A SPECTROSCOPIC STUDY OF THE GIANT LOW SURFACE BRIGHTNESS GALAXY MALIN 1

International audienceLow Surface Brightness galaxies (LSBs) represent a significant fraction of galaxies in the nearby universe. However, despite their large fraction, the structure and origin of this class of galaxies is still poorly understood, especially due to the lack of high-resolution kinematics and spectroscopy. Malin 1 is the largest known low surface brightness galaxy to date, the archetype of so-called giant LSBs. We present new results based on spectroscopic observations of Malin 1, using the Hα and [OII]3727 emission lines in order to bring new constraints on the internal dynamics of this galaxy. We have extracted a total of 16 spectra from different regions of Malin 1 and calculated the inner rotational velocities using the observed shift in the emission line wavelengths. We show for the first time a steep rise in the rotation curve of Malin 1 up to ∼400 km s −1 (within r < 10 kpc), which had not been observed in any of the previous works on this galaxy. We will discuss the implications of this result in comparison with existing works on Malin 1 and also the possibility for making a new mass model for this galaxy