Instrumentation and Methods for Astrophysics
PyCBC Live Search for Compact Binary Mergers in Advanced LIGO and Virgo's Fourth Observing Run
Max Trevor, Gareth S. Cabourn Davies, Tito Dal Canton et al. (+4 more)
PyCBC Live is a low-latency search pipeline that identifies gravitational waves from compact binary coalescences and provides alerts for electromagnetic follow-up. This paper presents improvements to PyCBC Live that were implemented for the fourth observing run (O4) of the LIGO-Virgo-KAGRA network, which operated from May 2023 to November 2025. The ranking statistic was enhanced to incorporate time-dependent background modeling using data quality streams and daily updates of the noise model. Follow-up capabilities were improved through refined probability of astrophysical origin calculations, optimized SNR recovery with reduced computational cost, and a method to incorporate Virgo as a sky-map-only detector. An Early Warning search was implemented to detect binary
neutron star and
neutron star-black hole systems before merger, providing pre-merger alerts with a pipeline latency of 2.5-3.5 seconds and warning times up to 60 seconds before coalescence. The autogating procedure was extended to apply to the full strain buffer rather than individual analysis segments, improving rejection of loud and rapidly successive glitches. Performance validation using the Mock Data Challenge showed sensitivity improvements of factors of 1.7 to 2.3 for the coincident search depending on source mass at an inverse false alarm rate of 10 years, and factors of 1.3 to 1.7 for the single-detector search. For injections in two-detector time, the O4 configuration identified 1979 of 2495 injections with a decisive SNR greater than 6 at a false alarm rate below one per year (79.3%), compared to 1262 (50.6%) with the O3 configuration. For injections in single-detector time, the O4 configuration identified 218 of 1174 injections (18.6%), compared to 170 (14.5%) with the O3 configuration. The search maintained a median latency of 15.94 seconds from merger to candidate upload.
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All authors Max Trevor, Gareth S. Cabourn Davies, Tito Dal Canton, Thomas Dent, Ian Harry, Stephanie Hoang, Arthur Tolley
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Lepton interactions from GeV to EeV
Reinaldo Francener
In this work, we investigate the phenomenological consequences of
neutrino and
muon interactions with matter. In our studies, we focused in phenomenological predictions for two experiments: FASER and IceCube. FASER is a detector located at the LHC that measures
neutrinos produced in
proton-
proton collisions. A new version of FASER, FASER2, has been proposed to operate in the Forward Physics Facility during the high-luminosity regime of the LHC. The intense flux of tau
neutrinos expected at FASER2 motivated us to study the polarization effects of the tau produced in charged current interactions. Our results show that the produced taus will not be completely polarized. Among the Standard Model particles, only
neutrinos and
muons produced in
proton-
proton collisions at the LHC can reach FASER. In our study, we show that
muon-initiated events can reveal interesting nucleon properties, such as
nuclear effects and the existence of an intrinsic charm. The high number of events induced by
neutrinos at FASER motivated us to study rare processes in
neutrino interaction, such as the
neutrino trident. Our results indicate that the
neutrino trident process can be observed at FASER2. We have also studied
muon trident at the LHC, and we showed that tau pair production can be observed for the first time in this reaction. In contrast to
neutrinos detected at the LHC, the
neutrinos observed at IceCube come from natural sources, being mainly atmospheric and astrophysical
neutrinos. IceCube is capable of observing
neutrinos across a wide energy spectrum, ranging from a few GeV to beyond PeV. We show that the study of these events can contribute to our understanding of the structure of target
hadrons, as well as the search for physics effects beyond the Standard Model in the propagation of these
neutrinos in the universe until they reach the Earth.
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Solar and Stellar Astrophysics
Magnetic field, rotation, and binarity of the first magnetic B[e] star, IRAS 17449+2320
I. Bermejo Lozano, G. A. Wade, C. P. Folsom et al. (+1 more)
IRAS 17449+2320 is the first identified
magnetic B[e]
star. It belongs to a subgroup of peculiar hot B-type
stars, called FS~CMa
stars. presenting the B[e] phenomenon, i.e., permitted and forbidden emission lines, and infrared excess as a result of the large amount of gas and
dust surrounding the central
star. The origin of this circumstellar material is unclear, with binarity being the most accepted scenario. However, the presence of a
magnetic field in IRAS 17449+2320 points to the merger origin. In this paper, we confirm and characterize the
magnetic field of this object, and constrain its rotation and binarity. We used a sample of 12 spectropolarimetric observations taken with ESPaDOnS at the CFHT. We obtained the least squares deconvolution (LSD) profile of the Stokes $V$ parameter of each spectropolarimetric observation. From the LSD profiles, we measured the longitudinal
magnetic field (B$_z$), and obtained the
magnetic field modulus ($|B|$) from the Zeeman splitting of some metallic lines of the spectra. We calculated a Lomb-Scargle periodogram over B$_z$ to obtain the rotational period of this
star. B$_z$ presents a sinusoidal variation with a stable period of 36.11 days, with values ranging from 3000 G to -1000 G. $|B|$ measurements range from $\sim$4400~G to $\sim$6000~G, and it shows a second order term periodic variation. The stable sinusoidal variation of B$_z$ implies an approximately dipolar surface field
topology. IRAS~17449+2320 is the first
magnetic B[e]
star detected. It presents Zeeman splitting in individual lines and consistent Stokes $V$ profiles. We see no evidence of binarity in this object, with stable radial velocities and no detectable lines of a secondary
star in the spectrum. We consider the possibility that this
star is the result of a merger, which could have generated the strong
magnetic field and the large amount of circumstellar material.
