We present an analysis of the environment of six QSO triplets at 1 ≲ z ≲ 1.5 by analysing multiband (r, i, z, or g, r, i) images obtained with Megacam at the CFHT telescope, aiming to investigate whether they are associated or not with galaxy protoclusters. This was done by using photometric redshifts trained using the high-accuracy photometric redshifts of the COSMOS2015 catalogue. To improve the quality of our photometric redshift estimation, we included in our analysis near-infrared photometry (3.6 and 4.5$\, \mu$m) from the unWISE survey available for our fields and the COSMOS survey. This approach allowed us to obtain good photometric redshifts with dispersion, as measured with the robust σNMAD statistics (which scales as (1 + z)−1), of ∼0.04 for our six fields. Our analysis setup was reproduced on lightcones constructed from the Millennium Simulation data and the latest version of the L-GALAXIES semi-analytic model to verify the protocluster detectability in such conditions. The density field in a redshift slab containing each triplet was then analysed with a Gaussian kernel density estimator. We did not find any significant evidence of the triplets inhabiting dense structures, such as a massive galaxy cluster or protocluster.

中文翻译：

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QSO 三元组在 1 ≲ z ≲ 1.5 的环境

我们通过分析在 CFHT 望远镜上使用 Megacam 获得的多波段 (r, i, z 或 g, r, i) 图像，对 1 ≲ z ≲ 1.5 的六个 QSO 三元组的环境进行分析，旨在调查它们是否相关或者不使用星系原星团。这是通过使用 COSMOS2015 目录的高精度光度红移训练的光度红移来完成的。为了提高我们的光度学红移估计的质量，我们在分析中包括了来自可用于我们领域的 unWISE 调查和 COSMOS 调查的近红外光度测量（3.6 和 4.5$\，\mu$m）。这种方法使我们能够获得良好的具有色散的光度红移，如使用稳健的 σNMAD 统计数据（缩放为 (1 + z)-1）所测量的，对于我们的六个场，约为 0.04。我们的分析设置是在由千年模拟数据和最新版本的 L-GALAXIES 半分析模型构建的光锥上复制的，以验证在这种条件下的原星团可检测性。然后用高斯核密度估计器分析包含每个三重态的红移板中的密度场。我们没有发现任何重要证据表明三胞胎居住在密集结构中，例如巨大的星系团或原星系团。