标题： 使用KOSMA望远镜对室女座星系团漩涡星系的12CO(J=2->1)和CO(J=3->2)观测：全局性质 显示英文标题

标题： 12CO(J=2->1) and CO(J=3->2) observations of Virgo Cluster spiral galaxies with the KOSMA telescope: global properties

摘要： 我们利用KOSMA 3米亚毫米波望远镜观测了处于静止状态的室女星系团旋涡星系的12CO(J=2→1)和CO(J=3→2)辐射。345 GHz处80"以及230 GHz处120"的波束尺寸非常适合研究室女星系团星系的整体性质。观测样本基于Stark等人（1986年）用AT&T贝尔实验室7米望远镜（波束尺寸100"）得到的先前12CO(J=1→0)探测结果进行选择。我们在12CO(2→1)中检测到18个旋涡星系，在12CO(3→2)中检测到16个。匹配波束的最低三个12CO跃迁观测使我们能够将我们的结果与之前关于（适度）星暴星系和星系核心区域的高空间分辨率研究进行比较。我们讨论了这些处于静止状态的旋涡星系中星际介质的整体激发条件。得到的CO(3–2)/(1–0)积分线比值在相对较小的范围内变化，从0.35到0.14（以K km/s为单位），随着CO(2–1)/(1–0)比值的增加（从0.5到1.1）。CO的三个最低旋转跃迁之间的线比不能通过任何具有单一源分量的辐射转移模型来拟合。假设一个温暖致密核和一个寒冷较稀疏盘分量的双分量模型允许通过选择合适的参数单独拟合大多数星系的观测线比。然而，该双分量模型未能解释线比的观测相关性。这是由于仅温气相对填充因子的变化，假定两个分量的一组典型参数适用于所有星系。 显示英文摘要

摘要： We present 12CO(J=2->1) and CO(J=3->2) observations of quiescent Virgo Cluster spiral galaxies with the KOSMA 3m submm telescope. The beam sizes of 80" at 345 GHz and 120" at 230 GHz are well suited for the investigation of global properties of Virgo Cluster galaxies. The observed sample was selected based on previous 12CO(J=1->0) detections by Stark et al. (1986), performed with the AT&T Bell Laboratory 7m telescope (beam size 100"). We were able to detect 18 spiral galaxies in 12CO(2->1) and 16 in 12CO(3->2). Beam matched observations of the lowest three 12CO transitions allow us to compare our results with previous high spatial resolution studies of (moderate) starburst galaxies and galactic core regions. We discuss the global excitation conditions of the ISM in these quiescent spiral galaxies. The resulting CO (3--2)/(1--0) integrated line ratios vary over a relatively narrow range of values from 0.35 to 0.14 (on a K km/s-scale) with increasing CO (2--1)/(1--0) ratio (from 0.5 to 1.1). The line ratios between the three lowest rotational transitions of CO cannot be fitted by any radiative transfer model with a single source component. A two-component model, assuming a warm, dense nuclear and a cold, less dense disc component allows us to fit the observed line ratios for most of the galaxies individually by selecting suitable parameters. The two-component model, however, fails to explain the observed correlation of the line ratios. This is due to a variation of the relative filling factor of the warm gas alone, assuming a typical set of parameters for the two components common for all galaxies.