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arXiv 1402.6736astro-ph.GAastro-ph.CO
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类星体反馈与射电宁静类星体射电辐射的起源

Quasar feedback and the origin of radio emission in radio-quiet quasars

Nadia L. Zakamska, Jenny E. Greene

摘要:

我们进行运动学分析的SDSS光谱的568遮蔽发光类星体,重点是运动学结构的[OIII]5007发射线。[OIII]发射倾向于显示蓝移和蓝色过量,这表明至少部分窄线气体正在经历有组织的流出。包含90%线功率的速度宽度范围从370到4780公里/秒,表明流出速度高达2000公里/秒。在射电宁静类星体中,[OIII]发射的速度宽度与射电光度呈正相关。我们提出,无线电宁静类星体中的无线电发射是由于类星体驱动的外流中的冲击加速的相对论粒子;类星体宿主中的恒星形成不足以解释观测到的无线电发射。样本的射电光度中值为nu L_nu[1.4GHz] = 10^40 erg/sec,表明类星体驱动风的动力学光度中值为L_wind=3x10^44 erg/sec,约为估计的中值热光度L_bol=8x10^45 erg/sec的4%。此外,[OIII]的速度宽度与中红外光度呈正相关,这表明外流最终是由类星体的辐射输出驱动的。随着外流速度的增加,一些准中性介质中激波特征的发射线也增加,我们认为这是类星体驱动风传播到宿主星系的星际介质的进一步证据。没有任何运动学分量与宿主星系的恒星速度色散相关,因此没有证据表明类星体窄线区域的任何气体与宿主星系处于动力学平衡。类星体反馈似乎在亮度阈值L_bol= 3 × 10^45 erg/sec以上起作用。

英文摘要:

We conduct kinematic analysis of the SDSS spectra of 568 obscured luminous quasars, with the emphasis on the kinematic structure of the [OIII]5007 emission line. [OIII] emission tends to show blueshifts and blue excess, which indicates that at least part of the narrow-line gas is undergoing an organized outflow. The velocity width containing 90% of line power ranges from 370 to 4780 km/sec, suggesting outflow velocities up to 2000 km/sec. The velocity width of the [OIII] emission is positively correlated with the radio luminosity among the radio-quiet quasars. We propose that radio emission in radio-quiet quasars is due to relativistic particles accelerated in the shocks within the quasar-driven outflows; star formation in quasar hosts is insufficient to explain the observed radio emission. The median radio luminosity of the sample of nu L_nu[1.4GHz] = 10^40 erg/sec suggests a median kinetic luminosity of the quasar-driven wind of L_wind=3x10^44 erg/sec, or about 4% of the estimated median bolometric luminosity L_bol=8x10^45 erg/sec. Furthermore, the velocity width of [OIII] is positively correlated with mid-infrared luminosity, which suggests that outflows are ultimately driven by the radiative output of the quasar. As the outflow velocity increases, some emission lines characteristic of shocks in quasi-neutral medium increase as well, which we take as further evidence of quasar-driven winds propagating into the interstellar medium of the host galaxy. None of the kinematic components show correlations with the stellar velocity dispersions of the host galaxies, so there is no evidence that any of the gas in the narrow-line region of quasars is in dynamical equilibrium with the host galaxy. Quasar feedback appears to operate above the threshold luminosity of L_bol=3x10^45 erg/sec.

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