PYTHIA are compared. The z and jT distributions from p+p and also d+Au are found to be consistent with PYTHIA event simulation version 6.205. RMS(jT) equals 612+/-12+/-30 MeV/c for p+p, and RMS(jT) equals 630+/-13+/-30 MeV/c for d+Au. The p+p kT Gaussian sigma (width) equals 2.08+/-0.12+/-0.13 GeV/c. This width is consistent with PYTHIA, kT literature surveys, and other RHIC measurements. A limit on nuclear jT broadening in the Au nucleus is also obtained, showing that nuclear jT is consistent with zero to within 0.5 GeV/c. The present status of the RdAu measurement from jets is also described. The nuclear kT broadening, in particular, is a measurement which has been done at this energy for the first time at RHIC. These measurements, while interesting by themselves, also will contribute ultimately to the understanding of Au+Au collisions at RHIC, and the properties of the high-density matter which results from them.

The Galactic Nova Rate Revisited

NASA Astrophysics Data System (ADS)

Shafter, A. W.

2017-01-01

Despite its fundamental importance, a reliable estimate of the Galactic nova rate has remained elusive. Here, the overall Galactic nova rate is estimated by extrapolating the observed rate for novae reaching m≤slant 2 to include the entire Galaxy using a two component disk plus bulge model for the distribution of stars in the Milky Way. The present analysis improves on previous work by considering important corrections for incompleteness in the observed rate of bright novae and by employing a Monte Carlo analysis to better estimate the uncertainty in the derived nova rates. Several models are considered to account for differences in the assumed properties of bulge and disk nova populations and in the absolute magnitude distribution. The simplest models, which assume uniform properties between bulge and disk novae, predict Galactic nova rates of ˜50 to in excess of 100 per year, depending on the assumed incompleteness at bright magnitudes. Models where the disk novae are assumed to be more luminous than bulge novae are explored, and predict nova rates up to 30% lower, in the range of ˜35 to ˜75 per year. An average of the most plausible models yields a rate of {50}-23+31 yr-1, which is arguably the best estimate currently available for the nova rate in the Galaxy. Virtually all models produce rates that represent significant increases over recent estimates, and bring the Galactic nova rate into better agreement with that expected based on comparison with the latest results from extragalactic surveys.

Far Noise Field of Air Jets and Jet Engines

NASA Technical Reports Server (NTRS)

Callaghan, Edmund E; Coles, Willard D

1957-01-01

An experimental investigation was conducted to study and compare the acoustic radiation of air jets and jet engines. A number of different nozzle-exit shapes were studied with air jets to determine the effect of exit shape on noise generation. Circular, square, rectangular, and elliptical convergent nozzles and convergent-divergent and plug nozzles were investigated. The spectral distributions of the sound power for the engine and the air jet were in good agreement for the case where the engine data were not greatly affected by reflection or jet interference effects. Such power spectra for a subsonic or slightly choked engine or air jet show that the peaks of the spectra occur at a Strouhal number of 0.3.

Discovery of Giant Gamma-ray Bubbles in the Milky Way

NASA Astrophysics Data System (ADS)

Su, Meng

Based on data from the Fermi Gamma-ray Space Telescope, we have discovered two gigantic gamma-ray emitting bubble structures in our Milky Way (known as the Fermi bubbles), extending ˜50 degrees above and below the Galactic center with a width of ˜40 degrees in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum (dN/dE ˜ E-2) than the inverse Compton emission from known cosmic ray electrons in the Galactic disk, or the gamma-rays produced by decay of pions from proton-ISM collisions. There is no significant difference in the spectrum or gamma-ray luminosity between the north and south bubbles. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; we also found features in the ROSAT soft X-ray maps at 1.5 -- 2 keV which line up with the edges of the bubbles. The Fermi bubbles are most likely created by some large episode of energy injection in the Galactic center, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last ˜ 10 Myr. Study of the origin and evolution of the bubbles also has the potential to improve our understanding of recent energetic events in the inner Galaxy and the high-latitude cosmic ray population. Furthermore, we have recently identified a gamma-ray cocoon feature within the southern bubble, with a jet-like feature along the cocoon's axis of symmetry, and another directly opposite the Galactic center in the north. If confirmed, these jets are the first resolved gamma-ray jets ever seen.

Galactic Surveys in the Gaia Era

NASA Astrophysics Data System (ADS)

Wyse, Rosemary F. G.

2018-04-01

The final astrometric data from the Gaia mission will transform our view of the stellar content of the Galaxy, particularly when complemented with spectroscopic surveys providing stellar parameters, line-of-sight kinematics and elemental abundances. Analyses with Gaia DR1 are already demonstrating the insight gained and the promise of what is to come with future Gaia releases. I present a brief overview of results and puzzles from recent Galactic Archaeology surveys for context, focusing on the Galactic discs.

Stretched Inertial Jets

NASA Astrophysics Data System (ADS)

Ghabache, Elisabeth; Antkowiak, Arnaud; Seon, Thomas; Villermaux, Emmanuel

2015-11-01

Liquid jets often arise as short-lived bursting liquid flows. Cavitation or impact-driven jets, bursting champagne bubbles, shaped-charge jets, ballistospores or drop-on-demand inkjet printing are a few examples where liquid jets are suddenly released. The trademark of all these discharge jets is the property of being stretched, due to the quenching injection. the present theoretical and experimental investigation, the structure of the jet flow field will be unraveled experimentally for a few emblematic occurrences of discharge jets. Though the injection markedly depends on each flow configuration, the jet velocity field will be shown to be systematically and rapidly attracted to the universal stretching flow z/t. The emergence of this inertial attractor actually only relies on simple kinematic ingredients, and as such is fairly generic. The universality of the jet velocity structure will be discussed.

Factorization for jet radius logarithms in jet mass spectra at the LHC

DOE PAGES

Kolodrubetz, Daniel W.; Pietrulewicz, Piotr; Stewart, Iain W.; ...

2016-12-14

To predict the jet mass spectrum at a hadron collider it is crucial to account for the resummation of logarithms between the transverse momentum of the jet and its invariant mass m J . For small jet areas there are additional large logarithms of the jet radius R, which affect the convergence of the perturbative series. We present an analytic framework for exclusive jet production at the LHC which gives a complete description of the jet mass spectrum including realistic jet algorithms and jet vetoes. It factorizes the scales associated with m J , R, and the jet veto, enablingmore » in addition the systematic resummation of jet radius logarithms in the jet mass spectrum beyond leading logarithmic order. We discuss the factorization formulae for the peak and tail region of the jet mass spectrum and for small and large R, and the relations between the different regimes and how to combine them. Regions of experimental interest are classified which do not involve large nonglobal logarithms. We also present universal results for nonperturbative effects and discuss various jet vetoes.« less

Smashing a Jet into a Cloud to Form Stars

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

What happens when the highly energetic jet from the center of an active galaxy rams into surrounding clouds of gas and dust? A new study explores whether this might be a way to form stars.The authors simulations at an intermediate (top) and final (bottom) stage show the compression in the gas cloud as a jet (red) enters from the left. Undisturbed cloud material is shown in blue, whereas green corresponds to cold, compressed gas actively forming stars. [Fragile et al. 2017]Impacts of FeedbackCorrelation between properties of supermassive black holes and their host galaxies suggest that there is some means of communication between them. For this reason, we suspect that feedback from an active galactic nucleus (AGN) in the form of jets, for instance controls the size of the galaxy by influencing star formation. But how does this process work?AGN feedback can be either negative or positive. In negative feedback, the gas necessary for forming stars is heated or dispersed by the jet, curbing or halting star formation. In positive feedback, jets propagate through the surrounding gas with energies high enough to create compression in the gas, but not so high that they heat it. The increased density can cause the gas to collapse, thereby triggering star formation.In a recent study, a team of scientists led by Chris Fragile (College of Charleston) modeled what happens when an enormous AGN jet slams into a dwarf-galaxy-sized, inactive cloud of gas. In particular, the team explored the possibility of star-forming positive feedback with the goal of reproducing recent observations of something called Minkowskis Object, a stellar nursery located at the endpoint of a radio jet emitted from the active galaxy NGC 541.The star formation rate in the simulated cloud increases dramatically as a result of the jets impact, reaching the rate currently observed for Minkowskis Objects within 20 million years. [Fragile et al. 2017]Triggering Stellar BirthFragile and collaborators used a

Detection of sulfur in the galactic center

NASA Technical Reports Server (NTRS)

Herter, T.; Briotta, D. A., Jr.; Gull, G. E.; Shure, M. A.; Houck, J. R.

1983-01-01

A strong detection at the S III forbidden 18.71 micron line is reported for the galactic center region, Sgr A West. A line flux of 1.7 + or - 0.2 x 10 to the -17th W/sq cm is found for a 20 inch beam size measurement centered on IRS 1. A preliminary analysis indicates that the S III abundance relative to hydrogen is consistent with the cosmic abundance of sulfur, 0.000016, if a filling factor of unity within the known clumps is assumed. However, the sulfur abundance in the galactic center may be as much as a factor of 3 overabundant if a filling factor of 0.03 is adopted, a value found to hold for some galactic H II regions.

The Radio Jets and Accretion Disk in NGC 4261

NASA Astrophysics Data System (ADS)

Jones, Dayton L.; Wehrle, Ann E.; Meier, David L.; Piner, B. Glenn

2000-05-01

The structure of active galactic nucleus (AGN) accretion disks on subparsec scales can be probed through free-free absorption of synchrotron emission from the base of symmetric radio jets. For objects in which both jet and counterjet are detectable with very long baseline interferometry (VLBI), the accretion disk will cover part of the counterjet and produce diminished brightness whose angular size and depth as a function of frequency can reveal the radial distribution of free electrons in the disk. The nearby (41 Mpc, independent of H0) FR I radio galaxy NGC 4261 contains a pair of symmetric kiloparsec-scale jets. On parsec scales, radio emission from the nucleus is strong enough for detailed imaging with VLBI. We present new Very Long Baseline Array (VLBA) observations of NGC 4261 at 22 and 43 GHz, which we combine with previous observations at 1.6 and 8.4 GHz to map absorption caused by an inner accretion disk. The relative closeness of NGC 4261 combined with the high angular resolution provided by the VLBA at 43 GHz gives us a very high linear resolution, approximately 2×10-2 pc ~4000 AU ~400 Schwarzschild radii for a 5×108 Msolar black hole. The jets appear more symmetric at 1.6 GHz because of the low angular resolution available. The jets are also more symmetric at 22 and 43 GHz, presumably because the optical depth of free-free absorption is small at high frequencies. At 8.4 GHz, neither confusion effect is dominant and absorption of counterjet emission by the presumed disk is detectable. We find that the orientation of the radio jet axis is the same on parsec and kiloparsec scales, indicating that the spin axis of the inner accretion disk and black hole has remained unchanged for at least 106 (and more likely >107) yr. This suggests that a single merger event may be responsible for the supply of gas in the nucleus of NGC 4261. The jet opening angle is between 0.3d and 20° during the first 0.2 pc of the jet and must be less than 5° during the first 0

Reversing cooling flows with AGN jets: shock waves, rarefaction waves and trailing outflows

NASA Astrophysics Data System (ADS)

Guo, Fulai; Duan, Xiaodong; Yuan, Ye-Fei

2018-01-01

The cooling flow problem is one of the central problems in galaxy clusters, and active galactic nucleus (AGN) feedback is considered to play a key role in offsetting cooling. However, how AGN jets heat and suppress cooling flows remains highly debated. Using an idealized simulation of a cool-core cluster, we study the development of central cooling catastrophe and how a subsequent powerful AGN jet event averts cooling flows, with a focus on complex gasdynamical processes involved. We find that the jet drives a bow shock, which reverses cooling inflows and overheats inner cool-core regions. The shocked gas moves outward in a rarefaction wave, which rarefies the dense core and adiabatically transports a significant fraction of heated energy to outer regions. As the rarefaction wave propagates away, inflows resume in the cluster core, but a trailing outflow is uplifted by the AGN bubble, preventing gas accumulation and catastrophic cooling in central regions. Inflows and trailing outflows constitute meridional circulations in the cluster core. At later times, trailing outflows fall back to the cluster centre, triggering central cooling catastrophe and potentially a new generation of AGN feedback. We thus envisage a picture of cool cluster cores going through cycles of cooling-induced contraction and AGN-induced expansion. This picture naturally predicts an anti-correlation between the gas fraction (or X-ray luminosity) of cool cores and the central gas entropy, which may be tested by X-ray observations.

Galactic Observations of Terahertz C+ (GOT C+): First Results: Inner Galaxy Survey

NASA Astrophysics Data System (ADS)

Langer, William; Velusamy, T.; Pineda, J. L.; Goldsmith, P. F.; Li, D.; Yorke, H. W.

2010-05-01

To understand the lifecycle of the interstellar gas and star formation we need detailed information about the diffuse atomic and diffuse molecular gas cloud properties. The ionized carbon [CII] 1.9 THz fine structure line is an important tracer of the atomic gas in the diffuse regions and the interface regions of atomic gas to molecular clouds. Furthermore, C+ is a major ISM coolant and among the Galaxy's strongest far-IR emission lines, and thus controls the thermal conditions throughout large parts of the Galaxy. Until now our knowledge of interstellar gas has been limited to the diffuse atomic phase traced by HI and to the dense molecular H2 phase traced by CO. However, we are missing an important phase of the ISM called "dark gas” in which there is no or little, HI, and mostly molecular hydrogen but with insufficient shielding of UV to allow CO to form. C+ emission and absorption lines at 1.9 THz have the potential to trace this gas. Galactic Observations of the Terahertz C+ Line (GOT C+) is a Herschel Space Observatory Open Time Key Program to study the diffuse interstellar medium by sampling [CII] 1.9 THz line emission throughout the Galactic disk. We discuss the broader perspective of this survey and the first results of GOT C+ obtained during the Science Demonstration Phase (SDP) and Priority Science Phase (PSP) of HIFI, which focus on approximately 100 lines of sight in the inner galaxy. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

Multi-frequency properties of synthetic blazar radio light curves within the shock-in-jet scenario

NASA Astrophysics Data System (ADS)

Fromm, C. M.; Fuhrmann, L.; Perucho, M.

