标题： 赫歇尔-PACS 观测的近红外明亮星系中的高J CO SLEDs 显示英文标题

标题： High-J CO SLEDs in nearby infrared bright galaxies observed by Herschel-PACS

摘要： 我们报告了在邻近活动星系核（AGN）和星爆星系，以及几个合并系统和超光度红外星系（ULIRGs）中检测到远红外（FIR）CO旋转发射。 使用赫歇尔-PACS，我们在J$_{upp}$ = 14 - 20范围内检测到了跃迁（$\lambda \sim$ 130 - 185 $\mu$m, $\nu \sim$ 1612 - 2300 GHz），并给出了CO谱线流量的上限（在两种情况下还进行了检测），最高达到J$_{upp}$ = 30。 此处获得的PACS CO数据为这一范围提供了第一个采样良好的河外FIR CO光谱线能量分布（SLEDs），并将是未来高红移研究的重要参考。 将这些数据与文献中低-J谱线强度相结合，我们提出了一个CO比值-比值图，并讨论了其在区分激发源和分子气体物理性质方面的潜在诊断价值。 随后，我们使用大速度梯度（LVG）辐射转移模型对部分检测到的源的CO发射进行定量分析，以拟合CO SLEDs。 使用单组分和双组分LVG模型来拟合气体的动能温度、速度梯度、数密度和柱密度，我们推导出每种相应源的分子气体质量以及相应的CO到H$_2$转换因子，$\alpha_{CO}$。 最后，我们将最佳拟合的LVG模型结果与之前对同一星系的研究结果进行比较，并评论其中的任何差异。 显示英文摘要

摘要： We report the detection of far-infrared (FIR) CO rotational emission from nearby active galactic nuclei (AGN) and starburst galaxies, as well as several merging systems and Ultra-Luminous Infrared Galaxies (ULIRGs). Using Herschel-PACS, we have detected transitions in the J$_{upp}$ = 14 - 20 range ($\lambda \sim$ 130 - 185 $\mu$m, $\nu \sim$ 1612 - 2300 GHz) with upper limits on (and in two cases, detections of) CO line fluxes up to J$_{upp}$ = 30. The PACS CO data obtained here provide the first well-sampled FIR extragalactic CO Spectral Line Energy Distributions (SLEDs) for this range, and will be an essential reference for future high redshift studies. Combining these data with low-J line intensities taken from the literature, we present a CO ratio-ratio diagram and discuss its potential diagnostic value in distinguishing excitation sources and physical properties of the molecular gas. We then quantitatively analyze the CO emission from a subset of the detected sources with Large Velocity Gradient (LVG) radiative transfer models to fit the CO SLEDs. Using both single-component and two-component LVG models to fit the kinetic temperature, velocity gradient, number density and column density of the gas, we derive the molecular gas mass and the corresponding CO-to-H$_2$ conversion factor, $\alpha_{CO}$, for each respective source. Finally, we compare our best-fit LVG model results with those obtained in previous studies of the same galaxies and comment on any differences.