Search

We thank the anonymous referee for his/her constructive report that improved the clarity of the manuscript. This work is supported by the Spanish 'Ministerio de Ciencia e Innovacion' and from the European Regional Development Fund (FEDER) via grants PID2020114414GB-I00 and PID2020-113689GB-I00, and from the 'Junta de Andalucia' (Spain) local government through the FQM108 and AFQM-510-UGR20 projects. EPM acknowledges financial support from the State Agency for Research of the Spanish 'Ministerio de Ciencia, Innovacon y Universidades' through the 'Center of Excellence Severo Ochoa' award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709) and to projects 'Estallidos7' PID2019107408GB-C44 (Spanish 'Ministerio de Ciencia e Innovacion'), and from the 'Junta de Andalucia' Excellence project EXC/2011 FQM7058, and also the assistance from his guide dog Rocko without whose daily help this work would have been much more difficult., We use a sample of 536 H II regions located in nearby spirals, with a homogeneous determination of their T e -based abundances, to obtain new empirical calibrations of the N2O2, N2S2, O3N2, and N2 strong-line indices to estimate the nitrogen-to-oxygen abundance ratio when auroral lines are not detected. All indices are strongly correlated with the T e -based log (N/O) for our H II re gion sample, ev en more strongly than with 12 + log (O/H). N2O2 is the most strongly correlated index, and the best fit to the log (N/O)–N2O2 relation is obtained with a second-order polynomial. The derived relation has a low dispersion (rms < 0.09 dex), being valid in the range −1.74 < N2O2 < 0.62 (or −1.81 < log (N/O) < −0.13). We have compared our calibration with previous ones and have discussed the differences between them in terms of the nature of the objects used as calibrators., Instituto de Salud Carlos III Spanish Government European Commission PID2020114414GB-I00 PID2020-113689GB-I00, 'Junta de Andalucia' (Spain) local government FQM108 AFQM-510-UGR20, State Agency for Research of the Spanish 'Ministerio de Ciencia, Innovacon y Universidades' through the 'Center of Excellence Severo Ochoa' SEV-2017-0709 PID2019107408GB-C44, Junta de Andalucia EXC/2011 FQM7058

We investigate the change in mean stellar population age and metallicity ([Z/H]) scaling relations for quiescent galaxies from intermediate redshift ($0.60\leq z\leq0.76$) using the LEGA-C Survey, to low redshift ($0.014\leq z\leq0.10$) using the SAMI Galaxy Survey. We find that, similarly to their low-redshift counterparts, the stellar metallicity of quiescent galaxies at $0.60\leq z\leq 0.76$ closely correlates with $M_*/R_\mathrm{e}$ (a proxy for the gravitational potential or escape velocity), in that galaxies with deeper potential wells are more metal-rich. This supports the hypothesis that the relation arises due to the gravitational potential regulating the retention of metals, by determining the escape velocity required by metal-rich stellar and supernova ejecta to escape the system and avoid being recycled into later stellar generations. On the other hand, we find no correlation between stellar age and $M_*/R_\mathrm{e}^2$ (stellar mass surface density $\Sigma$) in the LEGA-C sample, despite this being a strong relation at low redshift. We consider this change in the age--$\Sigma$ relation in the context of the redshift evolution of the star-forming and quiescent populations in the mass--size plane, and find our results can be explained as a consequence of galaxies forming more compactly at higher redshifts, and remaining compact throughout their evolution. Furthermore, galaxies appear to quench at a characteristic surface density that decreases with decreasing redshift. The $z\sim 0$ age--$\Sigma$ relation is therefore a result of building up the quiescent and star-forming populations with galaxies that formed at a range of redshifts and so a range of surface densities., Comment: 18 pages, 11 figures, accepted to MNRAS

For the first time, neon abundance has been derived in the narrow line region from a sample of Seyfert 2 nuclei. In view of this, we compiled from the literature fluxes of optical and infrared (IR) narrow emission lines for 35 Seyfert 2 nuclei in the local universe (z < ∼ 0.06). The relative intensities of emission lines were used to derive the ionic and total neon and oxygen abundances through electron temperature estimations (Te-method). For the neon, abundance estimates were obtained by using both Te-method and IR-method. Based on photoionization model results, we found a lower electron temperature [te(Ne iii)] for the gas phase where the Ne2+ is located in comparison with t3 for the O2+ ion. We find that the differences (D) between Ne2+/H+ ionic abundances calculated from IR-method and Te−method (assuming t3 in the Ne2+/H+ derivation) are similar to the derivations in star-forming regions (SFs) and they are reduced by a mean factor of ∼ 3 when te(Ne iii) is considered. We propose a semiempirical Ionization Correction Factor (ICF) for the neon, based on [Ne ii]12.81µm, [Ne iii]15.56µm and oxygen ionic abundance ratios. We find that the average Ne/H abundance for the Seyfert 2s sample is nearly 2 times higher than similar estimate for SFs. Finally, for the very high metallicity regime (i.e. [12 + log(O/H) > ∼ 8.80]) an increase in Ne/O with O/H is found, which likely indicates secondary stellar production for the neon., Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas

Large fractions of metals are missing from the observable gas-phase in the interstellar medium (ISM) because they are incorporated into dust grains, a phenomenon called dust depletion. The study of dust depletion in the ISM is important to investigate the origin and evolution of metals and cosmic dust. Here we aim at characterizing the dust depletion of several metals from the Milky Way to distant galaxies. We collect ISM metal column densities from absorption-line spectroscopy in the literature, and in addition, we determine Ti and Ni column densities from a sample of 70 damped Lyman-$\alpha$ absorbers (DLAs) towards quasars, observed with UVES/VLT. We use ISM relative abundances to estimate the dust depletion of 18 metals (C, P, O, Cl, Kr, S, Ge, Mg, Si, Cu, Co, Mn, Cr, Ni, Al, Ti, Zn and Fe) for different environments (the Milky Way, the Magellanic Clouds (MCs), DLAs towards quasars and towards gamma-ray bursts). We observe linear relations between the depletion of each metal and the strength of dust depletion, which we trace with the observed [Zn/Fe]. In the neutral ISM of the MCs we find small deviations from linearity observed as an overabundance of the $\alpha$-elements Ti, Mg, S and an underabundance of Mn. The deviations disappear if we assume that all OB stars observed towards the MCs in our sample have an $\alpha$-element enhancement and Mn underabundance. This may imply that the MCs have been recently enriched in $\alpha$-elements, potentially due to recent bursts of star formation. The observed strong correlations of the depletion sequences of the metals all the way from low metallicity QSO-DLAs to the Milky Way suggest that cosmic dust has a common origin, independently of the star formation history, which varies significantly between these different galaxies. This supports the importance of grain growth in the ISM as a significant process of dust production., Comment: 30 pages, 35 figures, 12 tables, Accepted for publication in A&A, Abstract abridged for arXiv

The evolution of the dust grain size distribution has been studied in recent years with great detail in cosmological hydrodynamical simulations taking into account all the channels under which dust evolves in the interstellar medium. We present a systematic analysis of the observed spectral energy distribution of a large sample of galaxies in the local Universe in order to derive not only the total dust masses but also the relative mass fraction between small and large dust grains ( D S / D L ). Simulations reproduce fairly well the observations except for the high-stellar mass regime where dust masses tend to be o v erestimated. We find that ∼45 per cent of galaxies exhibit D S / D L consistent with the expectations of simulations, while there is a subsample of massive galaxies presenting high D S / D L (log ( D S / D L ) ∼−0.5), and deviating from the prediction in simulations. For these galaxies which also have high-molecular gas mass fractions and metallicities, coagulation is not an important mechanism affecting the dust e volution. Including dif fusion, transporting large grains from dense regions to a more diffuse medium where they can be easily shattered, would explain the observed high D S / D L values in these galaxies. With this study, we reinforce the use of the small-to-large grain mass ratio to study the relative importance of the different mechanisms in the dust life cycle. Multiphase hydrodynamical simulations with detailed feedback prescriptions and more realistic subgrid models for the dense phase could help to reproduce the evolution of the dust grain size distribution traced by observations., MCIN/AEI PID2020-114414GB-100 Spanish Government AYA2017-84897-P, Junta de Andalucia P2000334 A-FQM-510-UGR20, FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades European Research Council (ERC) European Commission 851622, HPCI System Research Project hp200041 hp210090, Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT), Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research (KAKENHI) JP17H01111 19H05810 20H00180, Ministry of Science and Technology, China MOST 107-2923-M-001-003-MY3 MOST 108-2112-M-001-007-MY3, Academia Sinica - Taiwan AS-IA-109-M02, National Basic Research Program of China 2017YFA0402704, Comunidad de Madrid 2018-T1/TIC-11035

We analyse the chemical properties of three z~8 galaxies behind the galaxy cluster SMACS J0723.3-7327, observed as part of the Early Release Observations programme of the James Webb Space Telescope (JWST). Exploiting [O III]4363 auroral line detections in NIRSpec spectra, we robustly apply the direct Te method for the very first time at such high redshift, measuring metallicities ranging from extremely metal poor (12+log(O/H)~7) to about one-third solar. We also discuss the excitation properties of these sources, and compare them with local strong-line metallicity calibrations. We find that none of the considered diagnostics match simultaneously the observed relations between metallicity and strong-line ratios for the three sources, implying that a proper re-assessment of the calibrations may be needed at these redshifts. On the mass-metallicity plane, the two galaxies at z~7.6 (log(M*/M_sun) = 8.1, 8.7) have metallicities that are consistent with the extrapolation of the mass-metallicity relation at z~2-3, while the least massive galaxy at z~8.5 (log(M*/M_sun) = 7.8) shows instead a significantly lower metallicity . The three galaxies show different level of offset relative to the Fundamental Metallicity Relation, with two of them (at z~7.6) being marginally consistent, while the z~8.5 source deviating significantly, being probably far from the smooth equilibrium between gas flows, star formation and metal enrichment in place at later epochs., 13 pages, 7 figures. Accepted for publication on MNRAS

