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I want to epress my joy for: -sharing with you guys this time in this beatiful planet -sharing the excitement unveiling the secret live of the stars -sharing the friendship with Peter who opened roads to the big scenario of massive stars The Stellar Content of Galactic Giant HII Regions Augusto Damineli (IAGUSP) Robert Blum (NOAO) Peter Conti (JILA) Elysandra Figuerêdo (Open Un.) Alessandro Moisés (IAGUSP) Where are trhe arms? Longer wavelengths => clear view, but mixed structures Many methods indicate Sb-Sc types 2MASS Mellinger RVs of radio recombination lines from HII regions + rotation curve => Distances to HII regions (l,b) coordinates Clemens 1985 face-on map Sun HII Regions Russeil 2003 Limitations of the method: Radial velocities: - degenerate toward the GC line-of-sight - 2-valued r<R Non-rotational components: - warm gas outflows from HII regions (10 Km/s - density-wave attractive force ( up to 10 km/s) - collisions between GMCs Giant HII Regions Project started ~15 years ago by Conti, Hanson, Blum… -K-band imaging+spectra of ionizing O-type stars -Spectroscopic parallax: robust physics like in the optical window -Errors constrained by multiple stellar spectra Our Method: Giant HII Regions (NLyc=>1050 ph/s =>10 O7V*) good tracers of the spiral arms selected from radio and FIR surveys 50 imaged with Blanco/SOAR Colour- Magnitude Diagram: Candidates for spectroscopy foreground stars ZAMS of the HIIR Spectroscopy of O-type stars: lines used to determine the spectral type O6V Hanson, Conti & Rieke (1996) Spectral Type Late O-type stars Distance Module O8V DSpPt Sppdist kpc Id Kdist kpc ref ref M8 2.8 R03 0.6 Bik04 W31 >4.1-12.3 C&E04 3.4 ± 0.5 BDC M17 2.4 R03 1.3 Hans97 W42 3.7 -11.5 R03 2.2 ±0.8 BCD W43 6.2 R03 5.9 ± 0.7 BDC W49A 11.8 Wetal04 8.4 Bik04 W51A 5.5 R03 2.2 F07 W3OH 4.2 R03 1.95 Xu06 NGC3603* 7.9 R03 6.0 Stolte04 G282.0-1.2 G298.9-0.4 G333.1-0.4 G331.5–0.1 5.9 10.4 3.5 10.8 R03 R03 R03 5.3 ±1.2 3 2.4 ±0.4 4.5 ±0.3 F05 Bik04 F05 F05 All shifts are toward smaller distances! Sun GC Conti & Crowther 2004 Star Formation Rate in the Milky Way Conti & Crowther 2004 NLyC = 2.4 × 1052 ≥ 2.6 M/year Scaling the reduction to all sources NLyC = 1.7 × 1052 ≥ 1.8 M/year W3OH: emblematic for distance discrepancy Kin. distance d = 4.2 kpc (RV = -45 km/s) Russeil 2003 SpPht distance d = 2.2 kpc (optical) Humphreys 1978 Trig. VLBA OH masers d = 1.95±0.04 kpc Xu et al. 2006 Perseus arm is at wrong kinematic distance! Limitations of the method: --Calibration uncertainty: MV = ± 0.7 Vacca et al. 1996 – Unresolved blends: 2 identical stars => Distance 40% smaller – Projected stars in the cluster line-of-sight What is the role of the reddening law? AK ~ 1/la Mathis (1990) a=1.7 Nishiyama et al. (2006) a=1.99 G353.19+0.64 Ak=3 Ak=2 Ak=1 Name M8 DK DNish DMat kpc 2.8 0.9 0.8 W31 >4.1-12.3 3.9 3.3 M17 2.4 1.7 1.6 W42 3.7-11.5 2.8 2.5 W43 6.2 6.3 4.7 W49A 11.8 14.7 11.0 W51A 5.5 4.0 3.0 G298.2-0.3 10.4 4.6 3.9 G333.1-0.4 3.5 3.3 2.4 G331.5-0.1 10.8 5.5 4.5 The slope of the luminosity function is K-band independent of the Galactic ambient Luminosity Function --- NGC3576 --- G333.1-0.4 a = 0.35 0.05 Salpeter In line with Massey 2003 Morphologic Type of Milk Way L (H) [ergs/s]= ( 1.43 ×10-12 ) NLyC [photons/s] M17 W49A NGC3603 3GHIIR + luminous Kennicutt (1988) Conti & Crowther 2004