We place general constraints on the luminosity and mass of hot X-ray-emitting gas residing in extended "hot halos" around nearby massive galaxies. We examine stacked images of 2165 galaxies from the 2MASS Isolated Galaxy Catalog as well as subsets of this sample based on galaxy morphology and K-band luminosity. We detect X-ray emission at high confidence (ranging up to nearly 10σ) for each subsample of galaxies. The average LX within 50?kpc is 1.0 ± 0.1 (statistical) ±0.2 (systematic) × 1040?erg?s–1, although the early-type galaxies are more than twice as luminous as the late-type galaxies. Using a spatial analysis, we also find evidence for extended emission around five out of seven subsamples (the full sample, the luminous galaxies, early-type galaxies, luminous late-type galaxies, and luminous early-type galaxies) at 92.7%, 99.3%, 89.3%, 98.7%, and 92.1% confidence, respectively. Several additional lines of evidence also support this conclusion and suggest that about 1/2 of the total emission is extended, and about 1/3 of the extended emission comes from hot gas. For the sample of luminous galaxies, which has the strongest evidence for extended emission, the average hot gas mass is 4 × 109 M ☉ within 50?kpc and the implied accretion rate is 0.4 M ☉?yr–1.
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机译：我们对居住在附近大质量星系周围扩展的“热晕”中的热X射线发射气体的亮度和质量施加一般约束。我们检查了来自2MASS孤立星系目录的2165个星系的堆叠图像，以及基于星系形态和K波段光度的该样本子集。对于每个子星系，我们以高置信度（范围接近10σ）检测X射线发射。尽管早期类型的星系的发光强度是晚期类型的星系的两倍以上，但在50？kpc的平均LX值为1.0±0.1（统计）±0.2（系统的）×1040？er？s-1。使用空间分析，我们还发现了在七个子样本（完整样本，发光星系，早期类型星系，发光晚期类型星系和发光早期类型星系）中的五个子样本中有大约五个发射范围扩大的证据，分别为92.7％，99.3分别为％，89.3％，98.7％和92.1％。其他一些证据也支持这一结论，并表明总排放量的约1/2扩展了，而扩展排放的约1/3来自热气。对于具有最强发射证据的发光星系样本，平均热气体质量在50kkpc之内为4×109 M☉，隐含积聚率为0.4 M yryr-1。
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