Title: Constraining neutrino mass and extra relativistic degrees of freedom in dynamical dark energy models using Planck 2015 data in combination with low-redshift cosmological probes: basic extensions to $Λ$CDM cosmology Show Chinese title

Title: 使用Planck 2015数据结合低红移宇宙学探测器对动态暗能量模型中的中微子质量以及额外相对论自由度进行约束：对$Λ$CDM宇宙学的基本扩展

Abstract: We investigate how the properties of dark energy affect the cosmological measurements of neutrino mass and extra relativistic degrees of freedom. We limit ourselves to the most basic extensions of $\Lambda$ cold dark matter (CDM) model, i.e. the $w$CDM model with one additional parameter $w$, and the $w_{0}w_{a}$CDM model with two additional parameters, $w_{0}$ and $w_{a}$. In the cosmological fits, we employ the 2015 cosmic microwave background temperature and polarization data from the Planck mission, in combination with low-redshift measurements such as the baryon acoustic oscillations, Type Ia supernovae and the Hubble constant ($H_{0}$). Given effects of massive neutrinos on large-scale structure, we further include weak lensing, redshift space distortion, Sunyaev--Zeldovich cluster counts and Planck lensing data. We show that, though the cosmological constant $\Lambda$ is still consistent with the current data, a phantom dark energy ($w<-1$) or an early phantom dark energy (i.e. quintom evolving from $w<-1$ to $w>-1$) is slightly more favoured by current observations, which leads to the fact that in both $w$CDM and $w_0w_a$CDM models we obtain a larger upper limit of $\sum m_\nu$. We also show that in the three dark energy models, the constraints on $N_{\rm eff}$ are in good accordance with each other, all in favour of the standard value 3.046, which indicates that the dark energy parameters almost have no impact on constraining $N_{\rm eff}$. Therefore, we conclude that the dark energy parameters can exert a significant influence on the cosmological weighing of neutrinos, but almost cannot affect the constraint on dark radiation. Show Chinese abstract

Abstract: 我们研究暗能量的性质如何影响中微子质量及额外相对论自由度的宇宙学测量。 我们仅限于最基础的$\Lambda$冷暗物质(CDM)模型扩展，即具有一个额外参数$w$的$w$CDM模型，以及具有两个额外参数$w_{0}$和$w_{a}$的$w_{0}w_{a}$CDM模型。 在宇宙学拟合中，我们采用普朗克任务提供的2015年宇宙微波背景温度和极化数据，并结合低红移测量数据，如重子声学振荡、Ia型超新星和哈勃常数($H_{0}$)。 考虑到大尺度结构中质量中微子的影响，我们进一步包括弱透镜、红移空间扭曲、太阳亚-泽尔多维奇团簇计数和普朗克透镜数据。 我们表明，尽管宇宙学常数$\Lambda$仍然与当前数据一致，但幻影暗能量 ($w<-1$) 或早期幻影暗能量（即从$w<-1$演化到$w>-1$的 quintom）略微更受当前观测的青睐，这导致在$w$CDM 和$w_0w_a$CDM 模型中，我们得到$\sum m_\nu$的更大上限。 我们还表明，在三种暗能量模型中，对$N_{\rm eff}$的约束彼此高度一致，都支持标准值 3.046，这表明暗能量参数几乎不会影响对$N_{\rm eff}$的约束。 因此，我们得出结论，暗能量参数可以对中微子的宇宙质量测量产生显著影响，但几乎不会影响对暗辐射的约束。