Astronomie

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Measuring the cosmic web
(Vilnius : Lithuanian Astronomical Union, 2011) Müller, V.; Hoffmann, K.; Nuza, S.E.
A quantitative study of the clustering properties of the cosmic web as a function of absolute magnitude and color is presented using the SDSS Data Release 7 galaxy survey. Mark correlations are included in the analysis. We compare our results with mock galaxy samples obtained with four different semi-analytical models of galaxy formation imposed on the merger trees of the Millenium simulation. The clustering of both red and blue galaxies is studied separately.
The x-ray luminous galaxy cluster population at 0.9 < z ≲ 1.6 as revealed by the XMM-Newton Distant Cluster Project*
(Bristol : IOP, 2011) Fassbender, R.; Böhringer, H.; Nastasi, A.; Šuhada, R.; Mühlegger, M.; De Hoon, A.; Kohnert, J.; Lamer, G.; Mohr, J.J.; Pierini, D.; Pratt, G.W.; Quintana, H.; Rosati, P.; Santos, J.S.; Schwope, A.D.
We present the largest sample to date of spectroscopically confirmed x-ray luminous high-redshift galaxy clusters comprising 22 systems in the range 0.9 < z ≲ 1.6 as part of the XMM-Newton Distant Cluster Project (XDCP). All systems were initially selected as extended x-ray sources over 76.1 deg 2 of noncontiguous deep archival XMM-Newton coverage, of which 49.4 deg 2 are part of the core survey with a quantifiable selection function and 17.7 deg 2 are classified as 'gold' coverage as the starting point for upcoming cosmological applications. Distant cluster candidates were followed up with moderately deep optical and near-infrared imaging in at least two bands to photometrically identify the cluster galaxy populations and obtain redshift estimates based on the colors of simple stellar population models. We test and calibrate the most promising redshift estimation techniques based on the R-z and z-H colors for efficient distant cluster identifications and find a good redshift accuracy performance of the z-H color out to at least z ̃ 1.5, while the redshift evolution of the R-z color leads to increasingly large uncertainties at z ≳ 0.9. Photometrically identified high-z systems are spectroscopically confirmed with VLT/FORS 2 with a minimum of three concordant cluster member redshifts. We present first details of two newly identified clusters, XDCPJ0338.5+0029 at z = 0.916 and XDCP J0027.2+1714 at z = 0.959, and investigate the x-ray properties of SpARCS J003550-431224 at z = 1.335, which shows evidence for ongoing major merger activity along the line-of-sight. We provide x-ray properties and luminosity-based total mass estimates for the full sample of 22 high-z clusters, of which 17 are at z ≥ 1.0 and seven populate the highest redshift bin at z > 1.3. The median system mass of the sample is M 200 ≃ 2×10 14 M ⊙, while the probed mass range for the distant clusters spans approximately (0.7-7)×10 14 M ⊙. The majority (>70%) of the x-ray selected clusters show rather regular x-ray morphologies, albeit in most cases with a discernible elongation along one axis. In contrast to local clusters, the z > 0.9 systems mostly do not harbor central dominant galaxies coincident with the x-ray centroid position, but rather exhibit significant brightest cluster galaxy (BCG) offsets from the x-ray center with a median value of about 50 kpc in projection and a smaller median luminosity gap to the second-ranked galaxy of Δm 12 ≃ 0.3 mag. We estimate a fraction of cluster-associated NVSS 1.4 GHz radio sources of about 30%, preferentially located within 1' from the x-ray center. This value suggests an increase of the fraction of very luminous cluster-associated radio sources by about a factor of 2.5-5 relative to lowz systems. The galaxy populations in z ≳ 1.5 cluster environments show first evidence for drastic changes on the high-mass end of galaxies and signs of a gradual disappearance of a well-defined cluster red-sequence as strong star formation activity is observed in an increasing fraction of massive galaxies down to the densest core regions. The presented XDCP high-z sample will allow first detailed studies of the cluster population during the critical cosmic epoch at lookback times of 7.3-9.5Gyr on the aggregation and evolution of baryons in the cold and hot phases as a function of redshift and system mass.
BF Cyg during ITS current outburst
(Vilnius : Lithuanian Astronomical Union, 2012) Siviero, A.; Tamajo, E.; Lutz, J.; Wallerstein, G.
