The Angular Momentum of Gas in Protogalaxies. I. Implications for the Formation of Disk Galaxies

Bosch, Frank C. van den; Abel, Tom; Croft, Rupert A. C.; Hernquist, L.; White, Simon D. M.

doi:10.1086/341619

Cited by 216 publications

(210 citation statements)

References 58 publications

(69 reference statements)

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“…We also note that the spin vectors of dark matter and the gas are not closely aligned, with a median deviation angle of %30 , in good agreement with the results of van den Bosch et al (2002) for higher mass halos.…”

Section: The Angular Momenta Of Dark Matter and Gassupporting

confidence: 83%

Simulations of Early Structure Formation: Primordial Gas Clouds

Yoshida¹,

Abel²,

Hernquist³

et al. 2003

ApJ

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552

729

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We use cosmological simulations to study the origin of primordial star-forming clouds in a ÃCDM universe, by following the formation of dark matter halos and the cooling of gas within them. To model the physics of chemically pristine gas, we employ a nonequilibrium treatment of the chemistry of nine species (e À , H, H + , He, He + , He ++ , H 2 , H þ 2 , H À ) and include cooling by molecular hydrogen. By considering cosmological volumes, we are able to study the statistical properties of primordial halos, and the high resolution of our simulations enables us to examine these objects in detail. In particular, we explore the hierarchical growth of bound structures forming at redshifts z % 25 30 with total masses in the range %10 5 10 6 M . We find that when the amount of molecular hydrogen in these objects reaches a critical level, cooling by rotational line emission is efficient, and dense clumps of cold gas form. We identify these '' gas clouds '' as sites for primordial star formation. In our simulations, the threshold for gas cloud formation by molecular cooling corresponds to a critical halo mass of %5 Â 10 5 h À1 M , in agreement with earlier estimates, but with a weak dependence on redshift in the range z > 16. The complex interplay between the gravitational formation of dark halos and the thermodynamic and chemical evolution of the gas clouds compromises analytic estimates of the critical H 2 fraction. Dynamical heating from mass accretion and mergers opposes relatively inefficient cooling by molecular hydrogen, delaying the production of star-forming clouds in rapidly growing halos. We also investigate the effect of photodissociating ultraviolet radiation on the formation of primordial gas clouds. We consider two extreme cases, first by including a uniform radiation field in the optically thin limit and second by accounting for the maximum effect of gas self-shielding in virialized regions. For radiation with Lyman-Werner band flux J > 10 À23 ergs s À1 cm À2 Hz À1 sr À1 , hydrogen molecules are rapidly dissociated, rendering gas cooling inefficient. In both the cases we consider, the overall effect can be described by computing an equilibrium H 2 abundance for the radiation flux and defining an effective shielding factor. Based on our numerical results, we develop a semianalytic model of the formation of the first stars and demonstrate how it can be coupled with large N-body simulations to predict the star formation rate in the early universe.

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Section: The Angular Momenta Of Dark Matter and Gassupporting

confidence: 83%

Simulations of Early Structure Formation: Primordial Gas Clouds

Yoshida¹,

Abel²,

Hernquist³

et al. 2003

ApJ

Self Cite

552

729

View full text Add to dashboard Cite

show abstract

“…The models presented here are ''toy'' models in the sense that their theoretical motivation does not apply to highly nonlinear scales, and even on larger scales there is little observational basis for models of intrinsic galaxy ellipticity alignments. An alternative to analytic models is to estimate intrinsic alignments by calculating the ellipticities or angular momenta of dark matter haloes in N-body simulations [25][26][27]32], however one should keep in mind that there can be misalignment between the dark matter halo and the galaxy it contains [47], and so intrinsic alignment results based on N-body simulations are not definitive. In principle it would be possible to derive predictions for intrinsic correlations from a halo model, however this would require adding a prescription for the galaxy alignment to the current halo models.…”

