Résumé / Abstract Journal-club_Univers

Journal-club Univers / Journal-club Universe

« How does the cosmic web impact assembly bias? »

Marcello Musso
postdoc - Institut d'Astrophysique de Paris (Paris, France)

The mass, accretion rate and formation time of dark matter haloes near
proto-filaments (identified as saddle points of the potential) are
analytically predicted using a conditional version of the excursion set
approach in its so-called "upcrossing" approximation. The model predicts
that at fixed mass, mass accretion rate and formation time vary with
orientation and distance from the saddle, demonstrating that assembly bias
is indeed influenced by the tides imposed by the cosmic web. Starved, early
forming haloes of smaller mass lie preferentially along the main axis of
filaments, while more massive and younger haloes are found closer to the
nodes. Distinct gradients for distinct tracers such as typical mass and
accretion rate occur because the saddle condition is anisotropic, and
because the statistics of these observables depend on both the conditional
means and their covariances. The theory is extended to other critical points
of the potential field. The response of the mass function to variations of
the matter density field (the so-called large scale bias) is computed, and
its trend with accretion rate is shown to invert along the filament. The
signature of this model should correspond at low redshift to an excess of
reddened galactic hosts at fixed mass along preferred directions, as
recently reported in spectroscopic and photometric surveys and in
hydrodynamical simulations. The anisotropy of the cosmic web emerges
therefore as a significant ingredient to describe jointly the dynamics and
physics of galaxies, e.g. in the context of intrinsic alignments or
morphological diversity.
mardi 19 septembre 2017 - 11:15
Salle 281, Institut d'Astrophysique
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