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The diverse evolutionary paths of simulated high-$z$ massive, compact galaxies to $z = 0$ | | Sarah Wellons
; Paul Torrey
; Chung-Pei Ma
; Vicente Rodriguez-Gomez
; Annalisa Pillepich
; Dylan Nelson
; Shy Genel
; Mark Vogelsberger
; Lars Hernquist
; | | Date: |
8 Jul 2015 | | Abstract: | Massive quiescent galaxies at high redshift have been observed to have much
smaller physical sizes than their local counterparts. Several mechanisms have
been invoked to explain the strong evolution of galaxy size with redshift,
including progenitor bias, major and minor mergers, adiabatic expansion, and
renewed star formation. However, it is difficult to connect galaxy populations
between cosmological epochs to test these theories observationally. Herein, we
select a sample of 35 massive, compact galaxies ($M_*$ = 1-3 x $10^{11}$
M$_odot$, $M_*/R^{1.5}$ > $10^{10.5}$ M$_odot$/kpc$^{1.5}$) at z=2 in the
cosmological hydrodynamical simulation Illustris and trace them forward to z=0
to uncover how they evolve to the present day. By z=0, the original factor of 3
difference in stellar mass has spread to a factor of 20. The spread in dark
matter halo mass similarly increases from a factor of 5 to a factor of 40. The
compact galaxies’ evolutionary paths are diverse: about half acquire an ex-situ
envelope and exist as the core of a more massive descendant, 30% survive
undisturbed and gain very little mass, 15% are entirely consumed and destroyed
in a merger with a more massive galaxy, and the remainder are thoroughly mixed
by major mergers. Nearly all the galaxies grow in size as well as mass, so that
only about 10% of the z=2 compact galaxies still satisfy our compactness
criterion by z=0. The majority of the size growth is driven by the acquisition
of additional stellar mass at large radii through mergers and accretion. We
find a relationship between a galaxy’s z=0 stellar mass and its progenitors’
maximum past compactness: more massive galaxies are more likely to have had a
compact progenitor. However, this trend possesses significant dispersion which
precludes a direct linkage between massive galaxies at z=0 and compact galaxies
at z=2. (Abridged) | | Source: | arXiv, 1507.2291 | | Services: | Forum | Review | PDF | Favorites | |
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