分类： 天文学 >> 天文学 提交时间： 2023-02-19
X. Zhao
F. Civano
F. M. Fornasini
D. M. Alexander
N. Cappelluti
C. T. Chen
S. H. Cohen
M. Elvis
P. Gandhi
N. A. Grogin
R. C. Hickox
R. A. Jansen
A. Koekemoer
G. Lanzuisi
W. P. Maksym
A. Masini
D. J. Rosario
M. J. Ward
C. N. A. Willmer
R. A. Windhorst
摘要： We present the $NuSTAR$ extragalactic survey of the $James$ $Webb$ $Space$ $Telescope$ ($JWST$) North Ecliptic Pole (NEP) Time-Domain Field. The survey covers a $\sim$0.16 deg$^2$ area with a total exposure of 681 ks acquired in a total of nine observations from three epochs. The survey sensitivities at 20% of the area are 2.39, 1.14, 2.76, 1.52, and 5.20 $\times$ 10$^{-14}$ erg cm$^{-2}$ s$^{-1}$ in the 3-24, 3-8, 8-24, 8-16, and 16-24 keV bands, respectively. The NEP survey is one of the most sensitive extragalactic surveys with $NuSTAR$ so far. A total of 33 sources were detected above 95% reliability in at least one of the five bands. We present the number counts, log$N$-log$S$, measured in the hard X-ray 8-24 and 8-16 keV bands, uniquely accessible by $NuSTAR$ down to such faint fluxes. We performed source detection on the XMM-$Newton$ and $Chandra$ observations of the same field to search for soft X-ray counterparts of each $NuSTAR$ detection. The soft band positions were used to identify optical and infrared associations. We present the X-ray properties (hardness ratio and luminosity) and optical-to-X-ray properties of the detected sources. The measured fraction of candidate Compton-thick (N$\rm _H\ge10^{24} cm^{-2}$) active galactic nuclei, derived from the hardness ratio, is between 3% to 27%. As this survey was designed to have variability as its primary focus, we present preliminary results on multi-epoch flux variability in the 3-24 keV band.
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