De Vaucouleurs Atlas Type: SAB(s)d
Telescope: 0.5-m RC
North up , East left
Field Dimensions: 14.2 x 10.6 arcminutes
RC3 Type: SAB(s)cd
RSA Type: Sc(s)III
Surface Brightness Range Displayed: 18.0-26.0 mag per square arcsec
Absolute Blue Magnitude: -19.3
Elmegreen Spiral Arm Class: AC 4
De Vaucouleurs Atlas Description:
The possibility that a bar might be present in NGC 2403 is not evident at first sight. What suggests the classification as SAB is the fact that the central isophotes are rounder than the outer disk isophotes. Since the galaxy is essentially bulgeless, these rounder isophotes are likely due to an inner oval, viewed approximately end-on and probably significantly foreshortened.
NGC 2403 is a very good example of what should be classified as an Sd system in our view. It is a clear spiral with no trace of any bulge. It shows some asymmetry in that one of the two main arms is brighter and better defined than the other.
NGC 2403 is a very nearby galaxy and has been the subject of many studies. A recent study of the kinematics of the ionized gas revealed evidence for vertical outflows of gas from regions of active star formation (Fraternali, Oosterloo, and Sancisi 2004).