Superthin galaxies (STs) are low surface brightness galaxies (LSBs) (centralsurface brightness in $B$-band $>$ 23 magarcsec$^{-2}$) with a strikingly highplanar-to-vertical axes ratio of $\sim 10 - 20$ with no bulge component. Thesuperthin vertical structure of STGs results in significantly lower values ofdisc dynamical stability (Jog 1992) and hence higher values of the predictedSFR compared to face-on LSBs. We systematically study the star formation rate(SFR) of samples of STGs and LSBs and compare their relative values. UsingGALEX FUV, we estimate the SFR of 212 STGs and 158 LSBs, the median valuesbeing 0.057 $M_\odot /yr$ and 0.223 $M_\odot /yr$ respectively. We next obtainthe SFR from WISE (W3) of 549 STGs and 345 LSBs, with median values of 0.471$M_\odot /yr$ and 0.17 $M_\odot /yr$ respectively. Finally, from SED fitting ofphotometric data in ten bands (FUV, NUV of GALEX, u,g,r,i,z of SDSS \& J, H, Ksof 2MASS) in MAGPHYS, we find the SFR for a sample of 65 STGs and 103 LSBs tobe 0.357 $M_\odot /yr$ and 0.616 $M_\odot /yr$ respectively. Also, as isindicated by the median values of number of bursts after $t_{\rm{form}} = 1$and an exponential star formation time scale parameter $\gamma$ = 0.2${\rm{Gyr}}^{-1}$, the SFR remains fairly constant over time. Interestingly, inspite of having low SFR compared to ordinary star-forming galaxies, bothsuperthins and LSBs populate the star forming blue cloud region in the specificstar formation (sSFR) - stellar mass (M*) plane of galaxies.

Chemical abundances in the Leo ring, the largest HI cloud in the localUniverse, have recently been determined to be close or above solar,incompatible with a previously claimed primordial origin of the ring. The gas,pre-enriched in a galactic disk and tidally stripped, did not manage to formstars very efficiently in intergalactic space. We map nebular lines in 3 denseHI clumps of the Leo ring and complement these data with archival stellarcontinuum observations to investigate the slow building up of a sparsepopulation of stars in localized areas of the ring. Individual young stars asmassive as O7-types are powering some HII regions. The average star formationrate density is of order of 10^{-5} Msun/yr/kpc^2 and proceeds with localbursts a few hundred parsecs in size, where loose stellar associations of500-1000 Msun occasionally host massive outliers. The far ultraviolet-to-Halphaemission ratio in nebular regions implies recent stellar bursts, from 2 to 7Myr ago. The relation between the local HI gas density and the star formationrate in the ring is similar to what is found in dwarfs and outer disks with gasdepletion times as long as 100~Gyrs. We find a candidate planetary nebula in acompact and faint Halpha region with [OIII]/Halpha line enhancement, consistentwith the estimated mean stellar surface brightness of the ring. The presence of1 kpc partial ring emitting weak Halpha lines around the brightest and youngestHII region suggests that local shocks might be the triggers of new star formingevents.