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CHANNSGPSC - Chandra Nearby Spiral Galaxies Point Source Catalog

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Overview

Emission from discrete point sources dominates the X-ray luminosity in spiral galaxies. This table contains the results from a survey of 11 nearby, nearly face-on spiral galaxies observed with the Chandra X-ray Observatory in 22 observations for a total of 869 ks. The galaxies in this sample are at high Galactic latitude to minimize the absorbing column in the line of site, are nearby to minimize source confusion, and span the Hubble sequence for spirals (types 0-7), allowing insights into the X-ray source population of many diverse systems. More than 820 unique point sources are detected in at least one observation within the D25 ellipses of the galaxies. A minimum of 27% of the sources exhibit detectable long- or short-term variability, indicating a source population dominated by accreting XRBs. 17 ultraluminous X-ray sources are detected, with typical rates per galaxy of 1 or 2.

In this table, source lists for the 11 galaxies are presented, along with source counts, fluxes, luminosities, X-ray colors, and variability properties. It should be noted that the X-ray source counts presented in this table are raw, background-subtracted counts, so the count rates in sources from the same galaxy that fall on different CCDs cannot be directly compared. The colors presented have been corrected for the differences between front-illuminated and back-illuminated CCDs.


Catalog Bibcode

2005ApJS..159..214K

References

A Chandra Survey of Nearby Spiral Galaxies. I. Point Source Catalogs

  Kilgard, R.E., Cowan, J.J., Garcia, M.R., Kaaret, P., Krauss, M.L.,
  McDowell, J.C., Prestwich, A.H., Primini, F.A., Stockdale, C.J.,
  Trinchieri, G., Ward, M.J., Zezas, A.
 <Astrophys. J. Suppl., 159, 214-241 (2005)>
 =2005ApJS..159..214K

Erratum: A Chandra Survey of Nearby Spiral Galaxies. I. Point Source Catalogs

  Kilgard, R.E., Cowan, J.J., Garcia, M.R., Kaaret, P., Krauss, M.L.,
  McDowell, J.C., Prestwich, A.H., Primini, F.A., Stockdale, C.J.,
  Trinchieri, G., Ward, M.J., Zezas, A.
 <Astrophys. J. Suppl., 163, 424-425 (2006)>
 =2006ApJS..163..424K

Provenance

This table was created by the HEASARC in November 2006 based on the electronic version of Table 4 obtained from the electronic ApJ web site.

Parameters

Galaxy_Name
The name of the galaxy towards which the X-ray source lies.

Name
The name of the X-ray source using the usual position-based nomenclature scheme, the prefix 'CXOU J' and the J2000 coordinates of the source.

RA
The Right Ascension of 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 table.

Dec
The Declination of 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 table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

SB_Counts_1
The soft-band (0.3 - 1.0 keV) counts in the X-ray source in the first Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D.

SB_Counts_1_Error
The error in the soft-band (0.3 - 1.0 keV) counts in the X-ray source in the first Chandra observation.

SB_Counts_1_Flag
A flag for the first observation soft-band counts which is set to 'A' if the X-ray source is very absorbed.

MB_Counts_1
The medium-band (1.0 - 2.0 keV) counts in the X-ray source in the first Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D.

MB_Counts_1_Error
The error in the medium-band (1.0 - 2.0 keV) counts in the X-ray source in the first Chandra observation.

MB_Counts_1_Flag
A flag for the first observation medium-band counts which is set to 'A' if the X-ray source is very absorbed.

HB_Counts_1
The hard-band (2.0 - 8.0 keV) counts in the X-ray source in the first Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D.

HB_Counts_1_Error
The error in the hard-band (2.0 - 8.0 keV) counts in the X-ray source in the first Chandra observation.

HB_Counts_1_Flag
A flag for the first observation hard-band counts which is set to 'A' if the X-ray source is very absorbed.

FB_Counts_1
The total-band (0.3 - 8.0 keV) counts in the X-ray source in the first Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D.

FB_Counts_1_Error
The error in the total-band (0.3 - 8.0 keV) counts in the X-ray source in the first Chandra observation.

FB_Counts_1_Flag
A flag for the first observation total-band counts which is set to 'A' if the X-ray source is very absorbed.

SB_Counts_2
The soft-band (0.3 - 1.0 keV) counts in the X-ray source in the second Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D.

SB_Counts_2_Error
The error in the soft-band (0.3 - 1.0 keV) counts in the X-ray source in the second Chandra observation.

SB_Counts_2_Flag
A flag for the second observation soft-band counts which is set to 'A' if the X-ray source is very absorbed.