We estimate chemical abundances and ionization parameters in the nuclear region of a sample of 143 galaxies from the Palomar Spectroscopic Survey, composed by star-forming galaxies (87), Seyferts 2 (16), and LINERs (40) using the HII-CHI-MISTRY code. We also study for each spectral type the correlation of the derived quantities with other different properties of the host galaxies, such as morphology, stellar mass, luminosity, and mass of their supermassive black holes. The results obtained for star-forming galaxies are used to check the soundness of our methodology. Then, we replicate a similar study for our sample of AGN, distinguishing between Seyferts 2 and LINERs. We report a saturation of Oxygen abundances for the nuclear regions of SFG. The correlations between chemical abundances and their host galaxy properties for SFG are in good agreement with previous studies. We find that Seyferts 2 present slightly higher chemical abundances but this result must be reexamined in larger samples of Seyfert galaxies. In contrast, we obtain lower chemical abundances for LINERs than for SFG. We confirm these relatively lower abundances for another sample of infrared luminous LINERs in the same stellar mass range. Our analysis of AGNs (both LINERs and Seyferts) shows that their host galaxy properties are not correlated with our estimated chemical abundances. © 2021 The Author(s)., We acknowledge support from the Spanish MINECO grants AYA2016-76682C3-1-P, AYA2016-79724-C4, and PID2019-106027GB-C41. We also acknowledge financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). We acknowledge the fruitful discussions with our research team. BPD also acknowledges the support from CSIC grant JAEINT-19-00863. EPM acknowledges the assistance from his guide dog Rocko without whose daily help this work would have been much more difficult.

Matching the number counts of high-$z$ sub-millimetre-selected galaxies (SMGs) has been a long standing problem for galaxy formation models. In this paper, we use 3D dust radiative transfer to model the sub-mm emission from galaxies in the SIMBA cosmological hydrodynamic simulations, and compare predictions to the latest single-dish observational constraints on the abundance of 850$\mathrm{\mu m}$-selected sources. We find good agreement with the shape of the integrated 850$\mathrm{\mu m}$ luminosity function, and the normalisation is within 0.25 dex at $> 3 \; \mathrm{mJy}$, unprecedented for a fully cosmological hydrodynamic simulation, along with good agreement in the redshift distribution of bright SMGs. The agreement is driven primarily by SIMBA's good match to infrared measures of the star formation rate (SFR) function between $z = 2-4$ at high SFRs. Also important is the self-consistent on-the-fly dust model in SIMBA, which predicts, on average, higher dust masses (by up to a factor of 2.5) compared to using a fixed dust-to-metals ratio of 0.3. We construct a lightcone to investigate the effect of far-field blending, and find that 52% of sources are blends of multiple components, which makes a small contribution to the normalisation of the bright-end of the number counts. We provide new fits to the 850$\mathrm{\mu m}$ luminosity as a function of SFR and dust mass. Our results demonstrate that exotic solutions to the discrepancy between sub-mm counts in simulations and observations, such as a top-heavy IMF, are unnecessary, and that sub-millimetre-bright phases are a natural consequence of massive galaxy evolution., Comment: 23 pages, 21 figures, Accepted to MNRAS

The KBC void is a local underdensity with the observed relative density contrast $\delta \equiv 1 - \rho/\rho_{0} = 0.46 \pm 0.06$ between 40 and 300 Mpc around the Local Group. If mass is conserved in the Universe, such a void could explain the $5.3\sigma$ Hubble tension. However, the MXXL simulation shows that the KBC void causes $6.04\sigma$ tension with standard cosmology ($\Lambda$CDM). Combined with the Hubble tension, $\Lambda$CDM is ruled out at $7.09\sigma$ confidence. Consequently, the density and velocity distribution on Gpc scales suggest a long-range modification to gravity. In this context, we consider a cosmological MOND model supplemented with $11 \, \rm{eV}/c^{2}$ sterile neutrinos. We explain why this $\nu$HDM model has a nearly standard expansion history, primordial abundances of light elements, and cosmic microwave background (CMB) anisotropies. In MOND, structure growth is self-regulated by external fields from surrounding structures. We constrain our model parameters with the KBC void density profile, the local Hubble and deceleration parameters derived jointly from supernovae at redshifts $0.023 - 0.15$, time delays in strong lensing systems, and the Local Group velocity relative to the CMB. Our best-fitting model simultaneously explains these observables at the $1.14\%$ confidence level (${2.53 \sigma}$ tension) if the void is embedded in a time-independent external field of ${0.055 \, a_{_0}}$. Thus, we show for the first time that the KBC void can naturally resolve the Hubble tension in Milgromian dynamics. Given the many successful a priori MOND predictions on galaxy scales that are difficult to reconcile with $\Lambda$CDM, Milgromian dynamics supplemented by $11 \, \rm{eV}/c^{2}$ sterile neutrinos may provide a more holistic explanation for astronomical observations across all scales., Comment: Published in the Monthly Notices of the Royal Astronomical Society, 40 pages, 19 figures, 5 tables

We present here the second part of a project that aims at solving the controversy regarding the issue of the bar effect on the radial distribution of metals in the gas-phase of spiral galaxies. In Paper I, we presented a compilation of more than 2800 H ii regions belonging to 51 nearby galaxies for which we derived chemical abundances and radial abundance profiles from a homogeneous methodology. In this paper, we analyse the derived gas-phase radial abundance profiles of 12+log (O/H) and log (N/O), for barred and unbarred galaxies separately, and find that the differences in slope between barred and unbarred galaxies depend on galaxy luminosity. This is due to a different dependence of the abundance gradients (in dex kpc-1) on luminosity for the two types of galaxies: in the galaxy sample under consideration the gradients appear to be considerably shallower for strongly barred galaxies in the whole luminosity range, while profile slopes for unbarred galaxies become steeper with decreasing luminosity. Therefore, we only detect differences in slope for the lower luminosity (lower mass) galaxies (MB-19.5 or M∗ 1010.4 M). We discuss the results in terms of the disc evolution and radial mixing induced by bars and spiral arms. Our results reconcile previous discrepant findings that were biased by the luminosity (mass) distribution of the sample galaxies and possibly by the abundance diagnostics employed. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society., We acknowledge Simon Diaz-Garcia for useful discussions. We thank Calar Alto Observatory for allocation of director's discretionary time to this programme. We also thank the anonymous referee for his/her suggestions that improved the clarity of the manuscript. AZ, EF, and IP acknowledge support from the Spanish 'Ministerio de Economia, Industria y Competitividad' (MINECO) and from the European Regional Development Fund (FEDER) via grant AYA201784897-P, and from the Junta de Andaluc ' ia (Spain) local government through the FQM-108 project. EPM acknowledges funding from the Spanish MINECO project Estallidos 6 AYA2016-79724-C4 and from the Severo Ochoa excellence program (SEV-2017-0709). This research made use ofAstropy (http://www.astropy.org) a communitydeveloped core PYTHON package for ASTRONOMY (Astropy Collaboration 2013, 2018); MATPLOTLIB (Hunter 2007); and NUMPY (van der Walt et al. 2011).

The metallicity of star-forming gas in galaxies from the EAGLE simulations increases with stellar mass. Here we investigate whether the scatter around this relation correlates with morphology and/or stellar kinematics. At redshift $z=0$, galaxies with more rotational support have lower metallicities on average when the stellar mass is below $M_\star\approx 10^{10}~{\rm M}_\odot$. This trend inverts at higher values of $M_\star$, when prolate galaxies show typically lower metallicity. At increasing redshifts, the trend between rotational support and metallicity becomes weaker at low stellar mass but more pronounced at high stellar mass. We argue that the secondary dependence of metallicity on stellar kinematics is another manifestation of the observed anti-correlation between metallicity and star formation rate at a given stellar mass. At low masses, such trends seem to be driven by the different star-formation histories of galaxies and stellar feedback. At high masses, feedback from active galactic nuclei and galaxy mergers play a dominant role., Comment: 5 pages, 4 figures. Accepted for publication in MNRAS

The galaxy population is strongly bimodal in both colour and morphology, and the two measures correlate strongly, with most blue galaxies being late-types (spirals) and most early-types, typically ellipticals, being red. This observation has led to the use of colour as a convenient selection criteria to make samples which are then labelled by morphology. Such use of colour as a proxy for morphology results in necessarily impure and incomplete samples. In this paper, we make use of the morphological labels produced by Galaxy Zoo to measure how incomplete and impure such samples are, considering optical (ugriz), NUV and NIR (JHK) bands. The best single colour optical selection is found using a threshold of g-r = 0.742, but this still results in a sample where only 56% of red galaxies are smooth and 56% of smooth galaxies are red. Use of the NUV gives some improvement over purely optical bands, particularly for late-types, but still results in low purity/completeness for early-types. No significant improvement is found by adding NIR bands. With any two bands, including NUV, a sample of early-types with greater than two-thirds purity cannot be constructed. Advances in quantitative galaxy morphologies have made colour-morphology proxy selections largely unnecessary going forward; where such assumptions are still required, we recommend studies carefully consider the implications of sample incompleteness/impurity., Comment: 8 pages, 2 figures, Accepted 2021 December 07. Received 2021 December 06; in original form 2021 August 06

