@article{20974, abstract = {Thus far, Lyman-α damping wings towards quasars have been used to probe the global ionization state of the foreground intergalactic medium (IGM). A new parametrization has demonstrated that the damping wing signature also carries local information about the distribution of neutral hydrogen (H I) in front of the quasar before it started shining. Leveraging a recently introduced Bayesian JAX-based Hamiltonian Monte Carlo inference framework, we derive constraints on the Lorentzian-weighted H I column density NDW H I , the quasar’s distance rpatch to the first neutral patch, and its lifetime tQ based on James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) spectra of the two z ∼ 7.5 quasars J1007+2115 and J1342+0928. After folding in model-dependent topology information, we find that J1007+2115 (and J1342+0928) is most likely to reside in a (xH1)= 0.32+0.22 −0.20 (0.58+0.23 −0.23) neutral IGM while shining for a remarkably short lifetime of log10 tQ/yr = 4.14+0.74 −0.18 (an intermediate lifetime of 5.64+0.25 −0.43) along a sightline with log10 NDW H I /cm−2 = 19.70+0.35 −0.86 (20.24+0.25 −0.22) and rpatch = 28.9+54.0 −14.4 cMpc (10.9+5.6−5.9 cMpc). In light of the potential presence of local absorbers in the foreground of J1342+0928 as has been recently suggested, we also demonstrate how the Lorentzian-weighted column density NDW H I provides a natural means for quantifying their contribution to the observed damping wing signal.}, author = {Kist, Timo and Hennawi, Joseph F. and Davies, Frederick B. and Bañados, Eduardo and Bosman, Sarah E.I. and Cai, Zheng and Eilers, Anna Christina and Fan, Xiaohui and Haiman, Zoltán and Jun, Hyunsung D. and Liu, Yichen and Yang, Jinyi and Wang, Feige}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, publisher = {Oxford University Press}, title = {{First constraints on the local ionization topology in front of two quasars at z ∼ 7.5}}, doi = {10.1093/mnras/staf2219}, volume = {545}, year = {2026}, } @article{21038, abstract = {Little Red Dots (LRDs) are compact sources at z > 5 discovered through James Webb Space Telescope spectroscopy. Their spectra exhibit broad Balmer emission lines (>~1000 km s^−1), alongside absorption features and a pronounced Balmer break – evidence for a dense, neutral hydrogen medium, in which the n = 2 state is significantly populated. When interpreted as arising from active galactic nucleus broad-line regions, inferred black hole masses from local scaling relations exceed expectations given their stellar masses, challenging models of early black hole–galaxy co-evolution. However, radiative transfer effects in dense media may also impact the formation of hydrogen emission lines. We model three scattering processes shaping hydrogen line profiles: resonance scattering by hydrogen in the n = 2 state, Raman scattering of ultraviolet (UV) radiation by ground-state hydrogen, and Thomson scattering by free electrons. Using 3D Monte Carlo radiative transfer simulations, we examine their imprint on line shapes and ratios. Resonance scattering produces strong deviations from Case B flux ratios, clear differences between Hα and Hβ, and encodes gas kinematics in line profiles but cannot broaden Hβ due to conversion to Paα. While Raman scattering can yield broad wings, scattering of the UV continuum is disfavoured given the absence of strong full width at half-maximum variations across transitions. Raman scattering of higher Lyman-series emission can produce Hα/Hβ wing width ratios of >~1.28, agreeing with observations. Thomson scattering can reproduce the observed >~ 1000 km s^−1 wings under plausible conditions – e.g. Te ∼ 10^4 K and Ne ∼ 10^24 cm^−2 – and lead to black hole mass overestimates by factors 10. Our results provide a framework for interpreting hydrogen lines in LRDs and similar systems.}, author = {Chang, Seok Jun and Gronke, Max and Matthee, Jorryt J and Mason, Charlotte}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, publisher = {Oxford University Press}, title = {{Impact of resonance, Raman, and Thomson scattering on hydrogen line formation in Little Red Dots}}, doi = {10.1093/mnras/staf2131}, volume = {545}, year = {2026}, } @article{21745, abstract = {The small DAHe and DAe spectral classes comprise isolated, hydrogen-dominated atmosphere white dwarfs that exhibit variable photometric flux and Balmer line emission. These mysterious systems offer unique insight into the complex interplay between magnetic fields, stellar rotation and atmospheric activity in single white dwarfs. DAHe stars have detectable magnetic fields through Zeeman-split spectral lines, whereas DAe stars lack such splitting. We report the first discovery and characterization of magnetism in the DAe white dwarf WD J165335.21−100116.33 with new time-resolved spectropolarimetry from FORS2. We detect a weak but variable longitudinal magnetic field with values Bz > −9.2 ± 2.4 kG and Bz < −2.2 ± 1.0 kG. Independent ZTF and ATLAS photometry reveal a consistent period of P = 80.3070 ± 0.0007 h. Time-resolved optical spectroscopy obtained with six ground-based instruments demonstrates strong modulation in the strength of the Hα and Hβ Balmer line emission with P = 80.2922 ± 0.0108 h. The photometric flux and Balmer emission strength vary in antiphase, with the strongest magnetic detections coinciding with phases of low photometric flux and strong line emission. These characteristicssupport the theory that a magnetically active, temperature-inverted spot/region is producing an optically thin chromospheric emission region. Comparison with other DAe and DAHe white