Cosmology and Nongalactic Astrophysics
Quantifying the systematic impact of differential beam response on the BICEP CMB polarization data from 2016 through 2024
B. D. Elwood, P. A. R. Ade, Z. Ahmed et al. (+83 more)
As
cosmic microwave background (CMB) polarization experiments, including BICEP3, BICEP Array, and future BICEP experiments, achieve ever-deeper polarization maps in search of primordial B-modes sourced from inflation, constraining instrumental systematics below statistical uncertainties becomes progressively more challenging. Since polarimetry in the BICEP
telescopes is performed by pair-differencing co-located, orthogonally polarized detectors, differential beam response leads to temperature-to-polarization ($T \rightarrow P$) leakage, introducing a potential systematic bias on the inferred tensor-to-scalar ratio $r$. To mitigate this leakage, the lowest-order beam mismatch modes are filtered out of the CMB polarization maps through deprojection; however, residual undeprojected modes remain. To quantify this residual contamination, we perform dedicated in situ far-field beam measurements of the BICEP receivers during austral-summer calibration campaigns. We quantify the systematic impact of the undeprojected residuals with a specialized set of timestream simulations based on the measured per-detector beams. These "beam measurement-informed simulations" yield an estimate of the false polarized signal sourced by the undeprojected residuals. We summarize the beam measurements relevant to the BK24 data release and present preliminary residual-leakage results for BICEP3 at 95 GHz. For BICEP3 over 2016-2024, deprojecting all six standard templates together with readout-crosstalk templates and their radially smoothed counterparts reduces the equivalent-$r$ leakage amplitude from $\rho=(4.5\pm0.7)\times10^{-3}$ to $(1.12\pm0.06)\times10^{-3}$. We further describe an ongoing program to extend the deprojection basis beyond its historical six modes, guided by a forward optical model that relates candidate leakage modes to perturbations of physical instrument parameters.
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All authors B. D. Elwood, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Instrumentation and Methods for Astrophysics
Status of BICEP Array and Integration of the 220/270 GHz Receiver
A. Steiger, P. A. R. Ade, Z. Ahmed et al. (+83 more)
Measurements of the polarization of the
cosmic microwave background are critical for modern cosmology as they constrain the physics of the early universe and
cosmic inflation. BICEP Array is using a series of small-aperture polarimeters located at the South Pole to measure this signal with a projected uncertainty on the tensor-to-scalar ratio r of approximately 0.001 by 2034. The 30/40 GHz receiver and the 150 GHz receiver have been observing the
cosmic microwave background for multiple years, and data from these receivers will be included in the next published BICEP analysis result which includes all data taken through 2024. The 220/270 GHz receiver is partially completed with seven out of twelve detector modules installed, and is planned to be filled with five additional modules prior to the 2027 observation season. Finishing this receiver is a top priority for BA as the science goals of the experiment require the dust foreground cleaning this receiver will enable. On-site characterization efforts for this receiver from the 2025-26 austral summer show satisfactory spectroscopy, beam pointing, and 220 GHz efficiency, while the 270 GHz efficiency is an active area of work.
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All authors A. Steiger, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, G. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Instrumentation and Methods for Astrophysics
Optics and broadband anti-reflection coatings for the BA4-90/150 receiver
A. R. Polish, P. A. R. Ade, Z. Ahmed et al. (+84 more)
The BICEP Array
telescopes search for primordial B-mode polarization from inflationary gravitational waves. This signal is exceedingly faint, demanding excellent map depth and systematics control. The new BA4-90/150 receiver introduces a wide 80-169GHz dichroic band, requiring upgrades throughout the optics chain to reduce loss, reflections, and thermal loading. We developed improved anti-reflection (AR) coatings for our HMPE window, HDPE lenses, and nylon infrared filter, extending our AR technology to span more than an octave of bandwidth. The thermal filtering scheme and several mechanical elements were also updated to further suppress optical loss, reflections, and beam truncation. We aim to build on the proven success of deployed BICEP Array (BA)
telescopes to produce a new small aperture instrument with the lowest optical systematics to date.
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All authors A. R. Polish, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, T. Prouve, C. Pryke, C. D. Reintsema, P. J. Rioles, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Instrumentation and Methods for Astrophysics
Advanced Time-Division Multiplexed Readout Chain for the BICEP Array 90/150 GHz Receiver
B. Cantrall, P. A. R. Ade, Z. Ahmed et al. (+89 more)
This work presents the current performance of the advanced time-division multiplexed (TDM) readout chain for the BICEP Array 90/150 GHz receiver. BA4-90/150, scheduled for deployment to the South Pole in 2026–27, will use
photon-noise-limited, feedhorn-coupled transition edge sensor detectors and an upgraded DC SQUID-based TDM system to map the
cosmic microwave background. This new TDM system mitigates readout-induced systematics that are beginning to emerge above the noise floor of the most sensitive maps produced by the BICEP collaboration. Improvements include faster, fully differential SQUID designs, higher TES signal amplification, reduced crosstalk, and hierarchical row-addressing that reduces wiring required for row switching. Measurements made through legacy single-ended warm readout electronics show the upgraded cryogenic readout chain performs as well as or better than the TDM system currently fielded on the BICEP experiment. New warm electronics currently in development at SLAC National Accelerator Laboratory will provide matched fully differential
circuits and higher bandwidth, reducing RF susceptibility and aliased noise contributions. On-sky demonstration of this technology will establish a new low-noise, high-bandwidth TDM architecture for future CMB observatories.
