Photometry-based estimation of the total number of stars in the Universe.

PubMed

Manojlović, Lazo M

2015-07-20

A novel photometry-based estimation of the total number of stars in the Universe is presented. The estimation method is based on the energy conservation law and actual measurements of the extragalactic background light levels. By assuming that every radiated photon is kept within the Universe volume, i.e., by approximating the Universe as an integrating cavity without losses, the total number of stars in the Universe of about 6×10²² has been obtained.

VAO Tools Enhance CANDELS Research Productivity

NASA Astrophysics Data System (ADS)

Greene, Gretchen; Donley, J.; Rodney, S.; LAZIO, J.; Koekemoer, A. M.; Busko, I.; Hanisch, R. J.; VAO Team; CANDELS Team

2013-01-01

The formation of galaxies and their co-evolution with black holes through cosmic time are prominent areas in current extragalactic astronomy. New methods in science research are building upon collaborations between scientists and archive data centers which span large volumes of multi-wavelength and heterogeneous data. A successful example of this form of teamwork is demonstrated by the CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) and the Virtual Astronomical Observatory (VAO) collaboration. The CANDELS project archive data provider services are registered and discoverable in the VAO through an innovative web based Data Discovery Tool, providing a drill down capability and cross-referencing with other co-spatially located astronomical catalogs, images and spectra. The CANDELS team is working together with the VAO to define new methods for analyzing Spectral Energy Distributions of galaxies containing active galactic nuclei, and helping to evolve advanced catalog matching methods for exploring images of variable depths, wavelengths and resolution. Through the publication of VOEvents, the CANDELS project is publishing data streams for newly discovered supernovae that are bright enough to be followed from the ground.

Astrophysics of Reference Frame Tie Objects

NASA Technical Reports Server (NTRS)

Johnston, Kenneth J.; Boboltz, David; Fey, Alan Lee; Gaume, Ralph A.; Zacharias, Norbert

2004-01-01

The Astrophysics of Reference Frame Tie Objects Key Science program will investigate the underlying physics of SIM grid objects. Extragalactic objects in the SIM grid will be used to tie the SIM reference frame to the quasi-inertial reference frame defined by extragalactic objects and to remove any residual frame rotation with respect to the extragalactic frame. The current realization of the extragalactic frame is the International Celestial Reference Frame (ICRF). The ICRF is defined by the radio positions of 212 extragalactic objects and is the IAU sanctioned fundamental astronomical reference frame. This key project will advance our knowledge of the physics of the objects which will make up the SIM grid, such as quasars and chromospherically active stars, and relates directly to the stability of the SIM reference frame. The following questions concerning the physics of reference frame tie objects will be investigated.

Searching for Extragalactic Sources in the VISTA Variables in the Vía Láctea Survey

NASA Astrophysics Data System (ADS)

Baravalle, Laura D.; Alonso, M. Victoria; Nilo Castellón, José Luis; Beamín, Juan Carlos; Minniti, Dante

2018-01-01

We search for extragalactic sources in the VISTA Variables in the Vía Láctea survey that are hidden by the Galaxy. Herein, we describe our photometric procedure to find and characterize extragalactic objects using a combination of SExtractor and PSFEx. It was applied in two tiles of the survey: d010 and d115, without previous extragalactic IR detections, in order to obtain photometric parameters of the detected sources. The adopted criteria to define extragalactic candidates include CLASSSTAR< 0.3; 1.0 < R1/2< 5.0 arcsec; 2.1 < C < 5 and Φ > 0.002 and the colors: 0.5 < (J–K s ) < 2.0 mag; 0.0 < (J–H) < 1.0 mag; 0.0 < (H–K s ) < 2.0 mag and (J–H) + 0.9 (H–K s ) > 0.44 mag. We detected 345 and 185 extragalactic candidates in the d010 and d115 tiles, respectively. All of them were visually inspected and confirmed to be galaxies. In general, they are small and more circular objects, due to the near-IR sensitivity to select more compact objects with higher surface brightness. The procedure will be used to identify extragalactic objects in other tiles of the VVV disk, which will allow us to study the distribution of galaxies and filaments hidden by the Milky Way.

Probing the Dusty Stellar Populations of the Local Volume Galaxies with JWST/MIRI

NASA Astrophysics Data System (ADS)

Jones, Olivia C.; Meixner, Margaret; Justtanont, Kay; Glasse, Alistair

2017-05-01

The Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope (JWST) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich Spitzer-IRS spectroscopic data set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)-Spectroscopic survey of more than 1000 objects in the Magellanic Clouds, the Grid of Red Supergiant and Asymptotic Giant Branch Star Model (grams), and the grid of YSO models by Robitaille et al., we calculate the expected flux densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes to explore the JWST/MIRI colors and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI color classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars, and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colors.

Search for gamma-rays from M31 and other extragalactic objects

NASA Technical Reports Server (NTRS)

Cawley, M. F.; Fegan, D. J.; Gibbs, K.; Gorham, P. W.; Lamb, R. C.; Liebing, D. F.; Porter, N. A.; Stenger, V. J.; Weeles, T. C.

1985-01-01

Although the existence of fluxes of gamma-rays of energies 10 to the 12th power eV is now established for galactic sources, the detection of such gamma-rays from extragalactic sources has yet to be independently confirmed in any case. The detection and confirmation of such energetic photons is of great astrophysical importance in the study of production mechanisms for cosmic rays, and other high energy processes in extragalactic objects. Observations of m31 are discussed. It is reported as a 10 to the 12th power eV gamma-ray source. Flux limits on a number of other extragalactic objects chosen for study are given.

Nineteenth International Cosmic Ray Conference. Conference Papers: Invited Rapporteur, Highlight, Miscellaneous, Volume 9

NASA Technical Reports Server (NTRS)

Jones, F. C. (Compiler)

1986-01-01

Invited talks, rapporteur talks, and highlight talks are included. Topics of the invited and highlight talks include astrophysical jets, gamma-ray line astronomy, cosmic rays and gamma rays in astrophysics, the early universe, elementary particle physics, solar flares and acceleration of energetic particles, cosmogenic nuclei, extragalactic astronomy, composition of solar flare particles, very high energy gamma ray sources, gamma-ray bursts, shock acceleration in the solar wind, cosmic rays in deep underground detectors, spectrum of cosmic rays at 10 to the 19th power eV, and nucleus-nucleus interactions.

X-ray detection of warm ionized matter in the Galactic halo

NASA Astrophysics Data System (ADS)

Nicastro, F.; Senatore, F.; Gupta, A.; Guainazzi, M.; Mathur, S.; Krongold, Y.; Elvis, M.; Piro, L.

2016-03-01

We report on a systematic investigation of the cold and mildly ionized gaseous baryonic metal components of our Galaxy, through the analysis of high-resolution Chandra and XMM-Newton spectra of two samples of Galactic and extragalactic sources. The comparison between lines of sight towards sources located in the disc of our Galaxy and extragalactic sources allows us for the first time to clearly distinguish between gaseous metal components in the disc and halo of our Galaxy. We find that a warm ionized metal medium (WIMM) permeates a large volume above and below the Galaxy's disc, perhaps up to the circum-galactic space. This halo WIMM imprints virtually the totality of the O I and O II absorption seen in the spectra of our extragalactic targets, has a temperature of T_{WIMM}^{Halo}=2900 ± 900 K, a density < n_H > _{WIMM}^{Halo} = 0.023 ± 0.009 cm-3 and a metallicity Z_{WIMM}^{Halo} = (0.4 ± 0.1) Z⊙. Consistently with previous works, we also confirm that the disc of the Galaxy contains at least two distinct gaseous metal components, one cold and neutral (the CNMM: cold neutral metal medium) and one warm and mildly ionized, with the same temperature of the halo WIMM, but higher density (< n_H > _{WIMM}^{Disc} = 0.09 ± 0.03 cm-3) and metallicity (Z_{WIMM}^{Disc} = 0.8 ± 0.1 Z⊙). By adopting a simple disc+sphere geometry for the Galaxy, we estimate masses of the CNMM and the total (disc + halo) WIMM of MCNMM ≲ 8 × 108 M⊙ and MWIMM ≃ 8.2 × 109 M⊙.

Origin of the Galaxy Mass-Metallicity-Star Formation Relation

NASA Astrophysics Data System (ADS)

Harwit, Martin; Brisbin, Drew

2015-02-01

We describe an equilibrium model that links the metallicity of low-redshift galaxies to stellar evolution models. It enables the testing of different stellar initial mass functions and metal yields against observed galaxy metallicities. We show that the metallicities of more than 80,000 Sloan Digital Sky Survey galaxies in the low-redshift range 0.07 <= z <= 0.3 considerably constrain stellar evolution models that simultaneously relate galaxy stellar mass, metallicity, and star formation rates to the infall rate of low-metallicity extragalactic gas and outflow of enriched matter. A feature of our model is that it encompasses both the active star forming phases of a galaxy and epochs during which the same galaxy may lie fallow. We show that the galaxy mass-metallicity-star formation relation can be traced to infall of extragalactic gas mixing with native gas from host galaxies to form stars of observed metallicities, the most massive of which eject oxygen into extragalactic space. Most consequential among our findings is that, on average, extragalactic infall accounts for one half of the gas required for star formation, a ratio that is remarkably constant across galaxies with stellar masses ranging at least from M* = 2 × 109 to 6 × 1010 M ⊙. This leads us to propose that star formation is initiated when extragalactic infall roughly doubles the mass of marginally stable interstellar clouds. The processes described may also account quantitatively for the metallicity of extragalactic space, though to check this the fraction of extragalactic baryons will need to be more firmly established.

Erratum: The Extragalactic Distance Scale Key Project. III. The Discovery of Cepheids and a New Distance to M101 Using the Hubble Space Telescope

NASA Astrophysics Data System (ADS)

Kelson, Daniel D; Illingworth, Garth D.; Freedman, Wendy F.; Graham, John A.; Hill, Robert; Madore, Barry F.; Saha, Abhijit; Stetson, Peter B.; Kennicutt, Robert C., Jr.; Mould, Jeremy R.; Hughes, Shaun M.; Ferrarese, Laura; Phelps, Randy; Turner, Anne; Cook, Kem H.; Ford, Holland; Hoessel, John G.; Huchra, John

1997-03-01

In the paper ``The Extragalactic Distance Scale Key Project. III. The Discovery of Cepheids and a New Distance to M101 Using the Hubble Space Telescope'' by Daniel D. Kelson, Garth D. Illingworth, Wendy F. Freedman, John A. Graham, Robert Hill, Barry F. Madore, Abhijit Saha, Peter B. Stetson, Robert C. Kennicutt, Jr., Jeremy R. Mould, Shaun M. Hughes, Laura Ferrarese, Randy Phelps, Anne Turner, Kem H. Cook, Holland Ford, John G. Hoessel, and John Huchra (ApJ, 463, 26 [1996]), two of the tables are in error. The magnitudes in Tables B1 and B2, in Appendix B, are ordered incorrectly. As a result, the Julian dates are not associated with their correct Cepheid magnitudes. We have now corrected these data, and updated versions of the tables are available on the World Wide Web. The tables are available in ASCII format at our Key Project site (http://www.ipac.caltech.edu/H0kp/) and will appear in volume 7 of the AAS CDROM. PostScript and paper copies are also available from the first author (http://www.ucolick.org/~kelson/H0/home.html or kelson@ucolick.org).

A catalogue of AKARI FIS BSC extragalactic objects

NASA Astrophysics Data System (ADS)

Marton, Gabor; Toth, L. Viktor; Gyorgy Balazs, Lajos

2015-08-01

We combined photometric data of about 70 thousand point sources from the AKARI Far-Infrared Surveyor Bright Source Catalogue with AllWISE catalogue data to identify galaxies. We used Quadratic Discriminant Analysis (QDA) to classify our sources. The classification was based on a 6D parameter space that contained AKARI [F65/F90], [F90/F140], [F140/F160] and WISE W1-W2 colours along with WISE W1 magnitudes and AKARI [F140] flux values. Sources were classified into 3 main objects types: YSO candidates, evolved stars and galaxies. The training samples were SIMBAD entries of the input point sources wherever an associated SIMBAD object was found within a 30 arcsecond search radius. The QDA resulted more than 5000 AKARI galaxy candidate sources. The selection was tested cross-correlating our AKARI extragalactic catalogue with the Revised IRAS-FSC Redshift Catalogue (RIFSCz). A very good match was found. A further classification attempt was also made to differentiate between extragalactic subtypes using Support Vector Machines (SVMs). The results of the various methods showed that we can confidently separate cirrus dominated objects (type 1 of RIFSCz). Some of our “galaxy candidate” sources are associated with 2MASS extended objects, and listed in the NASA Extragalactic Database so far without clear proofs of their extragalactic nature. Examples will be presented in our poster. Finally other AKARI extragalactic catalogues will be also compared to our statistical selection.

Redshift-Independent Distances in the NASA/IPAC Extragalactic Database Surpass 166,000 Estimates for 77,000 Galaxies

NASA Astrophysics Data System (ADS)

Steer, Ian

2017-01-01

Redshift-independent extragalactic distance estimates are used by researchers to establish the extragalactic distance scale, to underpin estimates of the Hubble constant, and to study peculiar velocities induced by gravitational attractions that perturb the motions of galaxies with respect to the “Hubble flow” of universal expansion. In 2006, the NASA/IPAC Extragalactic Database (NED) began providing users with a comprehensive tabulation of the redshift-independent extragalactic distance estimates published in the astronomical literature since 1980. A decade later, this compendium of distances (NED-D) surpassed 100,000 estimates for 28,000 galaxies, as reported in our recent journal article (Steer et al. 2016). Here, we are pleased to report NED-D has surpassed 166,000 distance estimates for 77,000 galaxies. Visualizations of the growth in data and of the statistical distributions of the most used distance indicators will be presented, along with an overview of the new data responsible for the most recent growth. We conclude with an outline of NED’s current plans to facilitate extragalactic research further by making greater use of redshift-independent distances. Additional information about other extensive updates to NED is presented at this meeting by Mazzarella et al. (2017). NED is operated by and this research is funded by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Milagro Observations of Potential TeV Emitters

NASA Technical Reports Server (NTRS)

Abdo, A. A.; Abeysekara, A. U.; Allen, B. T.; Aune, T.; Barber, A. S.; Berley, D.; Braun, J.; Chen, C.; Christopher, G. E.; DeYoung, T.;

Spectroscopic limits to an extragalactic far-ultraviolet background.

PubMed

Martin, C; Hurwitz, M; Bowyer, S

1991-10-01

We use a spectrum of the lowest intensity diffuse far-ultraviolet background obtained from a series of observations in a number of celestial view directions to constrain the properties of the extragalactic FUV background. The mean continuum level, IEG = 280 +/- 35 photons cm-2 s-1 angstrom-1 sr-1, was obtained in a direction with very low H I column density, and this represents a firm upper limit to any extragalactic background in the 1400-1900 angstroms band. Previous work has demonstrated that the far-ultraviolet background includes (depending on a view direction) contributions from dust-scattered Galactic light, high-ionization emission lines, two-photon emission from H II, H2 fluorescence, and the integrated light of spiral galaxies. We find no evidence in the spectrum of line or continuum features that would signify additional extragalactic components. Motivated by the observation of steep BJ and U number count distributions, we have made a detailed comparison of galaxy evolution models to optical and UV data. We find that the observations are difficult to reconcile with a dominant contribution from unclustered, starburst galaxies at low redshifts. Our measurement rules out large ionizing fluxes at z = 0, but cannot strongly constrain the QSO background light, which is expected to be 0.5%-4% of IEG. We present improved limits on radiative lifetimes of massive neutrinos. We demonstrated with a simple model that IGM radiation is unlikely to make a significant contribution to IEG. Since dust scattering could produce a significant part of the continuum in this lowest intensity spectrum, we carried out a series of tests to evaluate this possibility. We find that the spectrum of a nearby target with higher NH I, when corrected for H2 fluorescence, is very similar to the spectrum obtained in the low H I view direction. This is evidence that the majority of the continuum observed at low NH I is also dust reflection, indicating either the existence of a hitherto unidentified dust component, or of a large enhancement in dust scattering efficiency in low-density gas. We also review the effects of an additional dust component on the far-infrared background and on extragalactic FUV observations. We conclude that dust reflection, combined with modest contributions from H II two-photon emission and from the integrated light of late-type galaxies, may account for virtually all of the FUV background in low H I column density directions.

Probing the Dusty Stellar Populations of the Local Volume Galaxies with JWST /MIRI

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

Jones, Olivia C.; Meixner, Margaret; Justtanont, Kay

The Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope ( JWST ) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich Spitzer -IRS spectroscopic data set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)–Spectroscopic survey of more than 1000 objects in the Magellanic Clouds, the Grid of Red Supergiant and Asymptotic Giant Branch Star Model (grams), and the grid of YSO models by Robitaille et al., we calculate the expected flux densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes tomore » explore the JWST /MIRI colors and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI color classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars, and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colors.« less

New Limits on Extragalactic Magnetic Fields from Rotation Measures

NASA Astrophysics Data System (ADS)

Pshirkov, M. S.; Tinyakov, P. G.; Urban, F. R.

2016-05-01

We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2 σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields.

Small-Scale Spatial Fluctuations in the Soft X-Ray Background. Degree awarded by Maryland Univ., 2000

NASA Technical Reports Server (NTRS)

Kuntz, K. D.; White, Nicolas E. (Technical Monitor)

2001-01-01

In order to isolate the diffuse extragalactic component of the soft X-ray background, we have used a combination of ROSAT All-Sky Survey and IRAS 100 micron data to separate the soft X-ray background into five components. We find a Local Hot Bubble similar to that described by Snowden et al (1998). We make a first calculation of the contribution by unresolved Galactic stars to the diffuse background. We constrain the normalization of the Extragalactic Power Law (the contribution of the unresolved extragalactic point sources such as AGN, QSO'S, and normal galaxies) to 9.5 +/- 0.9 keV/(sq cm s sr keV), assuming a power-law index of 1.46. We show that the remaining emission, which is some combination of Galactic halo emission and the putative diffuse extragalactic emission, must be composed of at least two components which we have characterized by thermal spectra. The softer component has log T - 6.08 and a patchy distribution; thus it is most probably part of the Galactic halo. The harder component has log T - 6.46 and is nearly isotropic; some portion may be due to the Galactic halo and some portion may be due to the diffuse extragalactic emission. The maximum upper limit to the strength of the emission by the diffuse extragalactic component is the total of the hard component, approx. 7.4 +/- 1.0 keV/(sq cm s sr keV) in the 3/4 keV band. We have made the first direct measure of the fluctuations due to the diffuse extragalactic emission in the 3/4 keV band. Physical arguments suggest that small angular scale (approx. 10') fluctuations in the Local Hot Bubble or the Galactic halo will have very short dissipation times (about 10(exp 5) years). Therefore, the fluctuation spectrum of the soft X-ray background should measure the distribution of the diffuse extragalactic emission. Using mosaics of deep, overlapping PSPC pointings, we find an autocorrelation function value of approx. 0.0025 for 10' < theta < 20', and a value consistent with zero on larger scales. Measurement of the fluctuations with a delta I/I method produces consistent results.

The Environments of Obscured Quasars

NASA Astrophysics Data System (ADS)

Jones, Kristen M.; Lacy, Mark; Nielsen, Danielle

2016-01-01

Supermassive Black Hole (SMBH) feedback is prescribed for driving the high-end shape of the galaxy luminosity function, clearing the circumnuclear environment during the end stages of mergers, and eventually turning off its own accretion. Yet the dominant processes and characteristics of active galactic nuclei are indistinct. Chief among this confusion is how significant the role of dust is in each galaxy. Orientation of the dusty torus is attributed to causing the differences between Sy1 and Sy2, but whether obscured quasars are found in particularly dusty host galaxies, if they exist at a different stage in the merger process (early on, before the dust is blown out), or if they are merely oriented differently than optical quasars is not yet so well distinguished. With obscured quasars now observed to make up 50% or greater of the population of quasars, the question of what causes obscuration becomes vital to address. With this in mind, I study matched samples of obscured and unobscured quasars to characterize their environments, with the intent of addressing what contribution environment has to obscuration levels. I investigate the megaparsec-scale environments of SIRTF Wide-field Infra-Red Extragalactic Survey (SWIRE) quasars at z ˜ 1-3 by cross-correlating the sample with 3.8 million galaxies from the Spitzer Extragalactic Representative Volume Survey (SERVS). Optically obscured quasars are compared to a control sample of optically-bright quasars via selection in the mid-infrared. Environments were observed at 3.6 and 4.5 μm to a depth of ≈ 2 μJy (AB = 23.1). Recent work has found diverse results in such studies, with dependence of environmental richness on both redshift and level of obscuration. I find that, within reasonable error, on average there is no distinct difference between the level of clustering for obscured and normal quasars, and that there is no dependence on redshift of this result within the range of 1.3 < z < 2.5. I compare our results with recent studies and investigate the role of selection criteria in the assessment of clustering. I also explore the large scale SED structure of obscured and unobscured quasar host galaxies.

EoR Foregrounds: the Faint Extragalactic Radio Sky

NASA Astrophysics Data System (ADS)

Prandoni, Isabella

2018-05-01

A wealth of new data from upgraded and new radio interferometers are rapidly improving and transforming our understanding of the faint extra-galactic radio sky. Indeed the mounting statistics at sub-mJy and μJy flux levels is finally allowing us to get stringent observational constraints on the faint radio population and on the modeling of its various components. In this paper I will provide a brief overview of the latest results in areas that are potentially important for an accurate treatment of extra-galactic foregrounds in experiments designed to probe the Epoch of Reionization.

Cosmic-ray antimatter - A primary origin hypothesis

NASA Technical Reports Server (NTRS)

Stecker, F. W.; Protheroe, R. J.; Kazanas, D.

1983-01-01

The present investigation is concerned with the possibility that the observed cosmic-ray protons are of primary extragalactic origin, taking into account the significance of the current antiproton data. Attention is given to questions regarding primary antiprotons, antihelium fluxes, and the propagation of extragalactic cosmic rays. It is concluded that the primary origin hypothesis should be considered as a serious alternative explanation for the cosmic-ray antiproton fluxes. Such extragalactic primary origin can be considered in the context of a baryon symmetric domain cosmology. The fluxes and propagation characteristics suggested are found to be in rough agreement with the present antiproton data.

Extragalactic astronomy: The universe beyond our galaxy

NASA Technical Reports Server (NTRS)

Jacobs, K. C.

1976-01-01

This single-topic brochure is for high school physical science teachers to use in introducing students to extragalactic astronomy. The material is presented in three parts: the fundamental content of extragalactic astronomy; modern discoveries delineated in greater detail; and a summary of the earlier discussions within the structure of the Big-Bang Theory of evolution. Each of the three sections is followed by student exercises (activities, laboratory projects, and questions-and-answers). The unit close with a glossary which explains unfamilar terms used in the text and a collection of teacher aids (literature references and audiovisual materials for utilization in further study).

Mapping extragalactic dark matter annihilation with galaxy surveys: A systematic study of stacked group searches

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

Lisanti, Mariangela; Mishra-Sharma, Siddharth; Rodd, Nicholas L.

Dark matter in the halos surrounding galaxy groups and clusters can annihilate to high-energy photons. Recent advancements in the construction of galaxy group catalogs provide many thousands of potential extragalactic targets for dark matter. In this paper, we outline a procedure to infer the dark matter signal associated with a given galaxy group. Applying this procedure to a catalog of sources, one can create a full-sky map of the brightest extragalactic dark matter targets in the nearby Universe (z≲0.03), supplementing sources of dark matter annihilation from within the local group. As with searches for dark matter in dwarf galaxies, thesemore » extragalactic targets can be stacked together to enhance the signals associated with dark matter. We validate this procedure on mock Fermi gamma-ray data sets using a galaxy catalog constructed from the DarkSky N-body cosmological simulation and demonstrate that the limits are robust, at O(1) levels, to systematic uncertainties on halo mass and concentration. We also quantify other sources of systematic uncertainty arising from the analysis and modeling assumptions. Lastly, our results suggest that a stacking analysis using galaxy group catalogs provides a powerful opportunity to discover extragalactic dark matter and complements existing studies of Milky Way dwarf galaxies.« less

Mapping extragalactic dark matter annihilation with galaxy surveys: A systematic study of stacked group searches

NASA Astrophysics Data System (ADS)

Lisanti, Mariangela; Mishra-Sharma, Siddharth; Rodd, Nicholas L.; Safdi, Benjamin R.; Wechsler, Risa H.

2018-03-01

Dark matter in the halos surrounding galaxy groups and clusters can annihilate to high-energy photons. Recent advancements in the construction of galaxy group catalogs provide many thousands of potential extragalactic targets for dark matter. In this paper, we outline a procedure to infer the dark matter signal associated with a given galaxy group. Applying this procedure to a catalog of sources, one can create a full-sky map of the brightest extragalactic dark matter targets in the nearby Universe (z ≲0.03 ), supplementing sources of dark matter annihilation from within the local group. As with searches for dark matter in dwarf galaxies, these extragalactic targets can be stacked together to enhance the signals associated with dark matter. We validate this procedure on mock Fermi gamma-ray data sets using a galaxy catalog constructed from the DarkSky N -body cosmological simulation and demonstrate that the limits are robust, at O (1 ) levels, to systematic uncertainties on halo mass and concentration. We also quantify other sources of systematic uncertainty arising from the analysis and modeling assumptions. Our results suggest that a stacking analysis using galaxy group catalogs provides a powerful opportunity to discover extragalactic dark matter and complements existing studies of Milky Way dwarf galaxies.

Mapping extragalactic dark matter annihilation with galaxy surveys: A systematic study of stacked group searches

DOE PAGES

Lisanti, Mariangela; Mishra-Sharma, Siddharth; Rodd, Nicholas L.; ...

2018-03-09

Dark matter in the halos surrounding galaxy groups and clusters can annihilate to high-energy photons. Recent advancements in the construction of galaxy group catalogs provide many thousands of potential extragalactic targets for dark matter. In this paper, we outline a procedure to infer the dark matter signal associated with a given galaxy group. Applying this procedure to a catalog of sources, one can create a full-sky map of the brightest extragalactic dark matter targets in the nearby Universe (z≲0.03), supplementing sources of dark matter annihilation from within the local group. As with searches for dark matter in dwarf galaxies, thesemore » extragalactic targets can be stacked together to enhance the signals associated with dark matter. We validate this procedure on mock Fermi gamma-ray data sets using a galaxy catalog constructed from the DarkSky N-body cosmological simulation and demonstrate that the limits are robust, at O(1) levels, to systematic uncertainties on halo mass and concentration. We also quantify other sources of systematic uncertainty arising from the analysis and modeling assumptions. Lastly, our results suggest that a stacking analysis using galaxy group catalogs provides a powerful opportunity to discover extragalactic dark matter and complements existing studies of Milky Way dwarf galaxies.« less

Measuring the Clustering Around Normal and Dust-Obscured Quasars at 2 in the Spitzer Extragalactic Representative Volume Survey (SERVS)

NASA Astrophysics Data System (ADS)

Jones, Kristen M.; Lacy, M.; Spitzer Extragalactic Representative Volume Survey Team

2014-01-01

Little is known about the environments of high redshift quasars, particularly those obscured by dust. Previous work suggests that dust-shrouded (type 2) quasars are at least as common as un-obscured optical (type 1) quasars; therefore, in order to fully understand the role quasars play in the evolutionary history of the universe, we must understand both types of objects. This project seeks to explore the environments in which obscured quasars form. In this poster, we present mid-infrared clustering measurements for a sample of 45 quasars with 1.3 < z < 2.5, a redshift range that is unexplored in the literature. The objects were selected using IRAC multi-color criteria to remove low-redshift starburst and quiescent galaxies, and subsequently had spectroscopy carried out to both obtain redshifts, and to distinguish between type 1 and type 2 quasars; the high-redshift sample presented in this paper is roughly evenly distributed between the two types. We use the SERVS galaxy catalogs to estimate the cross-correlation between each quasar and its surrounding galaxies. The amplitude of this function gives us the richness of the environments in which these quasars are found, and we compare our results with a matched sample with z < 1.3.

The VLBA Extragalactic Proper Motion Catalog and a Measurement of the Secular Aberration Drift

NASA Astrophysics Data System (ADS)

Truebenbach, Alexandra E.; Darling, Jeremy

2017-11-01

We present a catalog of extragalactic proper motions created using archival VLBI data and our own VLBA astrometry. The catalog contains 713 proper motions, with average uncertainties of ˜24 μas yr-1, including 40 new or improved proper motion measurements using relative astrometry with the VLBA. The observations were conducted in the X-band and yielded positions with uncertainties of ˜70 μas. We add 10 new redshifts using spectroscopic observations taken at Apache Point Observatory and Gemini North. With the VLBA Extragalactic Proper Motion Catalog, we detect the secular aberration drift—the apparent motion of extragalactic objects caused by the solar system’s acceleration around the Galactic center—at a 6.3σ significance. We model the aberration drift as a spheroidal dipole, with the square root of the power equal to 4.89 ± 0.77 μas yr-1, an amplitude of 1.69 ± 0.27 μas yr-1, and an apex at (275\\buildrel{\\circ}\\over{.} 2+/- 10\\buildrel{\\circ}\\over{.} 0, -29\\buildrel{\\circ}\\over{.} 4+/- 8\\buildrel{\\circ}\\over{.} 8). Our dipole model detects the aberration drift at a higher significance than some previous studies, but at a lower amplitude than expected or previously measured. The full aberration drift may be partially removed by the no-net-rotation constraint used when measuring archival extragalactic radio source positions. Like the cosmic microwave background dipole, which is induced by the observer’s motion, the aberration drift signal should be subtracted from extragalactic proper motions in order to detect cosmological proper motions, including the Hubble expansion, long-period stochastic gravitational waves, and the collapse of large-scale structure.

Star-Forming Regions in Orion as a Dust Evolution Laboratory

NASA Astrophysics Data System (ADS)

Wiebe, D.; Murga, M.; Sivkova, E.

2017-06-01

Star-forming regions (SFR) represent a convenient opportunity to study various processes related both to dust growth and to dust destruction. While extragalactic SFRs allow considering these processes in a wide range of metallicities, UV field intensities, etc., the Orion star-forming complex opens up a possibility to observe dust evolution with an unprecedented angular resolution. We review various observations related to dust evolution in some most prominent Orion regions, paying special attention to organic dust evolution, and introduce a new model of organic dust evolution.

X-ray Transients in the Advanced LIGO/Virgo Horizon

NASA Technical Reports Server (NTRS)

Kanner, Jonah; Baker, John G.; Blackburn, Lindy L.; Camp, Jordan B.; Mooley, Kunal; Mushotzky, Richard F.; Ptak, Andrew Francis

2013-01-01

Advanced LIGO and Advanced Virgo will be all-sky monitors for merging compact objects within a few hundred megaparsecs. Finding the electromagnetic counterparts to these events will require an understanding of the transient sky at low redshift (z < 0.1). We performed a systematic search for extragalactic, low redshift, transient events in the XMM-Newton Slew Survey. In a flux limited sample, we found that highly variable objects comprised 10% of the sample, and that of these, 10% were spatially coincident with cataloged optical galaxies. This led to 4 × 10(exp -4) transients per square degree above a flux threshold of 3×10(exp -12) erg/sq cm/s (0.2-2 keV) which might be confused with LIGO/Virgo counterparts. This represents the first extragalactic measurement of the soft X-ray transient rate within the Advanced LIGO/Virgo horizon. Our search revealed six objects that were spatially coincident with previously cataloged galaxies, lacked evidence for optical active galactic nuclei, displayed high luminosities approx. 10(exp 43) erg/s, and varied in flux by more than a factor of 10 when compared with the ROSAT All-Sky Survey. At least four of these displayed properties consistent with previously observed tidal disruption events.

The faint galaxy contribution to the diffuse extragalactic background light

NASA Technical Reports Server (NTRS)

Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

1992-01-01

Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

Optical variability of extragalactic objects used to tie the HIPPARCOS reference frame to an extragalactic system using Hubble space telescope observations

NASA Technical Reports Server (NTRS)

Bozyan, Elizabeth P.; Hemenway, Paul D.; Argue, A. Noel

1990-01-01

Observations of a set of 89 extragalactic objects (EGOs) will be made with the Hubble Space Telescope Fine Guidance Sensors and Planetary Camera in order to link the HIPPARCOS Instrumental System to an extragalactic coordinate system. Most of the sources chosen for observation contain compact radio sources and stellarlike nuclei; 65 percent are optical variables beyond a 0.2 mag limit. To ensure proper exposure times, accurate mean magnitudes are necessary. In many cases, the average magnitudes listed in the literature were not adequate. The literature was searched for all relevant photometric information for the EGOs, and photometric parameters were derived, including mean magnitude, maximum range, and timescale of variability. This paper presents the results of that search and the parameters derived. The results will allow exposure times to be estimated such that an observed magnitude different from the tabular magnitude by 0.5 mag in either direction will not degrade the astrometric centering ability on a Planetary Camera CCD frame.

A New Determination of the Extragalactic Diffuse X-Ray Background from EGRET Data

NASA Technical Reports Server (NTRS)

Strong, Andrew W.; Moskalenko, Igor V.; Reimer, Olaf

2004-01-01

We use the GALPROP model for cosmic-ray propagation to obtain a new estimate of the Galactic component of gamma rays, and show that away from the Galactic plane it gives an accurate prediction of the observed EGRET intensities in the energy range 30 MeV - 50 GeV. On this basis we re-evaluate the extragalactic gamma-ray background. We find that for some energies previous work underestimated the Galactic contribution at high latitudes and hence overestimated the background. Our new background spectrum shows a positive curvature similar to that expected for models of the extragalactic emission based on the blazar population.

Blazar Duty-Cycle at Gamma-Ray Frequecies: Constraints From Extragalactic Background Radiation And Prospects for AGILE And GLAST

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

Pittori, Carlotta; Cavazzuti, Elisabetta; Colafrancesco, Sergio

2011-11-29

We take into account the constraints from the observed extragalactic {gamma}-ray background to estimate the maximum duty cycle allowed for a selected sample of WMAP Blazars, in order to be detectable by AGILE and GLAST {gamma}-ray experiments. For the nominal sensitivity values of both instruments, we identify a subset of sources which can in principle be detectable also in a steady state without over-predicting the extragalactic background. This work is based on the results of a recently derived Blazar radio LogN-LogS obtained by combining several multi-frequency surveys.

Extragalactic Astronomy: The Universe Beyond Our Galaxy.

ERIC Educational Resources Information Center

Jacobs, Kenneth Charles

This booklet is part of an American Astronomical Society curriculum project designed to provide teaching materials to teachers of secondary school chemistry, physics, and earth science. The material is presented in three parts: one section provides the fundamental content of extragalactic astronomy, another section discusses modern discoveries in…

Extragalactic Gravitational Collapse

NASA Astrophysics Data System (ADS)

Rees, Martin J.

After some introductory "numerology", routes towards black hole formation are briefly reviewed; some properties of black holes relevant to theories for active galactic nuclei are then described. Applications are considered to specific models for energy generation and the production of relativistic beams. The paper concludes with a discussion of extragalactic sources of gravitational waves.

SERVS: the Spitzer Extragalactic Representative Volume Survey

NASA Astrophysics Data System (ADS)

Lacy, Mark; Afonso, Jose; Alexander, Dave; Best, Philip; Bonfield, David; Castro, Nieves; Cava, Antonio; Chapman, Scott; Dunlop, James; Dyke, Eleanor; Edge, Alastair; Farrah, Duncan; Ferguson, Harry; Foucaud, Sebastian; Franceschini, Alberto; Geach, Jim; Gonzales, Eduardo; Hatziminaoglou, Evanthia; Hickey, Samantha; Ivison, Rob; Jarvis, Matt; Le Fèvre, Olivier; Lonsdale, Carol; Maraston, Claudia; McLure, Ross; Mortier, Angela; Oliver, Seb; Ouchi, Masami; Parish, Glen; Perez-Fournon, Ismael; Petric, Andreea; Pierre, Mauguerite; Readhead, Tony; Ridgway, Susan; Romer, Katherine; Rottgering, Huub; Rowan-Robinson, Michael; Sajina, Anna; Seymour, Nick; Smail, Ian; Surace, Jason; Thomas, Peter; Trichas, Markos; Vaccari, Mattia; Verma, Aprajita; Xu, Kevin; van Kampen, Eelco

2008-12-01

We will use warm Spitzer to image 18deg^2 of sky to microJy depth. This is deep enough to undertake a complete census of massive galaxies from z~6 to ~1 in a volume ~0.8Gpc^3, large enough to overcome the effects of cosmic variance, which place severe limitations on the conclusions that can be drawn from smaller fields. We will greatly enhance the diagnostic power of the Spitzer data by performing most of this survey in the region covered by the near-IR VISTA-VIDEO survey, and in other areas covered by near-IR, Herschel and SCUBA2 surveys. We will build complete near-infrared spectral energy distributions using the superb datasets from VIDEO, in conjunction with our Spitzer data, to derive accurate photometric redshifts and the key properties of stellar mass and star formation rates for a large sample of high-z galaxies. Obscured star formation rates and dust-shrouded BH growth phases will be uncovered by combining the Spitzer data with the Herschel and SCUBA2 surveys. We will thus build a complete picture of the formation of massive galaxies from z~6, where only about 1% of the stars in massive galaxies have formed, to z~1 where ~50% of them haveE Our large volume will allow us to also find examples of rare objects such as high-z quasars (~10-100 at z>6.5), high-z galaxy clusters (~20 at z>1.5 with dark halo masses >10^14 solar masses), and evaluate how quasar activity and galaxy environment affect star formation. This survey makes nearly optimal use of warm Spitzer; (a) all of the complementary data is either taken or will be taken in the very near future, and will be immediately publicly accessible, (b) the slew overheads are relatively small, (c) the observations are deep enough to detect high redshift galaxies but not so deep that source confusion reduces the effective survey area.

THE ARECIBO LEGACY FAST ALFA SURVEY. VIII. H I SOURCE CATALOG OF THE ANTI-VIRGO REGION AT {delta} = +25 DEG

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

Martin, Ann M.; Giovanelli, Riccardo; Haynes, Martha P.

We present a fourth catalog of H I sources from the Arecibo Legacy Fast ALFA (ALFALFA) Survey. We report 541 detections over 136 deg{sup 2}, within the region of the sky having 22{sup h} < {alpha} < 03{sup h} and 24 deg. < {delta} < 26 deg. This complements a previous catalog in the region 26 deg. < {delta} < 28 deg. We present here the detections falling into three classes: (1) extragalactic sources with signal-to-noise ratio (S/N)>6.5, where the reliability of the catalog is better than 95%; (2) extragalactic sources 5.0 < S/N < 6.5 and a previously measuredmore » optical redshift that corroborates our detection; or (3) High Velocity Clouds (HVCs), or subcomponents of such clouds, in the periphery of the Milky Way. Of the 541 objects presented here, 90 are associated with HVCs, while the remaining 451 are identified as extragalactic objects. Optical counterparts have been matched with all but one of the extragalactic objects.« less

“Real-Time” Cosmology with Extragalactic Proper Motions: the Secular Aberration Drift and Evolution of Large-Scale Structure

NASA Astrophysics Data System (ADS)

Truebenbach, Alexandra; Darling, Jeremy

2018-01-01

We present the VLBA Extragalactic Proper Motion Catalog, a catalog of extragalactic proper motions created using archival VLBI data and our own VLBA astrometry. The catalog contains 713 proper motions, with average uncertainties of ~ 24 microarcsec/yr, including 40 new or improved proper motion measurements using relative astrometry with the VLBA. We detect the secular aberration drift – the apparent motion of extragalactic objects caused by the solar system's acceleration around the Galactic Center – at 6.3 sigma significance with an amplitude of 1.69 +/- 0.27 microarcsec/yr and an apex consistent with the Galactic Center (275.2 +/- 10.0 deg, -29.4 +/- 8.8 deg). Our dipole model detects the aberration drift at a higher significance than some previous studies (e.g., Titov & Lambert 2013), but at a lower amplitude than expected or previously measured. We then use the correlated relative proper motions of extragalactic objects to place upper limits on the rate of large-scale structure collapse (e.g., Quercellini et al. 2009; Darling 2013). Pairs of small separation objects that are in gravitationally interacting structures such as filaments of large-scale structure will show a net decrease in angular separation (> - 15.5 microarcsec/yr) as they move towards each other, while pairs of large separation objects that are gravitationally unbound and move with the Hubble expansion will show no net change in angular separation. With our catalog, we place a 3 sigma limit on the rate of convergence of large-scale structure of -11.4 microarcsec/yr for extragalactic objects within 100 comoving Mpc of each other. We also confirm that large separation objects (> 800 comoving Mpc) move with the Hubble flow to within ~ 2.2 microarcsec/yr. In the future, we plan to incorporate the upcoming Gaia proper motions into our catalog to achieve a higher precision measurement of the average relative proper motion of gravitationally interacting extragalactic objects and to refine our measurement of the collapse of large-scale structure. This research was performed with support from the NSF grant AST-1411605.Darling, J. 2013, AJ, 777, L21; Quercellini et al. 2009. Phys. Rev. Lett., 102, 151302; Titov, O. & Lambert, S. 2013, A&A, 559, A95

Wide extragalactic (sub-)millimeter surveys with SCUBA and AzTEC

NASA Astrophysics Data System (ADS)

Aretxaga, I.; Hughes, D. H.; SHADES Collaboration; AzTEC Collaboration

2009-05-01

We summarize the present status of our knowledge of the millimeter galaxy population derived from extensive (sub-) millimeter extragalactic surveys like the SCUBA HAlf Degree Survey (SHADES), and the current status of the next generation of surveys traced with the AzTEC camera, that has, so far, surveyed more than 2 degrees at 1.1wavelengths.

The CfA Einstein Observatory extended deep X-ray survey

NASA Technical Reports Server (NTRS)

Primini, F. A.; Murray, S. S.; Huchra, J.; Schild, R.; Burg, R.

1991-01-01

All IPC exposures in the Einstein Extended Deep X-ray Survey program have been reanalyzed. The current survey covers about 2.3 sq deg with a typical limiting sensitivity of about 5 x 10 to the -14th ergs/sq cm/s in the energy range from 0.8-3.5 keV. A total of 25 IPC sources are detected above a threshold of 4.5 sigma. A total of 18 are detected independently in the HRI, leading to the identification of six with stars and 11 with extragalactic objects. The remaining sources are classified as extragalactic. The population of identified extragalactic objects is dominated by QSOs, with one or two possible clusters. The basic conclusions of the original survey remain unchanged.

Diffuse Gamma Rays Galactic and Extragalactic Diffuse Emission

NASA Technical Reports Server (NTRS)

Moskalenko, Igor V.; Strong, Andrew W.; Reimer, Olaf

2004-01-01

Diffuse gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived average spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.

Determination of the extragalactic-planetary frame tie from joint analysis of radio interferometric and lunar laser ranging measurements

NASA Technical Reports Server (NTRS)

Folkner, W. M.; Charlot, P.; Finger, M. H.; Williams, J. G.; Sovers, O. J.; Newhall, XX; Standish, E. M., Jr.

1994-01-01

Very Long Baseline Interferometry (VLBI) observations of extragalactic radio sources provide the basis for defining an accurate non-rotating reference frame in terms of angular positions of the sources. Measurements of the distance from the Earth to the Moon and to the inner planets provide the basis for defining an inertial planetary ephemeris reference frame. The relative orientation, or frame tie, between these two reference frames is of interest for combining Earth orientation measurements, for comparing Earth orientation results with theories referred to the mean equator and equinox, and for determining the positions of the planets with respect to the extragalactic reference frame. This work presents an indirect determination of the extragalactic-planetary frame tie from a combined reduction of VLBI and Lunar Laser Ranging (LLR) observations. For this determination, data acquired by LLR tracking stations since 1969 have been analyzed and combined with 14 years of VLBI data acquired by NASA's Deep Space Network since 1978. The frame tie derived from this joint analysis, with an accuracy of 0.003 sec, is the most accurate determination obtained so far. This result, combined with a determination of the mean ecliptic (defined in the rotating sense), shows that the mean equinox of epoch J2000 is offset from the x-axis of the extragalactic frame adopted by the International Earth Rotation Service for astrometric and geodetic applications by 0.078 sec +/- 0.010 sec along the y-direction and y 0.019 sec +/- 0.001 sec. along the z-direction.

Neutrino diagnostics of ultrahigh energy cosmic ray protons

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

Ahlers, Markus; Sarkar, Subir; Anchordoqui, Luis A.

2009-04-15

The energy at which cosmic rays from extra-galactic sources begin to dominate over those from galactic sources is an important open question in astroparticle physics. A natural candidate is the energy at the 'ankle' in the approximately power-law energy spectrum which is indicative of a crossover from a falling galactic component to a flatter extra-galactic component. The transition can occur without such flattening but this requires some degree of conspiracy of the spectral shapes and normalizations of the two components. Nevertheless, it has been argued that extra-galactic sources of cosmic ray protons that undergo interactions on the CMB can reproducemore » the energy spectrum below the ankle if the crossover energy is as low as the 'second knee' in the spectrum. This low crossover model is constrained by direct measurements by the Pierre Auger Observatory, which indicate a heavier composition at these energies. We demonstrate that upper limits on the cosmic diffuse neutrino flux provide a complementary constraint on the proton fraction in ultra-high energy extra-galactic cosmic rays and forthcoming data from IceCube will provide a definitive test of this model.« less

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, T. M.; Pavlidou, V.

2013-01-01

The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Physics of cosmological cascades and observable properties

NASA Astrophysics Data System (ADS)

Fitoussi, T.; Belmont, R.; Malzac, J.; Marcowith, A.; Cohen-Tanugi, J.; Jean, P.

2017-04-01

TeV photons from extragalactic sources are absorbed in the intergalactic medium and initiate electromagnetic cascades. These cascades offer a unique tool to probe the properties of the universe at cosmological scales. We present a new Monte Carlo code dedicated to the physics of such cascades. This code has been tested against both published results and analytical approximations, and is made publicly available. Using this numerical tool, we investigate the main cascade properties (spectrum, halo extension and time delays), and study in detail their dependence on the physical parameters (extragalactic magnetic field, extragalactic background light, source redshift, source spectrum and beaming emission). The limitations of analytical solutions are emphasized. In particular, analytical approximations account only for the first generation of photons and higher branches of the cascade tree are neglected.

Understanding nature's particle accelerators using high energy gamma-ray survey instruments

NASA Astrophysics Data System (ADS)

Abeysekara, Anushka Udara

Nature's particle accelerators, such as Pulsars, Pulsar Wind Nebulae, Active Galactic Nuclei and Supernova Remnants accelerate charged particles to very high energies that then produce high energy photons. The particle acceleration mechanisms and the high energy photon emission mechanisms are poorly understood phenomena. These mechanisms can be understood either by studying individual sources in detail or, alternatively, using the collective properties of a sample of sources. Recent development of GeV survey instruments, such as Fermi-LAT, and TeV survey instruments, such as Milagro, provides a large sample of high energy gamma-ray flux measurements from galactic and extra-galactic sources. In this thesis I provide constraints on GeV and TeV radiation mechanisms using the X-ray-TeV correlations and GeV-TeV correlations. My data sample was obtained from three targeted searches for extragalactic sources and two targeted search for galactic sources, using the existing Milagro sky maps. The first extragalactic candidate list consists of Fermi-LAT GeV extragalactic sources, and the second extragalactic candidate list consists of TeVCat extragalactic sources that have been detected by Imaging Atmospheric Cerenkov Telescopes (IACTs). In both extragalactic candidate lists Markarian 421 was the only source detected by Milagro. A comparison between the Markarian 421 time-averaged flux, measured by Milagro, and the flux measurements of transient states, measured by IACTs, is discussed. The third extragalactic candidate list is a list of potential TeV emitting BL Lac candidates that was synthesized using X-ray observations of BL Lac objects and a Synchrotron Self-Compton model. Milagro's sensitivity was not sufficient to detect any of those candidates. However, the 95% confidence flux upper limits of those sources were above the predicted flux. Therefore, these results provide evidence to conclude that the Synchrotron Self-Compton model for BL Lac objects is still a viable model. Targeted searches for galactic candidates were able to measure TeV emission associated with 14 Fermi-LAT GeV pulsars. In this thesis I also presented a new multi-wavelength technique that I developed to isolate the flux correlation factor (fΩ ) of pulsars as a function of pulsar spin down luminosity. The correlation between fΩ and pulsar spin-down luminosity for a Fermi-LAT GeV pulsar sample was measured using the measurements obtained in the Milagro targeted search performed for galactic sources and from the literature. The measured correlation has some features that favor the Outer Gap model over the Polar Cap, Slot Gap and One Pole Caustic models for pulsar emission in the energy range of 0.1 to 100 GeV. However, these simulated models failed to explain many other important pulsar population characteristics. Therefore, further improvements on the galactic pulsar population simulations are needed to provide tighter constraints.

Some remarks on extragalactic globular clusters

NASA Astrophysics Data System (ADS)

Richtler, Tom

2006-03-01

I comment (in a review fashion) on a few selected topics in the field of extragalactic globular clusters with strong emphasis on recent work. The topics are: bimodality in the colour distribution of cluster systems, young massive clusters, and the brightest old clusters. Globular cluster research, per- haps more than ever, has lead to important (at least to astronomers) progress and problems in galaxy structure and formation.

Dark Matter and Extragalactic Gas Clouds in the NGC 4532/DDO 137 System

NASA Technical Reports Server (NTRS)

Hoffman, G. L.; Lu, N. Y.; Salpeter, E. E.; Connell, B. M.

1998-01-01

H I synthesis mapping of NGC 4532 and DDO 137, a pair of Sm galaxies on the edge of the Virgo cluster, is used to determine rotation curves for each of the galaxies and to resolve the structure and kinematics of three extragalactic H I clouds embedded in an extended envelope of diffuse HI discovered in earlier Arecibo studies of the system.

Observations of flat-spectrum radio sources at λ850 μm from the James Clerk Maxwell Telescope - I. 1997 April to 2000 April

NASA Astrophysics Data System (ADS)

Robson, E. I.; Stevens, J. A.; Jenness, T.

2001-11-01

Calibrated data for 65 flat-spectrum extragalactic radio sources are presented at a wavelength of 850μm, covering a three-year period from 1997 April. The data, obtained from the James Clerk Maxwell Telescope using the SCUBA camera in pointing mode, were analysed using an automated pipeline process based on the Observatory Reduction and Acquisition Control-Data Reduction (orac-dr) system. This paper describes the techniques used to analyse and calibrate the data, and presents the data base of results along with a representative sample of the better-sampled light curves.

Extragalactic optical and near-infrared foregrounds to 21-cm epoch of reionisation experiments

NASA Astrophysics Data System (ADS)

Jarvis, Matt J.; Bowler, Rebecca A. A.; Hatfield, Peter W.

2018-05-01

Foreground contamination is one of the most important limiting factors in detecting the neutral hydrogen in the epoch of reionisation. These foregrounds can be roughly split into galactic and extragalactic foregrounds. In these proceedings we highlight information that can be gleaned from multi-wavelength extragalactic surveys in order to overcome this issue. We discuss how clustering information from the lower-redshift, foreground galaxies, can be used as additional information in accounting for the noise associated with the foregrounds. We then go on to highlight the expected contribution of future optical and near-infrared surveys for detecting the galaxies responsible for ionising the Universe. We suggest that these galaxies can also be used to reduce the systematics in the 21-cm epoch of reionisation signal through cross-correlations if enough common area is surveyed.

Low-redshift Lyman-alpha absorption lines and the dark matter halos of disk galaxies

NASA Technical Reports Server (NTRS)

Maloney, Philip

1992-01-01

Ultraviolet observations of the low-redshift quasar 3C 273 using the Hubble Space Telescope have revealed many more Lyman-alpha absorption lines than would be expected from extrapolation of the absorption systems seen toward QSOs at z about 2. It is shown here that these absorption lines can plausibly be produced by gas at large radii in the disks of spiral and irregular galaxies; the gas is confined by the dark matter halos and ionized and heated by the extragalactic radiation field. This scenario does not require the extragalactic ionizing radiation field to decline as rapidly with decreasing z as the QSO emissivity. Observations of Ly-alpha absorption through the halos of known galaxies at low redshift will constrain both the extragalactic background and the properties of galactic halos.

Deep Extragalactic VIsible Legacy Survey (DEVILS): Motivation, Design and Target Catalogue

NASA Astrophysics Data System (ADS)

Davies, L. J. M.; Robotham, A. S. G.; Driver, S. P.; Lagos, C. P.; Cortese, L.; Mannering, E.; Foster, C.; Lidman, C.; Hashemizadeh, A.; Koushan, S.; O'Toole, S.; Baldry, I. K.; Bilicki, M.; Bland-Hawthorn, J.; Bremer, M. N.; Brown, M. J. I.; Bryant, J. J.; Catinella, B.; Croom, S. M.; Grootes, M. W.; Holwerda, B. W.; Jarvis, M. J.; Maddox, N.; Meyer, M.; Moffett, A. J.; Phillipps, S.; Taylor, E. N.; Windhorst, R. A.; Wolf, C.

2018-06-01

The Deep Extragalactic VIsible Legacy Survey (DEVILS) is a large spectroscopic campaign at the Anglo-Australian Telescope (AAT) aimed at bridging the near and distant Universe by producing the highest completeness survey of galaxies and groups at intermediate redshifts (0.3 < z < 1.0). Our sample consists of ˜60,000 galaxies to Y<21.2 mag, over ˜6 deg2 in three well-studied deep extragalactic fields (Cosmic Origins Survey field, COSMOS, Extended Chandra Deep Field South, ECDFS and the X-ray Multi-Mirror Mission Large-Scale Structure region, XMM-LSS - all Large Synoptic Survey Telescope deep-drill fields). This paper presents the broad experimental design of DEVILS. Our target sample has been selected from deep Visible and Infrared Survey Telescope for Astronomy (VISTA) Y-band imaging (VISTA Deep Extragalactic Observations, VIDEO and UltraVISTA), with photometry measured by PROFOUND. Photometric star/galaxy separation is done on the basis of NIR colours, and has been validated by visual inspection. To maximise our observing efficiency for faint targets we employ a redshift feedback strategy, which continually updates our target lists, feeding back the results from the previous night's observations. We also present an overview of the initial spectroscopic observations undertaken in late 2017 and early 2018.

REDSHIFT-INDEPENDENT DISTANCES IN THE NASA/IPAC EXTRAGALACTIC DATABASE: METHODOLOGY, CONTENT, AND USE OF NED-D

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

Steer, Ian; Madore, Barry F.; Mazzarella, Joseph M.

Estimates of galaxy distances based on indicators that are independent of cosmological redshift are fundamental to astrophysics. Researchers use them to establish the extragalactic distance scale, to underpin estimates of the Hubble constant, and to study peculiar velocities induced by gravitational attractions that perturb the motions of galaxies with respect to the “Hubble flow” of universal expansion. In 2006 the NASA/IPAC Extragalactic Database (NED) began making available a comprehensive compilation of redshift-independent extragalactic distance estimates. A decade later, this compendium of distances (NED-D) now contains more than 100,000 individual estimates based on primary and secondary indicators, available for more thanmore » 28,000 galaxies, and compiled from over 2000 references in the refereed astronomical literature. This paper describes the methodology, content, and use of NED-D, and addresses challenges to be overcome in compiling such distances. Currently, 75 different distance indicators are in use. We include a figure that facilitates comparison of the indicators with significant numbers of estimates in terms of the minimum, 25th percentile, median, 75th percentile, and maximum distances spanned. Brief descriptions of the indicators, including examples of their use in the database, are given in an appendix.« less

A-3 scientific results - extragalactic

NASA Technical Reports Server (NTRS)

Schwartz, D. A.

1979-01-01

The results of the HEAO A-3 experiment are summarized. Specific contributions of the experiment to extragalactic astronomy are emphasized. The discovery of relatively condensed X-ray emission in the cores of those clusters of galaxies which are dominated by a giant elliptical or cD galaxy, the discovery of extended X-ray emitting plasma in groups of galaxies, and the demonstration that BL Lac objects are a class of X-ray sources are among the topics discussed.

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-Ray Background

NASA Technical Reports Server (NTRS)

Venters, T. M.; Pavlidou, V.

2012-01-01

The intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the extragalactic gamma-ray background, through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thus inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that the two extreme cases (zero IGMF and IGMF strong enough to completely isotropize cascade photons) would be separable by ten years of Fermi observations and reasonable model parameters for the gamma-ray background. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Extragalactic photon-ALP conversion at CTA energies

DOE PAGES

Kartavtsev, A.; Raffelt, G.; Vogel, H.

2017-01-12

Magnetic fields in extragalactic space between galaxy clusters may induce conversions between photons and axion-like particles (ALPs), thereby shielding the photons from absorption on the extragalactic background light. For TeV gamma rays, the oscillation length (l osc) of the photon-ALP system becomes inevitably of the same order as the coherence length of the magnetic field l and the length over which the field changes significantly (transition length l t) due to refraction on background photons. We derive exact statistical evolution equations for the mean and variance of the photon and ALP transfer functions in the non-adiabatic regime (l osc ~more » l >> l t). We also make analytical predictions for the transfer functions in the quasi-adiabatic regime (l osc

Dust in Extragalactic Reflection Nebulae

NASA Astrophysics Data System (ADS)

Lee, Chris H.; Hodges-Kluck, Edmund J.

2017-08-01

Observational evidence for extragalactic dust has been recently found in the form of UV extragalactic reflection nebulae around edge-on spiral galaxies, but the nature of the dust is largely unknown. To derive dust parameters, UV fluxes from the spacecrafts GALEX and Swift have been compared with model UV halo SEDs, which have been created from galaxy template spectra and a silicate-graphite dust model. The model contains two free parameters, which are fractional composition and maximum grain size. These analyses have been done for a sample of 8 nearby edge-on spiral galaxies with bright UV halos, where the dust properties can be spatially resolved, such as inside and outside of galactic winds or as a function of height from the galactic disc. The dust properties give insight into how dust is expelled from the galactic disc, which can also be applied to understanding gaseous outflows from the galaxies as well.

Implications of Ultrahigh Energy Air Showers for Physics and Astrophysics

NASA Technical Reports Server (NTRS)

Stecker, F. W.; White, Nicholas E. (Technical Monitor)

2002-01-01

The primary ultrahigh energy particles which produce giant extensive air showers in the Earth atmosphere present an intriguing mystery from two points of view: (1) How are the base particles produced with such astounding energies, eight orders of magnitude higher than those produced by the best man-made terrestrial accelerators? (2) Since they are most likely extragalactic in origin, how do they reach us from extragalactic distances without suffering the severe losses expected from interactions with the 2.7 K thermal cosmic background photons, the so called GZK effect? The answers to these questions may involve new physics: violations of special relativity, grand unification theories, and quantum gravity theories involving large extra dimensions. They may involve new astrophysical sources, "zevatrons". Or some heretofore totally unknown physics or astrophysics may hold the answer. I will discuss here the mysteries involving the production and extragalactic propagation of ultrahigh energy cosmic rays and some suggested possible solutions.

Blazar Gamma-Rays, Shock Acceleration, and the Extragalactic Background Light

NASA Technical Reports Server (NTRS)

Stecker, Floyd W.; Baring, Matthew G.; Summerlin, Errol J.

2007-01-01

The observed spectra of blazars, their intrinsic emission, and the underlying populations of radiating particles are intimately related. The use of these sources as probes of the extragalactic infrared background, a prospect propelled by recent advances in TeV-band telescopes, soon to be augmented by observations by NASA's upcoming Gamma-Ray Large Area Space Telescope (GLAST), has been a topic of great recent interest. Here, it is demonstrated that if particles in blazar jets are accelerated at relativistic shocks, then GAMMA-ray spectra with indices less than 1.5 can be produced. This, in turn, loosens the upper limits on the near infrared extragalactic background radiation previously proposed. We also show evidence hinting that TeV blazars with flatter spectra have higher intrinsic TeV GAMMA-ray luminosities and we indicate that there may be a correlation of flatness and luminosity with redshift.

The Extragalactic Radio Background

NASA Technical Reports Server (NTRS)

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

2011-01-01

The existence of an isotropic component of the high-latitude radio sky has been recognized for nearly fifty years, but has typically been assumed to be Galactic in origin. We use recent radio observations to test whether the observed high-latitude component could originate within either an extended Galactic halo or a more local "bubble" structure. The lack of significant polarization from the isotropic component, combined with the lack of significant correlation with the Galactic far-infrared emission, rule out an origin within the Galaxy. We conclude that an extragalactic origin is the only viable alternative for the bulk of the isotropic high-latitude emission. The extragalactic component is 2-3 times brighter than local (Galactic) emission towards the Galactic poles and is consistent with a power law in frequency with amplitude T(sub r) = 24.1 plus or minus 2.1 K and spectral index beta = -2.599 plus or minus 0.036 evaluated at reference frequency 310 MHz.

Fixing the reference frame for PPMXL proper motions using extragalactic sources

DOE PAGES

Grabowski, Kathleen; Carlin, Jeffrey L.; Newberg, Heidi Jo; ...

2015-05-27

In this study, we quantify and correct systematic errors in PPMXL proper motions using extragalactic sources from the first two LAMOST data releases and the Vèron-Cetty & Vèron Catalog of Quasars. Although the majority of the sources are from the Vèron catalog, LAMOST makes important contributions in regions that are not well-sampled by previous catalogs, particularly at low Galactic latitudes and in the south Galactic cap. We show that quasars in PPMXL have measurable and significant proper motions, which reflect the systematic zero-point offsets present in the catalog. We confirm the global proper motion shifts seen by Wu et al.,more » and additionally find smaller-scale fluctuations of the QSO-derived corrections to an absolute frame. Finally, we average the proper motions of 158 106 extragalactic objects in bins of 3° × 3° and present a table of proper motion corrections.« less

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.

The Chandra Deep Wide-Field Survey: Completing the new generation of Chandra extragalactic surveys

NASA Astrophysics Data System (ADS)

Hickox, Ryan

2016-09-01

Chandra X-ray surveys have revolutionized our view of the growth of black holes across cosmic time. Recently, fundamental questions have emerged about the connection of AGN to their host large scale structures that clearly demand a wide, deep survey over a large area, comparable to the recent extensive Chandra surveys in smaller fields. We propose the Chandra Deep Wide-Field Survey (CDWFS) covering the central 6 sq. deg in the Bootes field, totaling 1.025 Ms (building on 550 ks from the HRC GTO program). CDWFS will efficiently probe a large cosmic volume, allowing us to carry out accurate new investigations of the connections between black holes and their large-scale structures, and will complete the next generation surveys that comprise a key part of Chandra's legacy.

