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NGC6530OID: Help

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


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.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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