Deep Intermediate-Band Surface Photometry of NGC 5907-猫眼课题宝

DOI：

10.1086/300866

发表时间：

1999-02

期刊：

The Astronomical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

Zhongyuan Zheng;Z. Shang;H. Su;D. Burstein;Jian-sheng Chen;Zugan;Deng;Y. Byun;Rui Chen;Wen-Ping Chen;L. Deng;Xiaohui Fan;Li Zhi Fang;Jeff;J. J. Hester-J.;Zhao-ji Jiang;Yong Li;Weipeng Lin;Wei‐hsin Sun;W. Tsay;A. Rogier;Windhorst;Hong Wu;X. Xia;Wen Xu;S. Xue;Haojing Yan;Z. Zheng;Xu;Zhou;Jin Zhu;Z. Zou

我们对最初报道的边侧Sc星系NGC 5907的垂直于盘面的扩展光度分布很感兴趣，我们用施密特望远镜、大幅面CCD和中心在6660和8020的中间波段滤光片获得了这个星系的非常深的曝光。这两个滤镜是15个滤镜组的一部分，是定制设计的，以避免最明亮（和最多变）的夜晚天际线。因此，我们的图像能够以较低的天空噪声比在类似有效波长下使用宽带滤波器拍摄的图像更深：例如，0.6我们的观测值为e-arcsec-2 s-1，而莫里森等人的R波段测量值为7.4 e-arcsec-2 s-1。在我们对随机误差和系统误差的评估中，结果表明，在6660 μ m图像上，观测误差达到1 mag arcsec-2的通量水平为29.00 mag arcsec-2（对应于R波段中的28.7）和8020射电望远镜图像中的27.4 mag arcsec-2（基本上在I波段系统上）。在以前的论文中，我们已经证明NGC 5907周围有一个发光的环，最有可能是由更大质量的螺旋对矮球状星系的潮汐破坏造成的。在这里，我们表明，对于比27 R等角秒-2更暗的值，NGC 5907周围的表面亮度是强烈不对称的，在银河系中平面的西北（环）侧最亮。这种不对称性排除了晕圈是我们看到的微弱表面亮度的原因。我们发现这种不对称性很可能是一个人工制品的结合造成的环光和残余表面亮度在微弱的水平，从我们的恒星掩蔽程序不能完全消除。我们的甚大阵H I观测表明，NGC 5907可能存在光学正面翘曲，这与前景星星污染太过混淆，无法独立研究。与其他观测者对NGC 5907的表面光度测量结果的良好一致性使我们得出结论，他们的数据在微弱的水平上同样受到环形光和星星掩蔽程序的残余效应的影响。对已发表图像的检查证实了这一点。因此，我们得出结论，NGC 5907没有一个微弱的扩展晕。

Intrigued by the initial report of an extended luminosity distribution perpendicular to the disk of the edge-on Sc galaxy NGC 5907, we have obtained very deep exposures of this galaxy with a Schmidt telescope, large-format CCD, and intermediate-band filters centered at 6660 Å and 8020 Å. These two filters, part of a 15-filter set, are custom designed to avoid the brightest (and most variable) night skylines. As a result, our images are able to go deeper with lower sky noise than those taken with broadband filters at similar effective wavelengths: e.g., 0.6 e- arcsec-2 s-1 for our observations versus 7.4 e- arcsec-2 s-1 for the R-band measures of Morrison et al. In our assessment of both random and systematic errors, we show that the flux level where the errors of observation reach 1 mag arcsec-2 are 29.00 mag arcsec-2 in the 6660 Å image (corresponding to 28.7 in the R band) and 27.4 mag arcsec-2 in the 8020 Å image (essentially on the I-band system). In a previous paper we have shown that NGC 5907 has a luminous ring around it, most plausibly caused by the tidal disruption of a dwarf spheroidal galaxy by the much more massive spiral. Here we show that, for values fainter than 27 R mag arcsec-2, the surface brightness around NGC 5907 is strongly asymmetric, being mostly brighter on the northwest (ring) side of the galactic midplane. This asymmetry rules out a halo as the cause of the faint surface brightness we see. We find this asymmetry is likely an artifact resulting from a combination of ring light and residual surface brightness at faint levels from stars that our star-masking procedure cannot completely eliminate. The possible existence of an optical face-on warp in NGC 5907, suggested by our Very Large Array H I observations, is too confused with foreground star contamination to be independently studied. Good agreement with the surface photometry of NGC 5907 by other observers leads us to conclude that their data are similarly affected at faint levels by ring light and the residual effects of star masking procedures. Inspection of published images confirm this to be the case. Thus, we conclude that NGC 5907 does not have a faint extended halo.

Deep Intermediate-Band Surface Photometry of NGC 5907

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