arXiv 2412.076522024-12-10astro-ph.GA

利用沿引力弧的 MgII 吸收绘制富 HI 吸收体的空间范围

Mapping the spatial extent of HI-rich absorbers using MgII absorption along gravitational arcs

Trystyn A. M. Berg, Andrea Afruni, Cédric Ledoux, Sebastian Lopez, Pasquier Noterdaeme, Nicolas Tejos, Joaquin Hernandez, Felipe Barrientos, Evelyn J. Johnston

备注：: 15 pages, 6 Figures, 3 appendices. Accepted for publication on Astronomy & Astrophysics

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AI总结：

本文利用 MUSE 对两个引力弧场的 MgII 吸收进行空间成图，建立气体云模型预测 HI 柱密度、覆盖分数和质量，表明二者可能是大质量 DLA。

摘要：

在类星体光谱中观测到的富 HI 吸收体包含宇宙中大部分中性气体。然而，由于类星体视线具有铅笔束性质，这些气体储库的空间范围尚未得到广泛研究。我们利用两个巨型引力弧场（红移分别为 1.17 和 2.06）作为二维背景源；这些场具有由 MUSE 积分场光谱仪（IFS）观测到的已知强 MgII 吸收。我们研究了空间成图的 MgII 吸收是否能够预测强 HI 系统的存在，并测定两个吸收系统的物理尺度和 HI 质量。我们建立了一个由气体云集合构成的简单模型，以便根据 IFS 空间像素（spaxel）中对 MgII 静止系等效宽度的观测，同时预测富 HI 吸收体的 HI 柱密度和气体覆盖分数。我们首先在已有文献 HI 观测的场上测试该模型，发现能够恢复与既往估计一致的 HI 柱密度（尽管不确定性较大）。随后，我们使用该框架同时预测两个场的气体覆盖分数、HI 柱密度和总 HI 质量（$M_{\rm{HI}}$）。我们发现，两个观测到的强系统均具有约 70% 的覆盖分数，并且很可能是阻尼 Lyα 系统（DLAs），其 $M_{\rm{HI}}>10^9\\ M_{\odot}$。模型表明，文献中用于识别 DLA 存在的典型 MgII 指标对气体覆盖分数敏感。尽管如此，这些 MgII 指标仍对强 HI 敏感，并仍可应用于朝向引力弧或其他空间延展背景源的吸收体。基于结果，我们推测这两个强吸收体很可能代表中性的内星系周介质，并且是宿主星系内恒星形成燃料的重要储库。

英文摘要：

HI-rich absorbers seen within quasar spectra contain the bulk of neutral gas in the Universe. However, the spatial extent of these reservoirs are not extensively studied due to the pencil beam nature of quasar sightlines. Using two giant gravitational arc fields (at redshifts 1.17 and 2.06) as 2D background sources with known strong MgII absorption observed with the MUSE integral field spectrograph (IFS), we investigated whether spatially mapped MgII absorption can predict the presence of strong HI systems, and determine both the physical extent and HI mass of the two absorbing systems. We created a simple model of an ensemble of gas clouds in order to simultaneously predict the HI column density and gas covering fraction of HI-rich absorbers based on observations of the MgII rest-frame equivalent width in IFS spaxels. We first test the model on the field with HI observations already available from the literature, finding that we can recover HI column densities consistent with the previous estimates (although with large uncertainties). We then use our framework to simultaneously predict the gas covering fraction, HI column density and total HI mass ($M_{\rm{HI}}$) for both fields. We find that both of the observed strong systems have a covering fraction of $\approx70$% and are likely damped Lyman $α$ systems (DLAs) with $M_{\rm{HI}}>10^9\ M_{\odot}$. Our model shows that the typical MgII metrics used in the literature to identify the presence of DLAs are sensitive to the gas covering fraction. However, these MgII metrics are still sensitive to strong HI, and can be still applied to absorbers towards gravitational arcs or other spatially extended background sources. Based on our results, we speculate that the two strong absorbers are likely representative of a neutral inner circumgalactic medium and are a significant reservoir of fuel for star formation within the host galaxies.

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