Section: Modelsmentioning

confidence: 99%

Intrinsic alignment-lensing interference as a contaminant of cosmic shear

2004

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Cosmic shear surveys have great promise as tools for precision cosmology, but can be subject to systematic errors including intrinsic ellipticity correlations of the source galaxies. The intrinsic alignments are believed to be small for deep surveys, but this is based on intrinsic and lensing distortions being uncorrelated. Here we show that the gravitational lensing shear and intrinsic shear need not be independent: correlations between the tidal field and the intrinsic shear cause the intrinsic shear of nearby galaxies to be correlated with the gravitational shear acting on more distant galaxies. We estimate the magnitude of this effect for two simple intrinsic-alignment models: one in which the galaxy ellipticity is linearly related to the tidal field, and one in which it is quadratic in the tidal field as suggested by tidal torque theory. The first model predicts a gravitational-intrinsic (GI) correlation that can be much greater than the intrinsic-intrinsic (II) correlation for broad redshift distributions, and that remains when galaxies pairs at similar redshifts are rejected. The second model, in its simplest form, predicts no gravitational-intrinsic correlation. In the first model, and assuming a normalization consistent with recently claimed detections of intrinsic correlations, we find that the GI correlation term can exceed the usual II term by >1 order of magnitude and the intrinsic correlation induced B-mode by 2 orders of magnitude. These interference effects can suppress the lensing power spectrum for a single broad redshift bin by of order 10% at z s 1 and 30% at z s 0:5. We conclude that, depending on the intrinsic-alignment model, the GI correlation may be the dominant contaminant of the lensing signal and can even affect cross spectra between widely separated bins. We describe two ways to constrain this effect, one based on density-shear correlations and one based on scaling of the cross correlation tomography signal with redshift.

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“…Despite the fact that galactic outflows, misaligned gas accretion, and mergers tend to complicate the detailed conservation of specific angular momentum during the formation of a galaxy (e.g. van den Bosch et al 2002;Brook et al 2011;Zjupa & Springel 2017), it is nevertheless expected that the largest galactic discs form preferentially in haloes with higher angular momentum (e.g. Fall & Efstathiou 1980;Fall 1983;Mo, Mao & White 1998).…”

Section: Introductionmentioning

confidence: 99%

The role of mergers and halo spin in shaping galaxy morphology

Rodríguez-Gómez

Sales

Genel

et al. 2017

Monthly Notices of the Royal Astronomical Society

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182

157

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Mergers and the spin of the dark matter halo are factors traditionally believed to determine the morphology of galaxies within a ΛCDM cosmology. We study this hypothesis by considering approximately 18,000 central galaxies at z = 0 with stellar masses M * = 10 9 -10 12 M selected from the Illustris cosmological hydrodynamic simulation. The fraction of accreted stars -which measures the importance of massive, recent and dry mergers -increases steeply with galaxy stellar mass, from less than 5 per cent in dwarfs to 80 per cent in the most massive objects, and the impact of mergers on galaxy morphology increases accordingly. For galaxies with M * 10 11 M , mergers have the expected effect: if gas-poor they promote the formation of spheroidal galaxies, whereas gas-rich mergers favour the formation and survivability of massive discs. This trend, however, breaks at lower masses. For objects with M * 10 11 M , mergers do not seem to play any significant role in determining the morphology, with accreted stellar fractions and mean merger gas fractions that are indistinguishable between spheroidal and disc-dominated galaxies. On the other hand, halo spin correlates with morphology primarily in the least massive objects in the sample (M * 10 10 M ), but only weakly for galaxies above that mass. Our results support a scenario where (1) mergers play a dominant role in shaping the morphology of massive galaxies, (2) halo spin is important for the morphology of dwarfs, and (3) the morphology of medium-sized galaxies -including the Milky Way -shows little dependence on galaxy assembly history or halo spin, at least when these two factors are considered individually.

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The Angular Momentum of Gas in Protogalaxies. I. Implications for the Formation of Disk Galaxies

Cited by 216 publications

References 58 publications

Simulations of Early Structure Formation: Primordial Gas Clouds

Simulations of Early Structure Formation: Primordial Gas Clouds

Intrinsic alignment-lensing interference as a contaminant of cosmic shear

The role of mergers and halo spin in shaping galaxy morphology

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