MB_Counts_2
The medium-band (1.0 - 2.0 keV) counts in the X-ray source in the second Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D.

MB_Counts_2_Error
The error in the medium-band (1.0 - 2.0 keV) counts in the X-ray source in the second Chandra observation.

MB_Counts_2_Flag
A flag for the second observation medium-band counts which is set to 'A' if the X-ray source is very absorbed.

HB_Counts_2
The hard-band (2.0 - 8.0 keV) counts in the X-ray source in the second Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D. Second Observation 2.0-8.0 keV Counts

HB_Counts_2_Error
The error in the hard-band (2.0 - 8.0 keV) counts in the X-ray source in the second Chandra observation.

HB_Counts_2_Flag
A flag for the second observation hard-band counts which is set to 'A' if the X-ray source is very absorbed.

FB_Counts_2
The total-band (0.3 - 8.0 keV) counts in the X-ray source in the second Chandra observation. Background-subtracted counts in four different energy bands were determined for each source using the CXC spectral fitting tool, Sherpa: a soft band (S) of 0.3 - 1 keV, a medium band (M) of 1 - 2 keV, a hard band (H) of 2 - 8 keV, and the total band (T) of 0.3 - 8 keV. Events below 0.3 keV and above 8 keV were excluded because they tend to be dominated by background and intrinsic detector noise. Sherpa is used due to potential overlaps in pulse-invariant (PI) to energy mapping. For example, if a PI channel is defined as having low- and high-energy bounds of 0.98 and 1.02 keV, respectively, then any counts that fall within that PI channel will be extracted in both the 0.3 - 1 keV and 1 - 2 keV bands. For each source, the authors determine the PI channels corresponding to the energies 0.3, 1.0, 2.0, and 8.0 keV. Referring to their PI channel-equivalents as A, B, C, and D, counts are then extracted in the PI regions A to B, B+1 to C, C+1 to D, and A to D.

FB_Counts_2_Error
The error in the total-band (0.3 - 8.0 keV) counts in the X-ray source in the second Chandra observation.

FB_Counts_2_Flag
A flag for the second observation total-band counts which is set to 'A' if the X-ray source is very absorbed.

Soft_Color_1
The soft color SC (also known as the soft hardness ratio) of the X-ray source in the first Chandra observation. This was calculated from the source's background-subtracted counts in the soft and medium bands using the standard relation SC = (M-S)/(M+S).

Soft_Color_1_Pos_Err
The positive error in the soft color SC (also known as the soft hardness ratio) of the X-ray source in the first Chandra observation. The errors in the colors are based on standard error propagation (see equation (4) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Soft_Color_1_Neg_Err
The negative error in the soft color SC (also known as the soft hardness ratio) of the X-ray source in the first Chandra observation. The errors in the colors are based on standard error propagation (see equation (4) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Hard_Color_1
The hard color HC (also known as the hard hardness ratio) of the X-ray source in the first Chandra observation. This was calculated from the source's background-subtracted counts in the medium and hard bands using the standard relation HC = (H-M)/(H+M).

Hard_Color_1_Pos_Err
The positive error in the hard color HC (also known as the hard hardness ratio) of the X-ray source in the first Chandra observation. The errors in the colors are based on standard error propagation (see equation (3) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Hard_Color_1_Neg_Err
The negative error in the hard color HC (also known as the hard hardness ratio) of the X-ray source in the first Chandra observation. The errors in the colors are based on standard error propagation (see equation (3) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Soft_Color_2
The soft color SC (also known as the soft hardness ratio) of the X-ray source in the second Chandra observation. This was calculated from the source's background-subtracted counts in the soft and medium bands using the standard relation SC = (M-S)/(M+S).

Soft_Color_2_Pos_Err
The positive error in the soft color SC (also known as the soft hardness ratio) of the X-ray source in the second Chandra observation. The errors in the colors are based on standard error propagation (see equation (4) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Soft_Color_2_Neg_Err
The negative error in the soft color SC (also known as the soft hardness ratio) of the X-ray source in the second Chandra observation. The errors in the colors are based on standard error propagation (see equation (4) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Hard_Color_2
The hard color HC (also known as the hard hardness ratio) of the X-ray source in the second Chandra observation. This was calculated from the source's background-subtracted counts in the medium and hard bands using the standard relation HC = (H-M)/(H+M).

