@article{21997, abstract = {The massive binary common envelope (CE) phase plays a pivotal role in the formation of close black hole (BH)/neutron star binaries, yet significant uncertainties remain in our understanding of this process. In this study, we aim to constrain the massive binary CE phase by systematically reconstructing three observed BH X-ray binaries (BHXBs): GRO J1655-40, SAX J1819.3-2525, and 4U 1543-47. Through comprehensive binary evolution simulations and parametric supernova modeling, we establish lower limits for the CE efficiency parameters under different energy considerations within the standard energy formalism. Specifically, we derive minimum values for three cases: α0.5U and αU, representing CE efficiencies with half and all of the internal energy contributing to the envelope ejection, respectively, and αH, accounting for the envelope’s enthalpy. Our analysis reveals that the self-consistent formation of these three BHXBs requires CE efficiency parameters satisfying α0.5U ≳ 6.7, αU ≳ 4.2, and αH ≳ 1.7. Notably, we find no viable solutions with CE efficiency values below unity, even when considering the most extreme scenarios, in which the envelope binding energy is significantly reduced through enthalpy inclusion. Our results strongly imply that either additional energy sources are required or the formalism itself must be revised. Furthermore, we quantitatively assess the impact of BH natal kicks on our results. A key finding is that 4U 1543-47’s formation requires substantial natal kicks (≳50 km s−1), as lower kick velocities are incompatible with isolated binary evolution.}, author = {Li, Zhenwei and Wei, Dandan and Jia, Shi and Chen, Hailiang and Ge, Hongwei and Chen, Zhuo and Zhang, Yangyang and Chen, Xuefei and Han, Zhanwen}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{A path to constraints on common envelope ejection in massive binaries: Full evolutionary reconstruction of three Black Hole X-ray binaries}}, doi = {10.3847/1538-4357/ae66fd}, volume = {1004}, year = {2026}, } @article{21999, abstract = {JWST has revealed an abundance of supermassive black holes (BHs) in the early Universe, and yet the lowest mass seed BHs that gave rise to these populations remain elusive. Here, we present a systematic search for broad-line active galactic nuclei (AGNs) in some of the faintest high-z galaxies surveyed yet by combining ultra-deep JWST/NIRSpec G395M spectroscopy with the strong lensing aid in AS1063. By employing the profile of the [O iii]λ5007 emission lines as a template for narrow-line components and carefully cross-validating with mock observations, we identify a sample of 10 broad-line AGNs at 4.5 < z < 7.0 (eight secure, two tentative). The inferred BH masses from the broad Hα line explore the intermediate BH mass regime down to ∼105.5 M⊙. The stellar mass (M*) is estimated with a galaxy+AGN composite model, and we find the BH to stellar mass ratio spans down to MBH/M* ≲ 0.1%, unveiling populations on the empirical MBH–M* relation observed in the local Universe. We also derive the BH mass function and investigate its low-mass end at this epoch. While we confirm the agreement of our results with previous studies at MBH ≳ 106.5M⊙, we find the mass range of ∼105.5 M⊙ features an enhanced abundance with respect to the extrapolated best-fit Schechter function. Comparison with theoretical models suggests that a possible origin for this enhanced abundance is the direct-collapse BH formation, supporting the scenario that the direct collapse of massive gas clouds is a significant pathway for the earliest supermassive BHs.}, author = {Fei, Qinyue and Fujimoto, Seiji and Naidu, Rohan P. and Chisholm, John and Atek, Hakim and Brammer, Gabriel and Asada, Yoshihisa and Berg, Danielle A. and Bromm, Volker and Furtak, Lukas J. and Greene, Jenny E. and Hsiao, Tiger Yu Yang and Jeon, Junehyoung and Kokorev, Vasily and Matthee, Jorryt J and Natarajan, Priyamvada and Pan, Richard and Richard, Johan and Saldana-Lopez, Alberto and Schaerer, Daniel and Volonteri, Marta and Zitrin, Adi}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{A GLIMPSE of intermediate mass Black Holes in the epoch of reionization: Witnessing the descendants of direct collapse?}}, doi = {10.3847/1538-4357/ae6248}, volume = {1003}, year = {2026}, } @article{21705, abstract = {We report the discovery of ATLAS J101342.5−451656.8 (hereafter ATLAS J1013−4516), an 8.56 minute orbital-period mass-transferring AM Canum Venaticorum (AM CVn) binary with a mean Gaia magnitude of G = 19.51, identified via periodic variability in light curves from the Asteroid Terrestrial-impact Last Alert System (ATLAS) of Gaia white dwarf candidates. Follow-up with the Large Lenslet Array Magellan Spectrograph shows a helium-dominated accretion disk, and high-speed ULTRACAM photometry reveals pronounced primary and secondary eclipses. We construct a decade-long timing baseline leveraging light curves from the ATLAS and Gaia surveys, as well as the high-speed imagers ULTRACAM on the New Energy Telescope and proto-Lightspeed on the Magellan Clay telescope. From this timing baseline, we measure an orbital period derivative of P 1.60 0.07 10 = ± × 12 s s−1. Interpreted in the context of stable mass transfer, the magnitude and sign of P indicate that the orbital evolution is governed by the interplay between gravitationalwave-driven angular-momentum losses and mass transfer, directly probing the donor’s structural response to mass loss. We constrain the accretor and donor mass based on stable mass-transfer arguments assuming angularmomentum loss dominated by gravitational-wave emission, allowing us to infer the characteristic gravitational wave strain of the binary for future space-based GW observatories such as the Laser Interferometer Space Antenna (LISA). We predict a characteristic strain corresponding to a 4 yr LISA signal-to-noise ratio ≳10, establishing ATLAS J1013−4516 as a strong prospective LISA source that will probe long-term orbital evolution in the mass-transferring regime.