Galaxy Motions with Radio (VLBI) Astrometry · Galaxy. Motions. with Radio (VLBI) Astrometry....

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

Galaxy Interactions

(Braun & Thilker

2003, A&A)

M31 subgroup

Galaxy Interactions

(Braun & Thilker

2003, A&A)

(McConnachie

et al. 2009, Nature)

M31 subgroup

Galaxy Interactions

Chynoweth

et al., NRAO/AUI/NSF, Digital Sky

Survey.

M81 group

of galaxies

Galaxy Interactions

(van Gorkom

et al.)

(McConnachie

et al. 2009)

Galaxy Interactions


Chynoweth


Survey. (van Gorkom

et al.)

(McConnachie

et al. 2009)

Galaxy Interactions


Chynoweth


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?



-

HST: 0.61 ±


dwarf at 140 kpc

(Dinescu

et al. 2004) 0.55 ±


Minor at 63 kpc

(Piatek

et al. 2005)


et al. 2006) Canis


(Dinescu

et al. 2005)

Carina dSph

(Piatek

et al. 2003)


et al. 2005, A&A)-


• HST limited to closest neighbours of Milky Way (< 150 kpc), -

impossible for M31 subgroup



-

HST: 0.61 ±


dwarf at 140 kpc

(Dinescu

et al. 2004) 0.55 ±


Minor at 63 kpc

(Piatek

et al. 2005)


et al. 2006) Canis


(Dinescu

et al. 2005)

Carina dSph

(Piatek

et al. 2003)


et al. 2005, A&A)-




• SIM Lite

will not be funded this decade

• Gaia might do some nearby galaxies



-

HST: 0.61 ±


dwarf at 140 kpc

(Dinescu

et al. 2004) 0.55 ±


Minor at 63 kpc

(Piatek

et al. 2005)


et al. 2006) Canis


(Dinescu

et al. 2005)

Carina dSph

(Piatek

et al. 2003)


et al. 2005, A&A)-




• 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


168 kpc


Astrometry of M33

VLBA observations

of water

masers:

3-8 μas/yr

in 4.5 years

(Image: T. Rector NRAU/AUI & NOAO/AURA/NSF)


•

3d motion

relative to Milky

Way: v =

190 ±

59 km/s•

rotation known


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:


• different formation scenarios predict different proper motions

(Sawa

& Fujimoto 2005, PASJ)


• different formation scenarios predict different proper motions• measured motions can falsify models

(Sawa

& Fujimoto 2005, PASJ)


(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

• 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


(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)


(van Gorkom)


(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)

•



-


Space motion of M31

1. Calculate

orbits

10 Gyr

backwards

in time

2. Run n-body

simulations

forward-

simulate


100 tracer

stars

(Loeb et al. 2005)

Separation between

M33 and M31

•



-


Space motion of M31

1. Calculate

orbits

10 Gyr

backwards

in time

2. Run n-body

simulations

forward-

simulate


100 tracer

stars

(Loeb et al. 2005)

•



-


Space motion of M31

1. Calculate

orbits

10 Gyr

backwards

in time

2. Run n-body

simulations

forward-

simulate


100 tracer

stars

(Loeb et al. 2005)

3. Calculate

fraction

of tidally

stripped

stars

(from

M33)

•



-


Space motion of M31

1. Calculate

orbits

10 Gyr

backwards

in time

2. Run n-body

simulations

forward-

simulate


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

•



-


Space motion of M31

1. Calculate

orbits

10 Gyr

backwards

in time

2. Run n-body

simulations

forward-

simulate


100 tracer

stars

(Loeb et al. 2005)

3. Calculate

fraction

of tidally

stripped

stars

(from

M33)


20%

50%

•



-


Space motion of M31

1. Calculate

orbits

10 Gyr

backwards

in time

2. Run n-body

simulations

forward-

simulate


100 tracer

stars

(Loeb et al. 2005)

3. Calculate

fraction

of tidally

stripped

stars

(from

M33)


=> 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

• M33-

two maser regions

-

reference QSO 1º

away-

check source 14’

away

• 6 epochs between 03/2001 and 06/2005

Astrometry of M33

IC133

M33/19

Galaxy Motions with Radio (VLBI) Astrometry · Galaxy. Motions. with Radio (VLBI) Astrometry....

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