A Direct Detection of Gas Accretion: The Lyman Limit System in 3C 232
A Direct Detection of Gas Accretion: The Lyman Limit System in 3C 232
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气体积聚的直接检测：3C 232 中的莱曼极限系统
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
C. Danforth
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作者：
J. Stocke;B. Keeney;C. Danforth
摘要在宇宙时间内，星系中的气体添加和移除极大地影响着星系中恒星的数量和星星的形成速率。在类星体/星系对中进行的类星体吸收线研究为研究这种气体的物理条件和运动学提供了一个独特的机会。在这里，我们提出了新的哈勃太空望远镜（HST）的类星体/星系对，3C 232/NGC 3067的图像。类星体光谱包含一个莱曼极限（NHi = 1 × 1020 cm−2）吸收系统（LLS），cz = 1421 km s−1，与附近的Sab星系NGC 3067有关。以前的工作确定这个吸收体是NGC 3067中的高速云（HVC），但吸收气体的运动学，下落或流出，是不确定的。这里展示的HST图像确定了NGC 3067的方向，因此确定了LLS/HVC正在坠落。使用这个系统作为原型，我们将这些结果扩展到更高z的MgII/LLS，建议MSTs/LLS是所谓的“冷模吸积”（CMA）落入发光星系的视线采样。为了匹配所观察到的MgII吸收统计，CMA必须在更高的红移更高度电离。进一步研究低z LLS所需的关键观测是HST紫外光谱，为此，刚刚安装了一台新仪器，即宇宙起源光谱仪，大大提高了我们的观测能力。
Abstract The gas added to and removed from galaxies over cosmic time greatly affects their stellar populations and star formation rates. QSO absorption line studies in close QSO/galaxy pairs create a unique opportunity to study the physical conditions and kinematics of this gas. Here we present new Hubble Space Telescope (HST) images of the QSO/galaxy pair, 3C 232/NGC 3067. The quasar spectrum contains a Lyman limit (NHi = 1 × 1020 cm−2) absorption system (LLS) at cz = 1421 km s−1 that is associated with the nearby Sab galaxy NGC 3067. Previous work identifies this absorber as a high-velocity cloud (HVC) in NGC 3067 but the kinematics of the absorbing gas, infalling or outflowing, were uncertain. The HST images presented here establish the orientation of NGC 3067 and so establish that the LLS/HVC is infalling. Using this system as a prototype, we extend these results to higher-z MgII/LLS to suggest that Mgii/LLSs are a sightline sampling of the so-called ‘cold mode accretion’ (CMA) infalling onto luminous galaxies. To match the observed MgII absorber statistics, the CMA must be more highly ionised at higher redshifts. The key observations needed to further the study of low-z LLSs is HST UV spectroscopy, for which a new instrument, the Cosmic Origins Spectrograph, has just been installed greatly enhancing our observational capabilities.