论文标题
在过去的11 Gyr中，中性氢通过HI 21 cm吸收的演变
The evolution of neutral hydrogen over the past 11 Gyr via HI 21 cm absorption
论文作者
论文摘要
我们介绍了盲目搜索HI 21 cm吸收的结果，该吸收是在Redshift范围内使用Green Bank望远镜在RedShift范围0 <Z <2.74的260个无线电来源。该调查具有检测用于HI自旋温度的sub缩写Lyman-Alpha（DLA）系统$ T_S/F $ = 100 K的敏感性，尽管在样品中成功地重新检测了十位已知的21 cm吸收器，但我们在完整的调查中尚无新的吸收线。还搜索了21 cm吸收中检测到的来源，以获取羟基（OH）18 cm吸收，我们将1667 MHz OH的吸收重新定位至PKS 1830-211。在删除受射电频率干扰影响的区域后，我们在每个来源中搜索了每个来源的HI 21 cm吸收，这些源$ΔZ$ = 88.64（$ΔX$ = 159.5）的总红移覆盖率（$ΔX$ = 159.5）。我们计算了柱密度频率分布的95％置信度上限$ f（n _ {\ rm hi}）$，并在100-1000 K范围内对旋转温度$ t_s $设置统计约束，与先前的红移光学DLA调查和同一红色速度的21 cm发射观察一致。我们推断出中性气体宇宙学质量密度的值，$ω_ {\ rm hi} $。 Through comparison with prior $Ω_{\rm HI}$ measurements, we place a statistical constraint on the mean spin temperature of $T_s/f$ = 175 K. Our derived $Ω_{\textrm {HI}}$ values support a relative mild evolution in $Ω_{\textrm {HI}}$ over the last 11 Gyr and are consistent with other methods that measure $ω_ {\ textrm {hi}} $。
We present the results of a blind search for intervening HI 21 cm absorption toward 260 radio sources in the redshift range 0<z<2.74 with the Green Bank Telescope. The survey has the sensitivity to detect sub-damped Lyman-alpha (DLA) systems for HI spin temperatures $T_s/f$ = 100 K, and despite the successful re-detection of ten known 21 cm absorbers in the sample, we detect no new absorption lines in the full survey. Sources detected in 21 cm absorption were also searched for hydroxyl (OH) 18 cm absorption and we re-detect 1667 MHz OH absorption toward PKS 1830-211. We searched for intervening HI 21 cm absorption along the line of sight in each source achieving a total redshift coverage of $Δz$ = 88.64 (comoving absorption path of $ΔX$ = 159.5) after removing regions affected by radio frequency interference. We compute a 95% confidence upper limit on the column density frequency distribution $f(N_{\rm HI})$ and set a statistical constraint on the spin temperature $T_s$ in the range 100-1000 K, consistent with prior redshifted optical DLA surveys and HI 21 cm emission observations at the same redshifts. We infer a value for the cosmological mass density of neutral gas, $Ω_{\rm HI}$. Through comparison with prior $Ω_{\rm HI}$ measurements, we place a statistical constraint on the mean spin temperature of $T_s/f$ = 175 K. Our derived $Ω_{\textrm {HI}}$ values support a relative mild evolution in $Ω_{\textrm {HI}}$ over the last 11 Gyr and are consistent with other methods that measure $Ω_{\textrm {HI}}$.
