THE CENTRAL MOLECULAR GAS STRUCTURE IN LINERS WITH LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI: EVIDENCE FOR GRADUAL DISAPPEARANCE OF THE TORUS
THE CENTRAL MOLECULAR GAS STRUCTURE IN LINERS WITH LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI: EVIDENCE FOR GRADUAL DISAPPEARANCE OF THE TORUS
复制标题
DOI：
10.1088/2041-8205/764/1/l1
复制
发表时间：
2012-12
期刊：
影响因子：
--
通讯作者：
F. Muller-S'anchez;M. Prieto;M. Mezcua;R. Davies;M. Malkan;M. I. D. A. D. Canarias-M.-I.-D.-A.-D.-Canarias-102993718;U. L. Laguna
中科院分区：
文献类型：
--
作者：
F. Muller-S'anchez;M. Prieto;M. Mezcua;R. Davies;M. Malkan;M. I. D. A. D. Canarias-M.-I.-D.-A.-D.-Canarias-102993718;U. L. Laguna
我们基于VLT/ sinoni ao辅助的H2 1 - 0 S(1)发射的积分场光谱，在角分辨率为~ 0.″17的基础上，对三个典型的低光度活动星系核（LLAGNs）核环境中的分子气体进行了观测。在50 ~ 150pc尺度上，分子气体的空间分布和运动学与旋转的薄圆盘一致，其中旋转(V)与色散（σ）之比大于1。然而，在中央50pc，观测显示了分子气体的几何和光学厚结构（V/σ 1023 cm−2），这可能与任何较小尺度的模糊结构的外部范围有关。与塞弗特星系相比，llagn中的分子气体在面积上的V/σ < 1，比塞弗特星系小9倍，柱密度平均小3倍。我们将这些结果解释为核模糊结构逐渐消失的证据。虽然盘状风可能无法在这样的光度下维持一个厚厚的旋转结构，但流入核区的物质可以提供足够的能量来维持它。在这种情况下，llagn可能代表了当前环面进化理论中吸积的最后阶段。虽然在塞弗特阶段流入速率相当大，但它正在缓慢下降，并且碰撞盘逐渐过渡到几何上变薄。此外，这些llagn的核区主要由中年/老年恒星群（很少或没有正在形成的恒星）主导，与演化的后期阶段一致。
We present observations of the molecular gas in the nuclear environment of three prototypical low-luminosity active galactic nuclei (LLAGNs), based on VLT/SINFONI AO-assisted integral-field spectroscopy of H2 1–0 S(1) emission at angular resolutions of ∼0.″17. On scales of 50–150 pc, the spatial distribution and kinematics of the molecular gas are consistent with a rotating thin disk, where the ratio of rotation (V) to dispersion (σ) exceeds unity. However, in the central 50 pc, the observations reveal a geometrically and optically thick structure of molecular gas (V/σ 1023 cm−2) that is likely to be associated with the outer extent of any smaller scale obscuring structure. In contrast to Seyfert galaxies, the molecular gas in LLAGNs has a V/σ < 1 over an area that is ∼9 times smaller and column densities that are on average ∼3 times smaller. We interpret these results as evidence for a gradual disappearance of the nuclear obscuring structure. While a disk wind may not be able to maintain a thick rotating structure at these luminosities, inflow of material into the nuclear region could provide sufficient energy to sustain it. In this context, LLAGNs may represent the final phase of accretion in current theories of torus evolution. While the inflow rate is considerable during the Seyfert phase, it is slowly decreasing, and the collisional disk is gradually transitioning to become geometrically thin. Furthermore, the nuclear region of these LLAGNs is dominated by intermediate-age/old stellar populations (with little or no ongoing star formation), consistent with a late stage of evolution.