galaxy motions with radio (vlbi) astrometry · galaxy. motions. with radio (vlbi) astrometry....
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GalaxyGalaxy
MotionsMotions
withwith
Radio (VLBI) Radio (VLBI) AstrometryAstrometry
Andreas Brunthaler
(van Maanen
1923) (Brunthaler et al. 2005)
Galaxy Interactions
• In ΛCDM, galaxies grow by accreting smaller ones
• Galaxy interactions are import to understand galaxy formation
• can be studies best in Local Group, neaby
groups and clusters
Galaxy Interactions
• In ΛCDM, galaxies grow by accreting smaller ones
• Galaxy interactions are import to understand galaxy formation
• can be studies best in Local Group, neaby
groups and clusters
(Nidever, Mellinger, et al.)
Magellanic
Stream
(McConnachie
et al. 2009)
Galaxy Interactions
(Nidever, Mellinger, et al.)
Chynoweth
et al., NRAO/AUI/NSF, Digital Sky
Survey. (van Gorkom
et al.)
(McConnachie
et al. 2009)
Galaxy Interactions
(Nidever, Mellinger, et al.)
Chynoweth
et al., NRAO/AUI/NSF, Digital Sky
Survey. (van Gorkom
et al.)
3d space
motions
of galaxies
essential
The Local Group of Galaxies
• proper motions needed, but not easy:
-
HST: 0.61 ±
0.23 mas/yr for Fornax
dwarf at 140 kpc
(Dinescu
et al. 2004) 0.55 ±
0.23 mas/yr for Ursa
Minor at 63 kpc
(Piatek
et al. 2005)
LMC, SMC (Kallivayalil
et al. 2006) Canis
Major, Sagittarius dSph
(Dinescu
et al. 2005)
Carina dSph
(Piatek
et al. 2003)
• most Milky Way satellites orbit in a plane (Kroupa
et al. 2005, A&A)-
challenge for ΛCDM?
The Local Group of Galaxies
• proper motions needed, but not easy:
-
HST: 0.61 ±
0.23 mas/yr for Fornax
dwarf at 140 kpc
(Dinescu
et al. 2004) 0.55 ±
0.23 mas/yr for Ursa
Minor at 63 kpc
(Piatek
et al. 2005)
LMC, SMC (Kallivayalil
et al. 2006) Canis
Major, Sagittarius dSph
(Dinescu
et al. 2005)
Carina dSph
(Piatek
et al. 2003)
• most Milky Way satellites orbit in a plane (Kroupa
et al. 2005, A&A)-
challenge for ΛCDM?
• HST limited to closest neighbours of Milky Way (< 150 kpc), -
impossible for M31 subgroup
The Local Group of Galaxies
• proper motions needed, but not easy:
-
HST: 0.61 ±
0.23 mas/yr for Fornax
dwarf at 140 kpc
(Dinescu
et al. 2004) 0.55 ±
0.23 mas/yr for Ursa
Minor at 63 kpc
(Piatek
et al. 2005)
LMC, SMC (Kallivayalil
et al. 2006) Canis
Major, Sagittarius dSph
(Dinescu
et al. 2005)
Carina dSph
(Piatek
et al. 2003)
• most Milky Way satellites orbit in a plane (Kroupa
et al. 2005, A&A)-
challenge for ΛCDM?
• HST limited to closest neighbours of Milky Way (< 150 kpc), -
impossible for M31 subgroup
• SIM Lite
will not be funded this decade
• Gaia might do some nearby galaxies
The Local Group of Galaxies
• proper motions needed, but not easy:
-
HST: 0.61 ±
0.23 mas/yr for Fornax
dwarf at 140 kpc
(Dinescu
et al. 2004) 0.55 ±
0.23 mas/yr for Ursa
Minor at 63 kpc
(Piatek
et al. 2005)
LMC, SMC (Kallivayalil
et al. 2006) Canis
Major, Sagittarius dSph
(Dinescu
et al. 2005)
Carina dSph
(Piatek
et al. 2003)
• most Milky Way satellites orbit in a plane (Kroupa
et al. 2005, A&A)-
challenge for ΛCDM?
