Strong evidence that the galactic bulge is shining in gamma rays

Oscar Macias; Shunsaku Horiuchi; Manoj Kaplinghat; Chris Gordon; Roland M. Crockery; David M. Nataf

doi:10.1088/1475-7516/2019/09/042

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Strong evidence that the galactic bulge is shining in gamma rays

Journal article

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Strong evidence that the galactic bulge is shining in gamma rays

Oscar Macias, Shunsaku Horiuchi, Manoj Kaplinghat, Chris Gordon, Roland M. Crockery and David M. Nataf

Journal of cosmology and astroparticle physics, Vol.2019(9), pp.42-42

09/20/2019

DOI: 10.1088/1475-7516/2019/09/042

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https://arxiv.org/pdf/1901.03822View

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Abstract

There is growing evidence that the Galactic Center Excess identified in the Fermi-LAT gamma-ray data arises from a population of faint astrophysical sources. We provide compelling supporting evidence by showing that the morphology of the excess traces the stellar over-density of the Galactic bulge. By adopting a template of the bulge stars obtained from a triaxial 3D fit to the diffuse near-infrared emission, we show that it is detected at high significance. The significance deteriorates when either the position or the orientation of the template is artificially shifted, supporting the correlation of the gamma-ray data with the Galactic bulge. In deriving these results, we have used more sophisticated templates at low-latitudes for the Fermi bubbles compared to previous work and the three-dimensional Inverse Compton (IC) maps recently released by the GALPROP team. Our results provide strong constraints on Millisecond Pulsar (MSP) formation scenarios proposed to explain the excess. We find that an admixture formation scenario, in which some of the relevant binaries are primordial and the rest are formed dynamically, is preferred over a primordial-only formation scenario at 7.6 sigma confidence level. Our detailed morphological analysis also disfavors models of the disrupted globular clusters scenario that predict a spherically symmetric distribution of MSPs in the Galactic bulge. For the first time, we report evidence of a high energy tail in the nuclear bulge spectrum that could be the result of IC emission from electrons and positrons injected by a population of MSPs and star formation activity from the same site.

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Astronomy & Astrophysics

Physics, Particles & Fields

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Details

Title: Subtitle: Strong evidence that the galactic bulge is shining in gamma rays
Creators: Oscar Macias - Virginia Tech
Shunsaku Horiuchi - Virginia Tech
Manoj Kaplinghat - University of California, Irvine
Chris Gordon - University of Canterbury
Roland M. Crockery - ACT
David M. Nataf - Johns Hopkins University
Resource Type: Journal article
Publication Details: Journal of cosmology and astroparticle physics, Vol.2019(9), pp.42-42
DOI: 10.1088/1475-7516/2019/09/042
ISSN: 1475-7516
eISSN: 1475-7516
Publisher: Iop Publishing Ltd
Number of pages: 33
Grant note: World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT) Allan C. and Dorothy H. Davis Fellowship PHY1620638 / NSF; National Science Foundation (NSF) JP17H04836; JP18H04340; JP18H04578 / JSPS KAKENHI; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT); Japan Society for the Promotion of Science; Grants-in-Aid for Scientific Research (KAKENHI) de-sc0018327 / U.S. Department of Energy; United States Department of Energy (DOE)
Language: English
Date published: 09/20/2019
Academic Unit: Physics and Astronomy
Record Identifier: 9984701830502771

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