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arXiv 0910.2492astro-ph.COgr-qchep-ph
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超新星距离测量与暗能量约束

Distance Measurements from Supernovae and Dark Energy Constraints

Yun Wang

摘要:

目前观测数据对暗能量的限制对如何从Ia型超新星(SN Ia)数据测量距离很敏感。我们发现,SNe Ia的通量平均可以用来测试未知的系统不确定性的存在,并产生更强大的距离测量SNe Ia。我们已经将这种方法应用于附近的+ SDSS +ESSENCE +SNLS +HST集合288 SNe Ia和集合397 SNe Ia的“宪法”。结合超新星Ia的观测数据、WMAP五年的CMB观测数据、Sloan数字巡天重子声学振荡测量数据、69个γ射线暴的观测数据和HST SHOES计划的哈勃常数测量数据,我们测量了暗能量密度函数X(z)=ρ X(z)/ρ X(0)作为红移的自由函数(假定z>1或z>1.5时为常数)。在没有超新星Ia的通量平均的情况下,使用超新星Ia的“宪法”集合的组合数据似乎表明,在0< z <0.8时,在~95%的置信水平下偏离了宇宙学常数;当超新星Ia是通量平均的时,它们与~68%的置信水平下的宇宙学常数一致。综合使用附近+SDSS +ESSENCE +SNLS +HST数据集的SNe Ia的宇宙学常数在68%的置信水平是一致的,或没有SNe Ia的通量平均,并给出暗能量约束,是显着更严格的比使用SNe Ia的“宪法”集。假设宇宙是平坦的,当z<= 0.75时,利用来自附近+ SDSS+ ESSENCE +SNLS +HST的288个SNe Ia的组合数据,在>98%的置信水平下检测到暗能量,与关于X(z>1)的假设无关。我们量化暗能量的限制,而不假设一个平坦的宇宙使用暗能量图的品质(FoM)的$X(z)$和暗能量状态方程的宇宙尺度因子的线性。

英文摘要:

Constraints on dark energy from current observational data are sensitive to how distances are measured from Type Ia supernova (SN Ia) data. We find that flux-averaging of SNe Ia can be used to test the presence of unknown systematic uncertainties, and yield more robust distance measurements from SNe Ia. We have applied this approach to the nearby + SDSS +ESSENCE +SNLS +HST set of 288 SNe Ia, and the ``Constitution''of set 397 SNe Ia. Combining the SN Ia data with CMB data from WMAP five year observations, the Sloan Digital Sky Survey baryon acoustic oscillation measurements, the data of 69 gammay-ray bursts, and the Hubble constant measurement from the HST project SHOES, we measure the dark energy density function X(z)=ρ_X(z)/ρ_X(0) as a free function of redshift (assumed to be a constant at z>1 or z>1.5). Without flux-averaging of SNe Ia, the combined data using the ``Constitution'' set of SNe Ia seem to indicate a deviation from a cosmological constant at ~95% confidence level at 0< z <0.8; they are consistent with a cosmological constant at ~68% confidence level when SNe Ia are flux-averaged. The combined data using the nearby +SDSS +ESSENCE +SNLS +HST data set of SNe Ia are consistent with a cosmological constant at 68% confidence level with or without flux-averaging of SNe Ia, and give dark energy constraints that are significantly more stringent than that using the ``Constitution'' set of SNe Ia. Assuming a flat universe, dark energy is detected at >98% confidence level for z<= 0.75 using the combined data with 288 SNe Ia from nearby + SDSS+ ESSENCE +SNLS +HST, independent of the assumptions about X(z>1). We quantify dark energy constraints without assuming a flat universe using the dark energy Figure-of-Merit (FoM) for both $X(z)$ and a dark energy equation-of-state linear in the cosmic scale factor.

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