dwarfsreveals all systems have a strikingly similar antiphase phenomenology, reinforcing the theory that they are subject to a unified physical mechanism. With the detection of a weak magnetic field, we reclassify WD J165335.21−100116.33 as a low-field DAHe white dwarf. }, author = {Elms, Abbigail K. and Bagnulo, Stefano and Tremblay, Pier Emmanuel and Cunningham, Tim and Munday, James and Landstreet, John and El-Badry, Kareem and Caiazzo, Ilaria and Melis, Carl and Pinter, Viktoria and Weinberger, Alycia}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, publisher = {Oxford University Press}, title = {{Detection of a weak magnetic field in the Balmer emission line white dwarf WDJ1653−1001}}, doi = {10.1093/mnras/stag505}, volume = {548}, year = {2026}, } @article{21780, abstract = {It is predicted that half or more of all cataclysmic variables (CVs) should have evolved past the period minimum and now exist as so-called period bouncers where a white dwarf should be accreting from a Roche lobe filling substellar companion. However, this prediction stands in stark contrast to observations, where only a few per cent of CVs are found in this evolutionary phase. A potential solution to this discrepancy is that a magnetic field emerges from within the white dwarf after the system has reached the period minimum. The transfer of angular momentum from the spin of the white dwarf into the orbit then pushes the two stars apart, detaching them for potentially billions of years. Here we present the discovery of ZTF J021804.16+071152.93, a detached 0.69 +- 0.01 M⁠, 19 MG magnetic white dwarf plus 37 +- 5MJup brown dwarf binary with an orbital period of 1.7 h. The kinematics of the system indicate that it is a high probability member of the Galactic thick disc. However, this strongly disagrees with the much younger age of the system obtained from the white dwarf parameters, implying that the system may have been accreting in the past. This system is therefore consistent with having detached as a result of the emergence of the magnetic field of the white dwarf when the system was still mass transferring, and may represent the ultimate fate for many (perhaps even most) CVs.}, author = {Parsons, S. G. and Brown, A. J. and Casewell, S. L. and Littlefair, S. P. and van Roestel, Joannes C and Rebassa-Mansergas, A. and Murillo-Ojeda, R. and Zorotovic, M. and Schreiber, M. R. and Bagnulo, S. and Stroet, M. A. and Castro Segura, N. and Dhillon, V. S. and Dyer, M. J. and Garbutt, J. A. and Green, M. J. and Jarvis, D. and Kennedy, M. R. and Kerry, P. and Mccormac, J. and Munday, J. and Pelisoli, I. and Pike, E. and Sahman, D. I. and Yates, A.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, publisher = {Oxford University Press}, title = {{ZTF J021804.16+071152.93: A dead cataclysmic variable and potential solution to the missing period bouncer cataclysmic variables}}, doi = {10.1093/mnras/stag521}, volume = {547}, year = {2026}, } @article{21897, abstract = {Ultracompact binary systems, consisting of two compact objects in an orbit $\lesssim 0.5 {\rm R}_\odot$, should exhibit measurable rates of orbital period change ($\dot{P} \ne 0$) due to the emission of gravitational waves (GWs). Measurements of $\dot{P}$ have so far been limited to the shortest-period ultracompact binaries ($\lesssim 20$  min). Among the AM CVn-type subclass, several works have proposed the presence of extra angular momentum loss beyond GW emission, with magnetic braking being a widely discussed mechanism. If present, this magnetic braking would dominate the angular momentum loss of AM CVn-type binaries with orbital periods $\gtrsim 30$ min. In this work, we present a long-term eclipse timing study of two AM CVn-type binaries, YZ LMi and Gaia14aae, with respective orbital periods of 28.3 min and 49.7 min and continuous observations since 2006 and 2015. Both systems show $\dot{P}$ consistent with zero within $2\sigma$. Their $3\sigma$ upper limits are $1.1 \times 10^{-13}\, {\rm s \, s}^{-1}$ and $9.7 \times 10^{-14}\, {\rm s \, s}^{-1}$, respectively. These non-detections are most simply explained by a scenario in which secular angular momentum loss is not substantially stronger than GW emission at all orbital periods, but is combined with deviations from the secular $\dot{P}$ whose time-scales span decades but whose amplitude is $\lesssim 10^{-13}\, {\rm s \, s}^{-1}$. Our non-detections of $\dot{P}$ represent a limit on the strength of any enhanced angular momentum loss beyond pure GW emission.}, author = {Green, Matthew J and Marsh, Thomas R and van Roestel, Joannes C and Wong, Tin Long Sunny and Belloni, Diogo and Kilic, Mukremin and Breedt, Elmé and Brown, Alex and Copperwheat, Chris M and Chakpor, Anurak and Dhillon, V S and Segura, Noel Castro and Dyer, Martin J and Garbutt, James and Jarvis, Dan and Kengkriangkrai, Vasu and Kennedy, Mark R and Kerry, Paul and Kupfer, Thomas and Littlefair, S P and McCormac, James and Munday, James and Parsons, Steven G and Pike, Eleanor and Pelisoli, Ingrid and Rodríguez-Gil, Pablo and Sahman, David I and Yates, Amalie}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {binaries: close – stars, dwarf novae – novae, cataclysmic variables – white dwarfs}, number = {3}, publisher = {Oxford University Press}, title = {{No period change in two long-period AM CVn binaries}}, doi = {10.1093/mnras/stag673}, volume = {548}, year = {2026}, } @article{21898, abstract = {We investigate the nature and spectroscopic diversity of early galaxies from a sample of 41 sources at $z\geqslant 10$ with James Webb Space Telescope (JWST)/NIRSpec prism