Data reduction strategy of the Effelsberg-Bonn HI Survey (EBHIS)

TL;DR

The paper presents a data reduction strategy for the EBHIS survey, utilizing advanced RFI mitigation and calibration techniques to improve data quality and scientific output from HI 21-cm line observations.

Contribution

It introduces a comprehensive data reduction software pipeline incorporating modern RFI mitigation, calibration, and source detection for the EBHIS survey.

Findings

RFI mitigation significantly improves data quality.

Simulations reveal reduced biases with the new data reduction methods.

Enhanced scientific yield from the survey data.

Abstract

Since autumn 2008 a new L-band 7-Feed-Array receiver is used for an HI 21-cm line survey performed with the 100-m Effelsberg telescope. The survey will cover the whole northern hemisphere comprising both, the galactic and extragalactic sky in parallel. Using state-of-the-art FPGA based digital Fast Fourier Transform spectrometers, superior in dynamic range and temporal resolution, allows to apply sophisticated radio frequency interferences (RFI) mitigation schemes to the survey data. The EBHIS data reduction software includes the RFI mitigation, gain-curve correction, intensity calibration, stray-radiation correction, gridding, and source detection. We discuss the severe degradation of radio astronomical HI data by RFI signals and the gain in scientific yield when applying modern RFI mitigation schemes. For this aim simulations of the galaxy distribution within the local volume (z<0.07) with and without RFI degradation were performed. These simulations, allow us to investigate potential biases and selection effects introduced by the data reduction software and the applied source parametrization methods.