Chandra X-ray Sources in the LALA Cetus Field

TL;DR

This paper reports on the detection and analysis of 188 X-ray sources in the LALA Cetus field using Chandra, including source counts, spectral analysis, and optical identifications, contributing to understanding X-ray background and source populations.

Contribution

It provides the first detailed catalog and spectral analysis of X-ray sources in the LALA Cetus field, comparing source densities with other fields and analyzing the X-ray background composition.

Findings

Detected 188 X-ray sources in the Cetus field.

Found a higher soft band X-ray source density compared to the LALA Bootes field.

Resolved a significant fraction of the X-ray background, with spectral properties characterized.

Abstract

The 174 ks Chandra Advanced CCD Imaging Spectrometer exposure of the Large Area Lyman Alpha Survey (LALA) Cetus field is the second of the two deep Chandra images on LALA fields. In this paper we present the Chandra X-ray sources detected in the Cetus field, along with an analysis of X-ray source counts, stacked X-ray spectrum, and optical identifications. A total of 188 X-ray sources were detected: 174 in the 0.5-7.0 keV band, 154 in the 0.5-2.0 keV band, and 113 in the 2.0-7.0 keV band. The X-ray source counts were derived and compared with LALA Bootes field (172 ks exposure). Interestingly, we find consistent hard band X-ray source density, but 36+-12% higher soft band X-ray source density in Cetus field. The weighted stacked spectrum of the detected X-ray sources can be fitted by a powerlaw with photon index Gamma = 1.55. Based on the weighted stacked spectrum, we find that the resolved fraction of the X-ray background drops from 72+-1% at 0.5-1.0 keV to 63+-4% at 6.0-8.0 keV. The unresolved spectrum can be fitted by a powerlaw over the range 0.5-7 keV, with a photon index Gamma = 1.22. We also present optical counterparts for 154 of the X-ray sources, down to a limiting magnitude of r' = 25.9 (Vega), using a deep r' band image obtained with the MMT.