http://www.ita.uni-heidelberg.de/~jmerten/misc/bartelmann_weaklensing.pdf

Weak Gravitational Lensing

We demonstrate a novel technology that combines the power of the multi-object spectrograph with the spatial multiplex advantage of an integral field spectrograph (IFS). The SydneyAAO (Australian Astronomical Observatory) Multi-object IFS (SAMI) is a prototype widefield system at the Anglo-Australian Telescope (AAT) that allows 13 imaging fibre bundles (‘hexabundles’) to be deployed over a 1-degree diameter field of view. Each hexabundle comprises 61 lightly fused multi-mode fibres with reduced cladding and yields a 75 per cent filling factor. Each fibre core diameter subtends 1.6 arcsec on the sky and each hexabundle has a field of view of 15 arcsec diameter. The fibres are fed to the flexible AAOmega double-beam spectrograph, which can be used at a range of spectral resolutions (R = λ/δλ ≈ 1700–13 000) over the optical spectrum (3700–9500 A). We present the first spectroscopic results obtained with SAMI for a sample of galaxies at z ≈ 0.05. We discuss the prospects of implementing hexabundles at a much higher multiplex over wider fields of view in order to carry out spatially resolved spectroscopic surveys of 10 4 –10 5 galaxies.

/pdf/the-sydney-aao-multi-object-integral-field-spectrograph-2jt8r4ekm4.pdf

The Sydney-AAO Multi-object Integral field spectrograph

Gravitational lensing has developed into one of the most powerful tools for the analysis of the dark universe. This review summarises the theory of gravitational lensing, its main current applications and representative results achieved so far. It has two parts. In the first, starting from the equation of geodesic deviation, the equations of thin and extended gravitational lensing are derived. In the second, gravitational lensing by stars and planets, galaxies, galaxy clusters and large-scale structures is discussed and summarised.

Gravitational Lensing

On very large scales, density fluctuations in the Universe are small, suggesting a perturbative model for large-scale clustering of galaxies (or other dark matter tracers), in which the galaxy density is written as a Taylor series in the local mass density, δ, with the unknown coefficients in the series treated as free ``bias'' parameters. We extend this model to include dependence of the galaxy density on the local values of ∇i∇j and ∇ivj, where is the potential and v is the peculiar velocity. We show that only two new free parameters are needed to model the power spectrum and bispectrum up to 4th order in the initial density perturbations, once symmetry considerations and equivalences between possible terms are accounted for. One of the new parameters is a bias multiplying sijsji, where sij = [∇i∇j∇−2−(1/3)δKij]δ. The other multiplies sijtji, where tij = [∇i∇j∇−2−(1/3)δKij](θ−δ), with θ = −(a H dln D/dln a)−1∇v. (There are other, observationally equivalent, ways to write the two terms, e.g., using θ−δ instead of sijsji.) We show how short-range (non-gravitational) non-locality can be included through a controlled series of higher derivative terms, starting with R2∇2δ, where R is the scale of non-locality (this term will be a small correction as long as k2R2 is small, where k is the observed wavenumber). We suggest that there will be much more information in future huge redshift surveys in the range of scales where beyond-linear perturbation theory is both necessary and sufficient than in the fully linear regime.

https://iopscience.iop.org/article/10.1088/1475-7516/2009/08/020/pdf

Clustering of dark matter tracers: generalizing bias for the coming era of precision LSS

The intrinsic alignment of galaxies and its impact on weak gravitational lensing in an era of precision cosmology

We investigate analytically a large-scale coherence in the orientation of galaxies embedded in two-dimensional sheet-like structures in the frame of the tidal torque theory. Assuming that the galaxy spin and the surrounding matter fields are intrinsically aligned in accordance with the tidal torque model, we first derive analytically the probability distribution of the galaxy position angles, and evaluate the degree of their inclinations relative to the plane of the sheet. Then, we apply our analytic approach to the nearby spirals in the Local Super Cluster, and provide theoretical explanations about why and to what degree the nearby spirals are inclined relative to the supergalatic plane. Finally, we conclude that the observed large-scale coherence in the orientation of nearby spirals relative to the supergalactic plane can be quantitatively understood in terms of galaxy intrinsic alignment predicted by the tidal torque theory, and that the spins of luminous galaxies might be more strongly aligned with the surrounding matter than the underlying dark halos. If applied to large scale surveys like Sloan Digital Sky Survey (SDSS), our analytic approach will allow us to measure accurately the strength of galaxy intrinsic alignment which plays a role of statistical error in weak lensing searches and can be used as a fossil record to reconstruct cosmology.

Intrinsic Inclination of Galaxies embedded in Cosmic Sheets and its Cosmological Implications: An Analytic Calculation

We investigate analytically a large-scale coherence in the orientation of galaxies embedded in two-dimensional sheetlike structures in the framework of tidal torque theory. Assuming that the galaxy spin and the surrounding matter fields are intrinsically aligned in accordance with the tidal torque model, we first derive analytically the probability distribution of the galaxy position angles and evaluate the degree of their inclinations relative to the plane of the sheet. Then, we apply our analytic approach to the nearby spiral galaxies in the Local Supercluster and provide theoretical explanations about why and to what degree the nearby spiral galaxies are inclined relative to the supergalactic plane. Finally, we conclude that the observed large-scale coherence in the orientation of nearby spiral galaxies relative to the supergalactic plane can be quantitatively understood in terms of the intrinsic galaxy alignment predicted by the tidal torque theory and that the spins of luminous galaxies might be more strongly aligned with the surrounding matter than with the underlying dark halos. If applied to large-scale surveys like the Sloan Digital Sky Survey, our analytic approach will allow us to measure accurately the strength of the intrinsic galaxy alignment, which plays the role of statistical error in weak lensing searches and can be used as a fossil record to reconstruct cosmology.

http://iopscience.iop.org/article/10.1086/425326/pdf

The Intrinsic Inclination of Galaxies Embedded in Cosmic Sheets and Its Cosmological Implications: An Analytic Calculation

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Intrinsic Inclination of Galaxies embedded in Cosmic Sheets and its Cosmological Implications: An Analytic Calculation

The Intrinsic Inclination of Galaxies Embedded in Cosmic Sheets and Its Cosmological Implications: An Analytic Calculation