ALFALFA Discovery of the Nearby Gas-Rich Dwarf Galaxy Leo P. I. HI Observations

Understand

The discovery of a previously unknown 21cm HI line source identified as an ultra-compact high velocity cloud in the ALFALFA survey is reported.

• The HI detection is barely resolved by the Arecibo 305m telescope ~4' beam and has a narrow HI linewidth (HPFW of 24 km/s).
• Further HI observations at Arecibo and with the VLA corroborate the ALFALFA HI detection, provide an estimate of the HI radius, ~1' at the 5 x 10^19 cm^-2 isophote, and show the cloud to exhibit rotation with an amplitude of ~9.0 +/- 1.5 km/s.
• In other papers, Rhode et al.