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IX/15 Einstein EMSS Survey (Gioia+ 1990, Stocke+ 1991)
================================================================================
The EINSTEIN Observatory Extended Medium-Sensitivity Survey (EMSS)
Gioia I.M., Maccacaro T., Schild R.E., Wolter A.
<Astrophys. J. Suppl. Ser. 72, 567 (1990)>
=1990ApJS...72..567G
Stocke J.T., Morris S.L., Gioia I.M., Maccacaro T., Schild R.E.,
Wolter A., Fleming T.A., Henry J.P.
<Astrophys. J. Suppl. Ser. 76, 813 (1991)>
=1991ApJS...76..813S
================================================================================
ADC_Keywords: X-ray sources ; Active gal. nuclei ; BL Lac objects ;
Clusters, galaxy ; Galactic plane
Mission_Name: Einstein
Description:
The Einstein Extended Medium Sensitivity Survey (EMSS) consists
of 835 serendipitous X-ray sources detected at or above 4 times the
rms level in 1435 IPC fields with their centers located away from the
galactic plane. Their limiting sensitivities range from ~5*10-14 to
to ~ 3*10-12 erg.cm-2.s-1 in the 0.3-3.5keV band. A total area of 778
square degrees of the high galactic latitude sky (|b|>20) has been
covered. The analysis has been performed using data from the Rev 1
processing system at the CfA.
The resulting EMSS catalog is a flux-limited and homogeneous
sample of astronomical objects that can be used for statistical
studies. Here we present the table listing all the sources taken from
the publication referenced below and the optical identifications. At
present over 96% of the 835 X-ray sources have been successfully
identified in the following proportions: active galactic nuclei (QSO's,
quasars and Seyfert), 51.1%; BL Lacertae objects, 4.3%; clusters of
galaxies, 12.2%; normal galaxies, 2.1%; cooling flow galaxies, 0.6%;
Galactic stars 25.8%; and unidentified, 3.9%. Most of the individual
optical counterparts are previously unknown objects and so constitute
large statistical samples independent of previously selection methods.
The contents of the table is described below. The sky coverage
computed for a specific assumed source spectrum is also given under
"Additional Information" below. For further details please see the
published articles: Gioia et al. 1990, Stocke et al. 1991.
Additional Information:
The EMSS sky coverage.
----------------------
This sky coverage has been produced using the counts in the
standard detection algorithm and assuming a power law spectrum with
energy index = 1 and the measured Galactic hydrogen column density in
the direction of each IPC pointing. We caution the user that this sky
coverage is not appropriate for computation of functions like
logN(>S)-logS, or Luminosity Functions of resolved sources, like
clusters of galaxies or "normal" galaxies, nor of stars. The fluxes
for these objects have been calculated either using extended counts,
when appropriate, and/or different assumptions for the incident
spectrum (see below).
Limiting Sensitivity Area Covered
(erg/cm**2/s) (sq. deg)
5.08E-14 0.09
6.09E-14 0.72
7.31E-14 2.54
8.78E-14 6.37
1.05E-13 15.1
1.26E-13 29.4
1.52E-13 55.2
1.82E-13 94.2
2.18E-13 139.4
2.62E-13 191.6
3.14E-13 249.5
3.77E-13 319.1
4.53E-13 402.0
5.43E-13 497.0
6.52E-13 582.9
7.83E-13 657.7
9.39E-13 711.8
1.13E-12 743.7
1.35E-12 762.7
1.62E-12 771.9
1.95E-12 775.7
2.34E-12 777.4
2.80E-12 777.9
3.36E-12 778.1
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File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 194 835 EMSS Catalogue
notes.dat 80 412 Notes to EMSS sources
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See also:
IX/18 : EINSTEIN extended source survey (EXSS) (Oppenheimer+ 1997)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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2- 14 A13 --- name *Name of EMSS source
17- 18 I2 h RAh *Right Ascension (B1950.0) hours
19- 20 I2 min RAm *RA minutes
21- 24 F4.1 s RAs *RA seconds
25 A1 --- DE- *Declination sign (B1950.0)
26- 27 I2 deg DEd *Dec degrees
28- 29 I2 arcmin DEm *Dec arcmin
30- 33 F4.1 arcsec DEs *Dec arcsec
35- 36 I2 arcsec e_pos *Positional Uncertainty
37- 40 I4 arcsec x *? Position offset between optical and X-ray
41- 44 I4 arcsec y *? Position offset between optical and X-ray
