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Abundances of light elements in dwarf stars of different ages are important constraints for stellar yields, Galactic chemical evolution and exoplanet chemical composition studies. We have measured C and N abundances and $^{12}$C/$^{13}$C ratios for a sample of 63 solar twins spanning a wide range in age, based on spectral synthesis of a comprehensive list of CH\,A-X and CN\,B-X features using HARPS spectra. The analysis of 55 thin disc solar twins confirms the dependences of [C/Fe] and [N/Fe] on [Fe/H]. [N/Fe] is investigated as a function of [Fe/H] and age for the first time for these stars. Our derived correlation [C/Fe]-age agrees with works for solar-type stars and solar twins, but the [N/Fe]-age correlation does not. The relations [C,N/Fe]-[Fe/H] and [C,N/Fe]-age for the solar twins lay under-solar. $^{12}$C/$^{13}$C is found correlated with [Fe/H] and seems to have decreased along the evolution of the local thin disc. Predictions from chemical evolution models for the solar vicinity corroborate the relations [C,N/Fe]-[Fe/H], $^{12}$C/$^{13}$C-age and [N/O]-[O/H], but do not for the $^{12}$C/$^{13}$C-[Fe/H] and [C/O]-[O/H] relations. The N/O ratio in the Sun is placed at the high end of the homogeneous distribution of solar twins, which suggests uniformity in the N-O budget for the formation of icy planetesimals, watery super-earths and giant planets. C and N had different nucleosynthetic origins along the thin disc evolution, as shown by the relations of [C/N], [C/O] and [N/O] against [O/H] and age. [C/N] and [C/O] are particularly observed increasing in time for solar twins younger than the Sun., Comment: Accepted for publication in MNRAS. The paper covers 20 pages, having 8 figures and 10 tables

In modern models and simulations of galactic evolution, the star formation in massive galaxies is regulated by an ad hoc active galactic nuclei (AGN) feedback process. However, the physics and the extension of such effects on the star formation history of galaxies is matter of vivid debate. In order to shed some light in the AGN effects over the star formation, we analysed the inner 500 × 500 pc of a sample of 14 Seyfert galaxies using GMOS and MUSE integral field spectroscopy. We fitted the continuum spectra in order to derive stellar age, metallicity, velocity, and velocity dispersion maps in each source. After stacking our sample and averaging their properties, we found that the contribution of young SP, as well as that of AGN featureless continuum both peak at the nucleus. The fraction of intermediate-age SPs is smaller in the nucleus if compared to outer regions, and the contribution of old SPs vary very little within our field of view (FoV). We also found no variation of velocity dispersion or metallicity within our FoV. Lastly, we detected an increase in the dust reddening towards the center of the galaxies. These results lead us to conclude that AGN phenomenon is usually related to a recent star formation episode in the circumnuclear region.

Este é um artigo de divulgação científica em que discutimos, resumidamente, a partir de [1], como são formadas as estrelas parecidas com o Sol.

We determine lithium (Li) abundances for solar twins in the M67 open cluster to add valuable information about the correlation between Li depletion and stellar age and, then, better understand stellar structure and evolution. We use high resolution and good signal-to-noise ratio spectra to characterize Li depletion in three solar twins from M67, using spectral synthesis in the region of the asymmetric 6707.75 \AA \, Li I feature. The mean Li abundance value of A(Li)$=1.6\pm0.2$ dex for our sample of M67 solar twins (our three stars plus a fourth solar twin from a previous analysis in the literature) presents Li abundance expected for its age. Also, the scatter estimated from the standard deviation of the Li abundances in this work is similar to the typical scatter found in a sample of field solar twins presented in the literature., Comment: 6 pages, 3 figures. Accepted for publication at MNRAS

Post-starburst galaxies, identified by their unusually strong Balmer absorption lines and weaker than average emission lines, have traditionally been selected based on their central stellar populations. Here we identify 360 galaxies with post-starburst regions from the MaNGA integral field survey and classify these galaxies into three types: 31 galaxies with central post-starburst regions (CPSB), 37 galaxies with off-center ring-like post-starburst regions (RPSB) and 292 galaxies with irregular post-starburst regions (IPSB). Focussing on the CPSB and RPSB samples, and comparing their radial gradients in D$_n$4000, H$\delta_{\rm A}$ and W(H$\alpha$) to control samples, we find that while the CPSBs have suppressed star formation throughout their bulge and disk, and clear evidence of rapid decline of star formation in the central regions, the RPSBs only show clear evidence of recently rapidly suppressed star formation in their outer regions and an ongoing central starburst. The radial profiles in mass-weighted age and stellar $v/\sigma$ indicate that CPSBs and RPSBs are not simply different evolutionary stages of the same event, rather that CPSB galaxies are caused by a significant disruptive event, while RPSB galaxies are caused by disruption of gas fuelling to the outer regions. Compared to the control samples, both CPSB and RPSB galaxies show a higher fraction of interactions/mergers, misaligned gas or bars that might be the cause of the gas inflows and subsequent quenching., Comment: 17 pages, 10 figures

We investigate the dust attenuation in both stellar populations and ionized gas in kpc-scale regions in nearby galaxies, using integral field spectroscopy data from MaNGA MPL-9. We identify star-forming (HII) and diffuse ionized gas (DIG) regions from MaNGA datacubes. From the stacked spectrum of each region, we measure the stellar attenuation, $E(B-V)_{\rm star}$, using the technique developed by Li et al.(2020), as well as the gas attenuation, $E(B-V)_{\rm gas}$, from the Balmer decrement. We then examine the correlation of $E(B-V)_{\rm star}$, $E(B-V)_{\rm gas}$, $E(B-V)_{\rm gas}-E(B-V)_{\rm star}$ and $E(B-V)_{\rm star}/E(B-V)_{\rm gas}$ with 16 regional/global properties, and for regions with different $\rm H{\alpha}$ surface brightnesses ($\Sigma_{\rm H\alpha}$). We find a stronger correlation between $E(B-V)_{\rm star}$ and $E(B-V)_{\rm gas}$ in regions of higher $\Sigma_{\rm H\alpha}$. Luminosity-weighted age ($t_L$) is found to be the property that is the most strongly correlated with $E(B-V)_{\rm star}$, and consequently with $E(B-V)_{\rm gas}-E(B-V)_{\rm star}$ and $E(B-V)_{\rm star}/E(B-V)_{\rm gas}$. At fixed $\Sigma_{\rm H\alpha}$, $\log_{10}t_L$ is linearly and negatively correlated with $E(B-V)_{\rm star}/E(B-V)_{\rm gas}$ at all ages. Gas-phase metallicity and ionization level are important for the attenuation in the gas. Our results indicate that the ionizing source for DIG regions is likely distributed in the outer-skirt of galaxies, while for HII regions our results can be well explained by the two-component dust model of Charlot & Fall (2000)., Comment: accepted by ApJ

Different processes have been proposed to explain the formation of S0s, including mergers, disc instabilities, and quenched spirals. These processes are expected to dominate in different environments, and thus leave characteristic footprints in the kinematics and stellar populations of the individual components within the galaxies. New techniques enable us to cleanly disentangle the kinematics and stellar populations of these components in IFU observations. In this paper, we use buddi to spectroscopically extract the light from the bulge, disc, and lens components within a sample of eight S0 galaxies in extreme environments observed with MUSE. While the spectra of bulges and discs in S0 galaxies have been separated before, this work is the first to isolate the spectra of lenses. Stellar populations analysis revealed that the bulges and lenses have generally similar or higher metallicities than the discs, and the α-enhancement of the bulges and discs are correlated, while those of the lenses are completely unconnected to either component. We conclude that the majority of the mass in these galaxies was built up early in the lifetime of the galaxy, with the bulges and discs forming from the same material through dissipational processes at high redshift. The lenses, on the other hand, formed over independent time-scales at more random times within the lifetime of the galaxy, possibly from evolved bars. The younger stellar populations and asymmetric features seen in the field S0s may indicate that these galaxies have been affected more by minor mergers than the cluster galaxies.

