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Quasars Are The Same All The Way Back


  02:04:29 am, by Nimble   , 313 words  
Categories: Thoughts, Science

Quasars Are The Same All The Way Back

You might have to be pretty darned science nerdy to sit and watch the entire presentation by Michael Strauss like I did.

These are some fairly serious results back from the Sloan Digital Sky Survey.

We are able to look back to at least a few quasars where their redshift is z>5. For reference, we should be able to see the very first galaxies form at about z=15, and z=6.5 is supposed to be about a billion years after the big bang.

One of the conclusions based on the sky survey was that luminous quasars have exactly the same spectra all the way back. No change in metals, gases, or any particular 'evolution' of any kind. From the presentation:

High-Redshift Quasars are "Normal"

* Metallicities are solar or above
* Optical spectrum and continuum (redward of Lyman alpha) is no different from that at lower redshift
* X-ray to optical ratio, and X-ray spectral slopes are independent of redshift
* Associated molecular gas mass typical of that at lower redshift
* Fractions of radio-loud quasars and Broad Absorption Line Quasars is normal

This is odd. We should expect to see some changes in the quasars themselves.

The presentation goes on to show some odd absorption of some spectral lines by the interstellar medium (the Lyman alpha forest - hydrogen absorbing light as it progressively shifts to the red end of the spectrum) at these high redshifts. In particular, there's a spot where there's far less absorption than there should be, then at z>5.7, the absorption is there, though it sounds like it can depend on which direction you're looking in.

Can the universe be as young as is commonly said, if quasars show no change back that far?

There was a most excellent slide that they put together with an image done by Xiaohui Fan of the spectra of quasars as the redshift increases. This is just plain cool:

Quasar spectra

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