}, author = {Chickles, Emma T. and Chakraborty, Joheen and Burdge, Kevin B. and Dhillon, Vik S. and Draghis, Paul and El-Badry, Kareem and Green, Matthew J. and Householder, Aaron and Hughes, Sarah and Layden, Christopher and Littlefair, Stuart P. and Munday, James and Pelisoli, Ingrid and Redden, Maya S. and Tonry, John and van Roestel, Joannes C and Angile, Francesco Elio and Brown, Alex J. and Segura, Noel Castro and Dinsmore, Jack and Dyer, Martin and Furesz, Gabor and Gabutti, Michelle and Garbutt, James and García-Mejía, Juliana and Jarvis, Daniel and Kennedy, Mark R. and Kerry, Paul and Mccormac, James and Mo, Geoffrey and Osip, Dave and Parsons, Steven and Pike, Eleanor and Piotrowski, John J. and Romani, Roger W. and Sahman, David and Simcoe, Rob}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{An eclipsing 8.56 minutes orbital period mass-transferring binary}}, doi = {10.3847/1538-4357/ae4871}, volume = {1000}, year = {2026}, } @article{21710, abstract = {Early results from JWST suggest that Epoch of Reionization (EoR) galaxies produce copious ionizing photons, which, if they escape efficiently, could cause reionization to occur too early. We study this problem using JWST imaging and prism spectroscopy for 412 galaxies at 4.5 < z < 9.0. We fit these data simultaneously with stellar population and nebular emission models that include a parameter for the fraction of ionizing photons that escape the galaxy, fesc. We find that the ionization production efficiency, ξion = Q(H0)/LUV, increases with redshift and decreasing UV luminosity, but shows significant scatter, (log ion z, MUV) 0.3 dex. The inferred escape fractions averaged over the population are low, ranging from〈fesc〉 ≃ 2.6% ± 1.4% at 6 < z < 9 to 6.5% ± 2.2% at 4.5 < z < 6, with weak or no indication of evolution with redshift. This implies that in our models most of the ionizing photons need to be absorbed to account for the nebular emission. We compute the impact of our results on reionization, including the distributions for ξion and fesc, and the evolution and uncertainty of the UV luminosity function. Considering galaxies brighter than MUV < −16 mag would produce an intergalactic medium hydrogen-ionized fraction of xe = 0.5 at 5.3 < z < 5.8, possibly too late compared to constraints from from quasistellar object (QSO) sight lines. Including fainter galaxies, MUV < −14 mag, we obtain xe = 0.5 at 6.0 < z < 8.1, fully consistent with QSO and cosmic microwave background data. This implies that EoR galaxies produce plenty of ionizing photons, but that these do not efficiently escape. This may be a result of high gas column densities combined with burstier star formation histories, which limit the time massive stars are able to clear channels through the gas for ionizing photons to escape.}, author = {Papovich, Casey and Cole, Justin W. and Hu, Weida and Finkelstein, Steven L. and Shen, Lu and Arrabal Haro, Pablo and Amorín, Ricardo O. and Backhaus, Bren E. and Bagley, Micaela B. and Bhatawdekar, Rachana and Calabrò, Antonello and Carnall, Adam C. and Cleri, Nikko J. and Daddi, Emanuele and Dickinson, Mark and Grogin, Norman A. and Holwerda, Benne W. and Jaskot, Anne E. and Koekemoer, Anton M. and Llerena, Mario and Lucas, Ray A. and Mascia, Sara and Pacucci, Fabio and Pentericci, Laura and Pérez-González, Pablo G. and Pirzkal, Nor and Raghunathan, Srinivasan and Seillé, Lise Marie and Somerville, Rachel S. and Yung, L. Y.Aaron}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{Galaxies in the epoch of reionization are all bark and no bite-plenty of ionizing photons, low escape fractions}}, doi = {10.3847/1538-4357/ae3b25}, volume = {1000}, year = {2026}, } @article{21712, abstract = {Supermassive black hole binary (SMBHB) systems are expected to form as a consequence of galaxy mergers. At subparsec separations, SMBHBs can be identified as quasars with periodic variability, with previous periodicity searches uncovering significant candidates. However, these searches focused primarily on sinusoidal signals, while theoretical models and hydrodynamical simulations predict that binaries produce more complex non-sinusoidal pulse shapes. Here we examine the efficacy of the Lomb–Scargle periodogram (LSP; one of the most popular tools for periodicity searches in unevenly sampled lightcurves) to detect periodicities with a sawtooth shape mimicking results of hydrodynamical simulations. We simulate idealized well-sampled lightcurves, lightcurves that mimic the data in the Palomar Transient Factory (PTF) analyzed in M. Charisi et al. (2016), and lightcurves that resemble our expectations for single-band data in the upcoming Legacy Survey of Space and Time (LSST) of the Rubin Observatory. We approximate quasar variability with a damped random walk (DRW) model, inject sinusoidal and sawtooth pulse shapes, and assess their statistical significance. We find that in the presence of red noise, the LSP detects a relatively low fraction of the sinusoidal signals (∼45%, ∼24%, and ∼23%, in the PTF-like, idealized, and LSST-like lightcurves, respectively). The fraction is significantly reduced for sawtooth periodicity (with only ∼9% in PTF-like and ∼1% in idealized and LSST-like lightcurves). These low recovery rates imply that previous searches have missed the large majority of binaries. They also have significant implications for the detection of SMBHBs in upcoming LSST necessitating the development of advanced tools that go beyond the simple LSP.