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arXiv:1601.00375 [astro-ph.GA]AbstractReferencesReviewsResources

Evolution of dwarf spheroidal satellites in the common surface-density dark halos

Yusuke Okayasu, Masashi Chiba

Published 2016-01-04Version 1

We investigate the growth histories of dark matter halos associated with dwarf satellites in Local Group galaxies and the resultant evolution of the baryonic component. Our model is based on the recently proposed property that the mean surface density of a dark halo inside a radius at maximum circular velocity $V_{\rm max}$ is universal over a large range of $V_{\rm max}$. Following that this surface density of 20 $M_{\odot}$~pc$^{-2}$ well explains dwarf satellites in the Milky Way and Andromeda, we find that the evolution of the dark halo in this common surface-density scale is characterized by the rapid increase of the halo mass assembled by the redshift $z_{\rm TT}$ of the tidal truncation by its host halo, at early epochs of $z_{\rm TT} \gsim 6$ or $V_{\rm max} \lsim 22$ km~s$^{-1}$. This mass growth of the halo is slow at lower $z_{\rm TT}$ or larger $V_{\rm max}$. Taking into account the baryon content in this dark halo evolution, under the influence of the ionizing background radiation, we find that the dwarf satellites are divided into roughly two families: those with $V_{\rm max} \lsim 22$ km~s$^{-1}$ having high star formation efficiency and those with larger $V_{\rm max}$ having less efficient star formation. This semi-analytical model is in good agreement with the high-resolution numerical simulation for galaxy formation and with the observed star formation histories for Fornax and Leo~II. This suggests that the evolution of a dark halo plays a key role in understanding star formation histories in dwarf satellites.

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