论文标题
Flash早期科学 - 从Gama 23 Field的Askap调查中发现了一个中间的HI 21厘米吸收器
FLASH Early Science -- Discovery of an intervening HI 21-cm absorber from an ASKAP survey of the GAMA 23 field
论文作者
论文摘要
我们提出了HI（Flash）的第一次大型吸收调查的早期科学结果，这是对使用澳大利亚平方英里阵列途径（ASKAP）在宇宙学距离处的冷氢HI气体中21厘米吸收线的光谱盲目调查。我们已经在GAMA 23字段中搜索了HI吸收，涵盖了$ z = 0.34 $和$ 0.79 $的红移，大约50 v $^{2} $。在纯粹的盲目搜索中，我们没有在可靠性阈值上方获得21厘米吸收剂的任何检测。假设HI自旋温度为$ t _ {\ rm spin} $ = 100 k的基准值，源覆盖分数$ c _ {\ rm f} = 1 $，对所有damped lyman $ lyman $α$ a $α$ pabsorbers（dlas; dlas; $ n _ _ _ _} {\ rm hi} \ geq {\ rm hi} \ geq {\ rm hi} \ geq { cm $^{ - 2} $）是$δ{x} = 6.6 \ pm 0.3 $（$δ{z} = 3.7 \ pm 0.2 $）和super-dlas（$ n _ {\ rm hi} \ geq q geq 2 \ geq 2 \ geq 2 \ geq 2 \ time times 10^{21}} $ cm $ cm $ cm $^pm^pm^pm^pm^{ - 2 pm} （$δ{z} = 63 \ pm 3 $）。我们估计了HI柱密度分布函数上的上限，该函数与先前调查的红移光学DLA的测量以及附近的21厘米发射和吸收一致。通过将我们在GAMA 23字段中星系的光谱识别的无线电源匹配的交叉匹配，我们能够检测21厘米的吸收$ z = 0.3562 $ to nvss j224500 $ - $ 343030，并具有$ n _ _ {\ rm hi}的列密度， （t _ {\ rm spin}/100〜 \ mathrm {k}）$ cm $^{ - 2} $。该吸收剂与GAMA J22450.05 $ - $ 343031.7相关，这是一个相对于无线电源为17 kpc的巨大早期类型的星系，与无线电源相对于无线电源，其中可能包含一个巨大的（$ m _ {\ rm hi} \ gtrsim 3 \ gtrsim 3 \ times 10^\ $ m $ m $ m _ _ =这种富含气体的早期类型很少见，但在附近的宇宙中被发现。
We present early science results from the First Large Absorption Survey in HI (FLASH), a spectroscopically blind survey for 21-cm absorption lines in cold hydrogen HI gas at cosmological distances using the Australian Square Kilometre Array Pathfinder (ASKAP). We have searched for HI absorption towards 1253 radio sources in the GAMA 23 field, covering redshifts between $z = 0.34$ and $0.79$ over a sky area of approximately 50 deg$^{2}$. In a purely blind search we did not obtain any detections of 21-cm absorbers above our reliability threshold. Assuming a fiducial value for the HI spin temperature of $T_{\rm spin}$ = 100 K and source covering fraction $c_{\rm f} = 1$, the total comoving absorption path length sensitive to all Damped Lyman $α$ Absorbers (DLAs; $N_{\rm HI} \geq 2 \times 10^{20}$ cm$^{-2}$) is $Δ{X} = 6.6 \pm 0.3$ ($Δ{z} = 3.7 \pm 0.2$) and super-DLAs ($N_{\rm HI} \geq 2 \times 10^{21}$ cm$^{-2}$) is $Δ{X} = 111 \pm 6$ ($Δ{z} = 63 \pm 3$). We estimate upper limits on the HI column density frequency distribution function that are consistent with measurements from prior surveys for redshifted optical DLAs, and nearby 21-cm emission and absorption. By cross matching our sample of radio sources with optical spectroscopic identifications of galaxies in the GAMA 23 field, we were able to detect 21-cm absorption at $z = 0.3562$ towards NVSS J224500$-$343030, with a column density of $N_{\rm HI} = (1.2 \pm 0.1) \times 10^{20} (T_{\rm spin}/100~\mathrm{K})$ cm$^{-2}$. The absorber is associated with GAMA J22450.05$-$343031.7, a massive early-type galaxy at an impact parameter of 17 kpc with respect to the radio source and which may contain a massive ($M_{\rm HI} \gtrsim 3 \times 10^{9}$ M$_{\odot}$) gas disc. Such gas-rich early types are rare, but have been detected in the nearby Universe.
