J/A+AS/136/519 Mg2 indices for early-type galaxies (Golev+, 1999) ================================================================================ Central Mg_2_ indices for early-type galaxies. Golev V., Prugniel P., Simien F., Longhetti M. =1999A&AS..136..519G (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxy catalogs ; Abundances, peculiar Keywords: galaxies: elliptical and lenticular, cD - galaxies: fundamental parameters - galaxies: stellar content Abstract: We present 210 new measurements of the central absorption line-strength Mg_2_ index for 87 early-type galaxies drawn from the Prugniel & Simien (1996, Cat. ) sample. 28 galaxies were not observed before. The results are compared to measurements published previously as available in HYPERCAT, and rescaled to the Lick system. The mean individual internal error on these measurements is 0.009mag+/-0.003mag and the mean external error is 0.012mag+/-0.002mag for this series of measurements. These data are also available from HYPERCAT. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 65 210 Individual measurements table3.dat 56 7 Dataset parameters table4.dat 49 87 Mean corrected Mg_2_ -------------------------------------------------------------------------------- See also: http://www-obs.univ-lyon1.fr/hypercat/ : the HYPERCAT database J/A+AS/132/255 : A catalogue of Mg_2_ indices (Golev+ 1998) J/A+A/309/749 : Fundamental plane of early type galaxies (Prugniel+ 1996) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- Name *Normalized galaxy identifier 13 A1 --- Obj *[G] Object type flag 15- 16 I2 h RAh ? Right Ascension (1950) (hours) 17- 18 I2 min RAm ? Right Ascension (1950) (minutes) 19- 22 F4.1 s RAs ? Right Ascension (1950) (seconds) 23 A1 --- DE- ? Declination (1950) (sign) 24- 25 I2 deg DEd ? Declination (1950) (degrees) 26- 27 I2 arcmin DEm ? Declination (1950) (minutes) 28- 29 I2 arcsec DEs ? Declination (1950) (seconds) 31- 36 F6.3 mag Mg2 *Measured Mg2 index strength 37- 42 F6.3 mag e_Mg2 Uncertainty of Mg2 index strength 44- 50 A7 --- Data *Dataset acronym 52 I1 --- n_Mg2c *[0/4] Measurement status flag 54- 59 F6.3 mag Mg2c *Corrected Mg2 index strength 60- 65 F6.3 mag e_Mg2c Uncertainty on Mg2c 67-108 A42 --- Notes *Description -------------------------------------------------------------------------------- Note on Name: The Name has been adopted by descending the hierarchy: 1) NGC (Cat. ) 2) IC (Cat. ) 3) UGC (Cat. ) 4) PGC (Cat. ) Lyon-Meudon Extragalactic Database internal identifier, also acronimed PGC for numbers greater than 73097. The galaxy identifiers follow the rule already used in Prugniel & Simien, 1996, Cat. and in Prugniel et al. 1998, Cat. . Note on Obj: The type of the object (G=galaxy). Not usefull here, it is given only to follow the file format defined in , table1 Note on Mg2: The Mg_2-index in magnitudes, corrected for velocity dispersion. Note on Data: Dataset acronym which refers to the observational parameters in table3.dat Note on n_Mg2c: The status flag of Mg_2_ index measurement which means as follows: 0= regular measurement; 1= discrepant measurement. Note on Mg2c: The aperture corrected and zero-pointed value of the Mg2 index. Note on Notes: Descriptive notes. Not usefull here, kept only to follow the file format defined in Cat. , table1 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 A7 --- Data Dataset acronym 9 I1 --- Datc *[0] Correction method flag 11- 16 F6.2 arcsec Xaper *Aperture size in X direction 18- 23 F6.2 arcsec Yaper *Aperture size in Y direction 24- 29 F6.3 mag ExtError *Estimated external error 31- 36 F6.3 mag ZeroPoint *Zero-point correction 37- 42 F6.3 mag Scal *Rescaling factor of the internal error 45- 47 I3 --- Ndata *Number of measurements in dataset 50- 52 I3 --- Ncomp *Number of comparison measurements 54 I1 --- Hmgnf *[1] Homogenisation flag -------------------------------------------------------------------------------- Note on Datc: Flag for aperture correction of the dataset, which is always 0, i.e. no aperture correction. Kept for consistency with Cat. , table2 Note on Xaper and Yaper: The aperture sizes X x Y in arcsec. Note on ExtError: rms of the difference between the corrected measurements and the mean value for each galaxy. Note on ZeroPoint and Scal: The dataset mean zero-point correction (corrected catalogue - dataset average), the r.m.s. error on it, and the corresponding rescaling factor of the internal error of the dataset. Iteratively, for each galaxy in the catalog, the error-weighted average of Mg_2_ is computed using the internal error. Then the mean is determined as well as the rms residual for each dataset after summing over all galaxies. The mean residual gives the zero-point for the considered dataset, and its rms is an estimate of the external error. The comparison between the external error and the mean internal error allows to rescale the latter. Note on Ndata: The number of measurements reported in the dataset. Not always equal to the number of observed objects (there are datasets which include multiple measurements of one object). Note on Ncomp: The number of measurements used for comparison with the homogeneous system. Note on Hmgnf: Always 1, i.e. these measurements are rescaled to the homogeneous system of Mg_2_ values defined in Hypercat. Kept for consistency with Cat. , table2 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 8 A8 --- Name Normalized galaxy identifier 13- 14 I2 h RAh *Right ascension (1950) 15- 16 I2 min RAm Right ascension (1950) 17- 20 F4.1 s RAs Right ascension (1950) 21 A1 --- DE- Declination (1950) 22- 23 I2 deg DEd Declination (1950) 24- 25 I2 arcmin DEm Declination (1950) 26- 27 I2 arcsec DEs Declination (1950) 28- 35 F8.0 km/s RV *Flow-smoothed corrected velocity 37- 41 F5.3 mag Mg2 *Homogeneous Mg2 index strength 43- 47 F5.3 mag e_Mg2 Uncertainty of Mg2 index strength 49- 50 I2 --- n_Mg2 Number of individual measurements -------------------------------------------------------------------------------- Note on RAh: Sorted by increasing of R.A. Note on RV: The flow-smoothed velocity used for aperture correction (defined as the velocity of the cosmologic flow associated with the galaxy). It is determined iteratively by averaging the velocity of galaxies found in the neighbourhood of given galaxy. At each step the size of the neighbouring region (in radius on the sky and in velocity interval) is computed from the distribution of the galaxies grouped at the previous step. The source of velocities is HYPERCAT (in turn updated from LEDA). The flow-smoothed velocity is then corrected for the deviations from the linear flow assuming the three-component velocity field model (Great Attractor, Virgocentric infall and Local Group Anomaly) described in Faber & Burstein (1988, in: Motions of galaxies in the neighbourhood of the local group, p.115) and Burstein et al. (1989, in Large-scale motions in the nearby universe, p. 179). Note on Mg2: Mean homogeneous value of the Mg2 index. -------------------------------------------------------------------------------- Acknowledgements: Valeri Golev ================================================================================ (End) Patricia Bauer [CDS] 10-May-1999