Simulation of a High-Redshift Line-Emitting Galaxy Detection with DESHIMA using TiEMPO

Abstract

In this report, we will focus on simulating galaxy observations with the Deep Spectroscopic High-redshift Mapper (DESHIMA). To do so, we will discuss and evaluate two main parts needed to accurately perform such a simulation:

Firstly, we will answer the question whether Time-dependent End-to-end Model for Post-process Optimization (TiEMPO), the modelling software used for DESHIMA observation simulations, is able to accurately simulate real life galaxy observations conditions. To do so, the simulation program is fed artificially created atmospheric data and its output is compared with sky brightness data of real measurements. More specifically, the time signal, power spectral density and noise equivalent flux density of both the simulation and the measurement data are derived and compared. This comparison showed, apart from a linear drift of the time signal data and a small offset of the power spectral density, good agreement between the simulation and the measurement.

The second part of this thesis discusses whether we can detect an artificially created galaxy, using the already verified atmospheric model of TiEMPO. To do so, the output of the simulation is run through a series of algorithms that calculate the observation spectrum of the telescope, as if it were a real measurement. In addition, the application of different observation tactics and telescope parameters are tested and visualised. Most importantly, two observational position-switching (chopping) techniques are applied and compared: the dual point and ABBA chopping techniques. To test the effectiveness of the two chopping techniques, both will be used to simulate atmospheric filtration using stationary, i.e. without telescope movement, simulation and measurement data, which do not contain the (to be detected) galactic data. As there is no telescope movement, nor galactic data, the spectra should ideally fluctuate around zero. However, as we will see in this report, this is not obtained in all cases. After further analysis, two main types of offsets could be identified: the first one originating from the linear drift of the measurement's time signal data, whereas the second one is due to the spatial displacement of the chopping positions. The former can be corrected by applying the ABBA chopping technique rather than the dual chopping method, whereas the latter cannot with either of the two.

Using the insights we acquire from running these simulations with observation conditions for DESHIMA, we are able to perform an actual galaxy observation simulation. The galactic data acquired from this observation simulation shows good agreement with the input values of the galaxy data of TiEMPO, assuring that TiEMPO can be used for galaxy observation simulations.