arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0712.4145astro-ph
收藏

射电星系3C 79的宿主星系和扩展发射线区

The Host Galaxy and The Extended Emission-Line Region of The Radio Galaxy 3C 79

Hai Fu, Alan Stockton

摘要:

我们提出了广泛的地面光谱和HST成像的3C 79,FR II射电星系与发光的扩展发射线区域(EELR)。无发射线的HST R波段图像的表面亮度模型显示,宿主星系是一个巨大的椭圆星系,有一个0.8”远的紧凑伴星,暗4等。主星系光谱最好的描述是一个中等年龄(1.3 Gyr)的恒星种群(4%质量),叠加在一个10 Gyr的恒星种群和一个幂律(α_λ = -1.8)上;恒星星族与超太阳金属丰度是一致的,最好的拟合是2.5 Z_sun模型。从速度色散出发,导出了4 E11 Msun在有效半径范围内的动力学质量。EELR的光谱清楚地表明,EELR是由隐藏的中央引擎光电离。光电离模拟表明,在EELR和核窄线区的气体金属丰度是温和的亚太阳(0.3 - 0.7 Z_sun)-显着低于超太阳的金属丰度推断典型的活动星系核在SDSS。EELR中更明亮的灯丝表现出与普通磁盘旋转一致的速度场。然而,较弱的云显示出与这种明显的圆盘旋转无关的高接近速度。这个EELR和陡谱射电噪类星体周围的EELR之间惊人的相似之处为依赖于方向的统一方案提供了进一步的证据。贫金属气体几乎肯定不是大质量宿主星系的原生气体。我们认为,密切的同伴星系可能是潮汐剥离隆起的晚型星系,正在与宿主星系合并。这样一个星系的星际介质可能是3C 79中低金属丰度气体的来源。

英文摘要:

We present extensive ground-based spectroscopy and HST imaging of 3C79, an FR II radio galaxy associated with a luminous extended emission-line region (EELR). Surface brightness modeling of an emission-line-free HST R-band image reveals that the host galaxy is a massive elliptical with a compact companion 0.8" away and 4 magnitudes fainter. The host galaxy spectrum is best described by an intermediate-age (1.3 Gyr) stellar population (4% by mass), superimposed on a 10 Gyr old population and a power law (α_λ = -1.8); the stellar populations are consistent with super-solar metallicities, with the best fit given by the 2.5 Z_sun models. We derive a dynamical mass of 4E11 M_sun within the effective radius from the velocity dispersion. The EELR spectra clearly indicate that the EELR is photoionized by the hidden central engine. Photoionization modeling shows evidence that the gas metallicity in both the EELR and the nuclear narrow-line region is mildly sub-solar (0.3 - 0.7 Z_sun) -- significantly lower than the super-solar metallicities deduced from typical active galactic nuclei in the SDSS. The more luminous filaments in the EELR exhibit a velocity field consistent with a common disk rotation. Fainter clouds, however, show high approaching velocities that are uncoupled with this apparent disk rotation. The striking similarities between this EELR and the EELRs around steep-spectrum radio-loud quasars provide further evidence for the orientation-dependent unification schemes. The metal-poor gas is almost certainly not native to the massive host galaxy. We suggest that the close companion galaxy could be the tidally stripped bulge of a late-type galaxy that is merging with the host galaxy. The interstellar medium of such a galaxy is probably the source for the low-metallicity gas in 3C79.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