First-generation science cases for ground-based terahertz telescopes

NASA Astrophysics Data System (ADS)

Hirashita, Hiroyuki; Koch, Patrick M.; Matsushita, Satoki; Takakuwa, Shigehisa; Nakamura, Masanori; Asada, Keiichi; Liu, Hauyu Baobab; Urata, Yuji; Wang, Ming-Jye; Wang, Wei-Hao; Takahashi, Satoko; Tang, Ya-Wen; Chang, Hsian-Hong; Huang, Kuiyun; Morata, Oscar; Otsuka, Masaaki; Lin, Kai-Yang; Tsai, An-Li; Lin, Yen-Ting; Srinivasan, Sundar; Martin-Cocher, Pierre; Pu, Hung-Yi; Kemper, Francisca; Patel, Nimesh; Grimes, Paul; Huang, Yau-De; Han, Chih-Chiang; Huang, Yen-Ru; Nishioka, Hiroaki; Lin, Lupin Chun-Che; Zhang, Qizhou; Keto, Eric; Burgos, Roberto; Chen, Ming-Tang; Inoue, Makoto; Ho, Paul T. P.

2016-02-01

Ground-based observations at terahertz (THz) frequencies are a newly explorable area of astronomy in the coming decades. We discuss science cases for a first-generation 10-m class THz telescope, focusing on the Greenland Telescope as an example of such a facility. We propose science cases and provide quantitative estimates for each case. The largest advantage of ground-based THz telescopes is their higher angular resolution (˜ 4″ for a 10-m dish), as compared to space or airborne THz telescopes. Thus, high-resolution mapping is an important scientific argument. In particular, we can isolate zones of interest for Galactic and extragalactic star-forming regions. The THz windows are suitable for observations of high-excitation CO lines and [N II] 205-μm lines, which are scientifically relevant tracers of star formation and stellar feedback. Those lines are the brightest lines in the THz windows, so they are suitable for the initiation of ground-based THz observations. THz polarization of star-forming regions can also be explored since it traces the dust population contributing to the THz spectral peak. For survey-type observations, we focus on "sub-THz" extragalactic surveys, the uniqueness of which is detecting galaxies at redshifts z ˜ 1-2, where the dust emission per comoving volume is the largest in the history of the Universe. Finally we explore possibilities of flexible time scheduling, which enables us to monitor active galactic nuclei, and to target gamma-ray burst afterglows. For these objects, THz and submillimeter wavelength ranges have not yet been explored.

Milagro Observations of Potential TeV Emitters

NASA Astrophysics Data System (ADS)

Abeysekara, Anushka; Linnemann, James

2012-03-01

We searched for point sources in Milagro sky maps at the locations in four catalogs of potential TeV emitting sources. Our candidates are selected from the Fermi 2FGL pulsars, Fermi 2FGL extragalactic sources, TeVCat extragalactic sources, and from the BL Lac TeV Candidate list published by Costamante and Ghisellini in 2002. The False Discovery Rate (FDR) statistical procedure is used to select the sources. The FDR procedure controls the fraction of false detections. Our results are presented in this talk.

Extragalactic radio sources - Accurate positions from very-long-baseline interferometry observations

NASA Technical Reports Server (NTRS)

Rogers, A. E. E.; Counselman, C. C., III; Hinteregger, H. F.; Knight, C. A.; Robertson, D. S.; Shapiro, I. I.; Whitney, A. R.; Clark, T. A.

1973-01-01

Relative positions for 12 extragalactic radio sources have been determined via wide-band very-long-baseline interferometry (wavelength of about 3.8 cm). The standard error, based on consistency between results from widely separated periods of observation, appears to be no more than 0.1 sec for each coordinate of the seven sources that were well observed during two or more periods. The uncertainties in the coordinates determined for the other five sources are larger, but in no case exceed 0.5 sec.

Large-scale anisotropy in the extragalactic gamma-ray background as a probe for cosmological antimatter

NASA Technical Reports Server (NTRS)

Gao, Yi-Tian; Stecker, Floyd W.; Gleiser, Marcelo; Cline, David B.

1990-01-01

Intrinsic anisotropies in the extragalactic gamma-ray background (EGB), which should be detectable with the forthcoming Gamma Ray Observatory, can be used to examine some of the mechanisms proposed to explain its origin, one of which, the baryon-symmetric big bang (BSBB) model, is investigated here. In this simulation, large domains containing matter and antimatter galaxies produce gamma rays by annihilation at the domain boundaries. This mechanism can produce mountain-chain-shaped angular fluctuations in the EGB flux.

22 GHz VLBI Survey: Status Report and Preliminary Results

NASA Technical Reports Server (NTRS)

Moellenbrock, G.; Fujisawa, K.; Preston, R.; Gurvits, L.; Dewey, R.; Hirabayashi, H.; Inoue, M.; Jauncey, D.; Migenes, V.; Roberts, D.;

Constraints on small-scale primordial power by annihilation signals from extragalactic dark matter minihalos

NASA Astrophysics Data System (ADS)

Nakama, Tomohiro; Suyama, Teruaki; Kohri, Kazunori; Hiroshima, Nagisa

2018-01-01

We revisit constraints on small-scale primordial power from annihilation signals from dark matter minihalos. Using gamma rays and neutrinos from extragalactic minihalos and assuming the delta-function primordial spectrum, we show the dependence of the constraints on annihilation modes, the mass of dark matter, and the annihilation cross section. We report conservative constraints by assuming minihalos are fully destructed when becoming part of halos originating from the standard almost-scale invariant primordial spectrum and optimistic constraints by neglecting destruction.

Direct reading of charge multipliers with a self-triggering CMOS analog chip with 105 k pixels at 50 μm pitch

NASA Astrophysics Data System (ADS)

Bellazzini, R.; Spandre, G.; Minuti, M.; Baldini, L.; Brez, A.; Cavalca, F.; Latronico, L.; Omodei, N.; Massai, M. M.; Sgro', C.; Costa, E.; Soffitta, P.; Krummenacher, F.; de Oliveira, R.

2006-10-01

We report on a large area (15×15 mm2), high channel density (470 pixel/mm2), self-triggering CMOS analog chip that we have developed as a pixelized charge collecting electrode of a Micropattern Gas Detector. This device represents a big step forward both in terms of size and performance, and is in fact the last version of three generations of custom ASICs of increasing complexity. The top metal layer of the CMOS pixel array is patterned in a matrix of 105,600 hexagonal pixels with a 50 μm pitch. Each pixel is directly connected to the underlying full electronics chain which has been realized in the remaining five metal and single poly-silicon layers of a 0.18 μm VLSI technology. The chip, which has customizable self-triggering capabilities, also includes a signal pre-processing function for the automatic localization of the event coordinates. Thanks to these advances it is possible to significantly reduce the read-out time and the data volume by limiting the signal output only to those pixels belonging to the region of interest. In addition to the reduced read-out time and data volume, the very small pixel area and the use of a deep sub-micron CMOS technology has allowed bringing the noise down to 50 electrons ENC. Results from in depth tests of this device when coupled to a fine pitch (50 μm on a triangular pattern) Gas Electron Multiplier are presented. It was found that matching the read-out and gas amplification pitch allows getting optimal results. The experimental detector response to polarized and unpolarized X-ray radiation when working with two gas mixtures and two different photon energies is shown and the application of this detector for Astronomical X-ray Polarimetry is discussed. Results from a full Monte-Carlo simulation for several galactic and extragalactic astronomical sources are also reported.

Energy spectrum of extragalactic gamma-ray sources

NASA Technical Reports Server (NTRS)

Protheroe, R. J.

1985-01-01

The result of Monte Carlo electron photon cascade calculations for propagation of gamma rays through regions of extragalactic space containing no magnetic field are given. These calculations then provide upper limits to the expected flux from extragalactic sources. Since gamma rays in the 10 to the 14th power eV to 10 to the 17th power eV energy range are of interest, interactions of electrons and photons with the 3 K microwave background radiation are considered. To obtain an upper limit to the expected gamma ray flux from sources, the intergalactic field is assumed to be so low that it can be ignored. Interactions with photons of the near-infrared background radiation are not considered here although these will have important implications for gamma rays below 10 to the 14th power eV if the near infrared background radiation is universal. Interaction lengths of electrons and photons in the microwave background radiation at a temperature of 2.96 K were calculated and are given.

The Astronomy Workshop Extragalactic: Web Tools for Use by Students

NASA Astrophysics Data System (ADS)

Hayes-Gehrke, Melissa N.; Bolatto, A. D.

2014-01-01

The Astronomy Workshop Extragalactic (http://carma.astro.umd.edu/AWE) is a collection of interactive web tools that were developed for use in undergraduate and high school classes and by the general public. The focus of the tools is on concepts encountered in extragalactic astronomy, which are typically quite difficult for students to understand. Current tools explore Olbers' Paradox; the appearance of galaxies in different wavelengths of light; the Doppler Effect; cosmological redshift; gravitational lensing; Hubble's Law; cosmological parameters; and measuring masses of black holes by observing stellar orbits. The tools have been developed by undergraduate students under our supervision and we are planning to continue to add more tools. This project was inspired by the Astronomy Workshop (http://janus.astro.umd.edu) by Doug Hamilton which has web tools exploring more general astronomical concepts. We would like to thank the NSF for support through the CAREER grant NSF-AST0955836, and the Research Corporation for Science Advancement for a Cottrell Scholar award.

Fast Radio Bursts from Extragalactic Light Sails

NASA Astrophysics Data System (ADS)

Lingam, Manasvi; Loeb, Abraham

2017-03-01

We examine the possibility that fast radio bursts (FRBs) originate from the activity of extragalactic civilizations. Our analysis shows that beams used for powering large light sails could yield parameters that are consistent with FRBs. The characteristic diameter of the beam emitter is estimated through a combination of energetic and engineering constraints, and both approaches intriguingly yield a similar result that is on the scale of a large rocky planet. Moreover, the optimal frequency for powering the light sail is shown to be similar to the detected FRB frequencies. These “coincidences” lend some credence to the possibility that FRBs might be artificial in origin. Other relevant quantities, such as the characteristic mass of the light sail, and the angular velocity of the beam, are also derived. By using the FRB occurrence rate, we infer upper bounds on the rate of FRBs from extragalactic civilizations in a typical galaxy. The possibility of detecting fainter signals is briefly discussed, and the wait time for an exceptionally bright FRB event in the Milky Way is estimated.

The host galaxy and Fermi -LAT counterpart of HESS J1943+213

DOE PAGES

Peter, D.; Domainko, W.; Sanchez, D. A.; ...

2014-11-06

The very-high energy (VHE, E> 100 GeV) gamma-ray sky shows diverse Galactic and extragalactic source populations. For some sources the astrophysical object class could not be identified so far. The nature (Galactic or extragalactic) of the VHE gamma-ray source HESS J1943+213 is explored. We specifically investigate the proposed near-infrared counterpart 2MASS J19435624+2118233 of HESS J1943+213 and investigate the implications of a physical association. We present K-band imaging from the 3.5 m CAHA telescope of 2MASS J19435624+2118233. Furthermore, 5 years of Fermi-LAT data were analyzed to search for a high-energy (HE, 100 MeV stat ± 0.6 sys) × 10 -15 cmmore » -2 s -1 MeV -1 at the decorrelation energy Edec = 15.1 GeV and a spectral index of Γ = 1.59 ± 0.19stat ± 0.13sys. This gamma-ray spectrum shows a rather sharp break between the HE and VHE regimes of ΔΓ = 1.47 ± 0.36. In conclusion, the infrared and HE data strongly favor an extragalactic origin of HESS J1943+213, where the infrared counterpart traces the host galaxy of an extreme blazar and where the rather sharp spectral break between the HE and VHE regime indicates attenuation on extragalactic background light. The source is most likely located at a redshift between 0.03 and 0.45 according to extension and EBL attenuation arguments.« less

IUE observations of extragalactic objects

NASA Technical Reports Server (NTRS)

Boksenberg, A.; Snijders, M. A. J.; Wilson, R.; Benvenuti, P.; Clavell, J.; Macchetto, F.; Penston, M.; Boggess, A.; Gull, T. R.; Gondhalekar, P.

1978-01-01

During the commissioning phase of IUE several extragalactic objects were observed spectrally at low dispersion in the UV range lambda lambda 1150-3200: the Seyfert galaxies NGC4151 and NGC1068, the QSO 3C273, the BL Lacertae object B2 1101+38, the giant elliptical galaxy M87 and the spiral galaxy M81. The results obtained are presented and a preliminary analysis given for all six objects, discussing the continuous spectrum, extinction, emission line spectrum and absorption line spectrum, where possible for each case. Several new or confirmatory astrophysical results are obtained.

Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. IV - Seventeen sources

NASA Technical Reports Server (NTRS)

Morabito, D. D.; Preston, R. A.; Linfield, R. P.; Slade, M. A.; Jauncey, D. L.

1986-01-01

VLBI measurements of time delay and delay rate at 2.29 and 8.42 GHz on baselines of 10,000 km have been used to determine the positions of the milliarcsecond nuclei in 17 extragalactic radio sources with estimated accuracies of 0.1 to 0.3 arcsec. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. In addition, slightly improved positions are presented for 101 sources originally reported by Morabito et al. (1983). Arcsecond positions have now been determined for 836 sources.

The Herschel ATLAS

NASA Technical Reports Server (NTRS)

Eales, S.; Dunne, L.; Clements, D.; Cooray, A.; De Zotti, G.; Dye, S.; Ivison, R.; Jarvis, M.; Lagache, G.; Maddox, S.;

Extragalactic radio surveys in the pre-Square Kilometre Array era

PubMed Central

2017-01-01

The era of the Square Kilometre Array is almost upon us, and pathfinder telescopes are already in operation. This brief review summarizes our current knowledge of extragalactic radio sources, accumulated through six decades of continuum surveys at the low-frequency end of the electromagnetic spectrum and the extensive complementary observations at other wavelengths necessary to gain this understanding. The relationships between radio survey data and surveys at other wavelengths are discussed. Some of the outstanding questions are identified and prospects over the next few years are outlined. PMID:28791175

Millimeter-wave Line Ratios and Sub-beam Volume Density Distributions

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

Leroy, Adam K.; Gallagher, Molly; Usero, Antonio

We explore the use of mm-wave emission line ratios to trace molecular gas density when observations integrate over a wide range of volume densities within a single telescope beam. For observations targeting external galaxies, this case is unavoidable. Using a framework similar to that of Krumholz and Thompson, we model emission for a set of common extragalactic lines from lognormal and power law density distributions. We consider the median density of gas that produces emission and the ability to predict density variations from observed line ratios. We emphasize line ratio variations because these do not require us to know themore » absolute abundance of our tracers. Patterns of line ratio variations have the potential to illuminate the high-end shape of the density distribution, and to capture changes in the dense gas fraction and median volume density. Our results with and without a high-density power law tail differ appreciably; we highlight better knowledge of the probability density function (PDF) shape as an important area. We also show the implications of sub-beam density distributions for isotopologue studies targeting dense gas tracers. Differential excitation often implies a significant correction to the naive case. We provide tabulated versions of many of our results, which can be used to interpret changes in mm-wave line ratios in terms of adjustments to the underlying density distributions.« less

Infrared-faint radio sources in the SERVS deep fields. Pinpointing AGNs at high redshift

NASA Astrophysics Data System (ADS)

Maini, A.; Prandoni, I.; Norris, R. P.; Spitler, L. R.; Mignano, A.; Lacy, M.; Morganti, R.

2016-12-01

Context. Infrared-faint radio sources (IFRS) represent an unexpected class of objects which are relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S1.4 GHz≳ 10 mJy) has provided evidence that most of them (if not all) contain an active galactic nuclei (AGN). Still uncertain is the nature of the radio-faintest IFRSs (S1.4 GHz≲ 1 mJy). Aims: The scope of this paper is to assess the nature of the radio-faintest IFRSs, testing their classification and improving the knowledge of their IR properties by making use of the most sensitive IR survey available so far: the Spitzer Extragalactic Representative Volume Survey (SERVS). We also explore how the criteria of IFRSs can be fine-tuned to pinpoint radio-loud AGNs at very high redshift (z > 4). Methods: We analysed a number of IFRS samples identified in SERVS fields, including a new sample (21 sources) extracted from the Lockman Hole. 3.6 and 4.5 μm IR counterparts of the 64 sources located in the SERVS fields were searched for and, when detected, their IR properties were studied. Results: We compared the radio/IR properties of the IR-detected IFRSs with those expected for a number of known classes of objects. We found that IR-detected IFRSs are mostly consistent with a mixture of high-redshift (z ≳ 3) radio-loud AGNs. The faintest ones (S1.4 GHz 100 μJy), however, could be also associated with nearer (z 2) dust-enshrouded star-burst galaxies. We also argue that, while IFRSs with radio-to-IR ratios >500 can very efficiently pinpoint radio-loud AGNs at redshift 2 < z < 4, lower radio-to-IR ratios ( 100-200) are expected for higher redshift radio-loud AGNs.

Radio mode feedback: Does relativity matter?

NASA Astrophysics Data System (ADS)

Perucho, Manel; Martí, José-María; Quilis, Vicent; Borja-Lloret, Marina

2017-10-01

Radio mode feedback, associated with the propagation of powerful outflows in active galaxies, is a crucial ingredient in galaxy evolution. Extragalactic jets are well collimated and relativistic, both in terms of thermodynamics and kinematics. They generate strong shocks in the ambient medium, associated with observed hotspots, and carve cavities that are filled with the shocked jet flow. In this Letter, we compare the pressure evolution in the hotspot and the cavity generated by relativistic and classical jets. Our results show that the classical approach underestimates the cavity pressure by a factor ≥2 for a given shocked volume during the whole active phase. The tension between both approaches can only be alleviated by unrealistic jet flow densities or gigantic jet areas in the classical case. As a consequence, the efficiency of a relativistic jet heating the ambient is typically ∼20 per cent larger compared with a classical jet, and the heated volume is 2 to 10 times larger during the time evolution. This conflict translates into two substantially disparate manners, both spatially and temporal, of heating the ambient medium. These differences are expected to have relevant implications on the star formation rates of the host galaxies and their evolution.

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.

The Tarantula Nebula as a template for extragalactic star forming regions from VLT/MUSE and HST/STIS

NASA Astrophysics Data System (ADS)

Crowther, Paul A.; Caballero-Nieves, Saida M.; Castro, Norberto; Evans, Christopher J.

2017-11-01

We present VLT/MUSE observations of NGC 2070, the dominant ionizing nebula of 30 Doradus in the LMC, plus HST/STIS spectroscopy of its central star cluster R136. Integral Field Spectroscopy (MUSE) and pseudo IFS (STIS) together provides a complete census of all massive stars within the central 30×30 parsec2 of the Tarantula. We discuss the integrated far-UV spectrum of R136, of particular interest for UV studies of young extragalactic star clusters. Strong He iiλ1640 emission at very early ages (1-2 Myr) from very massive stars cannot be reproduced by current population synthesis models, even those incorporating binary evolution and very massive stars. A nebular analysis of the integrated MUSE dataset implies an age of ~4.5 Myr for NGC 2070. Wolf-Rayet features provide alternative age diagnostics, with the primary contribution to the integrated Wolf-Rayet bumps arising from R140 rather than the more numerous H-rich WN stars in R136. Caution should be used when interpreting spatially extended observations of extragalactic star-forming regions.

SPECTRAL ANALYSIS OF FERMI -LAT BLAZARS ABOVE 50 GEV

DOE PAGES

Domínguez, Alberto; Ajello, Marco

2015-11-04

We present an analysis of the intrinsic (unattenuated by the extragalactic background light, EBL) power-law spectral indices of 128 extragalactic sources detected up to z ~ 2 with the Fermi-Large Area Telescope (LAT) at very high energies (VHEs, E ≥50 GeV). The median of the intrinsic index distribution is 2.20 (versus 2.54 for the observed distribution). We also analyze the observed spectral breaks (i.e., the difference between the VHE and high energy, HE, 100 MeV ≤ E ≤ 300 GeV, spectral indices). The Fermi-LAT has now provided a large sample of sources detected both at VHE and HE with comparablemore » exposure that allows us to test models of extragalactic γ-ray photon propagation. We find that our data are compatible with simulations that include intrinsic blazar curvature and EBL attenuation. There is also no evidence of evolution with redshift of the physics that drives the photon emission in high-frequency synchrotron peak (HSP) blazars. This makes HSP blazars excellent probes of the EBL.« less

The isotropic radio background revisited

NASA Astrophysics Data System (ADS)

Fornengo, Nicolao; Lineros, Roberto A.; Regis, Marco; Taoso, Marco

2014-04-01

We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky.

Dust and molecules in extra-galactic planetary nebulae

NASA Astrophysics Data System (ADS)

Garcia-Hernandez, Domingo Aníbal

2015-08-01

Extra-galactic planetary nebulae (PNe) permit the study of dust and molecules in metallicity environments other than the Galaxy. Their known distances lower the number of free parameters in the observations vs. models comparison, providing strong constraints on the gas-phase and solid-state astrochemistry models. Observations of PNe in the Galaxy and other Local Group galaxies such as the Magellanic Clouds (MC) provide evidence that metallicity affects the production of dust as well as the formation of complex organic molecules and inorganic solid-state compounds in their circumstellar envelopes. In particular, the lower metallicity MC environments seem to be less favorable to dust production and the frequency of carbonaceous dust features and complex fullerene molecules is generally higher with decreasing metallicity. Here, I present an observational review of the dust and molecular content in extra-galactic PNe as compared to their higher metallicity Galactic counterparts. A special attention is given to the level of dust processing and the formation of complex organic molecules (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene precursors) depending on metallicity.

Identificación de objetos extensos en el VVV

NASA Astrophysics Data System (ADS)

Baravalle, L.; Alonso, M. V.; Nilo Castellón, J. L.; Minniti, D.

2017-10-01

The Vista Variables en la Via Lactea (VVV) is an ESO public survey in the near infrared of the bulge and southern mid-plane of the Milky Way. The main goal of the VVV is the study of the stellar population and variable stars but it can also be useful for extragalactic investigations behind the Galaxy. Using the VVV images and the combination of SExtractor + PSFEx, we have obtained astrometric and photometric data of two peripheric regions of the Galactic disk. Our goal is to identify and characterise the extragalactic sources. In this work we show our detection algorithm and adopted methodology.

Smooth H I Low Column Density Outskirts in Nearby Galaxies

NASA Astrophysics Data System (ADS)

Ianjamasimanana, R.; Walter, Fabian; de Blok, W. J. G.; Heald, George H.; Brinks, Elias

2018-06-01

The low column density gas at the outskirts of galaxies as traced by the 21 cm hydrogen line emission (H I) represents the interface between galaxies and the intergalactic medium, i.e., where galaxies are believed to get their supply of gas to fuel future episodes of star formation. Photoionization models predict a break in the radial profiles of H I at a column density of ∼5 × 1019 cm‑2 due to the lack of self-shielding against extragalactic ionizing photons. To investigate the prevalence of such breaks in galactic disks and to characterize what determines the potential edge of the H I disks, we study the azimuthally averaged H I column density profiles of 17 nearby galaxies from the H I Nearby Galaxy Survey and supplemented in two cases with published Hydrogen Accretion in LOcal GAlaxieS data. To detect potential faint H I emission that would otherwise be undetected using conventional moment map analysis, we line up individual profiles to the same reference velocity and average them azimuthally to derive stacked radial profiles. To do so, we use model velocity fields created from a simple extrapolation of the rotation curves to align the profiles in velocity at radii beyond the extent probed with the sensitivity of traditional integrated H I maps. With this method, we improve our sensitivity to outer-disk H I emission by up to an order of magnitude. Except for a few disturbed galaxies, none show evidence of a sudden change in the slope of the H I radial profiles: the alleged signature of ionization by the extragalactic background.

Cumulative Neutrino and Gamma-Ray Backgrounds from Halo and Galaxy Mergers

NASA Astrophysics Data System (ADS)

Yuan, Chengchao; Mészáros, Peter; Murase, Kohta; Jeong, Donghui

2018-04-01

The merger of dark matter halos and the gaseous structures embedded in them, such as protogalaxies, galaxies, and groups and clusters of galaxies, results in strong shocks that are capable of accelerating cosmic rays (CRs) to ≳10 PeV. These shocks will produce high-energy neutrinos and γ-rays through inelastic pp collisions. In this work, we study the contributions of these halo mergers to the diffuse neutrino flux and to the nonblazar portion of the extragalactic γ-ray background. We formulate the redshift dependence of the shock velocity, galactic radius, halo gas content, and galactic/intergalactic magnetic fields over the dark matter halo distribution up to a redshift z = 10. We find that high-redshift mergers contribute a significant amount of the CR luminosity density, and the resulting neutrino spectra could explain a large part of the observed diffuse neutrino flux above 0.1 PeV up to several PeV. We also show that our model can somewhat alleviate tensions with the extragalactic γ-ray background. First, since a larger fraction of the CR luminosity density comes from high redshifts, the accompanying γ-rays are more strongly suppressed through γγ annihilations with the cosmic microwave background and the extragalactic background light. Second, mildly radiative-cooled shocks may lead to a harder CR spectrum with spectral indices of 1.5 ≲ s ≲ 2.0. Our study suggests that halo mergers, a fraction of which may also induce starbursts in the merged galaxies, can be promising neutrino emitters without violating the existing Fermi γ-ray constraints on the nonblazar component of the extragalactic γ-ray background.

Extragalactic Ultra-High Energy Cosmic-Rays - Part One - Contribution from Hot Spots in Fr-II Radio Galaxies

NASA Astrophysics Data System (ADS)

Rachen, J. P.; Biermann, P. L.

1993-05-01

The hot spots of Fanaroff-Riley class II radio galaxies, considered as working surfaces of highly collimated plasma jets, are proposed to be the dominant sources of the cosmic rays at energies above 1 EeV^a^. We apply the model of first order Fermi acceleration at strong, nonrelativistic shock waves to the hot spot region. The strength of the model has been demonstrated by Biermann & Strittmatter (1987) and by Meisenheimer et al. (1989), who explain their radio-to optical spectra and infer the physical conditions of the radiating plasma. Using synchrotron radiating electrons as a trace, we can calculate the spectrum and the maximum energy of protons accelerated under the same conditions. For simplicity, we disregard heavy nuclei, but their probable role is discussed. The normalization of proton flux injected in extragalactic space is performed by using estimates from Rawlings & Saunders (1991) for the total energy stored in relativistic particles inside the jets and radio galaxy evolution models given by Peacock (1985). We calculate the spectral modifications due to interactions of the protons with the microwave background photons in an evolving universe, following Berezinsky & Grigor'eva (1988). Constraints on the extragalactic magnetic field can be imposed, since it must permit an almost homogeneous filling of the universe with energetic protons. The observed ultra-high energy cosmic ray spectrum is reproduced in slope and flux, limited at high energies by the Greisen-cutoff at about 80 EeV. The requirements on the content of relativistic protons in jets and the constraints to the extragalactic magnetic field are consistent with common estimates. The data beyond the Greisen cutoff for protons may be explained by including heavy nuclei in our model, since they can propagate over cosmological distances up to more than 100 EeV.

The 3CR Chandra Snapshot Survey: Extragalactic Radio Sources with Redshifts between 1 and 1.5

NASA Astrophysics Data System (ADS)

Stuardi, C.; Missaglia, V.; Massaro, F.; Ricci, F.; Liuzzo, E.; Paggi, A.; Kraft, R. P.; Tremblay, G. R.; Baum, S. A.; O’Dea, C. P.; Wilkes, B. J.; Kuraszkiewicz, J.; Forman, W. R.; Harris, D. E.

2018-04-01

The aim of this paper is to present an analysis of newly acquired X-ray observations of 16 extragalactic radio sources listed in the Third Cambridge Revised (3CR) catalog and not previously observed by Chandra. Observations were performed during Chandra Cycle 17, extending X-ray coverage for the 3CR extragalactic catalog up to z = 1.5. Among the 16 targets, two lie at z < 0.5 (3CR 27 at z = 0.184 and 3CR 69 at z = 0.458) all of the remaining 14 have redshifts between 1.0 and 1.5. In the current sample, there are three compact steep spectrum (CSS) sources, three quasars, and an FR I radio galaxy, while the other nine are FR II radio galaxies. All radio sources have an X-ray counterpart. We measured nuclear X-ray fluxes as well as X-ray emission associated with radio jet knots, hotspots, or lobes in three energy bands: soft (0.5–1 keV), medium (1–2 keV), and hard (2–7 keV). We also performed standard X-ray spectral analysis for the four brightest nuclei. We discovered X-ray emission associated with the radio lobe of 3CR 124, a hotspot of the quasar 3CR 220.2, another hotspot of the radio galaxy 3CR 238, and the jet knot of 3CR 297. We also detected extended X-ray emission around the nuclear region of 3CR 124 and 3CR 297 on scales of several tens of kiloparsecs. Finally, we present an update on the X-ray observations performed with Chandra and XMM-Newton on the entire 3CR extragalactic catalog.

The JWST Extragalactic Mock Catalog: Modeling Galaxy Populations from the UV through the Near-IR over 13 Billion Years of Cosmic History

NASA Astrophysics Data System (ADS)

Williams, Christina C.; Curtis-Lake, Emma; Hainline, Kevin N.; Chevallard, Jacopo; Robertson, Brant E.; Charlot, Stephane; Endsley, Ryan; Stark, Daniel P.; Willmer, Christopher N. A.; Alberts, Stacey; Amorin, Ricardo; Arribas, Santiago; Baum, Stefi; Bunker, Andrew; Carniani, Stefano; Crandall, Sara; Egami, Eiichi; Eisenstein, Daniel J.; Ferruit, Pierre; Husemann, Bernd; Maseda, Michael V.; Maiolino, Roberto; Rawle, Timothy D.; Rieke, Marcia; Smit, Renske; Tacchella, Sandro; Willott, Chris J.

2018-06-01

We present an original phenomenological model to describe the evolution of galaxy number counts, morphologies, and spectral energy distributions across a wide range of redshifts (0.2< z< 15) and stellar masses [{log}(M/{M}ȯ )≥slant 6]. Our model follows observed mass and luminosity functions of both star-forming and quiescent galaxies, and reproduces the redshift evolution of colors, sizes, star formation, and chemical properties of the observed galaxy population. Unlike other existing approaches, our model includes a self-consistent treatment of stellar and photoionized gas emission and dust attenuation based on the BEAGLE tool. The mock galaxy catalogs generated with our new model can be used to simulate and optimize extragalactic surveys with future facilities such as the James Webb Space Telescope (JWST), and to enable critical assessments of analysis procedures, interpretation tools, and measurement systematics for both photometric and spectroscopic data. As a first application of this work, we make predictions for the upcoming JWST Advanced Deep Extragalactic Survey (JADES), a joint program of the JWST/NIRCam and NIRSpec Guaranteed Time Observations teams. We show that JADES will detect, with NIRCam imaging, 1000s of galaxies at z ≳ 6, and 10s at z ≳ 10 at {m}{AB}≲ 30 (5σ) within the 236 arcmin2 of the survey. The JADES data will enable accurate constraints on the evolution of the UV luminosity function at z > 8, and resolve the current debate about the rate of evolution of galaxies at z ≳ 8. Ready-to-use mock catalogs and software to generate new realizations are publicly available as the JAdes extraGalactic Ultradeep Artificial Realizations (JAGUAR) package.

Photoionization of disk galaxies: An explanation of the sharp edges in the H I distribution

NASA Technical Reports Server (NTRS)

Dove, James B.; Shull, J. Michael

1994-01-01

We have reproduced the observed radial truncation of the H I distribution in isolated spiral galaxies with a model in which extragalactic radiation photoionizes the gaseous disk. For a galactic mass distribution model that reproduces the observed rotation curves, including dark matter in the disk and halo, the vertical structure of the gas is determined self-consistently. The ionization structure and column densities of H and He ions are computed by solving the radiation transfer equation for both continuum and lines. Our model is similar to that of Maloney, and the H I structure differs by less than 10%. The radial structure of the column density of H I is found to be more sensitive to the extragalactic radiation field than to the distribution of mass. For this reason, considerable progress can be made in determining the extragalactic flux of ionizing photons, phi(sub ex), with more 21 cm observations of isolated galaxies. However, owing to the uncertainty of the radial distribution of total hydrogen at large radii, inferring the extragalactic flux by comparing the observed edges to photoionization models is somewhat subjective. We find 1 x 10(exp 4)/sq cm/s is less than or approximately phi(sub ex) is less than or approximately 5 x 10(exp 4)/sq cm/s, corresponding to 2.1 is less than or approximately iota(sub 0) is less than or approximately 10.5 x 10(exp -23) ergs/sq cm/s/Hz/sr for a 1/nu spectrum. Although somewhat higher, our inferred range of iota(sub 0) is consistent with the large range of values obtained by Kulkarni & Fall from the 'proximity effect' toward Quasi-Stellar Objects (QSOs) at approximately 0.5.

VLBI astrometry and the Hipparcos link to the extragalactic reference frame

NASA Technical Reports Server (NTRS)

Lestrade, J.-F.; Preston, R. A.; Gabuzda, D. C.; Phillips, R. B.

1991-01-01

Intermediate results are reported from a program of VLBI radio observations designed to establish a link between the rotating reference frame of the ESA Hipparcos astrometric satellite and the extragalactic VLBI frame being developed by the International Earth Rotation Service. A group of 12 link stars have been observed at various epochs since 1982, and more observations are being undertaken during the 3-yr Hipparcos mission (1989-1992). Analysis of data on Algol indicates that phase-reference VLBI can determine an expected sky displacement of 4 marcsec with an uncertainty of 0.5 marcsec, even when the activity is only a few mJy.

Extragalactic magnetic fields unlikely generated at the electroweak phase transition

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

Wagstaff, Jacques M.; Banerjee, Robi, E-mail: jwagstaff@hs.uni-hamburg.de, E-mail: banerjee@hs.uni-hamburg.de

2016-01-01

In this paper we show that magnetic fields generated at the electroweak phase transition are most likely too weak to explain the void magnetic fields apparently observed today unless they have considerable helicity. We show that, in the simplest estimates, the helicity naturally produced in conjunction with the baryon asymmetry is too small to explain observations, which require a helicity fraction at least of order 10{sup −14}–10{sup −10} depending on the void fields constraint used. Therefore new mechanisms to generate primordial helicity are required if magnetic fields generated during the electroweak phase transition should explain the extragalactic fields.

The HyperLeda project en route to the astronomical virtual observatory

NASA Astrophysics Data System (ADS)

Golev, V.; Georgiev, V.; Prugniel, Ph.

2002-07-01

HyperLeda (Hyper-Linked Extragalactic Databases and Archives) is aimed to study the evolution of galaxies, their kinematics and stellar populations and the structure of Local Universe. HyperLeda is involved in catalogue and software production, data-mining and massive data processing. The products are serviced to the community through web mirrors. The development of HyperLeda is distributed between different sites and is based on the background experience of the LEDA and Hypercat databases. The HyperLeda project is focused both on the European iAstro colaboration and as a unique database for studies of the physics of the extragalactic objects.

Fine structure of 25 extragalactic radio sources. [interferometric observations of quasars

NASA Technical Reports Server (NTRS)

Wittels, J. J.; Knight, C. A.; Shapiro, I. I.; Hinteregger, H. F.; Rogers, A. E. E.; Whitney, A. R.; Clark, T. A.; Hutton, L. K.; Marandino, G. E.; Niell, A. E.

1975-01-01

Interferometric observations taken at 7.8 GHz (gamma approximately = 3.8 cm) with five pairings of antennae of 25 extragalactic radio sources between April, 1972 and May, 1973 are reported. These sources exhibit a broad variety of fine structure from very simple to complex. The total flux and the correlated flux of some of the sources underwent large changes in a few weeks, while the structure and total power of others remained constant during the entire period of observation. Some aspects of the data processing and a discussion of errors are presented. Numerous figures are provided and explained. The individual radio sources are described in detail.

A catalog of selected compact radio sources for the construction of an extragalactic radio/optical reference frame (Argue et al. 1984): Documentation for the machine-readable version

NASA Technical Reports Server (NTRS)

1990-01-01

This document describes the machine readable version of the Selected Compact Radio Source Catalog as it is currently being distributed from the international network of astronomical data centers. It is intended to enable users to read and process the computerized catalog. The catalog contains 233 strong, compact extragalactic radio sources having identified optical counterparts. The machine version contains the same data as the published catalog and includes source identifications, equatorial positions at J2000.0 and their mean errors, object classifications, visual magnitudes, redshift, 5-GHz flux densities, and comments.

A NEW RESULT ON THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND

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

Zhou Ming; Wang Jiancheng, E-mail: mzhou@ynao.ac.cn

2013-06-01

In this paper, we repeatedly use the method of image stacking to study the origin of the extragalactic gamma-ray background (EGB) at GeV bands, and find that the Faint Images of the Radio Sky at Twenty centimeters (FIRST) sources undetected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope can contribute about (56 {+-} 6)% of the EGB. Because FIRST is a flux-limited sample of radio sources with incompleteness at the faint limit, we consider that point sources, including blazars, non-blazar active galactic nuclei, and starburst galaxies, could produce a much larger fraction of the EGB.

Peering Through the Muck: Notes on the the Influence of the Galactic Interstellar Medium on Extragalactic Observations

NASA Astrophysics Data System (ADS)

Lockman, Felix J.

This paper considers some effects of foreground Galactic gas on radiation received from extragalactic objects, with an emphasis on the use of the 21cm line to determine the total N(HI). In general, the opacity of the 21cm line makes it impossible to derive an accurate value of N(HI) by simply applying a formula to the observed emission, except in directions where there is very little interstellar matter. The 21cm line can be used to estimate the likelihood that there is significant molecular hydrogen in a particular direction, but carries little or no information on the amount of ionized gas, which can be a major source of foreground effects. Considerable discussion is devoted to the importance of small-scale angular structure in HI, with the conclusion that it will rarely contribute significantly to the total error compared to other factors (such as the effects of ionized gas) for extragalactic sight lines at high Galactic latitude. The direction of the Hubble/Chandra Deep Field North is used as an example of the complexities that might occur even in the absence of opacity or molecular gas.

The Cosmic Infrared Background Experiment (CIBER): A Sounding Rocket Payload to Study the near Infrared Extragalactic Background Light

NASA Astrophysics Data System (ADS)

Zemcov, M.; Arai, T.; Battle, J.; Bock, J.; Cooray, A.; Hristov, V.; Keating, B.; Kim, M. G.; Lee, D. H.; Levenson, L. R.; Mason, P.; Matsumoto, T.; Matsuura, S.; Nam, U. W.; Renbarger, T.; Sullivan, I.; Suzuki, K.; Tsumura, K.; Wada, T.

2013-08-01

The Cosmic Infrared Background Experiment (CIBER) is a suite of four instruments designed to study the near infrared (IR) background light from above the Earth's atmosphere. The instrument package comprises two imaging telescopes designed to characterize spatial anisotropy in the extragalactic IR background caused by cosmological structure during the epoch of reionization, a low resolution spectrometer to measure the absolute spectrum of the extragalactic IR background, and a narrow band spectrometer optimized to measure the absolute brightness of the zodiacal light foreground. In this paper we describe the design and characterization of the CIBER payload. The detailed mechanical, cryogenic, and electrical design of the system are presented, including all system components common to the four instruments. We present the methods and equipment used to characterize the instruments before and after flight, and give a detailed description of CIBER's flight profile and configurations. CIBER is designed to be recoverable and has flown four times, with modifications to the payload having been informed by analysis of the first flight data. All four instruments performed to specifications during the subsequent flights, and the scientific data from these flights are currently being analyzed.

Dissecting the Gamma-Ray Background in Search of Dark Matter

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

Cholis, Ilias; Hooper, Dan; McDermott, Samuel D.

2014-02-01

Several classes of astrophysical sources contribute to the approximately isotropic gamma-ray background measured by the Fermi Gamma-Ray Space Telescope. In this paper, we use Fermi's catalog of gamma-ray sources (along with corresponding source catalogs at infrared and radio wavelengths) to build and constrain a model for the contributions to the extragalactic gamma-ray background from astrophysical sources, including radio galaxies, star-forming galaxies, and blazars. We then combine our model with Fermi's measurement of the gamma-ray background to derive constraints on the dark matter annihilation cross section, including contributions from both extragalactic and galactic halos and subhalos. The resulting constraints are competitivemore » with the strongest current constraints from the Galactic Center and dwarf spheroidal galaxies. As Fermi continues to measure the gamma-ray emission from a greater number of astrophysical sources, it will become possible to more tightly constrain the astrophysical contributions to the extragalactic gamma-ray background. We project that with 10 years of data, Fermi's measurement of this background combined with the improved constraints on the astrophysical source contributions will yield a sensitivity to dark matter annihilations that exceeds the strongest current constraints by a factor of ~ 5 - 10.« less

The Impact of Electromagnetic Cascades of Very-high Energy Gamma Rays on the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, Tonia

2012-01-01

As very high energy (VHE) photons propagate through the extragalactic background light (EBL), they interact with the soft photons of the EBL and initiate electromagnetic cascades of photons and electrons. The collective intensity of a cosmological population emitting at VHEs (such as blazars) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. As such, depending on the space density and spectra of the sources and the model of the EBL, cascade radiation can provide a significant contribution to the extragalactic gamma-ray background (EGB). Through deflections of the charged particles of the cascade, an intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the EGB. The impact of a strong IGMF is to isotropize lower energy cascade photons, inducing a modulation in the anisotropy energy spectrum of the EGB. We discuss the implications of cascade radiation for the origins of the EGB and the nature of the IGMF, as well as insight that will be provided by data from the Fermi Large Area Telescope in the upcoming years.

An optical view of extragalactic gamma-ray emitters

NASA Astrophysics Data System (ADS)

Paiano, Simona; Falomo, Renato; Landoni, Marco; Treves, Aldo; Scarpa, Riccardo

2017-11-01

The Fermi Gamma-ray Observatory discovered about a thousand extragalactic sources emitting energy from 100 MeV to 100 GeV. The majority of these sources belong to the class of blazars characterized by a quasi-featureless optical spectrum (BL Lac Objects). This hampers the determination of their redshift and therefore hinders the characterization of this class of objects. To investigate the nature of these sources and to determine their redshift, we are carrying out an extensive campaign at the 10m Gran Telescopio Canarias to secure high signal-to-noise ratio optical spectra. These observations allow us to confirm the blazar nature of the targets, to find new redshifts or to set stringent limits on the redshift based on the minimum equivalent width of absorption features expected from their host galaxy, assuming it is a massive elliptical galaxy.These results are of importance for the multi-frequencies emission models of the blazars, to test their extreme physics, to shed light on their cosmic evolution and abundance in the far Universe.These gamma emitters are also of great importance for the characterization of the extragalactic background light through the absorption by the IR-optical background photons.

Radio outbursts in extragalactic sources

NASA Astrophysics Data System (ADS)

Kinzel, Wayne Morris

Three aspects of the flux density variability of extragalactic radio sources were examined: millimeter wavelength short timescale variability, the spectral evolution of outbursts, and whether the outbursts are periodically spaced. Observations of extragalactic radio sources were conducted using the Five College Radio Astronomy Observatory between January and June 1985 at 88.2 GHz and during June and July 1985 at 40.0 GHz. Many of the sources exhibited significant flux density variations during the observing span. In addition, the most rapid variations observed were comparable with those reported in previous works. Two sources, 0355+50 and OJ287, both exhibited outbursts whose rise and fall timescales were less than a month. An anomalous flux density dropout was observed in 3C446 and was interpreted as an occultation event. Data at five frequencies between 2.7 and 89.6 GHz from the Dent-Balonek monitoring program were used to investigate the spectral evolution of eight outbursts. Outburst profile fitting was used to deconvolve the individual outbursts from one another at each frequency. The fit profiles were used to generate multiple epoch spectra to investigate the evolution of the outbursts. A phase residual minimization method was used to examine four sources for periodic behavior.

Archival Investigation of Outburst Sites and Progenitors of Extragalactic Intermediate-Luminosity Mid-IR Transients

NASA Astrophysics Data System (ADS)

Bond, Howard

2017-08-01

Our team is using Spitzer in a long-term search for extragalactic mid-infrared (MIR) variable stars and transients-the SPIRITS project (SPitzer InfraRed Intensive Transients Survey). In this first exploration of luminous astrophysical transients in the infrared, we have discovered a puzzling new class. We call them SPRITEs: eSPecially Red Intermediate-luminosity Transient Events. They have maximum MIR luminosities between supernovae and classical novae, but are not detected in the optical to deep limits. To date, we have discovered more than 50 SPRITEs in galaxies out to 17 Mpc. In this Archival Research proposal, we request support in order to investigate the pre-eruption sites in HST images of some 3 dozen SPRITEs discovered to date, and an additional 2 dozen that we are likely to find until the end of Spitzer observing in late 2018. Our aims are (1) characterize the pre-outburst environments at HST resolution in the visible and near-IR, to understand the stellar populations, stellar ages and masses, and interstellar medium at the outburst sites; (2) search for progenitors; (3) help prepare the way for a better understanding of the nature of extragalactic IR transients that will be investigated by JWST.

THE COSMIC INFRARED BACKGROUND EXPERIMENT (CIBER): A SOUNDING ROCKET PAYLOAD TO STUDY THE NEAR INFRARED EXTRAGALACTIC BACKGROUND LIGHT

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

Zemcov, M.; Bock, J.; Hristov, V.

2013-08-15

The Cosmic Infrared Background Experiment (CIBER) is a suite of four instruments designed to study the near infrared (IR) background light from above the Earth's atmosphere. The instrument package comprises two imaging telescopes designed to characterize spatial anisotropy in the extragalactic IR background caused by cosmological structure during the epoch of reionization, a low resolution spectrometer to measure the absolute spectrum of the extragalactic IR background, and a narrow band spectrometer optimized to measure the absolute brightness of the zodiacal light foreground. In this paper we describe the design and characterization of the CIBER payload. The detailed mechanical, cryogenic, andmore » electrical design of the system are presented, including all system components common to the four instruments. We present the methods and equipment used to characterize the instruments before and after flight, and give a detailed description of CIBER's flight profile and configurations. CIBER is designed to be recoverable and has flown four times, with modifications to the payload having been informed by analysis of the first flight data. All four instruments performed to specifications during the subsequent flights, and the scientific data from these flights are currently being analyzed.« less

Space Infrared Extragalactic Surveys : Results from ISO and Future Prospects

NASA Astrophysics Data System (ADS)

Vaccari, Mattia

2004-02-01

This Thesis deals with the exploitation of space infrared extragalactic surveys as a powerful tool for astronomical investigation. More precisely, it deals with the development of a new method (LARI Method) for the reduction and analysis of data obtained by an infrared satellite (ISO), the application of this method to data obtained within the most ambitious extragalactic survey carried out with this satellite (ELAIS), the first scientific results obtained through this application, and finally the possible applications of such technical and scientific contributions to an infrared satellite which has recently started operations (Spitzer) as well as to future infrared missions. As a testimony to the particularly heterogeneous nature of the skills that are necessary in order to realize a successful space project, the Thesis stands at the boundary between several significantly different disciplines, such as detector physics, signal analysis and image processing, software engineering, galaxy formation and evolution and observational cosmology. Although focusing on a particular mission (ISO), throughout an attempt was made at putting the work into an "historical" perspective, with a keen eye both for the efforts of the "pioneers" of infrared astronomy and for the exciting prospects that space missions will offer to this dicipline in the years to come.

The SUrvey for Pulsars and Extragalactic Radio Bursts III: Polarization properties of FRBs 160102 & 151230

NASA Astrophysics Data System (ADS)

Caleb, M.; Keane, E. F.; van Straten, W.; Kramer, M.; Macquart, J. P.; Bailes, M.; Barr, E. D.; Bhat, N. D. R.; Bhandari, S.; Burgay, M.; Farah, W.; Jameson, A.; Jankowski, F.; Johnston, S.; Petroff, E.; Possenti, A.; Stappers, B.; Tiburzi, C.; Krishnan, V. Venkatraman

2018-05-01

We report on the polarization properties of two fast radio bursts (FRBs): 151230 and 160102 discovered in the SUrvey for Pulsars and Extragalactic Radio Bursts (SUPERB) at the Parkes radio telescope. FRB 151230 is observed to be 6 ± 11% circularly polarized and 35 ± 13 % linearly polarized with a rotation measure (RM) consistent with zero. Conversely, FRB 160102 is observed to have a circular polarization fraction of 30 ± 11 %, linear polarization fraction of 84 ± 15 % for RM =-221(6) rad m-2 and the highest measured DM (2596.1 ± 0.3 pc cm-3) for an FRB to date. We examine possible progenitor models for FRB 160102 in extragalactic, non-cosmological and cosmological scenarios. After accounting for the Galactic foreground contribution, we estimate the intrinsic RM to be -256(9) rad m-2 in the low-redshift case and ˜-2.4 × 102 rad m-2 in the high-redshift case. We assess the relative likeliness of these scenarios and how each can be tested. We also place constraints on the scattering measure and study the impact of scattering on the signal's polarization position angle.

New Self-lensing Models of the Small Magellanic Cloud: Can Gravitational Microlensing Detect Extragalactic Exoplanets?

NASA Astrophysics Data System (ADS)

Mróz, Przemek; Poleski, Radosław

2018-04-01

We use three-dimensional distributions of classical Cepheids and RR Lyrae stars in the Small Magellanic Cloud (SMC) to model the stellar density distribution of a young and old stellar population in that galaxy. We use these models to estimate the microlensing self-lensing optical depth to the SMC, which is in excellent agreement with the observations. Our models are consistent with the total stellar mass of the SMC of about 1.0× {10}9 {M}ȯ under the assumption that all microlensing events toward this galaxy are caused by self-lensing. We also calculate the expected event rates and estimate that future large-scale surveys, like the Large Synoptic Survey Telescope (LSST), will be able to detect up to a few dozen microlensing events in the SMC annually. If the planet frequency in the SMC is similar to that in the Milky Way, a few extragalactic planets can be detected over the course of the LSST survey, provided significant changes in the SMC observing strategy are devised. A relatively small investment of LSST resources can give us a unique probe of the population of extragalactic exoplanets.

Influence of synchrotron self-absorption on 21-cm experiments

NASA Astrophysics Data System (ADS)

Zheng, Qian; Wu, Xiang-Ping; Gu, Jun-Hua; Wang, Jingying; Xu, Haiguang

2012-08-01

The presence of spectral curvature resulting from the synchrotron self-absorption of extragalactic radio sources could break down the spectral smoothness feature. This leads to the premise that the bright radio foreground can be successfully removed in 21-cm experiments that search for the epoch of reionization (EoR). We present a quantitative estimate of the effect of the spectral curvature resulting from the synchrotron self-absorption of extragalactic radio sources on the measurement of the angular power spectrum of the low-frequency sky. We incorporate a phenomenological model, which is characterized by the fraction (f) of radio sources with turnover frequencies in the range of 100-1000 MHz and by a broken power law for the spectral transition around the turnover frequencies νm, into simulated radio sources over a small sky area of 10° × 10°. We compare statistically the changes in their residual maps with and without the inclusion of the synchrotron self-absorption of extragalactic radio sources after the bright sources of S150 MHz ≥100 mJy are excised. Furthermore, the best-fitting polynomials in the frequency domain on each pixel are subtracted. It has been shown that the effect of synchrotron self-absorption on the detection of the EoR depends sensitively on the spectral profiles of the radio sources around the turnover frequencies νm. A hard transition model, described by the broken power law with the turnover of spectral index at νm, would leave pronounced imprints on the residual background and would therefore cause serious confusion with the cosmic EoR signal. However, the spectral signatures on the angular power spectrum of the extragalactic foreground, generated by a soft transition model in which the rising and falling power laws of the spectral distribution around νm are connected through a smooth transition spanning ≥200 MHz in a characteristic width, can be fitted and consequently subtracted by the use of polynomials to an acceptable degree (δT < 1 mK). As this latter scenario seems to be favoured in both theoretical expectations and radio spectral observations, we conclude that the contamination of extragalactic radio sources by synchrotron self-absorption in 21-cm experiments is probably very minor.

The host galaxy and Fermi-LAT counterpart of HESS J1943+213

NASA Astrophysics Data System (ADS)

Peter, D.; Domainko, W.; Sanchez, D. A.; van der Wel, A.; Gässler, W.

2014-11-01

Context. The very-high energy (VHE, E> 100 GeV) gamma-ray sky shows diverse Galactic and extragalactic source populations. For some sources the astrophysical object class could not be identified so far. Aims: The nature (Galactic or extragalactic) of the VHE gamma-ray source HESS J1943+213 is explored. We specifically investigate the proposed near-infrared counterpart 2MASS J19435624+2118233 of HESS J1943+213 and investigate the implications of a physical association. Methods: We present K-band imaging from the 3.5 m CAHA telescope of 2MASS J19435624+2118233. Furthermore, 5 years of Fermi-LAT data were analyzed to search for a high-energy (HE, 100 MeV

The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Allafort, A.; Schady, P.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R; Blandford, R. D.;

Studying the Evolution of the Contamination of the Sunyaev-Zel'dovich effect due to High-redshift (sub-)mm Galaxies

NASA Astrophysics Data System (ADS)

Montana, Alfredo; Aretxaga, I.; Austermann, J.; Bock, J.; Chapin, E.; Gaztanaga, E.; Hughes, D.; Lowenthal, J.; Mauskopf, P.; Perera, T.; Scott, K.; Wilson, G.; Yun, M.

2007-05-01

We present simulations of the submillimetre/millimetre (sub-mm) sky to study the environment of luminous starburst galaxies, radio galaxies and AGN towards biased-regions (large-scale over-densities) in the high-redshift universe. Guided by recent results from AzTEC extragalactic surveys at 1.1mm, we describe the impact of this population of galaxies, that dominate the sub-mm extragalactic background, on the detectability of the Sunyaev-Zel'dovich effect (SZE) as a function of redshift. These results will be presented in the context of the next generation of wide-area surveys to identify high-redshift clusters via the SZE.

ANA: Astrophysical Neutrino Anisotropy

NASA Astrophysics Data System (ADS)

Denton, Peter

2017-08-01

ANA calculates the likelihood function for a model comprised of two components to the astrophysical neutrino flux detected by IceCube. The first component is extragalactic. Since point sources have not been found and there is increasing evidence that one source catalog cannot describe the entire data set, ANA models the extragalactic flux as isotropic. The second component is galactic. A variety of catalogs of interest are also provided. ANA takes the galactic contribution to be proportional to the matter density of the universe. The likelihood function has one free parameter fgal that is the fraction of the astrophysical flux that is galactic. ANA finds the best fit value of fgal and scans over 0

The diffuse gamma-ray background, light element abundances, and signatures of early massive star formation

NASA Technical Reports Server (NTRS)

Silk, Joseph; Schramm, David N.

1992-01-01

Attention is drawn to a potentially observable flux of diffuse extragalactic gamma rays produced by inelastic cosmic-ray interactions that is inevitably a by-product of spallation-synthesized Be. The epoch of cosmic ray-induced Population II light element nucleosynthesis is constrained to be at redshift greater than 0.5. A spectral feature in the diffuse extragalactic gamma-ray background with amplitude 0.1 above 10 MeV is predicted if the Be is synthesized at z less than 10. The possibility is discussed that the cosmic-ray flux responsible for Population II Be and B synthesis may be associated with a precursor hypothesized Population III.

A Clustered Extragalactic Foreground Model for the EoR

NASA Astrophysics Data System (ADS)

Murray, S. G.; Trott, C. M.; Jordan, C. H.

2018-05-01

We review an improved statistical model of extra-galactic point-source foregrounds first introduced in Murray et al. (2017), in the context of the Epoch of Reionization. This model extends the instrumentally-convolved foreground covariance used in inverse-covariance foreground mitigation schemes, by considering the cosmological clustering of the sources. In this short work, we show that over scales of k ~ (0.6, 40.)hMpc-1, ignoring source clustering is a valid approximation. This is in contrast to Murray et al. (2017), who found a possibility of false detection if the clustering was ignored. The dominant cause for this change is the introduction of a Galactic synchrotron component which shadows the clustering of sources.

First light from a very large area pixel array for high-throughput x-ray polarimetry

NASA Astrophysics Data System (ADS)

Bellazzini, R.; Spandre, G.; Minuti, M.; Baldini, L.; Brez, A.; Cavalca, F.; Latronico, L.; Omodei, N.; Massai, M. M.; Sgrò, C.; Costa, E.; Soffitta, P.; Krummenacher, F.; de Oliveira, R.

2006-06-01

We report on a large active area (15x15mm2), high channel density (470 pixels/mm2), self-triggering CMOS analog chip that we have developed as pixelized charge collecting electrode of a Micropattern Gas Detector. This device, which represents a big step forward both in terms of size and performance, is the last version of three generations of custom ASICs of increasing complexity. The CMOS pixel array has the top metal layer patterned in a matrix of 105600 hexagonal pixels at 50μm pitch. Each pixel is directly connected to the underneath full electronics chain which has been realized in the remaining five metal and single poly-silicon layers of a standard 0.18μm CMOS VLSI technology. The chip has customizable self-triggering capability and includes a signal pre-processing function for the automatic localization of the event coordinates. In this way it is possible to reduce significantly the readout time and the data volume by limiting the signal output only to those pixels belonging to the region of interest. The very small pixel area and the use of a deep sub-micron CMOS technology has brought the noise down to 50 electrons ENC. Results from in depth tests of this device when coupled to a fine pitch (50μm on a triangular pattern) Gas Electron Multiplier are presented. The matching of readout and gas amplification pitch allows getting optimal results. The application of this detector for Astronomical X-Ray Polarimetry is discussed. The experimental detector response to polarized and unpolarized X-ray radiation when working with two gas mixtures and two different photon energies is shown. Results from a full MonteCarlo simulation for several galactic and extragalactic astronomical sources are also reported.

Revisiting the Gamma-Ray Source 2FGL J1823.8+4312

NASA Astrophysics Data System (ADS)

Stern, Daniel; Assef, Roberto J.

2013-02-01

One of the great challenges of gamma-ray astronomy is identifying the lower energy counterparts to these high-energy sources. Recently, in this journal, Massaro et al. attempted to find the counterpart of 2FGL J1823.8+4312, a gamma-ray active galactic nucleus (AGN) of uncertain type from the Second Fermi Large Area Telescope catalog. After considering mid-infrared data in the field from the Wide-field Infrared Survey Explorer (WISE), those authors conclude that the preferred identification of 2FGL J1823.8+4312 is WISE J182352.33+431452.5, despite the fact that the mid-infrared source is undetected at radio energies. They claim that WISE J182352.33+431452.5 constitutes the discovery of a new class of extragalactic X-ray source, either a radio-faint blazar or the prototype of a new class of active galaxy with an enigmatic spectral energy distribution. This conclusion is claimed to be independent of whether or not the WISE source is the actual counterpart to 2FGL J1823.8+4312. Based on a re-analysis of public data in this field and new spectroscopy from Palomar, we conclude that WISE J182352.33+431452.5 is a dust-reddened quasar at z = 0.560, a representative example of a very common extragalactic AGN class. Were WISE J182352.33+431452.5 to be associated with the gamma-ray emission, this would be an unusual and exciting discovery. However, we argue that 2FGL J1823.8+4312 is more likely associated with either WISE J182409.25+431404.7 or, more likely, WISE J182419.04+430949.6, two radio-loud sources in the field. The former is a radio-loud quasar and the latter is an optically variable source with a featureless blue spectrum.

The PMA Catalogue: 420 million positions and absolute proper motions

NASA Astrophysics Data System (ADS)

Akhmetov, V. S.; Fedorov, P. N.; Velichko, A. B.; Shulga, V. M.

2017-07-01

We present a catalogue that contains about 420 million absolute proper motions of stars. It was derived from the combination of positions from Gaia DR1 and 2MASS, with a mean difference of epochs of about 15 yr. Most of the systematic zonal errors inherent in the 2MASS Catalogue were eliminated before deriving the absolute proper motions. The absolute calibration procedure (zero-pointing of the proper motions) was carried out using about 1.6 million positions of extragalactic sources. The mean formal error of the absolute calibration is less than 0.35 mas yr-1. The derived proper motions cover the whole celestial sphere without gaps for a range of stellar magnitudes from 8 to 21 mag. In the sky areas where the extragalactic sources are invisible (the avoidance zone), a dedicated procedure was used that transforms the relative proper motions into absolute ones. The rms error of proper motions depends on stellar magnitude and ranges from 2-5 mas yr-1 for stars with 10 mag < G < 17 mag to 5-10 mas yr-1 for faint ones. The present catalogue contains the Gaia DR1 positions of stars for the J2015 epoch. The system of the PMA proper motions does not depend on the systematic errors of the 2MASS positions, and in the range from 14 to 21 mag represents an independent realization of a quasi-inertial reference frame in the optical and near-infrared wavelength range. The Catalogue also contains stellar magnitudes taken from the Gaia DR1 and 2MASS catalogues. A comparison of the PMA proper motions of stars with similar data from certain recent catalogues has been undertaken.

Infrared fluorescence from PAHs in the laboratory

NASA Technical Reports Server (NTRS)

Cherchneff, Isabelle; Barker, John R.

1989-01-01

Several celestial objects, including UV rich regions of planetary and reflection nebulae, stars, H II regions, and extragalactic sources, are characterized by the unidentified infrared emission bands (UIR bands). A few years ago, it was proposed that polycyclic aromatic hydrocarbon species (PAHs) are responsible for most of the UIR bands. This hypothesis is based on a spectrum analysis of the observed features. Comparisons of observed IR spectra with lab absorption spectra of PAHs support the PAH hypothesis. An example spectrum is represented, where the Orion Bar 3.3 micron spectrum is compared with the absorption frequencies of the PAHs Chrysene, Pyrene, and Coronene. The laser excited 3.3 micron emission spectrum is presented from a gas phase PAH (azulen). The infrared fluorescence theory (IRF) is briefly explained, followed by a description of the experimental apparatus, a report of the results, and discussion.

Simulations of extragalactic magnetic fields and of their observables

NASA Astrophysics Data System (ADS)

Vazza, F.; Brüggen, M.; Gheller, C.; Hackstein, S.; Wittor, D.; Hinz, P. M.

2017-12-01

The origin of extragalactic magnetic fields is still poorly understood. Based on a dedicated suite of cosmological magneto-hydrodynamical simulations with the ENZO code we have performed a survey of different models that may have caused present-day magnetic fields in galaxies and galaxy clusters. The outcomes of these models differ in cluster outskirts, filaments, sheets and voids and we use these simulations to find observational signatures of magnetogenesis. With these simulations, we predict the signal of extragalactic magnetic fields in radio observations of synchrotron emission from the cosmic web, in Faraday rotation, in the propagation of ultra high energy cosmic rays, in the polarized signal from fast radio bursts at cosmological distance and in spectra of distant blazars. In general, primordial scenarios in which present-day magnetic fields originate from the amplification of weak (⩽nG ) uniform seed fields result in more homogeneous and relatively easier to observe magnetic fields than astrophysical scenarios, in which present-day fields are the product of feedback processes triggered by stars and active galaxies. In the near future the best evidence for the origin of cosmic magnetic fields will most likely come from a combination of synchrotron emission and Faraday rotation observed at the periphery of large-scale structures.

A morphological filter for removing 'Cirrus-like' emission from far-infrared extragalactic IRAS fields

NASA Technical Reports Server (NTRS)

Appleton, P. N.; Siqueira, P. R.; Basart, J. P.