2015-08-01

Context. Blazars are among the most powerful extragalactic objects as a sub-class of active galactic nuclei. They launch relativistic jets and their emitted radiation shows strong variability across the entire electro-magnetic spectrum. The mechanisms producing the variability are still controversial, and different models have been proposed to explain the observed variations in multi-frequency blazar light curves. Aims: We investigate the capabilities of the classical shock-in-jet model to explain and reconstruct the observed evolution of flares in the turnover frequency - turnover flux density (νm-Sm) plane and their frequency dependent light curve parameters. With a detailed parameter space study, we provide the framework for future, detailed comparisons of observed flare signatures with the shock-in-jet scenario. Methods: Based on the shock model, we compute synthetic single-dish light curves at different radio frequencies (2.6 to 345 GHz) and for different physical conditions in a conical jet (e.g. magnetic field geometry and Doppler factor). From those we extract the slopes of the different energy loss stages within the (νm-Sm) plane and deduce the frequency dependence of different light curve parameters, such as flare amplitude, time scale, and cross-band delays. Results: The evolution of the Doppler factor along the jet has the strongest influence on the evolution of the flare and on the frequency dependent light curve parameters. The synchrotron stage can be hidden in the Compton or in the adiabatic stage, depending mainly on the evolution of the Doppler factor, which makes it difficult to detect its signature in observations. In addition, we show that the time lags between different frequencies can be used as an efficient tool to better constrain the physical properties of these objects. Appendix A is available in electronic form at http://www.aanda.org

Relaxation near Supermassive Black Holes Driven by Nuclear Spiral Arms: Anisotropic Hypervelocity Stars, S-stars, and Tidal Disruption Events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamers, Adrian S.; Perets, Hagai B., E-mail: hamers@ias.edu

Nuclear spiral arms are small-scale transient spiral structures found in the centers of galaxies. Similarly to their galactic-scale counterparts, nuclear spiral arms can perturb the orbits of stars. In the case of the Galactic center (GC), these perturbations can affect the orbits of stars and binaries in a region extending to several hundred parsecs around the supermassive black hole (SMBH), causing diffusion in orbital energy and angular momentum. This diffusion process can drive stars and binaries to close approaches with the SMBH, disrupting single stars in tidal disruption events (TDEs), or disrupting binaries, leaving a star tightly bound to themore » SMBH and an unbound star escaping the galaxy, i.e., a hypervelocity star (HVS). Here, we consider diffusion by nuclear spiral arms in galactic nuclei, specifically the Milky Way GC. We determine nuclear-spiral-arm-driven diffusion rates using test-particle integrations and compute disruption rates. Our TDE rates are up to 20% higher compared to relaxation by single stars. For binaries, the enhancement is up to a factor of ∼100, and our rates are comparable to the observed numbers of HVSs and S-stars. Our scenario is complementary to relaxation driven by massive perturbers. In addition, our rates depend on the inclination of the binary with respect to the Galactic plane. Therefore, our scenario provides a novel potential source for the observed anisotropic distribution of HVSs. Nuclear spiral arms may also be important for accelerating the coalescence of binary SMBHs and for supplying nuclear star clusters with stars and gas.« less

Galactic Neighborhood and Laboratory Astrophysics

NASA Astrophysics Data System (ADS)

Wang, Q. D.

2011-05-01

The galactic neighborhood, extending from the Milky Way to redshifts of about 0.1, is our unique local laboratory for detailed study of galaxies and their interplay with the environment. Such study provides a foundation of knowledge for interpreting observations of more distant galaxies and their environment. The Astro 2010 Science Frontier Galactic Neighborhood Panel identified four key sci- entific questions: 1) What are the flows of matter and energy in the circumgalac- tic medium? 2) What controls the mass-energy-chemical cycles within galaxies? 3) What is the fossil record of galaxy assembly from first stars to present? 4) What are the connections between dark and luminous matter? These questions, essential to the understanding of galaxies as interconnected complexes, can be addressed most effectively and/or uniquely in the galactic neighborhood. The panel also highlighted the discovery potential of time-domain astronomy and astrometry with powerful new techniques and facilities to greatly advance our understanding of the precise connections among stars, galaxies, and newly dis- covered transient events. The relevant needs for laboratory astrophysics will be emphasized, especially in the context of supporting NASA missions.

Active Galactic Nucleus

NASA Image and Video Library

2017-09-14

SCI2017_0007: Artist illustration of the thick ring of dust that can obscure the energetic processes that occur near the supermassive black hole of an active galactic nuclei. The SOFIA studies suggest that the dust distribution is about 30 percent smaller than previously thought. Credit: NASA/SOFIA/Lynette Cook

Synthetic Jets in Cross-flow. Part 1; Round Jet

NASA Technical Reports Server (NTRS)

Zaman, K. B. M. Q.; Milanovic, Ivana M.

2003-01-01

Results of an experimental investigation on synthetic jets from round orifices with and without cross-flow are presented. Jet Reynolds number up to 46,000 with a fully turbulent approach boundary layer, and Stokes number up to 400. are covered. The threshold of stroke length for synthetic jet formation. in the absence of the cross-flow, is found to be Lo /D approximately 0.5. Above Lo /D is approximately 10, the profiles of normalized centerline mean velocity appear to become invariant. It is reasoned that the latter threshold may be related to the phenomenon of saturation of impulsively generated vortices. In the presence of the cross-flow, the penetration height of a synthetic jet is found to depend on the momentum- flux ratio . When this ratio is defined in terms of the maximum jet velocity and the cross-flow velocity. not only all data collapse but also the jet trajectory is predicted well by correlation equation available for steady jets-in-cross-flow. Distributions of mean velocity, streamwise vorticity as well as turbulence intensity for a synthetic jet in cross-flow are found to be similar to those of a steady jet-in-cross-flow. A pair of counter-rotating streamwise vortices, corresponding to the bound vortex pair of the steady case, is clearly observed. Mean velocity distribution exhibits a dome of low momentum fluid pulled up from the boundary layer, and the entire domain is characterized by high turbulence.

Multiple jet study data correlations. [data correlation for jet mixing flow of air jets

NASA Technical Reports Server (NTRS)

Walker, R. E.; Eberhardt, R. G.

1975-01-01

Correlations are presented which allow determination of penetration and mixing of multiple cold air jets injected normal to a ducted subsonic heated primary air stream. Correlations were obtained over jet-to-primary stream momentum flux ratios of 6 to 60 for locations from 1 to 30 jet diameters downstream of the injection plane. The range of geometric and operating variables makes the correlations relevant to gas turbine combustors. Correlations were obtained for the mixing efficiency between jets and primary stream using an energy exchange parameter. Also jet centerplane velocity and temperature trajectories were correlated and centerplane dimensionless temperature distributions defined. An assumption of a Gaussian vertical temperature distribution at all stations is shown to result in a reasonable temperature field model. Data are presented which allow comparison of predicted and measured values over the range of conditions specified above.

The structure and content of the galaxy and galactic gamma rays. [conferences

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Stecker, F. W.

1976-01-01

Papers are presented dealing with galactic structure drawing on all branches of galactic astronomy with emphasis on the implications of the new gamma ray observations. Topics discussed include: (1) results from the COS-B gamma ray satellite; (2) results from SAS-2 on gamma ray pulsar, Cygnus X-3, and maps of the galactic diffuse flux; (3) recent data from CO surveys of the galaxy; (4) high resolution radio surveys of external galaxies; (5) results on the galactic distribution of pulsars; and (6) theoretical work on galactic gamma ray emission.

Orbital Evolution of Planetesimals by the Galactic Tide

NASA Astrophysics Data System (ADS)

Higuchi, A.; Kokubo, E.; Mukai, T.

2005-05-01

The Oort cloud is a spherical comet reservoir surrounding the solar system. There is general agreement that the Oort cloud comets are the residual planetesimals of planet formation. The standard scenario of the Oort cloud formation consists of two dynamical stages: (1) giant planets raise the aphelia of planetesimals to the outer region of the solar system and (2) the galactic tide, passing stars, and giant molecular clouds pull up their perihelia out of the planetary region. Here we show the orbital evolution of planetesimals by the galactic tide. Planetesimals with large aphelion distances change their perihelion distances toward the outside of the planetary region by the galactic tide and become members of the Oort cloud. The effect of the galactic tide on the planetesimals with semimajor axes of ˜ 104AU is about 10-3 of the solar gravity. The timescale of the orbital evolution is ˜ 108 years. We consider only the vertical component of the galactic tide. Under the axisymmetric potential, some planetesimals may show the librations around ω (argument of perihelion)=π /2 and 3π /2 (the Kozai mechanism). The alternate increases of eccentricity and inclination of the Kozai mechanism are effective to form the Oort cloud. The secular perturbation theory demonstrates the Kozai mechanism and we can understand the motion of the planetesimals analytically. We apply the Kozai mechanism to the galactic tide and discuss the property of the Oort cloud formed by the Kozai mechanizm. This work was supported by the 21st Century COE Program Origin and Evolution of Planetary Systems of the Ministry of Education, Culture, Sports, Science, and Technology, Japan, and JSPS Research Fellowship for Young Scientists.

Active Region Jets II: Triggering and Evolution of Violent Jets

NASA Astrophysics Data System (ADS)

Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David; Panesar, Navdeep K.; Martinez, Francisco

2017-08-01

We study a series of X-ray-bright, rapidly evolving active-region coronal jets outside the leading sunspot of AR 12259, using Hinode/XRT, SDO/AIA and HMI, and IRIS/SJ data. The detailed evolution of such rapidly evolving “violent” jets remained a mystery after our previous investigation of active region jets (Sterling et al. 2016, ApJ, 821, 100). The jets we investigate here erupt from three localized subregions, each containing a rapidly evolving (positive) minority-polarity magnetic-flux patch bathed in a (majority) negative-polarity magnetic-flux background. At least several of the jets begin with eruptions of what appear to be thin (thickness ˜<2‧‧) miniature-filament (minifilament) “strands” from a magnetic neutral line where magnetic flux cancelation is ongoing, consistent with the magnetic configuration presented for coronal-hole jets in Sterling et al. (2015, Nature, 523, 437). For some jets strands are difficult/ impossible to detect, perhaps due to their thinness, obscuration by surrounding bright or dark features, or the absence of erupting cool-material minifilaments in those jets. Tracing in detail the flux evolution in one of the subregions, we find bursts of strong jetting occurring only during times of strong flux cancelation. Averaged over seven jetting episodes, the cancelation rate was ~1.5×10^19 Mx/hr. An average flux of ~5×10^18 Mx canceled prior to each episode, arguably building up ~10^28—10^29 ergs of free magnetic energy per jet. From these and previous observations, we infer that flux cancelation is the fundamental process responsible for the pre-eruption buildup and triggering of at least many jets in active regions, quiet regions, and coronal holes.

Detection of sulphur in the galactic center

NASA Technical Reports Server (NTRS)

Herter, T.; Briotta, D. A., Jr.; Gull, G. E.; Shure, M. A.; Houck, J. R.

1983-01-01

A strong detection at the (SIII) 18.71 micron line is reported for the Galactic Center region, Sgr A West. A line flux of 1.7 + or - 0.2x10 to the -17th power W cm(-2) is found for a 20-arc second beam-size measurement centered on IRS 1. A preliminary analysis indicates that the SIII abundance relative to hydrogen is consistent with the cosmic abundance of sulfur, 1.6x10 to the -5th power, if a filling factor of unity within the known clumps is assumed. However, the sulfur abundance in the Galactic Center may be as much as a factor of 3 overabundant if a filling factor of 0.03 is adopted, a value found to hold for some galactic HII regions.

Photometric Evidence for a Disc-Jet Connection in CH Cygni

NASA Astrophysics Data System (ADS)

Sokoloski, J. L.; Kenyon, S. J.

2001-12-01

We describe observations of the rapid optical variations of the symbiotic star CH Cygni on 12 nights between 1997 and 1999. The B-band differential light curves reveal an incredible diversity of flickering behavior, from large-amplitude (up to 0.5 mag) variations with a power-law power spectrum, to lower amplitude (0.1 mag) variations with both power-law and non-power-law power spectra, to the complete absence of rapid variations down to a level of mmag. The series of light curves from observations in 1997/1998 exhibit an evolution from smooth, low-amplitude variations, to high-amplitude flickering with power at all measurable time scales. This evolution may be showing us the re-creation of the inner accretion disc after its disruption in association with the jet that was produced in early 1997 (Karovska et al. 1998). We do not find any evidence for quasi-periodic oscillations in the power spectra of individual light curves, and we believe the instances in which flickering completely disappeared coincide with eclipse of the white dwarf and accretion disc. We discuss the implications of our results for magnetic propeller models of this system, as well as compare CH Cygni to other systems where disc-jet connections have been proposed, such as the Galactic microquasar GRS 1915+105. This work was funded in part by NSF grant INT-9902665 to J.L.S.

Active control of continuous air jet with bifurcated synthetic jets

NASA Astrophysics Data System (ADS)

Dančová, Petra; Vít, Tomáš; Jašíková, Darina; Novosád, Jan

The synthetic jets (SJs) have many significant applications and the number of applications is increasing all the time. In this research the main focus is on the primary flow control which can be used effectively for the heat transfer increasing. This paper deals with the experimental research of the effect of two SJs worked in the bifurcated mode used for control of an axisymmetric air jet. First, the control synthetic jets were measured alone. After an adjustment, the primary axisymmetric jet was added in to the system. For comparison, the primary flow without synthetic jets control was also measured. All experiments were performed using PIV method whereby the synchronization between synthetic jets and PIV system was necessary to do.

Radioactivity in the galactic plane

NASA Technical Reports Server (NTRS)

Walraven, G. D.; Haymes, R. C.

1976-01-01

The paper reports the detection of a large concentration of interstellar radioactivity during balloon-altitude measurements of gamma-ray energy spectra in the band between 0.02 and 12.27 MeV from galactic and extragalactic sources. Enhanced counting rates were observed in three directions towards the plane of the Galaxy; a power-law energy spectrum is computed for one of these directions (designated B 10). A large statistical deviation from the power law in a 1.0-FWHM interval centered near 1.16 MeV is discussed, and the existence of a nuclear gamma-ray line at 1.15 MeV in B 10 is postulated. It is suggested that Ca-44, which emits gamma radiation at 1.156 MeV following the decay of radioactive Sc-44, is a likely candidate for this line, noting that Sc-44 arises from Ti-44 according to explosive models of supernova nucleosynthesis. The 1.16-MeV line flux inferred from the present data is shown to equal the predicted flux for a supernova at a distance of approximately 3 kpc and an age not exceeding about 100 years.

