KiDS DR4 bright galaxy catalog

The catalog contains galaxies flux-limited to r<20 mag, selected from the Kilo-Degree Survey Data Release 4. The highly pure and complete dataset covers ~1000 deg² and contains about 1 million galaxies after artifact masking. Each galaxy has an associated photometric redshift, determined with the supervised machine learning neural network algorithm implemented in the ANNz2 software (Sadeh et al. 2016). The photo-zs are calibrated on Galaxy And Mass Assembly (GAMA) spectroscopy and use 9-band ugriZYJHK_s photometry available in KiDS.

In addition to the photo-z dataset, we also release a catalog of physical properties of KiDS DR4 bright galaxies, derived with LePhare (Arnouts et al. 1999; Ilbert et al. 2006). These include estimates of absolute luminosities, stellar masses and star formation rates.

Catalog format

Photometric redshift catalog: KiDS_DR4_brightsample.fits (85 MB)

Columns contained in the photometric redshift catalog:

Column nameDescription
ID Source identifier from the KiDS DR4 catalog (ESO ID)
RAJ2000 Centroid sky position right ascension (J2000)
DECJ2000Centroid sky position declination (J2000)
MAG_AUTO_calibZero-point calibrated and extinction-corrected Kron-like elliptical aperture magnitude in the r band; MAG_AUTO_calib = MAG_AUTO + DMAG – EXTINCTION_R
MAGERR_AUTORMS error for MAG_AUTO
zphot_ANNz2photometric redshift derived with ANNz2
MASK9-band mask information
maskedbinary flag, set to 0 for unmasked and to 1 for masked objects. Use masked == 0 for the default selection

 

Catalog of physical galaxy properties: KiDS_DR4_brightsample_LePhare.fits (246 MB)

Columns contained in the galaxy properties catalog:

Column nameDescription
ID Source identifier from the KiDS DR4 catalog (ESO ID)
RAJ2000 Centroid sky position right ascension (J2000)
DECJ2000Centroid sky position declination (J2000)
K_COR_xThe K-correction for the x-band
MAG_ABS_xThe absolute magnitude in the x-band
MABS_FILTxThe filter that is used for reference when computing the MABS
CONTEXTA Bit-flag which shows which filters contained photometry used in the fitting process. See Note 1.
REDSHIFTThe redshift values used for the stellar mass computation, in this case photo-zs derived with ANNz2
MASS_MEDThe median of the galaxy template stellar mass PDF measured by LePHARE. See Note 2 and Note 3.
MASS_INFThe lower-limit on the stellar mass from the galaxy mass PDF (68% confidence level)
MASS_SUPThe upper-limit on the stellar mass from the galaxy mass PDF (68% confidence level)
MASS_BESTThe best-fit stellar mass estimated by LePHARE. Use this column as the stellar mass, but make sure to apply the fluxscale correction (see Note 4)
SFR_INFThe lower-limit on the star formation rate from the galaxy SFR PDF (68% confidence level)
SFR_SUPThe lower-limit on the star formation rate from the galaxy SFR PDF (68% confidence level)
SFR_BESTBest-fit Star Formation Rate (SFR) estimated by LePHARE.

 

Note 1. CONTEXT examples: if 9-band information the bit flag is:
111111111=1+2+4+8+16+32+64+128+256=511;
if missing Z-band, then the bit flag is:
111101111=1+2+4+8+0+32+64+128+256=495
Note 2. The galaxies with MASS_MED == -99 were best-fit by a non-galaxy template, but the MASS_BEST value still shows the best fitting galaxy template mass for them, nonetheless.
Note 3. All the 'MASS' quantities stand for log10(M*/MSun).
Note 4. Fluxscale correction: Because the GAaP photometry only measures the galaxy magnitude within a specific aperture size, the stellar mass should be corrected using a "fluxscale" parameter, which is the ratio of AUTO and GAaP fluxes:
log10(fluxscale) = (MAG_GAAP_r −MAG_AUTO)/2.5 (1)
The 'total' stellar mass in then
M_TOT = M_BEST + log10(fluxscale) (2)
Similarly, also absolute magnitudes need corrections if 'total' measurements are required:
MAG_ABS_X,total = MAG_ABS_X −2.5 log10(fluxscale) (3)
All the LePhare quantities are computed assuming h = 0.7, and the estimated stellar masses are assumed to have a dependence on h dominated by the h-2 scaling of luminosities.
Therefore, if other Hubble constant value is used, the logarithmic stellar mass in Eq. (2) needs to be corrected by −2 log10(h/0.7), while the absolute magnitudes in Eq. (3) need to have 5log10(h/0.7) added.

Acknowledgements

If you use any of these data, please cite Bilicki et al. (2021, A&A in press, DOI:10.1051/0004-6361/202140352, arXiv:2101.06010) and include the KiDS DR4 acknowledgments.

Contact

bilicki[at]cft[dot]edu[dot]pl