Optical Imaging of HI-selected Local Group Galaxy Candidates with pODI
Abstract
A long standing problem in cosmology is the mismatch between the number of low mass dark matter halos predicted by simulations and the number of low mass galaxies observed in the Local Group. We recently presented a set of isolated ultra-compact high velocity clouds (UCHVCs) identified within the dataset of the Arecibo Legacy Fast ALFA (ALFALFA) HI line survey that are consistent with representing low mass gas bearing dark matter halos within the Local Group (Adams et al. 2013). At distances of ~1 Mpc, the UCHVCs have HI masses of ~10^5 Msun and indicative dynamical masses of ~10^7 Msun. The HI diameters of the UCHVCs range from 4' to 20', or 1 to 6 kpc at a distance of 1 Mpc. We have selected the most compact and isolated UCHVCs with the highest average column densities as representing the best galaxy candidates. We are undertaking an imaging campaign using pODI on the WIYN 3.5m telescope to search for resolved stellar counterparts to these UCHVCs. The central coverage region of pODI is well matched to the HI size of the UCHVCs and the outlying detectors allow a constraint on foreground and background contamination. Our g'- and i'-band observations allow us to probe to ~1.5 magnitude below the tip of the red giant branch out to distances of ~1 Mpc. We present preliminary results from the broadband imaging and discuss constraints on the stellar population of these objects. This work has been supported by NSF grants AST-0607007 and AST-1107390, grants from the Brinson Foundation, and a NSF GRFP.
- Publication:
-
American Astronomical Society Meeting Abstracts
- Pub Date:
- June 2013
- Bibcode:
- 2013AAS...22221416A