We use the Gemini NIFS instrument to map the H22.1218μm and Brγ flux distributions in the inner 0.04–2 kpc of a sample of 36 nearby active galaxies (0.001 ≲ z ≲ 0.056) at spatial resolutions from 4 to 250 pc. We find extended emission in 34 galaxies. In ∼55 per cent of them, the emission in both lines is most extended along the galaxy major axis, while in the other 45 per cent the extent follows a distinct orientation. The emission of H2 is less concentrated than that of Brγ, presenting a radius that contains half of the flux 60 per cent greater, on average. The H2 emission is driven by thermal processes – X-ray heating and shocks – at most locations for all galaxies, where 0.4 6 (seen in 40 per cent of the galaxies), shocks are the main H2 excitation mechanism, while in regions with H2/Brγ < 0.4 (25 per cent of the sample) the H2 emission is produced by fluorescence. The only difference we found between type 1 and type 2 active galactic nucleus (AGN) was in the nuclear emission-line equivalent widths that are smaller in type 1 than in type 2 due to a larger contribution to the continuum from the hot dusty torus in the former. The gas masses in the inner 125 pc radius are in the range 101−104 M⊙ for the hot H2 and 103−106 M⊙ for the ionized gas and would be enough to power the AGN in our sample for 105−108 yr at their current accretion rates.

Tese de Mestrado, Física (Astrofísica e Cosmologia), 2021, Universidade de Lisboa, Faculdade de Ciências Submitted by Cristina Manessiez (camanessiez@fc.ul.pt) on 2022-02-14T15:48:13Z No. of bitstreams: 1 TM_Henrique_Miranda.pdf: 6170733 bytes, checksum: aa657263d5cb7c73307f6a59aed97c80 (MD5) Made available in DSpace on 2022-02-14T15:48:27Z (GMT). No. of bitstreams: 1 TM_Henrique_Miranda.pdf: 6170733 bytes, checksum: aa657263d5cb7c73307f6a59aed97c80 (MD5) Previous issue date: 2021

In this work, we characterize the properties of the object SDSS J020536.84−081424.7, an extended nebular region with projected extension of 14 × 14 kpc2 in the line of sight of the ETG Mrk 1172, using unprecedented spectroscopic data from MUSE. We perform a spatially resolved stellar population synthesis and estimate the stellar mass for both Mrk 1172 (1 × 1011 M ) and our object of study (3 × 109 M ). While the stellar content of Mrk 1172 is dominated by an old (∼10 Gyr) stellar population, the extended nebular emission has its light dominated by young to intermediate age populations (from ∼100 Myr to ∼1 Gyr) and presents strong emission lines such as H β; [O III] λλ4959, 5007 Å; H α; [N II] λλ6549, 6585 Å; and [S II] λλ6717, 6732 Å. Using these emission lines, we find that it is metal poor (with Z ∼ 1/3 Z , comparable to the LMC) and is actively forming stars (0.70 M yr−1), especially in a few bright clumpy knots that are readily visible in H α. The object has an ionized gas mass ≥3.8 × 105 M . Moreover, the motion of the gas is well described by a gas in circular orbit in the plane of a disc and is being affected by interaction wtih Mrk 1172. We conclude that SDSS J020536.84−081424.7 is most likely a dwarf irregular galaxy (the dIGal).

The effect of active galactic nuclei (AGNs) feedback on the host galaxy, and its role in quenching or enhancing star formation, is still uncertain due to the fact that usual star formation rate (SFR) indicators – emission-line luminosities based on the assumption of photoionization by young stars – cannot be used for active galaxies as the ionizing source is the AGN. We thus investigate the use of SFR derived from the stellar population and its relation with that derived from the gas for a sample of 170 AGN hosts and a matched control sample of 291 galaxies. We compare the values of SFR densities obtained via the H α emission line (SFRGas) for regions ionized by hot stars according to diagnostic diagrams with those obtained from stellar population synthesis (SFR ) over the last 1 to 100 Myr. We find that the SFR over the last 20 Myr closely reproduces the SFRGas, although a better match is obtained via the transformation: log(SFR ) = (0.872 ± 0.004)log(SFRGas) − (0.075 ± 0.006) (or log(SFRGas) = (1.147 ± 0.005)log(SFR ) + (0.086 ± 0.080)), which is valid for both AGN hosts and non-active galaxies. We also compare the reddening obtained via the gas H α/H β ratio with that derived via the full spectral fitting in the stellar population synthesis. We find that the ratio between the gas and stellar extinction is in the range 2.64 ≤AVg/AV ≤ 2.85, in approximate agreement with previous results from the literature, obtained for smaller samples. We interpret the difference as being due to the fact that the reddening of the stars is dominated by that affecting the less obscured underlying older population, while the reddening of the gas is larger as it is associated with a younger stellar population buried deeper in the dust.

Extremely low-mass white dwarfs (ELM WDs) are the result of binary evolution in which a low-mass donor star is stripped by its companion leaving behind a helium-core white dwarf (WD). We explore the formation of ELM WDs in binary systems considering the Convection And Rotation Boosted magnetic braking treatment. Our evolutionary sequences were calculated using the Modules for Experiments in Stellar Astrophysics code, with initial masses of 1.0 and 1.2 M (donor), and 1.4 (accretor), compatible with low-mass X-ray binary (LMXB) systems. We obtain ELM models in the range 0.15–0.27 M from a broad range of initial orbital periods, 1–25 d. The bifurcation period, where the initial period is equal to the final period, ranges from 20 to 25 d. In addition to LMXBs, we show that ultracompact X-ray binaries (UCXBs) and wide-orbit binary millisecond pulsars can also be formed. The relation between mass and orbital period obtained is compatible with the observational data from He WD companions to pulsars.

As novas diretrizes da Base Nacional Comum Curricular sugere Unidades Temáticas onde os temas de Estrutura e Evolução das Estrelas têm um lugar natural. Porém, um levantamento recente mostrou que o tema da Formação das Estrelas quase nem é abordado na literatura. Apresentamos neste trabalho um panorama completo deste assunto com a intenção de fornecer subsídios para seu tratamento em sala de aula, atualizado e acessível aos professores da Ciências. The new directions of the National Common Curricular Standards suggest Thematic Units in which the Structure and Evolution of Stars have a natural plane. However, a recent survey showed that the Formation of Stars is almost not addressed in the literature. We present in this work a complete panoramic view of this subject with the intention of providing a base for its presentation in the classroom, updated and accessible to Science teachers.

In the local Universe, there are a handful of dwarf compact star-forming galaxies with extremely low oxygen abundances. It has been proposed that they are young, having formed a large fraction of their stellar mass during their last few hundred Myr. However, little is known about the fraction of young stellar populations in more massive galaxies. In a previous article, we analysed 404 000 Sloan Digital Sky Survey spectra to identify a surprisingly large sample of more massive very young galaxies (VYGs), defined to have formed at least 50 per cent of their stellar mass within the last 1 Gyr. Here, we investigate in detail the properties of a subsample of 207 galaxies that are VYGs according to all three of our spectral models. We compare their properties with those of control sample galaxies (CSGs). We find that VYGs tend to have higher surface brightness and to be more compact, dusty, asymmetric, and clumpy than CSGs. Analysis of a subsample with H I detections reveals that VYGs are more gas rich than CSGs. VYGs tend to reside more in the inner parts of low-mass groups and are twice as likely as CSGs to be interacting with a neighbour galaxy. On the other hand, VYGs and CSGs have similar gas metallicities and large-scale environments (relative to filaments and voids). These results suggest that gas-rich interactions and mergers are the main mechanisms responsible for the recent triggering of star formation in low-redshift VYGs, except for the lowest mass VYGs, where the starbursts would arise from a mixture of mergers and gas infall.

