ACDS V10.0 - Detailed Description of IX/15

ACDS V10.0 - Wed Jan 15 15:37:38 CET 2025

| # Detailed Description of IX/15 : Einstein EMSS Survey (Gioia+ 1990, Stocke+ 1991) |

Note : this is the description file of the original catalog. This HTML page corresponds well to the original description, but some minor changes in the format may have been introduced in the FITS output files in order to allow for arithmetic operations on quantities such as coordinates and times. h:m:s and d:m:s units are normally converted into degrees, and YYYY-MM-DD into julian days.
Similarly, some slight changes may have been introduced in the units; the value given in the HTML files supersedes the value indicated in the ReadMe file for this catalogue.

    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

    File Summary:

           FileName      Lrecl  Records   Explanations

    ×                   80        .   This file
    × ReadMe            80        .   This file
    × catalog.dat      194      835   EMSS Catalogue
    × notes.dat         80      412   Notes to EMSS sources

    See also:
        IX/18 : EINSTEIN extended source survey (EXSS) (Oppenheimer+ 1997)
        J/ApJ/461/127 : The Einstein Two-Sigma Catalog (Moran+ 1996)

    Byte-by-byte Description of file:  catalog.dat

       Bytes Format  Units     Label    Explanations

       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+25m-2  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).

    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