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SWIRELHCXO - SWIRE/Chandra Lockman Hole Field X-Ray Source Catalog

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Overview

The authors have carried out a moderate-depth (70 ks), contiguous 0.7 square degrees Chandra survey in the Lockman Hole Field of the Spitzer/SWIRE Legacy Survey coincident with a completed, ultra-deep VLA survey with deep optical and near-infrared imaging in-hand. The primary motivation is to distinguish starburst galaxies and active galactic nuclei (AGNs), including the significant, highly obscured (log N_H > 23 cm-2) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3 - 8 keV) flux of ~4 x 10-16 erg cm-2 s-1. This table contains the X-ray catalog, fluxes, hardness ratios, and multi-wavelength fluxes. The log N versus log S agrees with those of previous surveys covering similar flux ranges. The Chandra and Spitzer flux limits are well matched: 771 (99%) of the X-ray sources have infrared (IR) or optical counterparts, and 333 have MIPS 24-micron detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep (~2.7 microJansky rms) VLA data yield 251 (> 4 sigma) radio counterparts, 44% of the X-ray sources in the field. The authors confirm that the tendency for lower X-ray flux sources to be harder is primarily due to absorption. As expected, there is no correlation between observed IR and X-ray fluxes. Optically bright, type 1, and red AGNs lie in distinct regions of the IR versus X-ray flux plots, demonstrating the wide range of spectral energy distributions in this sample and providing the potential for classification/source selection. Many optically bright sources, which lie outside the AGN region in the optical versus X-ray plots (f_r/f_x > 10), lie inside the region predicted for red AGNs in IR versus X-ray plots, consistent with the presence of an active nucleus. More than 40% of the X-ray sources in the VLA field are radio-loud using the classical definition of R_L. The majority of these are red and relatively faint in the optical so that the use of R_L to select those AGNs with the strongest radio emission becomes questionable. Using the 24-micron to radio flux ratio (q_24) instead results in 13 of the 147 AGNs with sufficient data being classified as radio-loud, in good agreement with the ~10% expected for broad-lined AGNs based on optical surveys. The authors conclude that q_24 is a more reliable indicator of radio-loudness. Use of R_L should be confined to the optically selected type 1 AGN.

Catalog Bibcode

2009ApJS..185..433W

References

The SWIRE/Chandra Survey: The X-Ray Sources
    Wilkes B.J., Kilgard R., Kim D.-W., Kim M., Polleta M., Lonsdale C.,
    Smith H.E., Surace J., Owen F.N., Franceschini A., Siana B., Shupe, D.
   <astrophys. J. Suppl. 185, 433 (2009)>
   =2009ApJS..185..433W

Provenance

This table was created by the HEASARC in December 2009 based on the machine-readable versions of Tables 3, 4 and 7 from the reference paper which was obtained from the Astrophysical Journal web site.

Parameters

Name
The IAU-style name for the X-ray source as registered with the CDS Dictionary of Nomenclature of Celestial Objects, based on the J2000 equatorial coordinates of the X-ray source and the 'CXOSW' prefix (for Chandra X-Ray Observatory SWIRE survey).

RA
The Right Ascension of the X-ray source in the selected equinox. The RA was given in J2000 equatorial coordinates and to a precision of 0.01 seconds of time in the original source table.

Dec
The Declination of the X-ray source in the selected equinox. The Declination was given in J2000 equatorial coordinates and to a precision of 0.1 arcseconds in the original source table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The uncertainty in the X-ray source position, in arcseconds.

Counts
The net broad-band (0.3-8 keV) counts in the X-ray source.

Counts_Error
The error in the net broad-band (0.3-8 keV) counts in the X-ray source.

Count_Rate
The net 0.3-8.0 keV count rate of the X-ray source, in ct/s.

Count_Rate_Error
The error in the net 0.3-8.0 keV count rate of the X-ray source, in ct/s

Flux_Density_1_keV
The 1-keV flux density of the X-ray source, in erg/s/cm2/Hz. To estimate the flux of the X-ray point sources, the authors first calculated the energy conversion factor (ECF), which converts the count rate to the flux, assuming a single power-law model for the X-ray source spectrum with photon indices of Gamma = 1.2, 1.4, and 1.7 with the Galactic absorption column density N_H in this direction (see Section 3.2.4 of Kim et al. (2007, ApJS, 169, 401) for a detailed description of estimating ECF). The fluxes presented in this table assume Gamma = 1.7. For soft/hard-band fluxes where the net counts were negative, no flux estimation is provided.

FB_Flux
The broad-band 0.3-8.0 keV flux of the X-ray source, in erg/s/cm2. To estimate the flux of the X-ray point sources, the authors first calculated the energy conversion factor (ECF), which converts the count rate to the flux, assuming a single power-law model for the X-ray source spectrum with photon indices of Gamma = 1.2, 1.4, and 1.7 with the Galactic absorption column density N_H in this direction (see Section 3.2.4 of Kim et al. (2007, ApJS, 169, 401) for a detailed description of estimating ECF). The fluxes presented in this table assume Gamma = 1.7. For soft/hard-band fluxes where the net counts were negative, no flux estimation is provided.

