We present the results of optical identifications for 257 mid-infrared sources detected with a deep 15um survey over approximately 80 arcmin^2 area in the AKARI performance verification field near the North Ecliptic Pole. The 15um fluxes of the sources range from 1 mJy down to 40 uJy, approximately a half of which are below 100 uJy. Optical counterparts were searched for within a 2-3 arcsec radius in both the BVRi'z' catalog generated by using the deep Subaru/Suprime-cam field which covers one-third of the performance verification field, and the g'r'i'z' catalog based on observations made with MegaCam at CFHT. We found B-R and R-z' colours of sources with successful optical identifications are systematically redder than that of the entire optical sample in the same field. Moreover, approximately 40% of the 15um sources show colours R-L15>5, which cannot be explained by the spectral energy distribution (SED) of normal quiescent spiral galaxies, but are consistent with SEDs of redshifted (z>1) starburst or ultraluminous infrared galaxies. This result indicates that the fraction of the ultraluminous infrared galaxies in our faint 15um sample is much larger than that in our brighter 15um sources, which is consistent with the evolving mid-infrared luminosity function derived by recent studies based on the Spitzer 24um deep surveys. Based on an SED fitting technique, the nature of the faint 15um sources is further discussed for a selected number of sources with available K_s-band data.
Nature of Infrared Sources in 11 micron Selected Sample from Early Data of the AKARI North Ecliptic Pole Deep Survey
我们提出的11 $μ$ m选定的源中检测到的早期数据的北极深（NEP深）调查AKARI的属性。数据集覆盖了2.5 ~ 11 $μ$ m的6个波段，曝光时间为10 ~ 20分钟。基于SED的详细建模，该字段位于具有四个滤波器频带的CFHT调查范围内（$g', r', i',z'), enabling us to establish nearly continuous spectral energy distributions (SEDs) for wavelengths ranging from 0.4 to 11 $ μ $m. The main sample studied here consists of 71 sources whose 11 $ μ $m AB magnitudes are equal to or brighter than 18.5 (251 $ μ $Jy), which is complete to more than 90%. The 11 $ μ $m band has an advantage of sampling star forming galaxies with low to medium redshifts since the prominent PAH feature shifts into this band. As expecte…
A complete sample of radio sources in the North Ecliptic Cap, selected at 38 MHz -- III. further imaging observations and the photometric properties of the sample
本文对北南极帽的一个射电源样品作了进一步的成像观测，并作出了一些新的鉴定。使用来自同伴论文中提出的光谱数据的红移（Lacy et al. 1999 b），讨论了样品中星系的光度特性。结果表明：（1）至少z~0.6的射电星系是良好的标准烛光，与射电光度无关;（2）在0.6~<z~<1的情况下，大部分样品具有与非演化巨椭圆一致的量值和颜色;（3）在较高的红移处，R带对静止坐标系的紫外光通量进行采样，大多数天体的紫外线光度低于预期，如果它们在未被遮蔽的恒星形成区域以恒定的速率从高红移到$z\sim 1$形成恒星星族的话（假设是爱因斯坦-德西特宇宙学）。这些意见的后果进行了简要讨论。
我们用ROSAT全天巡天探测了北极地区一个z=0.087的超星系团。X射线数据极大地提高了我们对这个超星系团特征的理解，与光学发现数据相比，我们对结构空间范围的了解大约增加了一倍，星系团/星系团成员增加了两倍。超星系团是一个丰富的结构，包括至少21个星系团和星系群，12个AGN，61个IRAS星系和各种其他物体。这些成分中的大多数都是用X射线数据发现的，但超星系团也在光学，红外和紫外波段被稳健地探测到。北南极超星系团的长度为129 x 102 x 67（1/h50 Mpc）^[3]，呈扁平状，几乎与我们的视线垂直。由于ROSAT X射线通带的柔软性和大立体角的深度曝光，我们首次在超星系团中探测到了大量的X射线发射星系群。这些结果证明了连续覆盖的X射线观测对研究宇宙结构的有效性。
A wide field survey at the Northern Ecliptic Pole I: Number counts and angular correlation functions in K
我们目前的结果，从多色调查在北极（NEP）。这次巡天的目的是查明ROSAT全天巡天和红外天文卫星巡天中的对应微弱源，并研究其光学/近红外特性。在光学波段B_J、R和近红外波段K观察到了NEP周围的中心平方度。在光学I波段进行了较浅的调查。在这里，我们介绍了K波段调查的结果。讨论了7等< K <17.5等范围内的源计数和K <17.0等星系的角关联函数。NEP的星系计数显示了一个以dlog（N）/dm为单位的亚beuklidean斜率。我们较浅的斜率并不需要星系演化或密度演化的大效应来解释早期调查中发现的陡峭斜率。星系的角关联函数遵循幂律w（θ）= Aθ^-δ，其中A=5.7+-0.8 x 10^-3，δ=0.98+-0.15。这与稳定聚类的预期值一致。
