Star Formation and Millimetre Astronomy Michael Burton School of Physics University of New South Wales

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Star FormationandMillimetre AstronomyMichael
BurtonSchool of PhysicsUniversity of New South
Wales
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Outline

• Millimetre Science
• Star formation

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Millimetre Science

• Star Formation
• Dense Cores, Cloud collapse, molecular outflows
• Interstellar Medium
• Multi-phase medium (ionized, neutral, molecular)
• Chemistry
• Ion Molecule reactions, despite the low
  abundances
• No 3-body reactions, No activation energies
• Grain surface chemistry
• Galaxies
• All applies to other galaxies too!
• Red-shifted molecular gas
• CMBR
• Peaks at 1mm

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The 3mm Millimetre Spectrum
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125 Interstellar Molecules (August 2004)
wwwusr.obspm.fr/departement/demirm/list-mol.html
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Some Interesting MoleculesLeiden Astrochemistry
Groupwww.strw.leidenuniv.nl/astrochem
C3H2
Ethanol CH3CH2OH
Formaldehyde H2CO
Hydrogen Cyanide HCN
HC7N
PAH
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Evolution of Dense Cores (I)
Thanks Maria!
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Evolution of Dense Cores (II)
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Star Formation

• Molecular Clouds to Stars
• Forging of the Elements
• Stars to Gas to Dust to Stars
• Driven by the Massive Stars

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The Multi-Wavelength Milky Way
Sites of Massive Star Formation
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Millimetre Wavelength Molecular Lines in Orion
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Birth of the Solar System

• Collapse of a slowly rotating cloud of
  interstellar gas.
• Central condensation forms as clouds flattens and
  spins up.
• Young Sun shines within disk of gas and dust, in
  which planets are forming.

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Stardust the seeds for planets!
0.02 mm
Cosmic Dust Grain
Chondrules inside a meteorite
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Leonids
Geminids
Cosmic Dust stardust.wustl.edu
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Formation of the PlanetsI Protoplanetary Cloud
(0 years)
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Formation of the Planets II Planetesimals (50
million yrs)
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Formation of the Planets III Planets (100
million years)
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Numerical simulation of the Birth of the Solar
System
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Low Mass Star Formation
T 10K nH2 106 cm-3 B 10-6 G
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Low Mass Star Formation
Class 0
Core
I
Flux
Star Disk
II
Star
III
The Stages of LMSF are understood (sort of)!
?
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The Stages of LMSF and its Chemistry

1. Core Contracts
2. Inside-out collapse
3. Accretion Outflow
4. Proto-planetary Disk
5. Planetary System

Hogerheijde, after Shu 1987
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The Evolutionary Route to Massive Star Formation
Polyaromatic Hydrocarbons (PAHs _at_ 3.3µm)
Optical HII regionevolved star formation
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HII Regions and Molecular Cores
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Hot Molecular Cores
105 yr
Purcell

• Dense (n 106-7 cm-3), Warm (T 100300K),
  Compact (R 0.1 pc) phase at start of MSF
• Contains an embedded protostellar source
• Characterised by a rich chemistry
• High abundance of saturated hydrocarbons, fuelled
  by evaporation from grain mantles

Evidence for signatures of these phases?
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Three Phases of Hot Core Chemistry

• Cold Core chemistry, frozen onto grains as ices
  (e.g. CO)
• Grain surface chemistry (e.g. NH3, CH3OH)
• Desorbed as core heats up
• Gas Phase chemistry in hot core (e.g. CH3CN)

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Time-dependent Chemical Signatures?
N-rich or C-rich?

• Need to constrain the chemistry with
  observations!
• Need to understand how the chemistry works!

100 K
300 K
Abundance
Time
Rodgers Charnley, 2001
Ammonia injected from ice
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Hot Molecular Cores 86-92 GHz Line Survey of
G0.55-0.85
SiO
HNC
C2H
HC3N
CH3CN
Rich Organic Spectrum HCO, HCN, HNC, CH3CN,
C2H, HC3N, SiO
HCN
HCO
Mopra
Kim et al. 2002
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Hot Molecular CoresMethyl Cyanide (CH3CN)
G0.55-0.85
Mopra
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16272-4837 1.2-mm SIMBA emission

• Spectral Energy Distribution
• L 2.4 x 104 L?