We are intensively monitoring the current outburst on BF Cyg, both spectroscopically (high and low resolution modes) and photometrically (so far 450 BVRCRIC measurements have been collected). The outburst is photometrically reminiscent of the major event BF Cyg experienced in 1890 when it rose by 4 mag in the blue. In this contribution we present the data and describe the plans to investigate this object.
Abell-35 phenomena in symbiotic stars: Discovery of 1.2 and 6.4 day periods in VV8 (V471 per)
(Vilnius : Lithuanian Astronomical Union, 2012) Munari, U.; Siviero, A.; Tamajo, E.; Fiaschi, M.; Dallaporta, S.; Cherini, G.; Frigo, A.; Castellani, F.; Graziani, M.; Moretti, S.; Tomaselli, S.
We have collected high precision optical photometry of VV8, so far 782 individual observing runs uniformly distributed over the period 2005-2011. This dataset allows us to refine the known long periodicity of VV8 to P = 16.8 yr, with peak-to-valley amplitudes of ΔB = 0.18 and ΔV = 0.14 mag. In addition, we have discovered two new periodicities: 6.431 d (total amplitude Δ = ΔV = ΔI= 0.05 mag) and 1.185 d (ΔB = 0.022, ΔV = 0.018, ΔI = 0.014 mag). These two short periods are reminiscent of the Abell35 phenomena displayed by binary nuclei of planetary nebulae that have gone through a common envelope phase. Twice the 6.431 d period would nicely correspond to the double-peaked light-curve that the G5 III star in VV8 would display if its Roche lobe would be ellipsoidally distorted.
Polarization Calibration of the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO)
(Heidelberg : Springer, 2012) Schou, J.; Borrero, J.M.; Norton, A.A.; Tomczyk, S.; Elmore, D.; Card, G.L.
As part of the overall ground-based calibration of the Helioseismic and Magnetic Imager (HMI) instrument an extensive set of polarimetric calibrations were performed. This paper describes the polarimetric design of the instrument, the test setup, the polarimetric model, the tests performed, and some results. It is demonstrated that HMI achieves an accuracy of 1% or better on the crosstalks between Q, U, and V and that our model can reproduce the intensities in our calibration sequences to about 0.4%. The amount of depolarization is negligible when the instrument is operated as intended which, combined with the flexibility of the polarimeter design, means that the polarimetric efficiency is excellent.
The first SEPServer event catalogue ~68-MeV solar proton events observed at 1 AU in 1996-2010
(Les Ulis : EDP Sciences, 2013) Vainio, R.; Valtonen, E.; Heber, B.; Malandraki, O.E.; Papaioannou, A.; Klein, K.-L.; Afanasiev, A.; Agueda, N.; Aurass, H.; Battarbee, M.; Braune, S.; Dröge, W.; Ganse, U.; Hamadache, C.; Heynderickx, D.; Huttunen-Heikinmaa, K.; Kiener, J.; Kilian, P.; Kopp, A.; Kouloumvakos, A.; Maisala, S.; Mishev, A.; Miteva, R.; Nindos, A.; Oittinen, T.; Raukunen, O.; Riihonen, E.; Rodríguez-Gasén, R.; Saloniemi, O.; Sanahuja, B.; Scherer, R.; Spanier, F.; Tatischeff, V.; Tziotziou, K.; Usoskin, I.G.; Vilmer, N.
SEPServer is a three-year collaborative project funded by the seventh framework programme (FP7-SPACE) of the European Union. The objective of the project is to provide access to state-of-the-art observations and analysis tools for the scientific community on solar energetic particle (SEP) events and related electromagnetic (EM) emissions. The project will eventually lead to better understanding of the particle acceleration and transport processes at the Sun and in the inner heliosphere. These processes lead to SEP events that form one of the key elements of space weather. In this paper we present the first results from the systematic analysis work performed on the following datasets: SOHO/ERNE, SOHO/EPHIN, ACE/EPAM, Wind/WAVES and GOES X-rays. A catalogue of SEP events at 1 AU, with complete coverage over solar cycle 23, based on high-energy (~68-MeV) protons from SOHO/ERNE and electron recordings of the events by SOHO/EPHIN and ACE/EPAM are presented. A total of 115 energetic particle events have been identified and analysed using velocity dispersion analysis (VDA) for protons and time-shifting analysis (TSA) for electrons and protons in order to infer the SEP release times at the Sun. EM observations during the times of the SEP event onset have been gathered and compared to the release time estimates of particles. Data from those events that occurred during the European day-time, i.e., those that also have observations from ground-based observatories included in SEPServer, are listed and a preliminary analysis of their associations is presented. We find that VDA results for protons can be a useful tool for the analysis of proton release times, but if the derived proton path length is out of a range of 1 AU < s a 2 3 AU, the result of the analysis may be compromised, as indicated by the anti-correlation of the derived path length and release time delay from the associated X-ray flare. The average path length derived from VDA is about 1.9 times the nominal length of the spiral magnetic field line. This implies that the path length of first-arriving MeV to deka-MeV protons is affected by interplanetary scattering. TSA of near-relativistic electrons results in a release time that shows significant scatter with respect to the EM emissions but with a trend of being delayed more with increasing distance between the flare and the nominal footpoint of the Earth-connected field line.
