ИСТИНА

The formation scenario of thick galactic discs still remains a matter of debate in spite of the widespread that structure components. Spectroscopic observations of thick discs are challenging because of low surface brightness and thus require long exposures using large telescopes. We collected deep spectra of thick discs in some edge-on early-type disc galaxies using the Russian 6-m telescope BTA. In two objects we see intermediate age metal rich stellar populations that support their formation via minor merger induced disc heating over an extended period of time. In other case the thick disc is old (10 Gyr) and its alpha-element abundance suggests a 1.5-2 Gyr long formation epoch making it consistent with the turbulent rapid thick disc formation at high redshifts suggested by numerical simulations. Our results prove the diversity of thick disc formation scenarios.