钱德拉ACIS对M33的巡天：超新星遗迹的X射线、光学和射电性质
The Chandra ACIS Survey of M33: X-ray, Optical and Radio Properties of the Supernova Remnants
摘要：
M33包含大量的发射星云，根据冲击气体的高[S II]：Ha比率，这些星云被确定为超新星遗迹（SNRs）。使用来自ChASeM 33调查的Chandra数据，灵敏度为0.35-2 keV，约为2 x 10**34 ergs/s，我们已经检测到137个SNR候选者中的82个，确认（或至少强烈支持）它们的SNR识别。这提供了在包括银河系在内的任何星系中在光学和X射线波长下探测到的最大的残余样本。对七个X射线最亮的SNRs的光谱分析显示，其中两个G98-31和G98-35的光谱似乎表明，它们是由核心坍缩超新星爆炸的喷出物浓缩而成的。一般来说，与沿着M33的视线探测到的绝大多数源相比，X射线探测到的SNR具有软X射线谱。在ChASeM 33调查所覆盖的M33部分中，不太可能存在任何其他未被发现的光度超过约4 x 10**35尔格/秒的热主导X射线信噪比。我们结合了新的和存档的光学和无线电观测，试图更好地理解为什么有些物体被检测为X射线源，而另一些则不是。我们还开发了一个形态学分类方案的光学识别的信噪比，并讨论了该计划作为X射线可探测性的预测的有效性。最后，我们比较了在M33中发现的SNR，在银河系和麦哲伦云中观察到的SNR。在M33的观测区域中，没有与Cas A、Kepler SNR、Tycho SNR或蟹状星云相似的天体，但我们发现了一个具有幂律谱的X射线源，它与一个小直径射电源相吻合，这可能是M33中发现的第一个脉冲星风星云。
英文摘要：
M33 contains a large number of emission nebulae identified as supernova remnants (SNRs) based on the high [S II]:Ha ratios characteristic of shocked gas. Using Chandra data from the ChASeM33 survey with a 0.35-2 keV sensitivity of about 2 x 10**34 ergs/s, we have detected 82 of 137 SNR candidates, yielding confirmation of (or at least strongly support for) their SNR identifications. This provides the largest sample of remnants detected at optical and X-ray wavelengths in any galaxy, including the Milky Way. A spectral analysis of the seven X-ray brightest SNRs reveals that two, G98-31 and G98-35, have spectra that appear to indicate enrichment by ejecta from core-collapse supernova explosions. In general, the X-ray detected SNRs have soft X-ray spectra compared to the vast majority of sources detected along the line of sight to M33. It is unlikely that there are any other undiscovered thermally dominated X-ray SNRs with luminosities in excess of about 4 x 10**35 ergs/s in the portions of M33 covered by the ChASeM33 survey. We have used a combination of new and archival optical and radio observations to attempt to better understand why some objects are detected as X-ray sources and others are not. We have also developed a morphological classification scheme for the optically-identified SNRs, and discuss the efficacy of this scheme as a predictor of X-ray detectability. Finally, we have compared the SNRs found in M33 to those that have been observed in the Galaxy and the Magellanic Clouds. There are no close analogs of Cas A, Kepler's SNR, Tycho's SNR or the Crab Nebula in the regions of M33 surveyed, but we have found an X-ray source with a power law spectrum coincident with a small-diameter radio source that may be the first pulsar-wind nebula recognized in M33.
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