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arXiv 1702.07527astro-ph.GA
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在COSMOS场中对亚毫米星系的ALMA巡天:用甚大天线阵3 GHz成像揭示的射电发射区的范围

An ALMA survey of submillimetre galaxies in the COSMOS field: The extent of the radio-emitting region revealed by 3 GHz imaging with the Very Large Array

Oskari Miettinen, Mladen Novak, Vernesa Smolčić, Ivan Delvecchio, Manuel Aravena, Drew Brisbin, Alexander Karim, Eric J. Murphy, Eva Schinnerer, Marcus Albrecht… 展开作者

Oskari Miettinen, Mladen Novak, Vernesa Smolčić, Ivan Delvecchio, Manuel Aravena, Drew Brisbin, Alexander Karim, Eric J. Murphy, Eva Schinnerer, Marcus Albrecht, Hervé Aussel, Frank Bertoldi, Peter L. Capak, Caitlin M. Casey, Francesca Civano, Christopher C. Hayward, Noelia Herrera Ruiz, Olivier Ilbert, Chunyan Jiang, Clotilde Laigle, Olivier Le Fèvre, Benjamin Magnelli, Stefano Marchesi, Henry J. McCracken, Enno Middelberg, Alejandra M. Muñoz Arancibia, Felipe Navarrete, Nelson D. Padilla, Dominik A. Riechers, Mara Salvato, Kimberly S. Scott, Kartik Sheth, Lidia A. M. Tasca, Marco Bondi, Gianni Zamorani

摘要:

我们确定了一个大样本的152 SMG在宇宙中,ALMA在1.3毫米检测到的无线电尺寸分布。为此,我们使用的意见采取的VLA-宇宙3 GHz大型项目。在152个目标SMG中,发现有115个具有3 GHz对应物。在3 GHz的主轴半高宽的中值被导出为$4.6\pm0.4$ kpc。射电大小没有随红移而变化的趋势,也没有表现出不同星系形态之间的差异。我们还导出了1.4 ~ 3GHz的光谱指数和3GHz的亮温,其中值为$α=-0.67$和$T_{\rm B}=12.6\pm2$ K。三个目标SMG,这也与VLBA检测,显示出明显高于典型值的亮度温度。虽然观测到的射电辐射似乎主要是由恒星形成和超新星活动提供动力,但我们的研究结果强烈表明VLBA和X射线探测到的SMG AzTEC/C61中存在活动星系核。我们推导出的中等射电发射尺寸比SMG的典型远红外尘埃发射尺寸大1.5-3倍,但与SMG的分子气体成分通过CO的中$J$线发射追踪的相似。SMG的物理条件可能使宇宙射线电子的扩散效率低下,因此不太可能导致观察到的扩展射电尺寸。相反,我们的结果指向一个场景,SMG是由星系相互作用和合并驱动的。除了引发剧烈的恒星爆发,星系碰撞也可以从相互作用的圆盘中抽出磁化流体,并产生一个像太妃糖一样的同步辐射桥。这为SMG的空间扩展的无线电发射提供了解释,并且也可能导致与公知的IR-无线电相关性的偏差。

英文摘要:

We determine the radio size distribution of a large sample of 152 SMGs in COSMOS that were detected with ALMA at 1.3 mm. For this purpose, we used the observations taken by the VLA-COSMOS 3 GHz Large Project. One hundred and fifteen of the 152 target SMGs were found to have a 3 GHz counterpart. The median value of the major axis FWHM at 3 GHz is derived to be $4.6\pm0.4$ kpc. The radio sizes show no evolutionary trend with redshift, or difference between different galaxy morphologies. We also derived the spectral indices between 1.4 and 3 GHz, and 3 GHz brightness temperatures for the sources, and the median values were found to be $α=-0.67$ and $T_{\rm B}=12.6\pm2$ K. Three of the target SMGs, which are also detected with the VLBA, show clearly higher brightness temperatures than the typical values. Although the observed radio emission appears to be predominantly powered by star formation and supernova activity, our results provide a strong indication of the presence of an AGN in the VLBA and X-ray-detected SMG AzTEC/C61. The median radio-emitting size we have derived is 1.5-3 times larger than the typical FIR dust-emitting sizes of SMGs, but similar to that of the SMGs' molecular gas component traced through mid-$J$ line emission of CO. The physical conditions of SMGs probably render the diffusion of cosmic-ray electrons inefficient, and hence an unlikely process to lead to the observed extended radio sizes. Instead, our results point towards a scenario where SMGs are driven by galaxy interactions and mergers. Besides triggering vigorous starbursts, galaxy collisions can also pull out the magnetised fluids from the interacting disks, and give rise to a taffy-like synchrotron-emitting bridge. This provides an explanation for the spatially extended radio emission of SMGs, and can also cause a deviation from the well-known IR-radio correlation.

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