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SPICESCXO - SPICES Lynx Field Chandra X-Ray Source Catalog |
HEASARC Archive |
Overview
This table contains the first results on field X-ray sources detected in a deep, 184.7 ks observation with the Advanced CCD Imaging Spectrometer (ACIS-I) on the Chandra X-Ray Observatory. The observations target the Lynx field (J2000.0 RA = 08h 48m and Dec = +44d 54') of SPICES, the Spectroscopic Photometric Infrared-Chosen Extragalactic Survey, which contains three known X-ray-emitting clusters at redshifts of z = 0.57, 1.26, and 1.27. Not including the known clusters, in the 17' x 17' ACIS-I field the authors detect 132 sources in the 0.5 - 2 keV (soft) X-ray band down to a 2.1-sigma limiting flux of ~ 1.7 x 10-16 erg/cm2/s and 11 sources in the 2 - 10 keV (hard) X-ray band down to a 2.1-sigma limiting flux of ~ 1.3 x 10-15 erg/cm2/s. The combined catalog contains a total of 153 X-ray sources, of which 42 are detected only in the soft band and 21 are detected only in the hard band.Confirming previous Chandra results, the authors find that the fainter sources have harder X-ray spectra, providing a consistent solution to the long-standing "spectral paradox". From deep optical and near-infrared follow-up data, 77% of the X-ray sources have optical counterparts to I = 24, and 71% of the X-ray sources have near-infrared counterparts to Ks = 20. Four of the 24 sources in the near-IR field are associated with extremely red objects (EROs; I - Ks >= 4). The authors have obtained spectroscopic redshifts with the Keck telescopes of 18 of the Lynx Chandra sources. These sources comprise a mix of broad-lined active galaxies, apparently normal galaxies, and two late-type Galactic dwarfs. Intriguingly, one Galactic source (number 72) is identified with an M7 dwarf exhibiting non-transient, hard X-ray emission. Thirteen of the Chandra sources are located within regions for which the authors have Hubble Space Telescope imaging. Nine of the sources are detected, showing a range of morphologies: several show compact cores embedded within diffuse emission, while others are spatially extended showing typical galaxy morphologies. Two of the Chandra sources in this subsample appear to be associated with mergers.
ACIS-I observations of the Lynx field were obtained on 2000 May 3 (65 ks; OBS-ID 1708) and 2000 May 4 (125 ks; OBS-ID 927). Time intervals with background rates larger than 3 sigma over the quiescent value of ~ 0.30 counts s-1 per chip in the 0.3 - 10 keV band were removed. This procedure gave 60.7 ks of effective exposure out of the first observation and 124 ks out of the second, for a total of 184.7 ks. The two observations are almost coincident on the sky, so that the total coverage is 298 arcmin2. The aim point for the observations was RA = 08h 48m 54.79s, Dec = +44d 54' 32.9" (J2000.0), and both exposures were obtained in the faint mode when ACIS was at a temperature of -120 C. The Galactic absorbing column for this field is NH = 2 x 1020 cm-2. The position angle of the observations was 258.45 degrees.
Cosmology-dependent parameters are calculated for two models: an Einstein-de Sitter (EdS) universe consistent with previous work in this field (H0 = 50 h50 km s-1 Mpc-1, OmegaM = 1, and OmegaLambda = 0) and the dark energy cosmology (DEC) universe favored by recent work on high-redshift supernovae and fluctuations in the cosmic microwave background (H0 = 65 km s-1 Mpc-1, OmegaM = 0.35, and OmegaLambda = 0.65).
Catalog Bibcode
2002AJ....123.2223SReferences
SPICES II: optical and near-infrared identifications of faint X-ray sources
from deep CHANDRA observations of Lynx.
Stern D., Tozzi P., Stanford S.A., Rosati P., Holden B., Eisenhardt P.,
Elston R., Wu K.L., Connolly A., Spinrad H., Dawson S., Dey A.,
Chaffee F.H.
<Astron. J. 123, 2223 (2002)>
=2002AJ....123.2223S
Provenance
This table was created by the HEASARC in April 2007 based on CDS catalog J/AJ/123/2223 files table1.dat, table2.dat and table3.dat.Parameters
Source_Number
A running sequential identification number for the X-ray
source which uniquely identifies it.
