Re: Meeting approaching...

[Annie Robin <annie@obs-besancon.fr>]

Here is my preliminary comments on the proposals I have to report.



MSWG
Galactic structure proposals

4. A megaprime survey for structure in the halo of the galaxy (G.G. Fahlman) 
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This proposal contains2 subjects :
1) Search for tidal streams and reliques of merging in the halo. This requires
about 400 sq.deg. to V<24 (100 hours). Broad band filters, not specified.
Survey directions : not specific (Great Circle Cell counts).

2) Search for tidal tails around globular clusters, measurement of the tidal
boundaries. 
Filters : 3 bands (not specified)
V<26
6 clusters + 3 blank fields (direction not specific, high latitude)
Total 300 hours


5. Probing the deep halo (M. De Robertis) 
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Luminosity, mass function and metallicity distribution of low mass stars 
in the halo (10 < Mv < 14 that is 200 stars in 1 sq.deg).
Filters : BVRI, 1 sq.deg.
V<24 
Survey directions : not specific (high latitude)

Comments : 1 sq deg certainly not enough (200 stars). Require at least 10 times
or even more (30 to 50 sq.deg). Would be more interesting if done in 
various directions to disentangle density gradient effects.

6. Brown dwarf (BDs) and very low mass star (VLMS) (T. Forveille) 
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Mass function of very low mass stars and brown dwarfs. 
Filters : I, z
200 sq.deg. |b| > 30 deg
I<26, z<25 (1h en I, 30mn in z). Estimated time 300h, 35 nights on 3 years.
Proper motions in a time baseline of few years.

Comments : very important to do. About 100 times the volume of NIR 
all sky surveys.


7. Brown dwarf luminosity functions in the solar neighbourhood and 2 nearby
open clusters and The halo dark matter and the luminosity function of stars at
the bottom of the halo and thick disk main sequences (M. Haywood) 
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1) Disc BD luminosity function in clusters and in the field, with
trigonometric parallaxes.
I < 24 sigma(pi)=5 mas. Parallaxes measurable up to 100 pc in 3 years.
Filters : VRI (repeated in I only)
Field : Pleiades : 70 sq. deg.
	Praesepe : 40 sq. deg. (up to few tens BD in each cluster).
For 110 sq. deg.  I<24, S/N=5 => 32 nights on 3 years
V and R : 5 nights
If R=25.5 : 22 nights

Comments: Very complementary to the search for field BD (age known). May be
interesting to go deeper in magnitude and to add the z filter (more useful
for coolest dwarfs and to decontaminate from field stars). 

2) Halo and thick disc luminosity function and search for halo WD
Filters : UVRI
Field : 100 sq. deg. high latitude b>30.
I < 24.5 (MI=12 at 3000pc)
Proper motions on 3 years
Time required : 8 nights on 3 years + 7 nights (12 mn in I, 20mn in U, 
12 mn in V)

Comments : U may be not necessary (unless atmosphere model calibrations). 
(Exposure times look a bit short to me, may be S/N=5 is not sufficient).


8. Recherche de candidats a la matiere noire baryonique dans le halo (A. Robin)
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Halo mass function, search for ancient white dwarfs.
Filters : VRI
field : few hundreds of sq. deg. at high latitude (b>30) in various directions
Proper motions required (few years)
V<25-26, I<25-26
Time : 6 hours per field once a year for 3-4 years.


General comments :
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These proposals can be merged into 3 :
1) Low mass, brown and white dwarfs in the field : hundreds of sq. deg. in VRIz
or VIz, high latitude, up to I=25, repeated each year over 3-4 years. 
Would also do the search for tidal tails and inhomogeneities in the halo if
the observing directions are well distributed, could cross the requirement of
extragalactic large scale surveys.
May be add less deep survey in B to match De Robertis requirements.

2) Tidal tails of globular clusters
300 hours, on 6 globular clusters and 3 blank fields (V<26).  

3) Brown dwarfs in open clusters
Probably specific and cannot be merged with any other proposals.

........................................................................
Annie Robin                      Tel: (33)(0)381666941
Observatoire de Besancon         Fax: (33)(0)381666944
BP 1615                          e-mail : robin@obs-besancon.fr
F-25010 Besancon cedex
France
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