Compilation of central stellar velocity dispersion
HyperLeda routinely compiles measurements of central velocity dispersions.
The first version, published as an Appendix to a paper by Prugniel and Simien (1996)
is regularly updated since this epoch. In December 2007, it contained
12858 velocity dispersions for 7601 objects and from 418 references (four times more than the initial version).
In 2013 it contained 25400 measurements for 17000 objects from 489 references.
The first version (1995) is still
from the CDS
(anonymous ftp 22.214.171.124), or can be accessed through VizieR
The compilation includes galaxies, star clusters (Galactic and extra-galactic), and galaxy clusters.
For galaxies, most of the measurements are from slit or fiber spectroscopy, the rest being
from IFU spectroscopy or from velocity determinations of individual stars (for nearby galaxies, essentially dwarf spheroidals).
Click on the column headers of the catalogue page to get more information about the fields.
The individual measurements for a given galaxy are combined together to produce an estimate of
the mean velocity dispersion within an aperture of 0.595 kpc.
This homogenization proceeds in three steps:
- An aperture corrections following the prescriptions of Jorgensen et al. (1995) is computed and applied, using the distance estimated from the flow smoothed velocity, as computed in Prugniel et al. (1999).
- The individual measurements and their quoted precision are rescaled to correct for systematics between different datasets. The coefficients for these corrections are determined from a general inter-comparisons between all the datasets.
- The corrected measurements are combined, using a weighted average.
The mean homogenized dispersion is presented together with the original values in the catalogue page, and it is included in the Leda catalogue.
It is used to derive the distance through the Faber-Jackson and Fundamental Plane relations.
Dataset parameters table
The dataset parameters table contains the information needed to compute the homegenized mean velocity dispersion within an aperture of 0.595 kpc. The fields in this table are:
Data system (internal code)
Aperture correction (0: Uncorrected)
Data scaling factor
Error scaling factor (rescaled error = raw_error * scaling factor)
Intrumental resolution km/sec (FWHM), in km/s
Spectral dispersion (when the resolution is not stated), in Angstrom/mm
Width of the aperture extraction, in arcsec
Height of the aperture extraction, in arcsec