Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Skip to content

CANDELS H-Band Selected Chandra Source Catalog

Metadata Updated: September 19, 2025

Improving the capabilities of detecting faint X-ray sources is fundamental to increase the statistics on faint high-z AGN and star-forming galaxies. The authors performed a simultaneous maximum likelihood point-spread function (PSF) fit in the 0.5-2 keV and 2-7 keV energy bands of the 4 Ms Chandra Deep Field South (CDFS) data at the position of the 34,930 CANDELS H-band selected galaxies. For each detected source, they provide X-ray photometry and optical counterpart validation. The authors validated this technique by means of a ray-tracing simulation, and detected a total of 698 X-ray point-sources with a likelihood L > 4.98 (i.e.> 2.7sigma). They show that the prior knowledge of a deep sample of Optical-NIR galaxies leads to a significant increase of the detection of faint (i.e. ~ 10<sup>-17</sup> erg s<sup>-1</sup> cm<sup>-2</sup> in the 0.5-2 keV band) sources with respect to "blind" X-ray detections. By including previous catalogs, this work increases the total number of X-ray sources detected in the 4 Ms CDFS, CANDELS area to 793, which represents the largest sample of extremely faint X-ray sources assembled to date. These results suggest that a large fraction of the optical counterparts of our X-ray sources determined by likelihood ratio actually coincides with the priors used for the source detection. Most of the newly detected sources are likely star-forming galaxies or faint absorbed AGN. The authors identified a few sources with putative photometric redshift z > 4. Despite the low number statistics, this sample significantly increases the number of X-ray selected candidate high-z AGN. The 4-Ms CDFS consists of 23 observations described in Table 1 of Luo et al. (2008, ApJS, 179, 19) plus 31 other pointings described in Xue et al. (2011, ApJS, 195, 10, hereafter X11) for a total exposure of ~4 Ms. For the purpose of this paper, the authors employed only observations taken with a focal temperature of <= -120 C, since at higher temperatures the background cannot be modeled with their technique. This table was created by the HEASARC in July 2016 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/823/95">CDS Catalog J/ApJ/823/95</a> file catalog.dat. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

Downloads & Resources

Dates

Metadata Created Date April 11, 2025
Metadata Updated Date September 19, 2025

Metadata Source

Harvested from NASA Data.json

Additional Metadata

Resource Type Dataset
Metadata Created Date April 11, 2025
Metadata Updated Date September 19, 2025
Publisher High Energy Astrophysics Science Archive Research Center
Maintainer
Identifier ivo://nasa.heasarc/candelscxo
Data Last Modified 2025-09-10
Category Astrophysics
Public Access Level public
Bureau Code 026:00
Metadata Context https://project-open-data.cio.gov/v1.1/schema/catalog.jsonld
Schema Version https://project-open-data.cio.gov/v1.1/schema
Catalog Describedby https://project-open-data.cio.gov/v1.1/schema/catalog.json
Harvest Object Id 1f1269f1-7b89-4afb-bd07-a51b385d2fe6
Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
Harvest Source Title NASA Data.json
Homepage URL https://heasarc.gsfc.nasa.gov/W3Browse/all/candelscxo.html
Program Code 026:000
Source Datajson Identifier True
Source Hash 65e8e02a844014d08b2b7d64e83adc7e7925480655a9a2b74e04ed66ac777ab0
Source Schema Version 1.1

Didn't find what you're looking for? Suggest a dataset here.