PI: David M. Meyer, Northwestern University, email@example.com
Address: Department of Physics and Astronomy, 2145 Sheridan Road, Evanston, IL 60208, USA
CoI: James T. Lauroesch, Northwestern University
CoI: Katherine C. Roth, Gemini Observatories
Title: Compact High-Velocity Na I Clouds around M81
Abstract: The origin of the compact high-velocity clouds (CHVCs) seen in H I 21 cm emission has received considerable interest due to the possibility that they may trace the ``missing'' dark matter satellites around the Milky Way expected from (Lambda)CDM cosmologies. A key test would be the detection of a similar population of CHVCs around other galaxies. However, such a test (particularly beyond the Local Group) is beyond the resolution and sensitivity of current 21 cm surveys. Recently, we obtained WIYN DensePak spectra of the Na I D absorption toward the core of M81 at 4\arcsec resolution which reveal small-scale, high-velocity absorption components. From the perspective of the M81 core, these Na I clouds would appear to be infalling CHVCs. We propose to obtain long- slit echelle Na I observations of these clouds at higher spatial and spectral resolution. Our primary goals include determining if the cuspiness of the strongest absorber extends to smaller scales and looking for evidence of head-tail structures similar to some Galactic CHVCs.
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