The HI parameters of the observed galaxies,
obtained from our WSRT observations, are given in Table 3.
The HI flux values are corrected for the WSRT primary beam
attenuation. The total hydrogen content and heliocentric velocities
agree closely with previous results obtained from single dish
observations (e.g. Giovanelli et al. 1982, Giovanelli & Haynes 1985, and Wegner et
al. 1993). This shows that the synthesis observations did not miss
a significant fraction of HI, except for NGC 668 and NGC 753,
which are located far from their corresponding pointing centers.
Due to the primary beam response of the WSRT, roughly a Gaussian with a
FWHM of 
, the noise in the maps increases with
radius causing a corresponding loss of signal-to-noise. Finally,
detections far from the pointing centers have larger uncertainties
in their fluxes. The velocity widths reported in Table 4 (click here) are
systematically larger, within
our uncertainty, than those previously published by Giovanelli Haynes & Haynes
(1982), and Wegner et al. (1993). The cause of this
discrepancy is probably the low signal-to-noise ratio combined with the
uncertainty in our velocity widths, which is
of the order of the resolution (
).
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) |
| Name | field |  | 
|  | W20 | HI flux | source |
| CGCG 522-024 | 3 | 1 48 33.1 | 35 49 06 | 5311 | 258 | 1.56 | (1) |
| CGCG 522-053 | 4 | 1 50 59.9 | 36 23 42 | 4556 | -- | <1.15 | (2) |
| CGCG 522-055 | 4 | 1 51 22.6 | 36 23 07 | 5121 | 405 | 0.93 | (1) |
| CGCG 522-071 | 5 | 1 53 07.8 | 35 53 08 | 5336 | 962 | 1.37 | (1) |
Column 1: Galaxy name.
Column 2: Field where detection was expected.
Columns 3 and 4: 1950 R.A. and Dec.
Column 5: Heliocentric velocity, in 
.
Column 6: Observed 21 cm profile width, in , measured at a
level of 20% of the mean signal intensity.
Column 7: The 21 cm line flux in 
.
Column 8: References for HI data. (1) Wegner et al.
(1993), (2) Scodeggio & Gavazzi (1993).
In Figs. 1 (click here)-4 (click here), 5 (click here)a, 6 (click here), 7 (click here)a,
8 (click here), 9 (click here), and 10 (click here)a we show the HI maps for each
galaxy, with HI contours superposed on optical images from the DSS.
Figures 5 (click here)b and 10 (click here)b show velocity fields for the largest
objects in our sample, NGC 688 and NGC 753. For three galaxies (NGC 688,
UGC 1347, and NGC 753) we have also plotted the position-velocity diagram
together with the 
rotation curves obtained by Amram et al.
1994 (Figs. 5 (click here)c, 7 (click here)b, and 10 (click here)c). Position
angles are also taken from that work. The central velocities used in these
plots were taken from Wegner et al. (1993).
Table 4 (click here) lists four undetected galaxies located in our observed
fields, with total flux or upper limit higher than 
,
as measured from single dish observations.
The first, CGCG 522-024, remained undetected because its large distance
from the pointing center. In adittion, the field where we expected
this galaxy has the highest noise among the five observed fields (see
Table 1 (click here)). CGCG 522-071 was not detected
because its HI emission is spread
out over a width of almost 1000 km/s and is consequently very diluted.
CGCG 522-055 has a total flux of 0.93, which is lower than our detection
threshold. Finally, CGCG 522-053 has not been detected in previous
single dish 21 cm line surveys.
In the following we briefly discuss each detected galaxy.
). The
signal-to-noise ratio of this detection
is low because of its large distance (nearly 
) from
the pointing center.
The first contour in Fig. 1 (click here) is
. More sensitive measurement are
needed to confirm
the observed irregular distribution.
and 
.
In Fig. 5 (click here)c we show the position-velocity diagram and
the rotation curve obtained
by Amram et al. (1994), who explain this
rotation curve as due to the presence of a central bar. Even if
the spatial and velocity
resolution of the HI data are not sufficient to confirm
the increase seen at the end of the rotation curve
(Amram et al. 1994), we can at least exclude a
decreasing feature.
, Giovanelli &
Haynes 1985). Our flux of 
is slightly
lower than the one obtained by
Wegner et al. (1993)
(
). This difference could be explained
because NGC 710 falls at the edge of the velocity band. A stronger
smoothing was necessary to detect this galaxy, leading to a lower
resolution than the one used for the other objects. Therefore, the
asymmetry seen in the HI map, which arises from signal in only
one channel, should be taken with caution. This
asymmetry coincides
with an optical counterpart with unknown velocity. The HI
emission, seen in five channels, indicates that the dynamical
axis lies in the East-West direction, contrary to the optical
major axis (
). The receding side being in the
West part. NGC 710 is seen on projection on the X-ray source, and
its velocity is higher by 
compared to
the mean cluster velocity making this galaxy a good candidate
to show environmental effects. rotation curve (Amram et al. 1994) are
in good agreement (Fig. 7 (click here)b).
Our HI data confirm the flatness of the
rotation curve even beyond r25, the corrected
de Vaucouleurs radius at the 25th magnitude
(
for this galaxy).
are shown in
Fig. 8 (click here). These galaxies are projected close to the cluster
center. UGC 1361
has a normal HI content, with an hydrogen distribution which is
much more extended than the optical disk. One remarkable feature
is the clear asymmetry in the NW region, where the maximum of the
HI emission is seen without an optical counterpart.