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All authors I. Bermejo Lozano, G. A. Wade, C. P. Folsom, D. Korčáková
High Energy Astrophysical Phenomena
Direct simulations of very high energy cosmic ray acceleration in 3D MHD model of a compact star cluster
M. E. Kalyashova, A. M. Bykov and D. V. Badmaev
Young compact clusters of massive
stars contain dozens of O-, B- and WR-type
stars with fast powerful winds in a small $\sim$ pc radius core. The particle acceleration by ensembles of shocks accompanied with long-wavelength compressions and rarefactions in the turbulent environment of young massive
star clusters (YMSCs) is an alternative to the standard paradigm of
Galactic cosmic ray acceleration on
supernova shocks. In recent years, the topic has been of great interest due to the fact that modern gamma- and X-ray observatories have detected the radiation from YMSCs, which indicates particle acceleration processes in these objects. We study particle propagation and acceleration in a YMSC with the help of 3D magnetohydrodynamic (MHD) modeling using an open source PLUTO code. The code allows modeling of the turbulent environment of YMSCs and obtaining crucial for particle acceleration values of velocity, density, and
magnetic field inside the cluster core. The Particle module implemented in PLUTO allows solving the equations of motion for test charged particles together with MHD equations for the medium. We obtained that
protons acceleration up to hundreds of TeV takes place in the cluster core near the termination shocks of O-
stars, which are surrounded by shocks of their neighbour
stars. We also modeled an interesting case of a young
supernova remnant expanding inside the cluster core. In this case a very fast acceleration takes place: particle energies $\gtrsim$ 100 TeV can be obtained in $\lesssim$ 100 years. The particle spectra and spatial distribution are discussed.
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High Energy Astrophysical Phenomena
Matthew E Caplan, Nevin T Smith, Ashley J Bransgrove et al. (+1 more)
We use first-principles molecular dynamics simulations to study the deformation and breaking of
neutron star crusts. When simulating with strain rates several orders of magnitude slower than prior work, we find a new regime of steady plastic flow beyond the breaking point that is independent of the initial
crystal structure. Polycrystals exhibit a robust transition from linear elasticity to perfect plastic flow at shear strains of $\epsilon = 0.05$, while monocrystals break at $\epsilon = 0.11$ and then flow plastically. The universal post-break plasticity may arise because the
crystal self-consistently assumes a defect density to accommodate the imposed strain rate. If broken crusts can re-anneal to large
crystal sizes, crust breaking may repeat with implications for magnetar bursts and
flares.
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All authors Matthew E Caplan, Nevin T Smith, Ashley J Bransgrove, Charles J Horowitz
Solar and Stellar Astrophysics
Oscillatory Phase and Acoustic Travel-Time Inconsistencies Measured between SDO/HMI and GONG Dopplergrams
Junwei Zhao, Ruizhu Chen, S. P. Rajaguru et al. (+1 more)
We investigate the causes of discrepancies in meridional-circulation measurements derived from the helioseismic observations by the Helioseismic and
Magnetic Imager onboard the
Solar Dynamics Observatory (SDO/HMI) and the Global Oscillation Network Group (GONG). Using contemporaneous Dopplergrams from both instruments that are processed consistently, we measure relative oscillatory phase shifts at identical
solar locations and analyze north-south acoustic travel-time shifts on both sides of the
solar central meridian. Our analysis reveals a persistent area of phase-shift anomalies in the northwestern quadrant of the
solar disk, whose magnitude increases over the analysis period from 2010 through 2024. After removing the axisymmetric component, the phase-shift maps display a deceasing trend from the northeastern to the southwestern quadrant, which can be misinterpreted as flows in helioseismic analyses. The travel-time measurements also show significant inconsistencies on the eastern and western sides of the central meridian for both instruments, although a close agreement between both sides is expected. These findings indicate that both SDO/HMI and GONG carry systematic artifacts affecting meridional-circulation measurements, and that the time-varying phase anomalies and eastern-western asymmetry pose major challenges for their accurate characterization and correction.
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All authors Junwei Zhao, Ruizhu Chen, S. P. Rajaguru, Shukur Kholikov
Instrumentation and Methods for Astrophysics
Where Not to Look: A Parametric Avoidance Model for SETI Target Selection
Sahin Torlakcik
We present a simple, rule-based filter for SETI target selection that flags
stars unlikely to host complex life and produces an audit-ready exclusion catalog. Using seven
stellar parameters, including age,
metallicity, and multiplicity, the model excludes roughly half of a 1.74 million-
star Gaia DR3 sample, retaining 777,835 high-priority targets, mainly G and K
dwarfs. Age and
metallicity dominate the rejections. Importantly, using
Gaia's age upper bounds instead of point estimates saves 355,086
stars from exclusion. A comparison of empirical and synthetic proxies shows that while the overall exclusion rate is robust, individual target assignments change significantly; for instance, the commonly used RUWE indicator flags 2.7x more binaries than
Gaia's own non-single-
star flag. Cross-matching with the Breakthrough Listen target list reveals a 56.5% exclusion rate, highlighting the complementary nature of habitability-driven and proximity-driven surveys. The catalog, pipeline, and a generalized community tool are publicly available.
