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The extreme flatness of stellar discs in superthin galaxies is puzzling andthe apparent dearth of these objects in cosmological simulation poseschallenging problem to the standard cold dark matter paradigm. Irrespective ofmergers or accretion that a galaxy might be going through, stars are heated asthey get older while they interact with the spirals and bars which areubiquitous in disc galaxies -- leading to a puffed up stellar disc. It remainsunclear how superthin galaxies maintain their thinness through the cosmicevolution.  We follow the internal evolution of a sample of 16 initially extremely thinstellar discs using collisionless N-body simulation. All of these discseventually form a bar in their central region. Depending on the initialcondition, some of these stellar discs readily form strong bars while othersgrow weak bars over secular evolution time scale. We show that galaxies withstrong bars heat the stars very efficiently, eventually making their stellardiscs thicker. On the other hand, stars are heated very slowly by weak bars --as a result, galaxies hosting weak bars are able to maintain their thinnessover several billion years, if left isolated. We suggest that some of thesuperthin galaxies might as well be forming weak bars and thereby prevent anystrong vertical heating which in turn helps maintaining their thinness duringthe course of secular evolution.

Disc heating: possible link between weak bars and superthin galaxies