DUSTY04 – Paris ALMA and ISM / Star Formation Stéphane GUILLOTEAU Observatoire de Bordeaux

DUSTY04 – Paris

ALMA ALMA and and

ISM / Star FormationISM / Star Formation

Stéphane GUILLOTEAU

Observatoire de Bordeaux

26 Octobre 2004 S.Guilloteau – ISM & Star Formation

What’s new with ALMA ? (compared to current mm arrays)

• A fast instrument surveys become possible• A sensitive instrument weak lines, small objects

become accessible• High angular resolution details of star formation• Wide field imaging with ACA from large to small scales • Wide frequency coverage wide range of physical

conditions can be adressed• Polarisation • But a large survey, at high angular resolution, in full

polarisation, over arcmin scales, in several lines, would take forever Choices will have to be made


Star Formation Physics

• Initial mass function from large scale surveys (gas + dust images)

• Polarization: the role of magnetic fields• Complete samples in several types of star-forming regions• Velocity field (accretion) in envelopes of Class 0

protostars• (non)-Keplerian disks around YSOs:

– Star masses from disk kinematics– Evolutionary tracks of proto / PMS stars– Evolutionary status of disks– Planet formation

• Binarity (70 %): gas + dust distribution, tidal truncation of inner / outer disks


Structure of the ISM

• Mosaics of a few arcmin squared, at angular resolution of 0.4 to 2”, could reveal the filamentary structure of the ISM (e.g. Pety & Falgarone 2004)

• High spectral resolution required to reveal non Gaussian line wings which trace turbulence

• What is the inner scale of the turbulence cascade ?

• Chemistry in shocked regions or vortices? Several molecular lines required


Initial Conditions of Star Formation

• The link between condensations and IMF (Motte et al 1998)• Can be extended to much lower masses, and/or very different

environments (e.g. High mass star forming regions)


Initial Conditions of Star Formation

• Density and temperature gradients in starless cores

• Molecular chemistry of cloud cores: depletion and deuteration

• Searching for infall motions (e.g. Di Francesco et al 2001). Beware of interferometer filtering (Gueth et al

1997)


Massive Stars

• Formation by collapse or merging ?

• High angular resolution of massive protostars may help solving this issue

• Proper motions studies may be needed very high angular resolution + long term monitoring

• Will outflow contaminate the picture (Beuther et al 2004)


Fragmentation & Multiplicity

• Example from Looney et al 1997

• Small number of proto-binaries detected so far

• Comparison of fraction of binaries in proto-stars and PMS stars constrain theories

• Dependence upon environment (isolated vs cluster) is critical surveys of different regions required


Tidal Truncation

• It does exist (e.g. GG Tau, Guilloteau, Dutrey & Simon)


Tidal Truncations

• But not always: AS 205

• ALMA can study significant samples rather than a few objects


Disk around young stars

• Current arrays have done about 20 sources... (e.g. IRAM PdB Survey)

• ALMA sensitivity 50 times better ...

• ALMA could do hundreds of sources in continuum, to a much better level, and at much higher angular resolution


Zooming on inner disks

• Nice, circularly symmetric, Keplerian disks don’t really exists

• E.g. AB Aur 1.3 mm image at 0.6” resolution: “spiral” density enhancements 100 AU from the star (black: IR from Fukagawa et al 2004, White: mm from Piétu et al 2004)

• Are such phenomena comon? Long-lived ?


Stellar Masses (and more)

• From the (Keplerian) rotation curve, measured from CO (Simon et al 2000)

• Temperature from CO isotopes (Dartois et al 2003)

• A sample of 40 sources, in CO and its isotopes at 0.2” resolution requires 2600 hours of ALMA !


Transition Disks ?

• ALMA can image the “débris” disks around (young) stars• But also perhaps unveil the transition stage between proto-planetary

disks and “débris” disks• Small disks just being found: e.g. BP Tau (Dutrey et al 2003)• But studies will require long integration time even with ALMA (>> 10

hours / object)


Long term schedule

• Proper motions can be measured with ALMA

• Clumps in “debris” disks ( evidence for planets ?)

• Orbital motions of proto-stellar condensations in massive star forming regions

Plan in advance and for the long term...


Chemistry

• Chemistry is a major issue in all components of the ISM• ALMA will be invaluable in many areas, due to high

sensitivity, angular resolution and frequency coverage (especially sub-mm domain)

• Examples– Diffuse ISM in absorption against quasars (e.g. Lucas & Liszt)– Shock chemistry in outflows– Chemistry in proto-stellar envelopes– Chemistry in proto-stellar disks– Hot core chemistry– PDR regions


Diffuse Clouds

• e.g. Sulfur chemistry (Lucas & Liszt 2003)

• ALMA can reach much fainter sources

• ALMA can reach much weaker lines (isotopes...)


Outflows

• High angular resolution required to resolve multiple shocks in outflow system (L1157, Bachiller & Perez-Guttierez 1997)


Hot Cores

• Angular resolution is essential to separate multiple cores

• E.g. W3(OH) (Wyrowski et al 1997)


Proto-Stellar envelopes

• Short spacing information is essential (i.e. ACA and total power)

• E.g. N2H+ in IRAM 04191 (Belloche et al 2002)


Photo Dissociation Regions

• e.g. Orion Bar (Lis & Schilke 2003)

(False color: CO(7-6)

Black contours: H2 v = 1 0 S(1)

Red contours: O I 1.32 μm

Blue contours: H13CN(1-0)

White contours: 13CO(3-2) )

• Sub-mm data (for high excitation lines) and short-spacing information essential

Documents

DUSTY04 – Paris ALMA and ISM / Star Formation Stéphane GUILLOTEAU Observatoire de Bordeaux