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Dark Matter searches targeting Dwarf Spheroidal Galaxies with the Fermi Large Area Telescope
Stockholm University, Faculty of Science, Department of Physics. (Cosmology, Particle astrophysics and String theory)
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis I present our recent work on gamma-ray searches for dark matter with the Fermi Large Area Telescope (Fermi-LAT). We have targeted dwarf spheroidal galaxies since they are very dark matter dominated systems, and we have developed a novel joint likelihood method to combine the observations of a set of targets.

In the first iteration of the joint likelihood analysis, 10 dwarf spheroidal galaxies are targeted and 2 years of Fermi-LAT data is analyzed. The resulting upper limits on the dark matter annihilation cross-section range from about 10−26 cm3 s−1 for dark matter masses of 5 GeV to about 5 × 10−23 cm3 s−1 for dark matter masses of 1 TeV, depending on the annihilation channel. For the first time, dark matter models with a cross section above the canonical thermal relic cross section (∼ 3 × 10−26 cm3 s−1) are strongly disfavored by a gamma-ray experiment. In the second iteration we include 15 dwarf spheroidal galaxies in the combined analysis, employ 4 years of data and an improved calculation of the dark matter density. The obtained upper limits range from about 10−26 cm3 s−1 for dark matter masses of 2 GeV to about 10−21 cm3 s−1 for dark matter masses of 10 TeV, depending on the annihilation channel.

I briefly describe some of the evidence for dark matter, the Fermi-LAT instrument and public data releases, dwarf spheroidal galaxies, likelihood analysis, and results from analyses of Fermi-LAT data. I also document some of the tests made to verify the method and to compare different analysis setups.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University , 2015. , 120 p.
Keyword [en]
dark matter, Fermi-LAT, dwarf spheroidal galaxies
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Physics
Identifiers
URN: urn:nbn:se:su:diva-118905ISBN: 978-91-7649-224-6 (print)OAI: oai:DiVA.org:su-118905DiVA: diva2:842863
Public defence
2015-09-28, FB53, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2015-09-04 Created: 2015-07-21 Last updated: 2015-11-02Bibliographically approved
List of papers
1. Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area Telescope
Open this publication in new window or tab >>Constraining Dark Matter Models from a Combined Analysis of Milky Way Satellites with the Fermi Large Area Telescope
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2011 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, no 24, 241302Article in journal (Refereed) Published
Abstract [en]

Satellite galaxies of the Milky Way are among the most promising targets for dark matter searches in gamma rays. We present a search for dark matter consisting of weakly interacting massive particles, applying a joint likelihood analysis to 10 satellite galaxies with 24 months of data of the Fermi Large Area Telescope. No dark matter signal is detected. Including the uncertainty in the dark matter distribution, robust upper limits are placed on dark matter annihilation cross sections. The 95% confidence level upper limits range from about 10(-26) cm(3) s(-1) at 5 GeV to about 5 x 10(-23) cm(3) s(-1) at 1 TeV, depending on the dark matter annihilation final state. For the first time, using gamma rays, we are able to rule out models with the most generic cross section (similar to 3 x 10(-26) cm(3) s(-1) for a purely s-wave cross section), without assuming additional boost factors.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-70682 (URN)10.1103/PhysRevLett.107.241302 (DOI)000297797700002 ()
Projects
The Fermi-LAT Collaboration
Note

authorCount :152

Available from: 2012-01-23 Created: 2012-01-23 Last updated: 2017-12-08Bibliographically approved
2. Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope
Open this publication in new window or tab >>Dark matter constraints from observations of 25 Milky Way satellite galaxies with the Fermi Large Area Telescope
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2014 (English)In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 89, no 4, 042001Article in journal (Refereed) Published
Abstract [en]

The dwarf spheroidal satellite galaxies of the Milky Way are some of the most dark-matter-dominated objects known. Due to their proximity, high dark matter content, and lack of astrophysical backgrounds, dwarf spheroidal galaxies are widely considered to be among the most promising targets for the indirect detection of dark matter via gamma rays. Here we report on.-ray observations of 25 Milky Way dwarf spheroidal satellite galaxies based on 4 years of Fermi Large Area Telescope (LAT) data. None of the dwarf galaxies are significantly detected in. rays, and we present.-ray flux upper limits between 500 MeV and 500 GeV. We determine the dark matter content of 18 dwarf spheroidal galaxies from stellar kinematic data and combine LAT observations of 15 dwarf galaxies to constrain the dark matter annihilation cross section. We set some of the tightest constraints to date on the annihilation of dark matter particles with masses between 2 GeV and 10 TeV into prototypical standard model channels. We find these results to be robust against systematic uncertainties in the LAT instrument performance, diffuse.-ray background modeling, and assumed dark matter density profile.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:su:diva-106908 (URN)10.1103/PhysRevD.89.042001 (DOI)000339630400001 ()
Projects
Fermi-LAT Collaboration
Note

AuthorCount:121;

Available from: 2014-08-27 Created: 2014-08-26 Last updated: 2017-12-05Bibliographically approved

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