## Dissertations, Master's Theses and Master's Reports

2015

#### Document Type

Open Access Dissertation

#### Degree Name

Doctor of Philosophy in Physics (PhD)

Department of Physics

Petra Huentemeyer

Brian Fick

Robert Nemiroff

Robert Pastel

#### Abstract

Cosmic rays, with an energy density of $\sim1\,\text{eV}\,\text{cm}^{-3}$, play an important role in the evolution of our Galaxy. Very high energy (TeV) gamma rays provide unique information about the acceleration sites of Galactic cosmic rays. The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is an all-sky surveying instrument sensitive to gamma rays from 100\:GeV to 100\:TeV with a 2\,steradian instantaneous field of view and a duty cycle of $>95\%$. The array is located in Sierra Negra, Mexico at an elevation of 4,100\,m and was inaugurated in March 2015. Thanks to its modular design, science operation began in Summer 2013 with one third of the array. Using this data, a survey of the inner Galaxy region of Galactic longitude $l\in [+15\degree,\,+50\degree]$ and latitude $b\in[-4\degree,\,+4\degree]$ is performed. To address the ambiguities arising from unresolved sources in the data, a maximum likelihood technique is used to identify point source candidates. Ten sources and candidate sources are identified in this analysis. Eight of these are associated with known TeV sources but not all have differential fluxes compatible with previous measurements. Three sources are detected with significances $>5\,\sigma$ after accounting for statistical trials, and are associated with known TeV sources. With data taken with the full array and improved reconstruction algorithms, the significance on the Crab nebula increases from $3.1\,\sigma/\sqrt{\text{day}}$ to $5.5\,\sigma/\sqrt{\text{day}}$, which allows more sensitive sky surveys and more precise spectral and morphological analyses on individual sources.

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