In the present work we analyzed seven globular clusters (GCs) selected from their location in the Galactic bulge and with metallicity values in the range −1.30 lesssim [Fe/H] lesssim −0.50. The aim of this work is first to derive cluster ages assuming single stellar populations and second to identify the stars from first (1G) and second generations (2G) from the main sequence, subgiant, and red giant branches, and to derive their age differences. Based on a combination of UV and optical filters used in this project, we apply the Gaussian mixture models to distinguish the multiple stellar populations. Applying statistical isochrone fitting, we derive self-consistent ages, distances, metallicities, and reddening values for the sample clusters. An average age of 12.3 ± 0.4 Gyr was obtained both using DSED and BaSTI (accounting atomic diffusion effects) isochrones, without a clear distinction between the moderately metal-poor and the more metal-rich bulge clusters, except for NGC 6717 and the inner halo NGC 6362 with ~13.5 Gyr. We derived a weighted mean age difference between the multiple populations hosted by each GC of 41 ± 170 Myr adopting canonical He abundances; whereas for higher He in 2G stars, this difference reduces to 17 ± 170 Myr, but with individual uncertainties of 500 Myr.

Despite numerous efforts, it is still unclear whether lenticular galaxies (S0s) evolve from spirals whose star formation was suppressed, or formed trough mergers or disk instabilities. In this paper we present a pilot study of 21 S0 galaxies in extreme environments (field and cluster), and compare their spatially-resolved kinematics and global stellar populations. Our aim is to identify whether there are different mechanisms that form S0s in different environments. Our results show that the kinematics of S0 galaxies in field and cluster are, indeed, different. Lenticulars in the cluster are more rotationally supported, suggesting that they are formed through processes that involve the rapid consumption or removal of gas (e.g. starvation, ram pressure stripping). In contrast, S0s in the field are more pressure supported, suggesting that minor mergers served mostly to shape their kinematic properties. These results are independent of total mass, luminosity, or disk-to-bulge ratio. On the other hand, the mass-weighted age, metallicity, and star formation time-scale of the galaxies correlate more with mass than with environment, in agreement with known relations from previous work such as the one between mass and metallicity. Overall, our results re-enforce the idea that there are multiple mechanisms that produce S0s, and that both mass $and$ environment play key roles. A larger sample is highly desirable to confirm or refute the results and the interpretation of this pilot study., 18 pages, 11 figure, accepted for publication in MNRAS

Galaxy interaction is considered a key driver of galaxy evolution and star formation (SF) history. In this paper, we present an empirical picture of the radial extent of interaction-triggered SF along the merger sequence. The samples under study are drawn from the integral field spectroscopy (IFS) survey SDSS-IV MaNGA, including 205 star-forming galaxies in pairs/mergers and ~1350 control galaxies. For each galaxy in pairs, the merger stage is identified according to its morphological signatures: incoming phase, at first pericenter passage, at apocenter, in merging phase, and in final coalescence. The effect of interactions is quantified by the global and spatially resolved SF rate relative to the SF rate of a control sample selected for each individual galaxy ($\Delta$logSFR and $\Delta$logsSFR(r), respectively). Analysis of the radial $\Delta$logsSFR(r) distributions shows that galaxy interactions have no significant impact on the $\Delta$logsSFR(r) during the incoming phase. Right after the first pericenter passage, the radial $\Delta$logsSFR(r) profile decreases steeply from enhanced to suppressed activity for increasing galactocentric radius. Later on, SF is enhanced on a broad spatial scale out to the maximum radius we explore (~6.7 kpc) and the enhancement is in general centrally peaked. The extended SF enhancement is also observed for systems at their apocenters and in the coalescence phase, suggesting that interaction-triggered SF is not restricted to the central region of a galaxy. Further explorations of a wide range in parameter space of merger configurations (e.g., mass ratio) are required to constrain the whole picture of interaction-triggered SF., Comment: 18 pages, 6 figures, accepted for publication in ApJ

Negative feedback from accretion onto super-massive black holes (SMBHs), that is to remove gas and suppress star formation in galaxies, has been widely suggested. However, for Seyfert galaxies which harbor less active, moderately accreting SMBHs in the local universe, the feedback capability of their black hole activity is elusive. We present spatially-resolved H$\alpha$ measurements to trace ongoing star formation in Seyfert galaxies and compare their specific star formation rate with a sample of star-forming galaxies whose global galaxy properties are controlled to be the same as the Seyferts. From the comparison we find that the star formation rates within central kpc of Seyfert galaxies are mildly suppressed as compared to the matched normal star forming galaxies. This suggests that the feedback of moderate SMBH accretion could, to some extent, regulate the ongoing star formation in these intermediate to late type galaxies under secular evolution., Comment: 12 pages, 7 figures, accepted by MNRAS

Apresentamos mapas para as distribuições de fluxo nas linhas de emissão, excitação, densidade superficial de massa de gás ionizado e taxa de formação estelar para 150 Núcleos Ativos de Galáxias (AGN) observados com o SDSS-IV MaNGA, comparando-os com os obtidos para uma amostra controle de galáxias não ativas. Descobrimos que, para os AGNs early-type, o gás ionizado é mais concentrado na região nuclear quando comparado com as galáxias de controle, enquanto que para as galáxias late-type a distribuição de gás é semelhante à das galáxias de controle, sendo distribuída mais uniformemente por todo a galáxia. A massa total de gás ionizado varia de ≈ 104M a ≈ 109M. A principal diferença entre os AGNs e os controles está na densidade superficial central de massa de gás ionizado { dentro de 0,2R Re (raio efetivo) { que é maior para os AGNs do que para os controles, com uma diferença maior observada para as early-types do que para as late-types. Essa diferença entre os AGNs e os controles é maior para os AGNs de maior luminosidade e torna-se mais baixa à medida que a luminosidade dos AGNs diminui. Calculamos os perfis espaciais médios da densidade superficial de massa de gás ionizado e mostramos que eles decrescem mais rapidamente com o raio para os AGNs do que para os controles dentro de 0,4R e no caso dos AGNs de maior luminosidade (L([OIII]λ 5007) ≥ 3:8x1040 erg s-¹)sendo semelhantes aos dos controles além deste raio e para AGNs de menor luminosidade. Calculamos a taxa de formação estelar SFR nas regiões HII do corpo das galáxias hospedeiras de AGN e controles, encontrando uma diferença somente para as galáxias early-type, para as quais as que têm AGN apresentam um pequeno excesso no valor da SFR em relação às galáxias de controle. Estudamos também a relação entre o raio RNLR (onde NLR é a sigla para representar a Narrow Line Region) da região ionizada pelo AGN e a luminosidade L[OIII] do AGN e encontramos uma correlação positiva. Esta correlação indica que a região de gás ionizado pelo AGN cresce com a luminosidade do mesmo, de forma semelhante à encontrada previamente para a Broad Line Region e por outros autores para a NLR. Finalmente, obtivemos a metalicidade do gás para as regiões HII no corpo da galáxia que, extrapolada para a região central, mostra um bom acordo com a metalicidade derivada para o gás da NLR a partir de calibrações em termos de razões de linhas de emissão obtidas a partir de modelos de fotoionização. We present maps for the ionized gas density and star formation rates for 150 Active Galactic Nuclei (AGN) observed with SDSS-IV MaNGA, and compare them with those of a control sample of nonactive galaxies. We nd that, for the early-type AGN, the ionized gas is more concentrated in the nuclear region, when compared with the controls, while for the late-type galaxies the gas distribution is similar to that in the controls, being spread throughout the galaxies. The total ionized gas mass ranges from ≈ 104M to ≈109M . The main difference between the AGN and controls is on the central ionized gas surface mass density { within 0.2Re (effective radius) { that is larger for the AGN than for the controls, with a larger difference observed for the early-type than for the late-type galaxies. This di#erence between the AGN and controls is highest for the highest luminosity AGN and becomes lower as the AGN luminosity decreases. We have calculated average proles of the gas surface mass density and show that they are steeper in the AGN when compared to controls within the inner 0.4Re for the highest luminosity AGN (L([OIII]λ 5007) ≥ 3:8 x 1040 erg s1), being similar to those of the controls beyond this radius and for lower luminosity AGN. We have obtained the star-formation rate SFR for the HII regions along the body of the AGN host galaxies and controls, nding a di#erence only for the early-type galaxies, for which the AGN hosts present a small excess in the integrated SFR as compared to the control galaxies. We have also investigated the relation between the radius of the region ionized by the AGN RNLR (where NLR stands for Narrow- Line Region) and the AGN luminosity L[OIII], finding a positive correlation. This correlation indicates that the radius of the region ionized by the AGN increases with its luminosity, similarly to previously found for the Broad-Line Region and for the NLR itself in previous studies. Finally, we have derived the gas metallicity for the HII regions over the body of the galaxy that, when extrapolated to the central region, shows good agreement with the gas metalicity of the NLR obtained from calibrations in terms of emission-line ratios derived from photoionization models.