}, author = {Lin, Allison and Charisi, Maria and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Lomb-scargle periodogram struggles with non-sinusoidal supermassive Black Hole binary signatures in quasar lightcurves}}, doi = {10.3847/1538-4357/ae29a7}, volume = {997}, year = {2026}, } @article{21715, abstract = {New populations of red active galactic nuclei (known as “little red dots”) discovered by JWST exhibit remarkable spectral energy distributions. Leveraging X-ray through far-infrared observations of two of the most luminous known little red dots, we directly measure their bolometric luminosities. We find evidence that more than half of the bolometric luminosity likely emerges in the rest-frame optical, with Lbol/L5100 = 5, roughly half the value for “standard” active galactic nuclei. Meanwhile, the X-ray emitting corona, UV-emitting blackbody, and reprocessed mid to far-infrared emission are all considerably subdominant, assuming that the far-infrared luminosity is well below current measured limits. We present new bolometric corrections that dramatically lower inferred bolometric luminosities by a factor of 10 compared to published values in the literature. These bolometric corrections are in accord with expectations from models in which gas absorption and reprocessing are responsible for the red rest-frame optical colors of little red dots. We discuss how this lowered luminosity scale suggests a lower mass scale for the population by at least an order of magnitude (e.g., ∼105–107 M⊙ black holes, and ∼108 M⊙ galaxies), alleviating tensions with clustering, overmassive black holes, and the integrated black hole mass density in the Universe.}, author = {Greene, Jenny E. and Setton, David J. and Furtak, Lukas J. and Naidu, Rohan P. and Volonteri, Marta and Dayal, Pratika and Labbe, Ivo and Van Dokkum, Pieter and Bezanson, Rachel and Brammer, Gabriel and Cutler, Sam E. and Glazebrook, Karl and De Graaff, Anna and Hirschmann, Michaela and Hviding, Raphael E. and Kokorev, Vasily and Leja, Joel and Liu, Hanpu and Ma, Yilun and Matthee, Jorryt J and Nanayakkara, Themiya and Oesch, Pascal A. and Pan, Richard and Price, Sedona H. and Spilker, Justin S. and Wang, Bingjie and Weaver, John R. and Whitaker, Katherine E. and Williams, Christina C. and Zitrin, Adi}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{What you see is what you get: Empirically measured bolometric luminosities of Little Red Dots}}, doi = {10.3847/1538-4357/ae1836}, volume = {996}, year = {2026}, } @article{21725, abstract = {The initial–final mass relation (IFMR) links a star’s birth mass to the mass of its white dwarf (WD) remnant, providing key constraints on stellar evolution. Open clusters offer the most straightforward way to empirically determine the IFMR, as their well-defined ages allow for direct progenitor lifetime estimates. We construct the most comprehensive open cluster WD IFMR to date by combining new spectroscopy of 22 WDs with an extensive literature review of WDs with strong cluster associations. To minimize systematics, we restrict our analysis to spectroscopically confirmed hydrogen-atmosphere (DA) WDs consistent with single-stellar origins. We separately analyze a subset with reliable Gaia-based astrometric membership assessments, as well as a full sample that adds WDs with strong cluster associations whose membership cannot be reliably assessed with Gaia. The Gaia-based sample includes 69 spectroscopically confirmed DA WDs, more than doubling the sample size of previous Gaia-based open cluster IFMRs. The full sample, which includes 53 additional literature WDs, increases the total number of cluster WDs by over 50% relative to earlier works. We provide functional forms for both the Gaia-based and full-sample IFMRs. The Gaia-based result useful for Mi � 2.67 M⊙ is Mf = [0.179 0.100H (Mi 3.84 M )] × (Mi 3.84 M ) + 0.628 M , where H(x) is the Heaviside step function. Comparing our IFMR to recent literature, we identify significant deviations from best-fit IFMRs derived from both Gaia-based volume-limited samples of field WDs and double WD binaries, with the largest discrepancy occurring for initial masses of about 5 M⊙.}, author = {Miller, David R. and Caiazzo, Ilaria and Heyl, Jeremy and Richer, Harvey B. and Hollands, Mark A. and Tremblay, Pier Emmanuel and El-Badry, Kareem and Rodriguez, Antonio C. and Vanderbosch, Zachary P.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {White dwarf stars, Open star clusters, Compact objects, Stellar evolution}, number = {1}, publisher = {IOP Publishing}, title = {{The White Dwarf initial–final mass relation from open clusters in Gaia DR3}}, doi = {10.3847/1538-4357/ae18c8}, volume = {996}, year = {2026}, } @article{21760, abstract = {3I/ATLAS is the third interstellar object discovered to date, following 1I/‘Oumuamua and 2I/Borisov. Its unusually high excess velocity and active cometary nature make it a key probe of the Galactic population of icy planetesimals. Understanding its origin requires its past trajectory through the Galaxy to be traced and the possible role of stellar encounters to be assessed, both as a potential origin and a perturber to its orbit. We integrated the orbit of 3I/ATLAS backward in time for 10 Myr, together with a sample of Gaia DR3 stars with high-quality astrometry and radial velocities, to identify close passages within 2 pc. We identify 93 nominal encounters, 62 of which are significant at the 2σ level. However, none of these encounters produced any meaningful perturbation. The strongest perturber Gaia DR3 6863591389529611264 at 0.30 pc and with a relative velocity of 35 km s−1, imparted only a velocity change of ∣Δv∣ ≃ 5 × 10−4 km s−1 to the orbit of 3I/ATLAS. Our results indicate that no stellar flybys within the past 10 Myr and 500 pc contained in Gaia DR3 can account for the present trajectory of 3I/ATLAS or be associated with its origin. We further show that 3I/ATLAS is kinematically consistent with a thin-disk population, despite its large peculiar velocity.