arXiv subjects

Alberto Saldana-Lopez

Publications and source records attributed to Alberto Saldana-Lopez.

At least 19 recordsLinked to original sources

arXiv2026

MOCSS: Multi-Object Coronagraphy for JWST/NIRSpec Slitless Spectroscopy

We present an experimental JWST/NIRSpec observational method to obtain $R\gtrsim1000$ G140M/F100LP slitless spectroscopic observations. This "Multi-Object Coronagraphy for Slitless Spectroscopy" (MOCSS) technique involves opening essentially all microshutters on NIRSpec simultaneously while closing shutters corresponding on-sky with known bright objects. Through observations of the Hubble Ultra Deep Field, we demonstrate the discovery potential of these deep, high resolution observations without the need for target pre-selection. We obtain a catalog of 22 secure multi-line emitters at $1.3<z<4.6$, with observations of [OII], [OIII], H$α$, H$β$ and [NII] lines, accounting for $\sim80\%$ of the emission lines identified directly in the dispersed images. The MOCSS survey provides first time spectroscopic redshifts for 18 of these sources. We also demonstrate that first order traces of the NIRSpec/G140M/F100LP observing mode extend substantially beyond the nominal $\sim1.89\rm μm$ red cutoff, as far as $2.94\rm μm$ in the most extreme case. Compared to existing NIRISS WFSS of similar exposure times, we find that the MOCSS technique can observe very faint lines while covering the full $1-2 \rm μm$ regime without gaps in wavelength coverage. This study describes the highest-resolution slitless spectroscopy campaign of the $1-2 \rm μm$ regime and emphasizes the discovery potential of this unorthodox observational technique.

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arXiv2026

GLIMPSED: Direct evidence for a fast active galactic nucleus-driven outflow from a z=6.64 little red dot host galaxy

We report the discovery of GLIMPSED-329380, a z=6.64 galaxy behind Abell S1063, which shows signs of an extreme ionised outflow driven by an active galactic nucleus (AGN). The deep JWST/NIRSpec medium grating observations show spatially resolved structures of a host galaxy containing the very fast outflow and an AGN, which we analyse separately. The outflow, mainly traced by broad [O III]λ5008 and Hα emissions in the host, reaches a full-width-at-half-maximum velocity of ~5350km/s, velocities only observed in AGN-dominated systems. From the Balmer decrement, we observe that while the narrow emission lines show no dust attenuation, the outflowing gas is dusty. We use emission lines diagnostics to infer gas abundances within the host galaxy. The oxygen abundance is 12+log(O/H)~7.96 (~18% solar) and the host is slightly nitrogen-enriched with log(N/O) ~ -0.68. Unless the extreme outflow turns out to be very dusty, the mass loading factor (>5-10%), and the kinetic energy (>1e43erg/s) of the extreme outflow does not hint at a significant impact on the galaxy. The AGN component shows many similarities with little red dots (LRDs): a characteristic 'V shape', exponential profile in hydrogen lines, numerous detection of forbidden [Fe II] lines, a Balmer break, and a broad absorption feature at ~4550Å. This detection of a fast outflow in an LRD, rare in surveys dominated by low-resolution (e.g. PRISM) spectra, provides direct evidence of AGN activity in these systems.

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arXiv2026

Recovering Ionizing Photon Escape and Galaxy Scaling Relations in the LzLCS via Si II and C II Absorption Lines and Mock Spectra from a Radiation-Hydrodynamic Simulation

