THE DUAL ORIGIN OF STELLAR HALOS

By A. Zolotov, B. Willman, A. Brooks, Fabio Governato, C. Brook, David W. Hogg, Thomas R. Quinn, G. Stinson. 2009

238 citations recorded by the source corpus.

We investigate the formation of the stellar halos of four simulated disk galaxies using high-resolution, cosmological SPH + N-body simulations. These simulations include a self-consistent treatment of all the major physical processes involved in galaxy formation. The simulated galaxies presented here each have a total mass of ∼1012 M☉, but span a range of merger histories. These simulations allow us to study the competing importance of in situ star formation (stars formed in the primary galaxy) and accretion of stars from subhalos in the building of stellar halos in a ΛCDM universe. All four simulated galaxies are surrounded by a stellar halo, whose inner regions (r < 20 kpc) contain both accreted stars, and an in situ stellar population. The outer regions of the galaxies' halos were assembled through pure accretion and disruption of satellites. Most of the in situ halo stars formed at high redshift out of smoothly accreted cold gas in the inner 1 kpc of the galaxies' potential wells, possibly as part of their primordial disks. These stars were displaced from their central locations into the halos through a succession of major mergers. We find that the two galaxies with recently quiescent merger histories have a higher fraction of in situ stars (∼20%–50%) in their inner halos than the two galaxies with many recent mergers (∼5%–10% in situ fraction). Observational studies concentrating on stellar populations in the inner halo of the Milky Way will be the most affected by the presence of in situ stars with halo kinematics, as we find that their existence in the inner few tens of kpc is a generic feature of galaxy formation.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/a3210b7b9fa7a20944143385447ecfef0c3b259f

