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NGC404CXO - NGC 404 Chandra X-Ray Point Source Catalog

HEASARC
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Overview

This table contains a comprehensive X-ray point-source catalog of NGC 404, the closest face-on (inclination angle of 11 degrees) S0 galaxy to the Milky Way, which was obtained as part of the Chandra Local Volume Survey (CLVS) and originally published in Binder et al. (2013). A new 97-ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123 ks. This survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6 x 1035 erg/s in the 0.35-8 keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. The authors searched overlapping Hubble Space Telescope (HST) observations for optical counterparts to their X-ray detections, but found only two X-ray sources with candidate optical counterparts. They found 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei (AGN). The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented in the 2013 reference paper. The XLFs in the soft band (0.5-2 keV) and the hard band (2-8 keV) have a limiting luminosity at the 90% completeness limit of 1035 erg/s and 1036 erg/s, respectively, significantly lower than previous X-ray studies of NGC 404. The authors find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>1037 erg/s) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation ~0.5 Gyr ago.

NGC 404 was observed during Chandra X-Ray Observatory Cycle 12 on 2010 October 21-22 for 97 ks using the ACIS-S array (Obs. ID 12339). The authors additionally utilized archival observations: NGC 404 was observed on 1999 December 19 (Obs. ID 870) for ~24 ks and on 2000 August 30 (Obs. ID 384) for ~2 ks, both using the ACIS-S array. The authors created images in the following energy bands (keV): 0.35-8.0, 0.35-1.0, 1.0-2.0, 2.0-8.0 with bin sizes of 1, 2, 3, and 4.

The iterative source detection strategy that was used is described in Section 2.3 of Binder et al. (2012, ApJ, 758, 15). ACIS-Extract (AE) was run a final time on the source list that was produces after an initial run of wavdetect followed by several iterations of AE, and the Poisson probability of not being a source (pns) value was computed in each of the following nine energy bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0 - 8.0, 0.35 - 1.0 or 0.35 - 8.0 keV. To be included in the final NGC 404 catalog, a source was required to have a pns value less than 4 x 10-6 in any of the nine energy bands. The final CLVS source catalog for NGC 404 contains 74 sources. Given the survey size of these NGC 404 observations, there are expected to be ~1.6 false sources included in this NGC 404 final source catalog.

Three HST fields were used to search for optical counterparts for each of the X-ray sources. One field (labeled "DEEP") was taken as part of the Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST, GO-10915; Dalcanton et al. 2009, ApJS, 183, 67), while the other two shallower fields (labeled "NE" and "SW") were obtained as part of GO-11986. Details of the HST data acquisition and data reduction are provided in Williams et al. (2010, ApJ, 716, 71).


Catalog Bibcodes

2013ApJ...763..128B
2015AJ....150...94B

References

The Chandra Local Volume Survey: the X-ray point-source population of NGC 404.
    Binder B., Williams B.F., Eracleous M., Gaetz T.J., Kong A.K.H.,
    Skillman E.D., Weisz D.R.
   <Astrophys. J., 763, 128 (2013)>
   =2013ApJ...763..128B

The Chandra Local Volume Survey. I. The X-ray point-source populations of
NGC 55, NGC 2403, and NGC4214.
    Binder B., Williams B.F., Eracleous M., Plucinsky P.P., Gaetz T.J.,
    Anderson S.F., Skillman E.D., Dalcanton J.J., Kong A.K.H., Weisz D.R.
   <Astron. J., 150, 94 (2015)>
   =2015AJ....150...94B

Provenance

This table was created by the HEASARC in September 2015 primarily based on CDS Catalog J/ApJ/763/128 files table3.dat, table4.dat, table5.dat, table6.dat, table10.dat, table12.dat and table13.dat (Binder et al. 2013) which contain the properties of the 74 Chandra point sources found in this study.and of their multi-wavelength counterparts. As noted above, the HEASARC has added an extra parameter b4_flux which was taken from the machine-readable version of Table 5 of Binder et al. (2015).

Caveat for this Table

The CDS discovered while creating its version of this table that the data values for band 8 (0.35 - 2.0 keV) were identical to those for band 7 (2.6 - 8.0 keV) in every case. This can also be seen in the printed version of this paper (Tables 4, 5 and 6). The HEASARC has determined by comparison with the values for the other energy bands (particularly band 2, 0.5 - 2.0 keV) that the values for band 8 are erroneous and therefore has nullified the values for all band 8 parameters (names prefixed with 'b8') in its version of the table.

The HEASARC has added to the contents of its implementation of this table the 0.35-8.0 keV energy fluxes (in the parameter herein called b4_flux) for these 74 highly significant sources which were not given in the 2013 paper, but in a later paper by this same group (Binder et al. 2015).


Parameters

Source_Number
A running X-ray source number in order of increasing J2000.0 Right Ascension.

