Source population synthesis and the Galactic diffuse gamma-ray emission

Strong, A. W.

doi:10.1007/s10509-007-9480-1

Cited by 53 publications

(49 citation statements)

References 22 publications

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“…These include normal pulsars, as well as populations currently too faint to have had individual members detected by Fermi. The properties of these populations can be constrained by both lowlatitude and high-latitude source count analysis (in the case that individual members have been detected) [63], and also by the anisotropy analysis described in this study. We leave the detailed study of this to future work.…”

Section: Discussionmentioning

confidence: 99%

Anisotropies in the diffuse gamma-ray background measured by the Fermi LAT

et al. 2012

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The contribution of unresolved sources to the diffuse gamma-ray background could induce anisotropies in this emission on small angular scales. We analyze the angular power spectrum of the diffuse emission measured by the Fermi Large Area Telescope at Galactic latitudes jbj > 30 in four energy bins spanning 1-50 GeV. At multipoles ' ! 155, corresponding to angular scales & 2 , angular power above the photon noise level is detected at >99:99% confidence level in the 1-2 GeV, 2-5 GeV, and 5-10 GeV energy bins, and at >99% confidence level at 10-50 GeV. Within each energy bin the measured angular power takes approximately the same value at all multipoles ' ! 155, suggesting that it originates from the contribution of one or more unclustered source populations. The amplitude of the angular power normalized to the mean intensity in each energy bin is consistent with a constant value at all energies, C P =hIi 2 ¼ 9:05 AE 0:84 Â 10 À6 sr, while the energy dependence of C P is consistent with the anisotropy arising from one or more source populations with power-law photon spectra with spectral index À s ¼ 2:40 AE 0:07. We discuss the implications of the measured angular power for gamma-ray source populations that may provide a contribution to the diffuse gamma-ray background.

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Section: Discussionmentioning

confidence: 99%

Anisotropies in the diffuse gamma-ray background measured by the Fermi LAT

et al. 2012

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“…They are often difficult to separate from their clumpy interstellar environment, even with detectable fluxes, because of the limited angular resolution of Fermi -LAT. Populations of faint, unresolved sources, below the detection threshold, may also contaminate the interstellar emission (Ackermann et al 2013a, Strong 2007). It involves mainly young and recycled millisecond pulsars.…”

Section: Populations Of Unresolved γ-Ray Sourcesmentioning

confidence: 99%

The Nine Lives of Cosmic Rays in Galaxies

Grenier

Black

Strong

2015

Annu. Rev. Astron. Astrophys.

317

294

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Cosmic-ray astrophysics has advanced rapidly in recent years, and its impact on other astronomical disciplines has broadened. Many new experiments, measuring the particles both directly in the atmosphere or space, and indirectly via γ rays and synchrotron radiation, have widened the range and quality of the information available on their origin, propagation, and interactions. The impact of low-energy cosmic rays on interstellar chemistry is a fast-developing topic, including the propagation of these particles into the clouds where the chemistry occurs. Cosmic rays, via their γ-ray production, also provide a powerful way to probe the gas content of the interstellar medium. Substantial advances have been made in the observations and modelling of the interplay between cosmic rays and the interstellar medium. Focussing on energies up to 1 TeV, these inter-relating aspects are covered at various levels of detail, giving a guide to the state of the subject. CONTENTS

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“…These residuals can be ascribed to various limitations of the models: (1) imperfections in the modeling of gas and ISRF components, (2) simplified assumptions in the propagation setup (e.g., assumption of isotropy and homogeneity of the diffusion coefficient), (3) unresolved point sources, which are expected to contribute to the diffuse emission at a level of 10% (Strong 2007), and have not been taken into account in the modeling in Ackermann et al (2012b), and (4) missing structures like Loop I (Casandjian et al 2009) or the Galactic Bubbles/Lobes (Su et al 2010). …”

Section: Limitations Of the Modelmentioning

confidence: 99%

CONSTRAINTS ON THE GALACTIC HALO DARK MATTER FROMFERMI-LAT DIFFUSE MEASUREMENTS

Ackermann¹,

Ajello²,

Atwood³

et al. 2012

ApJ

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219

211

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We have performed an analysis of the diffuse gamma-ray emission with the Fermi Large Area Telescope (LAT) in the Milky Way halo region, searching for a signal from dark matter annihilation or decay. In the absence of a robust dark matter signal, constraints are presented. We consider both gamma rays produced directly in the dark matter annihilation/decay and produced by inverse Compton scattering of the e + /e − produced in the annihilation/decay. Conservative limits are derived requiring that the dark matter signal does not exceed the observed diffuse gamma-ray emission. A second set of more stringent limits is derived based on modeling the foreground astrophysical diffuse emission using the GALPROP code. Uncertainties in the height of the diffusive cosmic-ray halo, the distribution of the cosmic-ray sources in the Galaxy, the index of the injection cosmic-ray electron spectrum, and the column density of the interstellar gas are taken into account using a profile likelihood formalism, while the parameters governing the cosmic-ray propagation have been derived from fits to local cosmic-ray data. The resulting limits impact the range of particle masses over which dark matter thermal production in the early universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT cosmic ray anomalies as the annihilation of dark matter.

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Source population synthesis and the Galactic diffuse gamma-ray emission

Cited by 53 publications

References 22 publications

Anisotropies in the diffuse gamma-ray background measured by the Fermi LAT

Anisotropies in the diffuse gamma-ray background measured by the Fermi LAT

The Nine Lives of Cosmic Rays in Galaxies

CONSTRAINTS ON THE GALACTIC HALO DARK MATTER FROMFERMI-LAT DIFFUSE MEASUREMENTS

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