Galaxy structure from local kinematics

copygrouperMechanics

Nov 13, 2013 (3 years and 7 months ago)

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Galaxy structure from local
kinematics
Matthew Grant IoA
(short undergraduate project)
Supervisors: Martin Smith**, GG
** moving to Kavli Beijing, will be a lead in galactic structure survey with LAMOST
What is GREAT?

http://www.ast.cam.ac.uk/GREAT/index.html

The ESA Gaia Science Team and the Gaia Data Processing and Analysis
Consortium are working with others in the community to build the European science
capacity to successfully exploit the upcoming
ESA Gaia
cornerstone mission.
GREAT is the programme which will bring together relevant scientific expertise by
promoting topical workshops, training events, exchange visits, conferences and so
forth with the aim of addressing the major scientific issues that the Gaia satellite will
impact upon.

KickOff

Cambridge March 09: Set of WGs are being set up.

One is to promote wide
-
field spectroscopic capability on 4
-
m class telescopes

-
this is meeting in Cambridge, July 8/9

Coordinated with the two AstroNet/Opticon reviews

1) ETSRC

future of 2
-
4m telescopes co
-
chairs: Janet Drew, Jacqueline Bergeron
http://www.strw.leidenuniv.nl/2to4mtelescopes/

2) wide
-
field spectroscopy on 4
-
8m telescopes

being implemented now.
Bovy etal 0905.2980
New Hipparcos catalogue:
finds usual number of
local ``structures``
-
ten
Given the complexity of local phase
-
space, do full statistical/Jeans’ equation
analyses mean anything. If so, why??
Does RAVE tell us anything useful about the different
histories of thick and thin disks??
Do we see significant different mean motions?
Scales?
Element ratio data from Fuhrmann
Galactic
U
,
V
,
W
space velocities:
Quillen &
Garnett (2001)
189 F
-
G dwarf stars
W
U
U
V
V
W
Local sdss subdwarf kinematics

RAVE volume , 1800 stars Smith etal 0904.1012
RAVE sub
-
sample:
Sample: 248K internal list
log g >3*
sigma_rv < 5
[Fe/H]_corr >
-
1 (<+5)
selects 62611 stars
fitting uses 200 bootstrap
samples

This is a mistake
-
some giants survive the cut

Mean velocity vs colour

Extremely constant in U,W

Parenago discontinuity
at J
-
K = 0.3
U
V
W
J
-
K
0.2
0.4
0.6
0.8
Total velocity dispersion vs J
-
K colour
Asymmetric drift:
Mean U, V, W motion vs
velocity dispersion
Very constant in U, W
Very tight correlation in V
implies LSR for thin and thick disk
-
and halo
-
are the same

-
no large scale asymmetries
-
large
-
scale equilibrium
Diagonal dispersion (U^2, V^2, W^2)
vs J
-
K colour
Note:
-
smooth trend in U,V into thick disk
-
dip in red

giant contamination?
-
high sigma_W shows thick disk

Simple statistical fitting of kinematics for RAVE stars with
[Fe/H]>
-
1, log g>3

includes thin and thick disks

`solar motion` very well defined over whole range

no larger
scale thick disk motion

it has been there a long time?

Dispersion relation very smooth: similar Jeans’ fits to thin and
thick disk

similar radial scale lengths?

LSR values are robust, even though local velocity DF is
extremely clumpy

why is sampling noise not dominant?


velocity phase
-
space clumps cannot correspond to large
gravitational potential fluctuations?