Measuring Alignments between Galaxies and the Cosmic Web at z similar to 2-3 Using IGM Tomography

作者：Krolewski Alex; Lee Khee Gan; Lukic Zarija; White Martin

来源：Astrophysical Journal, 2017, 837(1): 31.

DOI：10.3847/1538-4357/837/1/31

• cosmology: observations
• galaxies: high-redshift
• intergalactic medium
• large-scale structure of universe
• quasars: absorption lines

Many galaxy formation models predict alignments between galaxy spin and the cosmic web (i.e., directions of filaments and sheets), leading to an intrinsic alignment between galaxies that creates a systematic error in weak-lensing measurements. These effects are often predicted to be stronger at high redshifts (z greater than or similar to 1) that are inaccessible to massive galaxy surveys on foreseeable instrumentation, but IGM tomography of the Ly alpha forest from closely spaced quasars and galaxies is starting to measure the z similar to 2-3 cosmic web with requisite fidelity. Using mock surveys from hydrodynamical simulations, we examine the utility of this technique, in conjunction with coeval galaxy samples, to measure alignment between galaxies and the cosmic web at z similar to 2.5. We show that IGM tomography surveys with less than or similar to 5 h(-1) Mpc sightline spacing can accurately recover the eigenvectors of the tidal tensor, which we use to define the directions of the cosmic web. For galaxy spins and shapes, we use a model parameterized by the alignment strength, Delta < cos theta >, with respect to the tidal tensor eigenvectors from the underlying density field, and also consider observational effects such as errors in the galaxy position angle, inclination, and redshift. Measurements using the upcoming similar to 1 deg(2) CLAMATO tomographic survey and 600 coeval zCOSMOS-Deep galaxies should place 3 sigma limits on extreme alignment models with Delta < cos theta > similar to 0.1, but much larger surveys encompassing > 10,000 galaxies, such as Subaru PFS, will be required to constrain models with Delta < cos theta > similar to 0.03. These measurements will constrain models of galaxy-cosmic web alignment and test tidal torque theory at z similar to 2, improving our understanding of the physics of intrinsic alignments.

• 出版日期2017-3-1