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Monthly Notices of the Royal Astronomical Society 510.4 (2022): 5392-5407 is available online at: https://academic.oup.com/mnras/article-abstract/510/4/5392/6505155?redirectedFrom=fulltext, New surv e ys such as European Space Agenc ys (ESA's) Euclid mission are planned to map with unprecedented precision the large-scale structure of the Universe by measuring the 3D positions of tens of millions of galaxies. It is necessary to develop theoretically modelled galaxy catalogues to estimate the expected performance and to optimize the analysis strategy of these surv e ys. We populate two pairs of (1 h -1 Gpc) 3 volume dark matter-only simulations from the UNIT project with galaxies using the Semi-Analytic Galaxy Evolution semi-analytic model of galaxy formation, coupled to the photoionization model GET EMLINES to estimate their H αemission. These catalogues represent a unique suite that includes galaxy formation physics and -thanks to the fixed-pair technique used -an ef fecti ve volume of ∼(5 h -1 Gpc ) 3 , which is several times larger than the Euclid surv e y. We present the performance of these data and create five additional emission-line galaxy (ELG) catalogues by applying a dust-attenuation model as well as adjusting the flux threshold as a function of redshift in order to reproduce Euclid-forecast d N /d z values. As a first application, we study the abundance and clustering of those model H αELGs: For scales greater than ∼5 h -1 Mpc, we find a scale- independent bias with a value of b ∼1 at redshift z ∼0.5, that can increase nearly linearly to b ∼4 at z ∼2, depending on the ELG catalogue. Model galaxy properties, including their emission-line fluxes (with and without dust extinction) are publicly available

This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record Monthly Notices of the Royal Astronomical Society 511.3 (2022): 4377–4392 is available online at: https://academic.oup.com/mnras/article-abstract/511/3/4377/6527580#no-access-message, 2+We present a methodology for the use of sulphur as global metallicity tracer in galaxies, allowing performing a complete abundance analysis using only the red-to-near-infrared spectral region. We have applied it to a compilation of high-quality data split into two samples: H II regions (DHR) in spiral and irregular galaxies, and dwarf galaxies dominated by a strong starburst (H II Gal). Sulphur abundances have been derived by direct methods under the assumption of an ionization structure composed of two zones: an intermediate-ionization one where S++ is originated, and a low-ionization one where S+ is formed. Ionization correction factors (ICF) have been calculated from the Ar/Ar3+ ratio and are shown to correlate with the hardness of the radiation field. Only about 10 per cent of the objects show S3+ contributions to the total abundance larger than 30 per cent. A good correlation exists between sulphur abundance and ionizing temperature with low-metallicity objects being ionized by hotter stars. No correlation is found between ionization parameter and total S/H abundance. Most of the H II Gal objects show S/O ratios below the solar value and a trend for increasing S/O ratios with increasing sulphur abundances, while DHR objects show S/O ratios larger than solar and a tendency for lower S/O ratios for higher metallicities. Finally, we present a calibration of the sulphur abundance through the S23 parameter that remains single valued up to sulphur abundances well beyond the solar value. S23 is independent of the ionization parameter and only weakly dependent on ionizing temperature

Feedback, in particular from active galactic nuclei (AGN), is believed to play a crucial role in the evolution of galaxies. In the local Universe, many galaxies with an AGN are indeed observed to reside in the so-called green valley, usually interpreted as a transition phase from a blue star-forming to a red quenched state. We use data from the Sloan Digital Sky Survey to show that such an interpretation requires substantial revision. Optically-selected nearby AGN galaxies follow exponentially declining star formation histories, as normal galaxies of similar stellar and dark matter halo mass, reaching in the recent past ($\sim$0.1 Gyr ago) star formation rate levels consistent with a quiescent population. However, we find that local AGN galaxies have experienced a sudden increase in their star formation rate, unfolding on timescales similar to those typical of AGN activity, suggesting that both star formation and AGN activity were triggered simultaneously. We find that this quenching followed by an enhancement in the star formation rate is common to AGN galaxies and more pronounced in early type galaxies. Our results demonstrate that local AGN galaxies are not just a simple transition type between star-forming and quiescent galaxies as previously postulated., Comment: Accepted for publication in MNRAS Letters. 5 pages, 5 figures, and 1 table containing the sample properties

Radial metallicity trends provide a key indicator of physical processes such as star formation and radial gas migration within a galaxy. Large IFU surveys allow for detailed studies of these radial variations, with recent observations detecting central dips in the metallicity, which may trace the impact of various evolutionary processes. However, the origin of these dips has not been conclusively determined, with suggestions that they may be diagnostic dependent. In this paper, we use the SDSS-IV MaNGA survey to investigate whether the observed dips represent genuine decreases in the central metallicity, or if they could be an artefact of the diagnostic used. Using a sub-sample of 758 local star-forming galaxies at low inclinations, we investigate in detail the impact of using different strong line diagnostics on the shapes of the returned profiles, and the prevalence of dips. We find no clear evidence of the dips being caused by changing values of the ionisation parameter within galaxies. To investigate physical causes, we explore both global and spatially-resolved parameters, finding that galaxies exhibiting central dips in the O3N2 metallicity profile have on average lower H$\alpha$EW values out to $R/R_\rm{e} \sim 1.5$, and higher values of D$_N$(4000) in the central regions. We additionally find a higher prevalence of dips in galaxies with high stellar mass, and lower values of global specific star formation rate, suggesting a possible link to central quenching. Nevertheless, these results are dependent on the diagnostic used, suggesting caution should be taken when interpreting observed features in galaxy metallicity gradients., Comment: Accepted for publication in MNRAS. 23 pages; 21 figures

Low-metallicity, compact starburst galaxies referred to as Green Peas (GPs) provide a unique window to study galactic evolution across cosmic epochs. In this work, we present new deep optical spectra for three GPs from OSIRIS at the 10-m Gran Telescopio Canarias, which are studied using a state-of-the-art methodology. A stellar population synthesis is conducted with 1098 spectral templates. The methodology succeeds at characterizing stellar populations from 0.5 Myr to 10 Gyr. The light distribution shows a large red excess from a single population with log(age)>8.5yr in the GP sample analysed. This points towards an incomplete characterization of the gas luminosity, whose continuum already accounts between 7.4 and 27.6 per cent in the galaxy sample. The emission spectra are fitted with the largest Bayesian chemical model consisting of an electron temperature, an electron density, the logarithmic extinction coefficient and eleven ionic species under the direct method paradigm. Additionally, building on previous work, we propose a neural networks sampler to constrain the effective temperature and ionization parameter of each source from photoionization model grids. Finally, we combine both methodologies into a 16-dimensional model, which for the first time, simultaneously explores the direct method and photoionization parameter spaces. Both techniques consistently indicate a low-metallicity gas, 7.76, This work was funded by the FONDECYT Postdoc 2020 project 3200340 from the National Agency for Research and Development (ANID). RA acknowledges support from ANID Fondecyt Regular 1202007. P.P. acknowledges support through FCT grants UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020 and the project ‘Identifying the Earliest Supermassive Black Holes with ALMA (IdEaS with ALMA)’ (PTDC/FIS-AST/29245/2017). EPM, CK, and JVM acknowledge financial support from the State Agency for Researchof the Spanish MCIU through the ‘Center of Excellence SeveroOchoa’ award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709).

Aims. We explore the so-called softness diagram - whose main function is to provide the hardness of the ionizing radiation in star-forming regions - in order to check whether hot and old low-mass evolved stars (HOLMES) are significant contributors to the ionization within star-forming regions, as suggested by previous MaNGA data analyses. Methods. We used the code HCM-TEFF to derive both the ionization parameter and the equivalent effective temperature (T-*), adopting models of massive stars and planetary nebulae (PNe), and exploring different sets of emission lines in the softness diagram to figure out the main causes of the observed differences in the softness parameter in the MaNGA and CHAOS star-forming region samples. Results. We find that the fraction of regions with a resulting T-* > 60 kK, which are supposedly ionised by sources harder than massive stars, is considerably larger in the MaNGA (66%) than in the CHAOS (20%) sample when the [S II] lambda lambda 6716,6731 angstrom emission lines are used in the softness diagram. However, the respective fractions of regions in this regime for both samples are considerably reduced (20% in MaNGA and 10% in CHAOS) when the [N II] emission line at lambda 6584 angstrom is used instead. This may indicate that diffuse ionised gas (DIG) contamination in the lower resolution MaNGA data is responsible for artificially increasing the measured T-* as opposed to there being a predominant role of HOLMES in the H II regions., Ministry of Science and Innovation, Spain (MICINN), Instituto de Salud Carlos III, Spanish Government, Junta de Andalucia, Spanish Government MCIN/AEI, FEDER/Junta de Andalucia-Consejeria de Transformacion Economica, Industria, Conocimiento y Universidades/Proyecto PID2019-107408GB-C44 P18-FR-2664 SEV-2017-0709 PID2020-114414GB-100 PID2020-113689GB-I00 A-FQM-510-UGR20

We present the first measurement of the metallicity gradient in extremely metal-poor galaxies (EMPGs). With Subaru/Faint Object Camera And Spectrograph (FOCAS) Integral Field Unit (IFU), we have observed a nearby, low-mass EMPG, HSC J1631+4426, whose oxygen abundance and stellar mass are known to be 12+log(O/H) $=6.9$ and $\log_{10}(M_*/{\rm M}_\odot)=5.8$, respectively. The measured metallicity gradient is $-0.36 \pm 0.04$ dex kpc$^{-1}$ corresponding to $-0.049 \pm 0.006$ dex R$_\mathrm{e}^{-1}$ for the continuum effective radius of $R_\mathrm{e} = 0.14$ kpc. Our observation has successfully demonstrated that three-dimensional spectroscopy with 8m-class telescopes is powerful enough to reveal the metallicity distribution in local EMPGs, providing precious information of the baryon cycle in local analogs of primordial galaxies in the early Universe., Comment: PASJ accepted, 7 pages, 4 figures

