View
216
Download
0
Category
Preview:
Citation preview
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
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
Tidal Truncation
• It does exist (e.g. GG Tau, Guilloteau, Dutrey & Simon)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
Tidal Truncations
• But not always: AS 205
• ALMA can study significant samples rather than a few objects
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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 ?
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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 !
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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...
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
Diffuse Clouds
• e.g. Sulfur chemistry (Lucas & Liszt 2003)
• ALMA can reach much fainter sources
• ALMA can reach much weaker lines (isotopes...)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
Outflows
• High angular resolution required to resolve multiple shocks in outflow system (L1157, Bachiller & Perez-Guttierez 1997)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
Hot Cores
• Angular resolution is essential to separate multiple cores
• E.g. W3(OH) (Wyrowski et al 1997)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
Proto-Stellar envelopes
• Short spacing information is essential (i.e. ACA and total power)
• E.g. N2H+ in IRAM 04191 (Belloche et al 2002)
26 Octobre 2004 S.Guilloteau – ISM & Star Formation
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
Recommended