The dependence of intrinsic alignment of galaxies on wavelength using KiDS and GAMA

Christos Georgiou, Harry Johnston, Henk Hoekstra, Massimo Viola, Konrad Kuijken, Benjamin Joachimi, Nora Elisa Chisari, Hendrik Hildebrandt, Arun Kannawadi

Research output: Contribution to journalArticleAcademicpeer-review


The outer regions of galaxies are more susceptible to the tidal interactions that lead to intrinsic alignments of galaxies. The resulting alignment signal may therefore depend on the passband if the colours of galaxies vary spatially. To quantify this, we measured the shapes of galaxies with spectroscopic redshifts from the GAMA survey using deep gri imaging data from the KiloDegree Survey. The performance of the moment-based shape measurement algorithm DEIMOS was assessed using dedicated image simulations, which showed that the ellipticities could be determined with an accuracy better than 1% in all bands. Additional tests for potential systematic errors did not reveal any issues. We measure a significant difference of the alignment signal between the g,r and i-band observations. This difference exceeds the amplitude of the linear alignment model on scales below 2 Mpc/h. Separating the sample into central/satellite and red/blue galaxies, we find that that the difference is dominated by red satellite galaxies.
Original languageEnglish
Article numberA90
Pages (from-to)1-15
Publication statusPublished - Feb 2019


  • astro-ph.CO
  • galaxies: evolution
  • large-scale structure of Universe
  • gravitational lensing: weak
  • cosmology: observations


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