University of Canterbury programs with SALT

Michael Albrow, Mita Brierley 1,

Peter Cottrell, Jeffrey Simpson, Clare Worley 2

1 now at Astronomy Australia Ltd

2 now at Institute of Astronomy, Cambridge

Other potential users : Jenni Adams, Loretta Dunne, Chris Gordon, John Hearnshaw, Steve Maddox, Karen Pollard, David Wiltshire

Globular Cluster integrated light studies

(Albrow/Brierley)

• Most spectroscopic studies of extragalactic globular clusters at low resolution

metallicity and alpha-element ratios using the Lick index system

• Beyond Milky Way & its satellite galaxies, moderate-to-high resolution spectral studies only on globular cluster system of M31

• Purpose of this research

acquire moderate-to-high resolution integrated light spectra of globular clusters in the Milky Way and Large Magellanic Cloud

these clusters have CMD-derived ages and spectroscopic abundances of individual stars

long slit, integrated-light spectra will be used to help calibrate our new high-resolution theoretical stellar populations spectral models

Young LMC clusters NGC 1831 (red, age 600 Myr) and NGC 1978 (blue, age 1.9 Gyr) in the region around H-beta

Old MW globular clusters NGC 362 (blue) and NGC 6218 (red) in the region around H-delta. Each is overlaid with a 10Gy, [Fe/H] = -1.5 model from

Brierley (2010). The clusters have similar metallicity ([Fe/H] = -1.15 and [Fe/H] = -1.37 on the Caretta & Gratton 1997 scale) but NGC 6218 is older than NGC 362 by a factor of 1.25 according to the main-sequence fitting results of Marin-Franch et al (2009). The two spectra are very similar and

don’t distinguish between the ages of old globular clusters at the 25% level.

Globular Clusters MOS studies

(Simpson/Cottrell/Worley)

• Large samples are the key to understanding stellar evolution processes in globular clusters

• Can medium resolution spectra provide the key signatures of the nulceosynthetic processes?

C, N, Fe, s-process, others

• Purpose of this research

acquire multi-object spectroscopy of a range of globular clusters

Cen, 47 Tuc, NGC 6752, NGC 362

Spectral Matching @ R~1600 in Cen ~200 & 850 stars with 2dF on AAT

Simpson, Cottrell & Worley, 2012, MNRAS, in press ; Simpson & Cottrell, submitted

220 stars

850 stars

SALT MOS

R~3000NGC 362(31 slits)

Future (personal) programs with SALT