arXiv subjects

I. Breda

Publications and source records attributed to I. Breda.

14 recordsLinked to original sources

arXiv2026

The MAGPI Survey: Emission Line Products Data Release and the Role of Spectroscopic Aperture Covering Fraction on the Balmer Decrement-Stellar Mass Relation

The Middle Ages Galaxy Properties with Integral field spectroscopy (MAGPI) survey is a Large Program on the European Southern Observatory Very Large Telescope using the MUSE instrument. This paper presents the data release for the MAGPI emission line products and includes emission line maps for 836 galaxies at $0.05\leq z_\mathrm{spec}\leq 0.424$ ($\mathrm{H}\alpha$-window) and aperture-based emission line measurements for 2,607 galaxies at $0.05\leq z_\mathrm{spec}\leq 1.50$ (upper bound is [OII] cut-off), both based on the GIST software, for all 56 MAGPI fields. We use these data to examine dust attenuation, which represents a major source of uncertainty in the derived properties of galaxies that are critical to constrain models of galaxy evolution. We examine the role that the spectroscopic aperture covering fraction ($f_c$) has on the relationship between the Balmer decrement ($\mathrm{BD}=F(\mathrm{H}\alpha)/F(\mathrm{H}\beta)$; a common proxy for dust attenuation) and the total stellar mass ($M_\star$). Several studies have suggested that the BD-$M_\star$ relation may be redshift invariant; however, the compared surveys often have different $f_c$ due to their differing fibre or slit sizes that can cause systematic offsets. Our results indicate that $f_c$ has a significant impact on this relationship, due to galaxies having negative BD radial gradients, which are more negative for more massive galaxies at $z\lesssim0.4$. Comparing spectroscopic surveys with $\left \gtrsim 0.5$, we find that the BD-$M_\star$ relation shows a preference for redshift evolution and is roughly consistent with the behaviour of UV stellar continuum attenuation redshift evolution ($A_\mathrm{FUV}$-$z$), with the average dust attenuation in galaxies peaking at $z\sim1.2$ and decreasing at lower and higher redshifts.

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arXiv2026

The MAGPI Survey: Evidence for Non-Universal Resolved Dust Attenuation Relations Beyond the Local Universe

We study the spatially resolved relation between dust attenuation ($A_V$) and star formation rate surface density ($\Sigma_{\mathrm{SFR}}$) in galaxies from the MAGPI survey ($0.25 < z < 0.42$). Using Balmer-decrement-based attenuation maps for 178 galaxies, we investigate whether the locally calibrated resolved $A_V$--$\Sigma_{\mathrm{SFR}}$ relation remains valid at intermediate redshift by comparing MAGPI with the local relation measured from MaNGA. We find a clear positive correlation between $A_V$ and $\Sigma_{\mathrm{SFR}}$ in MAGPI, with systematically higher attenuation than in MaNGA at fixed $\Sigma_{\mathrm{SFR}}$. After matching galaxies in stellar mass ($M_{*}$) and offset from the star-forming main sequence ($\Delta$SFMS), MAGPI galaxies remain more attenuated than MaNGA galaxies at fixed $\Sigma_{\mathrm{SFR}}$. The attenuation excess is strongest for galaxies below the SFMS ($\Delta A_V \sim 0.40$ mag), weaker for galaxies on the SFMS ($\Delta A_V \sim 0.28$ mag), and minimal for galaxies above the SFMS ($\Delta A_V \sim 0.07$ mag). The dependence of the offset on $\Delta$SFMS suggests that nebular attenuation on kpc scales is regulated not only by local star formation activity, but also by the global evolutionary state of the host galaxy. Together, these results indicate that the resolved $A_V$--$\Sigma_{\mathrm{SFR}}$ relation is not universal, and that locally calibrated attenuation relations may not fully describe galaxies at intermediate redshift. This highlights the need for attenuation calibrations that account for galaxy population and redshift when interpreting spatially resolved galaxy properties.

