Cosmology and Nongalactic Astrophysics
Cosmological constraints from the DESI DR1 Bispectrum Full-Shape and DR2 BAO
D. Forero-Sánchez, S. Novell-Masot, H. Gil-Marín et al. (+48 more)
We present cosmological constraints from DESI DR1 full-shape measurements, including the LRG bispectrum, combined with DESI DR2 BAO data. The analysis accounts for cross-covariance using mocks, while ShapeFit compression mitigates prior volume effects in beyond-$\Lambda$CDM analyses. In $\Lambda$CDM, the DESI1.5 (P+B) analysis yields $\sigma_8=0.868\pm0.026$ and $S_8=0.880\pm0.028$, compared with $\sigma_8=0.822\pm0.034$ and $S_8=0.827\pm0.036$ in the previous power-spectrum-only analysis. The marginalized uncertainties are reduced by 24% and 22%, respectively. For $w_0w_a$CDM, DESI-only analyses with the bispectrum shift dark energy parameters toward $\Lambda$CDM, consistent with a cosmological constant within $1\sigma$ in the $w_0$–$w_a$ plane. Adding CMB creates a preference for evolving dark energy: DESI+CMB (P+B) shows a $2.8\sigma$ deviation from $\Lambda$CDM. Including DES-Dovekie
supernovae alone reduces this to $1.6\sigma$, while the full combination gives $3.1\sigma$. The bispectrum weakens evidence for time-varying dark energy relative to power-spectrum-only analyses. It also enhances sensitivity to massive
neutrinos: in DESI-only data, the power-spectrum-only posterior for $\sum m_\nu$ is consistent with zero, whereas adding the bispectrum yields $0.26\pm0.18$ eV and a 95% upper limit of $0.59$ eV, shifting the peak into the positive region. For modified
gravity, the bispectrum constrains $\mu_0 = 0.12\pm0.51$ from DESI-only data, consistent with general relativity.
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All authors D. Forero-Sánchez, S. Novell-Masot, H. Gil-Marín, L. Verde, J. Aguilar, S. Ahlen, D. Bianchi, A. Brodzeller, D. Brooks, F. J. Castander, S. Cole, A. de la Macorra, J. Della Costa, Biprateep Dey, P. Doel, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, Satya Gontcho A Gontcho, G. Gutierrez, C. Hahn, H. K. Herrera-Alcantar, K. Honscheid, D. Huterer, M. Ishak, D. Kirkby, A. Kremin, O. Lahav, C. Lamman, M. Landriau, L. Le Guillou, M. E. Levi, M. Manera, A. Meisner, R. Miquel, J. Moustakas, S. Nadathur, J. A. Newman, G. Niz, N. Palanque-Delabrouille, W. J. Percival, F. Prada, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, M. Schubnell, J. Silber, G. Tarlé, B. A. Weaver
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
As above, so below: assessing extremeness of the neutron-star equation of state based on the unstable branch
Tyler Gorda, Oleg Komoltsev, Aleksi Kurkela et al. (+1 more)
Microscopic models of
neutron-
star matter have been widely used in astrophysical applications. The focus of
attention has been on densities up to the maximal densities reached in stable
neutron stars. The possibility that the underlying model assumptions may have important implications at higher densities has not been addressed. Here, we show that the behaviour at higher densities is strongly constrained by requiring a causal, stable, and thermodynamically consistent extension to the perturbative-QCD regime. We explicitly reveal what that behaviour must be and provide a tool for constructing and visualizing such extensions. We find that purely hadronic models trusted up to the maximal central density often require radically different behaviour at higher densities from that assumed in the original model, while models with additional degrees of freedom fare better. Our analysis disfavors purely nucleonic models for describing all stable
neutron stars and supports the appearance of some type of additional degrees of freedom in stable massive
neutron stars.
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All authors Tyler Gorda, Oleg Komoltsev, Aleksi Kurkela, Jürgen Schaffner-Bielich
Solar and Stellar Astrophysics
JWST NIRSpec Spectral Standards for M, L, and T Dwarfs and Subdwarfs
Evan Pritchard, Marylin Loritsch, Julia Haynes et al. (+3 more)
We present low resolution infrared spectral standards in the 0.76 to 5.0 {\mu}m range based on JWST NIRspec Prism data from deep sky surveys. Our standards encompass spectral types M, L, and T and
dwarf and subdwarf
metallicity classes. The standards extend ground based spectral templates and enable classification of low temperature
stellar substellar discoveries from deep JWST NIRSpec data.
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All authors Evan Pritchard, Marylin Loritsch, Julia Haynes, Sara Morrissey, Emma Softich, Adam Burgasser
High Energy Astrophysical Phenomena
Detection of relativistic orbital deformation from improved timing of PSR J1757$-$1854
Jaikhomba Singha, Vivek Venkatraman Krishnan, Marisa Geyer et al. (+12 more)
PSR~J1757$-$1854, a 21.5\,ms
pulsar, is a highly relativistic double
neutron star (DNS) system in a tight eccentric ($e = 0.61$) 4.4\,hr orbit. With extremely large gravitational wave luminosity and one of the fastest orbital decay rates of any known DNS system, it is ideal for testing general relativity (GR) in the strong-field regime. Here we present results from a high-precision timing campaign combining archival data from the Murriyang
telescope and Green Bank
Telescope (GBT) with new high-sensitivity observations from the MeerKAT
radio telescope and additional observations from the GBT. The extended baseline and superior sensitivity of MeerKAT have yielded substantial improvements to previously measured post-Keplerian parameters by a factor of around $\sim2$ or more. We report the first detection of the relativistic angular deformation, $\delta_\theta$ in this system, making PSR~J1757$-$1854 only the third DNS system for which $\delta_\theta$ has been measured, achieved here in just 9 yrs compared to the decades of timing required for both the double
pulsar and the Hulse-Taylor binary. We demonstrate how $\delta_\theta$ can be used to constrain the
spin-orbit geometry of the system, ruling out two of the four
geometric solutions previously identified, while remaining consistent with GR. We also evaluate higher-order contributions to the periastron advance $\dot{\omega}$, including the second post-Newtonian correction and the Lense-Thirring term, and show that these have a measurable systematic effect on the inferred total system mass. The observed orbital period derivative, $\dot{P}_\mathrm{b}$ remains consistent with the GR prediction for gravitational-wave damping across a wide range of plausible distances.
