Subject: LSST stellar pops telecon

From: Knut Olsen

Submitted: Thu, 06 Feb 2003 15:03:23 -0300

Message number: 68 (previous: 67, next: 69 up: Index)

Hello,

        For those interested, I am forwarding the minutes from the
February 4 telecon of the NOAO LSST stellar populations panel.  Our plan
is to explore in detail the stellar populations science case for the
LSST, and produce a document to be presented to the SWG.  

Thanks to Abi Saha for taking notes!  These will be posted to a web site
next week, once the site is established.  

        Cheers, Knut
        

NOAO LSST stellar populations panel
Minutes from the Feb. 4 telecon

Notes taken by Abi Saha
Modified by Knut Olsen

Present: 
Knut Olsen
Abi Saha
Ed Olszewski
You-Hua Chu
Raja Guhathakurta
Chuck Claver
Andy Dolphin
Nick Suntzeff
Rodrigo Ibata


We opened with a discussion on what we aim to accomplish through the
March panel meeting.  Chuck Claver put it well: we first want to
define a flagship stellar populations project for LSST, and see how
this pushes the technical aspects of the telescope, camera, and
observing cadence.  We realize that the bar has been set high by the
solar system and extragalactic science cases.  A secondary objective
is to identify science cases that enhance the argument for LSST, but
that live within the boundaries set by the solar system and
extragalactic cases.

  We discussed a variety of technical points that need to be integrated
into 
the science cases that we develop:

           - the observing cadence.  Solar system science seeks field
return
 within 10-20 minutes, argues against getting color as a function of
time. 
Our viewpoint on the importance of color can drive the choice of what
mode 
is adopted for NEA searches. 

           - LSST's astrometric capability is obvious. 10 Mas
astrometry, 
implies proper motions (1mas/yr over 10 yrs) to few km/s in the Galaxy

           - what about spectroscopic followup?  Possible role of
KAOS+Gemini 
(4000 fiber spectrograph, 1.5 degree-wide field), if this gets built?

           - are narrow band filters simply impossible? Interference
filters 
are certainly limited to widths of ~100 angstroms.  What about
non-interference narrow filters?  How much emphasis should we place on
ultimately getting spectral information?

	   - the absolute floor in image quality that we expect to get is 
~0.43" (0."35 from telescope and 0."25 from the atmosphere in the
absolute best cases), while the median delivered image quality will be
~ 0."7.  Using seeing statistics, we need to calculate the area and
depth of the static survey as a function of desired image quality.
Even with ~0."5 images, a single exposure will be equally crowding-
and photon-limited at surface brightnesses of 25 mags arcsec^-2.  

           - operationally speaking, what should the telescope do if we 
encounter an exquisite seeing night? Could we do a good seeing project?  
This would likely have a heavy impact on the operations plan.

	   - The current plan is to have a multicolor reference image taken 
during the first year of operation.  How many colors do we need, and
what 
do we expect the image quality will be?     


        We decided to store these and future communications on a stellar 
populations panel email exploder.  Dave Bell will set this up.

	We finished by having the participants declare their ideas for 
1-paragraph science ideas to be submitted to Knut Olsen and posted on 
the web site within 2 weeks.  The topics are:

       1)  Claver -- the white dwarf luminosity function

       2)  Chu -- tidal interactions of the Magellanic Clouds with our 
	       galaxy -- stellar remnants

       3)  GuhaThakurta -- A photometric M31 survey

       4)  Ibata  structure in M31? Microlensing; Gal struct from
astrometry

       5)  Olszewski  -- size and density distribution of the luminous 
	   matter in the Milky Way

       6)  Suntzeff -- dwarf galaxy statistics; a search for a complete
sample 
                 of `nearby galaxies' (TRGB) ; planetary transits.  Nick
will 
		 also provide brief background on the zoo of short period 
		 variable objects 


       7)  Saha - Cepheids / LPVs; Galactic structure from Astrometry

       8)  Olsen -- Old populations in the halos of galaxies. 
Short-lived 
	   stages of stellar evolution?

       9)  Dolphin -- Variable stars; the extended structure of dwarf 
	   galaxies -- population gradients

      10)  Monet (in absentia) -- planetary transits and astrometric
wiggles

      11)  Cook (in absentia) -- Microlensing and planetary transits 

      12) We are missing a contribution from Connie Rockosi, who was
absent

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