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The MALT90 survey
of massive star
forming regions
Ana Duarte Cabral
MW2011 Rome
19.09.2011
Sylvain Bontemps
James Jackson
Jill Rathborne
Jonathan Foster
and the MALT90 consortium
Outline
- Context and purpose of MALT90
- Current status and pilot results
- The first year of MALT90
- Searching for outflows in massive cores: SiO
Context
On the light of the large continuum submm surveys
Need of a large molecular line legacy towards sites
of high-mass star formation capable of:
- Estimate dynamical distances and understand the
Galactic distribution of high-mass star forming clouds
- Calculate statistical properties and search for chemical
and physical evolutionary changes
Survey
Millimetre Astronomy Legacy Team 90 GHz (MALT90) Survey,
using the 22m Mopra telescope in Australia.
PI: James Jackson, Boston University
Jill Rathborne, Jonathan Foster
• Mapping simultaneously 16 molecular transitions at 90GHz, providing
a range of high-density tracers.
• Targeting sites of massive star formation, designed to cover several
evolutionary stages, from quiescent to PDRs.
Key specifications
Nb of dense cores targeted:
- Pre-stellar (mid-IR dark)
- Protostellar (24 m emission)
- HII Region (bright 8, 24 m emission)
Angular Resolution:
Size of each map:
Spectral Resolution:
Sensitivity
3,000
1,000
1,000
1,000
38’’
3’ x 3’
0.11 km/s
0.2 K
Survey Region
+20° > l > +3° and -3° > l > 60°
Dates of data collection
Austral winter 2010-2014
Line
Frequency (GHz)
N2H+
93.17
13CS
92.49
H41α
92.03
CH3CN 91.98
HC3CN 91.19
13C34S
90.92
HNC
90.66
HC13CCN 90.59
HCO+
89.18
HCN
88.63
HNCO 41,3 88.24
HNCO 40,4 87.93
C2H
87.32
SiO
86.85
13
+
H CO
86.75
H13CN
86.34
Tracer
Density, chemically robust
Column density
Ionized gas
Hot core
Hot core
Column density
Density, cold chemistry
Hot core
Density
Density
Hot core
Hot core
Photo-dissociation
Shock/outflow
Column density
Column density
Current Status
• Pilot Survey, July09 - (182 targets) - complete
- Survey strategy
- Target source list
Foster et al. 2011
• Year 1, June-Sept10 - (499 targets) - complete
- ~ 830 hours
- Observations from Narrabri, Sydney
- Data released
Rathborne et al. in prep
Jackson et al. in prep
• Year 2, May-Sept11 - (~600 targets) - ongoing
- ~ 900 hours
- Observations from Narrabri, Sydney, Bordeaux, Moscow, Florida, Boston
- Mapped ~450 cores so far
• Logs, observing schedules, source lists available via team wiki
• Automated data reduction pipeline
Pilot Survey Outcome
Foster et al. 2011
- Source selection using ATLASGAL (870µm)
Schuller et al. 2009
- Importance of mapping V.S. pointed
observations
- Importance of spectral resolution (0.1km/s)
First Year
• Data available to everyone via the Australia Telescope Online
Archive (ATOA: http://atoa.atnf.csiro.au/MALT90)
• For each source in each line:
–
–
–
–
Raw data
Processed cubes
Moment maps (zeroth, first, second)
Signal-to-noise maps
• Database of line emission characteristics
– Peak spectra
• Temp, VLSR, DV
– 2-d Integrated emission
• morphology of emission, location of peak
– Line ratios, extended or compact, broad line-widths, shocked gas, complex chemistry
products - kinematical distances
With the VLSR we can derive a kinematical distance:
– Galaxy rotation models
– Reid et al. 2009
– Clemens 1985
 Extinction maps
 HI absorption
 CO clouds
Galactic CO emission (Dame et al. 2001)
Galaxy model from Reid et al. 2009
Needed for:
- Core masses
- Protostellar luminosities
- Physical relation of
adjacent filamentary
features
- Galactic structure
products - Chemical evolution
Chemical variations capable of indicating special
phases in the core’s chemical evolution
Initial collapse (CO freeze out)
Dense gas freeze-out
High N2H+ abundance
Protostar
HII region
Low N2H+ abundance
N2H+
HNC
N2H+
HNC
HCO+
HCN
HCO+
HCN
Lee et al. 2004
products - Chemical evolution
Hot vs Cold cores
Looking for outflows
Duarte-Cabral, Bontemps, et al. in prep
The expectations
Statistical study of outflow properties and SiO line profiles
Find evolutionary changes on the outflow properties
IR bright
vlsr (km/s)
IR quiet
vlsr (km/s)
Lopez-Sepulcre et al. 2011
Motte
et~al.0.009K)
2007
(1.5 km/s,
rms
(0.14 km/s, rms ~ 0.03K)
Lopez-Sepulcre et al. 2011
Looking for outflows
The reality…
The source sample:
235/499 young sources
129 protostars, 106 quiescent, 156 HII regions, 56 PDRs
30 % SiO detections:
49 % of protostars
20 % of quiescent
Velocity binned to 1.3 km/s (rms ~ 0.04K).
Looking for outflows
Some “not-too-bad” cases
Looking for outflows
• Some statistics - evolutionary trends?
Future
• Better distances and SED fittings
• Understand the real nature of sources and
perform (more) meaningful statistics
• Extension to the full 2000 sources
(from quiescent to protostars)
• Source list worth of follow up with ALMA
http://malt90.bu.edu
(ATOA: http://atoa.atnf.csiro.au/MALT90)