46- 51 F6.2 10-16W/m2 fX *X-ray flux (*1.E-13 ergs/cm**2/s or
*1.E-16 W/m**2) in the 0.3-3.5 keV band
52 A1 --- ext_flag *Flagged '*' if source is extended
53- 57 F5.2 10-16W/m2 e_fX *1 sigma error on X-ray flux
59- 64 F6.2 ct/ks ctrate *Corrected IPC count rate
66- 69 F4.1 --- sn *Signal to Noise Ratio
71- 76 F6.1 --- cts *Uncorrected net counts in 0.2-3.5 keV
78- 81 F4.1 --- e_cts *Error on net counts
83- 87 I5 s live *Corrected exposure time
89- 93 F5.1 --- bkgcts *Total background counts
95- 99 I5 --- seqno *IPC sequence number of the image used
101-104 I4 --- cts_ext *? Net extended counts
106-111 F6.4 10+25m2 nH *Hydrogen column density
(*E+25 m^-2 or *E+21 cm^-2)
113-117 F5.2 mag Vmag *? Visual magnitude
119 A1 --- n_fR '<' for upper limit in fR
120-125 F6.1 mJy fR *? Radio flux at 5 GHZ
127-131 F5.2 --- fX/fv *? Logarithm of X-ray to visual flux ratio
133-136 A4 --- class *Proposed identification class of the
X-ray source (see below)
138-141 A4 --- r_class *Reference for class
143-147 F5.3 --- z *? Redshift
149 A1 --- n 'n' if a note on the source is in file notes
151-194 A44 --- comment *Miscellaneous information on the source
--------------------------------------------------------------------------------
Note on name:
This column gives the source name; denoted by MS, followed by
right ascension in hours, minutes, and truncated fraction of minutes,
then declination in degrees and arcminutes (i.e. MS0013.4+1558).
Note on RAh, RAm, RAs, DE-, DEd, DEm, DEs:
The right ascension and declination (B1950) correspond to the
centroid of the X-ray source.
Note on e_pos:
The e_pos column gives the positional uncertainty, in arcseconds,
the error associated with the position (90% confidence error circle
radius). A positional uncertainty of 4" indicates sources detected
also by the HRI. In these cases the coordinates of the source come
from the HRI.
Note on x, y:
The offset in position between the X-ray centroid and the
proposed optical counterpart in arcseconds of R.A. (x)
and dec (y). Negative offsets indicate directions west
and south of the X-ray centroids. Most of the offsets were measured
automatically on the POSS or SRC J plates. They are accurate to
+/- 5". For the SAO stars we have used the equinox 1950, epoch
1980 positions from the SAO catalog. When the optical counterpart
is a radio source (Column <fR>), the VLA radio position is used
(+/-1"). If more than one optical object is visible on the POSS within 10"
of the offset position listed in this column, the identity of the
optical counterpart is clarified with a note in the note column.
When the optical counterpart is a cluster of galaxies, the optical
offset refers to the brightest cluster member.
Note on fX, ext_flag, e_fX,:
These columns give the X-ray flux (in units of 10E-13
erg/cm**2/s) and the one sigma error on the X-ray flux in the 0.3-3.5
keV band. The ext_flag column is flagged with an asterisk ('*') if
extended counts from the column cts_ext were used to calculate the
X-ray flux. The error on the X-ray flux is from photon counting
statistics only, and is computed as the square root of the total
observed counts in the detection cell. The flux has been computed
in the 0.3-3.5 keV band for consistency with previous work (note that
the Rev.1 processing computes it in the 0.2-3.5 keV band). The following
assumptions have been adopted:
(a) For the AGN, BL Lac objects and unidentified sources; we have
multiplied the corrected count rate given in the ctrate column by
a conversion factor appropriate for a power law spectrum with
an energy index alpha = 1.0 and with the measured Galactic
hydrogen column density in the direction of each IPC pointing.
(b) For unresolved galaxies and clusters of galaxies; the flux
has been computed using an identical procedure but with a
different conversion factor appropriate for a Raymond-Smith
thermal spectrum (Raymond and Smith, 1977) with temperature of
about 6 keV.
The above assumptions are justified by the results of the
analysis of the X-ray energy distribution of the EMSS sources
performed by Maccacaro et al. (1988). A number of sources are
resolved even with the moderate angular resolution of the IPC. They
are mainly clusters of galaxies but also 3 galaxies, 8 AGN, and 3 BL
Lacs.