• HST limited to closest neighbours of Milky Way (< 150 kpc), -
impossible for M31 subgroup
• SIM Lite
will not be funded this decade
• Gaia might do some nearby galaxies
Expected proper motions of few 10 μas/yr detectable with VLBI
•
3d motion
relative to Milky
Way: v =
190 ±
59 km/s•
rotation known
=> geometric distance: 730 ±
168 kpc
(Brunthaler et al. 2005, Science)
Astrometry of M33
VLBA observations
of water
masers:
(Image: T. Rector NRAU/AUI & NOAO/AURA/NSF)
•
3d motion
relative to Milky
Way: v =
190 ±
59 km/s•
rotation known
=> geometric distance: 730 ±
168 kpc
(Brunthaler et al. 2005, Science)
Astrometry of M33
VLBA observations
of water
masers:
3-8 μas/yr
in 4.5 years
(Image: T. Rector NRAU/AUI & NOAO/AURA/NSF)
(Brunthaler et al. 2005, Science)
•
3d motion
relative to Milky
Way: v =
190 ±
59 km/s•
rotation known
=> geometric distance: 730 ±
168 kpc
Astrometry of M33
VLBA observations
of water
masers:
(Image: D. Thilker
NRAO/AUI)
(Brunthaler et al. 2007, A&A)
•
One H2
O maser
in IC10 (660 kpc)•
3d motion
relative to Milky
Way: v = 215 ±
42 km/s
Astrometry of IC 10
VLBA observations
of water
masers:
The Local Group of Galaxies
• different formation scenarios predict different proper motions
(Sawa
& Fujimoto 2005, PASJ)
The Local Group of Galaxies
• different formation scenarios predict different proper motions• measured motions can falsify models
(Sawa
& Fujimoto 2005, PASJ)
The Local Group of Galaxies
(Peebles
2010, arXiv)
• different formation scenarios predict different proper motions• measured motions can falsify models
The Local Group of Galaxies
(Peebles
2010, arXiv)
• different formation scenarios predict different proper motions• measured motions can falsify models
Proper motion of M31
• The
proper motion
of M31-
holy
grale
of Local
Group physics
-
important
for
the
mass
of M31
• only
indirect
estimates-
weak
interaction
between
M31 and M33 (Loeb et al. 2005; McConnachie
et al. 2009)
-
average
motion
of satellites
(van
der
Marel
& Guhathakurta
2008)-
highly
uncertain
QSO?
Proper motion of M31
• The
proper motion
of M31-
holy
grale
of Local
Group physics
-
important
for
the
mass
of M31
• only
indirect
estimates-
weak
interaction
between
M31 and M33 (Loeb et al. 2005; McConnachie
et al. 2009)
-
average
motion
of satellites
(van
der
Marel
& Guhathakurta
2008)-
highly
uncertain
QSO?
Proper motion of M31
• The
proper motion
of M31-
holy
grale
of Local
Group physics
-
important
for
the
mass
of M31
• only
indirect
estimates-
weak
interaction
between
M31 and M33 (Loeb et al. 2005; McConnachie
et al. 2009)
-
average
motion
of satellites
(van
der
Marel
& Guhathakurta
2008)-
highly
uncertain
QSO?
Proper motion of M31
• The
proper motion
of M31-
holy
grale
of Local
Group physics
-
important
for
the
mass
of M31
• only
indirect
estimates-
weak
interaction
between
M31 and M33 (Loeb et al. 2005; McConnachie
et al. 2009)
-
average
motion
of satellites
(van
der
Marel
& Guhathakurta
2008)-
highly
uncertain
• High Sensitivity
Array (HSA) observation
of M31* (512 Mbps)-
tentative
detection
• VLBA (and HSA) sensitivity
upgrade
to 4 Gbpsincreases
sensitivity
by
almost
3
-
measurement
in the
next
few
years
• for water
masers
see
next
talk
(J. Darling)
QSO?
M31*
• Accuracy
of VLBA or
HSA is
good enough
for nearby
galaxy
groups
• M81 (3.6 Mpc) group
is
ideal laboratory-
M81* and three
water
masers
in M82
-
three
additional background
quasars
within
2°
• HSA observations
started
January
2007- 2 μas/yr
⇒ 30 km/s possible
in next
few
years
-
measure
motion
of M82 relative to M81-
also motion
of M81/M82 relative to Milky
Way
The Local Group is not enough…
(Yun
et al. 1994)
• Accuracy
of VLBA or
HSA is
good enough
for nearby
galaxy
groups
• M81 (3.6 Mpc) group
is
ideal laboratory-
M81* and three
water
masers
in M82
-
three
additional background
quasars
within
2°
• HSA observations
started
January
2007- 2 μas/yr
⇒ 30 km/s possible
in next
few
years
-
measure
motion
of M82 relative to M81-
also motion
of M81/M82 relative to Milky
Way
The Local Group is not enough…
(Yun
et al. 1994)
3500 AU
SN2008iz
• Accuracy
of VLBA or
HSA is
good enough
for nearby
galaxy
groups
and clusters
• Virgo Cluster (16.8 Mpc)-
5 galaxies
with
radio
cores
(M87, M89, M84, M58, NGC 4388)
-
several
background
quasars-
relative motions
up to 2000 km/s
- 2 μas/yr
⇒ 160 km/s
possible
in next
5-10 years
• detailed
study
of interactions-
e.g. ram
pressure
stripping
• also our
motion
relative to Virgo Cluster-
important
for interpretation
of motion
relative to CMB (Loeb & Narayan
2008)
The Local Group is not enough…
(van Gorkom)
The Local Group is not enough…
(Oosterloo
& van Gorkom
2005, A&A)
• Accuracy
of VLBA or
HSA is
good enough
for nearby
galaxy
groups
and clusters
• Virgo Cluster (16.8 Mpc)-
5 galaxies
with
radio
cores
(M87, M89, M84, M58, NGC 4388)
-
several
background
quasars-
relative motions
up to 2000 km/s
- 2 μas/yr
⇒ 160 km/s
possible
in next
5-10 years
• detailed
study
of interactions-
e.g. ram
pressure
stripping
• also our
motion
relative to Virgo Cluster-
important
for interpretation
of motion
relative to CMB (Loeb & Narayan
2008)
VLBI Astrometry in the Future
• VLBA (HSA) upgrade
to 32 Gbps
⇒ 8 ×
more
sensitive than
today-
more
target
sources
-
more
and closer
calibrators-
less
systematic
errors
VLBI Astrometry in the Future
1.
