Why is the Norma Cluster not in Norma?

[Robh]

Hi All,

I've been doing some reading on the Great Attractor and also on dark flow.
The Norma Cluster (Abell 3627) is associated with the Great Attractor.

In trying to locate its position from its coordinates, I realised the Cluster is not in fact in Norma but in Triangulum Australe.

Wikipedia gives the co-ordinates of Abell 3627 as 16h 15m 32.8s, -60 54' 30" and indicates the cluster is in Norma.
SIMBAD gives the coordinates as 16 14 22.5, -60 52 07 which is not far off that given in wikipedia.

Curiously, wikipedia states the spiral galaxy ESO 137-001 is located in Abell 3627 (Norma Cluster) but indicates it is in Triangulum Australe.

So, why is the Norma Cluster not in Norma but in Triangulum Australe?


Regards, Rob

[madbadgalaxyman]

This cluster has always been in Triangulum Australe, as far as I am concerned. I viewed the the three big ellipticals in this cluster, many years ago; they were not hard at all in a 10 inch........ at around blue 13th magnitude each.
(ESO 137-010, ESO 137-008, etc.)

The X-ray luminosity, and the mass, of this cluster are comparable to that of the Coma Cluster, but it is strongly obscured by foreground dust, so perhaps some near-infrared imaging would be the best, if our imagers wish to capture it......I read somewhere that there are now some Japanese CCDs that have their maximum sensitivity at nearly 1 micron, and this longer wavelength of observation greatly reduces the effects of the considerable extinction, as the photons tend to get past the <0.25 micron dust particles.

The other fields in the supercluster, to the north of this cluster of galaxies, are very obscured by dust in the Milky Way, but there are a surprising number of fairly bright galaxies at a similar recession velocity, in the rest of Triangulum Australe......it is possible to trace the supercluster structure in a star atlas, using galaxies at a similar recession velocity to the cluster.......the supercluster extends from Triangulum Australe through to Ara and then into Pavo.
If you set your magnitude limit faint on an electronic star chart that shows much of the original PGC (~100,000 galaxies for the whole sky), the supercluster structure is quite obvious to the south and east of Abell 3627.

[Robh]

Interesting, thanks.

I wasn't aware any of the galaxies could be seen with an amateur scope due to the supposed dust and stars in the line of sight. The images I've seen were either done in the infrared or X-ray spectrum.

Regards, Rob

[madbadgalaxyman]

Gday, Rob,
Three or four of the galaxies are "bleeding obvious" even with modest apertures.

Here is a screen dump from Guide V.8 (software) showing Abell 3627

The magn limit was set to 14.5, so there are not a lot of galaxies that are easily visible, despite the fact that this is a major mass concentration. I do not know what the extinction values are through this field, but they are probably high and variable.

It is a while since I looked at info about this cluster of galaxies. Three years ago, there had been little optical data published.

I seem to recall that the late Anthony Fairall, who was an authority on the Largest Scale Structures in the universe, told me that Patrick Woudt, at the University of Cape Town, keeps data on this cluster. However, he seems to be doing other types of astron. research at present.

Woudt and Kraan-Korteweg et al., published on this cluster in the 2007 MNRAS, and bizarrely enough they referred to it as the Norma Cluster!!!!E#%^^&&***(!!!!

cheers, robert

115816

Google search on "Atlas of Nearby Large-Scale Structures" to find Fairall's maps of nearby supergalactic structures.

[astroron]

Hi Rob, I was hoping Robert would answer your question;)
I have observed Four or five of the brighter galaxies and made a report in the observing forum about three years ago. I will try and see if I can find it ?
Cheers :thumbsup:

[Robh]

Thanks, Ron

Came across this by Steve Gottlieb in 2005.
http://observers.org/tac.mailing.list/2005/Jul/0446.html

He states that "Abell 3627 ... officially resides in the southern constellation of Triangulum Australe (Southern Triangle), although it is sometimes referred to as the "Norma Cluster" ". Still doesn't say why?

Has some interesting observations of ESO 137-006, ESO 137-010, ESO 137-008. He uses an 18 inch scope though.

Regards, Rob

[astroron]

Hi Rob,Robert, here is my report on Abell galaxy cluster 3627.
Observing Report 23/06/09
16" Truss Newtonian, eyepieces as mentioned in the report.