SB_Flux
The soft-band 0.3-2.5 keV flux of the X-ray source, in erg/s/cm2. To estimate the flux of the X-ray point sources, the authors first calculated the energy conversion factor (ECF), which converts the count rate to the flux, assuming a single power-law model for the X-ray source spectrum with photon indices of Gamma = 1.2, 1.4, and 1.7 with the Galactic absorption column density N_H in this direction (see Section 3.2.4 of Kim et al. (2007, ApJS, 169, 401) for a detailed description of estimating ECF). The fluxes presented in this table assume Gamma = 1.7. For soft/hard-band fluxes where the net counts were negative, no flux estimation is provided

HB_Flux
The hard-band 2.5-8.0 keV flux of the X-ray source, in erg/s/cm2. To estimate the flux of the X-ray point sources, the authors first calculated the energy conversion factor (ECF), which converts the count rate to the flux, assuming a single power-law model for the X-ray source spectrum with photon indices of Gamma = 1.2, 1.4, and 1.7 with the Galactic absorption column density N_H in this direction (see Section 3.2.4 of Kim et al. (2007, ApJS, 169, 401) for a detailed description of estimating ECF). The fluxes presented in this table assume Gamma = 1.7. For soft/hard-band fluxes where the net counts were negative, no flux estimation is provided

Hardness_Ratio
The hardness ratio HR of the X-ray source. Hardness ratios (defined as (Hc - Sc)/(Hc + Sc), where Hc and Sc are the counts in the conventional hard (2.0-8.0 keV) and soft (0.5-2.0 keV) bands, respectively) were determined with a Bayesian approach using the BEHR program (see http://hea-www.harvard.edu/AstroStat/BEHR and Park et al. (2006, ApJ, 652, 610). This method is designed for low count sources where a Poisson distribution is appropriate and uses as input the hard and soft source and background counts. It was applied as described in Kim et al. (2007, ApJS, 169, 401) to estimate the hardness ratio and its error for all sources detected in the broad band.

Hardness_Ratio_Pos_Err
The upper positive error in the hardness ratio HR.

Hardness_Ratio_Neg_Err
The lower negative error in the hardness ratio HR.

Swire_ID
The SWIRE identification number of the Spitzer counterpart to the Chandra X-ray source. A blank value for this parameter indicates that no SWIRE counterpart was fopund.

Offset
The angular distance offset between the X-ray and SWIRE sources, in arcseconds.

Rmag_Limit
The limit flag for the corresponding r-prime band magnitude of the optical counterpart to the Chandra X-ray source, where '>' means that no optical counterpart was detected in this band to the specified magnitude, which corresponds to the 5-sigma level.

Rmag
The r-prime band magnitude of the optical counterpart to the Chandra X-ray source.

Rmag_Error
The uncertainty in the r-prime band magnitude of the optical counterpart to the Chandra X-ray source.

Gmag_Limit
The limit flag for the corresponding g-prime band magnitude of the optical counterpart to the Chandra X-ray source, where '>' means that no optical counterpart was detected in this band to the specified magnitude, which corresponds to the 5-sigma level.

Gmag
The g-prime band magnitude of the optical counterpart to the Chandra X-ray source.

Gmag_Error
The uncertainty in the g-prime band magnitude of the optical counterpart to the Chandra X-ray source.

Flux_3p6_um
The 3.6-micron Spitzer IRAC flux density of the IR counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Flux_3p6_um_Error
The uncertainty in the 3.6-micron flux density of the IR counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Flux_8_um_Limit
The limit flag for the corresponding 8-micron band flux density of the IR counterpart to the Chandra X-ray source, where '<' means that no IR counterpart was detected in this band to the specified flux density, which corresponds to the 5-sigma level.

Flux_8_um
The 8-micron Spitzer IRAC flux density of the IR counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Flux_8_um_Error
The uncertainty in the 8-micron flux density of the IR counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Flux_24_um_Limit
The limit flag for the corresponding 24-micron band flux density of the IR counterpart to the Chandra X-ray source, where '<' means that no IR counterpart was detected in this band to the specified flux density, which corresponds to the 5-sigma level.

Flux_24_um
The 3.6-micron Spitzer MIPS flux density of the IR counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Flux_24_um_Error
The uncertainty in the 24-micron flux density of the IR counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Flux_20_cm_Limit
The limit flag for the corresponding 20-cm flux density of the radio counterpart to the Chandra X-ray source, where '<' means that no radio counterpart was detected at 20 cm to the specified flux density, which corresponds to the 4-sigma level.

Flux_20_cm
The 20-cm flux density of the VLA radio counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Flux_20_cm_Error
The uncertainty in the 20-cm flux density of the radio counterpart to the Chandra X-ray source, in mJy (converted from the microJy units which were given in the original reference table).

Notes
This parameter contains source-specific notes in some cases.


Contact Person

Questions regarding the SWIRELHCXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 8-Dec-2009