Assembly bias evidence in close galaxy pairs

I. Ferreras*, A. M. Hopkins, C. Lagos, A. E. Sansom, N. Scott, S. Croom, S. Brough

*Corresponding author for this work

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The growth channel of massive galaxies involving mergers can be studied via close pairs as putative merger progenitors, where the stellar populations of the satellite galaxies will be eventually incorporated into the massive primaries. We extend our recent analysis of the GAMA-based sample of close pairs presented in Ferreras et al. to the general spectroscopic data set of SDSS galaxies (DR14), for which the high S/N of the data enables a detailed analysis of the differences between satellite galaxies with respect to the mass of the primary galaxy. A sample of approximately 2000 satellites of massive galaxies is carefully selected within a relatively narrow redshift range (0.07<z<0.14). Two main parameters are considered as major drivers of the star formation history of these galaxies, namely: The stellar velocity dispersion of the satellite (σ), as a proxy of 'local' drivers, and the ratio between the stellar mass of the satellite and the primary, μ = MSAT/MPRI, meant to serve as an indicator of environment. Consistently with the independent, GAMA-based work, we find that satellites around the most massive primaries appear older, at fixed velocity dispersion, than satellites of lower mass primaries. This trend is more marked in lower mass satellites (σ ∼ 100 km s¯¹), with SSPequivalent age differences up to ∼0.5Gyr, and can be interpreted as a one-halo assembly bias, so that satellites corresponding to smaller values of μ represent older structures, akin to fossil groups.

Original languageEnglish
Pages (from-to)435-443
Number of pages9
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - Jul 2019

Bibliographical note

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 487, Issue 1, July 2019, Pages 435–443, Copyright 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


  • Galaxies: Evolution
  • Galaxies: Formation
  • Galaxies: Interactions
  • Galaxies: Stellar content


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