HARMONI: advancing science with the next-generation integral field spectrograph
Keywords: HARMONI
integral field spectroscopy
infrared astronomy
HxRG detectors
high redshift galaxy morphology
science prediction
SNR

We start by investigating the noise behaviour of Teledyne HxRG infrared detectors. We look at data from KMOS H2RG darks, along with data from a MOONS engineering grade H4RG detector. From these we determine read noise distributions for the HxRG detectors, and identify a number of other non-uniform noise contributions. We then incorporate this information, along with a pre-existing HxRG noise generation tool, into HSIM. We then use this new advanced detector systematics (ADS) mode to produce simulations investigating the point source sensitivities, spatial variation of noise, reproducibility of recovered point source flux, and signal-to-noise ratio (SNR) for a number of different noise components. We determine from this that these additional detector noise effects provide non-trivial contributions to the noise profile of the detectors. In particular we find pink noise to be problematic, as it is a spatially-varying noise component that has a large impact on the overall SNR. We recommend careful use of the detector reference pixels to correct this, accounting for the potential for bad pixels within these.
We also look at the impact of an under-illuminated spectrograph entrance slit on telluric correction. We model the SINFONI 250x125 mas H-band line spread function (LSF) and vary the level of the input illumination. From this we determine an expected reduction in LSF width of 14%. We then use observations of CD-23 13701 and Callisto taken with SINFONI with adaptive optics (AO) correction to confirm a result of 14.0+/-2.1% when fitted using molecfit. We attempt four methods of telluric correction; directly using CD-23 13701 as a telluric standard star, a synthetic spectrum created from molecfit run on CD-23 13701, this synthetic spectrum convolved with the appropriate LSF, and a synthetic spectrum created from molecfit run on the Callisto data. We perform this analysis on multiple spaxels within the Callisto data, and determine average residual sum of squares of 0.43, 0.34, 0.30, and 0.29 for the four methods. We determine from this that inadequate knowledge of the LSF leads to systematically worse telluric correction. Provided the LSF is known, the level of correction is similar between using a telluric standard star or the science target itself, with the remaining differences partly explained by variations in the atmospheric profile between the observations.
We end with testing a science case of HARMONI; recovering spatially resolved kinematics from high redshift galaxies. We use the NUTFB simulation to create a galaxy at an effective redshift of 1.44. We then produce a number of simulations using HSIM to determine how well we can recover the rotation curve and star formation rate (SFR), varying the simulated observation time and spectral resolution. We determine that 1 hour of HARMONI observation is sufficient to recover the kinematics to the point at which we become limited by effects within the galaxy. We also investigate the impact of the AO point spread function (PSF), particularly showing the effects of the PSF wings smearing out the rotation curve, as well as differences in the kinematics as a result of PSF elongation.