Variable Extended Objects in Selected Area 57
Variable Extended Objects in Selected Area 57
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选定区域中的可变扩展对象 57
DOI：
10.1086/305371
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
R. Kron
中科院分区：
文献类型：
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作者：
M. Bershady;D. Trèvese;R. Kron
我们已经分离出一个样本的14个候选可变对象与扩展的图像结构BJ = 22.5在0.284 deg 2的选定区域57。大多数候选者是蓝色的（U-B < 0），相对紧凑。在较暗的星等上，可变天体的数量急剧增加。这些物体也是紧凑和蓝色的，其中一些可能是真正的恒星。在有限的波长范围和各种信噪比范围内，已经观察到12个BJ ≤ 22.5的候选者。四个最亮的星系中有三个具有塞弗特1星系的宽发射线特征。第四个具有高度可变的光谱，与Seyfert样活动一致。第五个候选星系的发射线比率名义上与塞弗特2星系一致。在大多数情况下，我们还没有能够确认塞弗特光谱类型，光谱的质量或覆盖范围不足，以排除这种分类。根据光谱学和光度学的红移信息，大多数候选星系的光度小于类星体和活动星系核之间标称分界线的10%（MB =-23，H 0 = 50 km s-1 Mpc-1，q 0 = 0.5）。已确认的MB > -23至BJ = 22的活动星系核（AGN）的表面密度为~40 deg-2，包括恒星源，与该深度的其他调查结果一致。在扩展源中确认的活动星系核占这一群体的36%。因此，将可变性标准应用于具有扩展结构的图像增强了活性核普查的完整性。如果我们的大多数候选者是真正的活动星系核，那么对于MB > -23和BJ = 22的所有亮度，表面密度可能高达82 deg-2，扩展源贡献高达33%。
We have isolated a sample of 14 candidate variable objects with extended image structure to BJ = 22.5 in 0.284 deg2 of Selected Area 57. The majority of candidates are blue (U-B < 0) and relatively compact. At fainter magnitudes, there is a steep rise in the number of variable objects. These objects are also compact and blue, and some of them are likely to be truly stellar. Twelve of the BJ ≤ 22.5 candidates have been observed spectroscopically over limited ranges of wavelength and a variety of resulting signal-to-noise ratios. Three of the four brightest have broad emission lines characteristic of Seyfert 1 galaxies. The fourth has a highly variable spectrum consistent with Seyfert-like activity. A fifth candidate has emission-line ratios nominally consistent with a Seyfert 2 galaxy. In most cases where we have not been able to confirm a Seyfert spectroscopic type, the spectra are of insufficient quality or coverage to rule out such a classification. Based on spectroscopic and photometric redshift information, the majority of candidates have luminosities less than 10% of the nominal demarcation between QSOs and active galactic nuclei (MB = -23, H0 = 50 km s-1 Mpc-1, q0 = 0.5). The surface density of confirmed MB > -23 active galactic nuclei (AGNs) to BJ = 22, including stellar sources, is ~40 deg-2, in good agreement with other surveys at this depth. The confirmed AGNs in extended sources make up 36% of this population. Thus, the application of a variability criterion to images with extended structure enhances the completeness of the census of active nuclei. If the majority of our candidates are bona fide AGNs, the surface density could be as high as 82 deg-2 for MB > -23 and 162 deg-2 for all luminosities to BJ = 22, with extended sources contributing up to 33% of the total.