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.

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

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.

HOW FAR AWAY ARE THE SOURCES OF ICECUBE NEUTRINOS? CONSTRAINTS FROM THE DIFFUSE TERAELECTRONVOLT GAMMA-RAY BACKGROUND

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

Chang, Xiao-Chuan; Liu, Ruo-Yu; Wang, Xiang-Yu, E-mail: xywang@nju.edu.cn

The nearly isotropic distribution of teraelectronvolt to petaelectronvolt neutrinos recently detected by the IceCube Collaboration suggests that they come from sources at a distance beyond our Galaxy, but how far away they are is largely unknown because of a lack of any associations with known sources. In this paper, we propose that the cumulative TeV gamma-ray emission accompanying the production of neutrinos can be used to constrain the distance of these neutrino sources, since the opacity of TeV gamma rays due to absorption by the extragalactic background light depends on the distance these TeV gamma rays have traveled. As themore » diffuse extragalactic TeV background measured by Fermi is much weaker than the expected cumulative flux associated with IceCube neutrinos, the majority of IceCube neutrinos, if their sources are transparent to TeV gamma rays, must come from distances larger than the horizon of TeV gamma rays. We find that above 80% of the IceCube neutrinos should come from sources at redshift z > 0.5. Thus, the chance of finding nearby sources correlated with IceCube neutrinos would be small. We also find that, to explain the flux of neutrinos under the TeV gamma-ray emission constraint, the redshift evolution of neutrino source density must be at least as fast as the cosmic star formation rate.« less

The Fluence and Distance Distributions of Fast Radio Bursts

NASA Astrophysics Data System (ADS)

Vedantham, H. K.; Ravi, V.; Hallinan, G.; Shannon, R. M.

2016-10-01

Fast radio bursts (FRB) are millisecond-duration radio pulses with apparent extragalactic origins. All but two of the FRBs have been discovered using the Parkes dish, which employs multiple beams formed by an array of feed horns on its focal plane. In this paper, we show that (I) the preponderance of multiple-beam detections and (II) the detection rates for varying dish diameters can be used to infer the index α of the cumulative fluence distribution function (the logN-logF function: α = 1.5 for a non-evolving population in a Euclidean universe). If all detected FRBs arise from a single progenitor population, multiple-beam FRB detection rates from the Parkes telescope yield the constraint 0.52 < α < 1.0 with 90% confidence. Searches at other facilities with different dish sizes refine the constraint to 0.5 < α < 0.9. Our results favor FRB searches with smaller dishes, because for α < 1 the gain in field of view for a smaller dish is more important than the reduction in sensitivity. Further, our results suggest that (I) FRBs are not standard candles, and (II) the distribution of distances to the detected FRBs is weighted toward larger distances. If FRBs are extragalactic, these results are consistent with a cosmological population, which would make FRBs excellent probes of the baryonic content and geometry of the universe.

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.

Astronomical Distance Determination in the Space Age. Secondary Distance Indicators

NASA Astrophysics Data System (ADS)

Czerny, Bożena; Beaton, Rachael; Bejger, Michał; Cackett, Edward; Dall'Ora, Massimo; Holanda, R. F. L.; Jensen, Joseph B.; Jha, Saurabh W.; Lusso, Elisabeta; Minezaki, Takeo; Risaliti, Guido; Salaris, Maurizio; Toonen, Silvia; Yoshii, Yuzuru

2018-02-01

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations.

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

The HST Key Project on the Extragalactic Distance Scale

NASA Astrophysics Data System (ADS)

Freedman, W. L.

1994-12-01

One of the major unresolved problems in observational cosmology is the determination of the Hubble Constant, (H_0). The Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale aims to provide a measure of H_0 to an accuracy of 10%. Historically the route to H_0 has been plagued by systematic errors; hence there is no quick and easy route to a believeable value of H_0. Achieving plausible error limits of 10% requires careful attention to eliminating potential sources of systematic error. The strategy adopted by the Key Project team is threefold: First, to discover Cepheids in spiral galaxies located in the field and in small groups that are suitable for the calibration of several independent secondary methods. Second, to make direct Cepheid measurements of 3 spiral galaxies in the Virgo cluster and 2 members of the Fornax cluster. Third, to provide a check on the the Cepheid distance scale via independent distance estimates to nearby galaxies, and in addition, to undertake an empirical test of the sensitivity of the zero point of the Cepheid PL relation to heavy-element abundances. First results from the HST Key Project will be presented. We have now determined Cepheid distances to 4 galaxies using the HST: these are the nearby galaxies M81 and M101, the edge-on galaxy NGC 925, and the face-on spiral galaxy M100 in the Virgo cluster. Recently we have measured a Cepheid distance for M100 of 17 +/- 2 Mpc, which yields a value of H_0 = 80 +/- 17 km/sec/Mpc. This work was carried out in collaboration with the other members of the HST Key Project team, R. Kennicutt, J. Mould, F. Bresolin, S. Faber, L. Ferrarese, H. Ford, J. Graham, J. Gunn, M. Han, P. Harding, J. Hoessel, R. Hill, J. Huchra, S. Hughes, G. Illingworth, D. Kelson, B. Madore, R. Phelps, A. Saha, N. Silbermann, P. Stetson, and A. Turner.

Recent progress in the theoretical modelling of Cepheids and RR Lyrae stars

NASA Astrophysics Data System (ADS)

Marconi, Marcella

2017-09-01

Cepheids and RR Lyrae are among the most important primary distance indicators to calibrate the extragalactic distance ladder and excellent stellar population tracers, for Population I and Population II, respectively. In this paper I first mention some recent theoretical studies of Cepheids and RR Lyrae obtained with different theoretical tools. Then I focus the attention on new results based on nonlinear convective pulsation models in the context of some international projects, including VMC@VISTA and the Gaia collaboration. The open problems for both Cepheids and RR Lyrae are briefly discussed together with some challenging future application.

A Second Extragalactic Radio Burst: The Beginnings of a Population

NASA Astrophysics Data System (ADS)

Keane, Evan; Kramer, Michael; Lyne, Andrew; Stappers, Benjamin

2011-04-01

In August 2001 an extremely strong isolated burst of radio emission was detected at Parkes. This "Lorimer burst" is now infamous. It apparently originated from a cosmological distance and shows all the characteristics of having traversed this large distance: frequency-dependent dispersion and scattering. Despite this there have been some who have claimed this signal to be merely a terrestrial source of interference, masquerading as something astrophysical. Furthermore, many other such bursts were expected but had not been seen, until now. We have discovered another burst, which occured 2 months earlier, in a search of archival Parkes data. Its implied distance is also cosmological. Our observations will investigate the nature of this second burst and should help unravel the mystery of these phenomena.

Late-time spectra and type Ia supernova models: New clues from the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Ruiz-Lapuente, P.; Kirshner, R. P.; Phillips, M. M.; Challis, P. M.; Schmidt, B. P.; Filippenko, A. V.; Wheeler, J. C.

1995-01-01

Calculated late-time spectra of two classical hydrodynamical models for Type Ia supernovae (deflagration model W7 of Nomoto, Thielemann, & Yokoi, and delayed detonation model DD4 of Woosley & Weaver) are compared with observations of SN 1992A and other spectroscopically normal SNe Ia. An important new piece of information is provided by observations done with the Hubble Space Telescope (HST) which cover the ultraviolet range at the nebular phase of a SN Ia: SN 1992A in NGC 1380. For the first time a picture of SN Ia emission from the ultraviolet through the optical is obtained at these phases. Predictions of the classical model (W7 and DD4) are compared with the observed spectrum of SN 1992A and with the optical spectra of SN 1989M in NGC 4579 and SN 1990N in NGC 4639 at similar epochs. The absolute B and V magnitudes of the models are also estimated at these late phases. Taken at face value the nebular spectra of these 'classical' models are more consistent with the long extragalactic distance scale, pointing to distances to NGC 4579 around 21 +/- 3 Mpc and a slightly larger distance, 22 +/- 3 Mpc, to NGC 4639, on the back side of the Virgo Cluster. However, the calculated Fe(+3) luminosity as predicted from the models exceeds the observed limit from the HST data of SN 1992A. Other differences in the ratios of the line intensities between calculated and observed spectra, show some disagreement with the observed spectra at the nebular phases. They may not be the best choice for spectroscopically normal SNe Ia, and their use as an independent calibration of the extragalactic distance scale should be viewed with caution.

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.

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.

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)

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.

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.

Companions to isolated elliptical galaxies: revisiting the Bothun-Sullivan (1977) sample using the NASA/IPAC extragalactic database

NASA Technical Reports Server (NTRS)

Madore, B. F.; Freedman, W. L.; Bothun, G. D.

2002-01-01

We investigate the number of physical companion galaxies for a sample of relatively isolated elliptical galaxies. The NASA/IPAC Extragalactic Database (NED) has been usedto reinvestigate the incidence of satellite galaxies for a sample of 34 elliptical galaxies, firstinvestigated by Bothun & Sullivan (1977) using a visual inspection of Palomar Sky Survey prints out to a projected search radius of 75 kpc. We have repeated their original investigation usingdata cataloged data in NED. Nine of these ellipticals appear to be members of galaxy clusters:the remaining sample of 25 galaxies reveals an average of +1.0 f 0.5 apparent companions per galaxy within a projected search radius of 75 kpc, in excess of two equal-area comparisonregions displaced by 150-300 kpc. This is nearly an order of magnitude larger than the +0.12+/- 0.42 companions/galaxy found by Bothun & Sullivan for the identical sample. Making use of published radial velocities, mostly available since the completion of the Bothun-Sullivan study,identifies the physical companions and gives a somewhat lower estimate of +0.4 companions per elliptical. This is still a factor of 3x larger than the original statistical study, but giventhe incomplete and heterogeneous nature of the survey redshifts in NED, it still yields a firmlower limit on the number (and identity) of physical companions. An expansion of the searchradius out to 300 kpc, again restricted to sampling only those objects with known redshifts in NED, gives another lower limit of 4.3 physical companions per galaxy. (Excluding fiveelliptical galaxies in the Fornax cluster this average drops to 3.5 companions per elliptical.)These physical companions are individually identified and listed, and the ensemble-averagedradial density distribution of these associated galaxies is presented. For the ensemble, the radial density distribution is found to have a fall-off consistent with p c( R^-0.5 out to approximately150 kpc. For non-Fornax cluster companions the fall-off continues out to the 300-kpc limit of thesurvey. The velocity dispersion of these companions is found to be constant with projected radial distance from the central elliptical, holding at a value of approximately +/- 300-350 km/sec overall.

Galaxy distances and deviations from universal expansion; Proceedings of the NATO Advanced Research Workshop, Kona, HI, Jan. 13-17, 1986

NASA Astrophysics Data System (ADS)

Madore, Barry F.; Tully, R. Brent

A collection of papers on galaxy distances and deviations from universal expansion is presented. Individual topics addressed include: new results on the distance scale and the Hubble constant, Magellanic Clouds and the distance scale, CCD observations of Cepheids in nearby galaxies, distances using A supergiant stars, infrared calibration of the Cepheid distance scale, two stepping stones to the Hubble constant, physical models of supernovae and the distance scale, 21 cm line widths and distances of spiral galaxies, infrared color-luminosity relations for field galaxies, minimizing the scatter in the Tully-Fisher relation, photometry of galaxies and the local peculiar motion, elliptical galaxies and nonuniformities in the Hubble flow, and large-scale anisotropy in the Hubble flow. Also discussed are: improved distance indicator for elliptical galaxies, anisotropy of galaxies detected by IRAS, the local gravitational field, measurements of the CBR, measure of cosmological times, ages from nuclear cosmochronology, extragalactic gas at high redshift, supercluster infall models, Virgo infall and the mass density of the universe, dynamics of superclusters and Omega(0), distribution of galaxies versus dark matter, peculiar velocities and galaxy formation, cosmological shells and blast waves.

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.

Cannibalization of Dwarf Galaxies by the Milky Way: Distance to the Leading Arm of the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Antwi-Danso, Jacqueline; Barger, Kathleen; Haffner, L. Matthew

2016-01-01

Tidal interactions between two dwarf galaxies near the Milky Way, the Large and Small Magellanic Clouds, have caused large quantities of gas to be flung into the halo of the Milky Way. Much of this tidal debris, known as the Magellanic System, is currently headed towards the disk of the Milky Way, spearheaded by the Leading Arm, with the Bridge connecting the two dwarf galaxies, and the trailing Magellanic Stream at the end. Estimates for the amount of gas that the Magellanic System contains are in the range of (2 - 4) × 109 M⊙ and this could supply our Galaxy with (3.7 - 6.7) M⊙ yr-1 (Fox et al. 2014). Although this is higher than the present star-formation rate of the Galaxy, the position of the tidal debris predisposes it to ionizing radiation from the extragalactic background and Galactic disk, as well as ram-pressure stripping from the halo, hindering gas accretion. Some parts of the Leading Arm, however, appear to have already survived the trip to the disk as their morphology is indicative of interaction with the interstellar medium of the Galaxy. The exact amount of gas that this structure contains is uncertain because of weak constrains in its distance. In this study, we made seven pointed Hα observations using the Wisconsin Hα Mapper Telescope and then compared the Hα intensity we obtained to models of the anticipated ionizing flux from the Milky Way and extragalactic background. From this, we calculated the distance from the Sun to the Leading Arm of the Magellanic System at the locations of our observations.

Statistical analysis of catalogs of extragalactic objects. II - The Abell catalog of rich clusters

NASA Technical Reports Server (NTRS)

Hauser, M. G.; Peebles, P. J. E.

1973-01-01

The results of a power-spectrum analysis are presented for the distribution of clusters in the Abell catalog. Clear and direct evidence is found for superclusters with small angular scale, in agreement with the recent study of Bogart and Wagoner (1973). It is also found that the degree and angular scale of the apparent superclustering varies with distance in the manner expected if the clustering is intrinsic to the spatial distribution rather than a consequence of patchy local obscuration.

The HST Key Project on the Extragalactic Distance Scale VI. The Cepheids in NGC925

NASA Technical Reports Server (NTRS)

Silbermann, N. A.; Harding, Paul; Madore, Barry F.; Kennicutt, Robert C., Jr.; Saha, Abhijit; Stetson, Peter; Freedman, Wendy L.; Mould, Jeremy R.; Graham, John A.; Hill, Robert J.;

An application of Bayesian statistics to the extragalactic Cepheid distance scale

NASA Astrophysics Data System (ADS)

Barnes, Thomas G., III; Moffett, Thomas J.; Jefferys, W. H.; Forestell, Amy D.

2004-05-01

We have determined quasi-geometric distances to the Magellanic Clouds, M31 and M33. Our analysis uses a Bayesian statistical method to provide mathematically rigorous and objective solutions for individual Cepheids. We combine the individual distances with a hierarchial Bayesian model to determine the galactic distances. We obtain distance moduli 18.87 ± 0.07 mag (LMC, 12 stars), 19.14 ± 0.10 (SMC, 8 stars), 23.83 ± 0.35 mag (M33, 1 star) and 25.2 ± 0.6 mag (M31, 1 star) - all uncorrected for metallicity. The M31 and M33 distances are very preliminary. If the Pl relations of the LMC, SMC, and Galaxy are identical, our results exclude the metallicity effect in the V, (V - R) surface brightness method predicted by Hindsley and Bell (1989) at the 5σ level. Alternately, if Hindsley & Bell's prediction is adopted as true, we find a metallicity effect intrinsic to the Cepheid PL relation requiring a correction Δ(V - Mv) = (0.36 ± 0.07)Δ[A/H] mag. The latter has the opposite sign to other observational estimates of the Cepheid metallicity effect.

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

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.

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.

Initial HI results from the Arecibo Pisces-Perseus Supercluster Survey

NASA Astrophysics Data System (ADS)

Craig, David W.; Davis, Cory; Johnson, Cory; Koopmann, Rebecca A.; Jones, Michael G.; Hallenbeck, Gregory L.; O'Donoghue, Aileen A.; Haynes, Martha P.; Giovanelli, Riccardo; Rosenberg, Jessica L.; Venkatesan, Aparna; Undergraduate ALFALFA Team

2017-01-01

The Arecibo Pisces-Perseus Supercluster Survey is a targeted HI survey of galaxies that began its second observing season in October 2016. The survey is conducted by members of the Undergraduate ALFALFA Team (UAT) and extensively involves undergraduates in observations, data reduction, and analysis. It aims to complement the HI sources identified by the ALFALFA extragalactic HI line survey by probing deeper in HI mass (to lower masses) than the legacy survey itself. Measurements of the HI line velocity widths will be combined with uniform processing of images obtained in the SDSS and GALEX public databases to localize the sample within the baryonic Tully Fisher relation, allowing estimates of their redshift-independent distances and thus their peculiar velocities.The survey is designed to constrain Pisces-Perseus Supercluster infall models by producing 5-σ detections of infall velocities to a precision of about 500 km/s. By targeting galaxies based on SDSS and GALEX photometry, we have achieved detection rates of 68% of the galaxies in our sample. We will discuss the target selection process, HI velocities and mass estimates from the 2015 fall observing season, preliminary results from 2016 observations, and preliminary comparisons with inflow models predicted by numerical simulations.This work has been supported by NSF grants AST-1211005, AST-1637339, AST-1637262.

A publication database for optical long baseline interferometry

NASA Astrophysics Data System (ADS)

Malbet, Fabien; Mella, Guillaume; Lawson, Peter; Taillifet, Esther; Lafrasse, Sylvain

2010-07-01

Optical long baseline interferometry is a technique that has generated almost 850 refereed papers to date. The targets span a large variety of objects from planetary systems to extragalactic studies and all branches of stellar physics. We have created a database hosted by the JMMC and connected to the Optical Long Baseline Interferometry Newsletter (OLBIN) web site using MySQL and a collection of XML or PHP scripts in order to store and classify these publications. Each entry is defined by its ADS bibcode, includes basic ADS informations and metadata. The metadata are specified by tags sorted in categories: interferometric facilities, instrumentation, wavelength of operation, spectral resolution, type of measurement, target type, and paper category, for example. The whole OLBIN publication list has been processed and we present how the database is organized and can be accessed. We use this tool to generate statistical plots of interest for the community in optical long baseline interferometry.

Clustering of local group distances: publication bias or correlated measurements? I. The large Magellanic cloud

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

De Grijs, Richard; Wicker, James E.; Bono, Giuseppe

2014-05-01

The distance to the Large Magellanic Cloud (LMC) represents a key local rung of the extragalactic distance ladder yet the galaxy's distance modulus has long been an issue of contention, in particular in view of claims that most newly determined distance moduli cluster tightly—and with a small spread—around the 'canonical' distance modulus, (m – M){sub 0} = 18.50 mag. We compiled 233 separate LMC distance determinations published between 1990 and 2013. Our analysis of the individual distance moduli, as well as of their two-year means and standard deviations resulting from this largest data set of LMC distance moduli available tomore » date, focuses specifically on Cepheid and RR Lyrae variable-star tracer populations, as well as on distance estimates based on features in the observational Hertzsprung-Russell diagram. We conclude that strong publication bias is unlikely to have been the main driver of the majority of published LMC distance moduli. However, for a given distance tracer, the body of publications leading to the tightly clustered distances is based on highly non-independent tracer samples and analysis methods, hence leading to significant correlations among the LMC distances reported in subsequent articles. Based on a careful, weighted combination, in a statistical sense, of the main stellar population tracers, we recommend that a slightly adjusted canonical distance modulus of (m – M){sub 0} = 18.49 ± 0.09 mag be used for all practical purposes that require a general distance scale without the need for accuracies of better than a few percent.« less

The Hubble Space Telescope extragalactic distance scale key project. 2: Photometry of WFC images of M81

NASA Technical Reports Server (NTRS)

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

1994-01-01

The Extragalactic Distance Scale (H(sub o)) Key Project for Hubble Space Telescope (HST) aims to employ the Cepheid period-luminosity (P-L) relation to measure galaxy distances out as far as the Virgo Cluster. The vital steps in this program are (1) to obtain precise photometry of stellar images from the Wide Field Camera (WFC) exposures of selected galaxies, and (2) to calibrate this photometry to obtain reliable distances to these galaxies from the Cepheid P-L relation. We have used the DAOPHOT II and ALLFRAME programs to determine 28 instrumental magnitudes -- 22 of F555W (of about V) and six of F785LP (of about I) -- of all stars brighter than V of about 25 in each of two 2.56 arcmin x 2.56 arcmin WFC fields of M81. The reductions use a varying point-spread function to account for the field effects in the WFC optics and yield instrumental magnitudes with single epoch precision ranging from 0.09 to 0.24 mag, at V of about 21.8 to 23.8 -- the magnitude range of the 30 Cepheids that we have now identified in M81. For brighter stars (V of about 22), single epoch magnitudes are precise to 0.09 mag. The photometric calibration onto the Johnson V and Kron-Cousins I systems was determined from independent ground-based CCD observing at the Canada-France-Hawaii Telescope (CFHT) 3.6 m (confirmed by the Kitt Peak National Observatory (KPNO) 4.0 m) and from the Palomar 5.0 m (using the wide-field COSMIC camera) and 1.5 m telescopes. Secondary standards, taken from the COSMIC and CFHT frames, were established in each of the WFC fields in V and I, allowing a direct transformation from ALLFRAME magnitudes to calibrated V and I magnitudes, giving mean V of about 23 magnitudes accurate to of about +/- 0.1 mag. The stellar populations in M81 have been analyzed in terms of the luminosity functions and color magnitude diagrams (CMD) derived from these data, from which we identify numerous supergiants, and a CMD morphology similar to M33.

VizieR Online Data Catalog: Friends-of-friends galaxy group finder (Tempel+, 2016)

NASA Astrophysics Data System (ADS)

Tempel, E.; Kipper, R.; Tamm, A.; Gramann, M.; Einasto, M.; Sepp, T.; Tuvikene, T.

2016-01-01

To delineate galaxy groups in the local Universe, we used galaxy data from the extragalactic distance database (EDD2; Tully et al., 2009AJ....138..323T). The sample encompasses three datasets. As the main source, we used the Two Micron All Sky Survey (Skrutskie et al. 2006AJ....131.1163S, Cat. VII/233) Redshift Survey (2MRS) galaxies brighter than 11.75 mag in the Ks band (for a description of the catalogue, see Huchra et al., 2012, Cat. J/ApJS/199/26). We only used galaxies that are securely off the Galactic plane: Galactic latitude |b|>5°. Since the galaxy sample becomes extremely sparse farther away, we only used galaxies with a cosmic microwave background (CMB) corrected redshift z=0...0.1 (up to 430Mpc). This selection restricts our 2MRS sample to 43480 galaxies. For our analysis, we complemented the main 2MRS sample with two other sources. From the CosmicFlows-2 survey that contains 8198 galaxies with redshift-independent distance estimates (CF2; Tully et al., 2013, Cat. J/AJ/146/86), we added 3627 (of these, 2799 galaxies do not have a measured Ks magnitude). In addition, we made use of the 2M++ catalogue Lavaux & Hudson (2011, Cat. J/MNRAS/416/2840), which combines elements from the 2MRS, the 6DF Galaxy Survey (Jones et al. 2009MNRAS.399..683J, Cat. VII/259), and the Sloan Digital Sky Survey (York et al., 2000AJ....120.1579Y). Of the 64745 galaxies of the 2M++, we added 31271 galaxies down to Ks<12.54, which extends the sample well beyond the 2MRS magnitude limit. Our final galaxy dataset includes 78378 galaxies. (4 data files).

A Renewed Look at the Planetary Nebula Luminosity Function: Circumstellar Extinction and Contamination From Compact Supernova Remnants

NASA Astrophysics Data System (ADS)

Davis, Brian; Ciardullo, Robin; Feldmeier, John; Jacoby, George H.; McCarron, Adam; Herrmann, Kimberly

2018-01-01

The planetary nebula luminosity function (PNLF) has been used as an extragalactic distance indicator since 1988, but there are still unsolved problems associated with its use. The two most serious involve PNLF distances beyond ~ 10 Mpc, which tend to be slightly smaller than those of other methods, and the lack of a theoretical explanation for the technique. We investigate these questions using a combination of narrow-band imaging data from the KPNO 4-m telescope, and recent LRS2 spectroscopy from the Hobby-Eberly Telescope.For the first project, we consider the implications of spectroscopic investigations by Kreckel et al. (2017), who found that in M74, several of the brightest planetary nebula (PN) candidates found by Herrmann et al. (2008) are actually compact supernova remnants (SNRs). First, we measure the [O III] and H-alpha fluxes of all the known SNRs in M31 and M33, and test whether those objects could be misidentified as bright PNe at distances beyond ~ 8 Mpc. We also obtain spectroscopy of bright PN candidates in the Fireworks Galaxy, NGC 6946, to test for PN/SNR confusion via the strengths of the [N II] and [S II] emission lines. Both experiments suggest that compact supernova remnants are not an important source of contamination in photometric surveys for extragalactic PNe.For the second project, we, for the first time, determine the de-reddened PNLF of an old stellar population. By performing spectroscopy of the brightest PN in M31’s bulge and measuring the objects’ Balmer decrements, we remove the effects of circumstellar extinction and derive the true location of the PNLF’s bright-end cutoff. In future studies, these data can be used to directly test the latest PNLF models, which combine modern post-AGB stellar evolutionary tracks with the physics of expanding nebulae.

IDEOS: Fitting Infrared Spectra from Dusty Galaxies

NASA Astrophysics Data System (ADS)

Viola, Vincent; Rupke, D.

2014-01-01

We fit models to heavily obscured infrared spectra taken by the Spitzer Space Telescope and prepare them for cataloguing in the Infrared Database of Extragalactic Observables from Spitzer (IDEOS). When completed, IDEOS will contain homogeneously measured mid-infrared spectroscopic observables of more than 4200 galaxies beyond the Local Group. The software we use, QUESTFit, models the spectra using up to three extincted blackbodies (including silicate, water ice, and hydrocarbon absorption) and PAH templates. We present results from a sample of the approximately 200 heavily obscured spectra that will be present in IDEOS.

VizieR Online Data Catalog: Luminous persistent sources in nearby galaxies search (Ofek, 2017)

NASA Astrophysics Data System (ADS)

Ofek, E. O.

2018-04-01

I compiled a catalog of nearby galaxies within 108Mpc. The catalog is based on combining the HyperLEDA galaxies (Paturel+ 2003, VII/238 ; Makarov+ 2014A&A...570A..13M) with the NASA Extragalactic Database (NED) redshifts, and the Sloan Digital Sky Survey (SDSS; York+ 2000AJ....120.1579Y ; see V/147) galaxies with known redshifts. Both catalogs are restricted to the FIRST radio survey footprint (Becker+ 1995ApJ...450..559B ; see VIII/92). (1 data file).

Magnetically driven relativistic jets and winds: Exact solutions

NASA Technical Reports Server (NTRS)

Contopoulos, J.

1994-01-01

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

Extra-galactic Distances with Massive Stars: The Role of Stellar Variability in the Case of M33

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

Lee Chien-Hsiu, E-mail: leech@naoj.org

2017-08-01

In modern cosmology, determining the Hubble constant (H{sub 0}) using a distance ladder to percent level and comparing with the results from the Planck  satellite can shed light on the nature of dark energy, physics of the neutrino, and curvature of the universe. Thanks to the endeavor of the SH0ES team, the uncertainty of the H{sub 0} has be dramatically reduced, from 10% to 2.4%, and with the promise of even reaching 1% in the near future. In this regard, it is fundamentally important to investigate the systematics. This is best done using other good independent distance indicators. One promisingmore » method is the flux-weighted gravity luminosity relation (FGLR) of the blue supergiants (BSGs). As BSGs are the brightest objects in galaxies, they can probe distances up to 10 Mpc with negligible blending effects. While the FGLR method delivered distance is in good agreement with other distance indicators, it has been shown that this method delivers greater distances in the cases of M33 and NGC 55. Here, we investigate whether the M33 distance estimate of FGLR suffers systematics from stellar variability. Using CFHT M33 monitoring data, we found that 9 out of 22 BSGs showed variability during the course of 500 days, although with amplitudes as small as 0.05 mag. This suggests that stellar variability plays a negligible role in the FGLR distance determination.« less

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 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.

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.

Extragalactic Supergiants

NASA Astrophysics Data System (ADS)

Urbaneja, Miguel A.; Kudritzki, Rolf P.

2017-11-01

Blue supergiant stars of B and A spectral types are amongst the visually brightest non-transient astronomical objects. Their intrinsic brightness makes it possible to obtain high quality optical spectra of these objects in distant galaxies, enabling the study not only of these stars in different environments, but also to use them as tools to probe their host galaxies. Quantitative analysis of their optical spectra provide tight constraints on their evolution in a wide range of metallicities, as well as on the present-day chemical composition, extinction laws and distances to their host galaxies. We review in this contribution recent results in this field.

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.

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

Astronomical Surveys, Catalogs, Databases, and Archives

NASA Astrophysics Data System (ADS)

Mickaelian, A. M.

2016-06-01

All-sky and large-area astronomical surveys and their cataloged data over the whole range of electromagnetic spectrum are reviewed, from γ-ray to radio, such as Fermi-GLAST and INTEGRAL in γ-ray, ROSAT, XMM and Chandra in X-ray, GALEX in UV, SDSS and several POSS I and II based catalogues (APM, MAPS, USNO, GSC) in optical range, 2MASS in NIR, WISE and AKARI IRC in MIR, IRAS and AKARI FIS in FIR, NVSS and FIRST in radio and many others, as well as most important surveys giving optical images (DSS I and II, SDSS, etc.), proper motions (Tycho, USNO, Gaia), variability (GCVS, NSVS, ASAS, Catalina, Pan-STARRS) and spectroscopic data (FBS, SBS, Case, HQS, HES, SDSS, CALIFA, GAMA). Most important astronomical databases and archives are reviewed as well, including Wide-Field Plate DataBase (WFPDB), ESO, HEASARC, IRSA and MAST archives, CDS SIMBAD, VizieR and Aladin, NED and HyperLEDA extragalactic databases, ADS and astro-ph services. They are powerful sources for many-sided efficient research using Virtual Observatory tools. Using and analysis of Big Data accumulated in astronomy lead to many new discoveries.

Astronomical data analysis software and systems I; Proceedings of the 1st Annual Conference, Tucson, AZ, Nov. 6-8, 1991

NASA Technical Reports Server (NTRS)

Worrall, Diana M. (Editor); Biemesderfer, Chris (Editor); Barnes, Jeannette (Editor)

1992-01-01

Consideration is given to a definition of a distribution format for X-ray data, the Einstein on-line system, the NASA/IPAC extragalactic database, COBE astronomical databases, Cosmic Background Explorer astronomical databases, the ADAM software environment, the Groningen Image Processing System, search for a common data model for astronomical data analysis systems, deconvolution for real and synthetic apertures, pitfalls in image reconstruction, a direct method for spectral and image restoration, and a discription of a Poisson imagery super resolution algorithm. Also discussed are multivariate statistics on HI and IRAS images, a faint object classification using neural networks, a matched filter for improving SNR of radio maps, automated aperture photometry of CCD images, interactive graphics interpreter, the ROSAT extreme ultra-violet sky survey, a quantitative study of optimal extraction, an automated analysis of spectra, applications of synthetic photometry, an algorithm for extra-solar planet system detection and data reduction facilities for the William Herschel telescope.

Evidence for dwarf stars at D of about 100 kiloparsecs near the Sextans dwarf spheroidal galaxy

NASA Technical Reports Server (NTRS)

Gould, Andrew; Guhathakurta, Puragra; Richstone, Douglas; Flynn, Chris

1992-01-01

A method is presented for detecting individual, metal-poor, dwarf stars at distances less than about 150 kpc - a method specifically designed to filter out stars from among the much more numerous faint background field galaxies on the basis of broad-band colors. This technique is applied to two fields at high Galactic latitude, for which there are deep CCD data in four bands ranging from 3600 to 9000 A. The field in Sextans probably contains more than about five dwarf stars with BJ not greater than 25.5. These are consistent with being at a common distance about 100 kpc and lie about 1.7 deg from the newly discovered dwarf galaxy in Sextans whose distance is about 85 +/- 10 kpc. The stars lie near the major axis of the galaxy and are near or beyond the tidal radius. The second field, toward the south Galactic pole, may contain up to about five extra-Galactic stars, but these show no evidence for being at a common distance. Possible applications of this type technique are discussed, and it is shown that even very low surface brightness star clusters or dwarf galaxies may be detected at distances less than about 1 Mpc.

A search for pre-main-sequence stars in high-latitude molecular clouds. 3: A survey of the Einstein database

NASA Technical Reports Server (NTRS)

Caillault, Jean-Pierre; Magnani, Loris; Fryer, Chris

1995-01-01

In order to discern whether the high-latitude molecular clouds are regions of ongoing star formation, we have used X-ray emission as a tracer of youthful stars. The entire Einstein database yields 18 images which overlap 10 of the clouds mapped partially or completely in the CO (1-0) transition, providing a total of approximately 6 deg squared of overlap. Five previously unidentified X-ray sources were detected: one has an optical counterpart which is a pre-main-sequence (PMS) star, and two have normal main-sequence stellar counterparts, while the other two are probably extragalactic sources. The PMS star is located in a high Galactic latitude Lynds dark cloud, so this result is not too suprising. The translucent clouds, though, have yet to reveal any evidence of star formation.

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 interferometric parallax with interplanetary spacecraft

NASA Astrophysics Data System (ADS)

Rodeghiero, G.; Gini, F.; Marchili, N.; Jain, P.; Ralston, J. P.; Dallacasa, D.; Naletto, G.; Possenti, A.; Barbieri, C.; Franceschini, A.; Zampieri, L.

2017-07-01

We describe an experimental scenario for testing a novel method to measure distance and proper motion of astronomical sources. The method is based on multi-epoch observations of amplitude or intensity correlations between separate receiving systems. This technique is called Interferometric Parallax, and efficiently exploits phase information that has traditionally been overlooked. The test case we discuss combines amplitude correlations of signals from deep space interplanetary spacecraft with those from distant galactic and extragalactic radio sources with the goal of estimating the interplanetary spacecraft distance. Interferometric parallax relies on the detection of wavefront curvature effects in signals collected by pairs of separate receiving systems. The method shows promising potentialities over current techniques when the target is unresolved from the background reference sources. Developments in this field might lead to the construction of an independent, geometrical cosmic distance ladder using a dedicated project and future generation instruments. We present a conceptual overview supported by numerical estimates of its performances applied to a spacecraft orbiting the Solar System. Simulations support the feasibility of measurements with a simple and time-saving observational scheme using current facilities.

The extragalactic universe - An alternative view

NASA Technical Reports Server (NTRS)

Arp, H. C.; Burbidge, G.; Hoyle, F.; Wickramasing, N. C.; Narlikar, J. V.

1990-01-01

It is argued that the currently popular cosmological model is subject to many doubts based on observational data which suggest that there never was a Big Bang. It is further argued that the observational evidence concerning nonthermal objects with large redshifts leads to the conclusion that these redshifts are largely intrinsic in origin. These objects do not lie at large cosmological distances, but rather much closer with z(c) less than about 0.1. This in turn means that there is no evidence for evolution in the discrete objects, and that what is seen in them are creation events involving the ejection of new matter from the nuclei of galaxies.

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.

Randomized Approaches for Nearest Neighbor Search in Metric Space When Computing the Pairwise Distance Is Extremely Expensive

NASA Astrophysics Data System (ADS)

Wang, Lusheng; Yang, Yong; Lin, Guohui

Finding the closest object for a query in a database is a classical problem in computer science. For some modern biological applications, computing the similarity between two objects might be very time consuming. For example, it takes a long time to compute the edit distance between two whole chromosomes and the alignment cost of two 3D protein structures. In this paper, we study the nearest neighbor search problem in metric space, where the pair-wise distance between two objects in the database is known and we want to minimize the number of distances computed on-line between the query and objects in the database in order to find the closest object. We have designed two randomized approaches for indexing metric space databases, where objects are purely described by their distances with each other. Analysis and experiments show that our approaches only need to compute O(logn) objects in order to find the closest object, where n is the total number of objects in the database.

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.

The 3XMM spectral fit database

NASA Astrophysics Data System (ADS)

Georgantopoulos, I.; Corral, A.; Watson, M.; Carrera, F.; Webb, N.; Rosen, S.

2016-06-01

I will present the XMMFITCAT database which is a spectral fit inventory of the sources in the 3XMM catalogue. Spectra are available by the XMM/SSC for all 3XMM sources which have more than 50 background subtracted counts per module. This work is funded in the framework of the ESA Prodex project. The 3XMM catalog currently covers 877 sq. degrees and contains about 400,000 unique sources. Spectra are available for over 120,000 sources. Spectral fist have been performed with various spectral models. The results are available in the web page http://xraygroup.astro.noa.gr/ and also at the University of Leicester LEDAS database webpage ledas-www.star.le.ac.uk/. The database description as well as some science results in the joint area with SDSS are presented in two recent papers: Corral et al. 2015, A&A, 576, 61 and Corral et al. 2014, A&A, 569, 71. At least for extragalactic sources, the spectral fits will acquire added value when photometric redshifts become available. In the framework of a new Prodex project we have been funded to derive photometric redshifts for the 3XMM sources using machine learning techniques. I will present the techniques as well as the optical near-IR databases that will be used.

Establishing the Galactic Centre distance using VVV Bulge RR Lyrae variables

NASA Astrophysics Data System (ADS)

Majaess, D.; Dékány, I.; Hajdu, G.; Minniti, D.; Turner, D.; Gieren, W.

2018-06-01

This study's objective was to exploit infrared VVV (VISTA Variables in the Via Lactea) photometry for high latitude RRab stars to establish an accurate Galactic Centre distance. RRab candidates were discovered and reaffirmed (n=4194) by matching Ks photometry with templates via χ 2 minimization, and contaminants were reduced by ensuring targets adhered to a strict period-amplitude (Δ Ks) trend and passed the Elorietta et al. classifier. The distance to the Galactic Centre was determined from a high latitude Bulge subsample (|b|>4°, R_{GC}=8.30 ± 0.36 kpc, random uncertainty is relatively negligible), and importantly, the comparatively low color-excess and uncrowded location mitigated uncertainties tied to the extinction law, the magnitude-limited nature of the analysis, and photometric contamination. Circumventing those problems resulted in a key uncertainty being the M_{Ks} relation, which was derived using LMC RRab stars (M_{Ks}=-(2.66± 0.06) log {P}-(1.03± 0.06), (J-Ks)0=(0.31± 0.04) log {P} + (0.35± 0.02), assuming μ _{0,LMC}=18.43). The Galactic Centre distance was not corrected for the cone-effect. Lastly, a new distance indicator emerged as brighter overdensities in the period-magnitude-amplitude diagrams analyzed, which arise from blended RRab and red clump stars. Blending may thrust faint extragalactic variables into the range of detectability.

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.

Dismantling Hubble's Legacy?

NASA Astrophysics Data System (ADS)

Way, Michael J.

2014-01-01

Edwin Hubble is famous for a number of discoveries that are well known to amateur and professional astronomers, students and even the general public. The origins of three of the most well-known discoveries are examined: The distances to nearby spiral nebulae, the classification of extragalactic-nebulae and the Hubble constant. In the case of the first two a great deal of supporting evidence was already in place, but little credit was given. The Hubble Constant had already been estimated in 1927 by Georges Lemaitre with roughly the same value that Hubble obtained in 1929 using redshifts provided mostly by Vesto M. Slipher. These earlier estimates were not adopted or were forgotten by the astronomical community for complex scientific, sociological and psychological reasons.

A new supernova light curve modeling program

NASA Astrophysics Data System (ADS)

Jäger, Zoltán; Nagy, Andrea P.; Biro, Barna I.; Vinkó, József

2017-12-01

Supernovae are extremely energetic explosions that highlight the violent deaths of various types of stars. Studying such cosmic explosions may be important because of several reasons. Supernovae play a key role in cosmic nucleosynthesis processes, and they are also the anchors of methods of measuring extragalactic distances. Several exotic physical processes take place in the expanding ejecta produced by the explosion. We have developed a fast and simple semi-analytical code to model the the light curve of core collapse supernovae. This allows the determination of their most important basic physical parameters, like the the radius of the progenitor star, the mass of the ejected envelope, the mass of the radioactive nickel synthesized during the explosion, among others.

Bursting star formation and the overabundance of Wolf-Rayet stars

NASA Technical Reports Server (NTRS)

Bodigfee, G.; Deloore, C.

1985-01-01

The ratio of the number of WR-stars to their OB progenitors appears to be significantly higher in some extragalactic systems than in our Galaxy. This overabundance of Wolf-Rayet-stars can be explained as a consequence of a recent burst of star formation. It is suggested that this burst is the manifestation of a long period nonlinear oscillation in the star formation process, produced by positive feedback effects between young stars and the interstellar medium. Star burst galaxies with large numbers of WR-stars must generate gamma - fluxes but due to the distance, all of them are beyond the reach of present-day ray detectors, except probably 30 Dor.

Astronomers Set a New Galaxy Distance Record

NASA Image and Video Library

2015-05-06

This is a Hubble Space Telescope image of the farthest spectroscopically confirmed galaxy observed to date (inset). It was identified in this Hubble image of a field of galaxies in the CANDELS survey (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey). NASA’s Spitzer Space Telescope also observed the unique galaxy. The W. M. Keck Observatory was used to obtain a spectroscopic redshift (z=7.7), extending the previous redshift record. Measurements of the stretching of light, or redshift, give the most reliable distances to other galaxies. This source is thus currently the most distant confirmed galaxy known, and it appears to also be one of the brightest and most massive sources at that time. The galaxy existed over 13 billion years ago. The near-infrared light image of the galaxy (inset) has been colored blue as suggestive of its young, and hence very blue, stars. The CANDELS field is a combination of visible-light and near-infrared exposures. Credits: NASA, ESA, P. Oesch (Yale U.)

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.;

The many flavours of photometric redshifts

NASA Astrophysics Data System (ADS)

Salvato, Mara; Ilbert, Olivier; Hoyle, Ben

2018-06-01

Since more than 70 years ago, the colours of galaxies derived from flux measurements at different wavelengths have been used to estimate their cosmological distances. Such distance measurements, called photometric redshifts, are necessary for many scientific projects, ranging from investigations of the formation and evolution of galaxies and active galactic nuclei to precision cosmology. The primary benefit of photometric redshifts is that distance estimates can be obtained relatively cheaply for all sources detected in photometric images. The drawback is that these cheap estimates have low precision compared with resource-expensive spectroscopic ones. The methodology for estimating redshifts has been through several revolutions in recent decades, triggered by increasingly stringent requirements on the photometric redshift accuracy. Here, we review the various techniques for obtaining photometric redshifts, from template-fitting to machine learning and hybrid schemes. We also describe state-of-the-art results on current extragalactic samples and explain how survey strategy choices affect redshift accuracy. We close with a description of the photometric redshift efforts planned for upcoming wide-field surveys, which will collect data on billions of galaxies, aiming to investigate, among other matters, the stellar mass assembly and the nature of dark energy.

A water-vapour giga-maser in the active galaxy TXFS2226-184.

