Hunting Very Massive Metal-poor Stars Danny Lennon (ESA-STScI) Acknowledgements: Miriam Garcia (IAC), Artemio Herrero (IAC), Alex Fullerton (STScI), Joachim Puls (Munich), Chris Evans (ATC, Edinburgh), Derck Massa (STScI), Nolan Walborn (STScI), Paul Crowther (Sheffield), H. Sana (Amsterdam), Selma de Mink (STScI), J.C. Bouret (Marseille), Azalee Bostroem (STScI)

A very high level view of the science: OLD PICTURE The IMF stops at ~60 solar masses and a star’s evolution is determined by its initial mass and metallicity....simple. NEW PICTURE Stars have initial masses up to at least ~300 solar masses and....it’s complicated!

Rotation.. de Mink Rotation.. de Mink..or not? Hunter & Brott..or not? Hunter & Brott Most are not single de Mink Most are not single de Mink Upper IMF? Crowther Upper IMF? Crowther Clumping? Sundqvist Clumping? Sundqvist Magnetic Fields Wade Magnetic Fields Wade

We need spectra! Photometry is degenerate. Peter Conti

FUVUVOptical/NIRmid-IR ‣ Highly ionized wind & wind structure ‣ Cold ISM, H 2 ‣ Weak Wind ‣ Properties of inner wind ‣ Wind Clumping ‣ Abundances ‣ Diffuse ISM ‣ Stellar Parameters ‣ Turbulence ‣ Abundances ‣ Pulsation ‣ Magnetic fields ‣ IR excess ‣ Wind clumping ‣ disks ‣ CSM FUSE and now COS COS & STIS Ground-basedSpitzer & JWST Evolution and final fate of Massive Stars ISM and Extinction:  Chemical enrichment, feedback, mixing  Dynamics and distribution of the ISM Spectral Libraries:  Testing atmosphere/wind models  Population synthesis of low/high z populations

FUSE STIS/FUV COS Courtesy: Adi Pauldrach

low Z: The Magellanic Clouds Hubble has pioneered the investigation of radiation driven winds at low Z. In the SMC roughly 30 observed with STIS (Lennon: opposite), another 20 with COS (Hubeny & Lanz: not yet published). COS enables us to push into the “weak wind” regime at lower luminosities and masses. By contrast there are only ~10 such spectra for the LMC From FUSE there are ~100 good quality spectra for each galaxy.

lower Z: Beyond the Magellanic Clouds The sensitivity of COS allows us to investigate massive stars in galaxies out to ~1 Mpc and sample star forming irregular galaxies more metal poor than the LMC (0.5 solar) and SMC (0.2 solar). Examples include IC1613 (Garcia: 9 stars in IC1613, opposite) and WLM (Lanz: 2 in IC1613, 1 in WLM, yet to be observed). Both galaxies have [O/H] ~ 0.1 solar. Courtesy: Miriam Garcia Sana et al 2012

Spectroscopy in dense clusters: R136 Most massive of resolved massive clusters with M~5x10 4 M ʘ and the densest, most compact cluster: central parsec contains ~30 WN and O2/O3 stars, containing some very massive stars with >150M ⊙ (Crowther et al 2010). 4”~1pc HST/FOS - Massey & Hunter HST/STIS - Crowther et al

Long-slit spectrum of 30 Doradus (Azalee Bostroem)

Constructing the data cube. WFC3 Image: E. Sabbi

A lot of exciting science still to do with HST and UV/Optical spectroscopy!! Specific requests/needs: CTE mitigation for STIS CCDs Long slit package improvement: MULTISPEC? (Maiz-Apellaniz) Archive: target (fuzzy) type keywords would be useful (cf IUE) Improve spectrum previewing from the archive (and HLA) LSFs for convolution with models Summary