Emission sparks around M 81 and in some dSph galaxies

TL;DR

This study investigates emission regions around M81 and nearby dwarf spheroidal galaxies, analyzing star formation and gas dynamics through H-alpha imaging and stellar data to understand galaxy interactions and star formation activity.

Contribution

It provides new radial velocity measurements and star associations that clarify the origins of emission features in M81 and dwarf spheroidal galaxies.

Findings

Radial velocities indicate some emission regions are part of M81's gaseous disc.

The emission knot in DDO44 is confirmed to belong to DDO44.

Identification of young stars associated with H-alpha emission in DDO44.

Abstract

We use H-alpha 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 HII-region in the dSph galaxy KDG61 are compatible with their location at the outskirts of a large rotating gaseous disc around M81. In contrast to KDG61, radial velocity of the emission knot in the dSph galaxy DDO44, +213+-25 km/s, tells us that this H-alpha spark belongs to the dSph galaxy itself. F475W and F814W images of DDO44 extracted from the HST archive reveal 8 bluish (B-I < 0.8) stars apparently associated with the H-alpha knot.