observations. We compare the properties of strong ultraviolet (UV) line emitters, traced by intense C iv emission, with those of more ‘typical’ sources with weak or undetected C iv. The more typical (or ‘C iv-weak’) sources reveal significant scatter in their C iii] line strengths, UV continuum slopes, and physical sizes, spanning C iii] equivalent widths (EWs) of $\sim$1–51 Å, UV slopes of $\beta \sim -1.6$ to $-2.6$, and half-light radii of $\sim$50–1000 pc. In contrast, C iv-strong sources occupy the tail of these distributions, with C iii] EWs of 16–51 Å, UV slopes $\beta \lesssim -2.5$, compact morphologies ($r_{\rm 50} \lesssim 100$ pc), and elevated star formation surface densities ($\Sigma _{\rm SFR} \gtrsim 100\, M_\odot \, \mathrm{yr}^{-1}\, \mathrm{kpc}^{-2}$). These properties suggest concentrated starbursts that temporarily outshine the host galaxy. Comparing average properties from composite spectra, we find the diversity of the sample is primarily driven by bursty star formation on very short time-scales ($\le$3 Myr), with strong C iv emitters observed at the apex of the bursts and sources devoid of emission lines during relative inactivity. An apparent association between strong C iv and enhanced nitrogen abundance suggests both may be modulated by the same duty cycle, reflecting a generic mode of star formation. We show that active galactic nuclei are unlikely to contribute significantly to this duty cycle based on UV line diagnostics and photoionization models. Our results support a picture whereby brief bursts and lulls can explain the spectral diversity and early growth of bright galaxies in the first 500 Myr.}, author = {Roberts-Borsani, Guido and Oesch, Pascal A and Ellis, Richard and Weibel, Andrea and Giovinazzo, Emma and Bouwens, Rychard and Dayal, Pratika and Fontana, Adriano and Heintz, Kasper E and Matthee, Jorryt J and Meyer, Romain A and Pentericci, Laura and Shapley, Alice and Tacchella, Sandro and Treu, Tommaso and Walter, Fabian and Atek, Hakim and Bose, Sownak and Castellano, Marco and Fudamoto, Yoshinobu and Morishita, Takahiro and Naidu, Rohan P and Sanders, Ryan L and van der Wel, Arjen}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, publisher = {Oxford University Press}, title = {{JWST spectroscopic insights into the diversity of galaxies in the first 500 Myr: Short-lived snapshots along a common evolutionary pathway}}, doi = {10.1093/mnras/stag701}, volume = {548}, year = {2026}, } @article{21063, abstract = {We report the detection of a 13σ Hα emission line from HDF850.1 at z = 5.188 ± 0.001 using the FRESCO (First Reionization Era SpectroscopicallyComplete Observations) NIRCam F444W grism observations. Detection of Hα in HDF850.1 is noteworthy, given its high far-infrared (IR) luminosity, substantial dust obscuration, and the historical challenges in deriving its redshift. HDF850.1 shows a clear detection in the F444W imaging data, distributed between a northern and southern component, mirroring that seen in [C II] from the Plateau de Bure Interferometer. Modelling the spectral energy distribution of each component separately, we find that the northern component has a higher mass, star formation rate (SFR), and dust extinction than the southern component. The observed Hα emission appears to arise entirely from the less-obscured southern component and shows a similar v∼ + 130 km s −1 velocity offset to that seen for [C II] relative to the source systemic redshift. Leveraging Hα-derived redshiftsfrom FRESCO observations, we find that HDF850.1 isforming in one of the richest environments identified to date at z > 5, with 100 z = 5.17–5.20 galaxies distributed across 13 smaller structures and a ∼(15 cMpc)3 volume. Based on the evolution of analogous structures in cosmological simulations, the z = 5.17–5.20 structures seem likely to collapse into a single > 1014M cluster by z ∼ 0. Comparing galaxy properties forming within this overdensity with those outside, we find the masses, SFRs, and UV luminosities inside the overdensity to be clearly higher. The prominence of Hα line emission from HDF850.1 and other known highly obscured z > 5 galaxies illustrates the potential of NIRCam-grism programs to map both the early build-up of IR-luminous galaxies and overdense structures.}, author = {Herard-Demanche, Thomas and Bouwens, Rychard J and Oesch, Pascal A and Naidu, Rohan P and Decarli, Roberto and Nelson, Erica J and Brammer, Gabriel and Weibel, Andrea and Xiao, Mengyuan and Stefanon, Mauro and Walter, Fabian and Matthee, Jorryt J and Meyer, Romain A and Wuyts, Stijn and Reddy, Naveen and Rowland, Lucie and van Leeuwen, Ivana and Haro, Pablo Arrabal and Dannerbauer, Helmut and Shapley, Alice E and Chisholm, John and van Dokkum, Pieter and Labbe, Ivo and Illingworth, Garth and Schaerer, Daniel and Shivaei, Irene}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {788--808}, publisher = {Oxford University Press}, title = {{Mapping dusty galaxy growth at z > 5 with FRESCO: Detection of Hα in submm galaxy HDF850.1 and the surrounding overdense structures}}, doi = {10.1093/mnras/staf030}, volume = {537}, year = {2025}, } @article{21122, abstract = {The multimessenger combination of gravitational waves (GWs) from merging massive black hole binaries (MBHBs) and the electromagnetic (EM) counterpart from the surrounding circumbinary disc (CBD) will open avenues to new scientific pursuits. In order to realize this science, we need to correctly localize the host galaxy of the merging MBHB. Multiwavelength, time-dependent EM signatures can greatly facilitate the identification of the unique EM counterpart