J/A+AS/136/519 Mg2 indices for early-type galaxies (Golev+, 1999)
Central Mg2 indices for early-type galaxies.
Golev V., Prugniel P., Simien F., Longhetti M.
<Astron. Astrophys. Suppl. Ser. 136, 519 (1999)>
=1999A&AS..136..519G 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 Mg2 index for 87 early-type galaxies drawn from the
Prugniel & Simien (1996, Cat. J/A+A/309/749) 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 65 210 Individual measurements
table3.dat 56 7 Dataset parameters
table4.dat 49 87 Mean corrected Mg2
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See also:
http://www-obs.univ-lyon1.fr/hypercat/ : the HYPERCAT database
J/A+AS/132/255 : A catalogue of Mg2 indices (Golev+ 1998)
J/A+A/309/749 : Fundamental plane of early type galaxies (Prugniel+ 1996)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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Note on Name:
The Name has been adopted by descending the hierarchy:
1) NGC (Cat. VII/118)
2) IC (Cat. VII/118)
3) UGC (Cat. VII/26)
4) PGC (Cat. VII/119) 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. J/A+A/309/749 and in
Prugniel et al. 1998, Cat. J/A+AS/127/117.
Note on Obj:
The type of the object (G=galaxy). Not usefull here, it is given only
to follow the file format defined in J/A+AS/132/255, 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 Mg2 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. J/A+AS/132/255, table1
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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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
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Note on Datc:
Flag for aperture correction of the dataset, which is always 0,
i.e. no aperture correction.
Kept for consistency with Cat. J/A+AS/132/255, 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 Mg2 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 Mg2 values defined in Hypercat.
Kept for consistency with Cat. J/A+AS/132/255, table2
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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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
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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.
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Acknowledgements: Valeri Golev
(End) Patricia Bauer [CDS] 10-May-1999