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J/ApJ/549/820       Hα flux of ACCG 114 galaxies    (Couch+, 2001)

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
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 Hα-emitting galaxies in the cluster AC 114 at z=0.32. Spectra centered on Hα at the cluster redshift have been obtained for 586 galaxies to Itot∼22 out to a radius of ∼h50-1Mpc. At most, only ∼10% of these were found to be Hα-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 Hα emission; star formation and morphological evolution in cluster galaxies appear to be largely decoupled. Changes in the Hα detection rate and the strength of Hα 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 Hα emission not exceeding 4M/yr, and AC 114's Hα 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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 91 586 Relevant data for the 586 unique galaxies observed in this study
See also: J/ApJ/497/188 : A103, A118 and A114 morphological studies (Couch+ 1998) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
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 Hα flux in 10-17ergs/s/cm2 69- 75 F7.3 10-21W/m2 e_Ha Error in Ha in 10-17ergs/s/cm2 77- 83 F7.3 10+33W LHa Hα luminosity in 1040ergs/s (2) 85- 91 F7.3 solMass/yr SFR Star formation rate (2)
Note (1): 1 = confirmed by at least one other line 2 = only one line clearly detected 0 = no detection Note (2): Assuming Ω=0.3, Λ=0, H0=50km/s/Mpc. Relative uncertainties are the same as for Hα flux.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 17-May-2001
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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