}, author = {Pérez-Couto, X. and Torres Rodriguez, Santiago and Villaver, E. and Mustill, A. J. and Manteiga, M.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{3I/ATLAS: In search of the witnesses to its voyage}}, doi = {10.3847/1538-4357/ae56ff}, volume = {1001}, year = {2026}, } @article{21844, abstract = {Little red dots (LRDs) are a newly identified class of broad-line active galactic nuclei (AGNs) with a distinctive V-shaped spectrum characterized by red optical and blue UV continuum emission. Their high abundance at redshifts of z ∼ 6–8 and decline at lower redshifts suggest a transient origin. We propose that the spectral shape of LRDs originates from compact binary black hole systems, in which each black hole is surrounded by a mini-disk and embedded within a larger circumbinary disk. With a binary separation of ≲103 Schwarzschild radii, the Wien tail of a T ≃ 5000 K blackbody spectrum at the inner edge of the circumbinary disk produces the red optical emission, while the mini-disks power the UV continuum. Binary torques carve out a gap between the circumbinary disk and the mini-disks, setting the turnover wavelength of the V-shaped spectrum around the Balmer limit. This scenario naturally reproduces LRD spectra requiring only modest dust attenuation (AV ≲ 1 mag), resolving overestimated luminosities for LRDs in previous studies and alleviating a tension with the so-called Sołtan argument. This model predicts distinct spectral evolution as the binary orbit decays through binary disk interactions and gravitational-wave (GW) emission, linking early-stage “proto-LRD” binaries to the broader AGN population and late-stage “LRD descendants” to coalescing binaries detectable in GW experiments.}, author = {Inayoshi, Kohei and Shangguan, Jinyi and Chen, Xian and Ho, Luis C. and Haiman, Zoltán}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{The emergence of Little Red Dots from binary massive black holes}}, doi = {10.3847/1538-4357/ae548d}, volume = {1002}, year = {2026}, } @article{21882, abstract = {The nature of little red dots (LRDs) has largely been investigated through their continuum emission, with lines assumed to arise from a broad-line region. In this paper, we instead use recombination lines to infer the intrinsic properties of the central engine. Our analysis first reveals a tension between the ionizing properties implied from Hα and He ii λ4686. The high Hα EWs require copious H-ionizing photons, more than the bluest active galactic nucleus (AGN) ionizing spectra can provide. In contrast, He ii emission is marginally detected, and its low EW is, at most, consistent with the softest AGN spectra. The low He ii/Hβ (∼10−2, <20× local AGN median) further points to an unusually soft ionizing spectrum. We extend our analysis to dense gas envelopes (quasi-star/black-hole star) and find that hydrogen recombination lines become optically thick and lose diagnostic power, but He ii remains optically thin and a robust tracer. Photoionization modeling with Cloudy rules out standard AGN accretion disk spectra. Alternative explanations include exotic AGN with red rest-optical emission, high average optical depth (>10) from gas/dust, and soft ionizing spectra with abundant H-ionizing photons, consistent with, e.g., a cold accretion disk or a composite of AGN and stars. The latter is an intriguing scenario since high hydrogen densities are highly conducive for star formation, and nuclear star clusters are found in the vicinity of local massive black holes. While previous studies have mostly focused on features dominated by the absorbing hydrogen cloud, the He ii-based diagnostic proposed here represents a crucial step toward understanding the central engine of LRDs.}, author = {Wang, Bingjie and Leja, Joel and Katz, Harley and Inayoshi, Kohei and Cleri, Nikko J. and De Graaff, Anna and Hviding, Raphael E. and Van Dokkum, Pieter and Greene, Jenny E. and Labbé, Ivo and Matthee, Jorryt J and Mcconachie, Ian and Naidu, Rohan P. and Nelson, Erica J.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{The missing hard photons of Little Red Dots: Their incident ionizing spectra resemble massive stars}}, doi = {10.3847/1538-4357/ae5bab}, volume = {1003}, year = {2026}, } @article{21930, abstract = {We present the discovery of extreme nitrogen enrichment by Wolf Rayet nitrogen (WN) stars in the metal-poor (∼10%Z⊙), lensed, compact (Reff ∼ 20 pc) galaxy RXCJ2248 at z = 6.1, revealed by unprecedentedly deep JWST/NIRSpec medium-resolution spectroscopy from the GLIMPSE-D Survey. The exquisite signal-to-noise ratio reveals multiple high-ionization nebular lines and broad Balmer and [O III] components (FWHM ∼700–3000 km s −1 ). We detect broadened He II λ1640 and λ4687 (FWHM ∼ 530 km s −1 ) and strong N III λ4642 emission consistent with a population of WN stars, making RXCJ2248 the most distant galaxy with confirmed Wolf Rayet (WR) features to date. We measure