PubMed

Koekemoer, A M; Henkel, C; Greenhill, L J; Dey, A; van Breugel, W; Codella, C; Antonucci, R

1995-12-14

Active galactic nuclei are thought to be powered by gas falling into a massive black hole; the different types of active galaxy may arise because we view them through a thick torus of molecular gas at varying angles of inclination. One way to determine whether the black hole is surrounded by a torus, which would obscure the accretion disk around the black hole along certain lines of sight, is to search for water masers, as these exist only in regions with plentiful molecular gas. Since the first detection of an extra-galactic water maser in 1979, they have come to be associated primarily with active galaxies, and have even been used to probe the mass of the central engine. Here we report the detection of a water giga-maser in the radio galaxy TXFS2226-184. The strength of the emission supports a recently proposed theory of maser pumping that allows for even more powerful masers, which might be detectable at cosmological distances. Water masers may accordingly provide a way to determine distances to galaxies outside the usual distance ladder, providing an independent calibration of the Hubble constant.

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.

Constraining the redshift distribution of ultrahigh-energy-cosmic-ray sources by isotropic gamma-ray background

NASA Astrophysics Data System (ADS)

Liu, Ruo-Yu; Taylor, Andrew; Wang, Xiang-Yu; Aharonian, Felix

2017-01-01

By interacting with the cosmic background photons during their propagation through intergalactic space, ultrahigh energy cosmic rays (UHECRs) produce energetic electron/positron pairs and photons which will initiate electromagnetic cascades, contributing to the isotropic gamma-ray background (IGRB). The generated gamma-ray flux level highly depends on the redshift evolution of the UHECR sources. Recently, the Fermi-LAT collaboration reported that 86-14+16 of the total extragalactic gamma-ray flux comes from extragalactic point sources including those unresolved ones. This leaves a limited room for the diffusive gamma ray generated via UHECR propagation, and subsequently constrains their source distribution in the Universe. Normalizing the total cosmic ray energy budget with the observed UHECR flux in the energy band of (1-4)×1018 eV, we calculate the diffuse gamma-ray flux generated through UHECR propagation. We find that in order to not overshoot the new IGRB limit, these sub-ankle UHECRs should be produced mainly by nearby sources, with a possible non-negligible contribution from our Galaxy. The distance for the majority of UHECR sources can be further constrained if a given fraction of the observed IGRB at 820 GeV originates from UHECR. We note that our result should be conservative since there may be various other contributions to the IGRB that is not included here.

Cosmic mass spectrometer

NASA Astrophysics Data System (ADS)

Anchordoqui, Luis A.; Barger, Vernon; Weiler, Thomas J.

2018-03-01

We argue that if ultrahigh-energy (E ≳1010GeV) cosmic rays are heavy nuclei (as indicated by existing data), then the pointing of cosmic rays to their nearest extragalactic sources is expected for 1010.6 ≲ E /GeV ≲1011. This is because for a nucleus of charge Ze and baryon number A, the bending of the cosmic ray decreases as Z / E with rising energy, so that pointing to nearby sources becomes possible in this particular energy range. In addition, the maximum energy of acceleration capability of the sources grows linearly in Z, while the energy loss per distance traveled decreases with increasing A. Each of these two points tend to favor heavy nuclei at the highest energies. The traditional bi-dimensional analyses, which simultaneously reproduce Auger data on the spectrum and nuclear composition, may not be capable of incorporating the relative importance of all these phenomena. In this paper we propose a multi-dimensional reconstruction of the individual emission spectra (in E, direction, and cross-correlation with nearby putative sources) to study the hypothesis that primaries are heavy nuclei subject to GZK photo-disintegration, and to determine the nature of the extragalactic sources. More specifically, we propose to combine information on nuclear composition and arrival direction to associate a potential clustering of events with a 3-dimensional position in the sky. Actually, both the source distance and maximum emission energy can be obtained through a multi-parameter likelihood analysis to accommodate the observed nuclear composition of each individual event in the cluster. We show that one can track the level of GZK interactions on an statistical basis by comparing the maximum energy at the source of each cluster. We also show that nucleus-emitting-sources exhibit a cepa stratis structure on Earth which could be pealed off by future space-missions, such as POEMMA. Finally, we demonstrate that metal-rich starburst galaxies are highly-plausible candidate sources, and we use them as an explicit example of our proposed multi-dimensional analysis.

Sco X-1 - A galactic radio source with an extragalactic radio morphology

NASA Technical Reports Server (NTRS)

Geldzahler, B. J.; Corey, B. E.; Fomalont, E. B.; Hilldrup, K.

1981-01-01

VLA observations of radio emissions at 1465 and 4885 MHz, of Sco X-1 confirm the existence of a colinear triple structure. Evidence that the three components of Sco X-1 are physically associated is presented, including the morphology, spectrum, variability, volume emissivity and magnetic field strength. The possibility of a physical phenomenon occurring in Sco X-1 similar to that occurring in extragalactic radio sources is discussed, and two galactic sources are found having extended emission similar to that in extragalactic objects. The extended structure of Sco X-1 is also observed to be similar to that of the hot spots in luminous extragalactic sources, and a radio source 20 arcmin from Sco X-1 is found to lie nearly along the radio axis formed by the components of Sco X-1.

Enhancing the Spectral Hardening of Cosmic TeV Photons by Mixing with Axionlike Particles in the Magnetized Cosmic Web.

PubMed

Montanino, Daniele; Vazza, Franco; Mirizzi, Alessandro; Viel, Matteo

2017-09-08

Large-scale extragalactic magnetic fields may induce conversions between very-high-energy photons and axionlike particles (ALPs), thereby shielding the photons from absorption on the extragalactic background light. However, in simplified "cell" models, used so far to represent extragalactic magnetic fields, this mechanism would be strongly suppressed by current astrophysical bounds. Here we consider a recent model of extragalactic magnetic fields obtained from large-scale cosmological simulations. Such simulated magnetic fields would have large enhancement in the filaments of matter. As a result, photon-ALP conversions would produce a significant spectral hardening for cosmic TeV photons. This effect would be probed with the upcoming Cherenkov Telescope Array detector. This possible detection would give a unique chance to perform a tomography of the magnetized cosmic web with ALPs.

Distances to M101, NGC 2403, and NGC 2366 via Long Period Variables

NASA Astrophysics Data System (ADS)

Jurcevic, J. S.

1998-12-01

A new method of measuring accurately extra-Galactic distances has been developed based on the relationship between the luminosity of red supergiant variable (RSV) stars at optical wavelengths and their period of luminosity variation. This period-luminosity (PL) relationship has been calibrated in the broadband optical R and I-bands with RSVs from the Galactic Perseus OB1 association, the Large Magellanic Cloud, and M33. To verify the effectiveness of these RSV PL relations, the distances to the galaxies M101, NGC 2403, and NGC 2366 were determined. These galaxies were chosen because they had existing Cepheid based distances to use as a comparison between the two methods. These galaxies also span a range of metallicity to investigate any metallicity effects. Ground-based photometry of the galaxies in the R-band was obtained over four years to discover red variable stars with periods in the range 100--1200 days. The number of RSVs discovered in M101, NGC 2403, and NGC 2366 was 42, 61, and 20, respectively. By assuming a distance modulus for the Large Magellanic Cloud of 18.5 +/- 0.1 mag, single epoch I-band photometry of the RSVs was used to construct random phase PL relations resulting in distance moduli for M101, NGC 2403, and NGC 2366 of 29.40 +/- 0.16, 27.67 +/- 0.16, and 27.86 +/- 0.20 mag, respectively. These distances have been corrected for extinction by assuming values of E(B - V) = 0.10, 0.04, and 0.04 mag, respectively. These distances agree quite well with those found via recent Cepheid based measurements. In particular, the RSV distance modulus to M101 is very close to the HST Key Project Cepheid modulus of 29.34 +/- 0.17 mag (Kelson {et al. } 1996). These results show that RSVs, at optical wavelengths, provide a new method for measuring distances with a precision comparable to that of Cepheids with the advantages of being more luminous and more abundant than Cepheids.

Centaurus A, the core of the problem

NASA Technical Reports Server (NTRS)

Tingay, S. J.; Jauncey, D. L.; Preston, R. A.; Reynolds, J. E.; Meier, D. L.; Tzioumis, A. K.; Jones, D. L.; King, E. A.; Amy, S. W.; Biggs, J. D.

1994-01-01

The bright, peculiar elliptical galaxy Centaurus A (NGC 5128, PKS 1322-427) was one of the first extragalactic radio sources to be optically identified (Bolton et al. 1949). At a distance of 4 Mpc, Centaurus A is the closest active radio galaxy and affords the highest linear imaging resolution (1 mas approximately equal to 0.02 pc) and hence the best prospects for studying an active nucleus close to the central radio source. We present the results of multi-epoch, 8.4-GHz, very long baseline interferometry (VLBI), imaging observations of the nucleus made over the past three years. The nucleus possesses a core-jet structure where the inner portion of the jet shows apparent linear motion with a velocity substantially less than the speed of light.

High resolution in galaxy photometry and imaging

NASA Astrophysics Data System (ADS)

Nieto, J.-L.; Lelievre, G.

Techniques for increasing the resolution of ground-based photometric observations of galaxies are discussed. The theoretical limitations on resolution and their implications for choosing telescope size at a given site considered, with an emphasis on the importance of the Fried (1966) parameter r0. The techniques recommended are shortening exposure time, selection of the highest-resolution images, and a posteriori digital image processing (as opposed to active-mirror image stabilization or the cine-CCD system of Fort et al., 1984). The value of the increased resolution (by a factor of 2) achieved at Pic du Midi observatory for studies of detailed structure in extragalactic objects, for determining the distance to galaxies, and for probing the central cores of galaxies is indicated.

MAGiX in the Chandra Archive

NASA Astrophysics Data System (ADS)

Townsley, Leisa

2016-09-01

Massive star-forming regions (MSFRs) are engines of change across the Galaxy, providing its ionization, fueling the hot ISM, and seeding spiral arms with tens of thousands of new stars. Galactic MSFRs are springboards for understanding their extragalactic counterparts, which provide the basis for star formation rate calibrations and form the building blocks of starburst galaxies. This archive program will extend Chandra's lexicon of the Galaxy's MSFRs with in-depth analysis of 16 complexes, studying star formation and evolution on scales of tenths to tens of parsecs, distances <1 to >10 kpc, and ages <1 to >15 Myr. It fuses a "Physics of the Cosmos" mission with "Cosmic Origins" science, bringing new insight into star formation and feedback through Chandra's unique X-ray perspective.

More MAGiX in the Chandra Archive

NASA Astrophysics Data System (ADS)

Townsley, Leisa

2017-09-01

Massive star-forming regions (MSFRs) are engines of change across the Galaxy, providing its ionization, fueling the hot ISM, and seeding spiral arms with tens of thousands of new stars. Resolvable MSFRs are microscopes for understanding their more distant extragalactic counterparts, which provide the basis for star formation rate calibrations and form the building blocks of starburst galaxies. This archive program will extend Chandra's lexicon of MSFRs with in-depth analysis of 16 complexes, studying star formation and evolution on scales of tenths to tens of parsecs, distances <1 to >50 kpc, and ages <1 to 25 Myr. It fuses a "Physics of the Cosmos" mission with "Cosmic Origins" science, bringing new insight into star formation and feedback through Chandra's unique X-ray perspective.

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.

VizieR Online Data Catalog: VIMOS Public Extragalactic Survey (VIPERS) DR1 (Garilli+, 2014)

NASA Astrophysics Data System (ADS)

Garilli, B.; Guzzo, L.; Scodeggio, M.; Bolzonella, M.; Abbas, U.; Adami, C.; Arnouts, S.; Bel, J.; Bottini, D.; Branchini, E.; Cappi, A.; Coupon, J.; Cucciati, O.; Davidzon, I.; de Lucia, G.; de la Torre, S.; Franzetti, P.; Fritz, A.; Fumana, M.; Granett, B. R.; Ilbert, O.; Iovino, A.; Krywult, J.; Le Brun, V.; Le Fevre, O.; Maccagni, D.; Malek, K.; Marulli, F.; McCracken, H. J.; Paioro, L.; Polletta, M.; Pollo, A.; Schlagenhaufer, H.; Tasca, L. A. M.; Tojeiro, R.; Vergani, D.; Zamorani, G.; Zanichelli, A.; Burden, A.; di Porto, C.; Marchetti, A.; Marinoni, C.; Mellier, Y.; Moscardini, L.; Nichol, R. C.; Peacock, J. A.; Percival, W. J.; Phleps, S.; Wolk, M.

2014-09-01

We present the first Public Data Release (PDR-1) of the VIMOS Public Extragalactic Survey (VIPERS). It comprises 57204 spectroscopic measurements together with all additional information necessary for optimal scientific exploitation of the data, in particular the associated photometric measurements and quantification of the photometric and survey completeness. VIPERS is an ESO Large Programme designed to build a spectroscopic sample of =~100000 galaxies with iAB<22.5 and 0.5

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.

Characterizing Extragalactic Star Formation with GALEX Legacy Photometric Analysis of UV-Bright Stellar Complexes

NASA Astrophysics Data System (ADS)

Thilker, David

At the close of nearly a decade of observing, GALEX has accumulated an unprecedented archive of ultraviolet (UV) images revealing both the scope and intricacy of star formation (SF) in many thousands of galaxies inhabiting the local universe. If the observed hierarchical SF morphology can be quantified systematically, and physically interpreted with multi-wavelength ancillary data and modeling, then the low redshift GALEX legacy will approach completion. However, the GALEX GR6 pipeline database contains a highly incomplete census of young stellar complexes even for very well-studied galaxies. We propose to apply a dedicated photometry algorithm that has been optimized for measuring the properties of irregularly shaped sources in crowded galaxy images containing spatially variant, diffuse intra-clump emission. Structures will be selected in the UV, but we will compile UV-visible-MIR SEDs for each detection utilizing Pan-STARRS1+SDSS and WISE data. These SEDs will then be fit using population-synthesis models to derive estimated stellar mass, age, and extinction. Processing will be completed for the entire diameter-limited GALEX Large Galaxy Atlas (GLGA) sample of 20,000+ galaxies, at a variety of standardized spatial resolutions. Although the precise categorization of the cataloged substructures will depend on galaxy distance, the outcome of our analysis will be a catalog similar to the stellar association surveys of past decades for very nearby galaxies based on resolved stars (e.g. van den Bergh 1964, Hodge 1986, Efremov et al. 1987), except that our investigation will probe a galaxy sample of dramatically larger size using the integrated UV light from such groupings of young stars. Our algorithm is multi-scale in nature and will thus preserve the hierarchical properties of the stellar distribution, by linking sub-clumps to their larger-scale parent feature(s). The resulting database will be a fundamental resource for follow-up multi-wavelength studies probing SF-driven galaxy evolution using both existing NASA databases and operating instruments, in addition to upcoming space telescopes. While a legacy of our project will be the hierarchical photometric database (disseminated via MAST and NED) which supports extragalactic community science, our own goals from the proposed comprehensive measurements address some vital issues: (i) Currently there is controversy regarding the power-law slope of the empirical star formation law (SFL). Is there constant star formation efficiency above the HI-to-H_2 transition gas surface density (implying ~unity slope, see papers by Bigiel et al. and Leroy et al.), or is the SFL relation a stronger function of gas density with a super-linear form (as observed by Kennicutt et al. 2007)? Liu et al. (2011) have shown that the answer may depend critically on whether or not diffuse emission underlying star-forming substructures is removed. Our analysis will allow firm resolution of this issue, as we will also apply our photometry algorithm to Spitzer imaging for a subset of our sample galaxies, thus providing background-subtracted L(UV) and L(IR) measurements for substructures which can then be compared to existing and forthcoming (ALMA) CO imaging. (ii) We will also verify/calibrate our SED-fit based determination of age, extinction, and mass for UV-bright structures via direct comparison to the ground-truth stemming from resolved stellar populations (e.g. in ANGST galaxies) and also high-resolution HST UV-optical star cluster surveys (further out in the Local Volume). (iii) Finally, we will measure the diffuse UV fraction in a few hundred of the nearest galaxies (accounting for variation tied only to spatial resolution), trying to ascertain the characteristic fraction in galaxies of different Hubble type and dust-to-gas ratio. Systematic local variations in diffuse fraction and color will also be quantified as a function of environment.

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

The Carnegie Hubble Program: The Leavitt Law at 3.6 microns and 4.5 microns in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Scowcroft, Victoria; Freedman, Wendy L.; Madore, Barry F.; Monson, Andrew J.; Persson, S. E.; Seibert, Mark; Rigby, Jane R.; Sturch, Laura

2011-01-01

The Carnegie Hubble Program (CHP) is designed to improve the extragalactic distance scale using data from the post-cryogenic era of Spitzer. The ultimate goal is a determination of the Hubble constant to an accuracy of 2%. This paper is the first in a series on the Cepheid population of the Large Magellanic Cloud, and focuses on the period-luminosity relations (Leavitt laws) that will be used, in conjunction with observations of Milky Way Cepheids, to set the slope and zero-point of the Cepheid distance scale in the mid-infrared. To this end, we have obtained uniformly-sampled light curves for 85 LMC Cepheids, having periods between 6 and 140 days. Period- luminosity and period-color relations are presented in the 3.6 micron and 4.5 micron bands. We demonstrate that the 3.6 micron band is a superb distance indicator. The cyclical variation of the [3.6]-[4.5] color has been measured for the first time. We attribute the amplitude and phase of the color curves to the dissociation and recombination of CO molecules in the Cepheid s atmosphere. The CO affects only the 4.5 micron flux making it a potential metallicity indicator.

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.

The Carnegie Hubble Program

NASA Technical Reports Server (NTRS)

Freedman, Wendy L.; Madore, Barry F.; Scowcroft, Vicky; Mnso, Andy; Persson, S. E.; Rigby, Jane; Sturch, Laura; Stetson, Peter

2011-01-01

We present an overview of and preliminary results from an ongoing comprehensive program that has a goal of determining the Hubble constant to a systematic accuracy of 2%. As part of this program, we are currently obtaining 3.6 micron data using the Infrared Array Camera (IRAC) on Spitzer, and the program is designed to include JWST in the future. We demonstrate that the mid-infrared period-luminosity relation for Cepheids at 3.6 microns is the most accurate means of measuring Cepheid distances to date. At 3.6 microns, it is possible to minimize the known remaining systematic uncertainties in the Cepheid extragalactic distance scale. We discuss the advantages of 3.6 micron observations in minimizing systematic effects in the Cepheid calibration of the Hubble constant including the absolute zero point, extinction corrections, and the effects of metallicity on the colors and magnitudes of Cepheids. We are undertaking three independent tests of the sensitivity of the mid-IR Cepheid Leavitt Law to metallicity, which when combined will allow a robust constraint on the effect. Finally, we are providing a new mid-IR Tully-Fisher relation for spiral galaxies.

Implications for the Origin of GRB 051103 from LIGO Observations

NASA Technical Reports Server (NTRS)

Bizouard, M. A.; Dietz, A.; Guidi, G. M.; Was, M.; Camp, J. B.; Cannizzo, J.; Stroeer, A. S.; Blackburn, L.

2012-01-01

We present the results of a LIGO search for gravitational waves (GWs) associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst whose electromagnetically determined sky position is coincident with the spiral galaxy M81, which is 3.6Mpc from Earth. Possible progenitors for short-hard GRBs include compact object mergers and soft gamma repeater (SGR) giant flares. A merger progenitor would produce a characteristic GW signal that should be detectable at the distance of M81, while GW emission from an SGR is not expected to be detectable at that distance. We found no evidence of a GW signal associated with GRB 051103. Assuming weakly beamed gamma-ray emission with a jet semi-angle of 30. we exclude a binary neutron star merger in M81 as the progenitor with a confidence of 98%. Neutron star-black hole mergers are excluded with > 99% confidence. If the event occurred in M81 our findings support the hypothesis that GRB 051103 was due to an SGR giant flare, making it the most distant extragalactic magnetar observed to date.

Implications for the Origin of GRB 051103 from LIGO Observations

NASA Astrophysics Data System (ADS)

Abadie, J.; Abbott, B. P.; Abbott, T. D.; Abbott, R.; Abernathy, M.; Adams, C.; Adhikari, R.; Affeldt, C.; Ajith, P.; Allen, B.; Allen, G. S.; Amador Ceron, E.; Amariutei, D.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Arain, M. A.; Araya, M. C.; Aston, S. M.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballmer, S.; Barker, D.; Barnum, S.; Barr, B.; Barriga, P.; Barsotti, L.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Bauchrowitz, J.; Behnke, B.; Bell, A. S.; Belopolski, I.; Benacquista, M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biswas, R.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bondarescu, R.; Bork, R.; Born, M.; Bose, S.; Boyle, M.; Brady, P. R.; Braginsky, V. B.; Brau, J. E.; Breyer, J.; Bridges, D. O.; Brinkmann, M.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Brummitt, A.; Buonanno, A.; Burguet-Castell, J.; Burmeister, O.; Byer, R. L.; Cadonati, L.; Camp, J. B.; Campsie, P.; Cannizzo, J.; Cannon, K.; Cao, J.; Capano, C.; Caride, S.; Caudill, S.; Cavaglia, M.; Cepeda, C.; Chalermsongsak, T.; Chalkley, E.; Charlton, P.; Chelkowski, S.; Chen, Y.; Christensen, N.; Chua, S. S. Y.; Chung, S.; Chung, C. T. Y.; Clara, F.; Clark, D.; Clark, J.; Clayton, J. H.; Conte, R.; Cook, D.; Corbitt, T. R. C.; Cornish, N.; Costa, C. A.; Coughlin, M.; Coward, D. M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Culter, R. M.; Dahl, K.; Danilishin, S. L.; Dannenberg, R.; Danzmann, K.; Das, K.; Daudert, B.; Daveloza, H.; Davies, G.; Daw, E. J.; Dayanga, T.; DeBra, D.; Degallaix, J.; Dent, T.; Dergachev, V.; DeRosa, R.; DeSalvo, R.; Dhurandhar, S.; Di Palma, I.; Díaz, M.; Donovan, F.; Dooley, K. L.; Dorsher, S.; Douglas, E. S. D.; Drever, R. W. P.; Driggers, J. C.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Engel, R.; Etzel, T.; Evans, M.; Evans, T.; Factourovich, M.; Fairhurst, S.; Fan, Y.; Farr, B. F.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Finn, L. S.; Flanigan, M.; Foley, S.; Forsi, E.; Fotopoulos, N.; Frede, M.; Frei, M.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Garcia, J.; Garofoli, J. A.; Gholami, I.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Gill, C.; Goetz, E.; Goggin, L. M.; González, G.; Gorodetsky, M. L.; Goßler, S.; Graef, C.; Grant, A.; Gras, S.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Grosso, R.; Grote, H.; Grunewald, S.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Hage, B.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Heefner, J.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Hong, T.; Hooper, S.; Hosken, D. J.; Hough, J.; Howell, E. J.; Hughey, B.; Husa, S.; Huttner, S. H.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Johnson, W. W.; Jones, D. I.; Jones, G.; Jones, R.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kanner, J. B.; Katsavounidis, E.; Katzman, W.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Kells, W.; Kelner, M.; Keppel, D. G.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, N.; Kim, H.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kondrashov, V.; Kopparapu, R.; Koranda, S.; Korth, W. Z.; Kozak, D.; Kringel, V.; Krishnamurthy, S.; Krishnan, B.; Kuehn, G.; Kumar, R.; Kwee, P.; Landry, M.; Lantz, B.; Lastzka, N.; Lazzarini, A.; Leaci, P.; Leong, J.; Leonor, I.; Li, J.; Lindquist, P. E.; Lockerbie, N. A.; Lodhia, D.; Lormand, M.; Lu, P.; Luan, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Mageswaran, M.; Mailand, K.; Mandel, I.; Mandic, V.; Marandi, A.; Márka, S.; Márka, Z.; Maros, E.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; McCarthy, R.; McClelland, D. E.; McGuire, S. C.; McIntyre, G.; McIver, J.; McKechan, D. J. A.; Meadors, G.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Miller, J.; Mino, Y.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Miyakawa, O.; Moe, B.; Moesta, P.; Mohanty, S. D.; Moraru, D.; Moreno, G.; Mossavi, K.; Mow-Lowry, C. M.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murphy, D.; Murray, P. G.; Nash, T.; Nawrodt, R.; Nelson, J.; Newton, G.; Nishizawa, A.; Nolting, D.; Nuttall, L.; O'Reilly, B.; O'Shaughnessy, R.; Ochsner, E.; O'Dell, J.; Ogin, G. H.; Oldenburg, R. G.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Pan, Y.; Pankow, C.; Papa, M. A.; Patel, P.; Pedraza, M.; Pekowsky, L.; Penn, S.; Peralta, C.; Perreca, A.; Phelps, M.; Pickenpack, M.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Podkaminer, J.; Pöld, J.; Postiglione, F.; Predoi, V.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prokhorov, L.; Puncken, O.; Quetschke, V.; Raab, F. J.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C. R.; Rankins, B.; Mohapatra, S. R. P.; Raymond, V.; Redwine, K.; Reed, C. M.; Reed, T.; Reid, S.; Reitze, D. H.; Riesen, R.; Riles, K.; Roberts, P.; Robertson, N. A.; Robinson, C.; Robinson, E. L.; Roddy, S.; Rollins, J.; Romano, J. D.; Romie, J. H.; Röver, C.; Rowan, S.; Rüdiger, A.; Ryan, K.; Sakata, S.; Sakosky, M.; Salemi, F.; Salit, M.; Sammut, L.; Sancho de la Jordana, L.; Sandberg, V.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Saraf, S.; Sathyaprakash, B. S.; Sato, S.; Saulson, P. R.; Savage, R.; Schilling, R.; Schlamminger, S.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Searle, A. C.; Seifert, F.; Sellers, D.; Sengupta, A. S.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shihan Weerathunga, T.; Shoemaker, D. H.; Sibley, A.; Siemens, X.; Sigg, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G.; Slagmolen, B. J. J.; Slutsky, J.; Smith, R.; Smith, J. R.; Smith, M. R.; Smith, N. D.; Somiya, K.; Sorazu, B.; Soto, J.; Speirits, F. C.; Stein, A. J.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stefszky, M.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S.; Stroeer, A. S.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Szokoly, G. P.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, J. R.; Taylor, R.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Tokmakov, K. V.; Torres, C.; Torrie, C. I.; Traylor, G.; Trias, M.; Tseng, K.; Ugolini, D.; Urbanek, K.; Vahlbruch, H.; Vaishnav, B.; Vallisneri, M.; Van Den Broeck, C.; van der Sluys, M. V.; van Veggel, A. A.; Vass, S.; Vaulin, R.; Vecchio, A.; Veitch, J.; Veitch, P. J.; Veltkamp, C.; Villar, A. E.; Vorvick, C.; Vyachanin, S. P.; Waldman, S. J.; Wallace, L.; Wanner, A.; Ward, R. L.; Wei, P.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Wen, L.; Wen, S.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D.; Whiting, B. F.; Wilkinson, C.; Willems, P. A.; Williams, H. R.; Williams, L.; Willke, B.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, K.; Yamamoto, H.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yu, P.; Zanolin, M.; Zhang, L.; Zhang, Z.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.; LIGO Collaboration; Bizouard, M. A.; Dietz, A.; Guidi, G. M.; Was, M.

2012-08-01

We present the results of a LIGO search for gravitational waves (GWs) associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for short-hard GRBs include compact object mergers and soft gamma repeater (SGR) giant flares. A merger progenitor would produce a characteristic GW signal that should be detectable at a distance of M81, while GW emission from an SGR is not expected to be detectable at that distance. We found no evidence of a GW signal associated with GRB 051103. Assuming weakly beamed γ-ray emission with a jet semi-angle of 30°, we exclude a binary neutron star merger in M81 as the progenitor with a confidence of 98%. Neutron star-black hole mergers are excluded with >99% confidence. If the event occurred in M81, then our findings support the hypothesis that GRB 051103 was due to an SGR giant flare, making it one of the most distant extragalactic magnetars observed to date.

Real-Time Pathogen Detection in the Era of Whole-Genome Sequencing and Big Data: Comparison of k-mer and Site-Based Methods for Inferring the Genetic Distances among Tens of Thousands of Salmonella Samples.

PubMed

Pettengill, James B; Pightling, Arthur W; Baugher, Joseph D; Rand, Hugh; Strain, Errol

2016-01-01

The adoption of whole-genome sequencing within the public health realm for molecular characterization of bacterial pathogens has been followed by an increased emphasis on real-time detection of emerging outbreaks (e.g., food-borne Salmonellosis). In turn, large databases of whole-genome sequence data are being populated. These databases currently contain tens of thousands of samples and are expected to grow to hundreds of thousands within a few years. For these databases to be of optimal use one must be able to quickly interrogate them to accurately determine the genetic distances among a set of samples. Being able to do so is challenging due to both biological (evolutionary diverse samples) and computational (petabytes of sequence data) issues. We evaluated seven measures of genetic distance, which were estimated from either k-mer profiles (Jaccard, Euclidean, Manhattan, Mash Jaccard, and Mash distances) or nucleotide sites (NUCmer and an extended multi-locus sequence typing (MLST) scheme). When analyzing empirical data (whole-genome sequence data from 18,997 Salmonella isolates) there are features (e.g., genomic, assembly, and contamination) that cause distances inferred from k-mer profiles, which treat absent data as informative, to fail to accurately capture the distance between samples when compared to distances inferred from differences in nucleotide sites. Thus, site-based distances, like NUCmer and extended MLST, are superior in performance, but accessing the computing resources necessary to perform them may be challenging when analyzing large databases.

Real-Time Pathogen Detection in the Era of Whole-Genome Sequencing and Big Data: Comparison of k-mer and Site-Based Methods for Inferring the Genetic Distances among Tens of Thousands of Salmonella Samples

DOE PAGES

Pettengill, James B.; Pightling, Arthur W.; Baugher, Joseph D.; ...

2016-11-10

The adoption of whole-genome sequencing within the public health realm for molecular characterization of bacterial pathogens has been followed by an increased emphasis on real-time detection of emerging outbreaks (e.g., food-borne Salmonellosis). In turn, large databases of whole-genome sequence data are being populated. These databases currently contain tens of thousands of samples and are expected to grow to hundreds of thousands within a few years. For these databases to be of optimal use one must be able to quickly interrogate them to accurately determine the genetic distances among a set of samples. Being able to do so is challenging duemore » to both biological (evolutionary diverse samples) and computational (petabytes of sequence data) issues. We evaluated seven measures of genetic distance, which were estimated from either k-mer profiles (Jaccard, Euclidean, Manhattan, Mash Jaccard, and Mash distances) or nucleotide sites (NUCmer and an extended multi-locus sequence typing (MLST) scheme). Finally, when analyzing empirical data (wholegenome sequence data from 18,997 Salmonella isolates) there are features (e.g., genomic, assembly, and contamination) that cause distances inferred from k-mer profiles, which treat absent data as informative, to fail to accurately capture the distance between samples when compared to distances inferred from differences in nucleotide sites. Thus, site-based distances, like NUCmer and extended MLST, are superior in performance, but accessing the computing resources necessary to perform them may be challenging when analyzing large databases.« less

Real-Time Pathogen Detection in the Era of Whole-Genome Sequencing and Big Data: Comparison of k-mer and Site-Based Methods for Inferring the Genetic Distances among Tens of Thousands of Salmonella Samples

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

Pettengill, James B.; Pightling, Arthur W.; Baugher, Joseph D.

The adoption of whole-genome sequencing within the public health realm for molecular characterization of bacterial pathogens has been followed by an increased emphasis on real-time detection of emerging outbreaks (e.g., food-borne Salmonellosis). In turn, large databases of whole-genome sequence data are being populated. These databases currently contain tens of thousands of samples and are expected to grow to hundreds of thousands within a few years. For these databases to be of optimal use one must be able to quickly interrogate them to accurately determine the genetic distances among a set of samples. Being able to do so is challenging duemore » to both biological (evolutionary diverse samples) and computational (petabytes of sequence data) issues. We evaluated seven measures of genetic distance, which were estimated from either k-mer profiles (Jaccard, Euclidean, Manhattan, Mash Jaccard, and Mash distances) or nucleotide sites (NUCmer and an extended multi-locus sequence typing (MLST) scheme). Finally, when analyzing empirical data (wholegenome sequence data from 18,997 Salmonella isolates) there are features (e.g., genomic, assembly, and contamination) that cause distances inferred from k-mer profiles, which treat absent data as informative, to fail to accurately capture the distance between samples when compared to distances inferred from differences in nucleotide sites. Thus, site-based distances, like NUCmer and extended MLST, are superior in performance, but accessing the computing resources necessary to perform them may be challenging when analyzing large databases.« less

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.

The cosmic X-ray background. [heao observations

NASA Technical Reports Server (NTRS)

Boldt, E. A.

1980-01-01

The cosmic X-ray experiment carried out with the A2 Instrument on HEAO-1 made systematics-free measurements of the extra-galactic X-ray sky and yielded the broadband spectral characteristics for two extreme aspects of this radiation. For the apparently isotropic radiation of cosmological origin that dominates the extragalactic X-ray flux ( 3 keV), the spectrum over the energy band of maximum intensity is remarkably well described by a thermal model with a temperature of a half-billion degrees. At the other extreme, broadband observations of individual extragalactic X-ray sources with HEAO-1 are restricted to objects within the present epoch. While the non-thermal hard spectral components associated with unevolved X-ray emitting active galaxies could account for most of the gamma-ray background, the contribution of such sources to the X-ray background must be relatively small. In contrast, the 'deep-space' sources detected in soft X-rays with the HEAO-2 telescope probably represent a major portion of the extragalactic soft X-ray ( 3 keV) background.

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.

The Evryscopes: monitoring the entire sky for exciting events

NASA Astrophysics Data System (ADS)

Law, Nicholas; Corbett, Hank; Howard, Ward S.; Fors, Octavi; Ratzloff, Jeff; Barlow, Brad; Hermes, JJ

2018-01-01

The Evryscope is a new type of array telescope which monitors the entire accessible sky in each exposure. The system, with 700 MPix covering an 8000-square-degree field of view, is building many-year-length, high-cadence light curves for every accessible object brighter than ∼16th magnitude. Every night, we add 600 million object detections to our databases, including exoplanet transits, microlensing events, nearby extragalactic transients, and a wide range of other short timescale events. I will present our science plans, the status of our current Evryscope systems (operational in Chile and soon California), the big-data analysis required to explore the petabyte-scale dataset we are collecting over the next few years, and the first results from the telescopes.

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…

The Carnegie-Chicago Hubble Program. I. An Independent Approach to the Extragalactic Distance Scale Using Only Population II Distance Indicators

NASA Astrophysics Data System (ADS)

Beaton, Rachael L.; Freedman, Wendy L.; Madore, Barry F.; Bono, Giuseppe; Carlson, Erika K.; Clementini, Gisella; Durbin, Meredith J.; Garofalo, Alessia; Hatt, Dylan; Jang, In Sung; Kollmeier, Juna A.; Lee, Myung Gyoon; Monson, Andrew J.; Rich, Jeffrey A.; Scowcroft, Victoria; Seibert, Mark; Sturch, Laura; Yang, Soung-Chul

2016-12-01

We present an overview of the Carnegie-Chicago Hubble Program, an ongoing program to obtain a 3% measurement of the Hubble constant (H 0) using alternative methods to the traditional Cepheid distance scale. We aim to establish a completely independent route to H 0 using RR Lyrae variables, the tip of the red giant branch (TRGB), and Type Ia supernovae (SNe Ia). This alternative distance ladder can be applied to galaxies of any Hubble type, of any inclination, and, using old stars in low-density environments, is robust to the degenerate effects of metallicity and interstellar extinction. Given the relatively small number of SNe Ia host galaxies with independently measured distances, these properties provide a great systematic advantage in the measurement of H 0 via the distance ladder. Initially, the accuracy of our value of H 0 will be set by the five Galactic RR Lyrae calibrators with Hubble Space Telescope Fine-Guidance Sensor parallaxes. With Gaia, both the RR Lyrae zero-point and TRGB method will be independently calibrated, the former with at least an order of magnitude more calibrators and the latter directly through parallax measurement of tip red giants. As the first end-to-end “distance ladder” completely independent of both Cepheid variables and the Large Magellanic Cloud, this path to H 0 will allow for the high-precision comparison at each rung of the traditional distance ladder that is necessary to understand tensions between this and other routes to H 0. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs #13472 and #13691.

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

Khan, Rubab, E-mail: rubab@uw.edu

We present Spitzer IRAC 3.6–8 μ m and Multiband Imaging Photometer 24 μ m point-source catalogs for M31 and 15 other mostly large, star-forming galaxies at distances ∼3.5–14 Mpc, including M51, M83, M101, and NGC 6946. These catalogs contain ∼1 million sources including ∼859,000 in M31 and ∼116,000 in the other galaxies. They were created following the procedures described in Khan et al. through a combination of point-spread function (PSF) fitting and aperture photometry. These data products constitute a resource to improve our understanding of the IR-bright (3.6–24 μ m) point-source populations in crowded extragalactic stellar fields and to planmore » observations with the James Webb Space Telescope .« less

UV-optical from space

NASA Technical Reports Server (NTRS)

Illingworth, Garth; Savage, Blair; Angel, J. Roger; Blandford, Roger D.; Boggess, Albert; Bowyer, C. Stuart; Carruthers, George R.; Cowie, Lennox L.; Doschek, George A.; Dupree, Andrea K.

1991-01-01

The following subject areas are covered: (1) the science program (star formation and origins of planetary systems; structure and evolution of the interstellar medium; stellar population; the galactic and extragalactic distance scale; nature of galaxy nuclei, AGNs, and QSOs; formation and evolution of galaxies at high redshifts; and cosmology); (2) implementation of the science program; (3) the observatory-class missions (HST; LST - the 6m successor to HST; and next-generation 16m telescope); (4) moderate and small missions (Delta-class Explorers; imaging astrometric interferometer; small Explorers; optics development and demonstrations; and supporting ground-based capabilities); (5) prerequisites - the current science program (Lyman-FUSE; HTS optimization; the near-term science program; data analysis, modeling, and theory funding; and archives); (6) technologies for the next century; and (7) lunar-based telescopes and instruments.

LISA Mission Concept Study, Laser Interferometer Space Antenna for the Detection and Observation of Gravitational Waves

NASA Technical Reports Server (NTRS)

Folkner, W. M.; Bender, P. L.; Stebbins, R. T.

1998-01-01

This document presents the results of a design feasibility study for LISA (Laser Interferometer Space Antenna). The goal of LISA is to detect and study low-frequency astrophysical gravitational radiation from strongly relativistic regions. Astrophysical sources potentially visible to LISA include extra-galactic massive black hole binaries at cosmological distances, binary systems composed of a compact star and a massive black hole, galactic neutron star-black hole binaries, and background radiation from the Big Bang. The LISA mission will comprise three spacecraft located five million kilometers apart forming an equilateral triangle in an Earth-trailing orbit. Fluctuations in separation between shielded test masses located within each spacecraft will be determined by optical interferometry which determines the phase shift of laser light transmitted between the test masses.

Spitzer Photometry of Approximately 1 Million Stars in M31 and 15 Other Galaxies

NASA Technical Reports Server (NTRS)

Khan, Rubab

2017-01-01

We present Spitzer IRAC 3.6-8 micrometer and Multiband Imaging Photometer 24 micrometer point-source catalogs for M31 and 15 other mostly large, star-forming galaxies at distances approximately 3.5-14 Mpc, including M51, M83, M101, and NGC 6946. These catalogs contain approximately 1 million sources including approximately 859,000 in M31 and approximately 116,000 in the other galaxies. They were created following the procedures described in Khan et al. through a combination of pointspread function (PSF) fitting and aperture photometry. These data products constitute a resource to improve our understanding of the IR-bright (3.6-24 micrometer) point-source populations in crowded extragalactic stellar fields and to plan observations with the James Webb Space Telescope.

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.

Development of a Relational Database for Learning Management Systems

ERIC Educational Resources Information Center

Deperlioglu, Omer; Sarpkaya, Yilmaz; Ergun, Ertugrul

2011-01-01

In today's world, Web-Based Distance Education Systems have a great importance. Web-based Distance Education Systems are usually known as Learning Management Systems (LMS). In this article, a database design, which was developed to create an educational institution as a Learning Management System, is described. In this sense, developed Learning…

Distance correlation methods for discovering associations in large astrophysical databases

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

Martínez-Gómez, Elizabeth; Richards, Mercedes T.; Richards, Donald St. P., E-mail: elizabeth.martinez@itam.mx, E-mail: mrichards@astro.psu.edu, E-mail: richards@stat.psu.edu

2014-01-20

High-dimensional, large-sample astrophysical databases of galaxy clusters, such as the Chandra Deep Field South COMBO-17 database, provide measurements on many variables for thousands of galaxies and a range of redshifts. Current understanding of galaxy formation and evolution rests sensitively on relationships between different astrophysical variables; hence an ability to detect and verify associations or correlations between variables is important in astrophysical research. In this paper, we apply a recently defined statistical measure called the distance correlation coefficient, which can be used to identify new associations and correlations between astrophysical variables. The distance correlation coefficient applies to variables of any dimension,more » can be used to determine smaller sets of variables that provide equivalent astrophysical information, is zero only when variables are independent, and is capable of detecting nonlinear associations that are undetectable by the classical Pearson correlation coefficient. Hence, the distance correlation coefficient provides more information than the Pearson coefficient. We analyze numerous pairs of variables in the COMBO-17 database with the distance correlation method and with the maximal information coefficient. We show that the Pearson coefficient can be estimated with higher accuracy from the corresponding distance correlation coefficient than from the maximal information coefficient. For given values of the Pearson coefficient, the distance correlation method has a greater ability than the maximal information coefficient to resolve astrophysical data into highly concentrated horseshoe- or V-shapes, which enhances classification and pattern identification. These results are observed over a range of redshifts beyond the local universe and for galaxies from elliptical to spiral.« less

A protein relational database and protein family knowledge bases to facilitate structure-based design analyses.

PubMed

Mobilio, Dominick; Walker, Gary; Brooijmans, Natasja; Nilakantan, Ramaswamy; Denny, R Aldrin; Dejoannis, Jason; Feyfant, Eric; Kowticwar, Rupesh K; Mankala, Jyoti; Palli, Satish; Punyamantula, Sairam; Tatipally, Maneesh; John, Reji K; Humblet, Christine

2010-08-01

The Protein Data Bank is the most comprehensive source of experimental macromolecular structures. It can, however, be difficult at times to locate relevant structures with the Protein Data Bank search interface. This is particularly true when searching for complexes containing specific interactions between protein and ligand atoms. Moreover, searching within a family of proteins can be tedious. For example, one cannot search for some conserved residue as residue numbers vary across structures. We describe herein three databases, Protein Relational Database, Kinase Knowledge Base, and Matrix Metalloproteinase Knowledge Base, containing protein structures from the Protein Data Bank. In Protein Relational Database, atom-atom distances between protein and ligand have been precalculated allowing for millisecond retrieval based on atom identity and distance constraints. Ring centroids, centroid-centroid and centroid-atom distances and angles have also been included permitting queries for pi-stacking interactions and other structural motifs involving rings. Other geometric features can be searched through the inclusion of residue pair and triplet distances. In Kinase Knowledge Base and Matrix Metalloproteinase Knowledge Base, the catalytic domains have been aligned into common residue numbering schemes. Thus, by searching across Protein Relational Database and Kinase Knowledge Base, one can easily retrieve structures wherein, for example, a ligand of interest is making contact with the gatekeeper residue.

