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NGC6530OID - NGC 6530 Chandra Point Source Optical/IR Identifications Catalog

HEASARC
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Overview

The authors have obtained astrometry and BVI photometry, down to a V magnitude of ~22, of the very young open cluster NGC 6530, from observations taken with the Wide Field Imager (WFI) camera at the MPG/ESO 2.2m Telescope. They have positionally matched their optical catalog with the list of X-ray sources found in a Chandra-ACIS observation of this cluster (Damiani et al. 2004, ApJ, 608, 781: available in Browse both via links from this table and also as the NGC6530CXO table), finding a total of 828 stars in common, 90% of which are pre-main sequence stars in NGC 6530.

The data used in this work come from the combination of optical BVI images taken with the WFI camera made on 27-28 July 2000, a 60 ks Chandra ACIS X-ray observation, and public near-infrared data from the All-Sky Catalog of Point Sources of the Two Micron All Sky Survey (2MASS, CDS Cat. <II/24>).

The total number of optical sources falling in the Chandra FOV is 8956, while the Damiani et al. (2004, ApJ, 608, 781) Catalog contains 884 X-ray sources, who concluded that at least 90% of the X-ray sources are very probable cluster members. To cross-correlate the X-ray and optical catalogs, the authors used a matching distance of < 4 sigmaX, where sigmaX is the the X-ray positional error, or 1.5", whichever is smaller, after a systematic shift between the X-ray and WFI positions of 0.2" in RA and -0.26" in Dec had been included. This resulted in a number of multiple identifications, among which 4 turned into unique identifications when a reduced distance of 1.5" was used. This finally resulted in 721 single, 44 double, and 3 triple identifications in the optical catalog; in addition, one X-ray source has 4 optical identifications, and another has 6 optical identifications. The total number of X-ray sources with WFI counterparts is therefore 770; of them, only 15 X-ray identified stars come from the Sung et al. (2000, AJ, 120, 333) Catalog and are not in the WFI Catalog. The total number of optical sources with an X-ray counterpart is 828. The agreement between X-ray and WFI optical positions is excellent in most cases, with offsets below 1".


Catalog Bibcode

2005A&A...430..941P

References

The star formation region NGC 6530: Distance, ages and initial mass function.
    Prisinzano L., Damiani F., Micela G., Sciortino S.
   <Astron. Astrophys., 430, 941-957 (2005)>
   =2005A&A...430..941P

Provenance

This database table was created by the HEASARC in February 2007, based on CDS table J/A+A/430/941/table5.dat

Parameters

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

Dec
The Declination of the optical counterpart to the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.01 arcseconds in the original reference.

LII
The Galactic Longitude of the optical counterpart to the X-ray source.

BII
THe Galactic Latitude of the optical counterpart to the X-ray source.

Name
The name of the optical counterpart, where objects with names like 'SCB NNN' (referred to as 'Cl* NGC 6530 SCB NNN' in Simbad) come from the Sung et al. Catalog, CDS Cat. <J/AJ/120/333>, and those with names like 'WFI NNNNN' (WFI for Wide Field Imager) come from the optical catalog compiled by the authors and presented in the reference given above.

Bmag
The B Magnitude of the optical counterpart.

Bmag_Error
The uncertainty in the B magnitude of the optical counterpart.

Vmag
The V Magnitude of the optical counterpart.

Vmag_Error
The uncertainty in the V magnitude of the optical counterpart.

Imag
The I Magnitude of the optical counterpart.

Imag_Error
The uncertainty in the I magnitude of the optical counterpart.

Xray_Name
The name of the X-ray source in the Damiani et al. (2004, ApJ, 608, 781) Catalog, also available as the NGC6530CXO table in Browse.

Num_Opt_Ctrparts
The number of optical sources corresponding to the specified X-ray source.


Contact Person

Questions regarding the NGC6530OID database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 5-Feb-2007