Jeremy Bradford edited Introduction.tex  over 9 years ago

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Supermassive black holes (BHs) inhabit the centers of essentially all massive galaxies with bulges, however we do not know how the initial "seed" BHs formed in the early Universe or in what types of galaxies they formed. Observations of present-day dwarf galaxies hosting massive BHs, while apparently rare, can place valuable constraints on the hosts and formation mechanism of BH seeds. Using optical spectroscopy from the SDSS, we have systematically assembled the largest sample of dwarf galaxies hosting massive BHs to date (Reines et al. 2013). These dwarf galaxies have stellar masses comparable to the Magellanic Clouds ($M_{\rm stellar} ∼ 10^{8.5} − 10^{9.5} M_{\odot}$) and contain some of the least-massive BHs known in galaxy nuclei ($M_{\rm BH} ∼ 10^5 M_{\odot}$).  To \textbf{We propose new 21 cm neutral hydrogen (HI) emission observations to  study the properties of the least-massive and physically smallest galaxies known to contain massive BHs, \textbf{we propose new 21 cm neutral hydrogen (HI) emission observations}. BHs}.  These observations will enable us to investigate host galaxy properties and BH HI scaling relations at the sparsely-populated low-mass end. We will compare the gas content and scaling relations of our BH sample against the isolated dwarf control sample of Bradford et al., in prep. The results of our study will provide vital information on the demographics of the smallest galaxies hosting massive BHs, with implications for the origin of supermassive BH seeds as well as the effect of AGN feedback on the cold gas content of dwarf galaxies.