Intrinsic alignments: hydro-simulations & cosmology Elisa Chisari University of Oxford July 24, 2015 with F. Schmidt (MPA), C. Dvorkin (Harvard), S. Codis, C. Laigle, R. Gavazzi, C. Pichon, Y. Dubois, K. Benabed (IAP), L. Miller, J. Devriendt, A. Slyz (Oxford)
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Intrinsic alignments: hydro-simulations & cosmology · 2015. 8. 8. · Elisa Chisari Anisotropic inflation In these models, the amplitude of the squeezed-limit bispectrum of the curvature
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Intrinsic alignments:
hydro-simulations & cosmology
Elisa Chisari
University of Oxford
July 24, 2015
with F. Schmidt (MPA), C. Dvorkin (Harvard), S. Codis, C. Laigle, R. Gavazzi, C.Pichon, Y. Dubois, K. Benabed (IAP), L. Miller, J. Devriendt, A. Slyz (Oxford)
A dark matter halo, a cluster of galaxies
The central galaxy in the halo
A satellite galaxy
Galaxies along filaments connectingclusters
Intrinsic galaxy shape correlations
July 24, 2015Elisa Chisari
Image credit: STScI/NASA
LSS 2015
Current observations
Observed alignmentsOkumura & Jing (2009)
● Red galaxiespreferentially pointtowards each other.
● Blue galaxies showno shape alignment.
Int r
insi
c a
lig
nm
en
t
Projected separation between galaxies (Mpc/h)
Elisa Chisari
Okumura & Jing (2009)Blazek et al. (2011)
Chisari & Dvorkin (2013)
Chisari & Dvorkin (2013)
rp +
g
July 24, 2015LSS 2015
Current observations
Singh et al. (2014)
Elisa Chisari
Joachimi et al. (2011)
Early-type galaxies show radialalignments across a large range ofscales. On linear scales, the tidalalignment model provides a gooddescription of the data.
July 24, 2015LSS 2015
Alignments in simulations
Elisa Chisari July 24, 2015LSS 2015
Alignments in Horizon-AGN
Chisari+, in prep
See also: Tenneti+ (2014),Velliscig+ (2015), Codis+ (2015)
Orientation-separationvector correlation
Alignments in simulations
Elisa Chisari July 24, 2015LSS 2015
Chisari+, in prep
Evidence for two mechanisms for alignments
Alignments in simulations
Elisa Chisari July 24, 2015LSS 2015
Projected correlations for alignments
Chisari+, in prep
Monotonous trend with dynamics (or color), but not mass.
Shape measurementmethod matters
Red galaxies have random stellar motions andcarry most of the alignment signal.
Tidal alignment model
Elisa Chisari
Catelan+ (2001)
● Shapes are imprinted at formation● Model is valid on linear scales● C
1 is a free parameter to be constrained from observations
“intrinsic shear”
The tidal alignment model gives a good approximation to theobserved intrinsic alignments of Luminous Red Galaxies.
See also: halo model (Schneider & Bridle, 2010) perturbation theory approach (Blazek +, 2015)
July 24, 2015LSS 2015
Cosmology with intrinsic alignments
Elisa Chisari
Theoretical model in place(at least on the large scales!)
● Intrinsic alignments have been observed in the Universe.Observed alignments of Luminous Red Galaxies are consistentwith galaxies being stretched by the tidal field of the large-scalestructure.
● Hydrodynamical simulations show evidence of twomechanisms for alignments, which will give us insights intogalaxy formation processes that lead to alignments and will allow us toquantify their contamination to lensing.
● Anisotropic inflation induces a scale-dependent bias ongalaxy shapes, similar to the scale-dependent bias that arises fromf
NL (Dalal+, 2008).
● In the future, alignments may probe the physics of the earlyUniverse in novel ways, where clustering or lensing cannot reach.