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All authors B. Cantrall, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, W. B. Doriese, L. Duband, M. Durkin, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, J. Gard, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, G. Haller, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, L. Sapozhnikov, A. Schillaci, B. Schmitt, R. Shi, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Instrumentation and Methods for Astrophysics
Optical characterization of the BICEP array 150 and 220/270GHz CMB polarimeters in the 2026 season
M. Izquierdo Poza, P. A. R. Ade, Z. Ahmed et al. (+83 more)
BICEP Array (BA) is the current-generation instrument in the BICEP series of small-aperture, on-axis refracting
telescopes at the South Pole, designed to constrain the tensor-to-scalar ratio $r$ through degree-scale measurements of B-mode polarization in the
cosmic microwave background (CMB). As BA pushes to deeper sensitivity, control of instrumental systematics, and beam shape mismatch between the co-located orthogonally polarized detectors in particular, has become an increasingly important factor in translating raw sensitivity into a robust constraint on $r$. In these proceedings we report on the 2026 far field beam mapping (FFBM) campaign, which used a thermal chopped source to characterize the BA2 (150~GHz) and BA3 (220/270~GHz) beams. We fit two-dimensional elliptical Gaussians to each detector's beam, derive per-pair differential parameters (differential pointing, beamwidth, and ellipticity). The resulting high-signal-to-noise array-averaged beam maps are used to compute the beam window function $B_l$ for the power spectrum analysis, while the individual per-detector beams feed dedicated beam convolution simulations used to validate the temperature-to-polarization (T$\rightarrow$ P) deprojection procedure. After correcting for the chopper aperture, the recovered beamwidths follow the expected $\lambda/D$ ordering. We also describe two pipeline improvements carried out during the 2026 campaign: an out-and-back jackknife for noise quantification and an elnod-based gain calibration.
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All authors M. Izquierdo Poza, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Cosmology and Nongalactic Astrophysics · Cross-listed from physics.ins-det
Aliased noise characterization and mitigation in BICEP Array 150, 220 and 270 GHz time-division multiplexed detectors
S. Fatigoni, P. A. R. Ade, Z. Ahmed et al. (+83 more)
Early observations with the BICEP Array 150 GHz (BA2-150) and 220/270 GHz (BA3-220/270) receivers revealed detector noise equivalent temperatures (NETs) higher than expected, together with substantial detector-to-detector and module-to-module scatter. Noise measurements acquired with multiplexing off and high frequency sampling demonstrate that this excess originates from elevated high-frequency detector noise that aliases into the science band during time-division multiplexing. We show that the excess high-frequency noise is correlated with anomalously large logarithmic TES transition slopes, {\alpha}, resulting in elevated electrothermal loop gain and operation near the detector stability boundary. Measurements of {\alpha} indicate values substantially larger than expected, consistent with the sharper superconducting transitions introduced by the inverted TES fabrication process adopted for BA2-150 and BA3-220/270 detectors. Operational mitigation strategies were investigated through both increased multiplexing rates and elevated focal-plane operating temperatures. Faster multiplexing reduces aliasing by shifting the multiplexing Nyquist frequency beyond the excess noise roll-off, while elevated bath temperatures reduce TES electrical power and loop gain, improving detector stability and reducing NET by approximately 10%. These results demonstrate the importance of balancing TES responsivity, electrothermal stability, and multiplexed readout performance in next-generation CMB polarimeters.
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All authors S. Fatigoni, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Cosmology and Nongalactic Astrophysics
Slowly Rolling on a Quantum Correction
Ido Ben-Dayan, Ayushi Srivastava and Amresh Verma
Recent advances in cosmological measurements such as DESI and ACT may indicate an increase in the preferred value of the spectral tilt $n_s$ such that it disfavors rather popular models such as the
Higgs or Starobinski inflation models. We argue that it actually means that the data is now sensitive enough to
quantum corrections beyond simple tree-level models. Resurrecting the old theme of Coleman-Weinberg effective potential, we analyze the predictions of such models, as well as likelihood analysis, leading to a more established and interesting predictive framework.
