Showing new listings for Thursday, 9 October 2025

[olozhika]

Showing new listings for Thursday, 9 October 2025

Auto update Star Formation & Molecular Cloud papers at about 2:30am UTC (10:30am Beijing time) every weekday.

阅读 Usage.md了解如何使用此repo实现个性化的Arxiv论文推送

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Keyword list: ['star formation', 'star-forming', 'molecular cloud', 'interstellar medium', 'cloud', 'clump', 'core', 'filament', 'atomic gas', 'N-PDF']

Excluded: ['galaxies', 'galaxy cluster', ' AGN ', 'standard candle', 'X-ray binar', 'solar corona']

Today: 13papers

MUSEQuBES: Physical conditions, origins, and multi-element abundances of the circumgalactic medium of an isolated, star-forming dwarf galaxy at z=0.57

• Authors: Sean D. Johnson, Nishant Mishra, Sowgat Muzahid, Gwen C. Rudie, Fakhri S. Zahedy, Zhijie Qu, Claude-André Faucher-Giguère, Jonathan Stern, Jennifer I-Hsiu Li, Elise Fuller, Sebastiano Cantalupo, Hsiao-Wen Chen, Ahmad Kadri, Suyash Kumar, Zhuoqi Will Liu, Gregory Walth

• Subjects: Subjects:
  Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2510.06310

• Pdf link: https://arxiv.org/pdf/2510.06310

• Abstract
  In dwarf galaxy models, outflows expel metal-enriched interstellar medium (ISM) into the circumgalactic medium (CGM) to reproduce their observed low metallicities, but measurements of dwarf CGM properties are scarce. We present a study of the CGM of an isolated dwarf at $z=0.5723$ with a stellar mass of $\approx5\times10^7\rm,M_{\odot}$ and star-formation rate ($\approx0.05,\rm M_\odot,yr^{-1}$) and ISM metallicity ($\rm [O/H]\approx-0.9$) consistent with the star-forming main sequence and mass-metallicity relation. A background quasar sightline with archival UV spectra probes the dwarf's CGM at a projected distance of 28 kpc, corresponding to approximately half of the estimated virial radius. The dwarf's CGM is detected in H I, intermediate metal ions of C III, O III, and O IV, and kinematically broader, highly-ionized O VI, but is undetected in N IV and Ne VIII. Photoionization modeling of the intermediate ions indicates a modest volume-filling factor ($\sim 6%$ along the sightline or $\sim 2%$ globally), and a mass of $\sim2\times10^8 {\rm,M_\odot}$, $\sim4\times$ higher than the dwarf's stellar mass, but $\sim10\times$ less than the highly ionized CGM. The O VI kinematics are comparable to the dwarf's estimated virial velocity, suggesting it is likely associated with cool, photoionized, and volume-filling CGM, with bulk motion or turbulence dominating over thermal pressure. The metallicity inferred for the intermediate ions is $\rm [O/H]=-0.6$, but with low relative abundances of $\rm [C/O]=-0.6$ and $\rm [N/O]<-0.9$. The [N/O] is below levels expected of the dwarf's ISM, but consistent with core-collapse supernova ejecta, suggesting that supernova-enriched gas escaped the dwarf without mixing significantly with ISM enriched in nitrogen from evolved, low-mass stars.

Modeling gravitational wave sources in the MillenniumTNG simulations

• Authors: Federico Marinacci, Marco Baldi, Giuliano Iorio, M. Celeste Artale, Michela Mapelli, Volker Springel, Sownak Bose, Lars Hernquist

• Subjects: Subjects:
  Cosmology and Nongalactic Astrophysics (astro-ph.CO); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2510.06311

