The ATLAS3D project - XIV. The extent and kinematics of the molecular gas in early-type galaxies
The ATLAS3D project - XIV. The extent and kinematics of the molecular gas in early-type galaxies
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DOI：
10.1093/mnras/sts353
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发表时间：
2012-11
影响因子：
4.8
通讯作者：
T. Davis;K. Alatalo;M. Bureau;M. Cappellari;N. Scott;L. Young;L. Blitz;A. Crocker;E. Bayet;M. Bois;F. Bournaud;R. Davies;P. Zeeuw;P. Duc;E. Emsellem;S. Khochfar;D. Krajnovi'c;H. Kuntschner;P. Lablanche;R. McDermid;R. Morganti;T. Naab;T. Oosterloo;M. Sarzi;P. Serra;A. Weijmans
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文献类型：
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作者：
T. Davis;K. Alatalo;M. Bureau;M. Cappellari;N. Scott;L. Young;L. Blitz;A. Crocker;E. Bayet;M. Bois;F. Bournaud;R. Davies;P. Zeeuw;P. Duc;E. Emsellem;S. Khochfar;D. Krajnovi'c;H. Kuntschner;P. Lablanche;R. McDermid;R. Morganti;T. Naab;T. Oosterloo;M. Sarzi;P. Serra;A. Weijmans
我们使用干涉测量(CO)-C-12(1-0)观测来比较和对比富CO的ATLAS(3D)早期类型星系(ETG)和螺旋星系中分子气体的范围、表面亮度分布和运动学。我们发现，在ETGS中，分子气体的范围在绝对值上比在晚类型星系中小，但一旦用星系的光学/恒星特征标度长度来衡量，其大小分布是相似的。在ETG中，我们发现气体的范围与其运动失调(相对于恒星)无关，但确实取决于环境，处女座星团ETG的分子气藏扩展较少，进一步强调了星团ETG遵循与现场不同的演化路径。大约一半的ETG具有遵循恒星光轮廓的分子气体表面亮度轮廓。这些系统通常将气体释放到大半径，这表明它们不太可能发生最近的合并/吸积事件。三分之一的样本星系显示了分子气体表面的亮度曲线，其衰减速度慢于光线，有时还会出现截断。这些星系通常质量较低，要么扰动了分子气体，要么位于室女座星系团，这表明最近的合并、冲压剥离和/或热气体的存在可以压缩/截断气体。剩下的星系有环，或复合轮廓，我们认为这可能是由条状星系的影响造成的。我们用位置-速度图研究了分子气体的运动学，并将观测到的运动学与动力学模型的预测以及观测到的恒星和电离气体速度进行了比较。我们证实，分子气体到达圆周速度曲线的周转率约为我们的富CO ATLAS(3D)ETG的70%，验证了之前关于CO Tully-Fisher关系的工作。总的来说，我们发现在大多数星系中，分子气体是动态冷的，观测到的CO自转与圆周速度的模型预测很好地匹配。在分子质量最大的星系中，尘埃遮挡和/或布居梯度会导致圆周速度的模型预测与分子气体旋转的观测结果不一致；然而，这些影响仅限于大多数恒星形成系统。棒和非平衡条件也会使气体偏离圆形轨道。在这两种情况下，人们预计模型的圆周速度会高于观测到的CO速度，这与我们的观测结果是一致的。与电离气体相比，分子气体是更好的循环速度的直接示踪剂，这证明它可以用作Tully-Fisher和类似分析的运动学示踪剂。
We use interferometric (CO)-C-12(1-0) observations to compare and contrast the extent, surface brightness profiles and kinematics of the molecular gas in CO-rich ATLAS(3D) early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scalelengths. Amongst ETGs, we find that the extent of the gas is independent of its kinematic misalignment (with respect to the stars), but does depend on the environment, with Virgo cluster ETGs having less extended molecular gas reservoirs, further emphasizing that cluster ETGs follow different evolutionary pathways from those in the field. Approximately half of ETGs have molecular gas surface brightness profiles that follow the stellar light profile. These systems often have relaxed gas out to large radii, suggesting they are unlikely to have had recent merger/accretion events. A third of the sample galaxies show molecular gas surface brightness profiles that fall off slower than the light, and sometimes show a truncation. These galaxies often have a low mass, and either have disturbed molecular gas or are in the Virgo cluster, suggesting that recent mergers, ram pressure stripping and/or the presence of hot gas can compress/truncate the gas. The remaining galaxies have rings, or composite profiles, that we argue can be caused by the effects of bars. We investigated the kinematics of the molecular gas using position-velocity diagrams, and compared the observed kinematics with dynamical model predictions, and the observed stellar and ionized gas velocities. We confirm that the molecular gas reaches beyond the turnover of the circular velocity curve in approximate to 70 per cent of our CO-rich ATLAS(3D) ETGs, validating previous work on the CO Tully-Fisher relation. In general we find that in most galaxies the molecular gas is dynamically cold, and the observed CO rotation matches well model predictions of the circular velocity. In the galaxies with the largest molecular masses, dust obscuration and/or population gradients can cause model predictions of the circular velocity to disagree with observations of the molecular gas rotation; however, these effects are confined to the most star forming systems. Bars and non-equilibrium conditions can also make the gas deviate from circular orbits. In both these cases, one expects the model circular velocity to be higher than the observed CO velocity, in agreement with our observations. Molecular gas is a better direct tracer of the circular velocity than the ionized gas, justifying its use as a kinematic tracer for Tully-Fisher and similar analyses.