Imprint of inflation on galaxy shape correlations

Journal Article · Thu Oct 01 04:00:00 EDT 2015 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2015/10/032· OSTI ID:22525244

Schmidt, Fabian ^[1]; Chisari, Nora Elisa ^[2]; Dvorkin, Cora ^[3]

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1. Max-Planck-Institute for Astrophysics, Karl-Schwarzschild-Str. 1, 85741 Garching (Germany)
2. Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States)
3. Institute for Theory and Computation, Harvard University, 60 Garden St., Cambridge, MA 02138 (United States)

We show that intrinsic (not lensing-induced) correlations between galaxy shapes offer a new probe of primordial non-Gaussianity and inflationary physics which is complementary to galaxy number counts. Specifically, intrinsic alignment correlations are sensitive to an anisotropic squeezed limit bispectrum of the primordial perturbations. Such a feature arises in solid inflation, as well as more broadly in the presence of light higher spin fields during inflation (as pointed out recently by Arkani-Hamed and Maldacena). We present a derivation of the all-sky two-point correlations of intrinsic shapes and number counts in the presence of non-Gaussianity with general angular dependence, and show that a quadrupolar (spin-2) anisotropy leads to the analog in galaxy shapes of the well-known scale-dependent bias induced in number counts by isotropic (spin-0) non-Gaussianity. Moreover, in the presence of non-zero anisotropic non-Gaussianity, the quadrupole of galaxy shapes becomes sensitive to far superhorizon modes. These effects come about because long-wavelength modes induce a local anisotropy in the initial power spectrum, with which galaxies will correlate. We forecast that future imaging surveys could provide constraints on the amplitude of anisotropic non-Gaussianity that are comparable to those from the Cosmic Microwave Background (CMB). These are complementary as they probe different physical scales. The constraints, however, depend on the sensitivity of galaxy shapes to the initial conditions which we only roughly estimate from observed tidal alignments.

• OSTI ID: 22525244
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 10 Vol. 2015; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALIGNMENT
ANISOTROPY
COMPARATIVE EVALUATIONS
CORRELATIONS
COSMOLOGICAL INFLATION
DISTURBANCES
GALAXIES
GRAVITATIONAL LENSES
INFLATIONARY UNIVERSE
LIMITING VALUES
PROBES
RELICT RADIATION
SPIN
VISIBLE RADIATION