Cygnus A: A Long-Wavelength Resolution of the Hot Spots
Cygnus A: A Long-Wavelength Resolution of the Hot Spots
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Cygnus A：热点的长波长分辨率
DOI：
10.1086/504408
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
P. C. Crane
中科院分区：
文献类型：
--
作者：
T. Lazio;A. Cohen;N. Kassim;R. Perley;W. C. Erickson;C. Carilli;P. C. Crane
这封信介绍了天鹅座A在74和327兆赫的观测，角分辨率分别约为10“和3”。这些观测结果是该天体在1000 MHz以下获得的最高角分辨率之一。虽然74 MHz的角分辨率不足以将热点与波瓣清楚地分开，但在151和327 MHz图像的引导下，我们估计了热点的74 MHz发射。我们确认，从西部和东部热点的发射在低频率处是不对称的，并且两者之间存在光谱不对称性。对于东部热点，电子能谱中的低能截止似乎可以解释平坦化，这意味着截止洛伦兹因子γmin <$300，尽管我们不能排除可能存在中等水平的自由-自由吸收的可能性。对于西部热点，目前的观测不足以区分自由-自由吸收的幂律谱和同步加速器自吸收谱。
This Letter presents observations of Cygnus A at 74 and 327 MHz at angular resolutions of approximately 10'' and 3'', respectively. These observations are among the highest angular resolutions obtained below 1000 MHz for this object. While the angular resolution at 74 MHz is not sufficient to separate clearly the hot spots from the lobes, guided by 151 and 327 MHz images, we have estimated the 74 MHz emission from the hot spots. We confirm that the emission from both the western and eastern hot spots flattens at low frequencies and that there is a spectral asymmetry between the two. For the eastern hot spot, a low-energy cutoff in the electron energy spectrum appears to explain the flattening, which implies a cutoff Lorentz factor γmin ≈ 300, although we cannot exclude the possibility that there might be a moderate level of free-free absorption. For the western hot spot, the current observations are not sufficient to distinguish between a free-free absorbed power-law spectrum and a synchrotron self-absorbed spectrum.