We study the properties of galaxies with very thin discs using a sample of 85objects whose stellar disc radial-to-vertical scale ratio determined fromphotometric decomposition, exceeds nine. We present evidences of similaritiesbetween the very thin disc galaxies (VTD galaxies) and low surface brightness(LSB) disc galaxies, and conclude that both small and giant LSB galaxies mayreveal themselves as VTD, edge-on galaxies. Our VTD galaxies are mostlybulgeless, and those with large radial scale length tend to have redder colors.We performed spectral observations of 22 VTD galaxies with the Dual ImagingSpectrograph on the 3.5m telescope at the Apache Point Observatory. The spectrawith good resolution (R ~ 5000) allow us to determine the distance and theionized gas rotation curve maximum for the galaxies. Our VTD galaxies have lowdust content, in contrast to regular disc galaxies. Apparently, VTD galaxiesreside in specific cosmological low-density environments and tend to have lessconnection with filaments. Comparing a toy model that assumes marginally lowstar formation in galactic discs with obtained gas kinematics data, we concludethat there is a threshold central surface density of about 88 Mo/pc**2, whichwe observe in the case of very thin, rotationally supported galactic discs.

Andromeda is our nearest neighbouring disk galaxy and a prime target fordetailed modelling of the evolutionary processes that shape galaxies. Weanalyse the nature of M31's triaxial bulge with an extensive set of N-bodymodels, which include Box/Peanut (B/P) bulges as well as initial classicalbulges (ICBs). Comparing with IRAC 3.6$\mu m$ data, only one model matchessimultaneously all the morphological properties of M31's bulge, and requires anICB and a B/P bulge with 1/3 and 2/3 of the total bulge mass respectively. Wefind that our pure B/P bulge models do not show concentrations high enough tomatch the S\'ersic index ($n$) and the effective radius of M31's bulge.Instead, the best model requires an ICB component with mass $M^{\rmICB}=1.1\times10^{10}{\rm M_{\odot}}$ and three-dimensional half-mass radius$r_{\rm half}^{\rm ICB}$=0.53 kpc (140 arcsec). The B/P bulge component has amass of $M^{\rm B/P}=2.2\times10^{10}{\rm M_{\odot}}$ and a half-mass radius of$r_{\rm half}^{\rm B/P}$=1.3 kpc (340 arcsec). The model's B/P bulge extends to$r^{\rm B/P}$=3.2 kpc (840 arcsec) in the plane of the disk, as does M31'sbulge. In this composite bulge model, the ICB component explains the velocitydispersion drop observed in the centre within $R<$190 pc (50 arcsec), while theB/P bulge component reproduces the observed rapid rotation and the kinematictwist of the observed zero velocity line. This model's pattern speed is$\Omega_p$=38 km/s/kpc, placing corotation at $r_{\rm cor}$=5.8 kpc (1500arcsec). The outer Lindblad resonance (OLR) is then at $r_{\rm OLR}$=10.4kpc,near the 10kpc-ring of M31, suggesting that this structure may be related tothe bar's OLR. By comparison with an earlier snapshot, we estimate that M31'sthin bar extends to $r_{\rm bar}^{\rm thin}\sim$4.0 kpc (1000 arcsec) in thedisk plane, and in projection extends to $R_{\rm bar}^{\rm thin}\sim$2.3 kpc(600 arcsec).

Unlike spiral galaxies such as the Milky Way, the majority of the stars inmassive elliptical galaxies were formed in a short period early in the historyof the Universe. The duration of this formation period can be measured usingthe ratio of magnesium to iron abundance ([Mg/Fe]), which reflects the relativeenrichment by core-collapse and type Ia supernovae. For local galaxies, [Mg/Fe]probes the combined formation history of all stars currently in the galaxy,including younger and metal-poor stars that were added during late-timemergers. Therefore, to directly constrain the initial star-formation period, wemust study galaxies at earlier epochs. The most distant galaxy for which[Mg/Fe] had previously been measured is at z~1.4, with[Mg/Fe]=0.45(+0.05,-0.19). A slightly earlier epoch (z~1.6) was probed bystacking the spectra of 24 massive quiescent galaxies, yielding an average[Mg/Fe] of 0.31+/-0.12. However, the relatively low S/N of the data and the useof index analysis techniques for both studies resulted in measurement errorsthat are too large to allow us to form strong conclusions. Deeper spectra ateven earlier epochs in combination with analysis techniques based on fullspectral fitting are required to precisely measure the abundance patternshortly after the major star-forming phase (z>2). Here we report a measurementof [Mg/Fe] for a massive quiescent galaxy at z=2.1. With [Mg/Fe]=0.59+/-0.11,this galaxy is the most Mg-enhanced massive galaxy found so far, having twicethe Mg enhancement of similar-mass galaxies today. The abundance pattern of thegalaxy is consistent with enrichment exclusively by core-collapse supernovaeand with a star-formation timescale of 0.1-0.5 Gyr - characteristics that aresimilar to population II stars in the Milky Way. With an average past SFR of600-3000 Msol/yr, this galaxy was among the most vigorous star-forming galaxiesin the Universe.