从H $α$荧光测量z = 0 UV背景
A measurement of the z = 0 UV background from H$α$ fluorescence
摘要：
我们报告的检测扩展的H α发射从附近的边缘上的星系UGC 7321的HI盘的尖端，观察与多单元光谱探测器（MUSE）仪器在甚大望远镜。当HI柱密度降到N（HI）= 10^19 cm^-2以下时，H α表面亮度迅速衰减，这与电离前沿由河外紫外背景（UVB）光电离的气体产生的荧光一致。在这个位置测得的表面亮度为（1.2 +/- 0.5）x10^-19 erg/s/cm^2/arcsec ^2，其中误差主要是系统性的，是由于信号接近MUSE视场的边缘，以及在红移的H α波长旁边存在一条天空线。通过将H α和HI 21 cm图与UVB照射下指数圆盘的辐射转移计算相结合，我们得到HI光电离率的值为γ ~（6-8）x10^-14 1/s。这个值与Lyalpha森林的传输统计数据和类星体主导的UVB最近的模型是一致的。
英文摘要：
We report the detection of extended Halpha emission from the tip of the HI disk of the nearby edge-on galaxy UGC 7321, observed with the Multi Unit Spectroscopic Explorer (MUSE) instrument at the Very Large Telescope. The Halpha surface brightness fades rapidly where the HI column density drops below N(HI) = 10^19 cm^-2 , consistent with fluorescence arising at the ionisation front from gas that is photoionized by the extragalactic ultraviolet background (UVB). The surface brightness measured at this location is (1.2 +/- 0.5)x10^-19 erg/s/cm^2/arcsec^2, where the error is mostly systematic and results from the proximity of the signal to the edge of the MUSE field of view, and from the presence of a sky line next to the redshifted Halpha wavelength. By combining the Halpha and the HI 21 cm maps with a radiative transfer calculation of an exponential disk illuminated by the UVB, we derive a value for the HI photoionization rate of Gamma ~ (6-8)x10^-14 1/s . This value is consistent with transmission statistics of the Lyalpha forest and with recent models of a UVB which is dominated by quasars.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