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Earth and Planetary Astrophysics
Ultraviolet Radiation Effects on the Optical Properties of Water-Dominated Exoplanet Hazes
Lori Huseby, Sarah E. Moran, Tiffany Kataria et al. (+8 more)
Temperate sub-Neptune and terrestrial
exoplanets could contain large inventories of water in various phases, such as water-dominated atmospheres or even oceans. Observations have shown that many
exoplanets, including water worlds, likely contain photochemically-generated hazes. Haze particles are a key source of organic matter and may impact the
evolution or origin of life; their optical properties are imperative for interpreting observations through theoretical atmospheric modeling. Modelers have thus far assumed haze optical properties that may not represent hazes under sub-Neptune and terrestrial atmospheric conditions. Often orbiting close to M-
dwarf stars, these
planets receive large amounts of radiation, especially during flaring events, which may accelerate atmospheric escape and affect atmospheric compositions. Here, we present optical constants of experimentally-generated sub-Neptune haze analogs before and after UV irradiation across a broad wavelength range (0.5 to 8 {\mu}m). We find that UV-irradiation alters haze optical constants which become generally more absorbing in this wavelength range, which we hypothesize is due to our sample containing more oxygen-rich absorbing bands post irradiation. We use Virga and PICASO to simulate transmission spectra of potentially hazy water-dominated
planets GJ 1214b and LHS 1140b, accounting for irradiated haze layers in their atmospheres. For our GJ 1214b CH4-rich haze modeled case, we see a difference in the N-H feature at 2.6 {\mu}m in the resulting transmission spectrum between irradiated and unaltered haze that should be observable within current JWST capabilities. Broadly, we demonstrate the importance of using more representative optical constants, as they have an impact on current and future atmospheric composition interpretations.
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All authors Lori Huseby, Sarah E. Moran, Tiffany Kataria, Mark S. Marley, Chao He, Cara Pesciotta, Sarah M. Hörst, Neil Pearson, Vishnu Reddy, Nikole K. Lewis, Véronique Vuitton
Astrophysics of Galaxies
Star formation at z$\sim$0.9 from the OTELO survey: A comprehensive view combining deep optical spectroscopy and infrared data
Rocío Navarro Martínez, Miguel Cerviño, Ricardo Pérez-Martínez et al. (+14 more)
We aim to quantify the
star formation rate (SFR) from deep optical spectroscopic data and far-infrared (FIR) photometry from a sample of
galaxies at $z\sim 0.9$ from the OTELO survey and compare the activity estimated by optical tracers and FIR emission. We used the multi-wavelength OTELO catalogue to construct a sample of FIR sources. We identified and separated
galaxies with active
nuclei and derived the physical properties of the rest. We analysed their spectral energy distribution, obtaining estimates for
stellar mass,
dust attenuation, luminosity, and SFR based on infrared luminosity. We also studied H$\beta$ and [OIII] emission-line
galaxies without significant FIR emission from previous works. This approach allowed us to perform a comparative analysis among the SFR obtained through different calibrators, in particular H$\beta$, presented in a previous work. We find that FIR-based SFR estimates uncover a significant fraction of hidden
star formation. We determined that the SFR density obtained from the FIR emission is three times larger than that obtained from only emission-line sources. Likely related to the fact that each SFR tracer provides insight into
star formation over different timescales, we suggest that such indicators are also more or less suited for different
galaxy populations. Specifically, while optical emission lines effectively trace
star formation in lower-mass
galaxies, FIR-derived SFRs provide a more reliable measure in massive
dust-rich systems. By accounting for both optically visible and obscured
star formation, we provide a more comprehensive view of the
star-forming main sequence at $z \sim 0.9$ and reinforce the importance of infrared tracers in studying
galaxy evolution.
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All authors Rocío Navarro Martínez, Miguel Cerviño, Ricardo Pérez-Martínez, Ana María Pérez-García, Bernabé Cedrés, Ángel Bongiovanni, Jakub Nadolny, Miguel Sánchez-Portal, Jordi Cepa, Emilio Alfaro, Laia Barrufet, José A. de Diego, Jesús Gallego, J. Jesús González, Mauro González-Otero, J. Ignacio González-Serrano, Carmen P. Padilla Torres
Instrumentation and Methods for Astrophysics · Cross-listed from physics.acc-ph
Low Level RF and Timing System Design for the Cool Copper Collider
Chao Liu, Ankur Dhar, Martin Breidenbach et al. (+1 more)
The Cool Copper
Collider (C3) is a linear accelerator (LINAC) concept based on compact, high gradient, and normal conducting accelerator technology to support
Higgs boson studies at 250 GeV and 550 GeV center of mass. The C3 accelerator is ten kilometers in scale and consist of 2,200 RF stations for 550 GeV center of mass. To maintain the stringent beam quality required by the
collider across the LINACs, each of the cavities has a dedicated low-level RF (LLRF) system to stabilize the phase and amplitude of the field in the cavities from pulse to pulse and to compensate the fluctuation of the RF field within each pulse introduced by the beam loading process. To meet the design goals of being compact and affordable for future accelerators, we have designed the next generation LLRF (NG-LLRF) with a higher integration level based on
radio frequency system-on-chip (RFSoC) technology. The NG-LLRF system samples RF signals directly and performs RF mixing digitally. The NG-LLRF has been characterized in loopback mode to evaluate the performance of the system and has also been tested with a standing-wave accelerating structure, a prototype structure for the C3 with peak RF power level up to 16.45 MW. This paper will focus on introducing the LLRF system design and timing system for C3 and the current NG-LLRF design. The high-power test results at different stages of the test setup with several pulse modulation schemes, including square pulse, pulse with phase reversals, and pulse trains, will be summarized, analyzed, and discussed.