In this work, we use a radiation-hydrodynamic simulation of a single $\sim10^9M_{\odot}$ virtual galaxy to study Si II and C II line profiles seen in stacked HST/COS spectra of 58 galaxies from the LzLCS+ sample. We compare stacks across three mass bins ($M_{\star} \leq 10^8M_{\odot}$, $10^8$-$10^9M_{\odot}$, and $M_{\star} \geq 10^9M_{\odot}$) and three stacking methods (mean, median, and weighted average) to a library of 22,500 mock spectra. We investigate whether the simulation can accurately mimic real gas features, reveal clear trends with galaxy properties, and provide indirect estimates of the ionizing escape fraction ($f_{\rm esc}$). We find reasonable agreement between simulated and observed profiles ($χ^2 < 1$) across all mass regimes. Notably, extracting line properties such as EW and $R_f$ from best-fit mock profiles provides a robust alternative to direct empirical trends, particularly in the low-S/N regime where noise frequently biases results. The simulation-based LIS features, although derived from a single virtual object, exhibit clear correlations with $M_{\star}$, SFR, and $f_{\rm esc}$, mirroring established empirical scaling relations. We find that the best-matching mock spectra predominantly originate from simulation time steps corresponding to peak UV luminosity and intense starburst phases, suggesting that these active periods generate the ISM diversity observed in star-forming galaxies. Finally, simulation-based estimates ($f_{\rm esc}^{\rm virtual}$) reproduce the observed mass-dependent trends in $f_{\rm esc}$ and are in close agreement with the average $f_{\rm esc}$ of the generated stacks. This simulation-based framework establishes a relevant methodology for interpreting spectroscopic observations, including inferring $f_{\rm esc}$ and characterizing physical scaling relations, in high-redshift galaxies from the Epoch of Reionization.

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arXiv2026

The Evolution of Low-Ionization Electron Densities in Galaxies Across Cosmic Epochs

We investigate the low-ionization electron density in the interstellar medium of galaxies across $0$$<$$z$$<$$8$, derived with the [O II]$λ\lambda3727,3730$ and [S II]$λ\lambda6718,6733$ doublets, using both deep JWST NIRCam/grism and NIRSpec/MSA spectroscopy. Along with ancillary density samples from the literature at $0$$<$$z$$<$$6$, we assemble three samples containing a total of 703 galaxies spanning $3.7$$<$$z$$<$$7.8$ at $\langle z\rangle\sim5.6$; 691 galaxies in the luminosity-complete NIRCam/grism programs CONGRESS and FRESCO at $\langle z\rangle \sim4.3$ and $\langle z\rangle\sim5.3$, respectively, and 12 galaxies with high-resolution NIRSpec/MSA spectra from the GO 1871 and GLASS programs. We find median electron densities of $n_{\rm{e}}$[S II]$=$$463^{+281}_{-203}~{\rm{cm}}^{-3}$ for CONGRESS, $n_{\rm{e}}$[S II]$=$$301^{+388}_{-206}~{\rm{cm}}^{-3}$ for FRESCO, and $n_{\rm{e}}$[O II]$=$$202^{+145}_{-102}~{\rm{cm}}^{-3}$ for the NIRSpec/MSA sample. The median low-ionization $n_{\rm{e}}$ increases from $z= 0$ to $z=4$, in agreement with previous studies and those using JWST observations. However, beyond $z\sim4$ median $n_{\rm{e}}$ begins to deviate from a monotonically increasing evolution with $z$. We find a positive, but shallow, correlation between O$_{32}$ (a proxy for the ionization parameter) and $n_{\rm{e}}$, while also confirming a positive correlation between O$_{32}$ and $z$. We suggest that these trends are possibly due to an evolving ISM gas density and ionization structure, and propose a toy model where the gas clumping evolves with $z$ to explain the observed density and ionization variations.