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arXiv2026

A spectroscopic map of the Galactic centre: Integrated light and dynamical modelling

The centre of the Milky Way is occupied by a nuclear star cluster that contains the supermassive black hole Sgr A*. The cluster is embedded in the larger surrounding nuclear stellar disc. These three components dominate the mass budget of the Galactic centre at different radial scales. The mass distribution of the Galactic centre has been studied extensively using observations of individual bright stars and various dynamical modelling approaches. The situation differs for external galaxies, where observations are often limited to the integrated line-of-sight kinematics. For such systems, triaxial orbit-based dynamical modelling has become a standard method of deriving mass distributions and stellar orbit distributions. We aim to apply and test this method on the Galactic centre. We extracted stellar line-of-sight kinematic maps of the inner ~3 pc x 66 pc region of the Galactic centre. We used the DYNAMITE code, which calculates an orbit library in a given gravitational potential and computes model kinematic maps. These maps were then compared to the observed kinematic maps, and the gravitational potential and orbit distribution of the Galactic centre were constrained. We recover the correct mass of Sgr A*, and our stellar mass distributions are in agreement with the literature, albeit with larger uncertainties. The stellar structures are at most mildly triaxial and close to oblate. The stellar orbit distribution in the inner region is dominated by dynamically warm and hot orbits. At larger scales, dynamically cold -- highly rotating -- orbits have the largest weights. The dominance of hot and warm orbits is a consequence of short dynamical timescales in the inner Galactic centre, causing dynamical heating. The presence of cold orbits at large radii may be explained by the longer heating timescales in this region, and by the stars in the outer nuclear stellar disc being younger.[abridged]

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arXiv2026

Not So Isolated: Green Pea Galaxies in Overdense Environments revealed by VLT/MUSE

Context. Green Pea galaxies (GPs) are local starburst galaxies serving as analogues for high-redshift star-forming galaxies, particularly Lyman continuum leakers. It remains debated whether their starbursts are driven by internal secular processes or external triggers. Aims. We aim to constrain the role of environment in this triggering, testing whether external influence comes from close interactions or diffuse processes like gas accretion. Methods. We analyse VLT/MUSE observations of 24 GPs at $z \sim 0.2$ to identify companions via spectral line features. We derive key physical properties (extinction, SFR, stellar mass, age, metallicity) for GPs and companions, and estimate group dynamical masses. Results. We identify 22 emission-line galaxies, 11 being companions ($|\Delta v| \leq 500$ km s$^{-1}$). We find a high companion fraction ($33^{+11}_{-8}$%) and a $\sim$1 dex number density excess compared to the field, confirming GPs reside in overdense environments. Companions typically lie at projected separations of $\sim$100 kpc with no evidence of ongoing interactions. Physically, GPs form a homogeneous class of young (mass-weighted age $\sim$230 Myr), metal-poor, high-sSFR starbursts with elevated velocity dispersions. In contrast, companions are more evolved ($\sim$1.6 Gyr) and heterogeneous in stellar mass, metallicity, and dust attenuation. Inferred group dynamical masses are $\sim$3 dex higher than total stellar masses, suggesting significant dark matter and neutral gas. Conclusions. GPs do not appear triggered by ongoing major mergers with close (10-30 kpc) companions. Results favor a scenario where GPs are transient starbursts in overdense regions, plausibly sustained by gas accretion. Limited spatial resolution prevents ruling out very close mergers ($\lesssim 10$ kpc). High dynamical-to-stellar mass ratios imply substantial non-stellar mass in these systems.

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arXiv2026

OJAL\'A: Optimizing J-PAS Astronomy for Large-scale Analysis. A foundation model for the SED of galaxies, QSOs and stars

The advent of large-scale surveys requires efficient ML techniques to exploit the information of massive datasets. We present OJALA, a transformer-based autoregressive foundation model designed to simultaneously classify astronomical objects and infer their physical parameters using 54 narrow bands from J-PAS, combined with broad bands from the DESI Legacy Imaging Surveys and WISE. The model is trained on $\sim20$ million synthetic SEDs generated from DESI DR1 spectra. We validate OJALA using a cross-matched sample of $\sim121,000$ objects between J-PAS and DESI. The model achieves a weighted F1-score of approximately 0.9 for spectral classification (stars, galaxies, and QSOs) at $i < 21$. For galaxies, we recover photo-z with a precision of $\sigma_{\rm NMAD} < 0.01$, while for QSOs, the precision improves significantly at $z > 1.5$, reaching $\sigma_{\rm NMAD} \approx 0.006$ at $z \approx 3.5$. We demonstrate robust estimation of physical properties for galaxies, recovering stellar masses and SFR with a scatter of approximately 0.11 dex and 0.22 dex, respectively. Furthermore, the model accurately predicts EWs for major optical emission lines, allowing for the derivation of extinction-corrected H$\alpha$ luminosities with a scatter of 0.29 dex. OJALA successfully reproduces the BPT and WHAN diagnostic diagrams, classifying SF, AGN, and passive galaxies with F1-scores typically ranging from 70% to 90% depending on the diagnostic class. For stars, the model reliably infers effective temperature and metallicity, though surface gravity remains challenging. Finally, we show the modularity of the architecture by fine-tuning the pre-trained embeddings to predict BH masses, a property not included in the primary training, recovering spectroscopic virial estimates with a precision of approximately 0.5 dex. We release the code, model weights, and a comprehensive VAC for the J-PAS EDR.