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All authors Chao Liu, Ankur Dhar, Martin Breidenbach, Emilio Nanni
Astrophysics of Galaxies
EPISODE II: Variability in the CO and H$_2$O rovibrational absorption lines in a periodically variable protostar EC 53
Seokho Lee, Jeong-Eun Lee, Chul-Hwan Kim et al. (+19 more)
We present two-epoch JWST NIRSpec and MIRI observations of the young protostar EC 53 (V371 Ser), a periodically variable source with well-characterized quiescent and burst phases. The spectra in both epochs show absorption in the CO overtone ($\sim$2.3 $\mu$m) and fundamental ($\sim$4.6 $\mu$m) bands and the H$_2$O stretching ($\sim$2.7 $\mu$m) and bending ($\sim$6.0 $\mu$m) modes. We also obtained high-resolution ($R\approx45{,}000$) IGRINS spectra during the burst to constrain the CO overtone line profiles. LTE slab modeling yields gas temperatures of $\sim$1800 K (CO overtone) and $\sim$1200 K (CO fundamental), consistent with the overtone tracing hotter gas at smaller radii. The H$_2$O stretching-mode absorption shows no compelling evidence for variability, and the current JWST CO overtone data do not provide a robust constraint on overtone variability. In contrast, the CO fundamental and H$_2$O bending-mode features weaken by a factor of $\sim$2 during the burst, which is most naturally explained by continuum changes rather than large variations in absorbing gas. To quantify continuum dilution, we introduce a “relative veiling” that treats the quiescent spectrum as an internal reference and measures the change in the continuum excess between the two epochs. This formalism yields burst-to-quiescent hot-continuum ratios of $2.9\pm0.2$ for the CO overtone and $1.71\pm0.11$ for the CO fundamental. Using a viscous-disk prescription, these imply representative
accretion-rate ratios of $\sim$3.6 and $\sim$2.0, respectively. The differing ratios suggest that inner-disk regions traced at different temperatures, and thus radii, respond differently across the burst cycle, consistent with episodic mass buildup in the inner disk during quiescence followed by more efficient transport through the innermost disk onto the protostar during the burst.
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All authors Seokho Lee, Jeong-Eun Lee, Chul-Hwan Kim, Jaeyeong Kim, Young-Jun Kim, Gregory J. Herczeg, Doug Johnstone, Giseon Baek, Yuri Aikawa, Joel D. Green, Yao-Lun Yang, Logan Francis, Klaus M. Pontoppidan, Ho-Gyu Lee, Takahiro Nagayama, Yoichi Itoh, Tomohito Ohshima, Jun Takahashi, Jun Toshikawa, Tomoki Saito, Motohide Tamura, Takayoshi Kusune
Astrophysics of Galaxies
JWST reveals how black holes are fed: kiloparsec-scale multiphase filaments feed sub-kiloparsec circumnuclear disks
Julie Hlavacek-Larrondo, Hyunseop Choi, Minghao Guo et al. (+35 more)
The Centaurus cluster is one of the most important archetypes of
radio-mode AGN feedback, with its central
galaxy, NGC 4696, launching powerful jets that inflate X-ray cavities and regulate cooling and
star formation. NGC 4696 lies within a spectacular multiphase nebula of filaments extending over tens of kiloparsecs and spanning six decades in temperature, from hot (10^8 K) X-ray-emitting
plasma to cold molecular gas. Owing to its proximity, Hubble Space
Telescope H_alpha imaging reveals a striking S-shaped ionized-gas swirl within the black hole's sphere of influence - the first such structure identified in a cluster core. Here we present the first JWST observations of NGC 4696 with NIRSpec, probing the inner 618 pc * 618 pc at 10 pc resolution. These data reveal that the ionized swirl is a rotating, multiphase circumnuclear disk (CND) physically and kinematically connected to the larger-scale filamentary network. This provides the long-sought missing link between kiloparsec-scale cooling flows and black hole
accretion on <100 pc scales. Strikingly, the observed morphology and kinematics are reproduced by tailored magnetohydrodynamic simulations, in which filamentary gas condenses from the hot atmosphere, loses angular momentum, and feeds a rotating CND that mediates
accretion onto the black hole. A similar structure in NGC 1275, the Perseus cluster's central
galaxy, together with our results on NGC 4696 - two prototypical
radio-mode AGN feedback systems - points to a common mechanism: multiphase filaments transport gas from cluster scales down to the vicinity of the black hole via a CND, closing the AGN feedback loop and establishing a physically grounded framework for self-regulated
galaxy evolution.
