Galaxy Spin Statistics and Spin‐Density Correlation

Lee, Jounghun; Pen, Ue-Li

doi:10.1086/321472

Cited by 145 publications

(232 citation statements)

References 38 publications

(40 reference statements)

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“…We also discuss its dependence on the peak height. Note that similar calculations for the correlation of angular momentum L i ∝ ǫ ijk ξ jl I lk , where I lk is the inertia tensor of some Lagrangian region, can be found in [32,33] for instance.…”

Section: B Principal Axesmentioning

confidence: 52%

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Statistical properties of the linear tidal shear

2008

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Large-scale structures originate from coherent motions induced by inhomogeneities in the primeval gravitational potential. Here, we investigate the two-point statistics of the second derivative of the potential, the tidal shear, under the assumption of Gaussianity. We derive an exact closed form expression for the angular averaged, two-point distribution of the shear components which is valid for an arbitrary Lagrangian separation. This result is used to write down the two-point statistics of the shear eigenvalues in compact form. Next, we examine the large-scale asymptotics of the correlation of the shear eigenvalues and the alignment of the principal axes. The analytic results are in good agreement with measurements obtained from random realizations of the gravitational potential. Finally, we show that a number of two-point distributions of the shear eigenvalues are well approximated by Gaussian bivariates over a wide range of separation and smoothing scales. We speculate that the Gaussian approximation also holds for multiple point distributions of the shear eigenvalues. It is hoped that these results will be relevant for studies aimed at describing the properties of the (evolved) matter distribution in terms of the statistics of the primordial shear field.

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Section: B Principal Axesmentioning

confidence: 52%

“…The Ψ i can be equivalently expressed in terms of the auxiliary functions J n ≡ nr −n r 0 ds ψ(s)s n−1 [27,32,33], where…”

Section: A Shear Correlationsmentioning

confidence: 99%

Statistical properties of the linear tidal shear

2008

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“…The number density of galaxies is one possibility; recent observations have probed the galaxy-intrinsic shear correlation on 0:02-1h ÿ1 Mpc scales [51,60], and it would be useful to extend these studies to larger scales where linear biasing is valid. (At least one density-shear correlation measurement is available on large scales [29]. These authors were interested primarily in using intrinsic alignments to reconstruct the density field; they therefore did not use lensing shear estimators, and they measured threedimensional separations in redshift space, so their results are difficult to interpret in the present context.)…”

Section: Discussionmentioning

confidence: 99%

“…Another possible systematic error is intrinsic (i.e. not lensing-induced) correlations among the ellipticities of neighboring source galaxies [25][26][27][28][29][30][31][32][33][34], which could arise if the galaxy ellipticities are affected by large-scale tidal fields. This systematic error is particularly worrisome because it lies outside the control of the observer, and is dependent upon the poorly understood physics of galaxy formation.…”

Section: Introductionmentioning

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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“…In the past, both tidal torque theory Heavens, Refegier, & Heymans 2000;Natarajan et al 2001) and pure N-body simulations (Croft & Metzler 2000) have been used to calculate the possibility of intrinsic alignments of galaxy shapes, which may be responsible for part of the measured weak lensing signal (e.g. van Waerbecke et al 2000;McKay et al 2001) and may be used to reconstruct the shear field (Lee & Pen 2000, 2001. In these studies the assumption is made that the angular momentum vectors of the galaxies are aligned with those of the dark matter halos.…”

mentioning

confidence: 99%

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

Bosch

Abel

Croft

et al. 2002

ApJ

218

177

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We use numerical simulations of structure formation in a cold dark matter cosmology to compare the angular momentum distributions of dark matter and nonradiative gas in a large sample of halos. We show that the two components have identical spin parameter distributions and that their angular momentum distributions within individual halos are very similar, all in excellent agreement with standard assumptions. Despite these similarities, however, we find that the angular momentum vectors of the gas and dark matter are poorly aligned, with a median misalignment angle of $30 , which might have important implications for spin correlation statistics used in weak lensing studies. We present distributions for the component of the angular momentum that is aligned with the total angular momentum of each halo and find that for between 5% and 50% of the mass, this component is negative. This disagrees with the generally adopted '' universal '' angular momentum distribution, for which the mass fraction with negative specific angular momentum is zero. We discuss the implications of our results for the formation of disk galaxies. Since galactic disks generally do not contain counterrotating stars or gas, disk formation cannot occur under detailed conservation of specific angular momentum. We suggest that the material with negative specific angular momentum combines with positive angular momentum material to build a bulge component, and we show that in such a scenario the remaining material can form a disk with a density distribution that is very close to exponential.

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Galaxy Spin Statistics and Spin‐Density Correlation

Cited by 145 publications

References 38 publications

Statistical properties of the linear tidal shear

Statistical properties of the linear tidal shear

Intrinsic alignment-lensing interference as a contaminant of cosmic shear

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

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