Hot moons and cool stars
(Les Ulis : EDP Sciences, 2013) Heller, R.; Barnes, R.
The exquisite photometric precision of the Kepler space telescope now puts the detection of extrasolar moons at the horizon. Here, we firstly review observational and analytical techniques that have recently been proposed to find exomoons. Secondly, we discuss the prospects of characterizing potentially habitable extrasolar satellites. With moons being much more numerous than planets in the solar system and with most exoplanets found in the stellar habitable zone being gas giants, habitable moons could be as abundant as habitable planets. However, satellites orbiting planets in the habitable zones of cool stars will encounter strong tidal heating and likely appear as hot moons.
Differential population studies using asteroseismology: Solar-like oscillating giants in CoRoT fields LRc01 and LRa01
(Les Ulis : EDP Sciences, 2013) Miglio, A.; Chiappini, C.; Morel, T.; Barbieri, M.; Chaplin, W.J.; Girardi, L.; Montalbán, J.; Noels, A.; Valentini, M.; Mosser, B.; Baudin, F.; Casagrande, L.; Fossati, L.; Aguirre, V.S.; Baglin, A.
Solar-like oscillating giants observed by the space-borne satellites CoRoT and Kepler can be used as key tracers of stellar populations in the Milky Way. When combined with additional photometric/spectroscopic constraints, the pulsation spectra of solar-like oscillating giant stars not only reveal their radii, and hence distances, but also provide well-constrained estimates of their masses, which can be used as proxies for the ages of these evolved stars. In this contribution we provide supplementary material to the comparison we presented in Miglio et al. (2013) between populations of giants observed by CoRoT in the fields designated LRc01 and LRa01.
Constraining the formation of the Milky Way: Ages
(Les Ulis : EDP Sciences, 2013) Chiappini, C.; Minchev, I.; Martig, M.
We present a new approach for studying the chemodynamical evolution of the Milky Way, which combines a thin disk chemical evolution model with the dynamics from N-body simulation of a galaxy with properties similar to those of our Galaxy. A cosmological re-simulation is used as a surrogate in order to extract ∼11 Gyrs of self-consistent dynamical evolution. We are then in a position to quantify the impact of radial migration at the Solar Vicinity. We find that the distribution of birth radii, r0, of stars ending up in a solar neighborhood-like location after ∼11 Gyr of evolution peaks around r0 = 6 kpc due to radial migration. A wide range of birth radii is seen for different age groups. The strongest effect from radial migration is found for the oldest stars and it is connected to an early merger phase typical from cosmological simulations. We find that while the low-end in our simulated solar vicinity metallicity distribution is composed by stars with a wide range of birth radii, the tail at larger metallicities (0.25 <[Fe/H]< 0.6) results almost exclusively from stars with 3 < r0< 5 kpc. This is the region just inside the bar's corotation (CR), which is where the strongest outward radial migration occurs. The fraction of stars in this tail can, therefore, be related to the bar's dynamical properties, such as its strength, pattern speed and time evolution/formation. We show that one of the main observational constraints of this kind of models is the time variation of the abundance gradients in the disk. The most important outcome of our chemodynamical model is that, although we used only a thin-disc chemical evolution model, the oldest stars that are now in the solar vicinity show several of the properties usually attributed to the Galactic thick disc. In other words, in our model the MW "thick disc" emerges naturally from stars migrating from the inner disc very early on due to strong merger activity in the first couple of Gyr of disc formation, followed by further radial migration driven by the bar and spirals at later times. These results will be extended to other radius bins and more chemical elements in order to provide testable predictions once more precise information on ages and distances would become available (with Gaia, asteroseismology and future surveys such as 4MOST).
Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars
(London : Nature Publishing Group, 2013) Murdin, B.N.; Li, J.; Pang, M.L.Y.; Bowyer, E.T.; Litvinenko, K.L.; Clowes, S.K.; Engelkamp, H.; Pidgeon, C.R.; Galbraith, I.; Abrosimov, N.V.; Riemann, H.; Pavlov, S.G.; Hübers, H.-W.; Murdin, P.G.
Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10 5 T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. In this regime, the cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8 T by the effective mass and dielectric constant. The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics. They show the way for experiments on He and H 2 analogues, and for investigation of He 2, a bound molecule predicted under extreme field conditions.
Ion-Acoustic Instabilities in a Multi-Ion Plasma
(New York, NY [u.a.] : Hindawi, 2013) Abraham, Noble P.; Sebastian, Sijo; Sreekala, G.; Jayapal, R.; Anilkumar, C. P.; Chandu, Venugopal
We have, in this paper, studied the stability of the ion-acoustic wave in a plasma composed of hydrogen, positively and negatively charged oxygen ions, and electrons, which approximates very well the plasma environment around a comet. Modelling each cometary component (H+, O+, and O−) by a ring distribution, we find that ion-acoustic waves can be generated at frequencies comparable to the hydrogen ion plasma frequency. The dispersion relation has been solved both analytically and numerically. We find that the ratio of the ring speed (u⊥s) to the thermal spread (vts) modifies the dispersion characteristics of the ion-acoustic wave. The contrasting behaviour of the phase velocity of the ion-acoustic wave in the presence of O− ions for u⊥s > vts (and vice versa) can be used to detect the presence of negatively charged oxygen ions and also their thermalization.
A multi-model approach to X-ray pulsars: Connecting spectral and timing models to pin down the intrinsic emission characteristics of magnetized, accreting neutron stars
(Les Ulis : EDP Sciences, 2014) Schönherr, G.; Schwarm, F.; Falkner, S.; Becker, P.; Wilms, J.; Dauser, T.; Wolff, M.T.; Wolfram, K.; West, B.; Pottschmidt, K.; Kretschmar, P.; Ferrigno, C.; Klochkov, D.; Nishimura, O.; Kreykenbohm, I.; Caballero, I.; Staubert, R.
The emission characteristics of X-ray pulsars are governed by magnetospheric accretion within the Alfvén radius, leading to a direct coupling of accretion column properties and interactions at the magnetosphere. The complexity of the physical processes governing the formation of radiation within the accreted, strongly magnetized plasma has led to several sophisticated theoretical modelling efforts over the last decade, dedicated to either the formation of the broad band continuum, the formation of cyclotron resonance scattering features (CRSFs) or the formation of pulse profiles. While these individual approaches are powerful in themselves, they quickly reach their limits when aiming at a quantitative comparison to observational data. Too many fundamental parameters, describing the formation of the accretion columns and the systems' overall geometry are unconstrained and different models are often based on different fundamental assumptions, while everything is intertwined in the observed, highly phase-dependent spectra and energy-dependent pulse profiles. To name just one example: the (phase variable) line width of the CRSFs is highly dependent on the plasma temperature, the existence of B-field gradients (geometry) and observation angle, parameters which, in turn, drive the continuum radiation and are driven by the overall two-pole geometry for the light bending model respectively. This renders a parallel assessment of all available spectral and timing information by a compatible across-models-approach indispensable. In a collaboration of theoreticians and observers, we have been working on a model unification project over the last years, bringing together theoretical calculations of the Comptonized continuum, Monte Carlo simulations and Radiation Transfer calculations of CRSFs as well as a General Relativity (GR) light bending model for ray tracing of the incident emission pattern from both magnetic poles. The ultimate goal is to implement a unified fitting model for phase-resolved spectral and timing data analysis. We present the current status of this project.
Magnetic fields of Herbig Ae/Be stars
(Les Ulis : EDP Sciences, 2014) Hubrig, S.; Ilyin, I.; Schöller, M.; Cowley, C.R.; Castelli, F.; Stelzer, B.; Gonzalez, J.-F.; Wolff, B.