the multiphase nebular density across five ions, the direct-method metallicity ( 12 + log(O/H) = 7.753 ± 0.025 ), and a nonuniform elemental enrichment pattern of extreme N/O enhancement ( log(N/O) = 0.391 ± 0.037 from N+, N+2 , and N+3 ) but suppressed C/O relative to empirical C/N trends. We show that this abundance pattern can be explained by enrichment from a dual-burst with a low WR carbon/WN ratio, as expected at low metallicities. Crucially, these signatures can only arise during a brief, rare evolutionary window shortly after a burst (∼3–6 Myr), when WN stars dominate chemical feedback but before dilution by later yields (e.g., supernovae). The observed frequency of strong N emitters at high−z implies a ∼50 Myr burst duty cycle, suggesting that N/O outliers may represent a brief but ubiquitous phase in the evolution of highly star-forming early galaxies. The WN detection in RXCJ2248, therefore, provides the first direct evidence of WR-driven nitrogen enrichment in the first billion years of the Universe and a novel timing argument for the bursty star formation cycles that shaped galaxies at cosmic dawn.}, author = {Berg, Danielle A. and Naidu, Rohan P. and Chisholm, John and Atek, Hakim and Fujimoto, Seiji and Kokorev, Vasily and Furtak, Lukas J. and Kobayashi, Chiaki and Schaerer, Daniel and Adamo, Angela and Fei, Qinyue and Korber, Damien and Matthee, Jorryt J and Marques-Chaves, Rui and Martinez, Zorayda and Mcquinn, Kristen B.W. and Muñoz, Julian B. and Oesch, Pascal A. and Saldana-Lopez, Alberto and Stark, Daniel P. and Stephenson, Mabel G. and Hsiao, Tiger Yu Yang}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{A fleeting GLIMPSE of N/O enrichment at cosmic dawn: Evidence for Wolf Rayet N stars in a z = 6.1 galaxy}}, doi = {10.3847/1538-4357/ae5e4c}, volume = {1003}, year = {2026}, } @article{21057, abstract = {Among the most puzzling early discoveries of JWST are “little red dots” (LRDs), compact red sources that host broad Balmer emission lines, and in many cases exhibit a “V-shaped” change in slope in the rest-optical. The physical properties of LRDs currently have order-of-magnitude uncertainties, because models to explain the continuum of these sources differ immensely. Here, we leverage the complete selection of red sources in the RUBIES program, supplemented with public PRISM spectra, to study the origin of this V shape. By fitting a broken power law with a flexible inflection point, we find that a large fraction of red Hα emitters at 2 < z < 6 exhibit a strong change in slope, and that all strong inflections appear associated with the Balmer limit (0.3645 μm). Using a simple model of a reddened active galactic nucleus (AGN) with an unobscured scattered-light component, we demonstrate that the observed V shape in LRDs is unlikely to occur at any specific wavelength if the entire continuum is dominated by light from a power-law AGN continuum. In contrast, models with an intrinsic feature at the Balmer limit, such as those that are dominated by an evolved stellar population, can produce the observed spectral shapes, provided that a reddened component picks up sufficiently redward of the break. While no model can comfortably explain the full LRD spectral energy distribution, the common inflection location suggests that a single component consistently dominates the rest-frame UV optical in LRDs, and that this component is associated with T ∼ 10^4 K hydrogen.}, author = {Setton, David J. and Greene, Jenny E. and de Graaff, Anna and Ma, Yilun 逸伦 and Leja, Joel and Matthee, Jorryt J and Bezanson, Rachel and Boogaard, Leindert A. and Cleri, Nikko J. and Katz, Harley and Labbe, Ivo and Maseda, Michael V. and McConachie, Ian and Miller, Tim B. and Price, Sedona H. and Suess, Katherine A. and van Dokkum, Pieter and Wang 王, Bingjie 冰洁 and Weibel, Andrea and Whitaker, Katherine E. and Williams, Christina C.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{Little Red Dots at an inflection point: Ubiquitous v-shaped turnover consistently occurs at the Balmer limit}}, doi = {10.3847/1538-4357/ae1500}, volume = {995}, year = {2025}, } @article{21061, abstract = {Detecting the first generation of stars, Population III (Pop III), has been a long-standing goal in astrophysics, yet they remain elusive even in the JWST era. Here we present a novel NIRCam-based selection method for Pop III galaxies, and carefully validate it through completeness and contamination simulations. We systematically search ≃ 500 arcmin2 across JWST legacy fields for Pop III candidates, including GLIMPSE, which, assisted by gravitational lensing, has produced JWST’s deepest NIRCam imaging thus far. We discover one promising Pop III galaxy candidate (GLIMPSE-16043) at z=6.50 -0.24 +0.03, a moderately lensed galaxy (µ = + 2.9 -0.2 +0.1) with an intrinsic UV magnitude of MUV= -15.89 -0.14 +0.12. It exhibits key Pop III features: strong Hα emission (rest-frame EW 2810 ± 550 Å); a Balmer jump; no dust (UV slope β = −2.34 ± 0.36); and undetectable metal lines (e.g., [O III]; [O III]/Hβ < 0.44), implying a gas-phase metallicity of Zgas/Z⊙ < 0.5%. These properties indicate the presence of a nascent, metal-deficient young stellar population (<5 Myr) with a stellar mass of ≃105 M⊙. Intriguingly, this source deviates significantly from the extrapolated UV–metallicity relation derived from recent JWST observations at z = 4–10, consistent with UV enhancement by a top-heavy Pop III initial mass function or the presence of an extremely metal-poor active galactic nucleus. We also derive the first observational constraints on the Pop III UV luminosity function at z ≃ 6–7. The volume density of GLIMPSE-16043 (≈10^−4 cMpc−3) is in excellent agreement with theoretical predictions, independently reinforcing its plausibility. This study demonstrates the power of our novel NIRCam method to finally reveal distant galaxies even more pristine than the Milky Way’s most metal-poor satellites, thereby promising to bring us closer to the first generation of stars than we have ever been before.