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Solar and Stellar Astrophysics
Potsdam Wolf-Rayet stellar atmosphere grids of OB-type stars: I. Spectroscopic temperature diagnostics across metallicity
D. Pauli, H. Todt, W.-R. Hamann et al. (+5 more)
Massive hot
stars are among the major ionizing sources in the Universe. The ionizing flux of a
star strongly depends on its temperature, which is best measured spectroscopically using lines of different ionization stages of the same element. For the quantitative spectral analysis of O-type
stars, helium lines are commonly employed, and for B-type
stars, lines of silicon and magnesium are used. At low
metallicity, many of the diagnostic metal lines disappear. We conduct a systematic theoretical analysis of stellar atmosphere models of OB
stars to study the effect of
metallicity on key temperature diagnostic lines and how this impacts spectral classification. We computed large grids of state-of-the-art non-LTE stellar atmosphere models at four different
metallicities, ranging from solar to 1/31 solar. We presented equivalent widths of selected diagnostic lines in the temperature-
gravity plane and investigated their dependence on
metallicity. Using Galactic stellar templates of O- and B-type
stars, we established equivalent width ratios for spectral classification and applied them to our models. For the hottest
stars in our model grids, He I lines become detectable at lower
metallicity due to the reduced back-warming in the atmosphere, opening new possibilities for their classification. Metal lines used for the analysis of B-type
stars are mostly absent in the spectra of
stars with
metallicity below that of the Small Magellanic Cloud, except Si lines, challenging current classification schemes. Our stellar atmosphere grids reveal that the decrease in
metallicity causes many metal lines to disappear, leaving different sensitivities of He I lines the only temperature indicators for B-type
stars in the optical. The ionizing flux of OB-type
stars can be partially trapped within the stellar wind. As a result, at lower
metallicity, a larger fraction of
stars can emit hard ionizing radiation.
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All authors D. Pauli, H. Todt, W.-R. Hamann, L. M. Oskinova, A. A. C. Sander, T. Shenar, V. Ramachandran, S. Reyero Serantes
Solar and Stellar Astrophysics
Magnetic Heating Across the Sun and Solar-like Stars: Universal Scaling Laws from Chromospheres to Coronae
Shin Toriumi, Kosuke Namekata, Yuta Notsu et al. (+2 more)
Magnetic activity in cool
stars governs the thermal structure and high-energy radiative output of their outer atmospheres, thereby influencing stellar
evolution, stellar winds, and the atmospheres of orbiting (exo)
planets. A long-standing question in stellar astrophysics is whether the mechanisms responsible for atmospheric heating are universal across the Sun and cool
stars spanning different ages and activity levels. In this paper, we review recent progress in understanding
magnetic heating across the Sun and Sun-like
stars through empirical scaling relations between photospheric
magnetic flux and radiative output from the chromosphere, transition region, and corona. Analysis of more than a decade of Sun-as-a-
star observations reveals that irradiance and
magnetic flux follow power-law relationships over a wide temperature range. While coronal emissions exhibit superlinear scaling with
magnetic flux, chromospheric and transition-region diagnostics show weaker, sublinear dependencies. Remarkably, observations of G-type
stars with ages ranging from 50 Myr to 4.5 Gyr are found to lie on extensions of the solar scaling laws, suggesting that a common
magnetic-heating mechanism operates across different levels of stellar activity. We further discuss the application of these scaling relations to reconstructing stellar X-ray and ultraviolet (XUV) spectra from observed
magnetic fluxes. The resulting synthetic spectra reproduce actual observations of young, active solar analogs, providing a practical tool to estimate the ionizing radiation whose extreme UV emissions cannot be directly measured.
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All authors Shin Toriumi, Kosuke Namekata, Yuta Notsu, Mai Yamashita, Vladimir S. Airapetian
Solar and Stellar Astrophysics
Black hole astrometric binaries in the Roman Galactic Bulge Time Domain Survey
Casey Y. Lam, Jessica R. Lu, Kareem El-Badry et al. (+6 more)
The Nancy Grace Roman Space
Telescope (Roman), NASA's next flagship mission, is currently scheduled to launch in August 2026. As part of its mission, Roman will conduct the Galactic Bulge Time Domain Survey (GBTDS), which will generate $\sim$50,000 epochs of high-precision photometric and astrometric data for $\sim 10^8$ sources across 1.7 deg$^2$ in the Galactic Bulge. Roman GBTDS astrometry is comparable to Gaia Data Release 4 in terms of number of
stars, astrometric precision, and time baseline, and is highly complementary in terms of wavelength and sky location. In this paper, we investigate a synthetic population of GBTDS sources to characterize the detectability of unresolved astrometric binaries, in particular those with compact object companions. Assuming the occurrence rate of black holes (BHs) and
neutron stars (NSs) in AU-scale orbits around
stars is $10^{-7}$ and $10^{-6}$, respectively, and that Roman achieves an astrometric precision of $1\%$ of a pixel, $\mathcal{O}(10)$ BH+
star and $\mathcal{O}(10)$ NS+
star detached binaries will be detectable. The BHs will have median mass measurement uncertainties of $\sim 25\%$, increasing the existing sample of detached astrometric BH binaries by a factor of three. Together with the $\mathcal{O}(10^2)$ isolated BHs expected to be discovered by microlensing in the Roman GBTDS and an additional $\mathcal{O}(10)$ detached BH binaries in Gaia DR4, this will provide a representative view of the quiescent Galactic stellar-mass BH population.