Starburst clusters in the Galactic center

NASA Astrophysics Data System (ADS)

Habibi, Maryam

2014-09-01

The central region of the Galaxy is the most active site of star formation in the Milky Way, where massive stars have formed very recently and are still forming today. The rich population of massive stars in the Galactic center provide a unique opportunity to study massive stars in their birth environment and probe their initial mass function, which is the spectrum of stellar masses at their birth. The Arches cluster is the youngest among the three massive clusters in the Galactic center, providing a collection of high-mass stars and a very dense core which makes this cluster an excellent site to address questions about massive star formation, the stellar mass function and the dynamical evolution of massive clusters in the Galactic center. In this thesis, I perform an observational study of the Arches cluster using K_{s}-band imaging obtained with NAOS/CONICA at the VLT combined with Subaru/Cisco J-band data to gain a full understanding of the cluster mass distribution out to its tidal radius for the first time. Since the light from the Galactic center reaches us through the Galactic disc, the extinction correction is crucial when studying this region. I use a Bayesian method to construct a realistic extinction map of the cluster. It is shown in this study that the determination of the mass of the most massive star in the Arches cluster, which had been used in previous studies to establish an upper mass limit for the star formation process in the Milky Way, strongly depends on the assumed slope of the extinction law. Assuming the two regimes of widely used infrared extinction laws, I show that the difference can reach up to 30% for individually derived stellar masses and Δ A_{Ks}˜ 1 magnitude in acquired K_{s}-band extinction, while the present-day mass function slope changes by ˜ 0.17 dex. The present-day mass function slope derived assuming the more recent extinction law, which suggests a steeper wavelength dependence for the infrared extinction law, reveals

Intra-jet shocks in two counter-streaming, weakly collisional plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryutov, D. D.; Kugland, N. L.; Park, H.-S.

2012-07-15

Counterstreaming laser-generated plasma jets can serve as a test-bed for the studies of a variety of astrophysical phenomena, including collisionless shock waves. In the latter problem, the jet's parameters have to be chosen in such a way as to make the collisions between the particles of one jet with the particles of the other jet very rare. This can be achieved by making the jet velocities high and the Coulomb cross-sections correspondingly low. On the other hand, the intra-jet collisions for high-Mach-number jets can still be very frequent, as they are determined by the much lower thermal velocities of themore » particles of each jet. This paper describes some peculiar properties of intra-jet hydrodynamics in such a setting: the steepening of smooth perturbations and shock formation affected by the presence of the 'stiff' opposite flow; the role of a rapid electron heating in shock formation; ion heating by the intrajet shock. The latter effect can cause rapid ion heating which is consistent with recent counterstreaming jet experiments by Ross et al.[Phys. Plasmas 19, 056501 (2012)].« less

Rapid Confined Mixing Using Transverse Jets Part 2: Multiple Jets

NASA Astrophysics Data System (ADS)

Forliti, David; Salazar, David

2012-11-01

An experimental study has been conducted at the Air Force Research Laboratory at Edwards Air Force Base to investigate the properties of confined mixing devices that employ transverse jets. The experiment considers the mixing of water with a mixture of water and fluorescein, and planar laser induced fluorescence was used to measure instantaneous mixture fraction distributions in the cross section view. Part one of this study presents the scaling law development and results for a single confined transverse jet. Part two will describe the results of configurations including multiple transverse jets. The different regimes of mixing behavior, ranging from under to overpenetration of the transverse jets, are characterized in terms of a new scaling law parameter presented in part one. The level of unmixedness, a primary metric for mixing device performance, is quantified for different jet diameters, number of jets, and relative flow rates. It is apparent that the addition of a second transverse jet provides enhanced scalar uniformity in the main pipe flow cross section compared to a single jet. Three and six jet configurations also provide highly uniform scalar distributions. Turbulent scalar fluctuation intensities, spectral features, and spatial eigenfunctions using the proper orthogonal decomposition will be presented. Distribution A: Public Release, Public Affairs Clearance Number: 12656.

Diffuse Galactic gamma rays from shock-accelerated cosmic rays.

PubMed

Dermer, Charles D

2012-08-31

A shock-accelerated particle flux is proportional to p(-s), where p is the particle momentum, follows from simple theoretical considerations of cosmic-ray acceleration at nonrelativistic shocks followed by rigidity-dependent escape into the Galactic halo. A flux of shock-accelerated cosmic-ray protons with s≈2.8 provides an adequate fit to the Fermi Large Area Telescope γ-ray emission spectra of high-latitude and molecular cloud gas when uncertainties in nuclear production models are considered. A break in the spectrum of cosmic-ray protons claimed by Neronov, Semikoz, and Taylor [Phys. Rev. Lett. 108, 051105 (2012)] when fitting the γ-ray spectra of high-latitude molecular clouds is a consequence of using a cosmic-ray proton flux described by a power law in kinetic energy.

Galactic Abundance Patterns via Peimbert Types I & II Planetary Nebulae

NASA Astrophysics Data System (ADS)

Milingo, J. B.; Barnes, K. L.; Kwitter, K. B.; Souza, S. P.; Henry, R. B. C.; Skinner, J. N.

2005-12-01

Planetary Nebulae (PNe) are well known fonts of information about both stellar evolution and galactic chemical evolution. Abundance patterns in PNe are used to note signatures and constraints of nuclear processing, and as tracers of the distribution of metals throughout galaxies. In this poster abundance gradients and heavy element ratios are presented based upon newly acquired spectrophotometry of a sample of Galactic Peimbert Type I PNe. This new data set is extracted from spectra that extend from λ 3600 - 9600Å allowing the use of [S III] features at λ 9069 and 9532Å. Since a significant portion of S in PNe resides in S+2 and higher ionization stages, including these features improves the extrapolation from observed ion abundances to total element abundance. An alternate metallicity tracer, Sulfur is precluded from enhancement and depletion across the range of PNe progenitor masses. Its stability in intermediate mass stars makes it a useful tool to probe the natal conditions as well as the evolution of PNe progenitors. This is a continuation of our Type II PNe work, the impetus being to compile a relatively large set of line strengths and abundances with internally consistent observation, reduction, calibration, and abundance determination, minimizing systematic affects that come from compiling various data sets. This research is supported by the AAS Small Research Grants program, the Franklin & Marshall Committee on Grants, and NSF grant AST-0307118.

Turbulence measurements in axisymmetric jets of air and helium. I - Air jet. II - Helium jet

NASA Technical Reports Server (NTRS)

Panchapakesan, N. R.; Lumley, J. L.

1993-01-01

Results are presented of measurements on turbulent round jets of air and of helium of the same nozzle momentum efflux, using, for the air jets, x-wire hot-wire probes mounted on a moving shuttle and, for He jets, a composite probe consisting of an interference probe of the Way-Libby type and an x-probe. Current models for scalar triple moments were evaluated. It was found that the performance of the model termed the Full model, which includes all terms except advection, was very good for both the air and the He jets.

Search for anomalous C-jets in Chacaltaya emulsion chamber experiment

NASA Technical Reports Server (NTRS)

Kumano, H.

1985-01-01

Anomalous C-jets were measured in Chacaltaya emulsion chamber No.17. Measurement of 150 C-jets nuclear interactions occured in the target layer in the chamber itself with total visible energy greater than 5 TeV was completed. they are recorded in area of 11 sq m, corresponding to 17.1 sq m year exposure. Among them, seven events have no pinaught and two events are peculiar in that three showers out of four show abnormal cascade development. Two show remarkable characteristics indicating that they are coming from exotic interactions in the target layer. Illustrations of these events are presented and the thresholds of this type of event are discussed.

Spiral jet

NASA Astrophysics Data System (ADS)

Istomin, Ya N.

2018-05-01

We show that a quasi-cylindrical configuration of a jet in the central region, where direct electric current flows, is confined in a radial equilibrium by a spiral wave at the periphery of a jet. A spiral wave means that in a coordinate system moving with the velocity of the matter along the axis of the jet, all quantities are proportional to exp {ik∥z + imϕ}, z is the longitudinal coordinate, and ϕ is the azimuthal angle. The luminosity of such a jet corresponds to observations. It is also shown that the jet slowly expands with distance z from its base by the power law, R(z) ∝ zk, where the exponent k varies from ≃0.5 to ≃1.

A jet-dominated model for a broad-band spectral energy distribution of the nearby low-luminosity active galactic nucleus in M94

NASA Astrophysics Data System (ADS)

van Oers, Pieter; Markoff, Sera; Uttley, Phil; McHardy, Ian; van der Laan, Tessel; Donovan Meyer, Jennifer; Connors, Riley

2017-06-01

We have compiled a new multiwavelength spectral energy distribution (SED) for the closest obscured low-ionization emission-line region active galactic nucleus (AGN), NGC 4736, also known as M94. The SED comprises mainly high-resolution (mostly sub-arcsecond, or, at the distance to M94, ≲23 pc from the nucleus) observations from the literature, archival data, as well as previously unpublished sub-millimetre data from the Plateau de Bure Interferometer (PdBI) and the Combined Array for Research in Millimeter-wave Astronomy, in conjunction with new electronic MultiElement Radio Interferometric Network (e-MERLIN) L-band (1.5 GHz) observations. Thanks to the e-MERLIN resolution and sensitivity, we resolve for the first time a double structure composed of two radio sources separated by ˜1 arcsec, previously observed only at higher frequency. We explore this data set, which further includes non-simultaneous data from the Very Large Array, the Gemini telescope, the Hubble Space Telescope and the Chandra X-ray observatory, in terms of an outflow-dominated model. We compare our results with previous trends found for other AGN using the same model (NGC 4051, M81*, M87 and Sgr A*), as well as hard- and quiescent-state X-ray binaries. We find that the nuclear broad-band spectrum of M94 is consistent with a relativistic outflow of low inclination. The findings in this work add to the growing body of evidence that the physics of weakly accreting black holes scales with mass in a rather straightforward fashion.

A Simple test for the existence of two accretion modes in active galactic nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jester, Sebastian; /Fermilab

2005-02-01

By analogy to the different accretion states observed in black-hole X-ray binaries (BHXBs), it appears plausible that accretion disks in active galactic nuclei (AGN) undergo a state transition between a radiatively efficient and inefficient accretion flow. If the radiative efficiency changes at some critical accretion rate, there will be a change in the distribution of black hole masses and bolometric luminosities at the corresponding transition luminosity. To test this prediction, the author considers the joint distribution of AGN black hole masses and bolometric luminosities for a sample taken from the literature. The small number of objects with low Eddington-scaled accretionmore » rates m < 0.01 and black hole masses M{sub BH} < 10{sup 9} M{sub {circle_dot}} constitutes tentative evidence for the existence of such a transition in AGN. Selection effects, in particular those associated with flux-limited samples, systematically exclude objects in particular regions of the (M{sub BH}, L{sub bol}) plane. Therefore, they require particular attention in the analysis of distributions of black hole mass, bolometric luminosity, and derived quantities like the accretion rate. The author suggests further observational tests of the BHXB-AGN unification scheme which are based on the jet domination of the energy output of BHXBs in the hard state, and on the possible equivalence of BHXB in the very high (or steep power-law) state showing ejections and efficiently accreting quasars and radio galaxies with powerful radio jets.« less

Characterizing the Optical Variability of Bright Blazars: Variability-based Selection of Fermi Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Ruan, John J.; Anderson, Scott F.; MacLeod, Chelsea L.; Becker, Andrew C.; Burnett, T. H.; Davenport, James R. A.; Ivezić, Željko; Kochanek, Christopher S.; Plotkin, Richard M.; Sesar, Branimir; Stuart, J. Scott

2012-11-01

We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the ~30% of γ-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability τ, and driving amplitudes on short timescales \\hat{\\sigma }. Imposing cuts on minimum τ and \\hat{\\sigma } allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of γ-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously associated optical counterparts to Fermi active galactic nuclei with E >= 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8'. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other γ-ray blazars and is likely to be the γ-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is ~3 years in the rest frame of the jet, in contrast with the ~320 day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys and is also a probe of jet physics.

A NEW PERSPECTIVE OF THE RADIO BRIGHT ZONE AT THE GALACTIC CENTER: FEEDBACK FROM NUCLEAR ACTIVITIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jun-Hui; Morris, Mark R.; Goss, W. M., E-mail: jzhao@cfa.harvard.edu

2016-02-01

New observations of Sgr A have been carried out with the Jansky VLA in the B and C arrays using the broadband (2 GHz) continuum mode at 5.5 GHz. The field of view covers the central 13′ (30 pc) region of the radio-bright zone at the Galactic center. Using the multi-scale and multi-frequency-synthesis (MS-MFS) algorithms in CASA, we have imaged Sgr A with a resolution of 1″, achieving an rms noise of 8 μJy beam{sup −1}, and a dynamic range of 100,000:1. Both previously known and newly identified radio features in this region are revealed, including numerous filamentary sources. The radiomore » continuum image is compared with Chandra X-ray images, with a CN emission-line image obtained with the Submillimeter Array and with detailed Paschen-α images obtained with Hubble Space Telescope/NICMOS. We discuss several prominent features in the radio image. The “Sgr A west Wings” extend 2′ (5 pc) from the NW and SE tips of the Sgr A west H ii region (the “Mini-spiral”) to positions located 2.9 and 2.4 arcmin to the northwest and southeast of Sgr A*, respectively. The NW wing, along with several other prominent features, including the previously identified “NW Streamers,” form an elongated radio lobe (NW lobe), oriented nearly perpendicular to the Galactic plane. This radio lobe, with a size of 6.′3 × 3.′2 (14.4 pc × 7.3 pc), has a known X-ray counterpart. In the outer region of the NW lobe, a row of three thermally emitting rings is observed. A field containing numerous amorphous radio blobs extends for a distance of ∼2 arcmin beyond the tip of the SE wing; these newly recognized features coincide with the SE X-ray lobe. Most of the amorphous radio blobs in the NW and SE lobes have Paschen-α counterparts. We propose that they have been produced by shock interaction of ambient gas concentrations with a collimated nuclear wind or an outflow that originated from within the circumnuclear disk (CND). We also discuss the possibility that the

A New Perspective of the Radio Bright Zone at The Galactic Center: Feedback from Nuclear Activities

NASA Astrophysics Data System (ADS)

Zhao, Jun-Hui; Morris, Mark R.; Goss, W. M.

