The Chandra Deep Field-South Survey: 7 Ms Source Catalogs (1611.03501v2)

Abstract: We present X-ray source catalogs for the $\approx7$ Ms exposure of the Chandra Deep Field-South (CDF-S), which covers a total area of 484.2 arcmin$^2$. Utilizing WAVDETECT for initial source detection and ACIS Extract for photometric extraction and significance assessment, we create a main source catalog containing 1008 sources that are detected in up to three X-ray bands: 0.5-7.0 keV, 0.5-2.0 keV, and 2-7 keV. A supplementary source catalog is also provided including 47 lower-significance sources that have bright ($K_s\le23$) near-infrared counterparts. We identify multiwavelength counterparts for 992 (98.4%) of the main-catalog sources, and we collect redshifts for 986 of these sources, including 653 spectroscopic redshifts and 333 photometric redshifts. Based on the X-ray and multiwavelength properties, we identify 711 active galactic nuclei (AGNs) from the main-catalog sources. Compared to the previous $\approx4$ Ms CDF-S catalogs, 291 of the main-catalog sources are new detections. We have achieved unprecedented X-ray sensitivity with average flux limits over the central $\approx1$ arcmin$^2$ region of $\approx1.9\times10^{-17}$, $6.4\times10^{-18}$, and $2.7\times10^{-17}$ erg cm$^{-2}$ s$^{-1}$ in the three X-ray bands, respectively. We provide cumulative number-count measurements observing, for the first time, that normal galaxies start to dominate the X-ray source population at the faintest 0.5-2.0 keV flux levels. The highest X-ray source density reaches $\approx50\,500$ deg$^{-2}$, and $47\%\pm4\%$ of these sources are AGNs ($\approx23\,900$ deg$^{-2}$).

• The paper presents a comprehensive 7 Ms X-ray survey of the CDF-S, using a dual-step detection method for high source reliability.
• It compiles 1008 main and 47 supplementary sources with 98.4% multiwavelength counterparts, emphasizing a dominant AGN population.
• The findings enhance our understanding of supermassive black hole growth and galaxy evolution, setting a benchmark for future high-energy studies.

The Chandra Deep Field-South Survey: 7 Ms Source Catalogs

This paper presents the results and implications of the deepest X-ray survey conducted to date over the Chandra Deep Field-South (CDF-S), utilizing a 7 Megasecond (Ms) exposure undertaken by the Chandra X-ray Observatory. This ultradeep survey encompasses a sky area of 484.2 arcmin² and achieves unprecedented X-ray sensitivity, serving as a significant tool for exploring the high-redshift universe.

Catalog Compilation and Methodology

The authors have meticulously developed two distinct catalogs: a main catalog consisting of 1008 X-ray sources and a supplementary catalog of 47 sources with lower statistical significance but corroborated by bright near-infrared counterparts. Using a two-step detection methodology, where initial detection was carried out by the wavelet-based algorithm [wavdetect] and followed by photometric extraction and significance reassessment using ACIS Extract (AE), the survey ensured a high degree of source reliability.

Through cross-referencing with extensive multiwavelength datasets, the paper succeeded in identifying multiwavelength counterparts for 98.4% of the main catalog, substantially leveraging the survey's detection robustness. The catalogs include astrometrically aligned redshift data for the sources, further enriched by spectroscopic information for a significant fraction of sources.

Findings and Characterizations

Notably, the survey reveals a source population dominated by Active Galactic Nuclei (AGNs), accounting for 711 of the main catalog sources. It substantially expands our understanding of the demographics and accretion dynamics of supermassive black holes (SMBHs) across cosmic time, particularly through the capture of highly obscured AGNs. Moreover, the findings demonstrate a significant fraction of detected sources being normal galaxies, especially at faint flux levels where they surpass AGNs in population density, thereby contributing to the understanding of galaxy evolution in the early universe.

Implications and Future Prospects

The survey's detection limits recoil to as low as $\sim 1.9 \times 10^{-17}$ erg cm$^{-2}$ in the full band, reaching unprecedented sensitivity. This attribute facilitates the paper of X-ray binary populations in distant galaxies and contributes to our understanding of star formation history. The cumulative number counts provided indicate that normal galaxies start to dominate at the faintest fluxes observed, suggesting these levels encapsulate the peak periods of star formation and SMBH growth.

Furthermore, the archival nature of this dataset renders it a foundational tool, poised to support a diverse array of astrophysical research for decades. The results lead directly to intriguing challenges and questions in cosmology and high-energy astrophysics, stimulating new methods of probing the interactions of AGNs within their host galaxies and the intergalactic environment.

Future X-ray observatories, even those with next-generation sensitivity slated for the next decade, may struggle to exceed the sensitivity achieved here. Hence, the CDF-S 7 Ms data serves as both a reference benchmark and a rich dataset for ongoing and future theoretical and observational studies in high-energy astrophysics. The potential for new insights into the obscured universe and the epochs of galaxy formation remains significant, as researchers continue to exploit this resource.