A new determination of the primordial He abundance using the HeI 10830A emission line: cosmological implications
Y. I. Izotov, T. X. Thuan, N. G. Guseva
备注：
18 pages, 11 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society. arXiv admin note: text overlap with arXiv:1308.2100
We present near-infrared spectroscopic observations of the high-intensity HeI 10830 emission line in 45 low-metallicity HII regions. We combined these NIR data with spectroscopic data in the optical range to derive the primordial He abundance. The use of the HeI 10830A line, the intensity of which is very sensitive to the density of the HII region, greatly improves the determination of the physical conditions in the He^+ zone. This results in a considerably tighter Y - O/H linear regression compared to all previous studies. We extracted a final sample of 28 HII regions with Hbeta equivalent width EW(Hbeta)>150A, excitation parameter O^2+/O>0.8, and with helium mass fraction Y derived with an accuracy better than 3%. With this final sample we derived a primordial He mass fraction Yp = 0.2551+/-0.0022. The derived value of Yp is higher than the one predicted by the standard big bang nucleosynthesis (SBBN) model. Using our derived Yp together with D/H = (2.53+/-0.04)x10^-5, and the chi^2 technique, we found that the best agreement between these light element abundances is achieved in a cosmological model with a baryon mass density Omega_b h^2 = 0.0240+/-0.0017 (68% CL), +/-0.0028 (95.4% CL), +/-0.0034 (99% CL) and an effective number of neutrino species Neff = 3.58+/-0.25 (68% CL), +/-0.40 (95.4% CL), +/-0.50 (99% CL). A non-standard value of Neff is preferred at the 99% CL, implying the possible existence of additional types of neutrino species.
The LBT $Y_{\rm p}$ Project I: An Improved Determination of the Primordial Helium Abundance -- Project Description, Sample Selection, Observations, and Methodology
University of Minnesota（明尼苏达大学）；The Ohio State University（俄亥俄州立大学）；Gonzaga University（贡萨加大学）；Northwestern University（西北大学）；University of Texas at Austin（德克萨斯大学奥斯汀分校）
Fifty years of primordial helium abundances: A statistical reanalysis
Indian Institute of Science Education and Research (IISER) Mohali（印度科学教育研究所）；Macquarie University（麦考瑞大学）；International Space Science Institute–Beijing（国际空间科学研究所北京分部）；Università di Roma Tor Vergata（罗马托尔维加塔大学）；INAF, Rome Astronomical Observatory（意大利国家天体物理研究所罗马天文台）
The LBT $Y_{\rm p}$ Project V: Cosmological Implications of a New Determination of Primordial $^4$He
TRIUMF（特利安夫实验室）；William I. Fine Theoretical Physics Institute, School of Physics and Astronomy, University of Minnesota（明尼苏达大学物理与天文学院威廉·I·芬理论物理研究所）；University of Illinois（伊利诺伊大学）；Gonzaga University（冈萨加大学）；The Ohio State University（俄亥俄州立大学）；Northwestern University（西北大学）；University of Minnesota（明尼苏达大学）
Implications for Primordial Non-Gaussianity (f_NL) from weak lensing masses of high-z galaxy clusters
最近对高红移星系团XMMUJ 2235.3 -2557暗物质质量的弱透镜测量表明，在z=1.4时，如果假设该星系团是暗物质在标准LCDM模型中的原始高斯场中坍缩的结果，那么< 0.002 clusters in the observed area. Here we investigate how to boost the probability of XMMUJ2235.3-2557 in particular resorting to deviations from Gaussian initial conditions. We show that this abundance can be boosted by factors >如果非高斯参数f^local_NL在150-200的范围内，它的丰度应该是3-10。该值与通过CMB的电流约束获得的f_NL的限值相当。我们的结论是，质量测定高红移，大质量的集群可以提供一个补充探针的原始非高斯性。
The LBT Y$_\mathrm{p}$ Project IV: A New Value of the Primordial Helium Abundance
Gonzaga University（冈萨加大学）；University of Minnesota（明尼苏达大学）；The Ohio State University（俄亥俄州立大学）；Northwestern University（西北大学）；The University of Texas at Austin（得克萨斯大学奥斯汀分校）；Indiana University（印第安纳大学）
EMPRESS. XV. A New Determination of the Primordial Helium Abundance Suggesting a Moderately Low $Y_\mathrm{P}$ Value
Institute for Cosmic Ray Research, The University of Tokyo（东京大学宇宙射线研究所）；Department of Physics, Graduate School of Science, The University of Tokyo（东京大学理学研究科物理学系）；National Astronomical Observatory of Japan, National Institutes of Natural Sciences（日本国立天文台，国立自然科学研究院）；Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies)（SOKENDAI（ advanced studies研究生院）天体科学系）；Kavli Institute for the Physics and Mathematics of the Universe (WPI), University of Tokyo（东京大学 Kavli宇宙物理数学研究所 (WPI)）；Department of Physics, Tohoku University（东北大学物理学系）
EMPRESS. VIII. A New Determination of Primordial He Abundance with Extremely Metal-Poor Galaxies: A Suggestion of the Lepton Asymmetry and Implications for the Hubble Tension