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arXiv2026

A GLIMPSE of the 99%: a census of the faintest galaxies during the epoch of reionization and its implications for galaxy formation models

We present a comprehensive study of the galaxy UV luminosity function (UVLF) at $z=6-9$ leveraging deep JWST observations from the GLIMPSE survey. Thanks to gravitational lensing, we probe the UVLF to an unprecedented depth of $M_{\text{UV}} = -12$ mag, approximately three magnitudes deeper than previous robust constraints. Our UVLF determination incorporates a rigorous end-to-end uncertainty framework, including statistical and systematic lensing uncertainties. We find that the $z \sim 7$ UVLF continues to rise steeply with a faint-end slope of $α= -1.98_{-0.05}^{+0.06}$. Crucially, our data show no clear evidence of a turnover down to \muv $= -12.3$. The persistence of this faint population provides stringent constraints on galaxy formation models and cosmological simulations that predict an early flattening of the luminosity function due to radiative feedback or star-formation thresholds. Furthermore, post-JWST models specifically calibrated to match the UV-bright excess at $z > 10$ generally fail to reproduce the observed evolution toward lower redshifts and fainter magnitudes, highlighting a significant tension in our current understanding of early galaxy assembly. We derive a comoving ionizing emissivity at $z=7$ of log($n_{\mathrm ion}$ / s$^{-1}$ Mpc$^{-3}$) $\approx 50.85$, which suggests that faint galaxies dominate the ionizing budget, providing enough photons to maintain reionization even in a highly clumped IGM ($C_{\text{HII}} = 5$). As our detection of faint galaxies effectively rules out a luminosity function truncation at $M_{\text{UV}} \geq -15$, these results emphasize the need to either accurately characterize the ionizing properties of the global, low-mass galaxy population at $z > 6$, or to refine physical models of intergalactic medium clumping and its redshift evolution to maintain consistency with the observed reionization timeline.

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arXiv2026

Supernovae Driven Winds Impede Lyman Continuum Escape from Dwarf Galaxies in First 10 Myr

Observations suggest that UV-bright, compact star-forming galaxies produce enough ionizing (Lyman continuum; LyC) photons to reionize the Universe. Yet, the efficiency of LyC escape and the roles of radiation, stellar winds, and supernovae remain uncertain. Using medium-resolution spectra of six nearly identical local star-forming galaxies, we directly trace, for the first time, the evolution of a multiphase wind through individual spectral lines alongside measurements of the LyC escape fraction. We find that LyC escape peaks early, during a period dominated by intense radiation and stellar winds but lacking a fast galactic wind. As the starbursts age, supernovae drive and accelerate the wind, progressively suppressing LyC escape. These results highlight the need for cosmological simulations to incorporate early feedback as a key driver of reionization.

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arXiv2026

Unprecedented Constraints on Gas Flows at High Redshift Using Deep JWST/NIRSpec Observations from the LyC22, EXCELS, and AURORA Surveys

We investigate how low-ionization gas flows in typical star-forming galaxies at $z\sim3$ depend on galaxy intrinsic properties and viewing angle. For this analysis we use JWST/NIRSpec observations of rest-frame near-UV Fe II and Mg II absorption, and rest-frame optical Na D absorption. This study combines galaxies from the LyC22, EXCELS, and AURORA surveys and contains 176, 197, and 315 galaxies, respectively, with Fe II, Mg II, and Na D coverage. Based on both individual and composite spectra, we find no statistically significant correlations between outflow velocity and galaxy properties. However, galaxies with detected outflows tend towards higher stellar masses, SFR, and $Σ_{\rm SFR}$ than those without outflows, suggesting that the two samples are not drawn from the same parent population. Finally, we additionally find that Mg II emission is preferentially detected in galaxies with lower stellar mass and $A_V$, and higher sSFR, consistent with conditions that favor the escape of resonantly scattered line and ionizing continuum radiation. We present the first evidence in $z\sim3$ star-forming galaxies that properties of the absorption lines depend on galaxy inclination, with more face-on systems showing stronger absorption and higher outflow velocities, while inflowing gas is more frequently detected in more highly inclined galaxies. These trends are consistent with observations at $z\lesssim1$ and predictions from cosmological simulations in which galactic winds are launched perpendicular to the galactic disks, while accretion occurs primarily along the disk plane.

