NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-02-23 T19:27:10 PST
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Notes for object ARP 227

2 note(s) found in NED.


1. 1994CAG1..B...0000S
Re:ARP 227
NGC 474/470
Pair
RS0/a
(VE,L,0)
Sbc(s)II.8
P11-7866-S
Sep 5/6, 1980
IIIaJ
150 min
Racine wedge
NGC 474 (RS0/a) forms a close double with
NGC 470 (Sbc; panel 189), partially cut off at
the top middle of the print here. The projected
separation of the pair is 313". The redshifts are
v_o(470) = 2643 km/s, and v_o(474) = 2548 km/s.
The mean of = 2596 km/s gives a
redshift distance of 52 Mpc (H = 50) and therefore
a projected linear separation of 80 kpc for
the pair.
The multiple rims at many distances from
the center of NGC 474 are similar to the
theoretical expectations of the effect of mergers
calculated by Quinn (1984; see also the diagram
due to Toomre in Schweizer 1983). However, the
circumstantial evidence is not that a merger has
occurred but rather that a close encounter is
taking place with NGC 470.
Short-exposure plates taken with the Mount
Wilson 100-inch by van Maanen in 1938 and by
Sandage in 1975 fail to show evidence for a
merged companion. However, the absence of a
double nucleus may not be of consequence; it is
claimed that direct evidence of a merger would
rapidly disappear (Toomre 1977 in the discussion).
The common feature in NGC 474 and NGC
7585, above, is the exceptionally high surface
brightness of the central, almost point-like,
nucleus. This feature is seen on the low-contrast
prints of both galaxies in the secondary images of
the nuclei from the Racine wedge.
The print has been made from the same
original plate used for the image on the left.

2. 1994CAG1..B...0000S
Re:ARP 227
NGC 474/470
Pair
RS0/a
(VE,L,0)
Sbc(s)II.8
PH-7866-S
Sep 5/6, 1980
IIIaJ
150 min
Racine wedge
The print has been made from the same
original plate used for the image on the left.
The sharp rimmed arcs continue farther
into the center than is visible on the more heavily
exposed print at the left. The well-defined,
closely circular central bulge appears featureless
on short-exposure Mount Wilson 100-inch
plates, but it is of exceptionally high surface
brightness. At the center is an almost unresolved,
very bright nucleus. As in NGC 7585, above, its
secondary image from the Racine wedge is visible
to the right of the bulge, slightly below the
centerline at what appears to be the edge of the
central region. To locate this secondary image
note the relative position of the many other
Racine wedge images for the bright stars in the field.


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