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J/A+A/482/419   ESO Distant Cluster Survey, EDisCS. II   (Milvang-Jensen+, 2008)

Spectroscopy of clusters in the ESO distant cluster survey (EDisCS). II. Redshifts, velocity dispersions, and substructure for clusters in the last 15 fields. Milvang-Jensen B., Noll S., Halliday C., Poggianti B.M., Jablonka P., Aragon-Salamanca A., Saglia R.P., Nowak N., von der Linden A., De Lucia G., Pello R., Moustakas J., Poirier S., Bamford S.P., Clowe D.I., Dalcanton J.J., Rudnick G.H., Simard L., White S.D.M., Zaritsky D. <Astron. Astrophys. 482, 419 (2008)> =2008A&A...482..419M
ADC_Keywords: Clusters, galaxy ; Redshifts Keywords: galaxies: clusters: general - galaxies: distances and redshifts - galaxies: evolution Abstract: We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise for spectra from tilted slits. Redshifts for individual galaxies are presented and redshifts and velocity dispersions are presented for 21 galaxy clusters. For the 9 clusters with at least 20 spectroscopically confirmed members, we present the statistical significance of the presence of substructure obtained from the Dressler-Shectman test, and substructure is detected in two of the clusters. Together with data from our previous paper, spectroscopy and spectroscopic velocity dispersions are now available for 26 EDisCS clusters with redshifts in the range 0.40-0.96 and velocity dispersions in the range 166-1080km/s. Description: Spectroscopic observations obtained using VLT/FORS2 are presented for objects in 14 survey fields of the ESO Distant Cluster Survey (EDisCS). The fields contain galaxy clusters at z=0.40-0.96. The objects in the catalogues are either galaxies (which can be cluster members or fields galaxies), foreground stars, or objects for which no redshift could be determined. For a 15th field (1122.9-1136) which is part of the paper, no data are published, since very little data was obtained. We present tables of RA and DE positions for an equinox of 2000 (J2000, epoch 2001), I-band magnitudes for an aperture of radius 1", spectroscopic redshifts for objects in the 14 fields, and cluster membership and targeting flags to indicate whether the object is a cluster member and/or was targeted to be a cluster member respectively. The 'main' table contains one entry per unique object, and this is the table people normally should use. The 'supp' table contains possible extra redshifts obtained. If an object was observed N times, the best redshift (decided from a number of rules) is put in 'main' and the remaining N-1 redshifts are put in 'supp'. Cl 1238.5-1144 has no data in supp.dat file. The data tables have been prepared so that they can be read both using tools that expect data columns separated by white space (e.g. the UNIX tool awk) and tools that expect things to be at fixed character/byte locations in the file (e.g. the UNIX tool cut). The contents of the data tables are fully described in Sect. 4.3 of the paper (including the sample data in Table 4 in the paper). Some of the salient features are repeated as Notes. Finally, note that spectroscopic observations for 5 other EDisCS fields (1040.7-1155, 1054.4-1146, 1054.7-1245, 1216.8-1201 and 1232.5-1250 ) were presented in a previous paper (Halliday et al., 2004, Cat. J/A+A/427/397) but note that the format of the published data tables for that paper is not fully identical to the format used for this paper. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table5.dat 42 21 Cluster redshifts and velocity dispersions main.dat 80 1319 Redshift data for 14 fields, main catalog supp.dat 80 66 Redshift data for 13 fields, supplementary data
See also: J/ApJS/137/117 : Las Campanas Distant Cluster Survey (LCDCS) (Gonzalez+, 2001) J/A+A/427/397 : Redshifts of 5 EDisCS galaxy clusters (Halliday+, 2004) J/A+A/444/365 : ESO Distant Cluster Survey, EDisCS (White+, 2005) Byte-by-byte Description of file: table5.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [cl] 3- 14 A12 --- Cluster Cluster designation (HHMM+DDMMa, J2000) 16- 21 F6.4 --- z Redshift 23- 25 I3 km/s sigma Cluster dispersion velocity 27- 29 I3 km/s E_sigma Error on sigma (upper limit) 31- 33 I3 km/s e_sigma Error on sigma (lower limit) 35- 36 I2 --- Nm0 Number of (unique) cluster members having "secure" redshifts (1) 38- 39 I2 --- Nm01 Number of (unique) cluster members having "secure" or "secure but with larger uncertainties" redshifts (1) 41- 42 I2 --- Nm012 Number of (unique) cluster members having "secure", "secure but with larger uncertainties" or "not secure" redshifts (1)