1993-01-01

The presence of diffuse extended IR emission from the Galaxy in the form of the so called 'Galactic Cirrus' emission has hampered the exploration of the extragalactic sky at long IR wavelengths. We describe the development of a filter based on mathematical morphology which appears to be a promising approach to the problem of cirrus removal. The method of Greyscale Morphology was applied to a 100 micron IRAS image of the M81 group of galaxies. This is an extragalactic field which suffers from serious contamination from foreground Galactic 'cirrus'. Using a technique called 'sieving', it was found that the cirrus emission has a characteristic behavior which can be quantified in terms of an average spatial structure spectrum or growth function. This function was then used to attempt to remove 'cirrus' from the entire image. The result was a significant reduction of cirrus emission by an intensity factor of 15 compared with the original input image. The method appears to preserve extended emission in the spatially extended IR disks of M81 and M82 as well as distinguishing fainter galaxies within bright regions of galactic cirrus. The techniques may also be applicable to IR databases obtained with the Cosmic Background Explorer.

A low level of extragalactic background light as revealed by gamma-rays from blazars.

PubMed

Aharonian, F; Akhperjanian, A G; Bazer-Bachi, A R; Beilicke, M; Benbow, W; Berge, D; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Breitling, F; Brown, A M; Chadwick, P M; Chounet, L-M; Cornils, R; Costamante, L; Degrange, B; Dickinson, H J; Djannati-Ataï, A; Drury, L O'C; Dubus, G; Emmanoulopoulos, D; Espigat, P; Feinstein, F; Fontaine, G; Fuchs, Y; Funk, S; Gallant, Y A; Giebels, B; Gillessen, S; Glicenstein, J F; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hofmann, W; Holleran, M; Horns, D; Jacholkowska, A; de Jager, O C; Khélifi, B; Klages, S; Komin, Nu; Konopelko, A; Latham, I J; Le Gallou, R; Lemière, A; Lemoine-Goumard, M; Leroy, N; Lohse, T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; McComb, T J L; de Naurois, M; Nolan, S J; Noutsos, A; Orford, K J; Osborne, J L; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Pühlhofer, G; Punch, M; Raubenheimer, B C; Raue, M; Raux, J; Rayner, S M; Reimer, A; Reimer, O; Ripken, J; Rob, L; Rolland, L; Rowell, G; Sahakian, V; Saugé, L; Schlenker, S; Schlickeiser, R; Schuster, C; Schwanke, U; Siewert, M; Sol, H; Spangler, D; Steenkamp, R; Stegmann, C; Tavernet, J-P; Terrier, R; Théoret, C G; Tluczykont, M; van Eldik, C; Vasileiadis, G; Venter, C; Vincent, P; Völk, H J; Wagner, S J

2006-04-20

The diffuse extragalactic background light consists of the sum of the starlight emitted by galaxies through the history of the Universe, and it could also have an important contribution from the 'first stars', which may have formed before galaxy formation began. Direct measurements are difficult and not yet conclusive, owing to the large uncertainties caused by the bright foreground emission associated with zodiacal light. An alternative approach is to study the absorption features imprinted on the gamma-ray spectra of distant extragalactic objects by interactions of those photons with the background light photons. Here we report the discovery of gamma-ray emission from the blazars H 2356 - 309 and 1ES 1101 - 232, at redshifts z = 0.165 and z = 0.186, respectively. Their unexpectedly hard spectra provide an upper limit on the background light at optical/near-infrared wavelengths that appears to be very close to the lower limit given by the integrated light of resolved galaxies. The background flux at these wavelengths accordingly seems to be strongly dominated by the direct starlight from galaxies, thus excluding a large contribution from other sources-in particular from the first stars formed. This result also indicates that intergalactic space is more transparent to gamma-rays than previously thought.

Multiwavelength and parsec-scale properties of extragalactic jets. Doctoral Thesis Award Lecture 2015

NASA Astrophysics Data System (ADS)

Müller, C.

2016-07-01

Extragalactic jets originating from the central supermassive black holes of active galaxies are powerful, highly relativistic plasma outflows, emitting light from the radio up to the γ-ray regime. The details of their formation, composition and emission mechanisms are still not completely clear. The combination of high-resolution observations using very long baseline interferometry (VLBI) and multiwavelength monitoring provides the best insight into these objects. Here, such a combined study of sources of the TANAMI sample is presented, investigating the parsec-scale and high-energy properties. The TANAMI program is a multiwavelength monitoring program of a sample of the radio and γ-ray brightest extragalactic jets in the southern sky, below -30o declination. We obtain the first-ever VLBI images for most of the sources, providing crucial information on the jet kinematics and brightness distribution at milliarcsecond resolution. Two particular sources are discussed in detail: PMN J1603-4904 , which can be classified either as an atypical blazar or a γ-ray loud (young) radio galaxy, and Centaurus A, the nearest radio-loud active galaxy. The VLBI kinematics of the innermost parsec of Centaurus A's jet result in a consistent picture of an accelerated jet flow with a spine-sheath like structure.

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

Palladino, Andrea; Vissani, Francesco; Spurio, Maurizio, E-mail: andrea.palladino@gssi.infn.it, E-mail: maurizio.spurio@bo.infn.it, E-mail: francesco.vissani@lngs.infn.it

Recently it was noted that different IceCube datasets are not consistent with the same power law spectrum of the cosmic neutrinos: this is the IceCube spectral anomaly , that suggests that they observe a multicomponent spectrum. In this work, the main possibilities to enhance the description in terms of a single extragalactic neutrino component are examined. The hypothesis of a sizable contribution of Galactic high-energy neutrino events distributed as E {sup −2.7} [ Astrophys. J. 826 (2016) 185] is critically analyzed and its natural generalization is considered. The stability of the expectations is studied by introducing free parameters, motivated bymore » theoretical considerations and observational facts. The upgraded model here examined has 1) a Galactic component with different normalization and shape E {sup −2.4}; 2) an extragalactic neutrino spectrum based on new data; 3) a non-zero prompt component of atmospheric neutrinos. The two key predictions of the model concern the 'high-energy starting events' collected from the Southern sky. The Galactic component produces a softer spectrum and a testable angular anisotropy. A second, radically different class of models, where the second component is instead isotropic, plausibly extragalactic and with a relatively soft spectrum, is disfavored instead by existing observations of muon neutrinos from the Northern sky and below few 100 TeV.« less

ANATOMY OF HELICAL EXTRAGALACTIC JETS: THE CASE OF S5 0836+710

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

Perucho, M.; Kovalev, Y. Y.; Lobanov, A. P.

Helical structures are common in extragalactic jets. They are usually attributed in the literature to periodical phenomena in the source (e.g., precession). In this work, we use very long baseline interferometry data of the radio jet in the quasar S5 0836+710 and hypothesize that the ridgeline of helical jets like this corresponds to a pressure maximum in the jet and assume that the helically twisted pressure maximum is the result of a helical wave pattern. For our study, we use observations of the jet in S5 0836+710 at different frequencies and epochs. The results show that the structures observed aremore » physical and not generated artificially by the observing arrays. Our hypothesis that the observed intensity ridgeline can correspond to a helically twisted pressure maximum is confirmed by our observational tests. This interpretation allows us to explain jet misalignment between parsec and kiloparsec scales when the viewing angle is small, and also brings us to the conclusion that high-frequency observations may show only a small region of the jet flow concentrated around the maximum pressure ridgeline observed at low frequencies. Our work provides a potential explanation for the apparent transversal superluminal speeds observed in several extragalactic jets by means of transversal shift of an apparent core position with time.« less

On the IceCube spectral anomaly

NASA Astrophysics Data System (ADS)

Palladino, Andrea; Spurio, Maurizio; Vissani, Francesco

2016-12-01

Recently it was noted that different IceCube datasets are not consistent with the same power law spectrum of the cosmic neutrinos: this is the IceCube spectral anomaly, that suggests that they observe a multicomponent spectrum. In this work, the main possibilities to enhance the description in terms of a single extragalactic neutrino component are examined. The hypothesis of a sizable contribution of Galactic high-energy neutrino events distributed as E-2.7 [Astrophys. J. 826 (2016) 185] is critically analyzed and its natural generalization is considered. The stability of the expectations is studied by introducing free parameters, motivated by theoretical considerations and observational facts. The upgraded model here examined has 1) a Galactic component with different normalization and shape E-2.4 2) an extragalactic neutrino spectrum based on new data; 3) a non-zero prompt component of atmospheric neutrinos. The two key predictions of the model concern the `high-energy starting events' collected from the Southern sky. The Galactic component produces a softer spectrum and a testable angular anisotropy. A second, radically different class of models, where the second component is instead isotropic, plausibly extragalactic and with a relatively soft spectrum, is disfavored instead by existing observations of muon neutrinos from the Northern sky and below few 100 TeV.

The LBA Calibrator Survey of Southern Compact Extragalactic Radio Sources - LCS1

NASA Technical Reports Server (NTRS)

Petrov, Leonid; Phillips, Chris; Bertarini, Alessandra; Murphy, Tara; Sadler, Elaine M.

2011-01-01

We present a catalogue of accurate positions and correlated flux densities for 410 flat-spectrum, compact extragalactic radio sources previously detected in the Australia Telescope 20 GHz (AT20G) survey. The catalogue spans the declination range [-90deg, -40deg] and was constructed from four 24-h very long baseline interferometry (VLBI) observing sessions with the Australian Long Baseline Array at 8.3 GHz. The VLBI detection rate in these experiments is 97 per cent, the median uncertainty of the source positions is 2.6 mas and the median correlated flux density on projected baselines longer than 1000 km is 0.14 Jy. The goals of this work are (1) to provide a pool of southern sources with positions accurate to a few milliarcsec, which can be used for phase-referencing observations, geodetic VLBI and space navigation; (2) to extend the complete flux-limited sample of compact extragalactic sources to the Southern hemisphere; and (3) to investigate the parsec-scale properties of high-frequency selected sources from the AT20G survey. As a result of this VLBI campaign, the number of compact radio sources south of declination -40deg which have measured VLBI correlated flux densities and positions known to milliarcsec accuracy has increased by a factor of 3.5.

VizieR Online Data Catalog: Optically Bright extragalactic Radio Sources II (Petrov, 2013)

NASA Astrophysics Data System (ADS)

Petrov, L.

2014-06-01

The first VLBI (Very Long Baseline Interferometry) observing campaign in 2007 resulted in the detection of 398 targets with the European VLBI Network (EVN; Bourda et al., 2010, cat. J/A+A/520/A113). During the second observing campaign, a subset of 105 sources detected in the previous campaign was observed (Bourda et al., 2011, cat. J/A+A/526/A102). Their positions were derived by Petrov (2011, cat. J/AJ/142/105) and formed the OBRS-1 (Optically Bright extragalactic Radio Sources) catalog. The remaining sources were observed in the third campaign, called OBRS-2. During the OBRS-2 campaign, there were three observing sessions with 10 VLBA (Very Long Baseline Array) stations and 5-6 EVN stations from this list: EFLSBERG, MEDICINA, ONSALA60, YEBES40M, DSS63, HARTRAO, and NOTO. Observations were made on 2010 Mar 23 (session ID gc034a), on 2011 Nov 8 (gc034bcd), and on 2011 Mar 15 (gc034ef). The OBRS-2 catalog presents precise positions of the 295 extragalactic radio sources as well as median correlated flux densities at 8.4 and 2.2GHz at baseline lengths shorter than 900km and at baseline lengths longer than 5000km. (1 data file).

New look on the origin of cosmic rays

NASA Astrophysics Data System (ADS)

Istomin, Ya. N.

2017-06-01

From the analysis of the flux of high energy particles, E > 3 · 1018 eV, it is shown that the distribution of the power density of extragalactic rays over energy is of the power law, q̅(E) ∝ E-2.7, with the same index of 2.7 that has the distribution of Galactic cosmic rays before the so called `knee', E < 3 · 1015 eV. However, the average power of extragalactic sources, which is of ɛ ≃ 1043 erg s-1, exceeds by at least two orders the power emitted by the Galaxy in cosmic rays, assuming that the density of galaxies is estimated as Ng ≃ 1 Mpc-3. Considering that such power can be provided by relativistic jets from active galactic nuclei with the power ɛ ≃ 1045 - 1046 erg s-1, we estimate the density of extragalactic sources of cosmic rays as Ng ≃ 10-2 - 10-3 Mpc-3. Assuming the same nature of Galactic and extragalactic rays, we conclude that the Galactic rays were produced by a relativistic jet emitted from the Galactic center during the period of its activity in the past. The remnants of a bipolar jet are now observed in the form of bubbles of relativistic gas above and below the Galactic plane. The break, observed in the spectrum of Galactic rays (`knee'), is explained by fast escape of energetic particles, E > 3 · 1015 eV, from the Galaxy because of the dependence of the coefficient of diffusion of cosmic rays on energy, D∝E0.7. The obtained index of the density distribution of particles over energy, N(E)∝E-2.7-0.7/2=E-3.05, for E > 3 · 1015 eV agrees well with the observed one, N(E)∝E-3.1. The estimated time of the termination of the jet in the Galaxy is 4.2 · 104 years ago.

CONSTRAINING THE EMISSIVITY OF ULTRAHIGH ENERGY COSMIC RAYS IN THE DISTANT UNIVERSE WITH THE DIFFUSE GAMMA-RAY EMISSION

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

Wang Xiangyu; Liu Ruoyu; Aharonian, Felix

Ultrahigh cosmic rays (UHECRs) with energies {approx}> 10{sup 19} eV emitted at cosmological distances will be attenuated by cosmic microwave and infrared background radiation through photohadronic processes. Lower energy extragalactic cosmic rays ({approx}10{sup 18}-10{sup 19} eV) can only travel a linear distance smaller than {approx}Gpc in a Hubble time due to the diffusion if the extragalactic magnetic fields are as strong as nano-Gauss. These prevent us from directly observing most of the UHECRs in the universe, and thus the observed UHECR intensity reflects only the emissivity in the nearby universe within hundreds of Mpc. However, UHECRs in the distant universe,more » through interactions with the cosmic background photons, produce UHE electrons and gamma rays that in turn initiate electromagnetic cascades on cosmic background photons. This secondary cascade radiation forms part of the extragalactic diffuse GeV-TeV gamma-ray radiation and, unlike the original UHECRs, is observable. Motivated by new measurements of extragalactic diffuse gamma-ray background radiation by Fermi/Large Area Telescope, we obtained upper limit placed on the UHECR emissivity in the distant universe by requiring that the cascade radiation they produce not exceed the observed levels. By comparison with the gamma-ray emissivity of candidate UHECR sources (such as gamma-ray bursts (GRBs) and active galactic nuclei) at high redshifts, we find that the obtained upper limit for a flat proton spectrum is {approx_equal} 10{sup 1.5} times larger than the gamma-ray emissivity in GRBs and {approx_equal} 10 times smaller than the gamma-ray emissivity in BL Lac objects. In the case of iron nuclei composition, the derived upper limit of UHECR emissivity is a factor of 3-5 times higher. Robust upper limit on the cosmogenic neutrino flux is further obtained, which is marginally reachable by the Icecube detector and the next-generation detector JEM-EUSO.« less

The Cosmological Impact of Luminous TeV Blazars. II. Rewriting the Thermal History of the Intergalactic Medium

NASA Astrophysics Data System (ADS)

Chang, Philip; Broderick, Avery E.; Pfrommer, Christoph

2012-06-01

The universe is opaque to extragalactic very high energy gamma rays (VHEGRs, E > 100 GeV) because they annihilate and pair produce on the extragalactic background light. The resulting ultrarelativistic pairs are commonly assumed to lose energy primarily through inverse Compton scattering of cosmic microwave background (CMB) photons, reprocessing the original emission from TeV to GeV energies. In Broderick et al., we argued that this is not the case; powerful plasma instabilities driven by the highly anisotropic nature of the ultrarelativistic pair distribution provide a plausible way to dissipate the kinetic energy of the TeV-generated pairs locally, heating the intergalactic medium (IGM). Here, we explore the effect of this heating on the thermal history of the IGM. We collate the observed extragalactic VHEGR sources to determine a local VHEGR heating rate. Given the pointed nature of VHEGR observations, we estimate the correction for the various selection effects using Fermi observations of high- and intermediate-peaked BL Lac objects. As the extragalactic component of the local VHEGR flux is dominated by TeV blazars, we then estimate the evolution of the TeV blazar luminosity density by tying it to the well-observed quasar luminosity density and producing a VHEGR heating rate as a function of redshift. This heating is relatively homogeneous for z <~ 4, but there is greater spatial variation at higher redshift (order unity at z ~ 6) because of the reduced number of blazars that contribute to local heating. We show that this new heating process dominates photoheating in the low-redshift evolution of the IGM and calculate the effect of this heating in a one-zone model. As a consequence, the inclusion of TeV blazar heating qualitatively and quantitatively changes the structure and history of the IGM. Due to the homogeneous nature of the extragalactic background light, TeV blazars produce a uniform volumetric heating rate. This heating is sufficient to increase the temperature of the mean density IGM by nearly an order of magnitude, and at low densities by substantially more. It also naturally produces the inverted temperature-density relation inferred by recent observations of the high-redshift Lyα forest, a feature that is difficult to reconcile with standard reionization models. Finally, we close with a discussion on the possibility of detecting this hot low-density IGM suggested by our model either directly or indirectly via the local Lyα forest, the Comptonized CMB, or free-free emission, but we find that such measurements are currently not feasible.

Extragalactic sources in Cosmic Microwave Background maps

NASA Astrophysics Data System (ADS)

De Zotti, G.; Castex, G.; González-Nuevo, J.; Lopez-Caniego, M.; Negrello, M.; Cai, Z.-Y.; Clemens, M.; Delabrouille, J.; Herranz, D.; Bonavera, L.; Melin, J.-B.; Tucci, M.; Serjeant, S.; Bilicki, M.; Andreani, P.; Clements, D. L.; Toffolatti, L.; Roukema, B. F.

2015-06-01

We discuss the potential of a next generation space-borne CMB experiment for studies of extragalactic sources with reference to COrE+, a project submitted to ESA in response to the call for a Medium-size mission (M4). We consider three possible options for the telescope size: 1 m, 1.5 m and 2 m (although the last option is probably impractical, given the M4 boundary conditions). The proposed instrument will be far more sensitive than Planck and will have a diffraction-limited angular resolution. These properties imply that even the 1 m telescope option will perform substantially better than Planck for studies of extragalactic sources. The source detection limits as a function of frequency have been estimated by means of realistic simulations taking into account all the relevant foregrounds. Predictions for the various classes of extragalactic sources are based on up-to-date models. The most significant improvements over Planck results are presented for each option. COrE+ will provide much larger samples of truly local star-forming galaxies (by about a factor of 8 for the 1 m telescope, of 17 for 1.5 m, of 30 for 2 m), making possible analyses of the properties of galaxies (luminosity functions, dust mass functions, star formation rate functions, dust temperature distributions, etc.) across the Hubble sequence. Even more interestingly, COrE+ will detect, at |b| > 30°, thousands of strongly gravitationally lensed galaxies (about 2,000, 6,000 and 13,000 for the 1 m, 1.5 m and 2 m options, respectively). Such large samples are of extraordinary astrophysical and cosmological value in many fields. Moreover, COrE+ high frequency maps will be optimally suited to pick up proto-clusters of dusty galaxies, i.e. to investigate the evolution of large scale structure at larger redshifts than can be reached by other means. Thanks to its high sensitivity COrE+ will also yield a spectacular advance in the blind detection of extragalactic sources in polarization: we expect that it will detect up to a factor of 40 (1 m option) or of 160 (1.5 m option) more radio sources than can be detected by Planck and, for the first time, from several tens (1 m option) to a few hundreds (1.5 m option) of star forming galaxies. This will open a new window for studies of the global properties of magnetic fields in star forming galaxies and of their relationships with star formation rates.

Photoionization in the halo of the Galaxy

NASA Technical Reports Server (NTRS)

Bregman, Joel N.; Harrington, J. Patrick

1986-01-01

The ionizing radiation field in the halo is calculated and found to be dominated in the 13.6-45 eV range by light from O-B stars that escapes the disk, by planetary nebulae at 45-54 eV, by quasars and the Galactic soft X-ray background at 54-2000 eV, and by the extragalactic X-ray background at higher energies. Photoionization models are calculated with this radiation field incident on halo clouds of constant density for a variety of densities, for normal and depleted abundances, and with variations of the incident spectrum. For species at least triply ionized, such as Si IV, C IV, N V, and O VI, the line ratios are determined by intervening gas with the greatest volume, which is not necessarily the greatest mass component. Column densities from doubly ionized species like Si III should be greater than from triply ionized species. The role of photoionized gas in cosmic ray-supported halos and Galactic fountains is discussed. Observational tests of photoionization models are suggested.

Statistical Analysis of Large-Scale Structure of Universe

NASA Astrophysics Data System (ADS)

Tugay, A. V.

While galaxy cluster catalogs were compiled many decades ago, other structural elements of cosmic web are detected at definite level only in the newest works. For example, extragalactic filaments were described by velocity field and SDSS galaxy distribution during the last years. Large-scale structure of the Universe could be also mapped in the future using ATHENA observations in X-rays and SKA in radio band. Until detailed observations are not available for the most volume of Universe, some integral statistical parameters can be used for its description. Such methods as galaxy correlation function, power spectrum, statistical moments and peak statistics are commonly used with this aim. The parameters of power spectrum and other statistics are important for constraining the models of dark matter, dark energy, inflation and brane cosmology. In the present work we describe the growth of large-scale density fluctuations in one- and three-dimensional case with Fourier harmonics of hydrodynamical parameters. In result we get power-law relation for the matter power spectrum.

Matching radio catalogues with realistic geometry: application to SWIRE and ATLAS

NASA Astrophysics Data System (ADS)

Fan, Dongwei; Budavári, Tamás; Norris, Ray P.; Hopkins, Andrew M.

2015-08-01

Cross-matching catalogues at different wavelengths is a difficult problem in astronomy, especially when the objects are not point-like. At radio wavelengths, an object can have several components corresponding, for example, to a core and lobes. Considering not all radio detections correspond to visible or infrared sources, matching these catalogues can be challenging. Traditionally, this is done by eye for better quality, which does not scale to the large data volumes expected from the next-generation of radio telescopes. We present a novel automated procedure, using Bayesian hypothesis testing, to achieve reliable associations by explicit modelling of a particular class of radio-source morphology. The new algorithm not only assesses the likelihood of an association between data at two different wavelengths, but also tries to assess whether different radio sources are physically associated, are double-lobed radio galaxies, or just distinct nearby objects. Application to the Spitzer Wide-Area Infrared Extragalactic and Australia Telescope Large Area Survey CDF-S catalogues shows that this method performs well without human intervention.

Status of the GAMMA-400 Project

NASA Technical Reports Server (NTRS)

Galper, A. M.; Adriani, O.; Aptekar, R. L.; Arkhangelskaja, I. V.; Arkhangelskiy, A. I.; Boezio, M.; Bonvicini, V.; Boyarchuk, K. A.; Gusakov, Yu. V.; Farber, M. O.;

Precision Geodesy via Radio Interferometry.

PubMed

Hinteregger, H F; Shapiro, I I; Robertson, D S; Knight, C A; Ergas, R A; Whitney, A R; Rogers, A E; Moran, J M; Clark, T A; Burke, B F

1972-10-27

Very-long-baseline interferometry experiments, involving observations of extragalactic radio sources, were performed in 1969 to determine the vector separations between antenna sites in Massachusetts and West Virginia. The 845.130-kilometer baseline was estimated from two separate experiments. The results agreed with each other to within 2 meters in all three components and with a special geodetic survey to within 2 meters in length; the differences in baseline direction as determined by the survey and by interferometry corresponded to discrepancies of about 5 meters. The experiments also yielded positions for nine extragalactic radio sources, most to within 1 arc second, and allowed the hydrogen maser clocks at the two sites to be synchronized a posteriori with an uncertainty of only a few nanoseconds.

The lightest supersymmetric particle and the extragalactic gamma-ray background

NASA Technical Reports Server (NTRS)

Gao, Yi-Tian; Stecker, Floyd W.; Cline, David B.

1991-01-01

The possibility that cosmological photino annihilation is caused by the extragalactic gamma-ray background (EGB) is examined with particular attention given to the lightest supersymmetric particle (LSP). The LSP is considered a general type of the best-motivated candidates for cosmic dark matter (CDM). The theoretical analysis employs a corrected assumption for the annihilation cross section, and cosmological integrations are performed through the early phases of the universe. Romberg's method is used for numerical integration, and the total optical depth is developed for the gamma-ray region. The computed LSP-type annihilation fluxes are found to be negligible when compared to the total EGB observed, suggesting that the LSP candidates for CDM are not significant contributors to the EGB.

Structural Variability of 3C 111 on Parsec Scales

NASA Technical Reports Server (NTRS)

Grossberger, C.; Kadler, M.; Wilms, J.; Muller, C.; Beuchert, T.; Ros, E.; Ojha, R.; Aller, M.; Aller, H.; Angelakis, E.;

Deep Extragalactic X-Ray Surveys

NASA Astrophysics Data System (ADS)

Brandt, W. N.; Hasinger, G.

2005-09-01

Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-Ray Observatory and the X-Ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key results from deep surveys are highlighted, including (a) measurements of AGN evolution and the growth of supermassive black holes, (b) constraints on the demography and physics of high-redshift AGN, (c) the X-ray AGN content of infrared and submillimeter galaxies, and (d) X-ray emission from distant starburst and normal galaxies. We also describe some outstanding problems and future prospects for deep extragalactic X-ray surveys.

The Advanced Gamma-ray Imaging System (AGIS): Extragalactic Science

NASA Astrophysics Data System (ADS)

Coppi, Paolo S.; Extragalactic Science Working Group; AGIS Collaboration

2010-03-01

The Advanced Gamma-ray Imaging System (AGIS), a proposed next-generation array of Cherenkov telescopes, will provide an unprecedented view of the high energy universe. We discuss how AGIS, with its larger effective area, improved angular resolution, lower threshold, and an order of magnitude increase in sensitivity, impacts the extragalactic science possible in the very high energy domain. Likely source classes detectable by AGIS include AGN, GRBs, clusters, star-forming galaxies, and possibly the cascade radiation surrounding powerful cosmic accelerators. AGIS should see many of the sources discovered by Fermi. With its better sensitivity and angular resolution, AGIS then becomes a key instrument for identifying and characterizing Fermi survey sources, the majority of which will have limited Fermi photon statistics and localizations.

Astrophysics of Red Supergiants

NASA Astrophysics Data System (ADS)

Levesque, Emily M.

2017-12-01

'Astrophysics of Red Supergiants' is the first book of its kind devoted to our current knowledge of red supergiant stars, a key evolutionary phase that is critical to our larger understanding of massive stars. It provides a comprehensive overview of the fundamental physical properties of red supergiants, their evolution, and their extragalactic and cosmological applications. It serves as a reference for researchers from a broad range of fields (including stellar astrophysics, supernovae, and high-redshift galaxies) who are interested in red supergiants as extreme stages of stellar evolution, dust producers, supernova progenitors, extragalactic metallicity indicators, members of massive binaries and mergers, or simply as compelling objects in their own right. The book is accessible to a range of experience levels, from graduate students up to senior researchers.

The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

DOE PAGES

Ackermann, M.; Ajello, M.; Allafort, A.; ...

2012-11-30

The light emitted by stars and accreting compact objects through the history of the universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL is important to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are limited by galactic and other foreground emissions. In this paper, we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z ~ 1.6. Finally, this feature is caused by attenuation of gamma rays by the EBL at optical to ultravioletmore » frequencies and allowed us to measure the EBL flux density in this frequency band.« less

Cosmic ray antimatter and baryon symmetric cosmology

NASA Technical Reports Server (NTRS)

Stecker, F. W.; Protheroe, R. J.; Kazanas, D.

1982-01-01

The relative merits and difficulties of the primary and secondary origin hypotheses for the observed cosmic-ray antiprotons, including the new low-energy measurement of Buffington, et al. We conclude that the cosmic-ray antiproton data may be evidence for antimatter galaxies and baryon symmetric cosmology. The present bar P data are consistent with a primary extragalactic component having /p=/equiv 1+/- 3.2/0.7x10 = to the -4 independent of energy. We propose that the primary extragalactic cosmic ray antiprotons are most likely from active galaxies and that expected disintegration of bar alpha/alpha ban alpha/alpha. We further predict a value for ban alpha/alpha =/equiv 10 to the -5, within range of future cosmic ray detectors.

COBE's search for structure in the Big Bang

NASA Technical Reports Server (NTRS)

Soffen, Gerald (Editor); Guerny, Gene (Editor); Keating, Thomas (Editor); Moe, Karen (Editor); Sullivan, Walter (Editor); Truszkowski, Walt (Editor)

1989-01-01

The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle.

Astronomy in Georgia - Present Status and Perspectives

NASA Astrophysics Data System (ADS)

Todua, M.

2016-09-01

Astronomy in Georgia is generally represented in Abastumani Astrophysical Observatory found in 1932. It is one of the leading scientific institutes in the country. Main fields of research are solar system bodies (including near-Earth asteroids), various aspects of solar physics, stellar astronomy (including binary stars and open clusters), extragalactic objects (AGNs), theoretical astrophysics, cosmology, atmospheric and solar-terrestrial physics. Several telescopes are operational today, as well as the instruments for atmospheric studies. In 2007 the Observatory was integrated with Ilia State University, merging scientific research and education which facilitated the growth of a new generation of researchers. There are groups of astronomers and astrophysicists in other Georgian universities and institutions as well. Georgian scientists collaborate with research centers and universities worldwide. Research groups participate in various international scientific projects. The interest in astronomy in Georgia has been growing, which increases future perspectives of its development in the country.

The Radio Synchrotron Background: Conference Summary and Report

NASA Astrophysics Data System (ADS)

Singal, J.; Haider, J.; Ajello, M.; Ballantyne, D. R.; Bunn, E.; Condon, J.; Dowell, J.; Fixsen, D.; Fornengo, N.; Harms, B.; Holder, G.; Jones, E.; Kellermann, K.; Kogut, A.; Linden, T.; Monsalve, R.; Mertsch, P.; Murphy, E.; Orlando, E.; Regis, M.; Scott, D.; Vernstrom, T.; Xu, L.

2018-03-01

We summarize the radio synchrotron background workshop that took place 2017 July 19–21 at the University of Richmond. This first scientific meeting dedicated to the topic was convened because current measurements of the diffuse radio monopole reveal a surface brightness that is several times higher than can be straightforwardly explained by known Galactic and extragalactic sources and processes, rendering it by far the least well understood photon background at present. It was the conclusion of a majority of the participants that the radio monopole level is at or near that reported by the ARCADE 2 experiment and inferred from several absolutely calibrated zero-level lower frequency radio measurements, and unanimously agreed that the production of this level of surface brightness, if confirmed, represents a major outstanding question in astrophysics. The workshop reached a consensus on the next priorities for investigations of the radio synchrotron background.

HIGH-ENERGY NEUTRINOS FROM RECENT BLAZAR FLARES

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

Halzen, Francis; Kheirandish, Ali

The energy density of cosmic neutrinos measured by IceCube matches the one observed by Fermi in extragalactic photons that predominantly originate in blazars. This has inspired attempts to match Fermi sources with IceCube neutrinos. A spatial association combined with a coincidence in time with a flaring source may represent a smoking gun for the origin of the IceCube flux. In 2015 June, the Fermi Large Area Telescope observed an intense flare from blazar 3C 279 that exceeded the steady flux of the source by a factor of 40 for the duration of a day. We show that IceCube is likelymore » to observe neutrinos, if indeed hadronic in origin, in data that are still blinded at this time. We also discuss other opportunities for coincident observations that include a recent flare from blazar 1ES 1959+650 that previously produced an intriguing coincidence with AMANDA observations.« less

VizieR Online Data Catalog: Herschel Multi-tiered Extragalactic Survey (Oliver+, 2012)

NASA Astrophysics Data System (ADS)

Oliver, S. J.; Bock, J.; Altieri, B.; Amblard, A.; Arumugam, V.; Aussel, H.; Babbedge, T.; Beelen, A.; Bethermin, M.; Blain, A.; Boselli, A.; Bridge, C.; Brisbin, D.; Buat, V.; Burgarella, D.; Castro-Rodriguez, N.; Cava, A.; Chanial, P.; Cirasuolo, M.; Clements, D. L.; Conley, A.; Conversi, L.; Cooray, A.; Dowell, C. D.; Dubois, E. N.; Dwek, E.; Dye, S.; Eales, S.; Elbaz, D.; Farrah, D.; Feltre, A.; Ferrero, P.; Fiolet, N.; Fox, M.; Franceschini, A.; Gear, W.; Giovannoli, E.; Glenn, J.; Gong, Y.; Gonzalez Solares, E. A.; Griffin, M.; Halpern, M.; Harwit, M.; Hatziminaoglou, E.; Heinis, S.; Hurley, P.; Hwang, H. S.; Hyde, A.; Ibar, E.; Ilbert, O.; Isaak, K.; Ivison, R. J.; Lagache, G.; Le Floc'h, E.; Levenson, L.; Faro, B. L.; Lu, N.; Madden, S.; Maffei, B.; Magdis, G.; Mainetti, G.; Marchetti, L.; Marsden, G.; Marshall, J.; Mortier, A. M. J.; Nguyen, H. T.; O'Halloran, B.; Omont, A.; Page, M. J.; Panuzzo, P.; Papageorgiou, A.; Patel, H.; Pearson, C. P.; Perez-Fournon, I.; Pohlen, M.; Rawlings, J. I.; Raymond, G.; Rigopoulou, D.; Riguccini, L.; Rizzo, D.; Rodighier!, O. G.; Ros Eboom, I. G.; Rowan-Robinson, M.; Sanchez Portal, M.; Schulz, B.; Scott, D.; Seymour, N.; Shupe, D. L.; Smith, A. J.; Stevens, J. A.; Symeonidis, M.; Trichas, M.; Tugwell, K. E.; Vaccari, M.; Valtchanov, I.; Vieira, J. D.; Viero, M.; Vigroux, L.; Wang, L.; Ward, R.; Wardlow, J.; Wright, G.; Xu, C. K.; Zemcov, M.

2017-03-01

SPIRE maps (250, 350 and 500 microns) and PACS maps (100 and 160 microns) covering an area of more than 385 square degrees in the sky resulting from observations taken as part of HerMES (KPGTsoliver1), a Herschel Key Project whose main objective was to chart the formation and evolution of infrared galaxies throughout cosmic history, measuring the bolometric emission of infrared galaxies and their clustering properties. The associated catalogues extracted from these maps include over 1,200,000 entries representing over 340,000 galaxies. They consist of 'blind extraction' catalogues containing photometric information derived directly from these maps, 'band merged' catalogues extracted at SPIRE 250 micron positions plus 'cross-identification' catalogues based on prior Spitzer MIPS 24 micron source positions. The latest data releases contain also information derived from the complementary Herschel programmes HeLMS (GT2mviero1) and HeRS (OT2mviero2). (4 data files).

Review: Magnetic Fields of O-Type Stars

NASA Astrophysics Data System (ADS)

Wade, G. A.; MiMeS Collaboration

2015-04-01

Since 2002, strong, organized magnetic fields have been firmly detected at the surfaces of about 10 Galactic O-type stars. In this paper I will review the characteristics of the inferred fields of individual stars as well as the overall population. I will discuss the extension of the “magnetic desert,” first inferred among the A-type stars, to O stars up to 60 M⊙. I will discuss the interaction of the winds of the magnetic stars with the fields above their surfaces, generating complex “dynamical magnetosphere” structures detected in optical and UV lines, and in X-ray lines and continuum. Finally, I will discuss the detection of a small number of variable O stars in the LMC and SMC that exhibit spectral characteristics analogous to the known Galactic magnetic stars, and that almost certainly represent the first known examples of extragalactic magnetic stars.

ULTRAVIOLET HALOS AROUND SPIRAL GALAXIES. I. MORPHOLOGY

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

Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N., E-mail: hodgeskl@umich.edu

2016-12-10

We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that ultraviolet (UV) halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlationmore » between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 10{sup 6}–10{sup 7} M {sub ⊙} of dust within 2–10 kpc of the disk, whose properties may change with height in starburst galaxies.« less

The Spitzer-IRAC/MIPS Extragalactic Survey (SIMES) in the South Ecliptic Pole Field

NASA Astrophysics Data System (ADS)

Baronchelli, I.; Scarlata, C.; Rodighiero, G.; Franceschini, A.; Capak, P. L.; Mei, S.; Vaccari, M.; Marchetti, L.; Hibon, P.; Sedgwick, C.; Pearson, C.; Serjeant, S.; Menéndez-Delmestre, K.; Salvato, M.; Malkan, M.; Teplitz, H. I.; Hayes, M.; Colbert, J.; Papovich, C.; Devlin, M.; Kovacs, A.; Scott, K. S.; Surace, J.; Kirkpatrick, J. D.; Atek, H.; Urrutia, T.; Scoville, N. Z.; Takeuchi, T. T.

2016-03-01

We present the Spitzer-IRAC/MIPS Extragalactic survey (SIMES) in the South Ecliptic Pole field. The large area covered (7.7 deg2), together with one of the lowest Galactic cirrus emissions in the entire sky and a very extensive coverage by Spitzer, Herschel, Akari, and GALEX, make the SIMES field ideal for extragalactic studies. The elongated geometry of the SIMES area (≈4:1), allowing for significant cosmic variance reduction, further improves the quality of statistical studies in this field. Here we present the reduction and photometric measurements of the Spitzer/IRAC data. The survey reaches depths of 1.93 and 1.75 μJy (1σ) at 3.6 and 4.5 μm, respectively. We discuss the multiwavelength IRAC-based catalog, completed with optical, mid-, and far-IR observations. We detect 341,000 sources with {F}3.6μ {{m}}≥slant 3σ . Of these, 10% have an associated 24 μm counterpart, while 2.7% have an associated SPIRE source. We release the catalog through the NASA/IPAC Infrared Science Archive. Two scientific applications of these IRAC data are presented in this paper. First, we compute integral number counts at 3.6 μm. Second, we use the [3.6]-[4.5] color index to identify galaxy clusters at z > 1.3. We select 27 clusters in the full area, a result consistent with previous studies at similar depth.

VizieR Online Data Catalog: The VLBA Extragalactic Proper Motion Catalog (Truebenbach+, 2017)

NASA Astrophysics Data System (ADS)

Truebenbach, A. E.; Darling, J.

2017-11-01

We created our catalog of extragalactic radio proper motions using the 2017a Goddard VLBI global solution. The 2017a solution is computed from more than 30 years of dual-band VLBI observations --1979 August 3 to 2017 March 27. We also observed 28 objects with either no redshift or a "questionable" Optical Characteristic of Astrometric Radio Sources (OCARS; Malkin 2016ARep...60..996M) redshift at the Apache Point Observatory (APO) 3.5m telescope and/or at Gemini North. We conducted observations on the 3.5m telescope at Apache Point Observatory with the Dual Imaging Spectrograph (DIS) from 2015 April 18 to 2016 June 30. We chose two objects for additional observations with the Gemini Multi-Object Spectrograph-North (GMOS-N) at Gemini North Observatory. 2021+317 was observed on 2016 June 26 and 28, while 0420+417 was observed on 2016 November 8 and 26. We also observed 42 radio sources with the Very Long Baseline Array (VLBA) in the X-band (3.6cm/8.3GHz). Our targets had all been previously observed by VLBI. Our VLBA observations were conducted in two campaigns from 2015 September to 2016 January and 2016 October to November. The final extragalactic proper motion catalog (created primarily from archival Goddard VLBI data, with redshifts obtained from OCARS) contains 713 proper motions with average uncertainties of 24μas/yr. (5 data files).

Galaxies Detected by the Dwingeloo Obscured Galaxies Survey

NASA Astrophysics Data System (ADS)

Rivers, A. J.; Henning, P. A.; Kraan-Korteweg, R. C.

1999-04-01

The Dwingeloo Obscured Galaxies Survey (DOGS) is a 21-cm blind survey for galaxies hidden in the northern `Zone of Avoidance' (ZOA): the portion of the optical extragalactic sky which is obscured by dust in the Milky Way. Like the Parkes southern hemisphere ZOA survey, the DOGS project is designed to reveal hidden dynamically important nearby galaxies and to help `fill in the blanks' in the local large scale structure. To date, 36 galaxies have been detected by the Dwingeloo survey; 23 of these were previously unknown [no corresponding sources recorded in the NASA Extragalactic Database (NED)]. Among the interesting detections are three nearby galaxies in the vicinity of NGC 6946 and 11 detections in the Supergalactic plane crossing region. VLA follow-up observations have been conducted for several of the DOGS detections.

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arqueros, F.; Arsene, N.; Asorey, H.; Assis, P.; Aublin, J.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barreira Luz, R. J.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D'Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Di Giulio, C.; Di Matteo, A.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.; Dorosti, Q.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fick, B.; Figueira, J. M.; Filipčič, A.; Fratu, O.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaior, R.; García, B.; Garcia-Pinto, D.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi, A.; Gorham, P.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Johnsen, J. A.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Katkov, I.; Keilhauer, B.; Kemp, E.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; LaHurd, D.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lopes, L.; López, R.; López Casado, A.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Mostafá, M.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, H.; Núñez, L. A.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A. S.; Perlín, M.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.; Ravignani, D.; Revenu, B.; Ridky, J.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rogozin, D.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento, C. A.; Sato, R.; Schauer, M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Sorokin, J.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Stassi, P.; Strafella, F.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Swain, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Tapia, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Torralba Elipe, G.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiencke, L.; Wilczyński, H.; Winchen, T.; Wirtz, M.; Wittkowski, D.; Wundheiler, B.; Yang, L.; Yelos, D.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.

2017-03-01

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p-values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. These limits significantly constrain predictions of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.

An Empirical Decomposition of Near-IR Emission into Galactic and Extragalactic Components

NASA Technical Reports Server (NTRS)

Dwek, Eli; Arendt, Richard G.

2002-01-01

We decompose the COBE/DIRBE observations of the near-IR sky brightness (minus zodiacal light) into Galactic stellar and interstellar medium (ISM) components and an extragalactic background. This empirical procedure allows us to estimate the 4.9 micron cosmic infrared background (CIB) as a function of the CIB intensity at shorter wavelengths. A weak indication of a rising CIB intensity at wavelengths greater than 3.5$ microns hints at interesting astrophysics in the CIB spectrum, or warns that the foreground zodiacal emission may be incompletely subtracted. Subtraction of only the stellar component from the zodiacal-light-subtracted all--sky map reveals the clearest 3.5 micron ISM emission map, which is found to be tightly correlated with the ISM emission at far-IR wavelengths.

The shape of the extragalactic cosmic ray spectrum from galaxy clusters

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

Harari, Diego; Mollerach, Silvia; Roulet, Esteban, E-mail: harari@cab.cnea.gov.ar, E-mail: mollerach@cab.cnea.gov.ar, E-mail: roulet@cab.cnea.gov.ar

2016-08-01

We study the diffusive escape of cosmic rays from a central source inside a galaxy cluster to obtain the suppression in the outgoing flux appearing when the confinement times get comparable or larger than the age of the sources. We also discuss the attenuation of the flux due to the interactions of the cosmic rays with the cluster medium, which can be sizeable for heavy nuclei. The overall suppression in the total cosmic ray flux expected on Earth is important to understand the shape of the extragalactic contribution to the cosmic ray spectrum for E / Z < 1 EeVmore » . This suppression can also be relevant to interpret the results of fits to composition-sensitive observables measured at ultra-high energies.« less

Assembling the Infrared Extragalactic Background Light with CIBER-2: Probing Inter-Halo Light and the Epoch of Reionization.

NASA Astrophysics Data System (ADS)

Bock, James

We propose to carry out a program of observations with the Cosmic Infrared Background Experiment (CIBER-2). CIBER-2 is a near-infrared sounding rocket experiment designed to measure spatial fluctuations in the extragalactic background light. CIBER-2 scientifically follows on the detection of fluctuations with the CIBER-1 imaging instrument, and will use measurement techniques developed and successfully demonstrated by CIBER-1. With high-sensitivity, multi-band imaging measurements, CIBER-2 will elucidate the history of interhalo light (IHL) production and carry out a deep search for extragalactic background fluctuations associated with the epoch of reionization (EOR). CIBER-1 has made high-quality detections of large-scale fluctuations over 4 sounding rocket flights. CIBER-1 measured the amplitude and spatial power spectrum of fluctuations, and observed an electromagnetic spectrum that is close to Rayleigh-Jeans, but with a statistically significant turnover at 1.1 um. The fluctuations cross-correlate with Spitzer images and are significantly bluer than the spectrum of the integrated background derived from galaxy counts. We interpret the CIBER-1 fluctuations as arising from IHL, low-mass stars tidally stripped from their parent galaxies during galaxy mergers. The first generation of stars and their remnants are likely responsible for the for the reionization of the intergalactic medium, observed to be ionized out to the most distant quasars at a redshift of 6. The total luminosity produced by first stars is uncertain, but a lower limit can be placed assuming a minimal number of photons to produce and sustain reionization. This 'minimal' extragalactic background component associated with reionization is detectable in fluctuations at the design sensitivity of CIBER-2. The CIBER-2 instrument is optimized for sensitivity to surface brightness in a short sounding rocket flight. The instrument consists of a 28 cm wide-field telescope operating in 6 spectral bands between 0.5 and 2.0 um, cooled to a temperature of 77 K with a liquid nitrogen cryostat. Images are composed using 3 focal plane assemblies operating H2RG detector arrays. The instrument is currently being fabricated with expected delivery during summer 2014, and will be ready for its first flight in 2015. CIBER-2 will extend the CIBER-1 observations from the near-infrared into the optical, where the EOR and IHL components of the extragalactic background can be cleanly distinguished and separated. We will study the history of IHL production by implementing a multi-band cross-correlation analysis, and use this information to carry out a deep search for an EOR component. In subsequent flights we plan joint observations with weak lensing maps, with an optimized set of filter bands to measure spectral cross-correlations, to fully elucidate the history of IHL light production.

Source structure errors in radio-interferometric clock synchronization for ten measured distributions

NASA Technical Reports Server (NTRS)

Thomas, J. B.

1981-01-01

The effects of source structure on radio interferometry measurements were investigated. The brightness distribution measurements for ten extragalactic sources were analyzed. Significant results are reported.

A Multi-ionic Kinematic Investigation of NGC 595, a Giant Extragalactic H II Region in M33

NASA Astrophysics Data System (ADS)

Lagrois, Dominic; Joncas, Gilles

2009-08-01

Spectro-interferometric observations of the Hα, [O III], and [S II] optical emission lines are combined with radio observations of the 21 cm line in order to obtain a reliable kinematic image of NGC 595, the second largest giant extragalactic H II region in M33. The Hα and [O III] observations reveal that the nebula is exposed to two distinct kinematical regimes. While symmetric, broad velocity profiles dominate a sizeable fraction of the ionized extent, evidence for line splitting is detected in a small region near the most massive stars of the star cluster. A quantitative investigation proposes that two expanding wind-blown bubbles could be held responsible for the observed line splitting. The kinematics of the ionized material presenting one-component velocity profiles likely indicates that Champagne flows are present at the periphery of the molecular component leading to accelerated ionized material in the ambient interstellar medium. In areas not dominated by the photoionization of the molecular clouds, the H+ and S+ material shows a kinematical behavior roughly in agreement with the atomic gas. Mean nonthermal line widths show relatively large, supersonic values especially in [O III]. Models of structure functions indicate that the Hα and [O III] components could be exposed to different turbulent motions which could explain the broadening excess observed for the latter ion. On the full ionized extent of the nebula, the S+ material shows narrower line widths than the two other ions. Combined with the absence of line splitting, these peculiar characteristics indicate that the [S II] component is likely located at the periphery of the nebula and probably does not coexist with Hα and [O III]. The shape of the [S II] structure function is in agreement with a relatively low number of large-scale velocity gradients which partially explains the narrower profiles observed. The mean electron density in the nebula is estimated at 162 ± 106(1σ) cm-3, in agreement with previous studies of similar extragalactic H II regions. We provide the first bidimensional electron density map ever presented for a giant extragalactic nebula.

Recent Developments in Radioastronomy--Part 2.

ERIC Educational Resources Information Center

Booth, R. S.

1980-01-01

Described are recent developments and discoveries in radioastronomy. Topics discussed include galactic structures, stellar evolution, the binary pulsar and general relativity, extragalactic radioastronomy, model of the source of radioactive emission and quasars. (DS)

Stochastic Order Redshift Technique (SORT): a simple, efficient and robust method to improve cosmological redshift measurements

NASA Astrophysics Data System (ADS)

Tejos, Nicolas; Rodríguez-Puebla, Aldo; Primack, Joel R.

2018-01-01

We present a simple, efficient and robust approach to improve cosmological redshift measurements. The method is based on the presence of a reference sample for which a precise redshift number distribution (dN/dz) can be obtained for different pencil-beam-like sub-volumes within the original survey. For each sub-volume we then impose that: (i) the redshift number distribution of the uncertain redshift measurements matches the reference dN/dz corrected by their selection functions and (ii) the rank order in redshift of the original ensemble of uncertain measurements is preserved. The latter step is motivated by the fact that random variables drawn from Gaussian probability density functions (PDFs) of different means and arbitrarily large standard deviations satisfy stochastic ordering. We then repeat this simple algorithm for multiple arbitrary pencil-beam-like overlapping sub-volumes; in this manner, each uncertain measurement has multiple (non-independent) 'recovered' redshifts which can be used to estimate a new redshift PDF. We refer to this method as the Stochastic Order Redshift Technique (SORT). We have used a state-of-the-art N-body simulation to test the performance of SORT under simple assumptions and found that it can improve the quality of cosmological redshifts in a robust and efficient manner. Particularly, SORT redshifts (zsort) are able to recover the distinctive features of the so-called 'cosmic web' and can provide unbiased measurement of the two-point correlation function on scales ≳4 h-1Mpc. Given its simplicity, we envision that a method like SORT can be incorporated into more sophisticated algorithms aimed to exploit the full potential of large extragalactic photometric surveys.

Radio variability in complete samples of extragalactic radio sources at 1.4 GHz

NASA Astrophysics Data System (ADS)

Rys, S.; Machalski, J.

1990-09-01

Complete samples of extragalactic radio sources obtained in 1970-1975 and the sky survey of Condon and Broderick (1983) were used to select sources variable at 1.4 GHz, and to investigate the characteristics of variability in the whole population of sources at this frequency. The radio structures, radio spectral types, and optical identifications of the selected variables are discussed. Only compact flat-spectrum sources vary at 1.4 GHz, and all but four are identified with QSOs, BL Lacs, or other (unconfirmed spectroscopically) stellar objects. No correlation of degree of variability at 1.4 GHz with Galactic latitude or variability at 408 MHz has been found, suggesting that most of the 1.4-GHz variability is intrinsic and not caused by refractive scintillations. Numerical models of the variability have been computed.

The grand unified photon spectrum: A coherent view of the diffuse extragalactic background radiation

NASA Technical Reports Server (NTRS)

Ressell, M. Ted; Turner, Michael S.

1989-01-01

The spectrum of diffuse extragalactic background radiation (DEBRA) at wavelengths from 10(exp 5) to 10(exp -24) cm is presented in a coherent fashion. Each wavelength region, from the radio to ultra-high energy photons and cosmic rays, is treated both separately and as part of the grand unified photon spectrum (GUPS). A discussion of, and references to, the relevant literature for each wavelength region is included. This review should provide a useful tool for those interested in diffuse backgrounds, the epoch of galaxy formation, astrophysical/cosmological constraints to particle properties, exotic early Universe processes, and many other astrophysical and cosmological enterprises. As a worked example, researchers derive the cosmological constraints to an unstable-neutrino spies (with arbitrary branching ratio to a radiative decay mode) that follow from the GUPS.

Cumulative neutrino background from quasar-driven outflows

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

Wang, Xiawei; Loeb, Abraham, E-mail: xiawei.wang@cfa.harvard.edu, E-mail: aloeb@cfa.harvard.edu

2016-12-01

Quasar-driven outflows naturally account for the missing component of the extragalactic γ-ray background through neutral pion production in interactions between protons accelerated by the forward outflow shock and interstellar protons. We study the simultaneous neutrino emission by the same protons. We adopt outflow parameters that best fit the extragalactic γ-ray background data and derive a cumulative neutrino background of ∼ 10{sup −7} GeV cm{sup −2} s{sup −1} sr{sup −1} at neutrino energies E {sub ν} ∼> 10 TeV, which naturally explains the most recent IceCube data without tuning any free parameters. The link between the γ-ray and neutrino emission frommore » quasar outflows can be used to constrain the high-energy physics of strong shocks at cosmological distances.« less

Probing Extragalactic Planets Using Quasar Microlensing

NASA Astrophysics Data System (ADS)

Dai, Xinyu; Guerras, Eduardo

2018-02-01

Previously, planets have been detected only in the Milky Way galaxy. Here, we show that quasar microlensing provides a means to probe extragalactic planets in the lens galaxy, by studying the microlensing properties of emission close to the event horizon of the supermassive black hole of the background quasar, using the current generation telescopes. We show that a population of unbound planets between stars with masses ranging from Moon to Jupiter masses is needed to explain the frequent Fe Kα line energy shifts observed in the gravitationally lensed quasar RXJ 1131–1231 at a lens redshift of z = 0.295 or 3.8 billion lt-yr away. We constrain the planet mass-fraction to be larger than 0.0001 of the halo mass, which is equivalent to 2000 objects ranging from Moon to Jupiter mass per main-sequence star.

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

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

Aab, A.; Abreu, P.; Aglietta, M.

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p-values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. Lastly, these limits significantly constrain predictionsmore » of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.« less

Blazar 3C 66A: Another extragalactic source of ultra-high-energy gamma-ray photons

NASA Astrophysics Data System (ADS)

Neshpor, Yu. I.; Stepanyan, A. A.; Kalekin, O. P.; Fomin, V. P.; Chalenko, N. N.; Shitov, V. G.

1998-03-01

he observations of the object 3C 66A which were carried out with the GT-48 gamma-ray telescope at the Crimean Astrophysical Observatory in November-December 1996 revealed a flux of ultra-high-energy (>10^12 eV) gamma-ray photons from this blazar. According to preliminary estimates, the photon flux is (31) 10^11 photons cm^-2 s^-1. The blazar 3C 66A is the third extragalactic object from which a flux of ultra- high-energy gamma-ray photons was detected. Fluxes of gamma-ray photons were previously detected from the galaxies Mk 421 and Mk 501 at the Whipple observatory. This result provides further evidence that active processes proceed in blazars which are accompanied by the generation of cosmic rays responsible for the emission of gamma-ray photons.

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

DOE PAGES

Aab, A.; Abreu, P.; Aglietta, M.; ...

2017-03-09

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p-values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. Lastly, these limits significantly constrain predictionsmore » of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.« less

A Targeted Search for Point Sources of EeV Photons with the Pierre Auger Observatory

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

Aab, A.; Abreu, P.; Aglietta, M.

Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to reduce the statistical penalty of many trials from that of a blind search and are analyzed for a significant excess above the background expectation. The presented search does not find any evidence for photon emission at candidate sources, and combined p -values for every class are reported. Particle and energy flux upper limits are given for selected candidate sources. These limits significantly constrain predictionsmore » of EeV proton emission models from non-transient Galactic and nearby extragalactic sources, as illustrated for the particular case of the Galactic center region.« less

A precise extragalactic test of General Relativity.

PubMed

Collett, Thomas E; Oldham, Lindsay J; Smith, Russell J; Auger, Matthew W; Westfall, Kyle B; Bacon, David; Nichol, Robert C; Masters, Karen L; Koyama, Kazuya; van den Bosch, Remco

2018-06-22

Einstein's theory of gravity, General Relativity, has been precisely tested on Solar System scales, but the long-range nature of gravity is still poorly constrained. The nearby strong gravitational lens ESO 325-G004 provides a laboratory to probe the weak-field regime of gravity and measure the spatial curvature generated per unit mass, γ. By reconstructing the observed light profile of the lensed arcs and the observed spatially resolved stellar kinematics with a single self-consistent model, we conclude that γ = 0.97 ± 0.09 at 68% confidence. Our result is consistent with the prediction of 1 from General Relativity and provides a strong extragalactic constraint on the weak-field metric of gravity. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Diffuse radiation

NASA Technical Reports Server (NTRS)

1981-01-01

A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

Very Long Baseline Interferometry: Dependencies on Frequency Stability

NASA Astrophysics Data System (ADS)

Nothnagel, Axel; Nilsson, Tobias; Schuh, Harald

2018-04-01

Very Long Baseline Interferometry (VLBI) is a differential technique observing radiation of compact extra-galactic radio sources with pairs of radio telescopes. For these observations, the frequency standards at the telescopes need to have very high stability. In this article we discuss why this is, and we investigate exactly how precise the frequency standards need to be. Four areas where good clock performance is needed are considered: coherence, geodetic parameter estimation, correlator synchronization, and UT1 determination. We show that in order to ensure the highest accuracy of VLBI, stability similar to that of a hydrogen maser is needed for time-scales up to a few hours. In the article, we are considering both traditional VLBI where extra-galactic radio sources are observed, as well as observation of man-made artificial radio sources emitted by satellites or spacecrafts.

PLASMA EFFECTS ON EXTRAGALACTIC ULTRAHIGH-ENERGY COSMIC-RAY HADRON BEAMS IN COSMIC VOIDS. II. KINETIC INSTABILITY OF PARALLEL ELECTROSTATIC WAVES

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

Krakau, S.; Schlickeiser, R., E-mail: steffen.krakau@rub.de, E-mail: rsch@tp4.rub.de

2016-02-20

The linear instability of an ultrarelativistic hadron beam in the unmagnetized intergalactic medium (IGM) is investigated with respect to the excitation of parallel electrostatic and electromagnetic fluctuations. This analysis is important for the propagation of extragalactic ultrarelativistic cosmic rays from their distant sources to Earth. As opposed to the previous paper, we calculate the minimum instability growth time for Lorentz-distributed cosmic rays which traverse the hot IGM. The growth times are orders of magnitude higher than the cosmic-ray propagation time in the IGM. Since the backreaction of the generated plasma fluctuations (plateauing) lasts longer than the propagation time, the cosmic-raymore » hadron beam can propagate to the Earth without losing a significant amount of energy to electrostatic turbulence.« less

A giant planet around a metal-poor star of extragalactic origin.

PubMed

Setiawan, Johny; Klement, Rainer J; Henning, Thomas; Rix, Hans-Walter; Rochau, Boyke; Rodmann, Jens; Schulze-Hartung, Tim

2010-12-17

Stars in their late stage of evolution, such as horizontal branch stars, are still largely unexplored for planets. We detected a planetary companion around HIP 13044, a very metal-poor star on the red horizontal branch, on the basis of radial velocity observations with a high-resolution spectrograph at the 2.2-meter Max-Planck Gesellschaft-European Southern Observatory telescope. The star's periodic radial velocity variation of P = 16.2 days caused by the planet can be distinguished from the periods of the stellar activity indicators. The minimum mass of the planet is 1.25 times the mass of Jupiter and its orbital semimajor axis is 0.116 astronomical units. Because HIP 13044 belongs to a group of stars that have been accreted from a disrupted satellite galaxy of the Milky Way, the planet most likely has an extragalactic origin.

High-frequency predictions for number counts and spectral properties of extragalactic radio sources. New evidence of a break at mm wavelengths in spectra of bright blazar sources

NASA Astrophysics Data System (ADS)

Tucci, M.; Toffolatti, L.; de Zotti, G.; Martínez-González, E.

2011-09-01

We present models to predict high-frequency counts of extragalactic radio sources using physically grounded recipes to describe the complex spectral behaviour of blazars that dominate the mm-wave counts at bright flux densities. We show that simple power-law spectra are ruled out by high-frequency (ν ≥ 100 GHz) data. These data also strongly constrain models featuring the spectral breaks predicted by classical physical models for the synchrotron emission produced in jets of blazars. A model dealing with blazars as a single population is, at best, only marginally consistent with data coming from current surveys at high radio frequencies. Our most successful model assumes different distributions of break frequencies, νM, for BL Lacs and flat-spectrum radio quasars (FSRQs). The former objects have substantially higher values of νM, implying that the synchrotron emission comes from more compact regions; therefore, a substantial increase of the BL Lac fraction at high radio frequencies and at bright flux densities is predicted. Remarkably, our best model is able to give a very good fit to all the observed data on number counts and on distributions of spectral indices of extragalactic radio sources at frequencies above 5 and up to 220 GHz. Predictions for the forthcoming sub-mm blazar counts from Planck, at the highest HFI frequencies, and from Herschel surveys are also presented. Appendices are available in electronic form at http://www.aanda.org

Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources

NASA Technical Reports Server (NTRS)

Aatrokoski, J.; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Amaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.;

Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources

DOE PAGES

Aatrokoski, J.

2011-12-01

Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30 to 857GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativisticmore » jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper, physical modelling of the synchrotron bump using multiple components. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shock. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission.« less

DERIVING METALLICITIES FROM THE INTEGRATED SPECTRA OF EXTRAGALACTIC GLOBULAR CLUSTERS USING THE NEAR-INFRARED CALCIUM TRIPLET

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

Foster, Caroline; Forbes, Duncan A.; Proctor, Robert N.

2010-04-15

The Ca II triplet (CaT) feature in the near-infrared has been employed as a metallicity indicator for individual stars as well as integrated light of Galactic globular clusters (GCs) and galaxies with varying degrees of success, and sometimes puzzling results. Using the DEIMOS multi-object spectrograph on Keck we obtain a sample of 144 integrated light spectra of GCs around the brightest group galaxy NGC 1407 to test whether the CaT index can be used as a metallicity indicator for extragalactic GCs. Different sets of single stellar population models make different predictions for the behavior of the CaT as a functionmore » of metallicity. In this work, the metallicities of the GCs around NGC 1407 are obtained from CaT index values using an empirical conversion. The measured CaT/metallicity distributions show unexpected features, the most remarkable being that the brightest red and blue GCs have similar CaT values despite their large difference in mean color. Suggested explanations for this behavior in the NGC 1407 GC system are (1) the CaT may be affected by a population of hot blue stars, (2) the CaT may saturate earlier than predicted by the models, and/or (3) color may not trace metallicity linearly. Until these possibilities are understood, the use of the CaT as a metallicity indicator for the integrated spectra of extragalactic GCs will remain problematic.« less

Lecture Notes and Essays in Astrophysics.III. 3rd Symposium of the Astrophysics Group of the Spanish Royal Physical Society (RSEF).

NASA Astrophysics Data System (ADS)

Ulla, A.; Manteiga, M.

2008-12-01

The Third volume of "Lecture Notes and Essays in Astrophysics" highlights some important contributions of Spanish astrophysicists to Planetology, Solar and Stellar Physics, Extragalactic Astronomy, Cosmology and astronomical instrumentation. After decades without a dedicated mission, Venus is again in fashion. On the one hand, Ricardo Hueso and collaborators, and on the other Miguel Angel Lopez-Valverde, review ESA Venus Express contribution to the understanding of the atmosphere of the neighbouring planet. Carme Jordi describes in a comprehensive essay the main observational calibration techniques and methods for the determination of mass, radius, temperature, chemical composition and luminosity of a star. Dying stars are fundamental to understand the nature of dark energy, probably the most fundamental problem in Physics today. Type Ia supernovae have played a fundamental role showing the acceleration of the expansion rate of the Universe a decade ago. Inma Dominguez and collaborators go into detail on how the knowledge of the fundamental physics of thermonuclear supernovae explotions condition their role as astrophysical candles.