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arXiv2025

J-PAS: First Identification, Physical Properties and Ionization Efficiency of Extreme Emission Line Galaxies

Extreme emission line galaxies (EELGs) are key tracers of intense star formation and potential analogues of the sources that reionized the early Universe. Their low-redshift counterparts offer a unique opportunity to study the physical conditions that enable high ionizing-photon escape fractions. We present a robust method to photometrically identify EELGs in the J-PAS survey, which provides 56 optical bands over 8500 deg^2. Using data from a fully observed 30 deg^2 region, we combine narrow-band equivalent widths with machine-learning techniques to select galaxies with emission lines above 300 {\AA}. The method achieves 95% purity and 96% completeness for $i_\mathrm{SDSS}<22.5$ mag. We identify 917 EELGs up to $z=0.8$; spectroscopic cross-matching with DESI/DR1 confirms the reliability of our redshifts and emission-line measurements. The selected galaxies show strong correlations between $\xi_\mathrm{ion}$ and EW([OIII]), consistent with previous low- and high-z studies. Most sources exceed the ionizing efficiency threshold required for reionization, reinforcing their role as local analogues of early-Universe galaxies.

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arXiv2025

J-PAS: A value-added catalogue of optical line intensities for nebular emission galaxies (JOLINES)

We present the value-added catalogue JOLINES (J-PAS optical line intensities for nebular emission galaxies), which provides emission-line fluxes in galaxies at from the spectrophotometric catalogues of miniJPAS, J-NEP and the J-PAS early data release (EDR). This catalogue will be updated with future data releases, offering a growing resource for the study of emission-line galaxies. To obtain reliable emission-line fluxes from narrow-band photometry, we employed spectral energy distribution (SED) fitting using CIGALE, a robust tool that reconstructs the continuum emission and ensures accurate flux measurements. This method effectively mitigates uncertainties associated with direct continuum subtraction techniques, and systematics such as absorption components in the emission lines. We validate our approach using simulated observations of galaxy spectra with added noise, testing the method's performance across different equivalent width (EW) regimes and emission-line strengths. Additionally, we compare the recovered emission-line fluxes with spectroscopic measurements from the Sloan Digital Sky Survey (SDSS) and the Dark Energy Spectroscopic Instrument (DESI). Our results show a tight correlation between photometric and spectroscopic fluxes, particularly for bright emission lines, with a typical dispersion of $\sim$0.3 dex. Reliable fluxes are obtained for emission lines with EW $\gtrsim20\, \rm{\mathring{A}}$, in agreement with previous empirical studies. The current catalogue comprises approximately 13,900 sources with reliable flux measurements in the H$\alpha$+[NII] complex and 7,200 in [OIII]$\lambda 5007$, ensuring statistically robust samples for the brightest optical emission lines. This resource will be expanded in future J-PAS releases, facilitating large-scale studies of star formation, AGN activity, and galaxy evolution.

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arXiv2025

J-PAS: A Neural Network Approach to Single Stellar Population Characterization

J-PAS (Javalambre Physics of the Accelerating Universe Astrophysical Survey) will present a groundbreaking photometric survey covering 8500 deg$^2$ of the visible sky from Javalambre, capturing data in 56 narrow band filters. This survey promises to revolutionize galaxy evolution studies by observing $\sim$10$^8$ galaxies with low spectral resolution. A crucial aspect of this analysis involves predicting stellar population parameters from the observed galaxy photometry. In this study, we combine the exquisite J-PAS photometry with state-of-the-art single stellar population (SSP) libraries to accurately predict stellar age, metallicity, and dust attenuation with a neural network (NN) model. The NN is trained on synthetic J-PAS photometry from different SSP librares (E-MILES, Charlot & Bruzual, XSL), to enhance the robustness of our predictions against individual SSP model variations and limitations. To create mock samples with varying observed magnitudes we add artificial noise in the form of random Gaussian variations within typical observational uncertainties in each band. Our results indicate that the NN can accurately estimate stellar parameters for SSP models without evident degeneracies, surpassing a bayesian SED-fitting method on the same test set. We obtain median bias, scatter and percentage of outliers $\mu$ = (0.01 dex, 0.00 dex, 0.00 mag), $\sigma_{NMAD}$ = (0.23 dex, 0.29 dex, 0.04 mag), f$_{o}$ = (17 %, 24 %, 1 %) at $ i \sim$17 mag for age, metallicity and dust attenuation, respectively. The accuracy of the predictions is highly dependent on the signal-to-noise (S/N) ratio of the photometry, achieving robust predictions up to $i$ $\sim$ 20 mag.