For the extragalactic population, the X-ray flux listed has been
corrected ("de-reddened") for Galactic absorption. For stars
we have adopted a constant conversion factor of 1 IPC
count/s = 2E-11 erg/cm**2/s corresponding to a Raymond-Smith thermal
spectrum with temperatures in the range 8E05 - 3E06 K and no
correction for the hydrogen column density. Note that RS CVn and K
and M flare stars usually have a second temperature component in the
range 1 - 2E07 K which results in nearly identical conversion factors
to those derived from the Raymond-Smith models over these temperature
ranges (see also Fleming, 1988, for a discussion of flux estimate of
X-ray selected stars).
In the case of clusters of galaxies the flux estimate should be
evaluated in a region of constant physical size (e.g. 1 Mpc). Such a
procedure cannot be applied to the serendipitous EMSS clusters,
especially to the nearby ones, given their proximity to the ribs (or
edges) of the detector or, in some cases, to the target of the
observation. For all the resolved sources identified with clusters of
galaxies or galaxies, and flagged as extended in the ext_flag column,
we have used the extended counts measured according to the procedure
described below the cts_ext column to compute the flux.
Note on ctrate:
This column gives the corrected IPC count rate in units of
cts/kilosecond. The count rate is derived from the net counts given
in the cts column (which are then corrected for vignetting, mirror
scattering, and point response function scattering) and the livetime
given in the live column, which has already been corrected for instrumental
dead time.
Note on sn:
This column gives the signal-to-noise ratio (s/n) computed as the
source counts divided by the square root of the sum of the source
counts and the background counts:
Source Counts / (Source Counts + Background Counts)**(1/2)]
Note on cts, e_cts:
The uncorrected net counts in the 0.2-3.5 keV band are given in
the cts column. No correction has been applied to the counts. The
e_cts column gives the error on the net counts, computed as the
square root of the total observed counts in the detection cell. The
cts/e_cts ratio is the signal-to-noise given in the previous column.
The total background counts are given in the bkgcts column.
Note on live, bkgcts:
This column gives the livetime, the exposure time of the IPC
observation, corrected for instrumental dead time. It is given in
seconds. The second line gives the background counts.
Note on seqno, cts_ext:
This column gives the sequence number of the observation, a
unique numeric identifier for each observation which was allocated
sequentially at the time of proposal submission. It is an internal
index used to key on all references to an observation.
If the ext_flag column is flagged with an asterisk ('*') then
extended counts from the column cts_ext were used to calculate the
X-ray flux. The cts_ext column gives the net extended counts. For
IPC sources, this means that counts were computed manually to include
all counts belonging to the source. For sources resolved by the IPC,
the observed counts have been computed manually within a region
centered on the source and with a size evaluated case by case so as to
contain all the counts belonging to the source itself. Background
counts for these sources have been computed within this same area from
the background map produced by the REV.1 processing. In these cases
only the vignetting and mirror scattering corrections have been
applied.
At the edge of the IPC detector the point spread function becomes
significantly degraded so that some sources appear to be extended even
though they might not be. Observations with a higher resolution
instrument (e.g. the HRI or ROSAT) are needed to decide whether the
extension is true or an artifact of the degradation of the IPC point
spread function. This distortion of the point spread function cannot
be modeled easily, so indications that sources are extended when they
are near the IPC edge cannot be always trusted. Since these sources
include ones which are identified as AGN and BL Lac objects as well
as clusters, the indication of extension should be regarded as tentative.
Note on nH:
The hydrogen column density along the line of sight to the IPC field
target determined using the HI survey of Stark et al. (1989). For regions
of sky not surveyed by Stark et al. (south of declination -42 deg) the
surveys of Heiles and Cleary (1979) and Cleary Heiles and Haslam (1979)
have been used.
Note on Vmag:
The V band magnitude of the counterpart. Some entries are from
photoelectric aperture photometry (for the stellar sources, see
Fleming, 1988 and the Bright Star Catalog) or from CCD photometry with
the Whipple Observatory 24 inch (for the extragalactic sources). These
are typically accurate to 0.01 mag. Other entries are
from the literature or are estimated magnitudes (+/- 0.5 mag) from
the STScI digitized sky survey plates. A value of 0.0 indicates that
the source is still unidentified, so there is no magnitude listed.
Note on fR:
The radio flux or 5 sigma upper limit in mJy at 5 GHz for the
optical counterpart mostly comes from VLA observations. When a cluster
of galaxies is the X-ray counterpart, radio emission from any cluster
galaxy within the cluster is listed here.
