Tues. Dec 4, 2012

Spectra of Cosmic Ray Protons and Helium Produced in Supernova Remnants
Authors: V. S. Ptuskin, V. N. Zirakashvili, E. S. Seo
(Submitted on 3 Dec 2012)

Abstract: Data obtained in the ATIC-2 (Advanced Thin Ionization Calorimeter), CREAM (Cosmic Ray Energetics and Mass)) and PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) experiments suggest that elemental interstellar spectra of cosmic rays below the knee at a few times $10^{6}$ GeV are not simple power laws, but they experience hardening at magnetic rigidity above about 240 GV. Another essential feature is the difference between proton and Helium energy spectra, so that the He/p ratio increases by more than 50% in the energy range from $10^{2}$ to $10^{4}$ GV. We consider the concavity of particle spectrum resulting from the nonlinear nature of diffusive shock acceleration in supernova remnants (SNR) as a possible reason for the observed spectrum hardening. Helium-to-proton ratio increasing with energy can be interpreted as a consequence of cosmic ray acceleration by forward and reverse shocks in SNRs. The contribution of particles accelerated by reverse shocks makes the concavity of the produced overall cosmic ray spectrum more pronounced. The spectra of protons and helium nuclei accelerated in SNRs and released into the interstellar medium are calculated. The derived steady state interstellar spectra are in reasonably good agreement with observations.

Comments: 18 pages, 2 figures, accepted to ApJ
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE)
Cite as: arXiv:1212.0381 [astro-ph.HE]

Detection of Far Infrared Emission from Galaxies and Quasars in the Galactic Extinction Map by Stacking Analysis
Authors: Toshiya Kashiwagi, Kazuhiro Yahata, Yasushi Suto (Univ. of Tokyo)
(Submitted on 3 Dec 2012)

Abstract: We have performed stacking image analyses of galaxies over the Galactic extinction map constructed by Schlegel, Finkbeiner & Davis (1998). We select ~10^7 galaxies in total from the Sloan Digital Sky Survey (SDSS) DR7 photometric catalog. We detect clear signatures of the enhancement of the extinction in r-band, $\Delta A_r$, around galaxies, indicating that the extinction map is contaminated by their FIR (far infrared) emission. The average amplitude of the contamination per galaxy is well fitted to $\Delta A_r(m_r) = 0.64 \times 10^{0.17(18-m_r)}$ [mmag]. While this value is very small, it is directly associated with galaxies and may have a systematic effect on galaxy statistics. Indeed this correlated contamination leads to a relatively large anomaly of galaxy surface number densities against the SFD extinction A_SFD discovered by Yahata et al. (2007). We model the radial profiles of stacked galaxy images, and find that the FIR signal around each galaxy does not originate from the central galaxy alone, but is dominated by the contributions of nearby galaxies via galaxy angular clustering. The separation of the single galaxy and the clustering terms enables us to infer the statistical relation of the FIR and r-band fluxes of galaxies and also to probe the flux-weighted cross-correlation of galaxies, down to the magnitudes that are difficult to probe directly for individual objects. We repeat the same stacking analysis for SDSS DR6 photometric quasars and discovered the similar signatures but with weaker amplitudes. The implications of the present results for galaxy and quasar statistics and for correction to the Galactic extinction map are briefly discussed.

Comments: 11 pages, 19 figures, PASJ, 2013, vol65, No.3, in press
Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); Galaxy Astrophysics (astro-ph.GA)
Cite as: arXiv:1212.0307 [astro-ph.CO]
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