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The connection between quenching mechanisms, which rapidly turn star-forming systems into quiescent, and the properties of the galaxy population remains difficult to discern. In this work we investigate the physical properties of MaNGA and SAMI galaxies at different stages of their star formation history. Specifically, we compare galaxies with signatures of recent quenching (Quenched) -- $\rm H(\alpha)$ in absorption and low $D_n(4000)$ -- with the rest of the low star-forming and active population (Retired and Ageing, respectively). The analysis is performed in terms of characteristics such as the total stellar mass, half-light radius, velocity-to-dispersion ratio, metallicity, and environment. We find that the Ageing population comprises a heterogeneous mixture of galaxies, preferentially late-type systems, with diverse physical properties. Retired galaxies, formerly Ageing or Quenched systems, are dominated by early-type high-mass galaxies found both at low and dense environments. Most importantly, we find that recently quenched galaxies are consistent with a population of compact low-mass satellite systems, with higher metallicities than their Ageing analogues. We argue that this is compatible with being quenched after undergoing a star-burst phase induced by environmental processes (e.g. ram pressure). However, we also detect a non-negligible fraction of field central galaxies likely quenched by internal processes. This study highlights that, in order to constrain the mechanisms driving galaxy evolution, it is crucial to distinguish between old (Retired) and recently quenched galaxies, thus requiring at least two estimates of the specific star formation rate over different timescales., Comment: Accepted for publication in MNRAS

WEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, will see first light in late 2022. WEAVE comprises a new 2-degree field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366$-$959\,nm at $R\sim5000$, or two shorter ranges at $R\sim20\,000$. After summarising the design and implementation of WEAVE and its data systems, we present the organisation, science drivers and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for $\sim$3 million stars and detailed abundances for $\sim1.5$ million brighter field and open-cluster stars; (ii) survey $\sim0.4$ million Galactic-plane OBA stars, young stellar objects and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey $\sim400$ neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionised gas in $z<0.5$ cluster galaxies; (vi) survey stellar populations and kinematics in $\sim25\,000$ field galaxies at $0.3\lesssim z \lesssim 0.7$; (vii) study the cosmic evolution of accretion and star formation using $>1$ million spectra of LOFAR-selected radio sources; (viii) trace structures using intergalactic/circumgalactic gas at $z>2$. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator., Comment: 41 pages, 27 figures, accepted for publication by MNRAS; updated version including information on individual grants in a revised Acknowledgements section, corrections to the affiliation list, and an updated references list

We modelled dust grain-size distributions for carbonaceous and silicates dust, as well as for free-flying iron nanoparticles in the environment of a $\gamma$-ray burst (GRB) afterglow, GRB 180325A. This GRB, at $z=2.2486$, has an unambiguous detection of the 2175 \r{A} extinction feature with $R_V=4.58$ and $A_V=1.58$. In addition to silicates, polycyclic aromatic hydrocarbons (PAH), and graphite, we used iron nanoparticles grain-size distributions for the first time to model the observed extinction curve of GRB 180325A. We fit the observed extinction for four model permutations, using 232 sets of silicates, graphite, carbon abundance in hydrocarbon molecules ($b_C$), and fraction of iron abundance in free-flying nanoparticles ($b_{\text{Fe}}$). These four different permutations were chosen to test iron nanoparticles significance and carbon abundance in hydrocarbons. Our results indicate that iron nanoparticles contribution is insignificant and there is a degeneracy of carbon abundances, with the range $(0.0 \leq b_C \leq 0.7)\times10^{-5}$ providing the best-fit to the observed extinction curve of GRB 180325A. We therefore favour the simplest model of silicates and polycyclic aromatic hydrocarbons. The silicates are dominant and contribute to the entire wavelength range of the GRB extinction curve while graphite contributes towards both the 2175 \r{A} bump and the UV extinction. The afterglow peak luminosity ($1.5\times10^{51}$ ergs/s) indicates dust destruction may have taken place. We conclude that further investigations into other potential contributors of extinction are warranted, particularly for steep UV extinction., Comment: 13 pages, 7 figures, accepted for publication in MNRAS

