Dear All,
   after the group meeting on Wednesday, I played around just to get
a more quantitative sense of what kind of stars (at what distances,
and what velocities, [Fe/H] etc..) we should expect, I played around
with GUMS (=Gaia Universe Model Snapshot;
http://arxiv.org/pdf/1202.0132v2.pdf ).

This e-mail contains
a) a pointer to a roughly-DR1-TGAS-like mock catalog:
    https://www.dropbox.com/s/a1hiqrrdg1euqfs/GUMS_Gmag_11.5.fits?dl=0
    [provided by Jan; see http://www2.mpia.de/GC-NEW/wiki/GC/MWGroupMeeting ]
b) some plots and thoughts on the expected astrophysical
    properties of the sample members
c) if you take a however-simplistic model for the errors
    (e.g. 0.4mas, and 0.4mas/yr for TGAS<10.5). With that,
   I see no reason why you could not proceed, tune the code and make the plots
   for whatever Gaia-day1 paper you have in mind.

Details below.
HW


For technical reasons (travel web connectivity), I only downloaded the 1.5M
stars G<10.5; not the G<11.5-ish that may be most appropriate for;
Jan R. will put the full catalog on the MW@MPIA Wiki soon.
Let's look first at "all" sample members, and then at the
10^5 nearby ones, within 200pc. The catalog includes kinematics, binarity,
but is (largely) mute on white dwarfs, etc..

If we look at all 1.5M stars, we get the following distributions:




.. counts dominated by stars in the 3700k-5000K range.




.. giants and MS stars have approximately equal portions; the red clump
(at logg 2.3) sticks out a bit.




most stars are within 1kpc, but there's a LONG tail of distant stars (see below)...



at ~0.4 mas/year error, the DR1 measurement is precise and accurate for most stars




Now, let's look at the sky distribution, as a function of distance:

the most distant ones (>5kpc) are super giants in the Galactic plane


as we consider closer samples; they (of course) become increasingly
more homogeneously (yeah, a Mollweide projection would show that more nicely)







Just as a specific example of what to do with this,
here's a Galactic-top-down view of
the spatial distribution of some low-latitude tracers:
G-dwarfs & red clump stars in TGAS:



If you can pick out those two types of stars, you can make an instantaneous
map of the vertical motions of the Galactic disk (ideas on how to do this in a
subsequent communication).


Now, let's look at the very nearby stars; those may be good to calibrate
stellar physics:
There are 150.000 TGAS stars within 200pc.



their distribution is more dominated by warm/hot MS stars:

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