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All authors Casey Y. Lam, Jessica R. Lu, Kareem El-Badry, Anil Seth, Joshua D. Simon, Natasha S. Abrams, Andrea Bellini, Matthew W. Hosek Jr., Peter McGill
Cosmology and Nongalactic Astrophysics
Enhancing dark siren cosmology via Gaussian process reconstruction of incomplete galaxy catalogs
Matteo Tagliazucchi, Jonathan Gair, Riccardo Barbieri et al. (+1 more)
We present a novel framework for improving dark siren cosmology by applying a Gaussian process (GP) to the line-of-sight (LOS) reconstruction of incomplete
galaxy catalogs. In the standard
galaxy catalog method for inferring the Hubble constant $H_0$ from gravitational-wave (GW) dark sirens, missing
galaxies are typically assumed to follow a uniform distribution in comoving volume, an assumption that discards
galaxy redshift clustering information crucial for cosmological inference. We propose instead to model the LOS
galaxy redshift distribution as a non-parametric function drawn from a GP realization, which is fitted to the observed incomplete catalog via a hierarchical
Bayesian likelihood that explicitly accounts for the survey selection function. Applied to mock GW and
galaxy catalogs extending up to
redshift $z\leq0.4$, our method yields $H_0$ constraints that are on average 23% more precise than the standard homogeneous completion when using a 24%-complete
galaxy catalog, and 37% more precise for an 8%-complete catalog. The largest improvement, reaching 66%, is obtained in configurations where the GP most effectively reconstructs the
redshift over- and under-density features that the homogeneous completion fails to capture.
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All authors Matteo Tagliazucchi, Jonathan Gair, Riccardo Barbieri, Michele Moresco
Astrophysics of Galaxies
SMUDGes Below the Surface: Clusters Confirm the Diversity of Low-Surface-Brightness Galaxies
Donghyeon J. Khim, Dennis Zaritsky, Loraine Sandoval Ascencio et al. (+2 more)
We use spatially resolved Keck
Cosmic Web Imager spectroscopy to study high-surface-brightness stellar components and internal kinematics in 44 low-surface-brightness
galaxies from the SMUDGes survey, including 30 ultradiffuse
galaxies, spanning the red sequence, green valley, and blue cloud regions of the
galaxy color-magnitude diagram. Although these
galaxies appear largely smooth in survey imaging, we detect at least one cluster candidate in every
galaxy. We identify clusters with nebular emission lines in 24
galaxies. They are common in blue-cloud
galaxies but rare in red sequence
galaxies. We identify three nuclear
star cluster candidates, one of which shows nebular emission lines. Among clusters without nebular emission lines, bluer
galaxies tend to have brighter cluster luminosity functions, suggesting the presence of young or intermediate-age clusters in addition to old globular clusters. This age diversity may complicate the use of photometrically selected globular cluster populations as tracers of total
halo mass. We measure rotation velocities for 17
galaxies using the clusters with nebular emission lines and for 12 using diffuse stellar light. Within 0.5 effective radii, the inferred dynamical mass generally exceeds the stellar mass, although the inferred dark matter contribution varies by an order of magnitude. The variety in properties for this sample of ultradiffuse
galaxies and low-surface-brightness dwarfs suggests that no single formation mechanism explains the population of low-surface-brightness
galaxies.
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All authors Donghyeon J. Khim, Dennis Zaritsky, Loraine Sandoval Ascencio, Michael C. Cooper, Richard Donnerstein
Cosmology and Nongalactic Astrophysics
What would it take for dark matter to be literally warm?
Katelin Schutz
Warm dark matter (WDM) has served as a valuable
benchmark for constraining small-scale structure in the past decades. In this note, I examine what it would take for dark matter to be warm in the literal sense assumed by that
benchmark, i.e., a thermal relic that decoupled while relativistic. Satisfying current constraints on the WDM mass, which approach the $\sim$10 keV scale, requires one of three possibilities. One possibility is that there were $\sim 10^4$ relativistic degrees of freedom in the thermal bath at the time of decoupling, which is far beyond what is available in the Standard Model or plausible extensions of it. An alternative is that there was a period of early matter domination whose
entropy injection diluted the relic density. However, in this scenario, the perturbations would have evolved through an expansion history that was different from the radiation-dominated one assumed in deriving WDM transfer functions. The third possibility is a dark sector that was never in thermal contact with the Standard Model and was simply born colder via asymmetric reheating. All of these possibilities rely on strong coincidences, where physics that has nothing to do with WDM happens to provide the exact initial conditions assumed in a WDM cosmology. Meanwhile, WDM is often used as a proxy for models with self-consistent thermal histories that generically predict the suppression of structure formation on small scales in a way that is both quantitatively and qualitatively different from WDM. I therefore advocate for a transition to more expressive parameterizations and simulation-based methods in order to extract more useful information from the wealth of upcoming data.
