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Abstract:

We present a search for z ≃ 7 Lyman-break galaxies using the 1.72 deg 2 near-infrared (NIR) UltraVISTA survey in the COSMOS field, reaching 5 σ depths in Y of 26.2. We incorporated deep Euclid optical and Euclid + Spitzer NIR imaging for a full spectral energy distribution (SED) fitting analysis. We found 289 candidate galaxies at 6.5 ≤ z ≤ 7.5 covering −22.6 ≤ M UV ≤ −20.2, faint enough to overlap with Hubble Space Telescope studies. We conducted a separate selection by including complementary Euclid performance verification imaging (reaching 5 σ depths of 26.3), yielding 140 galaxies in 0.65 deg 2 , with 38 sources unique to this sample. We computed the rest-frame UV luminosity function (UV LF) from our samples, extending below the knee ( M ∗ = 21.14 +0.28 −0.25 ). We find that the shape of the UV LF is consistent with both a Schechter function and a double power law (DPL) at the magnitudes probed by this sample, with a DPL preferred at M UV < −22.5 when bright-end results are included. The UltraVISTA + Euclid sample provides a clean measurement of the LF due to the overlapping NIR filters identifying molecular absorption features in the SEDs of ultra-cool dwarf interlopers, and additional faint galaxies were recovered. A comparison with JWST LFs at z > 7 suggests a gentle evolution in the bright-end slope, although this is limited by a lack of robust bright-end measurements at z > 9. We forecast that in the Euclid Deep Fields, the removal of contaminant ultra-cool dwarfs as point sources will be possible at J E < 24.5. Finally, we present a high-equivalent-width Lyman- α emitter candidate identified by combining HSC, VISTA, and Euclid broadband photometry, highlighting the synergistic power these instruments will have in the Euclid Auxiliary Fields for identifying extreme sources in the epoch of reionisation.

Abstract:

Context. This paper presents new results from the ESO Large Programme Looking into the faintEst WIth MUSE (LEWIS). The LEWIS sample consists of low-surface-brightness galaxies (LSBs) and ultra-diffuse galaxies (UDGs) located inside 0.4 R vir of the Hydra I cluster. Integral-field spectroscopy is acquired for 24 galaxies with the MUSE spectrograph mounted on the Very Large Telescope (VLT). Aims. Our main objectives are to analyse possible correlations between the environment and the integrated stellar population properties of our targets, based on which we infer clues about their formation. Methods. For each galaxy in the sample, we extracted the 1D stacked spectrum in an aperture of one effective radius R e and adopted previously published stellar kinematics to derive the age, metallicity, and [Mg/Fe] through a full spectral fitting technique. Results. We find that the analysed LEWIS sample has a mean metallicity of ⟨[M/H]⟩= − 0.9 ± 0.2 dex and a mean age of 10 ± 2 Gyr, comparable to previous results of UDGs in other clusters. According to their position in the projected phase space, galaxies can be classified into two groups: very early infaller galaxies, which on average have slightly higher metallicities (⟨[M/H]⟩ early = −0.8 ± 0.1 dex), and late infaller galaxies, with slightly lower values (⟨[M/H]⟩ late = −1.0 ± 0.1 dex). According to their properties, late-infallers tend to be rotation-91̽��ed systems. Conversely, two types of galaxies are found in the early-infall region. Roughly half have metallicities consistent with the dwarf galaxy mass–metallicity relation. The other half show higher metallicities (with ⟨[M/H]⟩≥ − 1.0 dex) and are located outside the 1 σ scatter of the mass-metallicity relation. The two subgroups of early-infallers also display different timescales for stellar mass assembly. Metal-rich galaxies reached 50% of their stellar mass in less than 1 Gyr and show a prolonged and almost constant star formation over more than 12 Gyr. The other galaxies exhibit a star formation history similar to that found for galaxies in the late-infall region. Both early and late infallers show solar-like α abundances. Conclusions. From the analysis of stellar population properties presented in this work and of stellar kinematics previously obtained from LEWIS, we identified different classes of UDGs within the Hydra I cluster – as shown by metallicities, quenching timescales, and kinematics – which suggest different formation mechanisms. Almost all of the UDGs and LSBs in this cluster are consistent with the puffed-up dwarf formation scenario, having dwarf-like metallicities and being consistent with the mass-metallicity relation for dwarfs. In the innermost regions of the cluster, where more metal-rich UDGs are found, tidal effects or the environment might have influenced their formation and evolution.

