Linking galaxy structural properties and star formation activity to black hole activity with IllustrisTNG

Mélanie Habouzit*, Shy Genel, Rachel S. Somerville, Dale Kocevski, Michaela Hirschmann, Avishai Dekel, Ena Choi, Dylan Nelson, Annalisa Pillepich, Paul Torrey, Lars Hernquist, Mark Vogelsberger, Rainer Weinberger, Volker Springel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

Abstract

We study the connection between active galactic nuclei (AGN) and their host galaxies through cosmic time in the large-scale cosmological IllustrisTNG simulations. We first compare BH properties, i.e. the hard X-ray BH luminosity function, AGN galaxy occupation fraction, and distribution of Eddington ratios, to available observational constraints. The simulations produce a population of BHs in good agreement with observations, but we note an excess of faint AGN in hard X-ray (L-rm xsim 10 43-44, rm erg/s), and a lower number of bright AGN (L-rm xgt 10 44 , rm erg/s), a conclusion that varies quantitatively but not qualitatively with BH luminosity estimation method. The lower Eddington ratios of the 10 9, rm M-odot BHs compared to observations suggest that AGN feedback may be too efficient in this regime. We study galaxy star formation activity and structural properties, and design sample-dependent criteria to identify different galaxy types (star-forming/quiescent, extended/compact) that we apply both to the simulations and observations from the candels fields. We analyse how the simulated and observed galaxies populate the specific star formation rate - stellar mass surface density diagram. A large fraction of the z = 0 M-star geqslant 10 11, rm M-odot quiescent galaxies first experienced a compaction phase (i.e. reduction of galaxy size) while still forming stars, and then a quenching event. We measure the dependence of AGN fraction on galaxies' locations in this diagram. After correcting the simulations with a redshift and AGN luminosity-dependent model for AGN obscuration, we find good qualitative and quantitative agreement with observations. The AGN fraction is the highest among compact star-forming galaxies (16-20 rm per cent at z 1/4 1.5-2), and the lowest among compact quiescent galaxies (6-10 rm per cent at z 1/4 1.5-2).

Original languageEnglish
Pages (from-to)4413-4443
Number of pages31
JournalMonthly Notices of the Royal Astronomical Society
Volume484
Issue number4
DOIs
StatePublished - 21 Apr 2019

Bibliographical note

Publisher Copyright:
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.

Keywords

  • galaxies: evolution
  • galaxies: formation
  • methods: numerical

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