We report on the status of our spectropolarimetric studies of Herbig Ae/Be stars carried out during the last years. The magnetic field geometries of these stars, investigated with spectropolarimetric time series, can likely be described by centred dipoles with polar magnetic field strengths of several hundred Gauss. A number of Herbig Ae/Be stars with detected magnetic fields have recently been observed with X-shooter in the visible and the near-IR, as well as with the high-resolution near-IR spectrograph CRIRES. These observations are of great importance to understand the relation between the magnetic field topology and the physics of the accretion flow and the accretion disk gas emission.
Luminosity dependent accretion state change in GRO J1008-57
(Les Ulis : EDP Sciences, 2014) Kühnel, M.; Müller, S.; Kreykenbohm, I.; Fürst, F.; Pottschmidt, K.; Rothschild, R.E.; Caballero, I.; Grinberg, V.; Schönherr, G.; Shrader, C.; Klochkov, D.; Staubert, R.; Ferrigno, C.; Torrejón, J.-M.; Martínez-Núñez, S.; Wilms, J.
In a former publication, we have analyzed the transient neutron star X-ray binary GRO J1008-57 using all available RXTE-, Swift-, and Suzaku-data. As we have found, the source's spectral components, i.e., a power-law with high exponential cutoff and a black-body, are strongly correlated with the hard X-ray flux (15-50 keV). We update the analytical description of these dependence, including a change in the photon index behaviour from a flat to a logarithmic function. The flux, where the change occurs, is consistent with the onset of the black-body emission. Thus, a change of the accretion state always occurs in GRO J1008-57 at a particular flux level.
Simulation of cyclotron resonant scattering features: The effect of bulk velocity
(Les Ulis : EDP Sciences, 2014) Schwarm, F.-W.; Schönherr, G.; Kühnel, M.; Wilms, J.
X-ray binary systems consisting of a mass donating optical star and a highly magnetized neutron star, under the right circumstances, show quantum mechanical absorption features in the observed spectra called cyclotron resonant scattering features (CRSFs). We have developed a simulation to model CRSFs using Monte Carlo methods. We calculate Green's tables which can be used to imprint CRSFs to arbitrary X-ray continua. Our simulation keeps track of scattering parameters of individual photons, extends the number of variable parameters of previous works, and allows for more flexible geometries. Here we focus on the influence of bulk velocity of the accreted matter on the CRSF line shapes and positions.
The Herbig Ae SB2 system HD 104237
(Les Ulis : EDP Sciences, 2014) Cowley, C.R.; Castelli, J.; Hubrig, S.
We present here the most recent abundance analysis of this Herbig Ae system based on high-resolution UVES and HARPS spectra and the results of our magnetic field measurements using high-resolution spectra obtained with HARPSpol.
Large-scale globally propagating coronal waves
(Katlenburg-Lindau : MPS, 2015) Warmuth, Alexander
Large-scale, globally propagating wave-like disturbances have been observed in the solar chromosphere and by inference in the corona since the 1960s. However, detailed analysis of these phenomena has only been conducted since the late 1990s. This was prompted by the availability of high-cadence coronal imaging data from numerous spaced-based instruments, which routinely show spectacular globally propagating bright fronts. Coronal waves, as these perturbations are usually referred to, have now been observed in a wide range of spectral channels, yielding a wealth of information. Many findings have supported the “classical” interpretation of the disturbances: fast-mode MHD waves or shocks that are propagating in the solar corona. However, observations that seemed inconsistent with this picture have stimulated the development of alternative models in which “pseudo waves” are generated by magnetic reconfiguration in the framework of an expanding coronal mass ejection. This has resulted in a vigorous debate on the physical nature of these disturbances. This review focuses on demonstrating how the numerous observational findings of the last one and a half decades can be used to constrain our models of large-scale coronal waves, and how a coherent physical understanding of these disturbances is finally emerging.
XUV excitation followed by ultrafast non-adiabatic relaxation in PAH molecules as a femto-astrochemistry experiment
([London] : Nature Publishing Group UK, 2015) Marciniak, A.; Despré, V.; Barillot, T.; Rouzée, A.; Galbraith, M.C.E.; Klei, J.; Yang, C.-H.; Smeenk, C.T.L.; Loriot, V.; Nagaprasad Reddy, S.; Tielens, A.G.G.M.; Mahapatra, S.; Kuleff, A.I.; Vrakking, M.J.J.; Lépine, F.
