GAMA DR2 galaxy shapes in KiDS g-, r- and i-band data
These catalogues contain galaxy shape information for galaxies in the GAMA DR2 release as imaged by KiDS DR3 in the g-, r- and i-band data. Shapes are obtained with the DEIMOS shape measurement method (Melchior et al. 2011) using a weighting matching procedure for each galaxy’s centroid and ellipticity. The radial weighting applied is tied to each galaxy’s isophotal radius that lies 3-sigma above the background noise level. On average, this corresponds to about twice the half-light radius. For more information see Georgiou et al. (2019, A&A 622, A90).
For the r-band shapes, we also release catalogues with varying this radial weighting to some multiple of this isophotal radius. For more information see Georgiou et al. (2019, A&A 628, A31).
Note that the ellipticity components of the catalogues are not corrected for multiplicative bias. To correct for this, see Table 1 in the both papers referenced above.
Catalog format
Catalogues in different filters:
g-band shape catalogue: DEIMOS_GAMA_gband_shape_catalogue_size_1.0.fits
i-band shape catalogue: DEIMOS_GAMA_iband_shape_catalogue_size_1.0.fits
r-band shape catalogue: DEIMOS_GAMA_rband_shape_catalogue_size_1.0.fits
r- band catalogues for different radial weighting, a multiple of the isophotal radius of each galaxy at 3-sigma above the background (r_iso):
0.5*r_iso shape catalogue: DEIMOS_GAMA_rband_shape_catalogue_size_0.5.fits
1.25*r_iso shape catalogue: DEIMOS_GAMA_rband_shape_catalogue_size_1.25.fits
1.5*r_iso shape catalogue: DEIMOS_GAMA_rband_shape_catalogue_size_1.5.fits
2.0*r_iso shape catalogue: DEIMOS_GAMA_rband_shape_catalogue_size_2.0.fits
| Column name | Description |
|---|---|
| CATAID | ID of the galaxy in the GAMA catalogue. |
| Xpos_DEIMOS | X-centroid of the galaxy in the KiDS image, measured by DEIMOS (in pixels). |
| Ypos_DEIMOS | Y-centroid of the galaxy in the KiDS image, measured by DEIMOS (in pixels). |
| e1 | Ellipticity component of the third flattening in the x-axis. |
| e2 | Ellipticity component of the third flattening in the y-axis. |
| IsoRadius | This is sqrt(ISOAREA_IMAGE/pi) where ISOAREA_IMAGE is the number of pixels of the isophote measured at 3-sigma above the background. It is also the starting weight function size of DEIMOS. |
| SN_DEIMOS | Signal-to-Noise ratio measured by DEIMOS (using the weight function). |
| flag_DEIMOS | Flagging of DEIMOS: use "0000" for good measurements. |
| R0 | Resolution of the galaxy compared to the PSF. The closer to 1 the more resolved the galaxy. |
| e1psf | Ellipticity of the PSF model at the galaxy's position. |
| e2psf | Ellipticity of the PSF model at the galaxy's position. |
| Qij | Deweighted moments of the galaxy as measured by DEIMOS. |
| errQji | Error on the moments measurement. |
| Tile | Corresponding KiDS astrowise tile used for the galaxy’s shape measurement. |
| Mean_weight | Mean value of the weight image on a small stamp around the galaxy. Used to decide which measurement is best when galaxies have been imaged more than once. |
| MASK | Value of the AstroWise mask image on the position of the measured galaxy. A value of 0 means no masking is applied. See de Jong et al. 2017, Section 2.2.2 and table A.1. |
| RA_GAMA | Right ascension of the galaxy from the GAMA catalogue. |
| DEC_GAMA | Declination of the galaxy from the GAMA catalogue. |
Acknowledgements
If using any of the shape catalogue data, please cite Georgiou et al. (2019, A&A 622, A90) and Georgiou et al. (2019, A&A 628, A31).
Contact
c.georgiou[at]uu[dot]nl