The distribution of stellar metallicities within and across galaxies is an excellent relic of the chemical evolution across cosmic time. We present a detailed analysis of spatially resolved stellar populations based on $>2.6$ million spatial bins from 7439 nearby galaxies in the SDSS-IV MaNGA survey. To account for accurate inclination corrections, we derive an equation for morphology dependent determination of galaxy inclinations. Our study goes beyond the well-known global mass-metallicity relation and radial metallicity gradients by providing a statistically sound exploration of local relations between stellar metallicity $[Z/H]$, stellar surface mass density $\Sigma_\star$ and galactocentric distance in the global mass-morphology plane. We find a significant resolved mass density-metallicity relation $\rm r\Sigma_\star ZR$ for galaxies of all types and masses above $10^{9.8}\,\mathrm{M_\odot}$. Different radial distances make an important contribution to the spread of the relation. Particularly, in low and intermediate mass galaxies, we find that at fixed $\Sigma_\star$ metallicity increases with radius independently of morphology. For high masses, this radial dependence is only observed in high $\Sigma_\star$ regions of spiral galaxies. This result calls for a driver of metallicity, in addition to $\Sigma_\star$ that promotes chemical enrichment in the outer parts of galaxies more strongly than in the inner parts. We discuss gas accretion, outflows, recycling and radial migration as possible scenarios., Comment: 16 pages, 11 figures. MNRAS accepted, pending a few minor revisions

We present a study of the relationships and environmental dependencies between stellar mass, star formation rate, and gas metallicity for more than 700 galaxies in groups up to redshift 0.35 from the Galaxy And Mass Assembly (GAMA) survey. To identify the main drivers, our sample was analyzed as a function of group-centric distance, projected galaxy number density, and stellar mass. By using control samples of more than 16000 star-forming field galaxies and volume limited samples, we find that the highest enhancement in SFR (0.3 dex) occurs in galaxies with the lowest local density. In contrast to previous work, our data show small enhancements of $\sim$0.1 dex in SFR for galaxies at the highest local densities or group-centric distances. Our data indicates quenching in SFR only for massive galaxies, suggesting that stellar mass might be the main driver of quenching processes for star forming galaxies. We can discard a morphological driven quenching, since the S\'ersic index distribution for group and control galaxies are similar. The gas metallicity does not vary drastically. It increases $\sim$0.08 dex for galaxies at the highest local densities, and decreases for galaxies at the highest group-centric distances, in agreement with previous work. Altogether, the local density, rather than group-centric distance, shows the stronger impact in enhancing both, the SFR and gas metallicity. We applied the same methodology to galaxies from the IllustrisTNG simulations, and although we were able to reproduce the general observational trends, the differences between group and control samples only partially agree with the observations, Comment: Accepted by MNRAS

We derived the oxygen abundance (O/H), the nitrogen-To-oxygen (N/O) abundance ratio, and their corresponding radial gradients for a sample of 1431 galaxies from the MaNGA DR15 survey using two different realisations of the strong line method: empirical R calibration and the Bayesian model-based HII-CHI-MISTRY (HCM) code. We find that both abundance calculation methods reveal a correlation between the O/H gradient and the stellar mass of a galaxy. This relation is non-linear, with the steepest average gradients in the intermediate mass range and flatter average gradients for high-and low-mass galaxies. The relation between the N/O gradient and the stellar mass is, on average, non-linear with the steepest gradients in the intermediate mass range (log(M/M⊠)∼10), flatter gradients for high-mass galaxies, and the flattest gradients for low-mass galaxies. However, the general trend of steepening N/O gradients for higher masses, as reported in previous studies, remains evident. We find a dependence between the O/H and N/O gradients and the galaxy mean stellar age traced by the D(4000) index. For galaxies of lower masses, both gradients are, generally, steeper for intermediate values of D(4000) and flatter for low and high values of D(4000). Only the most massive galaxies do not show this correlation. We interpret this behaviour as an evolution of the metallicity gradients with the age of stellar population. Though the galaxies with a positive slope of the D(4000) radial gradient tend to have flatter O/H and N/O gradients, as compared to those with a negative D(4000) gradient. © ESO 2021., The work has been performed under the Project HPC-EUROPA3 (INFRAIA-2016-1-730897), with the support of the EC Research Innovation Action under the H2020 Programme; in particular, the authors gratefully acknowledge the support of the Instituto de Astrofísica de Andalucía, the computer resources and technical support provided by the Barcelona Supercomputing Center (BSC). I.A.Z., A.V.S. and M.S. acknowledge support by the National Academy of Sciences of Ukraine under the Research Laboratory Grant for young scientists No. 0120U100148. J.V.M., E.P.M. and S.D.P. acknowledge the support by projects “Estallidos7” PID2019-107408GB-C44 (Spanish Ministerio de Ciencia e Innovacion), the Junta de Andalucía for grant EXC/2011 FQM-7058 and the Spanish Science Ministry “Centro de Excelencia Severo Ochoa Program” under grant SEV-2017-0709. M.S. was partly sup ported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foun dation) Project-ID 138713538, SFB 881 (“The Milky Way System”) and by the Volkswagen Foundation under the Trilateral Partnerships grant No. 97778. M.S. acknowledges support by the Fellowship of the National Academy of Science of Ukraine for young scientists 2020-2022. S.D.P. is grateful to the Fonds de Recherche du Québec – Nature et Technologies. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foun dation, the U.S. Department of Energy Office of Science, and the Participat ing Institutions. SDSS-IV acknowledges support and resources from the Cen ter for High-Performance Computing at the University of Utah.

We perform spatially resolved stellar population analysis for a sample of 69 early-type galaxies (ETGs) from the CALIFA integral field spectroscopic survey, including 48 ellipticals and 21 S0's. We generate and quantitatively characterize profiles of light-weighted mean stellar age and metallicity within $\lesssim 2R_e$, as a function of radius and stellar-mass surface density $\mu_*$. We study in detail the dependence of profiles on galaxies' global properties, including velocity dispersion $\sigma_e$, stellar mass, morphology. ETGs are universally characterized by strong, negative metallicity gradients ($\sim -0.3\,\text{dex}$ per $R_e$) within $1\,R_e$, which flatten out moving towards larger radii. A quasi-universal local $\mu_*$-metallicity relation emerges, which displays a residual systematic dependence on $\sigma_e$, whereby higher $\sigma_e$ implies higher metallicity at fixed $\mu_*$. Age profiles are typically U-shaped, with minimum around $0.4\,R_e$, asymptotic increase to maximum ages beyond $\sim 1.5\,R_e$, and an increase towards the centre. The depth of the minimum and the central increase anti-correlate with $\sigma_e$. A possible qualitative interpretation of these observations is a two-phase scenario. In the first phase, dissipative collapse occurs in the inner $1\,R_e$, establishing a negative metallicity gradient. The competition between the outside-in quenching due to feedback-driven winds and some form of inside-out quenching, possibly caused by central AGN feedback or dynamical heating, determines the U-shaped age profiles. In the second phase, the accretion of ex-situ stars from quenched and low-metallicity satellites shapes the flatter stellar population profiles in the outer regions., Comment: Accepted version to appear in MNRAS. Improved discussion with respect to original submission and additional tests included

In the local universe, galaxies in clusters show different properties compared to more isolated systems. Understanding how this difference originates and whether it is already in place at high redshift is still a matter of debate. Thanks to uniquely deep optical spectra from the VANDELS survey, we investigate environmental effects on the stellar mass-metallicity relation (MZR) for a sample of ~1000 star-forming galaxies at 2, Comment: Accepted for publication in A&A ; 22 pages, 15 figures, 2 tables, and 1 Appendix

Chemical abundance determinations in Low-Ionization Nuclear Line Regions (LINERs) are especially complex and uncertain because the nature of the ionizing source of this kind of object is unknown. In this work, we study the oxygen abundance in relation to the hydrogen abundance (O/H) of the gas phase of the UGC4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies (MaNGA) survey was employed to derive the O/H abundance of the UGC4805 nucleus based on the extrapolation of the disk abundance gradient, on calibrations between O/H abundance and strong emission-lines for Active Galactic Nuclei (AGNs) as well as on photoionization models built with the Cloudy code, assuming gas accretion into a black hole (AGN) and post-Asymptotic Giant Branch (p-AGB) stars with different effective temperatures. We found that abundance gradient extrapolations, AGN calibrations, AGN and p-AGB photoionization models produce similar O/H values for the UGC4805 nucleus and similar ionization parameter values. The study demonstrated that the methods used to estimate the O/H abundance using nuclear emission-line ratios produce reliable results, which are in agreement with the O/H values obtained from the independent method of galactic metallicity gradient extrapolation. Finally, the results from the WHAN diagram combined with the fact that the high excitation level of the gas has to be maintained at kpc scales, we suggest that the main ionizing source of the UGC4805 nucleus probably has a stellar origin rather than an AGN., 17 pages, 13 figures