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arXiv2025

Exploring the spatially-resolved capabilities of the J-PAS survey with Py2DJPAS

We present Py2DJPAS, a Python-based tool to automate the analysis of spatially resolved galaxies in the \textbf{miniJPAS} survey, a 1~deg$^2$ precursor of the J-PAS survey, using the same filter system, telescope, and Pathfinder camera. Py2DJPAS streamlines the entire workflow: downloading scientific images and catalogs, performing PSF homogenization, masking, aperture definition, SED fitting, and estimating optical emission line equivalent widths via an artificial neural network. We validate Py2DJPAS on a sample of resolved miniJPAS galaxies, recovering magnitudes in all bands consistent with the catalog ($\sim 10$~\% precision using SExtractor). Local background estimation improves results for faint galaxies and apertures. PSF homogenization enables consistent multi-band photometry in inner apertures, allowing pseudo-spectra generation without artifacts. SED fitting across annular apertures yields residuals $<10$~\%, with no significant wavelength-dependent bias for regions with $S/N>5$. We demonstrate the IFU-like capability of J-PAS by analyzing the spatially resolved properties of galaxy 2470-10239 at $z = 0.078$, comparing them to MaNGA data within 1 half-light radius (HLR). We find excellent agreement in photometric vs. spectroscopic measurements and stellar mass surface density profiles. Our analysis extends to 4 HLR (S/N~$\sim$~5), showing that J-PAS can probe galaxy outskirts, enabling the study of evolutionary processes at large galactocentric distances.

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arXiv2023

A MUSE/VLT spatially resolved study of the emission structure of Green Pea galaxies

Green Pea galaxies are remarkable for their intense star formation and serve as a window into the early universe. In our study, we used integral field spectroscopy to examine 24 of these galaxies in the optical spectrum. We focused on the interaction between their ionized interstellar medium and the star formation processes within them. Our research generated spatial maps of emission lines and other properties like ionization structures and chemical conditions. These maps showed that areas with higher levels of excitation are usually located where starbursts are occurring. Continuum maps displayed more intricate structures than emission line maps and hinted at low brightness ionized gas in the galaxies' outer regions. We also analyzed integrated spectra from selected areas within these galaxies to derive physical properties like electron densities and temperatures. In some galaxies, we were able to determine metallicity levels. Our observations revealed the presence of high-ionizing lines in three galaxies, two of which had extremely high rates of star formation. Our findings provide valuable insights into the properties and star-forming processes in Green Pea galaxies, contributing to our broader understanding of galactic evolution in the early universe.

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arXiv2017

The continuous rise of bulges out of galactic disks

(abridged) This study revolves around dmB, a new distance- and extinction-independent measure of the contribution by stellar populations older than 9 Gyr to the mean r-band surface brightness of the bulge component in 135 late-type galaxies (LTGs) from the CALIFA survey, spanning a range of 2.6 dex and 3 dex in total and bulge stellar mass (M*T~10^(8.9-11.5) M_solar and M*B~10^(8.3-11.3) M_solar, respectively). The main insight from this study is that LTG bulges form a continuous sequence of increasing dmB with increasing M*T, M*B, stellar mass surface density S* and mass-weighted age and metallicity: high-dmB bulges are the oldest, densest and most massive ones, and vice versa. Furthermore, we find that the bulge-to-disk age and metallicity contrast, as well as the bulge-to-disk mass ratio increase with M*T, raising from, respectively, ~0 Gyr, 0 dex and 0.25 to ~3 Gyr, ~0.3 dex and 0.67 across the mass range covered by our sample. Whereas gas excitation in lower-mass bulges is invariably dominated by star formation (SF), LINER- and Seyfert-specific emission-line ratios were exclusively documented in high-mass, high-S* bulges. The continuity both in the properties of LTG bulges themselves and in their age and metallicity contrast to their parent disks suggests that these components evolve alongside in a concurrent process that leads to a continuum of physical and evolutionary characteristics. Our results are consistent with a picture where bulge growth in LTGs is driven by a superposition of quick-early and slow-secular processes, the relative importance of which increases with M*T. These processes, which presumably combine in situ SF in the bulge and inward migration of material from the disk, are expected to lead to a non-homologous radial growth of S* and a trend for an increasing Sersic index with increasing galaxy mass.

