From: njzy@vax5.cit.cornell.edu (T. Joseph Lazio, Cornell University)
Newsgroups: sci.astro
Subject: Re: Standard model of QSOs
Date: 21 Jul 92 08:31:18 EDT
Distribution: sci
Organization: Cornell University

In article <BrMB0I.8Mx@well.sf.ca.us>,
metares@well.sf.ca.us (Tom Van Flandern) writes: 
> 
> and yaron@astro.as.utexas.edu (Yaron Sheffer) writes:
> 
>> And another surprise for you: All the quasars in the survey above are X-ray
>> sources, and we now know at least 75% of quasars ARE X-ray sources and they
>> cover the entire sky with their radiation. So much for "cool" and
>> "unionizing" "supermassive stars" as a model for quasars...
> 
>      Even the Sun is an X-ray source.  Which is more plausible:  Quasars are
> the hughest objects in the universe, which blast out so much X-ray radiation
> that it gets through all those absorbing hydrogen clouds producing absorption
> lines, and still has more intensity when it arrives from half-way across the
> universe than combinations of hundreds of billions of stars in normal
> galaxies?  Or that the easily-absorbed X-rays are actually coming from
> modest-sized nearby sources whose high redshifts are produced by internal
> gravitation?

 Tom, you haven't answered Yaron's objection.  You have continually 
 described QSOs as being *cool*, supermassive stars (emphasis mine).  To 
 me, cool means T = 1000 K (or so).  How does a cool star emit in the 
 X-rays?

 Moreover, your comments about the absorbing HI clouds are simply wrong.
 In an earlier post I pointed out that gamma-rays should easily be able
 to penetrate the intergalactic HI clouds (i.e. those deduced from 
 Lyman alpha forest observations and interpreted with standard model
 assumptions).  There is no contradiction in seeing X-rays as well 
 (except maybe for the very softest X-ray bands).

 The Gunn-Peterson test tells us that there is very little intergalactic
 HI.  The Gunn-Peterson test is, briefly, the following:  Examine the 
 spectra of QSOs which are redshifted to the point that the Lyman alpha
 emission line can be seen in the optical (typically, the Lyman alpha 
 emission line is at 1215 Angstroms, too far into the UV to see from the 
 ground).  Is there emission in these spectra blueward of the Lyman 
 alpha line?  If so, there cannot be much intergalactic HI; the HI 
 cross-section for a Lyman alpha photon is huge.  If there was a reasonable
 amount of intergalactic HI, there would be a sharp cut-off on the 
 blue side of the Lyman alpha line.  Since sharp cut-offs are not observed, 
 the conclusion is that there is either very little hydrogren present in 
 intergalactic space or that it is largely ionized.

 Now if the Gunn-Peterson test tells us that there is very little HI 
 present, I would not expect X-radiation to be severely attenuated 
 in passing through the intergalactic medium.

-- 

 T. Joseph Lazio                | Why relativity? and Why  
 514 Space Sciences             | turbulence?  I really believe   
 Ithaca, NY  14853              | [God] will have an answer for the
 (607) 255-6420                 | first [question].
 lazio@astrosun.tn.cornell.edu  |   -- W. Heisenberg, on his death bed
ICBM:                           |
 42 deg. 20' 08" N              |              STOP RAPE
 76 deg. 28' 48" W              |