Abstract Details
| Name: Sayan Biswas Affiliation: Bose Institute Conference ID: ASI2016_539 Title : Searching for signatures of dark matter annihilation from low surface brightness galaxies using FERMI gamma ray data Authors and Co-Authors : Pooja Bhattacharjee (Bose Institute, Kolkata, India), Pratik Majumdar (Saha Institute of Nuclear Physics, Kolkata, India), Mousumi Das (Indian Institute of Astrophysics, Bengaluru, India), Partha S. Joarder (Bose Institute, Kolkata, India), Pijushpani Bhattacharjee (Saha Institute of Nuclear Physics, Kolkata, India) Abstract Type : Poster Abstract Category : Extragalactic astronomy Abstract : The physical nature of dark matter remains enigmatic even in these days of the advent of modern physics and astrophysics. Recent experimental evidences as well as theoretical arguments favor the existence of some form of non-baryonic cold dark matter (CDM) for explaining large scale structure of the Universe. Although such dark matter is supposed to constitute about one fourth of the total energy density of the Universe, its exact nature is not yet understood. Weakly interacting massive particles (WIMPs), predicted in several theories beyond the Standard Model (of particle physics), are the most probable candidates for CDM. Pair annihilation (or decay) of WIMPs would yield particles such as neutrinos, (anti-) protons and electron-positron pairs simultaneously producing a significant flux of high energy gamma rays. Low surface brightness (LSB) galaxies are one of the most dark matter dominated galaxies that we know of. Hence these galaxies are ideal laboratories for indirect dark matter search through the observations of dark matter (or decay) products. In t his paper, we have chosen a set of LSB galaxies and analyzed the FERMI data, obtained from these galaxies over approximately seven years, in the energy range 100 MeV to 50 GeV. We have determined the upper limits of gamma ray fluxes from those sources by fitting the data with spectra of appropriate power-law behavior. The theoretically possible gamma ray fluxes originating from WIMP annihilation in each of such sources can be divided into two factors, namely, the ``astrophysical factor'' and the ``particle physics factor''. Here, the astrophysical factors pertaining to each LSB galaxy are calculated by taking a standard dark matter density profile and the corresponding halo properties into account. These astrophysical factors are further used to calculate the particle physics factors so that a plausible (theoretical) upper limit of gamma ray flux due to the annihilation of WIMPs in each of the LSB galaxies, examined in this paper, is finally obtained. Such comparisons between theoretical and observational upper limits of gamma ray fluxes from LSB galaxies would hopefully be useful to put constraints on the pair-annihilation cross section of WIMPs in various widely studied extensions of the standard model including its supersymmetric extensions. The gamma ray limits presented by us may also constrain some WIMP models proposed to explain FERMI and PAMELA electron-positron data. |