The geometry and intrinsic ellipticity distribution of ultra diffuse galaxies(UDGs) is determined from the line-of-sight distribution of axial ratios q of alarge sample of UDGs, detected by Koda et al. (2015) in the Coma cluster. Withhigh significance the data rules out an oblate, disk-like geometry,characterised by major axi a=b>c. The data is however in good agreement withprolate shapes, corresponding to a=b<c. This indicates that UDGs are notthickened, rotating, axisymmetric disks, puffed up by violent processes.Instead they are anisotropic elongated cigar- or bar-like structures, similarto the prolate dwarf spheroidal galaxy population of the Local Group. Theintrinsic distribution of axial ratios of the Coma UDGs is flat in the range of0.4 <= a/c <= 0.9 which will provide important constraints for theoreticalmodels of their origin. Formation scenarios that could explain the extendedprolate nature of UDGs are discussed.

We investigate the recent star formation history (SFH) in the inner region of57 nearly face-on spiral galaxies selected from the Calar Alto Legacy IntegralField Area (CALIFA) survey. For each galaxy we use the integral fieldspectroscopy from CALIFA to obtain two-dimensional maps and radial profiles ofthree parameters that are sensitive indicators of the recent SFH: the 4000\AA\break (D$_n$(4000)), and the equivalent width of H$\delta$ absorption(EW(H$\delta_A$)) and H$\alpha$ emission (EW(H$\alpha$)). We have alsoperformed photometric decomposition of bulge/bar/disk components based on SDSSoptical image. We identify a class of 17 "turnover" galaxies whose centralregion present significant drop in D$_n$(4000), and most of themcorrespondingly show a central upturn in EW(H$\delta_A$) and EW(H$\alpha$).This indicates that the central region of the turnover galaxies has experiencedstar formation in the past 1-2 Gyr, which makes the bulge younger and morestar-forming than surrounding regions. We find almost all (15/17) the turnovergalaxies are barred, while only half of the barred galaxies in our sample(15/32) are classified as a turnover galaxy. This finding provides strongevidence in support of the theoretical expectation that the bar may drive gasfrom the disc inward to trigger star formation in galaxy center, an importantchannel for the growth/rejuvenation of pseudobulges in disc galaxies.

We derive a free-form mass distribution for the unrelaxed cluster A370(z=0.375), using the latest Hubble Frontier Fields images and GLASSspectroscopy. Starting from a reliable set of 10 multiply lensed systems weproduce a free-form lens model that identifies ~ 80 multiple-images. Goodconsistency is found between models using independent subsamples of theselensed systems, with detailed agreement for the well resolved arcs. The massdistribution has two very similar concentrations centred on the two prominentBrightest Cluster Galaxies (or BCGs), with mass profiles that are accuratelyconstrained by a uniquely useful system of long radially lensed images centredon both BCGs. We show that the lensing mass profiles of these BCGs are mainlyaccounted for by their stellar mass profiles, with a modest contribution fromdark matter within r<100 kpc of each BCG. This conclusion may favour a cooledcluster gas origin for BCGs, rather than via mergers of normal galaxies forwhich dark matter should dominate over stars. Growth via merging between BCGsis, however, consistent with this finding, so that stars still dominate overdark matter .

We here present the first spatially-resolved study of the IMF in externalgalaxies derived using a dynamical tracer of the mass-to-light ratio. We usethe kinematics of relaxed molecular gas discs in seven early-type galaxies(ETGs) selected from the ATLAS3D survey to dynamically determine mass-to-lightratio (M/L) gradients. These M/L gradients are not very strong in the innerparts of these objects, and galaxies that do show variations are those with thehighest specific star formation rates. Stellar population parameters derivedfrom star formation histories are then used in order to estimate the stellarinitial mass function function (IMF) mismatch parameter, and shed light on itsvariation within ETGs. Some of our target objects require a light IMF,otherwise their stellar population masses would be greater than their dynamicalmasses. In contrast, other systems seem to require heavier IMFs to explaintheir gas kinematics. Our analysis again confirms that IMF variation seems tobe occurring within massive ETGs. We find good agreement between our IMFnormalisations derived using molecular gas kinematics and those derived usingother techniques. Despite this, we do not see find any correlation between theIMF normalisation and galaxy dynamical properties or stellar populationparameters, either locally or globally. In the future larger studies which usemolecules as tracers of galaxy dynamics can be used to help us disentangle theroot cause of IMF variation.

We analyze photometry from deep B-band images of 59 void galaxies in the VoidGalaxy Survey (VGS), together with their near-infrared 3.6$\mu$m and 4.5$\mu$mSpitzer photometry. The VGS galaxies constitute a sample of void galaxies thatwere selected by a geometric-topological procedure from the SDSS DR7 datarelease, and which populate the deep interior of voids. Our void galaxies spana range of absolute B-magnitude from $\rm{M_B=-15.5}$ to $\rm{M_B=-20}$, whileat the 3.6$\mu$m band their magnitudes range from $\rm{M_{3.6}=-18}$ to$\rm{M_{3.6}=-24}$. Their B-[3.6] colour and structural parameters indicatethese are star forming galaxies. A good reflection of the old stellarpopulation, the near-infrared band photometry also provide a robust estimate ofthe stellar mass, which for the VGS galaxies we confirm to be smaller than $3\times 10^{10}$ M$_\odot$. In terms of the structural parameters andmorphology, our findings align with other studies in that our VGS galaxy sampleconsists mostly of small late-type galaxies. Most of them are similar to Sd-Smgalaxies, although a few are irregularly shaped galaxies. The sample evenincludes two early-type galaxies, one of which is an AGN. Their S\'{e}rsicindices are nearly all smaller than $n=2$ in both bands and they also havesmall half-light radii. In all, we conclude that the principal impact of thevoid environment on the galaxies populating them mostly concerns their lowstellar mass and small size.