Combined 22 23 odiandgalex wslit obsnames

Erik Tollerud

and 4 more

INTRODUCTION The properties of faint dwarf galaxies at or beyond the outer reaches of the Local Group (1 − 5 Mpc) probe the efficiency of environmentally driven galaxy formation processes and provide direct tests of cosmological predictions \citep[e.g., ][]{kl99ms, moo99ms, stri08commonmass, krav10satrev, kirby10, BKBK11, pontzen12, geha13}. However, searches for faint galaxies suffer from strong luminosity and surface brightness biases that render galaxies with LV ≲ 10⁶ L⊙ difficult to detect beyond the Local Group . Because of these biases, searching for nearby dwarf galaxies with methodologies beyond the standard optical star count methods are essential. This motivates searches for dwarf galaxies using the 21 cm emission line of neutral hydrogen (). While such searches cannot identify passive dwarf galaxies like most Local Group satellites, which lack , they have the potential to find gas-rich, potentially starforming dwarf galaxies. This is exemplified by the case of the Leo P dwarf galaxy, found first in and later confirmed via optical imaging . Here we describe two faint dwarf galaxies identified via emission in the first data release of the Galactic Arecibo L-band Feed Array (GALFA-HI) survey . As described below, they are likely within the Local Volume (<10 Mpc) but just beyond the Local Group (≳1 Mpc), so we refer to them as Pisces A and B. This paper is organized as follows: in Section [sec:data], we present the data used to identify these galaxies. In Section [sec:distance], we consider possible distance scenarios, while in Section [sec:conc] we provide context and some conclusions. Where relevant, we adopt a Hubble constant of $H_0=69.3 \; {\rm km \; s}^{-1}{\rm Mpc}^{-1}$ from WMAP9 .
Bpt arecibo v2

Jeremy Bradford

and 3 more

INTRODUCTION Supermassive black holes (BHs) live at the heart of essentially all massive galaxies with bulges. BHs power active galactic nuclei (AGN) and are thought to be important agents in the evolution of their hosts. Using optical spectroscopy from the SDSS, WE HAVE ASSEMBLED THE LARGEST SAMPLE OF LOW MASS (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 ($M_{\rm BH} ∼ 10^5 M_{\odot}$). Determining the impact of AGN on thier low-mass host galaxies will help constrain BH feedback and galaxy formation models at all mass scales. WE PROPOSE NEW 21 CM NEUTRAL HYDROGEN (HI) EMISSION OBSERVATIONS TO STUDY THE PROPERTIES OF THE LEAST-MASSIVE GALAXIES KNOWN TO CONTAIN MASSIVE BHS. By examining BH to HI scaling relations at the sparsely-populated low-mass end, these new observations will enable us to inspect the correlation of gas content and dynamical masses to the BH and galaxy properties of our BH hosts. In order to separate the effects of AGN feedback from environmental effects, we will compare our isolated dwarf galaxies that host BHs against the isolated control sample of Bradford, et al., (in prep.). The results of our study will provide vital information on the formation and evolution of the smallest galaxies hosting massive BHs as well as the effect of AGN feedback on the cold HI gas content of low mass galaxies.