Name
The designation for the X-ray source, using the prefix
'[STS2002]' (for Stern, Tozzi, Stanford 2002) and the source number, e.g.,
'[STS2002] 72', as recommended by the CDS Dictionary of Nomenclature of
Celestial Objects. Note that the X-ray sources are referred to in the
paper using a shorthand form with the prefix 'CXO', e.g., 'CXO 72'.
RA
The Right Ascension of the X-ray source in the selected equinox. This was
given in J2000.0 coordinates to a precision of 0.01 seconds of time in the
original table. Astrometric positions were initially determined from the ACIS-I
aspect solution. Following comparison of X-ray source positions with the deep,
ground-based imaging discussed in Section 4 of the reference paper, the authors
refined the absolute pointing of the X-ray data with an offset of 1.09" west,
1.35" south, and no rotation. These offsets were determined by matching X-ray
sources with greater than 25 total counts (0.5 - 7 keV) to 17.5 < I < 22.5
sources. The positions presented therefore match the astrometric frame of the
SPICES survey.
Dec
The Declination of the X-ray source in the selected equinox. This was
given in J2000.0 coordinates to a precision of 0.1 arcseconds in the
original table. Astrometric positions were initially determined from the ACIS-I
aspect solution. Following comparison of X-ray source positions with the deep,
ground-based imaging discussed in Section 4 of the reference paper, the authors
refined the absolute pointing of the X-ray data with an offset of 1.09" west,
1.35" south, and no rotation. These offsets were determined by matching X-ray
sources with greater than 25 total counts (0.5 - 7 keV) to 17.5 < I < 22.5
sources. The positions presented therefore match the astrometric frame of the
SPICES survey.
LII
The Galactic Longitude of the X-ray source.
BII
The Galactic Latitude of the X-ray source.
SB_Counts
The X-ray source net counts S in the soft band (0.5 - 2 keV).
Source counts were measured with simple aperture photometry within a
radius R_S = 2.4 FWHM_PSF, where FWHM_PSF is the modeled PSF full width at
half-maximum, determined as a function of off-axis angle to reproduce the
broadening of the PSF. A minimum R_S = 5" was used in the central regions.
The background for each source was calculated locally within an annulus of
inner radius R_S + 2" and an outer radius of R_S + 12". Numerical simulations
show that this aperture photometry systematically underestimates the net
counts by 4%.
SB_Counts_Error
The RMS uncertainty in the soft-band counts.
HB_Counts
The X-ray source net counts H in the hard band (2 - 7 keV).
Source counts were measured with simple aperture photometry within a
radius R_S = 2.4 FWHM_PSF, where FWHM_PSF is the modeled PSF full width at
half-maximum, determined as a function of off-axis angle to reproduce the
broadening of the PSF. A minimum R_S = 5" was used in the central regions.
The background for each source was calculated locally within an annulus of
inner radius R_S + 2" and an outer radius of R_S + 12". Numerical simulations
show that this aperture photometry systematically underestimates the net
counts by 4%.
HB_Counts_Error
The RMS uncertainty in the hard-band counts.
Hardness_Ratio
The hardness ratio (H-S)/(H+S) of the X-ray source, where
H is the net hard counts and S is the net soft counts.
SNR
The signal-to-noise ratio of the X-ray detection in the 0.5 - 7 keV
band.
Off_Axis
The off-axis angle of the X-ray source from the nominal
pointing direction, in arcminutes.
SB_Flux
The flux in the soft band (0.5 - 2 keV), in erg/s/cm2. The net count rate
was transformed into the energy flux in the soft 0.5 - 2 keV band and in the
hard 2 - 10 keV band. The conversion factors used were (4.52 +/- 0.3) x
10-12 ergs cm-2 count-1 in the soft band and (2.79 +/- 0.3) x 10-11
ergs cm-2 count-1 in the hard band, assuming an absorbing column of 2 x
1020 cm-2 (Galactic value) and a photon index Gamma = 1.4. The
uncertainties in the conversion factors reflect the range of possible values
for the photon index, Gamma = 1.1 - 1.8. As suggested by the spectral
analysis of the stacked spectra, these values are representative of this
sample. Since the conversion factors were computed at the aim point, where
the effective area of Chandra/ACIS is at its maximum, the count rate of each
source was corrected for vignetting. Namely, the net count rate was
multiplied by the ratio of the exposure map at the aim point to the value of
the exposure map averaged within the extraction region. Such a correction was
done in the soft and hard bands separately.
