Re: F814W-z vs F775W-z

From: Nino Panagia (panagia@stsci.edu)
Date: Wed Jan 18 2006 - 11:19:15 PST

  • Next message: Henk Hoekstra: "Re: F814W-z vs F775W-z"

    Hello Everyone,

    At the risk of saying something trivial (or even stupid...), I would
    like to remind that the QE of the z850 band is much lower than that of
    the i775 or I814 bands. This will imply the MOST of the observing time
    will be devoted to z850
    imaging, unless the gain in terms of a higher intrinsic flux toward the
    red is so high that we don't care.

    Honestly, I hope that this remark of mine is NOT important and that
    everything will work PERFECTLY the way is currently planned.

    Ciao - Nino

    P.S. [Mostly for Saul, but not only him...] On November 1, 2005, ESA
    "retired" me for reaching 62 years of age (this includes an EXCEPTIONAL
    2 years extension), and, therefore:
    - My affiliation should be listed as STScI only (I am going to be
    granted Emeritus status here), and the corresponding country US, instead
    of ESA (I applied for a green card in November and, judging from the
    success of a similar application by an ESA engineer at STScI who retired
    6 months earlier, it should be granted in a relatively short time...),
    and
    - THIS time I would need some salary support to do my research, up to
    two month-equivalent, which should be factored in the budget.
    Since my ESA pension provides EXCELLENT medical insurance and I do NOT
    need to save for retirement, it may eventually be much cheaper than it
    sounds...

    Marc Postman wrote:
    >
    > In preparation for discussion tomorrow (is the next telecon tomorrow?),
    > here are some predicted colors as a function of redshift and SED for
    > i775-z850 vs. F814W-z850 (in the AB mag system). The qualitative trends
    > are similar but, of course, the i-z color has quantitatively larger and
    > the (i775-z850) gap between z>1 galaxies and z<0.7 galaxies is also
    > quantitatively larger. This is important from the perspective of
    > isolating the red sequence in clusters without extensive redshift
    > information. For example, at zmag of 24, the foreground field galaxy
    > population has (i775-z850) colors in the range -0.1 < (i775-z850) <
    > 0.55. This is well below where the red sequence lies for z > 1 but only
    > a few tenths of a mag below where the RCS lies in (I814-z850). While we
    > could still distinguish the RCS in (I814-z850), using (i775-z850) would
    > be preferable, I think.
    >
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    -- 
    

    ========================================================================== Prof. Nino Panagia Senior Astronomer panagia@stsci.edu Space Telescope Science Institute Phone: 410-338-4916 3700 San Martin Drive FAX: 410-338-4767 Baltimore, MD 21218, USA www-int.stsci.edu/~panagia ==========================================================================



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