EPSAM

 Star and cluster formation timescales using the Gaia-ESO survey

Lead supervisor:  Prof R Jeffries

The Gaia-ESO spectroscopic survey will begin on the VLT in January 2012. Its ambitious aims are to provide high and medium resolution spectroscopy for >10^5 stars in our Galaxy in support of the general aims of understanding the formation and evolution of our Galaxy and the clusters of stars within it using Chemodynamical constraints along with the exquisitely precise astrometry that will emerge from Gaia. Keele is intimately involved in the project through its role in reducing data from the Giraffe medium resolution spectrograph.

The student project is to use the newly obtained Gaia-ESO data along with archival spectroscopy and photometry in the visible and infrared to examine the star formation history and kinematics of some very young clusters (e.g. the Orion Nebula Cluster, Chamaeleon). Much of this work will be done within the context of the Gaia-ESO project as a whole, but there are specific niches that have been carved out at Keele.

(i) Accretion diagnostics can be used as a crude age indicator and compared with ages derived conventionally from Hertzsprung-Russell diagrams. Preliminary work on the ONC indicates that stars with and without the signatures of accretion disks share similar apparent age distributions. This is incompatible with the idea that accretion decays on short timescales and instead indicates that HR-diagram ages are highly uncertain,
with drastic consequences for deduced star formation histories. This work can be expanded to other clusters and with much better statistics to provide more robust results.
(ii) Projected equatorial velocities from Gaia-ESO and archival VLT spectra can be used to estimate radii for stars with rotation periods. These will be use to test pre-main sequence models and to test the authenticity of ages in the Hertzprung-Russell diagram (e.g. are larger stars younger?) These techniques have been trialled in the ONC but can now be expanded to other clusters and larger samples.
(iii) Gaia-ESO and archival VLT spectra will be used to probe the spatial-kinematic distribution of stars in young star forming regions. These can be compared with theoretical models and with the gas kinematics to deduce early dynamical conditions within the cluster.