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SPICES Lynx Field Chandra X-Ray Source Catalog

Metadata Updated: October 30, 2025

This table contains the first results on field X-ray sources detected in a deep, 184.7 ks observation with the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-Ray Observatory. The observations target the Lynx field (J2000.0 RA = 08h 48m and Dec = +44d 54') of SPICES, the Spectroscopic Photometric Infrared-Chosen Extragalactic Survey, which contains three known X-ray-emitting clusters at redshifts of z = 0.57, 1.26, and 1.27. Not including the known clusters, in the 17' x 17' ACIS-I field the authors detect 132 sources in the 0.5 - 2 keV (soft) X-ray band down to a 2.1-sigma limiting flux of ~ 1.7 x 10<sup>-16</sup> erg/cm<sup>2</sup>/s and 11 sources in the 2 - 10 keV (hard) X-ray band down to a 2.1-sigma limiting flux of ~ 1.3 x 10<sup>-15</sup> erg/cm<sup>2</sup>/s. The combined catalog contains a total of 153 X-ray sources, of which 42 are detected only in the soft band and 21 are detected only in the hard band. Confirming previous Chandra results, the authors find that the fainter sources have harder X-ray spectra, providing a consistent solution to the long-standing "spectral paradox". From deep optical and near-infrared follow-up data, 77% of the X-ray sources have optical counterparts to I = 24, and 71% of the X-ray sources have near-infrared counterparts to K<sub>s</sub> = 20. Four of the 24 sources in the near-IR field are associated with extremely red objects (EROs; I - K<sub>s</sub> >= 4). The authors have obtained spectroscopic redshifts with the Keck telescopes of 18 of the Lynx Chandra sources. These sources comprise a mix of broad-lined active galaxies, apparently normal galaxies, and two late-type Galactic dwarfs. Intriguingly, one Galactic source (number 72) is identified with an M7 dwarf exhibiting non-transient, hard X-ray emission. Thirteen of the Chandra sources are located within regions for which the authors have Hubble Space Telescope imaging. Nine of the sources are detected, showing a range of morphologies: several show compact cores embedded within diffuse emission, while others are spatially extended showing typical galaxy morphologies. Two of the Chandra sources in this subsample appear to be associated with mergers. ACIS-I observations of the Lynx field were obtained on 2000 May 3 (65 ks; OBS-ID 1708) and 2000 May 4 (125 ks; OBS-ID 927). Time intervals with background rates larger than 3 sigma over the quiescent value of ~ 0.30 counts s<sup>-1</sup> per chip in the 0.3 - 10 keV band were removed. This procedure gave 60.7 ks of effective exposure out of the first observation and 124 ks out of the second, for a total of 184.7 ks. The two observations are almost coincident on the sky, so that the total coverage is 298 arcmin<sup>2</sup>. The aim point for the observations was RA = 08h 48m 54.79s, Dec = +44d 54' 32.9" (J2000.0), and both exposures were obtained in the faint mode when ACIS was at a temperature of -120 C. The Galactic absorbing column for this field is N<sub>H</sub> = 2 x 10<sup>20</sup> cm<sup>-2</sup>. The position angle of the observations was 258.45 degrees. Cosmology-dependent parameters are calculated for two models: an Einstein-de Sitter (EdS) universe consistent with previous work in this field (H<sub>0</sub> = 50 h<sub>50</sub> km s<sup>-1</sup> Mpc<sup>-1</sup>, Omega<sub>M</sub> = 1, and Omega<sub>Lambda</sub> = 0) and the dark energy cosmology (DEC) universe favored by recent work on high-redshift supernovae and fluctuations in the cosmic microwave background (H<sub>0</sub> = 65 km s<sup>-1</sup> Mpc<sup>-1</sup>, Omega<sub>M</sub> = 0.35, and Omega<sub>Lambda</sub> = 0.65). This table was created by the HEASARC in April 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/123/2223">CDS catalog J/AJ/123/2223</a> files table1.dat, table2.dat and table3.dat. 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.

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Dates

Metadata Created Date April 11, 2025
Metadata Updated Date October 30, 2025

Metadata Source

Harvested from NASA Data.json

Additional Metadata

Resource Type Dataset
Metadata Created Date April 11, 2025
Metadata Updated Date October 30, 2025
Publisher High Energy Astrophysics Science Archive Research Center
Maintainer
Identifier ivo://nasa.heasarc/spicescxo
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 7d6addb4-c593-41c7-8c88-45554e4f899f
Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
Harvest Source Title NASA Data.json
Homepage URL https://heasarc.gsfc.nasa.gov/W3Browse/all/spicescxo.html
Program Code 026:000
Source Datajson Identifier True
Source Hash 5f96f62e72b1b26169fcd6020d85c0cbc4511456bc9d4a481aa8333293528978
Source Schema Version 1.1

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