scholarly journals The Peculiar Velocity of the Local Group in the Direction of the Virgo Cluster

1987 ◽  
Vol 117 ◽  
pp. 115-115
Author(s):  
L. Staveley-Smith ◽  
R. D. Davies
Keyword(s):  
Local Group ◽  
Hubble Constant ◽  
Virgo Cluster ◽  
Density Parameter ◽  
Field Observations ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Scaling Methods ◽  
Crucial Test ◽  
Local Value

The measurement of the amplitude of the Local Group infall velocity towards the Virgo Cluster is a crucial test for the value of the universal density parameter Ωo and the ratio of the universal Hubble constant to its local value. However, a very large discrepancy exists between total infall velocities derived from peculiar velocity field observations and those derived from “scaling” methods using standard candles in the Virgo and Coma clusters. The former have tended to produce high Virgocentric peculiar velocities (350 to 500 km s−1) whilst the latter give much lower values (-70 to 100 km s−1).

scholarly journals Spiral Galaxies and the Peculiar Velocity Field

1996 ◽  
Vol 168 ◽  
pp. 183-191 ◽  
Author(s):  
Riccardo Giovanelli ◽  
Martha P. Haynes ◽  
Pierre Chamaraux ◽  
Luiz N. Da Costa ◽  
Wolfram Freudling ◽  
...  
Keyword(s):  
Velocity Field ◽  
Reference Frame ◽  
Large Scale ◽  
Local Group ◽  
Spiral Galaxies ◽  
Density Parameter ◽  
Compelling Evidence ◽  
Homogeneous Sample ◽  
Peculiar Velocity ◽  
Peculiar Velocities

We report results of a redshift-independent distance measurement survey that extends to all sky and out to a redshift of approximately 7500 km s−1. Tully–Fisher (TF) distances for a homogeneous sample of 1600 late spiral galaxies are used to analyze the peculiar velocity field. We find large peculiar velocities in the neighborhood of superclusters, such as Perseus–Pisces (PP) and Hydra–Centaurus, but the main clusters embedded in those regions appear to be virtually at rest in the CMB reference frame. We find no compelling evidence for large-scale bulk flows, whereby the Local Group, Hydra–Cen and PP would share a motion of several hundred km s−1with respect to the CMB. Denser sampling in the PP region allows a clear detection of infall and backflow motions, which can be used to map the mass distribution in the supercluster and to obtain an estimate of the cosmological density parameter.

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 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 Tully-Fisher Relation and its Application to the Distance Scale

1983 ◽  
Vol 6 ◽  
pp. 269-282 ◽  
Author(s):  
M. Aaronson
Keyword(s):  
Group Velocity ◽  
Deceleration Parameter ◽  
Local Group ◽  
Hubble Constant ◽  
Distance Scale ◽  
Expansion Rate ◽  
Distance Indicator ◽  
Fisher Relation ◽  
Hubble Flow ◽  
Local Value

AbstractThe Tully-Fisher relation applied in the infrared appears to be the best global distance indicator presently available for determining the expansion rate and deviations from uniform Hubble flow. In this article recent results obtained using the IR/H I method are reviewed. A Virgo-directed Local Group velocity of about 300 km s–1 is indicated (implying a local value for the deceleration parameter qo ~ 0.05 – 0.1) along with a “best guess” value for the Hubble Constant of 85 km s-1 Mpc-1.

scholarly journals Joint analysis of 6dFGS and SDSS peculiar velocities for the growth rate of cosmic structure and tests of gravity

2020 ◽  
Vol 497 (1) ◽  
pp. 1275-1293 ◽  
Author(s):  
Khaled Said ◽  
Matthew Colless ◽  
Christina Magoulas ◽  
John R Lucey ◽  
Michael J Hudson
Keyword(s):  
Growth Rate ◽  
Large Scale ◽  
Mass Density ◽  
Hubble Constant ◽  
Growth Index ◽  
Sloan Digital Sky Survey ◽  
Joint Analysis ◽  
Density Parameter ◽  
Peculiar Velocities ◽  
Fluctuation Amplitude

