PI: Shobita Satyapal, George Mason University, email@example.com
Address: Physics Department, 4400 Univ Dr, Fairfax, VA 22030, USA
CoI: Anil Seth, University of Utah
CoI: Nathan Secrest, George Mason University
CoI: Torsten Boeker, ESA, ESTEC
Title: The Lowest Mass Supermassive Black Hole in the Universe? The Gemini View of NGC 4178
Abstract: We propose \it GMOS-N long-slit optical observations of the nearby (d=16.8 Mpc) bulgeless disk galaxy NGC4178, which has been recently discovered by \it Spitzer to show prominent high ionization [NeV] emission thus far exclusively associated in extragalactic sources with AGNs. If the AGN is confirmed in this object, NGC4178 will be an exceptional source, since it will be one of only 3 known completely bulgeless disk (Hubble type Sd) galaxies with a supermassive black hole. Our \it Spitzer observations, together with recently obtained \it Chandra and archival \it VLA observations, suggests that NGC 4178 is the most luminous AGN known in a bulgeless disk galaxy, with a supermassive black hole mass that is possibly the lowest known in the Universe. While the \it Spitzer detection of the [NeV] line strongly suggests that NGC4178 harbors an AGN, [NeV] emission can originate in shock-heated gas produced by starburst-driven winds. The proposed \it GMOS observations, together with our recently obtained \it Chandra observations, are critical to: 1) confirm the AGN and constrain its location, 2) characterize its emission line properties, and 3) search for faint broad lines that can be used to constrain the black hole mass. \em We note that our target can also be observed with GMOS-S without compromising our science requirements.
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