Nearby Peculiar Velocities

Peculiar velocity measurements of 2500 southern spiral galaxies show large-scale flows in the direction of the Hydra-Centaurus clusters which fully participate in the flow themselves. The flow is not uniform over this region and seems to be associated with the denser regions which participate in the flow of amplitude about 400km/s. In the less dense regions the flow is small or non-existent. This makes the flow quite asymmetric and inconsistent with that expected from large-scale, parallel streaming flow that includes all galaxies out to 6000km/s as previously thought. The flow cannot be modelled by a Great Attractor at 4300km/s or the Centaurus clusters at 3500km/s. Indeed, from the density maps derived from the redshift surveys of “optical” and IRAS galaxies, it is difficult to see how the mass concentrations can be responsible particularly as they themselves participate in the flow. These results bring into question the generally accepted reason for the peculiar velocities of galaxies that they arise solely as a consequence of infall into the dense regions of the universe. To the N. of the Great Attractor region, the flow increases and shows no sign of diminishing out to the redshift limit of 8000km/s in this direction. We may have detected flow in the nearest section of the Great Wall.

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Brightest cluster galaxies: the centre can(not?) hold

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3286 ◽

2020 ◽

Vol 500 (1) ◽

pp. 310-318

Author(s):

Roberto De Propris ◽

Michael J West ◽

Felipe Andrade-Santos ◽

Cinthia Ragone-Figueroa ◽

Elena Rasia ◽

...

Keyword(s):

Dark Matter ◽

Local Environment ◽

Major Axis ◽

Theoretical Models ◽

Dark Matter Halo ◽

Gas Distribution ◽

X Ray ◽

Cluster Galaxies ◽

Peculiar Velocities ◽

Brightest Cluster Galaxies

ABSTRACT We explore the persistence of the alignment of brightest cluster galaxies (BCGs) with their local environment. We find that a significant fraction of BCGs do not coincide with the centroid of the X-ray gas distribution and/or show peculiar velocities (they are not at rest with respect to the cluster mean). Despite this, we find that BCGs are generally aligned with the cluster mass distribution even when they have significant offsets from the X-ray centre and significant peculiar velocities. The large offsets are not consistent with simple theoretical models. To account for these observations BCGs must undergo mergers preferentially along their major axis, the main infall direction. Such BCGs may be oscillating within the cluster potential after having been displaced by mergers or collisions, or the dark matter halo itself may not yet be relaxed.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3456 ◽

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.

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The Density of the Universe from the Peculiar Velocities of Sc Galaxies

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1995.tb17628.x ◽

1995 ◽

Vol 759 (1) ◽

pp. 654-657

Author(s):

Wolfram Freudling ◽

Luiz N. Costa ◽

Riccardo Giovanelli ◽

Martha P. Haynes ◽

John J. Salzer ◽

...

Keyword(s):

Peculiar Velocities ◽

The Universe

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Correlation between v sin i and the Peculiar Velocities of Be Stars

Symposium - International Astronomical Union ◽

10.1017/s0074180900195282 ◽

2004 ◽

Vol 215 ◽

pp. 85-86

Author(s):

J. Zorec ◽

J. Chauville ◽

R. Levenhagen ◽

N. V. Leister ◽

D. Ballereau

Keyword(s):

Be Stars ◽

Early Type ◽

Peculiar Velocities

Rough indications that v sin i is correlated with peculiar velocities exist only in the range of early-type Be Stars. Further corrections of space velocities of Be Stars for systematic movements of stellar groups to which they belong, as well as identifications of coeval stars have to be performed in order to decide whether the high rotation of some of them could be the consequence of gravitational encounters.

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Large-Scale Structure in the Universe: Spatial Distribution and Peculiar Velocities

Symposium - International Astronomical Union ◽

10.1017/s0074180900159303 ◽

1987 ◽

Vol 124 ◽

pp. 335-348

Author(s):

Neta A. Bahcall

Keyword(s):

Dark Matter ◽

Spatial Distribution ◽

Large Scale ◽

Large Scale Structure ◽

Scale Structure ◽

Clusters Of Galaxies ◽

Large Scale Structures ◽

Peculiar Velocities ◽

Scale Structures ◽

The Universe

The evidence for the existence of very large scale structures, ∼ 100h−1Mpc in size, as derived from the spatial distribution of clusters of galaxies is summarized. Detection of a ∼ 2000 kms−1 elongation in the redshift direction in the distribution of the clusters is also described. Possible causes of the effect are peculiar velocities of clusters on scales of 10–100h−1Mpc and geometrical elongation of superclusters. If the effect is entirely due to the peculiar velocities of clusters, then superclusters have masses of order 1016.5M⊙ and may contain a larger amount of dark matter than previously anticipated.

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Anti-symmetric clustering signals in the observed power spectrum

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2021/12/003 ◽

2021 ◽

Vol 2021 (12) ◽

pp. 003

Author(s):

José Fonseca ◽

Chris Clarkson

Keyword(s):

Dark Matter ◽

Power Spectrum ◽

Euler Equation ◽

Large Scale ◽

Signal To Noise Ratio ◽

Power Spectra ◽

Large Scale Structure ◽

Scale Structure ◽

Signal To Noise ◽

Peculiar Velocities

Abstract In this paper, we study how to directly measure the effect of peculiar velocities in the observed angular power spectra. We do this by constructing a new anti-symmetric estimator of Large Scale Structure using different dark matter tracers. We show that the Doppler term is the major component of our estimator and we show that we can measure it with a signal-to-noise ratio up to ∼ 50 using a futuristic SKAO HI galaxy survey. We demonstrate the utility of this estimator by using it to provide constraints on the Euler equation.

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