HB_Flux
The flux in the hard band (2 - 10 keV), in erg/s/cm2. The net count rate
was transformed into the energy flux in the soft 0.5 - 2 keV band and in the
hard 2 - 10 keV band. The conversion factors used were (4.52 +/- 0.3) x
10-12 ergs cm-2 count-1 in the soft band and (2.79 +/- 0.3) x 10-11
ergs cm-2 count-1 in the hard band, assuming an absorbing column of 2 x
1020 cm-2 (Galactic value) and a photon index Gamma = 1.4. The
uncertainties in the conversion factors reflect the range of possible values
for the photon index, Gamma = 1.1 - 1.8. As suggested by the spectral
analysis of the stacked spectra, these values are representative of this
sample. Since the conversion factors were computed at the aim point, where
the effective area of Chandra/ACIS is at its maximum, the count rate of each
source was corrected for vignetting. Namely, the net count rate was
multiplied by the ratio of the exposure map at the aim point to the value of
the exposure map averaged within the extraction region. Such a correction was
done in the soft and hard bands separately.
Source_Flag
This flag parameter is set to 'a' to indicate that the host is
more than 1.5 arcseconds away from the faint X-ray source.
RA_Offset
The X-ray to optical Right Ascension offset, in arcseconds.
Dec_Offset
The X-ray to optical Declination offset, in arcseconds.
Bmag
The Harris B-band magnitude (lambdac = 4313 Angstrom), delta lambda = 1069
A) of the optical counterpart to the X-ray source. X-ray sources whose
positions were outside the optical field, objects within the optical field
with non-detections in this band, and sources within the optical field but
having bad photometry, due either to source saturation or contamination from
the stellar bleed trail of a nearby bright source, are all listed with null
values.To distinguish these 3 cases for which there are no quoted magnitude
values, the HEASARC has created a parameter (called optical_field_flag) which
is set to 'Y' for all sources in the optical field having good photometry
(whether detected or not), to 'C' for sources in the optical field with bad
photometry in at least one of the optical bands (BRIz), and 'N' for sources
outside the optical field.
Rmag
The Harris R-band magnitude (lambdac = 6458 A, delta lambda = 1472 A) of the
optical counterpart to the X-ray source. X-ray sources whose positions were
outside the optical field, objects within the optical field with
non-detections in this band, and sources within the optical field but having
bad photometry, due either to source saturation or contamination from the
stellar bleed trail of a nearby bright source, are all listed with null
values.To distinguish these 3 cases for which there are no quoted magnitude
values, the HEASARC has created a parameter (called optical_field_flag) which
is set to 'Y' for all sources in the optical field having good photometry
(whether detected or not), to 'C' for sources in the optical field with bad
photometry in at least one of the optical bands (BRIz), and 'N' for sources
outside the optical field.
Rmag_Flag
This flag parameter is set to ':' to indicate that the measured
R magnitude was somewhat affected by a nearby stellar bleed trail on the
CCD.
Imag
The Harris I-band magnitude (lambdac = 8204 Angstrom, delta lambda = 1821 A)
of the optical counterpart to the X-ray source. X-ray sources whose positions
were outside the optical field, objects within the optical field with
non-detections in this band, and sources within the optical field but having
bad photometry, due either to source saturation or contamination from the
stellar bleed trail of a nearby bright source, are all listed with null
values.To distinguish these 3 cases for which there are no quoted magnitude
values, the HEASARC has created a parameter (called optical_field_flag) which
is set to 'Y' for all sources in the optical field having good photometry
(whether detected or not), to 'C' for sources in the optical field with bad
photometry in at least one of the optical bands (BRIz), and 'N' for sources
outside the optical field.
