The HI mass function in Ursa Major
  A deep blind HI survey of the nearby spiral rich Ursa Major cluster has been performed with the VLA in parallel with a wide-field R-band imaging campaign of most VLA fields with the CFHT. The goal is to measure the slope of the HI mass function down to HI masses of 10^7 Msun as well as the slope of the faint-end of the luminosity function down to M(R)=-10. The VLA survey sampled 16% of the Ursa Major cluster volume. Both the HIMF and the LF in Ursa Major are nearly flat at their faint-ends. No free- floating HI clouds were detected. 
Marc Verheijen, Neil Trentham, Brent Tully, Martin Zwaan