Cosmologists have often considered the Milky Way as a typical spiral galaxy, and its properties have considerably influenced the current scheme of galaxy formation. Here we compare the general properties of the Milky Way disk and halo with those of galaxies selected from the SDSS. Assuming the recent measurements of its circular velocity results in the Milky Way being offset by ~2 sigma from the fundamental scaling relations. On the basis of their location in the (M_K, R_d, V_flat) volume, the fraction of SDSS spirals like the MilkyWay is only 1.2% in sharp contrast with M31, which appears to be quite typical. Comparison of the Milky Way with M31 and with other spirals is also discussed to investigate whether or not there is a fundamental discrepancy between their mass assembly histories. Possibly the Milky Way is one of the very few local galaxies that could be a direct descendant of very distant, z=2-3 galaxies, thanks to its quiescent history since thick disk formation.
Detection of CO(J=1-0) Emission from Barred Spiral Galaxies at z~0.1
本文介绍了用野边山射电天文台45米望远镜对9个z=0.08-0.25的棒旋星系进行CO（J=1-0）观测的结果。这次巡天是第一次专门针对这个红移范围内的棒旋星系。我们在9个星系中的6个星系中探测到了CO辐射，它们的CO光度（L_CO '）范围为（1.09-10.8）\times 10^9 K km s^{-1} pc ^2。这些是迄今为止在z~0.1的CO中探测到的红外（IR）最暗的星系。它们遵循了局域旋涡星系、亮红外星系（LIRGs）、超亮红外星系（ULIRGs）和亚毫米波星系（SMGs）之间的L_CO '-L_IR关系。它们的L_CO'和L_IR都高于目前在CO中探测到的局域旋涡星系，而L_IR/L'_CO（恒星形成效率的度量）与局域旋涡星系相当或略高。这一结果表明，这些星系比本地螺旋星系更活跃地形成恒星，仅仅是因为它们有更多的燃料。
