Constrained realizations of 2MRS density and peculiar velocity fields: growth rate and local flow

Abstract

We generate constrained realizations (CRs) of the density and peculiar velocity fields within 200 ℎ −1 Mpc from the final release of the Two-Micron All-Sky Redshift Survey (2MRS) -the densest all-sky redshift survey to date. The CRs are generated by combining a Wiener filter estimator in spherical Fourier-Bessel space with random realizations of log-normally distributed density fields and Poisson-sampled galaxy positions. The algorithm is tested and calibrated on a set of semi-analytic mock catalogs mimicking the environment of the Local Group (LG), to rigorously account for the statistical and systematic errors of the reconstruction method. By comparing our peculiar velocity CRs with the observed velocities from the Cosmicflows-3 catalog, we constrain the normalized linear growth rate to 𝑓 𝜎 lin 8 = 0.363 ± 0.070, which is consistent with the latest Planck results as well as other direct probes. Simultaneously, we estimate a bulk flow contribution from sources beyond the 2MRS reconstruction volume of 𝐵 ext = 164 ± 68 km s −1 towards 𝑙 = 311 ± 24 • , 𝑏 = 0 ± 23 • . The total reconstructed velocity field at the position of the LG, smoothed with a 1 ℎ −1 Mpc Gaussian, is 552 ± 71 km s −1 towards 𝑙 = 274.3 ± 7.9 • , 𝑏 = 33.9 ± 8.1 • , in good agreement with the observed CMB dipole. The total reconstructed bulk flow within different radii is compatible with other measurements. Within a 50 ℎ −1 Mpc Gaussian window we find a bulk flow of 229 ± 45 km s −1 towards 𝑙 = 295 ± 11 • , 𝑏 = 5 ± 11 • . The code used to generate the CRs and obtain these results, dubbed CORAS, is made publicly available.

New Constraints on Anisotropic Expansion from Supernovae Type Ia

“…The latter approach has a long history, originally having been used to predict the peculiar velocities of FP and TF samples (Hudson 1993;Strauss & Willick 1995;Davis et al 1996) but more recently applied to peculiar velocity data that include SNe type Ia. (Riess et al 1997;Radburn-Smith et al 2004;Pike & Hudson 2005;Neill et al 2007;Turnbull et al 2012;Carrick et al 2015;Boruah et al 2020b;Lilow & Nusser 2021;Stahl et al 2021).…”

“…The term 𝜎 2 NL = 150 km/s represents uncertainty in the linear velocity prediction due to unaccounted-for non-linearities, which we fix at the value recommended in Carrick et al (2015). How-ever, the uncertainty in our reconstructed peculiar velocity increases with redshift, an effect that was ignored in previous work: firstly, the predicted peculiar velocities for tracers near the outer edge of the 2M++ catalogue (200 Mpc/ℎ) have larger uncertainty because of unaccounted-for structures outside of the survey limits, as well as because of lack of coverage beyond 125 Mpc/ℎ for part of the sky (Hollinger & Hudson 2021); secondly, the noise increases at larger distances due to the smaller number of galaxies with larger weights that are used to represent the density field (Lilow & Nusser 2021). We capture these effects via the redshift-dependent term:…”

Peculiar-velocity cosmology with Types Ia and II supernovae

“…with observed peculiar velocities from the Cosmicflows-3 catalogue (CF3;Tully et al 2016),Lilow & Nusser (2021) derive 𝑓 𝜎 lin 8 = 0.363 ± 0.070. We convert this to 𝑆 8 identically to our own result.…”

Galaxy flows within 8,000 km/s from Numerical Action methods

“…Most peculiar velocity studies invoke linear perturbation theory. Cosmicflows-3 distance and velocity information (Tully et al 2016) and 2MRS, the 2MASS red- shift survey to K s = 11.75 (Huchra et al 2012), have been used in linear regime studies (Graziani et al 2019;Lilow & Nusser 2021;Hoffman et al 2021) and there have been studies with variant samples (Carrick et al 2015;Jasche & Lavaux 2019;Kitaura et al 2021).…”

“…Likewise, our description of external tidal influences with 44 major clusters at 8, 000 − 16, 000 km s −1 is crude. Were we to repeat this exercise, we might use the description of matter in this velocity regime given by Lilow & Nusser (2021).…”