Context. Between the blue cloud and the red sequence peaks on the galaxy colour–magnitude diagram there is a region sparsely populated by galaxies called the green valley. In a framework where galaxies mostly migrate on the colour–magnitude diagram from star forming to quiescent, the green valley is considered a transitional galaxy stage. The details of the processes that drive galaxies from star-forming to passive systems still remain unknown. Aims.We aim to measure the transitional timescales of nearby galaxies across the green valley, through the analysis of Galaxy Evolution Explorer and Javalambre Photometric of Local Universe Survey photometric data. Specifically, we seek to study the impact of bars on the quenching timescales. Methods. We developed a method that estimates empirically the star formation quenching timescales of green valley galaxies, assuming an exponential decay model of the star formation histories and through a combination of narrow and broad bands from the Javalambre Photometric of Local Universe Survey and Galaxy Evolution Explorer. We correlated these quenching timescales with the presence of bars. Results.We find that the Javalambre Photometric of Local Universe Survey colours F0395 g and F0410 g are sensitive to di erent star formation histories, showing, consequently, a clear correlation with the Dn(4000) and H ;A spectral indices.We measured quenching timescales based on these colours and we find that quenching timescales obtained with our new approach are in agreement with those determined using spectral indices. We also compared the quenching timescales of green valley disc galaxies as a function of the probability of hosting a bar. We find that galaxies with high bar probability tend to quench their star formation slowly. Conclusions. We conclude that: (1) Javalambre Photometric of Local Universe Survey filters can be used to measure quenching timescales in nearby green valley galaxies; and (2) the resulting star formation quenching timescales are longer for barred green valley galaxies. Considering that the presence of a bar indicates that more violent processes (e.g. major mergers) are absent in host galaxies, we conclude that the presence of a bar can be used as a morphological signature for slow star formation quenching.

We present two-dimensional ionized gas and stellar kinematics in the inner 1.4 × 1.9 kpc2 of the Seyfert 2 galaxy ESO 153-G20 obtained with the Gemini-South/Gemini multi-object spectrograph integral field unit (GMOS-IFU) at a spatial resolution of ~250 pc and spectral resolution of 36 km s−1. Strong [O iii], Hα, [N ii] and [S ii] emission lines are detected over the entire field of view. The stellar kinematics trace circular rotation with a projected velocity amplitude of ±96 km s−1, a kinematic major axis in position angle of 11°, and an average velocity dispersion of 123 km s−1. To analyse the gas kinematics, we used aperture spectra, position–velocity diagrams and single/double Gaussian fits to the emission lines. All lines show two clear kinematic components: a rotating component that follows the stellar kinematics, and a larger-dispersion component, close to the systemic velocity (from which most of the [O iii] emission comes), mainly detected to the south-west. We interpret this second component as gas outflowing at ~400 km s−1 in a compact (300 pc) ionization cone with a half-opening angle ≤40°. The counter-cone is probably obscured behind a dust lane. We estimate a mass outflow rate of 1.1 M⊙ yr−1, 200 times larger than the estimated accretion rate on to the supermassive black hole, and a kinetic to radiative power ratio of 1.7 × 10−3. Bar-induced perturbations probably explain the remaining disturbances observed in the velocity field of the rotating gas component.

Spectra of galaxies contain a wealth of information about the stellar populations from which they are made. With integral-field unit (IFU) surveys, such data can be used to map out stellar population properties across the face of a galaxy, allowing one to go beyond simple radial profiles and study details of non-axisymmetric structure. To-date, however, such studies have been limited by the quality of available data and the power of spectral analysis tools. We now take the next step and study the barred spiral galaxy MCG+07-28-064 from observations obtained as part of the SDSS-IV MaNGA project. We find that we can decompose this galaxy into "time slices," which reveal the varying contributions that stars of differing ages make to its bar and spiral structure, offering new insight into the evolution of these features. We find evidence for the ongoing growth of the bar, including the most recent star formation on its leading edge, and for the underlying density wave responsible for spiral structure. This pilot study indicates that there is a wealth of untapped information on the spatial distribution of SFHs available in the current generation of IFU galaxy surveys., Comment: 6 pages, 3 figures. Accepted for publication in MNRAS. Figure 1 is an animation and requires a PDF viewer such as Adobe Acrobat Reader to properly render. An stand-alone version of the animation is available as supplementary material at https://doi.org/10.1093/mnras/stz2204

n this paper we aim to validate a methodology designed to obtain Hα emission line fluxes from J-PLUS photometric data. J-PLUS is a multi narrow-band filter survey carried out with the 2 deg2 field of view T80Cam camera, mounted on the JAST/T80 telescope in the OAJ, Teruel, Spain. The information of the twelve J-PLUS bands, including the J0660 narrow-band filter located at rest-frame Hα, is used over the first 42 deg2 observed to retrieve de-reddened and [NII] decontaminated Hα emission line fluxes of 46 star-forming regions with previous SDSS and/or CALIFA spectroscopic information. The agreement between the J-PLUS Hα fluxes and those obtained with spectroscopic data is remarkable, finding a median comparison ratio with a scatter of R = F J−PLUS Hα /F spec Hα = 1.05 ± 0.25. This demonstrates that it is possible to retrieve reliable Hα emission line fluxes from J-PLUS photometric data. With an expected area of thousands of square degrees upon completion, the J-PLUS dataset will allow the study of several star formation science cases in the nearby universe, as the spatially resolved star formation rate of nearby galaxies at z ≤ 0.015, and how it is influenced by the environment, morphology, stellar mass, and nuclear activity. As an illustrative example, the close pair of interacting galaxies NGC 3994 and NGC 3995 is analysed, finding an enhancement of the star formation rate not only in the centre, but also in outer parts of the disk of NGC 3994.

We analyze the intrinsic velocity dispersion properties of 648 star-forming galaxies observed by the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, to explore the relation of intrinsic gas velocity dispersions with star formation rates (SFRs), SFR surface densities ($\rm{\Sigma_{SFR}}$), stellar masses and stellar mass surface densities ($\rm{\Sigma_{*}}$). By combining with high z galaxies, we found that there is a good correlation between the velocity dispersion and the SFR as well as $\rm{\Sigma_{SFR}}$. But the correlation between the velocity dispersion and the stellar mass as well as $\rm{\Sigma_{*}}$ is moderate. By comparing our results with predictions of theoretical models, we found that the energy feedback from star formation processes alone and the gravitational instability alone can not fully explain simultaneously the observed velocity-dispersion/SFR and velocity-dispersion/$\rm{\Sigma_{SFR}}$ relationships., Comment: 11 pages, 11 figures. Accepted for publication in MNRAS

We present the results of a systematic search and characterization of galaxies with morphological signatures of ram pressure stripping, known as jellyfish galaxies, in the multicluster system A901/2, at z ~ 0.165, as part of the OMEGA survey. By visually inspecting Advanced Camera for Surveys/Hubble Space Telescope F606W images looking for morphological signatures of ram pressure stripping events in Hα-emitting galaxies, we identify a total of 70 jellyfish candidates. Of these, 53 are clearly star-forming galaxies and five are highly probable active galactic nucleus (AGN) hosts, the classification of the remaining galaxies is more uncertain. They have late-type and irregular morphologies, and most of them are part of the blue cloud with only. four being previously classified as dusty reds. The AGN activity is not prominent in the sample and, of the few cases of galaxies hosting AGN, such activity does not seem to be correlated to the gas-stripping phenomenon. Our jellyfish galaxy candidates do not have a preferential pattern of motion within the multicluster system, although the most compelling cases appear to inhabit the inner regions of the most massive sub-cluster centres. The specific star formation rate of these galaxies indicates that their star formation activity is enhanced, in contrast with what is observed for the rest of the star-forming galaxy population in the system. Half of the sample is forming stars at a higher rate than the main sequence for field galaxies, and this behaviour is more evident for the most compelling candidates. For some galaxies, the spatially resolved Hα emission appears to be as disturbed and extended as their continuum counterparts.Our findings point towards a scenario where the ram pressure stripping is triggering a period of intense and extended star formation throughout the galaxy while it is also disturbing the morphology. This is the largest sample of jellyfish galaxy candidates found in a single system suggesting that cluster mergers might be the ideal environment for studying ram pressure stripping effects.