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arXiv2026

GLIMPSE-D: Metallicity Decline in Faint Galaxies: Implications for [O III]+Hb Luminosity Function and Reionisation Budget

We report the measurement of the R3=[O III]5008/Hb ratios for 54 galaxies in the GLIMPSE-D survey. Thanks to gravitational lensing, our sample includes galaxies with -20 < Muv < -14 at z=6-9. We derive oxygen abundances using calibrated relationships. We observe a significant decline in R3 values below Muv > -18, which we interpret as evidence of decreasing metallicities in fainter regimes. We explore four prescription models of the evolution of R3 with UV emission based on the new measurements and results from previous surveys. Applying these models to the GLIMPSE [O III]+Hb luminosity functions, we measure and extrapolate the ionising photon production rate $\dot{N}_{ion}$ of galaxies down to very faint limits SFR(Ha) > 5e-3 Msun/yr. Our results support the dominant contribution of star-forming galaxies to reionisation, and are consistent with the recent discovery of ultra-faint metal-poor galaxies. Our measurements of the relative contribution of each luminosity bin show that galaxies with L(Ha)~1e41 to 1e42 erg/s dominate at 8<z<9, but the relative contributions become more uniform at $7<z<8$. Extreme models either under- or over-estimate the ionising photon budget, while intermediate models align with recent observational constraints.

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arXiv2026

The short and long of iPhoton science for a boosted Hubble

Boosting the Hubble Space Telescope (HST) will provide unique opportunities to carry out precursor science for the Habitable Worlds Observatory (HWO). Chief among them are science cases for determining the properties of star forming galaxies that contribute to creating and sustaining the universe in a mostly ionized state. The farUV and nearUV spectroscopic capabilities of the Cosmic Origins Spectrograph (COS) and the Space Telescope Imaging Spectrograph (STIS) are unique and unlikely to be replicated in the near future. Here we describe the benefits of a deep panchromatic spectroscopic effort to answer questions concerning the shape of the rest frame ionizing radiation escaping from star forming galaxies at modest redshift, capture crucial missing spectral regions, and explore whether their star formation histories are truly similar to the LyC leakers responsible for initiating and later sustaining the mostly-ionized-state of the universe. An observing program emphasizing multi-orbit observations, unencumbered by HST orbit competition and freely accessible to the wider ionizing photon (iPhoton) community, will catalyze crowd-sourced answers to these questions and offer a lower operating cost price point.

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arXiv2026

HST's Deep Blue: extremely deep UV imaging to reveal the contributors to reionization

Understanding galaxy evolution in the epoch of reionization and the effect these galaxies had on the transformation of the intergalactic medium from neutral to ionized, is a key goal of modern astrophsyics, and is central to both HST's and JWST's missions. The biggest remaining uncertainty is the escape fraction of ionizing photons from galaxies. Quantifying and understanding this at redshifts close to reionization is an objective only achievable through observations with HST, in particular, deep imaging with the WFC3/UVIS instrument to detect ionizing photons from galaxies at 2<z<4. A survey across 20 fields with supporting spectroscopy would both build up a sample similar to the state of the art at low redshift, and also overcome the uncertainty stemming from the unknown transmission of ionizing photons through the intergalactic medium. Such a program would establish the tracers of ionizing photon escape to use within the epoch of reionization and reconcile the growth of the first galaxies with the progression and topology of reionization.

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arXiv2026

Astronomical Advantages of a Boost Mission to Facilitate HST Science into the 2030s: Imaging the Circumgalactic Medium of Galaxies

We present the case for imaging ultraviolet line emission from highly ionized metals and HI Lya in the circumgalactic medium of galaxies, should the Hubble Space Telescope receive an orbital boost. Hubble can uniquely probe emission lines with ionization potentials between 13 and 200 electron-volts (Lya, CIV, OVI, NeVIII, etc). Spatial mapping of the diffuse material traced by these transitions is critical to constraining the physics of feedback and the energetic exchange between galaxies and their circumgalactic environments, as well as basic morphologies of the dominant mass component. Deep high-resolution mapping of these features will not be possible with any other observatory, existing or planned, until HWO is launched, which leaves HST as a critical observatory to test key science drivers for HWO. If HST receives an orbital boost, it can (a) provide the first statistical constraints on the spatial distribution of warm-hot CGM and (b) provide important avenues for science case development, as well as target/pointing selection, for HWO's upcoming spectroscopic facilities.