Galactic and Extragalactic Science with SITELLE

NASA Astrophysics Data System (ADS)

Martin, T. B.; Drissen, L.; Melchior, A.-L.

2017-12-01

We present in this paper some recent results obtained with SITELLE, an imaging Fourier transform spectrometer (iFTS) attached to the Canada-France-Hawaii telescope, in link with which the latest improvements in terms of data analysis.

Extragalactic High-energy Transients: Event Rate Densities and Luminosity Functions

NASA Astrophysics Data System (ADS)

Sun, Hui; Zhang, Bing; Li, Zhuo

2015-10-01

Several types of extragalactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (GRBs), short-duration GRBs, supernova shock breakouts (SBOs), and tidal disruption events (TDEs) without or with an associated relativistic jet. In this paper, we apply a unified method to systematically study the redshift-dependent event rate densities and the global luminosity functions (GLFs; ignoring redshift evolution) of these transients. We introduce some empirical formulae for the redshift-dependent event rate densities for different types of transients and derive the local specific event rate density, which also represents its GLF. Long GRBs (LGRBs) have a large enough sample to reveal features in the GLF, which is best charaterized as a triple power law (PL). All the other transients are consistent with having a single-power-law (SPL) LF. The total event rate density depends on the minimum luminosity, and we obtain the following values in units of Gpc-3 yr-1: {0.8}-0.1+0.1 for high-luminosity LGRBs above 1050 erg s-1 {164}-65+98 for low-luminosity LGRBs above 5 × 1046 erg s-1 {1.3}-0.3+0.4, {1.2}-0.3+0.4, and {3.3}-0.8+1.0 above 1050 erg s-1 for short GRBs with three different merger delay models (Gaussian, lognormal, and PL); {1.9}-1.2+2.4× {10}4 above 1044 erg s-1 for SBOs, {4.8}-2.1+3.2× {10}2 for normal TDEs above 1044 erg s-1 and {0.03}-0.02+0.04 above 1048 erg s-1 for TDE jets as discovered by Swift. Intriguingly, the GLFs of different kinds of transients, which cover over 12 orders of magnitude, are consistent with an SPL with an index of -1.6.

Laboratory Plasma Source as an MHD Model for Astrophysical Jets

NASA Technical Reports Server (NTRS)

Mayo, Robert M.

1997-01-01

The significance of the work described herein lies in the demonstration of Magnetized Coaxial Plasma Gun (MCG) devices like CPS-1 to produce energetic laboratory magneto-flows with embedded magnetic fields that can be used as a simulation tool to study flow interaction dynamic of jet flows, to demonstrate the magnetic acceleration and collimation of flows with primarily toroidal fields, and study cross field transport in turbulent accreting flows. Since plasma produced in MCG devices have magnetic topology and MHD flow regime similarity to stellar and extragalactic jets, we expect that careful investigation of these flows in the laboratory will reveal fundamental physical mechanisms influencing astrophysical flows. Discussion in the next section (sec.2) focuses on recent results describing collimation, leading flow surface interaction layers, and turbulent accretion. The primary objectives for a new three year effort would involve the development and deployment of novel electrostatic, magnetic, and visible plasma diagnostic techniques to measure plasma and flow parameters of the CPS-1 device in the flow chamber downstream of the plasma source to study, (1) mass ejection, morphology, and collimation and stability of energetic outflows, (2) the effects of external magnetization on collimation and stability, (3) the interaction of such flows with background neutral gas, the generation of visible emission in such interaction, and effect of neutral clouds on jet flow dynamics, and (4) the cross magnetic field transport of turbulent accreting flows. The applicability of existing laboratory plasma facilities to the study of stellar and extragalactic plasma should be exploited to elucidate underlying physical mechanisms that cannot be ascertained though astrophysical observation, and provide baseline to a wide variety of proposed models, MHD and otherwise. The work proposed herin represents a continued effort on a novel approach in relating laboratory experiments to astrophysical jet observation. There exists overwhelming similarity among these flows that has already produced some fascinating results and is expected to continue a high pay off in future flow similarity studies.

Unresolved versus resolved: testing the validity of young simple stellar population models with VLT/MUSE observations of NGC 3603

NASA Astrophysics Data System (ADS)

Kuncarayakti, H.; Galbany, L.; Anderson, J. P.; Krühler, T.; Hamuy, M.

2016-09-01

Context. Stellar populations are the building blocks of galaxies, including the Milky Way. The majority, if not all, extragalactic studies are entangled with the use of stellar population models given the unresolved nature of their observation. Extragalactic systems contain multiple stellar populations with complex star formation histories. However, studies of these systems are mainly based upon the principles of simple stellar populations (SSP). Hence, it is critical to examine the validity of SSP models. Aims: This work aims to empirically test the validity of SSP models. This is done by comparing SSP models against observations of spatially resolved young stellar population in the determination of its physical properties, that is, age and metallicity. Methods: Integral field spectroscopy of a young stellar cluster in the Milky Way, NGC 3603, was used to study the properties of the cluster as both a resolved and unresolved stellar population. The unresolved stellar population was analysed using the Hα equivalent width as an age indicator and the ratio of strong emission lines to infer metallicity. In addition, spectral energy distribution (SED) fitting using STARLIGHT was used to infer these properties from the integrated spectrum. Independently, the resolved stellar population was analysed using the colour-magnitude diagram (CMD) to determine age and metallicity. As the SSP model represents the unresolved stellar population, the derived age and metallicity were tested to determine whether they agree with those derived from resolved stars. Results: The age and metallicity estimate of NGC 3603 derived from integrated spectroscopy are confirmed to be within the range of those derived from the CMD of the resolved stellar population, including other estimates found in the literature. The result from this pilot study supports the reliability of SSP models for studying unresolved young stellar populations. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 60.A-9344.

The Hard X-ray 20-40 keV AGN Luminosity Function

NASA Technical Reports Server (NTRS)

Beckmann, V.; Soldi, S.; Shrader, C. R.; Gehrels, N.; Produit, N.

2006-01-01

We have compiled a complete, significance limited extragalactic sample based on approximately 25,000 deg(sup 2) to a limiting flux of 3 x 10(exp -11) ergs per square centimeter per second. (approximately 7,000 deg(sup 2)) to a flux limit of 10(exp -11) ergs per square centimeter per second)) in the 20 - 40 keV band with INTEGRAL. We have constructed a detailed exposure map to compensate for effects of non-uniform exposure. The flux-number relation is best described by a power-law with a slope of alpha = 1.66 plus or minus 0.11. The integration of the cumulative flux per unit area leads to f(sub 20-40 keV) = 2.6 x 10(exp -10) ergs per square centimeter per second per sr(sup -1) which is about 1% of the known 20-40 keV X-ray background. We present the first luminosity function of AGN in the 20-40 keV energy range, based on 68 extragalactic objects detected by the imager IBIS/ISGRI on-board INTEGRAL. The luminosity function shows a smoothly connected two power-law form, with an index of gamma (sub 1) = 0.9 below, and gamma (sub 2) = 2.2 above the turn-over luminosity of L(sub *), = 4.6 x 10(sup 43) ergs per second. The emissivity of all INTEGRAL AGNs per unit volume is W(sub 20-40keV)(greater than 10(sup 41) ergs per second) = 2.8 x 10(sup 38) ergs per second h(sup 3)(sub 70) Mpc(sup -3). These results are consistent with those derived in the 2-20keV energy band and do not show a significant contribution by Compton-thick objects. Because the sample used in this study is truly local (z(raised bar) = 0.022)), only limited conclusions can be drawn for the evolution of AGNs in this energy band. But the objects explaining the peak in the cosmic X-ray background are likely to be either low luminosity AGN (L(sub x) less than 10(sup 41) ergs per second) or of other type, such as intermediate mass black holes, clusters, and star forming regions.

Ice Mapping Observations in Galactic Star-Forming Regions: the AKARI Legacy

NASA Astrophysics Data System (ADS)

Fraser, Helen Jane; Suutarinnen, Aleksi; Noble, Jennifer

2015-08-01

It is becoming increasingly clear that explaining the small-scale distribution of many gas-phase molecules relies on our interpretation of the complex inter-connectivity between gas- and solid-phase interstellar chemistries. Inputs to proto-stellar astrochemical models are required that exploit ice compositions reflecting the historical physical conditions in pre-stellar environments when the ices first formed. Such data are required to translate the near-universe picture of ice-composition to our understanding of the role of extra-galactic ices in star-formation at higher redshifts.Here we present the first attempts at multi-object ice detections, and the subsequent ice column density mapping. The AKARI space telescope was uniquely capable of observing all the ice features between 2 and 5 microns, thereby detecting H2O, CO and CO2 ices concurrently, through their stretching vibrational features. Our group has successfully extracted an unprecedented volume of ice spectra from AKARI, including sources with not more than 2 mJy flux at 3 microns, showing:(a) H2O CO and CO2 ices on 30 lines of sight towards pre-stellar and star-forming cores, which when combined with laboratory experiments indicate how the chemistries of these three ices are interlinked (Noble et al (2013)),(b) ice maps showing the spatial distribution of water ice across 12 pre-stellar cores, in different molecular clouds (Suutarinnen et al (2015)), and the distribution of ice components within these cores on 1000 AU scales (Noble et al (2015)),(c) over 200 new detections of water ice, mostly on lines of sight towards background sources (> 145), indicating that water ice column density has a minimum value as a function of Av, but on a cloud-by-cloud basis typically correlates with Av, and dust emissivity at 250 microns (Suutarinnen et al (2015)),(d) the first detections of HDO ice towards background stars (Fraser et al (2015)).We discuss whether these results support the picture of a generic chemical evolutionary scenario for interstellar ice chemistry, ranging from pre-stellar to extra-galactic scales.

Ages of Extragalactic Intermediate-Age Star Clusters

NASA Technical Reports Server (NTRS)

Flower, P. J.

1983-01-01

A dating technique for faint, distant star clusters observable in the local group of galaxies with the space telescope is discussed. Color-magnitude diagrams of Magellanic Cloud clusters are mentioned along with the metallicity of star clusters.

Gamma-ray astrophysics

NASA Technical Reports Server (NTRS)

Stecker, F. W. (Editor); Trombka, J. I. (Editor)

1973-01-01

Conference papers on gamma ray astrophysics are summarized. Data cover the energy region from about 0.3 MeV to a few hundred GeV and theoretical models of production mechanisms that give rise to both galactic and extragalactic gamma rays.

Spitzer Observations of the North Ecliptic Pole

NASA Astrophysics Data System (ADS)

Nayyeri, H.; Ghotbi, N.; Cooray, A.; Bock, J.; Clements, D. L.; Im, M.; Kim, M. G.; Korngut, P.; Lanz, A.; Lee, H. M.; Lee, D. H.; Malkan, M.; Matsuhara, H.; Matsumoto, T.; Matsuura, S.; Nam, U. W.; Pearson, C.; Serjeant, S.; Smidt, J.; Tsumura, K.; Wada, T.; Zemcov, M.

2018-02-01

We present a photometric catalog for Spitzer Space Telescope warm mission observations of the North Ecliptic Pole (NEP; centered at R.A. = 18h00m00s, decl. = 66d33m38.ˢ552). The observations are conducted with IRAC in the 3.6 and 4.5 μm bands over an area of 7.04 deg2, reaching 1σ depths of 1.29 μJy and 0.79 μJy in the 3.6 μm and 4.5 μm bands, respectively. The photometric catalog contains 380,858 sources with 3.6 and 4.5 μm band photometry over the full-depth NEP mosaic. Point-source completeness simulations show that the catalog is 80% complete down to 19.7 AB. The accompanying catalog can be used for constraining the physical properties of extragalactic objects, studying the AGN population, measuring the infrared colors of stellar objects, and studying the extragalactic infrared background light.

VLA observations of a complete sample of extragalactic X-ray sources. II

NASA Technical Reports Server (NTRS)

Schild, R.; Zamorani, G.; Gioia, I. M.; Feigelson, E. D.; Maccacaro, T.

1983-01-01

A complete sample of 35 X-ray selected sources found with the Einstein Observatory has been observed with the Very Large Array at 6 cm to investigate the relationship between radio and X-ray emission in extragalactic objects. Detections include three active galactic nuclei (AGNs), two clusters or groups of galaxies, two individual galaxies, and two BL Lac objects. The frequency of radio emission in X-ray selected AGNs is compared with that of optically selected quasars using the integral radio-optical luminosity function. The result suggests that the probability for X-ray selected quasars to be radio sources is higher than for those optically selected. No obvious correlation is found in the sample between the richness of X-ray luminosity of the cluster and the presence of a galaxy with radio luminosity at 5 GHz larger than 10 to the 30th ergs/s/Hz.

THE CENTAURUS A ULTRAHIGH-ENERGY COSMIC-RAY EXCESS AND THE LOCAL EXTRAGALACTIC MAGNETIC FIELD

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

Yueksel, Hasan; Kronberg, Philipp P.; Stanev, Todor

2012-10-10

The ultrahigh-energy cosmic-ray (UHECR) anisotropies discovered by the Pierre Auger Observatory provide the potential to finally address both the particle origins and properties of the nearby extragalactic magnetic field (EGMF). We examine the implications of the excess of {approx}10{sup 20} eV events around the nearby radio galaxy Centaurus A. We find that, if Cen A is the source of these cosmic rays, the angular distribution of events constrains the EGMF strength within several Mpc of the Milky Way to {approx}> 20 nG for an assumed primary proton composition. Our conclusions suggest that either the observed excess is a statistical anomalymore » or the local EGMF is stronger than conventionally thought. We discuss several implications, including UHECR scattering from more distant sources, time delays from transient sources, and the possibility of using magnetic lensing signatures to attain tighter constraints.« less

The PMA Catalogue as a realization of the extragalactic reference system in optical and near infrared wavelengths

NASA Astrophysics Data System (ADS)

Akhmetov, Volodymyr S.; Fedorov, Peter N.; Velichko, Anna B.

2018-04-01

We combined the data from the Gaia DR1 and Two-Micron All Sky Survey (2MASS) catalogues in order to derive the absolute proper motions more than 420 million stars distributed all over the sky in the stellar magnitude range 8 mag < G < 21 mag (Gaia magnitude). To eliminate the systematic zonal errors in position of 2MASS catalogue objects, the 2-dimensional median filter was used. The PMA system of proper motion has been obtained by direct link to 1.6 millions extragalactic sources. The short analysis of the absolute proper motion of the PMA stars Catalogue is presented in this work. From a comparison of this data with same stars from the TGAS, UCAC4 and PPMXL catalogues, the equatorial components of the mutual rotation vector of these coordinate systems are determined.

TeV gamma rays from 3C 279 - A possible probe of origin and intergalactic infrared radiation fields

NASA Technical Reports Server (NTRS)

Stecker, F. W.; De Jager, O. C.; Salamon, M. H.

1992-01-01

The gamma-ray spectrum of 3C 279 during 1991 June exhibited a near-perfect power law between 50 MeV and over 5 GeV with a differential spectral index of -(2.02 +/- 0.07). If extrapolated, the gamma-ray spectrum of 3C 279 should be easily detectable with first-generation air Cerenkov detectors operating above about 0.3 TeV provided there is no intergalactic absorption. However, by using model-dependent lower and upper limits for the extragalactic infrared background radiation field, a sharp cutoff of the 3C 279 spectrum is predicted at between about 0.1 and about 1 TeV. The sensitivity of present air Cerenkov detectors is good enough to measure such a cutoff, which would provide the first opportunity to obtain a measurement of the extragalactic background infrared radiation field.

Evolution of the luminosity function of extragalactic objects

NASA Technical Reports Server (NTRS)

Petrosian, V.

1985-01-01

A nonparametric procedure for determination of the evolution of the luminosity function of extragalactic objects and use of this for prediction of expected redshift and luminosity distribution of objects is described. The relation between this statistical evolution of the population and their physical evolution, such as the variation with cosmological epoch of their luminosity and formation rate is presented. This procedure when applied to a sample of optically selected quasars with redshifts less than two shows that the luminosity function evolves more strongly for higher luminosities, indicating a larger quasar activity at earlier epochs and a more rapid evolution of the objects during their higher luminosity phases. It is also shown that absence of many quasars at redshifts greater than three implies slowing down of this evolution in the conventional cosmological models, perhaps indicating that this is near the epoch of the birth of the quasar (and galaxies).

Optical monitoring of QSO in the framework of the Gaia space mission

NASA Astrophysics Data System (ADS)

Taris, F.; Damljanovic, G.; Andrei, A.; Klotz, A.; Vachier, F.

2015-08-01

The Gaia astrometric mission of the European Space Agency has been launched the 19th December 2013. It will provide an astrometric catalogue of 500 000 extragalactic sources that could be the basis of a new optical reference frame. On the other hand, the current International Celestial Reference Frame (ICRF) is based on the observations of extragalactic sources at radio wavelength. The astrometric coordinates of sources in these two reference systems will have roughly the same uncertainty. It is then mandatory to observe a set of common targets at both optical and radio wavelength to link the ICRF with what could be called the GCRF (Gaia Celestial Reference Frame). We will show in this paper some results obtained with the TJO, Telescopi Juan Oro, from Observatori Astronomic del Montsec in Spain. It also presents some results obtained with the Lomb-Scargle and CLEAN algorithm methods applied to optical magnitude obtained with the TAROT telescopes.

Some aspects of cosmic synchrotron sources

NASA Technical Reports Server (NTRS)

Epstein, R. I.

1973-01-01

Synchrotron emission is considered from individual particles which have small pitch angles and the general properties of synchrotron sources which mainly contain such particles, as well as the emissivities and degrees of circular polarization for specific source distributions. The limitation of synchrotron source models for optical pulsars and compact extragalactic objects are discussed, and it is shown that several existing models for the pulsar NP 0532 are inconsistent with the measured time variations and polarizations of the optical emission. Discussion is made also of whether the low frequency falloffs in the extragalactic objects PKS 2134 + 004, OQ 208, and NGC 1068 is due to emission from particles with small pitch angles or absorption by a thermal plasma or synchrotron self-absorption. It is concluded that the absorption interpretations cannot account for the turnover in the spectrum of PKS 2134 + 004. Measurements of polarization, angular structure, and X-ray flux are also described.

CRPropa 2.0 - A public framework for propagating high energy nuclei, secondary gamma rays and neutrinos

NASA Astrophysics Data System (ADS)

Kampert, Karl-Heinz; Kulbartz, Jörg; Maccione, Luca; Nierstenhoefer, Nils; Schiffer, Peter; Sigl, Günter; van Vliet, Arjen René

2013-02-01

Version 2.0 of CRPropa [CRPropa is published under the 3rd version of the GNU General Public License (GPLv3). It is available, together with a detailed documentation of the code, at https://crpropa.desy.de.] is public software to model the extra-galactic propagation of ultra-high energy nuclei of atomic number Z⩽26 through structured magnetic fields and ambient photon backgrounds taking into account all relevant particle interactions. CRPropa covers the energy range 7×1016

Localizing the Position of an Ultraluminous X-ray Flare in an Extragalactic Globular Cluster

NASA Astrophysics Data System (ADS)

Irwin, Jimmy

2017-09-01

X-ray timing analysis has revealed two extragalactic sources that flare well above L_Edd for a stellar-mass BH by factors of >100 on time scales of less than a minute, joining only SGRs/AXPs in this category. One of these flares is coincident with the massive globular cluster/ultracompact dwarf galaxy of the elliptical galaxy NGC5128 known as HGHH-C21, which has a resolvable half-light radius of 0.4". Previous observations of the flare were far off-axis where the Chandra PSF was quite large, precluding an accurate position determination of the flare source within HHGH-C21. We propose an 80 ksec ACIS-S on-axis observation of the flare to determine the flare's position within HHGH-C21 to <0.2" uncertainty to distinguish between intermediate-mass BH and exotic accretion mechanism scenarios.

A Giant Planet Around a Metal-Poor Star of Extragalactic Origin

NASA Astrophysics Data System (ADS)

Setiawan, Johny; Klement, Rainer J.; Henning, Thomas; Rix, Hans-Walter; Rochau, Boyke; Rodmann, Jens; Schulze-Hartung, Tim

2010-12-01

Stars in their late stage of evolution, such as horizontal branch stars, are still largely unexplored for planets. We detected a planetary companion around HIP 13044, a very metal-poor star on the red horizontal branch, on the basis of radial velocity observations with a high-resolution spectrograph at the 2.2-meter Max-Planck Gesellschaft-European Southern Observatory telescope. The star’s periodic radial velocity variation of P = 16.2 days caused by the planet can be distinguished from the periods of the stellar activity indicators. The minimum mass of the planet is 1.25 times the mass of Jupiter and its orbital semimajor axis is 0.116 astronomical units. Because HIP 13044 belongs to a group of stars that have been accreted from a disrupted satellite galaxy of the Milky Way, the planet most likely has an extragalactic origin.

Division Viii: Galaxies and the Universe

NASA Astrophysics Data System (ADS)

Sadler, Elaine M.; Combes, Françoise; Okamura, Sadanori; Davies, Roger L.; Gallagher, John S.; Padmanabhan, Thanu; Schmidt, Brian P.

2012-04-01

The fields of extragalactic research and cosmology have continued to progress rapidly over the past three years, as detailed in the reports of the Commission Presidents, and we are pleased to acknowledge the award of the 2011 Nobel Prize in Physics to Saul Perlmutter, Brian P. Schmidt and Adam G. Riess for ``the discovery of the accelerating expansion of the Universe through observations of distant supernovae''. The Gruber Cosmology Prize was awarded in 2009 to Wendy L. Freedman, Robert C. Kennicutt and Jeremy Mould for their leadership of the Hubble Space Telescope Key Project on the Extragalactic Distance Scale, in 2010 to Charles Steidel for the identification and study of galaxies in the very distant universe, and in 2011 to Marc Davis, George Efstathiou, Carlos Frenk and Simon D.M. White for pioneering the use of numerical simulations as a tool to model and interpret the large-scale distribution of galaxies and dark matter.

Connection Between the ICRF and the Dynamical Reference Frame for the Outer Planets

NASA Astrophysics Data System (ADS)

da Silva Neto, D. N.; Assafin, M.; Andrei, A. H.; Vieira Martins, R.

2005-01-01

This work brings an approach intending to improve the connection between the Dynamical Reference Frame and the Extragalactic Reference Frame. For that, close encounters of outer Solar System objects and quasars are used. With this goal, Uranus, Neptune and two quasars were observed at Laborat´orio Nacional de Astrof´ısica (LNA), Brazil. The optical reference frame is the HCRF, as given by the UCAC2 catalogue. The first results show an accuracy of 45 mas - 50 mas in the optical positions. The optical minus radio offsets give the local orientation between the catalogue and radio frame. From this, it is possible to place the optical planet coordinates on the extragalactic frame. A comparison between the new corrected optical coordinates and the respective DE ephemeris to these planets can give the instant orientations of the Dynamical Reference Frame with regard to the ICRS, for this zone of outer Solar System.

Extragalactic Hard X-ray Surveys: From INTEGRAL to Simbol-X

NASA Astrophysics Data System (ADS)

Paltani, S.; Dwelly, T.; Walter, R.; McHardy, I. M.; Courvoisier, T. J.-L.

2009-05-01

We present some results of the deepest extragalactic survey performed by the INTEGRAL satellite. The fraction of very absorbed AGN is quite large. The sharp decrease in the absorption fraction with X-ray luminosity observed at lower-energy X-rays is not observed. The current lack of truly Compton-thick objects, with an upper limit of 14% to the size of this population, is just compatible with recent modeling of the cosmic X-ray background. We also study the prospects for a future hard X-ray serendipitous survey with Simbol-X. We show that Simbol-X will easily detect a large number of serendipitous AGN, allowing us to study the evolution of AGN up to redshifts about 2, opening the door to the cosmological study of hard X-ray selected AGN, which is barely possible with existing satellites like Swift and INTEGRAL.

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

Components of the Extragalactic Gamma-Ray Background

NASA Technical Reports Server (NTRS)

Stecker, Floyd W.; Venters, Tonia M.

2011-01-01

We present new theoretical estimates of the relative contributions of unresolved blazars and star-forming galaxies to the extragalactic gamma-ray background (EGB) and discuss constraints on the contributions from alternative mechanisms such as dark matter annihilation and truly diffuse gamma-ray production. We find that the Fermi source count data do not rule out a scenario in which the EGB is dominated by emission from unresolved blazars, though unresolved star-forming galaxies may also contribute significantly to the background, within order-of-magnitude uncertainties. In addition, we find that the spectrum of the unresolved star-forming galaxy contribution cannot explain the EGB spectrum found by EGRET at energies between 50 and 200 MeV, whereas the spectrum of unresolved flat spectrum radio quasars, when accounting for the energy-dependent effects of source confusion, could be consistent with the combined spectrum of the low-energy EGRET EGB measurements and the Fermi-Large Area Telescope EGB measurements.

UV, optical and infrared properties of star forming galaxies

NASA Technical Reports Server (NTRS)

Huchra, John P.

1987-01-01

The UVOIR properties of galaxies with extreme star formation rates are examined. These objects seem to fall into three distinct classes which can be called (1) extragalactic H II regions, (2) clumpy irregulars, and (3) starburst galaxies. Extragalactic H II regions are dominated by recently formed stars and may be considered 'young' galaxies if the definition of young is having the majority of total integrated star formation occurring in the last billion years. Clumpy irregulars are bursts of star formation superposed on an old population and are probably good examples of stochastic star formation. It is possible that star formation in these galaxies is triggered by the infall of gas clouds or dwarf companions. Starburst galaxies are much more luminous, dustier and more metal rich than the other classes. These objects show evidence for shock induced star formation where shocks may be caused by interaction with massive companions or are the result of an extremely strong density wave.

The SUrvey for Pulsars and Extragalactic Radio Bursts - I. Survey description and overview

NASA Astrophysics Data System (ADS)

Keane, E. F.; Barr, E. D.; Jameson, A.; Morello, V.; Caleb, M.; Bhandari, S.; Petroff, E.; Possenti, A.; Burgay, M.; Tiburzi, C.; Bailes, M.; Bhat, N. D. R.; Burke-Spolaor, S.; Eatough, R. P.; Flynn, C.; Jankowski, F.; Johnston, S.; Kramer, M.; Levin, L.; Ng, C.; van Straten, W.; Krishnan, V. Venkatraman

2018-01-01

We describe the Survey for Pulsars and Extragalactic Radio Bursts (SUPERB), an ongoing pulsar and fast transient survey using the Parkes radio telescope. SUPERB involves real-time acceleration searches for pulsars and single-pulse searches for pulsars and fast radio bursts. We report on the observational set-up, data analysis, multiwavelength/messenger connections, survey sensitivities to pulsars and fast radio bursts and the impact of radio frequency interference. We further report on the first 10 pulsars discovered in the project. Among these is PSR J1306-40, a millisecond pulsar in a binary system where it appears to be eclipsed for a large fraction of the orbit. PSR J1421-4407 is another binary millisecond pulsar; its orbital period is 30.7 d. This orbital period is in a range where only highly eccentric binaries are known, and expected by theory; despite this its orbit has an eccentricity of 10-5.

Global Infrared–Radio Spectral Energy Distributions of Galactic Massive Star-Forming Regions

NASA Astrophysics Data System (ADS)

Povich, Matthew Samuel; Binder, Breanna Arlene

2018-01-01

We present a multiwavelength study of 30 Galactic massive star-forming regions. We fit multicomponent dust, blackbody, and power-law continuum models to 3.6 µm through 10 mm spectral energy distributions obtained from Spitzer, MSX, IRAS, Herschel, and Planck archival survey data. Averaged across our sample, ~20% of Lyman continuum photons emitted by massive stars are absorbed by dust before contributing to the ionization of H II regions, while ~50% of the stellar bolometric luminosity is absorbed and reprocessed by dust in the H II regions and surrounding photodissociation regions. The most luminous, infrared-bright regions that fully sample the upper stellar initial mass function (ionizing photon rates NC ≥ 1050 s–1 and total infrared luminosity LTIR ≥ 106.8 L⊙) have higher percentages of absorbed Lyman continuum photons (~40%) and dust-reprocessed starlight (~80%). The monochromatic 70-µm luminosity L70 is linearly correlated with LTIR, and on average L70/LTIR = 50%, in good agreement with extragalactic studies. Calibrated against the known massive stellar content in our sampled H II regions, we find that star formation rates based on L70 are in reasonably good agreement with extragalactic calibrations, when corrected for the smaller physical sizes of the Galactic regions. We caution that absorption of Lyman continuum photons prior to contributing to the observed ionizing photon rate may reduce the attenuation-corrected Hα emission, systematically biasing extragalactic calibrations toward lower star formation rates when applied to spatially-resolved studies of obscured star formation.This work was supported by the National Science Foundation under award CAREER-1454333.

Origins Space Telescope: 3D infrared surveys of star formation and black hole growth in galaxies over cosmic time

NASA Astrophysics Data System (ADS)

Pope, Alexandra; Armus, Lee; bradford, charles; Origins Space Telescope STDT

2018-01-01

In the coming decade, new telescope facilities and surveys aim to provide a 3D map of the unobscured Universe over cosmic time. However, much of galaxy formation and evolution occurs behind dust, and is only observable through infrared observations. Previous extragalactic infrared surveys were fundamentally limited to a 2D mapping of the most extreme populations of galaxies due to spatial resolution and sensitivity. The Origins Space Telescope (OST) is the mission concept for the Far-Infrared Surveyor, one of the four science and technology definition studies sponsored by NASA to provide input to the 2020 Astronomy and Astrophysics Decadal survey. OST is planned to be a large aperture, actively-cooled telescope covering a wide span of the mid- to far-infrared spectrum, which will achieve spectral line sensitivities up to 1000 times deeper than previous infrared facilities. With powerful instruments such as the Medium Resolution Survey Spectrometer (MRSS), capable of simultaneous imaging and spectroscopy, the extragalactic infrared sky can finally be surveyed in 3D. In addition to spectroscopic redshifts, the rich suite of lines in the infrared provides unique diagnostics of the ongoing star formation (both obscured and unobscured) and the central supermassive black hole growth. In this poster, we present a simulated extragalactic survey with OST/MRSS which will detect millions of galaxies down to well below the knee of the infrared luminosity function. We demonstrate how this survey can map the coeval star formation and black hole growth in galaxies over cosmic time.

A Large-Scale Super-Structure at z=0.65 in the UKIDSS Ultra-Deep Survey Field

NASA Astrophysics Data System (ADS)

Galametz, Audrey; Candels Clustering Working Group

2017-07-01

In hierarchical structure formation scenarios, galaxies accrete along high density filaments. Superclusters represent the largest density enhancements in the cosmic web with scales of 100 to 200 Mpc. As they represent the largest components of LSS, they are very powerful tools to constrain cosmological models. Since they also offer a wide range of density, from infalling group to high density cluster core, they are also the perfect laboratory to study the influence of environment on galaxy evolution. I will present a newly discovered large scale structure at z=0.65 in the UKIDSS UDS field. Although statistically predicted, the presence of such structure in UKIDSS, one of the most extensively covered and studied extragalactic field, remains a serendipity. Our follow-up confirmed more than 15 group members including at least three galaxy clusters with M200 10^14Msol . Deep spectroscopy of the quiescent core galaxies reveals that the most massive structure knots are at very different formation stage with a range of red sequence properties. Statistics allow us to map formation age across the structure denser knots and identify where quenching is most probably occurring across the LSS. Spectral diagnostics analysis also reveals an interesting population of transition galaxies we suspect are transforming from star-forming to quiescent galaxies.

The XMM-SERVS survey: new XMM-Newton point-source catalog for the XMM-LSS field

NASA Astrophysics Data System (ADS)

Chen, C.-T. J.; Brandt, W. N.; Luo, B.; Ranalli, P.; Yang, G.; Alexander, D. M.; Bauer, F. E.; Kelson, D. D.; Lacy, M.; Nyland, K.; Tozzi, P.; Vito, F.; Cirasuolo, M.; Gilli, R.; Jarvis, M. J.; Lehmer, B. D.; Paolillo, M.; Schneider, D. P.; Shemmer, O.; Smail, I.; Sun, M.; Tanaka, M.; Vaccari, M.; Vignali, C.; Xue, Y. Q.; Banerji, M.; Chow, K. E.; Häußler, B.; Norris, R. P.; Silverman, J. D.; Trump, J. R.

2018-04-01

We present an X-ray point-source catalog from the XMM-Large Scale Structure survey region (XMM-LSS), one of the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) fields. We target the XMM-LSS region with 1.3 Ms of new XMM-Newton AO-15 observations, transforming the archival X-ray coverage in this region into a 5.3 deg2 contiguous field with uniform X-ray coverage totaling 2.7 Ms of flare-filtered exposure, with a 46 ks median PN exposure time. We provide an X-ray catalog of 5242 sources detected in the soft (0.5-2 keV), hard (2-10 keV), and/or full (0.5-10 keV) bands with a 1% expected spurious fraction determined from simulations. A total of 2381 new X-ray sources are detected compared to previous source catalogs in the same area. Our survey has flux limits of 1.7 × 10-15, 1.3 × 10-14, and 6.5 × 10-15 erg cm-2 s-1 over 90% of its area in the soft, hard, and full bands, respectively, which is comparable to those of the XMM-COSMOS survey. We identify multiwavelength counterpart candidates for 99.9% of the X-ray sources, of which 93% are considered as reliable based on their matching likelihood ratios. The reliabilities of these high-likelihood-ratio counterparts are further confirmed to be ≈97% reliable based on deep Chandra coverage over ≈5% of the XMM-LSS region. Results of multiwavelength identifications are also included in the source catalog, along with basic optical-to-infrared photometry and spectroscopic redshifts from publicly available surveys. We compute photometric redshifts for X-ray sources in 4.5 deg2 of our field where forced-aperture multi-band photometry is available; >70% of the X-ray sources in this subfield have either spectroscopic or high-quality photometric redshifts.

Probing cosmic strings with satellite CMB measurements

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

Jeong, E.; Baccigalupi, Carlo; Smoot, G.F., E-mail: ehjeong@sissa.it, E-mail: bacci@sissa.it, E-mail: gfsmoot@lbl.gov

2010-09-01

We study the problem of searching for cosmic string signal patterns in the present high resolution and high sensitivity observations of the Cosmic Microwave Background (CMB). This article discusses a technique capable of recognizing Kaiser-Stebbins effect signatures in total intensity anisotropy maps from isolated strings. We derive the statistical distributions of null detections from purely Gaussian fluctuations and instrumental performances of the operating satellites, and show that the biggest factor that produces confusion is represented by the acoustic oscillation features of the scale comparable to the size of horizon at recombination. Simulations show that the distribution of null detections convergesmore » to a χ{sup 2} distribution, with detectability threshold at 99% confidence level corresponding to a string induced step signal with an amplitude of about 100 μK which corresponds to a limit of roughly Gμ ∼ 1.5 × 10{sup −6}. We implement simulations for deriving the statistics of spurious detections caused by extra-Galactic and Galactic foregrounds. For diffuse Galactic foregrounds, which represents the dominant source of contamination, we construct sky masks outlining the available region of the sky where the Galactic confusion is sub-dominant, specializing our analysis to the case represented by the frequency coverage and nominal sensitivity and resolution of the Planck experiment. As for other CMB measurements, the maximum available area, corresponding to 7%, is reached where the foreground emission is expected to be minimum, in the 70–100 GHz interval.« less

Conference Summary

NASA Astrophysics Data System (ADS)

Sanders, David B.

2014-07-01

This conference on ``Multi-wavelength AGN Surveys and Studies'' has provided a detailed look at the explosive growth over the past decade, of available astronomical data from a growing list of large scale sky surveys, from radio-to-gamma rays. We are entering an era were multi-epoch (months to weeks) surveys of the entire sky, and near-instantaneous follow-up observations of variable sources, are elevating time-domain astronomy to where it is becoming a major contributor to our understanding of Active Galactic Nuclei (AGN). While we can marvel at the range of extragalactic phenomena dispayed by sources discovered in the original ``Markarian Survey'' - the first large-scale objective prism survey of the Northern Sky carried out at the Byurakan Astronomical Observtory almost a half-century ago - it is clear from the talks and posters presented at this meeting that the data to be be obtained over the next decade will be needed if we are to finally understand which phase of galaxy evolution each Markarian Galaxy represents.

Error Modeling of Multibaseline Optical Truss: Part 1: Modeling of System Level Performance

NASA Technical Reports Server (NTRS)

Milman, Mark H.; Korechoff, R. E.; Zhang, L. D.

2004-01-01

Global astrometry is the measurement of stellar positions and motions. These are typically characterized by five parameters, including two position parameters, two proper motion parameters, and parallax. The Space Interferometry Mission (SIM) will derive these parameters for a grid of approximately 1300 stars covering the celestial sphere to an accuracy of approximately 4uas, representing a two orders of magnitude improvement over the most precise current star catalogues. Narrow angle astrometry will be performed to a 1uas accuracy. A wealth of scientific information will be obtained from these accurate measurements encompassing many aspects of both galactic (and extragalactic science. SIM will be subject to a number of instrument errors that can potentially degrade performance. Many of these errors are systematic in that they are relatively static and repeatable with respect to the time frame and direction of the observation. This paper and its companion define the modeling of the, contributing factors to these errors and the analysis of how they impact SIM's ability to perform astrometric science.

The impact of clustering and angular resolution on far-infrared and millimeter continuum observations

NASA Astrophysics Data System (ADS)

Béthermin, Matthieu; Wu, Hao-Yi; Lagache, Guilaine; Davidzon, Iary; Ponthieu, Nicolas; Cousin, Morgane; Wang, Lingyu; Doré, Olivier; Daddi, Emanuele; Lapi, Andrea

2017-11-01

Follow-up observations at high-angular resolution of bright submillimeter galaxies selected from deep extragalactic surveys have shown that the single-dish sources are comprised of a blend of several galaxies. Consequently, number counts derived from low- and high-angular-resolution observations are in tension. This demonstrates the importance of resolution effects at these wavelengths and the need for realistic simulations to explore them. We built a new 2 deg2 simulation of the extragalactic sky from the far-infrared to the submillimeter. It is based on an updated version of the 2SFM (two star-formation modes) galaxy evolution model. Using global galaxy properties generated by this model, we used an abundance-matching technique to populate a dark-matter lightcone and thus simulate the clustering. We produced maps from this simulation and extracted the sources, and we show that the limited angular resolution of single-dish instruments has a strong impact on (sub)millimeter continuum observations. Taking into account these resolution effects, we are reproducing a large set of observables, as number counts and their evolution with redshift and cosmic infrared background power spectra. Our simulation consistently describes the number counts from single-dish telescopes and interferometers. In particular, at 350 and 500 μm, we find that the number counts measured by Herschel between 5 and 50 mJy are biased towards high values by a factor 2, and that the redshift distributions are biased towards low redshifts. We also show that the clustering has an important impact on the Herschel pixel histogram used to derive number counts from P(D) analysis. We find that the brightest galaxy in the beam of a 500 μm Herschel source contributes on average to only 60% of the Herschel flux density, but that this number will rise to 95% for future millimeter surveys on 30 m-class telescopes (e.g., NIKA2 at IRAM). Finally, we show that the large number density of red Herschel sources found in observations but not in models might be an observational artifact caused by the combination of noise, resolution effects, and the steepness of color- and flux density distributions. Our simulation, called Simulated Infrared Dusty Extragalactic Sky (SIDES), is publicly available. Our simulation Simulated Infrared Dusty Extragalactic Sky (SIDES) is available at http://cesam.lam.fr/sides.

The anatomy of the Orion B giant molecular cloud: A local template for studies of nearby galaxies

NASA Astrophysics Data System (ADS)

Pety, Jérôme; Guzmán, Viviana V.; Orkisz, Jan H.; Liszt, Harvey S.; Gerin, Maryvonne; Bron, Emeric; Bardeau, Sébastien; Goicoechea, Javier R.; Gratier, Pierre; Le Petit, Franck; Levrier, François; Öberg, Karin I.; Roueff, Evelyne; Sievers, Albrecht

2017-01-01

Context. Molecular lines and line ratios are commonly used to infer properties of extra-galactic star forming regions. The new generation of millimeter receivers almost turns every observation into a line survey. Full exploitation of this technical advancement in extra-galactic study requires detailed bench-marking of available line diagnostics. Aims: We aim to develop the Orion B giant molecular cloud (GMC) as a local template for interpreting extra-galactic molecular line observations. Methods: We use the wide-band receiver at the IRAM-30 m to spatially and spectrally resolve the Orion B GMC. The observations cover almost 1 square degree at 26'' resolution with a bandwidth of 32 GHz from 84 to 116 GHz in only two tunings. Among the mapped spectral lines are the , , C18O, C17O, HCN, HNC, , C2H, HCO+, N2H+(1-0), and , , SiO, c - C3H2, CH3OH (2-1) transitions. Results: We introduce the molecular anatomy of the Orion B GMC, including relationships between line intensities and gas column density or far-UV radiation fields, and correlations between selected line and line ratios. We also obtain a dust-traced gas mass that is less than approximately one third the CO-traced mass, using the standard XCO conversion factor. The presence of over-luminous CO can be traced back to the dependence of the CO intensity on UV illumination. As a matter of fact, while most lines show some dependence on the UV radiation field, CN and C2H are the most sensitive. Moreover, dense cloud cores are almost exclusively traced by N2H+. Other traditional high-density tracers, such as HCN(1-0), are also easily detected in extended translucent regions at a typical density of 500 H2 cm-3. In general, we find no straightforward relationship between line critical density and the fraction of the line luminosity coming from dense gas regions. Conclusions: Our initial findings demonstrate that the relationships between line (ratio) intensities and environment in GMCs are more complicated than often assumed. Sensitivity (I.e., the molecular column density), excitation, and, above all, chemistry contribute to the observed line intensity distributions, and they must be considered together when developing the next generation of extra-galactic molecular line diagnostics of mass, density, temperature, and radiation field.

The Astronomical Low Frequency Array: A Proposed Explorer Mission for Radio Astronomy

NASA Technical Reports Server (NTRS)

Jones, D.; Allen, R.; Basart, J.; Bastian, T.; Bougeret, J. L.; Dennison, B.; Desch, M.; Dwarakanath, K.; Erickson, W.; Finley, D.;

A-4 scientific results

NASA Technical Reports Server (NTRS)

Matteson, J.

1979-01-01

Observations of galactic sources, extragalactic sources and gamma bursts with the A-4 instrument at energy 1 energies of between 0.1 to 10 MeV are discussed. Aximuthal scans are presented. The Crab Nebula and its spectrum and the spectrum of Cygnus Z-1 are described.

Outlook for ultraviolet astronomy

NASA Technical Reports Server (NTRS)

Boehm-Vitense, E.

1981-01-01

A brief overview of galactic and extragalactic research is given with emphasis on the problems of temperature determination, chemical abundance determination, and the question about the energy sources for the high temperature regions. Stellar astronomy, stellar winds, and the interstellar medium are among the topics covered.

Submillimetric study of nearby galaxies: A tool for new extragalactic molecules

NASA Astrophysics Data System (ADS)

Villicana Pedraza, Ilhuiyolitzin; Guesten, Rolf; Armijos Abendaño, Jairo; Carreto, Francisco; Martin, Sergio; Martin-Pintado, Jesus; Requena-Torres, Miguel; Perez-Beaupuits, Juan Pablo

2016-07-01

We present the first submillimetre line survey of extragalactic sources carried out by APEX, the results were presented inside of Villicana-Pedraza phd thesis in 2015. The surveys cover the 0.8 mm atmospheric window toward NGC253, NGC4945 and Arp220. We found HCN, C2H, CN, CS, C34S, HCO+, HNC, CO, N2H+, CH3OH are presents in all the sources, while 13CO,C18O and C17O, HNCO, H2CO, H2CS, SO, NO, SO2 were detected toward NGC253 and NGC4945, 13CN, *CO+, OCS, H2S in Arp220, 13CS, NH2CN, SiO in NGC253, and c-C3H2 in NGC4945 were detected. Column densities and rotation temperatures have been determinate using the Local Thermodinamical Equilibrium(LTE) line profile simulation and fitting in the MADCUBA IJ software. The differences found in the 32S/34S and 18O/17O ratios between the GC and the starburst galaxies NGC 4945 and NGC 253 suggest that the gas is less processed in the latter than in the GC. The high 18O/17O ratios in the galaxies NGC 4945 and NGC 253 suggest also material less processed in the nuclei of these galaxies than in the GC. This is consistent with the claim that 17O is a more representative primary product than 18O in stellar nucleosynthesis (Wilson and Rood 1994); Also, we did a Multitransitions study of H3O+ at 307GHz, 364GHz, 388GHz and 396GHz. From our non-LTE analysis of H3O+ in NGC253 with RADEX we found that the collisional excitation cannot explain the observed intensity of the ortho 396 GHz line. Excitation by radiation from the dust in the Far-IR can roughly explain the observations if the H2 densities are relatively low. From the derived H3O+ column densities we conclude that the chemistry of this molecule is dominated by ionization produce by the starburst in NGC253 (UV radiation from the O stars) and Arp 220 (cosmic rays from the supernovae) and likely from the AGN in NGC4549 (X-rays ); We report, for the first time, the tentative detection of the molecular ion HCNH+ (precursor of HCN and HNC) toward a galaxy, NGC4945, the abundance is much larger than the Galactic center in the Milky Way, abundance explain the claimed enhancement of HCN abundance in the AGN, due to the enhancement of the ionization rate by X-rays. The survey help us to find a lot of molecules including the tentative detection of *CH2NH, CH3C2H, HCNH+ in NGC253 and NGC4945 by first time in the extragalactic medium.

Three-Dimensional Medical Image Analysis Using Local Dynamic Algorithm Selection on a Multiple-Instruction, Multiple-Data Architecture

DTIC Science & Technology

1989-01-01

is represented by a number, called a Hounsfield Unit (HU), which represents the attenuation within the volume relative to the attenuation of the same...volume of water. Hounsfield Unit values range from -1000 to +3000, with a value of zero assigned to the attenuation of water. A HU value of -1000...represented by a 3D array. Each array element represents a single voxel, and the value of the array entry is the corresponding scaled Hounsfield Unit value

CREPT-MCNP code for efficiency calibration of HPGe detectors with the representative point method.

PubMed

Saegusa, Jun

2008-01-01

The representative point method for the efficiency calibration of volume samples has been previously proposed. For smoothly implementing the method, a calculation code named CREPT-MCNP has been developed. The code estimates the position of a representative point which is intrinsic to each shape of volume sample. The self-absorption correction factors are also given to make correction on the efficiencies measured at the representative point with a standard point source. Features of the CREPT-MCNP code are presented.

An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Albuquerque, I. F. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arsene, N.; Asorey, H.; Assis, P.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barbato, F.; Barreira Luz, R. J.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caruso, R.; Castellina, A.; Catalani, F.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Cobos Cerutti, A. C.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Consolati, G.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D’Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D’Olivo, J. C.; Dorosti, Q.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farmer, J.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fenu, F.; Fick, B.; Figueira, J. M.; Filipčič, A.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaïor, R.; García, B.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi, A.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Halliday, R.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Johnsen, J. A.; Josebachuili, M.; Jurysek, J.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Keilhauer, B.; Kemmerich, N.; Kemp, E.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; Lago, B. L.; LaHurd, D.; Lang, R. G.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lo Presti, D.; Lopes, L.; López, R.; López Casado, A.; Lorek, R.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Merenda, K.-D.; Michal, S.; Micheletti, M. I.; Middendorf, L.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Morlino, G.; Mostafá, M.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Núñez, L. A.; Oikonomou, F.; Olinto, A.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A. S.; Perlin, M.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Pierog, T.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Poh, J.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.; Ravignani, D.; Ridky, J.; Riehn, F.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Schauer, M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schröder, S.; Schulz, A.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Soriano, J. F.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Stassi, P.; Stolpovskiy, M.; Strafella, F.; Streich, A.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Šupík, J.; Swain, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Torralba Elipe, G.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Vázquez, R. A.; Veberič, D.; Ventura, C.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiedeński, M.; Wiencke, L.; Wilczyński, H.; Wirtz, M.; Wittkowski, D.; Wundheiler, B.; Yang, L.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.; The Pierre Auger Collaboration

2018-02-01

A new analysis of the data set from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 {EeV} with zenith angles up to 80° recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include all types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects, and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0σ, the highest value of the test statistic being for energies above 39 {EeV}. The three alternative models are favored against isotropy with 2.7σ–3.2σ significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed. Any correspondence should be addressed to .

Extragalactic background light measurements and applications.

PubMed

Cooray, Asantha

2016-03-01

This review covers the measurements related to the extragalactic background light intensity from γ-rays to radio in the electromagnetic spectrum over 20 decades in wavelength. The cosmic microwave background (CMB) remains the best measured spectrum with an accuracy better than 1%. The measurements related to the cosmic optical background (COB), centred at 1 μm, are impacted by the large zodiacal light associated with interplanetary dust in the inner Solar System. The best measurements of COB come from an indirect technique involving γ-ray spectra of bright blazars with an absorption feature resulting from pair-production off of COB photons. The cosmic infrared background (CIB) peaking at around 100 μm established an energetically important background with an intensity comparable to the optical background. This discovery paved the way for large aperture far-infrared and sub-millimetre observations resulting in the discovery of dusty, starbursting galaxies. Their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. The extreme UV (EUV) background remains mostly unexplored and will be a challenge to measure due to the high Galactic background and absorption of extragalactic photons by the intergalactic medium at these EUV/soft X-ray energies. We also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. We motivate a precise direct measurement of the COB between 0.1 and 5 μm using a small aperture telescope observing either from the outer Solar System, at distances of 5 AU or more, or out of the ecliptic plane. Other future applications include improving our understanding of the background at TeV energies and spectral distortions of CMB and CIB.

The Extragalactic Background Light and the Gamma-ray Opacity of the Universe

NASA Technical Reports Server (NTRS)

Dwek, Eli; Krennrich, Frank

2012-01-01

The extragalactic background light (EBL) is one of the fundamental observational quantities in cosmology. All energy releases from resolved and unresolved extragalactic sources, and the light from any truly diffuse background, excluding the cosmic microwave background (CMB), contribute to its intensity and spectral energy distribution. It therefore plays a crucial role in cosmological tests for the formation and evolution of stellar objects and galaxies, and for setting limits on exotic energy releases in the universe. The EBL also plays an important role in the propagation of very high energy gamma-rays which are attenuated en route to Earth by pair producing gamma-gamma interactions with the EBL and CMB. The EBL affects the spectrum of the sources, predominantly blazars, in the approx 10 GeV to 10 TeV energy regime. Knowledge of the EBL intensity and spectrum will allow the determination of the intrinsic blazar spectrum in a crucial energy regime that can be used to test particle acceleration mechanisms and VHE gamma-ray production models. Conversely, knowledge of the intrinsic gamma-ray spectrum and the detection of blazars at increasingly higher redshifts will set strong limits on the EBL and its evolution. This paper reviews the latest developments in the determination of the EBL and its impact on the current understanding of the origin and production mechanisms of gamma-rays in blazars, and on energy releases in the universe. The review concludes with a summary and future directions in Cherenkov Telescope Array techniques and in infrared ground-based and space observatories that will greatly improve our knowledge of the EBL and the origin and production of very high energy gamma-rays.

A correlation between hard gamma-ray sources and cosmic voids along the line of sight

DOE PAGES

Furniss, A.; Sutter, P. M.; Primack, J. R.; ...

2014-11-25

We estimate the galaxy density along lines of sight to hard extragalactic gamma-ray sources by correlating source positions on the sky with a void catalog based on the Sloan Digital Sky Survey (SDSS). Extragalactic gamma-ray sources that are detected at very high energy (VHE; E > 100 GeV) or have been highlighted as VHE-emitting candidates in the Fermi Large Area Telescope hard source catalog (together referred to as “VHE-like” sources) are distributed along underdense lines of sight at the 2.4σ level. There is a less suggestive correlation for the Fermi hard source population (1.7σ). A correlation between 10-500 GeV fluxmore » and underdense fraction along the line of sight for VHE-like and Fermi hard sources is found at 2.4σ and 2.6σ, calculated from the Pearson correlation coefficients of r = 0.57 and 0.47, respectively. The preference for underdense sight lines is not displayed by gamma-ray emitting galaxies within the second Fermi catalog, containing sources detected above 100 MeV, or the SDSS DR7 quasar catalog. We investigate whether this marginal correlation might be a result of lower extragalactic background light (EBL) photon density within the underdense regions and find that, even in the most extreme case of a entirely underdense sight line, the EBL photon density is only 2% less than the nominal EBL density. Translating this into gamma-ray attenuation along the line of sight for a highly attenuated source with opacity τ(E, z) ~ 5, we estimate that the attentuation of gamma-rays decreases no more than 10%. This decrease, although non-neglible, is unable to account for the apparent hard source correlation with underdense lines of sight.« less

An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

DOE PAGES

Aab, A.; Abreu, P.; Aglietta, M.; ...

2018-02-02

A new analysis of the dataset from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 EeV with zenith angles up to 80 deg recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include allmore » types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0 sigma, the highest value of the test statistic being for energies above 39 EeV. The three alternative models are favored against isotropy with 2.7-3.2 sigma significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed.« less

An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources

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

Aab, A.; Abreu, P.; Aglietta, M.

A new analysis of the dataset from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 EeV with zenith angles up to 80 deg recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include allmore » types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0 sigma, the highest value of the test statistic being for energies above 39 EeV. The three alternative models are favored against isotropy with 2.7-3.2 sigma significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed.« less

CANDELS: The Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey

NASA Technical Reports Server (NTRS)

Grogin, Norman A.; Koekemoer, anton M.; Faber, S. M.; Ferguson, Henry C.; Kocevski, Dale D.; Riess, Adam G.; Acquaviva, Viviana; Alexander, David M.; Almaini, Omar; Ashby, Matthew L. N.;

The Hubble Space Telescope Extragalactic Distance Scale Key Project. 1: The discovery of Cepheids and a new distance to M81

NASA Technical Reports Server (NTRS)

Freedman, Wendy L.; Hughes, Shaun M.; Madore, Barry F.; Mould, Jeremy R.; Lee, Myung Gyoon; Stetson, Peter; Kennicutt, Robert C.; Turner, Anne; Ferrarese, Laura; Ford, Holland

1994-01-01

We report on the discovery of 30 new Cepheids in the nearby galaxy M81 based on observations using the Hubble Space Telescope (HST). The periods of these Cepheids lie in the range of 10-55 days, based on 18 independent epochs using the HST wide-band F555W filter. The HST F555W and F785LP data have been transformed to the Cousins standard V and I magnitude system using a ground-based calibration. Apparent period-luminosity relations at V and I were constructed, from which apparent distance moduli were measured with respect to assumed values of mu(sub 0) = 18.50 mag and E(B - V) = 0.10 mag for the Large Magellanic Cloud. The difference in the apparent V and I moduli yields a measure of the difference in the total mean extinction between the M81 and the LMC Cepheid samples. A low total mean extinction to the M81 sample of E(B - V) = 0.03 +/- 0.05 mag is obtained. The true distance modulus to M81 is determined to be 27.80 +/- 0.20 mag, corresponding to a distance of 3.63 +/- 0.34 Mpc. These data illustrate that with an optimal (power-law) sampling strategy, the HST provides a powerful tool for the discovery of extragalactic Cepheids and their application to the distance scale. M81 is the first calibrating galaxy in the target sample of the HST Key Project on the Extragalactic Distance Scale, the ultimate aim of which is to provide a value of the Hubble constant to 10% accuracy.

Statistics of the fractional polarization of extragalactic dusty sources in Planck HFI maps

NASA Astrophysics Data System (ADS)

Bonavera, L.; González-Nuevo, J.; De Marco, B.; Argüeso, F.; Toffolatti, L.

2017-11-01

We estimate the average fractional polarization at 143, 217 and 353 GHz of a sample of 4697 extragalactic dusty sources by applying stacking technique. The sample is selected from the second version of the Planck Catalogue of Compact Sources at 857 GHz, avoiding the region inside the Planck Galactic mask (fsky ∼ 60 per cent). We recover values for the mean fractional polarization at 217 and 353 GHz of (3.10 ± 0.75) per cent and (3.65 ± 0.66) per cent, respectively, whereas at 143 GHz we give a tentative value of (3.52 ± 2.48) per cent. We discuss the possible origin of the measured polarization, comparing our new estimates with those previously obtained from a sample of radio sources. We test different distribution functions and we conclude that the fractional polarization of dusty sources is well described by a log-normal distribution, as determined in the radio band studies. For this distribution we estimate μ217GHz = 0.3 ± 0.5 [that would correspond to a median fractional polarization of Πmed = (1.3 ± 0.7) per cent] and μ353GHz = 0.7 ± 0.4 (Πmed = (2.0 ± 0.8) per cent), σ217GHz = 1.3 ± 0.2 and σ353GHz = 1.1 ± 0.2. With these values we estimate the source number counts in polarization and the contribution given by these sources to the Cosmic Microwave Background B-mode angular power spectrum at 217, 353, 600 and 800 GHz. We conclude that extragalactic dusty sources might be an important contaminant for the primordial B-mode at frequencies >217 GHz.

Extragalactic background light measurements and applications

PubMed Central

Cooray, Asantha

2016-01-01

This review covers the measurements related to the extragalactic background light intensity from γ-rays to radio in the electromagnetic spectrum over 20 decades in wavelength. The cosmic microwave background (CMB) remains the best measured spectrum with an accuracy better than 1%. The measurements related to the cosmic optical background (COB), centred at 1 μm, are impacted by the large zodiacal light associated with interplanetary dust in the inner Solar System. The best measurements of COB come from an indirect technique involving γ-ray spectra of bright blazars with an absorption feature resulting from pair-production off of COB photons. The cosmic infrared background (CIB) peaking at around 100 μm established an energetically important background with an intensity comparable to the optical background. This discovery paved the way for large aperture far-infrared and sub-millimetre observations resulting in the discovery of dusty, starbursting galaxies. Their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. The extreme UV (EUV) background remains mostly unexplored and will be a challenge to measure due to the high Galactic background and absorption of extragalactic photons by the intergalactic medium at these EUV/soft X-ray energies. We also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. We motivate a precise direct measurement of the COB between 0.1 and 5 μm using a small aperture telescope observing either from the outer Solar System, at distances of 5 AU or more, or out of the ecliptic plane. Other future applications include improving our understanding of the background at TeV energies and spectral distortions of CMB and CIB. PMID:27069645

ON ULTRA-HIGH-ENERGY COSMIC RAYS AND THEIR RESULTANT GAMMA-RAYS

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

Gavish, Eyal; Eichler, David

2016-05-01

The Fermi Large Area Telescope collaboration has recently reported on 50 months of measurements of the isotropic extragalactic gamma-ray background (EGRB) spectrum between 100 MeV and 820 GeV. Ultra-high-energy cosmic ray (UHECR) protons interact with the cosmic microwave background photons and produce cascade photons of energies 10 MeV–1 TeV that contribute to the EGRB flux. We examine seven possible evolution models for UHECRs and find that UHECR sources that evolve as the star formation rate (SFR), medium low luminosity active galactic nuclei type-1 ( L = 10{sup 43.5} erg s{sup −1} in the [0.5–2] KeV band), and BL Lacertae objectsmore » (BL Lacs) are the most acceptable given the constraints imposed by the observed EGRB. Other possibilities produce too much secondary γ -radiation. In all cases, the decaying dark matter (DM) contribution improves the fit at high energy, but the contribution of still unresolved blazars, which would leave the smallest role for decaying DM, may yet provide an alternative improvement. The possibility that the entire EGRB can be fitted with resolvable but not-yet-resolved blazars, as recently claimed by Ajello et al., would leave little room in the EGRB to accommodate γ -rays from extragalactic UHECR production, even for many source evolution rates that would otherwise be acceptable. We find that under the assumption of UHECRs being mostly protons, there is not enough room for producing extragalactic UHECRs with active galactic nucleus, gamma-ray burst, or even SFR source evolution. Sources that evolve as BL Lacs, on the other hand, would produce much less secondary γ -radiation and would remain a viable source of UHECRs, provided that they dominate.« less

40 CFR 197.31 - What is a representative volume?

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 24 2010-07-01 2010-07-01 false What is a representative volume? 197.31 Section 197.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION PROTECTION PROGRAMS PUBLIC HEALTH AND ENVIRONMENTAL RADIATION PROTECTION STANDARDS FOR YUCCA MOUNTAIN, NEVADA...

40 CFR 197.31 - What is a representative volume?

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 26 2013-07-01 2013-07-01 false What is a representative volume? 197.31 Section 197.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION PROTECTION PROGRAMS PUBLIC HEALTH AND ENVIRONMENTAL RADIATION PROTECTION STANDARDS FOR YUCCA MOUNTAIN, NEVADA...

40 CFR 197.31 - What is a representative volume?

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 26 2012-07-01 2011-07-01 true What is a representative volume? 197.31 Section 197.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION PROTECTION PROGRAMS PUBLIC HEALTH AND ENVIRONMENTAL RADIATION PROTECTION STANDARDS FOR YUCCA MOUNTAIN, NEVADA Public...

40 CFR 197.31 - What is a representative volume?

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false What is a representative volume? 197.31 Section 197.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION PROTECTION PROGRAMS PUBLIC HEALTH AND ENVIRONMENTAL RADIATION PROTECTION STANDARDS FOR YUCCA MOUNTAIN, NEVADA...

40 CFR 197.31 - What is a representative volume?

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 25 2011-07-01 2011-07-01 false What is a representative volume? 197.31 Section 197.31 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) RADIATION PROTECTION PROGRAMS PUBLIC HEALTH AND ENVIRONMENTAL RADIATION PROTECTION STANDARDS FOR YUCCA MOUNTAIN, NEVADA...

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

None

Volume II of the Site Environmental Report for 2006 is provided by Ernest Orlando Lawrence Berkeley National Laboratory as a supplemental appendix to Volume I, which contains the body of the report. Volume II contains the environmental monitoring and sampling data used to generate summary results of routine and nonroutine activities at the Laboratory (except for groundwater sampling data, which may be found in the reports referred to in Chapter 4). Volume I summarizes the results from analyses of the data. The results from sample collections are more comprehensive in Volume II than in Volume I: For completeness, all resultsmore » from sample collections that began or ended in calendar year (CY) 2006 are included in this volume. However, the samples representing CY 2005 data have not been used in the summary results that are reported in Volume I. (For example, although ambient air samples collected on January 2, 2006, are presented in Volume II, they represent December 2005 data and are not included in Table 4-2 in Volume I.)« less

Imagery and spectroscopy of supernova remnants and H-2 regions

NASA Technical Reports Server (NTRS)

Dufour, R. J.

1984-01-01

Research activities relating to supernova remnants were summarized. The topics reviewed include: progenitor stars of supernova remnants, UV/optical/radio/X-ray imagery of selected regions in the Cygnus Loop, UV/optical spectroscopy of the Cygnus Loop spur, and extragalactic supernova remnant spectra.

High-Energy Cosmic Ray Self-Confinement Close to Extra-Galactic Sources.