We have used the Gemini Near-Infrared Integral Field Spectrograph in the J and K bands to map the distribution, excitation, and kinematics of the ionized H ii and warm molecular gas H2, in the inner few 100 pc of six nearby active galaxies: NGC 788, Mrk 607, NGC 3227, NGC 3516, NGC 5506, NGC 5899. For most galaxies, this is the first time that such maps have been obtained. The ionized and H2 gas show distinct kinematics: while the H2 gas is mostly rotating in the galaxy plane with low velocity dispersion (σ), the ionized gas usually shows signatures of outflows associated with higher σ values, most clearly seen in the [Fe ii] emission line. These two gas species also present distinct flux distributions: the H2 is more uniformly spread over the whole galaxy plane, while the ionized gas is more concentrated around the nucleus and/or collimated along the ionization axis of its active galactic nucleus (AGN), presenting a steeper gradient in the average surface mass density profile than the H2 gas. The total H ii masses cover the range 2×105--2×107 M⊙, with surface mass densities in the range 3–150 M⊙ pc−2, while for the warm H2 the values are 103–4 times lower. We estimate that the available gas reservoir is at least ≈ 100 times more massive than needed to power the AGN. If this gas forms new stars the star formation rates, obtained from the Kennicutt–Schmidt scaling relation, are in the range 1–260 × 10−3 M⊙ yr−1. But the gas will also – at least in part – be ejected as the observed outflows

We present a sample of 48 nearby galaxies with central, biconical outflows identified by the Mapping Nearby Galaxies at APO survey. All considered galaxies have star-formation-driven biconical (SFB) central outflows, with no signs of an active galactic nucleus. We find that the SFB outflows require high central concentration of the star formation rate. This increases the gas velocity dispersion over the equilibrium limit and helps maintain the gas outflows. The central starbursts increase the metallicity, extinction, and the [α/Fe] ratio in the gas. A significant amount of young stellar population at the centers suggests that the SFBs are associated with the formation of young bulges in galaxies. More than 70% of SFB galaxies are group members or have companions with no prominent interaction, or show asymmetry of external isophotes. In 15% of SFB cases, stars and gas rotate in the opposite directions, which points at the gas infall from satellites as the primary reason for triggering the SFB phenomena.

We present maps of the ionized gas flux distributions, excitation, star formation rate (SFR), surface mass density ΣH+, and obtain total values of SFR and ionized gas masses M for 62 active galactic nuclei (AGN) observed with SDSS-IV MaNGA and compare them with those of a control sample of 112 non-active galaxies. The most luminous AGN – with $L(\rm {[O\,{\small III}]}\lambda 5007) \ge 3.8\times 10^{40}\, \mbox{erg}\, \mbox{s}^{-1}$, and those hosted by earlier type galaxies are dominated by Seyfert excitation within 0.2 effective radius Re from the nucleus, surrounded by LINER excitation or transition regions, while the less luminous and hosted by later-type galaxies show equally frequent LINER and Seyfert excitation within $0.2\, R_\mathrm{ e}$. The extent R of the region ionized by the AGN follows the relation $R\propto \, L(\rm {[O\,{\small III}]})^{0.5}$ – as in the case of the broad-line region. The SFR distribution over the region ionized by hot stars is similar for AGN and controls, while the integrated SFR – in the range 10−3–10 M⊙ yr−1 is also similar for the late-type subsample, but higher in the AGN for 75 per cent of the early-type subsample. We thus conclude that there is no signature of AGN quenching star formation in the body of the galaxy in our sample. We also find that 66 per cent of the AGN have higher ionized gas masses M than the controls – in the range 105–3 × 107 M⊙ – while 75 per cent of the AGN have higher ΣH+ within $0.2\, R_\mathrm{ e}$ than the control galaxies.

We present a spatially resolved stellar population study of the inner∼200 pc radius ofNGC 4303 based on near-infrared integral field spectroscopy with SINFONI/VLT at a spatial resolution of 40–80 pc and using the STARLIGHT code. We found that the distribution of thestellar populations presents a spatial variation, suggesting an age stratification. Three main structures stand out. Two nuclear blobs, one composed by young stars (t≤50 Myr) and onewith intermediate-age stars (50 Myr2 Gyr) is distributed outside the two blob structures.For the nuclear region (inner∼60 pc radius) we derived an SFR of 0.43 M yr−1and foundno signatures of non-thermal featureless continuum and hot dust emission, supporting thescenario in which an LLAGN/LINER-like source is hidden in the centre of NGC 4303. Thus, our results reveal a rather complex star formation history in NGC 4303, with different stellar population components coexisting with a low efficiency accreting black hole in its centre.

Using deep wide-field photometry 3 yr data (Y3) from the Dark Energy Survey (DES), we present a panoramic study of the Fornax dwarf spheroidal galaxy. The data presented here—a small subset of the full survey—uniformly cover a region of 25 deg2 centered on the galaxy to a depth of g ~ 23.5. We use these data to study the structural properties of Fornax, overall stellar population, and its member stars in different evolutionary phases. We also search for possible signs of tidal disturbance. Fornax is found to be significantly more spatially extended than what early studies suggested. No statistically significant distortions or signs of tidal disturbances were found down to a surface brightness limit of ~32.1 mag arcsec−2. However, there are hints of shell-like features located ~20'–40' from the center of Fornax that may be stellar debris from past merger events. We also find that intermediate-age and young main-sequence populations show different orientation at the galaxy center and have many substructures. The deep DES Y3 data allow us to characterize the age of those young stellar substructures with great accuracy, both those previously known and those newly identified as possible overdensities in this work, on the basis of their color–magnitude diagram morphology. We find that the youngest overdensities are all found on the eastern side of Fornax, where the Fornax field population itself is slightly younger than in the west. In summary, the high-quality DES Y3 data reveal that Fornax has many rich structures and provide insights into its complex formation history

We present a 2D mapping of stellar population age components, emission-line fluxes, gas excitation, and kinematics within the inner ∼200 pc of the Seyfert 2 galaxy NGC 2110. We used the Gemini North Integral Field Spectrograph (NIFS) in the J and K bands at a spatial resolution of ∼22 pc. The unresolved nuclear continuum is originated in combined contributions of young stellar population (SP; age ≤ 100 Myr), a featureless AGN continuum and hot dust emission. The young-intermediate SP (100 < age ≤ 700 Myr) is distributed in a ring-shaped structure at ≈140 pc from the nucleus, which is roughly coincident with the lowest values of the stellar velocity dispersion. In the inner ≈115 pc the old SP (age > 2 Gyr) is dominant. The [Fe ii] λ1.2570μm emission-line flux distribution is correlated with the radio emission and its kinematics comprise two components, one from gas rotating in the galaxy plane and another from gas in outflow within a bicone-oriented along north–south. These outflows seem to originate in the interaction of the radio jet with the ambient gas producing shocks that are the main excitation mechanism of the [Fe ii] emission. We estimate: (1) an ionized gas mass outflow rate of ∼0.5 M⊙ yr−1 at ∼70 pc from the nucleus; and (2) a kinetic power for the outflow of only 0.05 per cent of the AGN bolometric luminosity implying weak feedback effect on the galaxy

We map optical and near-infrared (NIR) stellar population properties of the inner 320 × 535 pc2 of the elliptical galaxy NGC 1052. The optical and NIR spectra were obtained using the Gemini Integral Field Units of the GMOS instrument and NIFS, respectively. By performing stellar population synthesis in the optical alone, we find that this region of the galaxy is dominated by old (t > 10 Gyr) stellar populations. Using the NIR, we find the nucleus to be dominated by old stellar populations, and a circumnuclear ring with younger (~2.5 Gyr) stars. We also combined the optical and NIR datacubes and performed a panchromatic spatially resolved stellar population synthesis, which resulted in a dominance of older stellar populations, in agreement with optical results. We argue that the technique of combining optical and NIR data might be useful to isolate the contribution of stellar population ages with strong NIR absorption bands. We also derive the stellar kinematics and find that the stellar motions are dominated by a high (~240 km s−1) velocity dispersion in the nucleus, with stars also rotating around the centre. Lastly, we measure the absorption bands, both in the optical and in the NIR, and find a nuclear drop in their equivalent widths. The favoured explanation for this drop is a featureless continuum emission from the low luminosity active galactic nucleus.