among many sources in LISA’s localization volume. To this end, we studied merging unequal-mass MBHBs embedded in a CBD using high-resolution 2D simulations, with a $\Gamma$-law equation of state, incorporating viscous heating, shock heating, and radiative cooling. We simulate each binary starting from before it decouples from the CBD until just after the merger. We compute EM signatures and identify distinct features before, during, and after the merger. We corroborate previous findings of a several orders of magnitude drop in the thermal X-ray luminosity near the time of merger, but with delayed timing compared to an equal-mass system. The source remains X-ray dark for hours post-merger. Our main results are a potential new signature of a sharp spike in the thermal X-ray emission just before the tell-tale steep drop occurs. This feature may further help to identify EM counterparts of LISA’s unequal MBHBs before merger without the need for extensive pre-merger monitoring. Additionally, we find a role-reversal in which the primary out-accretes the secondary during late inspiral, which may diminish signatures originating from Doppler modulation.}, author = {Krauth, Luke Major and Davelaar, Jordy and Haiman, Zoltán and Westernacher-Schneider, John Ryan and Zrake, Jonathan and MacFadyen, Andrew}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2670--2685}, publisher = {Oxford University Press}, title = {{Thermal X-ray signatures in late-stage unequal-mass massive black hole binary mergers}}, doi = {10.1093/mnras/staf1583}, volume = {543}, year = {2025}, } @article{21127, abstract = {The early growth of black holes (BHs) in atomic-cooling haloes is likely influenced by feedback on the surrounding gas. While the effects of radiative feedback are well-documented, mechanical feedback, particularly from active galactic nucleus (AGN) jets, has been comparatively less explored. Building on our previous work that examined the growth of a 100 M BH in a constant density environment regulated by AGN jets, we expand the initial BH mass range from 1 to 104 M and adopt a more realistic density profile for atomic-cooling haloes. We reaffirm the validity of our analytic models for jet cocoon propagation and feedback regulation. We identify several critical radii – namely, the terminal radius of jet cocoon propagation, the isotropization radius of the jet cocoon, and the core radius of the atomic-cooling halo – that are crucial in determining BH growth given specific gas properties and jet feedback parameters. In a significant portion of the parameter space, our findings show that jet feedback substantially disrupts the halo’s core during the initial feedback episode, preventing BH growth beyond 104 M. Conversely, conditions characterized by low jet velocities and high gas densities enable sustained BH growth over extended periods. We provide a prediction for the BH mass growth as a function of time and feedback parameters. We found that, to form a supermassive BH (> 106 M) within 1 Gyr entirely by accreting gas from an atomic-cooling halo, the jet energy feedback efficiency must be 10−4M˙ BHc2 even if the seed BH mass is 104 M.}, author = {Su, Kung-Yi and Bryan, Greg L and Haiman, Zoltán}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {11--30}, publisher = {Oxford University Press}, title = {{Self-regulation of high-redshift black hole accretion via jets: Challenges for SMBH formation}}, doi = {10.1093/mnras/staf228}, volume = {538}, year = {2025}, } @article{21128, abstract = {The brightest steady sources of radiation in the universe, active galactic nuclei (AGNs), are powered by gas accretion on to a central supermassive black hole (SMBH). The large sizes and accretion rates implicated in AGN accretion discs are expected to lead to gravitational instability and fragmentation, effectively cutting off mass inflow to the SMBH. Radiative feedback from disc-embedded stars has been invoked to yield marginally stable, steady-state solutions in the outer discs. Here, we examine the consequences of this star formation with a semi-analytical model in which stellar-mass black hole (sBH) remnants in the disc provide an additional source of stabilizing radiative feedback. Assuming star formation seeds the embedded sBH population, we model the time-evolving feedback from both stars and the growing population of accreting sBHs. We find that in the outer disc, the luminosity of the sBHs quickly dominates that of their parent stars. However, because sBHs consume less gas than stars to stabilize the disc, the presence of the sBHs enhances the mass flux to the inner disc. As a result, star formation persists over the lifetime of the AGN, damped in the outer disc, but amplified in a narrow ring in the inner disc. Heating from the embedded sBHs significantly modifies the disc’s temperature profile and hardens its spectral energy distribution, and direct emission from the sBHs adds a new hard X-ray component.