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A latitude-dependent analysis of the leptonic hypothesis for the Fermi Bubbles

Journal Article · · Monthly Notices of the Royal Astronomical Society
DOI:https://doi.org/10.1093/mnras/stx577· OSTI ID:1535677
 [1];  [2]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Center for Theoretical Physics; DOE/OSTI
  2. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Center for Theoretical Physics
+ Show Author Affiliations
The Fermi Bubbles are giant Galactic structures observed in both gamma-rays and microwaves. Recent studies have found support for the hypothesis that the gamma-ray and microwave emission can both be understood as arising from a hard cosmic ray electron population within the volume of the Bubbles, via inverse Compton scattering and synchrotron radiation, respectively. The relative rates of these processes are set by the relative energy density of the interstellar radiation field and the magnetic field within the Bubbles; consequently, under the hypothesis of a common origin, the combination of the gamma-ray and microwave measurements can be used to estimate the magnetic field within the Bubbles. We revisit the consistency of this hypothesis on a latitude-by-latitude basis, using data from Fermi, WMAP and Planck; estimate the variation of the electron spectrum within the Bubbles; and infer bounds on the magnetic field within the Bubbles as a function of distance from the Galactic plane. We find that while the microwave and gamma-ray spectra are generally consistent with the leptonic hypothesis for few-microGauss magnetic fields, there appears to be a preference for spectral hardening in the microwaves at mid-latitudes (especially in the $|b|$ ~ 25°–35° range) that is not mirrored in the gamma-rays. This result may hint at a non-leptonic contribution to the gamma-ray spectra; however, the discrepancy can be reconciled in purely leptonic models if the cut-off energy for the electrons is lower in this latitude range and the spectrum below the cut-off is harder.
Research Organization:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Grant/Contract Number:
SC0013999
OSTI ID:
1535677
Report Number(s):
MIT--CTP/4788
Journal Information:
Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 3 Vol. 468; ISSN 0035-8711
Publisher:
Royal Astronomical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (4)

Fermi bubbles: high-latitude X-ray supersonic shell journal June 2018
Detection of Nonthermal Hard X-Ray Emission from the “Fermi Bubble” in an External Galaxy journal February 2019
The Large-scale Ionization Cones in the Galaxy journal November 2019
Detection of non-thermal hard X-ray emission from the "Fermi bubble" in an external galaxy text January 2019

Figures / Tables (25)

Figure 1.(p. 5)figure Figure 1.
Figure 2.(p. 5)figure Figure 2.
Figure 3.(p. 6)figure Figure 3.
Figure 4.(p. 9)figure Figure 4.
Figure 5.(p. 10)figure Figure 5.
Figure 6.(p. 11)figure Figure 6.
Figure 7.(p. 11)figure Figure 7.
Figure 8.(p. 11)figure Figure 8.
Figure 9.(p. 12)figure Figure 9.
Table 1.(p. 13)table Table 1.
Figure 10.(p. 14)figure Figure 10.
Figure 11.(p. 15)figure Figure 11.
Figure 12.(p. 15)figure Figure 12.
Table 2.(p. 16)table Table 2.
Figure A1.(p. 17)figure Figure A1.
Table A1.(p. 17)table Table A1.
Figure B1.(p. 18)figure Figure B1.
Figure B2.(p. 18)figure Figure B2.
Figure B3.(p. 19)figure Figure B3.
Table C1.(p. 19)table Table C1.
Table C2.(p. 19)table Table C2.
Figure C1.(p. 20)figure Figure C1.
Figure C2.(p. 21)figure Figure C2.
Figure D1.(p. 21)figure Figure D1.
Figure D2.(p. 22)figure Figure D2.

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Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ISM: jets and outflows
fermi bubbles
gamma-rays: ISM
radio continuum: ISM