Institut d'Estudis Espacials de Catalunya

ABSTRACT We present HECATEv2, the second release of the Heraklion Extragalactic Catalogue (HECATE), an all-sky, value-added galaxy catalogue comprising 204 733 galaxies from the Hyper Lyon-Meudon Extragalactic Database (HyperLEDA) with recession velocity $\lt 14\, 000 \, \rm {km\, s^{-1}}$ (D $\lesssim$ 200 Mpc). This release focuses on qualitative upgrades of the provided information while maintaining the same parent galaxy sample as HECATEv1. Improvements include a new cosmology-based distance framework, expanded and homogenized optical and mid-infrared (IR) photometry from SDSS-DR17/NSA, PS1-DR2, and All Wide-field Infrared Survey Explorer (AllWISE), and new quality-control flags for stellar contamination, incorrect photometry, and coordinate inconsistencies. We also extend the galaxy-size coverage and derive stellar population parameters for a substantially larger fraction of the sample. Star formation rates ($\mathrm{SFR}$) and stellar masses (${{M}_{\star }}$) are now available for $\gt 70$ per cent of galaxies using updated mid-IR/optical calibrations that account for stellar population age and dust attenuation, while gas-phase metallicities are derived for $\sim 90~{{\ \rm per\ cent}}$. Activity classifications are provided for $\gt 50$ per cent of galaxies based on spectroscopic and/or photometric diagnostics, and supermassive black hole (SMBH) masses for $\sim 86~{{\ \rm per\ cent}}$. In terms of $L_{B}$, $L_{Ks}$, $\mathrm{SFR}$, and ${{M}_{\star }}$, HECATEv2 is among the most complete local-universe catalogues with spectroscopic redshifts. We also provide spatial completeness maps as a function of distance and luminosity, highlighting variations across the sky. Compared to other catalogues (e.g. GLADE+ and NED-LVS), HECATEv2 offers broader (optical, near- and far-IR photometry, metallicity, and activity classifications) or comparable (mid-IR photometry, $\mathrm{SFR}$, and ${{M}_{\star }}$) coverage, making it a robust reference for studies of SMBH–host galaxy connections, gravitational-wave and high-energy transient hosts, population analyses, and rare galaxy subpopulations.

ABSTRACT The enigmatic Little Red Dots (LRDs) discovered by the James Webb Space Telescope (JWST) exhibit properties challenging their interpretation as common galaxies or active galactic nuclei (AGNs). Understanding their nature is key to placing them within our picture of early galaxy and massive black hole (MBH) evolution. To this aim, we build a realistic comparison between LRD observations with photometric properties of galaxies and AGN simulated by the L-GalaxiesBH model in a NIRCam mock sky. We model stellar continua and emission lines, the MBH emission from accretion disc, infrared radiation from dusty torus, and lines from narrow and broad-line regions, accounting for dust attenuation and obscuration. Using realistic photometric cuts, we select a population of LRDs including both AGN and galaxies. The LRD fraction peaks at 40 per cent ($\sim 10^{-4}\rm Mpc^{-3}$) at $z\sim 4$. Our LRDs are central galaxies spanning $M_\star =10^8{\!-\!}10^{10.5}\rm M_\odot$. A population of galaxies with $M_\star \lt 10^9\rm M_\odot$ appear as LRDs due to older stellar populations. At higher masses, LRDs dominate the halo and stellar mass functions ($M_{\rm vir} \gt 10^{11.5}\rm M_\odot$, $M_\star \gt 10^{9.5}\rm M_\odot$), and the interplay between AGN and galaxy emission drives the LRD selection. AGN dominate rest-frame UV-optical emission, while dust obscuration is secondary. LRDs host lighter MBHs ($\sim 10^{6.5}\rm M_\odot$) than non-LRDs ($\sim 10^{7.5}\rm M_\odot$), with fainter emission unable to balance their hosts Balmer breaks. We find no evidence for dominant heavy-seed origin of MBHs. LRD Galaxies (97 per cent hosting MBHs) and LRD AGNs are disc-dominated, with LRD AGNs showing larger bulges formed mainly via disc instabilities.