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All authors Jaikhomba Singha, Vivek Venkatraman Krishnan, Marisa Geyer, Victoria Blackmon, Paulo Freire, Norbert Wex, Maura McLaughlin, Michael Kramer, Amanda Weltman, David Champion, Matthew Bailes, Sarah Buchner, Fernando Camilo, Andrea Possenti, Maciej Serylak
Earth and Planetary Astrophysics · Cross-listed from gr-qc
Newtonian Shirokov Effect: Epicyclic Frequency Splitting from Mass Multipoles
Anuar Idrissov, Kuantay Boshkayev, Abylaikhan Tlemissov et al. (+1 more)
We analyze small oscillations of nearly circular orbits in an axisymmetric Newtonian potential expanded in mass multipoles, as the classical counterpart of the relativistic Shirokov effect. Computing the full Hessian of the effective potential at the true (possibly tilted)
equilibrium and solving the coupled two-mode oscillator exactly, we obtain a complete picture. (i) A quadrupole splits the radial and vertical epicyclic frequencies, $\Omega_\theta^2-\Omega_r^2=-3GQ/r_0^5=6GMJ_2R^2/r_0^5$, at first order in $J_2$; the Newtonian analogue of the Shirokov splitting, equivalent to the classical statement that an oblate body's apsidal and nodal rates differ. (ii) A gravitational dipole produces no splitting: it equals $M r_{\rm CM}$, is removable by re-centering at the center of mass, and cannot appear in any coordinate independent frequency; the apparent first order coupling cancels at the true tilted
equilibrium, any residual absorbed by the induced quadrupole of the shifted source, confirmed by direct orbit integration. (iii) A genuine octupole does split the frequencies, $\omega_+^2-\omega_-^2\approx6G|O|/r_0^6$. The selection rule is thus not even/odd parity: every multipole splits the frequencies except the dipole. These yield two complementary probes of an axisymmetric source: the frequency splitting measures the oblateness $J_2$, while the orbital plane tilt, $\delta\theta_0\simeq-r_{\rm CM}/r_0$, measures the center of mass offset $r_{\rm CM}$, an orbital geometry observable rather than a frequency one. We give
solar system estimates for both. Carried through to Shirokov's original observable – the secular transverse drift after $n$ orbits – the quadrupole effect gives $\xi^\theta=\xi_0^{\theta}\,\pi n\,(6J_2R^2/r_0^2)$, of order $10^{-8}$ cm at $1$ au and $\sim10^{-6}$ cm near $0.1$ au, comparable to Shirokov's Schwarzschild estimate.
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All authors Anuar Idrissov, Kuantay Boshkayev, Abylaikhan Tlemissov, Hernando Quevedo
Earth and Planetary Astrophysics
Effects of Super-rotating Jets on Phase-Resolved Transmission Spectra at High Spectral Resolution
Hayley Beltz and Arjun B. Savel
Hot Jupiter atmospheric circulation can be shaped by a range of processes and planetary parameters, including rotation rate, irradiation gradients from
tidal synchronization,
magnetic effects,
gravity, and clouds. Observations of exoplanetary spectral Doppler shifts as a function of phase, made possible with high-resolution spectrographs, can now probe the effects of exoplanetary winds at several points throughout transit. However, these measurements are difficult to interpret, given the variety of relevant atmospheric mechanisms. In this work, we generate high-resolution transmission spectra from two sets of circulation models: self-consistent dynamical models and idealized models that isolate circulation components. We identify how the strength of the jet — or the absence of one — alters the resultant net Doppler shifts. We find that the jet strength most prominently affects Doppler shifts during ingress and egress. During mid-transit, the strength of the jet linearly influences the Doppler shifts' slope; however, this effect is generally secondary to the overall blueshifting from planetary rotation. The slope induced by equatorial jets contrasts with the effect of pure day–night flows, which tend to add constant offsets to Doppler shifts during transit. Our modeling shows that jets also impact the cross-correlation function width; faster jets increase velocity dispersion across the limbs. We complement our simulations with semi-analytical arguments indicating that first-order changes of the cross-correlation function centroid and width (but not amplitude) probe thermal and velocity asymmetries. This work provides recommendations for interpreting net Doppler shifts in transmission and connecting these shifts with
exoplanets' atmospheric circulation.
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High Energy Astrophysical Phenomena
Deep Newtonian Afterglows: Theoretical Light Curves for Quasi-spherical Outflows
Nissim Fraija, Boris Betancourt-Kamenetskaia, Antonio Galván et al. (+1 more)
We investigate late-time gamma-ray burst (GRB) afterglows produced by quasi-spherical
outflows propagating into a stratified circumburst medium during the deep Newtonian phase. Sub-relativistic ejecta generated in compact binary mergers or core-collapse explosions naturally develop velocity structures, while additional energy injection from a long-lived central engine, through
spin-down luminosity and/or fallback
accretion, can substantially modify the afterglow
evolution. We develop an analytical framework for synchrotron emission from decelerated ejecta components undergoing energy injection in a stratified environment. The model provides multiwavelength light curves and corresponding closure relations for the deep Newtonian regime. We apply this framework to the late-time multiwavelength observations of GRB 171205A. In addition, we constrain the physical properties of quasi-spherical
outflows using observations of short GRBs associated with kilonova candidates, together with long-term
radio upper limits obtained years after the burst in a broader GRB sample. Our results show that late-time observations can place meaningful constraints on the dynamics, energetics, and energy-injection history of sub-relativistic quasi-spherical
outflows from GRB progenitors.
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All authors Nissim Fraija, Boris Betancourt-Kamenetskaia, Antonio Galván, Maria G. Dainotti
High Energy Astrophysical Phenomena
Indication for Decreasing Dispersion Measure in the Population of Repeating Fast Radio Bursts and Connection to Young Supernova Remnant Expansion
Xiang-han Cui, Cheng-min Zhang, Di Li et al. (+8 more)
Fast
Radio Bursts (FRBs) are millisecond-duration, highly energetic
radio transients of uncertain origin. Repeating FRBs provide an excellent population for investigating their nature, particularly through studies of parameter
evolution. Out of the 63 repeaters monitored by CHIME, we select the 19 sources with more than 10 detected bursts, and examine their long-term dispersion measure (DM)
evolution. Seven sources show statistically significant DM
evolution and are classified as the golden sample. Of these, five exhibit a decreasing DM trend and two show an increasing trend. We then perform a binomial test under the null hypothesis that decreasing and increasing DM variation trends have equal probabilities. The current combined sample, including our golden sample and additional repeaters with reported DM change rate from the literature, gives a p-value of 0.033, supporting that decreasing DM trends are more common in the repeating FRB population. This statistical result is consistent with scenarios in that the local electron density around repeaters generally decreases with time, for example, due to expansion of a young
supernova remnant (SNR). Finally, within the SNR expansion model, we provide an illustrative estimate of the SNR contributions to the DM for different ejecta masses.
