Radio Sources in Galaxy Clusters at 28.5 GHz
Radio Sources in Galaxy Clusters at 28.5 GHz
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28.5 GHz 星系团中的无线电源
DOI：
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发表时间：
1997
期刊：
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通讯作者：
J. Carlstrom
中科院分区：
文献类型：
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作者：
A. Cooray;L. Grego;W. Holzapfel;M. Joy;J. Carlstrom
我们偶然探测到了28.5 GHz(1厘米)的射电源，这是我们的计划在56个星系团中成像Sunyaev-Zeldovich(SZ)热效应的结果。在∼0.8°2的总面积内，我们发现了射电源，其通量从指向中心向下到∼0.4mJy(大于4σ)，在250“范围内。已公布低频通量密度的54个源的谱指数(S∝ν-α)在-0.6≲α≲2范围内，平均值为0.77±0.0 6，中位数为0.84。将射电源的低频测量扩展到Cl0016+16、Abell665和Abell2218星系团至28.5千兆赫，并选择S1.4千兆赫≥为7mJy的源组成无偏样本，得到的平均谱指数为0.71±0.08，中位数为0.71。在没有星系团的地区，我们发现的震源比一项低频调查预测的要多4到7倍。这种过剩不能通过星系团势对背景射电群体的引力透镜来解释，这表明大多数探测到的源与星系团有关。差分源计数斜率γ∼1.96(dN/ds∝S-γ)比未进化的欧几里德种群的预期值(γ=2.5)更平坦。对于星系团Abell2218，S28.5 GHz≤0.5mJy(∼5σ)的未减去射电源的存在可以将观测到的SZ温度降低10到25μK，通过综合分析28.5GHz SZ图像和X射线发射观测得出的相应的哈勃常数高估不到6%。
We present serendipitous detections of radio sources at 28.5 GHz (1 cm), which resulted from our program to image the thermal Sunyaev-Zeldovich (SZ) effect in 56 galaxy clusters. In a total area of ∼0.8 deg2, we find 64 radio sources with fluxes down to ∼0.4 mJy (greater than 4 σ) and within 250″ from the pointing centers. The spectral indices (S ∝ ν-α) of 54 sources with published low-frequency flux densities lie in the range -0.6 ≲ α ≲ 2, with a mean of 0.77 ± 0.06 and a median of 0.84. Extending low-frequency surveys of radio sources toward the galaxy clusters Cl 0016+16, Abell 665, and Abell 2218 to 28.5 GHz and selecting sources with S1.4 GHz ≥ 7 mJy to form an unbiased sample, we find a mean spectral index of 0.71 ± 0.08 and a median of 0.71. We find 4 to 7 times more sources than predicted from a low-frequency survey in areas without galaxy clusters. This excess cannot be accounted for by gravitational lensing of a background radio population by cluster potentials, indicating that most of the detected sources are associated with galaxy clusters. The differential source count slope, γ ∼ 1.96 (dN/dS ∝ S-γ), is flatter than what is expected for a nonevolving Euclidean population (γ = 2.5). For the cluster Abell 2218, the presence of unsubtracted radio sources with S28.5 GHz ≤ 0.5 mJy (∼5 σ) can reduce the observed SZ temperature decrement by ΔT ∼ 10 to 25 μK. The corresponding overestimation of the Hubble constant derived through a combined analysis of 28.5 GHz SZ images and X-ray emission observations is less than 6%.