PubMed

Blasi, Pasquale; Amato, Elena; D'Angelo, Marta

2015-09-18

The ultrahigh-energy cosmic rays observed on the Earth are most likely accelerated in extra-Galactic sources. For the typical luminosities invoked for such sources, the electric current associated to the flux of cosmic rays that leave them is large. The associated plasma instabilities create magnetic fluctuations that can efficiently scatter particles. We argue that this phenomenon forces cosmic rays to be self-confined in the source proximity for energies E

Planck intermediate results: XLV. Radio spectra of northern extragalactic radio sources

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Aller, H. D.; ...

2016-12-12

Continuum spectra covering centimetre to submillimetre wavelengths are presented in this paper for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at highmore » frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Finally, variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.« less

STATISTICS OF GAMMA-RAY POINT SOURCES BELOW THE FERMI DETECTION LIMIT

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

Malyshev, Dmitry; Hogg, David W., E-mail: dm137@nyu.edu

2011-09-10

An analytic relation between the statistics of photons in pixels and the number counts of multi-photon point sources is used to constrain the distribution of gamma-ray point sources below the Fermi detection limit at energies above 1 GeV and at latitudes below and above 30 deg. The derived source-count distribution is consistent with the distribution found by the Fermi Collaboration based on the first Fermi point-source catalog. In particular, we find that the contribution of resolved and unresolved active galactic nuclei (AGNs) to the total gamma-ray flux is below 20%-25%. In the best-fit model, the AGN-like point-source fraction is 17%more » {+-} 2%. Using the fact that the Galactic emission varies across the sky while the extragalactic diffuse emission is isotropic, we put a lower limit of 51% on Galactic diffuse emission and an upper limit of 32% on the contribution from extragalactic weak sources, such as star-forming galaxies. Possible systematic uncertainties are discussed.« less

Evolution of Extragalactic Radio Sources and Quasar/Galaxy Unification

NASA Astrophysics Data System (ADS)

Onah, C. I.; Ubachukwu, A. A.; Odo, F. C.; Onuchukwu, C. C.

2018-04-01

We use a large sample of radio sources to investigate the effects of evolution, luminosity selection and radio source orientation in explaining the apparent deviation of observed angular size - redshift (θ - z) relation of extragalactic radio sources (EGRSs) from the standard model. We have fitted the observed θ - z data with standard cosmological models based on a flat universe (Ω0 = 1). The size evolution of EGRSs has been described as luminosity, temporal and orientation-dependent in the form DP,z,Φ ≍ P±q(1 + z)-m sinΦ, with q=0.3, Φ=59°, m=-0.26 for radio galaxies and q=-0.5, Φ=33°, m=3.1 for radio quasars respectively. Critical points of luminosity, logPcrit=26.33 WHz-1 and logDc=2.51 kpc (316.23 kpc) of the present sample of radio sources were also observed. All the results were found to be consistent with the popular quasar/galaxy unification scheme.

MODELING EXTRAGALACTIC EXTINCTION THROUGH GAMMA-RAY BURST AFTERGLOWS

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

Zonca, Alberto; Mulas, Giacomo; Casu, Silvia

We analyze extragalactic extinction profiles derived through gamma-ray burst afterglows, using a dust model specifically constructed on the assumption that dust grains are not immutable but respond, time-dependently, to the local physics. Such a model includes core-mantle spherical particles of mixed chemical composition (silicate core, sp{sup 2}, and sp{sup 3} carbonaceous layers), and an additional molecular component in the form of free-flying polycyclic aromatic hydrocarbons. We fit most of the observed extinction profiles. Failures occur for lines of sight, presenting remarkable rises blueward of the bump. We find a tendency for the carbon chemical structure to become more aliphatic withmore » the galactic activity, and to some extent with increasing redshifts. Moreover, the contribution of the molecular component to the total extinction is more important in younger objects. The results of the fitting procedure (either successes and failures) may be naturally interpreted through an evolutionary prescription based on the carbon cycle in the interstellar medium of galaxies.« less

The diffuse infrared background - COBE and other observations

NASA Technical Reports Server (NTRS)

Hauser, M. G.; Kelsall, T.; Moseley, S. H., Jr.; Silverberg, R. F.; Murdock, T.; Toller, G.; Spiesman, W.; Weiland, J.

1991-01-01

The Diffuse Infrared Background Experiment (DIRBE) on the Cosmic Background Explorer (COBE) satellite is designed to conduct a sensitive search for an isotropic cosmic infrared background radiation over the spectral range from 1 to 300 micrometers. The cumulative emissions of pregalactic, protogalactic, and evolving galactic systems are expected to be recorded in this background. The DIRBE instrument, a 10 spectral band absolute photometer with an 0.7 deg field of view, maps the full sky with high redundancy at solar elongation angles ranging from 64 to 124 degrees to facilitate separation of interplanetary, Galactic, and extragalactic sources of emission. Initial sky maps show the expected character of the foreground emissions, with relative minima at wavelengths of 3.4 micrometers and longward of 100 micrometers. Extensive modelling of the foregrounds, just beginning, will be required to isolate the extragalactic component. In this paper, we summarize the status of diffuse infrared background observations from the DIRBE, and compare preliminary results with those of recent rocket and satellite instruments.

Planck intermediate results. XLV. Radio spectra of northern extragalactic radio sources

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gruppuso, A.; Gurwell, M. A.; Hansen, F. K.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hobson, M.; Hornstrup, A.; Hovatta, T.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Järvelä, E.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Max-Moerbeck, W.; Meinhold, P. R.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mingaliev, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nieppola, E.; Noviello, F.; Novikov, D.; Novikov, I.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Ramakrishnan, V.; Rastorgueva-Foi, E. A.; S Readhead, A. C.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Richards, J. L.; Ristorcelli, I.; Rocha, G.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savelainen, M.; Savini, G.; Scott, D.; Sotnikova, Y.; Stolyarov, V.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tammi, J.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tornikoski, M.; Tristram, M.; Tucci, M.; Türler, M.; Valenziano, L.; Valiviita, J.; Valtaoja, E.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wehrle, A. E.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-12-01

Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.

Planck intermediate results: XLV. Radio spectra of northern extragalactic radio sources

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

Ade, P. A. R.; Aghanim, N.; Aller, H. D.

Continuum spectra covering centimetre to submillimetre wavelengths are presented in this paper for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at highmore » frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Finally, variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.« less

Detecting the Attenuation of Blazar Gamma-ray Emission by Extragalactic Background Light with GLAST

NASA Technical Reports Server (NTRS)

Chen, Andrew; Ritz, Steven

1999-01-01

Gamma rays with energy above 10 GeV interact with optical-UV photons resulting in pair production. Therefore, a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight (EBL) by examining the redshift dependence of the attenuation of the flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope, will for the first time have the unique capability to detect thousands of gamma-ray blazars up to redshifts of at least z = 4, with enough angular resolution to allow identification of a large fraction of their optical counterparts. By combining recent determinations of the gamma-ray blazar luminosity function, recent calculations of the high energy gamma-ray opacity due to EBL absorption, and the expected GLAST instrument performance to produce simulated samples of blazars that GLAST would detect, including their redshifts and fluxes, we demonstrate that these blazars have the potential to be a highly effective probe of the EBL.

Sources of GeV Photons and the Fermi Results

NASA Astrophysics Data System (ADS)

Dermer, Charles D.

This chapter presents the elaborated lecture notes on Sources of GeV Photons and the Fermi Results given by Charles D. Dermer at the 40th Saas-Fee Advanced Course on "Astrophysics at Very High Energies". The Fermi Gamma-ray Space Telescope made important discoveries and established new results in various areas of astrophysics: from our solar system to remote gamma-ray bursts, from pulsar physics to limits on dark matter and Lorentz invariance violations. The author gives a broad overview of these results by discussing GeV instrumentation and the GeV sky as seen by Fermi, the Fermi catalogs on gamma-ray sources, pulsars and active galactic nuclei, relativistic jet physics and blazars, gamma-rays from cosmic rays in the Galaxy, from star-forming galaxies and from clusters of galaxies, the diffuse extra-galactic gamma-ray background, micro-quasars, radio galaxies, the extragalactic background light, gamma-ray bursts, Fermi acceleration, ultra-high energy cosmic rays, and black holes.

Observing the Extragalactic Universe with a Square Kilometer Array

NASA Astrophysics Data System (ADS)

Blandford, R. D.

2001-12-01

The Square Kilometer Array, SKA, is being developed to provide broad, radio survey capability to cm wavelength, with a 1 degree field of view, 1 arcsec resolution and 100 times the VLA sensitivity. In extragalactic astronomy, it will observe unobscured, normal and active galaxies, star formation and mergers, large scale structure and gravitational lenses throughout the universe. It will contribute mightily to our emerging, empirical description of the birth and growth of galaxies of all type. It should also advance our understanding of the conditions that existed prior to galaxy formation at the end of the dark age and help delineate the dark matter skeleton that supports mature galaxies. It will map and monitor, in quite different modes, the same objects as Chandra, SIRTF, HST/ACS, GLAST, SDSS as well as future missions like NGST and Constellation-X. The proposed scientific capability of SKA will be summarized. In addition, the importance of refining its goals and design criteria in a dialog with organizations making complementary plans throughout the electromagnetic spectrum will be emphasized.

Evolution of the NASA/IPAC Extragalactic Database (NED) into a Data Mining Discovery Engine

NASA Astrophysics Data System (ADS)

Mazzarella, Joseph M.; NED Team

2017-06-01

We review recent advances and ongoing work in evolving the NASA/IPAC Extragalactic Database (NED) beyond an object reference database into a data mining discovery engine. Updates to the infrastructure and data integration techniques are enabling more than a 10-fold expansion; NED will soon contain over a billion objects with their fundamental attributes fused across the spectrum via cross-identifications among the largest sky surveys (e.g., GALEX, SDSS, 2MASS, AllWISE, EMU), and over 100,000 smaller but scientifically important catalogs and journal articles. The recent discovery of super-luminous spiral galaxies exemplifies the opportunities for data mining and science discovery directly from NED's rich data synthesis. Enhancements to the user interface, including new APIs, VO protocols, and queries involving derived physical quantities, are opening new pathways for panchromatic studies of large galaxy samples. Examples are shown of graphics characterizing the content of NED, as well as initial steps in exploring the database via interactive statistical visualizations.

A survey of the Local Group of galaxies for symbiotic binary stars - I. First detection of symbiotic stars in M33

NASA Astrophysics Data System (ADS)

Mikołajewska, Joanna; Shara, Michael M.; Caldwell, Nelson; Iłkiewicz, Krystian; Zurek, David

2017-02-01

We present and discuss initial selection criteria and first results in M33 from a systematic search for extragalactic symbiotic stars. We show that the presence of diffuse ionized gas (DIG) emission can significantly contaminate the spectra of symbiotic star candidates. This important effect forces upon us a more stringent working definition of an extragalactic symbiotic star. We report the first detections and spectroscopic characterization of 12 symbiotic binaries in M33. We found that four of our systems contain carbon-rich giants. In another two of them, the giant seems to be a Zr-enhanced MS star, while the remaining six objects host M-type giants. The high number ratio of C to M giants in these binaries is consistent with the low metallicity of M33. The spatial and radial velocity distributions of these new symbiotic binaries are consistent with a wide range of progenitor star ages.

Measurement of the EBL spectral energy distribution using the VHE γ-ray spectra of H.E.S.S. blazars

NASA Astrophysics Data System (ADS)

H. E. S. S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Tjus, J. Becker; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; de Wilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.; Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Katz, U.; Kerszberg, D.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; Nakashima, S.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Rauth, R.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Richter, S.; Rieger, F.; Romoli, C.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Saito, S.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stycz, K.; Sushch, I.; Takahashi, T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2017-10-01

Very high-energy γ rays (VHE, E ≳ 100 GeV) propagating over cosmological distances can interact with the low-energy photons of the extragalactic background light (EBL) and produce electron-positron pairs. The transparency of the Universe to VHE γ rays is then directly related to the spectral energy distribution (SED) of the EBL. The observation of features in the VHE energy spectra of extragalactic sources allows the EBL to be measured, which otherwise is very difficult. An EBL model-independent measurement of the EBL SED with the H.E.S.S. array of Cherenkov telescopes is presented. It was obtained by extracting the EBL absorption signal from the reanalysis of high-quality spectra of blazars. From H.E.S.S. data alone the EBL signature is detected at a significance of 9.5σ, and the intensity of the EBL obtained in different spectral bands is presented together with the associated γ-ray horizon.

SPITZER 70 AND 160 {mu}m OBSERVATIONS OF THE COSMOS FIELD

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

Frayer, D. T.; Huynh, M. T.; Bhattacharya, B.

2009-11-15

We present Spitzer 70 and 160 {mu}m observations of the COSMOS Spitzer survey (S-COSMOS). The data processing techniques are discussed for the publicly released products consisting of images and source catalogs. We present accurate 70 and 160 {mu}m source counts of the COSMOS field and find reasonable agreement with measurements in other fields and with model predictions. The previously reported counts for GOODS-North and the extragalactic First Look Survey are updated with the latest calibration, and counts are measured based on the large area SWIRE survey to constrain the bright source counts. We measure an extragalactic confusion noise level ofmore » {sigma} {sub c} = 9.4 {+-} 3.3 mJy (q = 5) for the MIPS 160 {mu}m band based on the deep S-COSMOS data and report an updated confusion noise level of {sigma} {sub c} = 0.35 {+-} 0.15 mJy (q = 5) for the MIPS 70 {mu}m band.« less

10 CFR 63.332 - Representative volume.

Code of Federal Regulations, 2011 CFR

2011-01-01

... accessible environment; (2) Its position and dimensions in the aquifer are determined using average... determined by site characterization; and (3) It contains 3,000 acre-feet of water (about 3,714,450,000 liters... dimensions of the representative volume. The DOE must propose its chosen method, and any underlying...

10 CFR 63.332 - Representative volume.

Code of Federal Regulations, 2010 CFR

2010-01-01

... accessible environment; (2) Its position and dimensions in the aquifer are determined using average... determined by site characterization; and (3) It contains 3,000 acre-feet of water (about 3,714,450,000 liters... dimensions of the representative volume. The DOE must propose its chosen method, and any underlying...

The Bivariate Luminosity--HI Mass Distribution Function of Galaxies based on the NIBLES Survey

NASA Astrophysics Data System (ADS)

Butcher, Zhon; Schneider, Stephen E.; van Driel, Wim; Lehnert, Matt

2016-01-01

We use 21cm HI line observations for 2610 galaxies from the Nançay Interstellar Baryons Legacy Extragalactic Survey (NIBLES) to derive a bivariate luminosity--HI mass distribution function. Our HI survey was selected to randomly probe the local (900 < cz < 12,000 km/s) galaxy population in each 0.5 mag wide bin for the absolute z-band magnitude range of -13.5 < Mz < -24 without regard to morphology or color. This targeted survey allowed more on-source integration time for weak and non-detected sources, enabling us to probe lower HI mass fractions and apply lower upper limits for non-detections than would be possible with the larger blind HI surveys. Additionally, we obtained a factor of four higher sensitivity follow-up observations at Arecibo of 90 galaxies from our non-detected and marginally detected categories to quantify the underlying HI distribution of sources not detected at Nançay. Using the optical luminosity function and our higher sensitivity follow up observations as priors, we use a 2D stepwise maximum likelihood technique to derive the two dimensional volume density distribution of luminosity and HI mass in each SDSS band.

The Undergraduate ALFALFA Team

NASA Astrophysics Data System (ADS)

Koopmann, Rebecca A.; Higdon, S.; Balonek, T. J.; Haynes, M. P.; Giovanelli, R.

2010-01-01

The Undergraduate ALFALFA (Arecibo Legacy Fast ALFA) Team is a consortium of 16 institutions engaged in an NSF-sponsored program to promote undergraduate research within the extragalactic ALFALFA HI blind survey project. In the first two years of the program, more than three dozen undergraduate students have been closely involved in ALFALFA science, observing, and data analysis. A total of 34 students have attended the annual undergraduate workshops at Arecibo Observatory, interacting with faculty, their peers, ALFALFA experts, and Arecibo staff in lectures, group activities, tours, and observing runs. Team faculty have supervised 26 summer research projects and 14 academic year (e.g., senior thesis) projects. Students and faculty have traveled to Arecibo Observatory for observing runs and to national meetings to present their results. Eight Team schools have joined to work collaboratively to analyze HI properties of galaxy groups within the ALFALFA volume. (See O'Brien et al., O'Malley et al., and Odekon et al. posters, this meeting.) Students involved in this program are learning how science is accomplished in a large collaboration while contributing to the scientific goals of a major legacy survey. This work has been supported by NSF grants AST-0724918, AST-0725267, and AST-0725380.

KEGS Transients Discovered by a Pan-STARRS1 Search of the Kepler Campaign 16 Field

NASA Astrophysics Data System (ADS)

Smith, K. W.; Rest, A.; Tucker, B. E.; Garnavich, P. M.; Margheim, S.; Kasen, D.; Olling, R.; Shaya, E.; Narayan, G.; Villar, A.; Forster, F.; Mushotzky, R.; Zenteno, A.; James, D.; Smith, R. Chris; Dotson, J. L.; Barentsen, G.; Gully-Santiago, M.; Smartt, S. J.; Wright, D. E.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Schultz, A.; Magnier, E.; Waters, C.; Bulger, J.; Wainscoat, R. J.

2018-01-01

We report the following transients discovered by Pan-STARRS1 during a targeted search of the Kepler Campaign 16 field as part of the K2 Extragalactic Survey (KEGS) for Transients (see http://www.mso.anu.edu.au/kegs/).

PeV Neutrinos Observed by IceCube from Cores of Active Galactic Nuclei

NASA Technical Reports Server (NTRS)

Stecker, Floyd W.

2013-01-01

I show that the high energy neutrino flux predicted to arise from active galactic nuclei cores can explain the PeV neutrinos detected by IceCube without conflicting with the constraints from the observed extragalactic cosmic-ray and gamma-ray backgrounds.

Body Fluids Monitor

NASA Technical Reports Server (NTRS)

Siconolfi, Steven F. (Inventor)

2000-01-01

Method and apparatus are described for determining volumes of body fluids in a subject using bioelectrical response spectroscopy. The human body is represented using an electrical circuit. Intra-cellular water is represented by a resistor in series with a capacitor; extra-cellular water is represented by a resistor in series with two parallel inductors. The parallel inductors represent the resistance due to vascular fluids. An alternating, low amperage, multifrequency signal is applied to determine a subject's impedance and resistance. From these data, statistical regression is used to determine a 1% impedance where the subject's impedance changes by no more than 1% over a 25 kHz interval. Circuit component, of the human body circuit are determined based on the 1% impedance. Equations for calculating total body water, extra-cellular water, total blood volume, and plasma volume are developed based on the circuit components.

The VIMOS Public Extragalactic Redshift Survey (VIPERS). An unbiased estimate of the growth rate of structure at ⟨z⟩ = 0.85 using the clustering of luminous blue galaxies

NASA Astrophysics Data System (ADS)

Mohammad, F. G.; Granett, B. R.; Guzzo, L.; Bel, J.; Branchini, E.; de la Torre, S.; Moscardini, L.; Peacock, J. A.; Bolzonella, M.; Garilli, B.; Scodeggio, M.; Abbas, U.; Adami, C.; Bottini, D.; Cappi, A.; Cucciati, O.; Davidzon, I.; Franzetti, P.; Fritz, A.; Iovino, A.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; Marulli, F.; Polletta, M.; Pollo, A.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Arnouts, S.; Coupon, J.; De Lucia, G.; Ilbert, O.; Moutard, T.

2018-02-01

We used the VIMOS Public Extragalactic Redshift Survey (VIPERS) final data release (PDR-2) to investigate the performance of colour-selected populations of galaxies as tracers of linear large-scale motions. We empirically selected volume-limited samples of blue and red galaxies as to minimise the systematic error on the estimate of the growth rate of structure fσ8 from the anisotropy of the two-point correlation function. To this end, rather than rigidly splitting the sample into two colour classes we defined the red or blue fractional contribution of each object through a weight based on the (U - V ) colour distribution. Using mock surveys that are designed to reproduce the observed properties of VIPERS galaxies, we find the systematic error in recovering the fiducial value of fσ8 to be minimised when using a volume-limited sample of luminous blue galaxies. We modelled non-linear corrections via the Scoccimarro extension of the Kaiser model (with updated fitting formulae for the velocity power spectra), finding systematic errors on fσ8 of below 1-2%, using scales as small as 5 h-1 Mpc. We interpret this result as indicating that selection of luminous blue galaxies maximises the fraction that are central objects in their dark matter haloes; this in turn minimises the contribution to the measured ξ(rp,π) from the 1-halo term, which is dominated by non-linear motions. The gain is inferior if one uses the full magnitude-limited sample of blue objects, consistent with the presence of a significant fraction of blue, fainter satellites dominated by non-streaming, orbital velocities. We measured a value of fσ8 = 0.45 ± 0.11 over the single redshift range 0.6 ≤ z ≤ 1.0, corresponding to an effective redshift for the blue galaxies ⟨z⟩=0.85. Including in the likelihood the potential extra information contained in the blue-red galaxy cross-correlation function does not lead to an appreciable improvement in the error bars, while it increases the systematic error. Based on observations collected at the European Southern Observatory, Cerro Paranal, Chile, using the Very Large Telescope under programs 182.A-0886 and partly 070.A-9007. Also based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. The VIPERS web site is http://www.vipers.inaf.it/

Gamma Ray Astrophysics: New insight into the universe

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Trombka, J. I.

1981-01-01

Gamma ray observations of the solar system, the galaxy and extragalactic radiation are reported. Topics include: planets, comets, and asteroids; solar observations; interstellar medium and galactic structure; compact objects; cosmology; and diffuse radiation. The instrumentation used in gamma ray astronomy in covered along with techniques for the analysis of observational spectra.

KEGS Discovery of 28 Supernova Candidates in the K2 Campaign 17 Field with DECam

NASA Astrophysics Data System (ADS)

Narayan, G.; Rest, A.; Strampelli, G. M.; Zenteno, A.; James, D. J.; Smith, R. C.; Tucker, B. E.; Garnavich, P.; Margheim, S.; Kasen, D.; Olling, R.; Shaya, E.; Buron, F. Forster; Villar, V. A.

2018-05-01

The Kepler Extra-Galactic Survey (KEGS, see http://www.mso.anu.edu.au/kegs/ ) reports the discovery of 28 supernova candidates with the Dark Energy Camera (DECam, NOAO 2017B-0285) on the 4m Blanco Telescope at Cerro Tololo Inter-American Observatory (CTIO).

Double Layers in Astrophysics

NASA Technical Reports Server (NTRS)

Williams, Alton C. (Editor); Moorehead, Tauna W. (Editor)

1987-01-01

Topics addressed include: laboratory double layers; ion-acoustic double layers; pumping potential wells; ion phase-space vortices; weak double layers; electric fields and double layers in plasmas; auroral double layers; double layer formation in a plasma; beamed emission from gamma-ray burst source; double layers and extragalactic jets; and electric potential between plasma sheet clouds.

HEAO Science Symposium

NASA Technical Reports Server (NTRS)

Dailey, C. (Editor); Johnson, W. (Editor)

1979-01-01

Scientific results from the early analysis of data from the HEAO 1 mission are presented. Development of astronomical catalogs and maps, X-ray variability, extragalactic astronomy, X-ray iron line emission, and optical identification and spectroscopy of X-ray sources are among the topics discussed. Results from HEAO 2 imaging and nonimaging instruments are included.

Wisconsin H-Alpha Mapper | UW-Madison Astronomy

Science.gov Websites

Department of Astronomy Wisconsin H-Alpha Mapper Overview Description About WHAM Fabry-Perot Spectroscopy National Science Foundation Astronomy and... 02.20.2012 | Continue Reading » WHAM featured at Natural Astronomy Galactic Structure GALFA GLIMPSE GLIMPSE360 WHAM Extragalactic Astronomy & Cosmology Local

Balloon observations of galactic and extragalactic objects at 100 microns.

NASA Technical Reports Server (NTRS)

Hoffmann, W. F.

1972-01-01

Recent far-infrared balloon-borne instruments have yielded observations of a number of bright sources at 100 microns. Many of these coincide with HII regions where molecular line emision has been detected. There is some indication of 100 micron emission which does not coincide with radio measurements.

AzTEC half square degree survey of the SHADES fields - I. Maps, catalogues and source counts

NASA Astrophysics Data System (ADS)

Austermann, J. E.; Dunlop, J. S.; Perera, T. A.; Scott, K. S.; Wilson, G. W.; Aretxaga, I.; Hughes, D. H.; Almaini, O.; Chapin, E. L.; Chapman, S. C.; Cirasuolo, M.; Clements, D. L.; Coppin, K. E. K.; Dunne, L.; Dye, S.; Eales, S. A.; Egami, E.; Farrah, D.; Ferrusca, D.; Flynn, S.; Haig, D.; Halpern, M.; Ibar, E.; Ivison, R. J.; van Kampen, E.; Kang, Y.; Kim, S.; Lacey, C.; Lowenthal, J. D.; Mauskopf, P. D.; McLure, R. J.; Mortier, A. M. J.; Negrello, M.; Oliver, S.; Peacock, J. A.; Pope, A.; Rawlings, S.; Rieke, G.; Roseboom, I.; Rowan-Robinson, M.; Scott, D.; Serjeant, S.; Smail, I.; Swinbank, A. M.; Stevens, J. A.; Velazquez, M.; Wagg, J.; Yun, M. S.

2010-01-01

We present the first results from the largest deep extragalactic mm-wavelength survey undertaken to date. These results are derived from maps covering over 0.7deg2, made at λ = 1.1mm, using the AzTEC continuum camera mounted on the James Clerk Maxwell Telescope. The maps were made in the two fields originally targeted at λ = 850μm with the Submillimetre Common-User Bolometer Array (SCUBA) in the SCUBA Half-Degree Extragalactic Survey (SHADES) project, namely the Lockman Hole East (mapped to a depth of 0.9-1.3 mJy rms) and the Subaru/XMM-Newton Deep Field (mapped to a depth of 1.0-1.7 mJy rms). The wealth of existing and forthcoming deep multifrequency data in these two fields will allow the bright mm source population revealed by these new wide-area 1.1mm images to be explored in detail in subsequent papers. Here, we present the maps themselves, a catalogue of 114 high-significance submillimetre galaxy detections, and a thorough statistical analysis leading to the most robust determination to date of the 1.1mm source number counts. These new maps, covering an area nearly three times greater than the SCUBA SHADES maps, currently provide the largest sample of cosmological volumes of the high-redshift Universe in the mm or sub-mm. Through careful comparison, we find that both the Cosmic Evolution Survey (COSMOS) and the Great Observatories Origins Deep Survey (GOODS) North fields, also imaged with AzTEC, contain an excess of mm sources over the new 1.1mm source-count baseline established here. In particular, our new AzTEC/SHADES results indicate that very luminous high-redshift dust enshrouded starbursts (S1.1mm > 3mJy) are 25-50 per cent less common than would have been inferred from these smaller surveys, thus highlighting the potential roles of cosmic variance and clustering in such measurements. We compare number count predictions from recent models of the evolving mm/sub-mm source population to these sub-mm bright galaxy surveys, which provide important constraints for the ongoing refinement of semi-analytic and hydrodynamical models of galaxy formation, and find that all available models overpredict the number of bright submillimetre galaxies found in this survey.

On volume-source representations based on the representation theorem

NASA Astrophysics Data System (ADS)

Ichihara, Mie; Kusakabe, Tetsuya; Kame, Nobuki; Kumagai, Hiroyuki

2016-01-01

We discuss different ways to characterize a moment tensor associated with an actual volume change of ΔV C , which has been represented in terms of either the stress glut or the corresponding stress-free volume change ΔV T . Eshelby's virtual operation provides a conceptual model relating ΔV C to ΔV T and the stress glut, where non-elastic processes such as phase transitions allow ΔV T to be introduced and subsequent elastic deformation of - ΔV T is assumed to produce the stress glut. While it is true that ΔV T correctly represents the moment tensor of an actual volume source with volume change ΔV C , an explanation as to why such an operation relating ΔV C to ΔV T exists has not previously been given. This study presents a comprehensive explanation of the relationship between ΔV C and ΔV T based on the representation theorem. The displacement field is represented using Green's function, which consists of two integrals over the source surface: one for displacement and the other for traction. Both integrals are necessary for representing volumetric sources, whereas the representation of seismic faults includes only the first term, as the second integral over the two adjacent fault surfaces, across which the traction balances, always vanishes. Therefore, in a seismological framework, the contribution from the second term should be included as an additional surface displacement. We show that the seismic moment tensor of a volume source is directly obtained from the actual state of the displacement and stress at the source without considering any virtual non-elastic operations. A purely mathematical procedure based on the representation theorem enables us to specify the additional imaginary displacement necessary for representing a volume source only by the displacement term, which links ΔV C to ΔV T . It also specifies the additional imaginary stress necessary for representing a moment tensor solely by the traction term, which gives the "stress glut." The imaginary displacement-stress approach clarifies the mathematical background to the classical theory.

A model of the 8-25 micron point source infrared sky

NASA Technical Reports Server (NTRS)

Wainscoat, Richard J.; Cohen, Martin; Volk, Kevin; Walker, Helen J.; Schwartz, Deborah E.

1992-01-01

We present a detailed model for the IR point-source sky that comprises geometrically and physically realistic representations of the Galactic disk, bulge, stellar halo, spiral arms (including the 'local arm'), molecular ring, and the extragalactic sky. We represent each of the distinct Galactic components by up to 87 types of Galactic source, each fully characterized by scale heights, space densities, and absolute magnitudes at BVJHK, 12, and 25 microns. The model is guided by a parallel Monte Carlo simulation of the Galaxy at 12 microns. The content of our Galactic source table constitutes a good match to the 12 micron luminosity function in the simulation, as well as to the luminosity functions at V and K. We are able to produce differential and cumulative IR source counts for any bandpass lying fully within the IRAS Low-Resolution Spectrometer's range (7.7-22.7 microns as well as for the IRAS 12 and 25 micron bands. These source counts match the IRAS observations well. The model can be used to predict the character of the point source sky expected for observations from IR space experiments.

HI and Low Metal Ions at the Intersection of Galaxies and the CGM

NASA Astrophysics Data System (ADS)

Oppenheimer, Benjamin

2017-08-01

Over 1000 COS orbits have revealed a surprisingly complex picture of circumgalactic gas flows surrounding the diversity of galaxies in the evolved Universe. Cosmological hydrodynamic simulations have only begun to confront the vast amount of galaxy formation physics, chemistry, and dynamics revealed in the multi-ion CGM datasets. We propose the next generation of EAGLE zoom simulations, called EAGLE Cosmic Origins, to model HI and low metal ions (C II, Mg II, & Si II) throughout not just the CGM but also within the galaxies themselves. We will employ a novel, new chemistry solver, CHIMES, to follow time-dependent ionization, chemistry, and cooling of 157 ionic and molecular species, and include multiple ionization sources from the extra-galactic background, episodic AGN, and star formation. Our aim is to understand the complete baryon cycle of inflows, outflows, and gas recycling traced over 10 decades of HI column densities as well as the complex kinematic information encoded low ion absorption spectroscopy. This simulation project represents a pilot program for a larger suite of zoom simulations, which will be publicly released and lead to additional publications.

Truck Traffic Iowa : 2010

DOT National Transportation Integrated Search

2011-01-01

Truck volumes represented on this map are Annual Average Daily Traffic Volumes between major traffic generators: i.e., Highway Junctions and Cities. : Truck volumes include 6-Tire and 3 Axle single unit trucks, buses and all multiple unit trucks.

Hand surgery volume and the US economy: is there a statistical correlation?

PubMed

Gordon, Chad R; Pryor, Landon; Afifi, Ahmed M; Gatherwright, James R; Evans, Peter J; Hendrickson, Mark; Bernard, Steven; Zins, James E

2010-11-01

To the best of our knowledge, there have been no previous studies evaluating the correlation of the US economy and hand surgery volume. Therefore, in light of the current recession, our objective was to study our institution's hand surgery volume over the last 17 years in relation to the nation's economy. A retrospective analysis of our institution's hand surgery volume, as represented by our most common procedure (ie, carpal tunnel release), was performed between January 1992 and October 2008. Liposuction and breast augmentation volumes were chosen to serve as cosmetic plastic surgery comparison groups. Pearson correlation statistics were used to estimate the relationship between the surgical volume and the US economy, as represented by the 3 market indices (Dow Jones, NASDAQ, and S&P500). A combined total of 7884 hand surgery carpal tunnel release (open or endoscopic) patients were identified. There were 1927 (24%) and 5957 (76%) patients within the departments of plastic and orthopedic surgery, respectively. In the plastic surgery department, there was a strong negative (ie, inverse relationship) correlation between hand surgery volume and the economy (P < 0.001). In converse, the orthopedic department's hand surgery volume demonstrated a positive (ie, parallel) correlation (P < 0.001). The volumes of liposuction and breast augmentation also showed a positive correlation (P < 0.001). To our knowledge, we have demonstrated for the first time an inverse (ie, negative) correlation between hand surgery volumes performed by plastic surgeons in relation to the US economy, as represented by the 3 major market indices. In contrast, orthopedic hand surgery volume and cosmetic surgery show a parallel (ie, positive) correlation. This data suggests that plastic surgeons are increasing their cosmetic surgery-to-reconstructive/hand surgery ratio during strong economic times and vice versa during times of economic slowdown.

THE SPITZER-WISE SURVEY OF THE ECLIPTIC POLES

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

Jarrett, T. H.; Masci, F.; Cutri, R. M.

2011-07-10

We have carried out a survey of the north and south ecliptic poles, EP-N and EP-S, respectively, with the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE). The primary objective was to cross-calibrate WISE with the Spitzer and Midcourse Space Experiment (MSX) photometric systems by developing a set of calibration stars that are common to these infrared missions. The ecliptic poles were continuous viewing zones for WISE due to its polar-crossing orbit, making these areas ideal for both absolute and internal calibrations. The Spitzer IRAC and MIPS imaging survey covers a complete area of 0.40 deg{sup 2} formore » the EP-N and 1.28 deg{sup 2} for the EP-S. WISE observed the whole sky in four mid-infrared bands, 3.4, 4.6, 12, and 22 {mu}m, during its eight-month cryogenic mission, including several hundred ecliptic polar passages; here we report on the highest coverage depths achieved by WISE, an area of {approx}1.5 deg{sup 2} for both poles. Located close to the center of the EP-N, the Sy-2 galaxy NGC 6552 conveniently functions as a standard calibrator to measure the red response of the 22 {mu}m channel of WISE. Observations from Spitzer-IRAC/MIPS/IRS-LL and WISE show that the galaxy has a strong red color in the mid-infrared due to star-formation and the presence of an active galactic nucleus (AGN), while over a baseline >1 year the mid-IR photometry of NGC 6552 is shown to vary at a level less than 2%. Combining NGC 6552 with the standard calibrator stars, the achieved photometric accuracy of the WISE calibration, relative to the Spitzer and MSX systems, is 2.4%, 2.8%, 4.5%, and 5.7% for W1 (3.4 {mu}m), W2 (4.6 {mu}m), W3 (12 {mu}m), and W4 (22 {mu}m), respectively. The WISE photometry is internally stable to better than 0.1% over the cryogenic lifetime of the mission. The secondary objective of the Spitzer-WISE Survey was to explore the poles at greater flux-level depths, exploiting the higher angular resolution Spitzer observations and the exceptionally deep (in total coverage) WISE observations that potentially reach down to the confusion limit of the survey. The rich Spitzer and WISE data sets were used to study the Galactic and extragalactic populations through source counts, color-magnitude and color-color diagrams. As an example of what the data sets facilitate, we have separated stars from galaxies, delineated normal galaxies from power-law-dominated AGNs, and reported on the different fractions of extragalactic populations. In the EP-N, we find an AGN source density of {approx}260 deg{sup -2} to a 12 {mu}m depth of 115 {mu}Jy, representing 15% of the total extragalactic population to this depth, similar to what has been observed for low-luminosity AGNs in other fields.« less

Infrared astronomy research and high altitude observations

NASA Technical Reports Server (NTRS)

Jones, B.; Stein, W. A.; Willner, S. P.; Soifer, B. T.

1984-01-01

Highlights are presented of studies of the emission mechanisms in the 4 to 8 micron region of the spectrum using a circular variable filter wheel spectrometer with a PbSnTe photovoltaic detector. Investigations covered include the spectroscopy of planets, stellar atmospheres, highly obscured objects in molecular clouds, planetary nebulae, H2 regions, and extragalactic objects.

Hypercat: A Database for Extragalactic Astronomy

NASA Astrophysics Data System (ADS)

Prugniel, Ph.; Maubon, G.

The Hypercat Database is developed at Observatoire de Lyon and is distributed on the WEB(www-obs.univ-lyon1.fr/hypercat) through different mirrors in Europe. The goal of Hypercat is to gather data necessary for studying the evolution of galaxies (dynamics and stellar contains) and particularly for providing a z = 0 reference for these studies.

Photometry of Galactic and Extragalactic Far-Infrared Sources using the 91.5 cm Airborne Infrared Telescope

NASA Technical Reports Server (NTRS)

Harper, D. A.

1996-01-01

The objective of this grant was to construct a series of far infrared photometers, cameras, and supporting systems for use in astronomical observations in the Kuiper Airborne Observatory. The observations have included studies of galaxies, star formation regions, and objects within the Solar System.

Efficiency of centrifugal mechanism in producing PeV neutrinos from active galactic nuclei

NASA Astrophysics Data System (ADS)

Osmanov, Zaza; Mahajan, Swadesh; Machabeli, George; Chkheidze, Nino

2018-05-01

A several-step theoretical model is constructed to trace the origin of ultra high energy (UHE) [ 1 - 2 ] PeV neutrinos detected, recently, by the IceCube collaboration. Protons in the AGN magnetosphere, experiencing different gravitational centrifugal force, provide free energy for the parametric excitation of Langmuir waves via a generalized two-stream instability. Landau damping of these waves, outside the AGN magnetosphere, can accelerate protons to ultra high energies. The ultimate source for this mechanism, the Langmuir-Landau-Centrifugal-Drive (LLCD), is the gravitational energy of the compact object. The LLCD generated UHE protons provide the essential ingredient in the creation of UHE neutrinos via appropriate hadronic reactions; protons of energy 1017 eV can be generated in the plasmas surrounding AGN with bolometric luminosities of the order of 1043 ergs s-1. By estimating the diffusive energy flux of extragalactic neutrinos in the energy interval [ 1 - 2 ] PeV, we find that an acceptably small fraction 0.003% of the total bolometric luminosity will suffice to create the observed fluxes of extragalactic ultra-high energy neutrinos.

Cleaning HI Spectra Contaminated by GPS RFI

NASA Astrophysics Data System (ADS)

Sylvia, Kamin; Hallenbeck, Gregory L.; Undergraduate ALFALFA Team

2016-01-01

The NUDET systems aboard GPS satellites utilize radio waves to communicate information regarding surface nuclear events. The system tests appear in spectra as RFI (radio frequency interference) at 1381MHz, which contaminates observations of extragalactic HI (atomic hydrogen) signals at 50-150 Mpc. Test durations last roughly 20-120 seconds and can occur upwards of 30 times during a single night of observing. The disruption essentially renders the corresponding HI spectra useless.We present a method that automatically removes RFI in HI spectra caused by these tests. By capitalizing on the GPS system's short test durations and predictable frequency appearance we are able to devise a method of identifying times containing compromised data records. By reevaluating the remaining data, we are able to recover clean spectra while sacrificing little in terms of sensitivity to extragalactic signals. This method has been tested on 500+ spectra taken by the Undergraduate ALFALFA Team (UAT), in which it successfully identified and removed all sources of GPS RFI. It will also be used to eliminate RFI in the upcoming Arecibo Pisces-Perseus Supercluster Survey (APPSS).This work has been supported by NSF grant AST-1211005.

Fermi Large Area Telescope Constraints On The Gamma-Ray Opacity Of The Universe

DOE PAGES

Abdo, A. A.

2010-10-19

The extragalactic background light (EBL) includes photons with wavelengths from ultraviolet to infrared, which are effective at attenuating gamma rays with energy above ~10 GeV during propagation from sources at cosmological distances. This results in a redshift- and energy-dependent attenuation of the γ-ray flux of extragalactic sources such as blazars and gamma-ray bursts (GRBs). The Large Area Telescope on board Fermi detects a sample of γ-ray blazars with redshift up to z ~ 3, and GRBs with redshift up to z ~ 4.3. Using photons above 10 GeV collected by Fermi over more than one year of observations for thesemore » sources, we investigate the effect of γ-ray flux attenuation by the EBL. We place upper limits on the γ-ray opacity of the universe at various energies and redshifts and compare this with predictions from well-known EBL models. We find that an EBL intensity in the optical-ultraviolet wavelengths as great as predicted by the "baseline" model of Stecker et al. can be ruled out with high confidence.« less

Search for Dark Matter Annihilation in Galaxy Groups

NASA Astrophysics Data System (ADS)

Lisanti, Mariangela; Mishra-Sharma, Siddharth; Rodd, Nicholas L.; Safdi, Benjamin R.

2018-03-01

We use 413 weeks of publicly available Fermi Pass 8 gamma-ray data combined with recently developed galaxy group catalogs to search for evidence of dark matter annihilation in extragalactic halos. In our study, we use luminosity-based mass estimates and mass-to-concentration relations to infer the J factors and associated uncertainties for hundreds of galaxy groups within a redshift range z ≲0.03 . We employ a conservative substructure boost factor model, which only enhances the sensitivity by an O (1 ) factor. No significant evidence for dark matter annihilation is found, and we exclude thermal relic cross sections for dark matter masses below ˜30 GeV to 95% confidence in the b b ¯ annihilation channel. These bounds are comparable to those from Milky Way dwarf spheroidal satellite galaxies. The results of our analysis increase the tension but do not rule out the dark matter interpretation of the Galactic Center excess. We provide a catalog of the galaxy groups used in this study and their inferred properties, which can be broadly applied to searches for extragalactic dark matter.

Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos

NASA Astrophysics Data System (ADS)

Argüelles, Carlos A.; Kheirandish, Ali; Vincent, Aaron C.

2017-11-01

We show that the high-energy cosmic neutrinos seen by the IceCube Neutrino Observatory can be used to probe interactions between neutrinos and the dark sector that cannot be reached by current cosmological methods. The origin of the observed neutrinos is still unknown, and their arrival directions are compatible with an isotropic distribution. This observation, together with dedicated studies of Galactic plane correlations, suggests a predominantly extragalactic origin. Interactions between this isotropic extragalactic flux and the dense dark matter (DM) bulge of the Milky Way would thus lead to an observable imprint on the distribution, which would be seen by IceCube as (i) slightly suppressed fluxes at energies below a PeV and (ii) a deficit of events in the direction of the Galactic center. We perform an extended unbinned likelihood analysis using the four-year high-energy starting event data set to constrain the strength of DM-neutrino interactions for two model classes. We find that, in spite of low statistics, IceCube can probe regions of the parameter space inaccessible to current cosmological methods.

Intergalactic Extinction of High Energy Gamma-Rays

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1998-01-01

We discuss the determination of the intergalactic pair-production absorption coefficient as derived by Stecker and De Jager by making use of a new empirically based calculation of the spectral energy distribution of the intergalactic infrared radiation field as given by Malkan and Stecker. We show that the results of the Malkan and Stecker calculation agree well with recent data on the infrared background. We then show that Whipple observations of the flaring gamma-ray spectrum of Mrk 421 hint at extragalactic absorption and that the HEGRA observations of the flaring spectrum of Mrk 501 appear to strongly indicate extragalactic absorption. We also discuss the determination of the y-ray opacity at higher redshifts, following the treatment of Salamon and Stecker. We give a predicted spectrum, with absorption included for PKS 2155-304. This XBL lies at a redshift of 0.12, the highest redshift source yet observed at an energy above 0.3 TeV. This source should have its spectrum steepened by approx. 1 in its spectral index between approx. 0.3 and approx. 3 TeV and should show an absorption cutoff above approx. 6 TeV.

New Theoretical Estimates of the Contribution of Unresolved Star-Forming Galaxies to the Extragalactic Gamma-Ray Background (EGB) as Measured by EGRET and the Fermi-LAT

NASA Technical Reports Server (NTRS)

Venters, Tonia M.

2011-01-01

We present new theoretical estimates of the contribution of unresolved star-forming galaxies to the extragalactic gamma-ray background (EGB) as measured by EGRET and the Fermi-LAT. We employ several methods for determining the star-forming galaxy contribution the the EGB, including a method positing a correlation between the gamma-ray luminosity of a galaxy and its rate of star formation as calculated from the total infrared luminosity, and a method that makes use of a model of the evolution of the galaxy gas mass with cosmic time. We find that depending on the model, unresolved star-forming galaxies could contribute significantly to the EGB as measured by the Fermi-LAT at energies between approx. 300 MeV and approx. few GeV. However, the overall spectrum of unresolved star-forming galaxies can explain neither the EGRET EGB spectrum at energies between 50 and 200 MeV nor the Fermi-LAT EGB spectrum at energies above approx. few GeV.

Chemical composition of the stellar cluster Gaia1: no surprise behind Sirius

NASA Astrophysics Data System (ADS)

Mucciarelli, A.; Monaco, L.; Bonifacio, P.; Saviane, I.

2017-07-01

We observed six He-clump stars of the intermediate-age stellar cluster Gaia1 with the MIKE/Magellan spectrograph. A possible extra-galactic origin of this cluster, recently discovered thanks to the first data release of the ESA Gaia mission, has been suggested, based on its orbital parameters. Abundances for Fe, α, proton- and neutron-capture elements have been obtained. We find no evidence of intrinsic abundance spreads. The iron abundance is solar ([FeI/H] = + 0.00 ± 0.01; σ = 0.03 dex). All the other abundance ratios are generally solar-scaled, similar to the Galactic thin disk and open cluster stars of similar metallicity. The chemical composition of Gaia1 does not support an extra-galactic origin for this stellar cluster, which can be considered as a standard Galactic open cluster. The full Table A.1 is 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/603/L7

A Planetary Companion around a Metal-Poor Star with Extragalactic Origin

NASA Astrophysics Data System (ADS)

Setiawan, Johny; Klement, Rainer; Henning, Thomas; Rix, Hans-Walter; Rochau, Boyke; Schulze-Hartung, Tim; Rodmann, Jens

2011-03-01

We report the detection of a planetary companion around HIP 13044, a metal-poor star on the red Horizontal Branch. The detection is based on radial velocity observations with FEROS, a high-resolution spectrograph at the 2.2-m MPG/ESO telescope, located at ESO La Silla observatory in Chile. The periodic radial velocity variation of P = 16.2 days can be distinguished from the periods of the stellar activity indicators. We computed a minimum planetary mass of 1.25 MJup and an orbital semi-major axis of 0.116 AU for the planet. This discovery is unique in three aspects: First, it is the first planet detection around a star with a metallicity much lower than few percent of the solar value; second, the planet host star resides in a stellar evolutionary stage that is still unexplored in the exoplanet surveys; third, the star HIP 13044 belongs to one of the most significant stellar halo streams in the solar neighborhood, implying an extragalactic origin of the planetary system HIP 13044 in a disrupted former satellite of the Milky Way.

Extragalactic chemistry of molecular gas: lessons from the local universe.

PubMed

García-Burillo, S; Fuente, A; Martín-Pintado, J; Usero, A; Graciá-Carpio, J; Planesas, P

2006-01-01

Observational constraints provided by high resolution and high sensitivity observations of external galaxies made in the millimetre and sub-millimetre range have started to put on a firm footing the study of the extragalactic chemistry of molecular gas. In particular, the availability of multi-species and multi-line surveys of nearby galaxies is central to the interpretation of existent and forthcoming millimetre observations of the high redshift universe. Probing the physical and chemical status of molecular gas in starbursts and active galaxies (AGN) requires the use of specific tracers of the relevant energetic phenomena that are known to be at play in these galaxies: large-scale shocks, strong UV fields, cosmic rays and X-rays. We present below the first results of an ongoing survey, allying the IRAM 30 m telescope with the Plateau de Bure interferometer (PdBI), devoted to the study of the chemistry of molecular gas in a sample of starbursts and AGN of the local universe. These observations highlight the existence of a strong chemical differentiation in the molecular disks of starbursts and AGN.

Linking HIPPARCOS to the Extragalactic Reference Frame Part 5 OF 6, Newc, Cycle 2,CONTINUATION of 2565-HIGH

NASA Astrophysics Data System (ADS)

Hemenway, Paul

1991-07-01

Determination of a non-rotating Reference Frame is crucial to progress in many areas, including: Galactic motions, local (Oort's A and B) and global (R0) parameters derived from them, solar system motion discrepancies (Planet X); and in conjunction with the VLBI radio reference frame, the registration of radio and optical images at an accuracy well below the resolution limit of HST images (0.06 arcsec). The goal of the Program is to tie the HIPPARCOS and Extra- galactic Reference Frames together at the 0.0005 arcsec and 0.0005 arcsec/year level. The HST data will allow a deter- mination of the brightness distribution in the stellar and extragalactic objects observed and time dependent changes therein at the 0.001 arcsec/year level. The Program requires targets distributed over the whole sky to define a rigid Reference Frame. GTO observations will provide initial first epoch data and preliminary proper motions. The observations will consist of relative positions of Extra- galactic objects (EGOs) and HIPPARCOS stars, measured with the FGSs.

The ALFALFA Extragalactic Catalog and Data Processing Pipeline

NASA Astrophysics Data System (ADS)

Kent, Brian R.; Haynes, Martha P.; Giovanelli, Riccardo; ALFALFA Team

2018-06-01

The Arecibo Legacy Fast ALFA 21cm HI Survey has reached completion. The observations and data are used by team members and the astronomical community in a variety of scientific initiatives with gas-rich galaxies, cluster environments, and studies of low redshift cosmology. The survey covers nearly 7000 square degrees of high galactic latitude sky visible from Arecibo, Puerto Rico and ~4400 hours of observations from 2005 to 2011. We present the extragalactic HI source catalog of over ~31,000 detections, their measured properties, and associated derived parameters. The observations were carefully reduced using a custom made data reduction pipeline and interface. Team members interacted with this pipeline through observation planning, calibration, imaging, source extraction, and cataloging. We describe this processing workflow as it pertains to the complexities of the single-dish multi-feed data reduction as well as known caveats of the source catalog and spectra for use in future astronomical studies and analysis. The ALFALFA team at Cornell has been supported by NSF grants AST-0607007, AST-1107390 and AST-1714828 and by grants from the Brinson Foundation.

Search for Dark Matter Annihilation in Galaxy Groups.

PubMed

Lisanti, Mariangela; Mishra-Sharma, Siddharth; Rodd, Nicholas L; Safdi, Benjamin R

2018-03-09

We use 413 weeks of publicly available Fermi Pass 8 gamma-ray data combined with recently developed galaxy group catalogs to search for evidence of dark matter annihilation in extragalactic halos. In our study, we use luminosity-based mass estimates and mass-to-concentration relations to infer the J factors and associated uncertainties for hundreds of galaxy groups within a redshift range z≲0.03. We employ a conservative substructure boost factor model, which only enhances the sensitivity by an O(1) factor. No significant evidence for dark matter annihilation is found, and we exclude thermal relic cross sections for dark matter masses below ∼30  GeV to 95% confidence in the bb[over ¯] annihilation channel. These bounds are comparable to those from Milky Way dwarf spheroidal satellite galaxies. The results of our analysis increase the tension but do not rule out the dark matter interpretation of the Galactic Center excess. We provide a catalog of the galaxy groups used in this study and their inferred properties, which can be broadly applied to searches for extragalactic dark matter.

Cosmography and Data Visualization

NASA Astrophysics Data System (ADS)

Pomarède, Daniel; Courtois, Hélène M.; Hoffman, Yehuda; Tully, R. Brent

2017-05-01

Cosmography, the study and making of maps of the universe or cosmos, is a field where visual representation benefits from modern three-dimensional visualization techniques and media. At the extragalactic distance scales, visualization is contributing to our understanding of the complex structure of the local universe in terms of spatial distribution and flows of galaxies and dark matter. In this paper, we report advances in the field of extragalactic cosmography obtained using the SDvision visualization software in the context of the Cosmicflows Project. Here, multiple visualization techniques are applied to a variety of data products: catalogs of galaxy positions and galaxy peculiar velocities, reconstructed velocity field, density field, gravitational potential field, velocity shear tensor viewed in terms of its eigenvalues and eigenvectors, envelope surfaces enclosing basins of attraction. These visualizations, implemented as high-resolution images, videos, and interactive viewers, have contributed to a number of studies: the cosmography of the local part of the universe, the nature of the Great Attractor, the discovery of the boundaries of our home supercluster of galaxies Laniakea, the mapping of the cosmic web, and the study of attractors and repellers.

Secular Extragalactic Parallax and Geometric Distances with Gaia Proper Motions

NASA Astrophysics Data System (ADS)

Paine, Jennie; Darling, Jeremiah K.

2018-06-01

The motion of the Solar System with respect to the cosmic microwave background (CMB) rest frame creates a well measured dipole in the CMB, which corresponds to a linear solar velocity of about 78 AU/yr. This motion causes relatively nearby extragalactic objects to appear to move compared to more distant objects, an effect that can be measured in the proper motions of nearby galaxies. An object at 1 Mpc and perpendicular to the CMB apex will exhibit a secular parallax, observed as a proper motion, of 78 µas/yr. The relatively large peculiar motions of galaxies make the detection of secular parallax challenging for individual objects. Instead, a statistical parallax measurement can be made for a sample of objects with proper motions, where the global parallax signal is modeled as an E-mode dipole that diminishes linearly with distance. We present preliminary results of applying this model to a sample of nearby galaxies with Gaia proper motions to detect the statistical secular parallax signal. The statistical measurement can be used to calibrate the canonical cosmological “distance ladder.”

VLBI-resolution radio-map algorithms: Performance analysis of different levels of data-sharing on multi-socket, multi-core architectures

NASA Astrophysics Data System (ADS)

Tabik, S.; Romero, L. F.; Mimica, P.; Plata, O.; Zapata, E. L.

2012-09-01

A broad area in astronomy focuses on simulating extragalactic objects based on Very Long Baseline Interferometry (VLBI) radio-maps. Several algorithms in this scope simulate what would be the observed radio-maps if emitted from a predefined extragalactic object. This work analyzes the performance and scaling of this kind of algorithms on multi-socket, multi-core architectures. In particular, we evaluate a sharing approach, a privatizing approach and a hybrid approach on systems with complex memory hierarchy that includes shared Last Level Cache (LLC). In addition, we investigate which manual processes can be systematized and then automated in future works. The experiments show that the data-privatizing model scales efficiently on medium scale multi-socket, multi-core systems (up to 48 cores) while regardless of algorithmic and scheduling optimizations, the sharing approach is unable to reach acceptable scalability on more than one socket. However, the hybrid model with a specific level of data-sharing provides the best scalability over all used multi-socket, multi-core systems.

Calibration of Post-AGB Supergiants as Standard Extragalactic Candles for HST

NASA Technical Reports Server (NTRS)

Bond, Howard E.

1998-01-01

This report summarizes activities carried out with support from the NASA Ultraviolet, Visible, and Gravitational Astrophysics Research and Analysis Program. The aim of the program is to calibrate the absolute magnitudes of post-asymptotic-giant-branch (post-AGB or PAGB) stars, which we believe will be an excellent new "standard candle" for measuring extragalactic distances. The reason for this belief is that in old populations, the stars that are evolving through the PAGB region of the HR (Hertzsprung-Russell) diagram arise from only a single main-sequence turnoff mass. In addition, the theoretical PAGB evolutionary tracks show that they evolve through this region at constant luminosity; hence the PAGB stars should have an extremely narrow luminosity function. Moreover, as the PAGB stars evolve through spectral types F and A (en route from the AGB to hot stellar remnants and white dwarfs), they have the highest luminosities attained by old stars (both bolometrically and in the visual band). Finally, the PAGB stars of these spectral types are very easily identified, due to their large Balmer jumps, which are due to their very low surface gravities.

Implications of Fermi-LAT observations on the origin of IceCube neutrinos

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

Wang, Bin; Li, Zhuo; Zhao, Xiaohong, E-mail: wang_b@pku.edu.cn, E-mail: zhaoxh@ynao.ac.cn, E-mail: zhuo.li@pku.edu.cn

2014-11-01

The IceCube (IC) collaboration recently reported the detection of TeV-PeV extraterrestrial neutrinos whose origin is yet unknown. By the photon-neutrino connection in pp and pγ interactions, we use the Fermi-LAT observations to constrain the origin of the IC detected neutrinos. We find that Galactic origins, i.e., the diffuse Galactic neutrinos due to cosmic ray (CR) propagation in the Milky Way, and the neutrinos from the Galactic point sources, may not produce the IC neutrino flux, thus these neutrinos should be of extragalactic origin. Moreover, the extragalactic gamma-ray bursts (GRBs) may not account for the IC neutrino flux, the jets ofmore » active galactic nuclei may not produce the IC neutrino spectrum, but the starburst galaxies (SBGs) may be promising sources. As suggested by the consistency between the IC detected neutrino flux and the Waxman-Bahcall bound, GRBs in SBGs may be the sources of both the ultrahigh energy, ∼> 10{sup 19}eV, CRs and the 1–100 PeV CRs that produce the IC detected TeV-PeV neutrinos.« less

Initial results from the extreme ultraviolet explorer

NASA Technical Reports Server (NTRS)

Bowyer, S.; Malina, R. F.

1993-01-01

Data obtained during the first five months of calibration and science operation of the Extreme Ultraviolet Explorer (EUVE) are presented. Spectra of an extragalactic object were obtained; the object is detectable to wavelenghts longer than 100 A, demonstrating that extragalactic EUV astronomy is possible. Spectra of a hot white dwarf, and a late-type star in quiescence and flaring are shown as examples of the type of spectrographic data obtainable with EUVE. Other objects for which broad band photometric mode data have been obtained and analyzed include an RS CVn star and several late-type stars. The backgrounds in the EUVE detectors are quite low and the character of the diffuse astronomical EUV background has been investigated using these very low rates. Evidence is presented showing that, contrary to previously published reports, EUVE is about three times more sensitive than the English Wide Field Camera in the short wavelength bandpass covered by both instruments. Only limited information has been extracted from the longer bandpasses coered only by EUVE. Nonetheless, the brightest EUV source in the sky, a B star, has been discovered and is detected only in these longer bandpasses.

Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos.

PubMed

Argüelles, Carlos A; Kheirandish, Ali; Vincent, Aaron C

2017-11-17

We show that the high-energy cosmic neutrinos seen by the IceCube Neutrino Observatory can be used to probe interactions between neutrinos and the dark sector that cannot be reached by current cosmological methods. The origin of the observed neutrinos is still unknown, and their arrival directions are compatible with an isotropic distribution. This observation, together with dedicated studies of Galactic plane correlations, suggests a predominantly extragalactic origin. Interactions between this isotropic extragalactic flux and the dense dark matter (DM) bulge of the Milky Way would thus lead to an observable imprint on the distribution, which would be seen by IceCube as (i) slightly suppressed fluxes at energies below a PeV and (ii) a deficit of events in the direction of the Galactic center. We perform an extended unbinned likelihood analysis using the four-year high-energy starting event data set to constrain the strength of DM-neutrino interactions for two model classes. We find that, in spite of low statistics, IceCube can probe regions of the parameter space inaccessible to current cosmological methods.

Effect of direct neuroradiologist participation in physician marketing on imaging volumes in outpatient radiology.

PubMed

Grignon, L; Keiper, M; Vavricek, J; Horsley, W; Murphy, R; Grignon, A; Yu, F

2014-08-01

Over the past several years, decreased demand for and increased supply of imaging services has increased competition among outpatient imaging centers in the United States. This study hypothesizes that using a radiology sales representative and neuroradiologist as a team in marketing and sales will increase imaging referrals in outpatient imaging. From January to December 2009, baseline monthly physician referral data of CT and MR scans of 19 referring clinicians (neurologists, neurosurgeons, and anesthesiologists) to an outpatient radiology group were collected. During that time, a nonphysician radiology sales representative visited the referring clinicians' offices every 2 weeks. From January to June 2010, the same radiology sales representative visited the referring clinicians' offices every 2 weeks but was accompanied by a neuroradiologist once a month. From July 2010 to June 2011, the same radiology sales representative visited the referring clinicians' offices twice a month without a neuroradiologist. Cross-sectional imaging referral volumes were approximately 2.5 times greater during the 6-month period using the neuroradiologist for direct physician-to-physician marketing when compared with the volumes achieved with the sales representative alone, and continued neuroradiologist involvement in marketing and sales is required to maintain referral volumes over time. The impact on imaging referral volumes during the 6-month use of the neuroradiologist for direct physician-to-physician marketing in this study supports the assertion that neuroradiologist visits are an important element in establishing and maintaining a relationship with the referring clinician's office and thereby maximizing imaging referrals. © 2014 by American Journal of Neuroradiology.

Effect of boundary conditions on the numerical solutions of representative volume element problems for random heterogeneous composite microstructures

NASA Astrophysics Data System (ADS)

Cho, Yi Je; Lee, Wook Jin; Park, Yong Ho

2014-11-01

Aspects of numerical results from computational experiments on representative volume element (RVE) problems using finite element analyses are discussed. Two different boundary conditions (BCs) are examined and compared numerically for volume elements with different sizes, where tests have been performed on the uniaxial tensile deformation of random particle reinforced composites. Structural heterogeneities near model boundaries such as the free-edges of particle/matrix interfaces significantly influenced the overall numerical solutions, producing force and displacement fluctuations along the boundaries. Interestingly, this effect was shown to be limited to surface regions within a certain distance of the boundaries, while the interior of the model showed almost identical strain fields regardless of the applied BCs. Also, the thickness of the BC-affected regions remained constant with varying volume element sizes in the models. When the volume element size was large enough compared to the thickness of the BC-affected regions, the structural response of most of the model was found to be almost independent of the applied BC such that the apparent properties converged to the effective properties. Finally, the mechanism that leads a RVE model for random heterogeneous materials to be representative is discussed in terms of the size of the volume element and the thickness of the BC-affected region.

15 CFR 10.6 - Procedures for acceptance of a recommended standard.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., divided by three. No consideration will be given to volume of production or volume of distribution in... who use or consume the product covered by the standard. (8) “Acceptance by volume of production” means.... The weighting of each response will be made in accordance with the volume of production represented by...

Detection of very high energy gamma-ray emission from the gravitationally lensed blazar QSO B0218+357 with the MAGIC telescopes

NASA Astrophysics Data System (ADS)

Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Arcaro, C.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Buson, S.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; de Oña Wilhelmi, E.; Di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D. F.; Toyama, T.; Treves, A.; Vanzo, G.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.; Desiante, R.

