arXiv subjects

Valentina Abril-Melgarejo

Publications and source records attributed to Valentina Abril-Melgarejo.

10 recordsLinked to original sources

arXiv2026

Spectroscopic characterization of Young Stellar Populations and their Feedback in NGC 5253

We present the spectroscopic analysis of FUV observations taken with the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) targeting young massive clusters in the nearby, metal-poor, blue compact dwarf galaxy NGC 5253. We characterize the stellar populations observed across seven COS pointings and report on their inferred physical parameters, age, metallicity, mass, and reddening values. Comparison between our spectroscopic ages and those inferred using photometric methods show that the former are preferentially younger. We also investigate the impact of these young massive clusters on their surrounding ISM. Using Very Large Telescope/MUSE optical observations and matching the size of the COS aperture, we measured outflow velocities of the ionized gas along the line of sight of the COS pointing with values ranging from $\sim$125-300 km s$^{-1}$. We report on strong statistically-significant correlations between the outflow velocities and the stellar ages, masses, and total mechanical luminosity primarily driven by supernovae (SNe) as derived from our full-spectrum fitting analysis. Although theoretical models predict a delayed injection of mechanical energy and momentum in low-metallicity environments ($<$0.4 Z$_{\odot}$), our study shows that in this particular system (Z$\sim$ 0.3 Z$_{\odot}$), feedback from SNe appears evident at the nominal $>$ 5 Myr ages, with no apparent delay. One possible explanation is that the decrease and suppression of mechanical feedback due to SNe explosions might be dominant at even lower metallicities than those observed in NGC 5253.

astro-ph.GA↗

arXiv2025

CLASSY XIV: The Nitrogen Exception -- Multi-Phase Enrichment and Feedback in High-$z$ Analogs

We present a first-of-its-kind analysis of the metal content across two interstellar medium (ISM) phases in a sample of 31 local star-forming galaxies from the COS Legacy Archive Spectroscopic SurveY (CLASSY), selected as analogues of high-$z$ systems. Using co-spatial UV absorption and optical emission-line spectroscopy, we compare abundances of N, O, S, and Fe in the low-ionization (neutral) and high-ionization (ionized) gas, providing a multi-phase view of enrichment shortly after the current starburst and over longer timescales when ejecta from previous episodes have cooled and mixed. We find that O and S, produced predominantly in short-lived massive stars, are well mixed between the two phases, with scatter reflecting local inhomogeneities. Fe, predominantly produced by Type Ia supernovae on $\sim$1 Gyr timescales, is higher in the neutral gas, reflecting either delayed mixing of older Fe-enriched material or preferential depletion of Fe from the ionized phase through dust formation in core-collapse supernova ejecta. N exhibits the largest phase offset, with N/H$_{ion}$ systematically $\sim$0.7 dex higher than N/H$_{neu}$, and the magnitude of this offset correlates with stellar mass, metallicity, star-formation rate, and most strongly with the ISM outflow velocity. N/O ratios in the ionized phase rise rapidly within 3-6 Myr relative to the neutral gas, consistent with N enrichment dominated by Wolf-Rayet stars rather than intermediate-mass AGB stars on longer timescales. These results demonstrate that localized stellar feedback, outflows, and phase-dependent mixing collectively regulate the chemical evolution of star-forming galaxies, providing key insight into the extreme N/O abundances recently observed in galaxies at cosmic dawn.

