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M108CXO - M 108 Chandra X-Ray Compact Source Catalog

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Overview

This table contains a list of discrete sources found in a 60-ks Chandra ACIS-S observation of the isolated edge-on spiral galaxy NGC 3556 (M108). In the reference paper in which the authors present this table, they also give a multiwavelength analysis of the various discrete X-ray sources and of the diffuse X-ray features. Among 33 discrete X-ray sources detected within the IB = 25 mag arcsec-2 isophotal ellipse of the galaxy, the authors identify a candidate for the galactic nucleus, an ultraluminous X-ray source that might be an accreting intermediate-mass black hole, a possible X-ray binary with a radio counterpart, and two radio-bright giant H II regions. They also detect large amounts of extraplanar diffuse X-ray emission, which extend about 10 kpc radially in the disk and >~4 kpc away from the galactic plane. The diffuse X-ray emission exhibits significant substructures, possibly representing various blown-out superbubbles or chimneys of hot gas heated in massive star-forming regions.

This Chandra observation of NGC 3556 (observation ID 2025) was taken between 2001 September 8 and 9 for an exposure of 60 ks. The ACIS-S instrument was at the focal plane of the telescope.


Catalog Bibcode

2003ApJ...598..969W

References

Chandra observation of the edge-on galaxy NGC 3556 (M108):
violent galactic disk-halo interaction revealed.
    Wang Q.D., Chaves T., Irwin J.A.
   <Astrophys. J., 598, 969-981 (2003)>
   =2003ApJ...598..969W

Provenance

This table was created by the HEASARC in August 2015 based on the CDS Catalog J/ApJ/598/969 file table2.dat.

Parameters

Source_Number
A running source number (in order of increasing J2000.0 Right Ascension) which uniquely identifies an X-ray source.

Name
The J2000.0 position-based "unregistered" Chandra source designation, e.g., 'CXOU J111243.11+554241.3', as suggested by the authors in the reference paper. Note that the CDS created an alternative naming scheme for these sources which is described in the Dictionary of Nomenclature of Celestial Objects, viz., '[WCI2003] NN', where the prefix refers to the Wang, Chaves, Irwin (2003) reference paper and NN is the source number.

RA
The Right Ascension of the Chandra X-ray source in the selected equinox. This was not explicitly given in the reference paper, but was derived by the HEASARC from the J2000.0 position-based name. It is thus given to the same precision as implied by the name, viz., 0.01 seconds of time.

Dec
The Declination of the Chandra X-ray source in the selected equinox. This was not explicitly given in the reference paper, but was derived by the HEASARC from the J2000.0 position-based name. It is thus given to the same precision as implied by the name, viz., 0.1 arcseconds.

LII
The Galactic Longitude of the Chandra X-ray source.

BII
The Galactic Latitude of the Chandra X-ray source.

Error_Radius
The 1-sigma positional uncertainty of the Chandra X-ray source, in arcseconds.

Log_Prob_NS
The logarithm of the false detection probability P that the detected number of counts may result from the Poisson fluctuation of the local background within the detection aperture (a value of log P smaller than 20.0 is set to 20.0).

Count_Rate
The on-axis (exposure-corrected) net source count rate in the 0.3-7 keV energy band, in ct/s (converted by the HEASARC from the ct/ks unit used in the original table).

Count_Rate_Error
The error in the on-axis (exposure-corrected) source count rate in the 0.3-7 keV energy band, in ct/s (converted by the HEASARC from the ct/ks unit used in the original table).

Hardness_Ratio
The hardness ratio, HR = (H-S)/(H+S), of the Chandra X-ray source. H and S are the net source counts in the 1.5-7.0 and 0.3-1.5 keV energy bands, respectively. The hardness ratios are calculated only for sources with individual S/Ns greater than 4 in the broad band (B = S+H, i.e., 0.3-7.0 keV), and only the values with uncertainties less than 0.2 are included.

Hardness_Ratio_Error
The error in the hardness ratio, HR = (H-S)/(H+S), of the Chandra X-ray source.

Hardness_Ratio_1
The hardness ratio, HR1 = (S2-S1)/S, of the Chandra X-ray source. S1, S2 and S are the net source counts in the 0.3-0.7, 0.7-1.5 and 0.3-1.5 keV energy bands, respectively. The hardness ratios are calculated only for sources with individual S/Ns greater than 4 in the broad band (B = S+H, i.e., 0.3-7.0 keV), and only the values with uncertainties less than 0.2 are included.

Hardness_Ratio_1_Error
The error in the hardness ratio, HR1 = (S2-S1)/S, of the Chandra X-ray source.

Hardness_Ratio_2
The hardness ratio, HR2 = (H2-H1)/H, of the Chandra X-ray source. H1, H2 and H are the net source counts in the 1.5-3.0, 3.0-7.0 and 1.5-7.0 keV energy bands, respectively. The hardness ratios are calculated only for sources with individual S/Ns greater than 4 in the broad band (B = S+H, i.e., 0.3-7.0 keV), and only the values with uncertainties less than 0.2 are included.

Hardness_Ratio_2_Error
The error in the hardness ratio, HR2 = (H2-H1)/H, of the Chandra X-ray source.

Best_Position_Band
This flag parameter indicates in which band the source was detected with the most accurate position: 'B' if in the broad band (0.3-7.0 keV), 'S' if in the soft band (0.3-1.5 keV) or 'H' if in the hard band (1.5-7.0 keV).


Contact Person

Questions regarding the M108CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 31-Aug-2015