科研之友
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摘要
Recent studies have identified a population of compact quiescent galaxies at z similar to 2. These galaxies are very rare today and establishing the existence of a nearby analog could allow us to study its structure in greater detail than is possible at high redshift. Here we present such a local analog, NGC 5845, which has a dynamical mass of M-dyn = 4.3 +/- 0.6 x 10(10) M-circle dot and an effective radius of only r(e) = 0.45 +/- 0.05 kpc. We study the structure and kinematics with HST/WFPC2 data and previously published spatially resolved kinematics. We find that NGC 5845 is similar to compact quiescent galaxies at z similar to 2 in terms of size versus dynamical mass (r(e)-M-dyn), effective velocity dispersion versus size (sigma(e)-r(e)), and effective velocity dispersion versus dynamical mass (sigma(e)-M-dyn). The galaxy has a prominent rotating disk evident in both the photometry and the kinematics: it extends to well beyond greater than or similar to 1/3 effective radius and contribute to greater than or similar to 1/4 of the total light of the galaxy. Our results lend support to the idea that a fraction of z similar to 2 compact galaxies have prominent disks and positive mass-to-light ratio gradients, although we caution that NGC 5845 may have had a different formation history than the more massive compact quiescent galaxies at z similar to 2.
- 出版日期2012-4-10
