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Session 68 - Disk Galaxies.
Display session, Wednesday, January 15
Elliptical photometry in the H\alpha, V, J and H bands was performed on the giant irregular galaxy NGC 4449 in an attempt to determine the star formation history. The time comparison was based on the premise that the H\alpha will represent recent star formation, the V band an intermediate to young stellar population and the J and H bands an old population. The latter assumption is based upon the near-infrared detecting a population of G through M stars, and not a red giant population. This cannot be proved conclusively with the data; however, comparison with J-H values for elliptical galaxies suggests that NGC 4449's population is similar to ellipticals', namely a low-massed population. With regards to the star formation history, the surface brightnesses of the various bands were compared as a function of the radius. The slope of the bands track each other for the majority of the scope of the galaxy, implying a constant star formation rate (SFR) over time. For the outer edges of the galaxy, there is an indication that there has been a decrease in the SFR in the recent history of the galaxy.
Program listing for Wednesday