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

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

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

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= 0 - 250 Masgomas-1 Tr14+16 Cyg OB2 Westerlund 2 Accessible from La Palma

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= 0 - 250 Masgomas-1 Tr14+16 Cyg OB2 Westerlund 2 Accessible from La Palma

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= 0 - 250 Masgomas-1 Tr14+16 Cyg OB2 Westerlund 2 Accessible in the optical

The Milky Way is hidden Most of the Milky Way is too obscured to allow optical spectroscopy. Study of Cl 1813-178 with Keck + NIRSPEC (Messineo et al. 2011, ApJ 733, A41)

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 1813-178 with Keck + NIRSPEC (Messineo et al. 2011, ApJ 733, A41)

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

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

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

Importance of resolution

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

Pistol Star α/Fe= 2 !! Fe Solar Mg 2xSolar Si 2xSolar Najarro et al. 2007, 9

(>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)

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= 0 - 250 Masgomas-1 Tr14+16 Cyg OB2 Westerlund 2

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

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

RSGs of all tastes Negueruela et al., submitted

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

Tracers of Galactic structure Negueruela et al., submitted

AAOmega data Much higher multiplexing (>1000 stars in 3 nights) Wider field Much better access to cluster cores Higher resolution (R ~ 10 000) gives accuracy of 2 km/s (internal)

Heavy reddening Very variable obscuration No “interesting” features

Only 80 min total exposure Limited to I ~ 15

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

Field centred on Westerlund 1

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 near-IR @ moderate resolution ( 10 000 - 20 000 ) Capability to reach cluster cores  important MIRADAS (EMIR, LIRIS)

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  10 000 good for radial velocities, but not for abundances H band at  20 000 (MIRADAS, but also APOGEE) Davies et al. (2007, ApJ 671, 781)

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 WEAVE @ 10 000 (@ 5 000, AF2, HECATE)

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