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arXiv2026

Extending Hubble into the 2030s to Resolve the Physics of LyC Escape

Current observations with the James Webb Space Telescope (JWST) suggest that star-forming galaxies produce enough ionizing (LyC; $λ< 91.2$ nm) photons to drive cosmic reionization, but the efficiency with which these photons escape their host galaxies remains uncertain. Absorption by the neutral intergalactic medium progressively suppresses direct LyC detections above redshift $z\sim3$, forcing astronomers to rely on indirect diagnostics of LyC escape calibrated at low redshift. Low-resolution ultraviolet observations of high-redshift analogs obtained with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope (HST) have been critical for developing these diagnostics. These studies suggest that stellar feedback plays a central role in regulating LyC escape, although the role of galactic winds and the underlying physical mechanisms remain poorly constrained. High-resolution spectroscopy blueward of 160.0 nm (rest-frame) is required to resolve the kinematic structure of the winds and reveal the physics governing LyC escape. Such observations are currently only possible with HST and represent a major science driver for the future Habitable Worlds Observatory (HWO). Extending the lifetime of HST and prioritizing ultraviolet observations are essential for interpreting current JWST studies of the early Universe and important preparatory science for HWO.

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arXiv2026

Other red dots: A possible GLIMPSE of normal AGB stars at Cosmic Noon through extreme lensing

We report the discovery of four extremely faint ($m_{\mathrm{F444W}}\gtrsim29$) red point sources in recent ultra-deep JWST/NIRCam images of the strong lensing galaxy cluster Abell S1063. All four sources sit in lensed arcs, on the symmetry points very close to the critical curves for their host-galaxies' redshifts ($z\sim1-4$). Remarkably, these point sources appear in most arcs that are sufficiently faint close to the critical curve's position ($<21\,\mathrm{nJy}\,\mathrm{arcsec}^{-2}$ in F115W). This suggests that -- unlike previous caustic-crossing events or lensed stars -- thanks to the unprecedented depth of the GLIMPSE observations paired with the extreme lensing magnification (up to $μ\sim10^4$) we might be resolving the lower-mass ($M\sim1-11\,\mathrm{M}_{\odot}$) red stellar population. Concretely, we detect three likely extremely magnified asymptotic giant branch (AGB) stars ($T_{\mathrm{eff}}\sim3200-3750$ K), and one yellow super-giant star ($T_{\mathrm{eff}}\sim6750$ K) -- possibly a yellow hyper-giant or a Cepheid. In addition to offering the first glimpse at low-mass extremely magnified stars, these detections open a possible window into stellar populations, evolution, and chemical enrichment at high redshifts, and could pave the way for using lensed stars such as these as standard candles to populate the distance ladder at cosmological redshifts.

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arXiv2026

A GLIMPSE into the very faint-end of the H$β$+[OIII]$λλ$4960,5008 luminosity function at z=7-9 behind Abell S1063

