A new scale in the bias expansion

Cabass, Giovanni; Schmidt, Fabian

doi:10.48550/arxiv.1812.02731

Cited by 4 publications

(4 citation statements)

References 31 publications

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“…Figure 1 also justifies the approximations we used to compute the drag forces, as one can see by the excellent agreement with the full CAMB output. Other non-gravitational effects like pressure terms (Jeans instability) and radiative transfer effects [41][42][43][44], can be written in a similar form. Ratios of the transfer functions to the total matter one are shown in figure 2.…”

Section: Jcap06(2019)006mentioning

confidence: 99%

Biased tracers of two fluids in the Lagrangian picture

Chen

Castorina

White

2019

J. Cosmol. Astropart. Phys.

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We explore Lagrangian perturbation theory (LPT) for biased tracers in the presence of two fluids, focusing on the case of cold dark matter (CDM) and baryons. The presence of two fluids induces corrections to the Lagrangian bias expansion and tracer advection, both of which we formulate as expansions in the three linear modes of the Lagrangian equations of motion. We compute the linear-order two-fluid corrections in the Zeldovich approximation, finding that modifications to the bias expansion and tracer advection both enter as percentlevel corrections over a large range of wavenumbers at low redshift and draw parallels with the Eulerian formalism. We then discuss nonlinear corrections in the two-fluid picture, and calculate contributions from the relative velocity effect (∝ v 2 r ) at one loop order. Finally, we conduct an exploratory Fisher analysis to assess the impact of two-fluid corrections on baryon acoustic oscillations (BAO) measurements, finding that while modest values of the relative bias parameters can introduce systematic biases in the measured BAO scale of up to 0.5 σ, fitting for these effects as additional parameters increases the error bar by less than 30% across a wide range of bias values. Linear Equations of Motion in Lagrangian SpaceIn the Lagrangian picture, fluid dynamics is encoded in the displacements Ψ σ (q) of fluid elements of each species, σ, originally situated at Lagrangian positions q, such that their Eulerian positions at conformal time τ (dτ = a −1 dt) are given by [28,37,38] x σ (q, τ ) = q + Ψ σ (q, τ ).(2.1)The subscript σ = {c, b} denotes the species, either cold dark matter (CDM) or baryons, respectively, whose motion we are tracking. Assuming that initial displacements are infinitesimally small compared to those at the redshifts of interest, the overdensity, δ σ , of each species at Eulerian

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Section: Jcap06(2019)006mentioning

confidence: 99%

Biased tracers of two fluids in the Lagrangian picture

Chen

Castorina

White

2019

J. Cosmol. Astropart. Phys.

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“…The same scale for galaxies is however more uncertain and not necessarily the same. For instance, Ref [56]. noted that radiative-transfer effects during reionization introduce a new scale in the bias expansion for galaxies, of order the mean free path of ionizing photons.…”

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confidence: 99%

Baryon-CDM isocurvature galaxy bias with IllustrisTNG

Cabass

Nelson

2020

J. Cosmol. Astropart. Phys.

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We study the impact that baryon-CDM relative density perturbations δ bc have on galaxy formation using cosmological simulations with the IllustrisTNG model. These isocurvature (non-adiabatic) perturbations can be induced primordially, if multiple fields are present during inflation, and are generated before baryon-photon decoupling when baryons did not comove with CDM. The presence of long-wavelength δ bc perturbations in our simulations is mimicked by modifying the ratios of the cosmic densities of baryons Ω b and CDM Ω c , at fixed total matter density Ω m . We measure the corresponding galaxy bias parameter b bc δ as the response of galaxy abundances to δ bc . When selecting by total host halo mass, b bc δ is negative and it decreases with mass and redshift. Stellar-mass selected simulated galaxies show a weaker or even the opposite trend because of the competing effects of δ bc on the halo mass function and stellar-to-halo-mass relations. We show that simple modeling of the latter two effects describes b bc δ for stellar-mass-selected objects well. We find b bc δ = 0.6 for M * = 10 11 M /h and z = 0.5, which is representative of BOSS DR12 galaxies. For δ bc modes generated by baryon-photon interactions, we estimate the impact on the DR12 power spectrum to be below 1%, and shifts on inferred distance and growth rate parameters should not exceed 0.1%. arXiv:1907.04317v2 [astro-ph.CO]

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“…For halos this has the order of magnitude of the Lagrangian radius of the overdensity clump that collapses into a host halo. For the line emission this has the order of the Jeans scale of the diffuse gas [120,130]. For galaxies R * depends both on the host halo properties and on the details of galaxy formation, e.g.…”

Section: Biased Tracersmentioning

confidence: 99%