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J/ApJ/511/595       An X-Ray Survey of Galaxies in Pairs    (Henriksen+, 1999)
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An X-Ray Survey of Galaxies in Pairs
       Henriksen M., Cousineau S.
      <Astrophys. J. 511, 595 (1999)>
      =1999ApJ...511..595H
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ADC_Keywords: Clusters, galaxy; Surveys; X-ray sources
Mission_Name: ROSAT
Keywords: clusters: general - galaxies: interactions - surveys -
          X-rays: galaxies

Abstract:
    Results are reported from the first survey of X-ray emission from
    galaxies in pairs. The sample consists of 52 pairs of galaxies from
    the Catalog of Paired Galaxies (Cat. <VII/77>) whose coordinates
    overlap the ROSAT Position Sensitive Proportional Counter pointed
    observations. The mean observed log(L_x_) for early-type pairs is
    41.35+/-0.21, while the mean log(L_x_) predicted using the
    (L_X_-L_b_) relationship for isolated early-type galaxies is 42.10+/-0.19.
    With 95% confidence, the galaxies in pairs are underluminous in the
    X-ray, compared with isolated galaxies, for the same L_b_. A
    significant fraction of the mixed pair sample also appears similarly
    underluminous. A spatial analysis shows that the X-ray emission from
    pairs of both types typically has an extent of 10 - 50 kpc, much
    smaller than the group intergalactic medium, and thus likely
    originates from the galaxies. CPG 564, the most X-ray luminous
    early-type pair, 4.7x10^42^ergs/s, is an exception. The extent of
    its X-ray emission, greater than 169 kpc, and HWHM, {~}80 kpc, is
    comparable to that expected from an intergalactic medium. The sample
    shows only a weak correlation, {~}81% confidence, between L_X_ and
    L_b_, presumably due to variations in gas content within the galaxies.
    No correlation between L_X_ and the pair velocity difference
    ({delta}v), separation ({delta}r), or far-infrared luminosity (L_fir_)
    is found, although the detection rate is low, 22%.

File Summary:
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  FileName      Lrecl  Records   Explanations
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ReadMe             80        .   This file
table1.dat        101       52   Data for spiral galaxy pairs
table2.dat         92       16   Data for early-type galaxy pairs
table3.dat        101       36   Data for mixed galaxy pairs
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See also:
   VII/77 :  Catalogue of isolated pairs of galaxies in northern hemisphere
   J/other/ApL/30.1 : Southern catalogue of isolated pairs extension
                      (Reduzzi+ 1995)
   VII/113 : Catalogued Galaxies + QSOs observed in IRAS Survey,
             Vers.2 (IPAC 1989)
   II/156A : IRAS Faint Source Catalog, |b| > 10, Version 2.0 (Moshir+ 1989)

Byte-by-byte Description of file: table*.dat
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   Bytes Format Units       Label     Explanations
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   1-  3  I3    ---         CPG       Catalog of Paired Galaxies number (1)
   8- 19  A12   ---         Morph     Galaxy morphological type from NED
  21- 22  I2    h           RAh       Right Ascension (J2000)
  24- 25  I2    min         RAm       Right Ascension (J2000)
  27- 28  I2    s           RAs       Right Ascension (J2000)
      30  A1    ---         DE-       Sign of the Declination (J2000)
  31- 32  I2    deg         DEd       Declination (J2000)
  34- 35  I2    arcmin      DEm       Declination (J2000)
  37- 38  I2    arcsec      DEs       Declination (J2000)
  43- 48  F6.2  arcmin      Sep       ? Separation of Galaxy pairs
  50- 54  I5    km/s        Vel       Recessional velocity
  56- 60  F5.2  10+36W      LumB      Blue luminosity (10^43^ergs/s)
  68- 74  F7.3  10-2ct/s    Cnts      ? Background subtracted Xray counts
                                        (10^-2^/s)
  79- 83  F5.3  10-2ct/s  e_Cnts      ? 1 sigma error in Cnts (10^-2^/s)
      85  A1    ---       l_LumX      limit on LumX
  87- 92  F6.2  10+34W      LumX      ? Xray luminosity from 0.25-2 KeV
                                       (10^41^ergs/s)
  96-101  F6.2  [10-7W]     LumIR     ? Log of the Far IR luminosity (erg/s) (2)
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Note (1): Data in columns CPG and between RAh and LumB are based on
    information from Karachentsev (1972). A Hubble constant of 50
    km.s-1.Mpc-1 is used to calculate the luminosities.
Note (2): Calculated from fluxes obtained from the Catalogue of
    Galaxies and Quasars Observed in the IRAS Survey, version 2.1, as well
    as the Point Source Catalog and the Faint Source Catalog. The FIR
    sources occur within a 25 kpc search radius centered on each of the
    galaxy positions.
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History:
    From ApJ electronic edition

References:
   Karachentsev, I. 1972, Comm. Spec. Ap. Obs., USSR, 7, 1 (CPG)

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(End)                                      Greg Schwarz (AAS)        10-Feb-2000