We use the ultra-deep GLIMPSE JWST/NIRCam survey to constrain the faint-end of the H$β$+[OIII]$λλ$4960,5008 luminosity function (LF) down to $10^{39}$ erg/s at z=7-9 behind the lensed Hubble Frontier Field Abell S1063. We perform SED fitting on a Lyman-Break Galaxy sample, measuring combined H$β$+[OIII] fluxes to construct the emission-line LF. The resulting LF ($α$=-1.55 to -1.78) is flatter than the UV LF ($α<-2$), indicating a lower number density of low H$β$+[OIII] emitters at fixed MUV. We explore three explanations: (i) bursty star formation histories reducing the H$β$+[OIII]-to-UV ratio, (ii) metallicity effects on [OIII]/H$β$, or (iii) a faint-end turnover in the UV LF. Assuming an evolving [OIII]/H$β$ ratio, we derive a flatter [OIII]$λ$5008 LF ($α$=-1.45 to -1.66) and a steeper H$β$ LF ($α$=-1.68 to -1.95). The combination of decreasing metallicity and bursty star formation can reconcile the UV and H$β$+[OIII] LF differences. Converting the LF to the ionising photon production rate, we find that galaxies with H$α$ flux $>10^{39}$ erg/s (SFR(H$α$)$>5\times10^{-3} M_\odot$/yr) contribute 31%-90% and 46%-156% of the ionising photon budget at 7<z<8 and 8<z<9, respectively (for $f_{esc}=0.14$). The LF shape suggests faint galaxies contribute minimally to the ionising photon production rate. Our cosmic star formation rate density (CSFRD) estimates align with previous work, but GLIMPSE's sensitivity to low SFRs confirms that very faint galaxies are minor contributors to both the ionising photon production rate and the CSFRD. Our results suggest that GLIMPSE has detected the bulk of the total H$β$+[OIII] emission from star-forming galaxies, with fainter sources playing a limited role in cosmic reionisation.

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arXiv2026

The SPHINX public data release. II. Using low-ionisation absorption lines and dust attenuation to predict Lyman continuum escape

Low-ionisation state (LIS) absorption lines, such as SiII 1526, are widely used to trace the properties of the interstellar medium (ISM) in galaxies. These lines provide crucial insights into galaxy evolution, including feedback mechanisms, metal enrichment, and the escape fraction of ionising photons ($f_{\rm{esc}}$). We expand our understanding of LIS absorption lines as diagnostic tools for ISM properties and $f_{\rm{esc}}$. Using the SPHINX20 cosmological radiation-hydrodynamics simulation, we generated a comprehensive synthetic dataset of LIS absorption lines and tested their predictive power for $f_{\rm{esc}}$ in star-forming galaxies. Synthetic SiII 1260 and SiII 1526 lines were computed with the radiative transfer code RASCAS, incorporating resonant scattering of photons, fluorescent emission, and interactions with dust grains. The simulated data enhance the public SPHINX20 dataset with high-resolution LIS lines for the full 1380 galaxies and ten viewing angles per galaxy. We analysed correlations between line properties, dust attenuation, and $f_{\rm{esc}}$. We also tested our predictions on observed data using the LzLCS and CLASSY surveys. We found a strong correlation between the dust-corrected residual flux of SiII 1526, $\tilde{R} \equiv \rm{R_{flux}^{1526}} \cdot 10^{-0.4A_{1500}}$, and $f_{\rm{esc}}$. We found $f_{\rm{esc}} \approx 1.041\tilde{R}^{1.887} - 0.002$, with small error bars. When we applied observational conditions, the error increased, but the escape fraction was still well recovered. We show by applying common tools for fitting the spectral energy distribution to our mock data that the inferred dust attenuation is often far from the correct value, with an underestimation of the attenuation when the effect of dust is strongest. Our results demonstrate that the residual flux of SiII 1526 is a powerful predictor of the escape fraction of ionising photons.

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arXiv2026

The Far-Ultraviolet Extragalactic Legacy (FUEL) Survey: Hubble Far-UV Images and Catalogs of the Extragalactic Legacy Fields