Supermassive black holes (SMBHs) are present at the centre of most galaxies, with the related mass accretion processes giving origin to outflows in active galactic nuclei (AGNs). It has been presumed that only intense winds from luminous AGNs were able to suppress star formation until the discovery of a new class of galaxies with no recent star formation and with the nucleus in a quiescent state showing kpc scale outflows. We used SDSS MaNGA and Gemini Integral Field Spectroscopy of the prototype Red Geyser Akira and found that the orientation of the outflow changes by about 50° from its nucleus to kpc scales. A possible interpretation is that the outflow is produced by a precessing accretion disc due to a misalignment between the orientation of the disc and the spin of the SMBH. The precession of the central source is also supported by a similar change in the orientation of the ionization pattern. Although similar behaviour has commonly being reported for collimated relativistic jets, the precession of an AGN wide wind is reported here for the first time, implying on a larger work surface of the wind, which in turn increases the star formation suppression efficiency of the outflow.

We have obtained Gemini/GMOS spectra of 28 regions located across the interacting group NGC 6845, spanning from the inner regions of the four major galaxies (NGC 6845A, B, C, D) to the tidal tails of NGC 6845A. All regions in the tails are star-forming objects with ages younger than 10 Myr. We derived the gas-phase metallicity gradients across NGC 6845A and its two tails and we find that these are shallower than those for isolated galaxies. NGC 6845A has a gas-phase oxygen central metallicity of \mbox{12+log(O/H)$\sim$8.5} and a flat gas-phase metallicity gradient ($\beta$=0.002$\pm$0.004 dex kpc$^{-1}$) out to $\sim$4 $\times$ R$_{25}$ (to the end of the longest tidal tail). Considering the mass-metallicity relation, the central region of NGC 6845A displays a lower oxygen abundance than the expected for its mass. Taking into account this fact and considering the flat oxygen distribution measured along the eastern tidal tail, we suggest that an interaction event has produced a dilution in the central metallicity of this galaxy and the observed flattening in its metal distribution. We found that the star formation process along the eastern tidal structure has not been efficient enough to increase the oxygen abundances in this place, suggesting that this structure was formed from enriched material., Comment: Accepted for publication in MNRAS, 18 pages, 11 figures, 6 tables

Using new Atacama Pathfinder Experiment and James Clerk Maxwell Telescope spectroscopy of the CO 2→1 line, we undertake a controlled study of cold molecular gas in moderately luminous (Lbol = 1043–44.5 erg s−1) active galactic nuclei (AGN) and inactive galaxies from the Luminous Local AGN with Matched Analogs (LLAMA) survey.We use spatially resolved infrared photometry of the LLAMA galaxies from 2MASS, the Wide-field Infrared Survey Explorer the Infrared Astronomical Satellite and the Herschel Space Observatory (Herschel), corrected for nuclear emission using multicomponent spectral energy distribution fits, to examine the dust-reprocessed star formation rates, molecular gas fractions and star formation efficiencies (SFEs) over their central 1–3 kpc. We find that the gas fractions and central SFEs of both active and inactive galaxies are similar when controlling for host stellar mass and morphology (Hubble type). The equivalent central molecular gas depletion times are consistent with the discs of normal spiral galaxies in the local Universe. Despite energetic arguments that the AGN in LLAMA should be capable of disrupting the observable cold molecular gas in their central environments, our results indicate that nuclear radiation only couples weakly with this phase. We find a mild preference for obscured AGN to contain higher amounts of central molecular gas, which suggests connection between AGN obscuration and the gaseous environment of the nucleus. Systems with depressed SFEs are not found among the LLAMA AGN. We speculate that the processes that sustain the collapse of molecular gas into dense pre-stellar cores may also be a prerequisite for the inflow of material on to AGN accretion discs.

The Herschel Space Observatory has revealed a very different galaxyscape from that shown by optical surveys which presents a challenge for galaxy-evolution models. The Herschel surveys reveal (1) that there was rapid galaxy evolution in the very recent past and (2) that galaxies lie on a single Galaxy Sequence (GS) rather than a star-forming ‘main sequence’ and a separate region of ‘passive’ or ‘red-and-dead’ galaxies. The form of the GS is now clearer because far-infrared surveys such as the Herschel ATLAS pick up a population of optically red starforming galaxies that would have been classified as passive using most optical criteria. The space-density of this population is at least as high as the traditional star-forming population. By stacking spectra of H-ATLAS galaxies over the redshift range 0.001 < z < 0.4, we show that the galaxies responsible for the rapid low-redshift evolution have high stellar masses, high star-formation rates but, even several billion years in the past, old stellar populations – they are thus likely to be relatively recent ancestors of early-type galaxies in the Universe today. The form of the GS is inconsistent with rapid quenching models and neither the analytic bathtub model nor the hydrodynamical EAGLE simulation can reproduce the rapid cosmic evolution. We propose a new gentler model of galaxy evolution that can explain the new Herschel results and other key properties of the galaxy population.

Aims. Globular clusters are tracers of the history of star formation and chemical enrichment in the early Galaxy. Their abundance pattern can help understanding their chemical enrichment processes. In particular, the iron-peak elements have been relatively little studied so far in the Galactic bulge. Methods. The main aim of this work is to verify the strength of abundances of iron-peak elements for chemical tagging in view of identifying different stellar populations. Besides, the nucleosynthesis processes that build these elements are complex, therefore observational data can help constraining theoretical models, as well as give suggestions as to the kinds of supernovae that enriched the gas before these stars formed. Results. The abundances of iron-peak elements are derived for the sample clusters, and compared with bulge field, and thick disk stars. We derived abundances of the iron-peak elements Sc, V, Mn, Cu, and Zn in individual stars of five bulge globular clusters (NGC 6528, NGC 6553, NGC 6522, NGC 6558, HP 1), and of the reference thick disk/or inner halo cluster 47 Tucanae (NGC 104). High resolution spectra were obtained with the UVES spectrograph at the Very Large Telescope over the years. Conclusions. The sample globular clusters studied span metallicities in the range –1.2≤Fe/H]≤ 0.0. V and Sc appear to vary in lockstep with Fe, indicating that they are produced in the same supernovae as Fe. We find that Mn is deficient in metal-poor stars, confirming that it is underproduced in massive stars; Mn-over-Fe steadily increases at the higher metallicities due to a metallicity-dependent enrichment by supernovae of type Ia. Cu behaves as a secondary element, indicating its production in a weak-s process in massive stars. Zn has an alpha-like behaviour at low metallicities, which can be explained in terms of nucleosynthesis in hypernovae. At the metal-rich end, Zn decreases with increasing metallicity, similarly to the alpha-elements.

The galaxies found in optical surveys fall in two distinct regions of a diagram of optical colour versus absolute magnitude: the red sequence and the blue cloud, with the green valley in between. We show that the galaxies found in a submillimetre survey have almost the opposite distribution in this diagram, forming a ‘green mountain’. We show that these distinctive distributions follow naturally from a single, continuous, curved Galaxy Sequence in a diagram of specific star formation rate versus stellar mass, without there being the need for a separate star-forming galaxy main sequence and region of passive galaxies. The cause of the red sequence and the blue cloud is the geometric mapping between stellar mass/specific star formation rate and absolute magnitude/colour, which distorts a continuous Galaxy Sequence in the diagram of intrinsic properties into a bimodal distribution in the diagram of observed properties. The cause of the green mountain isMalmquist bias in the submillimetre waveband, with submillimetre surveys tending to select galaxies on the curve of the Galaxy Sequence, which have the highest ratios of submillimetre-to-optical luminosity. This effect, working in reverse, causes galaxies on the curve of the Galaxy Sequence to be underrepresented in optical samples, deepening the green valley. The green valley is therefore not evidence (1) for there being two distinct populations of galaxies, (2) for galaxies in this region evolving more quickly than galaxies in the blue cloud and the red sequence, and (3) for rapid-quenching processes in the galaxy population.