The capability of the ALICE@LHC and STAR@RHIC experiments to reconstruct <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>D</a:mi> </a:math> mesons has enabled femtoscopic correlation measurements of open-charm mesons in both small and large systems. In this work, we present a theoretical calculation of the correlation functions of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mi>D</c:mi> </c:math> and <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mover accent="true"> <e:mi>D</e:mi> <e:mo stretchy="false">¯</e:mo> </e:mover> </e:math> mesons with nucleons, based on the Koonin-Pratt formalism. We employ an effective Lagrangian to model the interaction between charmed mesons and baryons and apply the TROY formalism to obtain the off-shell <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mi>T</i:mi> </i:math> -matrix in coupled channels, incorporating the effect of the Coulomb interaction when the pair involves two charged particles. The resulting full coupled-channel wave function is inserted into the Koonin-Pratt equation with channel weights derived from a thermal model. Additionally, we compute the correlation functions using the Lednický-Lyuboshitz approximation with low-energy scattering parameters extracted from the unitarized amplitudes. We compare these two approaches and provide predictions for different correlated pairs. Our results can be tested against current and future experimental data from the ALICE and STAR Collaborations in both proton-proton and heavy-ion collisions.

This study presents an intercomparison of planetary boundary layer height (PBLH) estimates derived from three distinct approaches: the Morphological Image Processing Approach (MIPA) algorithm applied to ground-based lidar measurements, European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5th Generation (ERA5) and Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) reanalysis model outputs, and radiosonde (RS) observations, this latter being taken as reference. The intercomparison was conducted during three measurement episodes, encompassing a total of 153 h (6 days), as part of the Boundary Layer Extensive Campaign with muLti-instrumentaL Analysis (BELLA), carried out in spring and early summer 2024 at the CNR-IMAA Atmospheric Observatory (CIAO) in southern Italy (40.60N, 15.72E). The study provides insights into the performance and reliability of these PBLH estimation approaches under diverse atmospheric scenarios. Visual and statistical analyses of selected case studies indicate that MIPA often tracked the aerosol layering structure and diurnal PBLH evolution more closely than ERA5 and MERRA-2, particularly during convective growth and evening transitions. On the other hand, it is found that ERA5 provides more accurate estimates of the nighttime PBLH, where MIPA shows poor nighttime estimation capabilities. Quantitative comparison against radiosonde data reveals that MIPA reaches a weighted root mean square error (RMSEw) of 380±41 m with a coefficient of determination (R2) of 0.68±0.16, while ERA5 shows an RMSEw of 292±72 m and an R2 of 0.81±0.11; and MERRA-2 shows an RMSEw of 631±124 m and an R2 of 0.34±0.21. By combining MIPA daytime and ERA5 nighttime PBLH, the overall results are improved, obtaining an R2=0.86±0.08 and an RMSEw of 213±40 m. This intercomparison highlights the strengths and limitations of each method and demonstrates the benefits of combining complementary PBLH retrieval techniques. The findings contribute to refining boundary layer monitoring methodologies and provide guidance for operational atmospheric observation networks.

Abstract The High-latitude Time-domain Survey (HLTDS) for the Nancy Grace Roman Space Telescope (Roman) will discover thousands of high-redshift Type Ia supernovae (SNe Ia) to set generation-defining cosmological constraints on dark energy. To construct the Roman SN Hubble diagram, a strategy to obtain redshifts must be determined. While the nominal HLTDS will use only the Roman prism, in this work, we consider the utility of the Roman grism observations from overlap with the High-latitude Wide-area Survey for SN Ia cosmology. We determine a galaxy grism redshift recovery rate by simulating dispersed grism images and measuring redshifts with the Grizli software, obtaining an H -band 50% redshift recovery at magnitude 20.61 and 90% recovery at magnitude 19.27. To estimate the total number of spectroscopic redshifts expected for Roman SN cosmology, we also consider a Roman prism SN redshift efficiency and a ground-based telescope redshift efficiency for host galaxies. We apply these redshift efficiencies to SN Ia catalog-level simulations and predict that ∼6800 SNe will have an SN or host spectroscopic redshift. Second, we evaluate the size of potential systematics related to modeling the grism redshift efficiency by considering the impact of additional dependences on stellar mass and host-galaxy color. We estimate the largest potential size of this systematic to be 0.0066 ± 0.002 and −0.0266 ± 0.0079, roughly 42.9% and 49.6% of the statistical uncertainty, for w 0 and w a , respectively. Lastly, we consider the effects of assuming different redshift sources on the optimization of the HLTDS survey strategy by measuring relative changes to the dark energy figure of merit.

