NGC 4724 & NGC 4727 - mysterious galaxy pair

[madbadgalaxyman (Robert)]

For those of you who like unusual and challenging targets that are very poorly understood so far and that have hardly been studied by astronomers, I call your attention to my discussion of this galaxy pair in the Observation Reports forum;
the discussion was started by "pgc hunter" under the heading "Observation Report 4/6/11"

At first glance this interesting close pair seems to be a non-interacting alignment of two galaxies in the same line-of-sight, but I find that there are some definite oddities in the structure of one of the galaxies.

Despite the fact that this is a relatively prominent pair of galaxies, there is hardly any data in the data archives about it, and hardly any available imaging, and virtually no study of it in the literature!

[gregbradley]

Interesting target Robert.

Firstly the magnitude is a bit dim but imageable but it seems very small.

I may shot some luminance of it tonight as its an early evening target.

I'll see how it turns out.

Thanks for the tips. I am always looking for new imaging targets.

Greg.

[madbadgalaxyman (Robert)]

Hi greg,

I suppose the interest of this object is the element of mystery, rather than its brightness and size. The DSS image I attached is very poor....it ought to be possible to do much better with a CCD camera.

I ransacked numerous extragalactic databases, and usually found nothing much about this pair of galaxies. This is quite unusual these days, even for southern objects.

The whole point of thinking about this object or imaging it..... is that there may be nobody on earth who knows, beforehand, what can be seen in an image of this object!
(I would put my money on there being an interaction of the spiral with some small galaxies near it. This is a very distant object. )

I should really continue my series of articles about weird and wonderful southern galaxies, as there are a lot of strange ones about that have had little attention so far!
(6 hours per day of thinking about galaxies, and I have less time then ever)

[gregbradley]

I started taking a few shots of it although its very windy at the moment.

There seems to be a galaxy cluster in this area so it will make a reasonable image.

The 2 galaxies you mention are quite small though.

Greg.

[irwjager (Ivo)]

Can't wait to see your data Greg!
Robert, have you been able to find out the distances to these galaxies?

[madbadgalaxyman (Robert)]

This galaxy pair really is one of the most poorly known objects in the sky.......

I just interrogated the 6dF redshift survey, which was supposed to provide recession velocities for nearly all of the most obvious galaxies in the southern sky; yet it seems that one of these two fairly prominent galaxies does not have a redshift, even in this massive database!

Therefore.....I am unable to confirm the large velocity difference of about 3400 km/s that was reported in some older data.

It does seem that the spiral member of the pair is very distant, at 7622 km/s redshift (in the heliocentric frame).
However, as far as I am concerned, the question of whether this is an apparent pair or whether it is a physical pair, is not yet resolved at 100% certainty. Perhaps I should write to Prof Tony Fairall in South Africa....he knows most everything about southern redshifts.