Science with integral field spectrographs present and future

In the first part of this thesis we use the Oxford Short Wavelength Integral Field spec- Trograph (SWIFT) to trace radial variations of initial mass function (IMF) sensitive stellar absorption features in several galaxies. We observe M31 and M32, the two massive Coma brightest cluster galaxies (BCGs), NGC4889 and NGC4874, and the BCG in the Coma south-west cluster NGC4839. We measure equivalent widths of the sodium NaI λ8190 doublet, calcium triplet CaT λ8498, 8542, 8662 and Wing-Ford band FeH λ9916. In M31 we find a strong NaI gradient within the central 10 arcsec (38 pc) in contrast to a at FeH profile. M32 displays at profiles for all three indices, with similar FeH but lower NaI strengths compared with M31. Using stellar population synthesis (SPS) models we find that M31 and M32 are well described by a Chabrier IMF throughout, although M31 displays a strong negative gradient in Na abundance within the inner 30 pc reaching [Na/Fe] &Tilde; +1:0 at the centre. Within NGC4889 we again find a strong NaI gradient and flat FeH profile and derive a Chabrier, or even bottom-light IMF, with a strong Na abundance gradient. This suggests conflict with recent evidence for an increased IMF slope with increased velocity dispersion in early type galaxies. We also infer a Chabrier IMF for NGC4874. However, for NGC4839 we measure both strong NaI and strong FeH, which may be evidence for a bottom-heavy IMF. The IMFs we infer for the BCGs are supported by optical index measurements and dynamical modelling results from the literature. Our galaxies cover a wide range of central velocity dispersions (60-400kms-1) and we find no IMF variation at both lowest and highest masses, with only one galaxy showing evidence for a bottom-heavy IMF.
In the second part we present HSIM: a dedicated pipeline for simulating observations with HARMONI on the European ELT. HSIM takes high spectral and spatial resolution input data cubes, encoding physical descriptions of astrophysical sources, and incorporates detailed models of the sky, telescope and instrument to produce realistic mock data cubes. We employ a new method of incorporating the strongly wavelength dependent adaptive optics point spread functions. HSIM provides an advancement upon traditional exposure time calculators and allows us to predict the feasibility of a given observing programme with HARMONI through the full analysis of mock data. We use HSIM to predict the performance of the current HARMONI design, through point source sensitivities and noise regimes for each operating mode. We find that HARMONI will be predominately read-out noise limited in the R- and H-bands, but heavily background-limited for the majority of K- band modes. The coarsest 30x60 mas spatial scale offers background-limited observations in all bands. We compare the visible wavelength AO performance between HARMONI and MUSE, finding that HARMONI offers improved sensitivity at Hα, and longer, wavelengths. Lastly, we perform a suite of HSIM simulations of star-forming emission-line galaxies at z &Tilde;2-3. We detail the construction of input data cubes using two separate generation methods. We show that HARMONI will provide exquisite resolved spectroscopy of these objects, probing and deriving properties of individual star forming complexes down to at least &Tilde; 350 pc in size. It will be possible to spatially resolve the sub-kpc star-forming complexes of multiple bright galaxies in a single night, which represents a large increase in observing efficiency over current telescopes and instruments.

Advisor: Thatte, N
Houghton, R