Download ppt

QuickTime™ et u n
dé com press eur
so nt re quis pou r visio nne r ce tte imag e.
QuickTime™ et un
décompresseur
sont requis pour visionner cette image.
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)