论文标题
VLA-COSMOS 3 GHz大项目：活性银河核的平均无线电光谱能分布
The VLA-COSMOS 3 GHz Large Project: Average radio spectral energy distribution of active galactic nuclei
论文作者
论文摘要
由于预计SKA将在未来十年内运行，因此对100 MHz至10 GHz的无线电天空的调查对于SKA观察的模拟变得很重要。在从无线电数据中确定星系的物理特性时，通常假定无线电SED由简单的功率定律描述，通常所有源的光谱指数为0.7。即使已显示无线电SED与此假设表现出偏差，无论是在不同的光谱指数和复杂的光谱形状上，但通常认为它们的个体差异在大样本中取消。我们构建了无线电效率活性银河核（RXAGN）的平均无线电SED，该核定义为表现出3 $σ$无线电发光度过量相对于仅在恒星形成的贡献中预期的值，从Z〜4出现的值。我们将1.4 GHz的宇宙场和3 GHz的VLA观察结果与325 MHz和610 MHz的GMRT观测值结合在一起。为了说明GMRT地图中的非探测，我们采用了生存分析技术。我们选择了一个rxagn样品为z〜4。 We find that a sample of RxAGN can be described by a spectral index of $α_1=0.28\pm0.03$ below the break frequency $ν_b=(4.1\pm0.2)$ GHz and $α_2=1.16\pm0.04$ above, while a simple power-law model yields a single spectral index of $α=0.64\pm0.07$.通过以1.4 GHz的无线电发光度和红移键合成，我们发现较大源尺寸的幂律频谱指数以及损坏的幂律光谱指数可能会增加，而幂律频谱指数和低频（<4 GHz）损坏的幂律频谱与红移额正相关。
As the SKA is expected to be operational in the next decade, investigations of the radio sky in the range of 100 MHz to 10 GHz have become important for simulations of the SKA observations. In determining physical properties of galaxies from radio data, the radio SED is often assumed to be described by a simple power law, usually with a spectral index of 0.7 for all sources. Even though radio SEDs have been shown to exhibit deviations from this assumption, both in differing spectral indices and complex spectral shapes, it is often presumed that their individual differences cancel out in large samples. We constructed the average radio SED of radio-excess active galactic nuclei (RxAGN), defined as those that exhibit a 3 $σ$ radio luminosity excess with respect to the value expected only from contribution from star formation, out to z~4. We combined VLA observations of the COSMOS field at 1.4 GHz and 3 GHz with GMRT observations at 325 MHz and 610 MHz. To account for nondetections in the GMRT maps, we employed the survival analysis technique. We selected a sample of RxAGN out to z~4. We find that a sample of RxAGN can be described by a spectral index of $α_1=0.28\pm0.03$ below the break frequency $ν_b=(4.1\pm0.2)$ GHz and $α_2=1.16\pm0.04$ above, while a simple power-law model yields a single spectral index of $α=0.64\pm0.07$. By binning in 1.4 GHz radio luminosity and redshift, we find that the power-law spectral index, as well as broken power-law spectral indices, may increase for larger source sizes, while the power-law spectral index and lower-frequency (<4 GHz) broken power-law spectral index are additionally positively correlated with redshift.