The presence of infrared (IR) excess flux observed in white dwarfs is related to the existence of debris disks or substellar companions. These systems provide important clues in studies of extrasolar planetary material and binary evolution. However, fully characterising their properties requires a statistically significant, complete sample. This work aims to identify a complete sample of white dwarfs with IR excess emission within 100,pc of the Sun. We built the spectral energy distributions (SEDs) of the white dwarfs using synthetic photometry in 56 optical filters of the Javalambre Physics of the Accelerating Universe Astronomical Survey system, generated from Data Release 3 low-resolution spectra and complemented with the latest IR photometry available at the Virtual Observatory. We used ( ) to fit the SEDs with different atmospheric white dwarf models depending on the source spectral type. We visually checked the optical and IR images to identify any contaminated photometry. Virtual Observatory SED Analyzer VOSA We built a catalogue of 456 IR excess white dwarfs, of which 292 were robust identifications, and 164 were candidates; of the total, 351 (∼75%) were new identifications. This implies a fraction of IR excess white dwarfs between 5.9±0.3% and 9.2±0.4%, which is higher than previous works, but in agreement with some more recent estimates. Furthermore, for the sample of IR excess white dwarfs, the fraction of sources with non-hydrogen atmosphere increases with the G_ -G_ colour, in contrast to the general white dwarf population. However, this result should be interpreted with caution. Additionally, a thorough comparison of our catalogue with those of previous studies was performed. BP RP The sample of white dwarfs with IR excess emission within 100,pc presented in this work is the largest, most complete, and most reliable to date. Thanks to their proximity, they are ideal targets for follow-up studies aimed at characterising circumstellar disks and substellar companions, as well as the composition of accreted planetary material.

The proliferation of Low Earth Orbit (LEO) satellite constellations, driven by the NewSpace economy and reduced launch costs, has opened new opportunities for positioning, navigation, and timing (PNT) applications. Compared to traditional GNSS systems operating in Medium Earth Orbit, LEO satellites offer several advantages: higher received signal power, better satellite geometry and visibility in urban environments, and greater Doppler dynamics—enabling approaches such as single-satellite and Doppler-based positioning. Although dedicated LEO-PNT constellations are still under development, existing commercial LEO satellites can already be leveraged for experimental positioning applications. This paper presents a portable, multi-constellation testbed built using commercial off-the-shelf (COTS) hardware and software-defined radio (SDR) technologies. The platform enables the synchronous acquisition and processing of LEO signals from Orbcomm, Iridium, and Starlink, allowing for the extraction of key positioning observables. A comprehensive measurement campaign is conducted across both indoor and outdoor environments to evaluate signal visibility and Doppler tracking performance. Results highlight the potential of opportunistic LEO-based positioning, particularly in challenging scenarios such as indoor environments where traditional GNSS solutions are unreliable.

