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Constraints on dark matter annihilation by radio observations of M31

Egorov, A. E. and Pierpaoli, E. (2013) Constraints on dark matter annihilation by radio observations of M31. Physical Review D, 88 (2). Art. No. 023504. ISSN 2470-0010. doi:10.1103/PhysRevD.88.023504.

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We used radio observations of the neighbor galaxy M31 in order to put constraints on the dark matter particle mass and annihilation cross section. Dark matter annihilation in M31 halo produces highly energetic leptons, which emit synchrotron radiation on radio frequencies in the galactic magnetic field. We predicted expected radio fluxes for the two annihilation channels: χχ→bb̅ and χχ→τ^+τ^-. We then compared them with available data on the central radio emission of M31 as observed by four radio surveys: VLSS (74 MHz), WENSS (325 MHz), NVSS (1400 MHz), and GB6 (4850 MHz). Assuming a standard Navarro-Frenk-White dark matter density profile and a conservative magnetic field distribution inside the Andromeda galaxy, we find that the thermal relic annihilation cross section or higher ⟨σv⟩≥3×10^(-26)  cm^3/s are only allowed for weakly interacting massive particle masses greater than ≈100 and ≈55  GeV for annihilation into bb̅ and τ^+τ^-, respectively. Taking into account potential uncertainties in the distributions of dark matter density and the magnetic field, the mentioned weakly interacting massive particle limiting masses can be as low as 23 GeV for both channels, and as high as 280 and 130 GeV for annihilation into bb̅ and τ^+τ^-, respectively. These mass values exceed the best up-to-date known constraints from Fermi gamma observations: 40 and 19 GeV, respectively [A. Geringer-Sameth and S. M. Koushiappas, Phys. Rev. Lett. 107 241303 (2011)]. Precise measurements of the magnetic field in the relevant region and better reconstruction of the dark matter density profile of M31 will be able to reduce the uncertainties of our exclusion limits.

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Pierpaoli, E.0000-0002-7957-8993
Additional Information:© 2013 American Physical Society. Received 29 March 2013; published 2 July 2013. We would like to thank Wendy Lane, the Principal Investigator of the VLSS radio survey, for valuable discussions regarding observational aspects. Also, we are grateful to Jennifer Siegal-Gaskins for generally useful feedback. E. P. acknowledges support from JPL-Planck Subcontract No. 1290790. E. P. and A. E. E. were partially supported by NASA Grant No. NNX07AH59G. We acknowledge the use of the Legacy Archive for Microwave Background Data Analysis (LAMBDA), part of the High Energy Astrophysics Science Archive Center (HEASARC). HEASARC/LAMBDA is a service of the Astrophysics Science Division at the NASA Goddard Space Flight Center [7]. Note added in proof.—While our work was in preparation, the newer study [34] of the M31 dark halo was published. This study reported a quite similar value for the M_100 and c_100 ≈ 17 for the NFW profile. Since the value quoted for the concentration is in between the ones we considered, the implied constraints would lie within our current uncertainty regions for the case of the NFW profile.
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Issue or Number:2
Classification Code:PACS: 95.35.+d, 95.85.Bh, 98.56.Ne
Record Number:CaltechAUTHORS:20130814-142138433
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:39916
Deposited On:15 Aug 2013 14:09
Last Modified:09 Nov 2021 23:48

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