Early O-Type Stars in the W51-IRS2 Cluster A template to study the most massive (proto)stars Luis Zapata Max Planck Institut für Radioastronomie, GERMANY May 2009 THE EVLA VISION: STARS ON AND OFF THE MAIN SEQUENCE
Feb 02, 2016
Early O-Type Stars in the W51-IRS2 ClusterA template to study the most massive (proto)stars
Luis ZapataMax Planck Institut für Radioastronomie, GERMANY
May 2009THE EVLA VISION: STARS ON AND OFF THE MAIN SEQUENCE
Outline
• Comments on the formation of massive stars
• The young and massive cluster W51 IRS2
• VLA and SMA observations of the W51 IRS2
• Tracing the evolutionary phases of the early O-type (proto)stars Hot massive disks, molecular rings, and HC and UC HII regions
• The ELVA vision of massive young stars
The formation of the massive stars
Some fundamental theoretical problems to form massive stars (M* > 10 Msun):
o The Kelvin-Helmholtz time is much shorter than the free-fall time -- radiation pressure (spherical geometry)
o The strong UV fields will ionize the surrounding molecular gas by so fast
o The short main-sequence lifetime of high-mass stars
Some observational problems to study massive (proto)stars:
o They are located far away, more than 1 kpc (with exception of Orion)
o There are a short number of massive (proto)stars
o They are very embedded in the molecular cloud -- only observable in radio and IR bands
Some possible solutions
o Circumstellar Large Disks A Natural outcome !!
o Very high accretion rates that quenched or trapped the formation HII regions
o Mergers of low mass stars
o Competitive accretion
W51 ComplexSagittarius Arm
HJK-InfraredCFHT
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W51VLA 3.6 cm.Lacy et al. (2007)
Infrared: grey scale (VLT) 3.6 cm: contours
W51 IRS2
W51 IRS1
W51 East
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W51 IRS2Infrared (JHK)Barbosa et al. (2008)
IRS2W (O3-type)
IRS2E (O4-type)
Lbol= = 3 x 106 Lsun
D ~ 6, 000 pc~ 30 O-type protostars
7000 AU
One of most luminous regions in the Galaxy
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Ammonia (J,K)=(3,3)W51 North & W51 D1VLA
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Ho et al. (1983) Gaume et al. (1993)
1.3 cm emission: dashed contoursNH3: continuous contours
NH3: dashed contours3.6 cm: continuous contours
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Imai et al. (2002)
Einser et al. (2003)
H2O and SiO Maser SpotsVLBI
Powerful Bipolar very compact NW-SE Outflow !
NH3: dashed contours
1.3 cm: continuous contours
W51 North
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Classical profile inverse P-cygni
Accretion rate ~ 10-3 Msun/yr
Low mass stars ~ 10-6 Msun/yr
Cyanogen (CN) molecular emissionSubmillimter Array3” resolution
Zapata et al. (2008)
Moment zero
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Very Large Array7 mmC-configuration~ 0.4 arcsec
Submillimeter Array1 mmVery extended configuration ~ 0.4 arcsec
SiO, SO2, CH3CH, H3CN…
Sensitive and high angular resolution study of W51 North
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W51d2HC HII region+ outflowFlat SED
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W51dHII regionCometary
SO2
SiO(5-4) 7 mm
Disk + outflowsteeper SED
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W51 IRS2Infrared ( 2 m)Lacy et al. (2006)
W51d2
W51d
W51 North
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W51 d2W51 d2
Molecular Ring
HC HII region
outflow
W51 d
Cometary HII Region
O-type stars
Evolutive Phases !
Infrared stars
ELVA Vision of Massive (proto)stars
Very sensitive continuum and line observations towards far away bright clusters, e.g. Srg B, W49, G10.47, and G29.9
- Search for massive and large circumstellar disks at such distances Are they common?
- Confirming the evolutionary phases (more cases are needed)
Best angular resolution at millimeter wavelengths until ALMA
Many lines between 40 to 50 GHz to be exploited
Wonderful correlator…
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SED
TB=80±10 K
From the 7mm and 1.3 mm
measurements
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H92 and He92 recombination lines
Mehringer et al. (1994)
SO2 PV
MoleculesMolecules
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W51 North
W51 d2
H2CO
More Molecules in the RingMore Molecules in the Ring
CH3OH
More Molecules in the RingMore Molecules in the Ring
Summary
Our interferometric observations toward the extremely young (proto)star W51 North, revealing the presence of:
• A possible massive dusty disk with a size of about 3000 AU
• A molecular rotating and infalling ring with a inner cavity of about 3000 AU
• A powerful and massive outflow with the orientation nearly perpendicular to that of disk and ring
• The water maser spots are tracing the innermost parts of the outflow
• The mass of (proto)star is larger than 90 Msun
• The mass of the dusty disk is 40 Msun
We think that possibly in the center of the molecular ring there are more than one diskdue to the high multiplicity of the massive stars.
The formation of the massive stars seems to The formation of the massive stars seems to be similar to that of low mass stars in the be similar to that of low mass stars in the very early phases of their evolution !very early phases of their evolution !