scholarly journals Cosmic flows in the nearby Universe: new peculiar velocities from SNe and cosmological constraints

2020 ◽  
Vol 498 (2) ◽  
pp. 2703-2718 ◽  
Author(s):  
Supranta S Boruah ◽  
Michael J Hudson ◽  
Guilhem Lavaux
Keyword(s):  
Velocity Field ◽  
Velocity Fields ◽  
Bulk Flow ◽  
Peculiar Velocity ◽  
Cosmological Constraints ◽  
Peculiar Velocities ◽  
Type Ia ◽  
Galaxy Redshift ◽  
Ia Supernovae ◽  
Distance Indicators

ABSTRACT The peculiar velocity field offers a unique way to probe dark matter density field on large scales at low redshifts. In this work, we have compiled a new sample of 465 peculiar velocities from low redshift ($z$ < 0.067) Type Ia supernovae. We compare the reconstructed velocity field derived from the 2M++ galaxy redshift compilation to the supernovae, the SFI++ and the 2MTF Tully–Fisher distance catalogues. We used a forward method to jointly infer the distances and the velocities of distance indicators by comparing the observations to the reconstruction. Comparison of the reconstructed peculiar velocity fields to observations allows us to infer the cosmological parameter combination fσ8, and the bulk flow velocity arising from outside the survey volume. The residual bulk flow arising from outside the 2M++ volume is inferred to be $171^{+11}_{-11}$ km s−1 in the direction l = 301° ± 4° and b = 0° ± 3°. We obtain fσ8 = 0.400 ± 0.017, equivalent to S8 ≈ σ8(Ωm/0.3)0.55 = 0.776 ± 0.033, which corresponds to an approximately $4{{\ \rm per\ cent}}\,$ statistical uncertainty on the value of fσ8. Our inferred value is consistent with other low redshift results in the literature.

scholarly journals The effects of peculiar velocities in SN Ia environments on the local H0 measurement

2020 ◽  
Vol 500 (3) ◽  
pp. 3728-3742
Author(s):  
Thomas M Sedgwick ◽  
Chris A Collins ◽  
Ivan K Baldry ◽  
Philip A James
Keyword(s):  
Hubble Constant ◽  
Density Parameter ◽  
Host Galaxies ◽  
Peculiar Velocities ◽  
Standard Candle ◽  
Modern Cosmology ◽  
Type Ia ◽  
The Difference ◽  
Ia Supernovae ◽  
Distance Indicators

ABSTRACT The discrepancy between estimates of the Hubble constant (H0) measured from local (z ≲  0.1) scales and from scales of the sound horizon is a crucial problem in modern cosmology. Peculiar velocities (vpec) of standard candle distance indicators can systematically affect local H0 measurements. We here use 2MRS galaxies to measure the local galaxy density field, finding a notable z  <  0.05 underdensity in the SGC-6dFGS region of 27  ±  2 per cent. However, no strong evidence for a ‘Local Void’ pertaining to the full 2MRS sky coverage is found. Galaxy densities are used to measure a density parameter, Δϕ+−, which we introduce as a proxy for vpec that quantifies density gradients along a supernova (SN) line of sight. Δϕ+− is found to correlate with local H0 estimates from 88 Pantheon Type Ia supernovae (SNe Ia; 0.02  <  z  <  0.05). Density structures on scales of ∼50 Mpc are found to correlate strongest with H0 estimates in both the observational data and in mock data from the MDPL2-Galacticus simulation. Using trends of H0 with Δϕ+−, we can correct for the effects of density structure on local H0 estimates, even in the presence of biased vpec. However, the difference in the inferred H0 estimate with and without the peculiar velocity correction is limited to < 0.1  per cent. We conclude that accounting for environmentally induced peculiar velocities of SN Ia host galaxies does not resolve the tension between local and CMB-derived H0 estimates.

scholarly journals AN UNBIASED METHOD OF MODELING THE LOCAL PECULIAR VELOCITY FIELD WITH TYPE Ia SUPERNOVAE

2011 ◽  
Vol 732 (2) ◽  
pp. 65 ◽  
Author(s):  
Anja Weyant ◽  
Michael Wood-Vasey ◽  
Larry Wasserman ◽  
Peter Freeman
Keyword(s):  
Velocity Field ◽  
Type Ia Supernovae ◽  
Peculiar Velocity ◽  
Type Ia ◽  
Ia Supernovae

scholarly journals Correcting for peculiar velocities of Type Ia supernovae in clusters of galaxies

