Studying galaxy troughs and ridges using weak gravitational lensing with the Kilo-Degree Survey

Margot M. Brouwer*, Vasiliy Demchenko, Joachim Harnois-Déraps, Maciej Bilicki, Catherine Heymans, Henk Hoekstra, Konrad Kuijken, Mehmet Alpaslan, Sarah Brough, Yan Chuan Cai, Marcus V. Costa-Duarte, Andrej Dvornik, Thomas Erben, Hendrik Hildebrandt, Benne W. Holwerda, Peter Schneider, Cristóbal Sifón, Edo van Uitert

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We study projected underdensities in the cosmic galaxy density field known as 'troughs', and their overdense counterparts, which we call 'ridges'. We identify these regions using a bright sample of foreground galaxies from the photometric Kilo-Degree Survey (KiDS), specifically selected to mimic the spectroscopic Galaxy And Mass Assembly survey. Using background galaxies from KiDS, we measure the weak gravitational lensing profiles of the troughs/ridges. We quantify the amplitude of their lensing strength A as a function of galaxy density percentile rank P and galaxy overdensity δ, and find that the skewness in the galaxy density distribution is reflected in the total mass distribution measured by weak lensing. We interpret our results using the mock galaxy catalogue from the Marenostrum Institut de Ciències de l'Espai (MICE) simulation, and find a good agreement with our observations. Using signal-to-noise weights derived from the Scinet LIghtCone Simulations (SLICS) mock catalogue we optimally stack the lensing signal of KiDS troughs with an angular radius θA = (5, 10, 15, 20) arcmin, resulting in (16.8, 14.9, 10.13, 7.55) σ detections. Finally, we select troughs using a volume-limited sample of galaxies, split into two redshift bins between 0.1 < z < 0.3. For troughs/ridges with transverse comoving radius RA = 1.9 h 70 -1 Mpc, we find no significant difference in the comoving excess surface density as a function of P and δ between the low- and high-redshift sample. Using the MICE and SLICS mocks we predict that trough and ridge evolution could be detected with gravitational lensing using deeper and wider lensing surveys, such as those from the Large Synoptic Survey Telescope and Euclid.

Original languageEnglish
Pages (from-to)5189-5209
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Early online date24 Sep 2018
Publication statusPublished - 21 Dec 2018


  • Cosmology: dark matter
  • Galaxies: distances and redshifts
  • Gravitational lensing: weak -methods: statistical
  • Large-scale structure of the Universe
  • Surveys


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