2016-02-01

New observations of Sgr A have been carried out with the Jansky VLA in the B and C arrays using the broadband (2 GHz) continuum mode at 5.5 GHz. The field of view covers the central 13‧ (30 pc) region of the radio-bright zone at the Galactic center. Using the multi-scale and multi-frequency-synthesis (MS-MFS) algorithms in CASA, we have imaged Sgr A with a resolution of 1″, achieving an rms noise of 8 μJy beam-1, and a dynamic range of 100,000:1. Both previously known and newly identified radio features in this region are revealed, including numerous filamentary sources. The radio continuum image is compared with Chandra X-ray images, with a CN emission-line image obtained with the Submillimeter Array and with detailed Paschen-α images obtained with Hubble Space Telescope/NICMOS. We discuss several prominent features in the radio image. The “Sgr A west Wings” extend 2‧ (5 pc) from the NW and SE tips of the Sgr A west H II region (the “Mini-spiral”) to positions located 2.9 and 2.4 arcmin to the northwest and southeast of Sgr A*, respectively. The NW wing, along with several other prominent features, including the previously identified “NW Streamers,” form an elongated radio lobe (NW lobe), oriented nearly perpendicular to the Galactic plane. This radio lobe, with a size of 6.‧3 × 3.‧2 (14.4 pc × 7.3 pc), has a known X-ray counterpart. In the outer region of the NW lobe, a row of three thermally emitting rings is observed. A field containing numerous amorphous radio blobs extends for a distance of ˜2 arcmin beyond the tip of the SE wing; these newly recognized features coincide with the SE X-ray lobe. Most of the amorphous radio blobs in the NW and SE lobes have Paschen-α counterparts. We propose that they have been produced by shock interaction of ambient gas concentrations with a collimated nuclear wind or an outflow that originated from within the circumnuclear disk (CND). We also discuss the possibility that the ionized wind or

Rapid Confined Mixing with Transverse Jets Part 1: Single Jet

NASA Astrophysics Data System (ADS)

Salazar, David; Forliti, David

2012-11-01

Transverse jets have been studied extensively due to their relevance and efficiency in fluid mixing applications. Gas turbine burners, film cooling, and chemical reactors are some examples of rapid transverse jet mixing. Motivated by a lack of universal scaling laws for confined and unconfined transverse jets, a newly developed momentum transfer parameter was found to improve correlation of literature data. Jet column drag and entrainment arguments for momentum transfer are made to derive the parameter. A liquid-phase mixing study was conducted to investigate confined mixing for a low number of jets. Planar laser induced fluorescence was implemented to measure mixture fraction for a single confined transverse jet. Time-averaged cross-sectional images were taken with a light sheet located three diameters downstream of transverse injection. A mixture of water and sodium fluorescein was used to distinguish jet fluid from main flow fluid for the test section images. Image data suggest regimes for under- and overpenetration of jet fluid into the main flow. The scaling parameter is found to correlate optimum unmixedness for multiple diameter ratios at a parameter value of 0.75. Distribution A: Public Release, Public Affairs Clearance Number: 12655.

Understanding jet noise.

PubMed

Karabasov, S A

2010-08-13

Jets are one of the most fascinating topics in fluid mechanics. For aeronautics, turbulent jet-noise modelling is particularly challenging, not only because of the poor understanding of high Reynolds number turbulence, but also because of the extremely low acoustic efficiency of high-speed jets. Turbulent jet-noise models starting from the classical Lighthill acoustic analogy to state-of-the art models were considered. No attempt was made to present any complete overview of jet-noise theories. Instead, the aim was to emphasize the importance of sound generation and mean-flow propagation effects, as well as their interference, for the understanding and prediction of jet noise.

Heavy and light flavor jet quenching at RHIC and LHC energies

NASA Astrophysics Data System (ADS)

Cao, Shanshan; Luo, Tan; Qin, Guang-You; Wang, Xin-Nian

2018-02-01

The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark-gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. The dependence of the jet quenching parameter q ˆ on medium temperature and jet flavor is quantitatively extracted.

JASMINE: constructor of the dynamical structure of the Galactic bulge

NASA Astrophysics Data System (ADS)

Gouda, N.; Kobayashi, Y.; Yamada, Y.; Yano, T.; Tsujimoto, T.; Suganuma, M.; Niwa, Y.; Yamauchi, M.

2008-07-01

We introduce a Japanese space astrometry project which is called JASMINE. JASMINE (Japan Astrometry Satellite Mission for INfrared Exploration) will measure distances and tangential motions of stars in the Galactic bulge with yet unprecedented precision. JASMINE will operate in z-band whose central wavelength is 0.9 micron. It will measure parallaxes, positions with accuracy of about 10 micro-arcsec and proper motions with accuracy of about 10 micro- arcsec/year for the stars brighter than z=14 mag. The number of stars observed by JASMINE with high accuracy of parallaxes in the Galactic bulge is much larger than that observed in other space astrometry projects operating in optical bands. With the completely new “map of the Galactic bulge” including motions of bulge stars, we expect that many new exciting scientific results will be obtained in studies of the Galactic bulge. One of them is the construction of the dynamical structure of the Galactic bulge. Kinematics and distance data given by JASMINE are the closest approach to a view of the exact dynamical structure of the Galactic bulge. Presently, JASMINE is in a development phase, with a target launch date around 2016. We comment on the outline of JASMINE mission, scientific targets and a preliminary design of JASMINE in this paper.

How supernovae launch galactic winds?

NASA Astrophysics Data System (ADS)

Fielding, Drummond; Quataert, Eliot; Martizzi, Davide; Faucher-Giguère, Claude-André

2017-09-01

We use idealized three-dimensional hydrodynamic simulations of global galactic discs to study the launching of galactic winds by supernovae (SNe). The simulations resolve the cooling radii of the majority of supernova remnants (SNRs) and thus self-consistently capture how SNe drive galactic winds. We find that SNe launch highly supersonic winds with properties that agree reasonably well with expectations from analytic models. The energy loading (η _E= \\dot{E}_wind/ \\dot{E}_SN) of the winds in our simulations are well converged with spatial resolution while the wind mass loading (η _M= \\dot{M}_wind/\\dot{M}_\\star) decreases with resolution at the resolutions we achieve. We present a simple analytic model based on the concept that SNRs with cooling radii greater than the local scaleheight break out of the disc and power the wind. This model successfully explains the dependence (or lack thereof) of ηE (and by extension ηM) on the gas surface density, star formation efficiency, disc radius and the clustering of SNe. The winds our simulations are weaker than expected in reality, likely due to the fact that we seed SNe preferentially at density peaks. Clustering SNe in time and space substantially increases the wind power.

Clues from Bent Jets

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-04-01

Powerful jets emitted from the centers of distant galaxies make for spectacular signposts in the radio sky. Can observations of these jets reveal information about the environments that surround them?Signposts in the SkyVLA FIRST images of seven bent double-lobed radio galaxies from the authors sample. [Adapted from Silverstein et al. 2018]An active supermassive black hole lurking in a galactic center can put on quite a show! These beasts fling out accreting material, often forming intense jets that punch their way out of their host galaxies. As the jets propagate, they expand into large lobes of radio emission that we can spot from Earth observable signs of the connection between distant supermassive black holes and the galaxies in which they live.These distinctive double-lobed radio galaxies (DLRGs) dont all look the same. In particular, though the jets are emitted from the black holes two poles, the lobes of DLRGs dont always extend perfectly in opposite directions; often, the jets become bent on larger scales, appearing to us to subtend angles of less than 180 degrees.Can we use our observations of DLRG shapes and distributions to learn about their surroundings? A new study led by Ezekiel Silverstein (University of Michigan) has addressed this question by exploring DLRGs living in dense galaxy-cluster environments.Projected density of DLRGcentral galaxy matches (black) compared to a control sample of random positionscentral galaxy matches (red) for different distances from acluster center. DLRGs have a higher likelihood of being located close to a cluster center. [Silverstein et al. 2018]Living Near the HubTo build a sample of DLRGs in dense environments, Silverstein and collaborators started from a large catalog of DLRGs in Sloan Digital Sky Survey quasars with radio lobes visible in Very Large Array data. They then cross-matched these against three galaxy catalogs to produce a sample of 44 DLRGs that are each paired to a nearby massive galaxy, galaxy group

New detections of embedded clusters in the Galactic halo

NASA Astrophysics Data System (ADS)

Camargo, D.; Bica, E.; Bonatto, C.

2016-09-01

Context. Until recently it was thought that high Galactic latitude clouds were a non-star-forming ensemble. However, in a previous study we reported the discovery of two embedded clusters (ECs) far away from the Galactic plane (~ 5 kpc). In our recent star cluster catalogue we provided additional high and intermediate latitude cluster candidates. Aims: This work aims to clarify whether our previous detection of star clusters far away from the disc represents just an episodic event or whether star cluster formation is currently a systematic phenomenon in the Galactic halo. We analyse the nature of four clusters found in our recent catalogue and report the discovery of three new ECs each with an unusually high latitude and distance from the Galactic disc midplane. Methods: The analysis is based on 2MASS and WISE colour-magnitude diagrams (CMDs), and stellar radial density profiles (RDPs). The CMDs are built by applying a field-star decontamination procedure, which uncovers the cluster's intrinsic CMD morphology. Results: All of these clusters are younger than 5 Myr. The high-latitude ECs C 932, C 934, and C 939 appear to be related to a cloud complex about 5 kpc below the Galactic disc, under the Local arm. The other clusters are above the disc, C 1074 and C 1100 with a vertical distance of ~3 kpc, C 1099 with ~ 2 kpc, and C 1101 with ~1.8 kpc. Conclusions: According to the derived parameters ECs located below and above the disc occur, which gives evidence of widespread star cluster formation throughout the Galactic halo. This study therefore represents a paradigm shift, by demonstrating that a sterile halo must now be understood as a host for ongoing star formation. The origin and fate of these ECs remain open. There are two possibilities for their origin, Galactic fountains or infall. The discovery of ECs far from the disc suggests that the Galactic halo is more actively forming stars than previously thought. Furthermore, since most ECs do not survive the infant

Control of jet noise

NASA Technical Reports Server (NTRS)

Schreck, Stefan

1993-01-01

This reports describes experiments conducted at the High-Speed Jet Facility at the University of Southern California on supersonic jets. The goal of the study was to develop methods for controlling the noise emitted from supersonic jets by passive and/or active means. Work by Seiner et al (1991) indicates that eddy Mach wave radiation is the dominant noise source in a heated high speed jet. Eddy Mach radiation is caused by turbulent eddies traveling at supersonic speed in the shear layer of the jet. The convection velocity of the eddies decays with increasing distance from the nozzle exit due to the mixing of the jet stream with the ambient fluid. Once the convection speed reaches subsonic velocities, eddy Mach wave radiation ceases. To control noise, a rapid decay of the convection velocity is desired. This may be accomplished by enhanced mixing in the jet. In this study, small aspect ratio rectangular jet nozzles were tested. A flapping mode was noticed in the jets. By amplifying screech components of the jets and destabilizing the jet columns with a collar device, the flapping mode was excited. The result was a rapid decay of the jet velocity. A reduction in eddy Mach radiation in rectangular supersonic jets may be achieved with this device.

Exotic interactions among C-jets and Pb-jets

NASA Technical Reports Server (NTRS)

1985-01-01

The C-jets and Pb-jets were surveyed on the part of Chacaltaya emulsion chamber No.19 amounting to an exposure of 28.8 sq m yr. It is shown that the adopted events make up an unbiased sample of C-jets for sigma sub E gamma TeV. Mini-Centauro interaction gives the most natural explanation for the eight pinaught-less C-jets with three or more constituent shower core. Out of the eight double-cored pinaught-less events, three are found to have visible invariant masses 1.8 GeV/c. Three Pb-jets-lower are composed of double cores whose respective visible transverse momenta are greater than 0.5 GeV/c, suggesting that they are of Geminion origin or chiron origin. The energies of the parent particles are estimated to be 100 to 200 TeV for all three kinds of events. The implications of this energy estimate and the frequency of observed exotic events are discussed.

Blowout Jets: Hinode X-Ray Jets that Don't Fit the Standard Model

NASA Technical Reports Server (NTRS)

Moore, Ronald L.; Cirtain, Jonathan W.; Sterling, Alphonse C.; Falconer, David A.

2010-01-01

Nearly half of all H-alpha macrospicules in polar coronal holes appear to be miniature filament eruptions. This suggests that there is a large class of X-ray jets in which the jet-base magnetic arcade undergoes a blowout eruption as in a CME, instead of remaining static as in most solar X-ray jets, the standard jets that fit the model advocated by Shibata. Along with a cartoon depicting the standard model, we present a cartoon depicting the signatures expected of blowout jets in coronal X-ray images. From Hinode/XRT movies and STEREO/EUVI snapshots in polar coronal holes, we present examples of (1) X-ray jets that fit the standard model, and (2) X-ray jets that do not fit the standard model but do have features appropriate for blowout jets. These features are (1) a flare arcade inside the jet-base arcade in addition to the small flare arcade (bright point) outside that standard jets have, (2) a filament of cool (T is approximately 80,000K) plasma that erupts from the core of the jetbase arcade, and (3) an extra jet strand that should not be made by the reconnection for standard jets but could be made by reconnection between the ambient unipolar open field and the opposite-polarity leg of the filament-carrying flux-rope core field of the erupting jet-base arcade. We therefore infer that these non-standard jets are blowout jets, jets made by miniature versions of the sheared-core-arcade eruptions that make CMEs

Imprints to the terrestrial environment at galactic arm crossings of the solar system

NASA Astrophysics Data System (ADS)

Fahr, H. J.; Fichtner, H.; Scherer, K.; Stawicki, O.

At its itinerary through our milky way galaxy the solar system moves through highly variable interstellar environments. Due to its orbital revolution around the galactic center, the solar system also crosses periodically the spiral arms of our galactic plane and thereby expe riences pronounced enviromental changes. Gas densities, magnetic fields and galactic cosmic ray intensities are substantially higher there compared to interarm conditions. Here we present theoretical calculations describing the SN-averaged galactic cosmic ray spectrum for regions inside and outside of galactic arms which then allow to predict how periodic passages of the solar system through galactic arms should be reflected by enhanced particle irradiations of the earth`s atmosphere and by correlated terrestrial Be-10 production rates.

