Talk:Large quasar group

unique or a class of objects

Can anyone clarify whether this is the only LQG or if there are others. μηδείς (talk) 07:14, 12 January 2013 (UTC)

According to the sources, the existences of large quasar groups have been known since 1982. However, for the life of me, I cannot find the other distinct examples. All that I can find is this super-structure discovered this year. DarthBotto _talk•cont 00:29, 14 January 2013 (UTC)

With that in mind, if they do come up with a distinct name for this structure, I'll see to it that a separate article is created for expanded information. DarthBotto _talk•cont 00:31, 14 January 2013 (UTC)

Suggestion pictures to add to the article:

http://i.space.com/images/i/000/011/163/i235/black-hole-quasar-water-cloud.jpg?1311361757

http://i.space.com/images/i/000/024/209/original/most-distant-quasar.jpg?1354722731 Jiawhein (talk) 01:19, 19 January 2013 (UTC)

The first image is nasa, which would make it free, the second is here. These are pictures of quasars, not large groups, but would help make the article look better.

This artist’s impression shows how ULAS J1120+0641, a very distant quasar powered by a black hole with a mass two billion times that of the Sun, may have looked. This quasar is the most distant yet found and is seen as it was just 770 million years after the Big Bang. This object is by far the brightest object yet discovered in the early Universe.

Martin451 (talk) 06:08, 19 January 2013 (UTC)

Isn't this purely decorative? This isn't the quasar article, and an individual quasar doesn't illustrate a group of quasars. WP:PERTINENCE -- 76.65.128.43 (talk) 02:06, 20 January 2013 (UTC)

An illustration gives a much quicker idea of what a quasar might be like to those not already familiar with it, and many people will be coming here because this is in the news, and not because they already are familiar with the subject. I do think naming the specific quasar is beside the point, so I will remove that part of the caption. μηδείς (talk) 02:26, 20 January 2013 (UTC)

It would be better if we had some image of an LQG. (preferably a different one from the one at Huge-LQG, since that one is copyrighted and cannot be used here.) -- 76.65.128.43 (talk) 02:34, 20 January 2013 (UTC)

It is partly decorative, but does illustrate what a single quasar looks like. I do wonder about how useful a picture of a group would be, it will just be a group of dots. wrt the one at Huge-LQG that one illustrates a specific (well 2) groups, so is useful to the article, I assumed it was copyrighted as I could not find any other licence.Martin451 (talk) 07:14, 20 January 2013 (UTC)

LQGs are poor tracers of mass distribution

There is a major flaw in regarding any observed large quasar group as a "structure" and, in particular, as a structure which usefully traces mass distribution.

The flaw arises because quasars and related active galactic nuclei are well known to be dynamic objects varying in brightness and spectral energy distribution on timescales from seconds to decades (at least). The variability timescales may be much longer than a survey takes but are far shorter than the timescale for changes to mass distribution. Hence finding an apparent group of quasars in any incomplete survey (as they all are) amounts only to finding quasars that happen to be "on" at the time of the survey.

A simple analogy explains the problem, derived from observing flashing warning lamps around road works. Although the lamps may be distributed around the roadworks in a regular even pattern, they flash asynchronously. At any particular moment, one may then see some flashing close together while the rest are off. If one waits a short while, a different set will happen to be "on" at the same time. Does this mean the clustering of lamps has changed? No: only the observability has changed.

I therefore believe one cannot make valid statements about mass clustering derived from observed clustering of quasars. This also disposes of the issue of apparent quasar structures being "too large".

Please note that I include in this flaw the "Newman LQG" in the article discovered in my own thesis work (Large groups of quasars in an ultraviolet excess survey, Newman P.R., 1999, PhD thesis, University of Central Lancashire).

p.r.newman (talk) 17:23, 10 March 2024 (UTC)