CGCG 522-049 shows an asymmetric HI distribution, with an
extension on the opposite side of UGC 1361.
In spite of the irregular hydrogen distributions and the small
angular separation of only 
, the
evidence for interaction between these two galaxies is not conclusive;
their velocity difference is more than 
.
An interesting result, still to be confirmed,
is the weak HI emission found towards the
West of CGCG 522-049. Inspection of the DDS did not reveal
any obvious optical counterpart. The total HI mass is
, typical of dwarf galaxies. This would
imply a 
ratio of at least 4.7,
taking 19.5 as the magnitude limit in the DSS and a distance to A 262
of 47 Mpc.
Such objects, commonly associated with larger galaxies, have already been
noticed in some clusters: NGC 4694 in Virgo
(Cayatte et al. 1990), CGCG 160-106 in Coma
(Amram et al. 1992; Bravo-Alfaro et al.
1997), and several examples in Hydra (McMahon
1993). Tentative explanations for the HI cloud found
near NGC 4694, accretion or ejection from the larger galaxy nearby,
have been proposed by van Driel & van Woerden
(1989).
towards the NW (Fig. 9 (click here)). map, from Amram et al. (1994), shows
very few HII regions, while most of the brightest ones are in
the northern part. Our position-velocity diagram confirms the
overall shape of the
rotation curve (Fig. 10 (click here)c). Our total flux measure
is almost 50% lower than previous values (e.g. 
from Giovanelli & Haynes 1982) maybe
because of strong primary beam attenuation. This galaxy was observed
at 22 minutes of arc from the pointing center.
Figure 1: HI density distribution of
NGC 668, superposed on a B-band
gray scale image (from the DSS Survey). The contours are
4.7 (
), 9.4, 14.1, and 
. The FWHM is indicated by the hatched circle,
Figure 2: HI density distribution of UGC 1257,
superposed on a B-band
gray scale image (from the DSS Survey). The contours are
2.9 (
), 5.8 and 8.7, 11.5, and 
. The FWHM is indicated by the hatched circle,
Figure 3: HI density distribution of UGC 1277,
superposed on a B-band
gray scale image (from the DSS Survey). The contours are
2.3 (), 4.7, 7.0, 9.4, and 
.
The FWHM is indicated by the hatched circle,
Figure 4: HI density distribution of UGC 1299,
superposed on a B-band
gray scale image (from the DSS Survey). The contours are
2.7 (), 5.4, 8.1, 10.8, 13.5, and 
. The FWHM is indicated by the hatched circle,
Figure 5: a) HI density distribution of NGC 688, superposed
on a B-band
gray scale image (from the DSS Survey). The contours are
2.4 (), 4.8, 7.3, 9.7, and 
. The FWHM is indicated by the hatched circle,
Figure 5: b) Intensity weighted mean velocity field of NGC 688.
The numbers indicate
heliocentric velocity in 
. The FWHM is
indicated by the hatched circle,
Figure 5: c) Position velocity plot of NGC 688 along the major
axis. The position angle is 
. Contours are
-1.3 (dashed lines), 1.3 to 
in steps
of 
area. The resolution is indicated by
the cross in the lower right corner, the
rotation curve, from Amram et al. (1994), is
plotted with the corresponding error bars
Figure 6: HI density distribution of NGC 710, superposed on
a B-band
gray scale image (from the DSS Survey). The contours are
1.8 (), 4.1, 6.3, 8.5, 10.8, 13.0, and
.
The FWHM is indicated by the hatched circle,
Figure 7: a) HI density distribution of UGC 1347,
superposed on a B-band gray scale image (from the DSS Survey). The
contours are 3.2 (), 6.5, 9.7 and 
. The FWHM is indicated by the hatched circle,
Figure 7: b) Position velocity plot along the major axis, for
UGC 1347. The position angle is 
.
Contours
are -1.6 (dashed lines), 1.6 to 
in
steps of 
. The resolution is indicated
by the cross in the lower right corner, the
rotation curve, from
Amram et al. (1994), is plotted with the corresponding error
bars
Figure 8: HI density distribution of the couple UGC 1361 and
CGCG 522-49, superposed on a B-band gray scale image (from the DSS
Survey). For UGC 1361, the contours are 2.2 (), 3.8, 5.4,
7.5, 8.6 and 
. For CGCG 522-49 and the third
object in this figure, the contours are 2.2 (), 3.8, 5.4 and
. The FWHM is
Figure 9: HI density distribution of UGC 1387, superposed on
a B-band gray scale image (from the DSS Survey). The contours
are 3.9 (), 7.7, and 
. The FWHM is indicated by the hatched circle,
Figure 10: a) HI density distribution of NGC 753,
superposed on a B-band
gray scale image (from the DSS Survey). The contours are
6.4 (), 12.8 and 
. The FWHM is indicated by the hatched circle,
Figure 10: b) Intensity weighted mean velocity field of NGC 753.
The numbers indicate
heliocentric velocity in . The FWHM is
indicated by the hatched circle,
Figure 10: c) Position velocity plot of NGC 753 along the major
axis. The position
angle is 
. Contours are -1.3 (dashed lines), 1.3,
and 
. The resolution is indicated by
the cross in the lower right corner, the
rotation curve, from Amram et al. (1994), is
plotted with the corresponding error bars