}, author = {Epstein-Martin, Marguerite and Tagawa, Hiromichi and Haiman, Zoltán and Perna, Rosalba}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3396--3420}, publisher = {Oxford University Press}, title = {{Time-dependent models of AGN discs with radiation from embedded stellar-mass black holes}}, doi = {10.1093/mnras/staf237}, volume = {537}, year = {2025}, } @article{18984, abstract = {Although planets have been found orbiting binary systems, whether they can survive binary interactions is debated. While the tightest-orbit binaries should host the most dynamically stable and long-lived circumbinary planetary systems, they are also the systems that are expected to experience mass transfer, common envelope evolution, or stellar mergers. In this study, we explore the effect of stable non-conservative mass transfer on the dynamical evolution of circumbinary planets. We present a new script that seamlessly integrates binary evolution data from the 1D binary stellar evolution code MESA into the N-body simulation code REBOUND. This integration framework enables a comprehensive examination of the dynamical evolution of circumbinary planets orbiting mass-transferring binaries, while simultaneously accounting for the detailed stellar structure evolution. In addition, we introduce a recalibration method to mitigate numerical errors from updates of binary properties during the system's dynamical evolution. We construct a reference binary model in which a 2.21M⊙ star loses its hydrogen-rich envelope through non-conservative mass transfer to the 1.76M⊙ companion star, creating a 0.38M⊙ subdwarf. We find the tightest stable orbital separation for circumbinary planets to be ≃2.5 times the binary separation after mass transfer. Accounting for tides by using the interior stellar structure, we find that tidal effects become apparent after the rapid mass transfer phase and start to fade away during the latter stage of the slow mass transfer phase. Our research provides a new framework for exploring circumbinary planet dynamics in interacting binary systems.}, author = {Xing, Zepei and Torres Rodriguez, Santiago and Götberg, Ylva Louise Linsdotter and Trani, Alessandro A. and Korol, Valeriya and Cuadra, Jorge}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {285--292}, publisher = {Oxford University Press}, title = {{Combining REBOUND and MESA: Dynamical evolution of planets orbiting interacting binaries}}, doi = {10.1093/mnras/stae2820}, volume = {537}, year = {2025}, } @article{19066, abstract = {We present a sample of 1956 individual stellar clumps at redshift 0.7 < z < 10, detected with JWST/NIRCam in 476 galaxies lensed by the galaxy cluster Abell2744. The lensed clumps present magnifications ranging between μ = 1.8 and μ = 300. We perform simultaneous size-photometry estimates in 20 JWST/NIRCam median and broad-band filters from 0.7 to 5 μm. Spectral energy distribution (SED) fitting analyses enable us to recover the physical properties of the clumps. The majority of the clumps are spatially resolved and have effective radii in the range Reff = 10–700 pc. We restrict this first study to the 1751 post-reionization era clumps with redshift < 5.5. We find a significant evolution of the average clump ages, star formation rates (SFRs), SFR surface densities, and metallicity with increasing redshift, while median stellar mass and stellar mass surface densities are similar in the probed redshift range. We observe a strong correlation between the clump properties and the properties of their host galaxies, with more massive galaxies hosting more massive and older clumps. We find that clumps closer to their host galactic centre are on average more massive, while their ages do not show clear sign of migration. We find that clumps at cosmic noon sample the upper-mass end of the mass function to higher masses than at z > 3, reflecting the rapid increase towards the peak of the cosmic star formation history. We conclude that the results achieved over the studied redshift range are in agreement with expectation of in situ clump formation scenario from large-scale disc fragmentation. }, author = {Claeyssens, Adélaïde and Adamo, Angela and Messa, Matteo and Dessauges-Zavadsky, Miroslava and Richard, Johan and Kramarenko, Ivan and Matthee, Jorryt J and Naidu, Rohan P.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2535--2558}, publisher = {Oxford University Press}, title = {{Tracing star formation across cosmic time at tens of parsec-scales in the lensing cluster field Abell 2744}}, doi = {10.1093/mnras/staf058}, volume = {537}, year = {2025}, } @article{19840, abstract = {We report the discovery of two new magnetic cataclysmic variables with brown dwarf companions and long orbital periods (P_{\rm orb}=95\pm1 and 104\pm2 min). This discovery increases the sample of candidate magnetic period bouncers with confirmed sub-stellar donors from four to six. We also find their X-ray luminosity from archival XMM–Newton observations to be in the range L_{\rm X}\approx10^{28}-10^{29} \mathrm{erg\,s^{-1}} in the 0.25–10 keV band. This low luminosity is comparable with the other candidates, and at least an order of magnitude lower than the X-ray luminosities typically measured in cataclysmic variables. The X-ray fluxes imply mass transfer rates that are much lower than predicted by evolutionary models, even if some of the discrepancy is due to the accretion energy being emitted in other bands, such as via cyclotron emission at infrared wavelengths. Although it is possible that some or all of these systems formed directly as binaries containing a brown dwarf, it is likely that the donor used to be a low-mass star and that the systems followed the evolutionary track for cataclysmic variables, evolving past the period bounce. The donor in long period systems is expected to be a low-mass, cold brown dwarf. This hypothesis is supported by near-infrared photometric observations that constrain the donors in the two systems to be brown dwarfs cooler than 1100 K (spectral types T5 or later), most likely losing mass via Roche Lobe overflow or winds. The serendipitous discovery of two magnetic period bouncers in the small footprint of the XMM–Newton catalogue implies a large space density of these type of systems, possibly compatible with the prediction of 40–70 per cent of magnetic cataclysmic variables to be period bouncers.