Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infrared colour selection
Two bright z > 6 quasars from VST ATLAS and a new method of optical plus mid-infrared colour selection
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DOI：
10.1093/mnrasl/slv057
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发表时间：
2015-02
影响因子：
4.8
通讯作者：
A. Carnall;T. Shanks;B. Chehade;M. Fumagalli;M. Fumagalli;M. Rauch;M. Irwin;E. González-Solares-E.-González-Solare
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文献类型：
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作者：
A. Carnall;T. Shanks;B. Chehade;M. Fumagalli;M. Fumagalli;M. Rauch;M. Irwin;E. González-Solares-E.-González-Solare
我们提出了两个z > 6类星体的发现，被选为在甚大望远镜巡天望远镜ATLAS调查的i波段辍学。我们的第一个类星体有红移z = 6.31 ± 0.03，z波段星等zAB = 19.63 ± 0.08，静止坐标系1450 A绝对星等M1450 = −27.8 ± 0.2，使它成为已知z > 6的第二大类星体。第二个类星体的z = 6.02 ± 0.03，zAB = 19.54 ± 0.08，M1450 = −27.0 ± 0.1。我们还恢复了Venemans等人发现的z = 5.86的类星体，正在筹备中。为了选择我们的类星体，我们使用了一个新的3D颜色空间，将ATLAS光学颜色与来自宽视场红外巡天探测器的中红外数据相结合。我们用iAB − zAB色来排除主序星、星系和低红移类星体，用W1 − W2来排除L矮星，用zAB − W2来排除T矮星。一组限制性的颜色切割只返回我们的三个高红移类星体，没有污染物，尽管样品的完整性为50%。我们讨论了如何使用我们的3D颜色空间来拒绝明亮的5.7 < z < 6.3类星体样品中的大多数污染物，取代后续的近红外测光，同时保持高的完整性。
We present the discovery of two z > 6 quasars, selected as i-band dropouts in the Very Large Telescope Survey Telescope ATLAS survey. Our first quasar has redshift, z = 6.31 ± 0.03, z-band magnitude, zAB = 19.63 ± 0.08 and rest frame 1450 A absolute magnitude, M1450 = −27.8 ± 0.2, making it the joint second most luminous quasar known at z > 6. The second quasar has z = 6.02 ± 0.03, zAB = 19.54 ± 0.08 and M1450 = −27.0 ± 0.1. We also recover a z = 5.86 quasar discovered by Venemans et al., in preparation. To select our quasars, we use a new 3D colour space, combining the ATLAS optical colours with mid-infrared data from the Wide-field Infrared Survey Explorer. We use iAB − zAB colour to exclude main-sequence stars, galaxies and lower redshift quasars, W1 − W2 to exclude L dwarfs and zAB − W2 to exclude T dwarfs. A restrictive set of colour cuts returns only our three high redshift quasars and no contaminants, albeit with a sample completeness of ∼50 per cent. We discuss how our 3D colour space can be used to reject the majority of contaminants from samples of bright 5.7 < z < 6.3 quasars, replacing follow-up near-infrared photometry, whilst retaining high completeness.