I started the nights observing with Comet c/2008 Q3 Garradd which was just about on the zenith, it looked quite bright in the 30mm eyepiece in amongs the bright stars of Hydra
there was no hint of tail and no colour,but still a nice sight, at a guess mag 7 the Sky gives it at mag 12 ?
I then went to Comet C/2009 G1 Sterio which is low down in Darado,Faint round round patch against against the back ground sky, no other detail.
I should have looked for this comet earlyer.

Galaxy cluster Abell 3627
A challenge was issued by a well known 'Deep Sky' observer Steve Gottlieb on another Web site to observe some of the brighter
galaxies in Abell galaxy cluster 3627 on the boarder of Triangulum AUstrale and Norma.
I have observed this cluster a few times in the past couple of months but have not written down my observations.
Last night I rectified that.
Abell 3627 consist of 59 galaxies with the brightest being mag 12.46 and the faintest observed in my scope mag 14.84.
All the galaxies in this cluster are ESO Catalogue objects.
I will report these galaxies in the order I observed them.

I Started the observation 09:00 UT 19:00 local time with ESO 137-6 A Large eliptical galaxy haze brighter towards the middle, given mag 13.08.
There is a mag 13.0 star due north.
This galaxy is seperated from ESO 137-8 by a trapezium of stars with the brightest being mag 9.3.

Eso 137-8 Eliptical galaxy brighter in the middle, this galaxy seemed fainter to me but the given mag is 12.84,
as it is a bit larger this may account for it seeming to be a bit fainter.
Both these galaxies where seen with direct vision in both a 13mm Nagler and a 6mm Radian.

ESO 137-11 Seen as a faint round haze south of ESO 137-10, best seen with averted vision but also seen directly.
Given mag is 14.63.6MM Radian, just hinted at in 13mm Nagler.

ESO 137-10 Large round faint shows brightening towards the middle, mag 12.46. 6mm Radian 13 mm Nagler

ESO 137-2 Faint streak seen at times with direct vision, but best seen with averted vision. mag 14.84. 6mm Radian.

ESO 137-3 Faint elongated haze, two stars of mag 10-11 made it difficult to to descern any shape or form.mag 13.55
6mm Radian

ESO 137-1 Faint haze seen direct andslightly better with averted vision.no detail. Mag 13.75 6mm Radian

ESO 137-7 faint oval seen with averted vision, no other detail.mag 13.9 6mm Radian.

The sky is brilliant with stars in this area which made the observation of the fainter galaxies even more difficult.

What started of as a 9-10 night sky quickly deteriated as the mist came in so called it a night at 10:30 UT 20:30 local

I have left the preamble in just for a matter of interest sake.:)

I hope this is of some interest.
Cheers :thumbsup:

[astroron]

Hi Rob see my report above?
As mentioned in my report it was because of the Challenge from Steve that I did my observations. :)
I was just thinking:rolleyes: maybe when the constellations where given their present boundries in I think about 1930's that it might have been moved wholey into Triangulum:question:
Just a thought :shrug:
Cheers :thumbsup:

[Robh]

Hi Ron,

That list of observed galaxies is pretty impressive. I don't think I'd have much hope seeing them here. What a coincidence I should dig up Steve's report just minutes before your post!

I thought about a possible boundary change but concluded it was unlikely the cluster would have been known then. Maybe I'm wrong.

Regards, Rob

[astroron]

Hi Rob, just had another thought :rolleyes: as is noted the galaxies are also only ESO numbers and as they are so far south May not have been much observed till ESO was formed.
As Robert said the center of the cluster is in Triangulum but part drifts over to Norma .
Cheers :thumbsup:

[astroron]

Rob, This link may be of interest:question:
http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1998PASJ...5 0..195T&db_key=AST&page_ind=0&data_type=GIF&type=SCREEN_VIEW&classic=YES

Cheers:thumbsup:

[Robh]

Thanks Ron.

From the article the centre is put at 16h 17m 25s, -61 04 13. The X-ray map page 201, puts the boundary of the cluster between RA 16h 13m and 16h 20m and between Dec -60 30 and -61 30. Dimensions are roughly 1.8 by 1 degree.

Allowing for the relative tilt of the cluster to the border, the closest point to the Norma border is roughly 16h 15m, -60 30, the furthest point roughly 16h 17m, -61 30'. My calculations put the closest point roughly 15 arcminutes form the Norma/Tra border and the furthest point about 75 arcminutes from the border.

