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J/A+A/327/952       Centaurus cluster velocities (Stein+ 1997)

Velocity structure of the dwarf galaxy population in the Centaurus cluster Stein P., Jerjen H., Federspiel M. <Astron. Astrophys. 327, 952 (1997)> =1997A&A...327..952S (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Radial velocities Keywords: clusters of galaxies: general: Centaurus cluster - evolution of - galaxies: redshifts; evolution; NGC 4696 Abstract: Based on the photometric survey of the inner region of the Centaurus cluster (Jerjen & Dressler, 1997, Cat. J/A+AS/124/1) we measured redshifts for a deep, surface brightness limited sample of galaxies using the MEFOS multifibre spectrograph at the ESO 3.6m telescope. With the new data set radial velocities for 120 centrally located cluster members become available which is equivalent to 78% of all known cluster galaxies in the region brighter than BT=18.5. The relevant aspect of this investigation is that new redshifts for 32 dwarf galaxies have been measured, rising the total number to 48. We investigate the prominent bimodal velocity distribution of Centaurus in more detail, discussing the very different characteristics of the velocity distributions for the main Hubble types E&S0, spirals, Im&BCD, and dE&dS0. The nucleated, bright dwarf ellipticals are the only galaxies with a Gaussian-like distribution centred at 3148±98km/s. The remarkable coincidence of this velocity with the mean velocity of Cen 30 and the redshift of NGC 4696 in particular strongly suggests a connection of the dE&dS0s to the gravitational centre of the Centaurus cluster and/or to the cluster dominant E galaxy. The application of statistical tests reveals the existence of a population dwarf galaxies bound to NGC 4696. The dynamical parameters for the two velocity components suggest that Cen 30 is the real Centaurus cluster whereas Cen 45 can only be a loosely bound group of galaxies. This conclusion is followed up with a type-mixture analysis. All results are fully consistent with the cluster-group scenario. Whether Cen 45 is merging with the cluster or is located in the close background remains unclear. We show that the poorness of Cen 45 represents an intrinsic problem which makes it difficult to approach this question. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table5a.dat 81 36 New redshifts for Centaurus cluster members table5b.dat 81 14 New redshifts of background galaxies table5c.dat 81 65 Reobserved redshifts for Centaurus cluster members table5.tex 97 283 LaTeX version of table5 table5.ps 83 931 PostScript version of table5
See also: J/A+AS/124/1 : The Centaurus Cluster Catalogue (Jerjen+ 1997) Byte-by-byte Description of file: table5?.dat
Bytes Format Units Label Explanations
1- 3 I3 --- Seq Sequential number 5- 6 I2 h RAh Right ascension (1950.0) 8- 9 I2 min RAm Right ascension (1950.0) 11- 15 F5.2 s RAs Right ascension (1950.0) 17 A1 --- DE- Declination sign 18- 19 I2 deg DEd Declination (1950.0) 21- 22 I2 arcmin DEm Declination (1950.0) 24- 27 F4.1 arcsec DEs Declination (1950.0) 29- 31 I3 --- CCC Centaurus Cluster Catalogue (Jerjen & Dressler 1996, Cat. J/A+AS/124/1) reference number 33- 38 A6 --- Mtype Morphological type 40- 44 F5.2 mag BT Total blue magnitude 46- 49 F4.1 mag/arcsec+2 SBeff ? Effective surface brightness 51- 54 F4.2 % Prob ? Cen 45 cluster member probability (1) 56- 60 I5 km/s Vcc ? Cross-correlation redshift 62- 63 I2 km/s e_Vcc ? rms uncertainty on Vcc 65- 69 I5 km/s Vem ? Emission line redshift 71- 72 I2 km/s e_Vem ? rms uncertainty on Vem 74- 78 I5 km/s cz ? Heliocentric radial velocity (2) 80- 81 I2 km/s e_cz ? rms uncertainty on cz
Note (1): If prob=0.00, this automatically implies that the galaxy is a 100% Cen 30 member. Note (2): Weighted average of Vccf and Vemi.
Acknowledgements: Martin Federspiel
(End) Patricia Bauer [CDS] 26-Jan-1998
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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