Title: Relative Sizes of X-ray and Optical Images of Elliptical Galaxies; Correlation with X-ray Luminosity Show Chinese title

Title: 椭圆星系的X射线和光学图像的相对大小；与X射线亮度的相关性

Abstract: Optical parameters of elliptical galaxies are tightly correlated, but their x-ray parameters vary widely. The x-ray luminosity L_x ranges over more than an order of magnitude for ellipticals having similar optical luminosity L_B. The source of this scatter has been elusive. We show here that the dispersion in L_x for fixed optical luminosity L_B correlates strongly with the dimensionless ratio of the sizes of the x-ray and optical images, r_ex/r_e. Specifically, we find that (L_x/L_B) is proportional to (r_{ex}/r_e)^{0.60 \pm 0.30}, a version of the correlation that is independent of distance. This correlation may be a natural result of mergings and tidal truncations that are expected during the formation and early evolution of ellipticals in groups of galaxies. The radial structure of x-ray images also varies: some are compact (e.g. NGC 4649, 7626, 5044), others diffuse (e.g. NGC 4636, 1399). Show Chinese abstract

Abstract: 椭圆星系的光学参数紧密相关，但其 X 射线参数却变化很大。对于具有相似光学亮度 L_B 的椭圆星系，X 射线亮度 L_x 的范围超过一个量级。这种分散的原因一直难以捉摸。 我们在这里表明，在固定光学亮度 L_B 下，L_x 的离散程度与 X 射线和光学图像尺寸的无量纲比值 r_ex/r_e 强烈相关。 具体来说，我们发现 (L_x/L_B) 与 (r_{例如}/r_e)^{0.60 \pm 0.30}成正比，这是一种与距离无关的相关性版本。这种相关性可能是由于在星系团中椭圆星系形成和早期演化过程中预期会发生合并和潮汐截断的结果。 X 射线图像的径向结构也有所不同：有些较为紧凑（例如 NGC 4649、7626、5044），而另一些则较为弥散（例如 NGC 4636、1399）。