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All authors Julie Hlavacek-Larrondo, Hyunseop Choi, Minghao Guo, Mathieu Marquis, Olivia Pereira, G. Mark Voit, Loïc Albert, Jorge Barrera-Ballesteros, Rebecca E. A. Canning, Francesco D'Eugenio, Megan Donahue, Andrew C. Fabian, Gary J. Ferland, John S. Gallagher, Marie-Lou Gendron-Marsolais, Pierre Guillard, Nina Hatch, Ralf Kottulla, Yuan Li, Roberto Maiolino, Allison Man, Michael A. McDonald, Brian R. McNamara, Valeria Olivares, Marine Prunier, Michael Reefe, Christopher S. Reynolds, Carter Rhea, Annabelle Richard-Larrière, Helen R. Russell, Philippe Salomé, Ming Sun, Prathamesh Tamhane, Gregory Taylor, Auriane Thilloy, Grant R. Tremblay, Benjamin Vigneron, Stephen A. Walker
Astrophysics of Galaxies
The Pristine Dwarf Galaxy Survey – VII. The metallicity distributions of 12 Milky Way faint satellites
S. Taibi, P. Jablonka, N. Longeard et al. (+10 more)
Spectroscopic studies of ultra-faint
dwarf galaxies are typically limited to small samples of
stars due to the scarcity of sufficiently bright targets. The small number statistics and possible presence of contaminants still hamper solid determinations of their
metallicity distribution function. In this work, we characterise the
metallicity distributions of 12 Milky Way faint satellites by exploiting deep narrow-band CaHK photometry from the Pristine
dwarf galaxy survey. In order to derive accurate
stellar photometric
metallicities, we combined it with deep broad-band g and r photometry from Muñoz et al. (2018) and Pan-STARRS1, covering each system out to 5-8 times their half-light radius Rh, and reaching magnitudes as faint as g~23. Membership probabilities were determined incorporating the available spatial, photometric, astrometric, and spectroscopic information, further refined using the derived photometric
metallicities. We identified 3917 probable member
stars across the 12 systems, more than doubling the numbers recovered by previous spectroscopic studies. We deliver complete
metallicity distributions that yield robust average
metallicities and dispersions previously inaccessible for most of the systems examined in this study. We identify 170 candidate extremely metal-poor
stars distributed across all systems, and confirm a departure from the linear luminosity-
metallicity relation in the ultra-faint regime, with systems scattering around [Fe/H]~-2.3 dex. Given the extensive mass coverage of our sample, we were able to investigate the presence of
metallicity gradients, finding clear evidence of radial variations in massive systems, but none in the ultra-faint
dwarfs within 2.5xRh. The photometric strategy presented in this paper will continue to serve as an effective complement to future spectroscopic surveys.
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All authors S. Taibi, P. Jablonka, N. Longeard, N. F. Martin, Z. Yuan, G. Battaglia, A. Ardern-Arentsen, P. Côté, J. F. Navarro, R. Sanchez-Janssen, F. Sestito, E. Starkenburg, M. Hirschmann
Astrophysics of Galaxies
JWST absorption line spectroscopy with SPURS: ISM covering fractions and kinematics in individual galaxies at $z=5-9$
Keerthi Vasan G.C., Peter Senchyna, Charlotte A. Mason et al. (+11 more)
We present deep rest-ultraviolet (UV) spectra of six luminous $z=5$ – 9
galaxies in the Abell-2744 field taken as part of the JWST Cycle 4 Large Program SPURS. The individual
galaxy spectra show unambiguous detections of interstellar medium (ISM) metal absorption lines from low- and high-ionization states of enriched gas, which we use to probe the ISM gas porosity and kinematics. We find a striking diversity in the absorption profiles. We find low-ionization gas covering fractions ranging from 0.2 to 0.9, indicating a heterogeneous and patchy neutral ISM. The low-ionization kinematics also show a large diversity, with velocity centroid values ranging from $+$70 to a significantly blueshifted $-140$ km$\,$s$^{-1}$, while the high-ion gas shows mostly blueshifted absorption, indicating the presence of multiphase
outflows. While all sources show
outflow signatures in blueshifted wings, we also find that half of our sample, in particular those with the lowest
stellar masses and highest sSFRs, have low-ionization velocity centroids close to systemic velocities. This is in contrast to near-ubiquitous bulk low-ionization gas
outflows at lower
redshifts. We suggest that this diversity of kinematics may be due to the bulk of the cold gas having low
outflow velocities in the lowest mass and highest sSFR systems, potentially due to inefficient entrainment and/or an unresolved infalling component. These spectra reveal a metal-enriched ISM with complex gas geometry and kinematics, and highlight the potential of deep JWST grating spectroscopy to reveal the properties of the ISM during the reionization era.
