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arXiv 1003.4460astro-ph.CO
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DRAO普朗克深场:射电星系在1.4 GHz的偏振特性

The DRAO Planck Deep Fields: the polarization properties of radio galaxies at 1.4 GHz

Julie Grant, Russ Taylor, Jeroen Stil, Tom Landecker, Roland Kothes, Ryan Ransom, Douglas Scott

摘要:

我们目前的结果深偏振成像在1.4 GHz的自治领射电天体物理观测站的DRAO普朗克深场项目的一部分。这个深河外场覆盖15.16平方度,中心在RA = 16 h 14 m和DEC = 54 d 56 ',在场中心处的角分辨率为42”x 62”,在斯托克斯I中达到55微焦/束的灵敏度,在斯托克斯Q和U中达到45微焦/束。我们检测到958个射电源斯托克斯我其中136个被检测到偏振。我们提出了欧几里得归一化极化差分源计数下降到400微焦。这些计数表明,源有一个更高程度的分数偏振在较暗的斯托克斯我通量密度水平比较亮的来源,证实了早期的结果。我们发现,我们的偏振源的大多数是陡峭的光谱对象的平均光谱指数为-0.77,有没有分数偏振和光谱指数之间的相关性。我们还将深场源与20厘米射电天空微弱图像目录中的对应源进行了匹配。在极化源中,77%的源显示出弧秒尺度的结构,而没有检测到极化的源中只有38%显示出这种结构。分辨源的中值分数偏振为6.8%,而致密天体的中值分数偏振为4.4%。在我们的深场中,极化射电源主要是那些被分辨的源,并显示出最高程度的分数极化,这表明波瓣主导结构可能是高度极化源的来源。在P_0 = sqrt(Q^2 + U^2)< 3 mJy时,这些射电星系占主导地位。

英文摘要:

We present results of deep polarization imaging at 1.4 GHz with the Dominion Radio Astrophysical Observatory as part of the DRAO Planck Deep Fields project. This deep extragalactic field covers 15.16 square degrees centered at RA = 16h 14m and DEC = 54d 56', has an angular resolution of 42" x 62" at the field center, and reaches a sensitivity of 55 microJy/beam in Stokes I and 45 microJy/beam in Stokes Q and U. We detect 958 radio sources in Stokes I of which 136 are detected in polarization. We present the Euclidean-normalized polarized differential source counts down to 400 microJy. These counts indicate that sources have a higher degree of fractional polarization at fainter Stokes I flux density levels than for brighter sources, confirming an earlier result. We find that the majority of our polarized sources are steep-spectrum objects with a mean spectral index of -0.77, and there is no correlation between fractional polarization and spectral index. We also matched deep field sources to counterparts in the Faint Images of the Radio Sky at Twenty Centimeters catalogue. Of the polarized sources, 77% show structure at the arc-second scale whereas only 38% of the sources with no detectable polarization show such structure. The median fractional polarization is for resolved sources is 6.8%, while it is 4.4% for compact objects. The polarized radio sources in our deep field are predominantly those sources which are resolved and show the highest degrees of fractional polarization, indicating that the lobe dominated structure may be the source of the highly polarized sources. These resolved radio galaxies dominate the polarized source counts at P_0 = sqrt(Q^2 + U^2) < 3 mJy.

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