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Abstract: We present a multi-wavelength analysis of candidate Active Galactic Nuclei (AGNs) in dwarf galaxies in the local universe with the aim of improving constraints on the occupation fraction of accreting central black holes (BHs) in low-mass galaxies. Dwarf galaxies are particularly interesting hosts for AGNs as they may contain BHs that have not grown significantly since the epoch of their formation in the early Universe. We primarily rely on X-ray data to identify our sources and then follow up with optical-infrared data. Using detections from the Chandra X-ray Observatory, we find three X-ray luminous dwarf galaxies and we assess their candidacy as AGNs with standard multi-wavelength diagnostics. One of these sources is variable in the X-ray and we are able to observe it in a low- and high-flux phase, essential for studying AGN mechanisms. We fit various star-forming, dust emission, and AGN templates to the spectral energy distributions (SEDs). The star formation rates estimated from the SED fits are unable to explain the observed X-ray luminosities of the candidates, providing more support for the presence of AGNs. To estimate the masses of the central BHs, we employ various scaling relations, in particular the relationship between BH mass and stellar velocity dispersion. The masses are found to be MBH ~ 105 - 106 Msun in the intermediate-mass black hole (IMBH) regime. Finally, by studying the deviation from the linear relationships between X-ray and mid-infrared luminosities we find these systems to be significantly obscured. The BH masses allow us to compute the Eddington limit and we find that the BHs are rapidly accreting and have high Eddington ratios. Studying dwarf galaxies, AGNs, and IMBHs can help us understand the formation and co-evolution of galaxies-BHs in the early Universe and can also shed light on probable BH seeds. This is the first study of AGNs in dwarf galaxies in the Bootes field and the first to estimate occupation fractions of AGNs-hosting-IMBHs in the local universe.

Advisor: Professor Ryan Hickox

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https://dartmouth.zoom.us/j/93657781084?pwd=NkJLYS9JMjRvMFpKbll6Ym9kVHE0Zz09

Meeting ID: 936 5778 1084
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