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arXiv 1409.4468astro-ph.GA
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从NGC3256被遮蔽的次级核流出热和冷分子气体:接近反馈物理学

Outflow of hot and cold molecular gas from the obscured secondary nucleus of NGC3256: closing in on feedback physics

Bjorn Emonts, Javier Piqueras-Lopez, Luis Colina, Santiago Arribas, Montserrat Villar-Martin, Miguel Pereira-Santaella, Santiago Garcia-Burillo, Almudena Alonso-Herrero

摘要:

合并星系的核心通常深埋在致密的气体和尘埃层中。在这些区域,由星暴和活动星系核活动驱动的气体外流被认为在这些星系的演化中起着至关重要的作用。然而,要充分理解这一过程,它是必不可少的,以解决这种外流的形态和运动学。使用VLT/SINFONI获得的近红外积分场光谱,我们检测到的高速分子氢(H2)气体与深埋的第二核的IR发光合并NGC 3256的kpc尺度的结构。我们发现,这种结构很可能是分子外流的热成分,坂本等人也在冷分子气体中检测到了这种结构。这种外流的分子气体质量为M(H2)~2x10^7 Msun,是首先在VLT/SINFONI的热H2气体和ALMA的冷CO排放气体中得到空间分辨的。热组分和冷组分具有相似的形态学和运动学,热分子气体与冷分子气体的质量比约为6 × 10 ^-5。我们绘制热流出的几何形状和速度结构的高分辨率(~100 pc)揭示了一个双锥形态,开口角~40度,气体分布在FWZI~1200 km/s。由于这种平行流出的方向接近天空平面,分子气体可能达到最大的固有流出速度~1800 km/s,平均质量流出速率至少为~20 Msun/yr。通过模拟各种近红外H2跃迁的线比,我们表明流出的H2气体通过冲击或X射线加热到~ 1900 K的温度。驱动外流所需的能量很可能是由一个隐藏的康普顿厚度的活动星系核或核恒星暴提供的。我们发现,在NGC 3256的分子外流的全球运动学模仿那些已观察到的低空间分辨率的恒星爆发和活动星系的CO外流。

英文摘要:

The nuclei of merging galaxies are often deeply buried in dense layers of gas and dust. In these regions, gas outflows driven by starburst and AGN activity are believed to play a crucial role in the evolution of these galaxies. However, to fully understand this process it is essential to resolve the morphology and kinematics of such outflows. Using near-IR integral-field spectroscopy obtained with VLT/SINFONI, we detect a kpc-scale structure of high-velocity molecular hydrogen (H2) gas associated with the deeply buried secondary nucleus of the IR-luminous merger NGC3256. We show that this structure is likely the hot component of a molecular outflow, which is detected also in the cold molecular gas by Sakamoto et al. This outflow, with a molecular gas mass of M(H2)~2x10^7 Msun, is among the first to be spatially resolved in both the hot H2 gas with VLT/SINFONI and the cold CO-emitting gas with ALMA. The hot and cold components share a similar morphology and kinematics, with a hot-to-cold molecular gas mass ratio of ~6x10^-5. The high (~100 pc) resolution at which we map the geometry and velocity structure of the hot outflow reveals a biconical morphology with opening angle ~40 deg and gas spread across a FWZI~1200 km/s. Because this collimated outflow is oriented close to the plane of the sky, the molecular gas may reach maximum intrinsic outflow velocities of ~1800 km/s, with an average mass outflow rate of at least ~20 Msun/yr. By modeling the line-ratios of various near-IR H2 transitions, we show that the H2 gas in the outflow is heated through shocks or X-rays to a temperature of ~1900K. The energy needed to drive the outflow is likely provided by a hidden Compton-thick AGN or by the nuclear starburst. We show that the global kinematics of the molecular outflow in NGC3256 mimic those of CO-outflows that have been observed at low spatial resolution in starburst- and active galaxies.

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