Name
The name of the X-ray source using the 'CXOLV' prefix (for Chandra X-ray Observatory, Local Volume Survey source) and the J2000.0 coordinates of the source in the (higher precision than standard) HHMMSS.ss+DDMMSS.s format.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000 decimal degree coordinates and to a precision of 10-6 degrees in the original table.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000 decimal degree coordinates and to a precision of 10-6 degrees in the original table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The positional uncertainty of the X-ray source, being the radius of a simple error circle around the source position, in arcseconds.

Mean_Expo_Map_Value
The sum of the mean exposure map values in the X-ray source region, in s cm-2.

Extraction_Radius
The average radius of the source extraction region, in sky pixels, where 1 sky pixel = 0.392 arcseconds.

Off_Axis
The off-axis angle (theta) of the X-ray source, in arcminutes.

B1_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B1_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 0.5 - 8 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B2_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B2_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 0.5 - 2 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B3_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B3_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 2 - 8 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B4_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B4_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 0.35 - 8 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B5_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B5_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 0.35 - 1.1 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B6_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B6_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 1.1 - 2.6 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B7_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B7_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 2.6 - 8 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B8_Log_Prob_NS_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B8_Log_Prob_NS
The logarithm of the Poisson probability of not being a source (log prob_no_source or log pns) in the 0.35 - 2 keV band. Values smaller than -10 have been replaced by "<-10". All these cases are highly significant detections.

B1_Counts
The total net counts in the X-ray source in the 0.5 - 8.0 keV band.

B1_Counts_Pos_Err
The upper uncertainty in the net source counts in the 0.5 - 8.0 keV energy band.

B1_Counts_Neg_Err
The lower uncertainty in the net source counts in the 0.5 - 8.0 keV energy band.

B2_Counts
The total net counts in the X-ray source in the 0.5 - 2.0 keV band.

B2_Counts_Pos_Err
The upper uncertainty in the net source counts in the 0.5 - 2.0 keV energy band.

B2_Counts_Neg_Err
The lower uncertainty in the net source counts in the 0.5 - 2.0 keV energy band.

B3_Counts_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B3_Counts
The total net counts in the X-ray source in the 2.0 - 8.0 keV band.

B3_Counts_Pos_Err
The upper uncertainty in the net source counts in the 2.0 -8.0 keV energy band.

B3_Counts_Neg_Err
The lower uncertainty in the net source counts in the 2.0 - 8.0 keV energy band.

B4_Counts
The total net counts in the X-ray source in the 0.35 - 8.0 keV band.

B4_Counts_Pos_Err
The upper uncertainty in the net source counts in the 0.35 -8.0 keV energy band.

B4_Counts_Neg_Err
The lower uncertainty in the net source counts in the 0.35 - 8.0 keV energy band.

B5_Counts_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B5_Counts
The total net counts in the X-ray source in the 0.35 - 1.1 keV band.

B5_Counts_Pos_Err
The upper uncertainty in the net source counts in the 0.35 - 1.1 keV energy band.

B5_Counts_Neg_Err
The lower uncertainty in the net source counts in the 0.35 - 1.1 keV energy band.

B6_Counts_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B6_Counts
The total net counts in the X-ray source in the 1.1 - 2.6 keV band.

B6_Counts_Pos_Err
The upper uncertainty in the net source counts in the 1.1 - 2.6 keV energy band.

B6_Counts_Neg_Err
The lower uncertainty in the net source counts in the 1.1 - 2.6 keV energy band.

B7_Counts_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B7_Counts
The total net counts in the X-ray source in the 2.6 - 8.0 keV band.

B7_Counts_Pos_Err
The upper uncertainty in the net source counts in the 2.6 - 8.0 keV energy band.

B7_Counts_Neg_Err
The lower uncertainty in the net source counts in the 2.6 - 8.0 keV energy band.

B8_Counts_Limit
This limit parameter is set to '<' if the corresponding parameter value is an upper limit rather than an actual value.

B8_Counts
The total net counts in the X-ray source in the 0.35 - 2 keV band.

B8_Counts_Pos_Err
The upper uncertainty in the net source counts in the 0.35 - 2.0 keV energy band.

B8_Counts_Neg_Err
The lower uncertainty in the net source counts in the 0.35 - 2.0 keV energy band.

B1_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 0.5-8 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

B2_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 0.5-2 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

B3_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 2-8 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

B4_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 0.35-8 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

B5_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 0.35-1.1 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

B6_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 1.1-2.6 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

B7_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 2.6-8 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

B8_Log_Photon_Flux
The logarithm of the photon flux of the Chandra source in the 0.35-2 keV energy band, in photons cm-2 s-1. ACIS-Extract (AE) provides an estimate of the photon flux for each source, which is based on the net source counts, exposure time, and the mean of the auxiliary response file (ARF) in each energy band.

Hardness_Ratio_1
The hardness ratio HR1 (the "soft" color), where HR1 = (M-S)/(H+M+S) and S, M and H are the net counts in the following bandpasses:

     S = 0.35-1.1 keV;
     M = 1.1-2.6 keV;
     H = 2.6-8 keV.
  