}, author = {Cunningham, Tim and Caiazzo, Ilaria and Sienkiewicz, Gracjan and Wheatley, Peter J. and Gänsicke, Boris T. and El-Badry, Kareem and Arcodia, Riccardo and Charbonneau, David and Connor, Liam and De, Kishalay and Hakala, Pasi and Kenyon, Scott J. and Maheshwari, Sumit Kumar and Rodriguez, Antonio C. and Van Roestel, Jan and Tremblay, Pier Emmanuel}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {633--649}, publisher = {Oxford University Press}, title = {{Discovery of two new polars evolved past the period bounce}}, doi = {10.1093/mnras/staf561}, volume = {540}, year = {2025}, } @article{19855, abstract = {We present indirect constraints on the absolute escape fraction of ionizing photons (f_{\rm esc}^{\rm LyC}) of the system GN 42912 which comprises two luminous galaxies (M_{\rm UV} magnitudes of -20.89 and -20.37) at z\sim7.5, GN 42912-NE and GN 42912-SW, to determine their contribution to the ionizing photon budget of the Epoch of Reionization (EoR). The high-resolution James Webb Space Telescope NIRSpec and NIRCam observations reveal the two galaxies are separated by only ~0.1" (0.5 kpc) on the sky and have a 358 km s^{-1} velocity separation. GN 42912-NE and GN 42912-SW are relatively massive for this redshift (log(M_\ast/M_\odot) \sim 8.4 and 8.9, respectively), with gas-phase metallicities of 18 per cent and 23 per cent solar, O_{32} ratios of 5.3 and >5.8, and \beta slopes of -1.92 and -1.51, respectively. We use the Mg II\lambda\lambda2796,2803 doublet to constrain f_{\rm esc}^{\rm LyC}. Mg II has an ionization potential close to that of neutral hydrogen and, in the optically thin regime, can be used as an indirect tracer of the LyC leakage. We establish realistic conservative upper limits on f_{\rm esc}^{\rm LyC} of 8.5 per cent for GN 42912-NE and 14 per cent for GN 42912-SW. These estimates align with f_{\rm esc}^{\rm LyC} trends observed with \beta, O_{32}, and the H\beta equivalent width at z<4. The small inferred ionized region sizes (<0.3 pMpc) around both galaxies indicate they have not ionized a significant fraction of the surrounding neutral gas. While these z>7 f_{\rm esc}^{\rm LyC} constraints do not decisively determine a specific reionization model, they support a minor contribution from these two relatively luminous galaxies to the EoR.}, author = {Gazagnes, S. and Chisholm, J. and Endsley, R. and Berg, D. A. and Leclercq, F. and Jurlin, N. and Saldana-Lopez, A. and Finkelstein, S. L. and Flury, S. R. and Guseva, N. G. and Henry, A. and Izotov, Y. I. and Jung, I. and Matthee, Jorryt J and Schaerer, D.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2331--2348}, publisher = {Oxford University Press}, title = {{A negligible contribution of two luminous z ∼7.5 galaxies to the ionizing photon budget of reionization}}, doi = {10.1093/mnras/staf768}, volume = {540}, year = {2025}, } @article{20027, abstract = {We present the first results of the JWST Emission Line Survey (JELS). Utilizing the first NIRCam narrow-band imaging at 4.7 μm, over 63 arcmin2 in the PRIMER/COSMOS field, we have identified 609 emission line galaxy candidates. From these, we robustly selected 35 H α star-forming galaxies at z ∼ 6.1, with H α star-formation rates (SFRH α) of ∼ 0.9 − 15 M yr−1. Combining our unique H α sample with the exquisite panchromatic data in the field, we explored their physical properties and star-formation histories, and compared these to a broad-band selected sample at z ∼ 6 which has offered vital new insights into the nature of high-redshift galaxies. UV-continuum slopes (β) were considerably redder for our H α sample (β ∼ −1.92) compared to the broad-band sample (β ∼ −2.35). This was not due to dust attenuation as our H α sample was relatively dustpoor (median AV = 0.23); instead, we argue that the reddened slopes could be due to nebular continuum. We compared SFRH α and the UV-continuum-derived SFRUV to SED-fitted measurements averaged over canonical time-scales of 10 and 100 Myr (SFR10 and SFR100). We found an increase in recent SFR for our sample of H α emitters, particularly at lower stellar masses (< 109 M). We also found that SFRH α strongly traces SFR averaged over 10 Myr time-scales, whereas the UV-continuum overpredicts SFR on 100 Myr time-scales at low stellar masses. These results point to our H α sample undergoing ‘bursty’ star formation. Our F356W z ∼ 6 sample showed a larger scatter in SFR10/SFR100 across all stellar masses, which has highlighted how narrow-band photometric selections of H α emitters are key to quantifying the burstiness of star-formation activity. }, author = {Pirie, C. A. and Best, P. N. and Duncan, K. J. and Mcleod, D. J. and Cochrane, R. K. and Clausen, M. and Dunlop, J. S. and Flury, S. R. and Geach, J. E. and Hale, C. L. and Ibar, E. and Kondapally, R. and Li, Zefeng and Matthee, Jorryt J and Mclure, R. J. and Ossa-Fuentes, L. and Patrick, A. L. and Smail, Ian and Sobral, D. and Stephenson, H. M.O. and Stott, J. P. and Swinbank, A. M.