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All authors Xiang-han Cui, Cheng-min Zhang, Di Li, Pei Wang, Erbil Gügercinoğlu, Joeri van Leeuwen, Yi-dan Wang, Chao-wei Tsai, Xiang-lei Chen, Wen-qi Ma, Habtamu Menberu Tedila
Earth and Planetary Astrophysics
Hydrogen airglow from an escaping ultrahot Jupiter atmosphere
Yapeng Zhang, Chenliang Huang, Aaron Householder et al. (+17 more)
Intense high-energy irradiation of close-in gaseous
exoplanets drives the rapid escape of their atmospheres, fundamentally shaping planetary demographics. While atmospheric loss is routinely observed via transit absorption in atomic hydrogen, helium, and metal ions, the underlying physical properties, specifically the thermal structure,
outflow dynamics, and mass-loss rate, remain poorly constrained due to inherent degeneracies in the transmission geometry. Here we report the first detection of atomic hydrogen emission from the escaping atmosphere of a gas
giant. Using high-resolution spectroscopy of the ultrahot Jupiter KELT-9 b, we detect a hydrogen Balmer line (H{\alpha} 6564.6 Å) emission signature originating from the planetary dayside. The emission line profile features a distinctive double-peaked shape with 0.1-0.15% peak amplitudes at +/-30 km/s and central self-absorption. This profile breaks transmission degeneracies, providing direct observational constraints on the vertical thermal structure, excited-state hydrogen populations, and wind dynamics in the upper atmosphere of KELT-9 b. Initial modeling reveals a vigorous
outflow with a mass-loss rate above 10^{13} g/s, among the highest measured to date for gaseous
exoplanets. Our results establish hydrogen airglow emission as a powerful diagnostic of atmospheric escape, opening a new observational window into the
evolution of worlds in extreme radiation environments.
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All authors Yapeng Zhang, Chenliang Huang, Aaron Householder, James E. Owen, Fei Dai, Aurora Y. Kesseli, Andrew W. Howard, Julie Inglis, Howard Isaacson, Heather A. Knutson, Dimitri Mawet, Nicole Wallack, Jerry W. Xuan, Michael Zhang, Theron W. Carmichael, Daniel Huber, Rena A. Lee, Nicholas Saunders, Lauren M. Weiss, Jingwen Zhang
Astrophysics of Galaxies · Cross-listed from physics.chem-ph
Charge transfer from ammonia neutralizes propylene oxide cations: Implications for the astrochemistry of chiral molecules
Sanjana Maheshwari, Darya Kisuryna and Leah G. Dodson
To date only one
chiral species, propylene
oxide, has been observed in the interstellar medium but little is known about the chemistry that leads to a detectable abundance of this molecule in Sagittarius B2. We used a glow-discharge ion source and a room-temperature ion trap to study the neutralization reactions necessary to convert propylene
oxide cation (PO$^+$) – the assumed precursor for propylene
oxide in space – into the observed astrochemical. We found that the charge-transfer reaction between PO$^+$ and ammonia (NH$_3$) proceeds with a pressure-independent rate coefficient of $(1.39\pm0.03)\times10^{-12}$ cm$^{3}$ s$^{-1}$ to neutralize PO$^+$ and form the radical cation NH$_3$. Although this measured rate coefficient is much slower than that predicted by capture theories, the high abundance of NH$_3$ in Sagittarius B2 motivates the inclusion of this reaction in astrochemical models. We hypothesize that the low ionization energies of many
chiral molecules important to origin-of-life theories means these species may exist as cations in the interstellar medium.
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Astrophysics of Galaxies
A Strongly Lensed Ultra-faint Arc at $z \approx 10$ with an F200W excess in Abell S1063
Fujiang Yu, Mingyu Li, Zheng Cai et al. (+4 more)
Strong gravitational
lensing provides a powerful route to probing intrinsically faint
galaxies during the first few hundred million years of
cosmic history. In this Letter, we report the identification of GAR10, a highly magnified F115W-dropout
galaxy at $z\approx10$ in the Abell S1063 cluster field, using deep JWST/NIRCam imaging from the GLIMPSE and GO-1840 programs. The source shows an unusually blue ultraviolet (UV) continuum and a significant F200W excess relative to adjacent bands. Under our high-magnification
lensing solution, we infer a median magnification of $\mu=43^{+78}_{-20}$, corresponding to an intrinsic UV magnitude of $M_{\rm UV}\approx-15.8$. We use exploratory Prospector SED modeling to examine two physically motivated interpretations of the observed photometry. In Case I, GAR10 is described by an extremely metal-poor, continuum-dominated
stellar population at $z=10.75_{-0.34}^{+0.41}$, with a blue UV slope of $\beta=-2.92\pm0.12$ and a low
metallicity of $\log(Z/Z_\odot)=-3.56_{-0.85}^{+0.65}$, consistent with an extremely metal-poor or Pop III-like continuum-dominated interpretation under the adopted priors. In Case II, GAR10 is interpreted as an extremely young (1–3 Myr), high-ionization
galaxy at $z=10.45_{-0.21}^{+0.11}$, in which the F200W excess is produced by intense rest-frame UV emission lines, including CIV, HeII, and CIII]. Both cases can partially reproduce the current photometry within the adopted priors, but they imply distinct ionizing sources, enrichment histories, and possible contributions to
cosmic reionization. GAR10 therefore represents a rare laboratory for studying ultra-faint
galaxy formation at
cosmic dawn. Future JWST/NIRSpec spectroscopy will be essential to distinguishing between the steep continuum and emission-line origins of the F200W excess.
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All authors Fujiang Yu, Mingyu Li, Zheng Cai, Yuduo Guo, Hao Zhang, Jose M. Diego, Sijia Cai
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Energy Extraction via Magnetic Reconnection from a Rotating Dyonic Black Hole in $N = 2, \ U(1)^2$ Gauged Supergravity
Raid M Suleiman, Shanshan Rodriguez, Dominic O. Chang et al. (+1 more)
We study energy extraction via
magnetic reconnection from a rotating dyonic black hole in four-dimensional $N=2$, $U(1)^2$ gauged supergravity. Using the Comisso-Asenjo mechanism in the ZAMO frame, we derive the asymptotic hydrodynamic energy per unit enthalpy $\epsilon^{\infty}_\pm$ and determine when reconnection
outflows attained negative energy at infinity. By varying the
spin $a$, electric and
magnetic charges, NUT parameter $N_g$, and gauge coupling $g$, we compute the cutoff magnetization $\sigma_0^{\rm cutoff}$ and map the region of parameter space that admits $\epsilon^{\infty}_-<0$. We find that $\sigma_0^{\rm cutoff}$ and the very existence of Comisso-Asenjo extraction are tightly controlled by $g$ and the dyonic charges: increasing $g$ or pushing the charges toward extremality raises $\sigma_0^{\rm cutoff}$ and shrinks the CA-active part of the ergoregion. Unlike Kerr, the
spin enters through the normalization factor $\Xi$, and the quartic horizon function $\Delta_g$, so
geometric effects from the AdS/NUT deformation dominate the usual frame-dragging enhancement. As a result, the extracted power and efficiency are non-monotonic in $a$ and peak at intermediate
spin ($a\sim0.8$); near-extremal rotation is not required for high efficiency, provided $g$ is small and $Q$ is moderate. Efficient extraction further demands extreme magnetization and nearly radial
outflows, confining the active reconnection layer to a thin shell, just outside the horizon.