• Pdf link: https://arxiv.org/pdf/2510.06311

• Abstract
  (Edited) We introduce a flexible framework for building gravitational wave (GW) event catalogs in hydrodynamic simulations of galaxy formation. Our framework couples the state-of-the-art binary population synthesis code SEVN with Arepo-GW -- a module fully integrated into the moving-mesh code Arepo -- to assign merger events of binary compact objects to stellar particles in simulations by stochastically sampling merger tables generated with SEVN. Arepo-GW supports both on-the-fly operation, producing event catalogs during simulations, and post-processing, using snapshots from existing runs. The algorithm is fully parallel and can be readily adapted to outputs from other simulation codes. To demonstrate the capabilities of our new framework, we applied Arepo-GW in post-processing to simulations from the MillenniumTNG suite, including its flagship box. We investigate key properties of the resulting GW event catalog, built on SEVN predictions, focusing on comoving merger rates, formation efficiencies, delay-time distributions, and progenitor mass and metallicity distributions. We also examine how these properties vary with simulated volume. We find that GW progenitor rates closely track simulated star formation histories and are generally consistent with current observational constraints at low redshift, aside from a factor of $\sim 4.5$ excess in binary black hole mergers. Moreover, our binary black hole merger rates decline more slowly with redshift than current observational estimates for $z \lesssim 1$. Finally, the analysis of progenitor mass functions across different formation channels reveals only mild redshift evolution, while the binary black hole mass function displays features compatible with current observational determinations. These findings highlight the potential of our novel framework to enable detailed predictions for upcoming GW surveys within a full cosmological context.

Ensemble seismic study of the properties of the core of Red Clump stars

• Authors: Anthony Noll, Sarbani Basu, Saskia Hekker

• Subjects: Subjects:
  Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2510.06494

• Pdf link: https://arxiv.org/pdf/2510.06494

• Abstract
  Red clump stars still pose open questions regarding several physical processes, such as the mixing around the core, or the nuclear reactions, which are ill-constrained by theory and experiments. The oscillations of red clump stars, which are of mixed gravito-acoustic nature, allow us to directly investigate the interior of these stars and thereby better understand their physics. In particular, the measurement of their period spacing is a good probe of the structure around the core. We aim to explain the distribution of period spacings in red clump stars observed by Kepler by testing different prescriptions of core-boundary mixing and nuclear reaction rate. Using the MESA stellar evolution code, we computed several grids of core-helium burning tracks, with varying masses and metallicities. Each of these grids have been computed assuming a certain core boundary mixing scheme, or carbon-alpha reaction rate. We then sampled these grids, in a Monte-Carlo fashion, using observational spectroscopic metallicities and seismic masses priors, in order to retrieve a period spacing distribution that we compared to the observations. We found that the best fitting distribution was obtained when using a "maximal overshoot" core-boundary scheme, which has similar seismic properties as a model whose modes are trapped outside a semi-convective region, and which does not exhibit core breathing pulses at the end of the core-helium burning phase. If no mode trapping is assumed, then no core boundary mixing scheme is compatible with the observations. Moreover, we found that extending the core with overshoot worsens the fit. Additionally, reducing the carbon-alpha reaction rate (by around 15%) improves the fit to the observed distribution. Finally, we noted that an overpopulation of early red clump stars with period spacing values around 250s is predicted by the models but not found in the observations.

Spectropolarimetry of NGC 1275 reveals a narrow-line radio galaxy with polarization parallel to its radio jet axis

• Authors: F. Marin, T. Pursimo, I. Liodakis, E. Lindfors, J. Biedermann, D. Hutsemékers, M. Turkki

• Subjects: Subjects:
  Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2510.06713

• Pdf link: https://arxiv.org/pdf/2510.06713

• Abstract
  Concomitant with the Imaging X-ray Polarimetry Explorer (IXPE) observation of the Perseus cluster, we obtained optical spectropolarimetry of its central active galactic nucleus, NGC 1275, using the Alhambra Faint Object Spectrograph and Camera (ALFOSC) on the Nordic Optical Telescope (NOT). While the total-light spectrum confirms its edge-on, core obscured (type-2) classification, the polarized spectrum shows a polarization angle aligned with the arcsecond radio jet axis -- an exceptional behavior for type-2 objects. Our polarization analysis also reveals wavelength-dependent linear polarization at level 2-3% in the continuum, likely rising from a combination of variable syn

3D B-fieLds in the InterStellar medium and Star-forming regions (3D-BLISS): I. Using Starlight Polarization in Massive IRDC Filament G11.11-0.12

• Authors: Bao Truong, Thiem Hoang, Nguyen Bich Ngoc, Nguyen Chau Giang, Le Ngoc Tram, Ngan Le

• Subjects: Subjects:
  Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2510.06726

