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arXiv 1807.01503astro-ph.GAastro-ph.SR
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UWISH2巡天中的行星状星云

Planetary Nebulae in the UWISH2 survey

T. M. Gledhill, D. Froebrich, J. Campbell-White, A. M. Jones

摘要:

氢分子1 - 0 S(1)发射线的近红外成像能够探测到行星状星云(PNe),这些星云在光学发射线调查中被隐藏起来。我们目前的图像307个对象从UWISH 2调查的北银道面,并与援助的中红外彩色诊断制定了一份名单,291 PN候选人。大多数,即183个,是新发现的,其中85%在H $α$对该区域的调查中不存在。我们发现,超过一半(54%)的对象有一个双极形态和一些对象以前被认为是椭圆形或点源H $α$成像,出现双极UWISH 2图像。通过考虑一个小的子集的对象,其物理半径可从H $α$表面亮度半径的关系,我们发现的证据表明,H2表面亮度保持大致恒定的一个因素20范围内的半径从0.03至0.6 pc,包括大部分的可见光寿命的PN。这导致H $α$表面亮度变得与H2在大半径(> 0:5 pc)下的表面亮度相当。通过将没有H $α$检测的UWISH 2 PNe的数量与H2发射中PN检测效率的估计相结合,我们估计来自H $α$调查的PN数可能在UWISH 2调查区域内低估真实PN数1.5和2.5之间的因子。

英文摘要:

Near-infrared imaging in the 1 - 0 S(1) emission line of molecular hydrogen is able to detect planetary nebulae (PNe) that are hidden from optical emission line surveys. We present images of 307 objects from the UWISH2 survey of the northern Galactic Plane, and with the aid of mid-infrared colour diagnostics draw up a list of 291 PN candidates. The majority, 183, are new detections and 85 per cent of these are not present in H$α$ surveys of the region. We find that more than half (54 per cent) of objects have a bipolar morphology and that some objects previously considered as elliptical or point-source in H$α$ imaging, appear bipolar in UWISH2 images. By considering a small subset of objects for which physical radii are available from the H$α$ surface brightness-radius relation, we find evidence that the H2 surface brightness remains roughly constant over a factor 20 range of radii from 0.03 to 0.6 pc, encompassing most of the visible lifetime of a PN. This leads to the H$α$ surface brightness becoming comparable to that of H2 at large radius (> 0:5 pc). By combining the number of UWISH2 PNe without H$α$ detection with an estimate of the PN detection efficiency in H2 emission, we estimate that PN numbers from H$α$ surveys may underestimate the true PN number by a factor between 1.5 and 2.5 within the UWISH2 survey area.

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