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All authors Raid M Suleiman, Shanshan Rodriguez, Dominic O. Chang, Leo Rodriguez
Instrumentation and Methods for Astrophysics
Astrobiology in the Time of Artificial Intelligence
Caleb Scharf
The Viking missions showcased multiple spaceflight technologies representing state-of-the-art capabilities: from digital line-scan imaging to the operation of complex onboard laboratories and software-controlled process autonomy. Since Viking, there have been extraordinary, and still accelerating, advancements in computing technology impacting science, society, and exploration. These developments have occurred in both hardware and software, resulting in increasingly capable devices, advanced programming tools, and algorithmic innovations. The subset of artificial intelligence known as machine learning has emerged as one of the most transformative of these developments, with major implications for space exploration and for improvements to the search for evidence of life beyond the Earth. Those improvements include the integration of data across different scales and increased sensitivity to complex features in data, as well as the generation of adaptive strategies for sampling environments. In this paper, the present and future nature of space exploration and astrobiological research is examined through the contextual lens of Viking, and through the history and possible future of artificial intelligence.
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Earth and Planetary Astrophysics
Dynamical implications of the recently detected feature around Quaoar and constraints on the presence of additional satellites
Gustavo Madeira, Leandro Esteves, Bruno E. Morgado et al. (+4 more)
A recently reported opaque feature in the Quaoar system, detected during the 25 June 2025
stellar occultation, has been interpreted as either a 15 km-radius satellite or a dense, sharp-edged arc orbiting at about 5600-5900 km. Here, we investigate both scenarios through numerical integrations that include Quaoar, its triaxial shape, and Weywot. If the feature is a satellite, stability maps show that it acquires a forced eccentricity of about 0.002 and has only a minor dynamical effect on the Q1R and Q2R rings. Its main effect is to clear a narrow region around its orbit, associated with the overlap of mean-motion resonances, preventing the long-term survival of kilometre-scale moons within approximately one Quaoar radius of the satellite. If instead the feature is an arc, we test confinement around the triangular
equilibrium point of an unseen coorbital satellite. While azimuthal confinement is readily obtained for satellites with satellite-to-primary mass ratios up to 0.001, Weywot's secular perturbation induces large radial excursions in the arc particles, preventing reproduction of the observed radial extent. The required radial confinement is achieved only for confiners comparable to or more massive than Weywot, which would likely be detectable by direct imaging. We therefore disfavour triangular-point confinement as an explanation for a long-lived dense arc and argue that the feature is more dynamically consistent with a satellite. We identify broad stable zones where additional undetected moons could reside, including near the rings as possible shepherd moons. Furthermore, Quaoar's ellipticity alone is sufficient to induce non-resonant orbital excitation capable of preventing ring coagulation, an effect that may be enhanced by small moons near the rings.
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All authors Gustavo Madeira, Leandro Esteves, Bruno E. Morgado, Paulo V. S. Soares, Silvia M. Giuliatti Winter, Othon C. Winter, Bruno S. Chagas
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Primordial Black Holes: A Review of Formation and Evolution
S. Shankaranarayanan, Soumya Bhattacharya and Archit Vidyarthi
Primordial Black Holes (PBHs) have emerged as a leading non-particulate candidate for dark matter and a unique cosmological probe, a paradigm shift accelerated by the detection of anomalous binary mergers by the LIGO-Virgo-KAGRA (LVK) collaboration. While the literature is rich with phenomenological constraints, the fundamental
quantum and relativistic underpinnings governing PBH genesis and
evolution often receive comparatively less emphasis. This review aims to bridge that gap by systematically detailing the physics of PBH formation and their subsequent evolutionary trajectory. We critically examine the hydrodynamic complexity of the early universe, establishing the relativistic thresholds for collapse, the non-linear race against sound in the
primordial plasma, and the rigorous mathematical utility of the compaction function. Furthermore, by incorporating the dynamic nature of FLRW backgrounds, higher
curvature corrections, and
quantum backreaction via the
memory burden effect, we challenge the standard hawking evaporation and show that extreme-
curvature environments halt evaporation entirely, leaving Planck-scale relics that evade current extragalactic bounds. Finally, we map the multimessenger observational landscape, highlighting how the imminent search for sub-
solar mass inspirals by next-generation gravitational wave observatories such as the Einstein
Telescope and
Cosmic Explorer could yield smoking-gun evidence for the PBH paradigm, ultimately transforming these
primordial relics into unparalleled laboratories for high-energy physics.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.LG
The Degeneracy Distillery
T. Lucas Makinen, Deaglan J. Bartlett, Niall Jeffrey et al. (+1 more)
When two or more parameters or labels produce similar data, they are degenerate, or hard to distinguish. Degeneracies render both label prediction and inverse problems difficult, since both machine learning
algorithms and probabilistic samplers rely on the distinguishability of data and its gradients with respect to parameters. However, identifying degeneracies in physical models or real-world
datasets can be elucidating about the choice of model or the underlying process that produces the data. We present the degeneracy distillery, a method that (1) detects and (2) resolves degenerate parameter combinations (a) automatically and (b) symbolically, from parameter-data (or parameter-simulation) pairs alone, through estimation and flattening of the Fisher information
matrix. By exploring the information geometry of the likelihood, we characterize degeneracies as an intrinsic property of the physical model, requiring no realised data observation. We demonstrate our approach on a range of synthetic and real-world problems, discovering symbolic coordinate transformations that identify the combinations of parameters of a model which yield independent effects on the data. The resulting coordinates flatten the Fisher information in expectation globally, in contrast to posterior-based methods that flatten only at a single point, and substantially reduce the simulation budget required for downstream neural posterior estimation. In test cases we require up to $10\times$ fewer simulations for posterior estimation at matched validation calibration whilst simultaneously gaining physical insight on the system.