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arXiv2015

The warm ionized gas in CALIFA early-type galaxies: 2D emission-line patterns and kinematics for 32 galaxies

The morphological, spectroscopic and kinematical properties of the warm interstellar medium (wim) in early-type galaxies (ETGs) hold key observational constraints to nuclear activity and the buildup history of these massive, quiescent systems. High-quality integral field spectroscopy (IFS) data with a wide spectral and spatial coverage, such as those from the CALIFA survey, offer an unprecedented opportunity for advancing our understanding of the wim in ETGs. This article centers on a 2D investigation of the wim component in 32 nearby (<~150Mpc) ETGs from CALIFA, complementing a previous 1D analysis of the same sample (Papaderos et al. 2013; P13). We include here Hα intensity and equivalent width (EW) maps and radial profiles, diagnostic emission-line ratios, besides ionized-gas and stellar kinematics. This study is supplemented by τ-ratio maps as an efficient means to quantify the role of photoionization by pAGB stars, as compared to other mechanisms (e.g., AGN, low-level star formation). Additionally, we extend the tentative classification proposed in P13 by the type i+, which is assigned to a subset of type i ETGs exhibiting ongoing low-level star-formation (SF) in their periphery. This finding along with faint traces of localized SF in the extranuclear component of several of our sample ETGs points to a non-negligible contribution by OB stars to the total ionizing budget. We also demonstrate that, at the typical emission-line detection threshold of ~2Åin previous studies, most of the extranuclear wim emission in an ETG may evade detection, which could in turn prompt its classification as an entirely gas-devoid system. This study adds further observational evidence for a considerable heterogeneity among ETGs with regard to the physical properties and 2D kinematics of the wim component, and underscores the importance of IFS studies over their entire optical extent.

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arXiv2015

Spectroscopic aperture biases in inside-out evolving early-type galaxies from CALIFA

Integral field spectroscopy studies based on CALIFA data have recently revealed the presence of ongoing low-level star formation (SF) in the periphery of ~10% of local early-type galaxies (ETGs), witnessing a still ongoing inside-out galaxy growth process. A distinctive property of the nebular component in these ETGs, classified i+, is a two-radial-zone structure, with the inner zone displaying LINER emission with a Hαequivalent width EW~1Å, and the outer one (3Å<EW<~20Å) showing HII-region characteristics. Using CALIFA IFS data, we empirically demonstrate that the confinement of nebular emission to the galaxy periphery leads to a strong aperture (or, redshift) bias in spectroscopic single-fiber studies of type i+ ETGs: At low redshift (<~0.45), SDSS spectroscopy is restricted to the inner (SF-devoid LINER) zone, thereby leading to their erroneous classification as "retired" galaxies (systems lacking SF and whose faint emission is powered by pAGB stars). Only at higher z's the SDSS aperture can encompass the outer SF zone, permitting their unbiased classification as "composite SF/LINER". We also demonstrate that the principal effect of a decreasing aperture on the classification of i+ ETGs via standard BPT emission-line ratios consists in a monotonic up-right shift precisely along the upper-right wing of the "seagull" distribution. Motivated by these insights, we also investigate theoretically these biases in aperture-limited studies of inside-out growing galaxies as a function of z. To this end, we devise a simple model, which involves an outwardly propagating SF process, that reproduces the radial extent and two-zone EW distribution of i+ ETGs. By simulating on this model the spectroscopic SDSS aperture, we find that SDSS studies at z<~1 are progressively restricted to the inner LINER-zone, and miss an increasingly large portion of the Hα-emitting periphery.

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arXiv2015

Spiral-like star-forming patterns in CALIFA early-type galaxies

Based on a combined analysis of SDSS imaging and CALIFA integral field spectroscopy data, we report on the detection of faint (24 < μ$_r$ mag/arcsec$^2$ < 26) star-forming spiral-arm-like features in the periphery of three nearby early-type galaxies (ETGs). These features are of considerable interest because they document the still ongoing inside-out growth of some local ETGs and may add valuable observational insight into the origin and evolution of spiral structure in triaxial stellar systems. A characteristic property of the nebular component in the studied ETGs, classified i+, is a two-radial-zone structure, with the inner zone that displays faint (EW(Hα)$\simeq$1Å) low-ionization nuclear emission-line region (LINER) properties, and the outer one (3Å<EW(Hα)<~20Å) HII-region characteristics. This spatial segregation of nebular emission in two physically distinct concentric zones calls for an examination of aperture effects in studies of type i+ ETGs with single-fiber spectroscopic data.

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