射电星系中喷流驱动的氢分子发射
Jet-Powered Molecular Hydrogen Emission from Radio Galaxies
摘要：
用斯皮策红外光谱仪在红移z<0.22的射电星系中观测到17/55（31%）的热分子气体（100-1500 K）中的H2纯转动发射线。H2 0-0 S（0）-S（3）线的总光度为L（H2）= 7 E38 - 2 E42 erg/s，产生的H2暖质量高达2 E10 Msun。这些射电星系，两个FR射电形态类型，有助于牢固地建立新的一类无线电选择的分子氢发射星系（无线电MOHEGs）。MOHEGs有非常大的H2到7.7微米PAH的发射比：L（H2）/L（PAH7.7）= 0.04-4，比正常恒星形成星系的中值大300倍。尽管H2的质量很大，但MOHEGs似乎在形成恒星方面效率很低，这可能是因为分子气体在运动学上是不稳定和湍流的。低光度的中红外连续辐射和低电离发射线光谱表明，除了3个射电MOHEGs外，所有的活动星系核都是低光度的。钱德拉测量的活动星系核的X射线辐射亮度不足以为MOHEGs的H2辐射提供能量。几乎所有的射电MOHEGs都属于星团或近距离双星，包括4个冷核心星团（英仙座、长蛇座、A 2052和A 2199）。我们认为射电MOHEGs中的H2是在星系碰撞或冷却流中传递的，然后被射电喷流以激波或宇宙射线的动能耗散的形式反馈加热。
英文摘要：
H2 pure-rotational emission lines are detected from warm (100-1500 K) molecular gas in 17/55 (31% of) radio galaxies at redshift z<0.22 observed with the Spitzer IR Spectrograph. The summed H2 0-0 S(0)-S(3) line luminosities are L(H2)=7E38-2E42 erg/s, yielding warm H2 masses up to 2E10 Msun. These radio galaxies, of both FR radio morphological types, help to firmly establish the new class of radio-selected molecular hydrogen emission galaxies (radio MOHEGs). MOHEGs have extremely large H2 to 7.7 micron PAH emission ratios: L(H2)/L(PAH7.7) = 0.04-4, up to a factor 300 greater than the median value for normal star-forming galaxies. In spite of large H2 masses, MOHEGs appear to be inefficient at forming stars, perhaps because the molecular gas is kinematically unsettled and turbulent. Low-luminosity mid-IR continuum emission together with low-ionization emission line spectra indicate low-luminosity AGNs in all but 3 radio MOHEGs. The AGN X-ray emission measured with Chandra is not luminous enough to power the H2 emission from MOHEGs. Nearly all radio MOHEGs belong to clusters or close pairs, including 4 cool core clusters (Perseus, Hydra, A 2052, and A 2199). We suggest that the H2 in radio MOHEGs is delivered in galaxy collisions or cooling flows, then heated by radio jet feedback in the form of kinetic energy dissipation by shocks or cosmic rays.
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