2018 ◽  
Vol 615 ◽  
pp. A162 ◽  
Author(s):  
P.-F. Léget ◽  
M. V. Pruzhinskaya ◽  
A. Ciulli ◽  
E. Gangler ◽  
G. Aldering ◽  
...  
Keyword(s):  
Galaxy Clusters ◽  
Virgo Cluster ◽  
Type Ia Supernovae ◽  
Hubble Diagram ◽  
Cosmological Redshift ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Velocity Correction ◽  
Type Ia ◽  
Ia Supernovae

Context. Type Ia supernovae (SNe Ia) are widely used to measure the expansion of the Universe. To perform such measurements the luminosity and cosmological redshift (z) of the SNe Ia have to be determined. The uncertainty on z includes an unknown peculiar velocity, which can be very large for SNe Ia in the virialized cores of massive clusters. Aims. We determine which SNe Ia exploded in galaxy clusters using 145 SNe Ia from the Nearby Supernova Factory. We then study how the correction for peculiar velocities of host galaxies inside the clusters improves the Hubble residuals. Methods. We found 11 candidates for membership in clusters. We applied the biweight technique to estimate the redshift of a cluster. Then, we used the galaxy cluster redshift instead of the host galaxy redshift to construct the Hubble diagram. Results. For SNe Ia inside galaxy clusters, the dispersion around the Hubble diagram when peculiar velocities are taken into account is smaller compared with a case without peculiar velocity correction, which has a wRMS = 0.130 ± 0.038 mag instead of wRMS = 0.137 ± 0.036 mag. The significance of this improvement is 3.58σ. If we remove the very nearby Virgo cluster member SN2006X (z < 0.01) from the analysis, the significance decreases to 1.34σ. The peculiar velocity correction is found to be highest for the SNe Ia hosted by blue spiral galaxies. Those SNe Ia have high local specific star formation rates and smaller stellar masses, which is seemingly counter to what might be expected given the heavy concentration of old, massive elliptical galaxies in clusters. Conclusions. As expected, the Hubble residuals of SNe Ia associated with massive galaxy clusters improve when the cluster redshift is taken as the cosmological redshift of the supernova. This fact has to be taken into account in future cosmological analyses in order to achieve higher accuracy for cosmological redshift measurements. We provide an approach to do so.

scholarly journals The peculiar velocity field up to z ∼ 0.05 by forward-modelling Cosmicflows-3 data

2019 ◽  
Vol 488 (4) ◽  
pp. 5438-5451 ◽  
Author(s):  
R Graziani ◽  
H M Courtois ◽  
G Lavaux ◽  
Y Hoffman ◽  
R B Tully ◽  
...  
Keyword(s):  
Velocity Field ◽  
Initial Conditions ◽  
Selection Function ◽  
Data Sets ◽  
Forward Modelling ◽  
Local Universe ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
The Galaxy ◽  
Distance Indicators

Abstract A hierarchical Bayesian model is applied to the Cosmicflows-3 catalogue of galaxy distances in order to derive the peculiar velocity field and distribution of matter within z ∼ 0.054. The model assumes the ΛCDM model within the linear regime and includes the fit of the galaxy distances together with the underlying density field. By forward modelling the data, the method is able to mitigate biases inherent to peculiar velocity analyses, such as the Homogeneous Malmquist bias or the lognormal distribution of peculiar velocities. The statistical uncertainty on the recovered velocity field is about 150 km s−1 depending on the location, and we study systematics coming from the selection function and calibration of distance indicators. The resulting velocity field and related density fields recover the cosmography of the Local Universe which is presented in an unprecedented volume of our Universe 10 times larger than previously reached. This methodology opens the doors to reconstruction of initial conditions for larger and more accurate constrained cosmological simulations. This work is also preparatory to larger peculiar velocity data sets coming from Wallaby, TAIPAN, or LSST.

The 6dFGS peculiar velocity field

2012 ◽  
Vol 8 (S289) ◽  
pp. 269-273
Author(s):  
Christopher M. Springob ◽  
Christina Magoulas ◽  
Matthew Colless ◽  
D. Heath Jones ◽  
Lachlan Campbell ◽  
...  
Keyword(s):  
Velocity Field ◽  
Gaussian Model ◽  
Density Field ◽  
Bulk Flow ◽  
Bayesian Probability ◽  
Distortion Parameter ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Redshift Survey ◽  
Space Distortion

AbstractThe 6dF Galaxy Survey (6dFGS) is an all-southern-sky galaxy survey, including 125,000 redshifts and a Fundamental Plane (FP) subsample of 10,000 peculiar velocities. This makes 6dFGS the largest peculiar-velocity sample to date. We have fitted the FP with a tri-variate Gaussian model using a maximum-likelihood approach, and derive the Bayesian probability distribution of the peculiar velocity for each of the 10,000 galaxies. We fit models of the velocity field, including comparisons to the field predicted from the redshift-survey density field, to derive the values of the redshift-space distortion parameter β, the bulk flow and the residual bulk flow in excess of that predicted from the density field. We compare these results to those derived by other authors and discuss the cosmological implications.