Machine learning in infrared object classification - an all-sky selection of YSO candidates

NASA Astrophysics Data System (ADS)

Marton, Gabor; Zahorecz, Sarolta; Toth, L. Viktor; Magnus McGehee, Peregrine; Kun, Maria

2015-08-01

Object classification is a fundamental and challenging problem in the era of big data. I will discuss up-to-date methods and their application to classify infrared point sources.We analysed the ALLWISE catalogue, the most recent public source catalogue of the Wide-field Infrared Survey Explorer (WISE) to compile a reliable list of Young Stellar Object (YSO) candidates. We tested and compared classical and up-to-date statistical methods as well, to discriminate source types like extragalactic objects, evolved stars, main sequence stars, objects related to the interstellar medium and YSO candidates by using their mid-IR WISE properties and associated near-IR 2MASS data.In the particular classification problem the Support Vector Machines (SVM), a class of supervised learning algorithm turned out to be the best tool. As a result we classify Class I and II YSOs with >90% accuracy while the fraction of contaminating extragalactic objects remains well below 1%, based on the number of known objects listed in the SIMBAD and VizieR databases. We compare our results to other classification schemes from the literature and show that the SVM outperforms methods that apply linear cuts on the colour-colour and colour-magnitude space. Our homogenous YSO candidate catalog can serve as an excellent pathfinder for future detailed observations of individual objects and a starting point of statistical studies that aim to add pieces to the big picture of star formation theory.

Stereoselective virtual screening of the ZINC database using atom pair 3D-fingerprints.

PubMed

Awale, Mahendra; Jin, Xian; Reymond, Jean-Louis

2015-01-01

Tools to explore large compound databases in search for analogs of query molecules provide a strategically important support in drug discovery to help identify available analogs of any given reference or hit compound by ligand based virtual screening (LBVS). We recently showed that large databases can be formatted for very fast searching with various 2D-fingerprints using the city-block distance as similarity measure, in particular a 2D-atom pair fingerprint (APfp) and the related category extended atom pair fingerprint (Xfp) which efficiently encode molecular shape and pharmacophores, but do not perceive stereochemistry. Here we investigated related 3D-atom pair fingerprints to enable rapid stereoselective searches in the ZINC database (23.2 million 3D structures). Molecular fingerprints counting atom pairs at increasing through-space distance intervals were designed using either all atoms (16-bit 3DAPfp) or different atom categories (80-bit 3DXfp). These 3D-fingerprints retrieved molecular shape and pharmacophore analogs (defined by OpenEye ROCS scoring functions) of 110,000 compounds from the Cambridge Structural Database with equal or better accuracy than the 2D-fingerprints APfp and Xfp, and showed comparable performance in recovering actives from decoys in the DUD database. LBVS by 3DXfp or 3DAPfp similarity was stereoselective and gave very different analogs when starting from different diastereomers of the same chiral drug. Results were also different from LBVS with the parent 2D-fingerprints Xfp or APfp. 3D- and 2D-fingerprints also gave very different results in LBVS of folded molecules where through-space distances between atom pairs are much shorter than topological distances. 3DAPfp and 3DXfp are suitable for stereoselective searches for shape and pharmacophore analogs of query molecules in large databases. Web-browsers for searching ZINC by 3DAPfp and 3DXfp similarity are accessible at www.gdb.unibe.ch and should provide useful assistance to drug discovery projects. Graphical abstractAtom pair fingerprints based on through-space distances (3DAPfp) provide better shape encoding than atom pair fingerprints based on topological distances (APfp) as measured by the recovery of ROCS shape analogs by fp similarity.

Distances to Nearby Galaxies via Long Period Variables

NASA Astrophysics Data System (ADS)

Jurcevic, John S.

A new method of measuring extra-Galactic distances has been developed based on the relationship between the luminosity of red supergiant variable (RSV) stars at optical wavelengths and the period of their luminosity variation. This period-luminosity (PL) relationship has been calibrated with RSVs from the Galactic Perseus OB1 association, the Large Magellanic Cloud, and M33 in the broadband optical R and I-bands, in a narrow part of the I-band at 8250 Å, and in the infrared K-band. By using these RSV PL relations, the distances to a sample of nearby galaxies (M101, NGC 2403, and NGC 2366) were determined. These galaxies were chosen because they had existing Cepheid based distances which allowed for a comparison between the two methods and provided a means of verifying the effectiveness of the RSV PL relation. The galaxies were also chosen to span a range of metallicity to allow an investigation of any effects due to metallicity differences. Photometry in the R-band was obtained over a period of three years for the galaxies with a coverage of 20, 17, and 13 epochs for M101, NGC 2403, and NGC 2366, respectively. By looking for red variable stars with periods in the range 100-1200 days the total number of RSVs discovered in the three galaxies was 123. Assuming a distance modulus for the Large Magellanic Cloud of 18.5 +/- 0.1 mag, single epoch I-band photometry of the RSVs was used to construct random phase PL relations resulting in distance moduli for M101, NGC 2403, and NGC 2366 of 29.40 +/- 0.16, 27.67 +/- 0.16, and 27.86 +/- 0.20 mag, respectively. Similarly, PL relations were also found using phase averaged R-band magnitudes which produced distance moduli of 29.09 +/- 0.16, 27.56 +/- 0.16, and 27.76 +/- 0.21 mag, respectively. These distances have been corrected for extinction by assuming values of E(B - V) = 0.10, 0.04, and 0.04 mag. The distances derived agree with those found via Cepheids which indicates that RSVs provide a very useful new method for measuring distances.

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

New Parallaxes of Galactic Cepheids from Spatially Scanning the Hubble Space Telescope: Implications for the Hubble Constant

NASA Astrophysics Data System (ADS)

Riess, Adam G.; Casertano, Stefano; Yuan, Wenlong; Macri, Lucas; Anderson, Jay; MacKenty, John W.; Bowers, J. Bradley; Clubb, Kelsey I.; Filippenko, Alexei V.; Jones, David O.; Tucker, Brad E.

2018-03-01

We present new measurements of the parallax of seven long-period (≥10 days) Milky Way (MW) Cepheid variables (SS CMa, XY Car, VY Car, VX Per, WZ Sgr, X Pup, and S Vul) using one-dimensional astrometric measurements from spatial scanning of Wide-Field Camera 3 on the Hubble Space Telescope (HST). The observations were obtained at ∼6 month intervals over 4 years. The distances are 1.7–3.6 kpc, with a mean precision of 45 μas (signal-to-noise ratio (S/N) ≈ 10) and a best precision of 29 μas (S/N = 14). The accuracy of the parallaxes is demonstrated through independent analyses of >100 reference stars. This raises to 10 the number of long-period Cepheids with significant parallax measurements, 8 obtained from this program. We also present high-precision mean F555W, F814W, and F160W magnitudes of these Cepheids, allowing a direct, zeropoint-independent comparison to >1800 extragalactic Cepheids in the hosts of 19 SNe Ia. This sample addresses two outstanding systematic uncertainties affecting prior comparisons of MW and extragalactic Cepheids used to calibrate the Hubble constant (H 0): their dissimilarity of periods and photometric systems. Comparing the new parallaxes to their predicted values derived from reversing the distance ladder gives a ratio (or independent scale for H 0) of 1.037 ± 0.036, consistent with no change and inconsistent at the 3.5σ level with a ratio of 0.91 needed to match the value predicted by Planck cosmic microwave background data in concert with ΛCDM. Using these data instead to augment the Riess et al. measurement of H 0 improves the precision to 2.3%, yielding 73.48 ± 1.66 km s‑1 Mpc‑1, and the tension with Planck + ΛCDM increases to 3.7σ. The future combination of Gaia parallaxes and HST spatial scanning photometry of 50 MW Cepheids can support a <1% calibration of H 0.

“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

A binary linear programming formulation of the graph edit distance.

PubMed

Justice, Derek; Hero, Alfred

2006-08-01

A binary linear programming formulation of the graph edit distance for unweighted, undirected graphs with vertex attributes is derived and applied to a graph recognition problem. A general formulation for editing graphs is used to derive a graph edit distance that is proven to be a metric, provided the cost function for individual edit operations is a metric. Then, a binary linear program is developed for computing this graph edit distance, and polynomial time methods for determining upper and lower bounds on the solution of the binary program are derived by applying solution methods for standard linear programming and the assignment problem. A recognition problem of comparing a sample input graph to a database of known prototype graphs in the context of a chemical information system is presented as an application of the new method. The costs associated with various edit operations are chosen by using a minimum normalized variance criterion applied to pairwise distances between nearest neighbors in the database of prototypes. The new metric is shown to perform quite well in comparison to existing metrics when applied to a database of chemical graphs.

The expanding photosphere method applied to SN 1992am AT cz = 14 600 km/s

NASA Technical Reports Server (NTRS)

Schmidt, Brian P.; Kirshner, Robert P.; Eastman, Ronald G.; Hamuy, Mario; Phillips, Mark M.; Suntzeff, Nicholas B.; Maza, Jose; Filippenko, Alexei V.; Ho, Luis C.; Matheson, Thomas

1994-01-01

We present photometry and spectroscopy of Supernova (SN) 1992am for five months following its discovery by the Calan Cerro-Tololo Inter-American Observatory (CTIO) SN search. These data show SN 1992am to be type II-P, displaying hydrogen in its spectrum and the typical shoulder in its light curve. The photometric data and the distance from our own analysis are used to construct the supernova's bolometric light curve. Using the bolometric light curve, we estimate SN 1992am ejected approximately 0.30 solar mass of Ni-56, an amount four times larger than that of other well studied SNe II. SN 1992am's; host galaxy lies at a redshift of cz = 14 600 km s(exp -1), making it one of the most distant SNe II discovered, and an important application of the Expanding Photsphere Method. Since z = 0.05 is large enough for redshift-dependent effects to matter, we develop the technique to derive luminosity distances with the Expanding Photosphere Method at any redshift, and apply this method to SN 1992am. The derived distance, D = 180(sub -25) (sup +30) Mpc, is independent of all other rungs in the extragalactic distance ladder. The redshift of SN 1992am's host galaxy is sufficiently large that uncertainties due to perturbations in the smooth Hubble flow should be smaller than 10%. The Hubble ratio derived from the distance and redshift of this single object is H(sub 0) = 81(sub -15) (sup +17) km s(exp -1) Mpc(exp -1). In the future, with more of these distant objects, we hope to establish an independent and statistically robust estimate of H(sub 0) based solely on type II supernovae.

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.

Is the Universe transparent?

NASA Astrophysics Data System (ADS)

Liao, Kai; Avgoustidis, A.; Li, Zhengxiang

2015-12-01

We present our study on cosmic opacity, which relates to changes in photon number as photons travel from the source to the observer. Cosmic opacity may be caused by absorption or scattering due to matter in the Universe, or by extragalactic magnetic fields that can turn photons into unobserved particles (e.g., light axions, chameleons, gravitons, Kaluza-Klein modes), and it is crucial to correctly interpret astronomical photometric measurements like type Ia supernovae observations. On the other hand, the expansion rate at different epochs, i.e., the observational Hubble parameter data H (z ), are obtained from differential ageing of passively evolving galaxies or from baryon acoustic oscillations and thus are not affected by cosmic opacity. In this work, we first construct opacity-free luminosity distances from H (z ) determinations, taking into consideration correlations between different redshifts for our error analysis. Moreover, we let the light-curve fitting parameters, accounting for distance estimation in type Ia supernovae observations, free to ensure that our analysis is authentically cosmological-model independent and gives a robust result. Any nonzero residuals between these two kinds of luminosity distances can be deemed as an indication of the existence of cosmic opacity. While a transparent Universe is currently consistent with the data, our results show that strong constraints on opacity (and consequently on physical mechanisms that could cause it) can be obtained in a cosmological-model-independent fashion.

STELLAR X-RAY SOURCES IN THE CHANDRA COSMOS SURVEY

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

Wright, N. J.; Drake, J. J.; Civano, F., E-mail: nwright@cfa.harvard.ed

2010-12-10

We present an analysis of the X-ray properties of a sample of solar- and late-type field stars identified in the Chandra Cosmic Evolution Survey (COSMOS), a deep (160 ks) and wide ({approx}0.9 deg{sup 2}) extragalactic survey. The sample of 60 sources was identified using both morphological and photometric star/galaxy separation methods. We determine X-ray count rates, extract spectra and light curves, and perform spectral fits to determine fluxes and plasma temperatures. Complementary optical and near-IR photometry is also presented and combined with spectroscopy for 48 of the sources to determine spectral types and distances for the sample. We find distancesmore » ranging from 30 pc to {approx}12 kpc, including a number of the most distant and highly active stellar X-ray sources ever detected. This stellar sample extends the known coverage of the L{sub X}-distance plane to greater distances and higher luminosities, but we do not detect as many intrinsically faint X-ray sources compared to previous surveys. Overall the sample is typically more luminous than the active Sun, representing the high-luminosity end of the disk and halo X-ray luminosity functions. The halo population appears to include both low-activity spectrally hard sources that may be emitting through thermal bremsstrahlung, as well as a number of highly active sources in close binaries.« less

Infrared Spectroscopy of Star Formation in Galactic and Extragalactic Regions

NASA Technical Reports Server (NTRS)

Smith, Howard A.; Hasan, Hashima (Technical Monitor)

2002-01-01

This report details work done in a project involving spectroscopic studies, including data analysis and modeling, of star-formation regions using an ensemble of archival space-based data including some from the Infrared Space Observatory's Long Wavelength Spectrometer and Short Wavelength Spectrometer, and other spectroscopic databases. We will include four kinds of regions: (1) disks around more evolved objects; (2) young, low or high mass pre-main sequence stars in star-formation regions; (3) star formation in external, bright IR (infrared) galaxies; and (4) the galactic center. During this period, work proceeded fully on track and on time. Details on workshops and conferences attended and research results are presented. A preprint article entitled 'The Far Infrared Lines of OH as Molecular Cloud Diagnostics' is included as an appendix.

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.

ESO 243-49 HLX-1: scaling of X-ray spectral properties and black hole mass determination

NASA Astrophysics Data System (ADS)

Titarchuk, Lev; Seifina, Elena

2016-11-01

We report the results of Swift/XRT observations (2008-2015) of a hyper-luminous X-ray source, ESO 243-49 HLX-1. We demonstrate a strong observational evidence that ESO 243-49 HLX-1 undergoes spectral transitions from the low/hard state to the high/soft state during these observations. The spectra of ESO 243-49 HLX-1 are well fitted by the so-called bulk motion Comptonization model for all spectral states. We have established the photon index (Γ) saturation level, Γsat = 3.0 ± 0.1, in the Γ versus mass accretion rate (Ṁ) correlation. This Γ-Ṁ correlation allows us to estimate black hole (BH) mass in ESO 243-49 HLX-1 to be MBH 7 × 104 M⊙ assuming the distance to ESO 243-49 of 95 Mpc. For the BH mass estimate we use the scaling method taking Galactic BHs XTE J1550-564, H 1743-322 and 4U 1630-472, and an extragalactic BH source, M101 ULX-1 as reference sources. The Γ versus Ṁ correlation revealed in ESO 243-49 HLX-1 is similar to those in a number of Galactic and extragalactic BHs and it clearly shows the correlation along with the strong Γ saturation at ≈3. This is a robust observational evidence for the presence of a BH in ESO 243-49 HLX-1. We also find that the seed (disk) photon temperatures are quite low, of order of 50-140 eV which are consistent with high BH mass in ESO 243-49 HLX-1.

Multiwavelength Modeling of Nove Atmospheres

NASA Technical Reports Server (NTRS)

Huschildt, P. H.

2001-01-01

LMC 1988 #1 was a slow, CO type, dust forming classical nova. It was the first extragalactic nova to be observed with the IUE satellite. We have successfully fitted observed ultraviolet and optical spectra of LMC 1988 #1 taken within the first two months of its outburst (when the atmosphere was still optically thick) with synthetic spectra computed using PHOENIX nova model atmospheres. The synthetic spectra reproduce most of the features seen in the spectra and provide V band magnitudes consistent with the observed light curve. The fits are improved by increasing the CNO abundances to 10 times the solar values. The bolometric luminosity of LMC 1988 #1 was approximately constant at 2 x 10(exp 38) ergs per second at a distance of 47.3 kpc for the first 2 months of the outburst until the formation of the dust shell.

Low-z Type Ia Supernova Calibration

NASA Astrophysics Data System (ADS)

Hamuy, Mario

The discovery of acceleration and dark energy in 1998 arguably constitutes one of the most revolutionary discoveries in astrophysics in recent years. This paradigm shift was possible thanks to one of the most traditional cosmological tests: the redshift-distance relation between galaxies. This discovery was based on a differential measurement of the expansion rate of the universe: the current one provided by nearby (low-z) type Ia supernovae and the one in the past measured from distant (high-z) supernovae. This paper focuses on the first part of this journey: the calibration of the type Ia supernova luminosities and the local expansion rate of the universe, which was made possible thanks to the introduction of digital CCD (charge-coupled device) digital photometry. The new technology permitted us in the early 1990s to convert supernovae as precise tools to measure extragalactic distances through two key surveys: (1) the "Tololo Supernova Program" which made possible the critical discovery of the "peak luminosity-decline rate" relation for type Ia supernovae, the key underlying idea today behind precise cosmology from supernovae, and (2) the Calán/Tololo project which provided the low - z type Ia supernova sample for the discovery of acceleration.

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.

The remarkable AGN jets

NASA Astrophysics Data System (ADS)

Komissarov, Serguei

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

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

Using a Materials Database System as the Backbone for a Certified Quality System (AS/NZS ISO 9001:1994) for a Distance Education Centre.

ERIC Educational Resources Information Center

Hughes, Norm

The Distance Education Center (DEC) of the University of Southern Queensland (Australia) has developed a unique materials database system which is used to monitor pre-production, design and development, production and post-production planning, scheduling, and distribution of all types of materials including courses offered only on the Internet. In…

Properties of RR Lyrae stars in the inner regions of the Large Magellanic Cloud. III. Near-infrared study

NASA Astrophysics Data System (ADS)

Borissova, J.; Rejkuba, M.; Minniti, D.; Catelan, M.; Ivanov, V. D.

2009-08-01

Context: RR Lyrae variable stars are the primary Population II distance indicator. Likewise, the Large Magellanic Cloud (LMC) constitutes a key step in the extragalactic distance scale. Aims: By combining near-IR photometry and spectroscopically measured metallicities for a homogeneous sample of 50 RR Lyr stars in the LMC, we investigate the metallicity dependence of the period-luminosity relation in the near-infrared (IR), use the newly derived relations to re-derive the distance to the LMC, and compare the distance moduli obtained from RR Lyr and red clump stars. Methods: This paper presents new (single-epoch) J-band and (multi-epoch) K_s-band photometry of RR Lyr stars in 7 different LMC fields, observed with the near-IR camera SOFI at ESO's New Technology Telescope. Additional K_s-band data for another two LMC fields were taken with the ISPI infrared array at CTIO's Blanco 4m telescope. The near-IR photometry was cross-correlated with the MACHO and OGLE databases, resulting in a catalog of 62 RR Lyr stars with BVRIJKs photometry. A subsample of 50 stars also has spectroscopically measured metallicities. Results: In the deep JK color-magnitude diagrams of 7 fields, red giant branch, red clump and RR Lyr stars are detected. The majority of RR Lyr stars are located within the instability strip with near-IR colors between 0.14 ≤ (J-K_s)_0<0.32. The period-luminosity relation only has a very mild dependence on metallicity in the K band, consistent with no dependence: MKs =2.11(± 0.17) log{P} + 0.05(± 0.07) [Fe/H] - 1.05. In the J band the currently available data do not allow firm conclusions regarding the metallicity dependence of the period-luminosity relation. Conclusions: The distance modulus of the LMC, derived using our near-IR period-luminosity-metallicity relation for RR Lyr stars, is (m-M)_0=18.53 ± 0.13, in very good agreement with the distance modulus from the red clump stars, 18.46 ± 0.07. However, LMC modulus derived from the RR Lyrae stars depends on the parallax of the star RR Lyrae. Based on observations collected with European Southern Observatory's Very Large Telescope and New Technology Telescope, under programs 64.N-0176(B), 70.B-0547(A), and 072.D-0106(B) with the Blanco telescope at CTIO, under ISPI Prop. No. 0101; and at Gemini Observatory (observing program GS-2004A-Q-27), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and SECYT (Argentina). Table of the individual KS measurements with dates is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/502/505

Chapter 18: Web-based Tools - NED VO Services

NASA Astrophysics Data System (ADS)

Mazzarella, J. M.; NED Team

The NASA/IPAC Extragalactic Database (NED) is a thematic, web-based research facility in widespread use by scientists, educators, space missions, and observatory operations for observation planning, data analysis, discovery, and publication of research about objects beyond our Milky Way galaxy. NED is a portal into a systematic fusion of data from hundreds of sky surveys and tens of thousands of research publications. The contents and services span the entire electromagnetic spectrum from gamma rays through radio frequencies, and are continuously updated to reflect the current literature and releases of large-scale sky survey catalogs. NED has been on the Internet since 1990, growing in content, automation and services with the evolution of information technology. NED is the world's largest database of crossidentified extragalactic objects. As of December 2006, the system contains approximately 10 million objects and 15 million multi-wavelength cross-IDs. Over 4 thousand catalogs and published lists covering the entire electromagnetic spectrum have had their objects cross-identified or associated, with fundamental data parameters federated for convenient queries and retrieval. This chapter describes the interoperability of NED services with other components of the Virtual Observatory (VO). Section 1 is a brief overview of the primary NED web services. Section 2 provides a tutorial for using NED services currently available through the NVO Registry. The "name resolver" provides VO portals and related internet services with celestial coordinates for objects specified by catalog identifier (name); any alias can be queried because this service is based on the source cross-IDs established by NED. All major services have been updated to provide output in VOTable (XML) format that can be accessed directly from the NED web interface or using the NVO registry. These include access to images via SIAP, Cone- Search queries, and services providing fundamental, multi-wavelength extragalactic data such as positions, redshifts, photometry and spectral energy distributions (SEDs), and sizes (all with references and uncertainties when available). Section 3 summarizes the advantages of accessing the NED "name resolver" and other NED services via the web to replace the legacy "server mode" custom data structure previously available through a function library provided only in the C programming language. Section 4 illustrates visualization via VOPlot of an SED and the spatial distribution of sources from a NED All-Sky (By Parameters) query. Section 5 describes the new NED Spectral Archive, illustrating how VOTables are being used to standardize the data and metadata as well as the physical units of spectra made available by authors of journal articles and producers of major survey archives; quick-look spectral analysis through convenient interoperability with the SpecView (STScI) Java applet is also shown. Section 6 closes with a summary of the capabilities described herein, which greatly simplify interoperability of NED with other components of the VO, enabling new opportunities for discovery, visualization, and analysis of multiwavelength data.

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.

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.

Origin of superluminal radio jets in microquasars

NASA Astrophysics Data System (ADS)

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

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

Measuring cosmological parameters

PubMed Central

Freedman, Wendy L.

1998-01-01

In this review, the status of measurements of the matter density (Ωm), the vacuum energy density or cosmological constant (ΩΛ), the Hubble constant (H0), and the ages of the oldest measured objects (t0) are summarized. Three independent types of methods for measuring the Hubble constant are considered: the measurement of time delays in multiply imaged quasars, the Sunyaev–Zel’dovich effect in clusters, and Cepheid-based extragalactic distances. Many recent independent dynamical measurements are yielding a low value for the matter density (Ωm ≈ 0.2–0.3). A wide range of Hubble constant measurements appear to be converging in the range of 60–80 km/sec per megaparsec. Areas where future improvements are likely to be made soon are highlighted—in particular, measurements of anisotropies in the cosmic microwave background. Particular attention is paid to sources of systematic error and the assumptions that underlie many of the measurement methods. PMID:9419315

The young star cluster population of M51 with LEGUS - II. Testing environmental dependences

NASA Astrophysics Data System (ADS)

Messa, Matteo; Adamo, A.; Calzetti, D.; Reina-Campos, M.; Colombo, D.; Schinnerer, E.; Chandar, R.; Dale, D. A.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Elmegreen, B. G.; Fumagalli, M.; Johnson, K. E.; Kruijssen, J. M. D.; Östlin, G.; Shabani, F.; Smith, L. J.; Whitmore, B. C.

2018-06-01

It has recently been established that the properties of young star clusters (YSCs) can vary as a function of the galactic environment in which they are found. We use the cluster catalogue produced by the Legacy Extragalactic UV Survey (LEGUS) collaboration to investigate cluster properties in the spiral galaxy M51. We analyse the cluster population as a function of galactocentric distance and in arm and inter-arm regions. The cluster mass function exhibits a similar shape at all radial bins, described by a power law with a slope close to -2 and an exponential truncation around 105 M⊙. While the mass functions of the YSCs in the spiral arm and inter-arm regions have similar truncation masses, the inter-arm region mass function has a significantly steeper slope than the one in the arm region, a trend that is also observed in the giant molecular cloud mass function and predicted by simulations. The age distribution of clusters is dependent on the region considered, and is consistent with rapid disruption only in dense regions, while little disruption is observed at large galactocentric distances and in the inter-arm region. The fraction of stars forming in clusters does not show radial variations, despite the drop in the H2 surface density measured as a function of galactocentric distance. We suggest that the higher disruption rate observed in the inner part of the galaxy is likely at the origin of the observed flat cluster formation efficiency radial profile.

Testing Special Relativity at High Energies with Astrophysical Sources

NASA Technical Reports Server (NTRS)

Stecker, F. W.

2007-01-01

Since the group of Lorentz boosts is unbounded, there is a question as to whether Lorentz invariance (LI) holds to infinitely short distances. However, special and general relativity may break down at the Planck scale. Various quantum gravity scenarios such as loop quantum gravity, as well as some forms of string theory and extra dimension models may imply Lorentz violation (LV) at ultrahigh energies. The Gamma-Ray Large Area Space Telescope (GLAST), to be launched in mid-December, will measure the spectra of distant extragalactic sources of high energy gamma-rays, particularly active galactic nuclei and gamma-ray bursts. GLAST can look for energy-dependent gamma-ray propagation effects from such sources as a signal of Lorentz invariance violation. These sources may also exhibit the high energy cutoffs predicted to be the result of intergalactic annihilation interactions with low energy photons having a flux level as determined by various astronomical observations. With LV the threshold for such interactions can be significantly raised, changing the predicted absorption turnover in the observed spectrum of the sources. Stecker and Glashow have shown that the existence such absorption features in the spectra of extragalactic sources puts constraints on LV. Such constraints have important implications for some quantum gravity and large extra dimension models. Future spaceborne detectors dedicated to measuring gamma-ray polarization can look for birefringence effects as a possible signal of loop quantum gravity. A very small LV may also result in the modification or elimination of the GZK effect, thus modifying the spectrum of ultrahigh energy cosmic rays. This possibility can be explored with ground-based arrays such as Auger or with a space based detector system such as the proposed OWL satellite mission.

The Globular Cluster NGC 6402 (M14). II. Variable Stars

NASA Astrophysics Data System (ADS)

Contreras Peña, C.; Catelan, M.; Grundahl, F.; Stephens, A. W.; Smith, H. A.

2018-03-01

We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ∼137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006–2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive < {P}ab > =0.589 {{d}}{{a}}{{y}}{{s}}. This, together with the position of the RR Lyrae stars of both Bailey types in the period–amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster. Based on observations obtained with the 0.9 m and 1 m telescopes at the Cerro Tololo Inter-American Observatory, Chile, operated by the SMARTS consortium.

MALATANG: MApping the dense moLecular gAs in the sTrongest stAr-formiNg Galaxies

NASA Astrophysics Data System (ADS)

Gao, Yu; Zhang, Zhiyu; Greve, Thomas; MALATANG Team

2017-01-01

The MALATANG Large Program is a 390 hr campaign, using the heterodyne array HARP on the JCMT to map theHCN and HCO+ J = 4 - 3 line emission in 23 of the nearest IR-brightest galaxies beyond the Local Group. Theobservations will reach a sensitivity of 0.3 K km/s (~ 4.5 x 10^6 Msun) at linear resolutions of 0.2-2.8kpc. It is thefirst survey to systematically map the distribution of dense molecular gas out to large galactocentric distances in a statisticallysignificant sample of nearby galaxies. MALATANG will bridge the gap, in terms of physical scale and luminosity,between extragalactic (i.e., galaxy-integrated) and Galactic (i.e., single molecular clouds) observations. A primarygoal of the survey is to delineate for the first time the distributed dense gas star-formation relations, as traced by theHCN and HCO+ J = 4-3, on scales of ~1kpc across our targets. Exploring the behaviour of these star-formationrelations in low surface density regions found in the disks as well as in the nuclear regions where surface densitiesare high, will shed new light on whether such environments are host to fundamentally different star-formation modes.The MALATANG data products of resolved HCN and HCO+ J = 4-3 maps of 23 IR-bright local galaxies, will beof great value to the extragalactic community and, in and of themselves, carry significant legacy value. At the moment,about 50% (~195hrs) of the 390hrs of time allocated to MALATANG has been observed. We here show somevery preliminary results as well after introducing our project.

Revealing two radio-active galactic nuclei extremely near PSR J0437-4715

NASA Astrophysics Data System (ADS)

Li, Zhixuan; Yang, Jun; An, Tao; Paragi, Zsolt; Deller, Adam; Reynolds, Cormac; Hong, Xiaoyu; Wang, Jiancheng; Ding, Hao; Xia, Bo; Yan, Zhen; Guo, Li

2018-05-01

Newton's gravitational constant G may vary with time at an extremely low level. The time variability of G will affect the orbital motion of a millisecond pulsar in a binary system and cause a tiny difference between the orbital period-dependent measurement of the kinematic distance and the direct measurement of the annual parallax distance. PSR J0437-4715 is the nearest millisecond pulsar and the brightest at radio wavelengths. To explore the feasibility of achieving a parallax distance accuracy of one light-year, comparable to the recent timing result, with the technique of differential astrometry, we searched for compact radio sources quite close to PSR J0437-4715. Using existing data from the Very Large Array and the Australia Telescope Compact Array, we detected two sources with flat spectra, relatively stable flux densities of 0.9 and 1.0 mJy at 8.4 GHz and separations of 13 and 45 arcsec. With a network consisting of the Long Baseline Array and the Kunming 40-m radio telescope, we found that both sources have a point-like structure and a brightness temperature of ≥107 K. According to these radio inputs and the absence of counterparts in other bands, we argue that they are most likely the compact radio cores of extragalactic active galactic nuclei, rather than Galactic radio stars. The finding of these two radio active galactic nuclei will enable us to achieve a sub-pc distance accuracy with in-beam phase-referencing very-long-baseline interferometric observations and provide one of the most stringent constraints on the time variability of G in the near future.

The Cepheids of NGC 1866: a precise benchmark for the extragalactic distance scale and stellar evolution from modern UBVI photometry

NASA Astrophysics Data System (ADS)

Musella, I.; Marconi, M.; Stetson, P. B.; Raimondo, G.; Brocato, E.; Molinaro, R.; Ripepi, V.; Carini, R.; Coppola, G.; Walker, A. R.; Welch, D. L.

2016-04-01

We present the analysis of multiband time series data for a sample of 24 Cepheids in the field of the Large Magellanic Cloud cluster NGC 1866. Very accurate BVI Very Large Telescope photometry is combined with archival UBVI data, covering a large temporal window, to obtain precise mean magnitudes and periods with typical errors of 1-2 per cent and of 1 ppm, respectively. These results represent the first accurate and homogeneous data set for a substantial sample of Cepheid variables belonging to a cluster and hence sharing common distance, age and original chemical composition. Comparisons of the resulting multiband period-luminosity and Wesenheit relations to both empirical and theoretical results for the Large Magellanic Cloud are presented and discussed to derive the distance of the cluster and to constrain the mass-luminosity relation of the Cepheids. The adopted theoretical scenario is also tested by comparison with independent calibrations of the Cepheid Wesenheit zero-point based on trigonometric parallaxes and Baade-Wesselink techniques. Our analysis suggests that a mild overshooting and/or a moderate mass-loss can affect intermediate-mass stellar evolution in this cluster and gives a distance modulus of 18.50 ± 0.01 mag. The obtained V,I colour-magnitude diagram is also analysed and compared with both synthetic models and theoretical isochrones for a range of ages and metallicities and for different efficiencies of core overshooting. As a result, we find that the age of NGC 1866 is about 140 Myr, assuming Z = 0.008 and the mild efficiency of overshooting suggested by the comparison with the pulsation models.

Exploding Stars and the Accelerating Universe

NASA Astrophysics Data System (ADS)

Kirshner, Robert P.

2012-01-01

Supernovae are exceptionally interesting astronomical objects: they punctuate the end of stellar evolution, create the heavy elements, and blast the interstellar gas with energetic shock waves. By studying supernovae, we can learn how these important aspects of cosmic evolution take place. Over the decades, we have learned that some supernovae are produced by gravitational collapse, and others by thermonuclear explosions. By understanding what supernovae are, or at least learning how they behave, supernovae explosions have been harnessed for the problem of measuring cosmic distances with some astonishing results. Carefully calibrated supernovae provide the best extragalactic distance indicators to probe the distances to galaxies and to measure the Hubble constant. Even more interesting is the evidence from supernovae that cosmic expansion has been speeding up over the last 5 billion years. We attribute this acceleration to a mysterious dark energy whose effects are clear, but whose nature is obscure. Combining the cosmic expansion history traced by supernovae with clues from galaxy clustering and cosmic geometry from the microwave background has produced today's standard, but peculiar, picture of a universe that is mostly dark energy, braked (with diminishing effect) by dark matter, and illuminated by a pinch of luminous baryons. In this talk, I will show how the attempt to understand supernovae, facilitated by ever-improving instruments, has led to the ability to measure the properties of dark energy. Looking ahead, the properties of supernovae as measured at infrared wavelengths seem to hold the best promise for more precise and accurate distances to help us understand the puzzle of dark energy. My own contribution to this work has been carried out in joyful collaboration with many excellent students, postdocs, and colleagues and with generous support from the places I have worked, the National Science Foundation, and from NASA.

Investigations of the Local Supercluster velocity field. III. Tracing the backside infall with distance moduli from the direct Tully-Fisher relation

NASA Astrophysics Data System (ADS)

Ekholm, T.; Lanoix, P.; Teerikorpi, P.; Fouqué, P.; Paturel, G.

2000-03-01

We have extended the discussion of Paper II (Ekholm et al. \\cite{Ekholm99a}) to cover also the backside of the Local Supercluster (LSC) by using 96 galaxies within Theta <30degr from the adopted centre of LSC and with distance moduli from the direct B-band Tully-Fisher relation. In order to minimize the influence of the Malmquist bias we required log Vmax>2.1 and sigma B_T<0.2mag. We found out that if RVirgo<20 Mpc this sample fails to follow the expected dynamical pattern from the Tolman-Bondi (TB) model. When we compared our results with the Virgo core galaxies given by Federspiel et al. (\\cite{Federspiel98}) we were able to constrain the distance to Virgo: RVirgo=20-24 Mpc. When analyzing the TB-behaviour of the sample as seen from the origin of the metric as well as that with distances from the extragalactic Cepheid PL-relation we found additional support to the estimate RVirgo= 21 Mpc given in Paper II. Using a two-component mass-model we found a Virgo mass estimate MVirgo=(1.5 - 2)x Mvirial, where Mvirial=9.375*E14Msun for RVirgo= 21 Mpc. This estimate agrees with the conclusion in Paper I (Teerikorpi et al. \\cite{Teerikorpi92}). Our results indicate that the density distribution of luminous matter is shallower than that of the total gravitating matter when q0<= 0.5. The preferred exponent in the density power law, alpha ~2.5, agrees with recent theoretical work on the universal density profile of dark matter clustering in an Einstein-deSitter universe (Tittley & Couchman \\cite{Tittley99}).

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.

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.

Gamma-Ray Bursts: A Mystery Story

NASA Technical Reports Server (NTRS)

Parsons, Ann

2007-01-01

With the success of the Swift Gamma-Ray Burst Explorer currently in orbit, this is quite an exciting time in the history of Gamma Ray Bursts (GRBs). The study of GRBs is a modern astronomical mystery story that began over 30 years ago with the serendipitous discovery of these astronomical events by military satellites in the late 1960's. Until the launch of BATSE on the Compton Gamma-ray Observatory, astronomers had no clue whether GRBs originated at the edge of our solar system, in our own Milky Way Galaxy or incredibly far away near the edge of the observable Universe. Data from BATSE proved that GRBs are distributed isotropically on the sky and thus could not be the related to objects in the disk of our Galaxy. Given the intensity of the gamma-ray emission, an extragalactic origin would require an astounding amount of energy. Without sufficient data to decide the issue, a great debate continued about whether GRBs were located in the halo of our own galaxy or were at extragalactic - even cosmological distances. This debate continued until 1997 when the BeppoSAX mission discovered a fading X-ray afterglow signal in the same location as a GRB. This discovery enabled other telescopes, to observe afterglow emission at optical and radio wavelengths and prove that GRBs were at cosmological distances by measuring large redshifts in the optical spectra. Like BeppoSAX Swift, slews to new GRB locations to measure afterglow emission. In addition to improved GRB sensitivity, a significant advantage of Swift over BeppoSAX and other missions is its ability to slew very quickly, allowing x-ray and optical follow-up measurements to be made as early as a minute after the gamma-ray burst trigger rather than the previous 6-8 hour delay. Swift afterglow measurements along with follow-up ground-based observations, and theoretical work have allowed astronomers to identify two plausible scenarios for the creation of a GRB: either through core collapse of super massive stars or colliding compact objects in distant galaxies. The pieces of the puzzle are beginning to fall into place and yet the story isn't quite finished. I will frame the history of gamma-ray bursts as a mystery story and will end with a description of what we still don't know and what we'll have to do to get the next clues.

Aperture Fever and the Quality of AAVSO Visual Estimates: mu Cephei as an Example

NASA Astrophysics Data System (ADS)

Turner, D. G.

2014-06-01

(Abstract only) At the limits of human vision the eye can reach precisions of 10% or better in brightness estimates for stars. So why did the quality of AAVSO visual estimates suddenly drop to 50% or worse for many stars following World War II? Possibly it is a consequence of viewing variable stars through ever-larger aperture instruments than was the case previously, a time when many variables were observed without optical aid. An example is provided by the bright red supergiant variable mu Cephei, a star that has the potential to be a calibrating object for the extragalactic distance scale if its low-amplitude brightness variations are better defined. It appears to be a member of the open cluster Trumpler 37, so its distance and luminosity can be established provided one can pinpoint the amount of interstellar extinction between us and it. mu Cep appears to be a double-mode pulsator, as suggested previously in the literature, but with periods of roughly 700 and 1,000 days it is unexciting to observe and its red color presents a variety of calibration problems. Improving quality control for such variable stars is an issue important not only to the AAVSO, but also to science in general.

TRANSITING PLANETS WITH LSST. II. PERIOD DETECTION OF PLANETS ORBITING 1 M{sub ⊙} HOSTS

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

Jacklin, Savannah; Lund, Michael B.; Stassun, Keivan G.

2015-07-15

The Large Synoptic Survey Telescope (LSST) will photometrically monitor ∼10{sup 9} stars for 10 years. The resulting light curves can be used to detect transiting exoplanets. In particular, as demonstrated by Lund et al., LSST will probe stellar populations currently undersampled in most exoplanet transit surveys, including out to extragalactic distances. In this paper we test the efficiency of the box-fitting least-squares (BLS) algorithm for accurately recovering the periods of transiting exoplanets using simulated LSST data. We model planets with a range of radii orbiting a solar-mass star at a distance of 7 kpc, with orbital periods ranging from 0.5more » to 20 days. We find that standard-cadence LSST observations will be able to reliably recover the periods of Hot Jupiters with periods shorter than ∼3 days; however, it will remain a challenge to confidently distinguish these transiting planets from false positives. At the same time, we find that the LSST deep-drilling cadence is extremely powerful: the BLS algorithm successfully recovers at least 30% of sub-Saturn-size exoplanets with orbital periods as long as 20 days, and a simple BLS power criterion robustly distinguishes ∼98% of these from photometric (i.e., statistical) false positives.« less

Effectiveness of Asynchronous Reference Services for Distance Learning Students within Florida's Community College System

ERIC Educational Resources Information Center

Profeta, Patricia C.

2007-01-01

The provision of equitable library services to distance learning students emerged as a critical area during the 1990s. Library services available to distance learning students included digital reference and instructional services, remote access to online research tools, database and research tutorials, interlibrary loan, and document delivery.…

Distance indicators based on the luminosity-profile shapes of early-type galaxies-a reply

NASA Astrophysics Data System (ADS)

Young, Christopher Ke-Shih; Currie, Malcolm J.

1998-05-01

In a recent paper, Binggeli & Jerjen (1998) question the value of the extragalactic distance indicators presented by Young & Currie (1994 & 1995) and state that they have refuted `the claim that the Virgo dEs [dwarf-elliptical galaxies]...are distributed in a prolate structure stretching from 8 to 20 Mpc distance (Young & Currie 1995).' even though no such claim was ever made. In this paper, we examine Binggeli & Jerjen's claims that intrinsic scatter rather than spatial depth must be the main cause of the large scatters observed in the relevant scaling relationships for Virgo galaxies. We investigate the accuracy of Binggeli & Jerjen's photometric parameters and find that while their profile curvature and scalelength measurements are probably useful, their total magnitude and central surface-brightness measurements are not useful for the purpose of investigating scaling laws because they suffer from serious systematic and random errors. We also investigate Binggeli & Jerjen's criticisms of our (1995) analysis. We demonstrate that their test for strong mutual dependence between distance estimates based on the two different scaling laws is invalid because of its prior assumption of negligible cluster depth. We further demonstrate that the [relative] distance estimates on which their kinematical arguments are based cannot be meaningful, not only because of the seriousness of the photometric errors, but also because they are undermined by the prior assumption that depth effects can again be neglected. Interestingly, we also find that Binggeli & Jerjen's own dataset does itself contain evidence for large depth. Using the observed correlation between scale-length and profile-curvature, (the only correlation that can be investigated meaningfully using their dataset), we find that the frequency distribution of residuals with respect to the best fitting curve deviates significantly from that expected from a uni-modal Gaussian distribution. Clearly, if as Binggeli & Jerjen claim, the very large scatter observed in this scaling relationship for Virgo galaxies (which is not observed for Fornax or Local Group ones) were intrinsic, one would expect a uni-modal Gaussian distribution.

Molecular gas in supernova local environments unveiled by EDGE

NASA Astrophysics Data System (ADS)

Galbany, L.; Mora, L.; González-Gaitán, S.; Bolatto, A.; Dannerbauer, H.; López-Sánchez, Á. R.; Maeda, K.; Pérez, S.; Pérez-Torres, M. A.; Sánchez, S. F.; Wong, T.; Badenes, C.; Blitz, L.; Marino, R. A.; Utomo, D.; Van de Ven, G.

