Clustering of Galaxies at Z ∼ 3 around the Probable Damped Ly-alpha Absorber towards Qso Apm 08279+5255
Clustering of Galaxies at Z ∼ 3 around the Probable Damped Ly-alpha Absorber towards Qso Apm 08279+5255
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可能的阻尼 Ly-α 吸收体周围 Z 〜 3 处朝向 Qso Apm 08279+5255 的星系簇
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发表时间：
2003
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通讯作者：
J. Lowenthal
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作者：
Nicolas Bouché;J. Lowenthal
我们从包含类星体APM 08279+5255 （zem = 3.91）的深UBV I图像中获得了Lyman破碎星系（LBGs）围绕一个可能阻尼Lyα吸收（DLA）线云在zabs = 2.974处聚集的结果。我们的图像覆盖了0.31°2或约40 × 40 Mpc在红移z = 3处共移的大区域，它们的深度μI，AB(sky)≃27.6 mag弧秒，使我们能够识别出在2.75 < z < 3.25处比IAB = 24.80亮的约450个LBG候选点，它们离DLA的视线近（50 kpc），离DLA的视线最远（20 Mpc），即物理上不相关。LBG候选者是通过光度红移技术确定的，该技术除了颜色外，还包括I等作为先验估计。用贝叶斯定理将两者结合起来。这有助于打破在纯谱模板拟合方案中发生的简并性。在z ~ 3处，HDF-N的总体rms为σz≃0.15。从红移似然分布中，我们选择了以DLA的红移为中心，宽度为Wz = 0.15（≃σz）的LBG星系。在该红移片内，我们发现DLA附近的星系在表面密度（Σ/Σg≃3）和三维空间过密度（n/ng ~ 5±3）估计量的作用下得到增强。在2.5 < rθ < 5 Mpc共移尺度上，地表过密度Σ/Σg在> 95%显著水平上显著。由于QSO为zem = 3.91，因此超密度与QSO环境无关。这些结果表明，一些DLA可能存在于高密度区域。我们在距离DLA 45光年的范围内搜索，并找到了一个zphot = 3.03的候选星系，它距离我们26英寸（物理距离为145千公里）。由星等I = 24.65±0.2可知其光度为MI，AB =−21.35。然而，由于其巨大的撞击参数，这个星系不太可能成为吸收体的候选者。主题标题：星系：演化-星系：高红移-类星体：吸收线-类星体：个体
We present results on the clustering of Lyman break galaxies (LBGs) around a probable damped Lyα absorption (DLA) line cloud at zabs = 2.974 from deep UBV I images of the field containing the quasar APM 08279+5255 (zem = 3.91). The large area covered by our images, 0.31 deg 2 or ∼ 40 × 40 Mpc co-moving at redshift z = 3, and their depth, μI,AB(sky) ≃ 27.6 mag arcsec , allow us to identify ∼ 450 LBG candidates brighter than IAB = 24.80 at 2.75 < z < 3.25 both close (50 kpc) to the DLA line-of-sight and up to 20 Mpc (co-moving) from the DLA, i.e. physically unrelated. LBG candidates were identified using photometric redshift techniques that include the I magnitude as a prior estimate in addition to the colors. The two are combined using Bayes’ theorem. This helps to break the degenerancies that occur in a pure spectral template fitting scheme. The overall rms is σz ≃ 0.15 at z ∼ 3 based on our analysis of photometric redshifts in the HDF-N. From the redshift likelihood distributions, we selected LBG galaxies within a redshift slice of width Wz = 0.15(≃ σz) centered on the redshift of the DLA zabs. Within that redshift slice, we find an enhancement of galaxies near the DLA using both the surface density (Σ/Σg ≃ 3) and an estimator of the 3-D spatial overdensity (n/ng ∼ 5 ± 3). The surface overdensity Σ/Σg is significant at the > 95% significance level on scales 2.5 < rθ < 5 Mpc co-moving. The overdensity can not be related to the QSO environment since the QSO is at zem = 3.91. These results imply that some DLA could reside in high density regions. We search within 45 from the line of sight for galaxies responsible for the DLA, and find one candidate with zphot = 3.03 that is 26 ′′ (145 kpc physical) away. From its magnitude I = 24.65±0.2, its luminosity is MI,AB = −21.35. Due to its large impact parameter, however, this galaxy is not a likely candidate for the absorber. Subject headings: galaxies: evolution — galaxies: high-redshift — quasars: absorption lines — quasars: individual (APM08279+5255)