From: Ariel Goobar (ariel@physto.se)
Date: Sat Jun 11 2005 - 02:31:59 PDT
FYI: during the SCP-meeting last week Jakob and I mentioned that we had
found an inconsistency in the Benitez et al lensing analysis of 97ff.
Narciso has now confirmed that we were right. -Ariel
---------- Forwarded message ----------
Date: Fri, 10 Jun 2005 18:10:21 +0200
From: Narciso Benitez <benitez@iaa.es>
To: Ariel Goobar <ariel@physto.se>
Cc: txitxo@pha.jhu.edu, adam riess <ariess@stsci.edu>,
Subject: Re: GL magnification of 97ff
Dear Ariel,
I am afraid that your suspicion is right, I multiplied the velocity
dispersion obtained from Faber Jackson for the ellipticals by sqrt(2) to
have the same kind of velocity for all galaxies and then forgot to
divide by 2 in the formula for the Einstein radius. With the right
formula the magnification is ~0.16+-0.06.
Best regards,
Txitxo
Ariel Goobar wrote:
>Dear Narciso and Adam,
>
>we are in the process of re-analyzing the GL magnification probability
>distributions for all GOODS SNe + 97ff. Of course, we will cite your
>work on 97ff. However, we have found that we are unable to reproduce
>your result in astro-ph/020709. We think we have found a possible
>reason for the discrepancy. In table 1 (col 11), you give _circular_
>velocities for six galaxies, two of which are labeled as being
>ellipticals. This seems also to be the measure of velocity you use in
>your definition of the Einstein radius, where you refer to the
>Bartelmann & Schneider 2001 paper. Now, the definition seems to us to
>be in conflict with the quoted paper, in which the velocity used in
>the same expression is the velocity _dispersion_. This equation
>made us somewhat concerned that you may have mixed-up v_c and v_disp.
>
>As a test, we were able to
>reproduce your results when using your quoted circular velocities as
>the velocity dispersion. However, if we apply the sqrt(2) factor to the
>values in col 11 v_c=sqrt(2)*v_disp (as we think one should do),
>our results differ , and we find less magnification.
>
>So here is our question to you: can you specify which Tully-Fisher and
>Faber-Jackson relations you used to get your final result (0.34 +/- 0.12)?
>In the last paragraph of the left column in page 2, you say that you use
>the velocity dispersion. Do you think it is possible that you mixed up
>the two kinds of velocity? Or do you have some other clue that would
>explain a lower magnification (~0.2 mag) than what you found?
>
>Best regards,
>
>Jakob, Christofer and Ariel
>
>
>
>
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Narciso (Txitxo) Benítez |tel:(34)-958-230-606 Investigador Ramón y Cajal/Ramón y Cajal Scientist|fax:(34)-958-814-530Instituto de Astrofísica de Andalucía (CSIC) Camino Bajo de Huétor, 24 Granada 18008 Spain ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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