2017-06-01

CO observations allow estimation of the gas content of molecular clouds, which trace the reservoir of cold gas fuelling star formation, as well as determination of extinction via H2 column density, N(H2). Here, we study millimetric and optical properties at 26 supernovae (SNe) locations of different types in a sample of 23 nearby galaxies, by combining molecular 12C16O (J = 1 → 0) resolved maps from the Extragalactic Database for Galaxy Evolution (EDGE) survey and optical Integral Field Spectroscopy (IFS) from the Calar Alto Legacy Integral Field Area (CALIFA) survey. We found an even clearer separation between type II and type Ibc SNe in terms of molecular gas than is found in the optical using Hα emission as a proxy for the current star formation (SF) rate, which reinforces the fact that SNe Ibc are more associated with SF environments. While AV at SN locations is similar for SNe II and SNe Ibc and higher than for SNe Ia, N(H2) is significantly higher for SNe Ibc than for SNe II and Ia. When compared with alternative extinction estimations made directly from SN photometry and spectroscopy, we find that our SNe Ibc also have redder colour excess, but showed standard Na I D absorption pseudo-equivalent widths (˜1 Å). In some cases, we find no extinction when IT is estimated from the environment but high amounts of extinction when measured from SN observations, which suggests that circumstellar material or dust sublimation may be playing a role. This work serves as a benchmark for future studies combining last-generation millimetre and optical IFS instruments to reveal the local environmental properties of extragalactic SNe.

X-Ray Spectral Study of AGN Sources Content in Some Deep Extragalactic XMM-Newton Fields

NASA Astrophysics Data System (ADS)

Hassan, M. A.; Korany, B. A.; Misra, R.; Issa, I. A. M.; Ahmed, M. K.; Abdel-Salam, F. A.

2012-06-01

We undertake a spectral study of a sample of bright X-ray sources taken from six XMM-Newton fields at high galactic latitudes, where AGN are the most populous class. These six fields were chosen such that the observation had an exposure time more than 60 ksec, had data from the EPIC-pn detector in the full-Frame mode and lying at high galactic latitude | b|>25°. The analysis started by fitting the spectra of all sources with an absorbed power-law model, and then we fitted all the spectra with an absorbed power-law with a low energy black-body component model.The sources for which we added a black body gave an F-test probability of 0.01 or less (i.e. at 99% confidence level), were recognized as sources that display soft excess. We perform a comparative analysis of soft excess spectral parameters with respect to the underlying power-law one for sources that satisfy this criterion. Those sources, that do not show evidence for a soft excess, based on the F-test probability at a 99% confidence level, were also fitted with the absorbed power-law with a low energy black-body component model with the black-body temperature fixed at 0.1 and 0.2 keV. We establish upper limits on the soft excess flux for those sources at these two temperatures. Finally we have made use of Aladdin interactive sky atlas and matching with NASA/IPAC Extragalactic Database (NED) to identify the X-ray sources in our sample. For those sources which are identified in the NED catalogue, we make a comparative study of the soft excess phenomenon for different types of systems.

Exploring the Early Universe on Mobile Devices

NASA Astrophysics Data System (ADS)

Kocevski, Dale; McGrath, E. J.; CANDELS Collaboration

2014-01-01

The widespread adoption of smart phones and tablet computers has the potential to revolutionize the way in which educational material is shared with the general public. As part of the outreach effort for the CANDELS survey, we have developed a free interactive astronomy education application named Hubble Universe for iPad and iPhone devices. The application focuses on extragalactic science topics related to the CANDELS legacy survey, which is documenting galaxy evolution in the early universe. I will provide an overview of the application, which contains a wide range of interactive content, including 3D models of astrophysical phenomenon, informative diagrams and computer simulations. I will discuss how the application can be used to enhance classroom learning both by providing a database of interactive media and by encouraging students to explore astronomical topics away from traditional settings like the classroom or the desktop computer.

Fuzzy approach for improved recognition of citric acid induced piglet coughing from continuous registration

NASA Astrophysics Data System (ADS)

Van Hirtum, A.; Berckmans, D.

2003-09-01

A natural acoustic indicator of animal welfare is the appearance (or absence) of coughing in the animal habitat. A sound-database of 5319 individual sounds including 2034 coughs was collected on six healthy piglets containing both animal vocalizations and background noises. Each of the test animals was repeatedly placed in a laboratory installation where coughing was induced by nebulization of citric acid. A two-class classification into 'cough' or 'other' was performed by the application of a distance function to a fast Fourier spectral sound analysis. This resulted in a positive cough recognition of 92%. For the whole sound-database however there was a misclassification of 21%. As spectral information up to 10000 Hz is available, an improved overall classification on the same database is obtained by applying the distance function to nine frequency ranges and combining the achieved distance-values in fuzzy rules. For each frequency range clustering threshold is determined by fuzzy c-means clustering.

The UBIRIS.v2: a database of visible wavelength iris images captured on-the-move and at-a-distance.

PubMed

Proença, Hugo; Filipe, Sílvio; Santos, Ricardo; Oliveira, João; Alexandre, Luís A

2010-08-01

The iris is regarded as one of the most useful traits for biometric recognition and the dissemination of nationwide iris-based recognition systems is imminent. However, currently deployed systems rely on heavy imaging constraints to capture near infrared images with enough quality. Also, all of the publicly available iris image databases contain data correspondent to such imaging constraints and therefore are exclusively suitable to evaluate methods thought to operate on these type of environments. The main purpose of this paper is to announce the availability of the UBIRIS.v2 database, a multisession iris images database which singularly contains data captured in the visible wavelength, at-a-distance (between four and eight meters) and on on-the-move. This database is freely available for researchers concerned about visible wavelength iris recognition and will be useful in accessing the feasibility and specifying the constraints of this type of biometric recognition.

Asymmetric distances for binary embeddings.

PubMed

Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana

2014-01-01

In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques.

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.

Modern Geometric Methods of Distance Determination

NASA Astrophysics Data System (ADS)

Thévenin, Frédéric; Falanga, Maurizio; Kuo, Cheng Yu; Pietrzyński, Grzegorz; Yamaguchi, Masaki

2017-11-01

Building a 3D picture of the Universe at any distance is one of the major challenges in astronomy, from the nearby Solar System to distant Quasars and galaxies. This goal has forced astronomers to develop techniques to estimate or to measure the distance of point sources on the sky. While most distance estimates used since the beginning of the 20th century are based on our understanding of the physics of objects of the Universe: stars, galaxies, QSOs, the direct measures of distances are based on the geometric methods as developed in ancient Greece: the parallax, which has been applied to stars for the first time in the mid-19th century. In this review, different techniques of geometrical astrometry applied to various stellar and cosmological (Megamaser) objects are presented. They consist in parallax measurements from ground based equipment or from space missions, but also in the study of binary stars or, as we shall see, of binary systems in distant extragalactic sources using radio telescopes. The Gaia mission will be presented in the context of stellar physics and galactic structure, because this key space mission in astronomy will bring a breakthrough in our understanding of stars, galaxies and the Universe in their nature and evolution with time. Measuring the distance to a star is the starting point for an unbiased description of its physics and the estimate of its fundamental parameters like its age. Applying these studies to candles such as the Cepheids will impact our large distance studies and calibration of other candles. The text is constructed as follows: introducing the parallax concept and measurement, we shall present briefly the Gaia satellite which will be the future base catalogue of stellar astronomy in the near future. Cepheids will be discussed just after to demonstrate the state of the art in distance measurements in the Universe with these variable stars, with the objective of 1% of error in distances that could be applied to our closest galaxy the LMC, and better constrain the distances of large sub-structures around the Milky Way. Then exciting objects like X-Ray binaries will be presented in two parts corresponding to "low" or "high" mass stars with compact objects observed with X-ray satellites. We shall demonstrate the capability of these objects to have their distances measured with high accuracy with not only helps in the study of these objects but could also help to measure the distance of the structure they belong. For cosmological objects and large distances of megaparsecs, we shall present what has been developed for more than 20 years in the geometric distance measurements of MegaMasers, the ultimate goal being the estimation of the H0 parameter.

Distance Education at the Elementary and Secondary Level. A Select ERIC Bibliography. ERIC/IR Mini-Bib.

ERIC Educational Resources Information Center

Preston, Nancy R., Comp.

This annotated bibliography lists 10 articles and documents selected through a search of the Educational Resources Information Center (ERIC) database. They are: (1) "The Use of Computers in the Instructional Process in Australian Distance Education" (Geoff Arger and Debbie Clayton); (2) "Distance Education Technologies: All That Glitters Is Not…

Does Distance Determine Who Attends a University in Germany?

ERIC Educational Resources Information Center

Spiess, C. Katharina; Wrohlich, Katharina

2010-01-01

We analyze the role of distance to the nearest university in the demand for higher education in Germany. Distance could matter due to transaction costs or due to neighborhood effects. We use data from the German Socio-Economic Panel (SOEP) combined with a database on university postal codes to estimate a discrete choice model of the demand for…

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.

VizieR Online Data Catalog: Extragalactic peaked-spectrum radio sources (Callingham+, 2017)

NASA Astrophysics Data System (ADS)

Callingham, J. R.; Ekers, R. D.; Gaensler, B. M.; Line, J. L. B.; Hurley-Walker, N.; Sadler, E. M.; Tingay, S. J.; Hancock, P. J.; Bell, M. E.; Dwarakanath, K. S.; For, B.-Q.; Franzen, T. M. O.; Hindson, L.; Johnston-Hollitt, M.; Kapinska, A. D.; Lenc, E.; McKinley, B.; Morgan, J.; Offringa, A. R.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.

2017-09-01

The GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) extragalactic catalog represents a significant advance in selecting peaked-spectrum sources, since it is constituted of sources that were contemporaneously surveyed with the widest fractional radio bandwidth to date, with 20 flux density measurements between 72 and 231MHz. We also use the NRAO VLA Sky Survey (NVSS; Condon+ 1998, VIII/65) and the Sydney University Molonglo Sky Survey (SUMSS; See Mauch+ 2008, VIII/81). Since the combination of NVSS and SUMSS cover the entire GLEAM survey and are an order of magnitude more sensitive, this study is sensitive to peaked-spectrum sources that peak anywhere between 72MHz and 843MHz/1.4GHz. The GLEAM survey was formed from observations conducted by the Murchison Widefield Array (MWA), which surveyed the sky between 72 and 231MHz from 2013 August to 2014 July (Wayth+ 2015PASA...32...25W - see also VIII/100). (5 data files).

Content Based Image Retrieval based on Wavelet Transform coefficients distribution

PubMed Central

Lamard, Mathieu; Cazuguel, Guy; Quellec, Gwénolé; Bekri, Lynda; Roux, Christian; Cochener, Béatrice

2007-01-01

In this paper we propose a content based image retrieval method for diagnosis aid in medical fields. We characterize images without extracting significant features by using distribution of coefficients obtained by building signatures from the distribution of wavelet transform. The research is carried out by computing signature distances between the query and database images. Several signatures are proposed; they use a model of wavelet coefficient distribution. To enhance results, a weighted distance between signatures is used and an adapted wavelet base is proposed. Retrieval efficiency is given for different databases including a diabetic retinopathy, a mammography and a face database. Results are promising: the retrieval efficiency is higher than 95% for some cases using an optimization process. PMID:18003013

Post-AGB Stars in Nearby Galaxies as Calibrators for HST

NASA Technical Reports Server (NTRS)

Bond, Howard E.

2003-01-01

This report summarizes activities carried out with support from the NASA Ultraviolet, Visible, and Gravitational Astrophysics Research and Analysis Program under Grant NAG 5-6821. The Principal Investigator is Howard E. Bond (Space Telescope Science Institute). STScI Postdoctoral Associates Laura K. Fullton (1998), David Alves (1998-2001), and Michael Siegel (2001) were partially supported by this grant. 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 argument is that, in old populations, the stars that are evolving through the PAGB region of the HR diagram arise from only a single main-sequence turnoff mass. In addition, 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, PAGB stars of these spectral types are very easily identified. because of their large Balmer jumps, which are due to their very low surface gravities. Our approach is first to identify PAGB stars in Milky Way globular clusters and in other Local Group galaxies, which are at known distances, and thus to measure accurate absolute magnitudes for the PAGB stars. With this Milky Way and Local Group luminosity calibration, we will then be in a position to find PAGB stars in more distant galaxies from the ground, and ultimately from the Hubble Space Telescope. and thus derive distances. These PAGB stars are, as noted above, the visually brightest members of Population II, and hence will allow distance measurements to galaxies that do not contain Cepheids, such as elliptical galaxies, as well as distances to spirals using PAGB stars in their halos. Moreover, the method is entirely independent of Cepheids. and thus provides a direct test of the Cepheid distance scale. The program will also provide information on the evolutionary lifetimes of PAGB stars.

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

An improved real time image detection system for elephant intrusion along the forest border areas.

PubMed

Sugumar, S J; Jayaparvathy, R

2014-01-01

Human-elephant conflict is a major problem leading to crop damage, human death and injuries caused by elephants, and elephants being killed by humans. In this paper, we propose an automated unsupervised elephant image detection system (EIDS) as a solution to human-elephant conflict in the context of elephant conservation. The elephant's image is captured in the forest border areas and is sent to a base station via an RF network. The received image is decomposed using Haar wavelet to obtain multilevel wavelet coefficients, with which we perform image feature extraction and similarity match between the elephant query image and the database image using image vision algorithms. A GSM message is sent to the forest officials indicating that an elephant has been detected in the forest border and is approaching human habitat. We propose an optimized distance metric to improve the image retrieval time from the database. We compare the optimized distance metric with the popular Euclidean and Manhattan distance methods. The proposed optimized distance metric retrieves more images with lesser retrieval time than the other distance metrics which makes the optimized distance method more efficient and reliable.

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

The Full-sky Astrometric Mapping Explorer - Astrometry for the New Millennium

NASA Astrophysics Data System (ADS)

Horner, S. D.; Germain, M. E.; Greene, T. P.; Harris, F. H.; Johnson, M. S.; Johnson, K. J.; Monet, D. G.; Murison, M. A.; Phillips, J. D.; Reasenberg, R. D.; Seidelmann, P. K.; Urban, S. E.; Vassar, R. H.

FAME is designed to perform an all-sky, astrometric survey with unprecedented accuracy. It will create a rigid astrometric catalog of ~40,000,000 stars with visual band magnitudes 5 < V < 15. For bright stars, 5 < V < 9, FAME will determine positions and parallaxes accurate to < 50 microarcseconds, with proper motion errors < 50 microarcseconds/year. For fainter stars, 9 < V < 15, FAME will determine positions and parallaxes accurate to < 300 microarcseconds, with proper motion errors < 300 microarcseconds/year. It will also collect photometric data on these 40,000,000 stars in four Sloan DSS colors. The FAME data will provide a rigid, accurate, optical, astrometric grid. The proper motion data, combined with Hipparcos and other data should be ideal for use by the Space Interferometry Mission (SIM) to select its astrometric reference grid stars. FAME will also identify stars with nonlinear proper motions as candidates for further study by SIM, Terrestrial Planet Finder, and future ground based interferometers as possible planetary systems. The fundamental astrometric data provided at relatively low cost by FAME will help optimize the scientific return from these future projects. This is in addition to the considerable direct scientific return from FAME. It will redefine the extragalactic distance scale and provide a large, rich database of information on stellar properties that will enable numerous science investigations into stellar structure and evolution, the dynamics of the Milky Way, and stellar companions including brown dwarfs and giant planets. NASA has selected the Full-sky Astrometric Mapping Explorer (FAME) to be one of five MIDEX missions to be funded for a concept study. This concept study will be submitted to NASA on 18 June, with final selection, scheduled for September, of two of these missions for fli ght in 2003 or 2004. FAME is a joint development e ffort of the U.S. Naval Observatory, the Smithsonian Astrophysical Observatory, the Infrared Processing and Analysis Center, Lockheed Martin Missiles and Space, the Naval Research Laboratory, and Omitron Incorporated.

Datasets related to in-land water for limnology and remote sensing applications: distance-to-land, distance-to-water, water-body identifier and lake-centre co-ordinates.

PubMed

Carrea, Laura; Embury, Owen; Merchant, Christopher J

2015-11-01

Datasets containing information to locate and identify water bodies have been generated from data locating static-water-bodies with resolution of about 300 m (1/360 ∘ ) recently released by the Land Cover Climate Change Initiative (LC CCI) of the European Space Agency. The LC CCI water-bodies dataset has been obtained from multi-temporal metrics based on time series of the backscattered intensity recorded by ASAR on Envisat between 2005 and 2010. The new derived datasets provide coherently: distance to land, distance to water, water-body identifiers and lake-centre locations. The water-body identifier dataset locates the water bodies assigning the identifiers of the Global Lakes and Wetlands Database (GLWD), and lake centres are defined for in-land waters for which GLWD IDs were determined. The new datasets therefore link recent lake/reservoir/wetlands extent to the GLWD, together with a set of coordinates which locates unambiguously the water bodies in the database. Information on distance-to-land for each water cell and the distance-to-water for each land cell has many potential applications in remote sensing, where the applicability of geophysical retrieval algorithms may be affected by the presence of water or land within a satellite field of view (image pixel). During the generation and validation of the datasets some limitations of the GLWD database and of the LC CCI water-bodies mask have been found. Some examples of the inaccuracies/limitations are presented and discussed. Temporal change in water-body extent is common. Future versions of the LC CCI dataset are planned to represent temporal variation, and this will permit these derived datasets to be updated.

A search for radio emission from flare stars in the Pleiades

NASA Technical Reports Server (NTRS)

Bastian, T. S.; Dulk, G. A.; Slee, O. B.

1988-01-01

The VLA has been used to search for radio emission from flare stars in the Pleiades. Two observational strategies were employed. First, about 1/2 sq deg of cluster, containing about 40 known flare stars, was mapped at 1.4 GHz at two epochs. More than 120 sources with flux densities greater than 0.3 mJy exist on the maps. Detailed analysis shows that all but two of these sources are probably extragalactic. The two sources identified as stellar are probably not Pleiades members as judged by their proper motions; rather, based on their colors and magnitudes, they seem to be foreground G stars. One is a known X-ray source. The second observational strategy, where five rapidly rotating flare stars were observed at three frequencies, yielded no detections. The 0.3 mJy flux-density limit of this survey is such that only the most intense outbursts of flare stars in the solar neighborhood could have been detected if those stars were at the distance of the Pleiades.

X-ray emission from the Pleiades cluster

NASA Technical Reports Server (NTRS)

Agrawal, P. C.; Singh, K. P.; Riegler, G. R.

1983-01-01

The detection and identification of H0344+24, a new X-ray source located in the Pleiades cluster, is reported, based on observations made with HEAO A-2 low-energy detector 1 in the 0.15-3.0-keV energy band in August, 1977. The 90-percent-confidence error box for the new source is centered at 03 h 44.1 min right ascension (1950), near the center star of the 500-star Pleiades cluster, 25-eta-Tau. Since no likely galactic or extragalactic source of X-rays was found in a catalog search of the error-box region, identification of the source with the Pleiades cluster is considered secure. X-ray luminosity of the source is calculated to be about 10 to the 32nd ergs/sec, based on a distance of 125 pc. The X-ray characteristics of the Pleiades stars are discussed, and it is concluded that H0344+24 can best be explained as the integrated X-ray emission of all the B and F stars in the cluster.

The MUSE-Wide survey: detection of a clustering signal from Lyman α emitters in the range 3 < z < 6

NASA Astrophysics Data System (ADS)

Diener, C.; Wisotzki, L.; Schmidt, K. B.; Herenz, E. C.; Urrutia, T.; Garel, T.; Kerutt, J.; Saust, R. L.; Bacon, R.; Cantalupo, S.; Contini, T.; Guiderdoni, B.; Marino, R. A.; Richard, J.; Schaye, J.; Soucail, G.; Weilbacher, P. M.

2017-11-01

We present a clustering analysis of a sample of 238 Ly α emitters at redshift 3 ≲ z ≲ 6 from the MUSE-Wide survey. This survey mosaics extragalactic legacy fields with 1h MUSE pointings to detect statistically relevant samples of emission line galaxies. We analysed the first year observations from MUSE-Wide making use of the clustering signal in the line-of-sight direction. This method relies on comparing pair-counts at close redshifts for a fixed transverse distance and thus exploits the full potential of the redshift range covered by our sample. A clear clustering signal with a correlation length of r0=2.9^{+1.0}_{-1.1} Mpc (comoving) is detected. Whilst this result is based on only about a quarter of the full survey size, it already shows the immense potential of MUSE for efficiently observing and studying the clustering of Ly α emitters.

A giant gamma-ray flare from the magnetar SGR 1806-20.

PubMed

Palmer, D M; Barthelmy, S; Gehrels, N; Kippen, R M; Cayton, T; Kouveliotou, C; Eichler, D; Wijers, R A M J; Woods, P M; Granot, J; Lyubarsky, Y E; Ramirez-Ruiz, E; Barbier, L; Chester, M; Cummings, J; Fenimore, E E; Finger, M H; Gaensler, B M; Hullinger, D; Krimm, H; Markwardt, C B; Nousek, J A; Parsons, A; Patel, S; Sakamoto, T; Sato, G; Suzuki, M; Tueller, J

2005-04-28

Two classes of rotating neutron stars-soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars-are magnetars, whose X-ray emission is powered by a very strong magnetic field (B approximately 10(15) G). SGRs occasionally become 'active', producing many short X-ray bursts. Extremely rarely, an SGR emits a giant flare with a total energy about a thousand times higher than in a typical burst. Here we report that SGR 1806-20 emitted a giant flare on 27 December 2004. The total (isotropic) flare energy is 2 x 10(46) erg, which is about a hundred times higher than the other two previously observed giant flares. The energy release probably occurred during a catastrophic reconfiguration of the neutron star's magnetic field. If the event had occurred at a larger distance, but within 40 megaparsecs, it would have resembled a short, hard gamma-ray burst, suggesting that flares from extragalactic SGRs may form a subclass of such bursts.

New results and techniques in space radio astronomy.

NASA Technical Reports Server (NTRS)

Alexander, J. K.

1971-01-01

The methods and results of early space radioastronomy experiments are reviewed, with emphasis on the RAE 1 spacecraft which was designed specifically and exclusively for radio astronomical studies. The RAE 1 carries two gravity-gradient-stabilized 229-m traveling-wave V-antennas, a 37-m dipole antenna, and a number of radiometer systems to provide measurements over the 0.2 to 9.2 MHz frequency range with a time resolution of 0.5 sec and an absolute accuracy of plus or minus 25%. Observations of solar bursts at frequencies down to 0.2 MHz provide new information on the density, plasma velocity, and dynamics of coronal streamers out to distances greater than 50 solar radii. New information on the distribution of the ionized component of the interstellar medium is being obtained from galactic continuum background maps at frequencies around 4 MHz. Cosmic noise background spectra measured down to 0.5 MHz produce new estimates on the interstellar flux of cosmic rays, on magnetic fields in the galactic halo, and on distant extragalactic radio sources.

The Infrared Hubble Diagram of Type Ia Supernovae

NASA Astrophysics Data System (ADS)

Krisciunas, Kevin

Photometry of Type Ia supernovae reveals that these objects are standardizable candles in optical passbands - the peak luminosities are related to the rate of decline after maximum light. In the near-infrared bands, there is essentially a characteristic brightness at maximum light for each photometric band. Thus, in the near-infrared they are better than standardizable candles; they are essentially standard candles. Their absolute magnitudes are known to ±0.15 magnitude or better. The infrared observations have the extra advantage that interstellar extinction by dust along the line of sight is a factor of 3-10 smaller than in the optical B- and V -bands. The size of any systematic errors in the infrared extinction corrections typically become smaller than the photometric errors of the observations. Thus, we can obtain distances to the hosts of Type Ia supernovae to ±8 % or better. This is particularly useful for extragalactic astronomy and precise measurements of the dark energy component of the universe.

The near-infrared counterpart of a variable galactic plane radio source

NASA Technical Reports Server (NTRS)

Margon, Bruce; Phillips, Andrew C.; Ciardullo, Robin; Jacoby, George H.

1992-01-01

A near-infrared counterpart to the highly variable, unresolved galactic plane radio source GT 0116 + 622 is identified. This source is of particular interest, as it has been previously suggested to be the counterpart of the gamma-ray source Cas gamma-l. The present NIR and red images detect a faint, spatially extended (3 arcsec FWHM), very red object coincident with the radio position. There is complex spatial structure which may be due in part to an unrelated superposed foreground object. Observations on multiple nights show no evidence for flux variability, despite the high amplitude variability on a time-scale of days reported for the radio source. The data are consistent with an interpretation of GT 0116 + 622 as an unusually variable, obscured active galaxy at a distance of several hundred megaparsecs, although more exotic, and in particular galactic, interpretations cannot yet be ruled out. If the object is extragalactic, the previously suggested identification with the gamma-ray source would seem unlikely.

Nonlinear electrodynamics and CMB polarization

NASA Astrophysics Data System (ADS)

Mosquera Cuesta, Herman J.; Lambiase, G.

2011-03-01

Recently WMAP and BOOMERanG experiments have set stringent constraints on the polarization angle of photons propagating in an expanding universe: Δα = (-2.4±1.9)°. The polarization of the Cosmic Microwave Background radiation (CMB) is reviewed in the context of nonlinear electrodynamics (NLED). We compute the polarization angle of photons propagating in a cosmological background with planar symmetry. For this purpose, we use the Pagels-Tomboulis (PT) Lagrangian density describing NLED, which has the form L ~ (X/Λ4)δ-1 X, where X = ¼FαβFαβ, and δ the parameter featuring the non-Maxwellian character of the PT nonlinear description of the electromagnetic interaction. After looking at the polarization components in the plane orthogonal to the (x)-direction of propagation of the CMB photons, the polarization angle is defined in terms of the eccentricity of the universe, a geometrical property whose evolution on cosmic time (from the last scattering surface to the present) is constrained by the strength of magnetic fields over extragalactic distances.

Photometric Redshifts of High-z BL Lacs from 3FGL Catalog

NASA Astrophysics Data System (ADS)

Kaur, A.; Rau, Arne; Ajello, Marco; Paliya, Vaidehi; Hartmann, Dieter; Greiner, Jochen; Bolmer, Jan; Schady, Patricia

2017-08-01

Determining redshifts for BL Lacertae (BL Lac) objects using the traditional spectroscopic method is challenging due to the absence of strong emission lines in their optical spectra. We employ the photometric dropout technique to determine redshifts for this class of blazars using the combined 13 broad-band filters from Swift-UVOT and the multi-channel imager GROND at the MPG 2.2 m telescope at ESO's La Silla Observatory. The wavelength range covered by these 13 filters extends from far ultraviolet to the near-Infrared. We report results on 40 new Fermi detected BL Lacs with the photometric redshifts determinations for 5 sources, with 3FGL J1918.2-4110 being the most distance in our sample at z=2.16. Reliable upper limits are provided for 20 sources in this sample. Using the highest energy photons for these Fermi-LAT sources, we evaluate the consistency with the Gamma-ray horizon due to the extragalactic background light.

New trends in cosmology

NASA Technical Reports Server (NTRS)

Canuto, V. M.

1978-01-01

A review of big-bang cosmology is presented, emphasizing the big-bang model, hypotheses on the origin of galaxies, observational tests of the big-bang model that may be possible with the Large Space Telescope, and the scale-covariant theory of gravitation. Detailed attention is given to the equations of general relativity, the redshift-distance relation for extragalactic objects, expansion of the universe, the initial singularity, the discovery of the 3-K blackbody radiation, and measurements of the amount of deuterium in the universe. The curvature of the expanding universe is examined along with the magnitude-redshift relation for quasars and galaxies. Several models for the origin of galaxies are evaluated, and it is suggested that a model of galaxy formation via the formation of black holes is consistent with the model of an expanding universe. Scale covariance is discussed, a scale-covariant theory is developed which contains invariance under scale transformation, and it is shown that Dirac's (1937) large-numbers hypothesis finds a natural role in this theory by relating the atomic and Einstein units.

Pulsating stars and the distance scale

NASA Astrophysics Data System (ADS)

Macri, Lucas

2017-09-01

I present an overview of the latest results from the SH0ES project, which obtained homogeneous Hubble Space Telescope (HST) photometry in the optical and near-infrared for ˜ 3500 and ˜ 2300 Cepheids, respectively, across 19 supernova hosts and 4 calibrators to determine the value of H0 with a total uncertainty of 2.4%. I discuss the current 3.4σ "tension" between this local measurement and predictions of H0 based on observations of the CMB and the assumption of "standard" ΛCDM. I review ongoing efforts to reach σ(H0) = 1%, including recent advances on the absolute calibration of Milky Way Cepheid period-luminosity relations (PLRs) using a novel astrometric technique with HST. Lastly, I highlight recent results from another collaboration on the development of new statistical techniques to detect, classify and phase extragalactic Miras using noisy and sparsely-sampled observations. I present preliminary Mira PLRs at various wavelengths based on the application of these techniques to a survey of M33.

PANTHER. Trajectory Analysis

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

Rintoul, Mark Daniel; Wilson, Andrew T.; Valicka, Christopher G.

We want to organize a body of trajectories in order to identify, search for, classify and predict behavior among objects such as aircraft and ships. Existing compari- son functions such as the Fr'echet distance are computationally expensive and yield counterintuitive results in some cases. We propose an approach using feature vectors whose components represent succinctly the salient information in trajectories. These features incorporate basic information such as total distance traveled and distance be- tween start/stop points as well as geometric features related to the properties of the convex hull, trajectory curvature and general distance geometry. Additionally, these features can generallymore » be mapped easily to behaviors of interest to humans that are searching large databases. Most of these geometric features are invariant under rigid transformation. We demonstrate the use of different subsets of these features to iden- tify trajectories similar to an exemplar, cluster a database of several hundred thousand trajectories, predict destination and apply unsupervised machine learning algorithms.« less

Trajectory analysis via a geometric feature space approach

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

Rintoul, Mark D.; Wilson, Andrew T.

This study aimed to organize a body of trajectories in order to identify, search for and classify both common and uncommon behaviors among objects such as aircraft and ships. Existing comparison functions such as the Fréchet distance are computationally expensive and yield counterintuitive results in some cases. We propose an approach using feature vectors whose components represent succinctly the salient information in trajectories. These features incorporate basic information such as the total distance traveled and the distance between start/stop points as well as geometric features related to the properties of the convex hull, trajectory curvature and general distance geometry. Additionally,more » these features can generally be mapped easily to behaviors of interest to humans who are searching large databases. Most of these geometric features are invariant under rigid transformation. Furthermore, we demonstrate the use of different subsets of these features to identify trajectories similar to an exemplar, cluster a database of several hundred thousand trajectories and identify outliers.« less

Trajectory analysis via a geometric feature space approach

DOE PAGES

Rintoul, Mark D.; Wilson, Andrew T.

2015-10-05

This study aimed to organize a body of trajectories in order to identify, search for and classify both common and uncommon behaviors among objects such as aircraft and ships. Existing comparison functions such as the Fréchet distance are computationally expensive and yield counterintuitive results in some cases. We propose an approach using feature vectors whose components represent succinctly the salient information in trajectories. These features incorporate basic information such as the total distance traveled and the distance between start/stop points as well as geometric features related to the properties of the convex hull, trajectory curvature and general distance geometry. Additionally,more » these features can generally be mapped easily to behaviors of interest to humans who are searching large databases. Most of these geometric features are invariant under rigid transformation. Furthermore, we demonstrate the use of different subsets of these features to identify trajectories similar to an exemplar, cluster a database of several hundred thousand trajectories and identify outliers.« less

A data-based conservation planning tool for Florida panthers

USGS Publications Warehouse

Murrow, Jennifer L.; Thatcher, Cindy A.; Van Manen, Frank T.; Clark, Joseph D.

2013-01-01

Habitat loss and fragmentation are the greatest threats to the endangered Florida panther (Puma concolor coryi). We developed a data-based habitat model and user-friendly interface so that land managers can objectively evaluate Florida panther habitat. We used a geographic information system (GIS) and the Mahalanobis distance statistic (D2) to develop a model based on broad-scale landscape characteristics associated with panther home ranges. Variables in our model were Euclidean distance to natural land cover, road density, distance to major roads, human density, amount of natural land cover, amount of semi-natural land cover, amount of permanent or semi-permanent flooded area–open water, and a cost–distance variable. We then developed a Florida Panther Habitat Estimator tool, which automates and replicates the GIS processes used to apply the statistical habitat model. The estimator can be used by persons with moderate GIS skills to quantify effects of land-use changes on panther habitat at local and landscape scales. Example applications of the tool are presented.

A Remote Registration Based on MIDAS

NASA Astrophysics Data System (ADS)

JIN, Xin

2017-04-01

We often need for software registration to protect the interests of the software developers. This article narrated one kind of software long-distance registration technology. The registration method is: place the registration information in a database table, after the procedure starts in check table registration information, if it has registered then the procedure may the normal operation; Otherwise, the customer must input the sequence number and registers through the network on the long-distance server. If it registers successfully, then records the registration information in the database table. This remote registration method can protect the rights of software developers.

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.

A NEW CENSUS OF THE VARIABLE STAR POPULATION IN THE GLOBULAR CLUSTER NGC 2419

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

Di Criscienzo, M.; Greco, C.; Ripepi, V.

We present B, V, and I CCD light curves for 101 variable stars belonging to the globular cluster NGC 2419, 60 of which are new discoveries, based on data sets obtained at the Telescopio Nazionale Galileo, the Subaru telescope, and the Hubble Space Telescope. The sample includes 75 RR Lyrae stars (38 RRab, 36 RRc, and one RRd), one Population II Cepheid, 12 SX Phoenicis variables, two {delta} Scuti stars, three binary systems, five long-period variables, and three variables of uncertain classification. The pulsation properties of the RR Lyrae variables are close to those of Oosterhoff type II clusters, consistentmore » with the low metal abundance and the cluster horizontal branch morphology, disfavoring (but not totally ruling out) an extragalactic hypothesis for the origin of NGC 2419. The observed properties of RR Lyrae and SX Phoenicis stars are used to estimate the cluster reddening and distance, using a number of different methods. Our final value is {mu}{sub 0} (NGC 2419) = 19.71 {+-} 0.08 mag (D = 87.5 {+-} 3.3 kpc), with E(B - V) = 0.08 {+-} 0.01 mag, [Fe/H] = -2.1 dex on the Zinn and West metallicity scale, and a value of M{sub V} that sets {mu}{sub 0} (LMC) = 18.52 mag. This value is in good agreement with the most recent literature estimates of the distance to NGC 2419.« less

Fast radio bursts as giant pulses from young rapidly rotating pulsars

NASA Astrophysics Data System (ADS)

Lyutikov, Maxim; Burzawa, Lukasz; Popov, Sergei B.

2016-10-01

We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages ˜ tens to hundreds of years) born with regular magnetic field but very short - few milliseconds - spin periods. We assume that FRBs are extra-Galactic events coming from distances d ≲ 100 Mpc and that most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell. We then predict that for a given burst the DM should decrease with time and that FRBs are not expected to be seen below ˜300 MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star-forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers dot{E} in young energetic pulsars is consistent with equal birth rate per decade of dot{E}. Accepting this injection distribution and scaling the intrinsic brightness of FRBs with dot{E}, we predict the following properties of a large sample of FRBs: (I) the brightest observed events come from a broad distribution in distances; (II) for repeating bursts brightness either remains nearly constant (if the spin-down time is longer than the age of the pulsar) or decreases with time otherwise; in the latter case DM ∝ dot{E}.

Astronomers Set a New Galaxy Distance Record

NASA Image and Video Library

2015-05-06

This is a Hubble Space Telescope image of the farthest spectroscopically confirmed galaxy observed to date (inset). It was identified in this Hubble image of a field of galaxies in the CANDELS survey (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey). NASA’s Spitzer Space Telescope also observed the unique galaxy. The W. M. Keck Observatory was used to obtain a spectroscopic redshift (z=7.7), extending the previous redshift record. Measurements of the stretching of light, or redshift, give the most reliable distances to other galaxies. This source is thus currently the most distant confirmed galaxy known, and it appears to also be one of the brightest and most massive sources at that time. The galaxy existed over 13 billion years ago. The near-infrared light image of the galaxy (inset) has been colored blue as suggestive of its young, and hence very blue, stars. The CANDELS field is a combination of visible-light and near-infrared exposures. Read more: www.nasa.gov/feature/goddard/astronomers-set-a-new-galaxy... Credits: NASA, ESA, P. Oesch (Yale U.) NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

The Acceleration of the Barycenter of Solar System Obtained from VLBI Observations and Its Impact on the ICRS

NASA Astrophysics Data System (ADS)

Xu, M. H.

2016-03-01

Since 1998 January 1, instead of the traditional stellar reference system, the International Celestial Reference System (ICRS) has been realized by an ensemble of extragalactic radio sources that are located at hundreds of millions of light years away (if we accept their cosmological distances), so that the reference frame realized by extragalactic radio sources is assumed to be space-fixed. The acceleration of the barycenter of solar system (SSB), which is the origin of the ICRS, gives rise to a systematical variation in the directions of the observed radio sources. This phenomenon is called the secular aberration drift. As a result, the extragalactic reference frame fixed to the space provides a reference standard for detecting the secular aberration drift, and the acceleration of the barycenter with respect to the space can be determined from the observations of extragalactic radio sources. In this thesis, we aim to determine the acceleration of the SSB from astrometric and geodetic observations obtained by Very Long Baseline Interferometry (VLBI), which is a technique using the telescopes globally distributed on the Earth to observe a radio source simultaneously, and with the capacity of angular positioning for compact radio sources at 10-milliarcsecond level. The method of the global solution, which allows the acceleration vector to be estimated as a global parameter in the data analysis, is developed. Through the formal error given by the solution, this method shows directly the VLBI observations' capability to constrain the acceleration of the SSB, and demonstrates the significance level of the result. In the next step, the impact of the acceleration on the ICRS is studied in order to obtain the correction of the celestial reference frame (CRF) orientation. This thesis begins with the basic background and the general frame of this work. A brief review of the realization of the CRF based on the kinematical and the dynamical methods is presented in Chapter 2, along with the definition of the CRF and its relationship with the inertial reference frame. Chapter 3 is divided into two parts. The first part describes various effects that modify the geometric direction of an object, especially the parallax, the aberration, and the proper motion. Then the derivative model and the principle of determination of the acceleration are introduced in the second part. The VLBI data analysis method, including VLBI data reduction (solving the ambiguity, identifying the clock break, and determining the ionospheric effect), theoretical delay model, parameterization, and datum definition, is discussed in detail in Chapter 4. The estimation of the acceleration by more than 30-year VLBI observations and the results are then described in Chapter 5. The evaluation and the robust check of our results by different solutions and the comparison to that from another research group are performed. The error sources for the estimation of the acceleration, such as the secular parallax caused by the velocity of the barycenter in space, are quantitatively studied by simulation and data analysis in Chapter 6. The two main impacts of the acceleration on the CRF, the apparent proper motion with the magnitude of the μ as\\cdot yr^{-1} level and the global rotation in the CRF due to the un-uniformed distribution of radio sources on the sky, are discussed in Chapter 7. The definition and the realization of the epoch CRF are presented as well. The future work concerning the explanation of the estimated acceleration and potential research on several main problems in modern astrometry are discussed in the last chapter.

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.

Accelerating Smith-Waterman Alignment for Protein Database Search Using Frequency Distance Filtration Scheme Based on CPU-GPU Collaborative System.

PubMed

Liu, Yu; Hong, Yang; Lin, Chun-Yuan; Hung, Che-Lun

2015-01-01

The Smith-Waterman (SW) algorithm has been widely utilized for searching biological sequence databases in bioinformatics. Recently, several works have adopted the graphic card with Graphic Processing Units (GPUs) and their associated CUDA model to enhance the performance of SW computations. However, these works mainly focused on the protein database search by using the intertask parallelization technique, and only using the GPU capability to do the SW computations one by one. Hence, in this paper, we will propose an efficient SW alignment method, called CUDA-SWfr, for the protein database search by using the intratask parallelization technique based on a CPU-GPU collaborative system. Before doing the SW computations on GPU, a procedure is applied on CPU by using the frequency distance filtration scheme (FDFS) to eliminate the unnecessary alignments. The experimental results indicate that CUDA-SWfr runs 9.6 times and 96 times faster than the CPU-based SW method without and with FDFS, respectively.

The designing and implementation of PE teaching information resource database based on broadband network

NASA Astrophysics Data System (ADS)

Wang, Jian

2017-01-01

In order to change traditional PE teaching mode and realize the interconnection, interworking and sharing of PE teaching resources, a distance PE teaching platform based on broadband network is designed and PE teaching information resource database is set up. The designing of PE teaching information resource database takes Windows NT 4/2000Server as operating system platform, Microsoft SQL Server 7.0 as RDBMS, and takes NAS technology for data storage and flow technology for video service. The analysis of system designing and implementation shows that the dynamic PE teaching information resource sharing platform based on Web Service can realize loose coupling collaboration, realize dynamic integration and active integration and has good integration, openness and encapsulation. The distance PE teaching platform based on Web Service and the design scheme of PE teaching information resource database can effectively solve and realize the interconnection, interworking and sharing of PE teaching resources and adapt to the informatization development demands of PE teaching.

Converting Student Support Services to Online Delivery.

ERIC Educational Resources Information Center

Brigham, David E.

2001-01-01

Uses a systems framework to analyze the creation of student support services for distance education at Regents College: electronic advising, electronic peer network, online course database, online bookstore, virtual library, and alumni services website. Addresses the issues involved in converting distance education programs from print-based and…

The Mass Function of Abell Clusters

NASA Astrophysics Data System (ADS)

Chen, J.; Huchra, J. P.; McNamara, B. R.; Mader, J.

1998-12-01

The velocity dispersion and mass functions for rich clusters of galaxies provide important constraints on models of the formation of Large-Scale Structure (e.g., Frenk et al. 1990). However, prior estimates of the velocity dispersion or mass function for galaxy clusters have been based on either very small samples of clusters (Bahcall and Cen 1993; Zabludoff et al. 1994) or large but incomplete samples (e.g., the Girardi et al. (1998) determination from a sample of clusters with more than 30 measured galaxy redshifts). In contrast, we approach the problem by constructing a volume-limited sample of Abell clusters. We collected individual galaxy redshifts for our sample from two major galaxy velocity databases, the NASA Extragalactic Database, NED, maintained at IPAC, and ZCAT, maintained at SAO. We assembled a database with velocity information for possible cluster members and then selected cluster members based on both spatial and velocity data. Cluster velocity dispersions and masses were calculated following the procedures of Danese, De Zotti, and di Tullio (1980) and Heisler, Tremaine, and Bahcall (1985), respectively. The final velocity dispersion and mass functions were analyzed in order to constrain cosmological parameters by comparison to the results of N-body simulations. Our data for the cluster sample as a whole and for the individual clusters (spatial maps and velocity histograms) in our sample is available on-line at http://cfa-www.harvard.edu/ huchra/clusters. This website will be updated as more data becomes available in the master redshift compilations, and will be expanded to include more clusters and large groups of galaxies.

Is your prescription of distance running shoes evidence-based?

PubMed

Richards, C E; Magin, P J; Callister, R

2009-03-01

To determine whether the current practice of prescribing distance running shoes featuring elevated cushioned heels and pronation control systems tailored to the individual's foot type is evidence-based. MEDLINE (1950-May 2007), CINAHL (1982-May 2007), EMBASE (1980-May 2007), PsychInfo (1806-May 2007), Cochrane Database of Systematic Reviews (2(nd) Quarter 2007), Cochrane Central Register of Controlled trials (2(nd) Quarter 2007), SPORTSDiscus (1985-May 2007) and AMED (1985-May 2007). English language articles were identified via keyword and medical subject headings (MeSH) searches of the above electronic databases. With these searches and the subsequent review process, controlled trials or systematic reviews were sought in which the study population included adult recreational or competitive distance runners, the exposure was distance running, the intervention evaluated was a running shoe with an elevated cushioned heel and pronation control systems individualised to the wearer's foot type, and the outcome measures included either running injury rates, distance running performance, osteoarthritis risk, physical activity levels, or overall health and wellbeing. The quality of these studies and their findings were then evaluated. No original research that met the study criteria was identified either directly or via the findings of the six systematic reviews identified. The prescription of this shoe type to distance runners is not evidence-based.

