A Fabry-Perot Study of the Scd I galaxy NGC 5457
  We have analyzed Halpha Fabry-Perot interferograms of NGC 5457 (M101) in order to calculate the rotation curve. We have also isolated a sample of 263 HII regions and we determined for each one its radial velocity and velocity dispersion. The rotation curve agrees with previous determinations and the mass derived from it is 9.8E10 solar mass. The distribution of velocity dispersion values of the HII regions presents a normal behavior, with a mean value of 30 km/sec. 
Ivanio Puerari (1), Margarita Valdez-Gutierrez (1), Margarita Rosado   (2) ((1) INAOE - Mexico; (2) IA-UNAM - Mexico)