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All authors Keerthi Vasan G.C., Peter Senchyna, Charlotte A. Mason, Zuyi Chen, Daniel P. Stark, Tucker Jones, Lily Whitler, Kelsey S. Glazer, Manuel Aravena, Jorge Gonzalez-Lopez, Ryan Endsley, Viola Gelli, Mengtao Tang, Michael W. Topping
Earth and Planetary Astrophysics
Titan's Resources and their Utilization
Conor A. Nixon, Ye Lu and Jennifer Ruliffson
Saturn's moon Titan is a unique environment in the
solar system. It is the only moon with an atmosphere, composed primarily of the gases N2 and CH4. It is also the only world to have abundant surface hydrocarbons CxHy, which are found as both
liquids (seas, lakes) and solids (dunes). Meanwhile, oxygen is also readily accessible in the form of crustal water. This combination of abundant reduced carbon, along with available nitrogen and oxygen makes Titan an enticing world rich in resources that can be readily used to make food, fuel, building materials and more - potentially mission-enabling for long-duration voyages or habitats in the outer
solar system. At the same time Titan, as an icy moon, is likely to be depleted at the surface in heavier elements including metals, which must therefore be found and brought from elsewhere. In this article we describe both the available resources on Titan, and also their potential uses. We compare and contrast the resource availability and potential in-situ utilization (ISRU) with other destinations suggested for human habitation such as the Moon and Mars. We conclude by discussing what future work will be important to further characterize Titan's resources, and to develop technologies for their utilization.
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Cosmology and Nongalactic Astrophysics
Halo mass functions in mixed cold and fuzzy dark matter models
Sarah C. Johnston, Simon May, Tibor Dome et al. (+5 more)
We investigate the impact of mixed cold and fuzzy dark matter (MDM) cosmologies on the
halo mass function (HMF) using numerical simulations performed with the AxiREPO framework. We consider models in which an ultralight
axion-like component with mass $m =10^{-24.5} \mathrm{eV}$ constitutes a fraction $f \leq 0.3$ of the total dark matter. To enable consistent
halo identification in mixed-species scenarios, we develop a grid-based
halo-finding pipeline that combines the particle-based cold dark matter (CDM) and wave-like fuzzy dark matter (FDM) components into a unified density field. We find that FDM traces the large-scale CDM distribution while suppressing small-scale structure through wave interference effects, leading to a reduction in the abundance of low-mass
haloes and modifying the HMF in a manner dependent on
redshift and FDM fraction. Increasing the FDM fraction produces a systematic downward shift in the HMF and modifies its high-mass slope. Motivated by these trends, we introduce a phenomenological model that maps CDM HMFs to their MDM counterparts using a suppression function with parameters dependent on
redshift and FDM fraction. This model reproduces the simulated HMFs within approximately 0.1 to 0.2 dex across the parameter space explored ($1 \leq z \leq 4$, $f \leq 0.3$). Our results provide a computationally efficient method for predicting structure formation in MDM cosmologies without requiring dedicated simulations for each parameter choice, and establish a framework for exploring the impact of MDM on cosmological structure formation.
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All authors Sarah C. Johnston, Simon May, Tibor Dome, Sownak Bose, Alastair Basden, Carlton Baugh, Anastasia Fialkov, Alex Tocher
High Energy Astrophysical Phenomena
VLA Observations Confirm AT 2023mfm as an Off-nuclear Tidal Disruption Event
Wenkai Li, Collin T. Christy, Kate D. Alexander et al. (+15 more)
We report new
radio observations of the
tidal disruption event (TDE) AT 2023mfm, which we identified as a high-confidence candidate in a systematic search for off-
nuclear TDEs. High-resolution NSF Karl G. Jansky Very Large Array C-band (6 GHz) imaging resolves two
radio sources: one consistent with the host-
galaxy nucleus and one offset by $0.651\pm0.036^{\prime\prime}$ ($1.06\pm0.06$ kpc), consistent with the Zwicky Transient Facility and Pan-STARRS1 positions of AT 2023mfm. These observations confirm the off-
nuclear nature of AT 2023mfm, demonstrating the power of high-resolution
radio imaging to validate off-
nuclear TDE candidates and reveal hidden off-
nuclear massive black holes.
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All authors Wenkai Li, Collin T. Christy, Kate D. Alexander, Itai Sfaradi, Xinya Huang, Ning Jiang, Tanmoy Laskar, Andrew Mummery, Noah Franz, Adelle J. Goodwin, Walter W. Golay, Raffaella Margutti, Ryan Chornock, Jiazheng Zhu, Sjoert van Velzen, Yvette Cendes, Wenbin Lu, Jimmy Lynch
Astrophysics of Galaxies
The accretion history of the Milky Way V. The kinematics of most globular clusters trace the merger epochs
Istiak Akib, François Hammer and Yanbin Yang
Several studies have associated globular clusters (GCs) with former
Galactic accretion events by comparing their positions in the energy-angular momentum ($E$-$L_z$) plane, an approach further supported by similarities in their age-
metallicity relations. However, recent merger simulations suggest that GCs initially associated with the
Gaia-Sausage-Enceladus (GSE) disc may have lost their orbital energy and thus may not reliably trace this
accretion event. We extend this framework by considering three N-body simulations of the Milky Way-GSE merger with different initial masses, mass ratios, and gas content. In addition to GCs belonging to the GSE disc progenitor, we accounted for GCs in its
halo and, in gas-rich models, a population of GCs formed during the Milky Way-GSE merger. We confirm that most GCs originating in the disc have lost a significant part of their orbital energy during repeated passages through the dense disc medium, and we
conjecture that associated
tidal shocks may have destroyed many of them. In contrast, GCs from the
halo and GCs formed during the merger have largely retained their orbital energy, which remains comparable to that of GSE
stars even up to 9 Gyr after the completion of the merger. By using a more realistic GC population and GSE modelling, we find that most GCs linked to GSE can be associated with Milky Way
accretion events in the $E$-$L_z$ plane, which supports previous observational associations based on a combination of energy-angular momentum and age-
metallicity relations.
