UGC 2953 (IC 356) is by far the best resolved galaxy in our sample, with 117
independent data points in its rotation curve. The inner points, from the
optical spectrum, sample the rotation velocities at intervals of ~80 pc or
0.02R-band disc scalelengths, whereas the last measured point lies at a
projected radius of 59 kpc (14 disc scalelengths). The central rise in the
rotation curve is unresolved even in the optical spectrum; the rotation
velocities rise to ~200 km s^-1^ within 1 arcsec from the centre, and keep
rising more gradually from there to a maximum of 310 km s^-1^ at R ~= 100 arcsec
(~=7.5 kpc, two disc scalelengths). In the outer regions, the rotation curve
declines, with the asymptotic velocity about 15 per cent lower than the maximum.
The strong variation in the fitted inclination angles around R = 600 arcsec is
probably an artefact caused by streaming motions in the large spiral arm in the
western parts of the galaxy; it was not judged to be real and was therefore no t
used in the final tilted ring fits.
UGC 2953 (IC 356) is by far the best resolved galaxy in our sample. The gas is
concentrated in pronounced spiral arms that extend far beyond the bright optical
disk. The velocity field shows distinctive "wiggles" in the isovelocity contours
where the gas crosses the arms.
IC 356. NVSS did not detect this source. The 1.4 GHz, 54" resolution
observations of Condon (1987) did detect a diffuse 29.5 mJy source. We
detect a slightly resolved, ~1 mJy core, coincident with the optical
nucleus of the galaxy.
There is also another object (IC 356NE), having about 6 mJy, at about
3.5' from the target source. We have not been able to identify this
source using NED, which indicates that the two nearest objects are
87GB 040255.7+694248 and IRAS 04033+6942, about 13" away. It may possibly
be identified with the 80.1 mJy NVSS source at a distance of 5" from our
radio position for IC 356NE. There are no APM catalog data for this
Diffuse radio source.
IC 356 (Arp 213) has the strongest FIR emission of the very cold IRAS
galaxies (S_60_/S_100_ < 0.25) and is highly extincted. The only other CO
observation to our knowledge was a non-detection (Young et al. 1984). The
CO(2-1) appears marginally detected but the CO(1-0) does not. Given the
cold dust temperature, a 230 GHz detection without a 115 GHz detection is
particularly suspect and thus this galaxy is not considered as detected.
This puts IC 356 significantly below the CO emission expected and
observed for other galaxies with equivalent FIR emission.
= Arp 213
Photograph and Photometry:
Publ. U.S. Naval Obs., XX, Part IV, 1971.
A.J., 79, 767, 1974.
Radio Observations: (no detection)
Astr. Ap., 28, 379, 1973.
"Faint straight absorption lanes lead toward nucleus, become triple" (Arp)
See HA, 105, 229, 1937.