DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA

By F. Acero, M. Ackermann, M. Ajello, A. Albert, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, E. Bissaldi and 124 more. 2016

377 citations recorded by the source corpus.

Most of the celestial γ rays detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope originate from the interstellar medium when energetic cosmic rays interact with interstellar nucleons and photons. Conventional point-source and extended-source studies rely on the modeling of this diffuse emission for accurate characterization. Here, we describe the development of the Galactic Interstellar Emission Model (GIEM), which is the standard adopted by the LAT Collaboration and is publicly available. This model is based on a linear combination of maps for interstellar gas column density in Galactocentric annuli and for the inverse-Compton emission produced in the Galaxy. In the GIEM, we also include large-scale structures like Loop I and the Fermi bubbles. The measured gas emissivity spectra confirm that the cosmic-ray proton density decreases with Galactocentric distance beyond 5 kpc from the Galactic Center. The measurements also suggest a softening of the proton spectrum with Galactocentric distance. We observe that the Fermi bubbles have boundaries with a shape similar to a catenary at latitudes below 20° and we observe an enhanced emission toward their base extending in the north and south Galactic directions and located within ∼4° of the Galactic Center.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/378b56481cf2bba078743e36d5649d7bc9206c4f

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

The Search for Spatial Extension in High-latitude Sources Detected by the Fermi Large Area Telescope (2018, methodology): “Thermal dust emission has been shown to be correlated with components of the ISM, and the Planck τ353 map provides much better information than the ISM tracers used for the official Fermi IEM (Acero et al. 2016a).”
Cosmic-ray propagation with DRAGON2: I. numerical solver and astrophysical ingredients (2016, background): “This high-energy excess is the signature of a harder CR spectrum in the inner Galactic plane, as shown also in [15, 66, 67]; according to [68] the hardening can be explained by a progressively harder scaling of the diffusion coefficient in the inner Galaxy (see appendix C.”
The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2 (2018, background): “One major caveat is that the Galactic diffuse template provided by the Fermi Collaboration already absorbs extended excess emission on scales larger than about 2 ◦ (Acero et al. 2016), and so it is possible that Ant 2 has already been included in the background model.”
Sensitivity projections for dark matter searches with the Fermi large area telescope (2016, background): “On the other hand, it is reasonable to assume that variations in the cosmic-ray nuclei spectra are mild on the characteristic scale of interstellar gas complexes due to the moderate energy losses in propagation, so that the γ-ray emission from their mutual interactions can be assumed to be proportio”
MINUTE-TIMESCALE >100 MeV γ-RAY VARIABILITY DURING THE GIANT OUTBURST OF QUASAR 3C 279 OBSERVED BY FERMI-LAT IN 2015 JUNE (2016, methodology): “Additionally, the model included the isotropic and Galactic diffuse emission components55(Acero et al. 2016), with fixed normalizations during the fitting.”
The Fermi Galactic Center GeV Excess and Implications for Dark Matter (2017, methodology): “In the derivation of the new lists of PS, we did not account for large-scale residuals, as done, e.g., in Acero et al. (2016) for the derivation of the 3FGL catalog, or specifically for an excess near the GC.”
Fermi Large Area Telescope Fourth Source Catalog (2019, methodology): “They contain SNRs (Kes 73, Kes 79, and G42.”