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {1348--1376}, publisher = {Oxford University Press}, title = {{The JWST Emission Line Survey (JELS): An untargeted search for H α emission line galaxies at z > 6 and their physical properties}}, doi = {10.1093/mnras/staf1006}, volume = {541}, year = {2025}, } @article{20028, abstract = {We present the JWST Emission-Line Survey (JELS), a JWST imaging programme exploiting the wavelength coverage and sensitivity of the Near-Infrared Camera (NIRCam) to extend narrow-band rest-optical emission-line selection into the Epoch of Reionization (EoR) for the first time, and to enable unique studies of the resolved ionized gas morphology in individual galaxies across cosmic history. The primary JELS observations comprise ∼ 4.7 μm narrow-band imaging over ∼ 63 arcmin2 designed to enable selection of H α emitters at z ∼ 6.1 and a host of novel emission-line samples, including [O III] (z ∼ 8.3) and Paschen α/β (z ∼ 1.5/2.8). For the F466N/F470N narrow-band observations, the emission-line sensitivities achieved are up to ∼ 2× more sensitive than current slitless spectroscopy surveys (5σ limits of 0.8–1.2×10−18 erg s−1cm−2), corresponding to unobscured H α star formation rates (SFRs) of 0.9–1.3 M yr−1 at z ∼ 6.1, extending emission-line selections in the EoR to fainter populations. Simultaneously, JELS also adds F200W broad-band and F212N narrow-band imaging (H α at z ∼ 2.23) that probes SFRs 5× fainter than previous ground-based narrow-band studies (∼ 0.2 M yr−1), offering an unprecedented resolved view of star formation at cosmic noon. We present the detailed JELS design, key data processing steps specific to the survey observations, and demonstrate the exceptional data quality and imaging sensitivity achieved. We then summarize the key scientific goals of JELS, demonstrate the precision and accuracy of the expected redshift and measured emission-line recovery through detailed simulations, and present examples of spectroscopically confirmed H α and [O III] emitters discovered by JELS that illustrate the novel parameter space probed.}, author = {Duncan, K. J. and Mcleod, D. J. and Best, P. N. and Pirie, C. A. and Clausen, M. and Cochrane, R. K. and Dunlop, J. S. and Flury, S. R. and Geach, J. E. and Grogin, N. A. and Hale, C. L. and Ibar, E. and Kondapally, R. and Li, Zefeng and Matthee, Jorryt J and Mclure, R. J. and Ossa-Fuentes, Luis and Patrick, A. L. and Smail, Ian and Sobral, D. and Stephenson, H. M.O. and Stott, J. P. and Swinbank, A. M.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {1329--1347}, publisher = {Oxford University Press}, title = {{The JWST Emission-Line Survey: Extending rest-optical narrow-band emission-line selection into the Epoch of Reionization}}, doi = {10.1093/mnras/staf1061}, volume = {541}, year = {2025}, } @article{20250, abstract = {Population III stars are possible precursors to early supermassive black holes (BHs). The presence of soft UV Lyman–Werner (LW) background radiation can suppress Population III star formation in minihaloes and allow them to form in pristine atomic-cooling haloes. In the absence of molecular hydrogen (⁠H2⁠) cooling, atomic-cooling haloes enable rapid collapse with suppressed fragmentation. High background LW fluxes from preceding star-formation have been proposed to dissociate H2⁠. This flux can be supplemented by LW radiation from one or more Population III star(s) in the same halo, reducing the necessary background level. Here, we consider atomic-cooling haloes in which multiple protostellar cores form close to one another nearly simultaneously. We assess whether the first star’s LW radiation can dissociate nearby ⁠, enabling rapid accretion on to a nearby protostellar core, and the prompt formation of a second, supermassive star (SMS) from warm, atomically-cooled gas. We use a set of hydrodynamical simulations with the code enzo, with identical LW backgrounds centred on a halo with two adjacent collapsing gas clumps. When an additional large local LW flux is introduced, we observe immediate reductions in both the accretion rates and the stellar masses that form within these clumps. While the LW flux reduces the H2 fraction and increases the gas temperature, the halo core’s potential well is too shallow to promptly heat the gas to >1000 K and increase the second protostar’s accretion rate. We conclude that this internal LW feedback scenario is unlikely to facilitate SMS or massive BH seed formation.}, author = {Sullivan, James and Haiman, Zoltán and Kulkarni, Mihir and Visbal, Eli}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {822--838}, publisher = {Oxford University Press}, title = {{Can supermassive stars form in protogalaxies due to internal Lyman-Werner feedback?}}, doi = {10.1093/mnras/staf1269}, volume = {542}, year = {2025}, } @article{20545, abstract = {The H i gas distribution in damped Lyman $\alpha$ absorbers (DLAs) has remained elusive due to the point-source nature of background quasar emission. Observing DLAs against spatially extended background galaxies provides a new method for constraining their size and structure. Using the Keck Cosmic Web Imager, we present the first ‘silhouette’ image of a DLA at $z=3.34$, identified in the spectrum of a background galaxy at $z=3.61$. Although the silhouette remains unresolved due to limited spatial resolution, this represents a successful proof-of-concept for studying DLA morphology using extended background sources. Possible residual emission in the DLA trough suggests an optical depth contrast exceeding $10^7$ in the internal structure, implying a sharp edge or patchy structure. A Lyman $\alpha$ emitter (LAE) at $z_{\rm LAE}=3.3433\pm 0.0005$, consistent with the DLA redshift, is detected at an angular separation of $1{{_{.}^{\prime\prime}} }73\pm 0{{_{.