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All authors T. Lucas Makinen, Deaglan J. Bartlett, Niall Jeffrey, Benjamin D. Wandelt
Earth and Planetary Astrophysics
Photochemical Production of CS2 in Temperate-to-Warm Gas Giant Exoplanet Atmospheres
Jeehyun Yang, Vighnesh Nagpal, Michael Zhang et al. (+16 more)
Sulfur chemistry has emerged as an important probe of
exoplanet atmospheres in the JWST era, although observational constraints have thus far been largely limited to SO2 and H2S in warm and hot
exoplanets. Recent JWST observations have revealed CS2 in several cooler gas-
giant exoplanets, yielding a new tracer of sulfur chemistry. However, the detailed chemical pathways responsible for the formation of CS2 remain poorly understood. Here, we use TOI-6894 b, a temperate gas
giant with evidence for CS2, as a test case for one-dimensional photochemical kinetic-transport modeling and sensitivity analyses of CS2 chemistry. We show that CS2 is produced through coupled thermochemical and photochemical processes involving CH4 and H2S as the primary carbon and sulfur reservoirs, with S2 photolysis driving disequilibrium sulfur chemistry. Our models provide a physically consistent explanation for the observed CS2 feature in TOI-6894 b. Extending our analysis to gas
giant exoplanets spanning a wide range of Teq, we find that CS2 abundance peaks in temperate to warm atmospheres (Teq ~ 500 - 700 K), and declines toward both lower and higher temperatures. This temperature dependence provides a unified framework for interpreting current CS2 observations, accounting for reported detections in temperate to warm
planets and the lack of detections in colder and hotter
giant exoplanets. Our results establish CS2 as a complementary probe of sulfur inventories and atmospheric
metallicity in cool gas
giant exoplanets
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All authors Jeehyun Yang, Vighnesh Nagpal, Michael Zhang, Qiao Xue, Eliza M.-R. Kempton, Jacob L. Bean, Michael R. Line, Jonathan J. Fortney, Peter Gao, Matthew C. Nixon, Caroline Piaulet-Ghorayeb, Kevin B. Stevenson, Madison Brady, Joost P. Wardenier, Luis Welbanks, Jean-Michel Désert, Guangwei Fu, Vivien Parmentier, Diana Powell
Solar and Stellar Astrophysics
Calibrating angular momentum transport in intermediate-mass stars from gravity-mode asteroseismology. II. Modelling 2937 BAF-type stars
J. S. G. Mombarg and S. Mathis
Asteroseismology of
gravity (g)-mode pulsators covering BAF-type
stars have shown that angular momentum is redistributed during the main sequence. The efficiency of the transport, however, remains largely uncalibrated. This paper aims at exploiting a sample of 2937 characterized g-mode pulsators (the largest one to-date) to place constraints on the efficiency of angular momentum transport by assuming an effective viscosity or an Eddy-viscosity based on the Tayler-Spruit dynamo within a fully-diffusive framework. We compute grids of rotating
stellar evolution models that we then use to simulate a population of
stars by sampling from these grids with prior distributions on the mass, age and initial rotation rate. We then compare these simulated distributions of rotation frequencies and specific angular momentum ($J/M$) to the ones of the sample of observed
stars. We find that a fully-diffusive framework for the transport of angular momentum during the main sequence is sufficient to explain the observed
evolution of near-core rotation frequencies, the observed differential rotation, and the observed mass-dependence of $J/M$ when the effective viscosity (assumed constant) is $10^6\,{\rm cm^2\,{\rm s^{-1}}}$ or larger. Viscosities predicted by the Tayler-Spruit dynamo are in general far above this value and can explain the data as well. Future observational studies of main sequence g-mode pulsators are encouraged to measure core-to-surface rotation rates, particularly of B-type
stars. In this work we have exploited the constraining potential of near-core rotation frequencies alone, while the contrast with the surface rotation would allow us to unravel the mechanisms driving the transport further.
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High Energy Astrophysical Phenomena
Composition of Radiation-Driven Winds from Type I X-ray Bursts
Jason S. Pero and Nevin N. Weinberg
Recent NICER observations of photospheric radius expansion (PRE) X-ray bursts reveal absorption features consistent with photospheres enriched in intermediate-mass elements. These features may arise from radiation-driven winds that eject freshly synthesized
nuclear ashes, offering a new probe of X-ray bursts and
neutron star properties. Motivated by these observations, we use the MESA
stellar evolution code to simulate PRE bursts from
accretion through the hydrodynamic wind phase. We model a range of ignition depths for both pure helium and mixed hydrogen/helium
accretion and explore several prescriptions for convection during burst rise. We find that the wind abundances depend sensitively on both ignition depth and convective treatment, including the efficiency of semiconvective mixing and the prescription used to define convective boundaries. Bursts igniting at column depths greater than or equal to 5 x 10^8 g cm^-2 produce ash-enriched winds, with ejecta ranging from intermediate-mass to iron-peak elements depending on ignition depth,
accretion composition, and the treatment of convection.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
A thorough investigation of cross-correlation estimators for stochastic gravitational-wave background searches in ground-based detector data
Haowen Zhong, Joseph D. Romano, Vuk Mandic et al. (+2 more)
Detecting a
stochastic gravitational-wave background represents a crucial yet challenging objective within the field of gravitational-wave astronomy. Ground-based detectors currently rely almost exclusively on cross-correlation methods to detect
stochastic gravitational-wave background signals. Traditionally, these methods define and optimize a broadband
estimator initially constructed in the time domain. However, a growing number of analyses require precise narrowband
estimators to accurately characterize the energy density of the underlying signal in specific frequency bins. Transitioning from time-domain broadband
estimators to frequency-domain narrowband
estimators introduces significant complexities that have not yet been fully explored in the existing literature. In this study, we systematically revisit and rigorously reformulate the cross-correlation method in the frequency domain, explicitly addressing and resolving issues related to non-zero covariances induced by windowing and overlapping of data in the time domain. We provide new expressions for the narrowband
estimators and their covariances, which differ from those used in past searches. Fortunately, we show that the expressions that have been widely used in the field nonetheless lead to correct posterior distributions for parameter estimation and correct log-Bayes factors for model selection. By establishing a robust theoretical framework, our work facilitates more accurate and physically insightful interpretations of
stochastic gravitational-wave background observations, laying an essential foundation for current and future research in this field.
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All authors Haowen Zhong, Joseph D. Romano, Vuk Mandic, Shivaraj Kandhasamy, Arianna I. Renzini
Earth and Planetary Astrophysics
Interpreting the scattering surface in protoplanetary disks
Massimiliano Bolchini, Giovanni Rosotti, Marion Villenave et al. (+5 more)
In recent years, extreme adaptive optics have enabled high-resolution, high-contrast scattered-light observations of protoplanetary disks. Interpreting these observations requires an understanding of the scattering surface, which is shaped by the distribution of small
dust grains and determines how disks appear in scattered light. We aim to exploit measurements of the scattering surface height to directly constrain the masses of small
dust grains in disks. Starting from radiative transfer principles, we developed a semi-analytical model of the
stellar radiation path and its interaction with the disk, deriving the height of the scattering surface as a function of disk parameters such as mass, temperature, and opacity. We validated our predictions against the radiative transfer code MCFOST. Using measured scattering heights, we inferred the mass of
dust in small grains and the particle size distribution for a sample of ten disks. We confirm previous results indicating that the scattering surface coincides with the region where the integrated optical depth along the
stellar path is of order unity. The thermal structure of the disk significantly affects the surface height, while
dust settling and anisotropic scattering have comparatively minor effects. Applying our model to observations, we measure global small-
dust mass fractions of order (10^{-3}). Using
dust-opacity models, we show that these values are consistent with modest grain growth ((a_max \gtrsim 0.1,mm)) and grain-size distribution power-law indices of approximately 3–3.5, as commonly predicted by grain-growth models. Scattering-surface measurements, together with constraints on the disk thermal structure, provide a powerful method for determining the small-
dust content of protoplanetary disks.