astro-ph.GA↗

arXiv2025

CLASSY XII: Nitrogen Enrichment Shaped by Gas Density and Feedback

We investigate the chemical evolution of N/O using a sample of 45 local star-forming galaxies (SFGs) from the CLASSY survey. This sample spans a wide range of galaxy properties, with robust determinations of nitrogen and oxygen abundances via the direct-$T_{\rm e}$ method. We explore how N/O relates to density structure, stellar mass, star formation rate (SFR), stellar age, compactness, and gas kinematics. In addition, we compare our results with those of galaxies at $z =2-10$ where N/O ratios were derived from optical or UV nitrogen lines, aiming to identify chemical enrichment pathways across cosmic time. Our analysis shows that the N/O-O/H relation in CLASSY galaxies aligns with the trends seen in local galaxies and extragalactic HII regions, and that galaxies at $z = 2-6$ exhibit similar N/O values, indicating no significant redshift evolution in N/O for a fixed metallicity. We identify a significant correlation between electron density $n_{\rm e}$([S II]) and N/O, suggesting that density structure contributes to the scatter in the N/O-O/H relation. The CLASSY galaxies with high SFRs or compact star formation show elevated N/O, though no strong correlation with stellar mass is found. We also find that high-velocity outflows (v$_{out}$ > 350 km/s) and low mass-loading factors are linked to elevated N/O, indicating that feedback plays a significant role. These results highlight the importance of density, star formation, and feedback from young stellar populations in shaping N/O enrichment and provide key insights for interpreting high-$z$ galaxies observed with JWST.

astro-ph.GA↗

arXiv2025

JWST/MIRI detection of [Ne V] and [Ne VI] in M83: Evidence for the long sought-after AGN?

We report the first detections of [Ne V] 14.3 μm and [Ne VI] 7.7 μm at high confidence (S/N>=6) in the nuclear region of the nearby spiral galaxy M83. Emission line maps of these high ionization lines show several compact structures. Specifically, the [Ne VI] emission is located at 140 pc from the optical nucleus and appears as a point source of size ~<18 pc (FWHM =<0.8"). We investigate the possible source of this extreme emission through comparison with photoionization models and ancillary data. We find that photoionization models of fast radiative shocks are able to reproduce the observed high excitation emission line fluxes only for the lowest preshock density available in the library, n =0.01 cm^-3. Additionally, tailored active galactic nuclei (AGN) photoionization models assuming a two-zone structure are compatible with the observed high ionization fluxes. Our simple AGN model shows that the emission at the location of the [Ne VI] source can be the result of a cloud being ionized by the radiation cone of an AGN. We stress, however, that to definitively confirm an AGN as the main source of the observed emission, more complex modeling accounting for different geometries is required. Previously known as a purely starburst system, these new findings of the nuclear region of M83 will require a reassessment of its nature and of objects similar to it, particularly now that we have access to the unparalleled infrared sensitivity and spatial resolution of the James Webb Space Telescope.

astro-ph.GA↗

arXiv2024

Mapping Multi-Phase Metals in Star-forming Galaxies: a spatially resolved UV + Optical Study of NGC 5253

We present a pioneering spatially-resolved, multi-phase gas abundance study on the blue compact dwarf galaxy NGC~5253, targeting 10 star-forming (SF) clusters inside six FUV HST/COS pointings with co-spatial optical VLT/MUSE observations throughout the galaxy. The SF regions span a wide range of ages (1--15 Myr) and are distributed at different radii (50 -- 230 pc). We performed robust absorption-line profile fitting on the COS spectra, covering 1065--1430 Å in the FUV, allowing an accurate computation of neutral-gas abundances for 13 different ions sampling 8 elements. These values were then compared with the ionized-gas abundances, measured using the direct method on MUSE integrated spectra inside analog COS apertures. Our multi-phase, spatially resolved comparisons find abundances which are lower in the neutral gas than the ionized gas by 0.22 dex, 0.80 dex and 0.58 dex for log(O/H), log(N/H) and log(N/O), respectively. We modeled the chemical abundance distributions and evaluated correlations as a function of radius and age. It was found that while N, O and N/O abundances decrease as a function of age in the ionized gas, they increase with age in the neutral gas. No strong correlations for N, O or N/O were observed as a function of radius. The N/O and N/H offsets between the phases were found to decrease with age, providing evidence that chemical enrichment happens differentially, first in the ionized-gas phase around 2--5 Myrs (due to N-rich Wolf-Rayet stars) and then mixing out into the cold neutral gas on longer timescales of 10--15 Myr.

