The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach

By G. Lucia, A. Helmi. 2008

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We use a series of high-resolution simulations of a 'Milky Way' halo coupled to semi-analytic methods to study the formation of our own Galaxy and its stellar halo. The physical properties of our model Milky Way, as well as the age and metallicity distribution of stars in the different components, are in relatively good agreement with observational measurements. Assuming that the stellar halo builds up from the cores of the satellite galaxies that merged with the Milky Way over its lifetime, we are able to study the physical and structural properties of this component. In agreement with previous work, we find that the largest contribution to the stellar halo should come from a few relatively massive (10(8)-10(10) M circle dot) satellites accreted at early times. Our 'stellar halo' does not exhibit any clear metallicity gradient, but higher metallicity stars are more centrally concentrated than stars of lower abundance. This indicates that the probability of observing low-metallicity halo stars increases with distance from the Galactic Centre. We find that the proposed 'dual' nature of the Galactic stellar halo can be explained in our model as a result of a mass-metallicity relation imprinted in the building blocks of this component.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/da5a1f8388b8e87c1c27cfb680235f6a5bb1a97c

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Citations in the corpus

Cosmological simulations of the formation of the stellar haloes around disc galaxies (2011, background): “Models that form haloes by non-dissipative accretion and mergers have so far not been able to produce significant metallicity gradients (Font et al. 2006a; De Lucia & Helmi 2008; Cooper et al. 2010).”
Co-formation of the disc and the stellar halo (2018, result): “Our stellar halo realisations (based on tagging the most bound particles in satellites; De Lucia & Helmi 2008; Bailin et al. 2014) are similar to those presented in Bullock & Johnston (2005) and Amorisco (2017) in the way that they do not attempt to model the gas-dynamics and the feedback effects.”
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): “The Halos: Evidence from Theoretical Modeling De Lucia & Helmi (2008) have adapted a high-resolution simulation of a Milky Way-like halo, combined with a semianalytic approach, to explore the formation of the Galaxy.”
Galactic stellar haloes in the CDM model (2009, methodology): “Our approach has similarities with that of De Lucia & Helmi (2008), who tag the most bound 10 per cent of particles in satellite haloes with stars.”
The stellar halo of the Galaxy (2008, methodology): “As shown in Figure 14, also De Lucia & Helmi (2008) find that the stellar halo is much more centrally concentrated than the dark matter halo.”
LIGHT CURVE TEMPLATES AND GALACTIC DISTRIBUTION OF RR LYRAE STARS FROM SLOAN DIGITAL SKY SURVEY STRIPE 82 (2009, background): “For example, De Lucia & Helmi (2008) find evidence in their simulation for a strong concentration of (relatively) higher metallicity stars at distances close to the Galactic center, and the presence of (relatively) lower metallicity stars at distances beyond 20 kpc from the center.”
The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “The outer halo is built more recently than the inner halo, and the halo properties evolve, reflecting the history of accretion (Bullock & Johnston 2005, Font et al. 2006, De Lucia & Helmi 2008, Cooper et al. 2010, Pillepich et al. 2014).”
The biggest splash (2019, background): “…the -cold dark matter ( CDM) cosmology, the bulk of the stellar halo of a MW-sized galaxy is predicted to be dominated by a small E-mail: vasily@ast.cam.ac.uk number of massive early-accreted dwarfs (e.g. Bullock & Johnston 2005; Robertson et al. 2005; Font et al. 2006; De Lucia & Helmi 2008).”
The many manifestations of downsizing: hierarchical galaxy formation models confront observations (2009, methodology): “Beyond that point the merger time of the satellite is computed using the classical Chandrasekhar dynamical friction approximation (for more details, see De Lucia & Blaizot 2007; De Lucia & Helmi 2008).”
Chemodynamical evolution of the Milky Way disk - I. The solar vicinity (2012, result): “For a MW-size galaxy, the occurrence of mergers of this size aroundz ∼ 1 is consistent with the numerical results by a number of groups (e.g., Benson et al. 2004; Stoehr 2006; Kazantzidis et al. 2008; De Lucia and Helmi 2008; Stewart et al. 2008; Villalobos and Helmi 2008; Purcell et al. 2009).”
The Milky Way stellar halo out to 40 kpc: squashed, broken but smooth (2011, methodology): “This has been seen as vindication of modern theories of c© 2011 RAS galaxy formation, which predict that stellar haloes are built p almost exclusively from the debris of disrupting satellites (e.g. Bullock & Johnston 2005; De Lucia & Helmi 2008; Cooper et al. 2010).”