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arXiv 2011.10531astro-ph.GA
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潮汐相互作用和冲压压力剥离室女座螺旋星系NGC 4654中的气体压缩和恒星反馈

Gas compression and stellar feedback in the tidally interacting and ram-pressure stripped Virgo spiral galaxy NGC 4654

T. Lizée, B. Vollmer, J. Braine, F. Nehlig

摘要:

NGC 4654是一个几乎正面看的室女座星系,它经历了几乎侧面的气体冲压压力剥离和与另一个大质量星系NGC 4639的引力相互作用。NGC 4654在光盘的外缘附近显示了一个强烈压缩的气体区域,其HI表面密度(HSDR)超过了10-15 Msun/pc 2的标准值。利用NGC 4654的IRAM 30 mHERA CO(2-1)新数据研究了ISM的物理条件。CO到H的$_2$转换因子被估计并发现是银河值的1到2倍,在HSRD中分子分数和总ISM压力之间的比率显著降低,自引力气体,Toomre参数低于$Q=1$,恒星形成效率高1.5-2倍。分析模型被用来再现径向轮廓的SFR和原子和分子的表面密度。一个Toomre参数的$\rm Q \sim 0.8$结合速度色散的增加5公里/秒的必要条件,同时再现气体表面密度和SFR。用动力学模型再现了NGC 4654的气体分布。由矩2图给出的速度色散和来自模型的固有3D速度色散之间的比较用于区分由速度色散的实际增加引起的较宽线宽的区域和仅由未解决的速度梯度引起的较宽线宽的区域。我们发现,5公里/秒的内禀速度色散的增加是与观测兼容。在通过外部相互作用的气体压缩期间,气体表面密度增加,导致SFR和恒星反馈增加。在恒星反馈的影响下,气体密度仅适度增加。恒星反馈作为恒星形成的调节器,增加了区域内的湍流速度。

英文摘要:

NGC 4654 is a Virgo galaxy seen almost face-on, which undergoes nearly edge-on gas ram pressure stripping and a fly-by gravitational interaction with another massive galaxy, NGC 4639. NGC 4654 shows a strongly compressed gas region near the outer edge of the optical disk, with HI surface densities (HSDR), exceeding the canonical value of 10-15 Msun/pc2. New IRAM 30m HERA CO(2-1) data of NGC 4654 are used to study the physical conditions of the ISM. The CO-to-H$_2$ conversion factor was estimated and found to be one to two times the Galactic value with significant decrease in the ratio between the molecular fraction and the total ISM pressure in the HSDR, self-gravitating gas, a Toomre parameter below $Q=1$ and star-formation efficiency 1.5-2 times higher. Analytical models were used to reproduce radial profiles of the SFR and the atomic and molecular surface densities. A Toomre parameter of $\rm Q \sim 0.8$ combined with an increase in the velocity dispersion of 5 km/s are necessary conditions to simultaneously reproduce the gas surface densities and the SFR. A dynamical model was used to reproduce the gas distribution of NGC 4654. The comparison between the velocity dispersion given by the moment 2 map and the intrinsic 3D velocity dispersion from the model were used to discriminate between regions of broader linewidths caused by a real increase in the velocity dispersion and those caused by an unresolved velocity gradient only. We found that the 5 km/s increase in the intrinsic velocity dispersion is compatible with observations. During a period of gas compression through external interactions, the gas surface density is enhanced, leading to an increased SFR and stellar feedback. Under the influence of stellar feedback, the gas density increases only moderately. The stellar feedback acts as a regulator of star-formation, increasing the turbulent velocity within the region.

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