论文标题
高红移星系的灰尘和气体含量在CDF-S中占据了模糊的AGN
Dust and gas content of high-redshift galaxies hosting obscured AGN in the CDF-S
论文作者
论文摘要
遮盖的AGN代表了整个AGN种群的很大一部分，尤其是在高红移时（Z = 3--5时约70％）。它们通常以大型气体和灰尘储层的存在为特征，这些储层被认为可以维持并可能掩盖剧烈的恒星形成过程，从而使这些物体在Far-Ir和sub-MM波长处发光。我们利用ALMA循环4的观测值（〜2.1mm）和高J CO发射的六个X射线选择的SMG样品在7 ms Cdf-s中占据了Z_SPEC> 2.5的遮盖的AGN。我们测量了灰尘和分子气的质量和尺寸，并根据均匀的球体几何形状得出了气体密度和柱密度。最后，我们比较了测得的色谱柱密度与源自钱德拉X射线光谱的柱密度。我们检测到三个来源的连续性和线发射，我们测量了通量密度和大小。对于未检测到的来源，我们得出了通量密度的上限。 We found that the detected galaxies are rich in gas and dust (molecular gas mass in the range <0.5 - 2.7 x 10^10 M_sun for α_CO=0.8 and up to ~2 x 10^11~M_sun for α_CO=6.5, and dust mass <0.9 - 4.9 x 10^8 M_sun) and compact (gas major axis 2.1-3.0 kpc, dust major axis 1.4-2.7 kpc).与ISM相关的列密度在10^（23-24）cm-2的阶，与X射线光谱衍生的柱密度相当。对于检测到的来源，我们还得出了0.8-3.7 x 10^10 m_sun范围内的动态质量。我们得出的结论是，高红移星系的ISM可以实质上有助于核遮挡，直到Compton-Thick（> 10^24 cm-2）制度。此外，我们发现所有检测到的来源都显示出一个速度梯度，提醒一个旋转系统，即使其中两个在其形态中显示出特殊的特征，这些特征可能与混乱的，可能是合并的结构有关。
Obscured AGN represent a significant fraction of the entire AGN population, especially at high redshift (~70% at z=3--5). They are often characterized by the presence of large gas and dust reservoirs that are thought to sustain and possibly obscure vigorous star formation processes that make these objects shine at far-IR and sub-mm wavelengths. We exploit ALMA Cycle 4 observations of the continuum (~2.1mm) and high-J CO emission of a sample of six X-ray selected SMGs hosting an obscured AGN at z_spec>2.5 in the 7 Ms CDF-S. We measured the masses and sizes of the dust and molecular gas and we derived the gas density and column density on the basis of a uniform sphere geometry. Finally, we compared the measured column densities with those derived from the Chandra X-ray spectra. We detected both the continuum and line emission for three sources for which we measured both the flux density and size. For the undetected sources, we derived an upper limit on the flux density. We found that the detected galaxies are rich in gas and dust (molecular gas mass in the range <0.5 - 2.7 x 10^10 M_sun for α_CO=0.8 and up to ~2 x 10^11~M_sun for α_CO=6.5, and dust mass <0.9 - 4.9 x 10^8 M_sun) and compact (gas major axis 2.1-3.0 kpc, dust major axis 1.4-2.7 kpc). The column densities associated with the ISM are on the order of 10^(23-24) cm-2, which is comparable with those derived from the X-ray spectra. For the detected sources we also derived dynamical masses in the range 0.8 - 3.7 x 10^10 M_sun. We conclude that the ISM of high redshift galaxies can substantially contribute to nuclear obscuration up to the Compton-thick (>10^24 cm-2) regime. In addition, we found that all the detected sources show a velocity gradient reminding one rotating system, even though two of them show peculiar features in their morphology that can be associated with a chaotic, possibly merging, structure.