• Pdf link: https://arxiv.org/pdf/2510.06726

• Abstract
  Three-dimensional magnetic fields (3D B-fields) are essential to understand the formation and evolution of the interstellar medium and multi-scale star formation; however, the accurate measurement of 3D B-fields is still challenging. The angle of dust polarization by magnetically aligned grains provides the projected B-fields onto the plane-of-sky, while the degree of dust polarization provides the B-field's inclination angles with respect to the line-of-sight. Our previous theoretical studies proposed a new method of probing 3D B-fields using dust polarization combined with the Radiative Torque (RAT) alignment theory and demonstrated the accurate inference of B-field inclination angles using synthetic polarization data. In this paper, we report the first application of the new technique to study 3D B-fields and dust properties in the G11.11-0.12 filament (hereafter G11) from starlight polarization observations taken by ISRF/SIRPOL at $2.19,\rm\mu m$. Using both observed starlight polarization and optical dust extinction curve from Gaia mission, we constrained the maximum grain size of $0.25,\rm\mu m$ and the grain elongation with an axial ratio of $s\gtrsim 1.4$ in the outer regions of G11. We calculated the alignment properties in the G11 by using the \textsc{DustPOL_py} code based on the RAT theory. The B-field's inclination angles are then inferred from the observed starlight polarization efficiency when the grain alignment is included, showing the inclined B-fields in the G11 with a mean angle of $\sim 50$ degrees. From these inferred inclination angles, we found evidence of the local 3D arc-shaped B-field structure toward the sightline. These findings are important for fully understanding 3D B-field's roles in the formation and evolution of massive filamentary clouds.

A Sample of HeII λ4686 "Changing-Look" Quasars

• Authors: Wentao Lu, Jun-Xian Wang

• Subjects: Subjects:
  Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2510.06753

• Pdf link: https://arxiv.org/pdf/2510.06753

• Abstract
  We present the first systematic search for "changing-look" ("CL") behavior in the broad He ii {\lambda}4686 emission line in quasars, utilizing repeated spectroscopy from the Sloan Digital Sky Survey (SDSS). The He ii line, originating from high-ionization gas and powered by extreme ultraviolet photons, serves as a sensitive tracer of changes in the ionizing continuum. After applying strict spectral selection criteria and visual inspection to a parent sample of over 9,000 quasars with multi-epoch spectra, we identify a sample of 34 He ii "changing-look" quasars that show a significant appearance or disappearance of the broad He ii {\lambda}4686 line. Compared with previously known H{beta} "CL" quasars, the He ii "CL" sample exhibits similarly strong continuum variability and broad-line flux changes, yet shows a preference for higher Eddington ratios and lower host-galaxy contamination. These results highlight the value of He ii line in studying the central variable engines of AGNs and uncovering a more complete census of extreme quasar variability. A comparison with H{beta} "CL" further underscores the profound selection biases inherent in "changing-look" studies, especially those associated with line strength, host-galaxy contamination, and spectral signal-to-noise ratio.

JWST observations of photodissociation regions: II. Warm molecular Hydrogen spectroscopy in the Horsehead nebula

• Authors: M. Zannese, P. Guillard, A. Abergel, E. Habart, P. Dell'Ova, B. Trahin, J. Le Bourlot, K. Misselt, D. Van De Putte, A. N. Witt, K. D. Gordon, A. Noriega-Crespo, M. Baes, P. Bouchet, B. R. Brandl, M. Elyajouri, O. Kannavou, P. Klassen, N. Ysard

• Subjects: Subjects:
  Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2510.06812

