J/ApJ/681/1017      Chandra observations of lens groups       (Fassnacht+, 2008)
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The X-ray properties of moderate-redshift galaxy groups selected by association
with gravitational lenses.
    Fassnacht C.D., Kocevski D.D., Auger M.W., Lubin L.M., Neureuther J.L.,
    Jeltema T.E., Mulchaey J.S., McKean J.P.
   <Astrophys. J., 681, 1017-1034 (2008)>
   =2008ApJ...681.1017F
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ADC_Keywords: X-ray sources ; Clusters, galaxy ; Redshifts
Keywords: galaxies: clusters: general - gravitational lensing -
          X-rays: galaxies: clusters

Abstract:
    We present results from a systematic investigation of the X-ray
    properties of a sample of moderate-redshift (0.3<z<0.6) galaxy
    groups. These groups were selected not by traditional X-ray or optical
    search methods, but rather by an association, either physical or along
    the line of sight, with a strong gravitational lens. We calculate the
    properties of seven galaxy groups in the fields of six lens systems.
    Diffuse X-ray emission from the intragroup medium is detected in four
    of the groups. All of the detected groups have X-ray luminosities
    greater than 10^42^h^-2^ergs/s and lie on the L_X_^-{sigma}_v_^
    relations defined by local groups and clusters. The upper limits for
    the nondetections are also consistent with the local L_X_^-{sigma}_v_^
    relationships. Although the sample size is small and deeper optical
    and X-ray data are needed, these results suggest that lens-selected
    groups are similar to X-ray-selected samples and thus are more massive
    than the typical poor-group environments of local galaxies.

Description:
    The systems analyzed for this paper are all strong lenses for which we
    have obtained new observations with Chandra or for which data are
    available in the Chandra archive. Observation parameters as follows:
      ----------------------------------------------------------------
           Target    ObsID  Exp (s)  Obs.Date     PI
      ----------------------------------------------------------------
           B0712     4199   97742    2004/12/17   Fassnacht
           PG 1115    363   26489    2000/06/02   Garmire
           B1422      367   16888a   2000/06/02   Garmire
           B1600     3460   30176    2003/10/07   Kochanek
           B1608     3461   29717    2003/09/09   Kochanek
           B2108     6971   45507    2006/07/14   Fassnacht
      ----------------------------------------------------------------
      a = Reduced from 28429s due to flaring events.
      ----------------------------------------------------------------

File Summary:
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 FileName  Lrecl  Records   Explanations
--------------------------------------------------------------------------------
ReadMe        80        .   This file
group.dat     99        8   Properties of diffuse group emission (tables 2
                            and 3 of the paper)
table6.dat    69       51   Serendipitous sources detected in the field of
                            B0712+472
table7.dat    69       34   Serendipitous sources detected in the field of
                            B2108+213
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See also:
       B/chandra : The Chandra Archive Log (CXC, 1999-)
   J/ApJ/658/865 : Redshifts of galaxies in X-ray-luminous groups (Jeltema+,
                   2007)
   J/ApJ/496/39  : Properties of poor groups of galaxies. I. (Zabludoff+ 1998)

Byte-by-byte Description of file: group.dat
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   Bytes Format Units    Label    Explanations
--------------------------------------------------------------------------------
   1-  7  A7    ---      Group    Group name
  10- 11  I2    h        RAh      ? Hour of right ascension (J2000)
  13- 14  I2    min      RAm      ? Minute of right ascension (J2000)
  16- 19  F4.1  s        RAs      ? Second of right ascension (J2000)
      21  A1    ---      DE-      ? Declination sign (J2000)
  22- 23  I2    deg      DEd      ? Degree of declination (J2000)
  25- 26  I2    arcmin   DEm      ? Arcminute of declination (J2000)
  28- 29  I2    arcsec   DEs      ? Arcsecond of declination (J2000)
  31- 34  F4.1 10+20cm-2 nH       Neutral hydrogen column densities of
                                  Dickey & Lockman (1990ARA&A..28..215D)
  36- 38  I3    ---      Cts      ? Net counts in x-ray
  40- 43  F4.2  10-3/s   CtR      ? Count rate in x-ray
      45  A1    ---    l_Flux     Limit flag on Flux
  46- 49  F4.1  aW/m2    Flux     Soft band flux corrected from Galactic
                                  absorption (1)
  51- 53  F3.1  aW/m2  e_Flux     ? Uncertainty in Flux
      55  A1    ---    l_Lx       Limit flag on Lx
  56- 59  F4.2 10+35W    Lx       Rest-frame bolometric luminosity in
                                  10^42^h^-2^ergs/s units
  61- 64  F4.2 10+35W  e_Lx       ? Uncertainty in Lx
      66  A1    ---    l_Lx500    Limit flag on Lx500
  67- 70  F4.1  ---      Lx500    ? Rest-frame bolometric luminosity
                                  within R_500_  (in 10^42^h^-2^ergs/s)
  72- 74  F3.1 ---     e_Lx500    ? Uncertainty in Lx500
  76- 77  I2   ---       N        ? Group optical number of members
      78  A1   ---     n_N        [a] a = optical data in B2108-1 are for B2108
  80- 84  F5.3 ---       z        ? Group optical redshift
  86- 88  I3   km/s      sigma    ? Group optical radial velocity dispersion
  90- 91  I2   km/s    e_sigma    ? {sigma} uncertainty
  93- 95  I3   kpc       R500     ? Group optical radius at 500 times
                                  critical density, in h^-1^kpc units (2)
  97- 99  I3   arcsec    the500   ? Group optical position angle at 500
                                  times critical density
--------------------------------------------------------------------------------
Note (1): We determined the soft-band flux of the group emission by
     normalizing a Raymond-Smith spectral model in the CIAO package Sherpa
     to the net counts detected above the background in each system.
     Units are 10^-15^erg/cm^2^/s = aW/m^2^.
Note (2): The value of R500 for each system was estimated from the radial
     velocity dispersion that had been determined from the group galaxy
     redshifts as R_500_=2{sigma}_v_/[500H(z)^0.5]
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Byte-by-byte Description of file: table6.dat table7.dat
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   Bytes Format Units   Label     Explanations
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   1-  3  A3    ---     ---       [CXO]
   5- 20  A16   ---     CXO       Name (JHHMMSS.s+DDMMSS,
                                  <CXOU JHHMMSS.s+DDMMSS> in Simbad)
      21  A1    ---   f_CXO       [b] extended source flag
  23- 31  F9.5  deg     RAdeg     Right ascension in decimal degree (J2000)
  33- 40  F8.5  deg     DEdeg     Declination in decimal degree (J2000)
  42- 45  I4    ct      Scts      Soft (0.5-2.0keV) band net counts
  47- 49  I3    ct      Hcts      Hard (2.0-8.0keV) band net counts
  51- 54  I4    ct      Fcts      Full (0.5-8.0keV) band net counts
  56- 59  F4.1  ---     Ssig      Soft (0.5-2.0keV) band significance (3)
  61- 64  F4.1  ---     Hsig      Hard (2.0-8.0keV) band significance (3)
  66- 69  F4.1  ---     Fsig      Full (0.5-8.0keV) band significance (3)
--------------------------------------------------------------------------------
Note (3): The significances are calculated as the net counts from each
     source divided by the error of the background counts in the
     measurement aperture.
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History:
    From electronic version of the journal

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(End)                                     Emmanuelle Perret [CDS]    27-Oct-2010