scholarly journals Local Hole revisited: evidence for bulk motions and self-consistent outflow

2019 ◽  
Vol 490 (4) ◽  
pp. 4715-4720 ◽  
Author(s):  
T Shanks ◽  
L M Hogarth ◽  
N Metcalfe ◽  
J Whitbourn
Keyword(s):  
Velocity Measurements ◽  
Redshift Distribution ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Cent Increase ◽  
The Galaxy ◽  
Type Ia ◽  
Galaxy Redshift ◽  
Local Value ◽  
Good Agreement

ABSTRACT We revisit our mapping of the ‘Local Hole’, a large underdensity in the local galaxy redshift distribution that extends out to redshift z ≈ 0.05 and a potential source of outflows that may perturb the global expansion rate and thus help mitigate the present ‘H0 tension’. First, we compare local peculiar velocities measured via the galaxy average redshift–magnitude Hubble diagram, $\overline{z}(m)$, with a simple dynamical outflow model based on the average underdensity in the Local Hole. We find that this outflow model is in good agreement with our peculiar velocity measurements from $\overline{z}(m)$ and not significantly inconsistent with Type Ia supernova peculiar velocity measurements from at least the largest previous survey. This outflow could cause an ≈2–3 per cent increase in the local value of Hubble’s constant. Second, considering anisotropic motions, we find that the addition of the outflow model may improve the $\overline{z}(m)$ fit of a bulk flow where galaxies are otherwise at rest in the Local Group frame. We conclude that the Local Hole plus neighbouring overdensities such as the Shapley Supercluster may cause outflow and bulk motions out to ≈150 h−1 Mpc that are cosmologically significant and that need to be taken into account in estimating Hubble’s constant.

Cosmological constraints on the variable modified Chaplygin gas model by using MCMC approach

2015 ◽  
Vol 24 (08) ◽  
pp. 1550059 ◽  
Author(s):  
Jian-bin Chen ◽  
Zhen-qi Liu ◽  
Lili Xing
Keyword(s):  
Apparent Horizon ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Mean Values ◽  
Cosmological Constraints ◽  
Variable Modified Chaplygin Gas ◽  
Type Ia ◽  
Ia Supernovae

We investigate the cosmological constraints on the variable modified Chaplygin gas (VMCG) model from the latest observational data: Union2 dataset of Type Ia supernovae (SNIa), the observational Hubble data (OHD), the baryon acoustic oscillations (BAO) and the cosmic microwave background (CMB) data. By using the Markov chain Monte Carlo (MCMC) method, we obtain the mean values of parameters in the flat model: [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. Furthermore, we investigate the thermodynamical properties of VMCG model at apparent horizon, event horizon and particle horizon respectively.

scholarly journals On the cosmological performance of photometrically classified supernovae with machine learning

2020 ◽  
Vol 497 (3) ◽  
pp. 2974-2991
Author(s):  
Marcelo Vargas dos Santos ◽  
Miguel Quartin ◽  
Ribamar R R Reis
Keyword(s):  
Machine Learning ◽  
Mean Squared Error ◽  
Light Curves ◽  
Observational Cosmology ◽  
Automated Classification ◽  
Cosmological Constraints ◽  
Search Processes ◽  
Type Ia ◽  
Ia Supernovae

ABSTRACT The efficient classification of different types of supernovae is one of the most important problems for observational cosmology. However, spectroscopic confirmation of most objects in upcoming photometric surveys, such as the the Rubin Observatory Legacy Survey of Space and Time, will be unfeasible. The development of automated classification processes based on photometry has thus become crucial. In this paper, we investigate the performance of machine learning (ML) classification on the final cosmological constraints using simulated light-curves from the Supernova Photometric Classification Challenge, released in 2010. We study the use of different feature sets for the light-curves and many different ML pipelines based on either decision-tree ensembles or automated search processes. To construct the final catalogues we propose a threshold selection method, by employing a bias-variance tradeoff. This is a very robust and efficient way to minimize the mean squared error. With this method, we were able to obtain very strong cosmological constraints, which allowed us to keep $\sim 75{{\ \rm per\ cent}}$ of the total information in the Type Ia supernovae when using the SALT2 feature set, and $\sim 33{{\ \rm per\ cent}}$ for the other cases (based either on the Newling model or on standard wavelet decomposition).

Type IA supernovae and cosmic peculiar velocities

1992 ◽  
Vol 103 ◽  
pp. 379 ◽  
Author(s):  
Douglas L. Miller ◽  
David Branch
Keyword(s):  
Type Ia Supernovae ◽  
Peculiar Velocities ◽  
Type Ia ◽  
Ia Supernovae
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