2.
3.
4.
5.
• SKA: large field
of view
& sensitivity-
several
in-beam
calibrators
-
systematic
errors
greatly
reduced-
astrometric
accuracies
of a few
μas
-
parallaxes
of ~ 1 μas
• SKA mid
will cover
the
important
6.7 GHz methanol
maser
line-
even
a 5% trigonometric
parallax
to single
maser
in the
LMC possible
-
and a rotational
parallax
• SKA can
measure
proper motions
of nearby
galaxy
groups
and in clusters-
using
6.7 GHz methanol
masers
(e.g. in M31 Sjouwerman
et al. 2010)
-
even
fainter
radio
cores
• VLBA (HSA) upgrade
to 32 Gbps
⇒ 8 ×
more
sensitive than
today-
more
target
sources
-
more
and closer
calibrators-
less
systematic
errors
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
Separation between
M33 and M31
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
3. Calculate
fraction
of tidally
stripped
stars
(from
M33)
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
3. Calculate
fraction
of tidally
stripped
stars
(from
M33)
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
3. Calculate
fraction
of tidally
stripped
stars
(from
M33)
4. exclude proper motions of M31 with a large amount of stripped stars
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
3. Calculate
fraction
of tidally
stripped
stars
(from
M33)
4. exclude proper motions of M31 with a large amount of stripped stars
20%
50%
•
M31’s proper motion important-
n-body simulations of history of M33/M31/MW system
-
assume a trial proper motion for M31
Space motion of M31
1. Calculate
orbits
10 Gyr
backwards
in time
2. Run n-body
simulations
forward-
simulate
M33 stellar disk with
100 tracer
stars
(Loeb et al. 2005)
3. Calculate
fraction
of tidally
stripped
stars
(from
M33)
4. exclude proper motions of M31 with a large amount of stripped stars
=> vprop
>
80 km/s
The mass of M31
2
11
11
• If M33 or IC 10 are bound to M31,then
Vrel
< Vesc
or
MM31
> (V2rel
R)/2G
• Some regions excluded due tolack of strong disturbance of disk of M33 (Loeb et al. 2005)
• Consistent with weak interactionshown by McConnachie
Observations
of IC 10
•
observations with VLBA
6 epochs between 02/2001 and 06/2005
• IC10-
one maser region
-
reference QSO 1º
away-
check source 8’
away
1 degree
• Relative motion between IC133 and M33/19 depends only
on rotation• Assume vpec
< 20 km/s (radial velocities of maser and H I agree)
Rotation model of HI:(Corbelli
& Schneider 1997)
In RA: 106.4 ±
20 km/s
In DEC: 35.0 ±
20 km/s
Relative proper motions
⇔
29.9 ±
2 μas/yr
⇔
9.7 ±
5 μas/yr
D = 750 ±
140 ±
50 kpc
Rotation of M33
Reference Method Distance [kpc]
Lee et al. 2002 Cepheids
(revised) 802 ±
51
Kim et al. 2002 TRGB + RC 916 ±
55
McConnachie
et al. 2005 TRGB 809 ±
24
This work rotational parallax 750 ±
140 ±
50
Distance of M33
• Accuracy
of < 10 % possible-
better
rotation model
(higher
resolution
H I data)
-
new
observations
and third
maser
in M33
Reference Method Distance [kpc]
Lee et al. 2002 Cepheids
(revised) 802 ±
51
Kim et al. 2002 TRGB + RC 916 ±
55
McConnachie
et al. 2005 TRGB 809 ±
24
This work rotational parallax 750 ±
140 ±
50
Distance of M33
• Accuracy
of < 10 % possible-
better
rotation model
(higher
resolution
H I data)
-
new
observations
and third
maser
in M33