Driving towards obesity: a systematized literature review on the association between motor vehicle travel time and distance and weight status in adults.

PubMed

McCormack, Gavin R; Virk, Jagdeep S

2014-09-01

Higher levels of sedentary behavior are associated with adverse health outcomes. Over-reliance on private motor vehicles for transportation is a potential contributor to the obesity epidemic. The objective of this study was to review evidence on the relationship between motor vehicle travel distance and time and weight status among adults. Keywords associated with driving and weight status were entered into four databases (PubMed Medline Transportation Research Information Database and Web of Science) and retrieved article titles and abstracts screened for relevance. Relevant articles were assessed for their eligibility for inclusion in the review (English-language articles a sample ≥ 16 years of age included a measure of time or distance traveling in a motor vehicle and weight status and estimated the association between driving and weight status). The database search yielded 2781 articles, from which 88 were deemed relevant and 10 studies met the inclusion criteria. Of the 10 studies included in the review, 8 found a statistically significant positive association between time and distance traveled in a motor vehicle and weight status. Multilevel interventions that make alternatives to driving private motor vehicles more convenient, such as walking and cycling, are needed to promote healthy weight in the adult population. Copyright © 2014 Elsevier Inc. All rights reserved.

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.

Extragalactic circuits, transmission lines, and CR particle acceleration

NASA Astrophysics Data System (ADS)

Kronberg, Philipp P.; Lovelace, Richard V. E.

2015-08-01

A non-negligible fraction of a Supermassive Black Hole's (SMBH) rest mass energy gets transported into extragalactic space by a remarkable process in jets which are incompletely understood. What are the physical processes which transport this energy? It is likely that the energy flows electromagnetically, rather than via a particle beam flux. The deduced electromagnetic fields may produce particles of energy as high as ˜ 1020 eV. The energetics of SMBH accretion disk models and the electromagnetic energy transfer imply that a SMBH should generate a 1018 - 1019 Ampères current close to the black hole and its accretion disk. We describe the so far best observation-based estimate of the magnitude of the current flow along the axis of the jet extending from the nucleus of the active galaxy in 3C303. The current is measured to be I ˜ 1018 Ampères at ˜ 40 kpc away from the AGN. This indicates that organised current flow remains intact over multi-kpc distances. The electric current I transports electromagnetic power into free space, P = I2Z, where Z ˜ 30 Ohms is related to the impedance of free space, and this points to the existence of cosmic electric circuit. The associated electric potential drop, V = IZ, is of the order of that required to generate Ultra High Energy Cosmic Rays (UHECR). We also explore further implications, including disruption/deflection of the power flow and also why such measurements, exemplified by those on 3C303, are currently very difficult to make and to unambiguously interpret. This naturally leads to the topic of how such measurements can be extended and improved in the future. We describe the analogy of electromagnetically dominated jets with transmission lines. High powered jets in vacuo can be understood by approximate analogy with a waveguide. The importance of inductance, impedance, and other laboratory electrical concepts are discussed in this context.

EUV Spectroscopy of High-redshift X-ray Objects

NASA Astrophysics Data System (ADS)

Kowalski, Michael Paul; Wolff, M. T.; Wood, K. S.; Barbee, T. W., Jr.

2010-03-01

As astronomical observations are pushed to cosmological distances (z>3) the spectral energy distributions of X-ray objects, AGNs for example, will have their maxima redshifted into the EUV waveband ( 90-912 Å/0.1-0.01 keV). Consequently, a wealth of spectral diagnostics, provided by, for example, the Fe L-shell complex ( 60-6 Å/0.2-2.0 keV) and the O VII/VIII lines ( 20 Å/0.5 keV), will be lost to X-ray instruments operating at traditional ( 0.5-10 keV) and higher X-ray energies. There are precedents in other wavebands. For example, HST evolutionary studies will become largely the province of JWST. Despite the successes of EUVE, the ROSAT WFC, and the Chandra LETG, the EUV continues to be unappreciated and under-utilized, partly because of a preconception that absorption by neutral galactic Hydrogen in the ISM prevents any useful extragalactic measurements at all EUV wavelengths and, until recently, by a lack of a suitable enabling technology. Thus, if future planned X-ray missions (e.g., IXO, Gen-X) are optimized again for traditional X-ray energies, their performance (effective area, resolving power) will be cut off at ultrasoft X-ray energies or at best be radically reduced in the EUV. This opens up a critical gap in performance located right at short EUV wavelengths, where the critical X-ray spectral transitions occur in high-z objects. However, normal-incidence multilayer-grating technology, which performs best precisely at such wavelengths, together with advanced nano-laminate fabrication techniques have been developed and are now mature to the point where advanced EUV instrument designs with performance complementary to IXO and Gen-X are practical. Such EUV instruments could be flown either independently or as secondary instruments on these X-ray missions. We present here a critical examination of the limits placed on extragalactic EUV measurements by ISM absorption, the range where high-z measurements are practical, and the requirements this imposes on next-generation instrument designs.

Discovery of gamma-ray emission from the extragalactic pulsar wind nebula N 157B with H.E.S.S.

NASA Astrophysics Data System (ADS)

H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker, J.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Atäı, A.; Domainko, W.; Drury, L. O.'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; G´rard, L.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Göring, D.; Grondin, M.-H.; Häffner, S.; Hague, J. D.; Hahn, J.; Hampf, D.; Harris, J.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; K´ski, K.; Katz, U.; Kaufmann, S.; K´lifi, B.; Klochkov, D.; K´niak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Krayzel, F.; Laffon, H.; Lamanna, G.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; M´hault, J.; Menzler, U.; Moderski, R.; Mohamed, M.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Lstrok; .; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

2012-09-01

We present the significant detection of the first extragalactic pulsar wind nebula (PWN) detected in gamma rays, N 157B, located in the large Magellanic Cloud (LMC). Pulsars with high spin-down luminosity are found to power energised nebulae that emit gamma rays up to energies of several tens of TeV. N 157B is associated with PSR J0537-6910, which is the pulsar with the highest known spin-down luminosity. The High Energy Stereoscopic System telescope array observed this nebula on a yearly basis from 2004 to 2009 with a dead-time corrected exposure of 46 h. The gamma-ray spectrum between 600 GeV and 12 TeV is well-described by a pure power-law with a photon index of 2.8 ± 0.2stat ± 0.3syst and a normalisation at 1 TeV of (8.2 ± 0.8stat ± 2.5syst) × 10-13 cm-2 s-1 TeV-1. A leptonic multi-wavelength model shows that an energy of about 4 × 1049 erg is stored in electrons and positrons. The apparent efficiency, which is the ratio of the TeV gamma-ray luminosity to the pulsar's spin-down luminosity, 0.08% ± 0.01%, is comparable to those of PWNe found in the Milky Way. The detection of a PWN at such a large distance is possible due to the pulsar's favourable spin-down luminosity and a bright infrared photon-field serving as an inverse-Compton-scattering target for accelerated leptons. By applying a calorimetric technique to these observations, the pulsar's birth period is estimated to be shorter than 10 ms. Data set is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/L2

Two Red Clumps and the X-shaped Milky Way Bulge

NASA Astrophysics Data System (ADS)

McWilliam, Andrew; Zoccali, Manuela

2010-12-01

From Two Micron All Sky Survey infrared photometry, we find two red clump (RC) populations coexisting in fields toward the Galactic bulge at latitudes |b|>5fdg5, ranging over ~13° in longitude and 20° in latitude. These RC peaks indicate two stellar populations separated by ~2.3 kpc at (l, b) = (+1, - 8) the two RCs are located at 6.5 and 8.8 ± 0.2 kpc. The double-peaked RC is inconsistent with a tilted bar morphology. Most of our fields show the two RCs at roughly constant distance with longitude, also inconsistent with a tilted bar; however, an underlying bar may be present. Stellar densities in the two RCs change dramatically with longitude: on the positive longitude side the foreground RC is dominant, while the background RC dominates negative longitudes. A line connecting the maxima of the foreground and background populations is tilted to the line of sight by ~20°±4°, similar to claims for the tilt of a Galactic bar. The distance between the two RCs decreases toward the Galactic plane; seen edge-on the bulge is X-shaped, resembling some extragalactic bulges and the results of N-body simulations. The center of this X is consistent with the distance to the Galactic center, although better agreement would occur if the bulge is 2-3 Gyr younger than 47 Tuc. Our observations may be understood if the two RC populations emanate, nearly tangentially, from the Galactic bar ends, in a funnel shape. Alternatively, the X, or double funnel, may continue to the Galactic center. From the Sun, this would appear peanut/box shaped, but X-shaped when viewed tangentially.

Recent Hubble Space Telescope Imaging of the Light Echoes of Supernova 2016adj in Centaurus A

NASA Astrophysics Data System (ADS)

Hyder, Ali; Lawrence, Stephen; Sugerman, Ben

2018-01-01

Light echoes are one of the most powerful and efficient probes of the structure and composition of dust in circumstellar and interstellar environments. Observations of light echoes provide exact three dimensional (3-D) positions of dust while constraining its density, grain-size and chemical make-up. These can be used to study the evolutionary history of supernova (SN) progenitors, produce high-resolution maps of the structure and composition of interstellar media (ISM), and geometrically measure extragalactic distances. Here we report on our progress with analyzing our ongoing campaign of Hubble Space Telescope (HST) observations of the light echoes of SN 2016adj in Centaurus A. SN 2016adj was discovered on 08 Feb 2016 and identified as a core-collapse SN of either Type Ib or Type IIb. All observers agreed the SN was highly reddened, suffering A_V =2–4 mags of extinction, which is consistent with its location within the famous dust lane of its elliptical host galaxy. Tthe light echo first reported by Sugerman & Lawrence (2016) from the earliest epoch of WFC3 imaging with marked N-S asymmetry has expanded into a complete ring that is fairly well-centered on the SN. The ring is azimuthally non-uniform in brightness, but less dramatically so than at early times. By day 395 it has expanded to radii ranging from 0.62”(NW)—0.76”(SE). Adopting a distance of 3.42 Mpc, this indicates a sheet of ISM dust at foreground distances of 160—240 pc. These observations and analysis are supported by STScI grants 14146, 14487 and 14700.

Concordance of Commercial Data Sources for Neighborhood-Effects Studies

PubMed Central

Schootman, Mario

2010-01-01

Growing evidence supports a relationship between neighborhood-level characteristics and important health outcomes. One source of neighborhood data includes commercial databases integrated with geographic information systems to measure availability of certain types of businesses or destinations that may have either favorable or adverse effects on health outcomes; however, the quality of these data sources is generally unknown. This study assessed the concordance of two commercial databases for ascertaining the presence, locations, and characteristics of businesses. Businesses in the St. Louis, Missouri area were selected based on their four-digit Standard Industrial Classification (SIC) codes and classified into 14 business categories. Business listings in the two commercial databases were matched by standardized business name within specified distances. Concordance and coverage measures were calculated using capture–recapture methods for all businesses and by business type, with further stratification by census-tract-level population density, percent below poverty, and racial composition. For matched listings, distance between listings and agreement in four-digit SIC code, sales volume, and employee size were calculated. Overall, the percent agreement was 32% between the databases. Concordance and coverage estimates were lowest for health-care facilities and leisure/entertainment businesses; highest for popular walking destinations, eating places, and alcohol/tobacco establishments; and varied somewhat by population density. The mean distance (SD) between matched listings was 108.2 (179.0) m with varying levels of agreement in four-digit SIC (percent agreement = 84.6%), employee size (weighted kappa = 0.63), and sales volume (weighted kappa = 0.04). Researchers should cautiously interpret findings when using these commercial databases to yield measures of the neighborhood environment. PMID:20480397

Monitoring by Use of Clusters of Sensor-Data Vectors

NASA Technical Reports Server (NTRS)

Iverson, David L.

2007-01-01

The inductive monitoring system (IMS) is a system of computer hardware and software for automated monitoring of the performance, operational condition, physical integrity, and other aspects of the health of a complex engineering system (e.g., an industrial process line or a spacecraft). The input to the IMS consists of streams of digitized readings from sensors in the monitored system. The IMS determines the type and amount of any deviation of the monitored system from a nominal or normal ( healthy ) condition on the basis of a comparison between (1) vectors constructed from the incoming sensor data and (2) corresponding vectors in a database of nominal or normal behavior. The term inductive reflects the use of a process reminiscent of traditional mathematical induction to learn about normal operation and build the nominal-condition database. The IMS offers two major advantages over prior computational monitoring systems: The computational burden of the IMS is significantly smaller, and there is no need for abnormal-condition sensor data for training the IMS to recognize abnormal conditions. The figure schematically depicts the relationships among the computational processes effected by the IMS. Training sensor data are gathered during normal operation of the monitored system, detailed computational simulation of operation of the monitored system, or both. The training data are formed into vectors that are used to generate the database. The vectors in the database are clustered into regions that represent normal or nominal operation. Once the database has been generated, the IMS compares the vectors of incoming sensor data with vectors representative of the clusters. The monitored system is deemed to be operating normally or abnormally, depending on whether the vector of incoming sensor data is or is not, respectively, sufficiently close to one of the clusters. For this purpose, a distance between two vectors is calculated by a suitable metric (e.g., Euclidean distance) and "sufficiently close" signifies lying at a distance less than a specified threshold value. It must be emphasized that although the IMS is intended to detect off-nominal or abnormal performance or health, it is not necessarily capable of performing a thorough or detailed diagnosis. Limited diagnostic information may be available under some circumstances. For example, the distance of a vector of incoming sensor data from the nearest cluster could serve as an indication of the severity of a malfunction. The identity of the nearest cluster may be a clue as to the identity of the malfunctioning component or subsystem. It is possible to decrease the IMS computation time by use of a combination of cluster-indexing and -retrieval methods. For example, in one method, the distances between each cluster and two or more reference vectors can be used for the purpose of indexing and retrieval. The clusters are sorted into a list according to these distance values, typically in ascending order of distance. When a set of input data arrives and is to be tested, the data are first arranged as an ordered set (that is, a vector). The distances from the input vector to the reference points are computed. The search of clusters from the list can then be limited to those clusters lying within a certain distance range from the input vector; the computation time is reduced by not searching the clusters at a greater distance.

Isolated Early-type Galaxies in the 2dFGRS

NASA Astrophysics Data System (ADS)

Fuse, Christopher R.; Lamir, C.

2014-01-01

Isolated galaxies are systems that have experienced limited external perturbations, thus the properties of these galaxies are largely due to internal processes. The features of isolated early-type galaxies (IEGs) provide a baseline from which to compare early-type systems residing in higher-density environments. We use the Two-Degree Field Galaxy Redshift Survey (2dFGRS) and the NASA Extragalactic Database (NED) to identify IEGs in the nearby universe. Search criteria in the 2dFGRS were chosen to insure that the IEGs have remained separated from neighboring galaxies for the majority of their lifetimes. Isolated galaxies are chosen utilizing a minimum projected physical separation of 1 Mpc from any neighboring non-dwarf galaxy brighter than Mb = -16.5 mags. A minimum redshift separation of 350 km/s between a candidate galaxy and a neighboring was imposed to further insure the candidate’s isolation. Early results of the search for isolated early-type galaxies in the southern sky are presented.

Cost-efficient scheduling of FAST observations

NASA Astrophysics Data System (ADS)

Luo, Qi; Zhao, Laiping; Yu, Ce; Xiao, Jian; Sun, Jizhou; Zhu, Ming; Zhong, Yi

2018-03-01

A cost-efficient schedule for the Five-hundred-meter Aperture Spherical radio Telescope (FAST) requires to maximize the number of observable proposals and the overall scientific priority, and minimize the overall slew-cost generated by telescope shifting, while taking into account the constraints including the astronomical objects visibility, user-defined observable times, avoiding Radio Frequency Interference (RFI). In this contribution, first we solve the problem of maximizing the number of observable proposals and scientific priority by modeling it as a Minimum Cost Maximum Flow (MCMF) problem. The optimal schedule can be found by any MCMF solution algorithm. Then, for minimizing the slew-cost of the generated schedule, we devise a maximally-matchable edges detection-based method to reduce the problem size, and propose a backtracking algorithm to find the perfect matching with minimum slew-cost. Experiments on a real dataset from NASA/IPAC Extragalactic Database (NED) show that, the proposed scheduler can increase the usage of available times with high scientific priority and reduce the slew-cost significantly in a very short time.

Molecular diagnostics of Galactic star-formation regions

NASA Astrophysics Data System (ADS)

Loenen, Edo; Baan, Willem; Spaans, Marco

2007-10-01

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

Fuzzy Relational Databases: Representational Issues and Reduction Using Similarity Measures.

ERIC Educational Resources Information Center

Prade, Henri; Testemale, Claudette

1987-01-01

Compares and expands upon two approaches to dealing with fuzzy relational databases. The proposed similarity measure is based on a fuzzy Hausdorff distance and estimates the mismatch between two possibility distributions using a reduction process. The consequences of the reduction process on query evaluation are studied. (Author/EM)

Biometric sample extraction using Mahalanobis distance in Cardioid based graph using electrocardiogram signals.

PubMed

Sidek, Khairul; Khali, Ibrahim

2012-01-01

In this paper, a person identification mechanism implemented with Cardioid based graph using electrocardiogram (ECG) is presented. Cardioid based graph has given a reasonably good classification accuracy in terms of differentiating between individuals. However, the current feature extraction method using Euclidean distance could be further improved by using Mahalanobis distance measurement producing extracted coefficients which takes into account the correlations of the data set. Identification is then done by applying these extracted features to Radial Basis Function Network. A total of 30 ECG data from MITBIH Normal Sinus Rhythm database (NSRDB) and MITBIH Arrhythmia database (MITDB) were used for development and evaluation purposes. Our experimentation results suggest that the proposed feature extraction method has significantly increased the classification performance of subjects in both databases with accuracy from 97.50% to 99.80% in NSRDB and 96.50% to 99.40% in MITDB. High sensitivity, specificity and positive predictive value of 99.17%, 99.91% and 99.23% for NSRDB and 99.30%, 99.90% and 99.40% for MITDB also validates the proposed method. This result also indicates that the right feature extraction technique plays a vital role in determining the persistency of the classification accuracy for Cardioid based person identification mechanism.

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.

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.

Neuro-fuzzy model for estimating race and gender from geometric distances of human face across pose

NASA Astrophysics Data System (ADS)

Nanaa, K.; Rahman, M. N. A.; Rizon, M.; Mohamad, F. S.; Mamat, M.

2018-03-01

Classifying human face based on race and gender is a vital process in face recognition. It contributes to an index database and eases 3D synthesis of the human face. Identifying race and gender based on intrinsic factor is problematic, which is more fitting to utilizing nonlinear model for estimating process. In this paper, we aim to estimate race and gender in varied head pose. For this purpose, we collect dataset from PICS and CAS-PEAL databases, detect the landmarks and rotate them to the frontal pose. After geometric distances are calculated, all of distance values will be normalized. Implementation is carried out by using Neural Network Model and Fuzzy Logic Model. These models are combined by using Adaptive Neuro-Fuzzy Model. The experimental results showed that the optimization of address fuzzy membership. Model gives a better assessment rate and found that estimating race contributing to a more accurate gender assessment.

An Evaluation of Selected ASERL Web Pages: "Best Practices" for Serving Distance Learners

ERIC Educational Resources Information Center

Thomas, Melanie

2007-01-01

With the expansion in quantity of full-text content material made available through online database subscriptions, aggregator services, and over the Internet, the need for print materials seems to have diminished over recent years. Growing, too, are the numbers of students taking advantage of distance learning opportunities, scattered miles and…

Distance Education in Library and Information Science Education: Trends and Issues.

ERIC Educational Resources Information Center

Zepp, Diana

This study measured current trends in distance education in the United States within Library and Information Science programs. The study was conducted, for the period 1989 to 1998, through a content analysis of journal articles from the "Library Literature" database, and through a content analysis of graduate catalogs from American Library…

System and method employing a minimum distance and a load feature database to identify electric load types of different electric loads

DOEpatents

Lu, Bin; Yang, Yi; Sharma, Santosh K; Zambare, Prachi; Madane, Mayura A

2014-12-23

A method identifies electric load types of a plurality of different electric loads. The method includes providing a load feature database of a plurality of different electric load types, each of the different electric load types including a first load feature vector having at least four different load features; sensing a voltage signal and a current signal for each of the different electric loads; determining a second load feature vector comprising at least four different load features from the sensed voltage signal and the sensed current signal for a corresponding one of the different electric loads; and identifying by a processor one of the different electric load types by determining a minimum distance of the second load feature vector to the first load feature vector of the different electric load types of the load feature database.

The frequency and distribution of high-velocity gas in the Galaxy

NASA Technical Reports Server (NTRS)

Nichols, Joy S.

1995-01-01

The purpose of this study was to estimate the frequency and distribution of high-velocity gas in the Galaxy using UV absorption line measurements from archival high-dispersion IUE spectra and to identify particularly interesting regions for future study. Approximately 500 spectra have been examined. The study began with the creation of a database of all 0 and B stars with b less than or = to 30 deg observed with IUE at high dispersion over its 18-year lifetime. The original database of 2500 unique objects was reduced to 1200 objects which had optimal exposures available. The next task was to determine the distances of these stars so the high-velocity structures could be mapped in the Galaxy. Spectroscopic distances were calculated for each star for which photometry was available. The photometry was acquired for each star using the SIMBAD database. Preference was given to the ubvy system where available; otherwise the UBV system was used.

Enhancing AstroInformatics and Science Discovery from Data in Journal Articles

NASA Astrophysics Data System (ADS)

Mazzarella, Joseph

2011-05-01

Traditional methods of publishing scientific data and metadata in journal articles are in need of major upgrades to reach the full potential of astronomical databases and astroinformatics techniques to facilitate semi-automated, and eventually autonomous, methods of science discovery. I will review a growing collaboration involving the NASA/IPAC Extragalactic Database (NED), the Astrophysics Data System (ADS), the Virtual Astronomical Observatory (VAO), the AAS Journals and IOP, and the Data Conservancy that is aimed toward transforming the methodology used to publish, capture and link data associated with astrophysics journal articles. We are planning a web-based workflow to assist astronomers during the publication of journal articles. The primary goals are to facilitate the application of structure and standards to (meta)data, reduce errors, remove ambiguities in the identification of astrophysical objects and regions of sky, capture and preserve the images and spectral data files used to make plots, and accelerate the ingestion of the data into relevant repositories, search engines and integration services. The outcome of this community wide effort will address a recent public policy mandate to publish scientific data in open formats to allow reproducibility of results and to facilitate new discoveries. Equally important, this work has the potential to usher in a new wave of science discovery based on seamless connectivity between data relationships that are continuously growing in size and complexity, and increasingly sophisticated data visualization and analysis applications.

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.

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

Transformation of social networks in the late pre-Hispanic US Southwest.

PubMed

Mills, Barbara J; Clark, Jeffery J; Peeples, Matthew A; Haas, W R; Roberts, John M; Hill, J Brett; Huntley, Deborah L; Borck, Lewis; Breiger, Ronald L; Clauset, Aaron; Shackley, M Steven

2013-04-09

The late pre-Hispanic period in the US Southwest (A.D. 1200-1450) was characterized by large-scale demographic changes, including long-distance migration and population aggregation. To reconstruct how these processes reshaped social networks, we compiled a comprehensive artifact database from major sites dating to this interval in the western Southwest. We combine social network analysis with geographic information systems approaches to reconstruct network dynamics over 250 y. We show how social networks were transformed across the region at previously undocumented spatial, temporal, and social scales. Using well-dated decorated ceramics, we track changes in network topology at 50-y intervals to show a dramatic shift in network density and settlement centrality from the northern to the southern Southwest after A.D. 1300. Both obsidian sourcing and ceramic data demonstrate that long-distance network relationships also shifted from north to south after migration. Surprisingly, social distance does not always correlate with spatial distance because of the presence of network relationships spanning long geographic distances. Our research shows how a large network in the southern Southwest grew and then collapsed, whereas networks became more fragmented in the northern Southwest but persisted. The study also illustrates how formal social network analysis may be applied to large-scale databases of material culture to illustrate multigenerational changes in network structure.

Transformation of social networks in the late pre-Hispanic US Southwest

PubMed Central

Mills, Barbara J.; Clark, Jeffery J.; Peeples, Matthew A.; Haas, W. R.; Roberts, John M.; Hill, J. Brett; Huntley, Deborah L.; Borck, Lewis; Breiger, Ronald L.; Clauset, Aaron; Shackley, M. Steven

2013-01-01

The late pre-Hispanic period in the US Southwest (A.D. 1200–1450) was characterized by large-scale demographic changes, including long-distance migration and population aggregation. To reconstruct how these processes reshaped social networks, we compiled a comprehensive artifact database from major sites dating to this interval in the western Southwest. We combine social network analysis with geographic information systems approaches to reconstruct network dynamics over 250 y. We show how social networks were transformed across the region at previously undocumented spatial, temporal, and social scales. Using well-dated decorated ceramics, we track changes in network topology at 50-y intervals to show a dramatic shift in network density and settlement centrality from the northern to the southern Southwest after A.D. 1300. Both obsidian sourcing and ceramic data demonstrate that long-distance network relationships also shifted from north to south after migration. Surprisingly, social distance does not always correlate with spatial distance because of the presence of network relationships spanning long geographic distances. Our research shows how a large network in the southern Southwest grew and then collapsed, whereas networks became more fragmented in the northern Southwest but persisted. The study also illustrates how formal social network analysis may be applied to large-scale databases of material culture to illustrate multigenerational changes in network structure. PMID:23530201

Wavelet optimization for content-based image retrieval in medical databases.

PubMed

Quellec, G; Lamard, M; Cazuguel, G; Cochener, B; Roux, C

2010-04-01

We propose in this article a content-based image retrieval (CBIR) method for diagnosis aid in medical fields. In the proposed system, images are indexed in a generic fashion, without extracting domain-specific features: a signature is built for each image from its wavelet transform. These image signatures characterize the distribution of wavelet coefficients in each subband of the decomposition. A distance measure is then defined to compare two image signatures and thus retrieve the most similar images in a database when a query image is submitted by a physician. To retrieve relevant images from a medical database, the signatures and the distance measure must be related to the medical interpretation of images. As a consequence, we introduce several degrees of freedom in the system so that it can be tuned to any pathology and image modality. In particular, we propose to adapt the wavelet basis, within the lifting scheme framework, and to use a custom decomposition scheme. Weights are also introduced between subbands. All these parameters are tuned by an optimization procedure, using the medical grading of each image in the database to define a performance measure. The system is assessed on two medical image databases: one for diabetic retinopathy follow up and one for screening mammography, as well as a general purpose database. Results are promising: a mean precision of 56.50%, 70.91% and 96.10% is achieved for these three databases, when five images are returned by the system. Copyright 2009 Elsevier B.V. All rights reserved.

Interaction in Distance Education Environments: A Trend Analysis

ERIC Educational Resources Information Center

Karatas, Serçin; Yilmaz, Ayse Bagriacik; Dikmen, Cemal Hakan; Ermis, Ugur Ferhat; Gürbüz, Onur

2017-01-01

The aim of this study is to determine the trend concerning interaction in distance education between the years 2011 and 2015. According to this aim, 544 articles in the databases of EBSCO, Scopus, and Web of Science were examined. The examination has been conducted on the basis of various variables including year, country, number of authors,…

A Review of MS-DOS Bulletin Board Software Suitable for Long Distance Learning.

ERIC Educational Resources Information Center

Sessa, Anneliese

This paper describes the advantages of using computer bulletin boards systems (BBS) for distance learning, including the use of the New York City Education Network (NYCENET) to access various databases and to communicate with individuals or the public. Questions to be answered in order to determine the most appropriate software for running a BBS…

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

A VST and VISTA study of globular clusters in NGC 253

NASA Astrophysics Data System (ADS)

Cantiello, Michele; Grado, Aniello; Rejkuba, Marina; Arnaboldi, Magda; Capaccioli, Massimo; Greggio, Laura; Iodice, Enrica; Limatola, Luca

2018-03-01

Context. Globular clusters (GCs) are key to our understanding of the Universe, as laboratories of stellar evolution, fossil tracers of the past formation epoch of the host galaxy, and effective distance indicators from local to cosmological scales. Aim. We analyze the properties of the sources in the NGC 253 with the aim of defining an up to date catalog of GC candidates in the galaxy. Given the distance of the galaxy, GCs in NGC 253 are ideal targets for resolved color-magnitude diagram studies of extragalactic GCs with next-generation diffraction limited ground-based telescopes. Methods: Our analysis is based on the science verification data of two ESO survey telescopes, VST and VISTA. Using ugri photometry from VST and JKs from VISTA, GC candidates were selected using as reference the morpho-photometric and color properties of spectroscopically confirmed GCs available in the literature. The strength of the results was verified against available archival HST/ACS data from the GHOSTS survey: all but two of the selected GC candidates appear as star clusters in HST footprints. Results: The adopted GC selection leads to the definition of a sample of ˜350 GC candidates. At visual inspection, we find that 82 objects match all the requirements for selecting GC candidates and 155 are flagged as uncertain GC candidate; however, 110 are unlikely GCs, which are most likely background galaxies. Furthermore, our analysis shows that four of the previously spectroscopically confirmed GCs, i.e., ˜20% of the total spectroscopic sample, are more likely either background galaxies or high-velocity Milky Way stars. The radial density profile of the selected best candidates shows the typically observed r1/4-law radial profile. The analysis of the color distributions reveals only marginal evidence of the presence of color bimodality, which is normally observed in galaxies of similar luminosity. The GC luminosity function does not show the typical symmetry, mainly because of the lack of bright GCs. Part of the bright GCs missing might be at very large galactocentric distances or along the line of sight of the galaxy dusty disk. As an alternative possibility, we speculate that a fraction of low luminosity GC candidates might instead be metal-rich, intermediate age clusters, but fall in a similar color interval of old, metal-poor GCs. Conclusions: Defining a contaminant-free sample of GCs in extragalactic systems is not a straight forward exercise. Using optical and near-IR photometry we purged the list of GCs with spectroscopic membership and photometric GC candidates in NGC 253. Our results show that the use of either spectroscopic or photometric data only does not generally ensure a contaminant-free sample and a combination of both spectroscopy and photometry is preferred. Table 3 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/611/A21This work is based on observations taken at the ESO La Silla Paranal Observatory within the VST Science Verification Programme ID 60.A-9286(A) and VISTA Science Verification Programme ID 60.A-9285(A).

A framework of multitemplate ensemble for fingerprint verification

NASA Astrophysics Data System (ADS)

Yin, Yilong; Ning, Yanbin; Ren, Chunxiao; Liu, Li

2012-12-01

How to improve performance of an automatic fingerprint verification system (AFVS) is always a big challenge in biometric verification field. Recently, it becomes popular to improve the performance of AFVS using ensemble learning approach to fuse related information of fingerprints. In this article, we propose a novel framework of fingerprint verification which is based on the multitemplate ensemble method. This framework is consisted of three stages. In the first stage, enrollment stage, we adopt an effective template selection method to select those fingerprints which best represent a finger, and then, a polyhedron is created by the matching results of multiple template fingerprints and a virtual centroid of the polyhedron is given. In the second stage, verification stage, we measure the distance between the centroid of the polyhedron and a query image. In the final stage, a fusion rule is used to choose a proper distance from a distance set. The experimental results on the FVC2004 database prove the improvement on the effectiveness of the new framework in fingerprint verification. With a minutiae-based matching method, the average EER of four databases in FVC2004 drops from 10.85 to 0.88, and with a ridge-based matching method, the average EER of these four databases also decreases from 14.58 to 2.51.

Towards online iris and periocular recognition under relaxed imaging constraints.

PubMed

Tan, Chun-Wei; Kumar, Ajay

2013-10-01

Online iris recognition using distantly acquired images in a less imaging constrained environment requires the development of a efficient iris segmentation approach and recognition strategy that can exploit multiple features available for the potential identification. This paper presents an effective solution toward addressing such a problem. The developed iris segmentation approach exploits a random walker algorithm to efficiently estimate coarsely segmented iris images. These coarsely segmented iris images are postprocessed using a sequence of operations that can effectively improve the segmentation accuracy. The robustness of the proposed iris segmentation approach is ascertained by providing comparison with other state-of-the-art algorithms using publicly available UBIRIS.v2, FRGC, and CASIA.v4-distance databases. Our experimental results achieve improvement of 9.5%, 4.3%, and 25.7% in the average segmentation accuracy, respectively, for the UBIRIS.v2, FRGC, and CASIA.v4-distance databases, as compared with most competing approaches. We also exploit the simultaneously extracted periocular features to achieve significant performance improvement. The joint segmentation and combination strategy suggest promising results and achieve average improvement of 132.3%, 7.45%, and 17.5% in the recognition performance, respectively, from the UBIRIS.v2, FRGC, and CASIA.v4-distance databases, as compared with the related competing approaches.

Historical Notes on the Expanding Universe

NASA Technical Reports Server (NTRS)

Way, Michael J.; Belenkyi, Ari; Nussbaumer, Harry; Peacock, John

2014-01-01

The article Measuring the Hubble constant by Mario Livio and Adam Riess (Physics Today, October 2013, page 41) reviewed studies of the expanding universe from the 1920s to the present. Although the history of the subject underwent considerable compression to fit the length of a magazine article, we think it may leave a misleading impression of some of the key steps to our current understanding. We therefore offer the following clarifications. Most significantly, papers by Arthur Eddington and by Willem de Sitter in 1930, who successfully promoted Georges Lematres 1927 article for the Scientific Society of Brussels, effected a paradigm shift in interpretation of extragalactic redshifts in 1930. Before then, the astronomical community was generally unaware of the existence of nonstatic cosmological solutions and did not broadly appreciate that redshifts could be thought of locally as Doppler shifts in an expanding matter distribution. Certainly, in 1929 Edwin Hubble referred only to the de Sitter solution of 1917. At the time, the relation between distance and redshift predicted in that model was generally seen purely as a manifestation of static spacetime curvature.

An exceptionally bright flare from SGR 1806-20 and the origins of short-duration gamma-ray bursts.

PubMed

Hurley, K; Boggs, S E; Smith, D M; Duncan, R C; Lin, R; Zoglauer, A; Krucker, S; Hurford, G; Hudson, H; Wigger, C; Hajdas, W; Thompson, C; Mitrofanov, I; Sanin, A; Boynton, W; Fellows, C; von Kienlin, A; Lichti, G; Rau, A; Cline, T

2005-04-28

Soft-gamma-ray repeaters (SGRs) are galactic X-ray stars that emit numerous short-duration (about 0.1 s) bursts of hard X-rays during sporadic active periods. They are thought to be magnetars: strongly magnetized neutron stars with emissions powered by the dissipation of magnetic energy. Here we report the detection of a long (380 s) giant flare from SGR 1806-20, which was much more luminous than any previous transient event observed in our Galaxy. (In the first 0.2 s, the flare released as much energy as the Sun radiates in a quarter of a million years.) Its power can be explained by a catastrophic instability involving global crust failure and magnetic reconnection on a magnetar, with possible large-scale untwisting of magnetic field lines outside the star. From a great distance this event would appear to be a short-duration, hard-spectrum cosmic gamma-ray burst. At least a significant fraction of the mysterious short-duration gamma-ray bursts may therefore come from extragalactic magnetars.

First Hubble Space Telescope observations of the brightest stars in the Virgo galaxy M100 = NGC 4321

NASA Technical Reports Server (NTRS)

Freedman, Wendy L.; Madore, Barry F.; Stetson, Peter B.; Hughes, Shaun M. G.; Holtzman, Jon A.; Mould, Jeremy R.; Trauger, John T.; Gallagher, John S., III; Ballester, Gilda E.; Burrows, Christopher J.

1994-01-01

As part of both the Early Release Observations from the Hubble Space Telescope (HST) and the Key Project on the Extragalactic Distance Scale, we have obtained multiwavelength BVR Wide Field/Planetary Camera-2 (WFPC2) images for the face-on Virgo cluster spiral galaxy M100 = NGC 4321. We report here preliminary results from those observations, in the form of a color-magnitude diagram for approximately 11,500 stars down to V approximately 27 mag and a luminosity function for the brightest blue stars which is found to have a slope of 0.7, in excellent agreement with previous results obtained for significantly nearer galaxies. With the increased resolution now available using WFPC2, the number of galaxies in which we can directly measure Population I stars and thereby quantify the recent evolution, as well as test stellar evolution theory, has dramatically increased by at least a factor of 100. Finally, we find that the stars are present in M100 at the colors and luminosities expected for the brightest Cepheid variables in galaxies.

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

Indriolo, Nick; Bergin, E. A.; Goicoechea, J. R.

The relative populations in rotational transitions of CO can be useful for inferring gas conditions and excitation mechanisms at work in the interstellar medium. We present CO emission lines from rotational transitions observed with Herschel /HIFI in the star-forming cores Orion S, Orion KL, Sgr B2(M), and W49N. Integrated line fluxes from these observations are combined with those from Herschel /PACS observations of the same sources to construct CO spectral line energy distributions (SLEDs) from 5≤ J{sub u} ≤ 48. These CO SLEDs are compared to those reported in other galaxies, with the intention of empirically determining which mechanisms dominatemore » excitation in such systems. We find that CO SLEDs in Galactic star-forming cores cannot be used to reproduce those observed in other galaxies, although the discrepancies arise primarily as a result of beam filling factors. The much larger regions sampled by the Herschel beams at distances of several megaparsecs contain significant amounts of cooler gas, which dominate the extragalactic CO SLEDs, in contrast to observations of Galactic star-forming regions, which are focused specifically on cores containing primarily hot molecular gas.« less

Radioactivity in the galactic plane

NASA Technical Reports Server (NTRS)

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

1976-01-01

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

Recent progress in understanding the eruptions of classical novae

NASA Technical Reports Server (NTRS)

Shara, Michael M.

1988-01-01

Dramatic progress has occurred in the last two decades in understanding the physical processes and events leading up to, and transpiring during the eruption of a classical nova. The mechanism whereby a white dwarf accreting hydrogen-rich matter from a low-mass main-sequence companion produces a nova eruption has been understood since 1970. The mass-transferring binary stellar configuration leads inexorably to thermonuclear runaways detected at distances of megaparsecs. Summarized here are the efforts of many researchers in understanding the physical processes which generate nova eruptions; the effects upon nova eruptions of different binary-system parameters (e.g., chemical composition or mass of the white dwarf, different mass accretion rates); the possible metamorphosis from dwarf to classical novae and back again; and observational diagnostics of novae, including x ray and gamma ray emission, and the characteristics and distributions of novae in globular clusters and in extragalactic systems. While the thermonuclear-runaway model remains the successful cornerstone of nova simulation, it is now clear that a wide variety of physical processes, and three-dimensional hydrodynamic simulations, will be needed to explain the rich spectrum of behavior observed in erupting novae.

New prospects for detecting high-energy neutrinos from nearby supernovae

NASA Astrophysics Data System (ADS)

Murase, Kohta

2018-04-01

Neutrinos from supernovae (SNe) are crucial probes of explosive phenomena at the deaths of massive stars and neutrino physics. High-energy neutrinos are produced through hadronic processes by cosmic rays, which are accelerated during interaction between the supernova (SN) ejecta and circumstellar material (CSM). Recent observations of extragalactic SNe have revealed that a dense CSM is commonly expelled by the progenitor star. We provide new quantitative predictions of time-dependent high-energy neutrino emission from diverse types of SNe. We show that IceCube and KM3Net can detect ˜103 events from a SN II-P (and ˜3 ×105 events from a SN IIn) at a distance of 10 kpc. The new model also enables us to critically optimize the time window for dedicated searches for nearby SNe. A successful detection will give us a multienergy neutrino view of SN physics and new opportunities to study neutrino properties, as well as clues to the cosmic-ray origin. GeV-TeV neutrinos may also be seen by KM3Net, Hyper-Kamiokande, and PINGU.

Transparency of the Universe to gamma-rays

NASA Astrophysics Data System (ADS)

De Angelis, A.; Galanti, G.; Roncadelli, M.

2013-07-01

Using the most recent observational data concerning the extragalactic background light and the radio background for a source at an arbitrary redshift in the range zs ≤ 3, we compute the energy E0 of an observed γ-ray photon in the range 10 ≤ E0 ≤ 1013 GeV such that the resulting optical depth τγ(E0, zs) takes the values 1, 2, 3 and 4.6 corresponding to an observed flux dimming of e-1 ≃ 0.37, e-2 ≃ 0.14, e-3 ≃ 0.05 and e-4.6 ≃ 0.01, respectively. Below a distance D ≃ 8 kpc, we find that τγ(E0, DH0/c) < 1 for any value of E0. In the limiting case of a local Universe (zs ≃ 0), we compare our result with the one derived in 1997 by Coppi and Aharonian. The present achievement is of paramount relevance for the planned ground-based detectors like Cherenkov Telescope Array, High Altitude Water Cherenkov Experiment and Hundred Square-km Cosmic ORigin Explorer.

V1327 Aquilae: A New RR Lyrae variable with an extremely high radial velocity

NASA Astrophysics Data System (ADS)

Galeev, A. I.; Bikmaev, I. F.; Borisov, N. V.; Zhuchkov, R. Ya.; Shimanskii, V. V.; Khabibullina, M. L.; Sakhibullin, N. A.

2008-07-01

We have carried out photometry and spectroscopy of the star V1327 Aql ( R = 16 m ) as part of our program of observations of poorly studied cataclysmic variables using the 1.5-m optical Russian—Turkish telescope (RTT-150, Turkey) and the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. After analyzing our photometry, we have re-classified the variable as an RR Lyrae star. Our BV R photometry during 10 nights reveals brightness variations with the period 12h49m, with the B, V, and R amplitudes being 1.36 m , 1.13 m , and 1.11 m , respectively. We derived the first estimates of the star’s atmospheric parameters from our moderate-resolution spectra: T eff = 6280 K, log g = 3.3, [M/H] = -1.05. The extremely high radial velocity of the star’s motion ( V R = -470 km/s) and the star’s large distances to the Galactic center (13.1 kpc) and disk (4.2 kpc) testify to a probable extragalactic origin of this object.