2016-11-01

Context. QSO B0218+357 is a gravitationally lensed blazar located at a redshift of 0.944. The gravitational lensing splits the emitted radiation into two components that are spatially indistinguishable by gamma-ray instruments, but separated by a 10-12 day delay. In July 2014, QSO B0218+357 experienced a violent flare observed by the Fermi-LAT and followed by the MAGIC telescopes. Aims: The spectral energy distribution of QSO B0218+357 can give information on the energetics of z 1 very high energy gamma-ray sources. Moreover the gamma-ray emission can also be used as a probe of the extragalactic background light at z 1. Methods: MAGIC performed observations of QSO B0218+357 during the expected arrival time of the delayed component of the emission. The MAGIC and Fermi-LAT observations were accompanied by quasi-simultaneous optical data from the KVA telescope and X-ray observations by Swift-XRT. We construct a multiwavelength spectral energy distribution of QSO B0218+357 and use it to model the source. The GeV and sub-TeV data obtained by Fermi-LAT and MAGIC are used to set constraints on the extragalactic background light. Results: Very high energy gamma-ray emission was detected from the direction of QSO B0218+357 by the MAGIC telescopes during the expected time of arrival of the trailing component of the flare, making it the farthest very high energy gamma-ray source detected to date. The observed emission spans the energy range from 65 to 175 GeV. The combined MAGIC and Fermi-LAT spectral energy distribution of QSO B0218+357 is consistent with current extragalactic background light models. The broadband emission can be modeled in the framework of a two-zone external Compton scenario, where the GeV emission comes from an emission region in the jet, located outside the broad line region.

Detection of very high energy gamma-ray emission from the gravitationally lensed blazar QSO B0218+357 with the MAGIC telescopes

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

Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.

QSO B0218+357 is a gravitationally lensed blazar located at a redshift of 0.944. The gravitational lensing splits the emitted radiation into two components that are spatially indistinguishable by gamma-ray instruments, but separated by a 10–12 day delay. In July 2014, QSO B0218+357 experienced a violent flare observed by the Fermi-LAT and followed by the MAGIC telescopes. The spectral energy distribution of QSO B0218+357 can give information on the energetics of z ~ 1 very high energy gamma-ray sources. Furthermore, the gamma-ray emission can also be used as a probe of the extragalactic background light at z ~ 1. MAGIC performedmore » observations of QSO B0218+357 during the expected arrival time of the delayed component of the emission. The MAGIC and Fermi-LAT observations were accompanied by quasi-simultaneous optical data from the KVA telescope and X-ray observations by Swift-XRT. We construct a multiwavelength spectral energy distribution of QSO B0218+357 and use it to model the source. The GeV and sub-TeV data obtained by Fermi-LAT and MAGIC are used to set constraints on the extragalactic background light. We detected very high energy gamma-ray emission from the direction of QSO B0218+357 by the MAGIC telescopes during the expected time of arrival of the trailing component of the flare, making it the farthest very high energy gamma-ray source detected to date. We also observed emission spans the energy range from 65 to 175 GeV. The combined MAGIC and Fermi-LAT spectral energy distribution of QSO B0218+357 is consistent with current extragalactic background light models. The broadband emission can be modeled in the framework of a two-zone external Compton scenario, where the GeV emission comes from an emission region in the jet, located outside the broad line region.« less

Studying extragalactic background fluctuations with the Cosmic Infrared Background ExpeRiment 2 (CIBER-2)

NASA Astrophysics Data System (ADS)

Lanz, Alicia; Arai, Toshiaki; Battle, John; Bock, James; Cooray, Asantha; Hristov, Viktor; Korngut, Phillip; Lee, Dae Hee; Mason, Peter; Matsumoto, Toshio; Matsuura, Shuji; Morford, Tracy; Onishi, Yosuke; Shirahata, Mai; Tsumura, Kohji; Wada, Takehiko; Zemcov, Michael

2014-08-01

Fluctuations in the extragalactic background light trace emission from the history of galaxy formation, including the emission from the earliest sources from the epoch of reionization. A number of recent near-infrared measure- ments show excess spatial power at large angular scales inconsistent with models of z < 5 emission from galaxies. These measurements have been interpreted as arising from either redshifted stellar and quasar emission from the epoch of reionization, or the combined intra-halo light from stars thrown out of galaxies during merging activity at lower redshifts. Though astrophysically distinct, both interpretations arise from faint, low surface brightness source populations that are difficult to detect except by statistical approaches using careful observations with suitable instruments. The key to determining the source of these background anisotropies will be wide-field imaging measurements spanning multiple bands from the optical to the near-infrared. The Cosmic Infrared Background ExpeRiment 2 (CIBER-2) will measure spatial anisotropies in the extra- galactic infrared background caused by cosmological structure using six broad spectral bands. The experiment uses three 2048 x 2048 Hawaii-2RG near-infrared arrays in three cameras coupled to a single 28.5 cm telescope housed in a reusable sounding rocket-borne payload. A small portion of each array will also be combined with a linear-variable filter to make absolute measurements of the spectrum of the extragalactic background with high spatial resolution for deep subtraction of Galactic starlight. The large field of view and multiple spectral bands make CIBER-2 unique in its sensitivity to fluctuations predicted by models of lower limits on the luminosity of the first stars and galaxies and in its ability to distinguish between primordial and foreground anisotropies. In this paper the scientific motivation for CIBER-2 and details of its first flight instrumentation will be discussed, including detailed designs of the mechanical, cryogenic, and electrical systems. Plans for the future will also be presented.

Observing the Non-Thermal Universe with the Highest Energy Photons

NASA Astrophysics Data System (ADS)

Dingus, Brenda L.; HAWC, VERITAS, CTA

2016-01-01

Astrophysical sources of relativistic particles radiate gamma rays to such high energies that they can be detected from the ground. The existence of high energy gamma rays implies that even higher energy particles are being accelerated placing strong constraints on these non-thermal accelerators. Within our galaxy, TeV gamma rays have been detected from supernova remnants, pulsar wind nebula, x-ray binaries and some yet to be identified sources in the Galactic plane. In addition, these gamma rays have sufficient energy to be attenuated by the interaction with infrared photons producing an electron-positron pair. Thus the spectrum of gamma rays can also constrain the infrared photon density, which for distant extragalactic sources is a direct probe of cosmology. The known extragalactic TeV sources are primarily the blazer class of active galactic nuclei. And TeV gamma rays might even be produced by annihilating dark matter.The US currently supports two ground-based gamma-ray observatories—HAWC and VERITAS—and NSF is developing a prototype for the international Cherenkov Telescope Array (CTA) observatory. The HAWC (High Altitude Water Cherenkov) observatory just began operation of the full detector in March 2015 and with its wide field of view scans ~2/3 of the sky each day for TeV sources. VERITAS (Very EneRgetic Imaging Telescope Array System) is an array of four imaging atmospheric Cherenkov telescopes that follows individual sources to produce lightcurves and spectra from 85 GeV to > 30 TeV. The combination of both a survey and pointed observatory is very complementary with a broad scientific reach that includes the study of extragalactic and Galactic objects as well as the search for astrophysical signatures of dark matter and the measurement of cosmic rays. I will present the current view of the TeV sky and the latest results from HAWC and VERITAS as well as plans for CTA.

Resolving the Extragalactic γ-Ray Background above 50 GeV with the Fermi Large Area Telescope.

PubMed

Ackermann, M; Ajello, M; Albert, A; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Bissaldi, E; Blandford, R D; Bloom, E D; Bonino, R; Bregeon, J; Britto, R J; Bruel, P; Buehler, R; Caliandro, G A; Cameron, R A; Caragiulo, M; Caraveo, P A; Cavazzuti, E; Cecchi, C; Charles, E; Chekhtman, A; Chiang, J; Chiaro, G; Ciprini, S; Cohen-Tanugi, J; Cominsky, L R; Costanza, F; Cutini, S; D'Ammando, F; de Angelis, A; de Palma, F; Desiante, R; Digel, S W; Di Mauro, M; Di Venere, L; Domínguez, A; Drell, P S; Favuzzi, C; Fegan, S J; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giommi, P; Giordano, F; Giroletti, M; Godfrey, G; Green, D; Grenier, I A; Guiriec, S; Hays, E; Horan, D; Iafrate, G; Jogler, T; Jóhannesson, G; Kuss, M; La Mura, G; Larsson, S; Latronico, L; Li, J; Li, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Magill, J; Maldera, S; Manfreda, A; Mayer, M; Mazziotta, M N; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Negro, M; Nuss, E; Ohsugi, T; Okada, C; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Perkins, J S; Pesce-Rollins, M; Petrosian, V; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Reposeur, T; Romani, R W; Sánchez-Conde, M; Schmid, J; Schulz, A; Sgrò, C; Simone, D; Siskind, E J; Spada, F; Spandre, G; Spinelli, P; Suson, D J; Takahashi, H; Thayer, J B; Tibaldo, L; Torres, D F; Troja, E; Vianello, G; Yassine, M; Zimmer, S

2016-04-15

The Fermi Large Area Telescope (LAT) Collaboration has recently released a catalog of 360 sources detected above 50 GeV (2FHL). This catalog was obtained using 80 months of data re-processed with Pass 8, the newest event-level analysis, which significantly improves the acceptance and angular resolution of the instrument. Most of the 2FHL sources at high Galactic latitude are blazars. Using detailed Monte Carlo simulations, we measure, for the first time, the source count distribution, dN/dS, of extragalactic γ-ray sources at E>50  GeV and find that it is compatible with a Euclidean distribution down to the lowest measured source flux in the 2FHL (∼8×10^{-12}  ph cm^{-2} s^{-1}). We employ a one-point photon fluctuation analysis to constrain the behavior of dN/dS below the source detection threshold. Overall, the source count distribution is constrained over three decades in flux and found compatible with a broken power law with a break flux, S_{b}, in the range [8×10^{-12},1.5×10^{-11}]  ph cm^{-2} s^{-1} and power-law indices below and above the break of α_{2}∈[1.60,1.75] and α_{1}=2.49±0.12, respectively. Integration of dN/dS shows that point sources account for at least 86_{-14}^{+16}% of the total extragalactic γ-ray background. The simple form of the derived source count distribution is consistent with a single population (i.e., blazars) dominating the source counts to the minimum flux explored by this analysis. We estimate the density of sources detectable in blind surveys that will be performed in the coming years by the Cherenkov Telescope Array.

Detection of very high energy gamma-ray emission from the gravitationally lensed blazar QSO B0218+357 with the MAGIC telescopes

DOE PAGES

Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; ...

2016-11-04

QSO B0218+357 is a gravitationally lensed blazar located at a redshift of 0.944. The gravitational lensing splits the emitted radiation into two components that are spatially indistinguishable by gamma-ray instruments, but separated by a 10–12 day delay. In July 2014, QSO B0218+357 experienced a violent flare observed by the Fermi-LAT and followed by the MAGIC telescopes. The spectral energy distribution of QSO B0218+357 can give information on the energetics of z ~ 1 very high energy gamma-ray sources. Furthermore, the gamma-ray emission can also be used as a probe of the extragalactic background light at z ~ 1. MAGIC performedmore » observations of QSO B0218+357 during the expected arrival time of the delayed component of the emission. The MAGIC and Fermi-LAT observations were accompanied by quasi-simultaneous optical data from the KVA telescope and X-ray observations by Swift-XRT. We construct a multiwavelength spectral energy distribution of QSO B0218+357 and use it to model the source. The GeV and sub-TeV data obtained by Fermi-LAT and MAGIC are used to set constraints on the extragalactic background light. We detected very high energy gamma-ray emission from the direction of QSO B0218+357 by the MAGIC telescopes during the expected time of arrival of the trailing component of the flare, making it the farthest very high energy gamma-ray source detected to date. We also observed emission spans the energy range from 65 to 175 GeV. The combined MAGIC and Fermi-LAT spectral energy distribution of QSO B0218+357 is consistent with current extragalactic background light models. The broadband emission can be modeled in the framework of a two-zone external Compton scenario, where the GeV emission comes from an emission region in the jet, located outside the broad line region.« less

Resolving the Extragalactic γ -Ray Background above 50 GeV with the Fermi Large Area Telescope

DOE PAGES

Ackermann, M.; Ajello, M.; Albert, A.; ...

2016-04-14

The Fermi Large Area Telescope (LAT) Collaboration has recently released a catalog of 360 sources detected above 50 GeV (2FHL). This catalog was obtained using 80 months of data re-processed with Pass 8, the newest event-level analysis, which significantly improves the acceptance and angular resolution of the instrument. Most of the 2FHL sources at high Galactic latitude are blazars. In this paper, using detailed Monte Carlo simulations, we measure, for the first time, the source count distribution, dN/dS, of extragalactic γ-ray sources at E > 50 GeV and find that it is compatible with a Euclidean distribution down to the lowest measured source flux in the 2FHL (~8 x 10 -12 ph cm -2s -1). We employ a one-point photon fluctuation analysis to constrain the behavior of dN/dS below the source detection threshold. Overall, the source count distribution is constrained over three decades in flux and found compatible with a broken power law with a break flux, S b, in the range [8 x 10 -12, 1.5 x 10 -11] ph cm -2s -1 and power-law indices below and above the break of α 2 ϵ [1.60, 1.75] and α 1 = 2.49 ± 0.12, respectively. Integration of dN/dS shows that point sources account for at least 86more » $$+16\\atop{-14}$$ % of the total extragalactic γ-ray background. The simple form of the derived source count distribution is consistent with a single population (i.e., blazars) dominating the source counts to the minimum flux explored by this analysis. Finally, we estimate the density of sources detectable in blind surveys that will be performed in the coming years by the Cherenkov Telescope Array.« less

The LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap. I. The Spectroscopic Redshift Catalog

NASA Astrophysics Data System (ADS)

Yang, Ming; Wu, Hong; Yang, Fan; Lam, Man I.; Cao, Tian-Wen; Wu, Chao-Jian; Zhao, Pin-Song; Zhang, Tian-Meng; Zhou, Zhi-Min; Wu, Xue-Bing; Zhang, Yan-Xia; Shao, Zheng-Yi; Jing, Yi-Peng; Shen, Shi-Yin; Zhu, Yi-Nan; Du, Wei; Lei, Feng-Jie; He, Min; Jin, Jun-Jie; Shi, Jian-Rong; Zhang, Wei; Wang, Jian-Ling; Wu, Yu-Zhong; Zhang, Hao-Tong; Luo, A.-Li; Yuan, Hai-Long; Bai, Zhong-Rui; Kong, Xu; Gu, Qiu-Sheng; Zhou, Xu; Ma, Jun; Hu, Zou; Nie, Jun-Dan; Wang, Jia-Li; Zhang, Yong; Hou, Yong-Hui; Zhao, Yong-Heng

2018-01-01

We present a spectroscopic redshift catalog from the LAMOST Complete Spectroscopic Survey of Pointing Area (LaCoSSPAr) in the Southern Galactic Cap (SGC), which is designed to observe all sources (Galactic and extragalactic) by using repeating observations with a limiting magnitude of r=18.1 {mag} in two 20 {\\deg }2 fields. The project is mainly focusing on the completeness of LAMOST ExtraGAlactic Surveys (LEGAS) in the SGC, the deficiencies of source selection methods, and the basic performance parameters of the LAMOST telescope. In both fields, more than 95% of galaxies have been observed. A post-processing has been applied to the LAMOST 1D spectrum to remove the majority of remaining sky background residuals. More than 10,000 spectra have been visually inspected to measure the redshift by using combinations of different emission/absorption features with an uncertainty of {σ }z/(1+z)< 0.001. In total, 1528 redshifts (623 absorption and 905 emission line galaxies) in Field A and 1570 redshifts (569 absorption and 1001 emission line galaxies) in Field B have been measured. The results show that it is possible to derive redshift from low S/N galaxies with our post-processing and visual inspection. Our analysis also indicates that up to one-fourth of the input targets for a typical extragalactic spectroscopic survey might be unreliable. The multi-wavelength data analysis shows that the majority of mid-infrared-detected absorption (91.3%) and emission line galaxies (93.3%) can be well separated by an empirical criterion of W2-W3=2.4. Meanwhile, a fainter sequence paralleled to the main population of galaxies has been witnessed both in M r /W2-W3 and M */W2-W3 diagrams, which could be the population of luminous dwarf galaxies but contaminated by the edge-on/highly inclined galaxies (∼ 30 % ).

Ray Casting of Large Multi-Resolution Volume Datasets

NASA Astrophysics Data System (ADS)

Lux, C.; Fröhlich, B.

2009-04-01

High quality volume visualization through ray casting on graphics processing units (GPU) has become an important approach for many application domains. We present a GPU-based, multi-resolution ray casting technique for the interactive visualization of massive volume data sets commonly found in the oil and gas industry. Large volume data sets are represented as a multi-resolution hierarchy based on an octree data structure. The original volume data is decomposed into small bricks of a fixed size acting as the leaf nodes of the octree. These nodes are the highest resolution of the volume. Coarser resolutions are represented through inner nodes of the hierarchy which are generated by down sampling eight neighboring nodes on a finer level. Due to limited memory resources of current desktop workstations and graphics hardware only a limited working set of bricks can be locally maintained for a frame to be displayed. This working set is chosen to represent the whole volume at different local resolution levels depending on the current viewer position, transfer function and distinct areas of interest. During runtime the working set of bricks is maintained in CPU- and GPU memory and is adaptively updated by asynchronously fetching data from external sources like hard drives or a network. The CPU memory hereby acts as a secondary level cache for these sources from which the GPU representation is updated. Our volume ray casting algorithm is based on a 3D texture-atlas in GPU memory. This texture-atlas contains the complete working set of bricks of the current multi-resolution representation of the volume. This enables the volume ray casting algorithm to access the whole working set of bricks through only a single 3D texture. For traversing rays through the volume, information about the locations and resolution levels of visited bricks are required for correct compositing computations. We encode this information into a small 3D index texture which represents the current octree subdivision on its finest level and spatially organizes the bricked data. This approach allows us to render a bricked multi-resolution volume data set utilizing only a single rendering pass with no loss of compositing precision. In contrast most state-of-the art volume rendering systems handle the bricked data as individual 3D textures, which are rendered one at a time while the results are composited into a lower precision frame buffer. Furthermore, our method enables us to integrate advanced volume rendering techniques like empty-space skipping, adaptive sampling and preintegrated transfer functions in a very straightforward manner with virtually no extra costs. Our interactive volume ray tracing implementation allows high quality visualizations of massive volume data sets of tens of Gigabytes in size on standard desktop workstations.

ULTRA STEEP SPECTRUM RADIO SOURCES IN THE LOCKMAN HOLE: SERVS IDENTIFICATIONS AND REDSHIFT DISTRIBUTION AT THE FAINTEST RADIO FLUXES

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

Afonso, J.; Bizzocchi, L.; Grossi, M.

2011-12-20

Ultra steep spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z {approx}> 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here a first detailed analysis of the nature of the faintest USS sources is presented. By using Giant Metrewave Radio Telescope and Very Large Array radio observations of the Lockman Hole at 610 MHz and 1.4 GHz, a sample of 58 USS sources, with 610more » MHz integrated fluxes above 100 {mu}Jy, is assembled. Deep infrared data at 3.6 and 4.5 {mu}m from the Spitzer Extragalactic Representative Volume Survey (SERVS) are used to reliably identify counterparts for 48 (83%) of these sources, showing an average total magnitude of [3.6]{sub AB} = 19.8 mag. Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z = 0.1 to z = 2.8, peaking at z {approx} 0.6 and tailing off at high redshifts. The remaining 25 USS sources, with no redshift estimate, include the faintest [3.6] magnitudes, with 10 sources undetected at 3.6 and 4.5 {mu}m (typically [3.6] {approx}> 22-23 mag from local measurements), which suggests the likely existence of higher redshifts among the sub-mJy USS population. The comparison with the Square Kilometre Array Design Studies Simulated Skies models indicates that Fanaroff-Riley type I radio sources and radio-quiet active galactic nuclei may constitute the bulk of the faintest USS population, and raises the possibility that the high efficiency of the USS technique for the selection of high-redshift sources remains even at the sub-mJy level.« less

In Defense of the Alien. Volume IV. U.S. Immigration Today. Proceedings of the Annual National Legal Conference (Washington, D.C., March 26-27, 1981).

ERIC Educational Resources Information Center

Tomasi, Lydio F., Ed.; And Others

This volume presents viewpoints of government representatives, legal experts, economists, and private sector representatives on recommendations for reforms in U.S. immigration policy and legislation submitted to the President and to Congress by the Select Commission on Immigration and Refugee Policy. Included are: (1) a report of issues considered…

Ambient occlusion effects for combined volumes and tubular geometry.

PubMed

Schott, Mathias; Martin, Tobias; Grosset, A V Pascal; Smith, Sean T; Hansen, Charles D

2013-06-01

This paper details a method for interactive direct volume rendering that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube-shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The algorithm extends the recently presented the directional occlusion shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry. Stream tube geometries are computed using an effective spline-based interpolation and approximation scheme that avoids self-intersection and maintains coherent orientation of the stream tube segments to avoid surface deforming twists. Furthermore, strategies to reduce the geometric and specular aliasing of the stream tubes are discussed.

Ambient Occlusion Effects for Combined Volumes and Tubular Geometry

PubMed Central

Schott, Mathias; Martin, Tobias; Grosset, A.V. Pascal; Smith, Sean T.; Hansen, Charles D.

2013-01-01

This paper details a method for interactive direct volume rendering that computes ambient occlusion effects for visualizations that combine both volumetric and geometric primitives, specifically tube-shaped geometric objects representing streamlines, magnetic field lines or DTI fiber tracts. The algorithm extends the recently presented the directional occlusion shading model to allow the rendering of those geometric shapes in combination with a context providing 3D volume, considering mutual occlusion between structures represented by a volume or geometry. Stream tube geometries are computed using an effective spline-based interpolation and approximation scheme that avoids self-intersection and maintains coherent orientation of the stream tube segments to avoid surface deforming twists. Furthermore, strategies to reduce the geometric and specular aliasing of the stream tubes are discussed. PMID:23559506

Describing the observed cosmic neutrinos by interactions of nuclei with matter

NASA Astrophysics Data System (ADS)

Winter, Walter

2014-11-01

IceCube has observed neutrinos that are presumably of extra-Galactic origin. Since specific sources have not yet been identified, we discuss what could be learned from the conceptual point of view. We use a simple model for neutrino production from the interactions between nuclei and matter, and we focus on the description of the spectral shape and flavor composition observed by IceCube. Our main parameters are the spectral index, maximal energy, magnetic field, and composition of the accelerated nuclei. We show that a cutoff at PeV energies can be achieved by soft enough spectra, a cutoff of the primary energy, or strong enough magnetic fields. These options, however, are difficult to reconcile with the hypothesis that these neutrinos originate from the same sources as the ultrahigh-energy cosmic rays. We demonstrate that heavier nuclei accelerated in the sources may be a possible way out if the maximal energy scales appropriately with the mass number of the nuclei. In this scenario, neutrino observations can actually be used to test the ultrahigh-energy cosmic ray acceleration mechanism. We also emphasize the need for a volume upgrade of the IceCube detector for future precision physics, for which the flavor information becomes a statistically meaningful model discriminator as well as a qualitatively new ingredient.

H I-to-H2 Transition Layers in the Star-forming Region W43

NASA Astrophysics Data System (ADS)

Bialy, Shmuel; Bihr, Simon; Beuther, Henrik; Henning, Thomas; Sternberg, Amiel

2017-02-01

The process of atomic-to-molecular (H I-to-H2) gas conversion is fundamental for molecular-cloud formation and star formation. 21 cm observations of the star-forming region W43 revealed extremely high H I column densities, of 120-180 {M}⊙ {{pc}}-2, a factor of 10-20 larger than predicted by H I-to-H2 transition theories. We analyze the observed H I with a theoretical model of the H I-to-H2 transition, and show that the discrepancy between theory and observation cannot be explained by the intense radiation in W43, nor be explained by variations of the assumed volume density or H2 formation rate coefficient. We show that the large observed H I columns are naturally explained by several (9-22) H I-to-H2 transition layers, superimposed along the sightlines of W43. We discuss other possible interpretations such as a non-steady-state scenario and inefficient dust absorption. The case of W43 suggests that H I thresholds reported in extragalactic observations are probably not associated with a single H I-to-H2 transition, but are rather a result of several transition layers (clouds) along the sightlines, beam-diluted with diffuse intercloud gas.

Phase relationship in three-phase composites which include a void phase

NASA Technical Reports Server (NTRS)

Price, H. L.; Nelson, J. B.

1976-01-01

The paper shows the relationship among polymer, particles, and voids in a three-phase composite and how some of the properties of a composite may be changed by changing the proportions of the phases. The three-phase composite is an aggregate of microspheres bonded together with a small amount of polymer which may not form a continuous matrix. The void space (third phase) is obtained by limiting the amount of polymer which is mixed with the microspheres. A ternary phase diagram is used to show the proportional relationship among the three phases, with each apex representing a volume fraction of unity for a constituent while the side opposite the apex represents a volume fraction of zero for that constituent. The vertical dimension represents some composite property such as density or strength. The effect of composition on composite properties is shown by plotting them on a binary phase diagram which represents a perpendicular plane coincident with the 0.60 volume fraction microsphere line.

78 FR 7467 - Self-Regulatory Organizations; Chicago Board Options Exchange, Incorporated; Notice of Filing and...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-02-01

... Effectiveness of a Proposed Rule Change Relating to Minimum Volume Orders January 28, 2013. Pursuant to Section... to codify the ``Minimum Volume Order.'' The text of the proposed rule change is provided below... Circular. (a)-(v) No changes. (w) Minimum Volume Order. A minimum volume order is an order represented in...

Statistical representative elementary volumes of porous media determined using greyscale analysis of 3D tomograms

NASA Astrophysics Data System (ADS)

Bruns, S.; Stipp, S. L. S.; Sørensen, H. O.

2017-09-01

Digital rock physics carries the dogmatic concept of having to segment volume images for quantitative analysis but segmentation rejects huge amounts of signal information. Information that is essential for the analysis of difficult and marginally resolved samples, such as materials with very small features, is lost during segmentation. In X-ray nanotomography reconstructions of Hod chalk we observed partial volume voxels with an abundance that limits segmentation based analysis. Therefore, we investigated the suitability of greyscale analysis for establishing statistical representative elementary volumes (sREV) for the important petrophysical parameters of this type of chalk, namely porosity, specific surface area and diffusive tortuosity, by using volume images without segmenting the datasets. Instead, grey level intensities were transformed to a voxel level porosity estimate using a Gaussian mixture model. A simple model assumption was made that allowed formulating a two point correlation function for surface area estimates using Bayes' theory. The same assumption enables random walk simulations in the presence of severe partial volume effects. The established sREVs illustrate that in compacted chalk, these simulations cannot be performed in binary representations without increasing the resolution of the imaging system to a point where the spatial restrictions of the represented sample volume render the precision of the measurement unacceptable. We illustrate this by analyzing the origins of variance in the quantitative analysis of volume images, i.e. resolution dependence and intersample and intrasample variance. Although we cannot make any claims on the accuracy of the approach, eliminating the segmentation step from the analysis enables comparative studies with higher precision and repeatability.

Extragalactic Radio Sources: Rapid Variability at 90 GHz.

DTIC Science & Technology

1983-12-15

34 Nature 269, 493-494. 37. Kellermann, K. I. (1974). "Detection of a Strong and Possibly Variable Compact Millimeter Wave Component in Centaurus A...Quasi-periodic Bursts in the Nucleus of Centaurus A at -wavelengths," Mon. Not. R. Astron. Soc. 187, 23P-28P. 40. DuPuy, D., Schmitt, J., McClure, R

The Universe at Ultraviolet Wavelengths: The first two years of International Ultraviolet Explorer

NASA Technical Reports Server (NTRS)

Chapman, R. D. (Editor)

1981-01-01

Highlights of the results obtained from the IUE satellite are addressed. specific topics discussed include the solar system, O-A stars, F-M stars, binary stars and highly evolved objects, nebulae and interstellar medium, and extragalactic objects. Data reduction techniques employed in the analysis of the varied data are also discussed.

MASYS: The AKARI Spectroscopic Survey of Symbiotic Stars in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Angeloni, R.; Ciroi, S.; Marigo, P.; Contini, M.; Di Mille, F.; Rafanelli, P.

2009-12-01

MASYS is the AKARI spectroscopic survey of Symbiotic Stars in the Magellanic Clouds, and one of the European Open Time Observing Programmes approved for the AKARI (Post-Helium) Phase-3. It is providing the first ever near-IR spectra of extragalactic symbiotic stars. The observations are scheduled to be completed in July 2009.

Scientific Research with the Space Telescope: International Astronomical Union Colloquium No. 54. [conferences

NASA Technical Reports Server (NTRS)

Longair, M. S.; Warner, J. W.

1979-01-01

The application of the space telescope for extragalactic astronomy, planetary research, and stellar, interstellar, and galactic structural problems is discussed. Topics include investigations of small solar system objects, the physical characteristics of ionized gaseous nebulae, the central regions of active galaxies and quasars, problems of cosmology, and the distribution and composition of interstellar matter.

Methods and computer executable instructions for rapidly calculating simulated particle transport through geometrically modeled treatment volumes having uniform volume elements for use in radiotherapy

DOEpatents

Frandsen, Michael W.; Wessol, Daniel E.; Wheeler, Floyd J.

2001-01-16

Methods and computer executable instructions are disclosed for ultimately developing a dosimetry plan for a treatment volume targeted for irradiation during cancer therapy. The dosimetry plan is available in "real-time" which especially enhances clinical use for in vivo applications. The real-time is achieved because of the novel geometric model constructed for the planned treatment volume which, in turn, allows for rapid calculations to be performed for simulated movements of particles along particle tracks there through. The particles are exemplary representations of neutrons emanating from a neutron source during BNCT. In a preferred embodiment, a medical image having a plurality of pixels of information representative of a treatment volume is obtained. The pixels are: (i) converted into a plurality of substantially uniform volume elements having substantially the same shape and volume of the pixels; and (ii) arranged into a geometric model of the treatment volume. An anatomical material associated with each uniform volume element is defined and stored. Thereafter, a movement of a particle along a particle track is defined through the geometric model along a primary direction of movement that begins in a starting element of the uniform volume elements and traverses to a next element of the uniform volume elements. The particle movement along the particle track is effectuated in integer based increments along the primary direction of movement until a position of intersection occurs that represents a condition where the anatomical material of the next element is substantially different from the anatomical material of the starting element. This position of intersection is then useful for indicating whether a neutron has been captured, scattered or exited from the geometric model. From this intersection, a distribution of radiation doses can be computed for use in the cancer therapy. The foregoing represents an advance in computational times by multiple factors of time magnitudes.

Gender and Education. An Encyclopedia. Volume II

ERIC Educational Resources Information Center

Bank, Barbara J., Ed.

2007-01-01

This book represents the second of two volumes in a two-volume set where educators explore the intersection of gender and education. Their entries deal with educational theories, research, curricula, practices, personnel, and policies, but also with variations in the gendering of education across historical and cultural contexts. The various…

Cross-sectional changes in lung volume measured by electrical impedance tomography are representative for the whole lung in ventilated preterm infants.

PubMed

van der Burg, Pauline S; Miedema, Martijn; de Jongh, Frans H; Frerichs, Inez; van Kaam, Anton H

2014-06-01

Electrical impedance tomography measures lung volume in a cross-sectional slice of the lung. Whether these cross-sectional volume changes are representative of the whole lung has only been investigated in adults, showing conflicting results. This study aimed to compare cross-sectional and whole lung volume changes using electrical impedance tomography and respiratory inductive plethysmography. A prospective, single-center, observational, nonrandomized study. The study was conducted in a neonatal ICU in the Netherlands. High-frequency ventilated preterm infants with respiratory distress syndrome. Cross-sectional and whole lung volume changes were continuously and simultaneously measured by, respectively, electrical impedance tomography and respiratory inductive plethysmography during a stepwise recruitment procedure. End-expiratory lung volume changes were assessed by mapping the inflation and deflation limbs using both the pressure/impedance and pressure/inductance pairs and characterized by calculating the inflection points. In addition, oscillatory tidal volume changes were assessed at each pressure step. Twenty-three infants were included in the study. Of these, eight infants had to be excluded because the quality of the registration was insufficient for analysis (two electrical impedance tomography and six respiratory inductive plethysmography). In the remaining 15 infants (gestational age 28.0 ± 2.6 wk; birth weight 1,027 ± 514 g), end-expiratory lung volume changes measured by electrical impedance tomography were significantly correlated to respiratory inductive plethysmography measurements in 12 patients (mean r = 0.93 ± 0.05). This was also true for the upper inflection point on the inflation (r = 0.91, p < 0.01) and deflation limb (r = 0.83, p < 0.01). In 13 patients, impedance and inductance data also correlated significantly on oscillatory tidal volume/pressure relationships (mean r = 0.81 ± 0.18). This study shows that cross-sectional lung volume changes measured by electrical impedance tomography are representative for the whole lung and that this concept also applies to newborn infants.

Plasma volume status predicts prognosis in patients with acute heart failure syndromes.

PubMed

Yoshihisa, Akiomi; Abe, Satoshi; Sato, Yu; Watanabe, Shunsuke; Yokokawa, Tetsuro; Miura, Shunsuke; Misaka, Tomofumi; Sato, Takamasa; Suzuki, Satoshi; Oikawa, Masayoshi; Kobayashi, Atsushi; Yamaki, Takayoshi; Kunii, Hiroyuki; Saitoh, Shu-Ichi; Takeishi, Yasuchika

2017-01-01

The intravascular compartment is known as the plasma volume, and the extravascular compartment represents fluid within the interstitial space. Plasma volume expansion is a major symptom of heart failure. The aim of the current study was to investigate the impact of plasma volume status on the prognosis of acute heart failure syndromes. We analyzed 1115 patients with acute heart failure syndromes who were admitted to our hospital. These patients were divided into three groups based on their plasma volume status at admission: first tertile (plasma volume status <41.9%, n = 371), second tertile (41.9%⩽ plasma volume status <49.0%, n = 372), and third tertile (49.0%⩽ plasma volume status, n = 372). Plasma volume status was defined as follows: actual plasma volume = (1 - hematocrit) × [ a + ( b × body weight)] ( a=1530 in males and a=864 in females, b=41.0 in males and b=47.9 in females); ideal plasma volume = c × body weight ( c=39 in males and c=40 in females); and plasma volume status = [(actual plasma volume - ideal plasma volume)/ideal plasma volume] × 100 (%). In the Kaplan-Meier analysis, all-cause mortality, cardiac mortality and cardiac events increased progressively from the first to third tertile ( p <0.001, respectively). In the Cox proportional hazard analysis, after adjusting for potential confounding factors, plasma volume status was an independent predictor of all-cause mortality (hazard ratio 1.429, p < 0.001), cardiac mortality (hazard ratio 1.416, p = 0.001) and cardiac events (hazard ratio 1.207, p = 0.004). Increased congestion is associated with increased morbidity and mortality in heart failure patients. Plasma volume status, which represents intravascular compartment and congestion, can identify poor prognosis in patients with acute heart failure syndromes.

GLAST and Suzaku

NASA Technical Reports Server (NTRS)

Sambruna, Rita

2007-01-01

The upcoming years will see a formidable synergy of high-energy observatories for the study of extragalactic objects, especially AGN. In particular, the launch of GLAST will allow us coordinated monitoring of sources with Suzaku over a very large energy band, from medium X-rays to GeV energies. In this talk I will review the science issues that such a remarkable coverage will enable us to address.

Gamma ray cosmology: The extra galactic gamma spectrum and methods to detect the underlying source

NASA Technical Reports Server (NTRS)

Cline, David B.

1990-01-01

The possible sources of extragalactic gamma rays and methods to distinguish the different sources are discussed. The sources considered are early universe decays and annihilation of Particles, active galactic nuclei (AGN) sources, and baryon-antibaryon annihilation in a baryon symmetric cosmology. The energy spectrum and possible angular fluctuations due to these sources are described.

Accurate Measurements of the Local Deuterium Abundance from HST Spectra

NASA Technical Reports Server (NTRS)

Linsky, Jeffrey L.

1996-01-01

An accurate measurement of the primordial value of D/H would provide a critical test of nucleosynthesis models for the early universe and the baryon density. I briefly summarize the ongoing HST observations of the interstellar H and D Lyman-alpha absorption for lines of sight to nearby stars and comment on recent reports of extragalactic D/H measurements.

The joint NASA/Goddard-University of Maryland research program in charged particle and high energy photon detector technology

NASA Technical Reports Server (NTRS)

1986-01-01

Progress made in the following areas is discussed: low energy ion and electron experiments; instrument design for current experiments; magnetospheric measurement of particles; ion measurement in the earth plasma sheet; abundance measurement; X-ray data acquisition; high energy physics; extragalactic astronomy; compact object astrophysics; planetology; and high energy photon detector technology.

HI-bearing Ultra Diffuse Galaxies in the ALFALFA Survey

NASA Astrophysics Data System (ADS)

Leisman, Lukas; Janowiecki, Steven; Jones, Michael G.; ALFALFA Almost Darks Team

2018-01-01

The Arecibo Legacy Fast ALFA (Arecibo L-band Feed Array) extragalactic HI survey, with over 30,000 high significance extragalactic sources, is well positioned to locate gas-bearing, low surface brightness sources missed by optical detection algorithms. We investigate the nature of a population of HI-bearing sources in ALFALFA with properties similar to "ultra-diffuse" galaxies (UDGs): galaxies with stellar masses of dwarf galaxies, but radii of L* galaxies. These "HI-bearing ultra-diffuse" sources (HUDS) constitute a small, but pertinent, fraction of the dwarf-mass galaxies in ALFALFA. They are bluer and have more irregular morphologies than the optically-selected UDGs found in clusters, and they appear to be gas-rich for their stellar mass, indicating low star formation efficiency. To illuminate potential explanations for the extreme properties of these sources we explore their environments and estimate their halo properties. We conclude that environmental mechanism are unlikely the cause of HUDS' properties, as they exist in environments equivalent to that of the other ALFALFA sources of similar HI-masses, however, we do find some suggestion that these HUDS may reside in high spin parameter halos, a potential explanation for their "ultra-diffuse" nature.

Massive Star Formation Viewed through Extragalactic-Tinted Glasses

NASA Astrophysics Data System (ADS)

Willis, Sarah; Marengo, M.; Smith, H. A.; Allen, L.

2014-01-01

Massive Galactic star forming regions are the local analogs to the luminous star forming regions that dominate the emission from star forming galaxies. Their proximity to us enables the characterization of the full range of stellar masses that form in these more massive environments, improving our understanding of star formation tracers used in extragalactic studies. We have surveyed a sample of massive star forming regions with a range of morphologies and luminosities to probe the star formation activity in a variety of environments. We have used Spitzer IRAC and deep ground based J, H, Ks observations to characterize the Young Stellar Object (YSO) content of 6 massive star forming regions. These YSOs provide insight into the rate and efficiency of star formation within these regions, and enable comparison with nearby, low mass star forming regions as well as extreme cases of Galactic star formation including ‘mini-starburst’ regions. In addition, we have conducted an in-depth analysis of NGC 6334 to investigate how the star formation activity varies within an individual star forming region, using Herschel data in the far-infrared to probe the earliest stages of the ongoing star formation activity.

Particle Dark Matter Searches Outside the Local Group.

PubMed

Regis, Marco; Xia, Jun-Qing; Cuoco, Alessandro; Branchini, Enzo; Fornengo, Nicolao; Viel, Matteo

2015-06-19

If dark matter (DM) is composed by particles which are nongravitationally coupled to ordinary matter, their annihilations or decays in cosmic structures can result in detectable radiation. We show that the most powerful technique to detect a particle DM signal outside the Local Group is to study the angular cross-correlation of nongravitational signals with low-redshift gravitational probes. This method allows us to enhance the signal to noise from the regions of the Universe where the DM-induced emission is preferentially generated. We demonstrate the power of this approach by focusing on GeV-TeV DM and on the recent cross-correlation analysis between the 2MASS galaxy catalogue and the Fermi-LAT γ-ray maps. We show that this technique is more sensitive than other extragalactic γ-ray probes, such as the energy spectrum and angular autocorrelation of the extragalactic background, and emission from clusters of galaxies. Intriguingly, we find that the measured cross-correlation can be well fitted by a DM component, with a thermal annihilation cross section and mass between 10 and 100 GeV, depending on the small-scale DM properties and γ-ray production mechanism. This solicits further data collection and dedicated analyses.

The AGN fraction of submm-selected galaxies and contributions to the submm/mm-wave extragalactic background light

NASA Astrophysics Data System (ADS)

Serjeant, S.; Negrello, M.; Pearson, C.; Mortier, A.; Austermann, J.; Aretxaga, I.; Clements, D.; Chapman, S.; Dye, S.; Dunlop, J.; Dunne, L.; Farrah, D.; Hughes, D.; Lee, H.-M.; Matsuhara, H.; Ibar, E.; Im, M.; Jeong, W.-S.; Kim, S.; Oyabu, S.; Takagi, T.; Wada, T.; Wilson, G.; Vaccari, M.; Yun, M.

2010-05-01

We present a comparison of the SCUBA half degree extragalactic survey (SHADES) at 450 μm, 850 μm and 1100 μm with deep guaranteed time 15 μm AKARI FU-HYU survey data and Spitzer guaranteed time data at 3.6-24 μm in the Lockman hole east. The AKARI data was analysed using bespoke software based in part on the drizzling and minimum-variance matched filtering developed for SHADES, and was cross-calibrated against ISO fluxes. Our stacking analyses find AKARI 15 μm galaxies with ⪆200 μJy contribute >10% of the 450 μm background, but only <4% of the 1100 μm background, suggesting that different populations contribute at mm-wavelengths. We confirm our earlier result that the ultra-deep 450 μm SCUBA-2 cosmology survey will be dominated by populations already detected by AKARI and Spitzer mid-infrared surveys. The superb mid-infrared wavelength coverage afforded by combining Spitzer and AKARI photometry is an excellent diagnostic of AGN contributions, and we find that (23-52)% of submm-selected galaxies have AGN bolometric fractions fAGN > 0.3.

Cutting-Edge Science from Arecibo Observatory: Introduction

NASA Astrophysics Data System (ADS)

Schmelz, Joan T.

2017-01-01

The Arecibo Observatory is home to the largest radio telescope in the world operating above 2 GHz, where molecule emission pertaining to the origins of life proliferate. It also houses the most powerful radar system on the planet, providing crucial information for the assessment of impact hazards of near-Earth asteroids (NEA). It was built to study the ionosphere with a radar system that can also monitor the effects of Space Weather and climate change. Arecibo has a proven track record for doing excellent science, even after 50 years of operations. This talk will include brief summaries of several Arecibo astronomy topics including the (1) latest attempts to resolve the Pleiades distance controversy, which include VLBI and Gaia; (2) galactic and extragalactic molecules; and (3) Arecibo 3D orbit determinations of potentially hazardous asteroids, and the crucial observation required to select Bennu as the target for the recently launched NASA OSIRIS-REx mission. This introduction will set the stage for the invited talks in this session, which include such topics as Fast Radio Bursts, galactic and extragalactic HI results, the pulsar emission problem, and NANOGrav. This work is supported by NSF and NASA.

Fermi-LAT high-z active galactic nuclei and the extragalactic background light

NASA Astrophysics Data System (ADS)

Armstrong, Thomas; Brown, Anthony M.; Chadwick, Paula M.

2017-10-01

Observations of distant gamma-ray sources are hindered by the presence of the extragalactic background light (EBL). In order to understand the physical processes that result in the observed spectrum of sources, it is imperative that a good understanding of the EBL is included. In this work, an investigation into the imprint of the EBL on the observed spectra of high-redshift Fermi-LAT active galactic nuclei is presented. By fitting the spectrum below ˜10 GeV, an estimation of the unabsorbed intrinsic source spectrum is obtained; by applying this spectrum to data up to 300 GeV, it is then possible to derive a scaling factor for different EBL models. A second approach uses five sources (PKS 0426-380, 4C +55.17, Ton 116, PG 1246+586 and RBS 1432) that were found to exhibit very high energy (VHE) emission (Eγ > 100 GeV). Through Monte Carlo simulations, it is shown that the observation of VHE photons, despite the large distances of these objects, is consistent with current EBL models. Many of these sources would be observable with the upcoming ground-based observatory, the Cherenkov Telescope Array, leading to a better understanding of the EBL.

A Public Outreach Blog for the CANDELS Project

NASA Astrophysics Data System (ADS)

Kartaltepe, Jeyhan S.; Pforr, J.; CANDELS Collaboration

2013-01-01

In May 2012 the CANDELS collaboration launched a public outreach blog, aimed at the general public, where we discuss CANDELS related science. CANDELS (the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) is a large Hubble Space Telescope Multi-Cycle Treasury Program to image portions of the five most commonly studied deep fields in the near-infrared with WFC3. This large collaboration encompasses a wide range of science topics including galaxy evolution and observational cosmology. We seek to understand how galaxies in the early universe formed and evolved to become the galaxies we see today. We post on a wide variety of topics including general background discussion on many issues in extragalactic astronomy, current science results and papers, highlights from meetings that we have attended, and what life as an astronomer is like (going on observing runs, writing proposals, and how we became interested in astronomy). The posts are written by a large number of collaboration members at different career stages (including students, postdocs, and permanent staff/faculty members) and is widely read and advertised on Facebook, Twitter, and Google+. Our blog can be found here: http://candels-collaboration.blogspot.com

Particle Dark Matter Searches Outside the Local Group

NASA Astrophysics Data System (ADS)

Regis, Marco; Xia, Jun-Qing; Cuoco, Alessandro; Branchini, Enzo; Fornengo, Nicolao; Viel, Matteo

2015-06-01

If dark matter (DM) is composed by particles which are nongravitationally coupled to ordinary matter, their annihilations or decays in cosmic structures can result in detectable radiation. We show that the most powerful technique to detect a particle DM signal outside the Local Group is to study the angular cross-correlation of nongravitational signals with low-redshift gravitational probes. This method allows us to enhance the signal to noise from the regions of the Universe where the DM-induced emission is preferentially generated. We demonstrate the power of this approach by focusing on GeV-TeV DM and on the recent cross-correlation analysis between the 2MASS galaxy catalogue and the Fermi-LAT γ -ray maps. We show that this technique is more sensitive than other extragalactic γ -ray probes, such as the energy spectrum and angular autocorrelation of the extragalactic background, and emission from clusters of galaxies. Intriguingly, we find that the measured cross-correlation can be well fitted by a DM component, with a thermal annihilation cross section and mass between 10 and 100 GeV, depending on the small-scale DM properties and γ -ray production mechanism. This solicits further data collection and dedicated analyses.

A repeating fast radio burst

NASA Astrophysics Data System (ADS)

Spitler, L. G.; Scholz, P.; Hessels, J. W. T.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J.; Ferdman, R. D.; Freire, P. C. C.; Kaspi, V. M.; Lazarus, P.; Lynch, R.; Madsen, E. C.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Seymour, A.; Stairs, I. H.; Stappers, B. W.; van Leeuwen, J.; Zhu, W. W.

2016-03-01

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

The origin and development of extragalactic radio astronomy: the role of CSIRO's Division of Radiophysics Dover Heights Field Station in Sydney

NASA Astrophysics Data System (ADS)

Orchiston, Wayne; Robertson, Peter

2017-12-01

Initial post-war developments in non-solar radio astronomy were inspired by Hey, Phillips and Parson’s report in 1946 of an intense source of radio emission in Cygnus. This so-called ‘radio star’ was unique, and questions immediately were raised about its true nature. But it did not remain unique for long. Observing from Sydney, John Bolton, Gordon Stanley and Bruce Slee followed up the Cygnus discovery with more radio star detections, beginning what would evolve into a long-term multi-faceted research program and one of the mainstays of the CSIRO’s Division of Radiophysics. But more than this, these early discoveries in England and in Sydney opened up a whole new field of investigation, extragalactic radio astronomy, which has remained a major area of investigation through to the present day. This paper focusses on the early years of this program when the observations were carried out at Dover Heights Field Station in Sydney, and the ways in which new developments in instrumentation that allowed a major expansion of the program eventually led to the closure of Dover Heights and the founding of the Fleurs Field Station.

A repeating fast radio burst.

PubMed

Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

2016-03-10

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

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.

Revisiting Absolute Radio Backgrounds in Light of Juno Cruise Data

NASA Astrophysics Data System (ADS)

Chang, Tzu-Ching

Radio backgrounds have played a critical role in recent progress in astronomy and cosmology. Major amongst them, the Cosmic Microwave Background (CMB) is currently our most precise window on the physics of the early universe. Both its near perfect blackbody spectrum and its angular fluctuations led to unique cosmological inferences. Beyond the CMB, radio backgrounds have offered golden insights to Galactic and extragalactic astrophysics. In this proposal, we take note of the recently released "cruise data" collected over five years by the MicroWave Radiometer (MWR) instrument on board the Juno planetary mission to construct new, unprecedented and well-characterized full-sky maps at 6 frequencies ranging from 0.6 to 22 GHz. We propose to generate, validate and release these full-sky maps and investigate their rich and unique astrophysical implications. In particular, we expect the use of Juno data to shed light on the "ARCADE excess" and lead to new insights on Galactic and extragalactic radio signals. Over the past several years, evidence indicating the existence of a significant isotropic radio background has been hinted at by a number of instruments. In 2011, the Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission (ARCADE 2) collaboration reported measurements of the absolute sky temperature at a number of frequencies between 3 and 90 GHz (Fixsen et al. 2011). While these measurements are dominated by the CMB at frequencies above several GHz, they reveal the presence of significant excess power at the lowest measured frequencies (Seiffert et al. 2011). This conclusion is strengthened by a number of observations at lower frequencies, reported at 22 MHz, 45 MHz, 408 MHz and 1.42 GHz: the emission observed by each of these groups appears to be in significant excess to what can be attributed to Galactic emission, or to unresolved members of known extragalactic radio source populations. In addition, it appears to be anomalously spatially smooth to be extragalactic. Six years after the report of this excess, this situation remains unsettled and has not evolved due to the lack of new observations at these frequencies. For this reason, and for the intrinsic value of the unprecedented full-sky maps, the astrophysics impact of MWR Juno cruise observations will be very important. Our program will be articulated along five projects (labeled P1 to P5), loosely corresponding to research papers: (P1) We will generate well characterized full-sky maps at the Juno MWR six frequencies starting from the timestream data, released in September 2016 on the Planetary Data System (PDS) archive. We will validate these maps using cross-correlations with WMAP and Planck public maps at low frequencies. We will release our maps to the community via the NASA LAMBDA archive. This analysis will set the basis for the following projects. (P2) We will investigate the implication of these new maps for foreground modeling with a focus on CMB foreground separation. This analysis will be performed jointly with now standard WMAP and Planck component separation tools and products. (P3) We will investigate the implication of these new maps for foreground modeling with a focus on radio 21 cm intensity mapping signals, extending in the process current community foreground models. This analysis will be improve our understanding and characterization of radio foregrounds, and guide current and future redshifted 21 cm line mapping experiments. (P4) Using the above maps, we will revisit the ARCADE excess and perform absolute temperature measurement of the extragalactic radio backgrounds at multiple frequencies and angular positions over the sky. (P5) Using the above maps, we will revisit the ARCADE excess and perform absolute temperature measurement of the Galactic radio backgrounds at multiple frequencies and angular positions in the Galactic plane, using multiple other line surveys to guide our interpretation.

Probing the EBL Evolution at High Redshift Using GRBs Detected with the Fermi-LAT

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

Desai, A.; Ajello, M.; Omodei, N.

The extragalactic background light (EBL), from ultraviolet to infrared wavelengths, is predominantly due to emission from stars, accreting black holes and reprocessed light due to Galactic dust. The EBL can be studied through the imprint it leaves, via γ–γ absorption of high-energy photons, in the spectra of distant γ-ray sources. The EBL has been probed through the search for the attenuation it produces in the spectra of BL Lacertae (BL Lac) objects and individual γ-ray bursts (GRBs). GRBs have significant advantages over blazars for the study of the EBL especially at high redshifts. Here we analyze a combined sample ofmore » 22 GRBs, detected by the Fermi Large Area Telescope between 65 MeV and 500 GeV. We report a marginal detection (at the ~2.8σ level) of the EBL attenuation in the stacked spectra of the source sample. This measurement represents a first constraint of the EBL at an effective redshift of ~1.8. Here, we combine our results with prior EBL constraints and conclude that Fermi-LAT is instrumental to constrain the UV component of the EBL. We discuss the implications on existing empirical models of EBL evolution.« less

On the intrinsic spectrum of PKS 2155-304 from H.E.S.S. 2003 data

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

Costamante, L.; Benbow, W.; Horns, D.

2005-02-21

In 2003, PKS 2155-304 has been significantly detected by H.E.S.S. at Very High Energies (VHE), with an average spectrum of {gamma} = 3.3. Due to absorption by the Extragalactic Background Light (EBL), the intrinsic spectrum is heavily modified both in shape and intensity. To correct for this effect, and locate the Inverse Compton (IC) peak of the Spectral Energy Distribution (SED), we used three EBL models (representatives of three different flux levels for the stellar peak component). The resulting TeV spectrum has a peak around 1 TeV for stellar peak fluxes above the Primack (2001) calculation, while the spectrum ismore » steeper than {gamma} = 2 (thus locating the IC peak < 200 GeV) for fluxes below. With bulk Lorentz factors {delta} = 20 - 30 (typically used for this object), in the first case the IC peak is in the Klein-Nishina transition region, while in the other case it is in the Thompson regime, and in agreement with the commonly fitted source parameters (e.g. [17]). The constraint on {delta} given by transparency to 2 TeV photons is {delta} > 19 (for historical SED fluxes and 2 hours variability timescale)« less

Rotational relaxation of CF+(X1Σ) in collision with He(1S)

NASA Astrophysics Data System (ADS)

Denis-Alpizar, O.; Inostroza, N.; Castro Palacio, J. C.

2018-01-01

The carbon monofluoride cation (CF+) has been detected recently in Galactic and extragalactic regions. Therefore, excitation rate coefficients of this molecule in collision with He and H2 are necessary for a correct interpretation of the astronomical observations. The main goal of this work is to study the collision of CF+ with He in full dimensionality at the close-coupling level and to report a large set of rotational rate coefficients. New ab initio interaction energies at the CCSD(T)/aug-cc-pv5z level of theory were computed, and a three-dimensional potential energy surface was represented using a reproducing kernel Hilbert space. Close-coupling scattering calculations were performed at collisional energies up to 1600 cm-1 in the ground vibrational state. The vibrational quenching cross-sections were found to be at least three orders of magnitude lower than the pure rotational cross-sections. Also, the collisional rate coefficients were reported for the lowest 20 rotational states of CF+ and an even propensity rule was found to be in action only for j > 4. Finally, the hyperfine rate coefficients were explored. These data can be useful for the determination of the interstellar conditions where this molecule has been detected.

Do high energy astrophysical neutrinos trace star formation?

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

Emig, Kimberly; Windhorst, Rogier; Lunardini, Cecilia, E-mail: Kimberly.Emig@asu.edu, E-mail: Cecilia.Lunardini@asu.edu, E-mail: Rogier.Windhorst@asu.edu

2015-12-01

The IceCube Neutrino Observatory has provided the first map of the high energy (∼ 0.01–1 PeV) sky in neutrinos. Since neutrinos propagate undeflected, their arrival direction is an important identifier for sources of high energy particle acceleration. Reconstructed arrival directions are consistent with an extragalactic origin, with possibly a galactic component, of the neutrino flux. We present a statistical analysis of positional coincidences of the IceCube neutrinos with known astrophysical objects from several catalogs. When considering starburst galaxies with the highest flux in gamma-rays and infrared radiation, up to n=8 coincidences are found, representing an excess over the ∼4 predicted formore » the randomized, or ''null'' distribution. The probability that this excess is realized in the null case, the p-value, is p=0.042. This value falls to p=0.003 for a partial subset of gamma-ray-detected starburst galaxies and superbubble regions in the galactic neighborhood. Therefore, it is possible that starburst galaxies, and the typically hundreds of superbubble regions within them, might account for a portion of IceCube neutrinos. The physical plausibility of such correlation is discussed briefly.« less

Non-LTE model calculations for SN 1987A and the extragalactic distance scale

NASA Technical Reports Server (NTRS)

Schmutz, W.; Abbott, D. C.; Russell, R. S.; Hamann, W.-R.; Wessolowski, U.

1990-01-01

This paper presents model atmospheres for the first week of SN 1987A, based on the luminosity and density/velocity structure from hydrodynamic models of Woosley (1988). The models account for line blanketing, expansion, sphericity, and departures from LTE in hydrogen and helium and differ from previously published efforts because they represent ab initio calculations, i.e., they contain essentially no free parameters. The formation of the UV spectrum is dominated by the effects of line blanketing. In the absorption troughs, the Balmer line profiles were fit well by these models, but the observed emissions are significantly stronger than predicted, perhaps due to clumping. The generally good agreement between the present synthetic spectra and observations provides independent support for the overall accuracy of the hydrodynamic models of Woosley. The question of the accuracy of the Baade-Wesselink method is addressed in a detailed discussion of its approximations. While the application of the standard method produces a distance within an uncertainty of 20 percent in the case of SN 1987A, systematic errors up to a factor of 2 are possible, particularly if the precursor was a red supergiant.

On the intrinsic spectrum of PKS 2155-304 from H.E.S.S. 2003 data

NASA Astrophysics Data System (ADS)

Costamante, L.; Benbow, W.; Horns, D.; Reimer, A.; H.E.S.S. Collaboration

2005-02-01

In 2003, PKS 2155-304 has been significantly detected by H.E.S.S. at Very High Energies (VHE), with an average spectrum of Γ = 3.3. Due to absorption by the Extragalactic Background Light (EBL), the intrinsic spectrum is heavily modified both in shape and intensity. To correct for this effect, and locate the Inverse Compton (IC) peak of the Spectral Energy Distribution (SED), we used three EBL models (representatives of three different flux levels for the stellar peak component). The resulting TeV spectrum has a peak around 1 TeV for stellar peak fluxes above the Primack (2001) calculation, while the spectrum is steeper than Γ = 2 (thus locating the IC peak < 200 GeV) for fluxes below. With bulk Lorentz factors δ = 20 - 30 (typically used for this object), in the first case the IC peak is in the Klein-Nishina transition region, while in the other case it is in the Thompson regime, and in agreement with the commonly fitted source parameters (e.g. [17]). The constraint on δ given by transparency to 2 TeV photons is δ > 19 (for historical SED fluxes and 2 hours variability timescale).

Mach-Zehnder Fourier transform spectrometer for astronomical spectroscopy at submillimeter wavelengths

NASA Astrophysics Data System (ADS)

Naylor, David A.; Gom, Bradley G.; Schofield, Ian; Tompkins, Gregory; Davis, Gary R.

2003-02-01

Astronomical spectroscopy at submillimeter wavelengths holds much promise for fields as diverse as the study of planetary atmospheres, molecular clouds and extragalactic sources. Fourier transform spectrometers (FTS) represent an important class of spectrometers well suited to observations that require broad spectral coverage at intermediate spectral resolution. In this paper we present the design and performance of a novel FTS, which has been developed for use at the James Clerk Maxwell Telescope (JCMT). The design uses two broadband intensity beamsplitters in a Mach-Zehnder configuration, which provide access to all four interferometer ports while maintaining a high and uniform efficiency over a broad spectral range. Since the interferometer processes both polarizations it is twice as efficient as the Martin-Puplett interferometer (MPI). As with the MPI, the spatial separation of the two input ports allows a reference blackbody to be viewed at all times in one port, while continually viewing the astronomical source in the other. Furthermore, by minimizing the size of the optical beam at the beamsplitter, the design is well suited to imaging Fourier transform spectroscopy (IFTS) as evidenced by its selection for the SPIRE instrument on Herschel.

Probing the EBL Evolution at High Redshift Using GRBs Detected with the Fermi-LAT

DOE PAGES

Desai, A.; Ajello, M.; Omodei, N.; ...

2017-11-17

The extragalactic background light (EBL), from ultraviolet to infrared wavelengths, is predominantly due to emission from stars, accreting black holes and reprocessed light due to Galactic dust. The EBL can be studied through the imprint it leaves, via γ–γ absorption of high-energy photons, in the spectra of distant γ-ray sources. The EBL has been probed through the search for the attenuation it produces in the spectra of BL Lacertae (BL Lac) objects and individual γ-ray bursts (GRBs). GRBs have significant advantages over blazars for the study of the EBL especially at high redshifts. Here we analyze a combined sample ofmore » 22 GRBs, detected by the Fermi Large Area Telescope between 65 MeV and 500 GeV. We report a marginal detection (at the ~2.8σ level) of the EBL attenuation in the stacked spectra of the source sample. This measurement represents a first constraint of the EBL at an effective redshift of ~1.8. Here, we combine our results with prior EBL constraints and conclude that Fermi-LAT is instrumental to constrain the UV component of the EBL. We discuss the implications on existing empirical models of EBL evolution.« less

Monitored Natural Attenuation of Inorganic Contaminants in Ground Water Volume 1 – Technical Basis for Assessment

EPA Science Inventory

This document represents the first volume of a set of three volumes that address the technical basis and requirements for assessing the potential applicability of MNA as part of a ground-water remedy for plumes with non-radionuclide and/or radionuclide inorganic contaminants. Vo...

1978-79 Michigan Social Studies Textbook Study, Volume I.

ERIC Educational Resources Information Center

Chapman, John, M., Ed.

This document represents Volume I of a two volume study to determine the extent to which four elementary level social studies programs reflect the multi-racial, multi-cultural nature of American society. The document is presented in three parts. Part I covers the Michigan Social Studies Textbook Act, an historical overview of previous Michigan…

English Leadership Quarterly, 1997-1998.

ERIC Educational Resources Information Center

Kiernan, Henry, Ed.

1998-01-01

These six theme issues of the "English Leadership Quarterly" represent those published during 1997 and part of 1998--volume 19 consists of the traditional four issues, while volume 20 consists of only two issues because of a change in publication schedule. Articles in volume 19 number 1 deal with theories, issues, and personal accounts on the…

Control volume based hydrocephalus research

NASA Astrophysics Data System (ADS)

Cohen, Benjamin; Voorhees, Abram; Wei, Timothy

2008-11-01

Hydrocephalus is a disease involving excess amounts of cerebral spinal fluid (CSF) in the brain. Recent research has shown correlations to pulsatility of blood flow through the brain. However, the problem to date has presented as too complex for much more than statistical analysis and understanding. This talk will highlight progress on developing a fundamental control volume approach to studying hydrocephalus. The specific goals are to select physiologically control volume(s), develop conservation equations along with the experimental capabilities to accurately quantify terms in those equations. To this end, an in vitro phantom is used as a simplified model of the human brain. The phantom's design consists of a rigid container filled with a compressible gel. The gel has a hollow spherical cavity representing a ventricle and a cylindrical passage representing the aquaducts. A computer controlled piston pump supplies pulsatile volume fluctuations into and out of the flow phantom. MRI is used to measure fluid velocity, and volume change as functions of time. Independent pressure measurements and flow rate measurements are used to calibrate the MRI data. These data are used as a framework for future work with live patients.

Ultra-high-energy cosmic rays from radio galaxies

NASA Astrophysics Data System (ADS)

Eichmann, B.; Rachen, J. P.; Merten, L.; van Vliet, A.; Becker Tjus, J.