Velocity field near the jet orifice of a round jet in a crossflow

NASA Technical Reports Server (NTRS)

Fearn, R. L.; Benson, J. P.

1979-01-01

Experimentally determined velocities at selected locations near the jet orifice are presented and analyzed for a round jet in crossflow. Jet-to-crossflow velocity ratios of four and eight were studied experimentally for a round subsonic jet of air exhausting perpendicularly through a flat plate into a subsonic crosswind of the same temperature. Velocity measurements were made in cross sections to the jet plume located from one to four jet diameters from the orifice. Jet centerline and vortex properties are presented and utilized to extend the results of a previous study into the region close to the jet orifice.

A Precessing Jet in a Dying Star: Adaptive Optics Imaging of the ``Water-Fountain" Nebula IRAS16342-3814

NASA Astrophysics Data System (ADS)

Sahai, R.; Le Mignant, D.; Sánchez Contreras, C.; Campbell, R. D.; Chaffee, F. H.

2004-12-01

Collimated jets are one of the most intriguing, yet poorly understood phenomena in astrophysics. Jets have been found in a wide variety of object classes which include active galactic nuclei, young stellar objects, massive X-ray binaries, black hole X-ray transients, symbiotic stars, supersoft X-ray sources, and finally, planetary and preplanetary nebulae (PNe & PPNe). In the case of PNe and PPNe, it has been proposed that wobbling collimated jets may be the universal mechanism which can explain a wide variety of bipolar and multipolar morphologies seen in these objects (Sahai 2000, ASP Conf.Ser. 199, 209). The ``Water-Fountain Nebula'', IRAS16342-3814 (IRAS1634) belongs to a class of very young PPNe with high-velocity molecular outflows traced in either or both of radio H2O and OH maser line emission, and are believed to result from the interaction of fast jets with ambient circumstellar material shed by the AGB progenitors of these objects. Hubble Space Telescope (HST) imaging of IRAS1634 showed a small bipolar nebula, with the lobes separated by a dark equatorial waist (Sahai et al. 1999, ApJ, 514, L115) -- the morphology was interpreted as bubble-like reflection nebulae illuminated by starlight escaping through polar holes in a dense, dusty waist obscuring the central star, with the bubbles created by a fast jet-like outflow plowing into the AGB mass-loss envelope. Here we report Adaptive Optics (AO) observations with the W. M. Keck Observatory at near-infrared wavelengths (in the H, K', L', Ms bands) which probe much deeper into the lobes and reveal a remarkable corkscrew-shaped structure apparently etched into the lobe walls. The corkscrew structure represents the proverbial ``writing on the wall" signature of an underlying precessing jet, and we compare our results with predictions from published numerical simulations of such jets. The results shown provide a dramatic example of the power of ground-based AO imaging with large telescopes to uncover phenomena

The age of the galactic disk

NASA Technical Reports Server (NTRS)

Sandage, Allan

1988-01-01

The galactic disk is a dissipative structure and must, therefore be younger than the halo if galaxy formation generally proceeds by collapse. Just how much younger the oldest stars in the galactic disk are than the oldest halo stars remains an open question. A fast collapse (on a time scale no longer than the rotation period of the extended protogalaxy) permits an age gap of the order of approximately 10 to the 9th power years. A slow collapse, governed by the cooling rate of the partially pressure supported falling gas that formed into what is now the thick stellar disk, permits a longer age gap, claimed by some to be as long as 6 Gyr. Early methods of age dating the oldest components of the disk contain implicit assumptions concerning the details of the age-metallicity relation for stars in the solar neighborhood. The discovery that this relation for open clusters outside the solar circle is different that in the solar neighborhood (Geisler 1987), complicates the earlier arguments. The oldest stars in the galactic disk are at least as old as NGC 188. The new data by Janes on NGC 6791, shown first at this conference, suggest a disk age of at least 12.5 Gyr, as do data near the main sequence termination point of metal rich, high proper motion stars of low orbital eccentricity. Hence, a case can still be made that the oldest part of the galactic thick disk is similar in age to the halo globular clusters, if their ages are the same as 47 Tuc.

Conversion of gas into stars in the Galactic center

NASA Astrophysics Data System (ADS)

Longmore, S. N.

2014-05-01

The star formation rate in the central 500 pc of the Milky Way is lower by a factor of > 10 than expected for the substantial amount of dense gas it contains, which challenges current star formation theories. I discuss which physical mechanisms could be causing this observation and put forward a self-consistent cycle of star formation in the Galactic center, in which the plausible star formation inhibitors are combined. Their ubiquity suggests that the perception of a lowered central SFR should be a common phenomenon in other galaxies with direct implications for galactic star formation and also potentially supermassive black hole growth. I then describe a scenario to explain the presence of super star clusters in the Galactic center environment, in which their formation is triggered by gas streams passing close to the minimum of the global Galactic gravitational potential at the location of the central supermassive black hole, Sgr A*. If this triggering mechanism can be verified, we can use the known time interval since closest approach to Sgr A* to study the physics of stellar mass assembly in an extreme environment as a function of absolute time. I outline the first results from detailed numerical simulations testing this scenario. Finally, I describe a study showing that in terms of the baryonic composition, kinematics, and densities, the gas in the Galactic center is indistinguishable from high-redshift clouds and galaxies. As such, the Galactic center clouds may be used as a template to understand the evolution (and possibly the life cycle) of high-redshift clouds and galaxies.

Nuclear Gas Dynamics of NGC2110: A Black Hole Offset from the Host Galaxy Mass Center?

NASA Technical Reports Server (NTRS)

Mundell, C. G.; Ferruit, P.; Nagar, N.; Wilson, A. S.

2004-01-01

It has been suggested that the central regions of many galaxies are unlikely to be in a static steady state, with instabilities caused by sinking satellites, the influence of a supermassive black hole or residuals of galaxy formation, resulting in the nuclear black hole orbiting the galaxy center. The observational signature of such an orbiting black hole is an offset of the active nucleus (AGN) from the kinematic center defined by the galaxy rotation curve. This orbital motion may provide fuel for the AGN, as the hole 'grazes' on the ISM, and bent radio jets, due to the motion of their source. The early type (E/SO) Seyfert galaxy, NGC2210, with its striking twin, 'S'-shaped radio jets, is a unique and valuable test case for the offset-nucleus phenomenon since, despite its remarkably normal rotation curve, its kinematically-measured mass center is displaced both spatially (260 pc) and kinematically (170 km/s) from the active nucleus located in optical and radio studies. However, the central kinematics, where the rotation curve rises most steeply, have been inaccessible with ground-based resolutions. We present new, high resolution WFPC2 imaging and long-slit STIS spectroscopy of the central 300 pc of NGC2110. We discuss the structure and kinematics of gas moving in the galactic potential on subarcsecond scales and the reality of the offset between the black hole and the galaxy mass center.

Levels in N 12 via the N 14 ( p ,   t ) reaction using the JENSA gas-jet target

DOE PAGES

Chipps, K. A.; Pain, S. D.; Greife, U.; ...

2015-09-25

As one of a series of physics cases to demonstrate the unique benefit of the new Jet Experiments in Nuclear Structure and Astrophysics gas-jet target for enabling next-generation transfer reaction studies, the ¹⁴N (p, t)¹²N reaction was studied for the first time, using a pure jet of nitrogen, in an attempt to resolve conflicting information on the structure of ¹²N. A new level at 4.561-MeV excitation energy in ¹²N was found.

Massive stellar content of some Galactic supershells

NASA Astrophysics Data System (ADS)

Kaltcheva, Nadejda; Golev, Valeri

2015-08-01

The giant Galactic H II regions provide a unique opportunity to study the OB-star influence on the surrounding interstellar matter. In this contribution, several multi-wavelength surveys (Wisconsin H-α Mapper Northern Sky Survey, Southern H-α Sky Survey Atlas, MSX Mid-IR Galactic Plane Survey, WISE All-Sky Data Release, CO survey of the Milky Way, and the Southern Galactic Plane HI Survey) are combined with available intermediate-band uvbyβ photometry to attempt a precise spatial correlation between the OB-stars and the neutral and ionized material. Our study is focused on the H I supershell GSH 305+01-24 in Centaurus, the Car OB2 supershell, the Cygnus star-forming complex and the GSH 224-01+24 shell toward the GMN 39/Seagull nebula region. We refine the massive stellar content of these star-forming fields and study the energetics of its interaction with the shells’ material.

Jets in d (p )-A collisions: Color transparency or energy conservation

NASA Astrophysics Data System (ADS)

Kordell, Michael; Majumder, Abhijit

2018-05-01

The production of jets, and high momentum hadrons from jets, produced in deuteron-Au (d -Au) collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and proton-Pb (p -Pb) collisions at the CERN Large Hadron Collider (LHC) are studied as a function of centrality, a measure of the impact parameter of the collision. A modified version of the event generator pythia, widely used to simulate p -p collisions, is used in conjunction with a nuclear Monte Carlo event generator which simulates the locations of the nucleons within a large nucleus. We demonstrate how events with a hard jet may be simulated, in such a way that the parton distribution function of the projectile is "frozen" during its interaction with the extended nucleus. Using our approach, we demonstrate that the puzzling enhancement seen in peripheral events at RHIC and the LHC, as well as the suppression seen in central events at the LHC, are possibly due to mis-binning of central and semicentral events, containing a jet, as peripheral events. This occurs due to the suppression of soft particle production away from the jet, caused by the depletion of energy available in a nucleon of the deuteron (in d -Au at RHIC) or in the proton (in p -Pb at LHC), after the production of a hard jet. We conclude that partonic correlations built out of simple energy conservation are responsible for such an effect, though these are sampled at the hard scale of jet production and, as such, represent smaller states.

Opportunities for Geoscience Research Onboard Virgin Galactic's SpaceShipTwo

NASA Astrophysics Data System (ADS)

Pomerantz, W.; Beerer, I.; Stephens, K.; Griffith, J.; Persall, W.; Tizard, J.

2012-12-01

Virgin Galactic has developed a reusable spaceplane, called SpaceShipTwo (SS2), designed to make routine voyages into suborbital space. SS2 is air-launched from a jet aircraft at an altitude of 50,000 ft. before igniting its rocket motor engine. The vehicle reaches a maximum apogee as high as 110 km before gliding to a conventional runway landing. With the ability to fly multiple times per week, SS2 will be capable of providing routine access to a rarely sampled and poorly understood region of the atmosphere and ionosphere, making it a valuable platform for geoscience research. With a payload capacity up to 1300 lbs., SS2 provides access to space and the upper atmosphere for substantially larger payloads than sounding rockets and at a dramatically lower cost than orbital satellites. The main cabin provides as much as 500 cubic ft. of useable volume in a shirt-sleeve environment and payload mounting interfaces that are compatible with standard architectures, such as Middeck Lockers, Cargo Transfer Bags, and server racks. A flight test engineer will be available on board to operate payloads during flight. In the future, SS2 will also offer a variety of external payload mounting locations, enabling researchers to make frequent in situ measurements in the mesosphere (50-90 km), lower thermosphere (above 80 km), and lower ionosphere (above 60 km). SS2 may also offer optical quality windows, allowing optical investigations from main cabin payloads. Researchers will have access to their payloads until just hours before flight and within three hours post-flight. While commercial operations will begin out of Spaceport America in New Mexico, SS2 may eventually be able to launch from a variety of geographic locations. Funding to develop and fly payloads for SS2 is currently available through many NASA programs including the Flight Opportunities Program and the Game Changing Development Program. Virgin Galactic expects the SS2 research platform to enable significant progress

Electromagnetic dissociation effects in galactic heavy-ion fragmentation

NASA Technical Reports Server (NTRS)

Norbury, J. W.; Townsend, L. W.

1986-01-01

Methods for calculating cross sections for the breakup of galactic heavy ions by the Coulomb fields of the interacting nuclei are presented. By using the Weizsacker-Williams method of virtual quanta, estimates of electromagnetic dissociation cross sections for a variety of reactions applicable to galactic cosmic ray shielding studies are presented and compared with other predictions and with available experimental data.

The Effects of the Local Environment on Active Galactic Nuclei

NASA Astrophysics Data System (ADS)

Manzer, L. H.; De Robertis, M. M.

2014-06-01

There continues to be significant controversy regarding the mechanism(s) responsible for the initiation and maintenance of activity in galactic nuclei. In this paper we will investigate possible environmental triggers of nuclear activity through a statistical analysis of a large sample of galaxy groups. The focus of this paper is to identify active galactic nuclei (AGNs) and other emission-line galaxies in these groups and to compare their frequency with a sample of over 260,000 isolated galaxies from the same catalog. The galaxy groups are taken from the catalog of Yang et al., in which over 20,000 virialized groups of galaxies (2 <= N <= 20) with redshifts between 0.01 and 0.20 are from the Sloan Digital Sky Survey. We first investigate the completeness of our data set and find, though biases are a concern particularly at higher redshift, that our data provide a fair representation of the local universe. After correcting emission-line equivalent widths for extinction and underlying Balmer stellar absorption, we classify galaxies in the sample using traditional emission-line ratios, while incorporating measurement uncertainties. We find a significantly higher fraction of AGNs in groups compared with the isolated sample. Likewise, a significantly higher fraction of absorption-line galaxies are found in groups, while a higher fraction of star-forming galaxies prefer isolated environments. Within grouped environments, AGNs and star-forming galaxies are found more frequently in small- to medium-richness groups, while absorption-line galaxies prefer groups with larger richnesses. Groups containing only emission-line galaxies have smaller virial radii, velocity dispersions, and masses compared with those containing only absorption-line galaxies. Furthermore, the AGN fraction increases with decreasing distance to the group centroid, independent of galaxy morphology. Using properties obtained from Galaxy Zoo, there is an increased fraction of AGNs within merging systems

The effects of the local environment on active galactic nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manzer, L. H.; De Robertis, M. M., E-mail: liannemanzer@gmail.com, E-mail: mmdr@yorku.ca

There continues to be significant controversy regarding the mechanism(s) responsible for the initiation and maintenance of activity in galactic nuclei. In this paper we will investigate possible environmental triggers of nuclear activity through a statistical analysis of a large sample of galaxy groups. The focus of this paper is to identify active galactic nuclei (AGNs) and other emission-line galaxies in these groups and to compare their frequency with a sample of over 260,000 isolated galaxies from the same catalog. The galaxy groups are taken from the catalog of Yang et al., in which over 20,000 virialized groups of galaxies (2more » ≤ N ≤ 20) with redshifts between 0.01 and 0.20 are from the Sloan Digital Sky Survey. We first investigate the completeness of our data set and find, though biases are a concern particularly at higher redshift, that our data provide a fair representation of the local universe. After correcting emission-line equivalent widths for extinction and underlying Balmer stellar absorption, we classify galaxies in the sample using traditional emission-line ratios, while incorporating measurement uncertainties. We find a significantly higher fraction of AGNs in groups compared with the isolated sample. Likewise, a significantly higher fraction of absorption-line galaxies are found in groups, while a higher fraction of star-forming galaxies prefer isolated environments. Within grouped environments, AGNs and star-forming galaxies are found more frequently in small- to medium-richness groups, while absorption-line galaxies prefer groups with larger richnesses. Groups containing only emission-line galaxies have smaller virial radii, velocity dispersions, and masses compared with those containing only absorption-line galaxies. Furthermore, the AGN fraction increases with decreasing distance to the group centroid, independent of galaxy morphology. Using properties obtained from Galaxy Zoo, there is an increased fraction of AGNs within merging

The Galactic interstellar medium: foregrounds and star formation

NASA Astrophysics Data System (ADS)

Miville-Deschênes, Marc-Antoine

2018-05-01

This review presents briefly two aspects of Galactic interstellar medium science that seem relevant for studying EoR. First, we give some statistical properties of the Galactic foreground emission in the diffuse regions of the sky. The properties of the emission observed in projection on the plane of the sky are then related to how matter is organised along the line of sight. The diffuse atomic gas is multi-phase, with dense filamentary structures occupying only about 1% of the volume but contributing to about 50% of the emission. The second part of the review presents aspect of structure formation in the Galactic interstellar medium that could be relevant for the subgrid physics used to model the formation of the first stars.