0.4 pc at 3.4 kpc

• Optically Thin Dust
• M F ? D2 / Rdg ? B?(Td)
• M 2.0 x 103 M?

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Brooks et al, 2002
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Cold Cores1.2mm Continuum, SEST/SIMBA
CH3CN
HCN
HCO
CH3OH
Minier et al, 2003
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Delta Quadrant Survey (aka RCW106,
G333.6-0.2)1.2x0.6 at (l,b)(333.2,-0.4)
MSX 8µm SIMBA 1.2mm MOST 843MHz
Mopra 13CO
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The Search for Biogenic Molecules

• Propylene Oxide (86 GHz)
• Chiral-centred molecule
• Needed for self-replication, eg RNA
• Production mechanism (circularly polarized UV)
• But no chiral molecules yet seen in the ISM?
• Glycine (87 GHz)
• Simplest amino acid
• Found in carbonaceous chondrites (pre-solar
  nebula)
• Why now?
• Accurate wavelengths now available
• Many lines needed to confirm detection
• Requires large collecting area and long
  observations

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Mopra

• 22-m Telescope for ? gt 3mm
• 85115 GHz receiver (2.6 3.5 mm)
• 30 beam, Tsys 150 300 K
• Bandwidth 64, 128 or 256 MHz (200 - 800 km/s)
• 1024 Channels (0.2 - 0.8 km/s per channel)
• 2 Polarizations (1 freq., or 1 pol. SiO 86 GHz)
• Must Nod No chopping.
• Upgrade to 8 GHz, 16,000 channel system in
  progress

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Your local radio telescopes.
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The Australia TelescopeMillimetre Interferometer
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Australia Telescope Compact Array

• National Facility
• Six 22m antennas
• Five on movable 3km EW track
• Built for 110 GHz operation
• Recently upgraded to 3mm (100 GHz) 12mm (25
  GHz)
• Provision for 7mm (45 GHz) upgrade
• Focal Plane Arrays.

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MillimetreInterferometry
R Sault

• Poses special challenges
• Significant atmospheric opacity, mostly due to
  H2O
• Fluctuations in H2O produce phase shifts
• These increase with both baseline and frequency
• Instrumental requirements (e.g. surface,
  pointing, baseline accuracy) are more severe
• Need more bandwidth to cover same velocity range
  (1 MHz ? ? (mm) km/s)

Desai 1998
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Some Millimetre Telescopes

• SEST
• FCRAO
• LMT
• Nobeyama
• Nobeyama MM Array
• IRAM
• Plateau du Bure

• BIMA
• OVRO
• CARMA
• CSO / JCMT / SMA
• AST/RO / VIPER
• SPT
• NANTEN2
• ASTE
• APEX
• ALMA

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SEST 15m La Silla, ChileSwedish-European
Sub-millimetre Telescope
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FCRAO 14mFive College Radio Astronomy
ObservatoryQuabbin, Massachusetts
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The Large Millimetre TelescopeEl Gran Telescopio
Milimetrico50m, Sierra Negra, Puebla, Mexico
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Nobeyama 45m TelescopeJapan
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Nobeyama Millimetre Array ASTE Sub-millimetre
antenna
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IRAM 30m, SpainInstitute de Radioastronomie
Millimetrique
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Plateau de Bure Interferometer6x15m Antennae
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BIMA, Hat Creek, California10x6m
AntennaeBerkley-Illinois-Maryland Array
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Owens Valley Radio ObservatoryOVRO, 6x9m,
California
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CARMACombined Array for Research Millimeter
AstronomyCedar Flat, Inyo Mountains,
California(6x9m OVRO 9x6m BIMA)
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Mauna Kea, Hawaii Caltech Sub-Millimetre
Observatory (CSO), 10mJames Clerk Maxwell
Telescope (JCMT), 15mSub-Millimeter Array (SMA),
8x8m
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AST/RO 1.7m Submm TelescopeSouth Pole
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VIPER 2.1m Telescopeat the South Pole
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10m South Pole Telescope
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4m NANTEN2 AtacamaA University
CollaborationJapan - Korea - Germany - Chile -
Oz (?)
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12m APEXAtacama Pathfinder Experiment
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ALMAAtacama Large Millimetre Array
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Antarctica??