We present here a systematic search for cyanopolyynes in the shock region L1157-B1 and its associated protostar L1157-mm in the framework of the Large Program "Astrochemical Surveys At IRAM" (ASAI), dedicated to chemical surveys of solar-type star forming regions with the IRAM 30m telescope. Observations of the millimeter windows between 72 and 272 GHz permitted the detection of HC$_3$N and its $^{13}$C isotopologues, and HC$_5$N (for the first time in a protostellar shock region). In the shock, analysis of the line profiles shows that the emission arises from the outflow cavities associated with L1157-B1 and L1157-B2. Molecular abundances and excitation conditions were obtained from analysis of the Spectral Line Energy Distributions under the assumption of Local Thermodynamical Equilibrium or using a radiative transfer code in the Large Velocity Gradient approximation. Towards L1157mm, the HC$_3$N emission arises from the cold envelope ($T_{rot}=10$ K) and a higher-excitation region ($T_{rot}$= $31$ K) of smaller extent around the protostar. We did not find any evidence of $^{13}$C or D fractionation enrichment towards L1157-B1. We obtain a relative abundance ratio HC$_3$N/HC$_5$N of 3.3 in the shocked gas. We find an increase by a factor of 30 of the HC$_3$N abundance between the envelope of L1157-mm and the shock region itself. Altogether, these results are consistent with a scenario in which the bulk of HC$_3$N was produced by means of gas phase reactions in the passage of the shock. This scenario is supported by the predictions of a parametric shock code coupled with the chemical model UCL_CHEM., Comment: 13 pages, 12 figures. Accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal

We study the effect of inclination on the apparent brightness of star-forming galaxies in spectral passbands that are commonly used as star formation indicators. As diagnostics we use mass-to-light ratios in three passbands: the UV continuum at 280 nm, the Hα emission line, and the FIR 24μ band. We include a study of inclination trends in the IR/UV ratio (‘IRX’) and the IR/Hα ratio. Our sample comprises a few hundred galaxies from the region around the clusters Abell 901/902 with deep data and inclinations measured from outer discs in Hubble Space Telescope images. As a novelty, the Hα- and separately the N II emission are measured by tunable-filter imaging and encompass galaxies in their entirety. At galaxy stellar masses above logM∗/M 10 we find trends in the UV and Hα mass-to-light ratio that suggest an inclination-induced attenuation from face-on to edge-on of ~1 mag and ~0.7 mag in UV and Hα, respectively, implying that star formation rates of edge-on galaxies would be underestimated by ~2.5 × in UV and ~2 × in Hα. We find the luminosities in UV and Hα to be well correlated, but the optical depth of diffuse dust that causes inclination dependence appears to be lower for stars emitting at 280 nm than for gas clouds emitting Balmer lines. For galaxies with logM∗/M 9.7, we find no measurable effect at >0.1 mag. The absence of an inclination dependence at 24μ confirms that the average galaxy is optically thin in the FIR.

We present spatially resolved stellar population (SP) age maps, average radial profiles and gradients for the first 62 active galactic nuclei (AGN) observed with Sloan Digital Sky Survey (SDSS)-IV Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) to study the effects of the active nuclei on the star formation history of the host galaxies. These results, derived using the STARLIGHT code, are compared with a control sample of non-active galaxies matching the properties of the AGN hosts. We find that the fraction of young SPs in highluminosity AGN is higher in the inner (R ≤ 0.5 Re) regions when compared with the control sample; low-luminosity AGN, on the other hand, present very similar fractions of young stars to the control sample hosts for the entire studied range (1 Re). The fraction of intermediate-age SP of the AGN hosts increases outwards, with a clear enhancement when compared with the control sample. The inner region of the galaxies (AGN and control galaxies) presents a dominant old SP, whose fraction decreases outwards.We also compare our results (differences between AGN and control galaxies) for the early- and late-type hosts and find no significant differences. In summary, our results suggest that the most luminous AGN seems to have been triggered by a recent supply of gas that has also triggered recent star formation (t ≤40 Myr) in the central region.

Variabilidade fotométrica é uma das principais características de objetos estelares jovens, e entender suas particularidades em diferentes comprimentos de onda pode ajudar a entender os processos físicos em ação em tais objetos. A causa da variabilidade fotométrica mais comum em estrelas jovens é a modulação do brilho estelar pela rotação de uma superfície estelar com manchas. Esse tipo de variabilidade nos permite medir períodos de rotação em estas estrelas jovens. Nas últimas décadas, a evolução da rotação estelar durante o princípio da pré sequência principal foi o assunto de diversos estudos, focados em diferentes regiões jovens com diferentes idades. Estudos observacionais sugerem uma dependência da rotação com a massa da estrela, e para estrelas em certo intervalo de massa, uma dependência da rotação com a presença de um disco circunstelar também é esperada. Por outro lado, o papel das condições ambientais na regulação da rotação estelar ainda não é bem entendido. Nesta tese, nós exploramos a ocorrência e principais características da variabilidade fotométrica no infravermelho próximo em estrelas jovens, situadas na massiva associação Cygnus OB2, a qual está localizada a 1.4 kpc distante do Sol. Para objetos com variabilidade periódica associada com a rotação estelar, investigamos as propriedades rotacionais de membros de Cygnus OB2. Para a amostra de períodos de rotação, investigamos questões relacionadas ao efeito das propriedades ambientais na evolução rotacional durante a fase pré sequência principal. Investigamos variabilidade em 5083 candidatos a membros da associação (24% deles possuem disco circunstelar) nas bandas JHK do infravermelho próximo, usando dados observados com a Câmera Wide-eld (WFCAM) instalada no UKInfrared Telescope (UKIRT), no Mauna Kea, Havaí. Um total de 112 noites foi observado, compreendendo 217 dias. A amostra estudada está distribuída em um campo de 0.78 graus quadrados. A seleção de variáveis foi feita usando o índice de variabilidade de Stetson, e 60% das estrelas da amostra foram consideradas variáveis. Investigamos a morfologia das curvas deluz, e as variações de cores e magnitudes JHK dentro de diagramas cor-magnitude e corcor. Nos casos em que a variação em cor e magnitude eram altamente correlacionadas, as inclinações produzidas pela variação foram medidas. Tais inclinações foram comparadas comas inclinações esperadas a partir de modelos explicando os mecanismos físicos responsáveis por variabilidade fotométrica em estrelas jovens. A busca por períodos foi feita usando-se periodogramas de Lomb-Scargle para períodos entre 0.83-45 dias. As detecções de períodos foram vericadas utilizando-se os níveis de Probabilidade de Falso Alarme, a estatística de Saunders, os métodos de comprimento de string/rope, e a inspeção visual das curvas de luz. Simulações de Monte Carlo foram realizadas para estimar a completeza e os níveis de contaminação na amostra de estrelas periódicas. A partir das simulações, 894 períodos foram considerados conáveis. O presente estudo foi considerado completo para períodos entre 2 e 30 dias. O cenário geral para a evolução da rotação de estrelas jovens visto em outras regiões foi conrmado pelas distribuições de período para estrelas em Cygnus OB2. Estrelas com disco giram em média mais devagar do que estrelas sem disco. A dependência da rotação com a massa estelar também foi vericada, mas como é o caso de NGC 6530, estrelas de massa muito pequena (M < 0.4M ) giram mais devagar que estrelas mais massivas (0.4M < M < 1.4M). Observamos um excesso de rotores lentos entre a população de menor massa. A dependência da rotação com a presença de disco foi investigadaconsiderando-se o nível de radiação UV ambiente, provindo das estrelas do tipo O na associação.Resultados compatíveis com o fenômeno de trancamento pelo disco foram vericados para estrelas em regiões com baixa incidência de radiação UV, mas nenhuma relação com signicância estatística foi vericada entre a rotação e a presença de disco para estrelas em regiões com alta incidência de radiação UV. Isso sugere que estrelas de massa muito grande podem ter um importante papel na regulação das propriedades rotacionais de estrelas poucomassivas em sua vizinhança. Photometric variability is one of the main characteristics of young stellar objects and explore its particularities in different wavelengths may provide insights on the ongoing physical processes at work in such objects. The most common source of photometric variability in young stars is the brightness modulation, caused by the rotation of a spotted stellar surface. This type of variability allows to measure rotation periods in young stars. In the last decades, the early evolution of pre-main sequence stellar rotational picture has been constrained by studies targeting different young regions at a variety of ages. Observational studies suggest a dependence of rotation with mass, and for some mass ranges a connection between rotation and the presence of a circum stell ardisc. Not still fully explored, though, is the role of environmental conditions on the stellar rotational regulation. In this thesis, we explored the occurrence and main characteristics of near-infrared variability for young stars of the massive OB association Cygnus OB2, which is 1.4 kpc away from the Sun. For objects with periodic variability that could be associated with stellar rotation, we investigated the rotational properties of Cygnus OB2 members. For the sample of rotational periods evaluated, we addressed questions regarding the effect of environment properties on the pre-main sequence rotational evolution. We investigated JHK-band variability of 5083 candidate members (24% of which are disc-bearing stars), using data observed with the wide-eld camera (WFCAM) of the UK Infrared Telescope (UKIRT) on Mauna Kea, Hawaii. A total of 112 nights were observed, spanning 217 days. The sample studied is spread over a eld of 0.78 squared degrees. The selection of variable stars was done by using Stetson variability index, and 60% of the stars in the sample were found to be variable according to this criterion. We investigated the light-curve morphology, and the variations in the colour-colour and colour-magnitude diagrams for JHK-bands, and when the variability was highly correlated in different bands and colours, the slopes produced by the variations inside such diagrams were estimated. These slopes were compared to the slopes expected from the models explaining physicalmechanisms responsible by the variability in young stars, and the causes of variability were investigated. Period search was performed using Lomb-Scargle periodogram for periods between 0.8345 days. Period detection quality was veried by using False Alarm Probability levels, the Saunders statistics, string/rope length method, and visual verication of folded light curves. We identied 1224 periodic variable stars. Monte Carlo simulations were performed in order to evaluate completeness and contamination of the periodic sample, out of which 894 measured periods were considered as reliable. Our study was considered reasonably complete for periods between 2 and 30 days. The general scenario for the rotational evolution of young stars seen in other regions is conrmed by Cygnus OB2 period distributions, with disc-bearing stars rotating on average slower than stars without discs. A mass-rotation dependence was also veried, but as in NGC 6530, very low mass stars (M