Hard_Color_2_Pos_Err
The positive error in the hard color HC (also known as the hard hardness ratio) of the X-ray source in the second Chandra observation. The errors in the colors are based on standard error propagation (see equation (3) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Hard_Color_2_Neg_Err
The negative error in the hard color HC (also known as the hard hardness ratio) of the X-ray source in the second Chandra observation. The errors in the colors are based on standard error propagation (see equation (3) in the paper), where the errors in the counts were taken to be the statistical error using the Gehrels approximation (Gehrels 1986, ApJ, 303, 336).

Flux_1
The 0.3 - 8.0 keV flux of the X-ray source in the first Chandra observation, in erg/s/cm^2. Since most sources do not have sufficient counts for detailed spectral analysis, it is necessary to assume some spectral model for flux and luminosity calculations. For each source, fluxes were calculated for three assumed spectral models: a simple power law with Gamma = 1.5 and photoelectric absorption, a disk blackbody with Tin = 1.0 keV and photoelectric absorption, and a thermal bremsstrahlung model with kT = 5.0 keV and photoelectric absorption. These models were chosen as characteristic of the best-fit spectra to bright point sources in the sample. In all cases, the absorption was set to the Galactic value; since these galaxies are face-on, line-of-sight absorption in the host galaxy should be minimal. Fluxes were then calculated in Sherpa by rescaling the normalization of the models to the observed count rates. In this table, only the power-law fluxes and luminosities are listed.

Flux_1_Error
The error in the 0.3 - 8.0 keV power-law flux of the X-ray source in the first Chandra observation, in erg/s/cm^2.

Flux_1_Flag
A flag for the first observation X-ray flux which is set to 'A' if the X-ray source is very absorbed.

Lx_1
The X-ray luminosity of the X-ray source in the first Chandra observation, in erg/s, using the 0.3 - 8.0 keV power-law flux of the source and the distance to the galaxy as listed in Table 1 of the paper. A Hubble constant value of 73 km s^-1 Mpc^-1 was used.

Lx_1_Error
The error in the 0.3 - 8.0 keV power-law luminosity, in erg/s, of the X-ray source in the first Chandra observation.

Lx_1_Flag
A flag for the first observation X-ray luminosity which is set to 'A' if the X-ray source is very absorbed.

Flux_2
The 0.3 - 8.0 keV flux of the X-ray source in the second Chandra observation, in erg/s/cm^2. Since most sources do not have sufficient counts for detailed spectral analysis, it is necessary to assume some spectral model for flux and luminosity calculations. For each source, fluxes were calculated for three assumed spectral models: a simple power law with Gamma = 1.5 and photoelectric absorption, a disk blackbody with Tin = 1.0 keV and photoelectric absorption, and a thermal bremsstrahlung model with kT = 5.0 keV and photoelectric absorption. These models were chosen as characteristic of the best-fit spectra to bright point sources in the sample. In all cases, the absorption was set to the Galactic value; since these galaxies are face-on, line-of-sight absorption in the host galaxy should be minimal. Fluxes were then calculated in Sherpa by rescaling the normalization of the models to the observed count rates. In this table, only the power-law fluxes and luminosities are listed.

Flux_2_Error
The error in the 0.3 - 8.0 keV power-law flux of the X-ray source in the second Chandra observation, in erg/s/cm^2.

Flux_2_Flag
A flag for the second observation X-ray flux which is set to 'A' if the X-ray source is very absorbed.

Lx_2
The X-ray luminosity of the X-ray source in the second Chandra observation, in erg/s, using the 0.3 - 8.0 keV power-law flux of the source and the distance to the galaxy as listed in Table 1 of the paper. A Hubble constant value of 73 km s^-1 Mpc^-1 was used.

Lx_2_Error
The error in the 0.3 - 8.0 keV power-law luminosity, in erg/s, of the X-ray source in the second Chandra observation.

Lx_2_Flag
A flag for the second observation X-ray luminosity which is set to 'A' if the X-ray source is very absorbed.

Variability_Flag
This parameter is a flag which indicates that one of 3 statistical tests indicates variability is present: 'L' means that there is long-term variability in the count rates of the X-ray source between the two observations at the 90% confidence level, 'B' means that there is variability at the 99% confidence level within an observation detected using a Bayesian block method which is efficient at detecting localized structures (bursts or flaring) but is also sensitive to larger scale variability, while 'K' means that there is variability at the 99% confidence level within an observation detected using a Kolmogorov-Smirnov (KS) test which is sensitive to longer timescale variations as compared with the Bayesian block method.

Notes
This parameter contains additional notes, alternate source names from the literature, and the ACIS CCD number on which the X-ray source was detected, if it was not the S3 chip.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 16-Nov-2006