In the past, the cumulative metallicity distribution function (CMDF) turned out as a useful tool to constrain the accretion history of various components of the Milky Way. In this Letter, by means of analytical, leaky-box chemical evolution models (i.e. including both infall and galactic outflows) we study the CMDF of local star-forming galaxies that follow two fundamental empirical scaling relations, namely the mass-metallicity and main sequence relations. Our analysis shows that galactic winds, which are dominant mostly in low-mass systems, play a fundamental role in shaping this function and, in particular, in determining its steepness and curvature. We show that the CMDF of low-mass (M$_{\star}$/M$_{\odot} \le 10^{9.5}$) and high-mass (M$_{\star}$/M$_{\odot}$>10$^{10.5}$) galaxies deviate substantially from the results of a 'closed-box' model, as the evolution of the former (latter) systems is mostly dominated by outflows (infall). In the context of galactic downsizing, we show that downward-concave CMDFs (associated with systems with extremely small infall timescales and with very strong winds) are more frequent in low-mass galaxies, which include larger fractions of young systems and present more substantial deviations from equilibrium between gas accretion and reprocessing (either via star formation or winds)., Accepted for publication in Astronomy and Astrophysics Letters (A&A Letters), 6 pages, 4 figures

We use FIRE-2 simulations to examine 3-D variations of gas-phase elemental abundances of [O/H], [Fe/H], and [N/H] in 11 Milky Way (MW) and M31-mass galaxies across their formation histories at $z \leq 1.5$ ($t_{\rm lookback} \leq 9.4$ Gyr), motivated by characterizing the initial conditions of stars for chemical tagging. Gas within $1$ kpc of the disk midplane is vertically homogeneous to $\lesssim 0.008$ dex at all $z \leq 1.5$. We find negative radial gradients (metallicity decreases with galactocentric radius) at all times, which steepen over time from $\approx -0.01$ dex kpc$^{-1}$ at $z = 1$ ($t_{\rm lookback} = 7.8$ Gyr) to $\approx -0.03$ dex kpc$^{-1}$ at $z = 0$, and which broadly agree with observations of the MW, M31, and nearby MW/M31-mass galaxies. Azimuthal variations at fixed radius are typically $0.14$ dex at $z = 1$, reducing to $0.05$ dex at $z = 0$. Thus, over time radial gradients become steeper while azimuthal variations become weaker (more homogeneous). As a result, azimuthal variations were larger than radial variations at $z \gtrsim 0.8$ ($t_{\rm lookback} \gtrsim 6.9$ Gyr). Furthermore, elemental abundances are measurably homogeneous (to $\lesssim 0.05$ dex) across a radial range of $\Delta R \approx 3.5$ kpc at $z \gtrsim 1$ and $\Delta R \approx 1.7$ kpc at $z = 0$. We also measure full distributions of elemental abundances, finding typically negatively skewed normal distributions at $z \gtrsim 1$ that evolve to typically Gaussian distributions by $z = 0$. Our results on gas abundances inform the initial conditions for stars, including the spatial and temporal scales for applying chemical tagging to understand stellar birth in the MW., Comment: 24 pages, 17 figures, Accepted for publication in MNRAS

Context. Differential enrichment between α and Fe-peak elements is known to be strongly connected with the shape of the star formation history (SFH), the star formation efficiency (SFE), the inflow and outflow of material, and even the shape of the initial mass function (IMF). However, beyond the Local Group, detailed explorations are mostly limited to early-type galaxies due to the lack of a good proxy for [α/Fe] in late-type ones, limiting our understanding of the chemical enrichment process. Aims. We intent to extend the explorations of [α/Fe] to late-type galaxies in order to understand the details of the differential enrichment process. Methods. We compare the gas-phase oxygen abundance with the luminosity-weighted stellar metallicity in an extensive catalogue of 25 000 H II regions extracted from the Calar Alto Legacy Integral Field Area (CALIFA) survey, an exploration that uses the integral-field spectroscopy of 900 galaxies and covers a wide range of masses and morphologies. This way, we define [O/Fe] as the ratio between both parameters, proposing it as an indirect proxy of the [α/Fe] ratio. This procedure is completely different from the one adopted to estimate [α/Fe] from high-resolution spectroscopic data for stars in our Galaxy. 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 for the [α/Fe] ratio and (ii) its absolute scale depends on the stellar mass and the morphology. We reproduce both patterns using two different chemical evolution models, considering that galaxies with different stellar masses and morphologies present either different SFHs, SFEs, and inflow and outflow rates or a different maximum stellar mass cut for the IMF. We will explore the differential chemical enrichment using this new proxy galaxy by galaxy and region by region in further studies. © ESO 2021., SFS and J.B.-B. thanks CONACYT for grants CB-285080 and FC-2016-01-1916, and PAPIIT-DGAPA-IN100519 (UNAM) project. C.M. thanks UNAM/PAPIIT-IN101220. J.B.-B. thanks IA-100420 (DGAPA-PAPIIT, UNAM) and CONACYT grant CF19-39578 support. L.G. thanks M.S.-Curie grant 839090. R.G.B. acknowledges support from grants SEV-2017-0709 and P18-FRJ-2595. This study uses data provided by the Calar Alto Legacy Integral Field Area (CALIFA) survey (http://califa.caha.es/), observed at the Calar Alto Obsevatory.

We present an analysis of the chemical abundance properties of $\approx$650 star-forming galaxies at $z \approx0.6-1.8$. Using integral-field observations from the $K$-band Multi-Object Spectrograph (KMOS), we quantify the [NII]/H$\alpha$ emission-line ratio, a proxy for the gas-phase Oxygen abundance within the interstellar medium. We define the stellar mass-metallicity relation at $z \approx0.6-1.0$ and $z \approx1.2-1.8$ and analyse the correlation between the scatter in the relation and fundamental galaxy properties (e.g. H$\alpha$ star-formation rate, H$\alpha$ specific star-formation rate, rotation dominance, stellar continuum half-light radius and Hubble-type morphology). We find that for a given stellar mass, more highly star-forming, larger and irregular galaxies have lower gas-phase metallicities, which may be attributable to their lower surface mass densities and the higher gas fractions of irregular systems. We measure the radial dependence of gas-phase metallicity in the galaxies, establishing a median, beam smearing-corrected, metallicity gradient of $ \Delta Z/ \Delta R=0.002 \pm0.004$ dex kpc$^{-1}$, indicating on average there is no significant dependence on radius. The metallicity gradient of a galaxy is independent of its rest-frame optical morphology, whilst correlating with its stellar mass and specific star-formation rate, in agreement with an inside-out model of galaxy evolution, as well as its rotation dominance. We quantify the evolution of metallicity gradients, comparing the distribution of $\Delta Z/ \Delta R$ in our sample with numerical simulations and observations at $z \approx0-3$. Galaxies in our sample exhibit flatter metallicity gradients than local star-forming galaxies, in agreement with numerical models in which stellar feedback plays a crucial role redistributing metals., Comment: Accepted for publication in MNRAS. Comments welcome. 20 pages, 12 figures. Revised version with updated introduction and FMR evolution following comments

In this work, we study the evolution of the mass-metallicity relations (MZRs) as predicted by the GAlaxy Evolution and Assembly (GAEA) semi-analytic model. We contrast these predictions with recent results from the VANDELS survey, that allows us to expand the accessible redshift range for the stellar MZR up to $z\sim3.5$. We complement our study by considering the evolution of the gas-phase MZR in the same redshift range. We show that GAEA is able to reproduce the observed evolution of the $z, 12 pages, 8 figures, MNRAS accepted, replaced to match the published version

We are grateful for the support of the Consejo Nacional de Ciencia y Tecnolog ' ia (CONACYT) grants CB-285080 and FC-2016-01-1916, and funding from the Universidad Nacional Aut ' onoma de Mexico (UNAM) project PAPIIT-DGAPA-IN100519. LG was funded by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 839090. This work has been partially supported by the Spanish grant PGC2018-095317-B-C21 within the European Funds for Regional Development (FEDER). We thank P. Tissera, N. Vale-Asari, and J. E. Beckman for their many helpful comments and discussion on the content of the paper., We apply fossil record techniques to the CALIFA sample to study how galaxies in the Local Universe have evolved in terms of their chemical content.We show how the stellar metallicity and the mass–metallicity relation (MZR) evolve through time for the galaxies in our sample and how this evolution varies when we divide them based on their mass, morphology, and star-forming status. We also check the impact of measuring the metallicity at the centre or the outskirts. We find the expected results that the most massive galaxies were enriched more quickly, and that theMZR was steeper at higher redshifts. However, once we separate the galaxies into morphology bins this behaviour is less clear, which suggests that morphology is a primary factor in determining how quickly a galaxy becomes enriched, but with mass determining the final enrichment.We also find that star-forming galaxies (SFGs) appear to be asymptotic in their chemical evolution; that is, the metallicity of SFGs of any mass is very similar at recent times unlike several Gyr ago., Consejo Nacional de Ciencia y Tecnologia (CONACyT) CB-285080 FC-2016-01-1916, Universidad Nacional Autonoma de Mexico PAPIIT-DGAPA-IN100519, European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant 839090, Spanish grant within the European Funds for Regional Development (FEDER) PGC2018-095317-B-C21

Nuclear Activity in Galaxies Across Cosmic Time, Proceedings of the conference held 7-11 October 2019 in Addis Ababa, Ethiopia. Edited by Mirjana Pović et al. Proceedings of the International Astronomical Union, Volume 356, pp. 61-65, We present a new tool for the analysis of the optical emission lines of the gas in the Narrow Line Region (NLR) around Active Galactic Nuclei (AGNs). This new tool can be used in large samples of objects in a consistent way using different sets of optical emission-lines taking into the account possible variations from the O/H - N/O relation. The code compares certain observed emission-line ratios with the predictions from a large grid of photoionization models calculated under the most usual conditions in the NLR of AGNs to calculate the total oxygen abundance, nitrogen-to-oxygen ratio and ionization parameter. We applied our method to a sample of Seyfert 2 galaxies with optical emission-line fluxes from the literature. Our results confirm the high metallicity of the objects of the sample and provide consistent values with the direct method. The usage of models to calculate precise ICFs is mandatory when only optical emission lines are available to derive chemical abundances using the direct method in NLRs of AGN., Financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709)

