From: Tony Spadafora (ALSpadafora@lbl.gov)
Date: Sat Feb 01 2003 - 12:30:25 PST
attached mail follows:
Dear Tony,
In response to the questions raised by Ariel's recent e mail message, I
have done some further calculations on the X-ray halo optical depth, in
connection with the result of Paerels et al. These calculations are based on
eq'n 31 of the notes on x ray halos distributed last week. I obtain the
following results: If one assumes that the co-moving dust density is not
constant out to z=4.3, but rather cuts off abruptly at z=0.5, then the loss
in sensitivity by the Paerels experiment is a factor of 13 for omega m=1,
omega lambda =0; and it is a factor of 19 for omega m=0.3, omega
lambda=0.7. This would make the upper limit on the dust density achieved by
Paerels et al comparable to or even greater than that required by Aguirre's
hypothesis, rather than a factor of 10 lower.
If one assumes that the co-moving dust density is constant out to z=0.5
and then drops linearly to zero at z=3.0, the loss in sensitivity in the
Paerels experiment is a factor of 4.4 for omega m=1, omega lambda=0.0; and
it is a factor of 5.2 for omega m=0.3, omega lambda=0.7.
I do not know what Aguirre had in mind when he talked with Ariel, but it
might well have been something like the foregoing. I am also a bit worried
about the time delay between scattered and direct X-rays from the quasar.
This would require the quasar to be quite steady in X ray emission over a
time period of ‰1000 years, and we know that QSO's do show considerable
variability in luminosity over times of order 5-10 years.
Regards
Gene
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