ASTRO: Arp 271

Arp 271, in Virgo is a rather classic Arp pair, much photographed
compared to most Arp galaxies. Thus my desire for a better night than I
had. It is two spiral galaxies, NGC 5426 (bottom) and NGC 5427 that are
just now starting to interact as they orbit by each other, apparently
for the first time. Some distortion can be seen in each galaxy. The
arms of NGC 5426 seem to reaching out to connect with NGC 5427. It in
turn has some tidal effects showing. But we are seeing them in 2D
rather than 3D which makes determining the real relationship between
these in space difficult to determine. For some insight as to what is
happening here I will refer you to the article and great image taken by
the Gemini South telescope with nearly 6 times the resolution I can
achieve here. I wish now I'd have taken some H alpha data with this as
both galaxies are rich in HII regions as shown by the Gemini South
image. http://www.gemini.edu/twinspiral

Arp classed the pair under "Group character: connected arms". His
comment reads: "Arm's linked. Note bifurcation in arm of N spiral."
NGC 5426 is classed by NED as SAc pec. while NGC 5427 is classed as SAc
pec. Sy2. The latter meaning it is a Seyfert 2 galaxy with an active
nucleus. I find no consensus on their distance. Red shift puts them a
bit over 130 million light-years away but various papers I've seen put
them closer, more like 90 to 110 million light-years. The ability of
Gemini south to resolve so many HII regions would argue for these
somewhat closer distances.

While there are a lot of faint fuzzies in the image, most are cataloged
under the LCRS catalog, that stands for Las Campanas Redshift Survey.
Oddly, the nice big bright entries have no red shift value in NED. For
instance the large orange elliptical NW of Arp 271 is very obvious. It
is cataloged as LCRS B140024.4-054536 without a red shift. Most that do
carry a red shift are the tiny yellowish orange galaxies. Those fall
into two camps, those near Arp 271 are about 1.1 billion light-years
distant and those in the SW corner belong to a different group being 1.7
billion light-years distant. But the larger, likely closer galaxies
have no red shift data that I could find.

Arp's image of the pair with the 200" Palomar scope is at:
http://nedwww.ipac.caltech.edu/level...ig_arp271.jpeg

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

Wow, beautiful!