leda Compilation of photometry

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This catalogue (table a107 in the database) presents the compilation of apparent fluxes (magnitudes) of galaxies. They are collected from the litterature and from surveys and are not corrected for Galactic extinction or for any other effect.

As a short introduction, see this article on astronomical magnitude systems (by Wirth) and this one on magnitude of galaxies (from NED).
Read the review article Standard Photometric Systems (Bessell 2005), and consult the Asiago Database on Photometric Systems (Munary) and the General Catalogue of Photometric Data (Mermillod).

Some other resources:
Magnitude System and Color Conversion Formulas (Seiichi Yoshida)
Conversions between Johnson and AB magnitudes: Frei and Gunn 1995
Conversions between Vega and AB magnitudes: Blanton et al., Astronomical Journal 127, 2562-2578 (2005), eqs.(5))

In March 2006, the table counted 8.6 million measurements (in any color band) for 1.65 million galaxies.

Description of the fields

Field: mag

Magnitude with its uncertainty and quality flag in parentheses. The uncertainty flag (2) indicates a detection limit (the flux is fainter than the given value). Fluxes originally given in physical flux density are converted into AB magnitude (eg. magAB = -2.5 * log(flux/mJy) + 16.4 ).

Field: loga

Logarithm of aperture used for aperture photometry.
The diameter of the aperture is measured in 0.1 arcmin (e.g. logA=1 means that the aperture diameter is 1 arcmin)

Field: iso

Isophote: isophotal limiting surface brightness for isophotal magnitude in mag.arcsec-2

Field: bandname

Photometric Band. The definitions are given in the band_codes table:

The schema used to classify the bands follow the one of the Virtual Observatory (UCDs). For convenience and efficiency purpose the bands have an internal numerical code (normally not shown to the user) having the form 'ABnn', where the first digit 'A' corresponds to the first level of description of the band in the Virtual Observatory (eg. 'A=4' for 'Optical') and the second digit to the second level (eg. 'AB=41' for 'opt.U', U-Band). The last two digits 'nn' identify the actuall band-pass.

Field: tel

Telescope. Used for 21cm flux corrections during the homogenisation. The definitions are given in the "telescopes_codes" table:

Field: code_mag

Code for the type of magnitude as given in the"mag_codes" table:

Field: correction

The correction flag has the following meaning:
description of correction flag
0Direct (uncorrected) measurement
1HI observation corrected for beam filling factor
2Magnitude corrected for the Galactic extinction and k-correction

Field: quality

The quality flag has the following meaning:
description of quality flag
0regular measurement
1uncertain measurement, its weight is decreased by a factor 2 when computing the average value
2detection limit
3preliminary measurement, probably superseeded in a more recent publication, it is ignored unless no other measurement is available
4compilation, it is ignored unless no other measurement is available
9rejected measurement

HyperLeda Questions: leda@univ-lyon1.fr