J/AJ/125/2393 A2256 galaxies redshifts and 1.4GHz fluxes (Miller+, 2003)
A comprehensive radio and optical study of Abell 2256: activity from an infalling group. Miller N.A., Owen F.N., Hill J.M. <Astron. J. 125, 2393 (2003)> =2003AJ....125.2393M
ADC_Keywords: Clusters, galaxy ; Galaxies, radio ; Redshifts ; Magnitudes Keywords: galaxies: clusters: individual (Abell 2256) - galaxies: evolution - radio continuum Abstract: Abell 2256 is a nearby (z∼0.06), rich cluster of galaxies with fascinating observed properties across a range of wavelengths. Long believed to represent a cluster merger, recent X-ray and optical results have suggested that in addition to the primary cluster and subcluster there is evidence for a third, poorer system. We present wide-field high-sensitivity 1.4GHz VLA radio observations of Abell 2256 in conjunction with optical imaging and additional spectroscopy. Over 40 cluster radio galaxies are identified, with optical spectroscopy indicating the emission source (star formation or active galactic nucleus) for most of them. While the overall fraction of galaxies exhibiting radio emission is consistent with a large sample of other nearby clusters, we find an increase in the activity level of galaxies belonging to the third system (hereafter "the Group"). Specifically, the Group has relatively more star formation than both the primary cluster and main subcluster. The position of the Group is also coincident with the observed cluster radio relic. We suggest that the Group recently (0.3Gyr) merged with the primary cluster and that this merger, not the ongoing merger of the primary and the main subcluster, might be responsible for many of the unusual radio properties of Abell 2256. Furthermore, the greater star formation activity of the Group suggests that the infall of groups is an important driver of galaxy evolution in clusters. Description: Radio observations at 1.4GHz were made with the VLA in two configurations. The higher resolution observations were performed during 1998 July while the VLA was in its B configuration, and lower resolution observations were performed during 1999 May in the D configuration. Optical images (Rc) of Abell 2256 were obtained during 1999 July by using the KPNO 0.9m telescope. Optical spectra of galaxies in Abell 2256 were obtained during two separate observing runs in 1999. In 1999 May, 18 candidate cluster radio galaxies were observed using the Kitt Peak 2.1m telescope and the GoldCam spectrograph. Numerous cluster galaxies (including non-radio galaxies) were also observed using the MX Spectrometer and the Steward Observatory Bok Telescope (2.3m). File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 43 73 Galaxy Velocity Measurements table2.dat 82 40 Cluster Radio Galaxies table3.dat 82 18 Additional Radio Galaxies
See also: VII/99 : Radial Velocities of Galaxies (Palumbo+ 1986) VII/193 : The CfA Redshift Catalogue, Version June 1995 (Huchra+ 1995) J/AJ/123/2261 : Radial velocities in A2256 (Berrington+, 2002) J/A+AS/127/117 : Kinematics of galaxies (Prugniel+ 1998) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 h RAh Hour of right ascension (J2000) 4- 5 I2 min RAm Minute of right ascension (J2000) 7- 10 F4.1 s RAs Second of right ascension (J2000) 11 A1 --- DE- Sign of declination (J2000) 12- 13 I2 deg DEd Degree of declination (J2000) 15- 16 I2 arcmin DEm Arcminute of declination (J2000) 18- 19 I2 arcsec DEs Arcsecond of declination (J2000) 21- 25 I5 km/s cz Velocity measurement from this study 27- 28 I2 km/s e_cz Error in cz 30- 32 A3 --- n_cz Comment on cz (1) 34- 38 I5 km/s B02cz ? Velocity measurement from Berrington et al., 2002, Cat. J/AJ/123/2261 40- 42 I3 km/s e_B02cz ? Error in cz
Note (1): We classified the radio galaxies as star-forming or AGN on the basis of their emission and absorption features.
Byte-by-byte Description of file: table2.dat table3.dat
Bytes Format Units Label Explanations
1- 2 I2 h RAh Hour of right ascension (J2000) 4- 5 I2 min RAm Minute of right ascension (J2000) 7- 10 F4.1 s RAs Second of right ascension (J2000) 11 A1 --- DE- Sign of declination (J2000) 12- 13 I2 deg DEd Degree of declination (J2000) 15- 16 I2 arcmin DEm Arcminute of declination (J2000) 18- 19 I2 arcsec DEs Arcsecond of declination (J2000) 21- 25 I5 km/s cz ? Velocity measurement 27- 28 I2 km/s e_cz ? Error in cz 30- 34 A5 --- r_cz Reference for cz (1) 36- 40 F5.2 mag Rcmag Cousins R band magnitude (2) 42- 48 F7.3 mJy S1.4GHz The 1.4GHz flux density 50 A1 --- f_S1.4GHz [c] Flag on S1.4GHz (3) 52- 56 F5.3 mJy e_S1.4GHz Error in S1.4GHz 58- 60 F3.1 arcsec Sep ? Angular separation with associated galaxy 62 A1 --- f_Sep [a] Indicates extended radio galaxy (ID = A, B, C, I; see Figs. 2-5) 64- 73 A10 --- ID Identification (4) 75- 78 A4 --- Class Classification (5) 80- 82 A3 --- f_Class [a-f, ] Flag on Class (6)
Note (1): When both KPNO and MX spectra were available, the velocities are combined through weighting by their errors, as follows: K = Kitt Peak data; M = MX data; B = BLC02 velocity; f = Cross-correlation velocity; e = Emission-line velocity. Note (2): Calculated for the Gunn-Oke aperture and has an associated error of ≲0.05mag. Note (3): c: See Fig. 6. The reported flux is only that associated directly with the galaxy; significantly more flux is associated with the ultra-steep-spectrum source. Note (4): Identification acronyms are: [BF76] = Bridle & Folamont, 1976A&A....52..107B [RMS94] = Rottgering et al., 1994ApJ...436..654R Note (5): Determined from the galaxy spectra, as: SF = Star-forming galaxy; AGNl = AGN with a LINER spectrum; AGNo = AGN with absorption-line spectrum, sometimes with weak [NII] emission. Note (6): Additional notes, with the following meaning: a = Potential cluster radio galaxy. b = Background radio galaxy. c = Foreground radio galaxy. d = See Fig. 10. e = Cluster radio galaxy, magnitude fainter than formal limit. f = As a head-tail radio galaxy (see Fig. 3), this galaxy may safely be considered an AGN.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 16-Oct-2003
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