The Study on the Physical Properties of Blazar Jets

NASA Astrophysics Data System (ADS)

Kang, S. J.

2017-09-01

Active galactic nuclei (AGNs) belong to a special class of active galaxies, and have violent active phenomena and intense physical processes in the nuclei. Blazar is a subclass of AGNs, and has a relativistic jet with a small jet viewing angle. Therefore, the boosting effect is very important, and almost all the observed radiation is dominated by the jet. The relativistic jet physics is not very clear yet, such as the jet formation, collimation, and matter content etc. The multi-waveband radiation of blazar is dominated by jet, which provides an ideal laboratory for studying the jet physics. The first chapter of this thesis introduces the recent progress of AGNs and blazars. We further introduce the jet model that commonly used in blazars in the second chapter. In the third chapter, we fit simultaneously (or quasi-simultaneously) the multi-waveband spectral energy distributions (SEDs) for a sample of low-synchrotron-peaked (LSP) blazars with the jet model and χ2 procedure, which takes into account different soft photon fields (broad line region or a molecular torus). We find that the SED fitting with an external soft photon from IR torus is systematically better than that from the broad line region (BLR) based on a χ2 test, which suggests that the γ-ray emitting region most possibly stays outside the BLR. The minimum electron Lorentz factor, γmin, is constrained from the modeling of these LSP blazars with good soft X-ray data, and in a range from 5 to 160 (with a median value of 55), which plays a key role in jet power estimation. Assuming one-to-one ratio of proton and electron, we find that the jet power for LSP blazars is systematically higher than that of Fanaroff-Riley type II (FR II) radio galaxies. A possible reason for this is that there are some positrons in the jets of these blazars. If this is the case, the jet power will be reduced. Therefore, we propose a mixed composition of e±-p in the jets of these LSP blazars. If we assume that the jet power

The free jet as a simulator of forward velocity effects on jet noise

NASA Technical Reports Server (NTRS)

Ahuja, K. K.; Tester, B. J.; Tanna, H. K.

1978-01-01

A thorough theoretical and experimental study of the effects of the free-jet shear layer on the transmission of sound from a model jet placed within the free jet to the far-field receiver located outside the free-jet flow was conducted. The validity and accuracy of the free-jet flight simulation technique for forward velocity effects on jet noise was evaluated. Transformation charts and a systematic computational procedure for converting measurements from a free-jet simulation to the corresponding results from a wind-tunnel simulation, and, finally, to the flight case were provided. The effects of simulated forward flight on jet mixing noise, internal noise and shock-associated noise from model-scale unheated and heated jets were established experimentally in a free-jet facility. It was illustrated that the existing anomalies between full-scale flight data and model-scale flight simulation data projected to the flight case, could well be due to the contamination of flight data by engine internal noise.

Galactic dual population models of gamma-ray bursts

NASA Technical Reports Server (NTRS)

Higdon, J. C.; Lingenfelter, R. E.

1994-01-01

We investigate in more detail the properties of two-population models for gamma-ray bursts in the galactic disk and halo. We calculate the gamma-ray burst statistical properties, mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), as functions of the detection flux threshold for bursts coming from both Galactic disk and massive halo populations. We consider halo models inferred from the observational constraints on the large-scale Galactic structure and we compare the expected values of mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), with those measured by Burst and Transient Source Experiment (BATSE) and other detectors. We find that the measured values are consistent with solely Galactic populations having a range of halo distributions, mixed with local disk distributions, which can account for as much as approximately 25% of the observed BATSE bursts. M31 does not contribute to these modeled bursts. We also demonstrate, contrary to recent arguments, that the size-frequency distributions of dual population models are quite consistent with the BATSE observations.

Relativistic Dark Matter at the Galactic Center

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amin, Mustafa A.; /Stanford U., Phys. Dept. /KIPAC, Menlo Park; Wizansky, Tommer

2007-11-16

In a large region of the supersymmetry parameter space, the annihilation cross section for neutralino dark matter is strongly dependent on the relative velocity of the incoming particles. We explore the consequences of this velocity dependence in the context of indirect detection of dark matter from the galactic center. We find that the increase in the annihilation cross section at high velocities leads to a flattening of the halo density profile near the galactic center and an enhancement of the annihilation signal.

Heavy and light flavor jet quenching at RHIC and LHC energies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, Shanshan; Luo, Tan; Qin, Guang-You

The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark–gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. Finally, the dependence of the jet quenching parametermore » $$\\hat{q}$$ on medium temperature and jet flavor is quantitatively extracted.« less

Heavy and light flavor jet quenching at RHIC and LHC energies

DOE PAGES

Cao, Shanshan; Luo, Tan; Qin, Guang-You; ...

2017-12-14

The Linear Boltzmann Transport (LBT) model coupled to hydrodynamical background is extended to include transport of both light partons and heavy quarks through the quark–gluon plasma (QGP) in high-energy heavy-ion collisions. The LBT model includes both elastic and inelastic medium-interaction of both primary jet shower partons and thermal recoil partons within perturbative QCD (pQCD). It is shown to simultaneously describe the experimental data on heavy and light flavor hadron suppression in high-energy heavy-ion collisions for different centralities at RHIC and LHC energies. More detailed investigations within the LBT model illustrate the importance of both initial parton spectra and the shapes of fragmentation functions on the difference between the nuclear modifications of light and heavy flavor hadrons. Finally, the dependence of the jet quenching parametermore » $$\\hat{q}$$ on medium temperature and jet flavor is quantitatively extracted.« less

Large-scale gas dynamical processes affecting the origin and evolution of gaseous galactic halos

NASA Technical Reports Server (NTRS)

Shapiro, Paul R.

1991-01-01

Observations of galactic halo gas are consistent with an interpretation in terms of the galactic fountain model in which supernova heated gas in the galactic disk escapes into the halo, radiatively cools and forms clouds which fall back to the disk. The results of a new study of several large-scale gas dynamical effects which are expected to occur in such a model for the origin and evolution of galactic halo gas will be summarized, including the following: (1) nonequilibrium absorption line and emission spectrum diagnostics for radiatively cooling halo gas in our own galaxy, as well the implications of such absorption line diagnostics for the origin of quasar absorption lines in galactic halo clouds of high redshift galaxies; (2) numerical MHD simulations and analytical analysis of large-scale explosions ad superbubbles in the galactic disk and halo; (3) numerical MHD simulations of halo cloud formation by thermal instability, with and without magnetic field; and (4) the effect of the galactic fountain on the galactic dynamo.

NASA Jet Noise Research

NASA Technical Reports Server (NTRS)

Henderson, Brenda

2016-01-01

The presentation highlights NASA's jet noise research for 2016. Jet-noise modeling efforts, jet-surface interactions results, acoustic characteristics of multi-stream jets, and N+2 Supersonic Aircraft system studies are presented.

GLOBAL SIMULATIONS OF GALACTIC WINDS INCLUDING COSMIC-RAY STREAMING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruszkowski, Mateusz; Yang, H.-Y. Karen; Zweibel, Ellen, E-mail: mateuszr@umich.edu, E-mail: hsyang@astro.umd.edu, E-mail: zweibel@astro.wisc.edu

2017-01-10

Galactic outflows play an important role in galactic evolution. Despite their importance, a detailed understanding of the physical mechanisms responsible for the driving of these winds is lacking. In an effort to gain more insight into the nature of these flows, we perform global three-dimensional magnetohydrodynamical simulations of an isolated Milky Way-size starburst galaxy. We focus on the dynamical role of cosmic rays (CRs) injected by supernovae, and specifically on the impact of the streaming and anisotropic diffusion of CRs along the magnetic fields. We find that these microphysical effects can have a significant effect on the wind launching andmore » mass loading factors, depending on the details of the plasma physics. Due to the CR streaming instability, CRs propagating in the interstellar medium scatter on self-excited Alfvén waves and couple to the gas. When the wave growth due to the streaming instability is inhibited by some damping process, such as turbulent damping, the coupling of CRs to the gas is weaker and their effective propagation speed faster than the Alfvén speed. Alternatively, CRs could scatter from “extrinsic turbulence” that is driven by another mechanism. We demonstrate that the presence of moderately super-Alfvénic CR streaming enhances the efficiency of galactic wind driving. Cosmic rays stream away from denser regions near the galactic disk along partially ordered magnetic fields and in the process accelerate more tenuous gas away from the galaxy. For CR acceleration efficiencies broadly consistent with the observational constraints, CRs reduce the galactic star formation rates and significantly aid in launching galactic winds.« less

The age of the galactic disk

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sandage, A.

The galactic disk is a dissipative structure and must, therefore be younger than the halo if galaxy formation generally proceeds by collapse. Just how much younger the oldest stars in the galactic disk are than the oldest halo stars remains an open question. A fast collapse (on a time scale no longer than the rotation period of the extended protogalaxy) permits an age gap of the order of approximately 10 to the 9th power years. A slow collapse, governed by the cooling rate of the partially pressure supported falling gas that formed into what is now the thick stellar disk,more » permits a longer age gap, claimed by some to be as long as 6 Gyr. Early methods of age dating the oldest components of the disk contain implicit assumptions concerning the details of the age-metallicity relation for stars in the solar neighborhood. The discovery that this relation for open clusters outside the solar circle is different that in the solar neighborhood (Geisler 1987), complicates the earlier arguments. The oldest stars in the galactic disk are at least as old as NGC 188. The new data by Janes on NGC 6791, shown first at this conference, suggest a disk age of at least 12.5 Gyr, as do data near the main sequence termination point of metal rich, high proper motion stars of low orbital eccentricity. Hence, a case can still be made that the oldest part of the galactic thick disk is similar in age to the halo globular clusters, if their ages are the same as 47 Tuc.« less

Interaction of argon and helium plasma jets and jets arrays with account for gravity

NASA Astrophysics Data System (ADS)

Babaeva, Natalia Yu.; Naidis, George V.; Panov, Vladislav A.; Wang, Ruixue; Zhao, Yong; Shao, Tao

2018-06-01

In this paper, we discuss results from an experimental and computational study of the properties of a single jet and two-tube jet arrays operating in argon and helium. The jets are positioned horizontally. It was shown in experiments that the helium plasma plume bends upward and the plumes in the two-tubes jet array tend to divert due to the jet-jet interaction. To investigate these potential interactions, a computational study was performed of one- and two-tube argon and helium jet arrays having variable spacing. The effects of buoyancy forces on the jet-to-jet interaction of the plasma plumes are also investigated. Velocities of ionization waves inside and outside the tubes are estimated and compared for the argon and helium ionization waves. We show that in helium jet-jet interactions primarily depend on the spacing between the tubes and on the buoyancy forces. The helium plumes tend to merge into one single stream before dissipating, while the argon plasma plumes are less sensitive to the spacing of the jet tubes.

Jets in Planetary Atmospheres

NASA Astrophysics Data System (ADS)

Dowling, Tim

2018-05-01

Jet streams, "jets" for short, are remarkably coherent streams of air found in every major atmosphere. They have a profound effect on a planet's global circulation, and have been an enigma since the belts and zones of Jupiter were discovered in the 1600s. The study of jets, including what processes affect their size, strength, direction, shear stability, and predictability, are active areas of research in geophysical fluid dynamics. Jet research is multidisciplinary and global, involving collaborations between observers, experimentalists, numerical modelers, and applied mathematicians. Jets in atmospheres have strong analogies with shear instability in nonneutral plasmas, and these connections are highlighted throughout the article. The article begins with a description of four major challenges that jet researchers face: nonlinearity, non-intuitive wave physics, non-constant-coefficients, and copious nondimensional numbers. Then, two general fluid-dynamical tenets, the practice of rendering expressions dimensionally homogeneous (nondimensional), and the universal properties of shocks are applied to the open question of what controls the on-off switch of shear instability. The discussion progresses to how the physics of jets varies in equatorial, midlatitude, and polar regions, and how jets are observed to behave in each of these settings. The all-in-one conservation law of potential vorticity (PV), which combines the conservation laws of mass, momentum, and thermal energy into a single expression, is the common language of jet research. Earth and Uranus have weak retrograde equatorial jets, but most planets exhibit super-rotating equatorial jets, which require eddies to transport momentum up gradient in a non-intuitive manner. Jupiter and Saturn exhibit multiple alternating jets in their midlatitudes. The theory for why jets are invariably zonal (east-west orientated) is reviewed, and the particular challenges that Jupiter's sharp westward jets present to existing

Jet noise suppression

NASA Astrophysics Data System (ADS)

Gliebe, P. R.; Brausch, J. F.; Majjigi, R. K.; Lee, R.