astro-ph.GA↗

arXiv2023

The Tully-Fisher relation in dense groups at $z \sim 0.7$ in the MAGIC survey

Galaxies in dense environments are subject to interactions and mechanisms which directly affect their evolution by lowering their gas fractions and reducing their star-forming capacity earlier than their isolated counterparts. The aim of our project is to get new insights about the role of environment on the stellar and baryonic content of galaxies using a kinematic approach, through the study of the Tully-Fisher relation (TFR). We study a sample of galaxies in 8 groups spanning a redshift range of $0.5<z<0.8$ and located in 10 pointings of the MAGIC MUSE Guaranteed Time Observations program. We perform a morpho-kinematics analysis of this sample and set up a selection based on galaxy size, [OII] emission line doublet signal-to-noise ratio, bulge-to-disk ratio and nuclear activity to construct a robust kinematic sample of 67 star-forming galaxies. This selection considerably reduces the number of outliers in the TFR, which are predominantly dispersion-dominated galaxies. Our results suggest a significant offset of the TFR zero-point between galaxies in low- and high-density environments, whatever kinematics estimator is used. This can be interpreted as a decrease of either stellar mass by $\sim 0.05 - 0.3$ dex or an increase of rotation velocity by $\sim 0.02 - 0.06$ dex for galaxies in groups, depending on the samples used for comparison. We also studied the stellar and baryon mass fractions within stellar disks and found they both increase with stellar mass, the trend being more pronounced for the stellar component alone. These fractions do not exceed 50%. We show that this evolution of the TFR is consistent either with a decrease of star formation or with a contraction of the mass distribution due to the environment. These two effects probably act together with their relative contribution depending on the mass regime.

astro-ph.GA↗

arXiv2022

The MUSE Extremely Deep Field: a first panoramic view of an Mg II emitting intragroup medium

Using the exquisite MUSE eXtremely Deep Field data, we report the discovery of an MgII emission nebula with an area above a 2$σ$ significance level of 1000 proper kpc$^2$, providing the first panoramic view of the spatial distribution of magnesium in the intragroup medium of a low mass group of five star-forming galaxies at z=1.31. The galaxy group members are separated by less than 50 physical kpc in projection and $\approx$120 km/s in velocity space. The most massive galaxy has a stellar mass of 10$^{9.35}$ M$_\odot$ and shows an MgII P-Cygni line profile indicating the presence of an outflow, which is consistent with the spatially resolved spectral analysis showing $\approx+$120 km/s shift of the MgII emission lines with respect to the systemic redshift. The other galaxies are less massive and only show MgII in emission. The detected MgII nebula has a maximal projected extent of $\approx$70 kpc including a low surface brightness (2 $\times$ 10$^{-19}$ erg/s/cm$^{2}$/arcsec$^{2}$) gaseous bridge between two subgroups of galaxies. The presence of absorption features in the spectrum of a background galaxy located at an impact parameter of 19 kpc from the closest galaxy of the group indicates the presence of gas enriched in magnesium even beyond the detected nebula seen in emission, suggesting that we are observing the tip of a larger intragroup medium. The observed MgII velocity gradient suggests an overall rotation of the structure along the major axis of the most massive galaxy. Our MUSE data also reveal extended Fe II* emission in the vicinity of the most massive galaxy, aligned with its minor axis. Extended [OII] emission is found around the galaxy group members and at the location of the MgII bridge. Our results suggest that both tidal stripping effects from galaxy interactions and outflows are enriching the intragroup medium of this system.

astro-ph.GA↗

arXiv2022

The MUSE Hubble Ultra Deep Field Survey XVI. The angular momentum of low-mass star-forming galaxies. A cautionary tale and insights from TNG50