Zmag
The RG850 long-pass z-band magnitude of the optical counterpart to the X-ray
source. X-ray sources whose positions were outside the optical field, objects
within the optical field with non-detections in this band, and sources within
the optical field but having bad photometry, due either to source saturation
or contamination from the stellar bleed trail of a nearby bright source, are
all listed with null values.To distinguish these 3 cases for which there are
no quoted magnitude values, the HEASARC has created a parameter (called
optical_field_flag) which is set to 'Y' for all sources in the optical field
having good photometry (whether detected or not), to 'C' for sources in the
optical field with bad photometry in at least one of the optical bands
(BRIz), and 'N' for sources outside the optical field.
Jmag
The J-band magnitude (lambdac = 1.14 micron, delta lambda
= 0.29 micron)of the near-infrared counterpart to the X-ray source. X-ray
sources whose positions were outside the optical field have been given
magnitude values of -99.00 by the HEASARC.
Ks_Mag
The Ks-band magnitude (lambdac = 2.16 micron, delta lambda
= 0.33 micron)of the near-infrared counterpart to the X-ray source. X-ray
sources whose positions were outside the optical field have been given
magnitude values of -99.00 by the HEASARC.
Redshift
The spectroscopic redshift of the optical/near-IR counterpart
to the X-ray source.
Spices_ID
The SPICES identification of the optical/near-IR counterpart
to the X-ray source.
Abs_Bmag_Eds
The EdS cosmology (see overview for more details) rest-frame
absolute B magnitude of the optical/near-IR counterpart to the X-ray source
(only available for the 18 X-ray sources with known redshifts).
Log_SB_Lx_Eds
The EdS cosmology (see overview for more details) rest-frame
0.5 - 2 keV luminosity of the X-ray source, using an adopted X-ray power-law
spectral index Gamma of 1.4 (only available for the 18 X-ray sources with
known redshifts).
Log_HB_Lx_Eds
The EdS cosmology (see overview for more details) rest-frame
2 -10 keV luminosity of the X-ray source, using an adopted X-ray power-law
spectral index Gamma of 1.4 (only available for the 18 X-ray sources with
known redshifts).
Abs_Bmag_Dec
The Dark Energy cosmology (see overview for more details)
rest-frame absolute B magnitude of the optical/near-IR counterpart to the
X-ray source (only available for the 18 X-ray sources with known redshifts).
Log_SB_Lx_Dec
The Dark Energy cosmology (see overview for more details)
rest-frame 0.5 - 2 keV luminosity of the X-ray source, using an adopted X-ray
power-law spectral index Gamma of 1.4 (only available for the 18 X-ray sources
with known redshifts).
Log_HB_Lx_Dec
The Dark Energy cosmology (see overview for more details)
rest-frame 2 - 10 keV luminosity of the X-ray source, using an adopted X-ray
power-law spectral index Gamma of 1.4 (only available for the 18 X-ray sources
with known redshifts).
Source_Type
The galaxy or AGN class (or spectral type for X-ray sources
associated with stars): this is only available for the 18 X-ray sources
with known redshifts.
Class
The HEASARC Browse object classification, based on the source_type
parameter value.
Optical_Field_Flag
The HEASARC created this parameter to indicate
whether or not the X-ray source position was within ('Y') the optical field of
view (FOV), outside ('N') of the optical FOV, or within the optical FOV but
for which bad photometry was obtained for at least one of the B, R, I or z
bands ('C'), either due to the source being saturated or to it being severely
affected by a stellar `bleed trail'. Objects which were within the optical FOV
but had bad photometry were listed in Table 2 of the reference paper with
values of 99.00 or 99.99 for the affected magnitudes: the HEASARC set such
values to nulls in this implementation.
Contact Person
Questions regarding the SPICESCXO database table can be addressed to the HEASARC User Hotline.Page Author: Browse Software Development Team
Last Modified: Thursday, 19-Mar-2015 20:56:59 EDT
- HEASARC Director: Dr. Andy Ptak
- NASA Official: Dr. Andy Ptak
- Web Curator: J.D. Myers
- Last Modified: 19-Mar-2015