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 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 M sun ): 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 Complex Sagittarius Arm HJK-Infrared CFHT

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

W51 IRS2 Infrared (JHK) Barbosa et al. (2008) IRS2W (O3-type) IRS2E (O4-type) L bol= = 3 x 10 6 L sun D ~ 6, 000 pc ~ 30 O-type protostars 7000 AU One of most luminous regions in the Galaxy

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

Imai et al. (2002) Einser et al. (2003) H 2 O and SiO Maser Spots VLBI Powerful Bipolar very compact NW-SE Outflow ! NH3: dashed contours 1.3 cm: continuous contours W51 North

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

Very Large Array 7 mm C-configuration ~ 0.4 arcsec Submillimeter Array 1 mm Very extended configuration ~ 0.4 arcsec SiO, SO 2, CH 3 CH, H 3 CN… Sensitive and high angular resolution study of W51 North

W51d2 HC HII region + outflow Flat SED W51d HII region Cometary  SO 2  SiO(5-4)  7 mm Disk + outflow steeper SED

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

W51 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 G 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…

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

SO2 PV Molecules W51 North W51 d2

H2CO More Molecules in the Ring

CH3OH More 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 M sun The mass of the dusty disk is 40 M sun 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 !