Context. Extragalactic planetary nebulae (PNe) are useful distance indicators and are often used to trace the dark-matter content in external galaxies. At the same time, PNe can also be used as probes of their host galaxy stellar populations and to help understand the later stages of stellar evolution. Previous works have indicated that a specific number of PNe per stellar luminosity can vary across different galaxies and as a function of stellar-population properties, for instance increasing with decreasing stellar metallicity. Aims. In this study we further explore the importance of stellar metallicity in driving the properties of the PNe population in early-type galaxies, using three edge-on galaxies in the Fornax cluster offering a clear view into their predominantly metal-rich and metal-poor regions near the equatorial plane or both below and above it, respectively. Methods. Using very large telescope-multi unit spectroscopic explorer (VLT-MUSE) integral-field observations and dedicated PNe detection procedures, we constructed the PNe luminosity function and computed the luminosity-specific number of PNe α in both in- and off-plane regions of our edge-on systems. Results. Comparing these α values with metallicity measurements also based on the same MUSE data, we find no evidence for an increase in the specific abundance of PNe when transitioning between metal-rich and metal-poor regions. Conclusions. Our analysis highlights the importance of ensuring spatial consistency to avoid misleading results when investigating the link between PNe and their parent stellar populations, and suggest that in passively evolving systems variations in the specific number of PNe may pertain to rather extreme metallicity regimes found either in the innermost or outermost regions of galaxies.

Utilising optical and near-infrared broadband photometry covering $> 5\,{\rm deg}^2$ in two of the most well-studied extragalactic legacy fields (COSMOS and XMM-LSS), we measure the galaxy stellar mass function (GSMF) between $0.1 < z < 2.0$. We explore in detail the effect of two source extraction methods (SExtractor and ProFound) in addition to the inclusion/exclusion of Spitzer IRAC 3.6 and 4.5$��$m photometry when measuring the GSMF. We find that including IRAC data reduces the number of massive ($\log_{10}(M/M_\odot) > 11.25$) galaxies found due to improved photometric redshift accuracy, but has little effect on the more numerous lower-mass galaxies. We fit the resultant GSMFs with double Schechter functions down to $\log_{10}(M/M_\odot)$ = 7.75 (9.75) at z = 0.1 (2.0) and find that the choice of source extraction software has no significant effect on the derived best-fit parameters. However, the choice of methodology used to correct for the Eddington bias has a larger impact on the high-mass end of the GSMF, which can partly explain the spread in derived $M^*$ values from previous studies. Using an empirical correction to model the intrinsic GSMF, we find evidence for an evolving characteristic stellar mass with $��\log_{10}(M^*/M_\odot)/��z$ = $-0.16\pm0.05 \, (-0.11\pm0.05)$, when using SExtractor (ProFound). We argue that with widely quenched star formation rates in massive galaxies at low redshift ($z, 19 pages, 7 figures, 8 tables, submitted to MNRAS. Updated to accepted version from journal

Studies of gas-phase radial metallicity profiles in spirals published in the last decade have diminished the importance of galactic bars as agents that mix and flatten the profiles, contradicting results obtained in the 1990s. We have collected a large sample of 2831 published H ii region emission-line fluxes in 51 nearby galaxies, including objects both with and without the presence of a bar, with the aim of revisiting the issue of whether bars affect the radial metal distribution in spirals. In this first paper of a series of two, we present the galaxy and the H ii region samples. The methodology is homogeneous for the whole data sample and includes the derivation of H ii region chemical abundances, structural parameters of bars and discs, galactocentric distances, and radial abundance profiles. We have obtained O/H and N/O abundance ratios from the Te-based (direct) method for a subsample of 610 regions, and from a variety of strong-line methods for the whole H ii region sample. The strong-line methods have been evaluated in relation to the Te-based one from both a comparison of the derived O/H and N/O abundances for individual H ii regions and a comparison of the abundance gradients derived from both methodologies. The median value and the standard deviation of the gradient distributions depend on the abundance method, and those based on the O3N2 indicator tend to flatten the steepest profiles, reducing the range of observed gradients. A detailed analysis and discussion of the derived O/H and N/O radial abundance gradients and y-intercepts for barred and unbarred galaxies is presented in the companion Paper II. The whole H ii region catalogue including emission-line fluxes, positions, and derived abundances is made publicly available on the CDS VizieR facility, together with the radial abundance gradients for all galaxies. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society., We kindly thank all the authors who have previously published the HII data that form the basis for this work, and Simon Verley for his invaluable help with PYTHON. We also acknowledge the anonymous referee for his/her suggestions that improved the clarity of themanuscript. We thankCalar Alto Observatory for the allocation of director's discretionary time to this programme. AZ, EF, and IP acknowledge support from the Spanish 'Ministerio de Economia, Industria y Competitividad' (MINECO) and from the European Regional Development Fund (FEDER) via grant AYA2017-84897P, and from the Junta de Andalucia (Spain) local government through the FQM-108 project. EPM acknowledges funding from the Spanish MINECO project Estallidos 6 AYA2016-79724-C4 and from the Severo Ochoa excellence programme (SEV-20170709). This research made use of Astropy,15 a community-developed core PYTHON package for Astronomy (Astropy Collaboration 2013; Astropy Collaboration 2018); Matplotlib (Hunter 2007); APLpy, an open-source plotting package for PYTHON (Robitaille & Bressert 2012); NumPy (van der Walt et al. 2011) and seaborn (DOI: 10.5281/zenodo.1313201). We acknowledge the usage of the HyperLeda database (http://leda.univ-lyon1.fr).This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France (DOI: 10.26093/cds/vizier). The original description of the VizieR service was published in 2000, A&AS 143, 23. This research has made use of the NASA/IPAC Extragalactic Database (NED) that is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Based on SITELLE spectroscopy data, we studied the ionised gas emission for the 175 H alpha emission regions in the Stephan's Quintet (SQ). In this paper we perform a detailed analysis of the star formation rate (SFR), oxygen abundance, and nitrogen-to-oxygen abundance ratio (N/O) of the SQ regions, with the intention of exploring the provenance and evolution of this complex structure. According to the BPT diagram, we found 91 HII, 17 composite, and 7 active galactic nucleus-like regions in SQ. Several regions are compatible with fast shocks models without a precursor for solar metallicity and low density (n = 0.1 cm(-3)), with velocities in the range of 175-300 km s(-1). We derived the total SFR in SQ (log(SFR/M-circle dot yr(-1)=0.496)). Twenty-eight percent of the total SFR in SQ comes from starburst A, while 9% is in starburst B, and 45% comes from the regions with a radial velocity lower than 6160 km s(-1). For this reason, we assume that the material prior to the collision with the new intruder does not show a high SFR, and therefore SQ was apparently quenched. When considering the integrated SFR for the whole SQ and the new intruder, we found that both zones have a SFR consistent with those obtained in the SDSS star-forming galaxies. At least two chemically different gas components cohabit in SQ where, on average, the regions with high radial velocities (v> 6160 km s(-1)) have lower values of oxygen abundance and N/O than those with low radial velocities (v, We thank the anonymous referee for very constructive comments and suggestions that have helped us to improve this manuscript. Based on observations obtained with SITELLE, a joint project of Universite Laval, ABB, Universite de Montreal, and the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. The authors wish to recognise and acknowledge the very significant cultural role that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most grateful to have the opportunity to conduct observations from this mountain. SDP, JVM, JIP, CK, EPM, and AAP acknowledge financial support from the Spanish Ministerio de Economia y Competitividad under grants AYA2013-47742-C4-1-P and AYA2016-79724-C4-4-P, from Junta de Andalucia Excellence Project PEX2011-FQM-7058, and also acknowledge support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709). LD is grateful to the Natural Sciences and Engineering Research Council of Canada, the Fonds de Recherche du Quebec, and the Canada Foundation for Innovation for funding. This research made use of Python (http://www.python.org) and IPython; APLpy Hunter 2007), a suite of open-source Python modules that provides a framework for creating scientific plots. This research made use of Astropy, a community-developed core Python package for Astronomy

