Anisotropic Satellite Galaxy Quenching: A Unique Signature of Energetic Feedback by Supermassive Black Holes?
Juliana S. M.
Karp, Johannes U.
Lange, and Risa H.
Wechsler
Astrophysical Journal Letters, May 2023
"The quenched fraction of satellite galaxies is aligned with the
orientation of the halo’s central galaxy, such that on average,
satellites form stars at a lower rate along the major axis of
the central. This effect, called anisotropic satellite galaxy
quenching (ASGQ), has been found in observational data and
cosmological simulations. Analyzing the IllustrisTNG simulation,
Martı́n-Navarro et al. recently argued that ASGQ is caused
by anisotropic energetic feedback and constitutes “compelling
observational evidence for the role of black holes in regulating
galaxy evolution.” In this Letter, we study the causes of ASGQ
in state-of-the-art galaxy formation simulations to evaluate
this claim. We show that cosmological simulations predict that
on average, satellite galaxies along the major axis of the dark
matter halo tend to have been accreted at earlier cosmic times
and are hosted by subhalos of larger peak halo masses. As a
result, a modulation of the quenched fraction with respect to
the major axis of the central galaxy is a natural prediction of
hierarchical structure formation. We show that ASGQ is predicted
by the UniverseMachine galaxy formation model, a model without
anisotropic feedback. Furthermore, we demonstrate that even in
the IllustrisTNG simulation, anisotropic satellite accretion
properties are the main cause of ASGQ. Ultimately, we argue that
ASGQ is not a reliable indicator of supermassive black hole
feedback in galaxy formation simulations and, thus, should not
be interpreted as such in observational data."