Chemical Abundance Distributions of Galactic Halos and Their Satellite Systems in a ΛCDM Universe

By A. Font, K. Johnston, James S. Bullock, Brant Robertson. 2005

175 citations recorded by the source corpus.

We present a cosmologically motivated model for the hierarchical formation of the stellar halo that includes a semianalytic treatment of galactic chemical enrichment coupled to numerical simulations that track the orbital evolution and tidal disruption of satellites. A major motivating factor in this investigation is the observed systematic difference between the chemical abundances of stars in satellite galaxies and those in the Milky Way halo. Specifically, for the same [Fe/H] values, stars in neighboring satellite galaxies display significantly lower [α/Fe] ratios than stars in the halo. We find that the observed chemical abundance patterns are a natural outcome of the process of hierarchical assembly of the Galaxy. This result follows because the stellar halo in this context is built up from satellite galaxies accreted early on (more than 8-9 Gyr ago) and enriched in α-elements produced in Type II supernovae. In contrast, satellites that still survive today are typically accreted late (within the last 4-5 Gyr) with nearly solar [α/Fe] values as a result of contributions from both Type II and Type Ia supernovae. We use our model to investigate the abundance distribution functions (using both [Fe/H] and [α/Fe] ratios) for stars in the halo and in surviving satellites. Our results suggest that the shapes and peaks in the abundance distribution functions provide a direct probe of the accretion histories of galaxies.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/4b798be787407bff1210340ad4b16da5930c0fdf

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CHEMICAL TAGGING CAN WORK: IDENTIFICATION OF STELLAR PHASE-SPACE STRUCTURES PURELY BY CHEMICAL-ABUNDANCE SIMILARITY (2016, background): “…accretion history (as things that fall in are expected to be chemically distinct from those that form in the parent body; for example, Eggen 1970; Font et al. 2006; De Silva et al. 2007; Bubar & King 2010) and stellar-orbit diffusion processes like radial mixing and radial migration (for…”
A New View of the Dwarf Spheroidal Satellites of the Milky Way from VLT FLAMES: Where Are the Very Metal-poor Stars? (2006, background): “Font et al. (2006) point out that if the dSph had been accreted at early epochs, they could still have been the building blocks of hierarchical models.”
Is the SMC Bound to the LMC? The Hubble Space Telescope Proper Motion of the SMC (2006, methodology): “It is expected from current models of hierarchical structure formation (e.g., Zentner & Bullock 2003) that the interaction between the Clouds and the MW will have played an important role in the dynamical evolution of the MW’s outer parts (e.g., Font et al. 2006).”
Galactic stellar haloes in the CDM model (2009, background): “Notably, Font et al. (2006) observe that no satellites accreted >9 Gyr ago survive in their subsample of four of the Bullock & Johnston haloes, whereas we find that some satellites infalling even at redshifts z > 2 may survive (see also Fig.”
MULTI-ELEMENT ABUNDANCE MEASUREMENTS FROM MEDIUM-RESOLUTION SPECTRA. II. CATALOG OF STARS IN MILKY WAY DWARF SATELLITE GALAXIES (2010, background): “Nonetheless, the observed abundance differences can be compared with models of surviving galaxies and hierarchically formed halos (e.g., Robertson et al. 2005; Font et al. 2006).”
CHEMICAL EVOLUTION IN HIERARCHICAL MODELS OF COSMIC STRUCTURE. II. THE FORMATION OF THE MILKY WAY STELLAR HALO AND THE DISTRIBUTION OF THE OLDEST STARS (2009, background): “…while this is technique has a history of application to problems of galaxy formation at large, in cosmological volumes, its application to single galaxies, with full attention paid to detailed chemical evolution, is relatively new (BJ05; Paper I; Robertson et al. 2005; Font et al. 2006a).”
THE DUAL ORIGIN OF STELLAR HALOS (2009, background): “The work of Font et al. (2006a) also found that nearly 80% of the stars in the inner 20 kpc of simulated halos were in place at a lookback time of 9 Gyr.”
The Metal-poor Halo of the Andromeda Spiral Galaxy (M31) (2006, background): “Finally, since the most massive merging events that formed the inner parts of hosts like the Milky Way and M31 are also the most metal-rich (Font et al. 2006; Robertson et al. 2005; Renda et al. 2005; Brook et al. 2004), this formation scenario suggests that the inner parts of massive galaxies…”
Cosmological simulations of the formation of the stellar haloes around disc galaxies (2011, background): “…in situdominated to accretion-dominated stars, appears to resolve the longstanding problem of the inability of purely accretionbased models (e.g., Font et al. 2006a; De Lucia & Helmi 2008; Cooper et al. 2010) to reproduce the strong variation in the mean stellar metallicity with radius observed…”
Accreted versus in situ Milky Way globular clusters (2010, background): “In a ΛCDM Universe, Milky Way-like galaxy halos are built up by the accretion of smaller galaxies (Bullock & Johnson 2005; Abadi et al. 2006; Font et al. 2006).”
THE SAGITTARIUS DWARF GALAXY: A MODEL FOR EVOLUTION IN A TRIAXIAL MILKY WAY HALO (2010, background): “2 Department of Physics and Astronomy, University of California, Los Angeles, CA 90095; drlaw@astro.ucla.edu 3 Dept. of Astronomy, University of Virginia, Charlottesville, VA 22904-4325: srm4n@virginia.edu Font et al. 2006; Bell et al. 2008).”
The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach (2008, methodology): “9 are in good agreement with those by Font et al. (2006) who find that one or a few more satellites in the range 108−1010 M⊙ can make up 50-80 per cent of the stellar halo and most of them are accreted early on (taccr > 9 Gyr).”
GLOBULAR CLUSTERS IN THE OUTER GALACTIC HALO: NEW HUBBLE SPACE TELESCOPE/ADVANCED CAMERA FOR SURVEYS IMAGING OF SIX GLOBULAR CLUSTERS AND THE GALACTIC GLOBULAR CLUSTER AGE–METALLICITY RELATION (2011, methodology): “…akin to the fragmentation and accretion scenario advocated by Searle & Zinn (1978, see also Navarro et al. 1997) and featured in models of galaxy formation based on the cold dark matter paradigm with a cosmological constant (e.g., Zentner & Bullock 2003; Robertson et al. 2005; Font et al. 2006).”
Exploring Halo Substructure with Giant Stars. XI. The Tidal Tails of the Carina Dwarf Spheroidal Galaxy and the Discovery of Magellanic Cloud Stars in the Carina Foreground (2006, background): “…and even for why there seems to be a radial metallicity and age gradient in Carina: The present balance of populations bound to Carina likely reflects the competing interplay of star formation history and mass loss history (Font et al. 2006) in this disrupting analogue of the Sgr dSph galaxy.”
Galaxy formation theory (2010, background): “…to the build-up of the Milky Way’s stellar halo (Cooper et al. 2009), and there may be remnant tidal streams which could provide information about the hierarchical growth of the Milky Way’s halo (Bullock and Johnston 2005; Robertson et al. 2005; Font et al. 2006a,b; Johnston et al. 2008).”
Shredded Galaxies as the Source of Diffuse Intrahalo Light on Varying Scales (2007, background): “…heating processes to produce the diffuse, stellar halos around galaxies like theMilkyWay (Searle & Zinn 1978; Johnston et al. 1996, 2001; Johnston 1998; Bullock et al. 2001b; Bullock & Johnston 2005; Robertson et al. 2005; Diemand et al. 2005; Read et al. 2006; Font et al. 2006; Abadi et al. 2006).”