ABSTRACT Measurement of peculiar velocities by combining redshifts and distance indicators is a powerful way to measure the growth rate of a cosmic structure and test theories of gravity at low redshift. Here we constrain the growth rate of the structure by comparing observed Fundamental Plane peculiar velocities for 15 894 galaxies from the 6dF Galaxy Survey (6dFGS) and Sloan Digital Sky Survey (SDSS) with predicted velocities and densities from the 2M++ redshift survey. We measure the velocity scale parameter $\beta \equiv {\Omega _{\rm m}^\gamma }/b = 0.372^{+0.034}_{-0.050}$ and $0.314^{+0.031}_{-0.047}$ for 6dFGS and SDSS, respectively, where Ωm is the mass density parameter, γ is the growth index, and b is the bias parameter normalized to the characteristic luminosity of galaxies, L*. Combining 6dFGS and SDSS, we obtain β = 0.341 ± 0.024, implying that the amplitude of the product of the growth rate and the mass fluctuation amplitude is fσ8 = 0.338 ± 0.027 at an effective redshift z = 0.035. Adopting Ωm = 0.315 ± 0.007, as favoured by Planck and using γ = 6/11 for General Relativity and γ = 11/16 for DGP gravity, we get $S_8(z=0) = \sigma _8 \sqrt{\Omega _{\rm m}/0.3} =0.637 \pm 0.054$ and 0.741 ± 0.062 for GR and DGP, respectively. This measurement agrees with other low-redshift probes of large-scale structure but deviates by more than 3σ from the latest Planck CMB measurement. Our results favour values of the growth index γ &gt; 6/11 or a Hubble constant H0 &gt; 70 km s−1 Mpc−1 or a fluctuation amplitude σ8 &lt; 0.8 or some combination of these. Imminent redshift surveys such as Taipan, DESI, WALLABY, and SKA1-MID will help to resolve this tension by measuring the growth rate of cosmic structure to 1 per cent in the redshift range 0 &lt; z &lt; 1.

scholarly journals Brightest Stars in Galaxies as Distance Indicators

1986 ◽  
Vol 116 ◽  
pp. 31-41 ◽  
Author(s):  
Allan Sandage
Keyword(s):  
Local Group ◽  
Hubble Constant ◽  
Absolute Magnitude ◽  
Virgo Cluster ◽  
Current Status ◽  
Type I ◽  
Red Supergiants ◽  
Absolute Magnitudes ◽  
Distance Indicators ◽  
Eddington Limit

The current status of the absolute magnitude calibration of the brightest blue and red supergiants in galaxies of different absolute magnitudes shows trends of M(star) with M(parent galaxy). Red supergiants show a more shallow correlation than the blue stars for galaxies brighter than MB = −14. For fainter galaxies, the red supergiant method appears to become totally degenerate.Four areas of application of the brightest star data are discussed as (1) determining MB of the Eddington limit to be ∼−10 for blue supergiants, (2) calibration of MB(max) = −20.0±0.4 for type I supernovae, leading to a Hubble constant of HO = 43±10 km s−1 Mpc−1, (3) detection of the deceleration of the cosmological expansion by the Local Group leading to a Local Group mass of 4×1011 M⊙ and a mass-to-blue light ratio of 3, and (4) use of the brightest stars to map the Virgo cluster velocity perturbation of the Hubble flow.

scholarly journals The impact of peculiar velocities on the estimation of the Hubble constant from gravitational wave standard sirens

2020 ◽  
Vol 495 (1) ◽  
pp. 90-97 ◽  
Author(s):  
Constantina Nicolaou ◽  
Ofer Lahav ◽  
Pablo Lemos ◽  
William Hartley ◽  
Jonathan Braden
Keyword(s):  
Gravitational Wave ◽  
Hubble Constant ◽  
Host Galaxy ◽  
Nearby Galaxy ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Systematic Uncertainties ◽  
Proposed Model ◽  
Nearby Galaxies ◽  
The Impact

