Object of the Week, March 10, 2019 – Superluminous Spiral Galaxies

Name: CGCG 122-067
RA: 09 44 53.6, Dec: +22 53 06 (Leo)
Type: Sbc
Aliases: MCG +04-23-030 = PGC 27924 = OGC 1559
Size: 0.7' x 0.5'
V Mag = 14.7, B Mag = 15.7
z = .089

In 2016, a team of NED/IPAC (Caltech) astronomers led by Patrick Ogle announced the discovery of 53 super spirals -- massive, giant spiral galaxies that were optically as luminous as the brightest elliptical galaxies. These superluminous spirals were found by mining the NASA/IPAC Extragalactic Database. I recently wrote an article on observing distant (at least 1 billion l.y.) galaxies and quasars for the upcoming May issue of Sky & Tel but none of the objects I discussed in the article were spirals.

In the local universe (under 1 billion light years), the most massive galaxies are found at the center of rich galaxy clusters (cD type) such as the Coma Galaxy Cluster, and consist of bloated elliptical galaxies that have increased in mass and girth by cannibilizing their surrounding neighbors. A typical spiral in the local universe (such as the Milky Way) has a diameter of ~100,000 light years and may produce the equivalent of 1 solar mass of new stars per year.

But the NED group uncovered 53 superluminous spirals with diameters between 180,000 and 440,000 light years that are churning out stars at a furious rate of 5 to 65 solar masses per year. All of these objects have distances between 1 and 3.5 billion light years (redshifts between z = .089 and z = .300). So, here we have a survey of basically the biggest and baddest spirals within 3.5 billion light years!

Last weekend I visited Jimi Lowrey and brought along this list of super spirals to observe with his 48" in west Texas. The brightest and nearest of the 53 galaxies is CGCG 122-067 (or OGC 1559 for "Ogle Galaxy Catalogue"). This galaxy is located in northern Leo just 0.9° south of 3.0-magnitude Epsilon Leonis. With a redshift of z = .089, the light-travel time is 1.2 billion years -- more distant than the Corona Borealis galaxy cluster. Normally, a spiral this distant would be very difficult to see, but this one has a diameter of 265,000 light years and a star-forming rate of 13 solar masses/yr. This spiral should be just visible in an 18-inch scope.

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My notes read, "at 488x -- fairly faint, small, round, ~20" diameter, very small bright core, stellar nucleus. A faint but easy mag 16.7 star is superimposed on the west edge. This galaxy actually looks like a spiral with a small core and nucleus!" On the SDSS image, it appears to be a merger with a double nucleus. We looked for this, but mistakenly assumed the superimposed star on the west side was the second nucleus. It would likely require higher power to resolve the twin nuclei.

Interestingly, 4 of the super spirals in the paper are late-stage major mergers – a possible clue to these monsters. In addition at least 10 of super spirals seem to be in located in groups or galaxy clusters, but most of appear to be fairly isolated. So, how did they grow so massive?

While observing about 70 objects over two nights, we looked at a sample of 10 in the spring skies and were able to make successful observations of 7 of these. The most distant one we managed was SDSS J121644.34+122450.5 (OGC 1606). This galaxy has a diameter of 250,000 light years, a redshift z = .257 and a Vmag of 17.7. The redshift corresponds with a distance of just over 3 billion light years. Neither of us thought a spiral galaxy would be visible at this distance, so were quite pleased with the observation.

The largest Ogle spiral is 2MASX J16394598+4609058 with a whopping diameter of 437,000 light years. This giant appropriately lives in Hercules at a distance of 2.9 billion light years and has a V mag of ~17.2.

Attachment 3457

One of the more interesting spirals is PGC 56730 = KUG 1559+274 in Corona Borealis at 16 01 40.6 +27 18 16 i. This is apparently another spiral merger and its the most prominent member (if you can call V ~16.4 prominent) at a distance of 2.0 billion light years.

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As always,
"Give it a go and let us know!"

I'm not able to edit the post, but the broken image link Attachment 3457 refers to the giant 2MASX J16394598+4609058, which is attached at the end of the post.

Steve and Jimi gave me a heads up about CGCG 122-67 last week and I had a chance to observe it a few nights ago under superb conditions for my neck of the woods. I was at Chuck Dethloff's place in the Oregon Coast Range, where we normally get SQM readings in 21.2 to to 21.3 range, but while observing CGCG 122-67 on the second night the SQM was 21.49. And the seeing was pretty sharp too, so fabulous conditions for these parts.

On the other hand, the temperature got down to 18 F / -8 C and I discovered I need warmer boots, but it was good indication of how transparent the sky was.

I've attached my sketch, and as you see I was not able to split the nucleus of the galaxy with my 28-inch scope but I was able to see the field star next to it. I used 547x to make the sketch. It was awesome to see such old photons from a spiral galaxy!

We also tried to see it with Chuck's 16-inch, and although it was more difficult - as expected - we were able to see it at 187x without much difficulty. No field star, but the amorphous glow of the galaxy was definitely there. I wouldn't be surprised if a skilled observer could see it with a 12-inch scope under a top notch sky because of the galaxy's 14.7 magnitude. It's fairly is easy to star hop to as well.

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I'm going to try some of the other super luminous spirals on this list at my next opportunity - what a treat to see so far back / away!

This is a fun project,nothing like catching billion year old light from spiral galaxies! I am looking forward to looking for more galaxies from the Superspiral catalog Steve and I have just barely put a dent in the list.

CGCG 122-67 was an easy target for the 27-inch and could be detected with direct vision. Under strong wind and telescope shaking the star nearby was surly popping in and out of view. No thoughts for the spiral structure or the double nucleus.

Hi All,

I observed this target, during last new moon with my 25" Obsession, under very good conditions: NEML +/-7.0v, SQMLZ 21.96, FWHM 2.0".
The galaxy is seen as an elongated oval N / S, a / b 1.5 ~, D ~ 30 "x 20".
Adverted vision in moderately distant, and after adaptation, I perceived that there are two lights within the halo, the line joining the AP being ~ 90 °. When I close my VI, I had several glimpses safe, but one glow, never both at the same time. And for each one, I could not locate the one or the other glimmers against the halo (although I know that one is in the center, and the other on the edge W), otherwise they are "in the middle".
Returning to moderately distant VI, I have seen both lights at the same time, but very difficult, and still without power positioning relative to the halo.
http://www.deepsky-drawings.com/pgc-27924/dsdlang/fr

Clear skies
Bertrand
http://www.deepsky-drawings.com

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