• Pdf link: https://arxiv.org/pdf/2510.06812

• Abstract
  H2 is the most abundant molecule in the interstellar medium and is a useful tool to study photodissociation regions, where radiative feedback from massive stars on molecular clouds is dominant. The James Webb Space Telescope, with its high spatial resolution, sensitivity, and wavelength coverage provides unique access to the detection of most of H2 lines and the analysis of its spatial morphology. Our goal is to use H2 line emission detected with the JWST in the Horsehead nebula to constrain the physical parameters (e.g., extinction, gas temperature, thermal pressure) throughout the PDR and its geometry. The study of H2 morphology reveals that FUV-pumped lines peak closer to the edge of the PDR than thermalized lines. From H2 lines, we estimate the value of extinction throughout the PDR. We find that AV is increasing from the edge of the PDR to the second and third H2 filaments. Then, we study the H2 excitation in different regions across the PDR. The temperature profile shows that the observed gas temperature is quite constant throughout the PDR, with a slight decline in each of the dissociation fronts. This study also reveals that the OPR is far from equilibrium. We observe a spatial separation of para and ortho rovibrational levels, indicating that efficient ortho-para conversion and preferential ortho self-shielding are driving the spatial variations of the OPR. Finally, we derive a thermal pressure in the first filament around P > 6x10$^6$ K cm$^{-3}$, about ten times higher than that of the ionized gas. We highlight that template stationary 1D PDR models cannot account for the intrinsic 2D structure and the very high temperature observed in the Horsehead nebula. We argue the highly excited, over-pressurized H2 gas at the edge of the PDR interface could originate from the mixing between the cold and hot phase induced by the photo-evaporation of the cloud.

In-flight performance of the IXPE telescopes

• Authors: Riccardo Ferrazzoli, Enrico Costa, Sergio Fabiani, Philip Kaaret, Stephen L. O'Dell, Brian D. Ramsey, Paolo Soffitta, Luca Baldini, Ronaldo Bellazzini, Alessandro Di Marco, Fabio La Monaca, Luca Latronico, Alberto Manfreda, Fabio Muleri, John Rankin, Carmelo Sgrò, Stefano Silvestri, Martin C. Weisskopf

• Subjects: Subjects:
  Instrumentation and Methods for Astrophysics (astro-ph.IM)

• Arxiv link: https://arxiv.org/abs/2510.06963

• Pdf link: https://arxiv.org/pdf/2510.06963

• Abstract
  We present a comprehensive characterization of the on-orbit imaging performance of the three telescopes on board the Imaging X-ray Polarimetry Explorer (IXPE). Each telescope comprises a Wolter-I mirror module assembly and a Gas Pixel Detector focal-plane detector unit (DU). We analyze data from point-like X-ray sources and fit a composite point spread function (PSF) model that we compare with ground calibrations. We study the dependence of the PSF parameters and of the angular resolution, in terms of half-power diameter (HPD), on the time and source counting rate. We find no significant secular evolution of PSF parameters or HPD over 30 months on orbit, with average HPDs of $26.1 \pm 0.5$ arcsec (Telescope 1), $32.1 \pm 0.5$ arcsec (Telescope 2), and $30.9 \pm 0.6$ arcsec (Telescope 3), and rate trends consistent with zero up to source counting rates of $\sim60$ cts s$^{-1}$ in the 2-3 keV energy band for all three telescopes. We set a 99% C.L. upper limit of 4.4% on the optics-induced polarization in the PSF halo, and find no measurable degradation of the polarization modulation factor in the wings versus the core due to mis-reconstructed photoelectron tracks. IXPE's imaging performance thus is consistent with the $\leq30$ arcsec observatory requirement with high stability, ensuring robust spatially resolved polarization measurements for the mission's projected lifetime through 2030.

Protoplanetary disc population synthesis I. Constraining disc parameters to reproduce disc observations

• Authors: Jose L. Gomez, Octavio M. Guilera, Marcelo M. Miller Bertolami, Elisa Castro-Martínez, María Paula Ronco

• Subjects: Subjects:
  Earth and Planetary Astrophysics (astro-ph.EP)