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All authors Massimiliano Bolchini, Giovanni Rosotti, Marion Villenave, Antonio Garufi, Myriam Benisty, Tilman Birnstiel, Stefano Facchini, Leonardo Testi
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Nuclei in high-energy neutrino sources: A multimessenger study of in-source propagation
AmirFarzan Esmaeili, Arman Esmaili and Pasquale Dario Serpico
The joint observation of astrophysical sources in gamma rays and
neutrinos can provide invaluable insight into the physical conditions of the source, including its size, particle densities, and acceleration and production mechanisms. In this work, we investigate the role of
nuclear composition in high-energy astrophysical environments. Using NGC 1068 as a representative example, we perform detailed Monte Carlo simulations of
nuclear and electromagnetic cascades within the source and study the imprints of the injected
nuclear composition on the resulting
neutrino and gamma-ray emissions. We further discuss the importance of MeV-GeV gamma-ray observations for constraining the source composition in the context of future gamma-ray experiments. A dedicated re-analysis of archival COMPTEL observations is also presented.
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Astrophysics of Galaxies
First measurement of narrow-line flux ratios for a lensed quasar with JWST/NIRSpec IFS
Hadrien Paugnat, Tommaso Treu, Anna M. Nierenberg et al. (+3 more)
Strong gravitational
lensing is a powerful probe of dark matter (DM) structure on subgalactic scales: in particular, statistics of flux-ratio anomalies (discrepancies between mass model predictions and observed flux ratios) in quadruply imaged
quasars are sensitive to perturbations by low-mass DM
halos down to $\sim 10^6 M_\odot$. Studies leveraging these anomalies require high-quality flux-ratio measurements from an emission region insensitive to
stellar microlensing. In this paper, we present the first measurement of narrow-line flux ratios for a gravitationally lensed
quasar using JWST/NIRSpec with Integral Field Spectroscopy (IFS), targeting the well-studied system RXJ1131$-$1231. Flux ratios are extracted from the [S III] 9071/9533 $\r{A}$ narrow-line doublet - the first use of this doublet for substructure studies - by performing a full lens model reconstruction to isolate the unresolved
nuclear emission from extended narrow-line emission. The resulting spectra are jointly modeled using $\texttt{lensqso-specfit}$, a publicly available software package introduced in this work for the simultaneous spectral fitting of multiple lensed
quasar images. We achieve $\sim$ 5% uncertainties on the flux ratios, comparable to the precision of JWST/MIRI warm
dust measurements, and detect a clear anomaly in the cusp images relative to a standard smooth lens model. Our results are in good agreement with previous narrow-line measurements and broadly consistent with JWST/MIRI warm
dust flux ratios, with marginal ($\sim 2-3\sigma$) deviations. We demonstrate how such shifts between differently sized emission regions may be enhanced by small ($\sim 10$ pc) spatial offsets. Our method is generalizable to other systems with existing or future IFS observations, and the combination of narrow-line and warm
dust flux ratios offers a new avenue for improving DM constraints with flux-ratio anomaly statistics.
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All authors Hadrien Paugnat, Tommaso Treu, Anna M. Nierenberg, Anowar J. Shajib, Shawn Knabel, Daniel Gilman
Astrophysics of Galaxies
Characterising magnetic fields at the onset of star cluster formation: From giant molecular clouds to infrared dark clumps
Ria Ramkumar, Nicolas Peretto, Gary A. Fuller et al. (+2 more)
The role of
magnetic fields in the observed inefficiency of
star formation in
Galactic molecular clouds is a widely debated topic, with the past decade seeing an explosion of observational characterisation of
magnetic fields in
star-forming regions. However, few have studied the spatial
evolution of
magnetic fields from entire molecular clouds down to parsec-size cluster-forming clumps. In this work, the plane-of-sky morphology of the
magnetic fields of eight infrared dark clumps and their parent molecular clouds are derived from Planck and JCMT POL-2 polarisation data (including some from the BISTRO survey). We also use this data to test multiple methods of calculating B-field strengths. Our study shows that the morphologies of
magnetic fields in clumps and their parent molecular clouds systematically, and significantly, differ, supported by a line-of-sight correction of the cloud-scale
magnetic fields using the velocity gradient technique. We find a strong correlation between gas velocity dispersion and the
alignment of
magnetic field lines with column density gradients from scales of tens of parsecs to a few parsecs. This correlation is clear evidence of a link between the kinematic properties of the gas and the dynamical importance of
magnetic fields. Conversely, the higher
magnetic field strengths we measure on cloud scale compared to clump scale contradict
magnetic flux conservation and thus highlight the unreliability of such measurements. Altogether, our analysis supports a picture in which
magnetic fields have little impact on the dynamical
evolution of cluster-forming clumps but do play a role in providing support on larger scales.
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All authors Ria Ramkumar, Nicolas Peretto, Gary A. Fuller, Patrick M. Koch, Ya-Wen Tang
Earth and Planetary Astrophysics
Direct Imaging Discovery of Giant Exoplanet $\beta$ Pictoris d: A Decade-Long Game of Hide-and-Seek
Ben J. Sutlieff, Markus J. Bonse, Valentin Christiaens et al. (+94 more)
We report the direct imaging discovery of a third
exoplanet in the $\beta$ Pictoris system. We detect $\beta$ Pictoris d ($\beta$ Pic d) in non-coronagraphic observations obtained with VLT/ERIS as well as multi-epoch archival
datasets from JWST/NIRCam and VLT/SPHERE. Astrometric measurements over an 11-year baseline demonstrate that it is consistent with a gravitationally-bound source with orbital motion. Joint multi-
planet orbit fits of all three
planets in the system yield a semi-major axis of $26.0^{+2.2}_{-6.1}$ au and inclination $89.0^{+0.7}_{-0.6}$ deg for
planet d. $\beta$ Pic d has a larger orbital semi-major axis than the other known
planets in the system, but is coplanar with the inner two
planets, and its orbit is consistent with sculpting the inner edge of the debris disk. $\beta$ Pic d has a contrast of $\Delta L^{\prime}=12.11\pm0.15$ mag, with colors and luminosity that closely match those of 51 Eri b, another
exoplanet in the $\beta$ Pictoris moving group. Its VLT/ERIS and JWST/NIRCam colors are distinct from those of free-floating planetary-mass objects of a similar age and temperature. Its red $F410M-F444W$ color indicates strong CO$_2$ absorption in its atmosphere and suggests significant enhancement in metals compared to free-floating objects. From the ATMO hot-start evolutionary models, we estimate an effective temperature of $600^{+45}_{-60}$ K and mass of $2.4\pm0.6$ $M_{\rm Jup}$, which also closely matches similar estimates for 51 Eri b. $\beta$ Pic d is among the lowest-mass
exoplanets imaged from the ground. This discovery highlights the deep sensitivity achievable with ground-based imaging in the mid-infrared and the discovery potential of future high-contrast observations with the Extremely Large
Telescope.
