From: Greg Aldering (aldering@panisse.lbl.gov)
Date: Wed Oct 29 2003 - 00:46:48 PST
Hi Rob,
In your plan there is a big jump in the number of orbits in going from
cases 1 & 2 to cases 3 and 4; I would suggest an intermediate pair of
cases, with 6 orbits in z (1,1,2,2), with the option of 9 orbits of grism.
This would handle SNe of intermediate brightness/redshift, or be an easy
means to adjust the S/N we wish to reach at a given brightness/redshift.
I'd also like to rise the question of whether there should be additional
cases offering more J and/or H in the place of grism. We can study this in
detail later, but there could be benefit to having cases #2'and #2'' with
0 grism and one more epoch of J & H (say 3 orbits of J and 3 orbits of H)
or two more epochs of J (3 orbits each). Likewise, cases #4' and #4'',
with 0 grism and one more epoch of J & H (say 4 orbits of J and 4 orbits
of H), or two more epochs of J (say 4 orbits each and then 1 more ref
orbit). One motivation would be that we could implement C-magic if we have
the additional color points, which would add a little novelity to our
program wrt Adam's; and we may be able to distinguish the SN type (albeit
with somewhat less opportunity, I presume, to abort later orbits than the
grism might afford) using the color curves.
As it should not be hard to add these additional cases once the other
cases are entered, I would recommend adding these just so we don't have to
worry about them later (and then perhaps find that they can't be done). In
particular, as we must require that NICMOS orbits avoid the SAA, we should
lock-in as many such orbits we might possible want. Such orbits are very
valuable and so might be hard to get later on without a big ugly fuss.
Two other issues that we can study after the RPS2 is submitted:
1) Should the z, J, H observations be at the same epoch - which makes the
color calculation easier - or at slightly staggered epochs - which
helps fill in the lightcurve and possibly make the fit more robust?
2) What is the appropriate number of NICMOS references? If we use
a model (continuous or pixel-by-pixel), then the observations
which contain the SN provide information and we wouldn't get all of
the sqrt(2) hit that pixel-by-pixel subtraction introduces. Thus,
where I have added J or H visits of more than 3 and 2 orbits,
respectively, we may not need to increase the number of references.
(This decision is very likely to come down to how well the PSF
NICMOS is expected to be known; Vitaliy is exploring this type
of question in relation to Albinoni.)
- Greg
On Tue, 28 Oct 2003, Robert A. Knop Jr. wrote:
> For each search, we should have for different follow-up possibilities
> available, to be chosen via TOO. Note that in all cases, the orbit
> count includes IR final references. Estimates below for R-I are based
> on the z-J color, *not* on the J-H color. Note that both z and J are
> contributing to the stretch here.
>
> #1 : Low-redshift, no grism needed.
>
> 4 orbits in z, spaced as Rachel did
> 3 orbits in J, spaced as Rachel did
> 2 orbits in H at the first epoch
> (save 3 J, 2 H orbits for final ref)
>
> TOTAL = 14 orbits
>
> WORST CASE z=1.3 (usually we do better!)
> ds = 0.09
> dt = 2.5
> dmbcorr = 0.15
> d(R-I) = 0.038
>
> ==> For a galaxy with a very good photo-z
>
> #2 : Low-redshift, grism needed
>
> 4 orbits in z, spaced as Rachel did
> 3 orbits in J, spaced as Rachel did
> 2 orbits in H at the first epoch
> 7 orbits grism
> (save 3 J, 2 H for final reference)
>
> TOTAL = 21 orbits
>
> Worst case as #1
>
> #3 : High-redshift, no grism needed
>
> 8 orbits in z, spaced as Rachel did
> 3 orbits in J, spaced as Rachel did
> 2 orbits in H at the first epoch
> (save 3 J, 2 H for final referenced)
>
> TOTAL = 18 orbits
>
> WORST CASE z=1.5
> ds = 0.08
> dt = 2.2
> dmbcorr = 0.14
> d(R-I) = 0.046
>
> ===> For a galaxy with a very good photo-z
>
> #4 : High-redshift, grism needed
>
> 8 orbits in z, spaced yadda yadda
> 3 orbits in J
> 2 orbits in H
> (save 3 J, 2 H for final reference)
> 11 orbits grism
>
> TOTAL = 29 orbits
>
> Worst case as in #3.
>
> -Rob
>
> --
> --Prof. Robert Knop
> Department of Physics & Astronomy, Vanderbilt University
> robert.a.knop@vanderbilt.edu
>
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