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arXiv 1708.09503astro-ph.GA
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用VLT-SINFONI映射的超亮红外星系中热分子气体的流出

Outflows of hot molecular gas in ultra-luminous infra-red galaxies mapped with VLT-SINFONI

B. Emonts, L. Colina, J. Piqueras-Lopez, S. Garcia-Burillo, M. Pereira-Santaella, S. Arribas, A. Labiano, A. Alonso-Herrero

摘要:

我们目前的检测和形态特征的热分子气体外流在附近的超亮红外星系,使用近红外积分场光谱仪SINFONI的VLT。我们检测到在2.12微米H $_{2}$ 1-0 S(1)线中观察到的4个ULIRG中的3个的流出; IRAS 12112+0305、14348-1447和22491-1808。流出的比例尺为0.7-1.6千秒差距,显示出典型的流出速度为300-500公里/秒,似乎起源于核区域。流出物包括约6- 8 × 10 $^3$ M(太阳)的热分子气体质量。假设热-冷分子气体质量比为6 × 10 $^{-5}$,就像在附近明亮的红外星系中发现的那样,这些流出物中的总(热+冷)分子气体质量预计为~ 1 × 10 $^{8}$ M(太阳)。这转化为分子质量流出率约为30-85 M(太阳)/年,这比这些ULIRGs的恒星形成率低几倍。此外,大部分流出的分子气体没有达到这些合并系统的逃逸速度,这意味着大部分流出的分子气体在系统内重新分布,因此仍然可以用于未来的恒星形成。最快的H $_{2}$外流出现在IRAS 14348-1447的康普顿厚度活动星系核中,最大外流速度达到约900 km/s。另一个ULIRG,IRAS 17208-0014,显示了与其他三个ULIRG中观察到的流出不同的不对称H $_{2}$线轮廓。我们讨论了几种不同的解释,其线的不对称性,包括一个非常温和的银河风,内部气体动力学,低速气体外的磁盘,或两个叠加的气体磁盘。我们没有检测到与先前在IRAS 17208-0014中在CO(2-1)中检测到的流出物对应的热分子,但我们注意到,如果它具有小于9 × 10 $^{-6}$的小的热-冷分子气体质量比,则我们的SINFONI数据不足以检测这种流出物。

英文摘要:

We present the detection and morphological characterization of hot molecular gas outflows in nearby ultra-luminous infrared galaxies, using the near-IR integral-field spectrograph SINFONI on the VLT. We detect outflows observed in the 2.12 micron H$_{2}$ 1-0 S(1) line for three out of four ULIRGs analyzed; IRAS 12112+0305, 14348-1447, and 22491-1808. The outflows are mapped on scales of 0.7-1.6 kpc, show typical outflow velocities of 300-500 km/s, and appear to originate from the nuclear region. The outflows comprise hot molecular gas masses of ~6-8x10$^3$ M(sun). Assuming a hot-to-cold molecular gas mass ratio of 6x10$^{-5}$, as found in nearby luminous IR galaxies, the total (hot+cold) molecular gas mass in these outflows is expected to be ~1x10$^{8}$ M(sun). This translates into molecular mass outflow rates of ~30-85 M(sun)/yr, which is a factor of a few lower than the star formation rate in these ULIRGs. In addition, most of the outflowing molecular gas does not reach the escape velocity of these merger systems, which implies that the bulk of the outflowing molecular gas is re-distributed within the system and thus remains available for future star formation. The fastest H$_{2}$ outflow is seen in the Compton-thick AGN of IRAS 14348-1447, reaching a maximum outflow velocity of ~900 km/s. Another ULIRG, IRAS 17208-0014, shows asymmetric H$_{2}$ line profiles different from the outflows seen in the other three ULIRGs. We discuss several alternative explanations for its line asymmetries, including a very gentle galactic wind, internal gas dynamics, low-velocity gas outside the disk, or two superposed gas disks. We do not detect the hot molecular counterpart to the outflow previously detected in CO(2-1) in IRAS 17208-0014, but we note that our SINFONI data are not sensitive enough to detect this outflow if it has a small hot-to-cold molecular gas mass ratio of < 9x10$^{-6}$.

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