According to this, no part of the cluster is in Norma. At least not on current boundaries.

Regards, Rob

[madbadgalaxyman]

Hi Ron and Rob,

Thanks for the interesting links and for the observing report.

As I mentioned in my previous post, the title of a paper on Abell 3627 (more properly known as ACO 3627) refers to it as the Norma Cluster

The people who wrote this paper (Woudt, Fairall, Kraan-Korteweg), are probably the world authorities on the galaxies near the ZOA in the southern Milky Way (= "Zone of Avoidance")(which marks where we find it difficult to see external galaxies near the plane of our own Galaxy.),
yet they persist in referring to Abell 3627 as the Norma Cluster, even though it is in Triangulum Australe.
(for instance in their paper (2008), MNRAS, Volume 383, p.445)

Anthony Fairall and R.C. Kraan-Korteweg have studied the large-scale structures (supergalactic structures) in the universe, for many years.

(unfortunately, Anthony(A.P.) Fairall tragically died, quite recently, in a diving accident)
(It would seem that Fairall became so obsessed with southern superclusters, walls, and voids, that he has recently "flown upwards" to the Great Attractor......)

I don't think people who survey superclusters of galaxies are very concerned with where the constellation boundaries are!

P.S.
I note that when I do a search for papers containing ACO 3627 at //adswww.harvard.edu .....that there has recently been some near-infrared imaging done of this cluster. (good idea, due to the high extinction from intervening dust particles)

[Dave2042]

Maybe a linguistic explanation?

It's close enough to Norma, and Norma has two syllables while Triangulum Australe has seven. Lazy speech wins.

[astroron]

Thanks Robert, I will leave it at that.
Cheers:thumbsup:

[Robh]

Thanks Robert.

Interesting information and perspective.
Further confusion arises when sites (e.g. wikipedia) actually table the Norma Cluster as being in Norma!

Regards, Rob

[astroron]

Probably because the people who make the entries just troll it up from previous information and don't check to see if it is correct.:rolleyes:
Cheers:thumbsup:

[Terry B]

Is it a similar reason that 10 Ursae Majoris now is part of the constellation Lynx?

[Robh]

Hi Terry,

There were many stars re-allocated by the current constellation boundaries defined by the IAU around 1930. However, in the case of the Norma Cluster, I think the name is more recent (as Robert intimated earlier as well) and the cluster was probably unknown before 1930.

As Robert stated, maybe the astronomers didn't actually check where the Norma/TrA border actually was.

Regards, Rob

[madbadgalaxyman]

The idealists who founded Wikipedia felt that their encyclopedia would encompass "the knowledge of all humankind" and thus it would be inherently self-correcting.
They were obviously wrong.

Quite a few shorter wikipedia entries on astronomy are substantially wrong, and I know that I should be "out there" correcting them, but I feel that knowledge without attribution to a particular scholar is of little permanent value.

Even when you get someone like me (a very knowledgable amateur who reads the scientific literature a lot)
writing a public article on astronomy, the odds of a major error, while much less, are still significant.

[Robh]

Wikipedia is a great idea and has a lot of information on all aspects of astronomy and science. I often go to it for convenience but unfortunately what you say is true. You always have to double check the information.

A number of years ago, I was reading the wiki on the Jewel Box, which stated that the bright orange star is kappa Crucis. It still hasn't been corrected.

Regards, Rob

[madbadgalaxyman]

]

Perhaps the 13th magnitude members of this cluster of galaxies had to wait for the southern Schmidt surveys, before they were discovered. Maybe they were like the Circinus Galaxy, which was discovered in the late 1970s, if memory serves me correctly.

The ESO (B) survey (or atlas) discovered some 3500 southern galaxies in the 1970s, and I suspect that some of them were as bright as 12.5-13 blue magnitude

[madbadgalaxyman]

Wikipedia is not the only source of information that perpetuates nonsense, which becomes so called "truth" through constant repetition.

Writers of general astronomy textbooks have been doing this for a long time when they make these three incorrect statements:
- The Milky Way Galaxy is 100,000 light years across.
- Our Galaxy contains 100 billion stars
- The Andromeda Galaxy is like the Milky Way
(it sure isn't! The bulge and disk and halo properties of M31 are very different from those of the Milky Way)