1991-08-01

The objectives of this chapter are to review and summarize the jet noise suppression technology, to provide a physical and theoretical model to explain the measured jet noise suppression characteristics of different concepts, and to provide a set of guidelines for evolving jet noise suppression designs. The underlying principle for all jet noise suppression devices is to enhance rapid mixing (i.e., diffusion) of the jet plume by geometric and aerothermodynamic means. In the case of supersonic jets, the shock-cell broadband noise reduction is effectively accomplished by the elimination or mitigation of the shock-cell structure. So far, the diffusion concepts have predominantly concentrated on jet momentum and energy (kinetic and thermal) diffusion, in that order, and have yielded better noise reduction than the simple conical nozzles. A critical technology issue that needs resolution is the effect of flight on the noise suppression potential of mechanical suppressor nozzles. A more thorough investigation of this mechanism is necessary for the successful development and design of an acceptable noise suppression device for future high-speed civil transports.

Control of jet noise

NASA Technical Reports Server (NTRS)

Schreck, Stefan

1992-01-01

To investigate the possibility of active control of jet noise, knowledge of the noise generation mechanisms in natural jets is essential. Once these mechanisms are determined, active control can be used to manipulate the noise production processes. We investigated the evolution of the flow fields and the acoustic fields of rectangular and circular jets. A predominant flapping mode was found in the supersonic rectangular jets. We hope to increase the spreading of supersonic jets by active control of the flapping mode found in rectangular supersonic jets.

NASA Ames Arc Jets and Range, Capabilities for Planetary Entry

NASA Technical Reports Server (NTRS)

Fretter, Ernest F.

2005-01-01

NASA is pursuing innovative technologies and concepts as part of America's Vision for Space Exploration. The rapidly emerging field of nanotechnology has led to new concepts for multipurpose shields to prevent catastrophic loss of vehicles and crew against the triple threats of aeroheating during atmospheric entry, radiation (Solar and galactic cosmic rays) and Micrometorid/Orbital Debris (MMOD) strikes. One proposed concept is the Thermal Radiation Impact Protection System (TRIPS) using carbon nanotubes, hydrogenated carbon nanotubes, and ceramic coatings as a multi-use TPS. The Thermophysics Facilities Branch of the Space Technology Division at NASA Ames Research Center provides testing services for the development and validation of the present and future concepts being developed by NASA and national and International research firms. The Branch operates two key facilities - the Range Complex and the Arc Jets. The Ranges include both the Ames Vertical Gun Range (AVGR) and the Hypervelocity Free Flight (HFF) gas guns best suited for MMOD investigations. Test coupons can be installed in the AVGR or HFF and subjected to particle impacts from glass or metal particles from micron to _ inch (6.35-mm) diameters and at velocities from 5 to 8 kilometers per second. The facility can record high-speed data on film and provide damage assessment for analysis by the Principle Investigator or Ames personnel. Damaged articles can be installed in the Arc Jet facility for further testing to quantify the effects of damage on the heat shield s performance upon entry into atmospheric environments.

GRAVITATIONAL MODEL OF HIGH-ENERGY PARTICLES IN A COLLIMATED JET

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Freitas Pacheco, J. A.; Gariel, J.; Marcilhacy, G.

2012-11-10

Observations suggest that relativistic particles play a fundamental role in the dynamics of jets emerging from active galactic nuclei as well as in their interaction with the intracluster medium. However, no general consensus exists concerning the acceleration mechanism of those high-energy particles. A gravitational acceleration mechanism is proposed here in which particles leaving precise regions within the ergosphere of a rotating supermassive black hole (BH) produce a highly collimated flow. These particles follow unbound geodesics which are asymptotically parallel to the spin axis of the BH and are characterized by the energy E, the Carter constant Q, and zero angularmore » momentum of the component L{sub z} . If environmental effects are neglected, the present model predicts the presence of electrons with energies around 9.4 GeV at distances of about 140 kpc from the ergosphere. The present mechanism can also accelerate protons up to the highest energies observed in cosmic rays by the present experiments.« less

Positron annihilation in the nuclear outflows of the Milky Way

NASA Astrophysics Data System (ADS)

Panther, Fiona H.; Crocker, Roland M.; Birnboim, Yuval; Seitenzahl, Ivo R.; Ruiter, Ashley J.

2018-02-01

Observations of soft gamma rays emanating from the Milky Way from SPI/INTEGRAL reveal the annihilation of ˜2 × 1043 positrons every second in the Galactic bulge. The origin of these positrons, which annihilate to produce a prominent emission line centred at 511 keV, has remained mysterious since their discovery almost 50 yr ago. A plausible origin for the positrons is in association with the intense star formation ongoing in the Galactic centre. Moreover, there is strong evidence for a nuclear outflow in the Milky Way. We find that advective transport and subsequent annihilation of positrons in such an outflow cannot simultaneously replicate the observed morphology of positron annihilation in the Galactic bulge and satisfy the requirement that 90 per cent of positrons annihilate once the outflow has cooled to 104 K.

SMM detection of diffuse Galactic 511 keV annihilation radiation

NASA Technical Reports Server (NTRS)

Share, G. H.; Kinzer, R. L.; Kurfess, J. D.; Messina, D. C.; Purcell, W. R.

1988-01-01

Observations of the 511 keV annihilation line from the vicinity of the Galactic center from October to February for 1980/1981, 1981/1982, 1982/1983, 1984/1985, and 1985/1986 are presented. The measurements were made with the gamma-ray spectrometer on the SMM. The design of the instrument and some of its properties used in the analysis are described, and the methods used for accumulating, fitting, and analyzing the data are outlined. It is shown how the Galactic 511 keV line was separated from the intense and variable background observed in orbit. The SMM observations are compared with previous measurements of annihilation radiation from the Galactic center region, and the astrophysical implications are discussed. It is argued that most of the measurements made to date suggest the presence of an extended Galactic source of annihilation radiation.

Water Jetting

NASA Technical Reports Server (NTRS)

1985-01-01

Hi-Tech Inc., a company which manufactures water jetting equipment, needed a high pressure rotating swivel, but found that available hardware for the system was unsatisfactory. They were assisted by Marshall, which had developed water jetting technology to clean the Space Shuttles. The result was a completely automatic water jetting system which cuts rock and granite and removes concrete. Labor costs have been reduced; dust is suppressed and production has been increased.

Galactic supernova remnant candidates discovered by THOR

NASA Astrophysics Data System (ADS)

Anderson, L. D.; Wang, Y.; Bihr, S.; Rugel, M.; Beuther, H.; Bigiel, F.; Churchwell, E.; Glover, S. C. O.; Goodman, A. A.; Henning, Th.; Heyer, M.; Klessen, R. S.; Linz, H.; Longmore, S. N.; Menten, K. M.; Ott, J.; Roy, N.; Soler, J. D.; Stil, J. M.; Urquhart, J. S.

2017-09-01

Context. There is a considerable deficiency in the number of known supernova remnants (SNRs) in the Galaxy compared to that expected. This deficiency is thought to be caused by a lack of sensitive radio continuum data. Searches for extended low-surface brightness radio sources may find new Galactic SNRs, but confusion with the much larger population of H II regions makes identifying such features challenging. SNRs can, however, be separated from H II regions using their significantly lower mid-infrared (MIR) to radio continuum intensity ratios. Aims: Our goal is to find missing SNR candidates in the Galactic disk by locating extended radio continuum sources that lack MIR counterparts. Methods: We use the combination of high-resolution 1-2 GHz continuum data from The HI, OH, Recombination line survey of the Milky Way (THOR) and lower-resolution VLA 1.4 GHz Galactic Plane Survey (VGPS) continuum data, together with MIR data from the Spitzer GLIMPSE, Spitzer MIPSGAL, and WISE surveys to identify SNR candidates. To ensure that the candidates are not being confused with H II regions, we exclude radio continuum sources from the WISE Catalog of Galactic H II Regions, which contains all known and candidate H II regions in the Galaxy. Results: We locate 76 new Galactic SNR candidates in the THOR and VGPS combined survey area of 67.4° > ℓ > 17.5°, | b | ≤ 1.25° and measure the radio flux density for 52 previously-known SNRs. The candidate SNRs have a similar spatial distribution to the known SNRs, although we note a large number of new candidates near ℓ ≃ 30°, the tangent point of the Scutum spiral arm. The candidates are on average smaller in angle compared to the known regions, 6.4' ± 4.7' versus 11.0' ± 7.8', and have lower integrated flux densities. Conclusions: The THOR survey shows that sensitive radio continuum data can discover a large number of SNR candidates, and that these candidates can be efficiently identified using the combination of radio and

Aeroacoustic Experiments with Twin Jets

NASA Technical Reports Server (NTRS)

Bozak, Richard F.; Henderson, Brenda S.

2012-01-01

While the noise produced by a single jet is azimuthally symmetric, multiple jets produce azimuthally varying far-field noise. The ability of one jet to shield another reduces the noise radiated in the plane of the jets, while often increasing the noise radiated out of the plane containing the jets. The present study investigates the shielding potential of twin jet configurations over subsonic and over-expanded supersonic jet conditions with simulated forward flight. The experiments were conducted with 2 in. throat diameter nozzles at four jet spacings from 2.6d to 5.5d in center-to-center distance, where d is the nozzle throat diameter. The current study found a maximum of 3 dB reduction in overall sound pressure level relative to two incoherent jets in the peak jet noise direction in the plane containing the jets. However, an increase of 3 dB was found perpendicular to the plane containing the jets. In the sideline direction, shielding is observed for all jet spacings in this study.

CONNECTION BETWEEN THE ACCRETION DISK AND JET IN THE RADIO GALAXY 3C 111

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatterjee, Ritaban; Marscher, Alan P.; Jorstad, Svetlana G.

2011-06-10

We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4-10 keV), optical (R band), and radio (14.5, 37, and 230 GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuummore » flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero. This implies that the Fe line is generated within 90 lt-day of the source of the X-ray continuum. The power spectral density function of X-ray variations contains a break, with a steeper slope at shorter timescales. The break timescale of 13{sup +12}{sub -6} days is commensurate with scaling according to the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). The data are consistent with the standard paradigm, in which the X-rays are predominantly produced by inverse Compton scattering of thermal optical/UV seed photons from the accretion disk by a distribution of hot electrons-the corona-situated near the disk. Most of the optical emission is generated in the accretion disk due to reprocessing of the X-ray emission. The relationships that we have uncovered between the accretion disk and the jet in 3C 111, as well as in the Fanaroff-Riley class I radio galaxy 3C 120 in a previous paper, support the paradigm that active galactic nuclei and Galactic BHXRBs are fundamentally similar, with characteristic time and size scales proportional to the mass of the central black hole.« less

Studies of jet mass in dijet and W/Z + jet events

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.

Invariant mass spectra for jets reconstructed using the anti-kt and Cambridge-Aachen algorithms are studied for different jet "grooming" techniques in data corresponding to an integrated luminosity of 5 inverse femtobarns, recorded with the CMS detector in proton-proton collisions at the LHC at a center-of-mass energy of 7 TeV. Leading-order QCD predictions for inclusive dijet and W/Z+jet production combined with parton-shower Monte Carlo models are found to agree overall with the data, and the agreement improves with the implementation of jet grooming methods used to distinguish merged jets of large transverse momentum from softer QCD gluon radiation.

Solar Active Region Coronal Jets. II. Triggering and Evolution of Violent Jets

NASA Astrophysics Data System (ADS)

Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.; Panesar, Navdeep K.; Martinez, Francisco

2017-07-01

We study a series of X-ray-bright, rapidly evolving active region coronal jets outside the leading sunspot of AR 12259, using Hinode/X-ray telescope, Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI), and Interface Region Imaging Spectrograph (IRIS) data. The detailed evolution of such rapidly evolving “violent” jets remained a mystery after our previous investigation of active region jets. The jets we investigate here erupt from three localized subregions, each containing a rapidly evolving (positive) minority-polarity magnetic-flux patch bathed in a (majority) negative-polarity magnetic-flux background. At least several of the jets begin with eruptions of what appear to be thin (thickness ≲ 2\\prime\\prime ) miniature-filament (minifilament) “strands” from a magnetic neutral line where magnetic flux cancelation is ongoing, consistent with the magnetic configuration presented for coronal-hole jets in Sterling et al. (2016). Some jets strands are difficult/impossible to detect, perhaps due to, e.g., their thinness, obscuration by surrounding bright or dark features, or the absence of erupting cool-material minifilaments in those jets. Tracing in detail the flux evolution in one of the subregions, we find bursts of strong jetting occurring only during times of strong flux cancelation. Averaged over seven jetting episodes, the cancelation rate was ˜ 1.5× {10}19 Mx hr-1. An average flux of ˜ 5× {10}18 Mx canceled prior to each episode, arguably building up ˜1028-1029 erg of free magnetic energy per jet. From these and previous observations, we infer that flux cancelation is the fundamental process responsible for the pre-eruption build up and triggering of at least many jets in active regions, quiet regions, and coronal holes.

The galactic gamma-ray distribution: Implications for galactic structure and the radial cosmic ray gradient

NASA Technical Reports Server (NTRS)

Harding, A. K.; Stecker, F. W.

1984-01-01

The radial distribution of gamma ray emissivity in the Galaxy was derived from flux longitude profiles, using both the final SAS-2 results and the recently corrected COS-B results and analyzing the northern and southern galactic regions separately. The recent CO surveys of the Southern Hemisphere, were used in conjunction with the Northern Hemisphere data, to derive the radial distribution of cosmic rays on both sides of the galactic plane. In addition to the 5 kpc ring, there is evidence from the radial asymmetry for spiral features which are consistent with those derived from the distribution of bright HII regions. Positive evidence was also found for a strong increase in the cosmic ray flux in the inner Galaxy, particularly in the 5 kpc region in both halves of the plane.

Twin Jet Effects on Noise of Round and Rectangular Jets: Experiment and Model

NASA Technical Reports Server (NTRS)

Bozak, Rick

2014-01-01

Many subsonic and supersonic aircraft concepts proposed by NASA's Fundamental Aeronautics Program have asymmetric, integrated propulsion systems. The asymmetries in the exhaust of these propulsion systems create an asymmetric acoustic field. The asymmetries investigated in the current study are from twin jets and rectangular nozzles. Each effect produces its own variation of the acoustic field. An empirical model was developed to predict the acoustic field variation from round twin jets with twin jet spacing from 2.6 to 5.6, where s is the center-to-center spacing over the jet diameter. The model includes parameters to account for the effects of twin jet spacing, jet static temperature ratio, flight Mach number, frequency, and observer angle (both polar and azimuthal angles). The model was then applied to twin 2:1 and 8:1 aspect ratio nozzles to determine the impact of jet aspect ratio. For the round and rectangular jets, the use of the model reduces the average magnitude of the error over all frequencies, observation angles, and jet spacings by approximately 0.5dB when compared against the assumption of adding two jets incoherently.

