Astronomy and Astrophysics – Astrophysics
Scientific paper
2003-06-23
JCAP 0404:006,2004
Astronomy and Astrophysics
Astrophysics
Accepted for publication in JCAP. Increased sizes of polar regions examined, and added discussion of spectral data. Results un
Scientific paper
10.1088/1475-7516/2004/04/006
Measurements of the diffuse extragalactic gamma-ray background (EGRB) are complicated by a strong Galactic foreground. Estimates of the EGRB flux and spectrum, obtained by modeling the Galactic emission, have produced a variety of (sometimes conflicting) results. The latest analysis of the EGRET data found an isotropic flux I_x=1.45+-0.05 above 100 MeV, in units of 10^-5 s^-1 cm^-2 sr^-1. We analyze the EGRET data in search for robust constraints on the EGRB flux, finding the gamma-ray sky strongly dominated by Galactic foreground even at high latitudes, with no conclusive evidence for an additional isotropic component. The gamma-ray intensity measured towards the Galactic poles is similar to or lower than previous estimates of I_x. The high latitude profile of the gamma-ray data is disk-like for 40<|b[deg]|<70, and even steeper for |b|>70; overall it exhibits strong Galactic features and is well fit by a simple Galactic model. Based on the |b|>40 data we find that I_x<0.5 at a 99% confidence level, with evidence for a much lower flux. We show that correlations with Galactic tracers, previously used to identify the Galactic foreground and estimate I_x, are not satisfactory; the results depend on the tracers used and on the part of the sky examined, because the Galactic emission is not linear in the Galactic tracers and exhibits spectral variations across the sky. The low EGRB flux favored by our analysis places stringent limits on extragalactic scenarios involving gamma-ray emission, such as radiation from blazars, intergalactic shocks and production of ultra-high energy cosmic rays and neutrinos. We suggest methods by which future gamma-ray missions such as GLAST and AGILE could indirectly identify the EGRB.
Keshet Uri
Loeb Abraham
Waxman Eli
No associations
LandOfFree
The Case for a Low Extragalactic Gamma-ray Background does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Case for a Low Extragalactic Gamma-ray Background, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Case for a Low Extragalactic Gamma-ray Background will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-513948