[PDF] Mapping Correlation Of A Simulated Dark Matter Source And A Point Source In The Gamma Ray Sky Oral Presentation eBook

Author :
Publisher :
Page : 19 pages
File Size : 49,78 MB
Release : 2015
Category :
ISBN :

GET BOOK

In my research, I analyzed how two gamma-ray source models interact with one another when optimizing to fit data. This is important because it becomes hard to distinguish between the two point sources when they are close together or looking at low energy photons. The reason for the first is obvious, the reason why they become harder to distinguish at lower photon energies is the resolving power of the Fermi Gamma-Ray Space Telescope gets worse at lower energies. When the two point sources are highly correlated (hard to distinguish between), we need to change our method of statistical analysis. What I did was show that highly correlated sources have larger uncertainties associated with them, caused by an optimizer not knowing which point source's parameters to optimize. I also mapped out where their is high correlation for 2 different theoretical mass dark matter point sources so that people analyzing them in the future knew where they had to use more sophisticated statistical analysis.

Author :
Publisher :
Page : 6 pages
File Size : 29,67 MB
Release : 2015
Category :
ISBN :

GET BOOK

The Fermi Gamma-Ray Space Telescope has been taking data on high energy photons or [gamma] rays since June 11th, 2008, and people have been cataloging and profiling point sources of these [gamma] rays ever since. After roughly one year of being in operation over 1400 sources were cataloged. Now, in 2015 we have 3033 sources cataloged. With the increasing amount of sources it's important to think about the limitations of likelihood analysis for highly correlated sources. In this paper I will present the problems of using likelihood analysis for sources that are highly correlated as well as show under what circumstances sources can be considered highly correlated. Dark matter over densities may show up as a point source, so it is a necessary step to learn how the two signals will interact to allow for a proper search for dark matter.

Author : Wang Ping
Publisher : Stanford University
Page : 167 pages
File Size : 25,74 MB
Release : 2011
Category :
ISBN :

GET BOOK

This thesis focuses on the search for unknown dark matter (DM) satellites in the Milky Way using the Fermi Large Area Space Telescope (LAT). The Fermi Gamma-ray Space Telescope (Fermi) is a next generation space observatory, which was successfully launched on June 11th, 2008. The LAT is the principal scientific instrument onboard. Its unprecedented angular resolution and sensitivity in the 100 MeV to > 300 GeV energy range makes it an excellent instrument for probing the sky for DM satellites. Current N-body simulations based on the Lambda-CDM cosmology model predict a large number of as yet unobserved DM satellites in our galaxy; some satellites are predicted to be extended sources (> 1deg extension) as seen by the LAT. Our work assumes that a significant component of DM is a Weakly Interacting Massive Particle (WIMP) in the 100 GeV mass range. The annihilation of WIMPs results in many high energy gamma rays that can be well measured by the LAT. The WIMP produced gamma-ray spectrum from the putative DM satellites is considerably harder than most astrophysical sources. Also, DM satellites have no astronomical counterparts in the X-ray and radio bands, and the emission has no time variability. My thesis will focus on a blind analysis in the search for unknown DM satellites using one year of LAT data, and setting constraints on some WIMP models based on the results of our analysis in which we find no candidates.

Author :
Publisher :
Page : 4 pages
File Size : 32,50 MB
Release : 2011
Category :
ISBN :

GET BOOK

We discuss the possibility of GLAST detecting gamma-rays from the annihilation of neutralino dark matter in the Galactic halo. We have used 'Via Lactea', currently the highest resolution simulation of cold dark matter substructure, to quantify the contribution of subhalos to the annihilation signal. We present a simulated allsky map of the expected gamma-ray counts from dark matter annihilation, assuming standard values of particle mass and cross section. In this case GLAST should be able to detect the Galactic center and several individual subhalos. One of the most exciting discoveries that the Gamma-ray Large Area Space Telescope (GLAST) could make, is the detection of gamma-rays from the annihilation of dark matter (DM). Such a measurement would directly address one of the major physics problems of our time: the nature of the DM particle. Whether or not GLAST will actually detect a DM annihilation signal depends on both unknown particle physics and unknown astrophysics theory. Particle physics uncertainties include the type of particle (axion, neutralino, Kaluza-Klein particle, etc.), its mass, and its interaction cross section. From the astrophysical side it appears that DM is not smoothly distributed throughout the Galaxy halo, but instead exhibits abundant clumpy substructure, in the form of thousands of so-called subhalos. The observability of DM annihilation radiation originating in Galactic DM subhalos depends on their abundance, distribution, and internal properties. Numerical simulations have been used in the past to estimate the annihilation flux from DM substructure, but since the subhalo properties, especially their central density profile, which determines their annihilation luminosity, are very sensitive to numerical resolution, it makes sense to re-examine their contribution with higher resolution simulations.

Author :
Publisher :
Page : 2 pages
File Size : 33,63 MB
Release : 2007
Category :
ISBN :

GET BOOK

We present methods for the analysis of dark matter annihilation in the smooth halo of the Milky Way galaxy. We model the diffuse gamma-ray background using GALPROP, and model the halo using an NFW profile and the gamma-ray spectrum for WIMP pair annihilation. We plan to combine these models with the point source catalog and a simple model for the extragalactic gamma ray background. Using the downhill simplex method to converge on the maximum likelihood value, we can vary key parameters in these models and fit them to the gamma-ray data. Through the use of the Markov Chain Monte Carlo (MCMC) method we can then map out the likelihood as a function of the model parameters to estimate the correlated errors on these parameters.

Author :
Publisher :
Page : 8 pages
File Size : 39,12 MB
Release : 2007
Category :
ISBN :

GET BOOK

The GLAST satellite mission will study the gamma ray sky with considerably greater exposure than its predecessor EGRET. In addition, it will be capable of measuring the arrival directions of gamma rays with much greater precision. These features each significantly enhance GLAST's potential for identifying gamma rays produced in the annihilations of dark matter particles. The combined use of spectral and angular information, however, is essential if the full sensitivity of GLAST to dark matter is to be exploited. In this paper, we discuss techniques for separating dark matter annihilation products from astrophysical backgrounds, focusing on the Galactic Center region, and perform a forecast for such an analysis. We consider both point-like and diffuse astrophysical backgrounds and model them using a realistic point-spread-function for GLAST. While the results of our study depend on the specific characteristics of the dark matter signal and astrophysical backgrounds, we find that in many scenarios it is possible to successfully identify dark matter annihilation radiation, even in the presence of significant astrophysical backgrounds.

Author :
Publisher :
Page : 6 pages
File Size : 50,94 MB
Release : 2015
Category :
ISBN :

GET BOOK

The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view detector sensitive to 100 GeV - 100 TeV gamma rays and cosmic rays. Located at an elevation of 4100 m on the Sierra Negra mountain in Mexico, HAWC observes extensive air showers from gamma and cosmic rays with an array of water tanks which produce Cherenkov light in the presence of air showers. With a field-of-view capable of observing 2/3 of the sky each day, and a sensitivity of 1 Crab/day, HAWC will be able to map out the sky in gamma and cosmic rays in detail. In this paper, we discuss the capabilities of HAWC to map out the directions and spectra of TeV gamma rays and cosmic rays coming from sources of dark matter annihilation. We discuss the HAWC sensitivity to multiple extended sources of dark matter annihilation and the possibility of HAWC observations of annihilations in nearby dark matter subhalos.