• Arxiv link: https://arxiv.org/abs/2510.06978

• Pdf link: https://arxiv.org/pdf/2510.06978

• Abstract
  Context. Protoplanetary discs are the birthplaces of planets. Recent studies highlight the role of stellar mass sampling in determining disc lifetimes from the observed fraction of stars with discs. Low-mass stars tend to host longer-lived discs, allowing planet formation via solid accretion. Observations also reveal a strong correlation between stellar (and substellar) mass and accretion rate, typically following $\dot{M}\propto M_\star^2$. Aims. We aim to identify the optimal parameters of a disc evolution model that reproduces both the observed disc fractions and accretion rates in young stellar populations. Methods. We performed a population synthesis study exploring different dependencies of the viscosity parameter $\alpha$ on stellar mass. Disc evolution includes viscous accretion and photoevaporation (internal and external). Initial disc masses and radii were drawn from observationally motivated distributions, while stellar masses followed a given distribution and a time-dependent star formation rate (SFR) was introduced. Results. Matching observed disc fractions and accretion trends requires $\alpha$ to increase with stellar mass. External photoevaporation is necessary to produce low-mass discs with high accretion rates, and a time-dependent SFR enhances accretion in young clusters while extending disc lifetimes in older ones. A stellar mass cut-off reproduces the distance-dependent biases in observed disc fractions. Conclusions. Both stellar and environmental effects are essential to explain the observed properties of protoplanetary discs. A stellar-mass-dependent viscosity reproduces the $\dot{M}$-$M_\star$ relation, while external photoevaporation and extended star formation histories shape the accretion rate distribution across environments.

Machine Learning for Radial Velocity Analysis I: Vision Transformers as a Robust Alternative for Detecting Planetary Candidates

• Authors: Anoop Gavankar, Tanish Mittal, Joe Ninan, Shravan Hanasoge

• Subjects: Subjects:
  Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR)

• Arxiv link: https://arxiv.org/abs/2510.07034

• Pdf link: https://arxiv.org/pdf/2510.07034

• Abstract
  Extreme precision radial velocity (EPRV) surveys usually require extensive observational baselines to confirm planetary candidates, making them resource-intensive. Traditionally, periodograms are used to identify promising candidate signals before further observational investment, but their effectiveness is often limited for low-amplitude signals due to stellar jitter. In this work, we develop a machine learning (ML) framework based on a Transformer architecture that aims to detect the presence and likely period of planetary signals in time-series spectra, even in the presence of stellar activity. The model is trained to classify whether a planetary signal exists and assign it to one of several discrete period and amplitude bins. Injection-recovery tests on randomly selected 100 epoch observation subsets from NEID solar data (2020-2022 period) show that for low-amplitude systems ($<$1 ms$^{-1}$), our model improves planetary candidate identification by a factor of two compared to the traditional Lomb-Scargle periodogram. Our ML model is built on a Vision Transformer (ViT) architecture that processes reduced representations of solar spectrum observations to predict the period and semi-amplitude of planetary signal candidates. By analyzing multi-epoch spectra, the model reliably detects planetary signals with semi-amplitudes as low as 65 cms$^{-1}$. Even under real solar noise and irregular sampling, it identifies signals down to 35 cms$^{-1}$. Comparisons with the Lomb-Scargle periodogram demonstrate a significant improvement in detecting low-amplitude planetary candidates, particularly for longer orbital periods. These results underscore the potential of machine learning to identify planetary candidates early in EPRV surveys, even from limited observational counts.

Disk fraction among free-floating planetary-mass objects in Upper Scorpius

• Authors: Tommy Rodrigues, Hervé Bouy, Sean N. Raymond, Eduardo L. Martín, Emmanuel Bertin, Javier Olivares, David Barrado, Núria Huélamo, Motohide Tamura, Núria Miret Roig, Phillip A. B. Galli, Jean-Charles Cuillandre

• Subjects: Subjects:
  Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2510.07163

• Pdf link: https://arxiv.org/pdf/2510.07163

• Abstract
  Free-floating planetary-mass objects (FFPs) have been detected through direct imaging within several young, nearby star-forming regions. The properties of circumstellar disks around these objects may provide a valuable probe into their origin, but is currently limited by the small sizes of the sample explored. We aim to perform a statistical study of the occurrence of circumstellar disks down to the planetary-mass regime. We performed a systematic survey of disks among the population identified in the 5-10 Myr-old Upper Scorpius association (USC), restricted to members outside the younger, embedded Ophiuchus region and with estimated masses below 105 M_Jup. We took advantage of unWISE photometry to search for mid-infrared excesses in the WISE (W1-W2) color. We implemented a Bayesian outlier detection method that models the photospheric sequence and computes excess probabilities for each object, enabling statistically sound estimation of disk fractions. We explore disk fractions across an unprecedentedly fine mass grid, reaching down to objects as low as ~6 M_Jup assuming 5 Myr or ~8 M_Jup assuming 10 Myr, thus extending the previous lower boundary of disk fraction studies. Depending on the age, our sample includes between 17 and 40 FFPs. We confirm that the disk fraction steadily rises with decreasing mass and exceeds 30% near the substellar-to-planetary mass boundary at ~13 M_Jup. We find hints of a possible flattening in this trend around 25-45 M_Jup, potentially signaling a transition in the dominant formation processes. This change of trend should be considered with caution and needs to be confirmed with more sensitive observations. Our results are consistent with the gradual dispersal of disks over time, as disk fractions in Upper Scorpius appear systematically lower than those in younger regions.