}, author = {Fujimoto, Seiji and Naidu, Rohan P. and Chisholm, John and Atek, Hakim and Endsley, Ryan and Kokorev, Vasily and Furtak, Lukas J. and Pan, Richard and Liu, Boyuan and Bromm, Volker and Venditti, Alessandra and Visbal, Eli and Sarmento, Richard and Weibel, Andrea and Oesch, Pascal A. and Brammer, Gabriel and Schaerer, Daniel and Adamo, Angela and Berg, Danielle A. and Bezanson, Rachel and Bouwens, Rychard and Chemerynska, Iryna and Claeyssens, Adélaïde and Dessauges-Zavadsky, Miroslava and Frebel, Anna and Korber, Damien and Labbe, Ivo and Marques-Chaves, Rui and Matthee, Jorryt J and McQuinn, Kristen B. W. and Muñoz, Julian B. and Natarajan, Priyamvada and Saldana-Lopez, Alberto and Suess, Katherine A. and Volonteri, Marta and Zitrin, Adi}, issn = {1538-4357}, journal = {The Astrophysical Journal}, publisher = {IOP Publishing}, title = {{GLIMPSE: An ultrafaint ≃10^5 M⊙ Pop III galaxy candidate and first constraints on the Pop III UV luminosity function at z ≃ 6–7}}, doi = {10.3847/1538-4357/ade9a1}, volume = {989}, year = {2025}, } @article{21062, abstract = {JWST observations have unveiled faint active galactic nuclei (AGNs) at high redshift that provide insights into the formation of supermassive black holes (SMBHs). However, disentangling their stellar from AGN light is challenging. Here, we use an empirical approach to infer the average stellar mass of five faint broad-line (BL) Hα emitters at z = 4–5 with BH masses ≈6 × 10^6 M⊙, with a method independent of their spectral energy distribution (SED). We use the deep JWST/NIRcam grism survey “All the Little Things” to measure the overdensities around BL-Hα emitters and around a spectroscopic reference sample of ∼300 galaxies. In our reference sample, we find that megaparsec-scale overdensity correlates with stellar mass. Their large-scale environments suggest that BL-Hα emitters are hosted by galaxies with stellar masses ≈5 × 10^7 M⊙, ≈40 times lower than those inferred from galaxy-only SED fits. Adding measurements around more luminous z ≈ 6 AGNs, we find tentative correlations between line width, BH mass, and the overdensity, suggestive of a steep BH to halo mass relation. The main implications are (1) when BH masses are taken at face value, we confirm extremely high BH to stellar mass ratios of ≈10%, (2) the galaxies of low stellar mass that host growing SMBHs are in tension with typical hydrodynamical simulations, except those without feedback, (3) a 1% duty cycle implied by the host mass hints at super-Eddington accretion, (4) the masses are at odds with an interpretation of the line broadening in terms of high stellar density, (5) our results imply a luminosity-dependent diversity of galaxy masses, environments, and SEDs among AGN samples.}, author = {Matthee, Jorryt J and Naidu, Rohan P. and Kotiwale, Gauri and Furtak, Lukas J. and Kramarenko, Ivan and Mackenzie, Ruari and Greene, Jenny and Adamo, Angela and Bouwens, Rychard J. and Di Cesare, Claudia and Eilers, Anna-Christina and de Graaff, Anna and Heintz, Kasper E. and Kashino, Daichi and Maseda, Michael V. and Tacchella, Sandro and Torralba Torregrosa, Alberto}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Environmental evidence for overly massive Black Holes in low-mass galaxies and a Black Hole–Halo mass relation at z ∼ 5}}, doi = {10.3847/1538-4357/ade886}, volume = {988}, year = {2025}, } @article{21123, abstract = {We present a study of the late-time interaction between supermassive black hole binaries and retrograde circumbinary disks during the period of gravitational wave-driven inspiral. While mergers in prograde disks have received extensive study, retrograde disks offer distinct dynamics that could promote mergers and produce unique observational signatures. Through 2D numerical hydrodynamical simulations, we explore the process of binary-disk decoupling, where the binary’s orbital decay rate is faster than the disk’s viscous response rate. We find the point of decoupling to be comparable in prograde and retrograde disks, suggesting that any associated electromagnetic (EM) signatures will be produced at comparable times preceding the merger. However, we find smaller central cavities for retrograde disks, likely leading to higher-frequency EM emissions and shorter postmerger rebrightening timescales compared to their prograde counterparts. Retrograde disks form intrabinary bridges, which are prone to instabilities when the viscosity is low. These instabilities manifest as quasiperiodic flares in the accretion rate, which may produce distinctive EM signatures for retrograde disks.