ASTRO: NGC 1954

NGC 1954 is a galaxy in Lepus I had to image for two reasons. One it is
neat, and secondly or maybe primarily I finished building my first
telescope in March of 1954 (started in 1953), a 6" f/12 scope which I
still have 60 years later. It turned out to be a superb planetary scope
with optics Bob Cox (he did the optics for Mercury and Gemini and the
Gleanings for ATM's column in Sky and Telescope for years) described as
"Approach the eyepiece carefully lest you cut your eye on the image."
It started me down this long road. I'm glad NGC 1954 is a very
interesting galaxy. The MCG says of it: "Two extremely thin arcs do not
appear as spirals, nor as dense rings. They consist of 15 to 20 HII
regions." Indeed the outer arcs seem totally unrelated to the spiral
structure. Unfortunately it hasn't been studied that I found so I don't
have an explanation for how it looks like it was assembled from parts of
2 different galaxies. Maybe it was, I just don't know. Could the arcs
be a "polar ring" like structure? I doubt it but...

It is part of the triple galaxy system of HDCE 0361. The other two
members being NGC 1957 and the "red and dead" IC 3132. All have a
redshift distance of about 150 million light-years. This system is
located at -14 degrees making it very difficult from my latitude. I've
had it on my to-do list from day one but no night was good enough to do
it justice until I gave up and took it anyway on February 1st. It has
been a really cold but cloudy day snowing until after dark. Suddenly
the snow stopped. NGC 1954 was barely within one hour of the meridian,
my limit at this declination. Without waiting for the scope to cool
down I started in on it as this was the best (not great) night for this
galaxy I'd had since building the observatory 8 years ago. Since the
clouds could return any minute or seeing go bad I took the L data. That
resulted in tube currents that turned the bottom of the stars all wonky.
It didn't hurt the resolution of the galaxy significantly however.
This low I can only image east of the meridian due to my Meridian Tree
that blocks things about 10 minutes before I reach the meridian from the
east side and everything for an hour and half beyond the meridian to the
west. Thus I took the color data a different night. seeing was much
worse but no tube currents. That meant the wonky points had no color so
I blurred the brighter stars on the color image to cover the "points" in
the luminance image. Otherwise those colorless points looked even
worse. There are techniques for rounding the stars but I took the easy
route and left the "points" in. It never was steady enough to reshoot
the luminance as it soon was too far west and lost in the Meridian Tree.

NGC 1954 is classified as SA(rs)bc pec by NED and simply Sc by the NGC
project. NGC 1957 is listed as SB(rs0- by NED and E by the NGC
Project. As a ring structure is seen faintly I'll have to go with NED
on this one. IC 2132 is listed at NED as Sa pec: It is an example of
what now are known as red and dead galaxies due to their lack of recent
star formation. About all the remaining stars are old red stars and a
few red giants, the last of the more massive stars. Thus its spiral
structure is quite muted. Oddly it seems to have a strong dust lane but
for some reason that isn't forming stars or if it is they are hidden
behind the dust. It is a strong IR emitting galaxy as it is listed in
the 2MASS survey. That could be due to hot new stars heating dust that
emits in the IR part of the spectrum.

NGC 1954 is a huge galaxy. Measuring from the northwestern tip that
extends beyond a faint background galaxy to the southeastern tip that
seems to turn back on itself, it is 315 seconds of arc long. That makes
it some 229,000 light-years in size! Another reason to wonder if this
isn't due to the combining of two different galaxies. By comparison NGC
1957 (should it look like a Chevy?) is only 43,000 light-years across
and IC 3132 83,000 light-years in diameter. Large but not unusually so.

Only two other galaxies in the image had redshift data. That put those
two far beyond HDCE 0361. Both are shown on the annotated image. A
dozen or so galaxies from the 2MASS are also listed at NED, I've noted a
couple of them. One is also an X-ray source so likely is hiding
something very hot behind its red glow. Unfortunately I couldn't find
anything on it. I noted it on the annotated image southwest of NGC
1954. A couple of galaxies that looked interesting to me but were not
in NED are marked with question marks. Most of the galaxies in the
field didn't have enough IR to make the 2MASS so didn't make it into
NED, including one seen at the north end of NGC 1954.

So while NGC 1954 is a very strange galaxy Arp might have included in
his Atlas there's just not much at all on the entire field. Maybe
someone will eventually study at least NGC 1954.

14" LX200R @ f/10, L=4x10' RGB=2x10' STL-11000XM, Paramount ME

Rick
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