A Large Stellar Evolution Database for Population Synthesis Studies. I. Scaled Solar Models and Isochrones

NASA Astrophysics Data System (ADS)

Pietrinferni, Adriano; Cassisi, Santi; Salaris, Maurizio; Castelli, Fiorella

2004-09-01

We present a large and updated stellar evolution database for low-, intermediate-, and high-mass stars in a wide metallicity range, suitable for studying Galactic and extragalactic simple and composite stellar populations using population synthesis techniques. The stellar mass range is between ~0.5 and 10 Msolar with a fine mass spacing. The metallicity [Fe/H] comprises 10 values ranging from -2.27 to 0.40, with a scaled solar metal distribution. The initial He mass fraction ranges from Y=0.245, for the more metal-poor composition, up to 0.303 for the more metal-rich one, with ΔY/ΔZ~1.4. For each adopted chemical composition, the evolutionary models have been computed without (canonical models) and with overshooting from the Schwarzschild boundary of the convective cores during the central H-burning phase. Semiconvection is included in the treatment of core convection during the He-burning phase. The whole set of evolutionary models can be used to compute isochrones in a wide age range, from ~30 Myr to ~15 Gyr. Both evolutionary models and isochrones are available in several observational planes, employing an updated set of bolometric corrections and color-Teff relations computed for this project. The number of points along the models and the resulting isochrones is selected in such a way that interpolation for intermediate metallicities not contained in the grid is straightforward; a simple quadratic interpolation produces results of sufficient accuracy for population synthesis applications.We compare our isochrones with results from a series of widely used stellar evolution databases and perform some empirical tests for the reliability of our models. Since this work is devoted to scaled solar chemical compositions, we focus our attention on the Galactic disk stellar populations, employing multicolor photometry of unevolved field main-sequence stars with precise Hipparcos parallaxes, well-studied open clusters, and one eclipsing binary system with precise measurements of masses, radii, and [Fe/H] of both components. We find that the predicted metallicity dependence of the location of the lower, unevolved main sequence in the color magnitude diagram (CMD) appears in satisfactory agreement with empirical data. When comparing our models with CMDs of selected, well-studied, open clusters, once again we were able to properly match the whole observed evolutionary sequences by assuming cluster distance and reddening estimates in satisfactory agreement with empirical evaluations of these quantities. In general, models including overshooting during the H-burning phase provide a better match to the observations, at least for ages below ~4 Gyr. At [Fe/H] around solar and higher ages (i.e., smaller convective cores) before the onset of radiative cores, the selected efficiency of core overshooting may be too high in our model, as well as in various other models in the literature. Since we also provide canonical models, the reader is strongly encouraged to always compare the results from both sets in this critical age range.

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.

Jaccard distance based weighted sparse representation for coarse-to-fine plant species recognition.

PubMed

Zhang, Shanwen; Wu, Xiaowei; You, Zhuhong

2017-01-01

Leaf based plant species recognition plays an important role in ecological protection, however its application to large and modern leaf databases has been a long-standing obstacle due to the computational cost and feasibility. Recognizing such limitations, we propose a Jaccard distance based sparse representation (JDSR) method which adopts a two-stage, coarse to fine strategy for plant species recognition. In the first stage, we use the Jaccard distance between the test sample and each training sample to coarsely determine the candidate classes of the test sample. The second stage includes a Jaccard distance based weighted sparse representation based classification(WSRC), which aims to approximately represent the test sample in the training space, and classify it by the approximation residuals. Since the training model of our JDSR method involves much fewer but more informative representatives, this method is expected to overcome the limitation of high computational and memory costs in traditional sparse representation based classification. Comparative experimental results on a public leaf image database demonstrate that the proposed method outperforms other existing feature extraction and SRC based plant recognition methods in terms of both accuracy and computational speed.

Classification of malignant and benign lung nodules using taxonomic diversity index and phylogenetic distance.

PubMed

de Sousa Costa, Robherson Wector; da Silva, Giovanni Lucca França; de Carvalho Filho, Antonio Oseas; Silva, Aristófanes Corrêa; de Paiva, Anselmo Cardoso; Gattass, Marcelo

2018-05-23

Lung cancer presents the highest cause of death among patients around the world, in addition of being one of the smallest survival rates after diagnosis. Therefore, this study proposes a methodology for diagnosis of lung nodules in benign and malignant tumors based on image processing and pattern recognition techniques. Mean phylogenetic distance (MPD) and taxonomic diversity index (Δ) were used as texture descriptors. Finally, the genetic algorithm in conjunction with the support vector machine were applied to select the best training model. The proposed methodology was tested on computed tomography (CT) images from the Lung Image Database Consortium and Image Database Resource Initiative (LIDC-IDRI), with the best sensitivity of 93.42%, specificity of 91.21%, accuracy of 91.81%, and area under the ROC curve of 0.94. The results demonstrate the promising performance of texture extraction techniques using mean phylogenetic distance and taxonomic diversity index combined with phylogenetic trees. Graphical Abstract Stages of the proposed methodology.

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.

DNA barcoding commercially important aquatic invertebrates of Turkey.

PubMed

Keskin, Emre; Atar, Hasan Hüseyin

2013-08-01

DNA barcoding was used in order to identify aquatic invertebrates sampled from fisheries bycatch and discards. A total of 440 unique cytochrome c oxidase sub unit I (COI) barcodes were generated for 22 species from three important phyla (Arthropoda, Cnidaria, and Mollusca). All the species were sequenced and submitted to GenBank and Barcode of Life Database (BOLD) databases using 654 bp-long fragment of mitochondrial COI gene. Two of them (Pontastacus leptodactylus and Rapana bezoar) were first records of the species for the BOLD database and six of them (Carcinus aestuarii, Loligo vulgaris, Melicertus kerathurus, Nephrops norvegicus, Scyllarides latus, and Scyllarus arctus) were first standard (>648 bp) COI barcode records for the GenBank database. COI barcodes were analyzed for nucleotide composition, nucleotide pair frequencies, and Kimura's two-parameter genetic distance. Mean genetic distance among species was found increasing at higher taxonomic levels. Neighbor-joining trees generated were congruent with morphometric-based taxonomic classification. Findings of this study clearly demonstrate that DNA barcodes could be used as an efficient molecular tool in identification of not only target species from fisheries but also bycatch and discard species, and so it could provide us leverage for a better understanding in monitoring and management of fisheries and biodiversity.

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.

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.

The traveling salesman problem in surgery: economy of motion for the FLS Peg Transfer task.

PubMed

Falcone, John L; Chen, Xiaotian; Hamad, Giselle G

2013-05-01

In the Peg Transfer task in the Fundamentals of Laparoscopic Surgery (FLS) curriculum, six peg objects are sequentially transferred in a bimanual fashion using laparoscopic instruments across a pegboard and back. There are over 268 trillion ways of completing this task. In the setting of many possibilities, the traveling salesman problem is one where the objective is to solve for the shortest distance traveled through a fixed number of points. The goal of this study is to apply the traveling salesman problem to find the shortest two-dimensional path length for this task. A database platform was used with permutation application output to generate all of the single-direction solutions of the FLS Peg Transfer task. A brute-force search was performed using nested Boolean operators and database equations to calculate the overall two-dimensional distances for the efficient and inefficient solutions. The solutions were found by evaluating peg object transfer distances and distances between transfers for the nondominant and dominant hands. For the 518,400 unique single-direction permutations, the mean total two-dimensional peg object travel distance was 33.3 ± 1.4 cm. The range in distances was from 30.3 to 36.5 cm. There were 1,440 (0.28 %) of 518,400 efficient solutions with the minimized peg object travel distance of 30.3 cm. There were 8 (0.0015 %) of 518,400 solutions in the final solution set that minimized the distance of peg object transfer and minimized the distance traveled between peg transfers. Peg objects moved 12.7 cm (17.4 %) less in the efficient solutions compared to the inefficient solutions. The traveling salesman problem can be applied to find efficient solutions for surgical tasks. The eight solutions to the FLS Peg Transfer task are important for any examinee taking the FLS curriculum and for certification by the American Board of Surgery.

Optical Characteristics of Astrometric Radio Sources OCARS

NASA Astrophysics Data System (ADS)

Malkin, Z.

2013-04-01

In this paper, the current status of the catalog of Optical Characteristics of Astrometric Radio Sources OCARS is presented. The catalog includes radio sources observed in various astrometric and geodetic VLBI programs in 1979-2012. For these sources the physical object type, redshift and visual or infrared magnitude is given when available. Detailed comments are provided when some problems with published data were encountered. Since the first version created in December 2007, the catalog is continuously developed and expanded in respect to inclusion of new radio sources and addition of new or correction of old astrophysical data. Several sources of information are used for OCARS. The main of them are the NASA/IPAC Extragalactic Database (NED) and SIMBAD astronomical databases. Besides several astronomical journals and arXiv depository are regularly monitored, so that new data is included in OCARS just after publication. The redshift for about 150 sources have been determined from dedicated optical spectroscopic observations. As of October 2012, OCARS catalog includes 7173 radio sources. 3898 sources have known redshift, and 4860 sources have known magnitude. In 2009, it was used as a supplement material to the ICRF2. The list of radio sources with a good observational history but lacking astrophysical information is provide for planning of optical observations of the most important astrometric sources. The OCARS catalog is updated, in average every several weeks and is available at http://www.gao.spb.ru/english/as/ac_vlbi/ocars.txt.

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.

Performance analysis of a dual-tree algorithm for computing spatial distance histograms

PubMed Central

Chen, Shaoping; Tu, Yi-Cheng; Xia, Yuni

2011-01-01

Many scientific and engineering fields produce large volume of spatiotemporal data. The storage, retrieval, and analysis of such data impose great challenges to database systems design. Analysis of scientific spatiotemporal data often involves computing functions of all point-to-point interactions. One such analytics, the Spatial Distance Histogram (SDH), is of vital importance to scientific discovery. Recently, algorithms for efficient SDH processing in large-scale scientific databases have been proposed. These algorithms adopt a recursive tree-traversing strategy to process point-to-point distances in the visited tree nodes in batches, thus require less time when compared to the brute-force approach where all pairwise distances have to be computed. Despite the promising experimental results, the complexity of such algorithms has not been thoroughly studied. In this paper, we present an analysis of such algorithms based on a geometric modeling approach. The main technique is to transform the analysis of point counts into a problem of quantifying the area of regions where pairwise distances can be processed in batches by the algorithm. From the analysis, we conclude that the number of pairwise distances that are left to be processed decreases exponentially with more levels of the tree visited. This leads to the proof of a time complexity lower than the quadratic time needed for a brute-force algorithm and builds the foundation for a constant-time approximate algorithm. Our model is also general in that it works for a wide range of point spatial distributions, histogram types, and space-partitioning options in building the tree. PMID:21804753

Travel Distance and the Use of Inpatient Care among Patients with Schizophrenia

PubMed Central

Hemenway, David; Kawachi, Ichiro; Subramanian, S. V.; Chen, Wei J.

2009-01-01

This study examines the variations in the use of inpatient care that can be explained by travel distance among patients with schizophrenia living in Taiwan. Data were drawn from the Psychiatric Inpatient Medical Claims Database. We used mediation analysis and multilevel analysis to identify associations. Travel distance did not significantly account for lower readmission rates after an index admission, but significantly explained the longer length of stay of an index admission by 9.3 days (P < 0.001, 85% of variation) between remote and non-remote regions. Policies are discussed aimed at reducing the impact of travel distance on rural mental health care through inter-disciplinary collaboration and telepsychiatry. PMID:18512144

A Science Portal and Archive for Extragalactic Globular Cluster Systems Data

NASA Astrophysics Data System (ADS)

Young, Michael; Rhode, Katherine L.; Gopu, Arvind

2015-01-01

For several years we have been carrying out a wide-field imaging survey of the globular cluster populations of a sample of giant spiral, S0, and elliptical galaxies with distances of ~10-30 Mpc. We use mosaic CCD cameras on the WIYN 3.5-m and Kitt Peak 4-m telescopes to acquire deep BVR imaging of each galaxy and then analyze the data to derive global properties of the globular cluster system. In addition to measuring the total numbers, specific frequencies, spatial distributions, and color distributions for the globular cluster populations, we have produced deep, high-quality images and lists of tens to thousands of globular cluster candidates for the ~40 galaxies included in the survey.With the survey nearing completion, we have been exploring how to efficiently disseminate not only the overall results, but also all of the relevant data products, to the astronomical community. Here we present our solution: a scientific portal and archive for extragalactic globular cluster systems data. With a modern and intuitive web interface built on the same framework as the WIYN One Degree Imager Portal, Pipeline, and Archive (ODI-PPA), our system will provide public access to the survey results and the final stacked mosaic images of the target galaxies. In addition, the astrometric and photometric data for thousands of identified globular cluster candidates, as well as for all point sources detected in each field, will be indexed and searchable. Where available, spectroscopic follow-up data will be paired with the candidates. Advanced imaging tools will enable users to overlay the cluster candidates and other sources on the mosaic images within the web interface, while metadata charting tools will allow users to rapidly and seamlessly plot the survey results for each galaxy and the data for hundreds of thousands of individual sources. Finally, we will appeal to other researchers with similar data products and work toward making our portal a central repository for data related to well-studied giant galaxy globular cluster systems. This work is supported by NSF Faculty Early Career Development (CAREER) award AST-0847109.

Radio emissions from pulsar companions: a refutable explanation for galactic transients and fast radio bursts

NASA Astrophysics Data System (ADS)

Mottez, F.; Zarka, P.

2014-09-01

Context. The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources that are of unknown origin but extremely energetic. We propose here a new explanation that does not require an extreme release of energy and involves a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. Aims: We investigate a theory of radio waves associated with such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals to determine whether they could originate from pulsar-orbiting bodies. Methods: The analysis is based on the theory of Alfvén wings: for a body immersed in a pulsar wind, a system of two stationary Alfvén waves is attached to the body, provided that the wind is highly magnetised. When they are destabilised through plasma instabilities, Alfvén wings can be the locus of strong radio sources that are convected with the pulsar wind. By assuming a cyclotron maser instability operating in the Alfvén wings, we make predictions about the shape, frequencies, and brightness of the resulting radio emissions. Results: Because of the beaming by relativistic aberration, the signal is seen only when the companion is perfectly aligned between its parent pulsar and the observer, as is the case for occultations. For pulsar winds with a high Lorentz factor (≥104), the whole duration of the radio event does not exceed a few seconds, and it is composed of one to four peaks that last a few milliseconds each and are detectable up to distances of several Mpc. The Lorimer burst, the three isolated pulses of PSR J1928+15, and the recently detected fast radio bursts are all compatible with our model. According to it, these transient signals should repeat periodically with the companion's orbital period. Conclusions: The search of pulsar-orbiting bodies could be an exploration theme for new- or next-generation radio telescopes.

THE ARECIBO LEGACY FAST ALFA SURVEY: THE {alpha}.40 H I SOURCE CATALOG, ITS CHARACTERISTICS AND THEIR IMPACT ON THE DERIVATION OF THE H I MASS FUNCTION

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

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

We present a current catalog of 21 cm H I line sources extracted from the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey over {approx}2800 deg{sup 2} of sky: the {alpha}.40 catalog. Covering 40% of the final survey area, the {alpha}.40 catalog contains 15,855 sources in the regions 07{sup h}30{sup m} < R.A. < 16{sup h}30{sup m}, +04 Degree-Sign < decl. <+16 Degree-Sign , and +24 Degree-Sign < decl. <+28 Degree-Sign and 22{sup h} < R.A. < 03{sup h}, +14 Degree-Sign < decl. <+16 Degree-Sign , and +24 Degree-Sign < decl. < + 32 Degree-Sign . Of those, 15,041more » are certainly extragalactic, yielding a source density of 5.3 galaxies per deg{sup 2}, a factor of 29 improvement over the catalog extracted from the H I Parkes All-Sky Survey. In addition to the source centroid positions, H I line flux densities, recessional velocities, and line widths, the catalog includes the coordinates of the most probable optical counterpart of each H I line detection, and a separate compilation provides a cross-match to identifications given in the photometric and spectroscopic catalogs associated with the Sloan Digital Sky Survey Data Release 7. Fewer than 2% of the extragalactic H I line sources cannot be identified with a feasible optical counterpart; some of those may be rare OH megamasers at 0.16 < z < 0.25. A detailed analysis is presented of the completeness, width-dependent sensitivity function and bias inherent of the {alpha}.40 catalog. The impact of survey selection, distance errors, current volume coverage, and local large-scale structure on the derivation of the H I mass function is assessed. While {alpha}.40 does not yet provide a completely representative sampling of cosmological volume, derivations of the H I mass function using future data releases from ALFALFA will further improve both statistical and systematic uncertainties.« less

Bias properties of extragalactic distance indicators. 3: Analysis of Tully-Fisher distances for the Mathewson-Ford-Buchhorn sample of 1355 galaxies

NASA Technical Reports Server (NTRS)

Federspiel, Martin; Sandage, Allan; Tammann, G. A.

1994-01-01

The observational selection bias properties of the large Mathewson-Ford-Buchhorn (MFB) sample of axies are demonstrated by showing that the apparent Hubble constant incorrectly increases outward when determined using Tully-Fisher (TF) photometric distances that are uncorreted for bias. It is further shown that the value of H(sub 0) so determined is also multivlaued at a given redshift when it is calculated by the TF method using galaxies with differenct line widths. The method of removing this unphysical contradiction is developed following the model of the bias set out in Paper II. The model developed further here shows that the appropriate TF magnitude of a galaxy that is drawn from a flux-limited catalog not only is a function of line width but, even in the most idealistic cases, requires a triple-entry correction depending on line width, apparent magnitude, and catalog limit. Using the distance-limited subset of the data, it is shown that the mean intrinsic dispersion of a bias-free TF relation is high. The dispersion depends on line width, decreasing from sigma(M) = 0.7 mag for galaxies with rotational velocities less than 100 km s(exp-1) to sigma(M) = 0.4 mag for galaxies with rotational velocities greater than 250 km s(exp-1). These dispersions are so large that the random errors of the bias-free TF distances are too gross to detect any peculiar motions of individual galaxies, but taken together the data show again the offset of 500 km s(exp-1) fond both by Dressler & Faber and by MFB for galaxies in the direction of the putative Great Attractor but described now in a different way. The maximum amplitude of the bulk streaming motion at the Local Group is approximately 500 km s(exp-1) but the perturbation dies out, approaching the Machian frame defined by the CMB at a distance of approximately 80 Mpc (v is approximately 4000 km s(exp -1)). This decay to zero perturbation at v is approximately 4000 km s(exp -1) argues against existing models with a single attraction at approximately 4500 km s(exp -1) (the Great Attactor model) pulling the local region. Rather, the cause of the perturbation appears to be the well-known clumpy mass distribution within 4000 km s(exp -1) in the busy directions of Hydra, Centaurus, Antila and Dorado, as postulated earlier (Tammann & Sandage 1985).

Perceptions of distance education among nursing faculty members in North America.

PubMed

Mancuso, Josephine M

2009-06-01

A strategy to increase access to nursing education, train nurses for practice, and prepare future nurse educators is distance education. Faculty member shortages are cited as the main reason for not accepting qualified applicants. Faculty members are the core of nursing education. In order to address nursing faculty members' concerns regarding distance education and to assist in faculty member recruitment, retention, growth, and development in order to improve and enhance the quality of distance education, one must answer the question: What are nursing faculty members' perceptions of distance education in nursing? Utilizing a number of databases to locate research specific to this topic, this article provides an integrative review of the nursing literature to ascertain the faculty members' perspective of distance education. The research was analyzed, findings summarized, and limitations mentioned. Utilizing a brief supplementary review of the literature, the implications, recommendations, and need for future research are discussed.

Impact of muon detection thresholds on the separability of primary cosmic rays

NASA Astrophysics Data System (ADS)

Müller, S.; Engel, R.; Pierog, T.; Roth, M.

2018-01-01

Knowledge of the mass composition of cosmic rays in the transition region of galactic to extragalactic cosmic rays is needed to discriminate different astrophysical models on their origin, acceleration, and propagation. An important observable to separate different mass groups of cosmic rays is the number of muons in extensive air showers. We performed a CORSIKA simulation study to analyze the impact of the detection threshold of muons on the separation quality of different primary cosmic rays in the energy region of the ankle. Using only the number of muons as the composition-sensitive observable, we find a clear dependence of the separation power on the detection threshold for ideal measurements. Although the number of detected muons increases when lowering the threshold, the discrimination power is reduced. If statistical fluctuations for muon detectors of limited size are taken into account, the threshold dependence remains qualitatively the same for small distances to the shower core but is reduced for large core distances. We interpret the impact of the detection threshold of muons on the composition sensitivity in terms of a change of the correlation of the number of muons nμ with the shower maximum Xmax as function of the muon energy as a result of the underlying hadronic interactions and the shower geometry. We further investigate the role of muons produced in a shower by photon-air interactions and conclude that, in addition to the effect of the nμ -Xmax correlation, the separability of primaries is reduced as a consequence of the presence of more muons from photonuclear reactions in proton than in iron showers.

Testing Models of Stellar Structure and Evolution I. Comparison with Detached Eclipsing Binaries

NASA Astrophysics Data System (ADS)

del Burgo, C.; Allende Prieto, C.

2018-05-01

We present the results of an analysis aimed at testing the accuracy and precision of the PARSEC v1.2S library of stellar evolution models, combined with a Bayesian approach, to infer stellar parameters. We mainly employ the online DEBCat catalogue by Southworth, a compilation of detached eclipsing binary systems with published measurements of masses and radii to ˜ 2 per cent precision. We select a sample of 318 binary components, with masses between 0.10 and 14.5 solar units, and distances between 1.3 pc and ˜ 8 kpc for Galactic objects and ˜ 44-68 kpc for the extragalactic ones. The Bayesian analysis applied takes on input effective temperature, radius, and [Fe/H], and their uncertainties, returning theoretical predictions for other stellar parameters. From the comparison with dynamical masses, we conclude inferred masses are precisely derived for stars on the main-sequence and in the core-helium-burning phase, with respective uncertainties of 4 per cent and 7 per cent, on average. Subgiants and red giants masses are predicted within 14 per cent, and early asymptotic giant branch stars within 24 per cent. These results are helpful to further improve the models, in particular for advanced evolutionary stages for which our understanding is limited. We obtain distances and ages for the binary systems and compare them, whenever possible, with precise literature estimates, finding excellent agreement. We discuss evolutionary effects and the challenges associated with the inference of stellar ages from evolutionary models. We also provide useful polynomial fittings to theoretical zero-age main-sequence relations.

Implications of directed energy for SETI

NASA Astrophysics Data System (ADS)

Lubin, Philip

2016-09-01

We compute the detectability of directed-energy (DE) sources from distant civilizations that may exist. Recent advances in our own DE technology suggest that our eventual capabilities will radically enhance our capacity to broadcast our presence and hence allow us to ponder the reverse case of detection. We show that DE systems are detectable at vast distances, possibly across the entire horizon, which profoundly alters conceivable search strategies for extra-terrestrial, technologically-advanced civilizations. Even modest searches are extremely effective at detecting or constraining many civilization classes. A single civilization anywhere in our galaxy of comparable technological advancement to our own can be detected with near unity probability with a cluster of 0.1 m telescopes on Earth. A 1 m class telescope can detect a single civilization anywhere in the Andromeda galaxy. A search strategy is proposed using small Earth-based telescopes to observe 1012-1020 stellar and planetary systems. Such observations could address whether there exist other civilizations which are broadcasting with similar or more advanced DE capability. We show that such searches have near-unity probability of detecting comparably advanced civilizations anywhere in our galaxy within a few years, assuming the civilization: (1) adopts a simple "intelligent targeting" beacon strategy; (2) is beaconing at a wavelength we can detect; (3) broadcast the beacon long enough for the light to reach Earth now. In this blind-beacon, blind-search strategy, the civilization need not know where we are nor do we need to know where they are. The same basic strategy can be extended to extragalactic distances.

A COMPREHENSIVE, WIDE-FIELD STUDY OF PULSATING STARS IN THE CARINA DWARF SPHEROIDAL GALAXY

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

Vivas, A. Katherina; Mateo, Mario, E-mail: akvivas@cida.ve, E-mail: mmateo@umich.edu

2013-12-01

We report the detection of 388 pulsating variable stars (and some additional miscellaneous variables) in the Carina dwarf spheroidal galaxy over an area covering the full visible extent of the galaxy and extending a few times beyond its photometric (King) tidal radius along the direction of its major axis. Included in this total are 340 newly discovered dwarf Cepheids (DCs), which are mostly located ∼2.5 mag below the horizontal branch and have very short periods (<0.1 days), typical of their class and consistent with their location on the upper part of the extended main sequence of the younger populations ofmore » the galaxy. Several extra-tidal DCs were found in our survey up to a distance of ∼1° from the center of Carina. Our sample also includes RR Lyrae stars and anomalous Cepheids, some of which were found outside the galaxy's tidal radius as well. This supports past works that suggest that Carina is undergoing tidal disruption. We use the period-luminosity relationship for DCs to estimate a distance modulus of μ{sub 0} = 20.17 ± 0.10 mag, in very good agreement with the estimate from RR Lyrae stars. We find some important differences in the properties of the DCs of Carina and those in Fornax and the LMC, the only extragalactic samples of DCs currently known. These differences may reflect a metallicity spread, depth along the line of sight, and/or different evolutionary paths of the DC stars.« less

S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), a new-generation of 3D spectro-imager dedicated to night astronomy

NASA Astrophysics Data System (ADS)

Sayède, Frédéric; Puech, Mathieu; Mein, Pierre; Bonifacio, Piercarlo; Malherbe, Jean-Marie; Galicher, Raphaël.; Amans, Jean-Philippe; Fasola, Gilles

2014-07-01

Multichannel Subtractive Double Pass (MSDP) spectrographs have been widely used in solar spectroscopy because of their ability to provide an excellent compromise between field of view and spatial and spectral resolutions. Compared with other types of spectrographs, MSDP can deliver simultaneous monochromatic images at higher spatial and spectral resolutions without any time-scanning requirement (as with Fabry-Perot spectrographs), and with limited loss of flux. These performances are obtained thanks to a double pass through the dispersive element. Recent advances with VPH (Volume phase holographic) Grisms as well as with image slicers now make MSDP potentially sensitive to much smaller fluxes. We present S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), which is a new concept for extending MSDP to night-time astronomy. It is based on new generation reflecting plane image slicers working with large apertures specific to night-time telescopes. The resulting design could be potentially very attractive and innovative for different domains of astronomy, e.g., the simultaneous spatial mapping of accurately flux-calibrated emission lines between OH sky lines in extragalactic astronomy or the simultaneous imaging of stars, exoplanets and interstellar medium. We present different possible MSDP/S4EI configurations for these science cases and expected performances on telescopes such as the VLT.

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).

Earthquake-induced ground failures in Italy from a reviewed database

NASA Astrophysics Data System (ADS)

Martino, S.; Prestininzi, A.; Romeo, R. W.

2013-05-01

A database (Italian acronym CEDIT) of earthquake-induced ground failures in Italy is presented, and the related content is analysed. The catalogue collects data regarding landslides, liquefaction, ground cracks, surface faulting and ground-level changes triggered by earthquakes of Mercalli intensity 8 or greater that occurred in the last millennium in Italy. As of January 2013, the CEDIT database has been available online for public use (URL: http://www.ceri.uniroma1.it/cn/index.do?id=230&page=55) and is presently hosted by the website of the Research Centre for Geological Risks (CERI) of the "Sapienza" University of Rome. Summary statistics of the database content indicate that 14% of the Italian municipalities have experienced at least one earthquake-induced ground failure and that landslides are the most common ground effects (approximately 45%), followed by ground cracks (32%) and liquefaction (18%). The relationships between ground effects and earthquake parameters such as seismic source energy (earthquake magnitude and epicentral intensity), local conditions (site intensity) and source-to-site distances are also analysed. The analysis indicates that liquefaction, surface faulting and ground-level changes are much more dependent on the earthquake source energy (i.e. magnitude) than landslides and ground cracks. In contrast, the latter effects are triggered at lower site intensities and greater epicentral distances than the other environmental effects.

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.

Light curves of flat-spectrum radio sources (Jenness+, 2010)

NASA Astrophysics Data System (ADS)

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

2010-05-01

Calibrated data for 143 flat-spectrum extragalactic radio sources are presented at a wavelength of 850um covering a 5-yr period from 2000 April. The data, obtained at the James Clerk Maxwell Telescope using the Submillimetre Common-User Bolometer Array (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. A re-analysis of previously published data from 1997 to 2000 is also presented. The combined catalogue, comprising 10493 flux density measurements, provides a unique and valuable resource for studies of extragalactic radio sources. (2 data files).

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

Fragger: a protein fragment picker for structural queries.

PubMed

Berenger, Francois; Simoncini, David; Voet, Arnout; Shrestha, Rojan; Zhang, Kam Y J

2017-01-01

Protein modeling and design activities often require querying the Protein Data Bank (PDB) with a structural fragment, possibly containing gaps. For some applications, it is preferable to work on a specific subset of the PDB or with unpublished structures. These requirements, along with specific user needs, motivated the creation of a new software to manage and query 3D protein fragments. Fragger is a protein fragment picker that allows protein fragment databases to be created and queried. All fragment lengths are supported and any set of PDB files can be used to create a database. Fragger can efficiently search a fragment database with a query fragment and a distance threshold. Matching fragments are ranked by distance to the query. The query fragment can have structural gaps and the allowed amino acid sequences matching a query can be constrained via a regular expression of one-letter amino acid codes. Fragger also incorporates a tool to compute the backbone RMSD of one versus many fragments in high throughput. Fragger should be useful for protein design, loop grafting and related structural bioinformatics tasks.

Predictive landslide susceptibility mapping using spatial information in the Pechabun area of Thailand

NASA Astrophysics Data System (ADS)

Oh, Hyun-Joo; Lee, Saro; Chotikasathien, Wisut; Kim, Chang Hwan; Kwon, Ju Hyoung

2009-04-01

For predictive landslide susceptibility mapping, this study applied and verified probability model, the frequency ratio and statistical model, logistic regression at Pechabun, Thailand, using a geographic information system (GIS) and remote sensing. Landslide locations were identified in the study area from interpretation of aerial photographs and field surveys, and maps of the topography, geology and land cover were constructed to spatial database. The factors that influence landslide occurrence, such as slope gradient, slope aspect and curvature of topography and distance from drainage were calculated from the topographic database. Lithology and distance from fault were extracted and calculated from the geology database. Land cover was classified from Landsat TM satellite image. The frequency ratio and logistic regression coefficient were overlaid for landslide susceptibility mapping as each factor’s ratings. Then the landslide susceptibility map was verified and compared using the existing landslide location. As the verification results, the frequency ratio model showed 76.39% and logistic regression model showed 70.42% in prediction accuracy. The method can be used to reduce hazards associated with landslides and to plan land cover.

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.

Planet from another galaxy discovered - Galactic cannibalism brings an exoplanet of extragalactic origin within astronomers' reach

NASA Astrophysics Data System (ADS)

2010-11-01

An exoplanet orbiting a star that entered our Milky Way from another galaxy has been detected by a European team of astronomers using the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile. The Jupiter-like planet is particularly unusual, as it is orbiting a star nearing the end of its life and could be about to be engulfed by it, giving tantalising clues about the fate of our own planetary system in the distant future. Over the last 15 years, astronomers have detected nearly 500 planets orbiting stars in our cosmic neighbourhood, but none outside our Milky Way has been confirmed [1]. Now, however, a planet with a minimum mass 1.25 times that of Jupiter [2] has been discovered orbiting a star of extragalactic origin, even though the star now finds itself within our own galaxy. It is part of the so-called Helmi stream [3] - a group of stars that originally belonged to a dwarf galaxy that was devoured by our galaxy, the Milky Way, in an act of galactic cannibalism about six to nine billion years ago. The results are published today in Science Express. "This discovery is very exciting," says Rainer Klement of the Max-Planck-Institut für Astronomie (MPIA), who was responsible for the selection of the target stars for this study. "For the first time, astronomers have detected a planetary system in a stellar stream of extragalactic origin. Because of the great distances involved, there are no confirmed detections of planets in other galaxies. But this cosmic merger has brought an extragalactic planet within our reach." The star is known as HIP 13044, and it lies about 2000 light-years from Earth in the southern constellation of Fornax (the Furnace). The astronomers detected the planet, called HIP 13044 b, by looking for the tiny telltale wobbles of the star caused by the gravitational tug of an orbiting companion. For these precise observations, the team used the high-resolution spectrograph FEROS [4] attached to the 2.2-metre MPG/ESO telescope [5] at ESO's La Silla Observatory in Chile. Adding to its claim to fame, HIP 13044 b is also one of the few exoplanets known to have survived the period when its host star expanded massively after exhausting the hydrogen fuel supply in its core - the red giant phase of stellar evolution. The star has now contracted again and is burning helium in its core. Until now, these so-called horizontal branch stars have remained largely uncharted territory for planet-hunters. "This discovery is part of a study where we are systematically searching for exoplanets that orbit stars nearing the end of their lives," says Johny Setiawan, also from MPIA, who led the research. "This discovery is particularly intriguing when we consider the distant future of our own planetary system, as the Sun is also expected to become a red giant in about five billion years." HIP 13044 b is near to its host star. At the closest point in its elliptical orbit, it is less than one stellar diameter from the surface of the star (or 0.055 times the Sun-Earth distance). It completes an orbit in only 16.2 days. Setiawan and his colleagues hypothesise that the planet's orbit might initially have been much larger, but that it moved inwards during the red giant phase. Any closer-in planets may not have been so lucky. "The star is rotating relatively quickly for an horizontal branch star," says Setiawan. "One explanation is that HIP 13044 swallowed its inner planets during the red giant phase, which would make the star spin more quickly." Although HIP 13044 b has escaped the fate of these inner planets so far, the star will expand again in the next stage of its evolution. HIP 13044 b may therefore be about to be engulfed by the star, meaning that it is doomed after all. This could also foretell the demise of our outer planets - such as Jupiter - when the Sun approaches the end of its life. The star also poses interesting questions about how giant planets form, as it appears to contain very few elements heavier than hydrogen and helium - fewer than any other star known to host planets. "It is a puzzle for the widely accepted model of planet formation to explain how such a star, which contains hardly any heavy elements at all, could have formed a planet. Planets around stars like this must probably form in a different way," adds Setiawan. Notes [1] There have been tentative claims of the detection of extragalactic exoplanets through "gravitational microlensing" events, in which the planet passing in front of an even more distant star leads to a subtle, but detectable "flash". However, this method relies on a singular event - the chance alignment of a distant light source, planetary system and observers on Earth - and no such extragalactic planet detection has been confirmed. [2] Using the radial velocity method, astronomers can only estimate a minimum mass for a planet, as the mass estimate also depends on the tilt of the orbital plane relative to the line of sight, which is unknown. From a statistical point of view, this minimum mass is however often close to the real mass of the planet. [3] Astronomers can identify members of the Helmi stream as they have motions (velocity and orbits) that are rather different from the average Milky Way stars. [4] FEROS stands for Fibre-fed Extended Range Optical Spectrograph. [5] The 2.2-metre telescope has been in operation at La Silla since early 1984 and is on indefinite loan to ESO from the Max-Planck Society (Max Planck Gesellschaft or MPG in German). Telescope time is shared between MPG and ESO observing programmes, while the operation and maintenance of the telescope are ESO's responsibility. More information This research was presented in a paper, "A Giant Planet Around a Metal-poor Star of Extragalactic Origin", by J. Setiawan et al., to appear in Science Express on 18 November 2010. The team is composed of J. Setiawan, R. J. Klement, T. Henning, H.-W. Rix, and B. Rochau (Max-Planck-Institut für Astronomie, Heidelberg, Germany), J. Rodmann (European Space Agency, Noordwijk, the Netherlands), and T. Schulze-Hartung (Max-Planck-Institut für Astronomie, Heidelberg, Germany). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Emotion-independent face recognition

NASA Astrophysics Data System (ADS)

De Silva, Liyanage C.; Esther, Kho G. P.

2000-12-01

Current face recognition techniques tend to work well when recognizing faces under small variations in lighting, facial expression and pose, but deteriorate under more extreme conditions. In this paper, a face recognition system to recognize faces of known individuals, despite variations in facial expression due to different emotions, is developed. The eigenface approach is used for feature extraction. Classification methods include Euclidean distance, back propagation neural network and generalized regression neural network. These methods yield 100% recognition accuracy when the training database is representative, containing one image representing the peak expression for each emotion of each person apart from the neutral expression. The feature vectors used for comparison in the Euclidean distance method and for training the neural network must be all the feature vectors of the training set. These results are obtained for a face database consisting of only four persons.

Total Bregman Divergence and its Applications to Shape Retrieval.

PubMed

Liu, Meizhu; Vemuri, Baba C; Amari, Shun-Ichi; Nielsen, Frank

2010-01-01

Shape database search is ubiquitous in the world of biometric systems, CAD systems etc. Shape data in these domains is experiencing an explosive growth and usually requires search of whole shape databases to retrieve the best matches with accuracy and efficiency for a variety of tasks. In this paper, we present a novel divergence measure between any two given points in [Formula: see text] or two distribution functions. This divergence measures the orthogonal distance between the tangent to the convex function (used in the definition of the divergence) at one of its input arguments and its second argument. This is in contrast to the ordinate distance taken in the usual definition of the Bregman class of divergences [4]. We use this orthogonal distance to redefine the Bregman class of divergences and develop a new theory for estimating the center of a set of vectors as well as probability distribution functions. The new class of divergences are dubbed the total Bregman divergence (TBD). We present the l 1 -norm based TBD center that is dubbed the t-center which is then used as a cluster center of a class of shapes The t-center is weighted mean and this weight is small for noise and outliers. We present a shape retrieval scheme using TBD and the t-center for representing the classes of shapes from the MPEG-7 database and compare the results with other state-of-the-art methods in literature.

Overview of MAGIC results

NASA Astrophysics Data System (ADS)

Rico, Javier; MAGIC Collaboration

2016-04-01

MAGIC is a system of two 17-m diameter Cherenkov telescopes, located at the Observatorio del Roque de los Muchachos, in the Canary island La Palma (Spain). MAGIC performs astronomical observations of gamma-ray sources in the energy range between 50 GeV and 10 TeV. The first MAGIC telescope has been operating since 2004, and in 2009 the system was completed with the second one. During 2011 and 2012 the electronics for the readout system were fully upgraded, and the camera of the first telescope replaced. After that, no major hardware interventions are foreseen in the next years, and the experiment has undertaken a final period of steady astronomical observations. MAGIC studies particle acceleration in the most violent cosmic environments, such as active galactic nuclei, gamma-ray bursts, pulsars, supernova remnants or binary systems. In addition, it addresses some fundamental questions of Physics, such as the origin of Galactic cosmic rays and the nature of dark matter. Moreover, by observing the gamma-ray emission from sources at cosmological distances, we measure the intensity and evolution of the extragalactic background radiation, and perform tests of Lorentz Invariance. In this paper I present the status and some of the latest results of the MAGIC gamma-ray telescopes.

EUV spectroscopy of high-redshift x-ray objects

NASA Astrophysics Data System (ADS)

Kowalski, M. P.; Wolff, M. T.; Wood, K. S.; Barbee, T. W., Jr.; Barstow, M. A.

2010-07-01

As astronomical observations are pushed to cosmological distances (z>3) the spectral energy distributions of X-ray objects, AGN for example, will be redshifted into the EUV waveband. Consequently, a wealth of critical spectral diagnostics, provided by, for example, the Fe L-shell complex and the O VII/VIII lines, will be lost to future planned X-ray missions (e.g., IXO, Gen-X) if operated at traditional X-ray energies. This opens up a critical gap in performance located at short EUV wavelengths, where critical X-ray spectral transitions occur in high-z objects. However, normal-incidence multilayer-grating technology, which performs best precisely at such wavelengths, together with advanced nanolaminate replication techniques have been developed and are now mature to the point where advanced EUV instrument designs with performance complementary to IXO and Gen-X are practical. Such EUV instruments could be flown either independently or as secondary instruments on these X-ray missions. We present here a critical examination of the limits placed on extragalactic EUV measurements by ISM absorption, the range where high-z measurements are practical, and the requirements this imposes on next-generation instrument designs. We conclude with a discussion of a breakthrough technology, nanolaminate replication, which enables such instruments.

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

PubMed

Hardcastle, Martin J

2005-12-15

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

H-alpha LEGUS: Insights into the Field OB Star Population in Nearby Galaxies

NASA Astrophysics Data System (ADS)

Lee, Janice; Thilker, David; Kayitesi, Bridget; Chandar, Rupali; Halpha LEGUS Team

2018-01-01

The question of whether O-stars can form in isolation, without attendant clusters or associations of lower mass stars, is a topic of interest because the answer to the question can distinguish between models of star formation. To begin to investigate whether such isolated O-stars can be identified in nearby galaxies beyond the Local Group, we identify candidate field OB-stars in NGC 1313, NGC 4395 and NGC 7793, the three nearest spiral galaxies in the HST Legacy ExtraGalactic Ultraviolet Survey (LEGUS). Candidates are selected using a technique based on: (1) a reddening-free Q parameter, adapted for photometry in HST filters covering the NUV, U, & B bands; (2) isolation based on projected distance from the nearest young cluster and candidate OB star, and (3) the presence of an HII region, identified based on HST H-alpha narrowband imaging. Our catalogs enable a range of follow-up studies on massive stars, and in particular provide targets for future spectroscopic observation and analysis. We describe the candidate OB star sample, the spatial distribution of the stars, and their HII region properties, with special focus on the most isolated objects in the sample.

The Generation Model of Particle Physics and Galactic Dark Matter

NASA Astrophysics Data System (ADS)

Robson, B. A.

2013-09-01

Galactic dark matter is matter hypothesized to account for the discrepancy of the mass of a galaxy determined from its gravitational effects, assuming the validity of Newton's law of universal gravitation, and the mass calculated from the "luminous matter", stars, gas, dust, etc. observed to be contained within the galaxy. The conclusive observation from the rotation curves of spiral galaxies that the mass discrepancy is greater, the larger the distance scales involved implies that either Newton's law of universal gravitation requires modification or considerably more mass (dark matter) is required to be present in each galaxy. Both the modification of Newton's law of gravitation and the hypothesis of the existence of considerable dark matter in a galaxy are discussed. It is shown that the Generation Model (GM) of particle physics, which leads to a modification of Newton's law of gravitation, is found to be essentially equivalent to that of Milgrom's modified Newtonian dynamics (MOND) theory, with the GM providing a physical understanding of the MOND theory. The continuing success of MOND theory in describing the extragalactic mass discrepancy problems constitutes a strong argument against the existence of undetected dark matter haloes, consisting of unknown nonbaryonic matter, surrounding spiral galaxies.

AGN Science with AGIS

NASA Astrophysics Data System (ADS)

Coppi, Paolo

2009-05-01

AGIS, a proposed future gamma-ray telescope consisting of a square km array of 50 atmospheric Cherenkov telescopes, will provide a powerful new view of the high energy universe. The combination of its increased sensitivity (a factor 10 over current observatories), increased survey capabilities, and a low energy threshold (<30 GeV) that allows observations at energies not subject to absorption on extragalactic background light will result in a dramatic increase in the number of AGN accessible at high energies. The overall number of ``TeV blazar" AGN, those detected by current ground-based observatories, should increase by a factor 30 or more with a corresponding increase in the number of these that can be monitored at high statistical significance to test emission models rigorously. More excitingly, AGIS may also begin to pick up entirely new classes of AGN such as radio galaxies with X-ray emitting hotspots at large distances from the central engine, providing further insight into the outflows from AGN. The low AGIS threshold energy will also allow significant source overlap with objects detected by the recently launched Fermi gamma-ray space observatory at lower, GeV energies. AGIS will significantly improve on the localization and variability monitoring of the Fermi sources it sees.

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.

Partially supervised speaker clustering.

