First spectroscopic study of ionized gas emission lines in the extreme
  low surface brightness galaxy Malin 1
  Malin 1 is the largest known low surface brightness (LSB) galaxy, the
archetype of so-called giant LSBs. The structure and the origin of such
galaxies are still poorly understood, especially due to the lack of
high-resolution kinematics and spectroscopic data. We use emission lines from
spectroscopic observations of Malin 1 aiming to bring new constraints on the
internal dynamics and star formation history of Malin 1. We have extracted a
total of 16 spectra from different regions of Malin 1 and calculated the
rotational velocities of these regions from the wavelength shifts and star
formation rates from the observed H$\alpha$ emission line fluxes. We compare
our data with existing data and models for Malin 1. For the first time we
present the inner rotation curve of Malin 1, characterized in the radial range
r < 10 kpc by a steep rise in the rotational velocity up to at least 350 km/s
(with a large dispersion), which had not been observed previously. We use these
data to study a suite of new mass models for Malin 1. We show that in the inner
regions dynamics may be dominated by the stars (although none of our models can
explain the highest velocities measured) but that at large radii a massive dark
matter halo remains necessary. The H$\alpha$ fluxes derived star formation
rates are consistent with an early-type disk for the inner region, and with the
level found in extended UV galaxies for the outer parts of the giant disk of
Malin 1. We also find signs of high metallicity but low dust content for the
inner regions.