Context . The pristine stages of disk formation during the protostellar phase and the processes of dust evolution in young disks remain largely unconstrained. Dust thermal emission at millimeter wavelengths and its polarization offer key insights into the physical processes and spatial distribution of material at the envelope-disk interface, as well as on early dust evolution around solar-type protostars. Aims . We characterize the dust properties and polarization mechanisms from envelope to disk scales in two young stellar objects (YSOs), IRAS 04166+2706 (K04166) and IRAS 04169+2702 (K04169) embedded in the same Taurus filament. We explore the nature of the dust polarization across scales and investigate their stage of evolution. Methods . We present deep (∼1.4 mm and ∼3 mm) polarimetric observations sampling the dust emission from 25 au to 3000 au using the Atacama Large Millimeter/submillimeter Array (ALMA). We modeled Stokes I emission to characterize disk and envelope contributions, while the polarization properties were analyzed to identify the dominant polarization mechanisms. Finally, in this work, we discuss the physical properties of both sources across scales. Results . K04166 shows extended Stokes I and polarized emission tracing a tentative hourglass magnetic field morphology in its envelope. In the inner envelope and disk ( &lt; 100 au), the properties of the polarized emission change, suggesting the presence of a toroidal magnetic field around the disk or the presence of large grains in the inner envelope. K04169 exhibits compact Stokes I and polarized emission, consistent with self-scattering from the disk. Both disks are extremely compact, yet K04166 retains a substantial envelope while the one of K04169 is largely dissipated. Conclusions . Our multiscale ALMA polarimetric observations reveal a transition from magnetically aligned grains in envelopes to self-scattering in disks within the transition region of 20–50 au. These results provide important clues on dust grain growth and magnetic field morphology at the disk-envelope scales. The two sources, separated by &lt; 0.5 pc and embedded in a common filament, display striking differences, indicating that K04166 is a young embedded object with a substantial envelope threaded by relatively organized magnetic fields. Meanwhile, K04169 is more evolved, likely to be a young T-Tauri star. However, in both disks, the presence of large grains already suggest a scenario of early dust evolution in disks of the Class 0 stage.

The extragalactic background light (EBL) fluctuations in the optical/near-IR encode the cumulative integrated galaxy light (IGL), diffuse intra-halo light (IHL), and high-$z$ sources from the epoch of reionisation (EoR), but they are difficult to disentangle with auto-spectra alone. We aim to decompose the EBL into its principal constituents using multi-band intensity mapping combined with cosmic shear and galaxy clustering. We develop a joint halo-model framework in which IHL follows a mass- and redshift-dependent luminosity scaling, IGL is set by an evolving Schechter luminosity function, and EoR emission is modelled with Pop II/III stellar emissivities and a binned star-formation efficiency. Using mock surveys in a flat $Λ$CDM cosmology with ten spectral bands spanning 0.75-5.0$\rm μm$ in the NEP deep fields over about 100$°^2$ with source detections down to AB=20.5 for masking, and six redshift bins to $z=2.5$, we fit auto- and cross-power spectra using a MCMC method. The combined SPHEREx$\times$Euclid analysis recovers all fiducial parameters within 1$σ$ and reduces 1$σ$ uncertainties on IHL parameters by 10-35% relative to SPHEREx EBL-only, while EoR star-formation efficiency parameters improve by 20-35%. Cross-correlations reveal a stronger coupling of IHL than IGL to the shear field, enhancing component separation; conversely, the EoR contribution shows negligible correlation with cosmic shear and galaxy clustering, aiding its isolation in the EBL. Relative to the SPHEREx EBL-only case, the inferred IHL fraction as a function of halo mass is significantly tightened over $10^{11}-10^{14} M_{\odot}$, with uncertainties reduced by 5-30%, and the resulting star-formation rate density constraints extend to $z\sim 11$, with uncertainty reductions of 22-31%.

When the expansion rate of the Universe at recombination is used to infer the present expansion rate H0, the value derived in the ΛCDM model, H0=67.4 km s−1 Mpc−1, is about in 6σ tension with the value measured locally, H0=74 km s−1 Mpc−1. In this work, we consider instead the expansion history in the context of the symmetry of scale-invariant vacuum (SIV model). We first perform two major cosmological tests: the Hubble diagram for type-Ia supernovae and the fundamental relation between H0, the age of the Universe, and the total density of matter, Ωm. This allows us to constrain Ωm in SIV, with both tests giving the best agreement for Ωm = 0.20. We then study the physical connections of the dynamical and thermal states of the Universe at recombination with the present Hubble constant, H0, and the present temperature, T, in the ΛCDM and SIV contexts. We find that, in SIV, the properties at recombination may be conveyed to the present ones (T=2.726 and H0 at z=0) without any tension, indicating H0=74 km s−1 Mpc−1 in spite of the anchoring on the CMB. This is due to the slightly different expansion and temperature histories of the two cosmological models. Importantly, this happens to occur for Ωm = 0.20, as constrained in SIV with supernovae and cosmic age. This suggests that the Hubble tension currently found between H0 values in the early and late Universe may simply be the result of ΛCDM ignoring the small but still measurable effects of scale invariance.