Building blocks of the Milky Way's accreted spheroid

Oirschot, Pim van; Starkenburg, Else; Helmi, Amina; Nelemans, G.

doi:10.1093/mnras/stw2340

Cited by 4 publications

(2 citation statements)

References 92 publications

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“…This aligns well with mounting evidence from both numerical (Bullock & Johnston 2005;Cooper et al 2010;Deason et al 2016;van Oirschot et al 2017) and observational work (Fiorentino et al 2014;Deason et al 2015) that the bulk of the accreted stellar halo in MWsized galaxies is contributed by a small number of relatively massive satellites with stellar masses 10 8 − 10 10 M . For reference, the MW is thought to have a stellar halo M * ,h ≈ 1 × 10 9 M , corresponding to roughly 2% of its stellar mass (Carollo et al 2010;Licquia & Newman 2015).…”

Section: A Scenario For Biased Nsc Formationsupporting

confidence: 87%

The Next Generation Virgo Cluster Survey. XXIII. Fundamentals of Nuclear Star Clusters over Seven Decades in Galaxy Mass

Sánchéz-Janssen

Côté

Ferrarese

et al. 2019

ApJ

126

146

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Using deep, high resolution optical imaging from the Next Generation Virgo Cluster Survey we study the properties of nuclear star clusters (NSCs) in a sample of nearly 400 quiescent galaxies in the core of Virgo with stellar masses 10 5 M * /M 10 12 . The nucleation fraction reaches a peak value f n ≈ 90% for M * ≈ 10 9 M galaxies and declines for both higher and lower masses, but nuclei populate galaxies as small as M * ≈ 5 × 10 5 M . Comparison with literature data for nearby groups and clusters shows that at the low-mass end nucleation is more frequent in denser environments. The NSC mass function peaks at M N SC ≈ 7 × 10 5 M , a factor 3-4 times larger than the turnover mass for globular clusters (GCs). We find a nonlinear relation between the stellar masses of NSCs and of their host galaxies, with a mean nucleus-to-galaxy mass ratio that drops to M N SC /M ≈ 3.6 × 10 −3 for M * ≈ 5 × 10 9 M galaxies. Nuclei in both more and less massive galaxies are much more prominent: M N SC ∝ M 0.46 * at the low-mass end, where nuclei are nearly 50% as massive as their hosts. We measure an intrinsic scatter in NSC masses at fixed galaxy stellar mass of 0.4 dex, which we interpret as evidence that the process of NSC growth is significantly stochastic. At low galaxy masses we find a close connection between NSCs and GC systems, including a very similar occupation distribution and comparable total masses. We discuss these results in the context of current dissipative and dissipationless models of NSC formation.

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Section: A Scenario For Biased Nsc Formationsupporting

confidence: 87%

The Next Generation Virgo Cluster Survey. XXIII. Fundamentals of Nuclear Star Clusters over Seven Decades in Galaxy Mass

Sánchéz-Janssen

Côté

Ferrarese

et al. 2019

ApJ

126

146

View full text Add to dashboard Cite

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“…These results in turn have also been contested by Melia and collaborators [45]. Conceptual problems have also been raised against this model [25,[46][47][48][49][50][51], although some have been countered [52]. We note however so far this model is yet to reproduce the Cosmic Microwave Background temperature and polarization anisotropy measurements.…”

Section: Introductionmentioning

confidence: 97%

Model comparison of $$\Lambda $$CDM vs $$R_h=ct$$ using cosmic chronometers

Singirikonda

Desai

2020

Eur. Phys. J. C

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In 2012, Bilicki and Seikel (Mon Not R Astron Soc 425:1664, 2012) showed that H(z) data reconstructed using Gaussian Process Regression from cosmic chronometers and baryon acoustic oscillations, conclusively rules out the $$R_h=ct$$Rh=ct model. These results were disputed by Melia and collaborators in two different works (Melia and Maier in Mon Not R Astron Soc 432:2669, 2013; Melia and Yennapureddy in JCAP 2018:034, 2018), who showed using both an unbinned analysis and Gaussian Process reconstructed H(z) data from chronometers, that $$R_h=ct$$Rh=ct is favored over $$\Lambda $$ΛCDM model. To resolve this imbroglio, we carry out model comparison of $$\Lambda $$ΛCDM versus $$R_h=ct$$Rh=ct by independently reproducing the above claims using the latest chronometer data. We perform model selection between these two models using Bayesian model comparison. We find that no one model between $$\Lambda $$ΛCDM and $$R_h=ct$$Rh=ct is decisively favored when uniform priors on $$\Lambda $$ΛCDM parameters are used. However, if we use priors centered around the Planck best-fit values, then $$\Lambda $$ΛCDM is very strongly preferred over $$R_h=ct$$Rh=ct.

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White dwarfs in the building blocks of the Galactic spheroid

Oirschot

Nelemans

Starkenburg

et al. 2017

A&A

Self Cite

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Aims. The galactic halo likely grew over time in part by assembling smaller galaxies, the so-called building blocks. We investigate if the properties of these building blocks are reflected in the halo white dwarf (WD) population in the Solar neighborhood. Furthermore, we compute the halo WD luminosity functions (WDLFs) for four major building blocks of five cosmologically motivated stellar haloes. We compare the sum of these to the observed WDLF of the galactic halo, derived from selected halo WDs in the SuperCOSMOS Sky Survey, aiming to investigate if they match better than the WDLFs predicted by simpler models. Methods. We couple the SeBa binary population synthesis model to the Munich-Groningen semi-analytic galaxy formation model, applied to the high-resolution Aquarius dark matter simulations. Although the semi-analytic model assumes an instantaneous recycling approximation, we model the evolution of zero-age main sequence stars to WDs, taking age and metallicity variations of the population into account. To be consistent with the observed stellar halo mass density in the Solar neighborhood (ρ 0 ), we simulate the mass in WDs corresponding to this density, assuming a Chabrier initial mass function (IMF) and a binary fraction of 50%. We also normalize our WDLFs to ρ 0 . Results. Although the majority of halo stars is old and metal-poor and therefore the WDs in the different building blocks have similar properties (including present-day luminosity), we find in our models that the WDs originating from building blocks that have young and/or metal-rich stars can be distinguished from WDs that were born in other building blocks. In practice however, it will be hard to prove that these WDs really originate from different building blocks, as the variations in the halo WD population due to binary WD mergers result in similar effects. The five joined stellar halo WD populations that we modelled result in WDLFs that are very similar to each other. We find that simple models with a Kroupa or Salpeter IMF fit the observed luminosity function slightly better, since the Chabrier IMF is more top-heavy, although this result is dependent on our choice of ρ 0 .

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Building blocks of the Milky Way's accreted spheroid

Cited by 4 publications

References 92 publications

The Next Generation Virgo Cluster Survey. XXIII. Fundamentals of Nuclear Star Clusters over Seven Decades in Galaxy Mass

The Next Generation Virgo Cluster Survey. XXIII. Fundamentals of Nuclear Star Clusters over Seven Decades in Galaxy Mass

Model comparison of $$\Lambda $$CDM vs $$R_h=ct$$ using cosmic chronometers

White dwarfs in the building blocks of the Galactic spheroid

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