Luminous K-band Selected Quasars from UKIDSS
Luminous K-band Selected Quasars from UKIDSS
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DOI：
10.1111/j.1365-2966.2008.13138.x
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发表时间：
2008-02
影响因子：
4.8
通讯作者：
N. Maddox;P. Hewett;S. Warren;S. P. I. F. Astronomy;Cambridge;A. Potsdam;I. -. London;U. Sydney-U.-Sydne
中科院分区：
文献类型：
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作者：
N. Maddox;P. Hewett;S. Warren;S. P. I. F. Astronomy;Cambridge;A. Potsdam;I. -. London;U. Sydney-U.-Sydne
迄今为止，最大的K波段通量有限的发光类星体样本是由UKIRT（英国红外望远镜）红外深空巡天（UKIDSS）大面积巡天早期数据发布构建的，覆盖有效面积为12.8 deg 2。利用所有类星体相对于前景恒星的K波段过剩（KX），包括经历尘埃变红的类星体和具有非标准光谱能量分布（SED）的天体，构建了一个适合使用AAOmega多目标光谱仪进行光谱跟踪观测的目标列表，从而确定了200多个活动星系核（AGN）。KX选择成功地识别出了被排除在斯隆数字巡天（SDSS）类星体选择算法之外的类星体候选对象，因为它们的颜色与光学颜色空间中的恒星轨迹一致（排除对象的空间密度与现有完整性分析的结果一致）。在KX选择的类星体中，接近一半的K ≤ 17.0且z < 3的类星体在i波段太暗，无法被SDSS类星体选择算法锁定，这显示出大量的类星体具有redi-K色。这些天体中的大多数都有大量的宿主星系光贡献给它们的K波段星等，这与以前的预测一致。其余的天体在形态上是恒星，颜色与经历小麦哲伦云（SMC）型变红的类星体一致，0.10 < E（B - V）< 0.25。i-K颜色分布表明，<10%的类星体人口是从这个K波段选择的样本，由于尘埃变红失踪，与模拟的比较强烈支持一个模糊的分数<20%.Photometric红移和分类计算的候选人，没有观察到光谱。对于那些颜色与变红类星体一致的扩展天体，我们使用了适合于每个天体的星系表面亮度分布模型，以排除K ≤ 17.0类星体样本中存在足够明亮的核源的可能性。类星体的近红外颜色选择的有效性已经通过这个中等大小的样本得到了证明，随着可用数据量的增加，它只会变得更加明显。
The largest K-band flux-limited sample of luminous quasars to date has been constructed from the UKIRT (UK Infrared Telescope) Infrared Deep Sky Survey (UKIDSS) Large Area Survey Early Data Release, covering an effective area of 12.8 deg 2 . Exploiting the K-band excess (KX) of all quasars with respect to foreground stars, including quasars experiencing dust reddening and objects with non-standard spectral energy distributions (SEDs), a list of targets suitable for spectroscopic follow-up observations with the AAOmega multi-object spectrograph is constructed, resulting in more than 200 confirmed active galactic nuclei (AGN). KX selection successfully identifies as quasar candidates objects that are excluded from the Sloan Digital Sky Survey (SDSS) quasar selection algorithm due to their colours being consistent with the stellar locus in optical colour space (with the space density of the excluded objects agreeing well with results from existing completeness analyses). Nearly half of the KX-selected quasars with K ≤ 17.0 at z < 3 are too faint in the i band to have been targeted by the SDSS quasar selection algorithm, revealing a large population of quasars with redi - K colours. The majority of these objects have significant amounts of host galaxy light contributing to their K-band magnitudes, consistent with previous predictions. The remaining objects are morphologically stellar and have colours consistent with quasars experiencing Small Magellanic Cloud (SMC)-type reddening with 0.10 < E(B - V) < 0.25. The i - K colour distribution indicates that <10 per cent of the quasar population is missing from this K-band selected sample due to dust reddening, and comparisons with simulations strongly favour an obscured fraction of <20 per cent. Photometric redshifts and classifications are computed for the candidates that were not observed spectroscopically. For the extended objects whose colours are consistent with those of a reddened quasar, models of galaxy surface brightness profiles appropriate for each object are used to eliminate the possibility of the presence of a nuclear source bright enough for inclusion in a K ≤ 17.0 quasar sample. The effectiveness of near-infrared colour selection of quasars has been demonstrated by this modest-sized sample, and it will only become more apparent as the amount of available data increases.