Molecular gas and dust in NGC 4550 - A galaxy with two counterrotating stellar disks
Molecular gas and dust in NGC 4550 - A galaxy with two counterrotating stellar disks
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NGC 4550 中的分子气体和尘埃 - 具有两个反向旋转恒星盘的星系
DOI：
10.1051/0004-6361:20010860
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发表时间：
2001
影响因子：
6.5
通讯作者：
C. Henkel
中科院分区：
文献类型：
--
作者：
T. Wiklind;C. Henkel
我们报告在 S0/E7 星系 NGC 4550 的中心区域检测到 $1 \times 10^7$ $M_{\odot}$ 分子气体，这是根据 CO(1-0) 发射的观测推断的。在 HST WFPC2 图像中检测到灰尘，发现其不对称地分布在原子核周围，仅延伸到 7 英寸（600 pc）的星系中心距离。 CO 排放曲线的形状与灰尘后的分子气体分布一致。中心尘埃和气体的分布可能是 $m=1$ 不稳定的结果，这是反向旋转恒星盘中增长最快的不稳定模式。在全球范围内，NGC 4550 中的分子气体对于引力塌缩是稳定的，但恒星形成似乎仍在以正常的恒星形成效率和气体消耗时间尺度进行。 NGC 4550 中的恒星速度色散类似于椭圆星系。因此，热 X 射线发射等离子体可能会限制分子气体的寿命，而分子气体必须由最近的 (<1 Gyr) 吸积事件产生。
We report the detection of $1 \times 10^7$ $M_{\odot}$ of molecular gas in the central region of the S0/E7 galaxy NGC 4550, inferred from observations of CO(1-0) emission. Dust is detected in HST WFPC2 images and found to be asymmetrically distributed around the nucleus, only extending to a galactocentric distance of 7 '' (600 pc). The shape of the CO emission profile is consistent with a molecular gas distribution following the dust. The distribution of the dust and gas in the center could be the result of an $m=1$ instability, which is the fastest growing unstable mode in counterrotating stellar disks. On a global scale the molecular gas in NGC 4550 is stable against gravitational collapse but nevertheless star formation appears to be ongoing with normal star formation efficiency and gas consumption time scales. The stellar velocity dispersion in NGC 4550 resembles that of elliptical galaxies. It is therefore likely that a hot X-ray emitting plasma limits the lifetime of the molecular gas, that must arise from a recent ( ≪ 1 Gyr) accretion event.