}, author = {O’Neill, David and Tiede, Christopher and D’Orazio, Daniel J. and Haiman, Zoltán and MacFadyen, Andrew}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {2}, publisher = {IOP Publishing}, title = {{Gravitational wave decoupling in retrograde circumbinary disks}}, doi = {10.3847/1538-4357/ae0ca8}, volume = {993}, year = {2025}, } @article{21124, abstract = {The advent of the James Webb Space Telescope (JWST) has opened new horizons in the study of quasar host galaxies during the reionization epoch (z > 6). Building upon our previous initial measurements of stellar light from two quasar host galaxies at these redshifts, we now report the detection of the stellar light from the full Cycle 1 sample of 12 distant moderate-luminosity quasar (M1450 > −24 mag) host galaxies at z > 6 from the Hyper Suprime-Cam Subaru Strategic Program. Using JWST/NIRCam observations at 1.5 and 3.6 μm combined with 2D image decomposition analysis, we successfully detect the host galaxies in 11 of the 12 targets, underscoring the high detection rates achievable with moderate-luminosity quasars. Based on two-band photometry and spectral energy distribution fitting, we find that our host galaxies are massive, with log M*/M⊙ = 9.5–11.0. The effective radii range from 0.6 to 3.2 kpc, comparable to the sizes of inactive galaxies with similar masses at z ∼ 6 as measured with imaging from COSMOS-Web. Intriguingly, the two quasar hosts with post-starburst features, which reside at the high-mass end of our sample and exhibit relatively compact morphologies, have similar size and stellar mass surface densities to quiescent galaxies at z ∼ 4–5. These findings suggest that the so-called galaxy compaction scenario is already in place at the reionization epoch, in which gas inflows during starburst phases drive centrally concentrated star formation followed by rapid quenching, bridging the structural transition of massive galaxies from relatively extended star-forming disks to compact quiescent systems.}, author = {Ding, Xuheng and Onoue, Masafusa and Silverman, John D. and Matsuoka, Yoshiki and Izumi, Takuma and Strauss, Michael A. and Yang, Lilan and Jahnke, Knud and Phillips, Camryn L. and Treu, Tommaso and Andika, Irham T. and Aoki, Kentaro and Arita, Junya and Baba, Shunsuke and Bosman, Sarah E. I. and Eilers, Anna-Christina and Fujimoto, Seiji and Haiman, Zoltán and Imanishi, Masatoshi and Inayoshi, Kohei and Iwasawa, Kazushi and Kartaltepe, Jeyhan and Kashikawa, Nobunari and Kawaguchi, Toshihiro and Li, Junyao and Lee, Chien-Hsiu and Lupi, Alessandro and Schindler, Jan-Torge and Schramm, Malte and Shimasaku, Kazuhiro and Shuntov, Marko and Tanaka, Takumi S. and Toba, Yoshiki and Trakhtenbrot, Benny and Umehata, Hideki and Vestergaard, Marianne and Wang, Feige and Yang, Jinyi}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{SHELLQs-JWST unveils the host galaxies of 12 quasars at z > 6}}, doi = {10.3847/1538-4357/ae045b}, volume = {993}, year = {2025}, } @article{21129, abstract = {Recent hydrodynamical simulations have shown that circumbinary gas disks drive the orbits of massive binary black holes (BHs) to become eccentric, even when general relativistic (GR) corrections to the orbit are significant. Here, we study the GR apsidal precession of eccentric equal-mass massive binary BHs in circumbinary disks via two-dimensional hydrodynamical simulations. We perform a suite of simulations comparing precessing and nonprecessing binaries across a range of eccentricities, semimajor axes, and precession rates. We find that the GR precession of the binary’s semimajor axis can introduce a dominant modulation in the binary’s accretion rate and the corresponding high-energy electromagnetic light curves. We discuss the conditions under which this occurs and its detailed characteristics and mechanism. Finally, we discuss the potential to observe these precession signatures in electromagnetic- and gravitational-wave observations, as well as the precession signal’s unique importance as a potential tool to constrain the mass, eccentricity, and semimajor axis of binary merger events.}, author = {DeLaurentiis, Stanislav and Haiman, Zoltán and Westernacher-Schneider, John Ryan and Krauth, Luke Major and Davelaar, Jordy and Zrake, Jonathan and MacFadyen, Andrew}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{Relativistic binary precession: Impact on eccentric massive binary black hole accretion and hydrodynamics}}, doi = {10.3847/1538-4357/ada612}, volume = {980}, year = {2025}, } @article{21246, abstract = {Stellar astrophysics relies on diverse observational modalities—primarily photometric light curves and spectroscopic data—from which fundamental stellar properties are inferred. While machine learning (ML) has advanced analysis within individual modalities, the complementary information encoded across modalities remains largely underexploited. We present the dual embedding for stellar astronomy (DESA) model, a novel multimodal foundation model that integrates light curves and spectra to learn a unified, physically meaningful latent space for stars. DESA first trains separate modality-specific encoders using a hybrid supervised/self-supervised scheme, and then aligns them through DualFormer, a transformer-based cross-modal integration module tailored for astrophysical data. DualFormer combines cross- and self-attention, a novel dual-projection alignment loss, and a projection-space eigendecomposition that yields physically structured embeddings. We demonstrate that DESA significantly outperforms leading unimodal and self-supervised baselines across a range of tasks. In zero- and few-shot settings, DESA’s learned representations recover stellar color–magnitude and Hertzsprung–Russell diagrams with high fidelity (R2 = 0.92 for photometric regressions). In full fine-tuning, DESA achieves state-of-the-art accuracy for binary star detection (AUC = 0.99, AP = 1.00) and stellar age prediction (RMSE = 0.94 Gyr). As a compelling case, DESA naturally separates synchronized binaries from young stars—two populations with nearly identical light curves—purely from their embedded positions in UMAP space, without requiring external kinematic or luminosity information. DESA thus offers a powerful new framework for multimodal, data-driven stellar population analysis, enabling both accurate prediction and novel discovery.