ABSTRACT In this work, we investigate the systematic uncertainties that arise from the calculation of the peculiar velocity when estimating the Hubble constant (H0) from gravitational wave standard sirens. We study the GW170817 event and the estimation of the peculiar velocity of its host galaxy, NGC 4993, when using Gaussian smoothing over nearby galaxies. NGC 4993 being a relatively nearby galaxy, at ∼40 Mpc away, is subject to a significant effect of peculiar velocities. We demonstrate a direct dependence of the estimated peculiar velocity value on the choice of smoothing scale. We show that when not accounting for this systematic, a bias of ${\sim }200~{\rm km\, s^{-1}}$ in the peculiar velocity incurs a bias of ${\sim }4~{\rm km\, s^{-1}\, Mpc^{-1}}$ on the Hubble constant. We formulate a Bayesian model that accounts for the dependence of the peculiar velocity on the smoothing scale and by marginalizing over this parameter we remove the need for a choice of smoothing scale. The proposed model yields $H_0 = 68.6 ^{+14.0} _{-8.5}~{\rm km\, s^{-1}\, Mpc^{-1}}$. We demonstrate that under this model a more robust unbiased estimate of the Hubble constant from nearby GW sources is obtained.

scholarly journals Cosmological parameters from the comparison of peculiar velocities with predictions from the 2M++ density field

2014 ◽  
Vol 11 (S308) ◽  
pp. 318-321
Author(s):  
Michael J. Hudson ◽  
Jonathan Carrick ◽  
Stephen J. Turnbull ◽  
Guilhem Lavaux
Keyword(s):  
Cosmic Microwave Background ◽  
Local Group ◽  
Cosmological Parameters ◽  
Density Field ◽  
Bulk Flow ◽  
Microwave Background ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Best Fit ◽  
Good Agreement

AbstractUsing redshifts from the 2M++ redshift compilation, we reconstruct the density of galaxies within 200 h−1 Mpc, and compare the predicted peculiar velocities Tully-Fisher and SNe peculiar velocities. The comparison yields a best-fit value of β ≡ Ωm0.55/b* = 0.431 ± 0.021, suggesting Ωm0.55σ8,lin = 0.401 ± 0.024, in good agreement with other probes. The predicted peculiar velocity of the Local Group from sources within the 2M++ volume is 540 ± 40 km s−1, towards l = 268° ± 4°, b = 38° ± 6°, which is misaligned by only 10° with the Cosmic Microwave Background dipole. To account for sources outside the 2M++ volume, we fit simultaneously for β* and an external bulk flow in our analysis. The external bulk flow has a velocity of 159 ± 23 km s−1 towards l = 304° ± 11°, b6° ± 13°.

scholarly journals Standard siren speeds: improving velocities in gravitational-wave measurements of H0

2020 ◽  
Vol 492 (3) ◽  
pp. 3803-3815 ◽  
Author(s):  
Cullan Howlett ◽  
Tamara M Davis
Keyword(s):  
Gravitational Wave ◽  
Bayesian Model ◽  
Bayesian Model Averaging ◽  
Model Averaging ◽  
Hubble Constant ◽  
Host Galaxy ◽  
Peculiar Velocity ◽  
Additional Information ◽  
Wave Measurements ◽  
Peculiar Velocities

ABSTRACT We re-analyse data from the gravitational-wave event GW170817 and its host galaxy NGC 4993 to demonstrate the importance of accurate total and peculiar velocities when measuring the Hubble constant using this nearby standard siren. We show that a number of reasonable choices can be made to estimate the velocities for this event, but that systematic differences remain between these measurements depending on the data used. This leads to significant changes in the Hubble constant inferred from GW170817. We present Bayesian model averaging as one way to account for these differences, and obtain $H_{0}=66.8^{+13.4}_{-9.2}\, \mathrm{km\, s^{-1}\, Mpc^{-1}}$. Adding additional information on the viewing angle from high-resolution imaging of the radio counterpart refines this to $H_{0}=64.8^{+7.3}_{-7.2}\, \mathrm{km\, s^{-1}\, Mpc^{-1}}$. During this analysis, we also present an alternative Bayesian model for the posterior on H0 from standard sirens that works more closely with observed quantities from redshift and peculiar velocity surveys. Our results more accurately capture the true uncertainty on the total and peculiar velocities of NGC 4993 and show that exploring how well different data sets characterize galaxy groups and the velocity field in the local Universe could improve this measurement further. These considerations impact any low-redshift distance measurement, and the improvements we suggest here can also be applied to standard candles like Type Ia supernovae. GW170817 is particularly sensitive to peculiar velocity uncertainties because it is so close. For future standard siren measurements, the importance of this error will decrease as (i) we will measure more distant standard sirens and (ii) the random direction of peculiar velocities will average out with more detections.

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