Galactic accretion and the outer structure of galaxies in the CDM model

By A. Cooper, R. D’Souza, G. Kauffmann, Jing Wang, M. Boylan-Kolchin, Qi Guo, Carlos S. Frenk, Simon D. M. White. 2013

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We have combined the semi-analytic galaxy formation model of Guo et al. (2011) with the particle-tagging technique of Cooper et al. (2010) to predict galaxy surface brightness profiles in a representative sample of ~1900 massive dark matter haloes (10^12--10^14 M_sol) from the Millennium II Lambda-CDM N-body simulation. Here we present our method and basic results focusing on the outer regions of galaxies, consisting of stars accreted in mergers. These simulations cover scales from the stellar haloes of Milky Way-like galaxies to the 'cD envelopes' of groups and clusters, and resolve low surface brightness substructure such as tidal streams. We find that the surface density of accreted stellar mass around the central galaxies of dark matter haloes is well described by a Sersic profile, the radial scale and amplitude of which vary systematically with halo mass (M_200). The total stellar mass surface density profile breaks at the radius where accreted stars start to dominate over stars formed in the galaxy itself. This break disappears with increasing M_200 because accreted stars contribute more of the total mass of galaxies, and is less distinct when the same galaxies are averaged in bins of stellar mass, because of scatter in the relation between M_star and M_200. To test our model we have derived average stellar mass surface density profiles for massive galaxies at z~0.08 by stacking SDSS images. Our model agrees well with these stacked profiles and with other data from the literature, and makes predictions that can be more rigorously tested by future surveys that extend the analysis of the outer structure of galaxies to fainter isophotes. We conclude that it is likely that the outer structure of the spheroidal components of galaxies is largely determined by collisionless merging during their hierarchical assembly

Subfields: Astronomy and Astrophysics, Computer Vision and Pattern Recognition, Instrumentation

View Paper: https://www.semanticscholar.org/paper/6ee998c6cde2a92b6c94265088860d089db28895

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Citations in the corpus

Ultra–Low Surface Brightness Imaging with the Dragonfly Telephoto Array (2014, background): “…features should have lifetimes of up to half the Hubble time, so every large galaxy in the Universe is expected to live in an extended, irregular tidal debris field (e.g., Dubinski et al. 1996; Moore et al. 1999; Naab et al. 2007; Kazantzidis et al. 2008; Cooper et al. 2010, 2013). ar X iv :1 40 1.”
The stellar mass assembly of galaxies in the Illustris simulation: growth by mergers and the spatial distribution of accreted stars (2015, methodology): “…2006; Zolotov et al. 2009, 2010; Tissera, White & Scannapieco 2012; Tissera et al. 2013, 2014; Dubois et al. 2013; Pillepich, Madau & Mayer 2015; Hirschmann et al. 2015), or using N -body simulations along with particle tagging techniques (Cooper et al. 2010, 2013, 2015; Rashkov et al. 2012).”