Note (1): "secure" redshifts: redshifts without uncertainty flag "secure but with larger uncertainties" redshifts: redshifts with 1-colon uncertainty flag "not secure" redshifts: redhsifts with 2-colon uncertainty flag
Byte-by-byte Description of file: main.dat supp.dat
Bytes Format Units Label Explanations
1- 11 A11 --- Field Field designation 13- 33 A21 --- ID EDisCS name, EDCSNJHHMMSSs-DDMMSSs (1) 34 A1 --- --- [:] 35 A1 --- m_ID [AB] Multiplicity index on ID 37- 38 I2 h RAh Right Ascension J2000, Epoch 2001 (hours) 40- 41 I2 min RAm Right Ascension J2000 (minutes) 43- 47 F5.2 s RAs Right Ascension J2000 (seconds) 49 A1 --- DE- Declination (sign) 50- 51 I2 deg DEd Declination J2000, Epoch 2001 (degrees) 53- 54 I2 arcmin DEm Declination J2000 (minutes) 56- 59 F4.1 arcsec DEs Declination J2000 (seconds) 61- 66 F6.3 mag Imag ?=99.99 I-band Magnitude for aperture radius 1" (2) 68- 73 F6.4 --- z ?=9.9999 Spectroscopic redshift (z=0.0000 corresponds to stars) (3) 74- 75 A2 --- u_z [: ] Uncertainty flag on z (4) 77- 78 A2 --- Mem Membership flag (5) 80 I1 --- Tar [1-4] Targeting flag (6)
Note (1): Two features should be noted about the object IDs: * The 5th character in the ID can take on the following 3 values: N = Object in the photometric catalogues published in White et al., 2005, Cat. J/A+A/444/365, e.g. EDCSNJ1018552-1209405. X = Object from the old catalogue not found in the new catalogue, e.g. EDCSXJ1038015-1242187. Y = Object non-targeted (i.e. serendipitously-observed), neither existed in the old nor in the new catalogues, e.g. EDCSYJ1037449-1246098. We note that the EDCSXJ and the EDCSYJ objects are not found in the published photometric catalogues (e.g. the optical ones from White et al., 2005, Cat. J/A+A/444/365), since these catalogues are the new ones, but these objects can still be used for purposes that only use the redshift (and position), such as determining cluster velocity dispersions and substructure. * Most IDs are 21 characters long, but some are 23 characters long, where the last 2 characters are ':A' or ':B', which is used in the case where a single object from the photometric catalogue (White et al., 2005, Cat. J/A+A/444/365) turned out to be 2 physical objects in the obtained spectrum, (partially) superposed on the plane of the sky. e.g. EDCSNJ1018513-1209019:A and EDCSNJ1018513-1209019:B. Note (2): For the magnitude, a value of 99.99 signifies NULL, i.e. that no magnitude is available (this only happens for object with Y-IDs, EDCSYJHHMMSSs+DDMMSSs). Magnitudes are given with 3 decimals, except for objects with X-IDs (EDCSXJHHMMSSs+DDMMSSs), for which 2 decimals are given. Note (3): For the spectroscopic redshift a value of 9.9999 signifies NULL, i.e. that no spectroscopic redshift is available. A value of 0.0000 corresponds to stars. In this paper, spectroscopic redshifts are always given with 4 decimals. Note (4): The uncertainty on the spectroscopic redshift is: : = (i.e. one colon ): secure redshift but with larger uncertainty :: = (i.e. two colons): doubtful redshift blank = (i.e. no colons): secure redshift Note (5): The cluster membership flag can take on the following values: 1 = members of the main cluster 1a = members of the secondary "a" cluster 1b = members of the secondary "b" cluster 0 = field galaxies - = stars and objects without a determined redshift Note that the uncertainty on the spectroscopic redshift should be considered when using the cluster membership flag. Note (6): The targeting flag can take on the following values: 1 = Targeted as a candidate cluster member 2 = Targeted as a field galaxy (filling object) 3 = Serendipitous (not targeted) 4 = Targeted as a star to aid acquisition and to measure seeing
Acknowledgements: Bo Milvang-Jensen, milvang(at)
(End) Bo Milvang-Jensen [Dark Cosmology Centre, Denmark] 24-Apr-2008
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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