We study recent changes on the star formation history (SFH) of galaxies by means of the ageing diagram (AD), tracing the fraction of stars formed during the last $\sim 20$ Myr through the equivalent width of the H$\alpha$ line and $\sim 1-3$ Gyr through the dust-corrected optical colour $(g-r)_0$ or the Balmer break. We provide a physical characterization by using Pipe3D estimates of the SFH of CALIFA and MaNGA galaxies, in combination with the predictions from IllustrisTNG-100. Our results show that the AD may be divided into four domains that correlate with the stellar mass fractions formed in the last 20 Myr and 3 Gyr: Ageing systems, whose SFR changes on scales of several Gyr, account for $70-80\%$ of the galaxy population. Objects whose SFH was abruptly truncated in the last $\sim 1$ Gyr arrange along a detached Quenched sequence that represents $\sim 5-10\%$ by (volume-corrected) number for $10^9 < M_*/{\rm M_\odot} < 10^{12}$. Undetermined systems represent an intermediate population between the Ageing and Quenched regimes. Finally, Retired galaxies, dominated by old stellar populations, are located at the region in the AD where the Ageing and Quenched sequences converge. Defining different star formation activity levels in terms of the birth rate parameter $b\equiv \frac{SFR}{\langle SFR \rangle}$, we find that galaxies transit from the Ageing to Quenched sequences on scales $\sim 500$ Myr. We conclude that the ageing diagram provides a useful tool to discern recently Quenched galaxies from the dominant Ageing population., Comment: Accepted for publication in MNRAS

We present a self-consistent prediction of the interstellar radiation field (ISRF), from the extreme ultraviolet (EUV) to sub-mm range, based on two chemical evolution models of a Milky Way-like galaxy (MWG). To this end, we develop a new tool called Mixclask to include gas emission, absorption and scattering from the photoionization code Cloudy into the Monte Carlo radiative transfer code Skirt. Both algorithms are invoked iteratively, until the physical properties of the ISM converge. We have designed a first test, reminiscent of a HII region, and we find that the results of Mixclask are in good agreement with a spherically symmetric Cloudy simulation. Both MWG models based on chemical evolution codes give results broadly consistent with previous empirical models reported in the literature for the ISRF of our Galaxy, albeit they systematically underestimate the mid-infrared emission. We also find significant differences between our two models in the whole ultraviolet range, not fully explored in previous ISRF models. These results show the feasibility of our method of combining radiative transfer with chemical evolution models: there is increased predictive power and the interstellar radiation field obtained provides further constraints on the model parameters. Python source code to implement our method is publicly available at https://github.com/MarioRomeroC/Mixclask., Comment: 16 pages, 7 figures, 3 tables. Accepted for publication in MNRAS

This work investigates the fundamental mechanism(s) that drive galaxy evolution in the Local Universe. By comparing two proxies of star-formation sensitive to different timescales, such as EW(H$\alpha$) and colours like $g-r$, one may distinguish between smooth secular evolution (ageing) and sudden changes (quenching) on the recent star formation history of galaxies. Building upon the results obtained from a former study based on 80.000 SDSS single-fibre measurements, we now focus on spatially-resolved (on kpc scales) galaxies, comparing with a sample of 637 nearby objects observed by the CALIFA survey. In general, galaxies cannot be characterised in terms of a single `evolutionary stage'. Individual regions within galaxies arrange along a relatively narrow ageing sequence, with some intrinsic scatter possibly due to their different evolutionary paths. These sequences, though, differ from one galaxy to another, although they are broadly consistent with the overall distribution found for the (central) SDSS spectra. We find evidence of recent quenching episodes (relatively blue colours and strong H$\alpha$ absorption) in a small fraction of galaxies (most notably, low-mass ellipticals), on global scales and individual regions (particularly at high metallicity). However, we argue that most of the systems, over their entire extent, are compatible with a secular inside-out scenario, where the evolutionary stage correlates with both global (mass, morphology, and environment) as well as local (surface brightness and metallicity) properties., Comment: 17 pages + appendix, 12 figures. Submitted to MNRAS. Comments welcome!

For years, the extragalactic community has divided galaxies in two distinct populations. One of them, featuring blue colours, is actively forming stars, while the other is made up of "red-and-dead" objects with negligible star formation. Yet, are these galaxies really dead? Here we would like to highlight that, as previously reported by several independent groups, state-of-the-art cosmological numerical simulations predict the existence of a large number of quenched galaxies that have not formed any star over the last few Gyr. In contrast, observational measurements of large galaxy samples in the nearby Universe suggest that even the most passive systems still form stars at some residual level close to $sSFR\sim10^{-12}~\text{yr}^{-1}$. Unfortunately, extremely low star formation poses a challenge for both approaches. We conclude that, at present, the fraction of truly dead galaxies is still an important open question that must be addressed in order to understand galaxy formation and evolution., Comment: Accepted for publication in MNRAS. 9 pages, 8 figures