Emission sparks around M 81 and in some dwarf spheroidal galaxies†

Abstract

We use Hα images of three clumps of young stars situated between M81 and NGC3077 to estimate their star formation rate. Radial velocities of the clumps measured by us, as well as the velocity of the Hii region in the dwarf spheroidal (dSph) galaxy KDG61, are compatible with their location at the outskirts of a large rotating gaseous disc around M81. In contrast to KDG61, the radial velocity of the emission knot in the dSph galaxy DDO44,+213 ± 25 km s-1, tells us that this Hα spark belongs to the dSph galaxy itself.F475WandF814Wimages of DDO44 extracted from theHubble Space Telescopearchive reveal eight bluish (B-I< 0.8) stars apparently associated with the Hα knot. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.