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Instrumentation and Methods for Astrophysics
Connecting Granulation and Magnetic Activity in Radial Velocities: The Next Breakthrough for High-Precision Spectroscopy
Ancy Anna John, Khaled Al Moulla, Federica Rescigno et al. (+5 more)
Stellar variability has become the dominant limitation to achieving the radial velocity (RV) precision required for the detection and characterization of Earth-like
exoplanets. While significant progress has been made in mitigating the effects of oscillations and
magnetic activity, convective granulation and its interaction with stellar
magnetic fields remain among the least understood sources of RV variability. To address these challenges, we organized the splinter session `Connecting Granulation and
Magnetic Activity in Radial Velocities: The Next Breakthrough for High-Precision Spectroscopy' at Cool
Stars 23. The session brought together researchers working on observations, numerical simulations, and data-driven techniques to discuss the current understanding of granulation-driven RV signals and identify the most promising directions for future progress. Through invited and contributed talks, followed by community discussions, participants emphasized the importance of combining physically motivated models with data-driven approaches, developing standardized
benchmark datasets, and validating simulations against high-quality observations across a range of stellar types. The discussions also highlighted the need for coordinated observing strategies, improved characterization of individual spectral lines, and physically informed line-by-line analyses to disentangle convective and
magnetic signals. This contribution summarises the scientific discussions and community perspectives that emerged during the session and outlines the key challenges that must be addressed to reach the sub-40 cm/s precision required for the next generation of RV
planet searches.
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All authors Ancy Anna John, Khaled Al Moulla, Federica Rescigno, Carmen San Nicolas Martinez, Andrew Collier Cameron, Thomas G. Wilson, Nadège Meunier, Sophia Sulis
Cosmology and Nongalactic Astrophysics
Impact of Scale-dependent Primordial Non-Gaussianity on Scalar-induced Gravitational Waves
Alisha Marriott-Best, Devanshu Sharma, Anish Ghoshal et al. (+1 more)
Scalar-induced gravitational waves (SIGWs) probe primordial
curvature perturbations beyond
cosmic microwave background scales, while primordial black holes (PBHs) probe the rare tail of the same statistics. We ask whether SIGW morphology can reveal scale-dependent primordial non-Gaussianity. We adopt the internal-leg separable kernel, $\mathcal F_{\rm NL}(\mathbf{k};\mathbf q,\mathbf{k}-\mathbf q)=\bar f_{\rm NL}f(q)f(\lVert\mathbf{k}-\mathbf q\rVert)$, and compute Gaussian, reducible, and connected contributions through $\mathcal O(\bar f_{\rm NL}^{4})$ in the second-order tensor-source approximation. We compare persistent power-law running with a UV-matched tanh weight that saturates at high scalar momentum. Across narrow, finite-width, asymmetric, and multi-slope scalar spectra, running produces more than amplitude renormalization. Power-law running shifts the scalar support sampled by non-Gaussian convolutions, generating peak displacement, asymmetric shoulders, and persistent ultraviolet deformations. The tanh template instead produces a transition-localized modification and approaches a momentum-independent ultraviolet plateau. Analytical estimates of the perturbative hierarchy, weighted slopes, log-normal saddle displacement, peak shifts, and infrared scaling explain the trends and the enhanced sensitivity of the $\mathcal O(\bar f_{\rm NL}^{4})$ sector. For localized sources with finite weighted moments, smooth running preserves the leading $k^3$ infrared behavior up to logarithmic corrections. Since the PBH mass scales as $M\propto k^{-2}$, preferential high-wavenumber weighting conditionally favors lower PBH masses in a narrow-support interpretation. Peak position, spectral
curvature, shoulders, and ultraviolet slopes are diagnostics for PTAs, LISA, and third-generation observations, providing finite-order templates for primordial interactions on otherwise inaccessible scales.
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All authors Alisha Marriott-Best, Devanshu Sharma, Anish Ghoshal, Gianmassimo Tasinato
Earth and Planetary Astrophysics
Flyby-induced high-eccentricity migration and the prevalence of hot Jupiters in M67
Mika V. Kontiainen, Cathie J. Clarke and Andrew J. Winter
Few planetary systems form in isolation. Rather, interactions in their birth environments may sculpt their architectures or drive them into unstable configurations. Here we study the role of environmental perturbations in triggering dynamical instabilities leading to hot Jupiter formation in dense clusters, focusing on whether the elevated occurrence rate of hot Jupiters in the open cluster M67 can be explained through flyby-induced high-eccentricity migration. We develop a hybrid method for modelling the secular and tidal
evolution of planetary systems under external perturbations by passing
stars using a combination of analytic and numerical approaches. We evolve 10,000 realizations each of systems with either a single
planet, two
planets, or a
planet and a stellar companion for $\sim$4 Gyr in an M67-like cluster, comparing outcome statistics against a control sample without flybys. In single- and two-
planet systems, the rate of flyby-induced hot Jupiter formation is negligible. However, in systems with an initially isotropically oriented stellar companion, the cluster environment boosts hot Jupiter formation by a factor of $\sim$2, accompanied by a factor of $\sim$3 increase in the rate of
planets undergoing tidal disruption. Based on observationally motivated estimates of primordial populations, our hot Jupiter yields are consistent with both field and M67 occurrence rates, provided the primordial wide binary fraction among solar-type
stars is close to $\sim$50 per cent, binary-driven high-eccentricity migration is the dominant formation pathway, and a substantial fraction of tidally disrupted systems survive as hot Jupiters through partial mass loss.