}^{\prime\prime}} }28$ ($12.9\pm 2.1$ kpc). The DLA is surrounded by three galaxies within 140 kpc in projected distance and 500 km s$^{-1}$ in line-of-sight velocity, indicating that it resides in the circumgalactic medium of the LAE or within a galaxy group/protocluster environment. An O i  $\lambda 1302$ absorption at $z_{\rm OI}=3.3288\pm 0.0004$ is also detected along the line of sight. This absorber may trace metal-enriched outflow from the LAE or a gas-rich galaxy exhibiting the highest star formation activity among the surrounding galaxies. Future large spectroscopic surveys of galaxies will expand such a DLA sample, and three-dimensional spectroscopy for it will shed new light on the role of intergalactic dense gas in galaxy formation and evolution.}, author = {Komori, Fuga and Inoue, Akio K and Mawatari, Ken and Sugahara, Yuma and Umehata, Hideki and Shimakawa, Rhythm and Yamanaka, Satoshi and Hashimoto, Takuya and Matthee, Jorryt J and Misawa, Toru}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2943--2957}, publisher = {Oxford University Press}, title = {{The first direct imaging of the silhouette of a damped Lyman α system along the line-of-sight to a background galaxy}}, doi = {10.1093/mnras/staf1622}, volume = {543}, year = {2025}, } @article{20660, abstract = {We used observations from the JWST Emission Line Survey (JELS) to measure the half-light radii (re) of 23 Hα-emitting starforming (SF) galaxies at z = 6.1 in the PRIMER/COSMOS field. Galaxy sizes were measured in JWST near-infrared camera observations in rest-frame Hα (tracing recent star formation) with the F466N and F470N narrow-band filters from JELS, and compared against rest-R- and V -band (tracing established stellar populations) and near-ultraviolet sizes. We find a size–stellar mass(re − M∗) relationship with a slope that is consistent with literature values at lower redshifts, though offset to lowersizes. We observe a large scatter in re at low stellar mass (M∗ < 10^8.4 Mo) which we believe is the result of bursty star formation histories (SFHs) of SF galaxies at the Epoch of Reionization (EoR). We find that the stellar and ionized gas components are similar in size at z = 6.1. The evidence of already-established stellar components in these Hα emitters (HAEs) indicates previous episodes of star formation have occurred. As such, following other JELS studies finding our HAEs are undergoing a current burst of star formation, we believe our results indicate that SF galaxies at the end of the EoR have already experienced a bursty SFH. From our re − M∗ relationship, we find re,F444W = 0.76 ± 0.46 kpc for fixed stellar mass M∗ = 10^9.25 M, which is in agreement with other observations and simulations of SF galaxies in the literature. We find a close-pair (major) merger fraction of (fmaj. merger =0.44 ± 0.22) fmerger = 0.43 ± 0.11 for galaxy separations d <~ 25 kpc, which is in agreement with other z ≈ 6 studies.}, author = {Stephenson, H. M.O. and Stott, J. P. and Pirie, C. A. and Duncan, K. J. and Mcleod, D. J. and Best, P. N. and Brinch, M. and Clausen, M. and Cochrane, R. K. and Dunlop, J. S. and Flury, S. R. and Geach, J. E. and Hale, C. L. and Ibar, E. and Li, Zefeng and Matthee, Jorryt J and Mclure, R. J. and Ossa-Fuentes, L. and Patrick, A. L. and Sobral, D. and Swinbank, A. M.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {1412--1431}, publisher = {Oxford University Press}, title = {{The JWST Emission Line Survey (JELS): The sizes and merger fraction of star-forming galaxies during the Epoch of Reionization}}, doi = {10.1093/mnras/staf1725}, volume = {544}, year = {2025}, } @article{20661, abstract = {We analyse James Webb Space Telescope (JWST) Near Infrared Imager and Slitless Spectrograph (NIRISS) and Near Infrared Spectrograph (NIRSpec) spectroscopic observations in the Abell 2744 galaxy cluster field. From approximately 120 candidates, we identify 12 objects with at least two prominent emission lines among [O II] λ3727, H β λ4861, [O III] λ4959, [O III] λ5007, and H α λ6563 that are spectroscopically confirmed by both instruments. Our key findings reveal systematic differences between the two spectrographs based on source morphology and shutter aperture placement. Compact objects show comparable or higher integrated flux in NIRSpec relative to NIRISS (within 1σ uncertainties), while extended sources consistently display higher flux in NIRISS measurements. This pattern reflects NIRSpec’s optimal coverage for compact objects while potentially undersampling extended sources. Quantitative analysis demonstrates that NIRSpec recovers at least 63 per cent of NIRISS-measured flux when the slit covers >15 per cent of the source or when Re < 1 kpc. For lower coverage or larger effective radii, the recovered flux varies from 24 per cent to 63 per cent. When studying the H α λ6563/[O III] λ5007 emission line ratio, we observe that measurements from these different spectrographs can vary by up to ∼0.3 dex, with significant implications for metallicity and star formation rate characterizations for individual galaxies. These results highlight the importance of considering instrumental effects when combining multi-instrument spectroscopic data and demonstrate that source morphology critically influences flux recovery between slit-based and slitless spectroscopic modes in JWST observations.}, author = {Dalmasso, Nicolò and Watson, Peter J. and Treu, Tommaso and Trenti, Michele and Vulcani, Benedetta and Nanayakkara, Themiya and Bradač, Maruša and Jones, Tucker and Boyett, Kristan and Wang, Xin and Mascia, Sara and Pentericci, Laura}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {2}, pages = {1915--1925}, publisher = {Oxford University Press}, title = {{Quantifying spectroscopic flux variations between JWST NIRISS and NIRSpec: Slit losses in emission line measurements of z ∼ 1-3 galaxies}}, doi = {10.1093/mnras/staf1837}, volume = {544}, year = {2025}, }