Cytology [by] G.B. Wilson [and] John H. Morrison.

Morrison, John H.; Wilson, G. B.

doi:10.5962/bhl.title.6455

Cited by 12 publications

(20 citation statements)

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“…1 represent the general outcome for minor mergers, only that they are a possible outcome, compatible with the eccentricity of thick disk stars in the solar neighborhood (Dierickx et al 2010;Wilson et al 2010). Nevertheless, the eccentricity distribution found in our simulations, for the direct merger with a gas fraction of 20% in the disk, is remarkably similar to those observed in the Milky Way thick disk.…”

Section: Resultssupporting

confidence: 56%

“…Nevertheless, the eccentricity distribution found in our simulations, for the direct merger with a gas fraction of 20% in the disk, is remarkably similar to those observed in the Milky Way thick disk. Dierickx et al (2010) and Wilson et al (2010) found a peak at low eccentricities 2. Eccentricity distribution of thick disk stellar particles for a 2 × (1:10) consecutive minor merger with a gas fraction f gas = 0.2.…”

Section: Resultsmentioning

confidence: 99%

“…3. Comparison of the eccentricity distributions of stellar particles of one of our minor merger models with the distributions found by Dierickx et al (2010) and Wilson et al (2010) for stars in the solar neighborhood. For comparison, the distribution found by Sales et al (2009) for their "heating" (i.e., minor merger) scenario is also shown.…”

Section: Resultsmentioning

confidence: 99%

“…Similarly, Wilson et al (2010) found that the eccentricity distribution of a sample of solar neighborhood thick disk stars from RAVE survey data appears to be most consistent with the gasrich merger scenario. Within the limitations of any of these comparisons, their conclusions appear well justified.…”

Section: Introductionmentioning

confidence: 88%

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The formation of a thick disk through the heating of a thin disk: Agreement with orbital eccentricities of stars in the solar neighborhood

Matteo

Lehnert

et al. 2010

A&A

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We study the distribution of orbital eccentricities of stars in thick disks generated by the heating of a pre-existing thin stellar disk through a minor merger (mass ratio 1:10), using N-body/SPH numerical simulations of interactions that span a range of gas fractions in the primary disk and initial orbital configurations. The resulting eccentricity distributions have an approximately triangular shape, with a peak at 0.2−0.35, and a relatively smooth decline towards higher values. Stars originally in the satellite galaxy tend to have higher eccentricities (on average from e = 0.45 to e = 0.75), which is in general agreement with the models of Sales and collaborators, although in detail we find fewer stars with extreme values and no evidence of their secondary peak around e = 0.8. The absence of this high-eccentricity feature results in a distribution that qualitatively matches the observations. Moreover, the increase in the orbital eccentricities of stars in the solar neighborhood with vertical distance from the Galactic mid-plane found by Dierickx and collaborators can be qualitatively reproduced by our models, but only if the satellite is accreted onto a direct orbit. We thus speculate that if minor mergers were the dominant means of forming the Milky Way thick disk, the primary mechanism should be merging with satellite(s) on direct orbits.

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Section: Resultssupporting

confidence: 56%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 88%

See 2 more Smart Citations

The formation of a thick disk through the heating of a thin disk: Agreement with orbital eccentricities of stars in the solar neighborhood

Matteo

Lehnert

et al. 2010

A&A

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“…On the other hand, a thick disk component can also be formed by violent heating and relaxation due to satellite accretion(s) or from directly accreting dynamically hot stars through mergers and interactions (Statler 1988;Hernquist & Quinn 1989;Quinn et al 1993;Walker et al 1996;Aguerri et al 2001;Abadi et al 2003;Yoachim & Dalcanton 2005;Brook et al 2007;Villalobos & Helmi 2008). As recently discussed by Sales et al (2009) and Di Matteo et al (2010), these different formation mechanisms should produce different signatures in the eccentricities of the stellar orbits, thus providing a potential diagnostic to disentangle the dominant formation scenarios (see Di Matteo et al 2010;Dierickx et al 2010;Wilson et al 2011, andCasetti-Dinescu et al 2011, for a comparison of model predictions and observations). Nevertheless, the main astrophysical processes which drive thick disk formation remain unclear.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of thick disks formed through minor mergers: stellar excesses and scale lengths

Matteo

Lehnert

et al. 2011

A&A

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By means of a series of N-body/SPH simulations we investigate the morphological properties of thick stellar disks formed through minor mergers with, e.g. a range of gas-to-stellar mass ratios. We show that the vertical surface density profile of the post-merger thick disk follows a sech function and has an excess in the regions furthest away from the disk mid-plane (z 2 kpc). This stellar excess also follows a sech function with a larger scale height than the main thick disk component (except at large radii). It is usually dominated by stars from the primary galaxy, but this depends on the orbital configuration. Stars in the excess have a rotational velocity lower than that of stars in the thick disk, and they may thus be confused with stars in the inner galactic halo, which can have a similar lag. Confirming previous results, the thick disk scale height increases with radius and the rate of its increase is smaller for more gas rich primary galaxies. On the contrary, the scale height of the stellar excess is independent of both radius and gas fraction. We also find that the post-merger thick disk has a radial scale length which is 10−50% larger than that of the thin disk. Two consecutive mergers have basically the same effect on heating the stellar disk as a single merger of the same total mass, i.e., the disk heating effect of a few consecutive mergers does not saturate but is cumulative. To investigate how thick disks produced through secular processes may differ from those produced by minor mergers, we also simulated gravitationally unstable gas-rich disks ("clumpy disks"). These clumpy disks do not produce either a stellar excess or a ratio of thick to thin disk scale lengths greater than one. Comparing our simulation results with observations of the Milky Way and nearby galaxies shows that our results for minor mergers are consistent with observations of the ratio of thick to thin disk scale lengths and with the "Toomre diagram" (the sum in quadrature of the vertical and radial versus the rotational kinetic energies) of the Milky Way. The simulations of clumpy disks do not show such agreement. We conclude that minor mergers are a viable mechanism for the creation of galactic thick disks and investigating stars at several kpc above the mid-plane of the Milky Way and other galaxies may provide a quantitative method for studying the (minor) merger history of galaxies.

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Australia

Tonkinson

2012

The Wiley‐Blackwell Companion to Religion and Social Justice

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Cytology [by] G.B. Wilson [and] John H. Morrison.

Cited by 12 publications

References 0 publications

The formation of a thick disk through the heating of a thin disk: Agreement with orbital eccentricities of stars in the solar neighborhood

The formation of a thick disk through the heating of a thin disk: Agreement with orbital eccentricities of stars in the solar neighborhood

Characteristics of thick disks formed through minor mergers: stellar excesses and scale lengths

Australia

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