标题： 低红移星系电离气体晕中的氢发射 显示英文标题

标题： Hydrogen Emission from the Ionized Gaseous Halos of Low Redshift Galaxies

摘要： 使用近半百万星系的样本，这些星系被斯隆数字巡天数据发布第12版中的超过700万条视线交叉，我们追踪了从星系中心投影半径$r_p$处5千秒差距到超过100千秒差距的 H$\alpha$ + [N{\small 二}] 发射。发射通量表面亮度为$\propto r_p^{-1.9 \pm 0.4}$。我们仅使用 H$\alpha$或 [N{\small 二}] 流量获得了结果一致。我们在小尺度上测量到目标样本较蓝的一半比较红的一半信号更强，$r_p <$20千秒差距。 我们获得在50到100 kpc $r_p$ 区间内H$\alpha$ + [N{\small 二}] 辐射的$3\sigma$ 检测。 此区间内的平均发射通量为$(1.10 \pm 0.35) \times 10^{-20}$erg cm$^{-2}$s$^{-1}$ \AA $^{-1}$ ，这相当于$1.87 \times 10^{-20}$erg cm$^{-2}$s$^{-1}$arcsec$^{-2}$或 0.0033 Rayleigh. 这种检测比之前使用深度窄带成像获得的严格限制要暗34倍。 信号的微弱说明了为什么难以将复合辐射追踪到星系周围的大半径区域。 该信号结合已发表的n$_{\rm H}$估计值，使我们估计气体温度为12,000 K，这与基于金属离子吸收线的独立经验估计以及数值模拟的预期一致。 显示英文摘要

摘要： Using a sample of nearly half million galaxies, intersected by over 7 million lines of sight from the Sloan Digital Sky Survey Data Release 12, we trace H$\alpha$ + [N{\small II}] emission from a galactocentric projected radius, $r_p$, of 5 kpc to more than 100 kpc. The emission flux surface brightness is $\propto r_p^{-1.9 \pm 0.4}$. We obtain consistent results using only the H$\alpha$ or [N{\small II}] flux. We measure a stronger signal for the bluer half of the target sample than for the redder half on small scales, $r_p <$ 20 kpc. We obtain a $3\sigma$ detection of H$\alpha$ + [N{\small II}] emission in the 50 to 100 kpc $r_p$ bin. The mean emission flux within this bin is $(1.10 \pm 0.35) \times 10^{-20}$ erg cm$^{-2}$ s$^{-1}$ \AA$^{-1}$, which corresponds to $1.87 \times 10^{-20}$ erg cm$^{-2}$ s$^{-1}$ arcsec$^{-2}$ or 0.0033 Rayleigh. This detection is 34 times fainter than a previous strict limit obtained using deep narrow-band imaging. The faintness of the signal demonstrates why it has been so difficult to trace recombination radiation out to large radii around galaxies. This signal, combined with published estimates of n$_{\rm H}$, lead us to estimate the temperature of the gas to be 12,000 K, consistent with independent empirical estimates based on metal ion absorption lines and expectations from numerical simulations.