AAS 198th Meeting, June 2001
Session 89. Observing with the Upgraded Arecibo Telescope: Methods and Recent Results
Special Session Oral, Thursday, June 7, 2001, 2:00-3:30pm, C105

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[89.05] Arecibo Mapping of HI in High--Velocity Clouds and Dwarf Galaxies

T. Robishaw, J.D. Simon, L. Blitz, C.E. Heiles (University of California at Berkeley)

We have made high--resolution, wide--field H\rm\scriptstyle I images of High--Velocity Clouds (HVCs) and Local Group dwarf galaxies using the upgraded Arecibo telescope. Each map covers an area of ~1 square degree at a resolution of 3 arcmin; previous observations were generally either high--resolution or wide--field, but not both. Integration times were ~10\,s per pointing, yielding an RMS noise of ~0.18\,K in a 0.64 km\,s-1 channel. We compare results from maps made with two observing techniques, on--the--fly mapping and drift scanning; both were plagued by baseline ripples which masked low--level emission. We present a method for removing these ripples which significantly improves the image quality, and demonstrate how this technique was applied to disentangle the H\rm\scriptstyle I emission in the vicinity of the Local Group dwarf LGS3. Our image shows an H\rm\scriptstyle I cloud associated with the galaxy as well as an HVC offset by ~30 arcmin. An apparent tidal feature in the H\rm\scriptstyle I emission suggests that the HVC is at the same distance as LGS3.

This research was partially supported by the National Science Foundation.

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