Bright galaxy sample in the Kilo-Degree Survey Data Release 4: selection, photometric redshifts, and physical properties

Utrecht University Repository (Utrecht University)

Abstract

We present a bright galaxy sample with accurate and precise photometric redshifts (photo-zs), selected using $ugriZYJHK_\mathrm{s}$ photometry from the Kilo-Degree Survey (KiDS) Data Release 4 (DR4). The highly pure and complete dataset is flux-limited at $r<20$ mag, covers $\sim1000$ deg$^2$, and contains about 1 million galaxies after artifact masking. We exploit the overlap with Galaxy And Mass Assembly (GAMA) spectroscopy as calibration to determine photo-zs with the supervised machine learning neural network algorithm implemented in the ANNz2 software. The photo-zs have mean error of $|\langle δz \rangle| \sim 5 \times 10^{-4}$ and low scatter (scaled mean absolute deviation of $\sim 0.018(1+z)$), both practically independent of the $r$-band magnitude and photo-z at $0.05 < z_\mathrm{phot} < 0.5$. Combined with the 9-band photometry, these allow us to estimate robust absolute magnitudes and stellar masses for the full sample. As a demonstration of the usefulness of these data we split the dataset into red and blue galaxies, use them as lenses and measure the weak gravitational lensing signal around them for five stellar mass bins. We fit a halo model to these high-precision measurements to constrain the stellar-mass--halo-mass relations for blue and red galaxies. We find that for high stellar mass ($M_\star>5\times 10^{11} M_\odot$), the red galaxies occupy dark matter halos that are much more massive than those occupied by blue galaxies with the same stellar mass. The data presented here are publicly released via the KiDS webpage at http://kids.strw.leidenuniv.nl/DR4/brightsample.php.

Authors 19

1. Maciej Bilicki

   Polish Academy of Sciences

   Affiliation as printed

   Polish Academy of Sciences (PAN)

2. Andrej Dvornik
   Affiliation as printed

   German Centre for Cosmological Lensing

3. Henk Hoekstra Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands 0000-0001-5434-5942

4. Angus H. Wright
   Affiliation as printed

   German Centre for Cosmological Lensing

5. Nora Elisa Chisari

   Utrecht University

   Affiliation as printed

   Utrecht University

6. Mohammadjavad Vakili Aachen

   Leiden University

   Affiliation as printed

   Leiden University

7. Marika Asgari
   Affiliation as printed

   School of Physics and Astronomy

8. Benjamin Giblin
   Affiliation as printed

   School of Physics and Astronomy

9. Catherine Heymans

   University of Edinburgh

   Affiliation as printed

   University of Edinburgh

10. Hendrik Hildebrandt
    Affiliation as printed

    German Centre for Cosmological Lensing

11. Benne Willem Holwerda

    University of Louisville

    Affiliation as printed

    University of Louisville, Department of Physics and Astronomy, , 102 Natural Sciences Building, Louisville, KY 40292, USA

12. Andrew Hopkins

    Australian Astronomical Optics

    Affiliation as printed

    Australian Astronomical Optics

13. Harry Johnston

    Utrecht University

    Affiliation as printed

    Utrecht University

14. Arun Kannawadi

    Princeton University

    Affiliation as printed

    Princeton University

15. Konrad H. Kuijken Aachen Leiden Observatory

    Leiden University · Leiden Observatory

    Affiliation as printed

    Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden, The Netherlands 0000-0001-5434-5942

16. Szymon J. Nakoneczny

    National Centre for Nuclear Research

    Affiliation as printed

    National Centre for Nuclear Research (NCBJ)

17. Huanyuan Shan

    Shanghai Astronomical Observatory · University of Chinese Academy of Sciences

    Affiliation as printed

    CAS - Shanghai Astronomical Observatory

    UCAS (University of Chinese Academy of Sciences)

18. Alessandro Sonnenfeld Aachen

    Leiden University

    Affiliation as printed

    Leiden University

19. Edwin A. Valentijn
    Affiliation as printed

    Astronomy