422 research outputs found
On the Nature of the Gamma-Ray Source 2FGL J1823.8+4312: The Discovery of a New Class of Extragalactic X-Ray Sources
No full textOne of the unsolved mysteries of gamma-ray astronomy concerns the nature
of unidentified gamma-ray sources. Recently, using the Second Fermi LAT
source catalog (2FGL) and the Wide-field Infrared Survey Explorer (WISE)
archive, we discovered that the WISE counterparts of gamma-ray blazars,
a class of active galactic nuclei, delineate a region (the WISE
Gamma-ray Strip) in three-dimensional infrared color space well
separated from the locus of other astronomical objects. Based on this
result, we built an association procedure to recognize if there are WISE
blazar candidates within the positional uncertainty region of the
unidentified gamma-ray sources. Here we report on our analysis of 2FGL
J1823.8+4312, a gamma-ray active galactic nucleus of uncertain type
associated with the X-ray source 1RXS J182418.7+430954 according to the
2FGL, to verify whether it is a blazar. Applying our association method
we found two sources with IR colors typical of gamma-ray blazars,
located within the 99.9% confidence region of 2FGL J1823.8+4312: WISE
J182352.33+431452.5 and WISE J182409.25+431404.7. We then searched in
the Chandra, NVSS, and SDSS archival observations for their
counterparts. We discovered that WISE J182352.33+431452.5, our preferred
gamma-ray blazar candidate according to our WISE association procedure,
is detected in the optical and in the X-rays but not in the radio,
making it extremely unusual if it is a blazar. Given its enigmatic
spectral energy distribution, we considered the possibility that it is a
"radio-faint blazar" or the prototype of a new class of extragalactic
sources; our conclusion is independent of whether WISE
J182352.33+431452.5 is the actual counterpart of 2FGL J1823.8+4312
GLOBAL COSMIC-RAY-RELATED LUMINOSITY AND ENERGY BUDGET OF THE MILKY WAY
No full textWe use the GALPROP code for cosmic-ray (CR) propagation to calculate the broadband luminosity spectrum of the Milky Way related to CR propagation and interactions in the interstellar medium. This includes gamma-ray emission from the production and subsequent decay of neutral pions (pi(0)), bremsstrahlung, and inverse Compton scattering, and synchrotron radiation. The Galaxy is found to be nearly a CR electron calorimeter, but only if gamma-ray emitting processes are taken into account. Synchrotron radiation alone accounts for only one-third of the gamma-ray total electron energy losses with similar to 10%-20% of the total synchrotron emission from secondary CR electrons and positrons. The relationship between far-infrared and radio luminosity that we find from our models is consistent with that found for galaxies in general. The results will be useful for understanding the connection between diffuse emissions from radio through gamma-rays in "normal" (non-active galactic nucleus dominated) galaxies as well as for estimating the broadband extragalactic diffuse background from these kinds of galaxies
GALPROP WebRun: An internet-based service for calculating galactic cosmic ray propagation and associated photon emissions
No full textGALPROP is a numerical code for calculating the galactic propagation of relativistic charged particles and the diffuse emissions produced during their propagation. The code incorporates as much realistic astrophysical input as possible together with latest theoretical developments and has become a de facto standard in astrophysics of cosmic rays. We present GALPROP WebRun, a service to the scientific community enabling easy use of the freely available GALPROP code via web browsers. In addition, we introduce the latest GALPROP version 54, available through this service. (C) 2011 Elsevier B.V. All rights reserved
GALPROP code for galactic cosmic ray propagation and associated photon emissions
No full textResearch in many areas of modern physics such as, e.g., indirect searches for dark matter and particle acceleration in supernova remnant shocks rely heavily on studies of cosmic rays (CRs) and associated diffuse emissions (radio, microwave, X-rays, γ-rays). The numerical Galactic CR propagation code GALPROP has been shown to reproduce simultaneously observational data of many kinds related to CR origin and propagation. We report on the latest updates of GALPROP, development of WebRun, a service to the scientific community enabling easy use of the GALPROP code via web browsers, and a library of evaluated isotopic production cross sections. We also report the results of a full Bayesian analysis of propagation parameters using nested sampling and Markov Chain Monte Carlo methods (implemented in the SuperBayeS code)
Sammelrezension
No full text1.) Arndt Ahlers-Niemann / Edeltrud Freitag-Becker (Hrsg.)
Netzwerke: Begegnungen auf Zeit; Zwischen Uns und Ich. EHP-Verlag Andreas Kohlhage: Bergisch-Gladbach, 2011. 208 S. ISBN 978-3-89797-073-1.
2.) Sabine Digel / Annika Goeze / Josef Schrader: Aus Videofällen lernen
Einführung in die Praxis für Lehrkräfte: Trainer und Berater. W. Bertelsmann Verlag: Bielefeld, 2012. 170 S. ISBN 978-3-7639-4661-7.
3.) Reinhold Hedtke: Konzepte ökonomischer Bildung. Wochenschau Verlag, Schwalbach, 2011. 93 S. ISBN 978-389974658-7
4.) Rosemarie Klein / Gerhard Reutter / Dieter Zisenis (Hrsg.): Bildungsferne Menschen: menschenferne Bildung? Grundlagen und Praxis arbeitsbezogener Grundbildung. Institut für angewandte Kulturforschung e.V.: Göttingen, 2011.
GiWA-Schriftenreihe Grundbildung in Wirtschaft und Arbeit - mehrperspektivisch,
Band 4. 286 S. ISBN 978-3-9814152-0-9.
5.) Ingrid Miethe / Hans-Rüdiger Müller (Hrsg.): Qualitative Bildungsforschung und Bildungstheorie. Verlag Barbara Budrich: Opladen, 2012.311 S. ISBN 978-3-86649-405-3.
6.) Bernhard von Rosenbladt / Frauke Bilger (Hrsg.): Weiterbildungsbeteiligung 2010: Trends und Analysen auf Basis des deutschen AES. W. Bertelsmann Verlag: Bielefeld, 2011. 286 S. ISBN 978-3-7639-6906-9.
7.) Daniela Rothe: Lebenslanges Lernen als Programm: Eine diskursive Formation in der Erwachsenenbildung. Campus Verlag: Frankfurt a.M., 2011. 465 S. ISBN 978-3-593-39425-1
8.) Annette Sprung: Zwischen Diskriminierung und Anerkennung: Weiterbildung in der Migrationsgesellschaft. Waxmann Verlag: Münster, 2011. 354 S. ISBN 978-3-8309-2496-8
Broad Line Radio Galaxies Observed with Fermi-LAT: The Origin of the GeV Gamma-Ray Emission
No full textWe report on a detailed investigation of the {gamma}-ray emission from 18 broad line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope (LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed {gamma}-ray emission reveals in addition possible flux variability in both sources. No statistically significant {gamma}-ray detection of the other BLRGs was however found in the considered dataset. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in {gamma}-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the {gamma}-ray flux variability and a number of other arguments presented, indicate that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found none were detected in {gamma}-rays. A simple phenomenological hybrid model applied for the broad-band emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is {ge} 1% on average for BLRGs, while {le} 0.1% for Seyfert 1 galaxies
- …
