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arXiv 1203.3452astro-ph.COastro-ph.GA
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4C12.50外流中的冷暖分子气体

Cold and warm molecular gas in the outflow of 4C12.50

K. M. Dasyra, F. Combes

摘要:

本文利用射电天文研究所的30米望远镜对超亮红外射电星系4C12.50中的~(12)CO(1 - 0)和(3 - 2)谱线进行了深度观测。我们的观测揭示了以前从斯皮策太空望远镜数据中已知的温暖分子气体流出的冷分子气体成分。12CO(3 - 2)剖面表明,在距系统速度约950 km/s处存在吸收,中心光学深度为0.22。它的轮廓是类似的HI吸收,在无线电数据中看到这个来源。对(0 - 1)吸收的潜在探测使我们能够在其中心光学深度上设置0.03的上限,并将流出的CO气体的激发温度限制在>= 65K(假设气体是热化的)。如果分子云完全遮蔽了射电核心发射的背景毫米波连续谱,则H2柱密度>= 1.8 * 10^22/cm ^2。流出物沿着核视线携带着估计至少为4.2 * 10^3 M_sun的冷H2质量。当在几条视线上积分时,这个质量会更高,但如果它超过3 * 10^9 M_sun,流出物很可能会在发射中看到。由于4C12.50的环境冷气体储集层为1.0 * 10^10 M_sun,因此相对于冷气体,热气体的流出与环境的质量比(37%)可以升高。

英文摘要:

We present deep observations of the 12CO(1-0) and (3-2) lines in the ultra-luminous infrared and radio galaxy 4C12.50, carried out with the 30m telescope of the Institut de Radioastronomie Millimetrique. Our observations reveal the cold molecular gas component of a warm molecular gas outflow that was previously known from Spitzer Space Telescope data. The 12CO(3-2) profile indicates the presence of absorption at -950 km/s from systemic velocity with a central optical depth of 0.22. Its profile is similar to that of the HI absorption that was seen in radio data of this source. A potential detection of the (0-1) absorption enabled us to place an upper limit of 0.03 on its central optical depth, and to constrain the excitation temperature of the outflowing CO gas to >=65K assuming that the gas is thermalized. If the molecular clouds fully obscure the background millimeter continuum that is emitted by the radio core, the H2 column density is >=1.8*10^22 /cm^2. The outflow then carries an estimated cold H2 mass of at least 4.2*10^3 M_sun along the nuclear line of sight. This mass will be even higher when integrated over several lines of sight, but if it were to exceed 3*10^9 M_sun, the outflow would most likely be seen in emission. Since the ambient cold gas reservoir of 4C12.50 is 1.0*10^10 M_sun, the outflowing-to-ambient mass ratio of the warm gas (37%) could be elevated with respect to that of the cold gas.

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