Note on fX/fv:
The logarithmic X-ray to optical flux ratio calculated from
the observed X-ray and visible fluxes by log (fX/fv) = log fX +
V/2.5 +5.37 (Maccacaro et al. 1988). These values are used to
determine whether the optical counterpart is plausible. For
this reason the X-ray flux used for this computation is not the
value in the fX column but is rather the X-ray flux computed prior
to assigning an optical identification class to each source. These
"raw" X-ray fluxes use an assumed spectral index of -0.5 for all
sources and a correction for galactic extinction equal to 3 X 10**20
cm-2 for all sources. The V band magnitudes quoted in the mv column
were used for this calculation. For sources identified with clusters
of galaxies the fX/fv is not given (fX/fv = 0.0) since the fX does not
take into account the extended flux where present, and the V magnitude
refers to the brightest cluster galaxy.
Note on class:
The class column gives the proposed identification or classification
of the X-ray source. The following abbreviations are used:
AGN = Active Galactic Nucleus (quasar or Seyfert galaxy)
CL = Cluster of galaxies
*CL* = Cooling flow galaxy
BL = BL Lac object
GAL = "normal" galaxy
STAR = star
UNID = source still unidentified
Note on r_class:
The r_class column gives the reference for identification or
classification. Identifications come from either our own spectroscopic
work (EMSS in the 2nd line) or from other authors' work as indicated
in the r_class column. References to other authors are given when the
proposed identification has been published even if additional
spectroscopic observations may have been obtained by us.
References in column r_class of emss table:
(MSS1) Stocke, J.T., Liebert, J., Gioia, I.M., Griffiths, R.E.,
Maccacaro, T., Danziger, I.J., Kunth, D., & Lub, J., 1983,
ApJ, 273, 458 (1983ApJ...273..458S)
(MSS2) Gioia, I.M., Maccacaro, T., Schild, R.E., Stocke, J.T.,
Liebert, J.W., Danziger, I.J., Kunth, D., & Lub, J., 1984,
ApJ, 283, 495 (1984ApJ...283..495G)
(1) White, S., Silk, J., & Henry, J.P., 1981ApJ...251L..65W
(2) Margon, B., Downes, R., & Chanan, G., 1985ApJS...59...23M
(3) Pravdo, S., & Marshall, F., 1984ApJ...281..570P
(4) Huchra, J., Davis, M., Latham, D., & Tonry, J., 1983ApJS...52...89H
(5) Hewitt, A., & Burbridge, G., 1987ApJS...63....1H
(6) Kriss, G., & Canizares, C., 1982ApJ...261...51K
(7) Wolstencraft, R., Hu, W., Arp, H., & Scarrott, S., 1983,, MNRAS,
1983MNRAS.205...67W
(8) Chanan, G., Margon, B., & Downes, R., 1981ApJ...243L...5C
(9) Mundt, R., Walter, F., Feigelson, E., Finkenzeller, V., Herbig,
G., & Odell, A., 1983ApJ...269..229M
(10) Henry, J.P., Soltan, A., Briel, U., & Gunn, J., 1982ApJ...262....1H
(11) Margon, B., Boronson, T., Chanan, G., Thompson, I., & Schneider,
D., 1986PASP...98.1129M
(12) Caillault, J., Helfand, D., Nousek, J., & Takalo, L., 1986,
1986ApJ...304..318C
(13) Morris, S., Schmidt, G., Liebert, J., Stocke, J., Gioia, I.,
& Maccacaro, T., 1987ApJ...314..641M
(14) Biermann, P., Schmidt, G., Liebert, J., Stockman, H., Tapia, S.,
Strittmatter, P., West, S., & Lamb, D., 1985ApJ...293..303B
(15) Reichert, G., Mason, K., Thorstensen, J., & Bowyer, S., 1982,
1982ApJ...260..437R
(16) J. Huchra & M. Postman (private communication)
(17) de Vaucouleurs, G., de Vaucouleurs, A., & Corwin, H., 1976,
Second Reference Catalogue of Bright Galaxies (Austin:
University of Texas Press) (Cat. <VII/112>)
(18) I.J. Danziger (private communication)
(19) Maccagni, D., Garilli, B., Gioia, I.M., Maccacaro, T.
