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

Weyant, Anja; Wood-Vasey, Michael; Wasserman, Larry; Freeman, Peter E.

doi:10.1088/0004-637x/732/2/65

Cited by 22 publications

(44 citation statements)

References 105 publications

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“…Peculiar velocities typically determine f σ 8 at very low redshift, z < 0.1, and thus provide an important complementary test of both dark energy and modified gravity. There has been a lot of activity in using velocities to to test for consistency with expectations from the ΛCDM model [335,336,[344][345][346][347][348][349][350][351][352][353] and to measure cosmological parameters [337,354]; see figure 12. Chief concerns include the reliability of distance indicators which are required in order to infer the peculiar velocity.…”

Section: Peculiar Velocitiesmentioning

confidence: 99%

Dark energy two decades after: observables, probes, consistency tests

2017

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The discovery of the accelerating universe in the late 1990s was a watershed moment in modern cosmology, as it indicated the presence of a fundamentally new, dominant contribution to the energy budget of the universe. Evidence for dark energy, the new component that causes the acceleration, has since become extremely strong, owing to an impressive variety of increasingly precise measurements of the expansion history and the growth of structure in the universe. Still, one of the central challenges of modern cosmology is to shed light on the physical mechanism behind the accelerating universe. In this review, we briefly summarize the developments that led to the discovery of dark energy. Next, we discuss the parametric descriptions of dark energy and the cosmological tests that allow us to better understand its nature. We then review the cosmological probes of dark energy. For each probe, we briefly discuss the physics behind it and its prospects for measuring dark energy properties. We end with a summary of the current status of dark energy research.

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Section: Peculiar Velocitiesmentioning

confidence: 99%

Dark energy two decades after: observables, probes, consistency tests

2017

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“…In this paper, we use Type Ia supernovae (SNeIa) as our peculiar velocity tracers. SNe have also been used as peculiar velocity probes by a number of authors (Riess, Press & Kirshner 1995; Riess et al 1997; Radburn‐Smith, Lucey & Hudson 2004; Lucey, Radburn‐Smith & Hudson 2005; Pike & Hudson 2005; Haugbølle et al 2007; Colin et al 2011; Dai, Kinney & Stojkovic 2011; Weyant et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Cosmic flows in the nearby universe from Type Ia supernovae

Turnbull¹,

Hudson²,

Feldman³

et al. 2011

Monthly Notices of the Royal Astronomical Society

241

197

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Peculiar velocities are one of the only probes of very large scale mass density fluctuations in the nearby Universe. We present new ‘minimal variance’ bulk flow measurements based upon the ‘First Amendment’ compilation of 245 Type Ia supernovae (SNe) peculiar velocities and find a bulk flow of 249 ± 76 km s−1 in the direction l= 319°± 18°, b= 7°± 14°. The SNe bulk flow is consistent with the expectations of Λ cold dark matter (ΛCDM). However, it is also marginally consistent with the bulk flow of a larger compilation of non‐SNe peculiar velocities. By comparing the SNe peculiar velocities to predictions of the IRAS Point Source Catalogue Redshift Survey (PSCz) galaxy density field, we find Ω0.55mσ8,lin= 0.40 ± 0.07, which is in agreement with ΛCDM. However, we also show that the PSCz density field fails to account for 150 ± 43 km s−1 of the SNe bulk motion.

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“…For the sparsest sample with n ≥ 10 −6 h 3 Mpc −3 , the bias could attain 50% or more. This indicates that one should carefully account for this effect when low-order velocity statistics are measured from very sparse samples like supernovae [29,32,33,41].…”

Section: Discussionmentioning

confidence: 99%

“…Even more controversial are the claims of the very large scale (∼ 300h −1 Mpc) 'dark flow' by [24], which again is not corroborated by related analyses [25,26]. Thanks to the ever growing amount of observational data, there is continued interest in measuring the BF and, if these discrepancies could be resolved, using it as a cosmological probe; for some more recent results see [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43].…”

Section: Introductionmentioning

confidence: 99%

Uneven flows: On cosmic bulk flows, local observers, and gravity

2018

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Using N-body simulations we study the impact of various systematic effects on the low-order moments of the cosmic velocity field: the bulk flow (BF) and the Cosmic Mach Number (CMN). We consider two types of systematics: those related to survey properties and those induced by observer's location in the Universe. In the former category we model sparse sampling, velocity errors, and survey incompleteness (radial and geometrical). In the latter, we consider Local Group (LG) analogue observers, placed in a specific location within the Cosmic Web, satisfying various observational criteria. We differentiate such LG observers from Copernican ones, who are at random locations. We report strong systematic effects on the measured BF and CMN induced by sparse sampling, velocity errors and radial incompleteness. For BF most of these effects exceed 10% for scales R < ∼ 100h −1 Mpc. For CMN some of these systematics can be catastrophically large (i.e. > 50%) also on bigger scales. Moreover, we find that the position of the observer in the Cosmic Web significantly affects the locally measured BF (CMN), with effects as large as ∼ 20% (30%) at R < ∼ 50h −1 Mpc for a LG-like observer as compared to a random one. This effect is comparable to the sample variance at the same scales. Such location-dependent effects have not been considered previously in BF and CMN studies and here we report their magnitude and scale for the first time. To highlight the importance of these systematics, we additionally study a model of modified gravity with ∼ 15% enhanced growth rate (compared to general relativity). We found that the systematic effects can mimic the modified gravity signal. The worst-case scenario is realized for a case of a LG-like observer, when the effects induced by local structures are degenerate with the enhanced growth rate fostered by modified gravity. Our results indicate that dedicated constrained simulations and realistic mock galaxy catalogs will be absolutely necessary to fully benefit from the statistical power of the forthcoming peculiar velocity data from surveys such as TAIPAN, WALLABY, Cosmic Flows-4 and SKA.

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

Cited by 22 publications

References 105 publications

Dark energy two decades after: observables, probes, consistency tests

Dark energy two decades after: observables, probes, consistency tests

Cosmic flows in the nearby universe from Type Ia supernovae

Uneven flows: On cosmic bulk flows, local observers, and gravity

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