We present maps for the electron temperature in the inner kpc of three luminous Seyfert galaxies: Mrk 79, Mrk 348, and Mrk 607 obtained from Gemini Multi-Object Spectrograph-integral field unit observations at spatial resolutions of ∼110–280 pc. We study the distributions of electron temperature in active galaxies and find temperatures varying in the range from ∼8000 to ≳30000K. Shocks due to gas outflows play an important role in the observed temperature distributions of Mrk 79 and Mrk 348, while standard photoionization models reproduce the derived temperature values for Mrk 607. In Mrk 79 and Mrk 348, we find direct evidence for shock ionization with overall orientation orthogonal to the ionization axis, where shocks can be easily observed as the active galactic nuclei radiation field is shielded by the nuclear dusty torus. This also indicates that even when the ionization cones are narrow, the shocks can be much wider angle. © 2020 The Author(s)., This study was financed in part by CNPq, FAPERGS, and FAPESP. AF acknowledges the support from grant PRIN MIUR2017-20173ML3WW−001. EPM acknowledges financial support from the project ‘Estallidos6’ AYA2016-79724-C4. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NationalScience Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Context. We present a large homogeneous set of stellar parameters and abundances across a broad range of metallicities, involving 13 classical dwarf spheroidal (dSph) and ultra-faint dSph (UFD) galaxies. In total, this study includes 380 stars in Fornax, Sagittarius, Sculptor, Sextans, Carina, Ursa Minor, Draco, Reticulum II, Bootes I, Ursa Major II, Leo I, Segue I, and Triangulum II. This sample represents the largest, homogeneous, high-resolution study of dSph galaxies to date. Aims. With our homogeneously derived catalog, we are able to search for similar and deviating trends across different galaxies. We investigate the mass dependence of the individual systems on the production of α-elements, but also try to shed light on the long-standing puzzle of the dominant production site of r-process elements. Methods. We used data from the Keck observatory archive and the ESO reduced archive to reanalyze stars from these 13 classical dSph and UFD galaxies. We automatized the step of obtaining stellar parameters, but ran a full spectrum synthesis (1D, local thermal equilibrium) to derive all abundances except for iron to which we applied nonlocal thermodynamic equilibrium corrections where possible. Results. The homogenized set of abundances yielded the unique possibility of deriving a relation between the onset of type Ia supernovae and the stellar mass of the galaxy. Furthermore, we derived a formula to estimate the evolution of α-elements. This reveals a universal relation of these systems across a large range in mass. Finally, we show that between stellar masses of 2.1 × 107 M⊙ and 2.9 × 105 M⊙, there is no dependence of the production of heavy r-process elements on the stellar mass of the galaxy. Conclusions. Placing all abundances consistently on the same scale is crucial to answering questions about the chemical history of galaxies. By homogeneously analyzing Ba and Eu in the 13 systems, we have traced the onset of the s-process and found it to increase with metallicity as a function of the galaxy’s stellar mass. Moreover, the r-process material correlates with the α-elements indicating some coproduction of these, which in turn would point toward rare core-collapse supernovae rather than binary neutron star mergers as a host for the r-process at low [Fe/H] in the investigated dSph systems.

In hydrodynamic simulations, prevailing subgrid chemical-evolution models often use a single, "IMF-averaged" supernova yield, ignoring variations in elemental abundance ratios (particularly [$\alpha$/Fe]) in the ejecta of higher- and lower-mass supernova progenitors within a stellar population. To understand the impact of this simplification and understand the impact of more explicit models, we run FIRE simulations of a dwarf galaxy $(M_\star($z = 0$) \sim 10^6 M_\odot)$ using nucleosynthetic yields from the NuGrid database that depend on the stellar progenitor mass and metallicity. While NuGrid exhibits lower aggregate $\alpha$-element production than default-FIRE yields, we find that its explicit mass dependence substantially widens the intrinsic scatter in the simulated [Fe/H]-[$\alpha$/Fe] -- a phenomenon potentially visible in recent observations of dwarf galaxies., Comment: MNRAS accepted. 9 pages; 8 figures. Comments and questions welcome

We investigate the ionized gas kinematics, physical properties, and chemical abundances of Sloan Digital Sky Survey J142947, a Green Pea galaxy at redshift z∼ 0.17 with strong, double-peak Ly α emission and indirect evidence of Lyman continuum (LyC) leakage. Using high-dispersion spectroscopy, we perform a multicomponent analysis of emission-line profiles. Our model consistently fits all lines as a narrow component with intrinsic velocity dispersion σ ∼ 40 km s-1, and two broader blue-shifted components with σ ∼ 90 and ∼ 250 km s-1. We find electron densities and temperatures, ionization conditions, and direct O/H and N/O abundances for each component. A highly ionized, metal-poor, young and compact starburst dominates narrow emission, showing evidence of hard radiation fields and elevated N/O. The blue-shifted broader components are consistent with highly turbulent, possibly clumpy ionized gas at the base of a strong photoionized outflow, which accounts for ≳50 per cent of the integrated emission-line fluxes. The outflow is dense and metal-enriched compared to the H ii regions, with expansion velocities larger than those obtained from UV interstellar absorption lines under standard assumptions. Some of these metals may be able to escape, with outflows loading factors comparable to those found in high-z galaxies of similar SFR/Area. Our findings depict a two-stage starburst picture; hard radiation fields from young star clusters illuminate a turbulent and clumpy ISM that has been eroded by SNe feedback. Whilst UV data suggest an extended Ly α halo with high average H i column density, LyC photons could only escape from SDSS J142947 through low H i density channels or filaments in the ISM approaching density-bounded conditions, traced by outflowing gas. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, This study is based on observations made with the William Hersche Telescope operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrof´ısica de Canarias. We thank the anonymous referee for her/his helpful report. We would like to express our gratitude to David and Bridget Jacob for their support through the Astronomy Summer Internship Programme at University of Cambridge. Their generous funding made this project possible. LH thanks the hospitality of the Kavli Institute for Cosmology Cambridge during her Internship and subsequent visits. We would also like to thank Dr. A. Saintonge for her guidance during the compiliation of this paper. RA is also grateful to Roberto Maiolino and Polychronis Papaderos for useful discussions on this project. RA thanks the support of DIDULS (project 030503072341) and the ERC Advance Grant ‘QUENCH’. JVM and EPM acknowledge the support by the Spanish MINECO project Estallidos 6 AYA2016- 79724-C4, and by the Spanish Science Ministry ‘Centro de Excelencia Severo Ochoa Program’ under grant SEV-2017-0709. Supported by the international Gemini Observatory, a program of NSF’s OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership of Argentina, Brazil, Canada, Chile, the Republic of Korea, and the United States of America.

We compare the oxygen abundance (O/H) of the narrow-line regions (NLRs) of Seyfert 2 AGNs obtained through strong-line methods and from direct measurements of the electron temperature (Te-method). The aim of this study is to explore the effects of the use of distinct methods on the range of metallicity and on the mass-metallicity relation of active galactic nuclei (AGNs) at low redshifts (z, We thank the referee for helping to improve this paper with her/his constructive feedback. OLD and ACK thank FAPESP and CNPq for the financial support. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute forAstronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. We also thank to Max-Planck-Institute forAstrophysics and John Hopkins University for Physical properties for galaxies andAGNs in the SDSS: Data catalogues from SDSS studies atMPA/JHU. This research hasmade use of the VizieR catalogue access tool, CDS, Strasbourg, France (doi: 10.26093/cds/vizier). The original description of the VizieR service was published in AAS, 143, 23. This work has also made use of the computing facilities of the Laboratory of Astroinformatics (IAG/USP, NAT/Unicsul), whose purchase was made possible by the Brazilian agency FAPESP (grant no. 2009/54006-4) and the INCT-A.

In their evolution, star-forming galaxies are known to follow scaling relations between some fundamental physical quantities, such as the mass-metallicity and the main sequence relations. We aim at studying the evolution of galaxies that, at a given redshift, lie simultaneously on the mass-metallicity and main sequence relations (MZR, MSR). To this aim, we use the analytical, 'leaky-box' chemical evolution model of Spitoni et al. (2017), in which galaxy evolution is described by an infall timescale $\tau$ and a wind efficiency $\lambda$. We provide a detailed analysis of the temporal evolution of galactic metallicity, stellar mass, mass-weighted age and gas fraction. The evolution of the galaxies lying on the MZR and MSR at $z\sim0.1$ suggests that the average infall time-scale in two different bins of stellar masses ($M_{\star}10^{10} M_{\odot}$) decreases with decreasing redshift. This means that at each redshift, only the youngest galaxies can be assembled on the shortest timescales and still belong to the star-forming MSR. In the lowest mass bin, a decrease of the median $\tau$ is accompanied by an increase of the median $\lambda$ value. This implies that systems which have formed at more recent times will need to eject a larger amount of mass to keep their metallicity at low values. Another important result is that galactic downsizing, as traced by the age-mass relation, is naturally recovered by imposing that local galaxies lie on both the MZR and MSR. Finally, we study the evolution of the hosts of C$_{\rm IV}$ -selected AGN, which at $z\sim 2$ follow a flat MZR, as found by Mignoli et al. (2019). If we impose that these systems lie on the MSR, at lower redshifts we find an 'inverted' MZR, meaning that some additional processes must be at play in their evolution., Comment: Accepted for publication in Astronomy and Astrophysics (A&A), 20 pages, 26 figures