Highly excited molecular species are at play in the chemistry of interstellar media and are involved in the creation of radiation damage in a biological tissue. Recently developed ultrashort extreme ultraviolet light sources offer the high excitation energies and ultrafast time-resolution required for probing the dynamics of highly excited molecular states on femtosecond (fs) (1 fs=10−15s) and even attosecond (as) (1 as=10−18 s) timescales. Here we show that polycyclic aromatic hydrocarbons (PAHs) undergo ultrafast relaxation on a few tens of femtoseconds timescales, involving an interplay between the electronic and vibrational degrees of freedom. Our work reveals a general property of excited radical PAHs that can help to elucidate the assignment of diffuse interstellar absorption bands in astrochemistry, and provides a benchmark for the manner in which coupled electronic and nuclear dynamics determines reaction pathways in large molecules following extreme ultraviolet excitation.
A low pre-infall mass for the Carina dwarf galaxy from disequilibrium modeling
([London] : Nature Publishing Group UK, 2015) Ural, Uğur; Wilkinson, Mark I.; Read, Justin I.; Walker, Matthew G.
Dark matter-only simulations of galaxy formation predict many more subhalos around a Milky Way-like galaxy than the number of observed satellites. Proposed solutions require the satellites to inhabit dark matter halos with masses 109–1010Msun at the time they fell into the Milky Way. Here we use a modelling approach, independent of cosmological simulations, to obtain a pre-infall mass of Msun for one of the Milky Way’s satellites: Carina. This determination of a low halo mass for Carina can be accommodated within the standard model only if galaxy formation becomes stochastic in halos below ∼1010Msun. Otherwise Carina, the eighth most luminous Milky Way dwarf, would be expected to inhabit a significantly more massive halo. The implication of this is that a population of ‘dark dwarfs’ should orbit the Milky Way: halos devoid of stars and yet more massive than many of their visible counterparts.
The CALIFA Survey: Exploring the Oxygen Abundance in the Local Universe
(Basel : MDPI, 2015) Sánchez, Sebastian; Sánchez-Menguiano, Laura; Marino, Raffaella; Rosales-Ortega, F.; Pérez, Isabel; de Paz, Armando; Pérez, Enrique; Walcher, C.; López-Cobá, Carlos
We present here a review of the latest results on the spatially-resolved analysis of the stellar populations and ionized gas of disk-dominated galaxies based on Calar Alto Legacy Integral Field Area (CALIFA) data. CALIFA is an ongoing integral field spectroscopy (IFS) survey of galaxies in the Local Universe (0.005 < z < 0.03) that has already obtained spectroscopic information up to ∼2.5 re with a spatial resolution better than ∼1 kpc for a total number of more than 600 galaxies of different morphological types, covering the color-magnitude diagram up to MR<−18 mag. With nearly 2000 spectra obtained for each galaxy, CALIFA offers one of the best IFU datasets to study the star formation histories and chemical enrichment of galaxies. In this article, we focus on the main results from the analysis of the oxygen abundances based on the study of ionized gas in H II regions and individual spaxels and their relation to the global properties of galaxies, using an updated/revised dataset with more galaxies and ionized regions. In summary, we have confirmed previous published results indicating that: (1) the M-Z relation does not present a secondary relation to the star formation rate, when the abundance is measured at the effective radius; (2) the oxygen abundance presents a strong correlation with the stellar surface density (∑-Z relation); (3) the oxygen abundance profiles present three well-defined regimes: (i) an overall negative radial gradient between 0.5 and 2 re, with a characteristic slope of αO/H ∼−0.1 dex/re; (ii) a universal flattening beyond >2 re; and (iii) an inner drop at <0.5 re that depends on mass; (4) the presence of bending in the surface brightness profile of disk galaxies is not clearly related to either the change in the shape of the oxygen abundance profile or the properties of the underlying stellar population. All of these results indicate that disk galaxies present an overall inside-out growth, with chemical enrichment and stellar mass growth tightly correlated and dominated by local processes and limited effects of radial mixing or global outflows. However, clear deviations are shown with respect to this simple scenario, which affect the abundance profiles in both the innermost and outermost regions of galaxies

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