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Cosmology and Nongalactic Astrophysics
The colour variability of low-z SNe Ia is entirely explained by dust
Marco Giunta, Konstantin Karchev and Roberto Trotta
The relative importance of intrinsic colour variability of
supernovae type Ia (SN Ia) versus
dust-induced reddening remains an open question with important ramifications for understanding their environmental dependence, as well as for the validity of the traditionally employed Tripp linear correction for cosmological inference. We revisit this question in the light of two low-
redshift, homogeneous
datasets, the ZTF DR2 and Foundation DR1, which we analyse within the framework of the
Bayesian hierarchical model Simple-BayeSN. We demonstrate both with simulation and on real data that traditional colour cuts, which remove highly reddened samples, induce a previously unrecognized selection effect, which may have biased previous conclusions on the origin of SN Ia colour variability. Once this is accounted for, we are able to explain the entirety of the colour–magnitude correlation as due to
dust effects, with no need for an intrinsic colour correlation. This result is robust with respect to a host
galaxy mass split and projected distance from the center of the host. Our findings imply that the traditional linear Tripp correction maintains an empirical validity, even though it should be ascribed to
dust rather than intrinsic colour variation.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Measuring a Black Hole's Area Immediately after Merger: A Direct-Wave Test of Hawking's Area Law
Adrian Ka-Wai Chung, Kelvin Ka-Ho Lam, Anna Liu et al. (+1 more)
Black-hole area is the
geometric variable behind horizon thermodynamics. We introduce a gravitational-wave method to infer a Kerr-equivalent horizon area from direct waves in the near-merger signal, before quasinormal ringing dominates at late times. Applied to GW250114, and interpreting the fitted direct-wave frequency and damping rate as horizon quantities, we find that analyses initiated $3$–$4.5M$ before the peak-amplitude time yield an area consistent with the Kerr remnant. This result gives a first area measurement using direct waves and a new near-merger test of Hawking's area law.
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All authors Adrian Ka-Wai Chung, Kelvin Ka-Ho Lam, Anna Liu, Nicolas Yunes
Cosmology and Nongalactic Astrophysics
Impact of fiducial cosmology in model-agnostic cosmological inference with the BAO feature
Aseem Paranjape and Ravi K. Sheth
In recent work, we have developed a model-agnostic framework for cosmological inference using the
baryon acoustic oscillation (BAO) feature in
redshift space. The framework, which we dub the `Zel'dovich smearing approximation', involves several ingredients, including an optimal basis for the linear theory correlation function in real space, a Gaussian kernel that describes the smearing of the BAO feature due to bulk flows, and a model for the impact of scale dependent bias and mode coupling in
redshift space. Unlike traditional, template-based approaches, this framework does not assume any particular cosmological model. An important ingredient – which impacts both the traditional as well as model-agnostic frameworks – is the
geometric distortion introduced by the inevitable choice of the fiducial cosmology used for converting observed angles and
redshifts to comoving separations. In this work we show how this distortion, which was not yet included in our framework, affects the output of the Zel'dovich smearing approximation. We test our completed framework on two
halo samples derived from the AbacusSummit simulation suite and designed to mimic
galaxy samples from the ongoing DESI and Euclid surveys, respectively. We show that our framework produces unbiased cosmological constraints when applied to these semi-realistic samples and compare the organization of cosmological information in the model-agnostic and traditional approaches. We end with a roadmap to a detailed comparison of the performance of the traditional approach with the Zel'dovich smearing approximation, which is `data ready' as presented here.
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Astrophysics of Galaxies
The Combined Dense Gas and Excitation Atlas of the Milky Way I. Mass Distribution and Ripples in the Molecular Layer
Peter J Barnes
The first components of a new meta-survey, the Combined Dense Gas and Excitation Atlas (CODEX) of the Milky Way, are presented here with combined data from five previously published surveys: NANTEN+CHaMP, ThrUMMS, FUGIN, and MWISP. The CODEX is first used to harmonise the combination of parameters used to describe the
Galaxy's scale and rotation, including $R_0$ and $\Theta_0$ from recent work, since these are critical components of standard techniques for obtaining kinematic distances. An additional feature is added to these formulae to accommodate local clouds that are otherwise kinematically inconsistent with the Local Standard of Rest. The structure in the combined lV diagram spanning 230 deg of longitude is then analysed, yielding a new Ragged Spiral Arm model that better traces the deprojected (x,y) 12CO structure. The widespread existence of ripples in the molecular layer, first reported in the ThrUMMS data of the Fourth Quadrant (4Q), is confirmed in FUGIN data of the First Quadrant (1Q), averaging amplitudes $\sim$40 and $\sim$23 pc respectively, and wavelength $\sim$4 kpc in both. The (x,y) mass distributions as traced by the molecular line data and the published
dust extinction data match well across the 4Q+inner1Q, but poorly across the outer 1Q, probably due to lower sensitivity in the 1Q extinction data. In the 1Q+4Q, however, the two mean-z distributions do not match: the
dust ripple amplitude is $\sim$3x smaller than, and opposite in sign to, the gas ripples. This is nevertheless consistent since the
dust extinction is insensitive to the densest molecular gas.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
A New Origin of the Big Bang from Dark-Sector-Induced Vacuum Decay and Its Gravitational-Wave Signal
Haipeng An and Tingyu Li
We propose a novel scenario for the onset of the thermal Big Bang. In this framework, the inflaton transfers its energy exclusively into a dark sector, leaving the Standard Model (SM) sector temporarily trapped in a false
vacuum. As the Hubble expansion rate rapidly decreases, the SM phase transition eventually completes, and the standard thermal Big Bang era commences upon the thermalization of the highly energetic bubble walls. We demonstrate that the large Lorentz boost of these bubble walls, combined with their Hubble-scale macroscopic size, generates distinctive gravitational-wave signatures from the SM
vacuum decay. This
stochastic gravitational-wave background provides a powerful new probe of the early Universe's expansion history, with a present-day energy density fraction that can reach $\Omega_{\text{GW}} \sim 3\times10^{-8}$.
