Metallicity of the polar disk in NGC4650A: constraints for cold
  accretion scenario
  We used high resolution spectra in the optical and near-infrared wavelength
range to study the abundance ratios and metallicities of the HII regions
associated with the polar disk in NGC4650A, in order to put constraints on the
formation of the polar disk through cold gas accretion along a filament; this
might be the most realistic way by which galaxies get their gas. We have
compared the measured metallicities for the polar structure in NGC4650A with
those of different morphological types and we have found that they are similar
to those of late-type galaxies: such results is consistent with a polar disk
formed by accretion from cosmic web filaments of external cold gas.