2018-02-01

Radio galaxies are intensively discussed as the sources of cosmic rays observed above about 3 × 1018 eV, called ultra-high energy cosmic rays (UHECRs). We present a first, systematic approach that takes the individual characteristics of these sources into account, as well as the impact of the extragalactic magnetic-field structures up to a distance of 120 Mpc. We use a mixed simulation setup, based on 3D simulations of UHECRs ejected by observed, individual radio galaxies taken out to a distance of 120 Mpc, and on 1D simulations over a continuous source distribution contributing from beyond 120 Mpc. Additionally, we include the ultra-luminous radio galaxy Cygnus A at a distance of about 250 Mpc, as its contribution is so strong that it must be considered as an individual point source. The implementation of the UHECR ejection in our simulation setup, both that of individual radio galaxies and the continuous source function, is based on a detailed consideration of the physics of radio jets and standard first-order Fermi acceleration. This allows to derive the spectrum of ejected UHECR as a function of radio luminosity, and at the same time provides an absolute normalization of the problem involving only a small set of parameters adjustable within narrow constraints. We show that the average contribution of radio galaxies taken over a very large volume cannot explain the observed features of UHECRs measured at Earth. However, we obtain excellent agreement with the spectrum, composition, and arrival-direction distribution of UHECRs measured by the Pierre Auger Observatory, if we assume that most UHECRs observed arise from only two sources: the ultra-luminous radio galaxy Cygnus A, providing a mostly light composition of nuclear species dominating up to about 6 × 1019 eV, and the nearest radio galaxy Centaurus A, providing a heavy composition dominating above 6 × 1019 eV . Here we have to assume that extragalactic magnetic fields out to 250 Mpc, which we did not include in the simulation, are able to isotropize the UHECR events {at about 8 EeV} arriving from Cygnus A. Even in this case, significant anisotropy correlated with Cygnus A and Centaurus A could be present at higher energies, and thus allow for differences in UHECR spectrum and composition between the northern and southern hemispheres. If this scenario can be confirmed, it would also imply that the UHECR flux in our local cosmic environment is significantly above the average throughout the universe.

A WISE Measurement of the 2:4 mum Galaxy Luminosity Function and its Implications for the Extragalactic Background Light at 3:4 mum

NASA Astrophysics Data System (ADS)

Lake, Sean Earl

2017-05-01

The measurement of the the Extragalactic Background Light (EBL) has seen some controversy in recent works, with direct and indirect measures conflicting. Specifi- cally, upper limits based on analyzing the plausible opacity obscuring TeV spectra of blazars suggests that the density of radiation with wavelengths near 3.4 mum is onethirdtoonehalfasintenseasdirectmeasuresofthesame(forexample: Aharonian et al., 2006; Levenson et al., 2007; Matsumoto et al., 2005). The dominant contributor of the EBL at 3.4mum is expected to be ordinary starlight from relatively local, z < 1, galaxies, so an estimate of the amount of light emitted by galaxies based on the galaxy Luminosity Function (LF) should provide a useful lower limit to the EBL. While analyses of this sort have been done by others (Dominguez et al., 2011; Helgason et al., 2012), the full sky coverage of the AllWISE database has made it possible for us to improve the measurement of both the LF at 2.4 mum and the EBL using the large public spectroscopic redshift surveys. In order to do so, we had to develop a mathematical model for the measurement of a generalization of the LF, which is the density of galaxies per unit comoving volume per unit luminosity, to the Spectro-Luminosity Functional (SLF), which replaces the density per unit single luminosity, dL, with the density per luminosi- ii ties at all frequencies, DL nu. Our best combined analysis of the data yields present day Shechter Function LF parameters of: L⋆ = 6.4+/-[0.1 stat, 0.3sys]x1010 L2.4mum [solar mass](M⋆ = -21.67+/-[0.02 stat, 0.05sys] AB mag), φ⋆ = 5.8+/-[0.3stat, 0.3sys]x10 -3 Mpc-3, and alpha = -1.050 +/- [0.004stat, 0.03sys]; this implies a present day density of galaxies of 0.08 Mpc-3 brighter that 106 L2.4mum [solar mass] (10-3 Mpc-3 brighter than L⋆) and a luminosity density equivalent to 3.8 x 108 L2.4mum [solar mass] Mpc-3. The net EBL at 3.4mum that our synthesis model produces from galaxies closer than z = 5 is Inu = 9.0 +/- 0.5 kJy sr-1 (nuInu = 8.0 +/- 0.4 nW m-2 sr -1), largely in agreement with similar LF based estimates of the EBL.

Site Environmental Report for 2009, Volume 2

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

Xu, Suying

2010-08-19

Volume II of the Site Environmental Report for 2009 is provided by Ernest Orlando Lawrence Berkeley National Laboratory as a supplemental appendix to Volume I, which contains the body of the report. Volume II contains the environmental monitoring and sampling data used to generate summary results of routine and nonroutine sampling at the Laboratory, except for groundwater sampling data, which may be found in the reports referred to in Chapter 4 of Volume I. The results from sample collections are more comprehensive in Volume II than in Volume I: for completeness, all results from sample collections that began or endedmore » in calendar year (CY) 2009 are included in this volume. However, the samples representing CY 2008 data have not been used in the summary results that are reported in Volume I. (For example, although ambient air samples collected on January 6, 2009, are presented in Volume II, they represent December 2008 data and are not included in Table 4-2 in Volume I.) When appropriate, sampling results are reported in both conventional and International System (SI) units. For some results, the rounding procedure used in data reporting may result in apparent differences between the numbers reported in SI and conventional units. (For example, stack air tritium results reported as < 1.5 Bq/m3 are shown variously as < 39 and < 41 pCi/m3. Both of these results are rounded correctly to two significant digits.)« less

Extragalactic Astrophysics

NASA Astrophysics Data System (ADS)

Webb, James R.

2016-09-01

This book is intended to be a course about the creation and evolution of the universe at large, including the basic macroscopic building blocks (galaxies) and the overall large-scale structure. This text covers a broad range of topics for a graduate-level class in a physics department where students' available credit hours for astrophysics classes are limited. The sections cover galactic structure, external galaxies, galaxy clustering, active galaxies, general relativity and cosmology.

Documentation for the machine-readable version of A Catalogue of Extragalactic Radio Source Identifications (Veron-Cetty and Veron 1983)

NASA Technical Reports Server (NTRS)

Warren, W. H., Jr.

1983-01-01

Detailed descriptions of the data and reference files of the updated and final version of the machine-readable catalog are given. The computerized catalog has greatly expanded since the original published version (1974), and additional information is given. A separate reference file contains bibliographical citations ordered simultaneously by numerical reference and alphabetically by author.

Determining accurate distances to nearby galaxies

NASA Astrophysics Data System (ADS)

Bonanos, Alceste Zoe

2005-11-01

Determining accurate distances to nearby or distant galaxies is a very simple conceptually, yet complicated in practice, task. Presently, distances to nearby galaxies are only known to an accuracy of 10-15%. The current anchor galaxy of the extragalactic distance scale is the Large Magellanic Cloud, which has large (10-15%) systematic uncertainties associated with it, because of its morphology, its non-uniform reddening and the unknown metallicity dependence of the Cepheid period-luminosity relation. This work aims to determine accurate distances to some nearby galaxies, and subsequently help reduce the error in the extragalactic distance scale and the Hubble constant H 0 . In particular, this work presents the first distance determination of the DIRECT Project to M33 with detached eclipsing binaries. DIRECT aims to obtain a new anchor galaxy for the extragalactic distance scale by measuring direct, accurate (to 5%) distances to two Local Group galaxies, M31 and M33, with detached eclipsing binaries. It involves a massive variability survey of these galaxies and subsequent photometric and spectroscopic follow-up of the detached binaries discovered. In this work, I also present a catalog of variable stars discovered in one of the DIRECT fields, M31Y, which includes 41 eclipsing binaries. Additionally, we derive the distance to the Draco Dwarf Spheroidal galaxy, with ~100 RR Lyrae found in our first CCD variability study of this galaxy. A "hybrid" method of discovering Cepheids with ground-based telescopes is described next. It involves applying the image subtraction technique on the images obtained from ground-based telescopes and then following them up with the Hubble Space Telescope to derive Cepheid period-luminosity distances. By re-analyzing ESO Very Large Telescope data on M83 (NGC 5236), we demonstrate that this method is much more powerful for detecting variability, especially in crowded fields. I finally present photometry for the Wolf-Rayet binary WR 20a, which confirmed that the system consists of two extremely massive stars and refined the values of the masses. It is the most massive binary known with an accurate mass determination.

GaLactic and Extragalactic All-Sky MWA-eXtended (GLEAM-X) survey: Pilot observations

NASA Astrophysics Data System (ADS)

Hurley-Walker, N.; Seymour, N.; Staveley-Smith, L.; Johnston-Hollitt, M.; Kapinska, A.; McKinley, B.

2017-01-01

This proposal is a pilot study for the extension of the highly successful GaLactic and Extragalactic MWA (GLEAM) survey (Wayth et al. 2015). The aim is to test out new observing strategies and data reduction techniques suitable for exploiting the longer baselines of the extended phase 2 MWA array. Deeper and wide surveys at higher resolution will enable a legion of science capabilities pertaining to galaxy evolution, clusters and the cosmic web, whilst maintaining the advantages over LOFAR including larger field-of-view, wider frequency coverage and better sensitivity to extended emission. We will continue the successful drift scan mode observing to test the feasibility of a large-area survey in 2017-B and onward. We will also target a single deep area with a bright calibrator source to establish the utility of focussed deep observations. In both cases, we will be exploring calibrating and imaging strategies across 72-231 MHz with the new long baselines. The published extragalactic sky catalogue (Hurley-Walker et al. 2017) improves the prospects for good ionospheric calibration in this new regime, as well as trivialising flux calibration. The new Alternative Data Release of the TIFR GMRT Sky Survey (TGSS-ADR1; Intema et al. 2016), which has 30" resolution and covers the proposed observing area, allows us to test whether our calibration and imaging strategy correctly recovers the true structure of (high surface-brightness) resolved sources. GLEAM-X will have lower noise, higher surface brightness sensitivity, and have considerably wider bandwidth than TGSS. These properties will enable a wide range of science, such as: Detecting and characterising cluster relics and haloes beyond z=0.45; Accurately determining radio source counts at multiple frequencies; Measuring the low-v luminosity function to z 0.5; Performing Galactic plane science such as HII region detection and cosmic tomography; Determining the typical ionospheric diffractive scale at the MRO, feeding into SKA_Low calibration strategies. In addition the proposal is designed to be commensally used for transients science, and will also create a more accurate, higher-resolution foreground model for the EoR2 field, allowing better foreground subtraction and therefore increased sensitivity to the EoR signal.

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-ray variability to place limits on the emitting region size and magnetic field.

SPHEREx: Understanding the Origin and Evolution of Galaxies Through the Extragalactic Background Light

NASA Astrophysics Data System (ADS)

Zemcov, Michael; SPHEREx Science Team

2018-01-01

The near IR extragalactic background light (EBL) encodes the integrated light production over cosmic history, so traces the total emission from all galaxies along the line of sight up to the ancient first-light objects responsible for the epoch of reionization (EOR). The EBL can be constrained through measurements of anisotropies, taking advantage of the fact that extragalactic populations produce fluctuations with distinct spatial and spectral characteristics from local foregrounds. In particular, EBL anisotropies trace the underlying clustering of faint emission sources, such as stars, galaxies and accreting black holes present during the EOR, dwarf galaxies, and intra-halo light (IHL), all of which are components not readily detected in point source surveys. The fluctuation amplitude observed independently by a number of recent measurements exceeds that expected from the large-scale clustering of known galaxy populations, indicating the presence of a large integrated brightness from these faint and diffuse components. Improved large-area measurements covering the entire near-IR are required to constrain the possible models for the history of emission from stars back to the EOR.SPHEREx brings new capabilities to EBL fluctuation measurements, employing 96 spectral channels covering 0.75 to 5 microns with spectral resolving power R = 41 to 135 that enable SPHEREx to carry out a multi-frequency separation of the integrated light from galaxies, IHL, and EOR components using the rich auto- and cross-correlation information available from two 45 square degree surveys of the ecliptic poles. SPHEREx is an ideal intensity mapping machine, and has the sensitivity to disentangle the history of light production associated with EBL fluctuations. SPHEREx will search for an EOR component its to minimum required level through component separation and spectral fitting techniques optimized for the near-IR. In addition to broad-band intensity mapping that enhances and extends the Euclid survey, uniquely SPHEREx will enable tomography of cosmic large scale structure using line tracers such as Lya, Ha, Hb, O[II] and O[III], as highlighted in community workshops and AAS special sessions over the past several years.

Volume-weighted particle-tracking method for solute-transport modeling; Implementation in MODFLOW–GWT

USGS Publications Warehouse

Winston, Richard B.; Konikow, Leonard F.; Hornberger, George Z.

2018-02-16

In the traditional method of characteristics for groundwater solute-transport models, advective transport is represented by moving particles that track concentration. This approach can lead to global mass-balance problems because in models of aquifers having complex boundary conditions and heterogeneous properties, particles can originate in cells having different pore volumes and (or) be introduced (or removed) at cells representing fluid sources (or sinks) of varying strengths. Use of volume-weighted particles means that each particle tracks solute mass. In source or sink cells, the changes in particle weights will match the volume of water added or removed through external fluxes. This enables the new method to conserve mass in source or sink cells as well as globally. This approach also leads to potential efficiencies by allowing the number of particles per cell to vary spatially—using more particles where concentration gradients are high and fewer where gradients are low. The approach also eliminates the need for the model user to have to distinguish between “weak” and “strong” fluid source (or sink) cells. The new model determines whether solute mass added by fluid sources in a cell should be represented by (1) new particles having weights representing appropriate fractions of the volume of water added by the source, or (2) distributing the solute mass added over all particles already in the source cell. The first option is more appropriate for the condition of a strong source; the latter option is more appropriate for a weak source. At sinks, decisions whether or not to remove a particle are replaced by a reduction in particle weight in proportion to the volume of water removed. A number of test cases demonstrate that the new method works well and conserves mass. The method is incorporated into a new version of the U.S. Geological Survey’s MODFLOW–GWT solute-transport model.

Combining 3d Volume and Mesh Models for Representing Complicated Heritage Buildings

NASA Astrophysics Data System (ADS)

Tsai, F.; Chang, H.; Lin, Y.-W.

2017-08-01

This study developed a simple but effective strategy to combine 3D volume and mesh models for representing complicated heritage buildings and structures. The idea is to seamlessly integrate 3D parametric or polyhedral models and mesh-based digital surfaces to generate a hybrid 3D model that can take advantages of both modeling methods. The proposed hybrid model generation framework is separated into three phases. Firstly, after acquiring or generating 3D point clouds of the target, these 3D points are partitioned into different groups. Secondly, a parametric or polyhedral model of each group is generated based on plane and surface fitting algorithms to represent the basic structure of that region. A "bare-bones" model of the target can subsequently be constructed by connecting all 3D volume element models. In the third phase, the constructed bare-bones model is used as a mask to remove points enclosed by the bare-bones model from the original point clouds. The remaining points are then connected to form 3D surface mesh patches. The boundary points of each surface patch are identified and these boundary points are projected onto the surfaces of the bare-bones model. Finally, new meshes are created to connect the projected points and original mesh boundaries to integrate the mesh surfaces with the 3D volume model. The proposed method was applied to an open-source point cloud data set and point clouds of a local historical structure. Preliminary results indicated that the reconstructed hybrid models using the proposed method can retain both fundamental 3D volume characteristics and accurate geometric appearance with fine details. The reconstructed hybrid models can also be used to represent targets in different levels of detail according to user and system requirements in different applications.

The very high redshift component of the OTELO survey

NASA Astrophysics Data System (ADS)

Bongiovanni, A.; Ramón-Pérez, M.; Pérez García, A. M.; Cepa Nogué, J.; Cervino Saavedra, M.; OTELO Team

2017-03-01

Lyman-α emitters (LAEs) and Lyman-break galaxies (LBGs) stand out among the most used tools to study the galaxy formation in the early universe. Despite they constitute truly evolutionary probes of galaxy formation, evidence suggests that LAEs & LBGs correspond to different kinds of extragalactic sources regarding star formation modes, spatial distribution, gas and dust content, nuclear activity, etc., apart from the way they are detected. Such differences gain special significance near the reionization redshift. The OSIRIS Tunable Filter Emission-Line -OTELO- project is a very deep, 2D-spectroscopic (R ˜ 700) blind tomography, defined on a spectral window of 21 nm and centered on 915 nm, which aimsto obtains spectra of all emission line sources in the field, sampling unrelated cosmological volumes between z = 0.4 and 6 (see contributions of Cepa et al., Ramón-Pérez et al. and Nadolny et al. in this Meeting). Data from the OTELO's first pointing (Extended Groth Strip, EGS) and ancillary have been already gathered and reduced. Starting from a sample of 150+ candidates to z > 6 galaxies in the survey in a color diagnostic diagram, we have isolated 7 preliminary LAE candidates by hybrid SED fitting and emission line analysis, including considerations about possible interlopers (e.g. cool Galactic stars and z ˜ 1.3 post-starburst galaxies). A promising LAE candidate at z = 6.531 is shown in this contribution.

The ugrizYJHK luminosity distributions and densities from the combined MGC, SDSS and UKIDSS LAS data sets

NASA Astrophysics Data System (ADS)

Hill, David T.; Driver, Simon P.; Cameron, Ewan; Cross, Nicholas; Liske, Jochen; Robotham, Aaron

2010-05-01

We combine data from the Millennium Galaxy Catalogue, Sloan Digital Sky Survey and UKIRT Infrared Deep Sky Survey Large Area Survey to produce ugrizYJHK luminosity functions and densities from within a common, low-redshift volume (z < 0.1, ~ 71000h-31 Mpc3 for L* systems) with 100 per cent spectroscopic completeness. In the optical the fitted Schechter functions are comparable in shape to those previously reported values but with higher normalizations (typically 0, 30, 20, 15, 5 per cent higher φ* values in u, g, r, i, z, respectively, over those reported by the SDSS team). We attribute these to differences in the redshift ranges probed, incompleteness and adopted normalization methods. In the near-IR (NIR) we find significantly different Schechter function parameters (mainly in the M* values) to those previously reported and attribute this to the improvement in the quality of the imaging data over previous studies. This is the first homogeneous measurement of the extragalactic luminosity density which fully samples both the optical and NIR regimes. Unlike previous compilations that have noted a discontinuity between the optical and NIR regimes our homogeneous data set shows a smooth cosmic spectral energy distribution (CSED). After correcting for dust attenuation we compare our CSED to the expected values based on recent constraints on the cosmic star formation history and the initial mass function.

The Redshift Completeness of Local Galaxy Catalogs

NASA Astrophysics Data System (ADS)

Kulkarni, S. R.; Perley, D. A.; Miller, A. A.

2018-06-01

There is considerable interest in understanding the demographics of galaxies within the local universe (defined, for our purposes, as the volume within a radius of 200 Mpc or z ≤ 0.05). In this pilot paper, using supernovae (SNe) as signposts to galaxies, we investigate the redshift completeness of catalogs of nearby galaxies. In particular, type Ia SNe are bright and are good tracers of the bulk of the galaxy population, as they arise in both old and young stellar populations. Our input sample consists of SNe with redshift ≤0.05, discovered by the flux-limited ASAS-SN survey. We define the redshift completeness fraction (RCF) as the number of SN host galaxies with known redshift prior to SN discovery, determined, in this case, via the NASA Extragalactic Database, divided by the total number of newly discovered SNe. Using SNe Ia, we find {RCF}=78{+/- }76% (90% confidence interval) for z < 0.03. We examine the distribution of host galaxies with and without cataloged redshifts as a function of absolute magnitude and redshift, and, unsurprisingly, find that higher-z and fainter hosts are less likely to have a known redshift prior to the detection of the SN. However, surprisingly, some {L}* galaxies are also missing. We conclude with thoughts on the future improvement of RCF measurements that will be made possible from large SN samples resulting from ongoing and especially upcoming time-domain surveys.

Slitless spectroscopy with the James Webb Space Telescope Near-Infrared Camera (JWST NIRCam)

NASA Astrophysics Data System (ADS)

Greene, Thomas P.; Chu, Laurie; Egami, Eiichi; Hodapp, Klaus W.; Kelly, Douglas M.; Leisenring, Jarron; Rieke, Marcia; Robberto, Massimo; Schlawin, Everett; Stansberry, John

2016-07-01

The James Webb Space Telescope near-infrared camera (JWST NIRCam) has two 2.02 x 2.02 fields of view that are capable of either imaging or spectroscopic observations. Either of two R ~ 1500 grisms with orthogonal dispersion directions can be used for slitless spectroscopy over λ = 2.4 - 5.0 μm in each module, and shorter wavelength observations of the same fields can be obtained simultaneously. We present the latest predicted grism sensitivities, saturation limits, resolving power, and wavelength coverage values based on component measurements, instrument tests, and end-to-end modeling. Short wavelength (0.6 - 2.3 μm) imaging observations of the 2.4 - 5.0 μm spectroscopic field can be performed in one of several different filter bands, either in-focus or defocused via weak lenses internal to NIRCam. Alternatively, the possibility of 1.0 - 2.0 μm spectroscopy (simultaneously with 2.4 - 5.0 μm) using dispersed Hartmann sensors (DHSs) is being explored. The grisms, weak lenses, and DHS elements were included in NIRCam primarily for wavefront sensing purposes, but all have significant science applications. Operational considerations including subarray sizes, and data volume limits are also discussed. Finally, we describe spectral simulation tools and illustrate potential scientific uses of the grisms by presenting simulated observations of deep extragalactic fields, galactic dark clouds, and transiting exoplanets.

Hard X-ray luminosity function of tidal disruption events: First results from the MAXI extragalactic survey

NASA Astrophysics Data System (ADS)

Kawamuro, Taiki; Ueda, Yoshihiro; Shidatsu, Megumi; Hori, Takafumi; Kawai, Nobuyuki; Negoro, Hitoshi; Mihara, Tatehiro

2016-08-01

We derive the first hard X-ray luminosity function (XLF) of stellar tidal disruption events (TDEs) by supermassive black holes (SMBHs), which gives an occurrence rate of TDEs per unit volume as a function of peak luminosity and redshift, utilizing an unbiased sample observed by the Monitor of All-sky X-ray Image (MAXI). On the basis of the light curves characterized by a power-law decay with an index of -5/3, a systematic search using the MAXI data detected four TDEs in the first 37 months of observations, all of which have been found in the literature. To formulate the TDE XLF, we consider the mass function of SMBHs, that of disrupted stars, the specific TDE rate as a function of SMBH mass, and the fraction of TDEs with relativistic jets. We perform an unbinned maximum likelihood fit to the MAXI TDE list and check the consistency with the observed TDE rate in the ROSAT all-sky survey. The results suggest that the intrinsic fraction of the jet-accompanying events is 0.0007%-34%. We confirm that at z ≲ 1.5 the contamination of the hard X-ray luminosity functions of active galactic nuclei by TDEs is not significant and hence that their contribution to the growth of SMBHs is negligible at the redshifts.

Automotive Manufacturing Assessment System : Volume 4. Engine Manufacturing Analysis.

DOT National Transportation Integrated Search

1979-11-01

Volume IV represents the results of one of four major study areas under the Automotive Manufacturing Assessment System (AMAS) sponsored by the DOT/Transportation Systems Center. AMAS was designed to assist in the evaluation of industry's capability t...

Numeracy and Beyond. Proceedings of the Annual Meeting of the Mathematics Education Research Group of Australasia Incorporated (24th, Sydney, Australia, June 30-July 4, 2001). Volume 1 [and] Volume 2.

ERIC Educational Resources Information Center

Bobis, Janette, Ed.; Perry, Bob, Ed.; Mitchelmore, Michael, Ed.

This document represents volumes 1 and 2 of the proceedings of the 24th annual conference of the Mathematics Education Research Group of Australasia (MERGA) held at the University of Sydney, June 30-July 4, 2001. In volume 1, papers include: (1) "Connecting Mathematics Education Research to Practice" (Judith Sowder); (2) "Understanding, Assessing,…

Monitored Natural Attenuation of Inorganic Contaminants in Ground Water Volume 3 Assessment for Radionuclides IncludingTritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium

EPA Science Inventory

The current document represents the third volume of a set of three volumes that address the technical basis and requirements for assessing the potential applicability of MNA as part of a ground-water remedy for plumes with nonradionuclide and/or radionuclide inorganic contamina...

Monitored Attenuation of Inorganic Contaminants in Ground Water Volume 2 – Assessment for Non-Radionuclides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium

EPA Science Inventory

This document represents the second volume of a set of three volumes that address the technical basis and requirements for assessing the potential applicability of MNA as part of a ground-water remedy for plumes with non-radionuclide and/or radionuclide inorganic contaminants. V...

76 FR 21418 - Fiscal Year 2011 Allocation of Additional Tariff-Rate Quota Volume for Raw Cane Sugar and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-15

...-Rate Quota Volume for Raw Cane Sugar and Reallocation of Unused Fiscal Year 2011 Tariff-Rate Quota Volume for Raw Cane Sugar AGENCY: Office of the United States Trade Representative. ACTION: Notice...) for imported raw cane sugar and of country-by-country reallocations of the FY 2011 in-quota quantity...

77 FR 25012 - Fiscal Year 2012 Allocation of Additional Tariff-Rate Quota Volume for Raw Cane Sugar and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-26

...-Rate Quota Volume for Raw Cane Sugar and Reallocation of Unused Fiscal Year 2012 Tariff-Rate Quota Volume for Raw Cane Sugar AGENCY: Office of the United States Trade Representative. ACTION: Notice...) for imported raw cane sugar and of country-by-country reallocations of the FY 2012 in-quota quantity...

Contextualising Teaching and Learning in Rural Primary Schools: Using Agricultural Experience. Volume 1 [and] Volume 2. Education Research.

ERIC Educational Resources Information Center

Taylor, Peter; Mulhall, Abigail

This research project examined the potential role of agricultural experiences as a vehicle for meeting the diverse learning needs of rural primary students in developing countries. Volume 1 of the project report represents a literature review that investigated a "new role" for agriculture as a key element for developing rural students'…

The water masses and volumetry of the southern Agulhas Current region

NASA Astrophysics Data System (ADS)

Valentine, H. R.; Lutjeharms, J. R. E.; Brundrit, G. B.

1993-06-01

It has been suggested that the southern termination of the Agulhas Current plays a crucial role in the global circulation of thermocline water and thus in global climate. Due to a lack of modern hydrographic observations in this region, no detailed description of water masses or a fine-scale volumetric census for this geographic area had been carried out. Such an analysis of a collection of recent high-quality hydrographic measurements shows that the warm, saline, surface water of Agulhas Current origin contributes very little to the overall volume of the upper 1500 m of the water column in the area. Occasional equatorward leakages from south of the Subtropical Convergence are represented by a range of low-salinity outliers, but they represent <1% of the total volume. The distribution of water volume in temperature/salinity space for the Agulhas Retroflection is less diverse that that of the world ocean as a whole, 25% of the total volume of the region being contained in only 21 fine-scale temperature/salinity classes. North Atlantic Deep Water is the dominant water mass, accounting for 40% of the total volume. Deep Water in general accounts for 60% of the total volume.

PyEmir: Data Reduction Pipeline for EMIR, the GTC Near-IR Multi-Object Spectrograph

NASA Astrophysics Data System (ADS)

Pascual, S.; Gallego, J.; Cardiel, N.; Eliche-Moral, M. C.

2010-12-01

EMIR is the near-infrared wide-field camera and multi-slit spectrograph being built for Gran Telescopio Canarias. We present here the work being done on its data processing pipeline. PyEmir is based on Python and it will process automatically data taken in both imaging and spectroscopy mode. PyEmir is begin developed by the UCM Group of Extragalactic Astrophysics and Astronomical Instrumentation.

Redshifts for Superliminal Candidates.II.

NASA Astrophysics Data System (ADS)

Vermeulen, R. C.; Taylor, G. B.; Readhead, A. C. S.; Browne, I. W. A.

1996-03-01

Spectra are presented for 24 compact extragalactic radio sources from complete samples being studied with VLBI. New emission line redshifts are given for 21 of the objects; in 7 of these we have also identified associated or intervening absorption line systems. In 1 other source there are absorption lines which provide a lower limit to the redshift. The remaining 2 objects have strong featureless spectra and are likely to be blazars.

Supermassive black-hole growth over cosmic time: active galaxy demography, physics, and ecology from Chandra surveys.

PubMed

Brandt, W N; Alexander, D M

2010-04-20

Extragalactic X-ray surveys over the past decade have dramatically improved understanding of the majority populations of active galactic nuclei (AGNs) over most of the history of the universe. Here we briefly highlight some of the exciting discoveries about AGN demography, physics, and ecology, with a focus on results from Chandra. We also discuss some key unresolved questions and future prospects.

Supermassive black-hole growth over cosmic time: Active galaxy demography, physics, and ecology from Chandra surveys

PubMed Central

Brandt, W. N.; Alexander, D. M.

2010-01-01

Extragalactic X-ray surveys over the past decade have dramatically improved understanding of the majority populations of active galactic nuclei (AGNs) over most of the history of the universe. Here we briefly highlight some of the exciting discoveries about AGN demography, physics, and ecology, with a focus on results from Chandra. We also discuss some key unresolved questions and future prospects. PMID:20404160

Spallogenic Light Elements and Cosmic Ray Origin

NASA Technical Reports Server (NTRS)

Ramaty, Reuven

2000-01-01

Most of the Galactic Li-6, all of the Be and the bulk of the B are cosmic ray produced. I will discuss the production mechanisms and detail a recently developed evolutionary code for Fe,O and these light elements. I will review the leading models for Li, Be and B origin and discuss their implications on cosmic ray origin. I will also show evidence for extragalactic production of Li-6.

AT THE SOURCE OF AN EXTRAGALACTIC JET

NASA Technical Reports Server (NTRS)

2002-01-01

Artist's concept of the formation region of M87's jet. An accretion disk (red-yellow) surrounds the black hole, and its magnetic field lines twist tightly to channel the outpouring subatomic particles into a narrow jet. The jet opens widely near the black hole, then is shaped into a narrower beam within a light-year of the black hole. Credit: NASA and Ann Feild (Space Telescope Science Institute)

Cosmic ray antimatter: Is it primary or secondary?

NASA Technical Reports Server (NTRS)

Stecker, F. W.; Protheroe, R. J.; Kazanas, D.

1981-01-01

The relative merits and difficulties of the primary and secondary origin hypotheses for the observed cosmic ray antiprotons, including the low energy measurement of Buffington, were examined. It is concluded that the cosmic ray antiproton data may be strong evidence for antimatter galaxies and baryon symmetric cosmology. The present antiproton data are consistent with a primary extragalactic component having antiproton/proton approximately equal to .0032 + or - 0.7.

Search for cosmic-ray antimatter

NASA Technical Reports Server (NTRS)

Smoot, G. F.; Buffington, A.; Orth, C. D.

1975-01-01

It appears probable that some fraction of the cosmic rays has extragalactic origin. A search for antimatter nuclei was conducted with the aid of a balloon-borne superconducting magnetic spectrometer. The investigation made use of the fact that matter and antimatter nuclei, because of their opposite signs of charge, would be deflected in opposite directions when passing through a magnetic field. The antimatter flux limits set by the experiments are discussed.

The Gamma-Ray Properties of Radio-Selected Extragalactic Jets

DTIC Science & Technology

2010-06-01

Interferometry (VLBI) techniques. This information is important to understand the broad-band emission mechanism of these sources. In this work we... relativistic speed, thus the emission is Doppler boosted (Blandford & Rees, 1978; Maraschi et a!., 1992). This model is supported by the apparent... superluminal motion which is typically found in the inner radio-jets of blazars (Lister et al., 2009b, , and therein). Since 2008 August 11: the sky

Measurement of the Flux of Ultrahigh Energy Cosmic Rays from Monocular Observations by the High Resolution Fly's Eye Experiment

NASA Astrophysics Data System (ADS)

Abbasi, R. U.; Abu-Zayyad, T.; Amann, J. F.; Archbold, G.; Bellido, J. A.; Belov, K.; Belz, J. W.; Bergman, D. R.; Cao, Z.; Clay, R. W.; Cooper, M. D.; Dai, H.; Dawson, B. R.; Everett, A. A.; Fedorova, Yu. A.; Girard, J. H.; Gray, R. C.; Hanlon, W. F.; Hoffman, C. M.; Holzscheiter, M. H.; Hüntemeyer, P.; Jones, B. F.; Jui, C. C.; Kieda, D. B.; Kim, K.; Kirn, M. A.; Loh, E. C.; Manago, N.; Marek, L. J.; Martens, K.; Martin, G.; Matthews, J. A.; Matthews, J. N.; Meyer, J. R.; Moore, S. A.; Morrison, P.; Moosman, A. N.; Mumford, J. R.; Munro, M. W.; Painter, C. A.; Perera, L.; Reil, K.; Riehle, R.; Roberts, M.; Sarracino, J. S.; Sasaki, M.; Schnetzer, S. R.; Shen, P.; Simpson, K. M.; Sinnis, G.; Smith, J. D.; Sokolsky, P.; Song, C.; Springer, R. W.; Stokes, B. T.; Taylor, S. F.; Thomas, S. B.; Thompson, T. N.; Thomson, G. B.; Tupa, D.; Westerhoff, S.; Wiencke, L. R.; Vanderveen, T. D.; Zech, A.; Zhang, X.

2004-04-01

We have measured the cosmic ray spectrum above 1017.2 eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources.

An X-ray Expansion and Proper Motion Study of the Magellanic Cloud Supernova Remnant J0509-6731 with the Chandra X-ray Observatory

NASA Astrophysics Data System (ADS)

Roper, Quentin; Filipovi, Miroslav; Allen, Glenn E.; Sano, Hidetoshi; Park, Laurence; Pannuti, Thomas G.; Sasaki, Manami; Haberl, Frank; Kavanagh, Patrick J.; Yamane, Yumiko; Yoshiike, Satoshi; Fujii, Kosuke; Fukui, Yasuo; Seitenzahl, Ivo R.

2018-05-01

Using archival Chandra data consisting of a total of 78.46 ksec over two epochs seven years apart, we have measured the expansion of the young (˜400 years old) type Ia Large Magellanic Cloud supernova remnant (SNR) J0509-6731. In addition, we use radial brightness profile matching to detect proper-motion expansion of this SNR, and estimate an speed of 7 500±1 700 km s-1. This is one of the only proper motion studies of extragalactic SNRs expansion that is able to derive an expansion velocity, and one of only two such studies of an extragalactic SNR to yield positive results in the X-rays. We find that this expansion velocity is consistent with an optical expansion study on this object. In addition, we examine the medium into which the SNR is expanding by examining the CO and neutral H I gas using radio data obtained from Mopra, the Australia Telescope Compact Array and Parkes radio telescopes. We also briefly compare this result with a recent radio survey, and find that our results predict a radio spectral index α of -0.67±0.07. This value is consistent with high frequency radio observations of MCSNR J0509-6731.

Extragalactic Sources and Propagation of UHECRs

NASA Astrophysics Data System (ADS)

van Vliet, Arjen; Alves Batista, Rafael; Sigl, Günter

With the publicly available astrophysical simulation framework for propagating extraterrestrial UHE particles, CRPropa 3, it is now possible to study realistic UHECR source scenarios including deflections in Galactic and extragalactic magnetic fields in an efficient way. Here we discuss three recent studies that have already been done in that direction. The first one investigates what can be expected in the case of maximum allowed intergalactic magnetic fields. Here is shown that, even if voids contain strong magnetic fields, deflections of protons with energies ≳ 60 EeV from nearby sources might be small enough to allow for UHECR astronomy. The second study looks into several scenarios with a smaller magnetization focusing on large-scale anisotropies. Here is shown that the local source distribution can have a more significant effect on the large-scale anisotropy than the EGMF model. A significant dipole component could, for instance, be explained by a dominant source within 5 Mpc distance. The third study looks into whether UHECRs can come from local radio galaxies. If this is the case it is difficult to reproduce the observed low level of anisotropy. Therefore is concluded that the magnetic field strength in voids in the EGMF model used here is too low and/or there are additional sources of UHECRs that were not taken into account in these simulations.

eXtragalactic astronomy: the X-games of adaptive optics

NASA Astrophysics Data System (ADS)

Lai, Olivier

2000-07-01

Observing active nuclei, Ultra-Luminous Infrared Galaxies, starburst and merging galaxies, is both a challenge and a requirement for adaptive optics. It is a requirement, because models needed to explain the high infrared flux and the physics of these monsters need constraints that come, in part, from the fine details gleaned on high angular resolution images, and it is a challenge because, being distant, these objects are usually faint in apparent visual magnitude, meaning that the wavefront sensors have to operate in a photon starved regime. Many observations have been controversial in the past, and it is always difficult to tell an artifact such as astigmatism from an inner bar. The importance of observing the point spread function is therefore even more crucial than on bright objects, as PSF reconstruction methods 'a la Veran' break down when the photon noise dominates the statistics of the wave front, or when locking the loop on extended objects. Yet, while some cases have been controversial, some very clear and profound results have been obtained in the extragalactic domain, such as the detection of host galaxy to quasars and star formation studies. It turns out that the fundamental prerequisite to such success stories is a stable, well understood and well calibrated PSF.

Gamma-ray Monitoring of Active Galactic Nuclei with HAWC

NASA Astrophysics Data System (ADS)

Lauer, Robert; HAWC Collaboration

2016-03-01

Active Galactic Nuclei (AGN) are extra-galactic sources that can exhibit extreme flux variability over a wide range of wavelengths. TeV gamma rays have been observed from about 60 AGN and can help to diagnose emission models and to study cosmic features like extra-galactic background light or inter-galactic magnetic fields. The High Altitude Water Cherenkov (HAWC) observatory is a new extensive air shower array that can complement the pointed TeV observations of imaging air Cherenkov telescopes. HAWC is optimized for studying gamma rays with energies between 100 GeV and 100 TeV and has an instantaneous field of view of ~2 sr and a duty cycle >95% that allow us to scan 2/3 of the sky every day. By performing an unbiased monitoring of TeV emissions of AGN over most of the northern and part of the southern sky, HAWC can provide crucial information and trigger follow-up observations in collaborations with pointed TeV instruments. Furthermore, HAWC coverage of AGN is complementary to that provided by the Fermi satellite at lower energies. In this contribution, we will present HAWC flux light curves of TeV gamma rays from various sources, notably the bright AGN Markarian 421 and Markarian 501, and highlight recent results from multi-wavelengths and multi-instrument studies.

Dynamics of Magnetized Plasma Jets and Bubbles Launched into a Background Magnetized Plasma

NASA Astrophysics Data System (ADS)

Wallace, B.; Zhang, Y.; Fisher, D. M.; Gilmore, M.

2016-10-01

The propagation of dense magnetized plasma, either collimated with mainly azimuthal B-field (jet) or toroidal with closed B-field (bubble), in a background plasma occurs in a number of solar and astrophysical cases. Such cases include coronal mass ejections moving in the background solar wind and extragalactic radio lobes expanding into the extragalactic medium. Understanding the detailed MHD behavior is crucial for correctly modeling these events. In order to further the understanding of such systems, we are investigating the injection of dense magnetized jets and bubbles into a lower density background magnetized plasma using a coaxial plasma gun and a background helicon or cathode plasma. In both jet and bubble cases, the MHD dynamics are found to be very different when launched into background plasma or magnetic field, as compared to vacuum. In the jet case, it is found that the inherent kink instability is stabilized by velocity shear developed due to added magnetic tension from the background field. In the bubble case, rather than directly relaxing to a minimum energy Taylor state (spheromak) as in vacuum, there is an expansion asymmetry and the bubble becomes Rayleigh-Taylor unstable on one side. Recent results will be presented. Work supported by the Army Research Office Award No. W911NF1510480.

The Nature of the Unresolved Extragalactic Cosmic Soft X-Ray Background

NASA Technical Reports Server (NTRS)

Cappelluti, N.; Ranalli, P.; Roncarelli, M.; Arevalo, P.; Zamorani, G.; Comastri, A.; Gilli, R.; Rovilos, E.; Vignali, C.; Allevato, V.;

Spectrum measurement with the Telescope Array Low Energy Extension (TALE) fluorescence detector

NASA Astrophysics Data System (ADS)

Zundel, Zachary James

The Telescope Array (TA) experiment is the largest Ultra High Energy cosmic ray observatory in the northern hemisphere and is designed to be sensitive to cosmic ray air showers above 1018eV. Despite the substantial measurements made by TA and AUGER (the largest cosmic ray observatory in the southern hemisphere), there remains uncertainty about whether the highest energy cosmic rays are galactic or extragalactic in origin. Locating features in the cosmic ray energy spectrum below 1018eV that indicate a transition from galactic to extragalactic sources would clarify the interpretation of measurements made at the highest energies. The Telescope Array Low Energy Extension (TALE) is designed to extend the energy threshold of the TA observatory down to 1016.5eV in order to make such measurements. This dissertation details the construction, calibration, and operation of the TALE flu- orescence detector. A measurement of the flux of cosmic rays in the energy range of 1016.5 -- 1018.5eV is made using the monocular data set taken between September 2013 and January 2014. The TALE fluorescence detector observes evidence for a softening of the cosmic spectrum at 1017.25+/-0.5eV. The evidence of a change in the spectrum motivates continued study of 1016.5 -- 1018.5eV cosmic rays.

Erratum: The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant

NASA Astrophysics Data System (ADS)

Mould, Jeremy R.; Huchra, John P.; Freedman, Wendy L.; Kennicutt, Robert C., Jr.; Ferrarese, Laura; Ford, Holland C.; Gibson, Brad K.; Graham, John A.; Hughes, Shaun M. G.; Illingworth, Garth D.; Kelson, Daniel D.; Macri, Lucas M.; Madore, Barry F.; Sakai, Shoko; Sebo, Kim M.; Silbermann, Nancy A.; Stetson, Peter B.

2000-12-01

In the article ``The Hubble Space Telescope Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant'' (ApJ, 529, 786 [2000]), by Jeremy R. Mould, John P. Huchra, Wendy L. Freedman, Robert C. Kennicutt, Jr., Laura Ferrarese, Holland C. Ford, Brad K. Gibson, John A. Graham, Shaun M. G. Hughes, Garth D. Illingworth, Daniel D. Kelson, Lucas M. Macri, Barry F. Madore, Shoko Sakai, Kim M. Sebo, Nancy A. Silbermann, and Peter B. Stetson, some sign errors need to be corrected. 1. In equation (A2) the minus signs should be plus signs. The correct version is Vcosmic=VH+Vc,LG+Vin,Virgo+Vin,GA+Vin,Shap+... 2. In Table A1 the declination of the Great Attractor (GA) is -44°, and that of the Shapley supercluster is -31°, i.e., south declination, not north, as implied in the table. The first error is the authors' and the second occurred in the publication process. In both cases the computer code was correct, and the errors are in the published representation. None of the results presented in the paper are therefore affected in any way. The authors thank Dr. Jim Condon for pointing out the error in equation (A2)

CENTAURUS A: THE EXTRAGALACTIC SOURCE OF COSMIC RAYS WITH ENERGIES ABOVE THE KNEE

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

Biermann, Peter L.; De Souza, Vitor, E-mail: plbiermann@mpifr-bonn.mpg.de, E-mail: vitor@ifsc.usp.br

2012-02-10

The origin of cosmic rays at all energies is still uncertain. In this paper, we present and explore an astrophysical scenario to produce cosmic rays with energy ranging from below 10{sup 15} to 3 Multiplication-Sign 10{sup 20} eV. We show here that just our Galaxy and the radio galaxy Cen A, each with their own galactic cosmic-ray particles but with those from the radio galaxy pushed up in energy by a relativistic shock in the jet emanating from the active black hole, are sufficient to describe the most recent data in the PeV to near ZeV energy range. Data aremore » available over this entire energy range from the KASCADE, KASCADE-Grande, and Pierre Auger Observatory experiments. The energy spectrum calculated here correctly reproduces the measured spectrum beyond the knee and, contrary to widely held expectations, no other extragalactic source population is required to explain the data even at energies far below the general cutoff expected at 6 Multiplication-Sign 10{sup 19} eV, the Greisen-Zatsepin-Kuz'min turnoff due to interaction with the cosmological microwave background. We present several predictions for the source population, the cosmic-ray composition, and the propagation to Earth which can be tested in the near future.« less

Evidence of Cross-correlation between the CMB Lensing and the γ-Ray Sky

NASA Astrophysics Data System (ADS)

Fornengo, Nicolao; Perotto, Laurence; Regis, Marco; Camera, Stefano

2015-03-01

We report the measurement of the angular power spectrum of cross-correlation between the unresolved component of the Fermi-LAT γ-ray sky maps and the cosmic microwave background lensing potential map reconstructed by the Planck satellite. The matter distribution in the universe determines the bending of light coming from the last scattering surface. At the same time, the matter density drives the growth history of astrophysical objects, including their capability at generating non-thermal phenomena, which in turn give rise to γ-ray emissions. The Planck lensing map provides information on the integrated distribution of matter, while the integrated history of γ-ray emitters is imprinted in the Fermi-LAT sky maps. We report here the first evidence of their correlation. We find that the multipole dependence of the cross-correlation measurement is in agreement with current models of the γ-ray luminosity function for active galactic nuclei and star-forming galaxies, with a statistical evidence of 3.0σ. Moreover, its amplitude can in general be matched only assuming that these extragalactic emitters are also the bulk contribution of the measured isotopic γ-ray background (IGRB) intensity. This leaves little room for a big contribution from galactic sources to the IGRB measured by Fermi-LAT, pointing toward direct evidence of the extragalactic origin of the IGRB.

New Astrometric Limits on the Stochastic Gravitational Wave Background

NASA Astrophysics Data System (ADS)

Darling, Jeremiah K.; Truebenbach, Alexandra; Paine, Jennie

2018-06-01

We present new limits on the low frequency (f < 10-8 Hz) stochastic gravitational wave background using correlated extragalactic proper motions. The familiar methods for gravitational wave detection are ground- and space-based laser interferometry, pulsar timing, and polarization of the cosmic microwave background. Astrometry offers an additional path to gravitational wave detection because gravitational waves deflect the light rays of extragalactic objects, creating apparent proper motions in a quadrupolar (and higher order modes) pattern. Astrometry is sensitive to gravitational waves with frequencies between roughly 10-18 Hz and 10-8 Hz (between H0 and 1/3 yr-1), which overlaps and bridges the pulsar timing and CMB polarization regimes. We present the methods and results of two complementary approaches to astrometric gravitational wave detection: (1) a small ~500-object radio interferometric sample with low per-source proper motion uncertainty but large intrinsic proper motions caused by radio jets, and (2) a thousand-fold larger sample with large per-source uncertainties that has small intrinsic proper motions (Gaia active galactic nuclei). Both approaches produce limits on ΩGW, the energy density of gravitational waves as a fraction of the cosmological critical energy density.The authors acknowledge support from the NSF grant AST-1411605 and the NASA grant 14-ATP14-0086.

Forecasting the Contribution of Polarized Extragalactic Radio Sources in CMB Observations

NASA Astrophysics Data System (ADS)

Puglisi, G.; Galluzzi, V.; Bonavera, L.; Gonzalez-Nuevo, J.; Lapi, A.; Massardi, M.; Perrotta, F.; Baccigalupi, C.; Celotti, A.; Danese, L.

2018-05-01

We combine the latest data sets obtained with different surveys to study the frequency dependence of polarized emission coming from extragalactic radio sources (ERS). We consider data over a very wide frequency range starting from 1.4 GHz up to 217 GHz. This range is particularly interesting since it overlaps the frequencies of the current and forthcoming cosmic microwave background (CMB) experiments. Current data suggest that at high radio frequencies (ν ≥ 20 GHz) the fractional polarization of ERS does not depend on the total flux density. Conversely, recent data sets indicate a moderate increase of polarization fraction as a function of frequency, physically motivated by the fact that Faraday depolarization is expected to be less relevant at high radio frequencies. We compute ERS number counts using updated models based on recent data, and we forecast the contribution of unresolved ERS in CMB polarization spectra. Given the expected sensitivities and the observational patch sizes of forthcoming CMB experiments, about ∼200 (up to ∼2000) polarized ERS are expected to be detected. Finally, we assess that polarized ERS can contaminate the cosmological B-mode polarization if the tensor-to-scalar ratio is <0.05 and they have to be robustly controlled to de-lens CMB B-modes at the arcminute angular scales.

The Chandra Deep Field South as a test case for Global Multi Conjugate Adaptive Optics

NASA Astrophysics Data System (ADS)

Portaluri, E.; Viotto, V.; Ragazzoni, R.; Gullieuszik, M.; Bergomi, M.; Greggio, D.; Biondi, F.; Dima, M.; Magrin, D.; Farinato, J.

2017-04-01

The era of the next generation of giant telescopes requires not only the advent of new technologies but also the development of novel methods, in order to exploit fully the extraordinary potential they are built for. Global Multi Conjugate Adaptive Optics (GMCAO) pursues this approach, with the goal of achieving good performance over a field of view of a few arcmin and an increase in sky coverage. In this article, we show the gain offered by this technique to an astrophysical application, such as the photometric survey strategy applied to the Chandra Deep Field South as a case study. We simulated a close-to-real observation of a 500 × 500 arcsec2 extragalactic deep field with a 40-m class telescope that implements GMCAO. We analysed mock K-band images of 6000 high-redshift (up to z = 2.75) galaxies therein as if they were real to recover the initial input parameters. We attained 94.5 per cent completeness for source detection with SEXTRACTOR. We also measured the morphological parameters of all the sources with the two-dimensional fitting tools GALFIT. The agreement we found between recovered and intrinsic parameters demonstrates GMCAO as a reliable approach to assist extremely large telescope (ELT) observations of extragalactic interest.

Interpretation of the Arcade 2 Absolute Sky Brightness Measurement

NASA Technical Reports Server (NTRS)

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

Expanding the Discovery Potential of VERITAS via Moonlight Observations

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

Benbow, Wystan R.

2014-10-27

This grant partially supported the base research efforts of the Smithsonian Astrophysical Observatory (SAO), Very-High-Energy (VHE; E > 100 GeV) gamma-ray research group from 8/1/09 to 7/31/14. During the project period, the SAO gamma-ray group carried out a wide-range of research efforts, but focused on VHE observations of extragalactic sources with VERITAS. The SAO group led or co-lead nearly all VERITAS extragalactic working groups and the observations addressed themes in Particle Physics and Fundamental Laws, Cosmology, and Black Holes. The primary topics of this research were processes in exotic galaxies, especially active galactic nuclei and starburst galaxies, which have implicationsmore » for cosmology and Lorentz invariance violation, as well as indirect dark matter detection via VERITAS observations of dwarf spheroidal galaxies. In addition, the SAO group let the development of unique capabilities for VERITAS to observe during all periods of moonlight. Overall, this has increased the VERITAS data yield by 60% and these data are both scientifically useful and regularly published. This grant funded research that led to contributions towards the publication of 51 refereed journal articles during the project period, including several led by, or with significant contributions from, the SAO group.« less

Linking Deep Astrometric Standards to the ICRF

NASA Astrophysics Data System (ADS)

Frey, S.; Platais, I.; Fey, A. L.

2007-07-01

The next-generation large aperature and large field-of-view telescopes will address fundamantal questions of astrophysica and cosmology such as the nature of dark matter and dark energy. For a variety of applications, the CCD mosaic detectors in the focal plane arrays require astronomic calibrationat the milli-arcsecond (mas) level. The existing optical reference frames are insufficient to support such calibrations. To address this problem, deep optical astronomic fields are being established near the Galactic plane. In order to achiev a 5-10-mas or better positional accuracyfor the Deepp Astrometric Standards (DAS), and to obtain bsolute stellar proper motions for the study of Galactic structure, it is crucial to link these fields to the International Celestial Reference Frame (ICRF). To this end, we selected 15 candidate compact extragalactic radio sources in the Gemini-Orion-Taurus (GOT) field. These sources were observed with the European VLBI Network (EVN) at 5 GHz in phase-reference mode. The bright compact calibrator source J0603+2159 and seven other sources were detected and imaged at the angular resolution of -1.5-8 mas. Relative astrometric positions were derived for these sources at a milli-arcsecond accuracy level. The detection of the optical counterparts of these extragalactic radio sources will allow us to establish a direct link to the ICRF locally in the GOT field.

Neutrinos as a diagnostic of cosmic ray galactic-extragalactic transition

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

Ahlers, Markus; Ringwald, Andreas; Anchordoqui, Luis A.

2005-07-15

Motivated by a recent change in viewing the onset of the extragalactic component in the cosmic ray spectrum, we have fitted the observed data down to 10{sup 8.6} GeV and have obtained the corresponding power emissivity. This transition energy is well below the threshold for resonant p{gamma} absorption on the cosmic microwave background, and thus source evolution is an essential ingredient in the fitting procedure. Two-parameter fits in the spectral and redshift evolution indices show that a standard Fermi E{sub i}{sup -2} source spectrum is excluded at larger than 95% confidence level (CL). Armed with the primordial emissivity, we followmore » Waxman and Bahcall to derive the associated neutrino flux on the basis of optically thin sources. For pp interactions as the generating mechanism, the neutrino flux exceeds the AMANDA-B10 90% CL upper limits. In the case of p{gamma} dominance, the flux is consistent with AMANDA-B10 data. In the new scenario the source neutrino flux is considerably enhanced, especially below 10{sup 9} GeV. Should data from AMANDA-II prove consistent with the model, we show that IceCube can measure the characteristic power law of the neutrino spectrum, and thus provide a window on the source dynamics.« less

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

Kasliwal, M. M.; Kulkarni, S. R.; Ofek, E. O.

We present photometric and spectroscopic follow-up of a sample of extragalactic novae discovered by the Palomar 60 inch telescope during a search for 'Fast Transients In Nearest Galaxies' (P60-FasTING). Designed as a fast cadence (1 day) and deep (g < 21 mag) survey, P60-FasTING was particularly sensitive to short-lived and faint optical transients. The P60-FasTING nova sample includes 10 novae in M 31, 6 in M 81, 3 in M 82, 1 in NGC 2403, and 1 in NGC 891. This significantly expands the known sample of extragalactic novae beyond the Local Group, including the first discoveries in a starburstmore » environment. Surprisingly, our photometry shows that this sample is quite inconsistent with the canonical maximum-magnitude-rate-of-decline (MMRD) relation for classical novae. Furthermore, the spectra of the P60-FasTING sample are indistinguishable from classical novae. We suggest that we have uncovered a sub-class of faint and fast classical novae in a new phase space in luminosity-timescale of optical transients. Thus, novae span two orders of magnitude in both luminosity and time. Perhaps the MMRD, which is characterized only by the white dwarf mass, was an oversimplification. Nova physics appears to be characterized by a relatively rich four-dimensional parameter space in white dwarf mass, temperature, composition, and accretion rate.« less

Gas and dust spectral analysis of galactic and extragalactic symbiotic stars

NASA Astrophysics Data System (ADS)

Angeloni, Rodolfo

2009-02-01

Symbiotic stars are recognized as unique laboratories for studying a large variety of phenomena that are relevant to a number of important astro-physical problems. This PhD thesis deals with a spectral analysis of galactic and extragalactic symbiotic stars. The former are mainly D-type symbiotic stars for which a comprehensive study, from radio to X-ray spectral region, has been performed. With the latter, we refer to symbiotic stars in the Magellanic Clouds, to be analyzed mainly in the IR range. The common theoretical scenario that lies in the background of this work is the colliding-wind model, developed already during the 80's, supported by first observational evidence at the beginning of 90's (mainly thanks to Nussbaumer and collaborators), and finally completed with detailed and powerful hydrodynamical simulations by various authors in these recent years. In the light of this scenario, we have tried to interpret gas and dust spectra of our targets in a unique and self-consistent way. The spectral analysis has been performed by means of the numerical code SUMA, developed at the Instituto Astronomico e Geofisico of the University of Sao Paulo by Sueli M. Viegas (Aldrovandi) and Marcella Contini from the School of Physics and Astronomy of the Tel-Aviv University.

Cross-Correlation of the X-Ray Background with Nearby Galaxies: Erratum

NASA Astrophysics Data System (ADS)

Jahoda, Keith; Lahav, Ofer; Mushotzky, Richard F.; Boldt, Elihu

1992-11-01

In the Letter "Cross-Correlation of the X-Ray Background with Nearby Galaxies" by Keith Jahoda, Ofer Lahav, Richard F. Mushotzky, & Elihu Boldt (ApJ, 378, L37, [1991]) there is an error in the evaluation of equation(5): the numerical constant is too small by a factor of 4.5 (the solid angle of the HEAO 1 A2 beam). The revised X-ray emissivity values (over the volume sampled by the UGC and ESO galaxies) are as follows. For UGC (using the median of Table 1) ρ_x_ = (10.5 +/- 6.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^, where the error reflects the scatter in Table 1 and the uncertainty in R_*_, the effective depth of the catalogs (the Hubble constant is in units of H_0_ = 50 h_50_ km s^-1^ Mpc^-1^). Similarly for ESO ρ_x = (14.5 +/- 8.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^. For the combined data (UGC and ESO)our revised value is the mean of the two samples,ρ_x_ = (12.5 +/- 7.0) x 10^38^ h_50_ ergs s^-1^ Mpc^-3^. This correction has important consequences for the discussion section of the paper. First, the fraction of the X-ray background which can be produced by nonevolving X-ray sources distributed out to high redshift (assuming a look-back factor of f=0.5) can be as large as 50% +/- 30% and 70% +/- 40% for UGC and ESO, respectively. Second, this measurement of ρ_x_ exceeds the upper limit calculated by E. Boldt (IAU Colloq. 123,451 [1990]) based on an approximation of the total extragalactic X-ray dipole, unless b{OMEGA}^-0.6^<~ 1.3, less than about half the value derived for bright X-ray AGNs by T. Miyaji & E. Boldt (ApJ, 353, L3 [1990]) and T. Miyaji, K. Jahoda, & E. Boldt (AIP Conf. Proc. 222,431 [1991]). However, an improved determination of the extragalactic X-ray dipole, now obtained by performing a direct vector sum of the all-sky X-ray data (excluding only points near known Galactic point sources and their antipodes and points with |b| < 20^deg^), and subtracting the high-latitude contribution predicted by the Galactic model of D. Iwan et al. (ApJ, 260,111 [1982]) and that arising from the Compton-Getting effect, gives an estimate (rather than an upper limit) that ρ_x_ ~ 30 x 10^38^ h_50_(b{OMEGA}^- 0.6^)^-1^ ergs s^-1^ Mpc^-3^, consistent with the revised volume emissivity estimated in this work and the same bias parameter deduced for the bright AGNs. These two results suggest that a substantial fraction of the X-ray background could be produced by present-epoch objects and that these have a bias parameter similar to or only slightly smaller than the X-ray bright AGNs. We would also like to point out a minor error after equation (3). The correct sentence should be "where W_gg_, a galaxy autocorrelation estimator defined in analogy to equation (1), is, for example, 023 and 0.24 for UGC and ESO, respectively (for 17 deg^2^ cells)." The rest of the calculation is as before. We thank Andy Fabian for bringing the error to our attention and Takamitsu Miyaji for discussion.

2016 Billion-Ton Report: Environmental Sustainability Effects of Select Scenarios from Volume 1 (Volume 2)

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

Efroymson, R. A.; Langholtz, M. H.; Johnson, K. E.

On behalf of all the authors and contributors, it is a great privilege to present the 2016 Billion-Ton Report (BT16), volume 2: Environmental Sustainability Effects of Select Scenarios from volume 1. This report represents the culmination of several years of collaborative effort among national laboratories, government agencies, academic institutions, and industry. BT16 was developed to support the U.S. Department of Energy’s efforts towards national goals of energy security and associated quality of life.

Fourth - generation languages. Volume 2. Representative 4GLs

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

Martin, J.

1986-01-01

The chapters in Part II each describe one representative product marketed by a vendor other than IBM. (Volume III of this work covers IBM languages.) The chapters in Part II cover the following 4GLs: ADS/ONLINE, APPLICATION FACTORY, DATATRIEVE, FOCUS, IDEAL, INTELLECT, MANTIS, MIMER, NATURAL, NOMAD2, RAMIS II, SYSTEM W, and USE-IT. The Perspective section of Part II presents a general overview of the product and describes its role in the marketplace. The Tutorial section describes how a user employs the language in application development.

A Graph Based Interface for Representing Volume Visualization Results

NASA Technical Reports Server (NTRS)

Patten, James M.; Ma, Kwan-Liu

1998-01-01

This paper discusses a graph based user interface for representing the results of the volume visualization process. As images are rendered, they are connected to other images in a graph based on their rendering parameters. The user can take advantage of the information in this graph to understand how certain rendering parameter changes affect a dataset, making the visualization process more efficient. Because the graph contains more information than is contained in an unstructured history of images, the image graph is also helpful for collaborative visualization and animation.

A CMB foreground study in WMAP data: Extragalactic point sources and zodiacal light emission

NASA Astrophysics Data System (ADS)

Chen, Xi

The Cosmic Microwave Background (CMB) radiation is the remnant heat from the Big Bang. It serves as a primary tool to understand the global properties, content and evolution of the universe. Since 2001, NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite has been napping the full sky anisotropy with unprecedented accuracy, precision and reliability. The CMB angular power spectrum calculated from the WMAP full sky maps not only enables accurate testing of cosmological models, but also places significant constraints on model parameters. The CMB signal in the WMAP sky maps is contaminated by microwave emission from the Milky Way and from extragalactic sources. Therefore, in order to use the maps reliably for cosmological studies, the foreground signals must be well understood and removed from the maps. This thesis focuses on the separation of two foreground contaminants from the WMAP maps: extragalactic point sources and zodiacal light emission. Extragalactic point sources constitute the most important foreground on small angular scales. Various methods have been applied to the WMAP single frequency maps to extract sources. However, due to the limited angular resolution of WMAP, it is possible to confuse positive CMB excursions with point sources or miss sources that are embedded in negative CMB fluctuations. We present a novel CMB-free source finding technique that utilizes the spectrum difference of point sources and CMB to form internal linear combinations of multifrequency maps to suppress the CMB and better reveal sources. When applied to the WMAP 41, 64 and 94 GHz maps, this technique has not only enabled detection of sources that are previously cataloged by independent methods, but also allowed disclosure of new sources. Without the noise contribution from the CMB, this method responds rapidly with the integration time. The number of detections varies as 0( t 0.72 in the two-band search and 0( t 0.70 in the three-band search from one year to five years, separately, in comparison to t 0.40 from the WMAP catalogs. Our source catalogs are a good supplement to the existing WMAP source catalogs, and the method itself is proven to be both complementary to and competitive with all the current source finding techniques in WMAP maps. Scattered light and thermal emission from the interplanetary dust (IPD) within our Solar System are major contributors to the diffuse sky brightness at most infrared wavelengths. For wavelengths longer than 3.5 mm, the thermal emission of the IPD dominates over scattering, and the emission is often referred to as the Zodiacal Light Emission (ZLE). To set a limit of ZLE contribution to the WMAP data, we have performed a simultaneous fit of the yearly WMAP time-ordered data to the time variation of ZLE predicted by the DIRBE IPD model (Kelsallet al. 1998) evaluated at 240 mm, plus [cursive l] = 1 - 4 CMB components. It is found that although this fitting procedure can successfully recover the CMB dipole to a 0.5% accuracy, it is not sensitive enough to determine the ZLE signal nor the other multipole moments very accurately.

