|Figure 1: NGC 784 in the V band. As for all the other images, North is to the top, East is to the left. The upper right corner corresponds to X=0, Y=0of the frame coordinates given in the photometry tables, i.e. X increases to the East and Y to the South|
This irregular galaxy seen nearly edge-on with angular dimensions of
and an integral apparent magnitude of
has a radial
km s-1 (NASA Extragalactic Database = NED).
In spite of its expected
small distance, NGC 784 has not yet been resolved into stars.
Broeils & van Woerden (1994) studied the structure and kinematics of
NGC 784 in the H I line,
showing that its neutral hydrogen content as well as rotational amplitude
are typical of an irregular galaxy. The central part of NGC 784 is
represented in Fig. 1 from our V CCD frame.
The basic parameters of NGC 784 and of the other considered galaxies are given in Table 2. Its first six lines indicate the standard major and minor diameters of the galaxy, its integral apparent magnitude, galactic extinction, morphological type, and heliocentric radial velocity from the NED. The next lines contain the radial velocity with respect to the centroid of the Local Group (Karachentsev & Makarov 1996), number of measured brightest stars, mean magnitude and colour of three brightest blue stars, the distance modulus and linear distance of the galaxy, and its absolute blue magnitude.
Note that recent H I observations by Huchtmeier et al. (2000) reveal in the NGC 784 neighbourhood two dwarf galaxies, kk16 and kk17, with radial velocities +399 and +348 km s-1, respectively, which are probable companions of NGC 784.
A view of this Sb-type galaxy is shown in a mosaic
(Fig. 3) constructed from three frames in the R filter
with 30 s exposure each.
|Figure 5: CMD for 327 stars in NGC 2683. The filled circles are for stars measured in the northern region, the open squares indicate stars in the southern side|
This large (
similar to M 81
still remained unresolved into stars. In its wide vicinity there is no other
bright galaxy. This is why Karachentseva (1973) included
NGC 2903 in her Catalog of isolated galaxies (KIG).
around NGC 2903
there are two dwarf galaxies: UGC 5086 and F565-v1 imaged by Makarova &
Karachentsev (1998). An image of NGC 2903 from the Digital Sky Survey is
shown in Fig. 6. Our two CCD frames indicated by
the boxes cover the basic part
of its spiral pattern except the faint outer arms.
|Figure 8: CMD for 273 brightest stars in NGC 2903. The filled circles correspond to stars measured in the northern region and open squares indicate stars in the southern side|
|Figure 9: Composite B+V image of the central part of NGC 5204 after subtraction of the median smoothed frame|
A complete image of this irregular galaxy in the B+V bands
is shown in Fig. 9 after subtraction of the median
smoothed frame. It shows many more resolved
stars than the reproduction in the Atlas of Sandage & Bedke (1988).
|Figure 11: R band image of NGC 5474 from the Isaac Newton Telescope Archive. The two squares correspond to 6 m BTA CCD frames|
The structure of this nearest companion to M 101 is strongly disturbed by
tidal interaction. A view of the galaxy imaged in the R band is shown
in Fig. 11. It has been taken from the archive of the
Isaac Newton telescope (La Palma).
Positions of two CCD frames obtained with the 6-m telescope are indicated
|Figure 14: I band inlay of NGC 5585 from the 1 m Kapteyn telescope image with the position of the 6 m BTA CCD frame|
As the two previous galaxies, NGC 5585 is a probable member of the M 101 group, but it looks rather isolated with respect to the neighbouring galaxies. Fig. 14 reproduces a view of NGC 5585 in the Iband taken from the archive of the John Kapteyn telescope (La Palma).
Figure 15 shows the main body of the galaxy from the CCD image obtained with the 6-m telescope in the I band after subtraction of the median smoothed frame.
The results of stellar photometry averaged over two observing runs are presented as a CMD, Fig. 16. The mean apparent magnitude of the three brightest blue stars is , which agrees better with the old estimate of Sandage & Tammann (1974) 20.9, than with the value of 20.02 derived by Karachentsev et al. (1994). However, all three brightest blue stars used by Karachentsev et al. (1994) are situated on the NE side of NGC 5585 beyond the boundaries of our present frame. Despite the somewhat uncertain distance of NGC 5585, 5.7 Mpc (former estimate), and 8.7 Mpc (the present paper), this galaxy seems to be peripheric member of the M 101 group.
|Parameter||N 784||N 2683||N 2903||N 5204||N 5474||N 5585|
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