Hardness_Ratio_1_Error
The uncertainty in the hardness ratio HR1.

Hardness_Ratio_2
The hardness ratio HR2 (the "hard" color), where HR2 = (H-M)/(H+M+S) and S, M and H are the net counts in the following bandpasses:

     S = 0.35-1.1 keV;
     M = 1.1-2.6 keV;
     H = 2.6-8 keV.
  

Hardness_Ratio_2_Error
The uncertainty in the hardness ratio HR2.

Hardness_Ratio_Class
The classification of the Chandra source based on the X-ray hardness ratios HR1 and HR2. The authors define six categories of X-ray sources: "XRB" (which is likely contaminated with background AGNs, given their X-ray similarities to LMXBs), "BKG" for likely background sources with an indeterminate spectral shape, "ABS" for heavily absorbed sources, "SNR" (although, given the morphology and star formation history of NGC 404, these sources are likely to be foreground stars or SSSs, and not true supernova remnants), and indeterminate "HARD" and "SOFT" sources. The details of the authors' color-color classification scheme, along with the number of sources belonging to each category, are given in Table 9 of the 2013 reference paper.

GALEX_NUV_Mag
The NUV magnitude of the GALEX (GR6 data release) counterpart to the Chandra X-ray source.

GALEX_NUV_Mag_Error
GALEX GR6 NUV Magnitude Uncertainty

GALEX_FUV_Mag
The FUV magnitude of the GALEX (GR6 data release) counterpart to the Chandra X-ray source.

GALEX_FUV_Mag_Error
GALEX GR6 FUV Magnitude Uncertainty

HST_F606w_Mag
The HST F606W band magnitude of the optical counterpart to the Chandra X-ray source.

HST_F606w_Mag_Error
The uncertainty in the HST F606W band magnitude of the optical counterpart to the Chandra X-ray source.

HST_F814w_Mag
The HST F814W band magnitude of the optical counterpart to the Chandra X-ray source.

HST_F814w_Mag_Error
The uncertainty in the HST F814W band magnitude of the optical counterpart to the Chandra X-ray source.

Bmag
The USNO-B1 B-band magnitude of the optical counterpart to the Chandra X-ray source.

Rmag
The USNO-B1 R-band magnitude of the optical counterpart to the Chandra X-ray source.

Jmag
The 2MASS J-band magnitude of the infrared counterpart to the Chandra X-ray source.

Jmag_Error
The uncertainty in the 2MASS J-band magnitude of the infrared counterpart to the Chandra X-ray source.

Hmag
The 2MASS H-band magnitude of the infrared counterpart to the Chandra X-ray source.

Hmag_Error
The uncertainty in the 2MASS H-band magnitude of the infrared counterpart to the Chandra X-ray source.

Ks_Mag
The 2MASS Ks-band magnitude of the infrared counterpart to the Chandra X-ray source.

Ks_Mag_Error
The uncertainty in the 2MASS Ks-band magnitude of the infrared counterpart to the Chandra X-ray source.

Flux_1p4_GHz
The NVSS 1.4-GHz flux density of the radio counterpart to the Chandra X-ray source, in mJy.

Flux_1p4_GHz_Error
The uncertainty in the NVSS 1.4-GHz flux density of the radio counterpart to the Chandra X-ray source, in mJy.

Best_Spectral_Fit
The best spectral fit model to the X-ray spectrum of the Chandra source, where "apec" refers to the vapec model (Astrophysical Plasma Emission Code, Smith et al. 2001, ApJ, 556, L91) and "pow" to a power-law model. For source number 35, an intrinsic (additional to the Galactic column) absorbing column density of 3.7 (+1.3, -1.1) x 1022 H atoms cm-2 was required, hence this model is referred to as "abs apec". For apec models, kT is the temperature in keV, while for power-law models, Gamma is the power law spectral index.

Variability
This parameter value, if non-blank, indicates that the source exhibits (i) short-term variability within the Chandra observation with ObsID = 12239 if set to "rapid", or, (ii) if set to "long" or "long?" indicates definite or possible long-term variability between the individual Chandra exposures. See Section 3.1 and Table 8 of the 2013 reference paper for more details.

Galcen_Radius
The galactocentric distance of the Chandra source, assuming it is indeed in NGC 404, in kpc.

Counterpart_Flags
This parameter indicates the wavelength regimes of any detected counterpart(s) to the Chandra source, or is set to "none" if there are no multiwavelength counterparts.

B4_Flux
This parameter contains the unabsorbed X-ray flux of the Chandra source in the 0.35-8 keV energy band, in erg cm-2 s-1.

Source_Type
The final object classification of the Chandra source: AGN, XRB, SSS (super-soft source), FS (foreground star) or NUCLEUS for source number 41, the central engine of NGC 404. The methodology used by the authors for this classification is described in detail in Section 4.3 of the 2013 reference paper.


Contact Person

Questions regarding the NGC404CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 24-Sep-2015