L6O: 2MASX J00140398 2310555 = NGC 45: the 2MASS source is a bright HII
region in the outer disc of this large (D_25_ =7.4') spiral, whose E-W
extent far exceeds the 3.6' Nancay HPBW. This explains why our
integrated HI line flux of 66 Jy km s^-1^, is much lower than the mean
literature value of 245 Jy km s^-1^ (LEDA), which was measured with
larger telescope beams covering the entire galaxy.
Hubble Atlas, p. 37
Oct 1/2, 1978
103aO + GG385
NGC 45 is very highly resolved into
individual stars starting at about V = 19.5. This
level is only slightly fainter than the brightest
stars in M101 (Sandage and Tammann 1974c,
Sandage 1983b), but is 2 mag fainter than the
brightest stars in NGC 300, NGC 55, and NGC 247
in the South Polar Group. The estimate that
NGC 45 is located about two times the distance
of the mean of the South Polar Group, based on
the magnitude of the brightest stars in each
(V = 17.5 in the SPG; V = 19 for NGC 45), is
consistent with the redshifts. NGC 45 has
v_o = 533 km/s; the mean of the SPG is
NGC 55, NGC 247, NGC 253, NGC 300, and NGC 7793.
The morphology of NGC 45 is similar to that
of NGC 300 (Sc; panels 261, S6) and NGC 598
(M33, panel 262) although it is later in the
classification sequence than the latter. The
surface brightness of the inner disk of NGC 45 is
lower than in M33. As in M33 and NGC 300,
many associations exist in the multiple arms. The
largest of these has an angular diameter of 30"
which, at a distance of 6 Mpc (m - M = 29),
corresponds to a linear diameter of 900 psc.
The resolution into stars is so complete, the
crowding so small, the surface brightness of the
disk so low, and the dust content so nearly negligible
as to make NGC 45 an ideal galaxy in which
to measure photometrically its brightest stars
and to search for Cepheids for calibration studies
of the extragalactic distance scale.
This is one of the closest and lowest surface brightness galaxies
contained in this atlas. Although associated with the Sculptor group of
galaxies, cluster mass models (Puche & Carignan 1988) suggest NGC 45 is
merely an "interloper." Imaging studies of this galaxy are hampered
somewhat by the presence of both a 10.6 and a 6.5 mag star within 4' of
Pretty low surface brightness, very faint nucleus, many knots on faint arms.
Star superposed 1.5 south-south-following. Superposed on group.
=ESO 473- G 01
= DDO 223
Possibly in Sculptor Group,
or it is a non-interacting pair with NGC 0024 in the background.
Ap. J., 150, 9, 1967
Australian J. Phys., 25, 315, 1972.
= NGC 0045
= NGC 0045
In the Sculptor Group with NGC 0055, NGC 0247, NGC 0253,
NGC 0300, and NGC 7793 (Ap. J., 130, 718, 1959).
Bright middle, no bright nucleus.
Many irregular, weak, well resolved arms.
Very low surface brightness.
Mt. Wilson velocity is for a bright emission patch
0.8 arcmin [north-following] the nucleus.
Sept. 24/25, 1951
NGC 0045 has one of the lowest surface brightnesses of any
galaxy in the sky. This reproduction has been double-printed
from the original 200-inch negative to increase the contrast.
The entire face of NGC 0045 is covered with resolved stars.
There must be very little internal absorption due to dust
because many background galaxies can be seen through the main
body of NGC 0045. This galaxy is a member of a group of
near-by systems of large angular diameter which includes NGC 0024,
NGC 0045, NGC 0055, NGC 0247, NGC 0300, and NGC 7793.
This is probably the nearest group of galaxies to
the Local Group, but it is too far south for adequate work
from the northern hemisphere.
3. NGC 55 Group
De Vaucouleurs (1959) has argued that NGC 45, 55, 247, 253, 300, and 7793 form a
physical group about 8X 10^5^ pc in diameter. The group is only about 2.5 X
10^6^ pc distant and the galaxies are all spirals. The argument for their
forming a physical group is based on their distribution among the other bright
galaxies in the southern hemisphere. From the radial velocities, de Vaucouleurs
showed that the virial theorem would not be satisfied unless the average masses
of the galaxies were in excess of 10^12^ M_sun_, with a mass-to-light ratio
greater than 500. Thus if the galaxies form a physical group, it must be
expanding, unless there is a large concentration of intergalactic matter.
Only the central regions of this object of very low surface
brightness are visible on this print.
The nucleus is very small and faint in a central, amorphous
mass from which emerge very faint, irregular and branching arms.
Compare with NGC 0300 (Plate 33), and NGC 5204 (Plate 35).