COSMOGRAIL XVI：四重成像类星体DES J0408-5354与高节奏光度监测的时间延迟
COSMOGRAIL XVI: Time delays for the quadruply imaged quasar DES J0408-5354 with high-cadence photometric monitoring
摘要：
我们目前的时间延迟测量新的四重成像类星体DES J 0408 -5354，第一个四重成像类星体中发现的暗能量调查（DES）。我们的结果是可能的，通过实施一个新的观测策略，使用几乎每天的观测与MPIA 2.2米望远镜在拉西拉天文台和深曝光达到信噪比约1000每类星体图像。这种数据质量使我们能够捕捉到类星体的小光度变化（几个mmag rms），作用于比微透镜短得多的时间尺度，因此使时间延迟测量对微透镜非常鲁棒。在仅仅7个月的时间里，我们非常准确地测量了DES J 0408 -5354中的一个时间延迟：Dt（AB）= -112.1 +- 2.1天（1.8%），仅使用MPIA 2.2 m数据。结合1.2米欧拉瑞士望远镜的数据，我们还测量了两个延迟，涉及系统的D分量Dt（AD）= -155.5 +-12.8天（8.2%）和Dt（BD）= -42.4 +-17.6天（41%），其中所有的误差条包括系统学。将这些时间延迟转化为宇宙学约束将需要深层HST成像或地基自适应光学（AO），以及透镜星系速度场的信息。
英文摘要：
We present time-delay measurements for the new quadruply imaged quasar DES J0408-5354, the first quadruply imaged quasar found in the Dark Energy Survey (DES). Our result is made possible by implementing a new observational strategy using almost daily observations with the MPIA 2.2m telescope at La Silla observatory and deep exposures reaching a signal-to-noise ratio of about 1000 per quasar image. This data quality allows us to catch small photometric variations (a few mmag rms) of the quasar, acting on temporal scales much shorter than microlensing, hence making the time delay measurement very robust against microlensing. In only 7 months we measure very accurately one of the time delays in DES J0408-5354: Dt(AB) = -112.1 +- 2.1 days (1.8%) using only the MPIA 2.2m data. In combination with data taken with the 1.2m Euler Swiss telescope, we also measure two delays involving the D component of the system Dt(AD) = -155.5 +- 12.8 days (8.2%) and Dt(BD) = -42.4 +- 17.6 days (41%), where all the error bars include systematics. Turning these time delays into cosmological constraints will require deep HST imaging or ground-based Adaptive Optics (AO), and information on the velocity field of the lensing galaxy.
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