Does anyone have a link or information about the numerical distribution of quasars by red shift? I know it is roughly a bell type curve with the peak at a little over a red shift factor, z, of 2 but I would like a more accurate figure than what I generated with a sample of 15 quasars.

Thanks
Snowflake

Here is recently published study with 200,000 quasars, figure 1 shows the distribution, but only between z = 1 and z = 2.2. (There is a thread about this in General Astronomy forum).

If you want to fiddle around with raw data, here's Sloan Digital Sky Survey's Third edition of the SDSS Quasar Catalog. Just download the "dr3qso.dat" from the end of that page. Apparently, the catalog contains 46,420 quasars. Have fun!

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Many graphs available

http://www.sdss.org/news/releases/20....edr.img6.html

http://www.astro.princeton.edu/~step...search/quasar/

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Just for clarity the second graph is a cumulative number count. The first graph is a redshift distribution.

Figure 2 of this paper shows the redshift distribution of 44,000 SDSS quasars from z<1 to z>4.

Thanks Ari Jokimaki and ToSeek

Your links were helpful, but I trying to find a graph of the number of quasars observed verses z. I know it is a bell shape curve and ToSeeks link shows the tail end at the highest red shift occurring at about a z of 6. I know that the lowest z of a quasar is about .06 (z) and the greatest so far is 6.4 (z) .

Ari Jokimaki’s link does show some of the middle part of bell shape curve, which is helpful. I had determined that the peak was with a z slightly greater than 2, but I was only basing that on a set of 15 quasars that I had statistical information on. The much more inclusive information in Ari’s link indicates the peak is closer to a z of 1.8. The plot also shows the skewed bell shape curve with the higher red shifts “compressing” the bell shape.

I down loaded all 2400 pages of SDSS but it is raw data and none of it kept to it’s tablature form.

Snowflake.

Hi dgruss23

Thanks for the link, it contained surprising information. (Figure 2 link). I did not know that there was evidence of a periodic variation in the distribution of quasars based upon red shift.


Snowflake

The periodic variation, (if as indicated by observation of quasars numbers per elongation of space), indicates that there has to be some kind of rhythmic function that exists on a cosmological scale of observation.

This is a very interesting observation.

It raises very interesting questions? (Like; why?)

Lemaître was right.

Snowflake.

This paper about SDSS quasar catalog III contains the graph you're after (it's figure 3 on page 29).

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Hi Ari Jokimaki

That is exactly what I wanted. Thank you very much.

John.