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arXiv 0806.1014astro-ph
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恒星形成星系在高低红移时的磁场

Magnetic fields in star-forming galaxies at high and low redshift

Timothy Garn, Dominic Ford, Paul Alexander, David A. Green, Julia M. Riley

摘要:

作为正在进行的一系列深GMRT调查的一部分,我们观察了斯皮策河外第一眼调查领域,产生了迄今为止最深的宽场610 MHz调查。在初级束校正之前,我们达到了30 microJy/束的均方根噪声,在~4平方度的区域上具有~6 arcsec的分辨率。通过将这些观测结果与Condon等人(2003)现有的1.4-GHz VLA巡天结合起来,再加上斯皮策太空望远镜的7个波段的红外数据,SDSS的光学光度测量和一系列光谱红移巡天,我们能够研究z ~ 1范围内恒星形成星系的射电光度与恒星形成率之间的关系。由于有大量的多波长数据可用,因此可以在无线电中进行精确的k-校正,这是由于了解了无线电光谱指数,并通过使用半经验辐射转移模型在红外线中进行精确的k-校正,该模型模拟了恒星形成区域、这些区域周围的温暖尘埃和弥漫的星际尘埃,并考虑到恒星形成率,恒星形成历史和每个星系内的氢柱密度。射电光度和红外衍生的恒星形成率之间有很强的相关性,这是最好的拟合略有非线性幂律。我们通过寻找偏离全球关系的恒星形成星系的相对射电亮度来寻找宇宙演化。任何这样的偏差都表明控制同步辐射的一个或多个属性的系统性变化,特别是恒星形成星系的磁场强度的增加。数据显示没有证据表明这种效应,这表明自z ~ 1以来星系的磁场几乎没有演化。

英文摘要:

As part of an ongoing series of deep GMRT surveys we have observed the Spitzer extragalactic First Look Survey field, producing the deepest wide-field 610-MHz survey published to date. We reach an rms noise of 30 microJy/beam before primary beam correction, with a resolution of ~6 arcsec over an area of ~4 square degrees. By combining these observations with the existing 1.4-GHz VLA survey produced by Condon et al. (2003), along with infrared data in up to seven wavebands from the Spitzer Space Telescope, optical photometry from SDSS and a range of spectroscopic redshift surveys, we are able to study the relationship between radio luminosity and star formation rate in star-forming galaxies up to z ~ 1. The large amount of multi-wavelength data available allows accurate k-corrections to be performed in the radio due to the knowledge of the radio spectral index, and in the infrared through the use of a semi-empirical radiative transfer model which models star-forming regions, warm dust surrounding these regions, and diffuse interstellar dust, taking into account the star formation rate, star formation history and hydrogen column density within each galaxy. A strong correlation is seen between radio luminosity and infrared-derived star formation rates, which is best fit by a slightly non-linear power-law. We look for cosmic evolution in the comparative radio brightness of star-forming galaxies by searching for deviations away from the global relationship. Any such deviation would indicate a systematic variation in one or more of the properties controlling synchrotron radiation, in particular an increase in the magnetic field strengths of star-forming galaxies. The data shows no evidence for such an effect, suggesting that there has been little evolution in the magnetic fields of galaxies since z ~ 1.

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