8
Parameter
Value
Reference
Optical Center
1950
8
h
13
m
53
:
s
5
Dressel & Condon 1976
1950
70 52
0
13
00
Dynamical Center
1950
8
h
13
m
53
s
Westpfahl 1997
1950
70 52
0
47
:
00
3
Distance
3.05 Mpc
Hoessel, Saha, & Danielson 1998
M
B
,
16.52
RC3, de Vaucouleurs
et
al.
1991
Inclination
41
Puche
et
al.
1992
Position Angle
177
Puche
et
al.
1992
Axial Ratio, q=b a
0.74
Huchtmeier & Richter 1988
A
B
0.10
RC3, de Vaucouleurs
et
al.
1991
A
FUV
0.20
This study
Table 1.1. Adopted Parameters for Holmberg II
1.2.2 IC2574
The late-type dwarf spiral galaxy IC2574 DDO 81 = UGC 5666, also a
member of the M81-NGC 2403 group, has intense star formation occurring in its
outer parts. It is a low metallicity system with an abundance of Z Z
'
0
:
14
Vigroux
et
al.
1987, similar to that of the Small Magellanic Cloud SMC.
Although classi ed as a SABsm de Vaucouleurs, G.
et
al.
1991, the mass
distribution is more similar to that of dwarf irregulars than late-type spirals.
Martimbeau
et
al.
1994 estimate that the dark component comprises 90 of
the total mass and is the main contributor to the rotation cure at nearly all radii.
As seen in other galaxies at the low mass end of the spiral sequence, the optical
and HI disks contribute very little to the total galaxy mass. Miller & Hodge
1994 catalog 289 HII regions in the galaxy and derive a current star formation
rate of 0.08 M yr
,
1
, roughly the average rate over its lifetime. Like HoII, IC2574
has numerous holes in its neutral gas disk. The characteristics of 48 HI holes in
the galaxy are cataloged by Walter
et
al.
1998a, who nd that positions of HII
regions correspond to the rims of these structures. The supergiant HI shell in the
northeastern part of the galaxy is studied in detail by Walter
et
al.
1998b. The
