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E.D. Miller (MIT), S.L. Ellison (Univ. of Victoria), M.T. Murphy (IoA, Cambridge), J.N. Bregman (Univ. of Michigan)
We present UV and optical spectroscopy of the quasar Ton 1480, which is projected behind the outer HI ring of the lenticular galaxy NGC 4203. The spectra from HST, FUSE, and the VLT/UVES show absorption from a variety of low- and high-ionization species, including HI, NI, OI, NaI, CII, MgII, SiII, CaII, FeII, SiIII, CIV (marginal), and OVI. This absorber appears to be a Lyman limit system, with log(NH) = 19.7 calculated from the Ly series lines. The line centers for the low-ionization lines, mostly observed at low spectral resolution, indicate absorption at velocities similar to the HI ring/disk. The high-resolution UVES observation of CaII shows additional line components shifted -70 to -100 km/s from the HI velocity. OVI absorption is also seen near these velocities, and both lines can arise in either a superposed high-velocity cloud or, as this is close to the systemic velocity (1086 km/s), an extended gaseous halo. In addition, the NaI/CaII ratio is very low (~ 0.2), implying a lack of Ca depletion onto dust grains in this part of the galaxy. We discuss the implications of our results in the context of relaxed early-type galaxies and quasar absorption line systems in general.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.