We investigate the specific angular momentum (sAM) $ j(<r)$ profiles of intermediate redshift ($0.4<z<1.4$) star-forming galaxies (SFGs) in the relatively unexplored regime of low masses (down to $M_\star\sim 10^8$M$_{\odot}$), and small sizes (down to $R_{\rm e}\sim 1.5$ kpc) and characterize the sAM scaling relation and its redshift evolution. We have developed a 3D methodology to constrain sAM profiles of the star-forming gas using a forward modeling approach with \galpak{} that incorporates the effects of beam smearing, yielding the intrinsic morpho-kinematic properties even with limited spatial resolution data. Using mock observations from the TNG50 simulation, we find that our 3D methodology robustly recovers the star formation rate (SFR)-weighted $j(<r)$ profiles down to low effective signal-to-noise ratio (SNR) of $\gtrapprox3$. We applied our methodology blindly to a sample of 494 \OII{}-selected SFGs in the MUSE Ultra Deep Field (UDF) 9~arcmin$^2$ mosaic data, covering the unexplored $8<\log M_*/$M$_{\odot}<9$ mass range. We find that the (SFR-weighted) sAM relation follows $j\propto M_\star^α$ with an index $α$ varying from $α=0.3$ to $α=0.5$, from $\log M_\star/$M$_{\odot}=8$ to $\log M_*/$M$_{\odot}=10.5$. The UDF sample supports a redshift evolution consistent with the $(1+z)^{-0.5}$ expectation from a Universe in expansion. The scatter of the sAM sequence is a strong function of the dynamical state with $\log j|_{M_*}\propto 0.65 \times \log(V_{\rm max}/σ)$ where $σ$ is the velocity dispersion at $2 R_{\rm e}$. In TNG50, SFGs also form a $j-M_{\star}-(V/σ)$ plane but it correlates more with galaxy size than with morphological parameters. Our results suggest that SFGs might experience a dynamical transformation before their morphological transformation to becoming passive via either merging or secular evolution.

astro-ph.GA↗

arXiv2021

The MUSE Extremely Deep Field: Evidence for SFR-induced cores in dark-matter dominated galaxies at z=1

Disc-halo decomposition on rotationally supported star-forming galaxies (SFGs) at $z>1$ are often limited to massive galaxies ($M_\star>10^{10}~M_\odot$) and rely on either deep Integral Field Spectroscopy data or stacking analyses. We present a study of the dark matter (DM) content of nine $z\approx1$ SFGs selected Using the brightest [OII] emitters in the deepest Multi-Unit Spectrograph Explorer (MUSE) field to date, namely the 140hr MUSE Extremely Deep Field, we perform disk-halo decompositions on 9 low-mass SFGs (with $10^{8.5} 10^{10}~M_\odot$. The DM halos show constant surface densities of $\sim100~M_\odot$ pc$^{-2}$. Half of the sample shows a strong preference for cored over cuspy DM profiles. The presence of DM cores appears to be related to galaxies with stellar-to-halo mass $\log M_\star/M_{\rm vir}\approx-2.5$. In addition, the cuspiness of the DM profiles is found to be a strong function of the recent star-formation activity. Both of these results are interpreted as evidence for feedback-induced core formation in the Cold Dark Matter context.

astro-ph.GA↗

arXiv2021

The MUSE Extremely Deep Field: the Cosmic Web in Emission at High Redshift

We report the discovery of diffuse extended Ly-alpha emission from redshift 3.1 to 4.5, tracing cosmic web filaments on scales of 2.5-4 comoving Mpc. These structures have been observed in overdensities of Ly-alpha emitters in the MUSE Extremely Deep Field, a 140 hour deep MUSE observation located in the Hubble Ultra Deep Field. Among the 22 overdense regions identified, 5 are likely to harbor very extended Ly-alpha emission at high significance with an average surface brightness of $\mathrm{5 \times 10^{-20} erg s^{-1} cm^{-2} arcsec^{-2}}$. Remarkably, 70% of the total Ly-alpha luminosity from these filaments comes from beyond the circumgalactic medium of any identified Ly-alpha emitters. Fluorescent Ly-alpha emission powered by the cosmic UV background can only account for less than 34% of this emission at z$\approx$3 and for not more than 10% at higher redshift. We find that the bulk of this diffuse emission can be reproduced by the unresolved Ly-alpha emission of a large population of ultra low luminosity Ly-alpha emitters ($\mathrm{<10^{40} erg s^{-1}}$), provided that the faint end of the Ly-alpha luminosity function is steep ($α\lessapprox -1.8$), it extends down to luminosities lower than $\mathrm{10^{38} - 10^{37} erg s^{-1}}$ and the clustering of these Ly-alpha emitters is significant (filling factor $< 1/6$). If these Ly-alpha emitters are powered by star formation, then this implies their luminosity function needs to extend down to star formation rates $\mathrm{< 10^{-4} M_\odot yr^{-1}}$. These observations provide the first detection of the cosmic web in Ly-alpha emission in typical filamentary environments and the first observational clue for the existence of a large population of ultra low luminosity Ly-alpha emitters at high redshift.

astro-ph.CO↗