Vettolani, G., & Wolter, A., 1988ApJ...334L...1M
(20) Katgert, P., Thuan, T., & Windhorst, R., 1983ApJ...271....1K
(21) Mason, K., Spinrad, H., Bowyer, S., Reichert, G., & Stauffer,
J., 1981AJ.....86..803M
(22) Hoessel, J., Gunn, J., & Thuan, T., 1980ApJ...241..486H
(23) F. Walter (private communication)
(24) Morris, S.L., Liebert, J., Stocke, J.T, Gioia, I.M., Maccacaro,
T., Schild, R.E., & Wolter, A., 1990, ApJ, 383, 686
(1990ApJ...365..686M)
(25) Chanan, G., Margon, B., Helfand, D., Downes, R., & Chance, D.,
1982ApJ...261L..31C
(26) Kowalski, M., Ulmer, M., & Cruddace, R., 1983ApJ...268..540K
(27) Nesci, R., Gioia, I., Maccacaro, T., Morris, S., Perola, G.,
Schild, R., & Wolter, A., 1989ApJ...344..104N
(28) Maia, M., DeCosta, L., Willmer, C., Pellegrini, P., & Rite, C.,
1987AJ.....93..546M
(29) Marschall, L., Stefanik, R., Nations, R., & Karshner, G., 1989,
BAAS, 21, 1083 (1989BAAS...21.1083M)
(30) Fleming, T.A., Gioia, I.M., & Maccacaro, T., 1989AJ.....98..692F
(31) Robb, R., 1989, IBUS, Nos. 3346 and 3370
(32) R. Robb, private communication;
(33) Carter, B., Inglis, I., Ellis, R., Efstathiou, G., & Godwin, J.,
1985MNRAS.212..471C
(34) Kurtz, M., Huchra, J., Beers, T., Geller, M., Gioia, I.M.,
Maccacaro, T., Schild, R., & Stauffer, J., 1985AJ.....90.1665K
(35) Silva, D., Liebert, J., Stocke, J.T. & Aaronson M., 1985,
1985PASP...97.1096S
Note on z:
If the counterpart is extragalactic the redshift is listed (+/- 0.003).
Note on comment:
This column gives miscellaneous information on the source (i.e.
radio catalogued source, SAO name, X-ray variable source, IRAS source,
EXOSAT source, etc.). The EXOSAT CMA position is reported with the
positional accuracy in parentheses. EMSS sources already published as
part of the MSS samples are labelled as MSS1 (Maccacaro et al. 1982
and Stocke et al. 1983) and MSS2 (Gioia et al. 1984).
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History and Modifications:
* 19-Jan-1993: Original version received from Isabella Gioia, table
adapted by F.Ochsenbein[CDS]
* 19-Jan-1993. Documentation reformatted to v1.4 of standard by
Paul Kuin [ADC] 31-Jul-1995.
* 29-Aug-1997: catalogue number changed from VII/152 to IX/15
(high energy data)
References:
Cleary, M.N., Heiles, C., and Haslam, C.G.T., 1979A&AS...36...95C
Fleming, T.A. 1988, Ph. D. Thesis, University of Arizona
Gioia, I.M., Maccacaro, T., Schild, R.E., Stocke, J.T., Liebert, J.W.,
Danziger, I.J., Kunth, D., & Lub, J., 1984ApJ...283..495G
Gioia, I.M., Maccacaro, T., Morris, S.L., Schild, R.E., Stocke, J.T., Wolter,
A., & Henry, P.H., 1990ApJS...72..567G
Heiles, C. and Cleary, M.N., 1979, Australian J.Pys. Ap. Suppl, 47, 1.
Maccacaro, T., & al. 1982ApJ...253..504M
Maccacaro, T., Gioia, I.M., Wolter, A., Morris, S.L., & Stocke, J.T., 1988,
1988ApJ...326..680M
Raymond, J.C. & Smith, B.W., 1977ApJS...35..419R
Stark, A.A., Heiles, C., Bally, J., and Linker, R., 1989, Bells Lab,
privately distributed magnetic tape
Stocke, J.T., Liebert, J., Gioia, I.M., Griffiths, R.E., Maccacaro, T.,
Danziger, I.J., Kunth, D., & Lub, J., 1983ApJ...273..458S
Stocke, J.T., Morris, S.L., Gioia, I.M., Maccacaro, T., Schild, R.E.,
Wolter, A., Fleming, T.A., & Henry, J.P., 1991ApJS...76..813S
Contact: Isabella Gioia, Institute for Astronomy;
gioia@galileo.ifa.hawaii.edu
================================================================================
(End) I.Gioia, F.Ochsenbein, P. Kuin 31-Jul-1995