PubMed

Tang, Hao; Chu, Stephen Mingyu; Hasegawa-Johnson, Mark; Huang, Thomas S

2012-05-01

Content-based multimedia indexing, retrieval, and processing as well as multimedia databases demand the structuring of the media content (image, audio, video, text, etc.), one significant goal being to associate the identity of the content to the individual segments of the signals. In this paper, we specifically address the problem of speaker clustering, the task of assigning every speech utterance in an audio stream to its speaker. We offer a complete treatment to the idea of partially supervised speaker clustering, which refers to the use of our prior knowledge of speakers in general to assist the unsupervised speaker clustering process. By means of an independent training data set, we encode the prior knowledge at the various stages of the speaker clustering pipeline via 1) learning a speaker-discriminative acoustic feature transformation, 2) learning a universal speaker prior model, and 3) learning a discriminative speaker subspace, or equivalently, a speaker-discriminative distance metric. We study the directional scattering property of the Gaussian mixture model (GMM) mean supervector representation of utterances in the high-dimensional space, and advocate exploiting this property by using the cosine distance metric instead of the euclidean distance metric for speaker clustering in the GMM mean supervector space. We propose to perform discriminant analysis based on the cosine distance metric, which leads to a novel distance metric learning algorithm—linear spherical discriminant analysis (LSDA). We show that the proposed LSDA formulation can be systematically solved within the elegant graph embedding general dimensionality reduction framework. Our speaker clustering experiments on the GALE database clearly indicate that 1) our speaker clustering methods based on the GMM mean supervector representation and vector-based distance metrics outperform traditional speaker clustering methods based on the “bag of acoustic features” representation and statistical model-based distance metrics, 2) our advocated use of the cosine distance metric yields consistent increases in the speaker clustering performance as compared to the commonly used euclidean distance metric, 3) our partially supervised speaker clustering concept and strategies significantly improve the speaker clustering performance over the baselines, and 4) our proposed LSDA algorithm further leads to state-of-the-art speaker clustering performance.

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)

RBOOST: RIEMANNIAN DISTANCE BASED REGULARIZED BOOSTING

PubMed Central

Liu, Meizhu; Vemuri, Baba C.

2011-01-01

Boosting is a versatile machine learning technique that has numerous applications including but not limited to image processing, computer vision, data mining etc. It is based on the premise that the classification performance of a set of weak learners can be boosted by some weighted combination of them. There have been a number of boosting methods proposed in the literature, such as the AdaBoost, LPBoost, SoftBoost and their variations. However, the learning update strategies used in these methods usually lead to overfitting and instabilities in the classification accuracy. Improved boosting methods via regularization can overcome such difficulties. In this paper, we propose a Riemannian distance regularized LPBoost, dubbed RBoost. RBoost uses Riemannian distance between two square-root densities (in closed form) – used to represent the distribution over the training data and the classification error respectively – to regularize the error distribution in an iterative update formula. Since this distance is in closed form, RBoost requires much less computational cost compared to other regularized Boosting algorithms. We present several experimental results depicting the performance of our algorithm in comparison to recently published methods, LP-Boost and CAVIAR, on a variety of datasets including the publicly available OASIS database, a home grown Epilepsy database and the well known UCI repository. Results depict that the RBoost algorithm performs better than the competing methods in terms of accuracy and efficiency. PMID:21927643

Spatial Distribution of Star Formation in High Redshift Galaxies

NASA Astrophysics Data System (ADS)

Cunnyngham, Ian; Takamiya, M.; Willmer, C.; Chun, M.; Young, M.

2011-01-01

Integral field unit spectroscopy taken of galaxies with redshifts between 0.6 and 0.8 utilizing Gemini Observatory’s GMOS instrument were used to investigate the spatial distribution of star-forming regions by measuring the Hβ and [OII]λ3727 emission line fluxes. These galaxies were selected based on the strength of Hβ and [OII]λ3727 as measured from slit LRIS/Keck spectra. The process of calibrating and reducing data into cubes -- possessing two spatial dimensions, and one for wavelength -- was automated via a custom batch script using the Gemini IRAF routines. Among these galaxies only the bluest sources clearly show [OII] in the IFU regardless of total galaxy luminosity. The brightest galaxies lack [OII] emission and it is posited that two different modes of star formation exist among this seemingly homogeneous group of z=0.7 star-forming galaxies. In order to increase the galaxy sample to include redshifts from 0.3 to 0.9, public Gemini IFU data are being sought. Python scripts were written to mine the Gemini Science Archive for candidate observations, cross-reference the target of these observations with information from the NASA Extragalactic Database, and then present the resultant database in sortable, searchable, cross-linked web-interface using Django to facilitate navigation. By increasing the sample, we expect to characterize these two different modes of star formation which could be high-redshift counterparts of the U/LIRGs and dwarf starburst galaxies like NGC 1569/NGC 4449. The authors acknowledge funds provided by the National Science Foundation (AST 0909240).

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.

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

Facilitating Science Discoveries from NED Today and in the 2020s

NASA Astrophysics Data System (ADS)

Mazzarella, Joseph M.; NED Team

2018-06-01

I will review recent developments, work in progress, and major challenges that lie ahead as we enhance the capabilities of the NASA/IPAC Extragalactic Database (NED) to facilitate and accelerate multi-wavelength research on objects beyond our Milky Way galaxy. The recent fusion of data for over 470 million sources from the 2MASS Point Source Catalog and approximately 750 million sources from the AllWISE Source Catalog (next up) with redshifts from the SDSS and other data in NED is increasing the holdings to over a billion distinct objects with cross-identifications, providing a rich resource for multi-wavelength research. Combining data across such large surveys, as well as integrating data from over 110,000 smaller but scientifically important catalogs and journal articles, presents many challanges including the need to update the computing infrastructure and re-tool production and operations on a regular basis. Integration of the Firefly toolkit into the new user interface is ushering in a new phase of interative data visualization in NED, with features and capabilities familiar to users of IRSA and the emerging LSST science user interface. Graphical characterizations of NED content and estimates of completeness in different sky and spectral regions are also being developed. A newly implemented service that follows the Table Access Protocol (TAP) enables astronomers to issue queries to the NED object directory using Astronomical Data Language (ADQL), a standard shared in common with the NASA mission archives and other virtual observatories around the world. A brief review will be given of new science capabilities under development and planned for 2019-2020, as well as initiatives underway involving deployment of a parallel database, cloud technologies, machine learning, and first steps in bringing analysis capabilities close to the database in collaboration with IRSA. I will close with some questions for the community to consider in helping us plan future science capabilities and directions for NED in the 2020s.

Association between reliance on devices and people for walking and ability to walk community distances among persons with spinal cord injury.

PubMed

Brotherton, Sandra S; Saunders, Lee L; Krause, James S; Morrisette, David C

2012-05-01

To identify and describe the frequency of reliance on assistive devices and/or people for ambulating distances and stair climbing. Survey. A total of 429 adults with traumatic spinal cord injury who were able to walk at least 10 m were identified through inpatient and outpatient hospital databases at a specialty hospital in the southeast United States. Data were collected using a self-report questionnaire including items related to distances walked and devices used for ambulation. Participants best able to ambulate community distances were those who were independent with ambulation and those who used one cane or crutch. Reliance on people or use of a walker was associated with walking shorter distances. Regression analysis indicated reliance on devices or people for walking predicted variation in ability to ambulate community distances after controlling for demographic and injury characteristics. This study suggests that reliance on devices or a person for assistance is important to consider when assessing potential for achieving functional community ambulation.

Image indexing using color correlograms

DOEpatents

Huang, Jing; Kumar, Shanmugasundaram Ravi; Mitra, Mandar; Zhu, Wei-Jing

2001-01-01

A color correlogram is a three-dimensional table indexed by color and distance between pixels which expresses how the spatial correlation of color changes with distance in a stored image. The color correlogram may be used to distinguish an image from other images in a database. To create a color correlogram, the colors in the image are quantized into m color values, c.sub.i . . . c.sub.m. Also, the distance values k.epsilon.[d] to be used in the correlogram are determined where [d] is the set of distances between pixels in the image, and where dmax is the maximum distance measurement between pixels in the image. Each entry (i, j, k) in the table is the probability of finding a pixel of color c.sub.i at a selected distance k from a pixel of color c.sub.i. A color autocorrelogram, which is a restricted version of the color correlogram that considers color pairs of the form (i,i) only, may also be used to identify an image.

Through thick and thin: Structure of the Galactic thick disc from extragalactic surveys

NASA Astrophysics Data System (ADS)

Kordopatis, G.; Hill, V.; Irwin, M.; Gilmore, G.; Wyse, R. F. G.; Tolstoy, E.; de Laverny, P.; Recio-Blanco, A.; Battaglia, G.; Starkenburg, E.

2013-07-01

Context. We aim to understand the accretion history of the Milky Way by exploring the vertical and radial properties of the Galactic thick disc. Aims: We study the chemical and kinematic properties of roughly a thousand spectra of faint magnitude foreground Galactic stars observed serendipitously during extra-galactic surveys in four lines-of-sight: three in the southern Galactic hemisphere (surveys of the Carina, Fornax and Sculptor dwarf spheroidal galaxies) and one in the northern Galactic hemisphere (a survey of the Sextans dwarf spheroidal galaxy). The foreground stars span distances up to ~3 kpc from the Galactic plane and Galactocentric radii up to 11 kpc. Methods: The stellar atmospheric parameters (effective temperature, surface gravity, metallicity) are obtained by an automated parameterisation pipeline and the distances of the stars are then derived by a projection of the atmospheric parameters on a set of theoretical isochrones using a Bayesian approach. The metallicity gradients are estimated for each line-of-sight and compared with predictions from the Besançon model of the Galaxy, in order to test the chemical structure of the thick disc. Finally, we use the radial velocities in each line-of-sight to derive a proxy for either the azimuthal or the vertical component of the orbital velocity of the stars. Results: Only three lines-of-sight have a sufficient number of foreground stars for a robust analysis. Towards Sextans in the Northern Galactic hemisphere and Sculptor in the South, we measure a consistent decrease in mean metallicity with height from the Galactic plane, suggesting a chemically symmetric thick disc. This decrease can either be due to an intrinsic thick disc metallicity gradient, or simply due to a change in the thin disc/thick disc population ratio and no intrinsic metallicity gradients for the thick disc. We favour the latter explanation. In contrast, we find evidence of an unpredicted metal-poor population in the direction of Carina. This population was earlier detected, but our more detailed analysis provides robust estimates of its location (|Z| < 1 kpc), metallicity (-2 < [M/H] < -1 dex) and azimuthal orbital velocity (Vφ ~ 120 km s-1). Conclusions: Given the chemo-dynamical properties of the over-density towards the Carina line-of-sight, we suggest that it represents the metal-poor tail of the canonical thick disc. In spite of the small number of stars available, we suggest that this metal-weak thick disc follows the often suggested canonical thick disc velocity-metallicity correlation of ∂Vφ/∂ [M/H] ~ 40-50 km s-1 dex-1. Based on observations collected at the European Southern Observatory at Paranal, Chile, ESO Large Programme 171.B-0588 (DART) and 171.B-0520(A).Full Tables 2 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A12

How to select equivalent and complimentary reversed phase liquid chromatography columns from column characterization databases.

PubMed

Borges, Endler M

2014-01-07

Three RP-LC column characterization protocols [Tanaka et al. (1989), Snyder et al. (PQRI, 2002), and NIST SRM 870 (2000)] were evaluated using both Euclidian distance and Principal Components Analysis to evaluate effectiveness at identifying equivalent columns. These databases utilize specific chromatographic properties such as hydrophobicity, hydrogen bonding, shape/steric selectivity, and ion exchange capacity of stationary phases. The chromatographic parameters of each test were shown to be uncorrelated. Despite this, the three protocols were equally successful in identifying similar and/or dissimilar stationary phases. The veracity of the results has been supported by some real life pharmaceutical separations. The use of Principal Component Analysis to identify similar/dissimilar phases appears to have some limitations in terms of loss of information. In contrast, the use of Euclidian distances is a much more convenient and reliable approach. The use of auto scaled data is favoured over the use of weighted factors as the former data transformation is less affected by the addition or removal of columns from the database. The use of these free databases and their corresponding software tools shown to be valid for identifying similar columns with equivalent chromatographic selectivity and retention as a "backup column". In addition, dissimilar columns with complimentary chromatographic selectivity can be identified for method development screening strategies. Copyright © 2013 Elsevier B.V. All rights reserved.

Earthquake-induced ground failures in Italy from a reviewed database

NASA Astrophysics Data System (ADS)

Martino, S.; Prestininzi, A.; Romeo, R. W.

2014-04-01

A database (Italian acronym CEDIT) of earthquake-induced ground failures in Italy is presented, and the related content is analysed. The catalogue collects data regarding landslides, liquefaction, ground cracks, surface faulting and ground changes triggered by earthquakes of Mercalli epicentral intensity 8 or greater that occurred in the last millennium in Italy. As of January 2013, the CEDIT database has been available online for public use (http://www.ceri.uniroma1.it/cn/gis.jsp ) and is presently hosted by the website of the Research Centre for Geological Risks (CERI) of the Sapienza University of Rome. Summary statistics of the database content indicate that 14% of the Italian municipalities have experienced at least one earthquake-induced ground failure and that landslides are the most common ground effects (approximately 45%), followed by ground cracks (32%) and liquefaction (18%). The relationships between ground effects and earthquake parameters such as seismic source energy (earthquake magnitude and epicentral intensity), local conditions (site intensity) and source-to-site distances are also analysed. The analysis indicates that liquefaction, surface faulting and ground changes are much more dependent on the earthquake source energy (i.e. magnitude) than landslides and ground cracks. In contrast, the latter effects are triggered at lower site intensities and greater epicentral distances than the other environmental effects.

Controls of earthquake faulting style on near field landslide triggering: The role of coseismic slip

NASA Astrophysics Data System (ADS)

Tatard, L.; Grasso, J. R.

2013-06-01

compare the spatial distributions of seven databases of landslides triggered by Mw=5.6-7.9 earthquakes, using distances normalized by the earthquake fault length. We show that the normalized landslide distance distributions collapse, i.e., the normalized distance distributions overlap whatever the size of the earthquake, separately for the events associated with dip-slip, buried-faulting earthquakes, and surface-faulting earthquakes. The dip-slip earthquakes triggered landslides at larger normalized distances than the oblique-slip event of Loma Prieta. We further identify that the surface-faulting earthquakes of Wenchuan, Chi-Chi, and Kashmir triggered landslides at normalized distances smaller than the ones expected from their Mw ≥ 7.6 magnitudes. These results support a control of the seismic slip (through amplitude, rake, and surface versus buried slip) on the distances at which landslides are triggered. In terms of coseismic landslide management in mountainous areas, our results allow us to propose distances at which 95 and 75% of landslides will be triggered as a function of the earthquake focal mechanism.

Mediagraphy: Print and Nonprint Resources.

ERIC Educational Resources Information Center

Educational Media and Technology Yearbook, 1996

1996-01-01

This annotated list includes media-related resources classified under the following headings: artificial intelligence and robotics, CD-ROM, computer-assisted instruction, databases and online searching, distance education, educational research, educational technology, electronic publishing, information science and technology, instructional design…

Mediagraphy: Print and Nonprint Resources.

ERIC Educational Resources Information Center

Educational Media and Technology Yearbook, 1997

1997-01-01

This annotated list includes media-related resources classified under the following headings: artificial intelligence and robotics, CD-ROM, computer-assisted instruction, databases and online searching, distance education, educational research, educational technology, electronic publishing, information science and technology, instructional design…

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.

Stellar Populations and Nearby Galaxies with the LSST

NASA Astrophysics Data System (ADS)

Saha, Abhijit; Olsen, K.; Monet, D. G.; LSST Stellar Populations Collaboration

2009-01-01

The LSST will produce a multi-color map and photometric object catalog of half the sky to r=27.6 (AB mag; 5-sigma). Time-space sampling of each field spanning ten years will allow variability, proper motion and parallax measurements for objects brighter than r=24.7. As part of providing an unprecedented map of the Galaxy, the accurate multi-band photometry will permit photometric parallaxes, chemical abundances and a handle on ages via colors at turn-off for main-sequence (MS) stars at all distances within the Galaxy as well as in the Magellanic Clouds, and dwarf satellites of the Milky Way. This will support comprehensive studies of star formation histories and chemical evolution for field stars. The structures of the Clouds and dwarf spheroidals will be traced with the MS stars, to equivalent surface densities fainter than 35 mag/square arc-second. With geometric parallax accuracy of 1 milli-arc-sec, comparable to HIPPARCOS but reaching more than 10 magnitudes fainter, a robust complete sample of solar neighborhood stars will be obtained. The LSST time sampling will identify and characterize variable stars of all types, from time scales of 1 hr to several years, a feast for variable star astrophysics. The combination of wide coverage, multi-band photometry, time sampling and parallax taken together will address several key problems: e.g. fine tuning the extragalactic distance scale by examining properties of RR Lyraes and Cepheids as a function of parent populations, extending the faint end of the galaxy luminosity function by discovering them using star count density enhancements on degree scales tracing, and indentifying inter-galactic stars through novae and Long Period Variables.

Searching For Water Megamasers In Type-2 QSOs

NASA Astrophysics Data System (ADS)

Bennert, Nicola; Barvainis, R.; Henkel, C.; Antonucci, R.

2009-01-01

Using the Robert C. Byrd Green Bank Telescope and the Effelsberg 100-m radio telescope, we searched for water megamasers in 274 SDSS type-2 AGNs (0.3 < z < 0.83; Zakamska et al. 2003), half of which can be classified as type-2 QSOs on the basis of their [OIII] 5007 luminosity. While this survey lead to the discovery of the most luminous water vapor megamaser known so far, the gigamaser SDSS J080430.99+360718.1 (Barvainis & Antonucci 2005), no additional line emission is found. We discuss possible scenarios leading to this high rate of non-detections. From the extragalactic water masers known to date, a water maser luminosity function (LF) is created. The extrapolation to the higher luminosities of gigamasers that we would have been able to detect, given the sensitivity of our survey, suggests that gigamasers may simply be rare. We compile the properties of the known megamasers and discuss possible intrinsic differences between these low-luminous AGNs, mainly Seyfert-2 galaxies and LINERs in the local universe, and our sample consisting of high-luminous AGNs at higher redshift. It is notable that the known megamasers reside almost exclusively in spiral galaxies while our sample most likely consists of elliptical host galaxies. Also, the properties of the dust torus, in which the maser emission is thought to arise, might evolve with AGN luminosity. However, at this point, we cannot distinguish between the different possibilities discussed. Detecting megamasers at cosmological distances remains a challenging and yet, if successful, highly rewarding project not only for its potential to determine black hole masses but especially to constrain distances and thus probe the existence and properties of the elusive dark energy.

A CATALOG OF ULTRA-COMPACT HIGH VELOCITY CLOUDS FROM THE ALFALFA SURVEY: LOCAL GROUP GALAXY CANDIDATES?

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

Adams, Elizabeth A. K.; Giovanelli, Riccardo; Haynes, Martha P., E-mail: betsey@astro.cornell.edu, E-mail: riccardo@astro.cornell.edu, E-mail: haynes@astro.cornell.edu

2013-05-01

We present a catalog of 59 ultra-compact high velocity clouds (UCHVCs) extracted from the 40% complete ALFALFA HI-line survey. The ALFALFA UCHVCs have median flux densities of 1.34 Jy km s{sup -1}, median angular diameters of 10', and median velocity widths of 23 km s{sup -1}. We show that the full UCHVC population cannot easily be associated with known populations of high velocity clouds. Of the 59 clouds presented here, only 11 are also present in the compact cloud catalog extracted from the commensal GALFA-HI survey, demonstrating the utility of this separate dataset and analysis. Based on their sky distributionmore » and observed properties, we infer that the ALFALFA UCHVCs are consistent with the hypothesis that they may be very low mass galaxies within the Local Volume. In that case, most of their baryons would be in the form of gas, and because of their low stellar content, they remain unidentified by extant optical surveys. At distances of {approx}1 Mpc, the UCHVCs have neutral hydrogen (H I) masses of {approx}10{sup 5}-10{sup 6} M{sub Sun }, H I diameters of {approx}2-3 kpc, and indicative dynamical masses within the H I extent of {approx}10{sup 7}-10{sup 8} M{sub Sun }, similar to the Local Group ultra-faint dwarf Leo T. The recent ALFALFA discovery of the star-forming, metal-poor, low mass galaxy Leo P demonstrates that this hypothesis is true in at least one case. In the case of the individual UCHVCs presented here, confirmation of their extragalactic nature will require further work, such as the identification of an optical counterpart to constrain their distance.« less

Best Practices for Data Publication to Facilitate Integration into NED: A Reference Guide for Authors

NASA Astrophysics Data System (ADS)

Schmitz, Marion; Mazzarella, J. M.; Madore, B. F.; Ogle, P. M.; Ebert, R.; Baker, K.; Chan, H.; Chen, X.; Fadda, D.; Frayer, C.; Jacobson, J. D.; LaGue, C.; Lo, T. M.; Pevunova, O.; Terek, S.; Steer, I.

2014-01-01

At the urging of the NASA/IPAC Extragalactic Database (NED) Users Committee, the NED Team has prepared and published on its website a new document titled "Best Practices for Data Publication to Facilitate Integration into NED: A Reference Guide for Authors" (http://ned.ipac.caltech.edu/docs/BPDP/NED_BPDP.pdf). We hope that journal publishers will incorporate links to this living document in their Instructions to Authors to provide a practical reference for authors, referees, and science editors so as to help avoid various pitfalls that often impede the interpretation of data and metadata, and also delay their integration into NED, SIMBAD, ADS and other systems. In particular, we discuss the importance of using proper naming conventions, providing the epoch and system of coordinates, including units and uncertainties, and giving sufficient metadata for the unambiguous interpretation of tabular, imaging, and spectral data. The biggest impediments to the assimilation of new data from the literature into NED are ambiguous object names and non-unique, coordinate-based identifiers. A Checklist of Recommendations will be presented which includes links to sections of the Best Practices document that provide further examples, explanation, and rationale.

What do data used to develop ground-motion prediction equations tell us about motions near faults?

USGS Publications Warehouse

Boore, David M.

2014-01-01

A large database of ground motions from shallow earthquakes occurring in active tectonic regions around the world, recently developed in the Pacific Earthquake Engineering Center’s NGA-West2 project, has been used to investigate what such a database can say about the properties and processes of crustal fault zones. There are a relatively small number of near-rupture records, implying that few recordings in the database are within crustal fault zones, but the records that do exist emphasize the complexity of ground-motion amplitudes and polarization close to individual faults. On average over the whole data set, however, the scaling of ground motions with magnitude at a fixed distance, and the distance dependence of the ground motions, seem to be largely consistent with simple seismological models of source scaling, path propagation effects, and local site amplification. The data show that ground motions close to large faults, as measured by elastic response spectra, tend to saturate and become essentially constant for short periods. This saturation seems to be primarily a geometrical effect, due to the increasing size of the rupture surface with magnitude, and not due to a breakdown in self similarity.

Method of locating related items in a geometric space for data mining

DOEpatents

Hendrickson, B.A.

1999-07-27

A method for locating related items in a geometric space transforms relationships among items to geometric locations. The method locates items in the geometric space so that the distance between items corresponds to the degree of relatedness. The method facilitates communication of the structure of the relationships among the items. The method is especially beneficial for communicating databases with many items, and with non-regular relationship patterns. Examples of such databases include databases containing items such as scientific papers or patents, related by citations or keywords. A computer system adapted for practice of the present invention can include a processor, a storage subsystem, a display device, and computer software to direct the location and display of the entities. The method comprises assigning numeric values as a measure of similarity between each pairing of items. A matrix is constructed, based on the numeric values. The eigenvectors and eigenvalues of the matrix are determined. Each item is located in the geometric space at coordinates determined from the eigenvectors and eigenvalues. Proper construction of the matrix and proper determination of coordinates from eigenvectors can ensure that distance between items in the geometric space is representative of the numeric value measure of the items' similarity. 12 figs.

Nonlinear dimensionality reduction methods for synthetic biology biobricks' visualization.

PubMed

Yang, Jiaoyun; Wang, Haipeng; Ding, Huitong; An, Ning; Alterovitz, Gil

2017-01-19

Visualizing data by dimensionality reduction is an important strategy in Bioinformatics, which could help to discover hidden data properties and detect data quality issues, e.g. data noise, inappropriately labeled data, etc. As crowdsourcing-based synthetic biology databases face similar data quality issues, we propose to visualize biobricks to tackle them. However, existing dimensionality reduction methods could not be directly applied on biobricks datasets. Hereby, we use normalized edit distance to enhance dimensionality reduction methods, including Isomap and Laplacian Eigenmaps. By extracting biobricks from synthetic biology database Registry of Standard Biological Parts, six combinations of various types of biobricks are tested. The visualization graphs illustrate discriminated biobricks and inappropriately labeled biobricks. Clustering algorithm K-means is adopted to quantify the reduction results. The average clustering accuracy for Isomap and Laplacian Eigenmaps are 0.857 and 0.844, respectively. Besides, Laplacian Eigenmaps is 5 times faster than Isomap, and its visualization graph is more concentrated to discriminate biobricks. By combining normalized edit distance with Isomap and Laplacian Eigenmaps, synthetic biology biobircks are successfully visualized in two dimensional space. Various types of biobricks could be discriminated and inappropriately labeled biobricks could be determined, which could help to assess crowdsourcing-based synthetic biology databases' quality, and make biobricks selection.

Method of locating related items in a geometric space for data mining

DOEpatents

Hendrickson, Bruce A.

1999-01-01

A method for locating related items in a geometric space transforms relationships among items to geometric locations. The method locates items in the geometric space so that the distance between items corresponds to the degree of relatedness. The method facilitates communication of the structure of the relationships among the items. The method is especially beneficial for communicating databases with many items, and with non-regular relationship patterns. Examples of such databases include databases containing items such as scientific papers or patents, related by citations or keywords. A computer system adapted for practice of the present invention can include a processor, a storage subsystem, a display device, and computer software to direct the location and display of the entities. The method comprises assigning numeric values as a measure of similarity between each pairing of items. A matrix is constructed, based on the numeric values. The eigenvectors and eigenvalues of the matrix are determined. Each item is located in the geometric space at coordinates determined from the eigenvectors and eigenvalues. Proper construction of the matrix and proper determination of coordinates from eigenvectors can ensure that distance between items in the geometric space is representative of the numeric value measure of the items' similarity.

What Do Data Used to Develop Ground-Motion Prediction Equations Tell Us About Motions Near Faults?

NASA Astrophysics Data System (ADS)

Boore, David M.

2014-11-01

A large database of ground motions from shallow earthquakes occurring in active tectonic regions around the world, recently developed in the Pacific Earthquake Engineering Center's NGA-West2 project, has been used to investigate what such a database can say about the properties and processes of crustal fault zones. There are a relatively small number of near-rupture records, implying that few recordings in the database are within crustal fault zones, but the records that do exist emphasize the complexity of ground-motion amplitudes and polarization close to individual faults. On average over the whole data set, however, the scaling of ground motions with magnitude at a fixed distance, and the distance dependence of the ground motions, seem to be largely consistent with simple seismological models of source scaling, path propagation effects, and local site amplification. The data show that ground motions close to large faults, as measured by elastic response spectra, tend to saturate and become essentially constant for short periods. This saturation seems to be primarily a geometrical effect, due to the increasing size of the rupture surface with magnitude, and not due to a breakdown in self similarity.

Improving the understanding of sleep apnea characterization using Recurrence Quantification Analysis by defining overall acceptable values for the dimensionality of the system, the delay, and the distance threshold.

PubMed

Martín-González, Sofía; Navarro-Mesa, Juan L; Juliá-Serdá, Gabriel; Ramírez-Ávila, G Marcelo; Ravelo-García, Antonio G

2018-01-01

Our contribution focuses on the characterization of sleep apnea from a cardiac rate point of view, using Recurrence Quantification Analysis (RQA), based on a Heart Rate Variability (HRV) feature selection process. Three parameters are crucial in RQA: those related to the embedding process (dimension and delay) and the threshold distance. There are no overall accepted parameters for the study of HRV using RQA in sleep apnea. We focus on finding an overall acceptable combination, sweeping a range of values for each of them simultaneously. Together with the commonly used RQA measures, we include features related to recurrence times, and features originating in the complex network theory. To the best of our knowledge, no author has used them all for sleep apnea previously. The best performing feature subset is entered into a Linear Discriminant classifier. The best results in the "Apnea-ECG Physionet database" and the "HuGCDN2014 database" are, according to the area under the receiver operating characteristic curve, 0.93 (Accuracy: 86.33%) and 0.86 (Accuracy: 84.18%), respectively. Our system outperforms, using a relatively small set of features, previously existing studies in the context of sleep apnea. We conclude that working with dimensions around 7-8 and delays about 4-5, and using for the threshold distance the Fixed Amount of Nearest Neighbours (FAN) method with 5% of neighbours, yield the best results. Therefore, we would recommend these reference values for future work when applying RQA to the analysis of HRV in sleep apnea. We also conclude that, together with the commonly used vertical and diagonal RQA measures, there are newly used features that contribute valuable information for apnea minutes discrimination. Therefore, they are especially interesting for characterization purposes. Using two different databases supports that the conclusions reached are potentially generalizable, and are not limited by database variability.

Presentation and Analysis of a Worldwide Database of Earthquake-Induced Landslide Inventories

NASA Astrophysics Data System (ADS)

Tanyaş, Hakan; van Westen, Cees J.; Allstadt, Kate E.; Anna Nowicki Jessee, M.; Görüm, Tolga; Jibson, Randall W.; Godt, Jonathan W.; Sato, Hiroshi P.; Schmitt, Robert G.; Marc, Odin; Hovius, Niels

2017-10-01

Earthquake-induced landslide (EQIL) inventories are essential tools to extend our knowledge of the relationship between earthquakes and the landslides they can trigger. Regrettably, such inventories are difficult to generate and therefore scarce, and the available ones differ in terms of their quality and level of completeness. Moreover, access to existing EQIL inventories is currently difficult because there is no centralized database. To address these issues, we compiled EQIL inventories from around the globe based on an extensive literature study. The database contains information on 363 landslide-triggering earthquakes and includes 66 digital landslide inventories. To make these data openly available, we created a repository to host the digital inventories that we have permission to redistribute through the U.S. Geological Survey ScienceBase platform. It can grow over time as more authors contribute their inventories. We analyze the distribution of EQIL events by time period and location, more specifically breaking down the distribution by continent, country, and mountain region. Additionally, we analyze frequency distributions of EQIL characteristics, such as the approximate area affected by landslides, total number of landslides, maximum distance from fault rupture zone, and distance from epicenter when the fault plane location is unknown. For the available digital EQIL inventories, we examine the underlying characteristics of landslide size, topographic slope, roughness, local relief, distance to streams, peak ground acceleration, peak ground velocity, and Modified Mercalli Intensity. Also, we present an evaluation system to help users assess the suitability of the available inventories for different types of EQIL studies and model development.

Presentation and analysis of a worldwide database of earthquake-induced landslide inventories

USGS Publications Warehouse

Tanyas, Hakan; van Westen, Cees J.; Allstadt, Kate E.; Nowicki Jessee, M. Anna; Gorum, Tolga; Jibson, Randall W.; Godt, Jonathan W.; Sato, Hiroshi P.; Schmitt, Robert G.; Marc, Odin; Hovius, Niels

2017-01-01

Earthquake-induced landslide (EQIL) inventories are essential tools to extend our knowledge of the relationship between earthquakes and the landslides they can trigger. Regrettably, such inventories are difficult to generate and therefore scarce, and the available ones differ in terms of their quality and level of completeness. Moreover, access to existing EQIL inventories is currently difficult because there is no centralized database. To address these issues, we compiled EQIL inventories from around the globe based on an extensive literature study. The database contains information on 363 landslide-triggering earthquakes and includes 66 digital landslide inventories. To make these data openly available, we created a repository to host the digital inventories that we have permission to redistribute through the U.S. Geological Survey ScienceBase platform. It can grow over time as more authors contribute their inventories. We analyze the distribution of EQIL events by time period and location, more specifically breaking down the distribution by continent, country, and mountain region. Additionally, we analyze frequency distributions of EQIL characteristics, such as the approximate area affected by landslides, total number of landslides, maximum distance from fault rupture zone, and distance from epicenter when the fault plane location is unknown. For the available digital EQIL inventories, we examine the underlying characteristics of landslide size, topographic slope, roughness, local relief, distance to streams, peak ground acceleration, peak ground velocity, and Modified Mercalli Intensity. Also, we present an evaluation system to help users assess the suitability of the available inventories for different types of EQIL studies and model development.

Angular declination and the dynamic perception of egocentric distance.

PubMed

Gajewski, Daniel A; Philbeck, John W; Wirtz, Philip W; Chichka, David

2014-02-01

The extraction of the distance between an object and an observer is fast when angular declination is informative, as it is with targets placed on the ground. To what extent does angular declination drive performance when viewing time is limited? Participants judged target distances in a real-world environment with viewing durations ranging from 36-220 ms. An important role for angular declination was supported by experiments showing that the cue provides information about egocentric distance even on the very first glimpse, and that it supports a sensitive response to distance in the absence of other useful cues. Performance was better at 220-ms viewing durations than for briefer glimpses, suggesting that the perception of distance is dynamic even within the time frame of a typical eye fixation. Critically, performance in limited viewing trials was better when preceded by a 15-s preview of the room without a designated target. The results indicate that the perception of distance is powerfully shaped by memory from prior visual experience with the scene. A theoretical framework for the dynamic perception of distance is presented. PsycINFO Database Record (c) 2014 APA, all rights reserved.

In the Literature.

ERIC Educational Resources Information Center

Kilpatrick, Thomas L., Ed.

1998-01-01

Provides annotations of 29 journal articles and six book reviews on a variety of topics related to technology in libraries, including collection development, computer-assisted instruction, databases, distance education, ergonomics, hardware, information technology, interlibrary loan and document supply, Internet, online catalogs, preservation,…

Telecommunications Is Here and Now.

ERIC Educational Resources Information Center

Clark, Chris

1988-01-01

Presents an overview of telecommunications and its use in the field of education. Topics discussed include conferencing, electronic messaging, distance learning, networking, database searching, and projects relating to educational telecommunications sponsored by the International Council for Computers in Education (ICCE). (LRW)

Virtual Teaching on the Tundra.

ERIC Educational Resources Information Center

McAuley, Alexander

1998-01-01

Describes how a teacher and a distance-learning consultant collaborate in using the Internet and Computer Supported Intentional Learning Environment (CISILE) to connect multicultural students on the harsh Baffin Island (Canada). Discusses the creation of the class's database and future implications. (AEF)

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.

Observations of flat-spectrum radio sources at λ850μm from the James Clerk Maxwell Telescope II. April 2000 to June 2005

NASA Astrophysics Data System (ADS)

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

2010-01-01

Calibrated data for 143 flat-spectrum extragalactic radio sources are presented at a wavelength of 850μm covering a 5-yr period from 2000 April. The data, obtained at the James Clerk Maxwell Telescope using the Submillimetre Common-User Bolometer Array (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. A re-analysis of previously published data from 1997 to 2000 is also presented. The combined catalogue, comprising 10493 flux density measurements, provides a unique and valuable resource for studies of extragalactic radio sources.

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.

Virus Database and Online Inquiry System Based on Natural Vectors.

PubMed

Dong, Rui; Zheng, Hui; Tian, Kun; Yau, Shek-Chung; Mao, Weiguang; Yu, Wenping; Yin, Changchuan; Yu, Chenglong; He, Rong Lucy; Yang, Jie; Yau, Stephen St

2017-01-01

We construct a virus database called VirusDB (http://yaulab.math.tsinghua.edu.cn/VirusDB/) and an online inquiry system to serve people who are interested in viral classification and prediction. The database stores all viral genomes, their corresponding natural vectors, and the classification information of the single/multiple-segmented viral reference sequences downloaded from National Center for Biotechnology Information. The online inquiry system serves the purpose of computing natural vectors and their distances based on submitted genomes, providing an online interface for accessing and using the database for viral classification and prediction, and back-end processes for automatic and manual updating of database content to synchronize with GenBank. Submitted genomes data in FASTA format will be carried out and the prediction results with 5 closest neighbors and their classifications will be returned by email. Considering the one-to-one correspondence between sequence and natural vector, time efficiency, and high accuracy, natural vector is a significant advance compared with alignment methods, which makes VirusDB a useful database in further research.

Human grasping database for activities of daily living with depth, color and kinematic data streams.

PubMed

Saudabayev, Artur; Rysbek, Zhanibek; Khassenova, Raykhan; Varol, Huseyin Atakan

2018-05-29

This paper presents a grasping database collected from multiple human subjects for activities of daily living in unstructured environments. The main strength of this database is the use of three different sensing modalities: color images from a head-mounted action camera, distance data from a depth sensor on the dominant arm and upper body kinematic data acquired from an inertial motion capture suit. 3826 grasps were identified in the data collected during 9-hours of experiments. The grasps were grouped according to a hierarchical taxonomy into 35 different grasp types. The database contains information related to each grasp and associated sensor data acquired from the three sensor modalities. We also provide our data annotation software written in Matlab as an open-source tool. The size of the database is 172 GB. We believe this database can be used as a stepping stone to develop big data and machine learning techniques for grasping and manipulation with potential applications in rehabilitation robotics and intelligent automation.

Distance restraints from crosslinking mass spectrometry: mining a molecular dynamics simulation database to evaluate lysine-lysine distances.

PubMed

Merkley, Eric D; Rysavy, Steven; Kahraman, Abdullah; Hafen, Ryan P; Daggett, Valerie; Adkins, Joshua N

2014-06-01

Integrative structural biology attempts to model the structures of protein complexes that are challenging or intractable by classical structural methods (due to size, dynamics, or heterogeneity) by combining computational structural modeling with data from experimental methods. One such experimental method is chemical crosslinking mass spectrometry (XL-MS), in which protein complexes are crosslinked and characterized using liquid chromatography-mass spectrometry to pinpoint specific amino acid residues in close structural proximity. The commonly used lysine-reactive N-hydroxysuccinimide ester reagents disuccinimidylsuberate (DSS) and bis(sulfosuccinimidyl)suberate (BS(3) ) have a linker arm that is 11.4 Å long when fully extended, allowing Cα (alpha carbon of protein backbone) atoms of crosslinked lysine residues to be up to ∼24 Å apart. However, XL-MS studies on proteins of known structure frequently report crosslinks that exceed this distance. Typically, a tolerance of ∼3 Å is added to the theoretical maximum to account for this observation, with limited justification for the chosen value. We used the Dynameomics database, a repository of high-quality molecular dynamics simulations of 807 proteins representative of diverse protein folds, to investigate the relationship between lysine-lysine distances in experimental starting structures and in simulation ensembles. We conclude that for DSS/BS(3), a distance constraint of 26-30 Å between Cα atoms is appropriate. This analysis provides a theoretical basis for the widespread practice of adding a tolerance to the crosslinker length when comparing XL-MS results to structures or in modeling. We also discuss the comparison of XL-MS results to MD simulations and known structures as a means to test and validate experimental XL-MS methods. © 2014 The Protein Society.

Distance restraints from crosslinking mass spectrometry: Mining a molecular dynamics simulation database to evaluate lysine–lysine distances

PubMed Central

Merkley, Eric D; Rysavy, Steven; Kahraman, Abdullah; Hafen, Ryan P; Daggett, Valerie; Adkins, Joshua N

2014-01-01

Integrative structural biology attempts to model the structures of protein complexes that are challenging or intractable by classical structural methods (due to size, dynamics, or heterogeneity) by combining computational structural modeling with data from experimental methods. One such experimental method is chemical crosslinking mass spectrometry (XL-MS), in which protein complexes are crosslinked and characterized using liquid chromatography-mass spectrometry to pinpoint specific amino acid residues in close structural proximity. The commonly used lysine-reactive N-hydroxysuccinimide ester reagents disuccinimidylsuberate (DSS) and bis(sulfosuccinimidyl)suberate (BS3) have a linker arm that is 11.4 Å long when fully extended, allowing Cα (alpha carbon of protein backbone) atoms of crosslinked lysine residues to be up to ∼24 Å apart. However, XL-MS studies on proteins of known structure frequently report crosslinks that exceed this distance. Typically, a tolerance of ∼3 Å is added to the theoretical maximum to account for this observation, with limited justification for the chosen value. We used the Dynameomics database, a repository of high-quality molecular dynamics simulations of 807 proteins representative of diverse protein folds, to investigate the relationship between lysine–lysine distances in experimental starting structures and in simulation ensembles. We conclude that for DSS/BS3, a distance constraint of 26–30 Å between Cα atoms is appropriate. This analysis provides a theoretical basis for the widespread practice of adding a tolerance to the crosslinker length when comparing XL-MS results to structures or in modeling. We also discuss the comparison of XL-MS results to MD simulations and known structures as a means to test and validate experimental XL-MS methods. PMID:24639379

Evaluation of proximity of mandibular molars and second premolar to inferior alveolar nerve canal among central Indians: A cone-beam computed tomographic retrospective study.

PubMed

Hiremath, Hemalatha; Agarwal, Rolly; Hiremath, Vishwanath; Phulambrikar, Tushar

2016-01-01

A study was done to assess the average distances of root apices of mandibular first molar, second molar, and second premolar to inferior alveolar nerve canal (IANC), among males and females in central India. High-resolution full-volume cone-beam computed tomography (CBCT) scans were obtained from the radiology database at the Sri Aurobindo College of Dentistry, Indore. After scrutinizing the database, CBCT of 40 males and 40 females that conformed to the inclusion and exclusion criteria were selected for the study. All the data were analyzed using SPSS, Version 16. Descriptive statistics of the variables and measurements are presented using Students t-test (paired and unpaired), and correlation between age was tabled by Karl Pearson's correlation coefficient method. For the second premolar, the average distance to the IANC was 0.88-13.03 mm for males and 0.00-5.49 mm for females. The average distance of IANC to the mesial root apex of first molar was 1.46-13.23 mm for males and 0.93-8.03 mm for females. For the second molar, the average distance was 1.31-14.71 mm for males and 0.00-6.91 mm for females (values on left side were shorter as compared to right side). In the overall population, only second molar exhibited significant difference in the distance from root apex to IANC when compared bilaterally. In addition to gender differences, age-related differences were found to be significant for the first molar on left side and second molar on the right side of the population (P< 0.05).

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.

SELECTION OF BURST-LIKE TRANSIENTS AND STOCHASTIC VARIABLES USING MULTI-BAND IMAGE DIFFERENCING IN THE PAN-STARRS1 MEDIUM-DEEP SURVEY

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

Kumar, S.; Gezari, S.; Heinis, S.

