Baryon Oscillations Working Group 
Telecon 22 Sep 2004

Attending: Tamas Budavari, Saul Perlmutter, Martin White, Ivan Baldry, 
Nikhil Padmanabhan, Bhuvnesh Jain, Karl Glazebrook, Daniel Eisenstein, 
Mike Lampton, Mike Levi, David Gerdes, Eric Linder

Multihump filters: Tamas Budavari outlined their use for improving 
photometric redshifts.  He is awaiting throughput numbers specific 
to SNAP to carry out more detailed filter investigation.  Such 
filters have not been implemented but there do exist interference 
filters with high resolution from Barr Associates.  Finer photo-z 
would help cosmological parameter determination but also in 
preselection for spectroscopic followup. 

Ground:  Photometric redshifts from the ground for redshifts z>1 
are regarded as an iffy possibility.  One can do ok out to z=1 
but the IR is very difficult.  One will gain something by having 
photo-z's for z=1 and z=3.  Karl Glazebrook argues that spectroscopy 
with OH filters can work past z=1 without a huge hit.  Time will 
be a large factor.  A dedicated telescope covering 10000 sq.deg. 
might work for baryon oscillations - one would like a testbed first. 
Question as to whether for a dedicated telescope one could get away 
with a 4m rather than 8m. 

Space: Daniel Eisenstein said "The infrared is transformative for 
photo-z's".  The different groups need to agree on what the 
percent improvement is for moving from a photometric to a grism 
survey.  Caution about adding a new instrument component if it 
only offsets three years of work on ground.  "You are giving 
back the advantage of space, the low noise, when you go slitless." 

Grism survey: does one get a systematics floor in a 
H\alpha survey from NII confusion - bias from the ionization state 
in the galaxy.  Have we converged on 0.3% \delta z/(1+z) for the 
precision needed?  Remember that R=75 on a point source may be 
only R=7 on a large galaxy.  A diffuse line across the galaxy 
will make use of zeroth order for location of the galaxy very 
difficult. 

ACTION ITEMS: 

* The various groups should rationalize their photometric survey 
estimates on cosmological parameters, as a start.  Eric will 
check derivatives and covariances with Hee-Jong. 

* Carry out the calculations for multihump filters for photo-z. 
Do we want finer resolution in dz at z=0.6-1 (to offset low 
volume) or z=1-1.6 (because more cosmological leverage). 

* Plan for another telecon first week in November. 

-Eric Linder (evlinder@lbl.gov)