We build detailed composite models of photoionization and shock ionization based on the suma code to reproduce emission lines emitted from the Narrow Line Regions (NLR) of Seyfert 2 nuclei. The aim of this work is to investigate diagram active galactic nucleus (AGN) positions according to shock parameters, shock effects on the gas temperature and ionization structures and derive a semi-empirical abundance calibration based on emission-line ratios little sensitive to the shock presence. The models were used to reproduce optical (3000 < λ(Å) < 7000) emission line intensities of 244 local ($z \: \lesssim \: 0.4$) Seyfert 2s, whose observational data were selected from Sloan Digital Sky Survey DR7. Our models suggest that shocks in Seyfert 2 nuclei have velocities in the range of 50-300 $\rm km \: s^{-1}$ and imply a narrower metallicity range ($0.6 \: \lesssim \: (Z/Z_{\odot }) \: \lesssim \: 1.6$) than those derived using pure photoionization models. Our results indicate that shock velocity in AGNs cannot be estimated using standard optical line ratio diagrams, based on integrated spectra. Our models predict a different temperature structure and $\rm O^{+}$/O and $\rm O^{2+}$/O fractional abundances throughout the NLR clouds than those derived from pure photoionization models, mainly in shock-dominated objects. This suggests that, in order to minimize the shock effects, the combination of emission-lines emitted by ions with similar intermediate ionization potential could be good metallicity indicators. Finally, we derive two calibrations between the N/O abundance ratio and the N2O2 = log([N ii]λ6584/[O ii]λ3727) and N2 = log([N ii]λ6584/H α) indexes which agree with that derived from pure photoionization models. © 2020 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society, We are grateful to the referee for his/her dedicated work in reviewing our paper. OLD and ACK are grateful to Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) and Conselho Nacional de Desenvolvimento Cient ' ifico e Tecnologico (CNPq). RAR thanks partial financial support from Fundacao de Amparo a Pesquisa do Estado do Rio Grande do Sul (17/2551-0001144-9 and 16/25510000251-7) and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (302280/2019-7). MVC and GFH are grateful to Consejo Nacional de Investigaciones Cient ' ificas y T ' ecnicas (CONICET)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We present a semi-empirical calibration between the metallicity (Z) of Seyfert 2 active galactic nuclei and the N2 = log([N HP.6584/11 cy) emission-line intensity ratio. This calibration was derived through the [0 m]..5007/[0 u[),3727 versus N2 diagram containing observational data and photoionization model results obtained with the CLOUDY code. The observational sample consists of 463 confirmed Seyfert 2 nuclei (redshift z < 0.4) taken from the Sloan Digital Sky Survey DR7 data set. The obtained Z N2 relation is valid for the range 0.3 r< ( Z/Zo) 2.0 that corresponds to 0.7 < (N2) < 0.6. The effects of varying the ionization parameter (U), electron density and the slope of the spectral energy distribution on the Z estimations are of the order of the uncertainty produced by the error measurements of N2. This result indicates the large reliability of our Z N2 calibration. A relation between U and the IOutj/[OIII line ratio, almost independent of other nebular parameter, was obtained., This work is partially supported by the Brazilian agencies FAPESP, CAPES, and CNPq. EPM acknowledges support from the Spanish MINECO project Estallidos 6 AYA2016-79724-C4 and by the Spanish Science Ministry Centro de Excelencia Severo Ochoa Program under grant no. SEV-2017-0709.

The trends of chemical abundances and abundance ratios observed in stars of different ages, kinematics, and metallicities bear the imprints of several physical processes that concur to shape the host galaxy properties. By inspecting these trends, we get precious information on stellar nucleosynthesis, the stellar mass spectrum, the timescale of structure formation, the efficiency of star formation, as well as any inward or outward flows of gas. In this paper, we analyse recent determinations of carbon-to-iron and carbon-to-oxygen abundance ratios in different environments (the Milky Way and elliptical galaxies) using our latest chemical evolution models that implement up-to-date stellar yields and rely on the tight constraints provided by asteroseismic stellar ages (whenever available). A scenario where most carbon is produced by rotating massive stars, with yields largely dependent on the metallicity of the parent proto-star clouds, allows us to fit simultaneously the high-quality data available for the local Galactic components (thick and thin discs) and for microlensed dwarf stars in the Galactic bulge, as well as the abundance ratios inferred for massive elliptical galaxies. Yet, more efforts are needed from both observers and theoreticians in order to base these conclusions on firmer grounds., Comment: 10 pages, 8 figures, 1 table, accepted for publication in A&A

We present a new set of surface brightness fluctuation (SBF) spectra computed with the E-MILES stellar population synthesis models. The model SBF spectra cover the range λλ1680–50 000 at moderately high resolution, all based on extensive empirical stellar libraries. The models span the metallicity range −2.3 ≤ [M/H] ≤ +0.26 for a suite of intial mass function types with varying slopes. These predictions can complement and aid fluctuation magnitude studies, permitting a first-order approximation by applying filter responses to the SBF spectra to obtain spectroscopic SBF magnitudes. We provide a recipe for obtaining the latter and discuss their uncertainties and limitations. We compare our spectroscopic SBF magnitudes to photometric data of a sample of early-type galaxies. We also show that the SBF spectra can be very useful for constraining relevant stellar population parameters. We find small (, With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

The spatial distribution of metals reflects, and can be used to constrain, the processes of chemical enrichment and mixing. Using PHANGS-MUSE optical integral field spectroscopy, we measure the gas phase oxygen abundances (metallicities) across 7,138 HII regions in a sample of eight nearby disc galaxies. In Paper I (Kreckel et al. 2019) we measure and report linear radial gradients in the metallicities of each galaxy, and qualitatively searched for azimuthal abundance variations. Here, we examine the two-dimensional variation in abundances once the radial gradient is subtracted, Delta(O/H), in order to quantify the homogeneity of the metal distribution and to measure the mixing scale over which HII region metallicities are correlated. We observe low (0.03--0.05 dex) scatter in Delta(O/H) globally in all galaxies, with significantly lower (0.02--0.03 dex) scatter on small (, 17 pages, 14 figures. Accepted for publication in MNRAS

Using new Very Large Telescope (VLT)/XShooter spectral observations we analyse the physical properties of five z similar to 0.3-0.4 confirmed Lyman continuum (LyC) leakers. Strong resonant MgII lambda lambda 2796, 2803 angstrom emission lines (I(lambda lambda 2796, 2803)/I(H beta) similar or equal to 10-38 per cent) and non-resonant Fe II* lambda lambda 2612, 2626 angstrom emission lines are observed in spectra of five and three galaxies, respectively. We find high electron densities N-e similar to 400 cm(-3), significantly higher than in typical low-z, but comparable to those measured in z similar to 2-3 star-forming galaxies (SFGs). The galaxies have a mean value of log N/O = -1.16, close to the maximum values found for SFGs in the metallicity range of 12 + logO/H similar or equal to 7.7-8.1. All 11 low-z LyC emitting galaxies found by Izotov et al., including the ones considered in this study, are characterized by high equivalent width (EW) (H beta) similar to 200-400 angstrom, high ionization parameter (log(U) = -2.5 to -1.7), high average ionizing photon production efficiency xi = 10(25.54) Hz erg(-1), and hard ionizing radiation. On the Baldwin-Phillips-Terlevich (BPT) diagram we find the same offset of our leakers from low-z main-sequence SFGs as that for local analogues of Lyman-break galaxies (LBGs) and extreme SFGs at z similar to 2-3. We confirm the effectiveness of the He I emission lines diagnostics proposed by Izotov et al. in searching for LyC leaker candidates and find that their intensity ratios correspond to those in a median with low neutral hydrogen column density N(H I) = 10(17)-5 x 10(17) cm(-2) that permit leakage of LyC radiation, likely due to their density-bounded HII regions. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society, NGG and YII acknowledge support from the National Academy of Sciences of Ukraine by its priority project `Fundamental properties of the matter in the relativistic collisions of nuclei and in the early Universe' (No. 0120U100935). JMV, EP-M, JI-P, and CK acknowledge financial support from the StateAgency for Research of the Spanish MCIU through the 'Center of Excellence Severo Ochoa' award to the Instituto de Astrofisica de Andaluc ' ia (SEV-2017-0709) and project A2016-79724-C4-4-P. RA acknowledges support from FONDECYT Regular 1202007. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org.SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

We investigate star-galaxy classification for astronomical surveys in the context of four methods enabling the interpretation of black-box machine learning systems. The first is outputting and exploring the decision boundaries as given by decision tree based methods, which enables the visualization of the classification categories. Secondly, we investigate how the Mutual Information based Transductive Feature Selection (MINT) algorithm can be used to perform feature pre-selection. If one would like to provide only a small number of input features to a machine learning classification algorithm, feature pre-selection provides a method to determine which of the many possible input properties should be selected. Third is the use of the tree-interpreter package to enable popular decision tree based ensemble methods to be opened, visualized, and understood. This is done by additional analysis of the tree based model, determining not only which features are important to the model, but how important a feature is for a particular classification given its value. Lastly, we use decision boundaries from the model to revise an already existing method of classification, essentially asking the tree based method where decision boundaries are best placed and defining a new classification method. We showcase these techniques by applying them to the problem of star-galaxy separation using data from the Sloan Digital Sky Survey (hereafter SDSS). We use the output of MINT and the ensemble methods to demonstrate how more complex decision boundaries improve star-galaxy classification accuracy over the standard SDSS frames approach (reducing misclassifications by up to $\approx33\%$). We then show how tree-interpreter can be used to explore how relevant each photometric feature is when making a classification on an object by object basis., Comment: 12 pages, 8 figures, 8 tables

Using a representative sample of 14 star-forming dwarf galaxies in the local Universe, we show the existence of a spaxel-to-spaxel anticorrelation between the index N2≡log([N II]λ6583/Hα) and the Hα flux. These two quantities are commonly employed as proxies for gas-phase metallicity and star formation rate (SFR), respectively. Thus, the observed N2 to Hα relation may reflect the existence of an anticorrelation between the metallicity of the gas forming stars and the SFR it induces. Such an anticorrelation is to be expected if variable external metal-poor gas fuels the star-formation process. Alternatively, it can result from the contamination of the star-forming gas by stellar winds and SNe, provided that intense outflows drive most of the metals out of the star-forming regions. We also explore the possibility that the observed anticorrelation is due to variations in the physical conditions of the emitting gas, other than metallicity. Using alternative methods to compute metallicity, as well as previous observations of HII regions and photoionization models, we conclude that this possibility is unlikely. The radial gradient of metallicity characterizing disc galaxies does not produce the correlation either.© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society., We thank Sebastian Sanchez for providing some of the data used in Section 4.2, Enrique Perez-Montero for help with the use of HIIC, and Matteo Miluzio for discussions and support during the early stages of the analysis. We also thank an anonymous referee whose comments help us improving the reliability of our argumentation. MF gratefully acknowledges the financial support of the Fundacao para a Ciencia e Tecnologia (FCT - Portugal), through the research grant SFRH/BPD/107801/2015. This work has been partly funded by the Spanish Ministry of Economy and Competitiveness, projects Estallidos AYA2013-47742-C04-02-P and AYA2016-79724-C4-2-P, as well as AYA2014-58861-C3-1-P.