Hunting very massive metal poor stars
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Hunting Very Massive Metal-poor Stars. Danny Lennon (ESA-STScI)

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Hunting very massive metal poor stars
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
A very high level view of the science:


The IMF stops at ~60 solar masses and a star’s evolution is determined by its initial mass and metallicity....simple.


Stars have initial masses up to at least ~300 solar masses and’s complicated!

Hunting very massive metal poor stars


de Mink

..or not?

Hunter & Brott

Most are not single

de Mink

Upper IMF?




Magnetic Fields


We need spectra

Peter Conti

We need spectra!

  • Photometry is degenerate.

Hunting very massive metal poor stars





FUSE and now COS


Spitzer & JWST


  • Weak Wind

  • Properties of inner wind

  • Wind Clumping

  • Abundances

  • Diffuse ISM

  • Highly ionized wind & wind structure

  • Cold ISM, H2

  • IR excess

  • Wind clumping

  • disks

  • CSM

  • Stellar Parameters

  • Turbulence

  • Abundances

  • Pulsation

  • Magnetic fields

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

Hunting very massive metal poor stars




Courtesy: Adi Pauldrach

Winds @ low z the magellanic clouds
Winds @ 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.

Winds @ lower z beyond the magellanic clouds
Winds @ lower Z: Beyond the Magellanic Clouds

Courtesy: Miriam Garcia

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.

Sana et al 2012

Spectroscopy in dense clusters r136
Spectroscopy in dense clusters: R136

  • Most massive of resolved massive clusters with M~5x104 Mʘ 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).


HST/STIS - Crowther et al

HST/FOS - Massey & Hunter

Hunting very massive metal poor stars

WFC3 Image: E. Sabbi

  • Constructing the data cube.


  • 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