From: Ariel Goobar (ariel@physto.se)
Date: Tue Dec 14 2004 - 06:09:18 PST
Message from Tomas on photo-z below. As he is not on hstsearch@lbl.gov
he cannot himself post this message.
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Hi Rachel et al.
Based on the latest photometry, I get the following phot-zs for the host:
SE knot, 0.18 arcsec aperture: z=1.47
NW knot, 0.18 arcsec aperture: z=1.58
SW knot, 0.18 arcsec aperture: z=1.65
all, 0.75 arcsec aperture: z=1.59
all, 1.05 arcsec aperture: z=1.62.
I wouldn't trust the 'knot' measurements too much since these are
measured in small
apertures where color dependent aperture corrections should be applied
(and where
alignment/registration between filters/instruments is crucial).
The 'large aperture' measurements should be more correct. This, of course,
assumes that the knots really are at the same redshift. Considering the
close phot-zs for the knots, I think we can assume that they are. My
choice between the two large aperture would be the 1 arcsec, i.e.,
the phot-z is z ~1.62. From the plotted probability distributions, I would
assume a 1sigma error of about ±0.08. I more conservative estimate
would be z=1.6 ±0.1
The spectral type of the host is approximately consistent an Sab spiral
In the attached plot, IDs=6, 7, 8, 9 and 10, corresponds to SE, NW, SW
knots and 0.75+1.05 apertures, respectively.
Tomas
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