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Citations in the corpus

THE RELATIONSHIPS AMONG COMPACT STELLAR SYSTEMS: A FRESH VIEW OF ULTRACOMPACT DWARFS (2011, background): “These interpretations can be connected to a broad framework for different modes of galaxy assembly (e.g., Carollo et al. 2007; Zolotov et al. 2009; Forbes & Bridges 2010; Forbes et al. 2011; Oser et al. 2010; Arnold et al. 2011; Font et al. 2011).”
WIDE-FIELD PRECISION KINEMATICS OF THE M87 GLOBULAR CLUSTER SYSTEM (2011, background): “A metallicity transition with radius may be seen as a sign of a two-phase assembly scenario, with the inner component having formed in situ (Zolotov et al. 2009; Coccato et al. 2010; Font et al. 2011).”
Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “…terms on an inner component that may have formed in situ during the evolution of the Milky Way, together with a more diffuse outer one that originated from past accretion and tidal disruption of dwarf galaxies (Zolotov et al. 2009, 2010, Font et al. 2011, McCarthy et al. 2012, Tissera et al. 2014).”
LIGHT CURVE TEMPLATES AND GALACTIC DISTRIBUTION OF RR LYRAE STARS FROM SLOAN DIGITAL SKY SURVEY STRIPE 82 (2009, background): “Zolotov et al. (2009) find from their simulations that their inner halos include stars from both in-situ formed stars and accreted populations, while their outer halos appear to originate through pure accretion and disruption of satellites.”
METALLICITY EVOLUTION OF DAMPED Lyα SYSTEMS OUT TO z ∼ 5 (2012, background): “…with the inner halo formed from a combination of accretion of early rapid mergers and in-situ formation, and the outer halo formed purely from the disruption of lower mass satellite galaxies and accretion (Carollo et al. 2007; Zolotov et al. 2009; Carollo et al. 2010; Cooper et al. 2010).”
Cosmological simulations of the formation of the stellar haloes around disc galaxies (2011, methodology): “, we will show that a large fraction of the in situ stars formed from the cooling of hot gas (rather than cold flows, as advocated by Zolotov et al. 2009) during the initial assembly of the disc.”
THE CASE FOR THE DUAL HALO OF THE MILKY WAY (2011, background): “It is important to note that recent high-resolution, cosmologically-based simulations, in particular those of Zolotov et al. (2009, 2010), Font et al. (2011), and Tissera et al. (2011), now include at least approximate prescriptions for the star formation and dissipative accretion processes, as…”
BARYONS MATTER: WHY LUMINOUS SATELLITE GALAXIES HAVE REDUCED CENTRAL MASSES (2012, unknown): “While past simulations have overproduced stellar mass at a given halo mass (Zolotov et al. 2009; Guo et al. 2010; Sawala et al. 2011; Brooks et al. 2011; Leitner 2012), it has been suggested that restricting star formation to depend on the mass in molecular gas (rather than total gas mass) will…”
The bifurcated age–metallicity relation of Milky Way globular clusters and its implications for the accretion history of the galaxy (2013, background): “Certainly there is theoretical work suggesting that some fraction of the MW halo stars may have formed in-situ from high-redshift accreted gas, and then been dynamically heated into the MW halo through later mergers (e.g., Zolotov et al. 2009).”
THE GENESIS OF THE MILKY WAY'S THICK DISK VIA STELLAR MIGRATION (2010, methodology): “Thus, our model galaxy lacks some structural components such as a stellar halo, which in ΛCDM is built up primarily during the merging process (e.g. Bullock & Johnston 2005; Zolotov et al. 2009).”
KINEMATICS OF THE STELLAR HALO AND THE MASS DISTRIBUTION OF THE MILKY WAY USING BLUE HORIZONTAL BRANCH STARS (2012, background): “Additionally, duality in the formation history of the halo hasl o been seen in the recent smooth particle hydrodynamics and N-body simulations by Zolotov et al. (2009); McCarthy et al. (2012); Font et al. (2011).”
The biggest splash (2019, background): “Zolotov et al. (2009) and McCarthy et al. (2012) agree that the in situ component MNRAS 494, 3880–3898 (2020) D ow nloaded from https://academ ic.oup.com /m nras/article/494/3/3880/5817346 by U C L, London user on 09 Septem ber 2020 ought to be old and metal-rich, while forecasting rather different…”
Cuspy No More: How Outflows Affect the Central Dark Matter and Baryon Distribution in Lambda CDM Galaxies (2012, background): “…shown to reproduce many galaxy properties over a range of redshifts: Stinson et al. (2006); Brooks et al. (2007); Governato et al. (2007); Pontzen et al. (2008); Governato et al. (2009); Zolotov et al. (2009); Pontzen et al. (2010); Brook et al. (2011); Brooks et al. (2011); Guedes et al. (2011).”
Accreted versus in situ Milky Way globular clusters (2010, methodology): “Simulations suggest that the transition from an in situ to accretion-dominated stellar halo occurs at a galactocentric radius of ∼ 20 kpc for a Milky Way-like galaxy (Abadi et al. 2006; Zolotov et al. 2009).”
A BARYONIC SOLUTION TO THE MISSING SATELLITES PROBLEM (2012, result): “This is consistent with the idea that early, massive satellites contribute to the growth of the inner stellar halo in Milky Way-mass galaxies (Bullock & Johnston 2005; Zolotov et al. 2009).”
Chemical signatures of formation processes in the stellar populations of simulated galaxies (2011, background): “Our stellar haloes have a dual formation process since the ratio of accreted to in situ stars typically increases from 1 to 5 between the inner and outer haloes (see also Zolotov et al. (2009)).”
The stellar mass assembly of galaxies in the Illustris simulation: growth by mergers and the spatial distribution of accreted stars (2015, background): “…of galaxies (Font et al. 2011; McCarthy et al. 2012; Pillepich et al. 2014) or highly resolved individual galaxies (Abadi, Navarro & Steinmetz 2006; Zolotov et al. 2009, 2010; Tissera, White & Scannapieco 2012; Tissera et al. 2013, 2014; Dubois et al. 2013; Pillepich, Madau & Mayer 2015;…”
STRUCTURE AND KINEMATICS OF THE STELLAR HALOS AND THICK DISKS OF THE MILKY WAY BASED ON CALIBRATION STARS FROM SLOAN DIGITAL SKY SURVEY DR7 (2009, methodology): “In a recent paper, Zolotov et al. (2009) have investigated the formation of the stellar halos in simulated disk galaxies, using high-resolution SPH + N-Body simulations.”