From: Ariel Goobar (ariel@physto.se)
Date: Tue Apr 09 2002 - 09:24:41 PDT
Some quick comments,
On Wed, 10 Apr 2002 clidman@eso.org wrote:
> Dear Ariel,
> This is a good suggestion and it was something that Saul had proposed.
I mentioned this possibility to Saul last night. The thing to remember is
that if you assume that the rate of Ia's is proportional to the rest-frame
B-band galaxy magnitude, then you expect about 50% of the SN host
galaxies with 22<I<23 to be at z>0.8 (see Dahlen & Goobar, PASP, also
in astro-ph/02 + something.
>
> In terms of grisms, we plan to do the following.
>
> If the candidate is brighter that I=23.4 (The median I-band discovery magnitude for
> z=0.75), we will use the 300V grism. If it fainter, we will use the 300I grism.
> Even though the 200I grism is slightly more efficient and has a slightly larger
> wavelength range, we will go for the higher resolution grism.
>
> Cheers, Chris.
>
>
> Ariel Goobar wrote:
>
> > Dear Chris,
> > w.r.t the issue of trying out how FORS2 works there is
> > another possibility worth considering. Assuming we get Subaru
> > candidates in the next hours we may want to start with a shorter
> > exposure (<1 hour) of a host galaxy for a case where there is a
> > good candidate on top of a visible galaxy. If the galaxy redshift
> > is in the interesting range we could go for the SN the next night.
> > By then we would also know the performance of the instrument.
> > Cheers,
> > Ariel
> >
> > On Tue, 9 Apr 2002 clidman@eso.org wrote:
> >
> > > Dear Ariel,
> > > At I=24.5, FORS2 should deliver a S/N ratio of approximately 2 per
> > > pixel (3.28 Angstroms) or 4 per resolution element (4 pixels with the
> > > one arc second slit) in 3 hours with the 300I grism. There is a second grism, 200I,
> > > with lower resolution but increased efficiency. The new CCD is meant to have less
> > > fringing, so the 200I may be better, but without data, it is difficult to judge.
> > >
> > > Although our main aim is to observe supernovae with z > 0.85, we may want to
> > > consider observing one relatively nearby supernovae (z<0.5) to make sure
> > > everything is working fine. We will be one of the first users of FORS2 with the new
> > > CCD.
> > >
> > > Gaston and I will plan our schedule in the following way. I will stay up until
> > > the observations have started and Gaston will come early in the morning to
> > > do the data reduction and post the results on the web.
> > >
> > > Contact Information
> > > ===============
> > >
> > > Gaston and I are sharing an office in Santiago. The number is (++56) 2 463 3106.
> > >
> > > Our results will be posted at the URL http://www.sc.eso.org/~clidman/
> > >
> > > Cheers, Chris.
> > >
> > > Ariel Goobar wrote:
> > >
> > > > Dear Chris & Gaston,
> > > > (CC: Saul)
> > > >
> > > > as you know, we had a short teleconference about the immediate run.
> > > > One of the things that were briefly touched upon is what fraction of
> > > > the FORS2 time we should spend in April vs May. We argued that we
> > > > probably want to bank >10 hs for May, especially for the early
> > > > half nights (May 4-6), as then we should have both Subaru and CFHT
> > > > candidates and still 5 mights to go before the first Keck night.
> > > >
> > > > As the first priority for the april run is 1 SN @ z>1 and 2 @ z~0.85
> > > > we are really looking at candidates with I>23.5. In fact, it is
> > > > only at I>24 where we have the largest probability of having
> > > > a z>1 candidate. That, in turns means, that cannot do more
> > > > than 3 candidates this week without exceeding our budget (unless
> > > > seeing is superb, of ocurse).
> > > >
> > > > Maybe you could elaborate a bit more on the table that Gaston
> > > > started to do here about the minimal exposure lengths needed
> > > > for identifying a Ia at z>0.8. I think it will become important
> > > > when making the last minute decission on which targets to observe
> > > > at Paranal.
> > > >
> > > > Cheers,
> > > > Ariel
> > > >
> > > > --
> > > > ___________________________________________________________________
> > > > Ariel Goobar (ariel@physto.se)
> > > > FYSIKUM, Stockholm University
> > > > Stockholm Center for Physics, Astronomy & Biotechnology
> > > > tel: +46 8 55378659
> > >
> >
> > --
> > ___________________________________________________________________
> > Ariel Goobar (ariel@physto.se)
> > FYSIKUM, Stockholm University
> > Stockholm Center for Physics, Astronomy & Biotechnology
> > tel: +46 8 55378659
>
-- ___________________________________________________________________ Ariel Goobar (ariel@physto.se) FYSIKUM, Stockholm University Stockholm Center for Physics, Astronomy & Biotechnology tel: +46 8 55378659
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