The First MAXI/GSC Catalog in the High Galactic-Latitude Sky

TL;DR

This paper presents the first high-latitude X-ray source catalog from MAXI, detecting 143 sources in 7 months with detailed analysis, and compares the results with previous surveys like HEAO-1.

Contribution

It introduces a new unbiased catalog of high-latitude X-ray sources from MAXI data using a maximum likelihood detection method, expanding the known X-ray source list.

Findings

Detected 143 X-ray sources above 7 sigma significance

Catalog includes various object types: galaxies, clusters, AGNs, blazars

Log N - log S relation aligns with previous HEAO-1 results

Abstract

We present the first unbiased source catalog of the Monitor of All-sky X-ray Image (MAXI) mission at high Galactic latitudes ($|b| > 10^{\circ}$), produced from the first 7-month data (2009 September 1 to 2010 March 31) of the Gas Slit Camera in the 4--10 keV band. We develop an analysis procedure to detect faint sources from the MAXI data, utilizing a maximum likelihood image fitting method, where the image response, background, and detailed observational conditions are taken into account. The catalog consists of 143 X-ray sources above 7 sigma significance level with a limiting sensitivity of $\sim1.5\times10^{-11}$ ergs cm$^{-2}$ s$^{-1}$ (1.2 mCrab) in the 4--10 keV band. Among them, we identify 38 Galactic/LMC/SMC objects, 48 galaxy clusters, 39 Seyfert galaxies, 12 blazars, and 1 galaxy. Other 4 sources are confused with multiple objects, and one remains unidentified. The log $N$ - log $S$ relation of extragalactic objects is in a good agreement with the HEAO-1 A-2 result, although the list of the brightest AGNs in the entire sky has significantly changed since that in 30 years ago.