26
dynamical center caused by noncircular motions in the center of the galaxy. Since
the galaxy has a somewhat spiral structure, the light is more or less organized the
same in each bandpass.
The extinction value for Galactic reddening in the FUV is derived assuming
the Galactic reddening curve of Savage and Mathis 1979 integrated over the UIT
B1 bandpass. These are related by A
FUV
EB
,
V = 8.33 Hill 1997. Despite
the high inclination angle of IC2574, a correction for inclination e ects, A
i
, is not
applied to its FUV magnitude. Since the UV light is not smoothly distributed
and extinction is probably very localized, the uncertainty in the correction would
be so great that it would be meaningless. The errors in the magnitudes listed
in Table 3.1 account for the photometric uncertainty and the uncertainty in the
distance estimate.
The FUV magnitudes are at the faint end of the range of absolute magnitudes
observed by the UIT. In a sample of 35 galaxies exhibiting recent massive star for-
mation, the range of observed absolute magnitudes spans from
,
17 to
,
22 Fanelli
et
al.
1997a. The corresponding FUV
,
B =
,
1.74
0.03, and
,
1.20
0.05 col-
ors for HoII and Sextans A respectively, fall into the range observed by FAUST
a balloon-born UV camera for a sample of Im-type galaxies Deharveng
et
al.
1994.
3.2.3
FUV
Gro
wth
Curv
es
The integrated FUV ux as a function of radius provides information regarding
the concentration of recent massive star formation. To demonstrate the utility of
the FUV data, the growth curve of the FUV magnitude for each galaxy is derived
and corrected for Galactic extinction. Figure 3.4 illustrates that recent massive
star formation is not particularly centrally concentrated in HoII despite the pres-
ence of the prominent central star forming arc. The aperture containing this
feature in its entirety 1
:
0
7 only contains
43 of the total FUV ux. Therefore,
