Transcript Document

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