We report the characterization of the first 62 Mapping Nearby Galaxies at the Apache Point Observatory active galactic nuclei (AGNs) hosts and the definition of a control sample of non-active galaxies. This control sample was selected in order to match the AGN hosts in terms of stellar mass, redshift, visual morphology and inclination. The stellar masses are in the range 9.4 < log M/M < 11.5, and most objects have redshifts ≤0.08. The AGN sample is mostly comprised low-luminosity AGN, with only 17 ‘strong AGN’ with L([O III]λ5007 Å) ≥ 3.8 × 1040 erg s−1. The inner 1–3 kpc of the control sample galaxies are dominated by the oldest (≥ 4Gyr) component, with a small contribution of intermediate age and young stars (

We present the discovery of a z=0.65 low-ionization broad absorption line (LoBAL) quasar in a post-starburst galaxy in data from the Dark Energy Survey (DES) and spectroscopy from the Australian Dark Energy Survey (OzDES). LoBAL quasars are a minority of all BALs, and rarer still is that this object also exhibits broad FeII (an FeLoBAL) and Balmer absorption. This is the first BAL quasar that has signatures of recently truncated star formation, which we estimate ended about 40 Myr ago. The characteristic signatures of an FeLoBAL require high column densities, which could be explained by the emergence of a young quasar from an early, dust-enshrouded phase, or by clouds compressed by a blast wave. The age of the starburst component is comparable to estimates of the lifetime of quasars, so if we assume the quasar activity is related to the truncation of the star formation, this object is better explained by the blast wave scenario., 7 pages, 4 figures, and 1 table; Submitted to MNRAS. For a brief video summarizing the paper, please see the Coffee Brief at this link: https://www.youtube.com/watch?v=jLhHSFU9u3g&feature=youtu.be Authors updated!

We report the discovery of a stellar over-density 8$^{\circ}$ north of the center of the Small Magellanic Cloud (Small Magellanic Cloud Northern Over-Density; SMCNOD) using data from the first two years of the Dark Energy Survey (DES) and the first year of the MAGellanic SatelLITEs Survey (MagLiteS). The SMCNOD is indistinguishable in age, metallicity and distance from the nearby SMC stars, being primarly composed of intermediate-age stars (6 Gyr, Z=0.001), with a small fraction of young stars (1 Gyr, Z=0.01). The SMCNOD has an elongated shape with an ellipticity of 0.6 and a size of $\sim$ 6x2 deg. It has an absolute magnitude of $M_V \cong$ -7.7, $r_h = 2.1$ kpc, and $\mu_V(r, Comment: 14 pages, 10 color figures

The Canis Major OB1 Association has an intriguing scenario of star formation, especially in the Canis Major R1 (CMa R1) region traditionally assigned to a reflection nebula, but in reality an ionized region. This work is focused on the young stellar population associated to CMa R1, for which our previous results from ROSAT, optical and near-infrared data had revealed two stellar groups with different ages, suggesting a possible mixing of populations originated from distinct star-formation episodes. The X-ray data allow the detected sources to be characterized according to hardness ratios, light curves and spectra. Estimates of mass and age were obtained from the 2MASS catalogue, and used to define a complete subsample of stellar counterparts, for statistical purposes. A catalogue of 387 XMM-Newton sources is provided, 78% being confirmed as members or probable members of the CMa R1 association. Flares were observed for 13 sources, and the spectra of 21 bright sources could be fitted by a thermal plasma model. Mean values of fits parameters were used to estimate X-ray luminosities. We found a minimum value of log(L$_X$[erg/s]) = 29.43, indicating that our sample of low-mass stars (M$_\star$ $\leq$ 0.5 M$_\odot$), being faint X-ray emitters, is incomplete. Among the 250 objects selected as our complete subsample (defining our best sample), 171 are found to the East of the cloud, near Z CMa and dense molecular gas, 50% of them being young (< 5 Myr) and 30% being older (> 10 Myr). The opposite happens to the West, near GU CMa, in areas lacking molecular gas: among 79 objects, 30% are young and 50% are older. These findings confirm that a first episode of distributed star formation occurred in the whole studied region ~10 Myr ago and dispersed the molecular gas, while a second, localized episode (< 5 Myr) took place in the regions where molecular gas is still present., 38 pages, 21 figures, accepted for A&A

It has been well established in the past decades that the central black hole masses of galaxies correlate with dynamical properties of their harbouring bulges. This notion begs the question of whether there are causal connections between the active galactic nucleus (AGN) and its immediate vicinity in the host galaxy. In this paper, we analyse the presence of circumnuclear star formation in a sample of 15 AGN using mid-infrared observations. The data consist of a set of 11.3 μm polycyclic aromatic hydrocarbon emission and reference continuum images, taken with ground-based telescopes, with sub-arcsecond resolution. By comparing our star formation estimates with AGN accretion rates, derived from X-ray luminosities, we investigate the validity of theoretical predictions for the AGN–starburst connection. Our main results are: (i) circumnuclear star formation is found, at distances as low as tens of parsecs from the nucleus, in nearly half of our sample (7/15); (ii) star formation luminosities are correlated with the bolometric luminosity of the AGN (LAGN) only for objects with LAGN ≥ 1042 erg s−1; (iii) low-luminosity AGNs (LAGN < 1042 erg s−1) seem to have starburst luminosities far greater than their bolometric luminosities.