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All authors Ben J. Sutlieff, Markus J. Bonse, Valentin Christiaens, Clémence Fontanive, Elisabeth C. Matthews, Luke T. Parker, Tim D. Pearce, Jayne L. Birkby, Beth A. Biller, Trent J. Dupuy, Emily O. Garvin, Leyla Iskandarli, Jens Kammerer, Yifan Zhou, Robert J. De Rosa, Aarynn L. Carter, Sasha Hinkley, Matthew A. Kenworthy, William O. Balmer, Iain Hammond, James Mang, Caroline V. Morley, Mark J. Neeser, Olivier Absil, Anthony Boccaletti, Mariangela Bonavita, Brendan P. Bowler, Xueqing Chen, Felix A. Dannert, Julien H. Girard, Markus Kasper, Anne-Marie Lagrange, Pengyu Liu, Gilles Orban de Xivry, Michael Poon, Sascha P. Quanz, Benoît Serra, Johanna M. Vos, Kevin Wagner, Jason Wang, Bernhard Schölkopf, Guido Agapito, Alex Agudo Berbel, Dániel Apai, Andrea Baruffolo, Martin Black, Marco Bonaglia, Runa Briguglio, Yixian Cao, Luca Carbonaro, Lee Chapman, Giovanni Cresci, Yigit Dallilar, Richard Davies, Matthias Deysenroth, Ivan Di Antonio, Amico Di Cianno, Gianluca Di Rico, David Doelman, Mauro Dolci, Frank Eisenhauer, Simone Esposito, Debora Ferruzzi, Helmut Feuchtgruber, Natascha Förster-Schreiber, Kyle Franson, Reinhard Genzel, Stefan Gillessen, Eileen C. Gonzales, Michael Hartl, Jean Hayoz, Heinrich Huber, Christoph Keller, Kateryna Kravchenko, Jarron Leisenring, John Lightfoot, David Lunney, Dieter Lutz, Mike Macintosh, Filippo Mannucci, Stanimir Metchev, Thomas Ott, David Pearson, Alfio Puglisi, Sebastian Rabien, Christian Rau, Armando Riccardi, Bernardo Salasnich, Taro Shimizu, Frans Snik, Eckhard Sturm, Genaro Suárez, Linda Tacconi, Xianyu Tan, William Taylor, Christopher Waring, Marco Xompero
Astrophysics of Galaxies
The PICO-Cluster Project: presenting the galaxy cluster sample and studying magnetic field growth, Faraday rotation and Braginskii heating
Thomas Berlok, Christoph Pfrommer, Ewald Puchwein et al. (+9 more)
Galaxy clusters constitute a microcosm of the Universe and offer a unique laboratory for studying
plasma astrophysics, encompassing processes such as
cosmic-ray acceleration and non-thermal
radio emission,
turbulence, weakly collisional
plasma physics, and transformative mechanisms in
galaxy evolution. To investigate these phenomena, we introduce the PICO-Cluster project, studying '
Plasmas In COsmological Clusters' using a suite of high-resolution cosmological zoom-in simulations of massive
galaxy clusters with masses $\gtrsim10^{15}$M$_\odot$ selected from a parent simulation box with a comoving side length of 1 $h^{-1}$Gpc. In this work, we present 24 baseline simulations performed with the moving-mesh AREPO code and the IllustrisTNG
galaxy formation model, achieving a baryonic mass resolution of up to $1.4\times10^{6}\mathrm{M}_\odot$. The initial conditions are carefully designed to exclude low-resolution particle contamination within the high-resolution region; as a result, all clusters remain free of such contamination out to at least 2.7 $R_{200}$ at all times. Our
galaxy and cluster properties agree with recent simulations and many observational constraints, including scaling relations and thermodynamic profiles. The
magnetic energy within the cluster is numerically converged once the small-scale dynamo has saturated, yielding a remarkably tight volume-averaged
plasma-beta of $\beta\approx100$ inside $R_{200}$ across our sample after
redshift $z\sim1.2$. Faraday rotation measure profiles, which trace the line-of-sight
magnetic field and electron density, decline with cylindrical radius; notably, the mean decreases more rapidly than the root-mean-square due to the increasing relative contribution of
galaxies at larger radii. Finally, viscous heating rates in Braginskii theory are highly intermittent and, on average, approach radiative cooling rates in the cluster outskirts.
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All authors Thomas Berlok, Christoph Pfrommer, Ewald Puchwein, Rosie Talbot, Rüdiger Pakmor, Lorenzo Perrone, Rainer Weinberger, Volker Springel, Joseph Whittingham, Larissa Tevlin, Niklas Dusch, Martin Sparre
Earth and Planetary Astrophysics
MINDS: Complementary inclinations in the binary system HK Tau reveal gas- and ice-phase chemistry
Alice Somigliana, Giulia Perotti, Nicolás T. Kurtovic et al. (+18 more)
[Abridged] HK Tau is a roughly equal mass pre-main sequence binary system consisting of a low-inclination primary (57 deg) and an edge-on (83 deg) secondary. We present JWST/MIRI observations targeting both sources, taken as part of the JWST GTO program MINDS. The spectra reveal a line-rich, CO2-dominated primary and a line-poor secondary; this evidence, albeit in line with the evolutionary-motivated trend uncovered by recent observations of binaries at MIRI wavelengths, is likely due to the different configuration of the two sources. Indeed, thermochemical disc models coupled with radiative transfer show that, at inclinations comparable to that of HK Tau B, only ionised atomic lines are expected to remain visible in the spectra. While blocking molecular emission lines, however, the edge-on configuration allows ice absorption bands to be visible against the continuum; in this framework, the HK Tau system provides an unprecedented opportunity to have a simultaneous view of the solid and gaseous component of a pair of coeval protoplanetary discs, thanks to the complementary inclination of the two sources. We detect water ice at 6.2 and 13.6um, CO2 ice at 15.2um, and NH4+ ice at 6.85um in the spectrum of HK Tau B; an additional absorption band between 8.3 and 9um is compatible with both silicate stretching and C-H bending. Neither of the two sources show signs of PAHs. Extended H2 emission is present around both discs, although much more elongated in HK Tau B. The distinctive 'X' shape centred in B, combined with the intensity, morphology, and spectral characteristics of the ionised atomic lines [Ar II], [Ne II], and [Ne III] suggests a low-velocity wind origin with a wide (~ 70 deg) semi-opening angle. The lower forbidden line fluxes and smaller extent of the H2 emission around A imply that, if a wind is launched from the primary as well, it is too cold or dense to be ionised.
