Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.atnf.csiro.au/management/atuc/2012oct/science_meeting/docs/Westmeier_Magellanic_Clouds.pdf Äàòà èçìåíåíèÿ: Mon Oct 29 02:14:38 2012 Äàòà èíäåêñèðîâàíèÿ: Tue Feb 5 23:53:39 2013 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: interacting galaxies

The Magellanic System: A Laboratory for Galaxy Interactions
Tobias Westmeier (ICRAR/UWA)

International Centre for Radio Astronomy Research


Introduction

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Introduction
Magellanic Stream discovered in s and early s.

Leading Arm

Ma gel lan ic S tre am

SMC

LMC

Mathewson, Cleary Murray ()

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Introduction
Why do we care?

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Introduction
Why do we care?
The Magellanic system is the nearest example of an interacting system of galaxies with pronounced gaseous tidal tails.


Hierarchical ()CDM structure formation happening on our doorstep (d 50 kpc). System can be studied in great detail on a large range of spatial scales. Impact of interaction on star formation history of LMC/SMC. Impact of interaction with/accretion of Magellanic Clouds on evolution of Milky Way.

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Introduction
Why do we care?
The Magellanic system is the nearest example of an interacting system of galaxies with pronounced gaseous tidal tails.


Hierarchical ()CDM structure formation happening on our doorstep (d 50 kpc). System can be studied in great detail on a large range of spatial scales. Impact of interaction on star formation history of LMC/SMC. Impact of interaction with/accretion of Magellanic Clouds on evolution of Milky Way. "Uncovering the Magellanic Stream and its surroundings is crucial to the understanding of the formation and evolution of not only the Milky Way, but the entire Local Group [...]" "[...] the MW­LMC­SMC system is regarded as an important laboratory with which to study the formation, evolution, and interaction of galaxies and their stellar populations."
The Magellanic System: A Laboratory for Galaxy Interactions

Putman et al. ():


Nidever et al. ():


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The Magellanic Stream and Leading Arm

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Magellanic Stream/Leading Arm
Leading Arm found to be more extended than previously thought:
For et al. (submitted) Venzmer et al. (in press)
For et al. (submitted)

Morphological difference between LA and MS possibly due to varying environmental conditions.
October The Magellanic System: A Laboratory for Galaxy Interactions

For et al. (submitted)

Head­tail structures common, suggesting importance of ram-pressure stripping.

Venzmer et al. (in press)

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Magellanic Stream/Leading Arm
Evidence of Leading Arm colliding with the Galactic disc.
McClure-Griffiths et al. ()
McClure-Griffiths et al. ()

Relevance:
Distance/galactocentric radius: r = kpc ± % Constraint for numerical simulations of Magellanic system. Test of LMC/SMC proper motion measurements. Test case for hydrodynamical simulations of HVC interaction.
October

McClure-Griffiths et al. ()

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Magellanic Stream/Leading Arm
Recent discoveries of extended filaments of the Magellanic Stream:
Braun Thilker () Westmeier Koribalski () Stanimirovi et al. () Nidever et al. ()

Magellanic Stream is at least
°­° long (Nidever et al., in prep.) and tens of degrees wide (Westmeier Koribalski )
October

Nidever et al. ()

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Magellanic Stream/Leading Arm
Study of interaction between Magellanic Stream and Galactic halo
Variation of line width with Magellanic longitude implies temperature gradient along the stream and change of physical conditions in ambient medium for different galactocentric radii. Head­tail structure common in stream clouds, indicating ram-pressure stripping.
Westmeier Koribalski, in prep.

HVC -

Westmeier Koribalski, in prep.

HVC -

Westmeier Koribalski, in prep.

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Magellanic Stream/Leading Arm
Lifetime of clouds:
Hydrodynamical simulations by Bland-Hawthorn et al. () suggest lifetime of Ma. Clouds would get destroyed within a fraction of the orbital time scale.
Bland-Hawthorn et al. ()

= Ma

= Ma

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Magellanic Stream/Leading Arm
Lifetime of clouds:
Hydrodynamical simulations by Bland-Hawthorn et al. () suggest lifetime of Ma. Clouds would get destroyed within a fraction of the orbital time scale.
Bland-Hawthorn et al. ()

= Ma

Magnetic stabilisation:
Magneto-hydrodynamical simulations of neutral gas cloud moving through hot, magnetised plasma (Konz, BrÝns Birk ). Stabilising effects by magnetic field of B > .â- T:


Konz, BrÝns Birk ()

Plasma deflected by magnetic field barrier near front of cloud. Reduced thermal conduction between cold gas and surrounding plasma.