}, author = {Kamai, Ilay and Bronstein, Alexander and Perets, Hagai B.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, publisher = {IOP Publishing}, title = {{Machine Learning inference of stellar properties using integrated photometric and spectroscopic data}}, doi = {10.3847/1538-4357/ae0cbc}, volume = {994}, year = {2025}, } @article{21724, abstract = {The next generation of weak-gravitational-lensing surveys has the potential to place stringent constraints on cosmological parameters. However, their analysis is limited by systematics such as the intrinsic alignments of galaxies, which alter weak-lensing convergence and can lead to biases in cosmological parameter estimations. For the first time, in this work, we investigate the impact of intrinsic alignments on non-Gaussian statistics of the weak-lensing field using galaxy shapes derived from the IllustrisTNG hydrodynamical simulation. We create two catalogs of ray-traced convergence maps: one that includes the measured intrinsic shape of each galaxy and another where all galaxies are randomly rotated to eliminate intrinsic alignments. We compare a range of weak-lensing statistics between the two catalogs, including the shear–shear correlation function, the map-level angular power spectrum, one-point, peak count, and minimum distribution functions, and Minkowski functionals. For each statistic, we assess the level of statistical distinguishability between catalogs for a set of future survey angular areas. Our results reveal strong small-scale correlation in the alignment of galaxies and statistically significant boosts in weak-lensing convergence in both positive and negative directions for high-significance peaks and minima, respectively. We note that our analysis is at a fixed number density of ˜ 5 arcmin^-2, drawn from a single realization of initial conditions, and does not include observational uncertainties or supersample covariance contributions. Weak-lensing analyses utilizing non-Gaussian statistics must account for intrinsic alignments to avoid significantly compromised cosmological inferences.}, author = {Lee, Max E. and Haiman, Zoltán and Pandey, Shivam and Genel, Shy}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{The effect of intrinsic alignments on weak-lensing statistics in hydrodynamical simulations}}, doi = {10.3847/1538-4357/ae1ca7}, volume = {996}, year = {2025}, } @article{21727, abstract = {We present a comprehensive analysis of the MIRI Extremely Red Object Virgil, a Lyα emitter at zspec = 6.6379 ± 0.0035 with the photometric properties of a Little Red Dot. Leveraging new JWST/MIRI imaging from the MIDIS and PAHSPECS programs, we confirm Virgil’s extraordinary nature among galaxies in JADES/GOODS-South, exhibiting a strikingly red NIRCam-to-MIRI color (F444W–F1500W = 2.84 ± 0.04 mag). Deep NIRSpec/PRISM spectroscopy from the OASIS program offers key insights into the host galaxy, revealing properties of an average star-forming galaxy during Cosmic Reionization, such as a subsolar metallicity, low-to-moderate dust content, and a relatively high ionization parameter and electron temperature. By estimating the star formation rate of Virgil from UV and Hα, we find evidence that the galaxy is either entering or fading out of a bursty episode. Although line-ratio diagnostics employed at high z would classify Virgil as an active galactic nucleus (AGN), this classification becomes ambiguous once redshift evolution is considered. Nonetheless, Virgil occupies the same parameter space as recently confirmed AGNs at similar redshifts. The new deep MIRI data at 15 μm reinforce the AGN nature of Virgil, as inferred from multiple spectral energy distribution (SED) fitting codes. Virgil’s rising infrared SED and UV excess resemble those of Dust-Obscured Galaxies (DOGs) studied with Spitzer at Cosmic Noon, particularly blue-excess HotDOGs. Our results highlight the need for a multiwavelength approach incorporating MIRI to uncover such extreme sources at z ≳ 6 and to shed light on the interplay between galaxy evolution and early black hole growth during Cosmic Reionization.}, author = {Rinaldi, Pierluigi and Pérez-González, Pablo G. and Rieke, George H. and Lyu, Jianwei and D’Eugenio, Francesco and Wu, Zihao and Carniani, Stefano and Looser, Tobias J. and Shivaei, Irene and Boogaard, Leindert A. and Diaz-Santos, Tanio and Colina, Luis and Östlin, Göran and Alberts, Stacey and Álvarez-Márquez, Javier and Annuziatella, Marianna and Aravena, Manuel and Bhatawdekar, Rachana and Bunker, Andrew J. and Caputi, Karina I. and Charlot, Stéphane and Crespo Gómez, Alejandro and Curti, Mirko and Eckart, Andreas and Gillman, Steven and Hainline, Kevin and Kumari, Nimisha and Hjorth, Jens and Iani, Edoardo and Inami, Hanae and Ji, Zhiyuan and Johnson, Benjamin D. and Jones, Gareth C. and Labiano, Álvaro and Maiolino, Roberto and Melinder, Jens and Moutard, Thibaud and Peissker, Florian and Rieke, Marcia and Robertson, Brant and Scholtz, Jan and Tacchella, Sandro and Van Der Werf, Paul P. and Walter, Fabian and Williams, Christina C. and Willott, Chris and Witstok, Joris and Übler, Hannah and Zhu, Yongda}, issn = {1538-4357}, journal = {The Astrophysical Journal}, number = {1}, publisher = {IOP Publishing}, title = {{Deciphering the nature of Virgil: An obscured active galactic nucleus lurking within an apparently normal Lyα emitter during cosmic reionization}}, doi = {10.3847/1538-4357/ae089c}, volume = {994}, year = {2025}, }