The All-Sky Swift - INTEGRAL X-Ray Survey

NASA Astrophysics Data System (ADS)

Michelson, Peter

All-sky surveys at hard X-ray energies (above 15 keV) have proven to be a powerful technique in detecting Galactic and extragalactic source populations. Most of the radiation at hard X-ray energies originates in non-thermal processes. These processes take place in extreme conditions of gravitational fields, of electromagnetic field, and also in explosive events. Such extreme conditions can be found in the Milk Way in the vicinity of neutron stars, black holes, and supernovae. Also extragalactic sources are known to be hard X-ray emitters like Active Galactic Nuclei (AGNs), blazars, and Clusters of Galaxies. Currently the most sensitive flying hard X-ray detectors are the Burst Alert Telescope (BAT) on board the NASA mission Swift and the INTEGRAL Soft-Gamma Ray Imager (IBIS/ISGRI) on board the ESA mission INTEGRAL. BAT and IBIS/ISGRI are coded- mask telescopes that shed continuously light on the Galactic and the extragalactic source populations. However, coded-mask telescopes suffer from heavy systematic effects (errors) preventing them from reaching their theoretical limiting sensitivity. Furthermore, by design, they block ~50% of the incident photons causing and increase of statistical noise. As a consequence BAT and IBIS/ISGRI are not sensitive enough to detect faint objects. In addition it has been proven that the Galactic survey of these instruments is limited by systematic uncertainties. Therefore, further observations on the Galactic plane will not improve the sensitivity of the survey of BAT and IBIS/ISGRI. In this project we show that it is possible to overcome the limits of BAT and of IBIS/ISGRI by combining their observations in the 18 55 keV energy range. We call it the SIX survey that stands for Swift - INTEGRAL X-ray survey. Two major advantages are obtained by merging the observations of BAT and IBIS/ISGRI: 1) the exposure is greatly enhanced (sum of BAT and IBIS/ISGRI) and therefore the sensitivity is improved; 2) the systematic errors of both instruments are not correlated and therefore the resulting SIX survey suffers less from systematic uncertainties. We propose to perform the all-sky SIX survey. We have performed a pilot SIX survey on 6200 deg2 (~15%) of sky area. The results obtained from this survey allow us to make precise predictions on the results that we expect when surveying the entire sky with the SIX. We aim to study extragalactic and Galactic source populations. The AGN sample will be used to address their evolution in the local Universe (z < 0.4), that is marginally detected in the pilot SIX survey. Blazars will be detected at high redshift (z>4) and we will probe their evolution. We expect to detect new Clusters of Galaxies constraining their physical environment. With the sample derived from the Galactic plane we will perform the X-ray luminosity function of High Mass X-ray Binaries and study their connection to the Star Formation Rate of the Milky Way. Finally we expect new discoveries as it is likely possible with a survey of a virtual new mission.

Hierarchical Theoretical Methods for Understanding and Predicting Anisotropic Thermal Transport Release in Rocket Propellant Formulations

DTIC Science & Technology

2016-12-08

mesoscopic models of interfaces and interphases, and microstructure-resolved representative volume element simulations. Atomic simulations were...title and subtitle with volume number and part number, if applicable. On classified documents, enter the title classification in parentheses. 5a...careful prediction of the pressure- volume -temperature equation of state, pressure- and temperature-dependent crystal and liquid thermal and transport

40 CFR 440.143 - Effluent limitations representing the degree of effluent reduction attainable by the application...

Code of Federal Regulations, 2014 CFR

2014-07-01

... which may be discharged from an open-cut mine plant site shall not exceed the volume of infiltration... site shall not exceed the volume of infiltration, drainage and mine drainage waters which is in excess...

40 CFR 440.143 - Effluent limitations representing the degree of effluent reduction attainable by the application...

Code of Federal Regulations, 2012 CFR

2012-07-01

... which may be discharged from an open-cut mine plant site shall not exceed the volume of infiltration... site shall not exceed the volume of infiltration, drainage and mine drainage waters which is in excess...

Testing Our Fundamental Assumptions

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-06-01

Science is all about testing the things we take for granted including some of the most fundamental aspects of how we understand our universe. Is the speed of light in a vacuum the same for all photons regardless of their energy? Is the rest mass of a photon actually zero? A series of recent studies explore the possibility of using transient astrophysical sources for tests!Explaining Different Arrival TimesArtists illustration of a gamma-ray burst, another extragalactic transient, in a star-forming region. [NASA/Swift/Mary Pat Hrybyk-Keith and John Jones]Suppose you observe a distant transient astrophysical source like a gamma-ray burst, or a flare from an active nucleus and two photons of different energies arrive at your telescope at different times. This difference in arrival times could be due to several different factors, depending on how deeply you want to question some of our fundamental assumptions about physics:Intrinsic delayThe photons may simply have been emitted at two different times by the astrophysical source.Delay due to Lorentz invariance violationPerhaps the assumption that all massless particles (even two photons with different energies) move at the exact same velocity in a vacuum is incorrect.Special-relativistic delayMaybe there is a universal speed for massless particles, but the assumption that photons have zero rest mass is wrong. This, too, would cause photon velocities to be energy-dependent.Delay due to gravitational potentialPerhaps our understanding of the gravitational potential that the photons experience as they travel is incorrect, also causing different flight times for photons of different energies. This would mean that Einsteins equivalence principle, a fundamental tenet of general relativity (GR), is incorrect.If we now turn this problem around, then by measuring the arrival time delay between photons of different energies from various astrophysical sources the further away, the better we can provide constraints on these fundamental assumptions.A recent focus set in the Astrophysical Journal Letters, titled Focus on Exploring Fundamental Physics with Extragalactic Transients, consists of multiple published studies doing just that.Testing General RelativitySeveral of the articles focus on the 4th point above. By assuming that the delay in photon arrival times is only due to the gravitational potential of the Milky Way, these studies set constraints on the deviation of our galaxys gravitational potential from what GR would predict. The study by He Gao et al. uses the different photon arrival times from gamma-ray bursts to set constraints at eVGeV energies, and the study by Jun-Jie Wei et al. complements this by setting constraints at keV-TeV energies using photons from high-energy blazar emission.Photons or neutrinos from different extragalactic transients each set different upper limits on delta gamma, the post-Newtonian parameter, vs. particle energy or frequency. This is a test of Einsteins equivalence principle: if the principle is correct, delta gamma would be exactly zero, meaning that photons of different energies move at the same velocity through a vacuum. [Tingay Kaplan 2016]S.J. Tingay D.L. Kaplan make the case that measuring the time delay of photons from fast radio bursts (FRBs; transient radio pulses that last only a few milliseconds) will provide even tighter constraints if we are able to accurately determine distances to these FRBs.And Adi Musser argues that the large-scale structure of the universe plays an even greater role than the Milky Way gravitational potential, allowing for even stricter testing of Einsteins equivalence principle.The ever-narrower constraints from these studies all support GR as a correct set of rules through which to interpret our universe.Other Tests of Fundamental PhysicsIn addition to the above tests, Xue-Feng Wu et al. show that FRBs can be used to provide severe constraints on the rest mass of the photon, and S. Croft et al. even touches on what we might learn from transients using multi-messenger astrophysics (astrophysics involving observations of particles besides photons, such as neutrinos or gravitational waves).In general, extragalactic transients provide a rich prospect for better understanding the laws that govern the universe. Check out the entire focus set below to learn more about the tests of fundamental physics that can be done with observations of extragalactic transients!CitationFocus Set: Focus on Exploring Fundamental Physics With Extragalactic TransientsHe Gao et al. 2015 ApJ 810 121. doi:10.1088/0004-637X/810/2/121Jun-Jie Wei et al. 2016 ApJ 818 L2. doi:10.3847/2041-8205/818/1/L2S. Croft et al. 2016 ApJ 820 L24. doi:10.3847/2041-8205/820/2/L24S. J. Tingay and D. L. Kaplan 2016 ApJ 820 L31. doi:10.3847/2041-8205/820/2/L31Adi Nusser 2016 ApJ 821 L2. doi:10.3847/2041-8205/821/1/L2Xue-Feng Wu et al. 2016 ApJ 822 L15. doi:10.3847/2041-8205/822/1/L15

40 CFR 411.32 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the...

Code of Federal Regulations, 2010 CFR

2010-07-01

... Storage Piles Runoff Subcategory § 411.32 Effluent limitations guidelines representing the degree of... facilities designed, constructed and operated to treat the volume of runoff from materials storage piles...

Passenger fluid volumes measured before and after a prolonged commercial jet flight.

NASA Technical Reports Server (NTRS)

Johnson, P. C.; Carpentier, W. R.; Driscoll, T. B.; Lapinta, C. K.; Rummel, J. A.; Sawin, C. F.

1972-01-01

Interstitial and intracellular fluid volumes were calculated from measured plasma volume, extracellular volume and total body water of six subjects before and after a 24-hour commercial overseas flight. No change occurred in these spaces or in peripheral hematocrit or total serum protein concentration. The subjective feeling of dehydration and the actual swelling of the lower extremities characteristically found among passengers at the end of a long trip of this type seems to represent a shift in body fluids to the dependent portions of the body rather than water retention or a decrease in the intravascular water volume.

Oak Ridge Reservation environmental report for 1992. Volume 1: Narrative

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

Koncinski, W.S.

The two volumes of this report present data and supporting narratives regarding the impact of the US Department of Energy`s (DOE`s) Oak Ridge Reservation (ORR) on its environs and the public during 1992. This Volume (Volume 1) includes all narrative descriptions, summaries, and conclusions and is intended to be a ``stand-alone`` report for the reader who does not want to review in detail all of the 1992 data for the ORR. Volume 2 includes the detailed data in formats that ensure all the environmental data are represented. Narratives are not included in Vol. 2.

KEGS Discovery of 9 Supernova Candidates in the K2 Campaign 17 field with Pan-STARRS PS1

NASA Astrophysics Data System (ADS)

Smith, K. W.; Rest, A.; Tucker, B. E.; Garnavich, P. M.; Margheim, S.; Kasen, D.; Olling, R.; Shaya, E.; Narayan, G.; Villar, A.; Forster, F.; Mushotzky, R.; Zenteno, A.; James, D.; Smith, R. Chris; Dotson, J. L.; Barentsen, G.; Gully-Santiago, M.; Smartt, S. J.; Wright, D. E.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Schultz, A.; Magnier, E.; Waters, C.; Bulger, J.; Wainscoat, R. J.

2018-05-01

We report the following transients discovered by Pan-STARRS1 during a targeted search of the Kepler Campaign 17 field as part of the K2 Extragalactic Survey (KEGS) for Transients (see http://www.mso.anu.edu.au/kegs/ ) Information on the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

A FORTRAN version implementation of block adjustment of CCD frames and its preliminary application

NASA Astrophysics Data System (ADS)

Yu, Y.; Tang, Z.-H.; Li, J.-L.; Zhao, M.

2005-09-01

A FORTRAN version implementation of the block adjustment (BA) of overlapping CCD frames is developed and its flowchart is shown. The program is preliminarily applied to obtain the optical positions of four extragalactic radio sources. The results show that because of the increase in the number and sky coverage of reference stars the precision of optical positions with BA is improved compared with the single CCD frame adjustment.

Shuttle VLBI experiment. Technical working group summary report

NASA Technical Reports Server (NTRS)

Morgan, S. H. (Editor); Roberts, D. H. (Editor)

1982-01-01

The gain in interferometric resolution of extragalactic sources at radio frequencies which can be achieved by placing a very long baseline interferometry (VLBI) antenna in space is quantitatively described and a VLBI demonstration experiment using a large deployable antenna, which if realized could be a very acceptable first venture for VLBI in space is discussed. A tutorial on VLBI, a summary of the technology available for the experiment, and a preliminary mission scenario are included.

Radio Recombination Lines at Decametre Wavelengths. Prospects for the Future

DTIC Science & Technology

2010-09-15

dark matter decay) can produce either an absorption or emission H  signal relative to the cosmic microwave background (CMB). At least three distinct...and 2). Most observations have focussed on sightlines towards known bright background sources or pass- ing through gas-rich regions along the inner...combina- tion of the Galactic synchrotron emission and the extragalactic background but is likely to be dominated by the former (Bridle, 1967). The

Measurement of the flux of ultrahigh energy cosmic rays from monocular observations by the High Resolution Fly's Eye experiment.

PubMed

Abbasi, R U; Abu-Zayyad, T; Amann, J F; Archbold, G; Bellido, J A; Belov, K; Belz, J W; Bergman, D R; Cao, Z; Clay, R W; Cooper, M D; Dai, H; Dawson, B R; Everett, A A; Fedorova, Yu A; Girard, J H V; Gray, R C; Hanlon, W F; Hoffman, C M; Holzscheiter, M H; Hüntemeyer, P; Jones, B F; Jui, C C H; Kieda, D B; Kim, K; Kirn, M A; Loh, E C; Manago, N; Marek, L J; Martens, K; Martin, G; Matthews, J A J; Matthews, J N; Meyer, J R; Moore, S A; Morrison, P; Moosman, A N; Mumford, J R; Munro, M W; Painter, C A; Perera, L; Reil, K; Riehle, R; Roberts, M; Sarracino, J S; Sasaki, M; Schnetzer, S R; Shen, P; Simpson, K M; Sinnis, G; Smith, J D; Sokolsky, P; Song, C; Springer, R W; Stokes, B T; Taylor, S F; Thomas, S B; Thompson, T N; Thomson, G B; Tupa, D; Westerhoff, S; Wiencke, L R; VanderVeen, T D; Zech, A; Zhang, X

2004-04-16

We have measured the cosmic ray spectrum above 10(17.2) eV using the two air-fluorescence detectors of the High Resolution Fly's Eye observatory operating in monocular mode. We describe the detector, phototube, and atmospheric calibrations, as well as the analysis techniques for the two detectors. We fit the spectrum to a model consisting of galactic and extragalactic sources.

SOLVENT-BASED TO WATERBASED ADHESIVE-COATED SUBSTRATE RETROFIT - VOLUME I: COMPARATIVE ANALYSIS

EPA Science Inventory

This volume represents the analysis of case study facilities' experience with waterbased adhesive use and retrofit requirements. (NOTE: The coated and laminated substrate manufacturing industry was selected as part of NRMRL'S support of the 33/50 Program because of its significan...

Waterborne Transportation Lines of the United States : calendar year 2008. Volume 1 : national summaries

DOT National Transportation Integrated Search

2009-11-16

The National Summaries, Volume 1, is one : of three publications for the annual revision of : the WTLUS, which provides a condensation of : the vessel data detailed in the WTLUS. : Summarized vessel characteristics are : represented in both tabular a...

Concept for a Satellite-Based Advanced Air Traffic Management System : Volume 9. System and Subsystem Performance Models.

DOT National Transportation Integrated Search

1973-02-01

The volume presents the models used to analyze basic features of the system, establish feasibility of techniques, and evaluate system performance. The models use analytical expressions and computer simulations to represent the relationship between sy...

Numerical Cerebrospinal System Modeling in Fluid-Structure Interaction.

PubMed

Garnotel, Simon; Salmon, Stéphanie; Balédent, Olivier

2018-01-01

Cerebrospinal fluid (CSF) stroke volume in the aqueduct is widely used to evaluate CSF dynamics disorders. In a healthy population, aqueduct stroke volume represents around 10% of the spinal stroke volume while intracranial subarachnoid space stroke volume represents 90%. The amplitude of the CSF oscillations through the different compartments of the cerebrospinal system is a function of the geometry and the compliances of each compartment, but we suspect that it could also be impacted be the cardiac cycle frequency. To study this CSF distribution, we have developed a numerical model of the cerebrospinal system taking into account cerebral ventricles, intracranial subarachnoid spaces, spinal canal and brain tissue in fluid-structure interactions. A numerical fluid-structure interaction model is implemented using a finite-element method library to model the cerebrospinal system and its interaction with the brain based on fluid mechanics equations and linear elasticity equations coupled in a monolithic formulation. The model geometry, simplified in a first approach, is designed in accordance with realistic volume ratios of the different compartments: a thin tube is used to mimic the high flow resistance of the aqueduct. CSF velocity and pressure and brain displacements are obtained as simulation results, and CSF flow and stroke volume are calculated from these results. Simulation results show a significant variability of aqueduct stroke volume and intracranial subarachnoid space stroke volume in the physiological range of cardiac frequencies. Fluid-structure interactions are numerous in the cerebrospinal system and difficult to understand in the rigid skull. The presented model highlights significant variations of stroke volumes under cardiac frequency variations only.

7 CFR 1218.72 - Suspension and termination.

Code of Federal Regulations, 2013 CFR

2013-01-01

... AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BLUEBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Blueberry Promotion, Research, and Information Order Miscellaneous § 1218.72... voting for approval who also represent a majority of the volume of blueberries represented in the...

7 CFR 1218.72 - Suspension and termination.

Code of Federal Regulations, 2012 CFR

2012-01-01

... AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BLUEBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Blueberry Promotion, Research, and Information Order Miscellaneous § 1218.72... voting for approval who also represent a majority of the volume of blueberries represented in the...

7 CFR 1218.72 - Suspension and termination.

Code of Federal Regulations, 2014 CFR

2014-01-01

... AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BLUEBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Blueberry Promotion, Research, and Information Order Miscellaneous § 1218.72... voting for approval who also represent a majority of the volume of blueberries represented in the...

7 CFR 1218.72 - Suspension and termination.

Code of Federal Regulations, 2010 CFR

2010-01-01

... AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BLUEBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Blueberry Promotion, Research, and Information Order Miscellaneous § 1218.72... voting for approval who also represent a majority of the volume of blueberries represented in the...

7 CFR 1218.72 - Suspension and termination.

Code of Federal Regulations, 2011 CFR

2011-01-01

... AGREEMENTS AND ORDERS; MISCELLANEOUS COMMODITIES), DEPARTMENT OF AGRICULTURE BLUEBERRY PROMOTION, RESEARCH, AND INFORMATION ORDER Blueberry Promotion, Research, and Information Order Miscellaneous § 1218.72... voting for approval who also represent a majority of the volume of blueberries represented in the...

Potential Refinement of the ICRF

NASA Technical Reports Server (NTRS)

Ma, Chopo

2003-01-01

The analysis and data used for the ICRF represented the state of the art in global, extragalactic, X/S band microwave astrometry in 1995. The same general analysis method was used to extend the ICRF with subsequent VLBI data in a manner consistent with the original catalog. Since 1995 there have been considerable advances in the geodetic/astrometric VLBI data set and in the analysis that would significantly improve the systematic errors, stability, and density of the next realization of the ICRS when the decision is made to take this step. In particular, data acquired since 1990, including extensive use of the VLBA, are of higher quality and astrometric utility because of changes in instrumentation, schedule design, and networks as well as specifically astrometric intent. The IVS (International VLBI Service for Geodesy and Astrometry) continues to devote a portion of its observing capability to systematic extension of the astrometric data set. Sufficient data distribution exists to select a better set of defining sources. Improvements in troposphere modeling will minimize known systematic astrometric errors while accurate modeling and estimation of station effects from loading and nonlinear motions will permit the reintegration of the celestial reference frame, terrestrial reference frame and Earth orientation parameters though a single VLBI solution. The differences between the current ICRF and the potential next realization will be described.

Five Years of the Fermi LAT Flare Advocate

NASA Astrophysics Data System (ADS)

Carpenter, Bryce; Ojha, R.; Gasparrini, D.; Ciprini, S.; Fermi LAT Collaboration; Fermi LAT Flare Advocates

2014-01-01

Since the launch of the Fermi satellite, the Fermi Large Area Telescope (LAT) team has run a program that provides a daily review of the the gamma-ray sky as soon as Fermi LAT data becomes available. The Flare Advocate/Gamma-ray Sky Watcher (FA-GSW) program allows a rapid analysis of the Automatic Science Processing (ASP) products and triggers dedicated followup analyses by several LAT science groups such as those studying Galactic transients, extragalactic sources and new gamma-ray sources. Significant gamma-ray detections also trigger rapid communications to the entire astrophysical community via astronomical telegrams and gamma-ray coordination network notices. The FA-GSW program plays a key role in maximizing the science return from Fermi by increasing the rate of multi-frequency observations of sources in an active gamma-ray state. In the past ~5 years blazar flaring activity of varying strength and duty cycles, gravitationally lensed blazars, flares from Galactic sources (like Nova Delphini and the Crab Nebula), unidentified transients near and off the Galactic plane, and emission from the quiet and flaring Sun, represent the range of detections made. Flare Advocates have published about 250 Astronomical Telegrams and they publish a weekly blog. Timely, extensive multi-frequency campaigns have been organized to follow-up on these phenomena leading to some of Fermi’s most interesting results.

A Comparison Between Spectral Properties of ULXs and Luminous X-ray Binaries

NASA Astrophysics Data System (ADS)

Berghea, C. T.; Colbert, E. J. M.; Roberts, T. P.

2004-05-01

What is special about the 1039 erg s-1 limit that is used to define the ULX class? We investigate this question by analyzing Chandra X-ray spectra of 71 X-ray bright point sources from nearby galaxies. Fifty-one of these sources are ULXs (LX(0.3-8.0 keV) ≥ 1039 erg s-1), and 20 sources (our comparison sample) are less-luminous X-ray binaries with LX(0.3-8.0 keV) = 1038-39 erg s-1. Our sample objects were selected from the Chandra archive to have ≥1000 counts and thus represent the highest quality spectra in the Chandra archives for extragalactic X-ray binaries and ULXs. We fit the spectra with one-component models (e.g., cold absorption with power-law, or cold absorption with multi-colored disk blackbody) and two-component models (e.g. absorption with both a power-law and a multi colored disk blackbody). A crude measure of the spectral states of the sources are determined observationally by calibrating the strength of the disk (blackbody) and coronal (power-law) components. These results are then use to determine if spectral properties of the ULXs are statistically distinct from those of the comparison objects, which are assumed to be ``normal'' black-hole X-ray binaries.

On the intrinsic spectrum of PKS 2155-304 from the H.E.S.S. 2003 data.

NASA Astrophysics Data System (ADS)

Costamante, L.; Aharonian, F.; Benbow, W.; Horns, D.; Reimer, A.; Reimer, O.; Rowell, G.; H.E.S.S. Collaboration

2004-08-01

In 2003, PKS 2155-304 (z=0.116) has been significantly detected by H.E.S.S. ( 44sigma) at TeV energies, with an average spectrum of Γ =3.3. Due to absorption by the Extragalactic Background Light (EBL), the intrinsic spectrum is heavily modified both in shape and intensity. To correct for this effect, and see where could be the Inverse Compton (IC) peak of the SED, we used 3 EBL models (representatives of 3 different flux levels for the stellar peak component). The resulting TeV spectrum has a peak around 1 TeV for stellar peak fluxes above the Primack (2001) calculation, while the spectrum is steeper than 2 (thus locating the IC peak <200 GeV) for fluxes below. With bulk Lorentz factors δ =20-30 (typically used for this object), in the first case the IC peak is in the Klein-Nishina transition region, while in the other case it is in the Thomson regime, and in agreement with the commonly fitted source parameters (e.g. Tavecchio et al. 1998). The constraint on δ given by transparency to 1-2 TeV photons is δ >19 (for historical SED fluxes and 2 hrs variability timescale).

Control volume based hydrocephalus research; a phantom study

NASA Astrophysics Data System (ADS)

Cohen, Benjamin; Voorhees, Abram; Madsen, Joseph; Wei, Timothy

2009-11-01

Hydrocephalus is a complex spectrum of neurophysiological disorders involving perturbation of the intracranial contents; primarily increased intraventricular cerebrospinal fluid (CSF) volume and intracranial pressure are observed. CSF dynamics are highly coupled to the cerebral blood flows and pressures as well as the mechanical properties of the brain. Hydrocephalus, as such, is a very complex biological problem. We propose integral control volume analysis as a method of tracking these important interactions using mass and momentum conservation principles. As a first step in applying this methodology in humans, an in vitro phantom is used as a simplified model of the intracranial space. The phantom's design consists of a rigid container filled with a compressible gel. Within the gel a hollow spherical cavity represents the ventricular system and a cylindrical passage represents the spinal canal. A computer controlled piston pump supplies sinusoidal volume fluctuations into and out of the flow phantom. MRI is used to measure fluid velocity and volume change as functions of time. Independent pressure measurements and momentum flow rate measurements are used to calibrate the MRI data. These data are used as a framework for future work with live patients and normal individuals. Flow and pressure measurements on the flow phantom will be presented through the control volume framework.

Investigating parameters participating in the infant respiratory control system attractor.

PubMed

Terrill, Philip I; Wilson, Stephen J; Suresh, Sadasivam; Cooper, David M; Dakin, Carolyn

2008-01-01

Theoretically, any participating parameter in a non-linear system represents the dynamics of the whole system. Taken's time delay embedding theory provides the fundamental basis for allowing non-linear analysis to be performed on physiological, time-series data. In practice, only one measurable parameter is required to be measured to convey an accurate representation of the system dynamics. In this paper, the infant respiratory control system is represented using three variables-a digitally sampled respiratory inductive plethysmography waveform, and the derived parameters tidal volume and inter-breath interval time series data. For 14 healthy infants, these data streams were analysed using recurrence plot analysis across one night of sleep. The measured attractor size of these variables followed the same qualitative trends across the nights study. Results suggest that the attractor size measures of the derived IBI and tidal volume are representative surrogates for the raw respiratory waveform. The extent to which the relative attractor sizes of IBI and tidal volume remain constant through changing sleep state could potentially be used to quantify pathology, or maturation of breathing control.

National Trends in Prostate Biopsy and Radical Prostatectomy Volumes Following the US Preventive Services Task Force Guidelines Against Prostate-Specific Antigen Screening.

PubMed

Halpern, Joshua A; Shoag, Jonathan E; Artis, Amanda S; Ballman, Karla V; Sedrakyan, Art; Hershman, Dawn L; Wright, Jason D; Shih, Ya Chen Tina; Hu, Jim C

2017-02-01

Studies demonstrate that use of prostate-specific antigen screening decreased significantly following the US Preventive Services Task Force (USPSTF) recommendation against prostate-specific antigen screening in 2012. To determine downstream effects on practice patterns in prostate cancer diagnosis and treatment following the 2012 USPSTF recommendation. Procedural volumes of certifying and recertifying urologists from 2009 through 2016 were evaluated for variation in prostate biopsy and radical prostatectomy (RP) volume. Trends were confirmed using the New York Statewide Planning and Research Cooperative System and Nationwide Inpatient Sample. The study included a representative sample of urologists across practice settings and nationally representative sample of all RP discharges. We obtained operative case logs from the American Board of Urology and identified urologists performing at least 1 prostate biopsy (n = 5173) or RP (n = 3748), respectively. The 2012 USPSTF recommendation against routine population-wide prostate-specific antigen screening. Change in median biopsy and RP volume per urologist and national procedural volume. Following the USPSTF recommendation, median biopsy volume per urologist decreased from 29 to 21 (interquartile range [IQR}, 12-34; P < .001). After adjusting for physician and practice characteristics, biopsy volume decreased by 28.7% following 2012 (parameter estimate, -0.25; SE, 0.03; P < .001). Similarly, following the USPSTF recommendation, median RP volume per urologist decreased from 7 (IQR, 3-15) to 6 (IQR, 2-12) (P < .001), and in adjusted analyses, RP volume decreased 16.2% (parameter estimate, -0.15; SE, 0.05; P = .003). Following the 2012 USPSTF recommendation, prostate biopsy and RP volumes decreased significantly. A panoramic vantage point is needed to evaluate the long-term consequences of the 2012 USPSTF recommendation.

The relationship between trading volumes, number of transactions, and stock volatility in GARCH models

NASA Astrophysics Data System (ADS)

Takaishi, Tetsuya; Chen, Ting Ting

2016-08-01

We examine the relationship between trading volumes, number of transactions, and volatility using daily stock data of the Tokyo Stock Exchange. Following the mixture of distributions hypothesis, we use trading volumes and the number of transactions as proxy for the rate of information arrivals affecting stock volatility. The impact of trading volumes or number of transactions on volatility is measured using the generalized autoregressive conditional heteroscedasticity (GARCH) model. We find that the GARCH effects, that is, persistence of volatility, is not always removed by adding trading volumes or number of transactions, indicating that trading volumes and number of transactions do not adequately represent the rate of information arrivals.

IMPACT OF MAN ON THE COASTAL ENVIRONMENT

EPA Science Inventory

This volume represents EPA's effort to take stock of scientific advances in research pertaining to the coastal environment since the inception of the Agency and to gauge what progress has been made and what remains to be accomplished. The essays in this volume present a range of ...

Science Learning: Processes and Applications.

ERIC Educational Resources Information Center

Santa, Carol Minnick, Ed.; Alvermann, Donna E., Ed.

Reflecting a collaboration in terms of content areas, levels, and audience, this volume represents the efforts of science teachers and reading teachers to understand and help one another fine tune their craft. Chapters in the volume include: (1) "Metacognition, Reading and Science Education" (Linda Baker); (2) "Science and Reading:…

Current Topics in Early Childhood Education. Volume II.

ERIC Educational Resources Information Center

Katz, Lilian G., Ed.; And Others

The ten papers in this volume present integrative reviews, analyses and syntheses of research and development of current concern to early childhood educators. Four papers represent investigations and reports of programmatic or educational activities. House and Hutchins critically analyze Abt Associates' national evaluation of Project Follow…

Pituitary Volume Prospectively Predicts Internalizing Symptoms in Adolescence

ERIC Educational Resources Information Center

Zipursky, Amy R.; Whittle, Sarah; Yucel, Murat; Lorenzetti, Valentina; Wood, Stephen J.; Lubman, Dan I.; Simmons, Julian G.; Allen, Nicholas B.

2011-01-01

Background: Early adolescence is a critical time for the development of both internalizing and externalizing disorders. We aimed to investigate whether pituitary volume, an index of hypothalamic-pituitary-adrenal (HPA) axis function, represents a vulnerability factor for the emergence of internalizing and externalizing symptoms during adolescence…

ICESat (GLAS) Science Processing Software Document Series. Volume 3; GLAS Science Software Requirements Document; Ver 2.1

NASA Technical Reports Server (NTRS)

Jester, Peggy L.; Lee, Jeffrey; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

This document addresses the software requirements of the Geoscience Laser Altimeter System (GLAS) Standard Data Software (SDS) supporting the GLAS instrument on the EOS ICESat Spacecraft. This Software Requirements Document represents the initial collection of the technical engineering information for the GLAS SDS. This information is detailed within the second of four main volumes of the Standard documentation, the Product Specification volume. This document is a "roll-out" from the governing volume outline containing the Concept and Requirements sections.

Molecular transitions as probes of the physical conditions of extragalactic environments

NASA Astrophysics Data System (ADS)

Viti, Serena

2017-11-01

Aims: We present a method to interpret molecular observations and molecular line ratios in nearby extragalactic regions. Methods: Ab initio grids of time dependent chemical models, varying in gas density, temperature, cosmic ray ionization rate, and radiation field, are used as inputs into RADEX calculations. Tables of abundances, column densities, theoretical line intensities, and line ratios for some of the most used dense gas tracers are provided. The degree of correlation as well as degeneracy inherent in molecular ratios is discussed. Comparisons of the theoretical intensities with example observations are also provided. Results: We find that, within the parameters space explored, chemical abundances can be constrained by a well-defined set of gas density, gas temperature, and cosmic ray ionization rates for the species we investigate here. However, line intensities, and more importantly line ratios, from different chemical models can be very similar, thereby leading to a clear degeneracy. We also find that the gas subjected to a galactic cosmic ray ionization rate will not necessarily have reached steady state in 1 million years. The species most affected by time dependency effects are HCN and CS, which are both high density tracers. We use our ab initio method to fit an example set of data from two galaxies, I.e. M 82 and NGC 253. We find that (I) molecular line ratios can be easily matched even with erroneous individual line intensities; (II) no set of species can be matched by a one-component interstellar medium (ISM); and (III) a species may be a good tracer of an energetic process but only under specific density and temperature conditions. Conclusions: We provide tables of chemical abundances and line intensities ratios for some of the most commonly observed extragalactic tracers of dense gas for a grid of models. We show that by taking the chemistry behind each species and the individual line intensities into consideration, many degeneracies that arise by just using molecular line ratios can be avoided. Finally we show that using a species or a ratio as a tracer of an individual energetic process, such as cosmic rays and UV, ought to be done with caution. Tables 2-11 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/607/A118

The cosmic infrared background experiment-2 (CIBER-2) for studying the near-infrared extragalactic background light

NASA Astrophysics Data System (ADS)

Shirahata, Mai; Arai, Toshiaki; Battle, John; Bock, James; Cooray, Asantha; Enokuchi, Akito; Hristov, Viktor; Kanai, Yoshikazu; Kim, Min Gyu; Korngut, Phillip; Lanz, Alicia; Lee, Dae-Hee; Mason, Peter; Matsumoto, Toshio; Matsuura, Shuji; Morford, Tracy; Ohnishi, Yosuke; Park, Won-Kee; Sano, Kei; Takeyama, Norihide; Tsumura, Kohji; Wada, Takehiko; Wang, Shiang-Yu; Zemcov, Michael

2016-07-01

We present the current status of the Cosmic Infrared Background ExpeRiment-2 (CIBER-2) project, whose goal is to make a rocket-borne measurement of the near-infrared Extragalactic Background Light (EBL), under a collaboration with U.S.A., Japan, South Korea, and Taiwan. The EBL is the integrated light of all extragalactic sources of emission back to the early Universe. At near-infrared wavelengths, measurement of the EBL is a promising way to detect the diffuse light from the first collapsed structures at redshift z˜10, which are impossible to detect as individual sources. However, recently, the intra-halo light (IHL) model is advocated as the main contribution to the EBL, and our new result of the EBL fluctuation from CIBER-1 experiment is also supporting this model. In this model, EBL is contributed by accumulated light from stars in the dark halo regions of low- redshift (z<2) galaxies, those were tidally stripped by the interaction of satellite dwarf galaxies. Thus, in order to understand the origin of the EBL, both the spatial fluctuation observations with multiple wavelength bands and the absolute spectroscopic observations for the EBL are highly required. After the successful initial CIBER- 1 experiment, we are now developing a new instrument CIBER-2, which is comprised of a 28.5-cm aluminum telescope and three broad-band, wide-field imaging cameras. The three wide-field (2.3×2.3 degrees) imaging cameras use the 2K×2K HgCdTe HAWAII-2RG arrays, and cover the optical and near-infrared wavelength range of 0.5-0.9 μm, 1.0-1.4 μm and 1.5-2.0 μm, respectively. Combining a large area telescope with the high sensitivity detectors, CIBER-2 will be able to measure the spatial fluctuations in the EBL at much fainter levels than those detected in previous CIBER-1 experiment. Additionally, we will use a linear variable filter installed just above the detectors so that a measurement of the absolute spectrum of the EBL is also possible. In this paper, the scientific motivation and the expected performance for CIBER-2 will be presented. The detailed designs of the telescope and imaging cameras will also be discussed, including the designs of the mechanical, cryogenic, and electrical systems.

A novel analytical description of periodic volume coil geometries in MRI

NASA Astrophysics Data System (ADS)

Koh, D.; Felder, J.; Shah, N. J.

2018-03-01

MRI volume coils can be represented by equivalent lumped element circuits and for a variety of these circuit configurations analytical design equations have been presented. The unification of several volume coil topologies results in a two-dimensional gridded equivalent lumped element circuit which compromises the birdcage resonator, its multiple endring derivative but also novel structures like the capacitive coupled ring resonator. The theory section analyzes a general two-dimensional circuit by noting that its current distribution can be decomposed into a longitudinal and an azimuthal dependency. This can be exploited to compare the current distribution with a transfer function of filter circuits along one direction. The resonances of the transfer function coincide with the resonance of the volume resonator and the simple analytical solution can be used as a design equation. The proposed framework is verified experimentally against a novel capacitive coupled ring structure which was derived from the general circuit formulation and is proven to exhibit a dominant homogeneous mode. In conclusion, a unified analytical framework is presented that allows determining the resonance frequency of any volume resonator that can be represented by a two dimensional meshed equivalent circuit.

Computational analysis of particle reinforced viscoelastic polymer nanocomposites - statistical study of representative volume element

NASA Astrophysics Data System (ADS)

Hu, Anqi; Li, Xiaolin; Ajdari, Amin; Jiang, Bing; Burkhart, Craig; Chen, Wei; Brinson, L. Catherine

2018-05-01

The concept of representative volume element (RVE) is widely used to determine the effective material properties of random heterogeneous materials. In the present work, the RVE is investigated for the viscoelastic response of particle-reinforced polymer nanocomposites in the frequency domain. The smallest RVE size and the minimum number of realizations at a given volume size for both structural and mechanical properties are determined for a given precision using the concept of margin of error. It is concluded that using the mean of many realizations of a small RVE instead of a single large RVE can retain the desired precision of a result with much lower computational cost (up to three orders of magnitude reduced computation time) for the property of interest. Both the smallest RVE size and the minimum number of realizations for a microstructure with higher volume fraction (VF) are larger compared to those of one with lower VF at the same desired precision. Similarly, a clustered structure is shown to require a larger minimum RVE size as well as a larger number of realizations at a given volume size compared to the well-dispersed microstructures.

Geostatistics and the representative elementary volume of gamma ray tomography attenuation in rocks cores

USGS Publications Warehouse

Vogel, J.R.; Brown, G.O.

2003-01-01

Semivariograms of samples of Culebra Dolomite have been determined at two different resolutions for gamma ray computed tomography images. By fitting models to semivariograms, small-scale and large-scale correlation lengths are determined for four samples. Different semivariogram parameters were found for adjacent cores at both resolutions. Relative elementary volume (REV) concepts are related to the stationarity of the sample. A scale disparity factor is defined and is used to determine sample size required for ergodic stationarity with a specified correlation length. This allows for comparison of geostatistical measures and representative elementary volumes. The modifiable areal unit problem is also addressed and used to determine resolution effects on correlation lengths. By changing resolution, a range of correlation lengths can be determined for the same sample. Comparison of voxel volume to the best-fit model correlation length of a single sample at different resolutions reveals a linear scaling effect. Using this relationship, the range of the point value semivariogram is determined. This is the range approached as the voxel size goes to zero. Finally, these results are compared to the regularization theory of point variables for borehole cores and are found to be a better fit for predicting the volume-averaged range.

Method and apparatus for reflection mode imaging

NASA Technical Reports Server (NTRS)

Heyser, Richard C. (Inventor); Rooney, James A. (Inventor)

1989-01-01

A volume is scanned with a raster scan about a center of rotation using a transmitter/receiver at a selected range while gating a range window on the receiver with a selected range differential. The received signals are then demodulated to obtain signals representative of a property within the volume being scanned such as the density of a tumor. The range is varied until the entire volume has been scanned at all ranges to be displayed. An imaging display is synchronously scanned together with the raster scan to display variations of the property on the display. A second transmitter/receiver with associated equipment may be offset from the first and variations displayed from each of the transmitter/receivers on its separate display. The displays may then be combined stereoscopically to provide a three-dimensional image representative of variations of the property.

Skin-electrode circuit model for use in optimizing energy transfer in volume conduction systems.

PubMed

Hackworth, Steven A; Sun, Mingui; Sclabassi, Robert J

2009-01-01

The X-Delta model for through-skin volume conduction systems is introduced and analyzed. This new model has advantages over our previous X model in that it explicitly represents current pathways in the skin. A vector network analyzer is used to take measurements on pig skin to obtain data for use in finding the model's impedance parameters. An optimization method for obtaining this more complex model's parameters is described. Results show the model to accurately represent the impedance behavior of the skin system with error of generally less than one percent. Uses for the model include optimizing energy transfer across the skin in a volume conduction system with appropriate current exposure constraints, and exploring non-linear behavior of the electrode-skin system at moderate voltages (below ten) and frequencies (kilohertz to megahertz).

21 CFR 101.30 - Percentage juice declaration for foods purporting to be beverages that contain fruit or vegetable...

Code of Federal Regulations, 2010 CFR

2010-04-01

..., diluted, or contain no juice. For example, a soft drink (soda) that does not represent or suggest by its... product computed on a volume/volume basis. (k) If the product is a beverage that contains a juice whose...

Environmental Design Research. Volume Two: Symposia and Workshops. Community Development Series.

ERIC Educational Resources Information Center

Preiser, Wolfgang F. E., Ed.

The contents of this volume represent the invited contributions to the conference and are categorized according to special (invited) addresses, symposia, and workshops. Special addresses were conceptualized to view environmental design research in a holistic way, incorporating changing societal and political conditions. Lynton K. Caldwell spoke on…

A Franco-American Overview. Volume 6. Louisiana.

ERIC Educational Resources Information Center

Allain, Mathe, Comp.; Brasseaux, Carl A., Comp.

Intended to help readers develop an appreciation of the contributions of Franco-Americans to the cultural heritage of the United States, this book, the sixth of six volumes, presents 26 chapters representing many perspectives--from the historical to the sociological--illustrating the thinking and feelings of those in the forefront of…

16 CFR 306.12 - Labels.

Code of Federal Regulations, 2011 CFR

2011-01-01

... biodiesel, biomass-based diesel, biodiesel blends, and biomass-based diesel blends. The label is 3 inches (7... biodiesel blends containing more than 5 percent and no greater than 20 percent biodiesel by volume. (i) The...” followed immediately by the numerical value representing the volume percentage of biodiesel in the fuel (e...

Annual Review of Psychology, Volume 32, 1981.

ERIC Educational Resources Information Center

Rosenzweig, Mark R., Ed.; Porter, Lyman W., Ed.

This volume contains 19 essays on current research in representative areas of psychology. All of the authors are professors and researchers at universities in the United States. A wide range of topics is discussed. Included among these are human learning and memory; behavioral decision theory; categorization of natural objects; developmental…

Advances in Environmental Science and Technology, Volume Two.

ERIC Educational Resources Information Center

Pitts, James N., Jr., Ed.; Metcalf, Robert L., Ed.

The aim of this volume is to help delineate and solve the multitude of environmental problems our technology has created. Representing a diversity of notable approaches to crucial environmental issues, it features eight self-contained chapters by noted scientists. Topics range from broad considerations of air pollution and specific techniques for…

Annual Review of Psychology, Volume 33, 1982.

ERIC Educational Resources Information Center

Rosenzweig, Mark R., Ed.; Porter, Lyman W., Ed.

This volume contains 20 essays on current research in representative areas of psychology. The authors are professors and researchers at universities in the United States, England, Colombia, Poland, Australia, the Netherlands, France, and Canada. A wide range of topics is discussed. Included among these are social psychology of intergroup…

The Quest for Relevance: Effective College Teaching. Volume I. The Humanities.

ERIC Educational Resources Information Center

American Association for Higher Education, Washington, DC.

Responding to a widely expressed discontent about college teaching shared by students, faculty and administrators, representatives of national professional and higher educational associations formed a committee to study means of revitalizing and reorienting instruction. Each contributor in Volume I, selected for his outstanding teaching skills in…

A Franco-American Overview. Volume 5. Louisiana.

ERIC Educational Resources Information Center

Allain, Mathe, Comp.; Brasseaux, Carl A., Comp.

Intended to help readers develop an appreciation of the contributions of Franco-Americans to the cultural heritage of the United States, this book, the fifth of six volumes, presents 18 chapters representing many perspectives--from the historical to the sociological--illustrating the thinking and feelings of those in the forefront of…

A Franco-American Overview. Volume 1.

ERIC Educational Resources Information Center

Albert, Renaud S., Comp.

Intended to help readers develop an appreciation of the contributions of Franco-Americans to the cultural heritage of the United States, this book, the first of six volumes, presents 14 readings representing many perspectives--from the historical to the sociological--illustrating the thinking and feelings of those in the forefront of…

The VIMOS Public Extragalactic Redshift Survey (VIPERS). Measuring non-linear galaxy bias at z ~ 0.8

NASA Astrophysics Data System (ADS)

Di Porto, C.; Branchini, E.; Bel, J.; Marulli, F.; Bolzonella, M.; Cucciati, O.; de la Torre, S.; Granett, B. R.; Guzzo, L.; Marinoni, C.; Moscardini, L.; Abbas, U.; Adami, C.; Arnouts, S.; Bottini, D.; Cappi, A.; Coupon, J.; Davidzon, I.; De Lucia, G.; Fritz, A.; Franzetti, P.; Fumana, M.; Garilli, B.; Ilbert, O.; Iovino, A.; Krywult, J.; Le Brun, V.; Le Fèvre, O.; Maccagni, D.; Małek, K.; McCracken, H. J.; Paioro, L.; Polletta, M.; Pollo, A.; Scodeggio, M.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zanichelli, A.; Burden, A.; Marchetti, A.; Martizzi, D.; Mellier, Y.; Nichol, R. C.; Peacock, J. A.; Percival, W. J.; Viel, M.; Wolk, M.; Zamorani, G.

2016-10-01

Aims: We use the first release of the VImos Public Extragalactic Redshift Survey of galaxies (VIPERS) of ~50 000 objects to measure the biasing relation between galaxies and mass in the redshift range z = [ 0.5,1.1 ]. Methods: We estimate the 1-point distribution function [PDF] of VIPERS galaxies from counts in cells and, assuming a model for the mass PDF, we infer their mean bias relation. The reconstruction of the bias relation is performed through a novel method that accounts for Poisson noise, redshift distortions, inhomogeneous sky coverage. and other selection effects. With this procedure we constrain galaxy bias and its deviations from linearity down to scales as small as 4 h-1 Mpc and out to z = 1.1. Results: We detect small (up to 2%) but statistically significant (up to 3σ) deviations from linear bias. The mean biasing function is close to linear in regions above the mean density. The mean slope of the biasing relation is a proxy to the linear bias parameter. This slope increases with luminosity, which is in agreement with results of previous analyses. We detect a strong bias evolution only for z> 0.9, which is in agreement with some, but not all, previous studies. We also detect a significant increase of the bias with the scale, from 4 to 8 h-1 Mpc , now seen for the first time out to z = 1. The amplitude of non-linearity depends on redshift, luminosity, and scale, but no clear trend is detected. Owing to the large cosmic volume probed by VIPERS, we find that the mismatch between the previous estimates of bias at z ~ 1 from zCOSMOS and VVDS-Deep galaxy samples is fully accounted for by cosmic variance. Conclusions: The results of our work confirm the importance of going beyond the over-simplistic linear bias hypothesis showing that non-linearities can be accurately measured through the applications of the appropriate statistical tools to existing datasets like VIPERS. Based on observations collected at the European Southern Observatory, Paranal, Chile, under programmes 182.A-0886 (LP) at the Very Large Telescope, and also based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. The VIPERS web site is http://vipers.inaf.it/

Personal, societal, and ecological values of wilderness: Sixth World Wilderness Congress proceedings on research, management, and allocation, Volume II

Treesearch

Alan E. Watson; Greg H. Aplet; John C. Hendee

2000-01-01

The papers contained in Volume II of these Proceedings represent a combination of papers originally scheduled for the delayed 1997 meeting of the World Wilderness Congress and those submitted in response to a second call for papers when the Congress was rescheduled for October 24-29, 1998, in Bangalore, India. Just as in Volume I, the papers are divided into seven...

Radio and X-ray properties of the source G29.37+0.1 linked to HESS J1844-030

NASA Astrophysics Data System (ADS)

Castelletti, G.; Supan, L.; Petriella, A.; Giacani, E.; Joshi, B. C.

2017-06-01

Aims: We report on the first detailed multiwavelength study of the radio source G29.37+0.1, which is an as-yet-unclassified object linked to the very-high-energy γ-emitting source HESS J1844-030. The origin of the multiwavelength emission toward G29.37+0.1 has not been clarified so far, leaving open the question about the physical relationship between these sources. Methods: Using observations carried out with the Giant Metrewave Radio Telescope (GMRT), we performed high-quality full-synthesis imaging at 610 MHz of the field containing G29.37+0.1. The obtained data, combined with observations at 1400 MHz from The Multi-Array Galactic Plane Imaging Survey (MAGPIS) were used to investigate in detail the properties of its radio emission. Additionally, we reprocessed archival data obtained with the XMM-Newton and Chandra observatories in order to get a multiwavelength view of this unusual source. Results: The radio source G29.37+0.1 mainly consists of a bright twisted structure, named the S-shaped feature. The high sensitivity of the new GMRT observations allowed the identification of potential lobes, jets, and a nuclear central region in the S-shaped morphology of G29.37+0.1. We also highlight the detection of diffuse and low surface brightness emission enveloping the brightest emitting regions. The brightest emission in G29.37+0.1 has a radio synchrotron spectral index α = 0.59 ± 0.09. Variations in the spectral behaviour are observed across the whole radio source with the flattest spectral features in the central nuclear and jets components (α 0.3). These results lead us to conclude that the brightest radio emission from G29.37+0.1 likely represents a newly recognized radio galaxy. The identification of optical and infrared counterparts to the emission arising from the core of G29.37+0.1 strengthens our interpretation of an extragalactic origin of the radio emission. We performed several tests to explain the physical mechanism responsible for the observed X-ray emission, which appears overlapping the northeastern part of the radio emission. Our spectral analysis demonstrated that a non-thermal origin for the X-ray emission compatible with a pulsar wind nebula is quite possible. The analysis of the spatial distribution of the CO gas revealed the presence of a complex of molecular clouds located in projection adjacent to the radio halo emission and probably interacting with it. We propose that the faint halo represents a composite supernova remnant with a pulsar powered component given by the diffuse X-ray emission superimposed along the line of sight to the radio galaxy. Further broadband observations of HESS J1844-030 are needed to disentangle its origin, although its shape and position suggest an extragalactic origin connected to G29.37+0.1. The reduced GMRT image (FITS file) is 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/602/A31

Extragalactic Fields Optimized for Adaptive Optics

DTIC Science & Technology

2011-03-01

DAVID MONETIO Received 2010 luly 19; accepted 2010 December 30; published 2011 March 1 ABSTRACT. In this article we present the coordinates of 67 55’ x...Window, contains most of the patches we have identified. Our optimal field, centered at R.A.: 7h24m3s, decl.: - 1 °27󈧓", has an additional advantage of...equivalent observations undertaken in existing deep fields. Online material: color figures 1 . INTRODUCTION Our understanding of the high-redshift

Directory of astronomical data files

NASA Technical Reports Server (NTRS)

1978-01-01

This Directory of Astronomical Data Files was prepared by the Data Task Force of the Interagency Coordination Committee for Astronomy (ICCA) in cooperation with the National Space Science Data Center (NSSDC). The purpose of the Directory is to provide a listing which will enable a user to locate stellar and extragalactic data sources keyed along with sufficient descriptive information to permit him to assess the value of the files for his use as well as the status and availability of the compilations.

Simbol-X: Synergies with JWST, ALMA and Herschel

NASA Astrophysics Data System (ADS)

Maiolino, R.

2009-05-01

I discuss the synergies between Simbol-X and three among the major astronomical facilities that, in the next decade, will be operative in the infrared-millimeter spectral range, namely JWST, Herschel and ALMA. I first provide a brief overview of the main features and observing capabilities offered by these facilities. Then I will discuss a few research fields (mostly extragalactic) that will geatly benefit of the joint exploitation of Simbol-X and these IR-mm observatories.

3D Spectroscopy in Astronomy

NASA Astrophysics Data System (ADS)

Mediavilla, Evencio; Arribas, Santiago; Roth, Martin; Cepa-Nogué, Jordi; Sánchez, Francisco

2011-09-01

Preface; Acknowledgements; 1. Introductory review and technical approaches Martin M. Roth; 2. Observational procedures and data reduction James E. H. Turner; 3. 3D Spectroscopy instrumentation M. A. Bershady; 4. Analysis of 3D data Pierre Ferruit; 5. Science motivation for IFS and galactic studies F. Eisenhauer; 6. Extragalactic studies and future IFS science Luis Colina; 7. Tutorials: how to handle 3D spectroscopy data Sebastian F. Sánchez, Begona García-Lorenzo and Arlette Pécontal-Rousset.

New NED XML/VOtable Services and Client Interface Applications

NASA Astrophysics Data System (ADS)

Pevunova, O.; Good, J.; Mazzarella, J.; Berriman, G. B.; Madore, B.

2005-12-01

The NASA/IPAC Extragalactic Database (NED) provides data and cross-identifications for over 7 million extragalactic objects fused from thousands of survey catalogs and journal articles. The data cover all frequencies from radio through gamma rays and include positions, redshifts, photometry and spectral energy distributions (SEDs), sizes, and images. NED services have traditionally supplied data in HTML format for connections from Web browsers, and a custom ASCII data structure for connections by remote computer programs written in the C programming language. We describe new services that provide responses from NED queries in XML documents compliant with the international virtual observatory VOtable protocol. The XML/VOtable services support cone searches, all-sky searches based on object attributes (survey names, cross-IDs, redshifts, flux densities), and requests for detailed object data. Initial services have been inserted into the NVO registry, and others will follow soon. The first client application is a Style Sheet specification for rendering NED VOtable query results in Web browsers that support XML. The second prototype application is a Java applet that allows users to compare multiple SEDs. The new XML/VOtable output mode will also simplify the integration of data from NED into visualization and analysis packages, software agents, and other virtual observatory applications. We show an example SED from NED plotted using VOPlot. The NED website is: http://nedwww.ipac.caltech.edu.

Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter

NASA Astrophysics Data System (ADS)

Abreu, P.; Aglietta, M.; Ahn, E. J.; Allard, D.; Allekotte, I.; Allen, J.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antičić, T.; Anzalone, A.; Aramo, C.; Arganda, E.; Arisaka, K.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Bäcker, T.; Badagnani, D.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Beatty, J. J.; Becker, B. R.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; Berat, C.; Bergmann, T.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brogueira, P.; Brown, W. C.; Bruijn, R.; Buchholz, P.; Bueno, A.; Burton, R. E.; Busca, N. G.; Caballero-Mora, K. S.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chudoba, J.; Clay, R. W.; Colombo, E.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; Decerprit, G.; del Peral, L.; Deligny, O.; Della Selva, A.; Dembinski, H.; Denkiewicz, A.; Di Giulio, C.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Dobrigkeit, C.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Ferrero, A.; Fick, B.; Filevich, A.; Filipčič, A.; Fleck, I.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fröhlich, U.; Fuchs, B.; Fulgione, W.; Gamarra, R. F.; Gambetta, S.; García, B.; García Gámez, D.; Garcia-Pinto, D.; Garrido, X.; Gascon, A.; Gelmini, G.; Gemmeke, H.; Gesterling, K.; Ghia, P. L.; Giaccari, U.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gonçalves, P.; Gonzalez, D.; Gonzalez, J. G.; Gookin, B.; Góra, D.; Gorgi, A.; Gouffon, P.; Gozzini, S. R.; Grashorn, E.; Grebe, S.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hague, J. D.; Hansen, P.; Harari, D.; Harmsma, S.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horneffer, A.; Hrabovský, M.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jiraskova, S.; Kadija, K.; Kaducak, M.; Kampert, K. H.; Karhan, P.; Karova, T.; Kasper, P.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuehn, F.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; Lautridou, P.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Lemiere, A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martínez Bravo, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; McEwen, M.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Meurer, C.; Mičanović, S.; Micheletti, M. I.; Miller, W.; Miramonti, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Morris, C.; Mostafá, M.; Mueller, S.; Muller, M. A.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nhung, P. T.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Nyklicek, M.; Oehlschläger, J.; Olinto, A.; Oliva, P.; Olmos-Gilbaja, V. M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Parrisius, J.; Parsons, R. D.; Pastor, S.; Paul, T.; Pavlidou, V.; Payet, K.; Pech, M.; Peķala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrinca, P.; Petrolini, A.; Petrov, Y.; Petrovic, J.; Pfendner, C.; Phan, N.; Piegaia, R.; Pierog, T.; Pimenta, M.; Pirronello, V.; Platino, M.; Ponce, V. H.; Pontz, M.; Privitera, P.; Prouza, M.; Quel, E. J.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rivera, H.; Rivière, C.; Rizi, V.; Robledo, C.; Rodriguez, G.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodriguez-Cabo, I.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Rouillé-d'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Salamida, F.; Salazar, H.; Salina, G.; Sánchez, F.; Santander, M.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, S.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Schmidt, F.; Schmidt, T.; Scholten, O.; Schoorlemmer, H.; Schovancova, J.; Schovánek, P.; Schroeder, F.; Schulte, S.; Schüssler, F.; Schuster, D.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Stapleton, J.; Stasielak, J.; Stephan, M.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Šuša, T.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Tamashiro, A.; Tapia, A.; Tarutina, T.; Taşcău, O.; Tcaciuc, R.; Tcherniakhovski, D.; Tegolo, D.; Thao, N. T.; Thomas, D.; Tiffenberg, J.; Timmermans, C.; Tiwari, D. K.; Tkaczyk, W.; Todero Peixoto, C. J.; Tomé, B.; Tonachini, A.; Travnicek, P.; Tridapalli, D. B.; Tristram, G.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van den Berg, A. M.; Vargas Cárdenas, B.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Venters, T.; Verzi, V.; Videla, M.; Villaseñor, L.; Wahlberg, H.; Wahrlich, P.; Wainberg, O.; Warner, D.; Watson, A. A.; Weidenhaupt, K.; Weindl, A.; Whelan, B. J.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Winders, L.; Winnick, M. G.; Wommer, M.; Wundheiler, B.; Yamamoto, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Ziolkowski, M.; Pierre Auger Collaboration

Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, 6 × 10 19 eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1° from the position of an active galactic nucleus within 75 Mpc (using the Véron-Cetty and Véron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is 38-6+7%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of 69-13+11%. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation.

Galactic magnetic deflections and Centaurus A as a UHECR source

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

Farrar, Glennys R.; Jansson, Ronnie; Feain, Ilana J.

2013-01-01

We evaluate the validity of leading models of the Galactic magnetic field for predicting UHECR deflections from Cen A. The Jansson-Farrar 2012 GMF model (JF12), which includes striated and random components as well as an out-of-plane contribution to the regular field not considered in other models, gives by far the best fit globally to all-sky data including the WMAP7 22 GHz synchrotron emission maps for Q, U and I and ≈ 40,000 extragalactic Rotation Measures (RMs). Here we test the models specifically in the Cen A region, using 160 well-measured RMs and the Polarized Intensity from WMAP, nearby but outsidemore » the Cen A radio lobes. The JF12 model predictions are in excellent agreement with the observations, justifying confidence in its predictions for deflections of UHECRs from Cen A. We find that up to six of the 69 Auger events above 55 EeV are consistent with originating in Cen A and being deflected ≤ 18°; in this case three are protons and three have Z = 2−4. Others of the 13 events within 18° must have another origin. In order for a random extragalactic magnetic field between Cen A and the Milky Way to appreciably alter these conclusions, its strength would have to be ∼>80 nG — far larger than normally imagined.« less

The Science and Prospects of Astrophysical Observations with New Horizons

NASA Astrophysics Data System (ADS)

Nguyen, Chi; Zemcov, Michael; Cooray, Asantha; Lisse, Carey; Poppe, Andrew

2018-01-01

Astrophysical observation from the outer solar system provides a unique and quiet vantage point from which to understand our cosmos. If properly designed, such observations enable several niche science cases that are difficult or impossible to perform near Earth. NASA's New Horizons mission includes several instruments with ~10cm telescopes that provide imaging capability from UV to near-IR wavelengths with moderate spectral resolution. A carefully designed survey can optimize the expendable propellant and limited data telemetry bandwidth to allow several unique measurements, including a detailed understanding of the cosmic extragalactic background light in the optical and near-IR, studies of the local and extragalactic UV background, measurements of the properties of dust and ice in the outer solar system, searches for moons and other faint structures around exoplanets, and determinations of the mass of planets far from their parent stars using gravitational microlensing. New Horizons is currently in an extended mission, that will conclude in 2021, designed to survey distant objects in the Kuiper Belt at high phase angles and perform a close flyby of KBO 2014 MU69. Afterwards, the astrophysics community will have a unique, generational opportunity to use this mission for astronomical observations at heliocentric distances beyond 50 AU. In this poster, we present the science case for an extended 2021 - 2026 astrophysics mission, and discuss some of the practical considerations that must be addressed to maximize the potential science return.

The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background

NASA Technical Reports Server (NTRS)

Venters, Tonia M.; Pavlidou, Vasiliki

2011-01-01

The spectral shapes of the contributions of different classes of unresolved gamma-ray emitters can provide insight into their relative contributions to the extragalactic gamma-ray background (EGB) and the natures of their spectra at GeV energies, We calculate the spectral shapes of the contributions to the EGB arising from BL Lacertae type objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) assuming blazar spectra can be described as broken power laws, We fit the resulting total blazar spectral shape to the Fermi Large Area Telescope measurements of the EGB, finding that the best-fit shape reproduces well the shape of the Fermi EGB for various break scenarios. We conclude that a scenario in which the contribution of blazars is dominant cannot be excluded on spectral grounds alone, even if spectral breaks are shown to be common among Fermi blazars. We also find that while the observation of a featureless (within uncertainties) power-law EGB spectrum by Fermi does not necessarily imply a single class of contributing unresolved sources with featureless individual spectra, such an observation and the collective spectra of the separate contributing populations determine the ratios of their contributions. As such, a comparison with studies including blazar gamma-ray luminosity functions could have profound implications for the blazar contribution to the EGB, blazar evolution, and blazar gamma-ray spectra and emission.

BLAST: The Balloon-Borne Large Aperture Submillimeter Telescope

NASA Technical Reports Server (NTRS)

Devlin, Mark; Ade, Peter; Bock, Jamie; Dicker, Simon; Griffin, Matt; Gunderson, Josh; Halpern, Mark; Hargrave, Peter; Hughes, David; Klein, Jeff

2004-01-01

BLAST is the Balloon-borne Large-Aperture Sub-millimeter Telescope. It will fly from a Long Duration Balloon (LDB) platform from Antarctica. The telescope design incorporates a 2 m primary mirror with large-format bolometer arrays operating at 250, 350 and 500 microns. By providing the first sensitive large-area (10 sq. deg.) sub-mm surveys at these wavelengths, BLAST will address some of the most important galactic and cosmological questions regarding the formation and evolution of stars, galaxies and clusters. Galactic and extragalactic BLAST surveys will: (1) identify large numbers of high-redshift galaxies; (2) measure photometric redshifts, rest-frame FIR luminosities and star formation rates thereby constraining the evolutionary history of the galaxies that produce the FIR and sub-mm background; (3) measure cold pre-stellar sources associated with the earliest stages of star and planet formation; (4) make high-resolution maps of diffuse galactic emission over a wide range of galactic latitudes. In addition to achieving the above scientific goals, the exciting legacy of the BLAST LDB experiment will be a catalogue of 3000-5000 extragalactic sub-mm sources and a 100 sq. deg. sub-mm galactic plane survey. Multi-frequency follow-up observations from SIRTF, ASTRO-F, and Herschel, together with spectroscopic observations and sub-arcsecond imaging from ALMA are essential to understand the physical nature of the BLAST sources.