2015-03-20

We present a novel method for the light-curve characterization of Pan-STARRS1 Medium Deep Survey (PS1 MDS) extragalactic sources into stochastic variables (SVs) and burst-like (BL) transients, using multi-band image-differencing time-series data. We select detections in difference images associated with galaxy hosts using a star/galaxy catalog extracted from the deep PS1 MDS stacked images, and adopt a maximum a posteriori formulation to model their difference-flux time-series in four Pan-STARRS1 photometric bands g {sub P1}, r {sub P1}, i {sub P1}, and z {sub P1}. We use three deterministic light-curve models to fit BL transients; a Gaussian, a Gamma distribution, and anmore » analytic supernova (SN) model, and one stochastic light-curve model, the Ornstein-Uhlenbeck process, in order to fit variability that is characteristic of active galactic nuclei (AGNs). We assess the quality of fit of the models band-wise and source-wise, using their estimated leave-out-one cross-validation likelihoods and corrected Akaike information criteria. We then apply a K-means clustering algorithm on these statistics, to determine the source classification in each band. The final source classification is derived as a combination of the individual filter classifications, resulting in two measures of classification quality, from the averages across the photometric filters of (1) the classifications determined from the closest K-means cluster centers, and (2) the square distances from the clustering centers in the K-means clustering spaces. For a verification set of AGNs and SNe, we show that SV and BL occupy distinct regions in the plane constituted by these measures. We use our clustering method to characterize 4361 extragalactic image difference detected sources, in the first 2.5 yr of the PS1 MDS, into 1529 BL, and 2262 SV, with a purity of 95.00% for AGNs, and 90.97% for SN based on our verification sets. We combine our light-curve classifications with their nuclear or off-nuclear host galaxy offsets, to define a robust photometric sample of 1233 AGNs and 812 SNe. With these two samples, we characterize their variability and host galaxy properties, and identify simple photometric priors that would enable their real-time identification in future wide-field synoptic surveys.« less

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.

Technical issues for the eye image database creation at distance

NASA Astrophysics Data System (ADS)

Oropesa Morales, Lester Arturo; Maldonado Cano, Luis Alejandro; Soto Aldaco, Andrea; García Vázquez, Mireya Saraí; Zamudio Fuentes, Luis Miguel; Rodríguez Vázquez, Manuel Antonio; Pérez Rosas, Osvaldo Gerardo; Rodríguez Espejo, Luis; Montoya Obeso, Abraham; Ramírez Acosta, Alejandro Álvaro

2016-09-01

Biometrics refers to identify people through their physical characteristics or behavior such as fingerprints, face, DNA, hand geometries, retina and iris patterns. Typically, the iris pattern is to acquire in short distance to recognize a person, however, in the past few years is a challenge identify a person by its iris pattern at certain distance in non-cooperative environments. This challenge comprises: 1) high quality iris image, 2) light variation, 3) blur reduction, 4) specular reflections reduction, 5) the distance from the acquisition system to the user, and 6) standardize the iris size and the density pixel of iris texture. The solution of the challenge will add robustness and enhance the iris recognition rates. For this reason, we describe the technical issues that must be considered during iris acquisition. Some of these considerations are the camera sensor, lens, the math analysis of depth of field (DOF) and field of view (FOV) for iris recognition. Finally, based on this issues we present experiment that show the result of captures obtained with our camera at distance and captures obtained with cameras in very short distance.

Student outcomes of distance learning in nursing education: an integrative review.

PubMed

Patterson, Barbara J; Krouse, Anne M; Roy, Linda

2012-09-01

Distance learning offers a distinctive environment to educate nursing students. While there is a significant body of evidence in the literature related to course, program, and faculty outcomes of distance education, little attention has been given by researchers to evaluate student outcomes, with the exception of student satisfaction. There is a need to evaluate and translate findings related to student outcomes in distance learning into educational practice. Integrative reviews offer one strategy to contribute to evidence-based teaching practice initiatives. A search of available published qualitative and quantitative research on student outcomes of distance learning from 1999 to 2009 was conducted using a number of databases. Astin's Input-Environment-Output conceptual model provided a framework for this review. Thirty-three studies met the inclusion criteria. Bothcognitive and affective student outcomes emerged. The cognitive outcomes were student learning, learning process, and technology proficiency. Affective outcomes included personal and professional growth, satisfaction, and connectedness. Implications, recommendations, and future research are discussed.

Landslide database dominated by rainfall triggered events

NASA Astrophysics Data System (ADS)

Devoli, G.; Strauch, W.; Álvarez, A.

2009-04-01

A digital landslide database has been created for Nicaragua to provide the scientific community and national authorities with a tool for landslide hazard assessment. Valuable information on landslide events has been obtained from a great variety of sources. On the basis of the data stored in the database, preliminary analyses performed at national scale aimed to characterize landslides in terms of spatial and temporal distribution, types of slope movements, triggering mechanisms, number of casualties and damage to infrastructure. A total of about 17000 events spatially distributed in mountainous and volcanic terrains have been collected in the database. The events are temporally distributed between 1826 and 2003, but a large number of the records (62% of the total number) occurred during the disastrous Hurricane Mitch in October 1998. The results showed that debris flows are the most common types of landslides recorded in the database (66% of the total amount), but other types, including rockfalls and slides, have also been identified. Rainfall, also associated with tropical cyclones, is the most frequent triggering mechanism of landslides in Nicaragua, but also seismic and volcanic activities are important triggers or, especially, the combination of one of them with rainfall. Rainfall has caused all types of failures, but debris flows and translational shallow slides are more frequent types. Earthquakes have most frequently triggered rockfalls and slides, while volcanic eruptions rockfalls and debris flows. Landslides triggered by rainfall were limited in time to the wet season that lasts from May to October and an increase in the number of events is observed during the months of September and October, which is in accord with the period of the rainy season in the Pacific and Northern and Central regions and when the country has the highest probability of being impacted by hurricanes. Both Atlantic and Pacific tropical cyclones have triggered landslides. At the medium scale, the influence of topographic and lithologic parameters on the occurrence of landslides was also analyzed and the physical characterization of landslides was done to better understand the landslide dynamics and run-out distances in both volcanic and non-volcanic areas. Data from fairly well documented events in Nicaragua were compared with other similar events in Central America and elsewhere and treated statistically to search for possible correlations and empirical relationships to predict run-out distances for different types of landslides, knowing the height of fall or the volume. The empirical relationships showed that debris flows and debris avalanches at volcanoes have the highest mobility and reach longer distances compared to other types of landslides. Because of their characteristics and downstream behaviour (long run-out distances and large volumes) both types of landslides have produced the highest number of victims in the country being the most dangerous to life and property.

Attenuation relation for strong motion in Eastern Java based on appropriate database and method

NASA Astrophysics Data System (ADS)

Mahendra, Rian; Rohadi, Supriyanto; Rudyanto, Ariska

2017-07-01

The selection and determination of attenuation relation has become important for seismic hazard assessment in active seismic region. This research initially constructs the appropriate strong motion database, including site condition and type of the earthquake. The data set consisted of large number earthquakes of 5 ≤ Mw ≤ 9 and distance less than 500 km that occurred around Java from 2009 until 2016. The location and depth of earthquake are being relocated using double difference method to improve the quality of database. Strong motion data from twelve BMKG's accelerographs which are located in east Java is used. The site condition is known by using dominant period and Vs30. The type of earthquake is classified into crustal earthquake, interface, and intraslab based on slab geometry analysis. A total of 10 Ground Motion Prediction Equations (GMPEs) are tested using Likelihood (Scherbaum et al., 2004) and Euclidean Distance Ranking method (Kale and Akkar, 2012) with the associated database. The evaluation of these methods lead to a set of GMPEs that can be applied for seismic hazard in East Java where the strong motion data is collected. The result of these methods found that there is still high deviation of GMPEs, so the writer modified some GMPEs using inversion method. Validation was performed by analysing the attenuation curve of the selected GMPE and observation data in period 2015 up to 2016. The results show that the selected GMPE is suitable for estimated PGA value in East Java.

Developing STR databases on structured populations: the native South Siberian population versus the Russian population.

PubMed

Zhivotovsky, Lev A; Malyarchuk, Boris A; Derenko, Miroslava V; Wozniak, Marcin; Grzybowski, Tomasz

2009-09-01

Developing a forensic DNA database on a population that consists of local ethnic groups separated by physical and cultural barriers is questionable as it can be genetically subdivided. On the other side, small sizes of ethnic groups, especially in alpine regions where they are sub-structured further into small villages, prevent collecting a large sample from each ethnic group. For such situations, we suggest to obtain both a total population database on allele frequencies across ethnic groups and a list of theta-values between the groups and the total data. We have genotyped 558 individuals from the native population of South Siberia, consisting of nine ethnic groups, at 17 autosomal STR loci of the kit packages AmpFlSTR SGM Plus i, Cyrillic AmpFlSTR Profiler Plus. The groups differentiate from each other with average theta-values of around 1.1%, and some reach up to three to four percent at certain loci. There exists between-village differentiation as well. Therefore, a database for the population of South Siberia is composed of data on allele frequencies in the pool of ethnic groups and data on theta-values that indicate variation in allele frequencies across the groups. Comparison to additional data on northeastern Asia (the Chukchi and Koryak) shows that differentiation in allele frequencies among small groups that are separated by large geographic distance can be even greater. In contrast, populations of Russians that live in large cities of the European part of Russia are homogeneous in allele frequencies, despite large geographic distance between them, and thus can be described by a database on allele frequencies alone, without any specific information on theta-values.

Scheduled Civil Aircraft Emission Inventories for 1999: Database Development and Analysis

NASA Technical Reports Server (NTRS)

Sutkus, Donald J., Jr.; Baughcum, Steven L.; DuBois, Douglas P.

2001-01-01

This report describes the development of a three-dimensional database of aircraft fuel burn and emissions (NO(x), CO, and hydrocarbons) for the scheduled commercial aircraft fleet for each month of 1999. Global totals of emissions and fuel burn for 1999 are compared to global totals from 1992 and 2015 databases. 1999 fuel burn, departure and distance totals for selected airlines are compared to data reported on DOT Form 41 to evaluate the accuracy of the calculations. DOT Form T-100 data were used to determine typical payloads for freighter aircraft and this information was used to model freighter aircraft more accurately by using more realistic payloads. Differences in the calculation methodology used to create the 1999 fuel burn and emissions database from the methodology used in previous work are described and evaluated.

PDAs and the Library Without a Roof.

ERIC Educational Resources Information Center

Foster, Clifton Dale

1995-01-01

A project demonstrated the feasibility of accessing library information (online public access catalogs, commercial online databases, Internet) from a distance using handheld personal digital assistants (PDAs) equipped with cellular communication capability. The study is described, and other uses of wireless communications in libraries and…

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.;

ISO Key Project: Exploring the Full Range of Quasar/Agn Properties

NASA Technical Reports Server (NTRS)

Wilkes, Belinda; Oliversen, Ronald J. (Technical Monitor)

2003-01-01

While most of the work on this program has been completed, as previously reported, the portion of the program dealing with the subtopic of ISO LWS data analysis and reduction for the LWS Extragalactic Science Team and its leader, Dr. Howard Smith, is still active. This program in fact continues to generate results, and newly available computer modeling has extended the value of the datasets. As a result the team requests a one-year no-cost extension to this program, through 31 December 2004. The essence of the proposal is to perform ISO spectroscopic studies, including data analysis and modeling, of star-formation regions using an ensemble of archival space-based data from the Infrared Space Observatory's Long Wavelength Spectrometer and Short Wavelength Spectrometer, but including as well some other spectroscopic databases. Four kinds of regions are considered in the studies: (1) disks around more evolved objects; (2) young, low or high mass pre-main sequence stars in star-formation regions; (3) star formation in external, bright IR galaxies; and (4) the galactic center. One prime focus of the program is the OH lines in the far infrared. The program has the following goals: 1) Refine the data analysis of ISO observations to obtain deeper and better SNR results on selected sources. The ISO data itself underwent 'pipeline 10' reductions in early 2001, and additional 'hands-on data reduction packages' were supplied by the ISO teams in 2001. The Fabry-Perot database is particularly sensitive to noise and slight calibration errors; 2) Model the atomic and molecular line shapes, in particular the OH lines, using revised Monte-Carlo techniques developed by the SWAS team at the Center for Astrophysics; 3) Attend scientific meetings and workshops; 4) Perform E&PO activities related to infrared astrophysics and/or spectroscopy.

Ultraviolet studies of the intergalactic medium, active galactic nuclei, and the low-z Ly-alpha forest

NASA Astrophysics Data System (ADS)

Penton, Steven Victor

1999-05-01

A database of all active galactic nuclei (AGN) observed with the International Ultraviolet Explorer (IUE, 1976-1995) was created to determine the brightest UV (1250 Å) extragalactic sources. Combined spectra, and continuum lightcurves are available for ~700 AGN. Fifteen targets were selected from this database for observation of the low-z Lyα forest with the Hubble Space Telescope. These observations were taken with the Goddard High Resolution spectrograph and the G160M grating (1991-1997). 111 significance level >3σ Lyα absorbers were detected in the redshift range, 0.002 < z < 0.069. This Thesis evaluates the physical properties of these Lyα absorbers and compares them to their high-z counterparts. In addition, we use large galaxy catalogs (i.e. the CfA Redshift Survey) to compare the relationship between known galaxies and the low-z Lyα forest. We find that the low-z absorbers are similar in physical characteristic and density to those detected at high- z. Some of these clouds appear to be primordial matter, owing to the lack of detected metallicity. A comparison to the known galaxy distribution indicates that the low-z Lyα forest clusters less than galaxies, but more than random. This suggests that at least a fraction of the absorbers are associated with the gas in galaxy associations (i.e. filaments), while a second population is distributed more uniformly. Over equal pathlengths (cΔz ~60,000 km s -1 each) of galaxy-rich and galaxy-poor environments (voids), we determine that 80% of Lyα absorbers are near large-scale galactic structures (i.e. filaments), while 20% are in galaxy voids.

Convolutional Neural Network-Based Human Detection in Nighttime Images Using Visible Light Camera Sensors.

PubMed

Kim, Jong Hyun; Hong, Hyung Gil; Park, Kang Ryoung

2017-05-08

Because intelligent surveillance systems have recently undergone rapid growth, research on accurately detecting humans in videos captured at a long distance is growing in importance. The existing research using visible light cameras has mainly focused on methods of human detection for daytime hours when there is outside light, but human detection during nighttime hours when there is no outside light is difficult. Thus, methods that employ additional near-infrared (NIR) illuminators and NIR cameras or thermal cameras have been used. However, in the case of NIR illuminators, there are limitations in terms of the illumination angle and distance. There are also difficulties because the illuminator power must be adaptively adjusted depending on whether the object is close or far away. In the case of thermal cameras, their cost is still high, which makes it difficult to install and use them in a variety of places. Because of this, research has been conducted on nighttime human detection using visible light cameras, but this has focused on objects at a short distance in an indoor environment or the use of video-based methods to capture multiple images and process them, which causes problems related to the increase in the processing time. To resolve these problems, this paper presents a method that uses a single image captured at night on a visible light camera to detect humans in a variety of environments based on a convolutional neural network. Experimental results using a self-constructed Dongguk night-time human detection database (DNHD-DB1) and two open databases (Korea advanced institute of science and technology (KAIST) and computer vision center (CVC) databases), as well as high-accuracy human detection in a variety of environments, show that the method has excellent performance compared to existing methods.

When degenerate stars collide: Understanding A New Explosion Phenomena

NASA Astrophysics Data System (ADS)

Bloom, Joshua

2007-07-01

Explosive events seen at extragalactic distances mark the end-state of violent and catastrophic physical processes. Most supernovae and gamma-ray bursts {GRBs}, in particular, are thought to herald the death of massive stars and the birth of solar-mass black holes. A minority fraction of GRBs, however, have been circumstantially associated with the merger of degenerate systems {such as black holes and neutron stars}. These short-duration bursts are rare and difficult to localize, with only about 2 dozen studied to any degree of detail to date. We believe that we have finally discovered, in the last few days, one of the tell-tale signatures of degenerate merger products -- a "mini-supernova" from the non-relativistic ejecta left over after merger. If true, this long-theorized phenomenon would be an entirely new sort of explosion in the universe. In several rapidly executed visits, HST, coupled with a recently approved Chandra DD proposal to search for underlying afterglow, could make a substantial contribution to our understanding of this phenomena by honing the physical parameters of the event and helping to rule out alternatives. If we are correct in our hypothesis, we have found the first clear cut observational signature in the electromagnetic spectrum of what are expected to the be the dominant sources of gravitational waves for advanced LIGO.

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

NASA Technical Reports Server (NTRS)

Angelini, Lorella; White, Nicholas E.

2003-01-01

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

Very high energy γ-rays from the universe's middle age: detection of the z = 0.940 blazar PKS 1441+25 with magic

DOE PAGES

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

2015-12-15

The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5σ using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 (z = 0.944), PKS 1441+25 is the most distant very high energy (VHE) blazar detected to date. The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi. Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. In the band covered by MAGIC, the variability timescale ismore » estimated to be 6.4 ± 1.9 days. Modeling the broadband spectral energy distribution with an external Compton model, the location of the emitting region is understood as originating in the jet outside the broad-line region (BLR) during the period of high activity, while being partially within the BLR during the period of low (typical) activity. In conclusion, the observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy.« less

A FIVE-YEAR SPECTROSCOPIC AND PHOTOMETRIC CAMPAIGN ON THE PROTOTYPICAL {alpha} CYGNI VARIABLE AND A-TYPE SUPERGIANT STAR DENEB

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

Richardson, N. D.; Morrison, N. D.; Kryukova, E. E.

2011-01-15

Deneb is often considered the prototypical A-type supergiant and is one of the visually most luminous stars in the Galaxy. A-type supergiants are potential extragalactic distance indicators, but the variability of these stars needs to be better characterized before this technique can be considered reliable. We analyzed 339 high-resolution echelle spectra of Deneb obtained over the five-year span of 1997 through 2001 as well as 370 Stroemgren photometric measurements obtained during the same time frame. Our spectroscopic analysis included dynamical spectra of the H{alpha} profile, H{alpha} equivalent widths, and radial velocities measured from Si II {lambda}{lambda} 6347, 6371. Time-series analysismore » reveals no obvious cyclic behavior that proceeds through multiple observing seasons, although we found a suspected 40 day period in two, non-consecutive observing seasons. Some correlations are found between photometric and radial velocity data sets and suggest radial pulsations at two epochs. No correlation is found between the variability of the H{alpha} profiles and that of the radial velocities or the photometry. Lucy found evidence that Deneb was a long-period single-lined spectroscopic binary star, but our data set shows no evidence for radial velocity variations caused by a binary companion.« less

VERY HIGH ENERGY γ-RAYS FROM THE UNIVERSE’S MIDDLE AGE: DETECTION OF THE z = 0.940 BLAZAR PKS 1441+25 WITH MAGIC

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

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

2015-12-20

The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5σ using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 (z = 0.944), PKS 1441+25 is the most distant very high energy (VHE) blazar detected to date. The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi. Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. In the band covered by MAGIC, the variability timescale is estimated to bemore » 6.4 ± 1.9 days. Modeling the broadband spectral energy distribution with an external Compton model, the location of the emitting region is understood as originating in the jet outside the broad-line region (BLR) during the period of high activity, while being partially within the BLR during the period of low (typical) activity. The observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy.« less

Tracing the Mass of Early-type Galaxies using Planetary Nebulae

NASA Astrophysics Data System (ADS)

Sluis, A. P. N.; William, T. B.

2002-12-01

We report on observations of two ellipticals (NGC 3379 and NGC 1549) and two S0s (NGC 3384 and NGC 4636) performed with the Rutgers Fabry-Perot (RFP). The observations are part of a larger project to study the distribution of mass in the outer regions of early-type galaxies. Efforts to determine this distribution are generally hampered by the scarcity of useful tracers of the potential at large radii. Ellipticals and S0s have steep surface brightness profiles that make absorption line spectroscopy of the stellar population practically impossible beyond a few kpc from the center. Also, their gas content is low and does not extend far beyond the nucleus. Planetary Nebulae (PNe) offer a way around these problems: as remants of intermediate mass stars we expect them to follow the stellar light distribution and be numerous enough to be an effective tracer. PNe radiate hundreds of solar luminosities in a few emission lines (mostly [OIII] 5007 Å), making it possible to detect them over extragalactic distances and at the same time measure their line of sight velocities using the RFP. We present the photometry and the kinematics of the PN systems as well as some simple dynamical mass models for the four galaxies mentioned above.

First limits on the very-high energy gamma-ray afterglow emission of a fast radio burst. H.E.S.S. observations of FRB 150418

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.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Coffaro, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; Dewilt, 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.; Gajdus, M.; 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.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; 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.; Kieffer, M.; 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.; Öttl, S.; 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.; 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.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.; Superb Collaboration; Jankowski, F.; Keane, E. F.; Petroff, E.

2017-01-01

Aims: Following the detection of the fast radio burst FRB150418 by the SUPERB project at the Parkes radio telescope, we aim to search for very-high energy gamma-ray afterglow emission. Methods: Follow-up observations in the very-high energy gamma-ray domain were obtained with the H.E.S.S. imaging atmospheric Cherenkov telescope system within 14.5 h of the radio burst. Results: The obtained 1.4 h of gamma-ray observations are presented and discussed. At the 99% C.L. we obtained an integral upper limit on the gamma-ray flux of Φγ(E > 350 GeV) < 1.33 × 10-8 m-2 s-1. Differential flux upper limits as function of the photon energy were derived and used to constrain the intrinsic high-energy afterglow emission of FRB 150418. Conclusions: No hints for high-energy afterglow emission of FRB 150418 were found. Taking absorption on the extragalactic background light into account and assuming a distance of z = 0.492 based on radio and optical counterpart studies and consistent with the FRB dispersion, we constrain the gamma-ray luminosity at 1 TeV to L < 5.1 × 1047 erg/s at 99% C.L.

Creating a normative database of age-specific 3D geometrical data, bone density, and bone thickness of the developing skull: a pilot study.

PubMed

Delye, Hans; Clijmans, Tim; Mommaerts, Maurice Yves; Sloten, Jos Vnder; Goffin, Jan

2015-12-01

Finite element models (FEMs) of the head are used to study the biomechanics of traumatic brain injury and depend heavily on the use of accurate material properties and head geometry. Any FEM aimed at investigating traumatic head injury in children should therefore use age-specific dimensions of the head, as well as age-specific material properties of the different tissues. In this study, the authors built a database of age-corrected skull geometry, skull thickness, and bone density of the developing skull to aid in the development of an age-specific FEM of a child's head. Such a database, containing age-corrected normative skull geometry data, can also be used for preoperative surgical planning and postoperative long-term follow-up of craniosynostosis surgery results. Computed tomography data were processed for 187 patients (age range 0-20 years old). A 3D surface model was calculated from segmented skull surfaces. Skull models, reference points, and sutures were processed into a MATLAB-supported database. This process included automatic calculation of 2D measurements as well as 3D measurements: length of the coronal suture, length of the lambdoid suture, and the 3D anterior-posterior length, defined as the sum of the metopic and sagittal suture. Skull thickness and skull bone density calculations were included. Cephalic length, cephalic width, intercoronal distance, lateral orbital distance, intertemporal distance, and 3D measurements were obtained, confirming the well-established general growth pattern of the skull. Skull thickness increases rapidly in the first year of life, slowing down during the second year of life, while skull density increases with a fast but steady pace during the first 3 years of life. Both skull thickness and density continue to increase up to adulthood. This is the first report of normative data on 2D and 3D measurements, skull bone thickness, and skull bone density for children aged 0-20 years. This database can help build an age-specific FEM of a child's head. It can also help to tailor preoperative virtual planning in craniosynostosis surgery toward patient-specific normative target values and to perform objective long-term follow-up in craniosynostosis surgery.

Allelic database and accession divergence of a Brazilian mango collection based on microsatellite markers.

PubMed

Dos Santos Ribeiro, I C N; Lima Neto, F P; Santos, C A F

2012-12-19

Allelic patterns and genetic distances were examined in a collection of 103 foreign and Brazilian mango (Mangifera indica) accessions in order to develop a reference database to support cultivar protection and breeding programs. An UPGMA dendrogram was generated using Jaccard's coefficients from a distance matrix based on 50 alleles of 12 microsatellite loci. The base pair number was estimated by the method of inverse mobility. The cophenetic correlation was 0.8. The accessions had a coefficient of similarity from 30 to 100%, which reflects high genetic variability. Three groups were observed in the UPGMA dendrogram; the first group was formed predominantly by foreign accessions, the second group was formed by Brazilian accessions, and the Dashehari accession was isolated from the others. The 50 microsatellite alleles did not separate all 103 accessions, indicating that there are duplicates in this mango collection. These 12 microsatellites need to be validated in order to establish a reliable set to identify mango cultivars.

DCT-based iris recognition.

PubMed

Monro, Donald M; Rakshit, Soumyadip; Zhang, Dexin

2007-04-01

This paper presents a novel iris coding method based on differences of discrete cosine transform (DCT) coefficients of overlapped angular patches from normalized iris images. The feature extraction capabilities of the DCT are optimized on the two largest publicly available iris image data sets, 2,156 images of 308 eyes from the CASIA database and 2,955 images of 150 eyes from the Bath database. On this data, we achieve 100 percent Correct Recognition Rate (CRR) and perfect Receiver-Operating Characteristic (ROC) Curves with no registered false accepts or rejects. Individual feature bit and patch position parameters are optimized for matching through a product-of-sum approach to Hamming distance calculation. For verification, a variable threshold is applied to the distance metric and the False Acceptance Rate (FAR) and False Rejection Rate (FRR) are recorded. A new worst-case metric is proposed for predicting practical system performance in the absence of matching failures, and the worst case theoretical Equal Error Rate (EER) is predicted to be as low as 2.59 x 10(-4) on the available data sets.

Interprofessional education and distance education: A review and appraisal of the current literature.

PubMed

McCutcheon, Livia R M; Alzghari, Saeed K; Lee, Young R; Long, William G; Marquez, Robyn

2017-07-01

Interprofessional education (IPE) is becoming essential for students and healthcare professionals. An evolving approach to implement it is via distance education. Distance education can provide a viable solution to deliver IPE in a variety of settings. A literature search on PubMed and Academic Search Complete databases was conducted, revealing 478 articles ranging from the years of 1971-2015. The articles were screened for relevance using the following inclusion criteria: 1) Is this study implementing IPE? 2) Is this study utilizing the instructional delivery method of distance education? 3) Does this study contain students from two or more healthcare professions? Fifteen studies met the inclusion criteria and were systematically analyzed to identify data relevant for this review. Findings from this review provide a description of the teaching methods involved in distance education in promoting IPE and an assessment of the continuing use of distance education to foster IPE. Success varied depending upon on the distance-based instructional model utilized to facilitate IPE. Incorporating distance education to implement IPE can be an opportunity to develop team collaboration and communication skills among students. Teaching models presented in this review have the potential to be adapted to methods that leverage the power of evolving technology. Further research is needed to understand which distance education instructional delivery models best maximize the IPE experience. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Construction of crystal structure prototype database: methods and applications.

PubMed

Su, Chuanxun; Lv, Jian; Li, Quan; Wang, Hui; Zhang, Lijun; Wang, Yanchao; Ma, Yanming

2017-04-26

Crystal structure prototype data have become a useful source of information for materials discovery in the fields of crystallography, chemistry, physics, and materials science. This work reports the development of a robust and efficient method for assessing the similarity of structures on the basis of their interatomic distances. Using this method, we proposed a simple and unambiguous definition of crystal structure prototype based on hierarchical clustering theory, and constructed the crystal structure prototype database (CSPD) by filtering the known crystallographic structures in a database. With similar method, a program structure prototype analysis package (SPAP) was developed to remove similar structures in CALYPSO prediction results and extract predicted low energy structures for a separate theoretical structure database. A series of statistics describing the distribution of crystal structure prototypes in the CSPD was compiled to provide an important insight for structure prediction and high-throughput calculations. Illustrative examples of the application of the proposed database are given, including the generation of initial structures for structure prediction and determination of the prototype structure in databases. These examples demonstrate the CSPD to be a generally applicable and useful tool for materials discovery.

Active browsing using similarity pyramids

NASA Astrophysics Data System (ADS)

Chen, Jau-Yuen; Bouman, Charles A.; Dalton, John C.

1998-12-01

In this paper, we describe a new approach to managing large image databases, which we call active browsing. Active browsing integrates relevance feedback into the browsing environment, so that users can modify the database's organization to suit the desired task. Our method is based on a similarity pyramid data structure, which hierarchically organizes the database, so that it can be efficiently browsed. At coarse levels, the similarity pyramid allows users to view the database as large clusters of similar images. Alternatively, users can 'zoom into' finer levels to view individual images. We discuss relevance feedback for the browsing process, and argue that it is fundamentally different from relevance feedback for more traditional search-by-query tasks. We propose two fundamental operations for active browsing: pruning and reorganization. Both of these operations depend on a user-defined relevance set, which represents the image or set of images desired by the user. We present statistical methods for accurately pruning the database, and we propose a new 'worm hole' distance metric for reorganizing the database, so that members of the relevance set are grouped together.

Construction of crystal structure prototype database: methods and applications

NASA Astrophysics Data System (ADS)

Su, Chuanxun; Lv, Jian; Li, Quan; Wang, Hui; Zhang, Lijun; Wang, Yanchao; Ma, Yanming

2017-04-01

Crystal structure prototype data have become a useful source of information for materials discovery in the fields of crystallography, chemistry, physics, and materials science. This work reports the development of a robust and efficient method for assessing the similarity of structures on the basis of their interatomic distances. Using this method, we proposed a simple and unambiguous definition of crystal structure prototype based on hierarchical clustering theory, and constructed the crystal structure prototype database (CSPD) by filtering the known crystallographic structures in a database. With similar method, a program structure prototype analysis package (SPAP) was developed to remove similar structures in CALYPSO prediction results and extract predicted low energy structures for a separate theoretical structure database. A series of statistics describing the distribution of crystal structure prototypes in the CSPD was compiled to provide an important insight for structure prediction and high-throughput calculations. Illustrative examples of the application of the proposed database are given, including the generation of initial structures for structure prediction and determination of the prototype structure in databases. These examples demonstrate the CSPD to be a generally applicable and useful tool for materials discovery.

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 .

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.;

VizieR Online Data Catalog: Improved multi-band photometry from SERVS (Nyland+, 2017)

NASA Astrophysics Data System (ADS)

Nyland, K.; Lacy, M.; Sajina, A.; Pforr, J.; Farrah, D.; Wilson, G.; Surace, J.; Haussler, B.; Vaccari, M.; Jarvis, M.

2017-07-01

The Spitzer Extragalactic Representative Volume Survey (SERVS) sky footprint includes five well-studied astronomical deep fields with abundant multi-wavelength data spanning an area of ~18deg2 and a co-moving volume of ~0.8Gpc3. The five deep fields included in SERVS are the XMM-LSS field, Lockman Hole (LH), ELAIS-N1 (EN1), ELAIS-S1 (ES1), and Chandra Deep Field South (CDFS). SERVS provides NIR, post-cryogenic imaging in the 3.6 and 4.5um Spitzer/IRAC bands to a depth of ~2uJy. IRAC dual-band source catalogs generated using traditional catalog extraction methods are described in Mauduit+ (2012PASP..124..714M). The Spitzer IRAC data are complemented by ground-based NIR observations from the VISTA Deep Extragalactic Observations (VIDEO; Jarvis+ 2013MNRAS.428.1281J) survey in the south in the Z, Y, J, H, and Ks bands and UKIRT Infrared Deep Sky Survey (UKIDSS; Lawrence+ 2007, see II/319) in the north in the J and K bands. SERVS also provides substantial overlap with infrared data from SWIRE (Lonsdale+ 2003PASP..115..897L) and the Herschel Multitiered Extragalactic Survey (HerMES; Oliver+ 2012, VIII/95). As shown in Figure 1, one square degree of the XMM-LSS field overlaps with ground-based optical data from the Canada-France-Hawaii Telescope Legacy Survey Deep field 1 (CFHTLS-D1). The CFHTLS-D1 region is centered at RAJ2000=02:25:59, DEJ2000=-04:29:40 and includes imaging through the filter set u', g', r', i', and z'. Thus, in combination with the NIR data from SERVS and VIDEO that overlap with the CFHTLS-D1 region, multi-band imaging over a total of 12 bands is available. (2 data files).

An Application of Multi-band Forced Photometry to One Square Degree of SERVS: Accurate Photometric Redshifts and Implications for Future Science

NASA Astrophysics Data System (ADS)

Nyland, Kristina; Lacy, Mark; Sajina, Anna; Pforr, Janine; Farrah, Duncan; Wilson, Gillian; Surace, Jason; Häußler, Boris; Vaccari, Mattia; Jarvis, Matt

2017-05-01

We apply The Tractor image modeling code to improve upon existing multi-band photometry for the Spitzer Extragalactic Representative Volume Survey (SERVS). SERVS consists of post-cryogenic Spitzer observations at 3.6 and 4.5 μm over five well-studied deep fields spanning 18 deg2. In concert with data from ground-based near-infrared (NIR) and optical surveys, SERVS aims to provide a census of the properties of massive galaxies out to z ≈ 5. To accomplish this, we are using The Tractor to perform “forced photometry.” This technique employs prior measurements of source positions and surface brightness profiles from a high-resolution fiducial band from the VISTA Deep Extragalactic Observations survey to model and fit the fluxes at lower-resolution bands. We discuss our implementation of The Tractor over a square-degree test region within the XMM Large Scale Structure field with deep imaging in 12 NIR/optical bands. Our new multi-band source catalogs offer a number of advantages over traditional position-matched catalogs, including (1) consistent source cross-identification between bands, (2) de-blending of sources that are clearly resolved in the fiducial band but blended in the lower resolution SERVS data, (3) a higher source detection fraction in each band, (4) a larger number of candidate galaxies in the redshift range 5 < z < 6, and (5) a statistically significant improvement in the photometric redshift accuracy as evidenced by the significant decrease in the fraction of outliers compared to spectroscopic redshifts. Thus, forced photometry using The Tractor offers a means of improving the accuracy of multi-band extragalactic surveys designed for galaxy evolution studies. We will extend our application of this technique to the full SERVS footprint in the future.

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.

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⊙.

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

The High Time Resolution Radio Sky

NASA Astrophysics Data System (ADS)

Thornton, D.

2013-11-01

Pulsars are laboratories for extreme physics unachievable on Earth. As individual sources and possible orbital companions can be used to study magnetospheric, emission, and superfluid physics, general relativistic effects, and stellar and binary evolution. As populations they exhibit a wide range of sub-types, with parameters varying by many orders of magnitude signifying fundamental differences in their evolutionary history and potential uses. There are currently around 2200 known pulsars in the Milky Way, the Magellanic clouds, and globular clusters, most of which have been discovered with radio survey observations. These observations, as well as being suitable for detecting the repeating signals from pulsars, are well suited for identifying other transient astronomical radio bursts that last just a few milliseconds that either singular in nature, or rarely repeating. Prior to the work of this thesis non-repeating radio transients at extragalactic distances had possibly been discovered, however with just one example status a real astronomical sources was in doubt. Finding more of these sources was a vital to proving they were real and to open up the universe for millisecond-duration radio astronomy. The High Time Resolution Universe survey uses the multibeam receiver on the 64-m Parkes radio telescope to search the whole visible sky for pulsars and transients. The temporal and spectral resolution of the receiver and the digital back-end enable the detection of relatively faint, and distant radio sources. From the Parkes telescope a large portion of the Galactic plane can be seen, a rich hunting ground for radio pulsars of all types, while previously poorly surveyed regions away from the Galactic plane are also covered. I have made a number of pulsar discoveries in the survey, including some rare systems. These include PSR J1226-6208, a possible double neutron star system in a remarkably circular orbit, PSR J1431-471 which is being eclipsed by its companion with each orbit, PSR J1729-2117 which is an unusual isolated recycled pulsar, and PSR J2322-2650 which has a companion of very low mass - just 7 × 10^{-4} {M}_{⊙}, amongst others. I begin this thesis with the study of these pulsars and discuss their histories. In addition, I demonstrate that optical observations of the companions to some of the newly discovered pulsars in the High Time Resolution Universe survey may result in a measurement of their age and that of the pulsar. I have discovered five new extragalactic single radio bursts, confirming them as an astronomical population. These appear to occur frequently, with a rate of 1.0^{+0.6}_{-0.5} × 10^4 sky^{-1} day^{-1}. The sources are likely at cosmological distances - with redshifts between 0.45 and 1.45, making them more than half way to the Big Bang in the most distant case. This implies their luminosities must be enormous, 10^{31} to 10^{33} J emitted in just a few milliseconds. Their source is unknown but I present an analysis of the options. I also perform a population simulation of the bursts which demonstrates how their intrinsic spectrum could be measured, even for unlocalised FRBs: early indications are that the spectral index of FRBs < 0.

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.

The VIMOS Public Extragalactic Redshift Survey (VIPERS): Science Highlights and Final Data Release

NASA Astrophysics Data System (ADS)

Guzzo, L.; Vipers Team

2017-06-01

The VIMOS Public Extragalactic Redshift Survey (VIPERS) released its final set of nearly 90 000 galaxy redshifts in November 2016, together with a series of science papers that range from the detailed evolution of galaxies over the past 8 Gyr to the growth rate and the power spectrum of cosmological structures measured at about half the Hubble time. These are the results of a map of the distribution of galaxies and their properties which is unprecedented in its combination of large volume and detailed sampling at 0.5 < z < 1.2. In this article, the survey design and data properties are briefly summarised and an overview of the key scientific results published so far is provided. The VIPERS data, obtained within the framework of an ESO Large Programme over the equivalent of just under 55 nights at the Very Large Telescope, will remain the largest legacy of the VIMOS spectrograph and its still unsurpassed ability to reach target densities close to 10000 spectra per square degree.

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.

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.

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

How Well Can Modern Density Functionals Predict Internuclear Distances at Transition States?

PubMed

Xu, Xuefei; Alecu, I M; Truhlar, Donald G

2011-06-14

We introduce a new database called TSG48 containing 48 transition state geometrical data (in particular, internuclear distances in transition state structures) for 16 main group reactions. The 16 reactions are the 12 reactions in the previously published DBH24 database (which includes hydrogen transfer reactions, heavy-atom transfer reactions, nucleophilic substitution reactions, and association reactions plus one unimolecular isomerization) plus four H-transfer reactions in which a hydrogen atom is abstracted by the methyl or hydroperoxyl radical from the two different positions in methanol. The data in TSG48 include data for four reactions that have previously been treated at a very high level in the literature. These data are used to test and validate methods that are affordable for the entire test suite, and the most accurate of these methods is found to be the multilevel BMC-CCSD method. The data that constitute the TSG48 database are therefore taken to consist of these very high level calculations for the four reactions where they are available and BMC-CCSD calculations for the other 12 reactions. The TSG48 database is used to assess the performance of the eight Minnesota density functionals from the M05-M08 families and 26 other high-performance and popular density functionals for locating transition state geometries. For comparison, the MP2 and QCISD wave function methods have also been tested for transition state geometries. The MC3BB and MC3MPW doubly hybrid functionals and the M08-HX and M06-2X hybrid meta-GGAs are found to have the best performance of all of the density functionals tested. M08-HX is the most highly recommended functional due to the excellent performance for all five subsets of TSG48, as well as having a lower cost when compared to doubly hybrid functionals. The mean absolute errors in transition state internuclear distances associated with breaking and forming bonds as calculated by the B2PLYP, MP2, and B3LYP methods are respectively about 2, 3, and 5 times larger than those calculated by MC3BB and M08-HX.

The extraction of drug-disease correlations based on module distance in incomplete human interactome.

PubMed

Yu, Liang; Wang, Bingbo; Ma, Xiaoke; Gao, Lin

2016-12-23

Extracting drug-disease correlations is crucial in unveiling disease mechanisms, as well as discovering new indications of available drugs, or drug repositioning. Both the interactome and the knowledge of disease-associated and drug-associated genes remain incomplete. We present a new method to predict the associations between drugs and diseases. Our method is based on a module distance, which is originally proposed to calculate distances between modules in incomplete human interactome. We first map all the disease genes and drug genes to a combined protein interaction network. Then based on the module distance, we calculate the distances between drug gene sets and disease gene sets, and take the distances as the relationships of drug-disease pairs. We also filter possible false positive drug-disease correlations by p-value. Finally, we validate the top-100 drug-disease associations related to six drugs in the predicted results. The overlapping between our predicted correlations with those reported in Comparative Toxicogenomics Database (CTD) and literatures, and their enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways demonstrate our approach can not only effectively identify new drug indications, but also provide new insight into drug-disease discovery.

Supervisor-employee power distance incompatibility, gender similarity, and relationship conflict: A test of interpersonal interaction theory.

PubMed

Graham, Katrina A; Dust, Scott B; Ziegert, Jonathan C

2018-03-01

According to interpersonal interaction theory, relational harmony surfaces when two individuals have compatible interaction styles. Building from this theory, we propose that supervisor-employee power distance orientation incompatibility will be related to employees' experience of higher levels of relationship conflict with their supervisors. Additionally, we propose an asymmetrical incongruence effect such that relationship conflict will be highest when supervisors are high in power distance and employees are low in power distance. Furthermore, we address calls in interpersonal interaction research for more direct attention to the social context of the dyadic interaction and explore the moderating effects of supervisor-employee gender (dis)similarity on the relationship between this incompatibility and conflict. We propose that supervisor-employee gender dissimilarity (e.g., male-female or female-male pairs) acts as a conditional moderator, neutralizing the power distance incongruence effect and the asymmetrical incongruence effect. Using 259 supervisor-employee dyads in the physical therapy industry, the hypotheses were generally supported. Theoretical and practical implications regarding the unique benefits of power distance compatibility and gender diversity in supervisor-employee dyads are discussed. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Visibiome: an efficient microbiome search engine based on a scalable, distributed architecture.

PubMed

Azman, Syafiq Kamarul; Anwar, Muhammad Zohaib; Henschel, Andreas

2017-07-24

Given the current influx of 16S rRNA profiles of microbiota samples, it is conceivable that large amounts of them eventually are available for search, comparison and contextualization with respect to novel samples. This process facilitates the identification of similar compositional features in microbiota elsewhere and therefore can help to understand driving factors for microbial community assembly. We present Visibiome, a microbiome search engine that can perform exhaustive, phylogeny based similarity search and contextualization of user-provided samples against a comprehensive dataset of 16S rRNA profiles environments, while tackling several computational challenges. In order to scale to high demands, we developed a distributed system that combines web framework technology, task queueing and scheduling, cloud computing and a dedicated database server. To further ensure speed and efficiency, we have deployed Nearest Neighbor search algorithms, capable of sublinear searches in high-dimensional metric spaces in combination with an optimized Earth Mover Distance based implementation of weighted UniFrac. The search also incorporates pairwise (adaptive) rarefaction and optionally, 16S rRNA copy number correction. The result of a query microbiome sample is the contextualization against a comprehensive database of microbiome samples from a diverse range of environments, visualized through a rich set of interactive figures and diagrams, including barchart-based compositional comparisons and ranking of the closest matches in the database. Visibiome is a convenient, scalable and efficient framework to search microbiomes against a comprehensive database of environmental samples. The search engine leverages a popular but computationally expensive, phylogeny based distance metric, while providing numerous advantages over the current state of the art tool.

Motion data classification on the basis of dynamic time warping with a cloud point distance measure

NASA Astrophysics Data System (ADS)

Switonski, Adam; Josinski, Henryk; Zghidi, Hafedh; Wojciechowski, Konrad

2016-06-01

The paper deals with the problem of classification of model free motion data. The nearest neighbors classifier which is based on comparison performed by Dynamic Time Warping transform with cloud point distance measure is proposed. The classification utilizes both specific gait features reflected by a movements of subsequent skeleton joints and anthropometric data. To validate proposed approach human gait identification challenge problem is taken into consideration. The motion capture database containing data of 30 different humans collected in Human Motion Laboratory of Polish-Japanese Academy of Information Technology is used. The achieved results are satisfactory, the obtained accuracy of human recognition exceeds 90%. What is more, the applied cloud point distance measure does not depend on calibration process of motion capture system which results in reliable validation.