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arXiv 1706.04248astro-ph.GA
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Messier 33的HI动力学和质量分布

HI Kinematics and Mass Distribution of Messier 33

S. Zacharie Kam, Claude Carignan, Laurent Chemin, Tyler Foster, Ed Elson, Tom H. Jarrett

摘要:

根据自治领射电天体物理天文台的观测结果,对梅西耶33星系进行了一次新的深HI巡天。我们观察到一个扰动的外部气体分布和运动学在M33,并确认磁盘翘曲作为一个显着的运动学扭曲的主轴的速度场,虽然没有强烈的倾斜测量,与以前的工作。一个新的低亮度HI分量与异常速度的证据报告。它拥有一个大的速度散射,因为它的运动学都超过和滞后于磁盘的旋转,并在明显的反向旋转的速度禁区泄漏。观测结果还揭示了宽和多峰HI配置文件,这可以部分地解释拥挤的轨道的翘曲模型的框架。不对称运动的速度场中确定,作为一个不平衡的潜在的和翘曲的可能签名。混合Halpha-HI旋转曲线的质量分布模型有利于尖状暗物质晕,其浓度与Lambda CDM暗晕质量浓度关系不一致。在23 kpc中的总质量为8 10^10 Msol,其中11%是恒星和气体。在尖状晕的维里半径处,得到的总质量为5 10^11 Msol,但重子质量分数仅为2%。这强烈地暗示了包含M33总质量的一个更真实的半径比晕的维里半径小得多,可能与HI盘的大小相当。

英文摘要:

A new deep HI survey of the galaxy Messier 33 is presented, based on observations obtained at the Dominion Radio Astrophysical Observatory. We observe a perturbed outer gas distribution and kinematics in M33, and confirm the disk warping as a significant kinematical twist of the major axis of the velocity field, though no strong tilt is measured, in agreement with previous work. Evidence for a new low brightness HI component with anomalous velocity is reported. It harbours a large velocity scatter, as its kinematics both exceeds and lags the rotation of the disk, and leaks in the forbidden velocity zone of apparent counter-rotation. The observations also reveal wide and multiple peak HI profiles which can be partly explained by crowded orbits in the framework of the warp model. Asymmetric motions are identified in the velocity field, as possible signatures of a lopsided potential and the warp. The mass distribution modeling of the hybrid Halpha-HI rotation curve favours a cuspy dark matter halo with a concentration in disagreement with the LambdaCDM dark halo mass-concentration relationship. The total mass enclosed in 23 kpc is 8 10^10 Msol, of which 11% are stars and gas. At the virial radius of the cuspy halo, the resulting total mass is 5 10^11 Msol, but with a baryonic mass fraction of 2% only. This strongly suggests a more realistic radius encompassing the total mass of M33 well smaller than the virial radius of the halo, maybe comparable to the size of the HI disk.

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