1. Tracing Galactic structure with obscured luminous stars
Madrid
March 2012
Tracing Galactic structure with obscured luminous stars
Ignacio Negueruela

2. Tracing Galactic structure with obscured luminous stars
Madrid
March 2012
Tracing Galactic structure with obscured luminous stars
+ High-mass stars in the infrared
Francisco Najarro
Artemio Herrero
Ignacio Negueruela

3. Outline Piercing the dust Obscured clusters Galactic structure
The obscuration problem
Obscured clusters
Very massive clusters
Obscured populations
Galactic structure
High-mass stars (preferably clusters) as tracers of structure

4. Distribution of massive clusters in the Milky Way
Sagitarius
Crux
Cygnus
Orion
Perseus
Scutum
Carina
Norma
Distribution of massive clusters in the Milky Way
Center
Arches
Quintuplet
RSG2 RSG1
RSGC3
Alicante 7, 10
Alicante 8
Westerlund 1
NGC 3603
The last identified massive cluster (Alicante 8, Negueruela et al., 2010) has already been studied with WHT
Desde Paranal se ve l= 70 – 180 (aprox.)
Desde La Palma se ve l=
Masgomas-1
Tr14+16
Cyg OB2
Westerlund 2
Accessible from La Palma

5. Distribution of massive clusters in the Milky Way
Sagitarius
Crux
Cygnus
Orion
Perseus
Scutum
Carina
Norma
Distribution of massive clusters in the Milky Way
Accessible from Paranal
Center
Arches
Quintuplet
RSG2 RSG1
RSGC3
Alicante 7
Alicante 8
Westerlund 1
NGC 3603
The last identified massive cluster (Alicante 8, Negueruela et al., 2010) has already been studied with WHT
Desde Paranal se ve l= 70 – 180 (aprox.)
Desde La Palma se ve l=
Masgomas-1
Tr14+16
Cyg OB2
Westerlund 2
Accessible from La Palma

6. Distribution of massive clusters in the Milky Way
Sagitarius
Crux
Cygnus
Orion
Perseus
Scutum
Carina
Norma
Distribution of massive clusters in the Milky Way
Center
Arches
Quintuplet
RSG2 RSG1
RSGC3
Alicante 7
Alicante 8
Westerlund 1
NGC 3603
The last identified massive cluster (Alicante 8, Negueruela et al., 2010) has already been studied with WHT
Desde Paranal se ve l= 70 – 180 (aprox.)
Desde La Palma se ve l=
Masgomas-1
Tr14+16
Cyg OB2
Westerlund 2
Accessible in the optical

7. The Milky Way is hidden
Most of the Milky Way is too obscured to allow optical spectroscopy.
Study of Cl with Keck + NIRSPEC (Messineo et al. 2011, ApJ 733, A41)

8. The Milky Way is hidden
Most of the Milky Way is too obscured to allow optical spectroscopy.
Extinction is complex and poorly known.
OB stars are needed to determine it.
Combined optical+near-IR spectrophotometry.
Study of Cl with Keck + NIRSPEC (Messineo et al. 2011, ApJ 733, A41)

9. Searching for obscured massive star clusters
Near-IR
Optical
Mid-IR 9

10. Galactic centre and beyond
Molecular Clouds and Clumps in the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey.
Roman-Duval et al. 2010, ApJ 723, 492

11. High-mass Stars in Obscured Regions
Effects of extinction !
AV = 30
Black Body

12. Importance of resolution

13. Metallicity Studies Why metallicity? Determinations in the IR
α-elements vs Fe ratio. Top heavy IMFs
constraints to evolutionary models
2-D metallicity map of the Milky Way to provide constraints to galactic chemical evolution models
Determinations in the IR
Direct estimates  LBV phase
Indirect estimates  WNL phase
Direct estimates  OIf phase

14. Pistol Star α/Fe= 2 !! Fe Solar Mg 2xSolar Si 2xSolar
Najarro et al , 9

15. (>80h allocated over the last 3 years)
IR survey of open clusters with VLT/ISAAC by the CAB high-mass star group
(>80h allocated over the last 3 years)
Infrared diagnostics for OB SGs
(Najarro et al. 2011, A&A 535, A32)

16. Distribution of massive clusters in the Milky Way
Sagitarius
Crux
Cygnus
Orion
Perseus
Scutum
Carina
Norma
Distribution of massive clusters in the Milky Way
Center
Arches
Quintuplet
RSG2 RSG1
RSGC3
Alicante 7, 10
Alicante 8
Westerlund 1
NGC 3603
The last identified massive cluster (Alicante 8, Negueruela et al., 2010) has already been studied with WHT
Desde Paranal se ve l= 70 – 180 (aprox.)
Desde La Palma se ve l=
Masgomas-1
Tr14+16
Cyg OB2
Westerlund 2

17. Stephenson 2 Concentration of > 26 RSGs Implied mass > 5x104 M
(Davies et al. 2007, ApJ 671, 781)
Implied mass > 5x104 M
False colour image from JHK UKIDSS frames

18. Multiplexing Stephenson 2
Photometric criteria detect only luminous red stars.
About 230 unique objects observed.
Intruders are always bright giants in the foreground or very late (>M4) giants.
We observe ~35 RSGs with high vrad (compatible with Ste 2) over the whole field (at distances >50’ from Stephenson 2).
There are many RSGs with significantly different vrad over the whole area.
WHT + WYFFOS, 2009
Around ℓ = 26°
Negueruela et al., submitted

19. RSGs of all tastes
Negueruela et al., submitted

20. Tracers of Galactic structure
Masers
HII regions
RSGs *
Negueruela et al., submitted

21. Tracers of Galactic structure
Negueruela et al., submitted

22. AAOmega data Much higher multiplexing (>1000 stars in 3 nights)
Wider field
Much better access to cluster cores
Higher resolution (R ~ )
gives accuracy of 2 km/s (internal)

23. Heavy reddening
Very variable obscuration
No “interesting” features

24. Only 80 min total exposure
Limited to I ~ 15

25. Field centred on Westerlund 1
Huge luminous population
>80 previously unknown SGs

26. Field centred on Westerlund 1

27. Requirements – OB stars in the IR
The hidden Milky Way:
Star formation
Very massive clusters
Galactic structure
Wide field  interesting, but not fundamental
Multiplexing in the moderate resolution ( )
Capability to reach cluster cores  important
MIRADAS (EMIR, LIRIS)

28. Requirements – Galactic structure
Survey of red supergiants towards the inner Galaxy:
Ideally in the 850 nm range (parameters, many lines, easy access), but then limited by extinction.
K band at  good for radial velocities, but not for abundances
H band at 
(MIRADAS, but also APOGEE)
Davies et al. (2007, ApJ 671, 781)

29. Requirements – Galactic structure
Survey of red supergiants towards the inner Galaxy:
Dynamics
Galactic structure
Wide field  decisive, at least 1°
High throughput around 850 nm
Capability to reach cluster cores  important
, AF2, HECATE)

30. Tracing Galactic structure with obscured luminous stars
Madrid
March 2012
Tracing Galactic structure with obscured luminous stars
Ignacio Negueruela