Abstract:

We present a photometric and spectroscopic analyses of the Type Ibn supernova (SN) 2024acyl. It rises to an absolute magnitude peak of M o = −17.58 ± 0.15 mag in 10.6 days, and displays a rapid linear post-peak light-curve decline in all bands (e.g. γ 0 − 60 ( V ) = 0.097 ± 0.002 mag day −1 ), similar to most SNe Ibn. The optical pseudobolometric light curve peaks at (3.5 ± 0.8)×10 42 erg s −1 , with a total radiated energy of (5.0 ± 0.4)×10 48 erg. The spectra are dominated by a blue continuum at early stages, with narrow P-Cygni He  I lines and flash-ionisation emission lines of C  III , N  III , and He  II . The P-Cygni He  I features gradually evolve and become emission-dominated in late-time spectra. The H α line is detected throughout the entire spectral evolution, which indicates that the circumstellar material (CSM) is helium-rich with some residual amount of hydrogen. Our multi-band light-curve modelling yields estimates of the ejecta mass of M ej = 0.49 +0.11 −0.09 M ⊙ with a kinetic energy of E k = 0.06 +0.01 −0.01 × 10 51 erg, and a 56 Ni mass of M Ni = 0.018 M ⊙ . The inferred CSM properties are characterised by a mass of M CSM = 0.51 +0.05 −0.04 M ⊙ , an inner radius of R 0 =17.8 +3.6 −3.0 AU, and a density of ρ CSM = (8.3 +2.7 −1.2 ) × 10 −12 g cn −3 . The multi-epoch spectra are well reproduced by the CMFGEN/ he4p0 model, corresponding to a He-ZAMS mass of 4 M ⊙ (H-ZAMS mass 18.11 M ⊙ , pre-SN mass 3.16 M ⊙ ). These findings are consistent with a scenario of an SN powered by ejecta-CSM interaction originating from a low-mass helium star that evolved within an interacting binary system where the CSM with some residual hydrogen may originate from the mass-transfer process. We also discuss an extreme scenario involving the possible merger of a helium white dwarf. In addition, a channel of core-collapse explosion of a late-type Wolf-Rayet (WR) star with hydrogen, or a transitional star between an Of and a WR type (e.g. an Ofpe/WN9 star) with fallback accretion cannot be entirely ruled out.

Abstract:

Supernovae (SNe) IIn are terminal explosions of massive stars that are surrounded by a dense circumstellar medium (CSM). Among SNe IIn, a notable subset is the SN 2009ip-like, which exhibits an initial, fainter peak attributed to stellar variability in the late evolutionary stages, followed by a brighter peak, interpreted as the SN explosion itself. In this context, we analysed the spectrophotometric evolution of SN 2024hpj, an object with a triple-peaked light curve and spectra typical of a SN IIn but with a complex line profile composed of broad P-Cygni features topped by narrow emissions. Comparing it with other SN 2009ip-like events in the literature, as well as with other unpublished objects (SNe 2019mry, 2022ytx, 2024uzf, and 2025csc), we identify star-forming regions as their preferred formation environment. On the other hand, the diversity of spectrophotometric features within the sample suggests that variations in CSM mass and distribution may influence the observed characteristics. We identify four sub-classes based on the luminosity and rapidity of the light curve evolution, which provides insights into possible differences in the progenitors, while a statistical analysis of their observed rate indicates progenitor masses around 25 − 31 M ⊙ or lower.

Abstract:

We present the third data release of the LOFAR Two-metre Sky Survey (LoTSS-DR3). The survey images cover 88% of the northern sky and were created from 12 950 h of data (18.6 PB) accumulated over 10.5 years. Producing the images took 20 million core hours of processing through direction-independent and direction-dependent calibration pipelines that correct for instrumental effects as well as spatially and temporally varying ionospheric distortions. In our 120–168 MHz continuum mosaic images with an angular resolution of 6″ (9″ below declination 10°) we catalogue 13 667 877 sources, formed from 16 943 656 Gaussian components. The scatter in the astrometric precision approximately follows the expected noise-like behaviour but with an additional systematic component of at least 0.24″ that is likely due to calibration imperfections. The random flux density scale error is 6%, while the systematic offset was previously shown to be within 2%. The median sensitivity of our mosaics is 92 μJy beam −1 , improving to 68 μJy beam −1 at high observing elevations, but degrading to 183 μJy beam −1 at the celestial equator due to station area projection effects. Completeness simulations, accounting for realistic source models, time- and bandwidth-smearing effects, and astrometric errors, indicate that we detect more than 95% of compact sources with integrated flux densities exceeding 9 times the local root mean square (RMS) noise. However, the recovered source counts in a particular integrated flux density bin do not match the injected counts until flux densities exceed 45 times the local RMS noise. The Euclidean-normalised differential source counts derived from the survey constrain the radio source population over five orders of magnitude and are in good agreement with previous deep and wide-area surveys. All data products are publicly available, including catalogues, individual-field Stokes I , Q , U , and V images, mosaicked Stokes I images, and uv data with associated direction-dependent calibration solutions.