Cosmic Chronometers in t he GAMA fields

Project Description

Here, we seek funding from the Royal Astronomical Society, with in-kind contributions from the University of Hull, to undertake a summer project of 8 weeks in length to determine the frequency and prevalence of cosmic chronometers in the GAMA data set.

Explicitly, we wish to construct the highest purity sample of cosmic chronometers delivered to date. Such a robust set of galaxies free of young stellar population frosting will be created using the methods established by us and others cited in the references above. Significantly, the selection of this sample will require re-processing spectra from GAMA to incorporate our recent work on the H:K line ratios (Pimbblet et al., 2019, MNRAS, 490, 455) as this has not been included in any analysis to date. The frequency of such chronometers is important to establish the viability of this method at low to intermediate redshifts, and at magnitude limits slightly lower than SDSS (i.e. pushing down the galaxy luminosity function). As time permits, we will determine what effect the metallicity of these galaxies using stellar population synthesis modelling since the dt values between pairs of galaxies must be computed from the strength of the D4000 line break such that dt=A(z)dD4000, where A(z) is a slope that critically depends on metallicity.

This work will, in turn, inform us of the viability of GAMA and future surveys (explicitly: TAIPAN) to provide us with a suite of cosmic chronometers from which we could compute H(z) in the coming years. As such, this application has the potential to provide the ground work for a much bigger future endeavour by our group to ascertain H(z) from cosmic chronometry and therefore also ties in strongly with the STFC roadmap objective of how the Universe began is how it is evolving.