We investigate the impact of spiral structure on global star formation usinga sample of 2226 nearby bright disk galaxies. Examining the relationshipbetween spiral arms, star formation rate (SFR), and stellar mass, we find thatarm strength correlates well with the variation of SFR as a function of stellarmass. Arms are stronger above the star-forming galaxy main sequence (MS) andweaker below it: arm strength increases with higher $\log\,({\rm SFR}/{\rmSFR}_{\rm MS})$, where ${\rm SFR}_{\rm MS}$ is the SFR along the MS. Likewise,stronger arms are associated with higher specific SFR. We confirm this trendusing the optical colors of a larger sample of 4378 disk galaxies, whoseposition on the blue cloud also depends systematically on spiral arm strength.This link is independent of other galaxy structural parameters. For the subsetof galaxies with cold gas measurements, arm strength positively correlates withHI and H$_2$ mass fraction, even after removing the mutual dependence on$\log\,({\rm SFR}/{\rm SFR}_{\rm MS})$, consistent with the notion that spiralarms are maintained by dynamical cooling provided by gas damping. For a givengas fraction, stronger arms lead to higher $\log\,({\rm SFR}/{\rm SFR}_{\rmMS})$, resulting in a trend of increasing arm strength with shorter gasdepletion time. We suggest a physical picture in which the dissipation processprovided by gas damping maintains spiral structure, which, in turn, boosts thestar formation efficiency of the gas reservoir.

Most cosmological structures in the universe spin. Although structures in theuniverse form on a wide variety of scales from small dwarf galaxies to largesuper clusters, the generation of angular momentum across these scales ispoorly understood. We have investigated the possibility that filaments ofgalaxies - cylindrical tendrils of matter hundreds of millions of light-yearsacross, are themselves spinning. By stacking thousands of filaments togetherand examining the velocity of galaxies perpendicular to the filament's axis(via their red and blue shift), we have found that these objects too displaymotion consistent with rotation making them the largest objects known to haveangular momentum. The strength of the rotation signal is directly dependent onthe viewing angle and the dynamical state of the filament. Just as it iseasiest to measure rotation in a spinning disk galaxy viewed edge on, so too isfilament rotation clearly detected under similar geometric alignment.Furthermore, the mass of the haloes that sit at either end of the filamentsalso increases the spin speed. The more massive the haloes, the more rotationis detected. These results signify that angular momentum can be generated onunprecedented scales.

Stellar prolate rotation in dwarf galaxies is rather uncommon, with only twoknown galaxies in the Local Group showing such feature (Phoenix and And II).Cosmological simulations show that in massive early-type galaxies prolaterotation likely arises from major mergers. However, the origin of suchkinematics in the dwarf galaxies regime has only been explored using idealizedsimulations. Here we made use of hydrodynamical cosmological simulations ofdwarfs galaxies with stellar mass between $3\times10^5$ and $5\times10^8$M$_{\odot}$ to explore the formation of prolate rotators. Out of $27$ dwarfs,only one system showed clear rotation around the major axis, whose culprit is amajor merger at $z=1.64$, which caused the transition from an oblate to aprolate configuration. Interestingly, this galaxy displays a steep metallicitygradient, reminiscent of the one measured in Phoenix and And II: this is theoutcome of the merger event that dynamically heats old, metal-poor stars, andof the centrally concentrated residual star formation. Major mergers in dwarfgalaxies offer a viable explanation for the formation of such peculiar systems,characterized by steep metallicity gradients and prolate rotation.

Differential enrichment between $\alpha$- and Fe-peak elements is known to bestrongly connected with the shape of the star formation history (SFH), the starformation efficiency (SFE), the inflow and outflow of material, and even theshape of the Initial Mass Function (IMF). However, beyond the Local Groupdetailed explorations are mostly limited to early-type galaxies due to the lackof a good proxy for [$\alpha$/Fe] in late-type ones, limiting our understandingof the chemical enrichment process. We intent to extend the explorations of[$\alpha$/Fe] to late-type galaxies, in order to understand the details of thedifferential enrichment process. We compare the gas phase oxygen abundance withthe luminosity weighted stellar metallicity in an extensive catalog of$\sim$25,000 H ii regions extracted from the Calar Alto Legacy Integral FieldArea (CALIFA) survey, an exploration using integral field spectroscopy of$\sim$900 galaxies, covering a wide range of masses and morphologies. This waywe define [O/Fe] as the ratio between both parameters, proposing it as anindirect proxy of the [$\alpha$/Fe] ratio. Results. We illustrate how the[O/Fe] parameter describes the chemical enrichment process in spiral galaxies,finding that: (i) it follows the decreasing pattern with [Fe/H] reported forthe [$\alpha$/Fe] ratio and (ii) its absolute scale depends of the stellar massand the morphology. We reproduce both patterns using two different chemicalevolution models (ChEM), considering that galaxies with different stellar massand morphology present (i) different SFHs, SFEs and different inflow/outflowrates, or (ii) a different maximum stellar mass cut for the IMF. We willexplore the differential chemical enrichment using this new proxy galaxy bygalaxy and region by region in further studies.