We present far-ultraviolet (FUV) images and catalogs from the Hubble Space Telescope (HST) Advanced Camera for Surveys/Solar Blind Channel (ACS/SBC) F150LP (about 1600 Angstrom) of three extragalactic fields: GOODS-S, GOODS-N, and COSMOS. The data comprise 365 orbits of high-resolution imaging of 151 pointings covering an area of 44.7 square arcmin to typical depths of FUV about 28.7 AB (3-sigma, 0.5 arcsec diameter aperture). We provide a new model of the spatially varying dark "glow" created from all 365 orbits of data, and scale and subtract it from all pointings. We provide drizzled image mosaics, weight maps, and exposure time maps matched in coordinates and pixel scale to the Hubble Legacy Fields (HLF) frame, and the original COSMOS tiles. Galaxy photometry is measured within isophotes defined with existing deep Hubble F606W or F814W optical filters. We detect 1068 galaxies and provide catalogs of all optical detections, including matched IDs to existing 3D-HST and CANDELS catalogs. The redshift distribution of FUV-detected galaxies peaks at z about 0.6 and declines to z = 1.2, where the Lyman limit shifts redward of any filter transmission. These data fill the redshift gap of high-resolution far-UV imaging between z about 0 and z > 1, enabling studies of star-forming regions, dust properties, the FUV extragalactic background, and Lyman continuum emission from galaxies at z > 1.2.

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arXiv2026

The Ly$α$ and Continuum Origins Survey. III. Investigating the Link between Galaxy Morphology, Merger Properties and LyC Escape

Characterizing the mechanisms and galaxy properties conducive to the emission and escape of ionizing (LyC) emission is necessary to accurately model the Epoch of Reionization, and identify the sources that powered it. The Ly$α$ and Continuum Origins Survey (LaCOS) is the first program to obtain uniform, multi-wavelength subkiloparsec imaging for a large sample (42) of galaxies observed in LyC and enable statistically robust studies between LyC and resolved galaxy properties. Here, we characterize the morphology and galaxy merger properties of LaCOS galaxies and investigate their connection with the escape fraction of LyC emission $f_{esc}^{LyC}$. We find strong anticorrelations between $f_{esc}^{LyC}$ and size ($r_{20}$, $r_{50}$, and $r_{80}$) measured in filters containing emission from star-forming regions, and with the asymmetry and clumpiness in F150LP, the bluest filter in our dataset, tracing UV continuum and Ly$α$. We find that $\geq48\%$ of LaCOS galaxies, and $\geq41\%$ of LaCOS LyC-emitters are visually classified as galaxy mergers. Galaxies robustly identified as mergers in LaCOS are at advanced stages of interaction, close to coalescence. The $f_{esc}^{LyC}$ properties of robust mergers and low-probability mergers cannot be differentiated statistically, and we only find significant difference between the two populations in terms of their of their sizes and LyC luminosity: robust mergers having larger values. We conclude that (i) $f_{esc}^{LyC}$ tends to be larger in galaxies with a small number of compact, centrally-located, UV-emitting star-forming regions, (ii) at advanced stages of interaction represent a sizable fraction of LyC-emitting samples at $z\sim0.3$, $z\sim0$, and (iii) mergers can facilitate the escape of LyC photons from galaxies.

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arXiv2026

A first GLIMPSE into star clusters populations across cosmic time

We present the first sample of 222 high-redshift (z>0.5) star clusters, detected with JWST/NIRCam in 78 magnified galaxies from different galaxy cluster fields. The majority of the systems (~60%) is observed in the very deep NIRCam observations of the cluster AbellS1063 (GLIMPSE program), showing the power that deep observations, combined with lensing, has to reveal these primordial stellar structures. We perform simultaneous size-flux estimates in all available NIRCam filters and spectral energy distribution (SED) fitting analysis to recover star cluster physical properties. All star cluster candidates have very high magnification. Star clusters and clumps show similar ages and redshift distributions, although noticeable differences are seen in their masses, sizes and stellar surface densities inherent to the lack of resolution in the latter group. We reconstruct the formation redshift of star clusters and find that the large majority of the observed star clusters show young ages (<100 Myr) and seems to form at cosmic noon (CN,1 1, based on a subsample of 60 star clusters younger than 100 Myr and with masses above 2e6 Msun. The star cluster mass function is well described by a power-law with slope beta = -1.89 suggesting that a power-law -2 function might already be in place in the distant Universe.

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