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All authors Alice Somigliana, Giulia Perotti, Nicolás T. Kurtovic, Thomas Henning, Myriam Benisty, Andrew D. Sellek, Melissa McClure, Zak L. Smith, Aditya M. Arabhavi, Alessio Caratti o Garatti, Valentin Christiaens, Ewine F. van Dishoeck, Danny Gasman, Sierra L. Grant, Manuel Güdel, Till Kaeufer, Inga Kamp, Lucas Stapper, Benoît Tabone, Milou Temmink, Marissa Vlasblom
Astrophysics of Galaxies
Discovery of a Barred-Spiral Galaxy at $z_{spec}$ = 3.16 II. The Star Formation History
Yingjie Cheng, Mauro Giavalisco, Daniel Ivanov et al. (+6 more)
We present a detailed analysis of a massive barred
galaxy at $z_{spec}=3.1591$ using deep multi-band imaging from HST and JWST. For the first time, we resolve its morphology and
stellar structures thanks to the JWST/NIRCam NIR and MIR photometry. The
galaxy possesses two distinct components with significantly different colors. Through careful image decomposition and masking, we isolate and characterize the flux contribution from each component. The
galaxy exhibits a clear spiral morphology, and in a separate companion paper, we present evidence suggesting the presence of a
stellar bar. Based on spatially resolved spectral energy distribution modeling with Prospector, we derive the
star formation history and other physical properties of the bar and the surrounding regions. The total
stellar mass of the
galaxy is constrained as $\log(M_*/M_{\odot}) = 10.63\pm0.13$. We find that the bar region contains around 30% of the total
stellar mass, but only accounts for around 8% of the recent
star formation rate. The region containing the potential bar shows a significantly older mass-weighted
stellar age, supporting the inside-out scenario for
galaxy formation, and providing tentative evidence for bar quenching in the early stage. The quick onset of a
stellar bar at this
redshift requires a low dark matter fraction, suggesting the
baryon-dominated nature of high-$z$ massive
galaxies, and offering rare insight into
galaxy evolution at around two billion years after the Big Bang.
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All authors Yingjie Cheng, Mauro Giavalisco, Daniel Ivanov, Luca Costantin, Elena D'Onghia, Yuchen Guo, Shardha Jogee, John R. Weaver, Katherine E. Whitaker
Astrophysics of Galaxies
Discovery of a Barred-Spiral Galaxy at $z_{spec}$ = 3.16 I: Bar Identification and Properties
Daniel Ivanov, Mauro Giavalisco, Yingjie Cheng et al. (+6 more)
The formation of
stellar bars is an important milestone in the secular
evolution of spiral
galaxies, which typically indicates the presence of a massive rotationally supported disk. Determining when these structures first appeared in the early universe is crucial to constraining the timeline of
galactic disk assembly. Here, we report the discovery of COSMOS-74706, a barred spiral
galaxy at $z_{spec} = 3.159$. Imaging of COSMOS-74706 with JWST/NIRCam indicates a disk-like morphology and spiral structure with an elongated central feature aligned between the spiral arms, most conspicuously visible in the F200W, F277W, and F356W filters. Three independent methods all support the presence of a bar: visual inspection of residuals from Sérsic-profile fitting shows a linear structure, isophotal ellipse-fitting displays characteristic profiles of ellipticity and position angle consistent with a bar signature, and
Fourier decomposition of the
galaxy produces a central bisymmetric mode above a threshold strength calibrated to $z=1-3$ barred spirals. Leveraging archival Keck/MOSDEF spectroscopy overlapping with a blue clump on the edge of the
galaxy, a robust
redshift is inferred, with photometric constraints indicating that this structure lies at the same
redshift as the main spiral. This spectroscopic evidence, placing an unlensed barred spiral at $z>3$ supports the idea that
galaxies with rotationally supported disks and disk-
halo properties that are conducive to bar formation were already in place within 2 Gyr after the Big Bang.
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All authors Daniel Ivanov, Mauro Giavalisco, Yingjie Cheng, Yuchen Guo, Luca Costantin, Elena D'Onghia, John R. Weaver, Shardha Jogee, Katherine E. Whitaker
Astrophysics of Galaxies
Anisotropic quenching beyond $z=1$ and its implications for preprocessing around high-redshift galaxy clusters
Makoto Ando, Kazuhiro Shimasaku, Kei Ito et al. (+2 more)
Recent studies have shown that, within
galaxy clusters, quenched satellite
galaxies tend to be distributed preferentially along the major axis of the central
galaxy, dubbed anisotropic quenching. There are various discussions about the origin of this anisotropy: some link it to active
galactic nucleus activity in the central
galaxy, while others attribute it to the preprocessing of
galaxies within large-scale structures outside clusters. However, the definitive cause and its
redshift dependence remain unclear. In this study, we investigate anisotropic quenching with 12 spectroscopically confirmed
galaxy clusters at $0.9<z<1.4$. We calculate the quiescent satellite
galaxy fraction as a function of orientation angle measured from the central
galaxy's major axis. Although the statistical significance is modest ($\sim 2\sigma$), we detect anisotropic quenching in the highest
redshift ever. To understand the origin of the observed anisotropy, we examine the
accretion history of satellite
galaxies in a cosmological simulation. We find that, in the $z=1.25$ clusters, the majority of satellite
galaxies are recently ($\lesssim 2\,\mathrm{Gyr}$) infalled
galaxies. In addition, the orientation angles of satellites are randomized immediately after
accretion in $\sim 2\,\mathrm{Gyr}$, suggesting that only recently accreted
galaxies contribute to the observed anisotropy. We adopt a semi-analytic approach that combines the
accretion history of satellite
galaxies with a quenching model based on a delay-then-rapid quenching framework and parameterizes both intrahalo quenching and preprocessing effects. We find that preprocessing is the dominant contributor to quenching and that the quenched fraction attributable to preprocessing is higher along the major axis than along the minor axis by $\sim20\%$, reproducing the observed anisotropic quenching signal.
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All authors Makoto Ando, Kazuhiro Shimasaku, Kei Ito, Takumi S. Tanaka, Suin Matsui