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Earth and Planetary Astrophysics
Magnesium silicate condensation in sub-Neptune envelopes: the fundamental link between chemistry, structure, and observables
William Misener, Peter Gao, Nicole L. Wallack et al. (+2 more)
Chemical interactions between the hydrogen-dominated envelopes and silicate-rich interiors of sub-Neptunes likely play a key role in shaping their atmospheric structure, mass-radius relations, and upper atmosphere composition. While atmospheric abundances and structure deeply influence each other, many existing models have either considered the effects of chemical interactions without the structural implications or have modeled the envelope structure using oversimplified chemical networks. In this work, we introduce Rocky Raccoon, a coupled chemical
equilibrium-atmospheric structure model. This model incorporates Mg, Si, O, C, and H species and produces self-consistent atmospheric chemical and thermal profiles for sub-Neptune envelopes, treating multi-species condensation for the first time. We find that the condensation sequence of magnesium silicates above a magma ocean is determined by the basal magma composition. We show that these condensation sequences drive the upper atmospheric composition to two endmembers: high oxygen abundances in the underlying melt produce compositions rich in oxygen-bearing volatiles (sub-solar C/O) and higher mean molecular weight atmospheres with $\mu \sim 4$ amu, while oxygen-poor melts produce lower mean molecular weight atmospheres dominated by methane and silane (super-solar C/O). The transition between the two regimes is abrupt and depends on melt properties like Mg/Si ratios and oxygen abundances. The different condensation sequences also lead to different thermal profiles, as deep convection is inhibited over different regions due to varying molecular weight gradients. Further experiments and simulations are key to resolving critical uncertainties in the condensation sequences and the corresponding significant impacts on sub-Neptune composition and thermal structure.
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All authors William Misener, Peter Gao, Nicole L. Wallack, Maggie A. Thompson, Anat Shahar
High Energy Astrophysical Phenomena
The GPSP Atlas: High-resolution Galactic Photon Survival Probability Atlas for Very-High- and Ultra-High-Energy Gamma-Ray Astronomy
Ekrem Oğuzhan Angüner
The emergence of Galactic PeV astronomy makes
photon–
photon ($\gamma\gamma$) absorption an increasingly important component of gamma-ray data analysis. In this work, the Galactic
Photon Survival Probability (GPSP) atlas is presented as the first Galactic framework describing gamma-ray survival probabilities over the full parameter space $P(l,b,d,E_\gamma)$ between 1 TeV and 10 PeV. The atlas is constructed using two independent GALPROP-based interstellar radiation field (ISRF) models, allowing direct assessment of ISRF-related systematics, and is released in a FITS format compatible with standard analysis frameworks. A novel gamma-ray survival phase space representation is introduced, extending 1D survival profiles into a 2D energy–distance framework that visualizes Galactic transparency and gamma-ray horizons. Using the full atlas, Galactic transparency and Galactic plane survival maps are constructed. These reveal that Galactic opacity is highly structured, with enhanced attenuation along spiral-arm tangent directions in the $\sim$100–300 TeV regime, while attenuation becomes nearly isotropic and
cosmic microwave background (CMB) dominated near PeV energies. The framework naturally accommodates attenuation calculations for extended and diffuse sources. The atlas is further extended to subluminal Lorentz invariance violation (LIV) scenarios through the GPSP-LIV atlas, incorporating LIV-modified pair production kinematics and cross sections. Sources emitting in the 2–3 PeV regime beyond gamma-ray horizons are identified as promising targets for probing LIV effects. Finally, practical applications are presented for the Galactic Center PeVatron and the Cygnus X-3 regions. The GPSP and GPSP-LIV atlases establish a publicly available foundation for studies of Galactic PeVatrons, diffuse gamma-ray emission, and fundamental physics searches in the emerging era of Galactic PeV astronomy.