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Astrophysics of Galaxies
A Population of Red Galaxies with Very Strong Emission Lines at $z > 5$ Revealed by the NIRCam Medium Bands: ”Classic” LRDs, Dusty Star-Forming Galaxies, and a Missing Population of LRDs
Sunna Withers, Adam Muzzin, Swara Ravindranath et al. (+16 more)
The NIRCam medium-bands have proven to be efficient at identifying Emission Line
Galaxies (ELGs) with high equivalent width (EW) H$\alpha$ and [OIII]+H$\beta$ emission lines. In this paper we exploit this efficiency to identify a sample of ELGs at $4.9 \lesssim z \lesssim 8.9$ using medium-band imaging from the CANUCS, Technicolor, and JUMPS surveys. We find that the ELGs exhibit a strong correlation between continuum color and emission line strength, such that
galaxies with bluer UV/optical continua have stronger H$\alpha$ and [OIII]+H$\beta$ emission lines. We identify 26
galaxies that are outliers from this relation, which we call the Red Emission line
Galaxies (REGs), because of their red continuum color and strong emission lines. We classify the REGs into three categories: 1) ”classic” Little Red Dots (LRDs) selected with common literature criteria, 2) extended REGs, resolved in F444W and consistent with being Dusty
Star Forming
Galaxies (DSFGs), and 3) compact REGs, unresolved in F444W but not classified as LRDs. The compact REGs fail common LRD selections for several reasons, including faint continuua, contamination from emission lines (very strong [OIII]+H$\beta$), and UV/optical colors that are flatter than those of LRDs. We conclude that the compact REGs are likely LRDs that ”classic” selection criteria miss, and are therefore missing from existing samples. Our results suggest that medium-band selection can provide more complete samples of these objects.
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All authors Sunna Withers, Adam Muzzin, Swara Ravindranath, Chris J. Willott, Nicholas S. Martis, Roberta Tripodi, Yoshihisa Asada, Maruša Bradač, Maya Merchant, Lamiya Mowla, Gaël Noirot, Ghassan T. E. Sarrouh, Marcin Sawicki, Jacqueline Antwi-Danso, Anishya Harshan, Naadiyah Jagga, Danilo Marchesini, Katherine Myers, Visal Sok
Instrumentation and Methods for Astrophysics
The short and long of iPhoton science for a boosted Hubble
Stephan R. McCandliss, Jack Ford, Anne E. Jaskot et al. (+7 more)
Boosting the Hubble Space
Telescope (HST) will provide unique opportunities to carry out precursor science for the Habitable Worlds Observatory (HWO). Chief among them are science cases for determining the properties of
star forming
galaxies that contribute to creating and sustaining the universe in a mostly ionized state. The farUV and nearUV spectroscopic capabilities of the
Cosmic Origins Spectrograph (COS) and the Space
Telescope Imaging Spectrograph (STIS) are unique and unlikely to be replicated in the near future. Here we describe the benefits of a deep panchromatic spectroscopic effort to answer questions concerning the shape of the rest frame ionizing radiation escaping from
star forming
galaxies at modest
redshift, capture crucial missing spectral regions, and explore whether their
star formation histories are truly similar to the LyC leakers responsible for initiating and later sustaining the mostly-ionized-state of the universe. An observing program emphasizing multi-orbit observations, unencumbered by HST orbit competition and freely accessible to the wider ionizing
photon (iPhoton) community, will catalyze crowd-sourced answers to these questions and offer a lower operating cost price point.
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All authors Stephan R. McCandliss, Jack Ford, Anne E. Jaskot, Matthew J. Hayes, Alberto Saldana-Lopez, Alaina Henry, Timothy Heckman, Sophia R. Flury, Claudia Scarlata, Cody Carr
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Three Advanced Lectures on Inflation
Martin S. Sloth
Lecture notes on inflation. The lectures are three double lectures, held for the first time at the Nordita Winter School 2024 - Particle Physics and Cosmology, covering an advanced introduction to the theory of
primordial inflation, as well as the linear and non-linear perturbation theory of slow-roll inflation/quasi-de Sitter spacetimes.
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