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arXiv 1012.2912astro-ph.CO
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奇特速度对超新星宇宙学的影响

The effect of peculiar velocities on supernova cosmology

Tamara M Davis, Lam Hui, Joshua A Frieman, Troels Haugbølle, Richard Kessler, Benjamin Sinclair, Jesper Sollerman, Bruce Bassett, John Marriner, Edvard Mörtsell… 展开作者

Tamara M Davis, Lam Hui, Joshua A Frieman, Troels Haugbølle, Richard Kessler, Benjamin Sinclair, Jesper Sollerman, Bruce Bassett, John Marriner, Edvard Mörtsell, Robert C Nichol, Michael W Richmond, Masao Sako, Donald P Schneider

摘要:

我们提出了一个特殊的速度和超新星宇宙学的影响进行分析。特别是,我们研究(a)由于我们自己的运动的修正,(b)的影响,在特殊的速度引起的大尺度结构的相关性,和(c)可能的局部欠或过密度所产生的不确定性。对于所有这些影响,我们提出了一个案例研究的斯隆数字巡天II超新星巡天(SDSS-II SN巡天)得出的宇宙学的影响。修正CMB偶极的超新星红移稍微过度修正了与我们共享一些局部运动的附近超新星。我们表明,虽然忽略CMB偶极子将导致偏移的状态方程的δ w ~ 0.04(在固定的物质密度)的额外的局部运动修正是目前可以忽略不计(δ w<0.01)。我们使用协方差矩阵的方法来统计相关的奇特的速度。这降低了附近超新星的重量,有效地充当了通常急剧的低红移削减的渐进版本。忽视当前样本中的相干速度会导致w的首选值发生~2%的系统偏移,因此,当未来的调查目标是百分比级别的准确度时,必须仔细考虑。最后,我们进行了n体模拟,以估计任何局部密度波动的可能幅度(density fluctuation,density fluctuation),并估计作为低红移截止函数的影响。我们看到,在这方面,z=0.02的低z截止值在理论上是合理的,但是生活在假定的局域密度涨落中会给星等-红移关系留下不可磨灭的印记。

英文摘要:

We present an analysis of peculiar velocities and their effect on supernova cosmology. In particular, we study (a) the corrections due to our own motion, (b) the effects of correlations in peculiar velocities induced by large-scale structure, and (c) uncertainties arising from a possible local under- or over-density. For all of these effects we present a case study of their impact on the cosmology derived by the Sloan Digital Sky Survey-II Supernova Survey (SDSS-II SN Survey). Correcting supernova redshifts for the CMB dipole slightly over-corrects nearby supernovae that share some of our local motion. We show that while neglecting the CMB dipole would cause a shift in the derived equation of state of Delta w ~ 0.04 (at fixed matter density) the additional local-motion correction is currently negligible (Delta w<0.01). We use a covariance-matrix approach to statistically account for correlated peculiar velocities. This down-weights nearby supernovae and effectively acts as a graduated version of the usual sharp low-redshift cut. Neglecting coherent velocities in the current sample causes a systematic shift of ~2% in the preferred value of w and will therefore have to be considered carefully when future surveys aim for percent-level accuracy. Finally, we perform n-body simulations to estimate the likely magnitude of any local density fluctuation (monopole) and estimate the impact as a function of the low-redshift cutoff. We see that for this aspect the low-z cutoff of z=0.02 is well-justified theoretically, but that living in a putative local density fluctuation leaves an indelible imprint on the magnitude-redshift relation.

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