Multiple jet study

NASA Technical Reports Server (NTRS)

Walker, R. E.; Kors, D. L.

1973-01-01

Test data is presented which allows determination of jet penetration and mixing of multiple cold air jets into a ducted subsonic heated mainstream flow. Jet-to-mainstream momentum flux ratios ranged from 6 to 60. Temperature profile data is presented at various duct locations up to 24 orifice diameters downstream of the plane of jet injection. Except for two configurations, all geometries investigated had a single row of constant diameter orifices located transverse to the main flow direction. Orifice size and spacing between orifices were varied. Both of these were found to have a significant effect on jet penetration and mixing. The best mixing of the hot and cold streams was achieved with duct height.

Blazar Jets Push Closer to Cosmic Speed Limit

NASA Astrophysics Data System (ADS)

2005-01-01

Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have discovered jets of plasma blasted from the cores of distant galaxies at speeds within one-tenth of one percent of the speed of light, placing these plasma jets among the fastest objects yet seen in the Universe. "This tells us that the physical processes at the cores of these galaxies, called blazars, are extremely energetic and are capable of propelling matter very close to the absolute cosmic speed limit," said Glenn Piner of Whittier College in Whittier, California. Piner, who worked on the project with student Dipesh Bhattari, also of Whittier College, Philip Edwards of the Japan Aerospace Exploration Agency, and Dayton Jones of NASA's Jet Propulsion Laboratory, presented their findings to the American Astronomical Society's meeting in San Diego, California. According to Einstein's Special Theory of Relativity, no object with mass can be accelerated to the speed of light. To get even close to the speed of light requires enormous amounts of energy. "For example, to accelerate a bowling ball to the speed newly measured in these blazars would require all the energy produced in the world for an entire week," Piner said, "and the blobs of plasma in these jets are at least as massive as a large planet". Blazars are active galactic nuclei -- energetic regions surrounding massive black holes at the centers of galaxies. Material being drawn into the black hole forms a spinning disk called an accretion disk. Powerful jets of charged particles are ejected at high speeds along the poles of accretion disks. When these jets happen to be aimed nearly toward the Earth, the objects are called blazars. Taking advantage of the extremely sharp radio "vision" of the continent-wide VLBA, the scientists tracked individual features in the jets of three blazars at distances from Earth ranging from 7.3 to 9 billion light-years. A Boston University team led by Svetlana Jorstad earlier had identified

Jet simulations and gamma-ray burst afterglow jet breaks

NASA Astrophysics Data System (ADS)

van Eerten, H. J.; Meliani, Z.; Wijers, R. A. M. J.; Keppens, R.

2011-01-01

The conventional derivation of the gamma-ray burst afterglow jet break time uses only the blast wave fluid Lorentz factor and therefore leads to an achromatic break. We show that in general gamma-ray burst afterglow jet breaks are chromatic across the self-absorption break. Depending on circumstances, the radio jet break may be postponed significantly. Using high-accuracy adaptive mesh fluid simulations in one dimension, coupled to a detailed synchrotron radiation code, we demonstrate that this is true even for the standard fireball model and hard-edged jets. We confirm these effects with a simulation in two dimensions. The frequency dependence of the jet break is a result of the angle dependence of the emission, the changing optical depth in the self-absorbed regime and the shape of the synchrotron spectrum in general. In the optically thin case the conventional analysis systematically overestimates the jet break time, leading to inferred opening angles that are underestimated by a factor of ˜1.3 and explosion energies that are underestimated by a factor of ˜1.7, for explosions in a homogeneous environment. The methods presented in this paper can be applied to adaptive mesh simulations of arbitrary relativistic fluid flows. All analysis presented here makes the usual assumption of an on-axis observer.

Mixing augmentation of transverse hydrogen jet by injection of micro air jets in supersonic crossflow

NASA Astrophysics Data System (ADS)

Anazadehsayed, A.; Barzegar Gerdroodbary, M.; Amini, Y.; Moradi, R.

2017-08-01

In this study, the influences of the micro air jet on the mixing of the sonic transverse hydrogen through micro-jets subjected to a supersonic crossflow are investigated. A three-dimensional numerical study has been performed to reveal the affects of micro air jet on mixing of the hydrogen jet in a Mach 4.0 crossflow with a global equivalence ratio of 0.5. Parametric studies were conducted on the various air jet conditions by using the Reynolds-averaged Navier-Stokes equations with Menter's Shear Stress Transport (SST) turbulence model. Complex jet interactions were found in the downstream region with a variety of flow features depending upon the angle of micro air jet. These flow features were found to have subtle effects on the mixing of hydrogen jets. Results indicate a different flow structure as air jet is presented in the downstream of the fuel jet. According to the results, without air, mixing occurs at a low rate. When the air jet is presented in the downstream of fuel jet, significant increase (up to 300%) occurs in the mixing performance of the hydrogen jet at downstream. In multi fuel jets, the mixing performance of the fuel jet is increased more than 200% when the micro air jet is injected. Consequently, an enhanced mixing zone occurs downstream of the injection slots which leads to flame-holding.

Orbits of Selected Globular Clusters in the Galactic Bulge

NASA Astrophysics Data System (ADS)

Pérez-Villegas, A.; Rossi, L.; Ortolani, S.; Casotto, S.; Barbuy, B.; Bica, E.

2018-05-01

We present orbit analysis for a sample of eight inner bulge globular clusters, together with one reference halo object. We used proper motion values derived from long time base CCD data. Orbits are integrated in both an axisymmetric model and a model including the Galactic bar potential. The inclusion of the bar proved to be essential for the description of the dynamical behaviour of the clusters. We use the Monte Carlo scheme to construct the initial conditions for each cluster, taking into account the uncertainties in the kinematical data and distances. The sample clusters show typically maximum height to the Galactic plane below 1.5 kpc, and develop rather eccentric orbits. Seven of the bulge sample clusters share the orbital properties of the bar/bulge, having perigalactic and apogalatic distances, and maximum vertical excursion from the Galactic plane inside the bar region. NGC 6540 instead shows a completely different orbital behaviour, having a dynamical signature of the thick disc. Both prograde and prograde-retrograde orbits with respect to the direction of the Galactic rotation were revealed, which might characterise a chaotic behaviour.

Gamma-ray spectroscopy: The diffuse galactic glow

NASA Technical Reports Server (NTRS)

Hartmann, Dieter H.

1991-01-01

The goal of this project is the development of a numerical code that provides statistical models of the sky distribution of gamma-ray lines due to the production of radioactive isotopes by ongoing Galactic nucleosynthesis. We are particularly interested in quasi-steady emission from novae, supernovae, and stellar winds, but continuum radiation and transient sources must also be considered. We have made significant progress during the first half period of this project and expect the timely completion of a code that can be applied to Oriented Scintillation Spectrometer Experiment (OSSE) Galactic plane survey data.

Experimental investigation of turbulent wall jet

NASA Astrophysics Data System (ADS)

Andre, Matthieu A.; Bardet, Philippe M.

2011-11-01

Water jet flowing on a flat plate surrounded by quiescent air constitutes a standard case for the study of the interaction between turbulence and the liquid-air interface. This is of particular interest in the understanding of heat and mass transfers across interfaces. The structure of the surface has a great influence on the rate of the transfers which is critical for chemical processes like separation or absorption; pool-type nuclear reactor; climate modeling etc. This study focuses on high Froude (8 to 12) and Weber (3300 to 7400) numbers at which the surface exhibits small wavelength and large amplitude deformations, such as ligaments, surface break up with air entrainment and droplets projection. The experiment features a high velocity (up to 7.5 m/s) water wall jet (19.05mm thick at the nozzle exit) flowing on a flat plate (Re =105 to 1 . 5 .105). High speed movies and PLIF visualization show the evolution of the surface from smooth to 2D structures, then 3D disturbances as the turbulence arising from the wall interacts with the surface.

Galactic Supernova Remnant Candidates Discovered by THOR

NASA Astrophysics Data System (ADS)

Anderson, Loren; Wang, Yuan; Bihr, Simon; Rugel, Michael; Beuther, Henrik; THOR Team

2018-01-01

There is a considerable deficiency in the number of known supernova remnants (SNRs) in the Galaxy compared to that expected. Searches for extended low-surface brightness radio sources may find new Galactic SNRs, but confusion with the much larger population of HII regions makes identifying such features challenging. SNRs can, however, be separated from HII regions using their significantly lower mid-infrared (MIR) to radio continuum intensity ratios. We use the combination of high-resolution 1-2 GHz continuum data from The HI, OH, Recombination line survey of the Milky Way (THOR) and lower-resolution VLA 1.4 GHz Galactic Plane Survey (VGPS) continuum data, together with MIR data from the Spitzer GLIMPSE, Spitzer MIPSGAL, and WISE surveys to identify SNR candidates. To ensure that the candidates are not being confused with HII regions, we exclude radio continuum sources from the WISE Catalog of Galactic HII Regions, which contains all known and candidate H II regions in the Galaxy. We locate 76 new Galactic SNR candidates in the THOR and VGPS combined survey area of 67.4deg>l>17.5deg, |b|<1.25deg and measure the radio flux density for 52 previously-known SNRs. The candidate SNRs have a similar spatial distribution to the known SNRs, although we note a large number of new candidates near l=30deg, the tangent point of the Scutum spiral arm. The candidates are on average smaller in angle compared to the known regions, 6.4'+/-4.7' versus 11.0'+/-7.8', and have lower integrated flux densities. If the 76 candidates are confirmed as true SNRs, for example using radio polarization measurements or by deriving radio spectral indices, this would more than double the number of known Galactic SNRs in the survey area. This large increase would still, however, leave a discrepancy between the known and expected SNR populations of about a factor of two.

Does the Galactic Bulge Have Fewer Planets?

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-12-01

The Milky Ways dense central bulge is a very different environment than the surrounding galactic disk in which we live. Do the differences affect the ability of planets to form in the bulge?Exploring Galactic PlanetsSchematic illustrating how gravitational microlensing by an extrasolar planet works. [NASA]Planet formation is a complex process with many aspects that we dont yet understand. Do environmental properties like host star metallicity, the density of nearby stars, or the intensity of the ambient radiation field affect the ability of planets to form? To answer these questions, we will ultimately need to search for planets around stars in a large variety of different environments in our galaxy.One way to detect recently formed, distant planets is by gravitational microlensing. In this process, light from a distant source star is bent by a lens star that is briefly located between us and the source. As the Earth moves, this momentary alignment causes a blip in the sources light curve that we can detect and planets hosted by the lens star can cause an additional observable bump.Artists impression of the Milky Way galaxy. The central bulge is much denserthan the surroundingdisk. [ESO/NASA/JPL-Caltech/M. Kornmesser/R. Hurt]Relative AbundancesMost source stars reside in the galactic bulge, so microlensing events can probe planetary systems at any distance between the Earth and the galactic bulge. This means that planet detections from microlensing could potentially be used to measure the relative abundances of exoplanets in different parts of our galaxy.A team of scientists led by Matthew Penny, a Sagan postdoctoral fellow at Ohio State University, set out to do just that. The group considered a sample of 31 exoplanetary systems detected by microlensing and asked the following question: are the planet abundances in the galactic bulge and the galactic disk the same?A Paucity of PlanetsTo answer this question, Penny and collaborators derived the expected

A Speeding Binary in the Galactic Halo

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-04-01

The recent discovery of a hyper-velocity binary star system in the halo of the Milky Way poses a mystery: how was this system accelerated to its high speed?Accelerating StarsUnlike the uniform motion in the Galactic disk, stars in the Milky Ways halo exhibit a huge diversity of orbits that are usually tilted relative to the disk and have a variety of speeds. One type of halo star, so-called hyper-velocity stars, travel with speeds that can approach the escape velocity of the Galaxy.How do these hyper-velocity stars come about? Assuming they form in the Galactic disk, there are multiple proposed scenarios through which they could be accelerated and injected into the halo, such as:Ejection after a close encounter with the supermassive black hole at the Galactic centerEjection due to a nearby supernova explosionEjection as the result of a dynamical interaction in a dense stellar population.Further observations of hyper-velocity stars are necessary to identify the mechanism responsible for their acceleration.J1211s SurpriseModels of J1211s orbit show it did not originate from the Galactic center (black dot). The solar symbol shows the position of the Sun and the star shows the current position of J1211. The bottom two panels show two depictions(x-y plane and r-z plane) of estimated orbits of J1211 over the past 10 Gyr. [Nmeth et al. 2016]To this end, a team of scientists led by Pter Nmeth (Friedrich Alexander University, Erlangen-Nrnberg) recently studied the candidate halo hyper-velocity star SDSS J121150.27+143716.2. The scientists obtained spectroscopy of J1211 using spectrographs at the Keck Telescope in Hawaii and ESOs Very Large Telescope in Chile. To their surprise, they discovered the signature of a companion in the spectra: J1211 is actually a binary!Nmeth and collaborators found that J1211, located roughly 18,000 light-years away, is moving at a rapid ~570 km/s relative to the galactic rest frame. The binary system consists of a hot (30,600 K) subdwarf and a

Evidence of b-jet quenching in PbPb collisions at √(s(NN))=2.76  TeV.

PubMed

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2014-09-26

The production of jets associated to bottom quarks is measured for the first time in PbPb collisions at a center-of-mass energy of 2.76 TeV per nucleon pair. Jet spectra are reported in the transverse momentum (p(T)) range of 80-250  GeV/c, and within pseudorapidity |η|<2. The nuclear modification factor (R(AA)) calculated from these spectra shows a strong suppression in the b-jet yield in PbPb collisions relative to the yield observed in pp collisions at the same energy. The suppression persists to the largest values of p(T) studied, and is centrality dependent. The R(AA) is about 0.4 in the most central events, similar to previous observations for inclusive jets. This implies that jet quenching does not have a strong dependence on parton mass and flavor in the jet p(T) range studied.

AC electrified jets in a flow-focusing device: Jet length scaling