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High Energy Astrophysical Phenomena
Thermal Stability of Radiation-Pressure-Dominated Accretion Disks Threaded by Net Vertical Magnetic Flux
Shahram Abbassi, Armin Memarian and Samik Mitra
The classical radiation-pressure instability predicts strong thermal variability in luminous black-hole
accretion disks, whereas most disk-dominated X-ray binary soft states remain comparatively stable. We examine whether net vertical
magnetic flux can weaken this instability through its contribution to the radial stress. The stability depends not only on the
equilibrium magnetic stress but also on how that stress changes during a thermal perturbation. We write the local stability condition in terms of the logarithmic heating response, $q_+<q_{+,\rm crit}$, which avoids specifying how the turbulent stress is divided into reference and net-flux components. For the illustrative closure $\delta=\zeta\sqrt{\bpol\btor}/\alpha$, $\etad=-d\ln\delta/d\ln H$ describes the response of the fractional stress correction, while $\Gnf=d\ln W_{\rm nf}/d\ln H$ describes the response of the additional net-flux stress itself. For an
accretion disk around a $10M_\odot$ black hole at $R=20\rg$ and $\Mdot=0.5\MEdd$, we adopt fixed local mass flux on the thermal timescale, $(\gamma,\gp)=(1,0)$, and $d\ln\zeta/d\ln H=0$. Marginal stability then occurs at $\bpol^{\rm crit}=0.0176$ for $\zeta=1$ and $0.1338$ for $\zeta=0.25$. These thresholds depend on the adopted stress closure and field-response prescription and should not be interpreted as universal
magnetic-pressure fractions. Fixed-$B_z$
equilibrium sequences, using a separate relation for the variation of $B_\varphi$ between steady states, show that increasing vertical field narrows the thermally unstable
accretion-rate interval but does not eliminate it for either $H/R<0.1$ or $H/R<0.2$. The relevant quantity for stabilization is therefore the thermal response of the stress associated with net vertical flux rather than the vertical
magnetic-pressure fraction alone.
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Astrophysics of Galaxies
The Mass Dependence of the Fundamental Metallicity Relation in Observations and Simulations
Laura Carnevale, Alex M. Garcia, Paul Torrey et al. (+8 more)
The metal content of
galaxies provides direct insight into the underlying physical processes that drive
galaxy evolution. An example of this is the three-parameter relationship between stellar mass, gas-phase
metallicity, and
star formation rate, commonly referred to as the Fundamental
Metallicity Relation (FMR). Previous studies have suggested that the FMR is
redshift-invariant (at $z \lesssim 4$) and fully accounts for the scatter in the mass-
metallicity relation (MZR). In this work, we test this 'fundamental' relation in both cosmological simulations (EAGLE, SIMBA, Illustris, IllustrisTNG) and Sloan Digital Sky Survey (SDSS) observations. We find that the canonical anti-correlation between
metallicity and specific
star formation rate (sSFR) inverts in massive
galaxies ($M_\star \gtrsim 10^{10.5} \mathrm{M}_\odot$) in EAGLE, IllustrisTNG, and SDSS. When including lower
star forming
galaxies, the positive correlation appears for all four simulations and SDSS. We speculate that this inversion may being driven by strong nuclear outflows (from, e.g., active galactic
nuclei or stellar feedback), which quench
star formation while simultaneously expelling preferentially enriched gas from the center of the
galaxy. We also find that this 'inversion' appears in a number of
metallicity diagnostics in observations (though the details depend on diagnostic) and persists out to $z \sim 1$ in the simulations. These results demonstrate that these strong nuclear outflows challenge simple gas regulator-type models and provide a new framework to test models of the baryon cycle in both future simulations and observations.
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All authors Laura Carnevale, Alex M. Garcia, Paul Torrey, Sara L. Ellison, Shweta Jain, Peixin Zhu, Kathryn Grasha, Ryan L. Sanders, Lars Hernquist, Lisa J. Kewley, Jillian M. Scudder
High Energy Astrophysical Phenomena
Measurement of spin-orbit misalignment in binary black holes via the total spin
Charles F. A. Gibson, Isha Anantpurkar and Javier Roulet
The degree of
spin-orbit
alignment in merging binary black holes is a powerful probe of their formation history. However, assessing
spin-orbit misalignment in individual events remains challenging, as most parameters commonly used to characterize precession tend to be poorly constrained. In this work, we introduce the angle between the total
spin and orbital angular momentum, $\theta_{LS}$, as an alternative measure of
spin-orbit misalignment. Using synthetic observations, we show that $\theta_{LS}$ retains more information to discriminate between the aligned- and isotropic-
spins hypotheses than commonly used alternatives, including $\chi_{\rm p}$. We then study this parameter on binary black hole mergers observed in the GWTC-5.0 catalog, and identify multiple events that are inconsistent with having aligned
spins. In several of the examples, this is not apparent from the posteriors of the effective
spin parameters ($\chi_{\rm p}$ or $\chi_\mathrm{eff}$) nor the individual
spin-orbit tilts ($\theta_1$ or $\theta_2$) alone, and thus had not been previously identified. We highlight GW241127_061008 as a compelling case for a second-generation merger, with a large, tilted primary
spin, unequal masses, and a large primary mass near the pair-instability-
supernova mass gap. Finally, we perform population inference using $\cos\theta_{LS}$ and confirm that the binary black hole population is inconsistent with either a purely isotropic or a purely aligned-
spin distribution, and requires substantial
spin-orbit misalignment.