The cosmic web's Lyman-$α$ glow at $z \approx 2.5$; varying hydrodynamic models, dust, and wide-field, narrow-band imaging detection

• Authors: Oleksii Sokoliuk, John K. Webb, Kenneth M. Lanzetta, Michael M. Shara, Stefan Gromoll, James S. Bolton, Robert F. Carswell, Gaspar Galaz, Cédric Ledoux, Gaspare Lo Curto, Alain Smette, David Valls-Gabaud, Anja von der Linden, Frederick M. Walter, Joris Witstok

• Subjects: Subjects:
  Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA)

• Arxiv link: https://arxiv.org/abs/2510.07259

• Pdf link: https://arxiv.org/pdf/2510.07259

• Abstract
  The diffuse glow of the cosmic web in Lyman-$\alpha$ emission has long been predicted, yet remained elusive to direct wide field detection. We present theoretical calculations that, when compared with recent observations made using the Condor Array Telescope in New Mexico reported in Lanzetta et al. 2024, point to its discovery at $z \approx 2.5$. Synthetic Lyman-$\alpha$ surface brightness maps are constructed from five state-of-the-art hydrodynamic simulations (Illustris-TNG, SIMBA, EAGLE, CROCODILE, and Sherwood), incorporating dust attenuation, star formation, collisional excitation, and recombination physics. Our cosmic web Lyman-$\alpha$ surface brightness predictions are consistent with the UV excess detected at high significance in the recent deep, wide field, narrow-band imaging Condor data. The calculations presented here thus demonstrate that diffuse Lyman-$\alpha$ emission is observable with current (and next-generation) wide field low surface brightness facilities, opening the path to direct cartographic mapping of the cosmic web. These findings mark a turning point: for the first time, cosmology moves beyond inference from absorption and high-density peaks, into panoramic imaging of the faint intergalactic scaffolding that underpins structure formation in the Universe.

Probing evolution of Long GRB properties through their cosmic formation history aided by Machine Learning predicted redshifts

• Authors: Dhruv S. Bal, Aditya Narendra, Maria Giovanna Dainotti, Nikita S. Khatiya, Aleksander L. Lenart, Dieter H. Hartmann

• Subjects: Subjects:
  High Energy Astrophysical Phenomena (astro-ph.HE); Cosmology and Nongalactic Astrophysics (astro-ph.CO)

• Arxiv link: https://arxiv.org/abs/2510.07306

• Pdf link: https://arxiv.org/pdf/2510.07306

• Abstract
  Gamma-ray Bursts (GRBs) are valuable probes of cosmic star formation reaching back into the epoch of reionization, and a large dataset with known redshifts ($z$) is an important ingredient for these studies. Usually, $z$ is measured using spectroscopy or photometry, but $\sim80%$ of GRBs lack such data. Prompt and afterglow correlations can provide estimates in these cases, though they suffer from systematic uncertainties due to assumed cosmologies and due to detector threshold limits. We use a sample with $z$ estimated via machine learning models, based on prompt and afterglow parameters, without relying on cosmological assumptions. We then use an augmented sample of GRBs with measured and predicted redshifts, forming a larger dataset. We find that the predicted redshifts are a crucial step forward in understanding the evolution of GRB properties. We test three cases: no evolution, an evolution of the beaming factor, and an evolution of all terms captured by an evolution factor $(1+z)^\delta$. We find that these cases can explain the density rate in the redshift range between 1-2, but neither of the cases can explain the derived rate densities at smaller and higher redshifts, which may point towards an evolution term different than a simple power law. Another possibility is that this mismatch is due to the non-homogeneity of the sample, e.g., a non-collapsar origin of some long GRB within the sample.

by olozhika (Xing Yuchen).

2025-10-09