论文标题
$λ$ cdm $ - $的巨大打击 - $高红移，质量和碰撞速度，互动星系集群el Gordo与Coostance Cosmology矛盾
A massive blow for $Λ$CDM $-$ the high redshift, mass, and collision velocity of the interacting galaxy cluster El Gordo contradicts concordance cosmology
论文作者
论文摘要
El Gordo（ACT-CL J0102-4915）是一个极为巨大的星系群（$ M_ {200} \大约3 \ times 10^{15} $ $ M _ {\ odot} $），在redshift $ z = 0.87 $组成的两个子群体中，$ z = 0.87 $ 3.6合并$ km $ km $ km/km km km km in inffall $ km {inff v _ {inff v_ v_ {inffall n inffall spep $ km。在Lambda冷暗物质（$λ$ CDM）宇宙学中，在这种高$ z $的lambda冷暗物质（$λ$ CDM）中，这种迅速的碰撞是出乎意料的。然而，这对于合并的非化学流体动力学模拟需要与其观察到的特性相匹配（Zhang等，2015）。在这里，我们确定使用带有侧面长度$ 6 \，h^{ - 1} $ gpc的Jubilee模拟框中在$λ$ CDM上下文中找到类似对象的概率。我们在宇宙扩展中搜索了与宇宙扩张的质量，质量比，红移和碰撞速度相对于病毒速度，其特性与El Gordo相似。我们非常准确地拟合了对总质量的分布，其中拟合在两种方法中用于推断被调查区域中观察El Gordo的概率。更为保守的（和详细的）方法涉及考虑对与$ z = 0 $ observer的lightcone相似的模拟对的成对质量和红移的预期分布。检测一对质量和红移排除$6.16σ$的$λ$ CDM宇宙学。我们还使用Kraljic＆Sarkar（2015）的结果表明，一旦考虑到其发现调查的天空覆盖范围，子弹群的张力为2.78σ$张力。使用$χ^2 $方法，合并的张力估计为$6.43σ$。这两种碰撞自然出现在带有轻型无菌中微子的Milgromian动力学（MOND）宇宙学中。
El Gordo (ACT-CL J0102-4915) is an extremely massive galaxy cluster ($M_{200} \approx 3 \times 10^{15}$ $M_{\odot}$) at redshift $z = 0.87 $ composed of two subclusters with mass ratio 3.6 merging at speed $V_{infall} \approx 2500$ km/s. Such a fast collision between individually rare massive clusters is unexpected in Lambda cold dark matter ($Λ$CDM) cosmology at such high $z$. However, this is required for non-cosmological hydrodynamical simulations of the merger to match its observed properties (Zhang et al. 2015). Here, we determine the probability of finding a similar object in a $Λ$CDM context using the Jubilee simulation box with side length $6 \, h^{-1}$ Gpc. We search for galaxy cluster pairs that have turned around from the cosmic expansion with properties similar to El Gordo in terms of total mass, mass ratio, redshift, and collision velocity relative to virial velocity. We fit the distribution of pair total mass quite accurately, with the fits used in two methods to infer the probability of observing El Gordo in the surveyed region. The more conservative (and detailed) method involves considering the expected distribution of pairwise mass and redshift for analogue pairs with similar dimensionless parameters to El Gordo in the past lightcone of a $z = 0$ observer. Detecting one pair with its mass and redshift rules out $Λ$CDM cosmology at $6.16σ$. We also use the results of Kraljic & Sarkar (2015) to show that the Bullet Cluster is in $2.78σ$ tension once the sky coverage of its discovery survey is accounted for. Using a $χ^2$ approach, the combined tension can be estimated as $6.43 σ$. Both collisions arise naturally in a Milgromian dynamics (MOND) cosmology with light sterile neutrinos.
