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Early O-Type Stars in the W51-IRS2 Cluster A template to study the most massive (proto)stars

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. Outline. Comments on the formation of massive stars

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Early O-Type Stars in the W51-IRS2 Cluster A template to study the most massive (proto)stars

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  1. 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

  2. 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

  3. The formation of the massive stars • Some fundamental theoretical problems to form massive stars (M* > 10 Msun): • The Kelvin-Helmholtz time is much shorter than the free-fall time • -- radiation pressure (spherical geometry) • The strong UV fields will ionize the surrounding molecular gas by so fast • The short main-sequence lifetime of high-mass stars • Some observational problems to study massive (proto)stars: • They are located far away, more than 1 kpc (with exception of Orion) • There are a short number of massive (proto)stars • They are very embedded in the molecular cloud • -- only observable in radio and IR bands

  4. Some possible solutions • Circumstellar Large Disks • A Natural outcome !! • Very high accretion rates that • quenched or trapped the • formation HII regions • Mergers of low mass stars • Competitive accretion

  5. W51 Complex Sagittarius Arm HJK-Infrared CFHT

  6. W51 VLA 3.6 cm. Lacy et al. (2007) W51 IRS2 W51 IRS1 Infrared: grey scale (VLT) 3.6 cm: contours W51 East

  7. One of most luminous regions in the Galaxy W51 IRS2 Infrared (JHK) Barbosa et al. (2008) IRS2W (O3-type) IRS2E (O4-type) 7000 AU Lbol= = 3 x 106 Lsun D ~ 6, 000 pc ~ 30 O-type protostars

  8. Ammonia (J,K)=(3,3) W51 North & W51 D1 VLA NH3: dashed contours 3.6 cm: continuous contours 1.3 cm emission: dashed contours NH3: continuous contours Ho et al. (1983) Gaume et al. (1993)

  9. H2O and SiO Maser Spots VLBI NH3: dashed contours 1.3 cm: continuous contours W51 North Imai et al. (2002) Powerful Bipolar very compact NW-SE Outflow ! Einser et al. (2003)

  10. Cyanogen (CN) molecular emission Submillimter Array 3” resolution Moment zero Classical profile inverse P-cygni Accretion rate ~ 10-3 Msun/yr Low mass stars ~ 10-6 Msun/yr Zapata et al. (2008)

  11. Sensitive and high angular resolution study of W51 North Submillimeter Array 1 mm Very extended configuration ~ 0.4 arcsec SiO, SO2, CH3CH, H3CN… Very Large Array 7 mm C-configuration ~ 0.4 arcsec

  12. W51d2 HC HII region + outflow Flat SED Disk + outflow steeper SED W51d HII region Cometary • SO2 • SiO(5-4) • 7 mm

  13. W51d W51d2 W51 North W51 IRS2 Infrared ( 2 m) Lacy et al. (2006)

  14. Evolutive Phases ! W51 d2 W51 d2 outflow Infrared stars W51 d HC HII region Molecular Ring O-type stars Cometary HII Region

  15. 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…

  16. H92 and He92 recombination lines SED TB=80±10 K From the 7mm and 1.3 mm measurements Mehringer et al. (1994)

  17. Molecules SO2 PV W51 North W51 d2

  18. More Molecules in the Ring H2CO

  19. More Molecules in the Ring CH3OH

  20. 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 disk due to the high multiplicity of the massive stars. The formation of the massive stars seems to be similar to that of low mass stars in the very early phases of their evolution !

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