利用萊曼-阿爾法吸收光譜探討極端軸子暗物質模型

Abstract

我們利用帶有均衡紫外光背景的字宙學流體模型去模擬不同類型 暗物質模型所預測的萊曼-阿爾法森林現象，其中包括冷暗物質、波動 暗物質以及不同軸子角度的極端軸子暗物質。以極端軸子暗物質的玻 色子質量為1.1X 10^-22 電子伏的前提下，我們發現極端軸子暗物質所 預測的萊曼-阿爾法森林現象比起冷暗物質所預測的結果更能符合重 子振蕩光譜巡天計畫得到的結果，這是與[17, 1] 所預測的結果大為不 同–冷暗物質的萊曼-阿爾法森林現象較為符合觀測事實。因此，我們 的研究為暗物質是由超低質量粒子所組成的猜想帶來新的證據。

Using cosmological particle hydrodynamical simulations and uniform ultraviolet background, we test Lyman-alpha forest flux spectra predicted by the conventional cold dark matter (CDM) model, the free-particle wave dark matter (FPpsiDM) model and extreme-axion wave dark matter (EApsiDM) models of different initial axion field angles against the BOSS Lyman-alpha forest absorption spectra. The boson mass mb of all DM models is fixed to mb ~ 10^-22eV. We recover the results reported previously [17, 1] that the CDM model agrees better with the BOSS data than the FPpsiDM model by a large margin, where the difference of total chi-square is 19 for 420 data bins. These previous results demand a larger boson mass by a factor > 10 and are in tension with the favoured value. However, we find this tension can be alleviated as a range of EA DM models predict Lyman- flux spectra agree better with the BOSS data than the CDM prediction by an even larger margin; the difference of total chi-square can be as large as 24. This finding is perhaps not surprising since EA DM models can have a unique spectral bump in excess of the power of CDM near the more extended spectral cutoff in the initial matter power spectrum [51, 50].