Λ Cold Dark Matter, Stellar Feedback, and the Galactic Halo Abundance Pattern

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

181 citations recorded by the source corpus.

The hierarchical formation scenario for the stellar halo requires the accretion and disruption of dwarf galaxies, yet low-metallicity halo stars are enriched in α-elements compared to similar, low-metallicity stars in dwarf spheroidal (dSph) galaxies. We address this primary challenge for the hierarchical formation scenario for the stellar halo by combining chemical evolution modeling with cosmologically motivated mass accretion histories for the Milky Way dark halo and its satellites. We demonstrate that stellar halo and dwarf galaxy abundance patterns can be explained naturally within the ΛCDM framework. Our solution relies fundamentally on the ΛCDM model prediction that the majority of the stars in the stellar halo were formed within a few relatively massive, ~5 × 1010 M☉, dwarf irregular (dIrr) sized dark matter halos, which were accreted and destroyed ~10 Gyr in the past. These systems necessarily have short-lived, rapid star formation histories, are enriched primarily by Type II supernovae, and host stars with enhanced [α/Fe] abundances. In contrast, dwarf dSph galaxies exist within low-mass dark matter hosts of ~109 M☉, where supernovae winds are important in setting the intermediate [α/Fe] ratios observed. Our model includes enrichment from Type Ia and Type II supernovae, as well as stellar winds, and includes a physically motivated supernovae feedback prescription calibrated to reproduce the local dwarf galaxy stellar mass-metallicity relation. We use representative examples of the type of dark matter halos that we expect to host a destroyed "stellar halo progenitor" dwarf, a surviving dIrr, and a surviving dSph galaxy, and show that their derived abundance patterns, stellar masses, and gas masses are consistent with those observed for each type of system. Our model also self-consistently reproduces the observed stellar mass-vcirc relation for local group satellites and produces the correct cumulative mass for the Milky Way stellar halo. We predict that the lowest metallicity stars in intermediate-mass dIrr galaxies such as the SMC and LMC should follow abundance patterns similar to that observed in the stellar halo. Searches for accreted, disrupted, low-mass dwarfs may be enhanced by searching for unbound stars with dSph-like chemical abundance patterns.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/614f2d6c8be6ae75844209b485f8b2ae0400bf3f

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Citations in the corpus

Galactic stellar haloes in the CDM model (2009, background): “…and so distinguish between rapidly forming massive populations, truncated by early accretion to the halo, and populations reaching similar mass and metallicity through gradual star formation (e.g. Shetrone, Côté & Sargent 2001; Tolstoy et al. 2003; Venn et al. 2004; Robertson et al. 2005).”
Globular clusters, satellite galaxies and stellar haloes from early dark matter peaks (2005, methodology): “Recent studies including chemical modelling of this process support this scenario (e.g. Font et al. 2006; Robertson et al. 2005).”
Merger Histories of Galaxy Halos and Implications for Disk Survival (2007, background): “The most massive Milky Way satellite, the LMC, was likely accreted with a mass no larger than m ∼ 4 × 1010h−1M⊙ (van der Marel et al. 2002; Robertson et al. 2005).”
HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: URSA MAJOR II and COMA BERENICES (2009, background): “The chemical evolution model of Robertson et al. (2005), Font et al. (2006), and Johnston et al. (2008) predicts that, although massive dwarf galaxies are the source of the vast majority of the mass in the stellar halo, low luminosity, metalpoor, galaxies accreted at early times contribute some…”
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).”
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).”
Tracing Galaxy Formation with Stellar Halos. I. Methods (2005, background): “A more quantitative investigation of the consequences of the difference between the ”accretion age” of stars and satellites in the halo is underway (Robertson et al. 2005; Font et al. 2005).”
The Metal-poor Halo of the Andromeda Spiral Galaxy (M31) (2006, background): “…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 should be…”
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).”
LIGHT CURVE TEMPLATES AND GALACTIC DISTRIBUTION OF RR LYRAE STARS FROM SLOAN DIGITAL SKY SURVEY STRIPE 82 (2009, unknown): “3 in Robertson et al. 2005).”
METALLICITY EVOLUTION OF DAMPED Lyα SYSTEMS OUT TO z ∼ 5 (2012, methodology): “We compare the stars to DLAs withz> 2, as the majority of the halo stars are believed to have formed by then (Freeman & Bland-Hawthorn 2002; Bullock & Johnston 2005; Robertson et al. 2005; Johnston et al. 2008).”
On the fraction of star formation occurring in bound stellar clusters (2012, background): “This feedback efficiency is often taken to be χ fb ∼ 0.05 (see the discussion in Appendix B and e.g. Efstathiou 2000; Abadi et al. 2003; Robertson et al. 2005; Dubois & Teyssier 2008), but unfortunately, a detailed understanding of this parameter is still lacking (Silk 1997; Mac Low & Ferrara 1999;…”
The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach (2008, methodology): “This argument has been put forward in a recent series of papers by Bullock & Johnston (2005), Robertson et al. (2005), and Font et al. (2006) who reproduce the observed chemical abundance pattern by combining mass accretion histories of galaxy-size haloes with a chemical evolution model for…”
Determining the Properties and Evolution of Red Galaxies from the Quasar Luminosity Function (2005, methodology): “…al. 2005a), morphologies (Cox et al. 2005b, in preparation), metallicities (Cox et al. 2005c, in preparation),MBH − σ relation (Di Matteo et al. 2005), fine structure (e.g. Hernquist & Spergel 1992), and fundamental plane relations (Robertson et al. 2005c, in preparation) agree with observations.”
On Extending the Mass-Metallicity Relation of Galaxies by 2.5 Decades in Stellar Mass (2006, background): “Robertson et al. (2005) developed models to describe chemical abundance patterns observed in the Galactic halo, Local Group dwarf spheroidals, and Local Group dwarf irregular galaxies.”
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).”
OBSERVATIONS OF STARBURST GALAXIES WITH FAR-ULTRAVIOLET SPECTROGRAPHIC EXPLORER: GALACTIC FEEDBACK IN THE LOCAL UNIVERSE (2009, background): “…of a universe dominated by dark matter and dark energy have led to a robust understanding of the large-scale structure of the universe, many questions remain when studying smaller scales where baryonic physics become important (Robertson et al. 2005; Sommer-Larsen et al. 1999; Benson et al. 2003).”
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, methodology): “This behavior, and the scaling with halo circular velocity, are consistent with the treatment by Robertson et al. (2005), with two key differences in formulation.”