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J/ApJ/549/820       H{alpha} flux of ACCG 114 galaxies    (Couch+, 2001)
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A low global star formation rate in the rich galaxy cluster AC 114 at z=0.32.
      Couch W.J., Balogh M.L., Bower R.G., Smail I., Glazebrook K., Taylor M.
     <Astrophys. J. 549, 820 (2001)>
     =2001ApJ...549..820C
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ADC_Keywords: Clusters, galaxy ; Galaxies, spectra ; Photometry, H-alpha
Keywords: galaxies: clusters: general - galaxies: evolution -
          galaxies: formation

Abstract:
    We present the results of a wide-field survey for H{alpha}-emitting
    galaxies in the cluster AC 114 at z=0.32. Spectra centered on H{alpha}
    at the cluster redshift have been obtained for 586 galaxies to
    I_tot_~22 out to a radius of ~h_50_^-1^Mpc. At most, only ~10% of
    these were found to be H{alpha}-emitting cluster members. These
    objects are predominantly blue and of late-type spiral morphology,
    consistent with them hosting star formation. However, ~65% of the
    cluster members classified morphologically as spirals (with HST) have
    no detectable H{alpha} emission; star formation and morphological
    evolution in cluster galaxies appear to be largely decoupled. Changes
    in the H{alpha} detection rate and the strength of H{alpha} emission
    with environment (as traced by local galaxy density) are found to be
    weak within the region studied. Star formation within the cluster
    members is also found to be strongly and uniformly suppressed with the
    rates inferred from the H{alpha} emission not exceeding 4M_{sun}_/yr,
    and AC 114's H{alpha} luminosity function being an order of magnitude
    below that observed for field galaxies at the same redshift. None of
    the galaxies detected have the high star formation rates associated
    with "starburst" galaxies; however, this may still be reconcilable
    with the known (8%+/-3%) fraction of "post-starburst" galaxies within
    AC 114, given the poorly determined but short lifetimes of starbursts
    and the possibility that much of the associated star formation is
    obscured by dust.

File Summary:
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 FileName      Lrecl  Records   Explanations
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ReadMe            80        .   This file
table1.dat        91      586   Relevant data for the 586 unique galaxies
                                 observed in this study
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See also:
    J/ApJ/497/188 : A103, A118 and A114 morphological studies (Couch+ 1998)

Byte-by-byte Description of file: table1.dat
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   Bytes Format Units       Label     Explanations
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   1-  4  I4    ---         [CBB2001] Galaxy identification
   6-  7  I2    h           RAh       Right Ascension (J2000)
   9- 10  I2    min         RAm       Right Ascension (J2000)
  12- 18  F7.4  s           RAs       Right Ascension (J2000)
      20  A1    ---         DE-       Sign of the Declination (J2000)
  21- 22  I2    deg         DEd       Declination (J2000)
  24- 25  I2    arcmin      DEm       Declination (J2000)
  27- 32  F6.3  arcsec      DEs       Declination (J2000)
  34- 38  F5.2  mag         Imag      I band magnitude
  41- 42  I2    ---         Ttype     ? T-type classification
  44- 49  A6    ---         Htype     ? Hubble classification
      51  I1    ---         Detect    Detection class (1)
  53- 59  F7.5  ---         z         ? Redshift
  61- 67  F7.3 10-21W/m2    Ha        H{alpha} flux in 10^-17^ergs/s/cm^2^
  69- 75  F7.3 10-21W/m2  e_Ha        Error in Ha in 10^-17^ergs/s/cm^2^
  77- 83  F7.3  10+33W      LHa       H{alpha} luminosity in 10^40^ergs/s (2)
  85- 91  F7.3 solMass/yr   SFR       Star formation rate (2)
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Note (1):
    1 = confirmed by at least one other line
    2 = only one line clearly detected
    0 = no detection
Note (2): Assuming {Omega}=0.3, {Lambda}=0, H_0_=50km/s/Mpc.
    Relative uncertainties are the same as for H{alpha} flux.
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History:
    From electronic version of the journal
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(End)                    Greg Schwarz [AAS], Patricia Bauer [CDS]    17-May-2001