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arXiv 2102.10600astro-ph.GAastro-ph.CO
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用低频射电观测追踪超铝质红外星系向射电星系的演化

Tracing the Evolution of Ultraluminous Infrared Galaxies into Radio Galaxies with Low Frequency Radio Observations

S. Nandi, M. Das, K. S. Dwarakanath

摘要:

我们目前的无线电观测超亮红外星系(ULIRGs)使用巨型米波射电望远镜(GMRT),并将它们与档案多频观测,以了解是否ULIRGs是在本地宇宙中的强大的射电大声星系的祖先。超红外类星体的特点是红外线光度大($L_{IR}>$ 10 $^{12}$ L $\odot$),尘埃质量大($\sim10^{8}M_{\odot}$),恒星形成活跃(恒星形成速率$\sim$ 10-100 $M_{\odot}~$ yr $^{-1}$)。研究表明,它们代表了富含气体的螺旋星系合并的最后阶段。它们的光度可以归因于星暴活动和活动星系核(AGN)。我们研究了13个ULIRG样本,这些样本通过1.28~GHz的GMRT观测数据光学识别了活动星系核特征。我们的目标是解决任何核心喷流结构或核扩展,从而检查是否ULIRGs正在演变成无线电响亮的椭圆。我们的深,低频观测显示只有一个源的边际扩展。然而,9个ULIRG的综合无线电频谱表现出类似于GPS/CSS/CSO/年轻射电源的特征。估计的光谱年龄为0.4至20百万年,表明它们是年轻的射电源和可能的射电星系的祖先。因此,我们的结论是,虽然大多数ULIRG不显示kpc尺度的扩展无线电发射与核活动,其无线电频谱能量分布确实显示年轻的射电星系的签名。

英文摘要:

We present radio observations of ultraluminous infrared galaxies (ULIRGs) using the Giant Metrewave Radio Telescope (GMRT) and combine them with archival multi-frequency observations to understand whether ULIRGs are the progenitors of the powerful radio loud galaxies in the local Universe. ULIRGs are characterized by large infrared luminosities ($L_{IR}>$10$^{12}$L$\odot$), large dust masses ($\sim10^{8}M_{\odot}$) and vigorous star formation (star formation rates $\sim$10-100 $M_{\odot}~$yr$^{-1}$). Studies show that they represent the end stages of mergers of gas-rich spiral galaxies. Their luminosity can be due to both starburst activity and active galactic nuclei (AGN). We study a sample of 13 ULIRGs that have optically identified AGN characteristics with 1.28~GHz GMRT observations. Our aim is to resolve any core-jet structures or nuclear extensions and hence examine whether the ULIRGs are evolving into radio loud ellipticals. Our deep, low frequency observations show marginal extension for only one source. However, the integrated radio spectra of 9 ULIRGs show characteristics that are similar to that of GPS/CSS/CSO/young radio sources. The estimated spectral ages are 0.4 to 20 Myr and indicate that they are young radio sources and possible progenitors of radio galaxies. Hence, we conclude that although most ULIRGs do not show kpc scale extended radio emission associated with nuclear activity, their radio spectral energy distributions do show signatures of young radio galaxies.

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