The Tianlai Cylinder Pathfinder Array: System Functions and Basic Performance Analysis

TL;DR

The Tianlai Cylinder Pathfinder is a radio interferometer array designed for 21 cm intensity mapping, with initial system performance analysis demonstrating its potential for cosmological observations.

Contribution

This paper presents the first detailed analysis of the Tianlai Cylinder Pathfinder's system performance, including calibration, beam profiling, and sensitivity estimation.

Findings

System temperature around 90 K

Beam profile characterized in east-west direction

Calibration stability confirmed

Abstract

The Tianlai Cylinder Pathfinder is a radio interferometer array designed to test techniques for 21 cm intensity mapping in the post-reionization Universe, with the ultimate aim of mapping the large scale structure and measuring cosmological parameters such as the dark energy equation of state. Each of its three parallel cylinder reflectors is oriented in the north-south direction, and the array has a large field of view. As the Earth rotates, the northern sky is observed by drift scanning. The array is located in Hongliuxia, a radio-quiet site in Xinjiang, and saw its first light in September 2016. In this first data analysis paper for the Tianlai cylinder array, we discuss the sub-system qualification tests, and present basic system performance obtained from preliminary analysis of the commissioning observations during 2016-2018. We show typical interferometric visibility data, from which we derive the actual beam profile in the east-west direction and the frequency band-pass response. We describe also the calibration process to determine the complex gains for the array elements, either using bright astronomical point sources, or an artificial on site calibrator source, and discuss the instrument response stability, crucial for transit interferometry. Based on this analysis, we find a system temperature of about 90 K, and we also estimate the sensitivity of the array.