Life times in excess of Ma.
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Magellanic Stream/Leading Arm
Detection of magnetic field in the Leading Arm (McClure-Griffiths et al. ).
= RMâ2 RM ne(r) B dr

Coherent magnetic flux density:
B . nT (= µG)
>0 =0 <0
McClure-Griffiths et al. ()

Sufficient to dynamically and thermally stabilise the gas.

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Magellanic Stream/Leading Arm
Measurement of chemical abundances
Follow-up observations with the Hubble Space Telescope (PI: C. Thom) Detection of different transitions (C, C, C, Si, Si, Si, etc.)


Constrain ionisation mechanism, temperature, density, abundances.

Shock-ionisation

Thom et al. (in prep.)

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Magellanic Stream/Leading Arm
Measurement of chemical abundances
H observations with Parkes to get NH.
Thom et al. (in prep.) .â cm-


.â cm- .â cm-




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Magellanic Stream/Leading Arm
Comparison with simulations:
Different formation scenarios:


Diaz Bekki ()

tidal forces ram pressure outflows
. Ga

Details of models:




Orientation and distance of stream Origin of different filaments
Connors, Kawata Gibson ()

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The Future: Gaskap

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Gaskap
Gaskap:
Galactic ASKAP Survey PIs: N. McClure-Griffiths, J. Dickey
Dickey et al. (in press)

Improvements over existing surveys:
H/OH simultaneously Large area covered Velocity resolution: . kms- Surface brightness: . K . K H column density: â cm â cm
October

(MS at , kms-) (MCs at , kms-)
- -

(MS, , , kms-) (MCs, , , kms-)

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Gaskap
Combination of ATCA/ASKAP data with single-dish data essential for recovery of flux of extended sources.
Both H and diffuse OH line emission. Important aspect of the Gaskap project.

Multi-scale CLEAN

Model convolved with 30 beam

MS CLEAN + single-dish data

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Summary Conclusions

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Summary Conclusions
Deep H mapping:
Tracing low-NH environment of MS/MW Zero-spacings data for ASKAP:


H line ( MHz) OH lines (­ MHz)

MB/FPA receiver at .­. GHz

Deep, pointed H observations:
Complement absorption line studies Crucial for metal abundances in the MS

Parkes is the only telescope of its kind in the southern hemisphere and hence essential for future studies of the Magellanic system.
October The Magellanic System: A Laboratory for Galaxy Interactions

GASS; Credit: S. Janowiecki

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Thank you!

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Additional Material

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Parkes Receiver Fleet
Current Parkes receivers:
Methanol 6 Ku S/C/X 13 mm

S/C/X

10/50

GALILEO

MB H-OH

10/50 M AR S

S/C/X

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Parkes-based Publications of Magellanic Science
Publications from ­:
Papers by topic:


Details:


H/HVCs in Magellanic Stream CO/dust in Magellanic Clouds OH/CH3OH masers Others (magn. fields, PNÔ, pulsars, etc.) Methanol Multibeam Survey Galactic All-Sky Survey Others MB­ MMB ­ GHz S/C/X H­OH



/ / / /







Papers by citations:


Search for "Magellanic Parkes" in ADS abstracts on //. peer-reviewed papers in total, of which are submitted/in press. / papers are using archival data. / papers related to MMB/GASS surveys.

/ / / / / / /

Papers by receivers:


Green et al. () McClure-Griffiths et al. ()

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Beyond H

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Maser Emission
Surveys of masers in LMC and SMC:
OH CH3OH H2O (e.g. (e.g. (e.g. Green et al. , ) Ellingsen , Green et al. , ) Oliveira et al. )
Green et al. ()

Green et al. ()

van Loon ()

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Pulsars/Magnetic Fields
Pulsars:
Magellanic Clouds are the only external galaxies where pulsars can be detected and studied.

Manchester et al. ()

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Pulsars/Magnetic Fields
Pulsars:
Magellanic Clouds are the only external galaxies where pulsars can be detected and studied.

Radio continuum observations:
Polarisation Magnetic fields
Mao et al. (in press) Manchester et al. ()

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