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Earth and Planetary Astrophysics
Atmospheric Retrieval of Combined JWST, HST, and Ground-Based Observations Reveals a Featureless Transmission Spectrum for GJ 1132 b
Mohammad Senobar and Sareh Ataiee
We present a panchromatic transmission spectrum of GJ1132b spanning $0.71$–$5.16~\mu$m, combining published transit observations from Magellan/LDSS3C, HST/WFC3 G141, and JWST/NIRSpec (G395H and G395M). Using petitRADTRANS and PyMultiNest, we perform
Bayesian atmospheric
retrievals, comparing a flat-line, Gaussian-feature models, and clear and cloudy atmospheric scenarios, including tests with and without the first JWST visit flagged as a potential outlier in a previous study. The inclusion of shorter-wavelength spectra shifts the marginal molecular preference from H$_2$O (JWST-only) to NH$_3$ (panchromatic). Of the seven molecules tested (NH$_3$, CO$_2$, CO, CH$_4$, H$_2$O, HCN, and N$_2$O), only NH$_3$ shows a marginal preference, which is weakened when the JWST first visit is excluded. Cloudy atmospheres yield higher
Bayesian evidence than high-mean-molecular-weight clear models, but none provides compelling evidence over the flat-line scenario. A thin ($P_{\rm ref} \sim 10^{-3}$~bar), N$_2$-dominated atmosphere ($\mu \sim 16$~amu) with traces of NH$_3$, H$_2$O, and CH$_4$, combined with a grey, optically thin power-law cloud (opacity at 350~nm $\le 10^{-3}~{\rm cm^2\,g^{-1}}$), remains indistinguishable from the flat-line model when the first JWST visit is included and is further disfavoured when it is excluded, strengthening a bare-rock interpretation. We conclude that current spectra show no evidence for an atmosphere on GJ1132b. The observations are best explained by a bare rocky
planet with $R_{\rm p} = 1.129 \pm 0.002\,R_\oplus$, though a tenuous, obscured atmosphere cannot be excluded when the JWST first visit is included.
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High Energy Astrophysical Phenomena
Supernova 1987A was a "failed supernova" twenty thousand years before its jet-driven explosion
Noam Soker
I show that the progenitor of
supernova (SN) 1987A faded substantially and became red for hundreds of years to observers in and near the plane of the equatorial ring, because the equatorial ring, which was formed by a binary interaction between the SN 1987A progenitor and a main-sequence companion that ejected material about 20,000 years before the explosion, obscured the progenitor. For a few hundred years, the luminosity for such hypothetical observers was mainly light scattered by the two outer rings, which amounted to ~5% of the progenitor luminosity. In present terms, this event would have been classified as a "failed
supernova" by these observers, although there was no core collapse, no black hole formation, and nothing failed. Rather, this event was a type II ILOT (intermediate-luminosity optical transient), in which equatorial ejecta temporarily obscured the central source. After a few hundred years, the outer rings became transparent, the inner ring became more transparent, and the SN 1987A progenitor brightened over a few thousand years to its normal luminosity for equatorial observers. This finding strengthens the claim that "failed
supernova" candidates are likely to be type II ILOTs. Although the binary interaction also spun up the core, the bipolar morphology of SN 1987A (its Keyhole) is misaligned with the triple-ring system. I use the jittering jets explosion mechanism (JJEM) to speculate on a scenario that might explain this misalignment. This study adds small but unique support to the claim that the JJEM is the primary explosion mechanism of CCSNe.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Dynamical Friction as Environmental Gravitational Self-Force
Sayak Datta
Dynamical friction (DF) and gravitational-wave radiation reaction are conventionally treated as distinct dissipative mechanisms acting on a compact object inspiraling through a matter environment. We show that DF is not an additional force but a term at order $q^2\epsilon$ in a covariant multiparameter expansion of the MiSaTaQuWa force equation that vanishes identically in the absence of a particle-induced perturbation of the environment's matter fields, where $q$ and $\epsilon$ are respectively the mass ratio and environmental parameter. As a test of this identification, we evaluate it in weak and adiabatic field limit, solving the polar density-perturbation equation sourced by the particle's own order-$q$
vacuum metric perturbation. The reduction reproduces the Chandrasekhar-Ostriker drag force and predicts two features in strong
gravity. An $\ell$-dependent splitting of the wake that only recombines into the Ostriker source in the weak-field limit, and a purely relativistic axial contribution with no Newtonian counterpart. This establishes dynamical friction as an intrinsic piece of self-force theory, extending to strong field, generic orbits, and generic environments, with direct consequences for extreme-mass-ratio inspiral waveform modeling for LISA.
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High Energy Astrophysical Phenomena
Quantum-Gravity-Inspired Effects in Neutron Stars: A Critical Map from Microscopic Assumptions to Observables
Randall Hell Vargas Pradinett
Claims that
neutron stars constrain
quantum gravity often compare models whose new physics enters at different stages of the stellar calculation. This article provides a critical map of three representative routes: generalized-uncertainty-principle deformations of microscopic thermodynamics, noncommutative-inspired modifications of the effective matter source, and higher-
curvature or scale-dependent modifications of gravitational dynamics. For each route we identify the quantity that is changed, the dimensionless parameter controlling the correction, and the consistency conditions required before masses, radii, or tidal deformabilities can be compared with observations. A deformed phase-space measure must be implemented in a thermodynamically consistent interacting equation of state; a smeared density must be completed by a conserved stress-energy tensor, generally with anisotropic pressure; and a gravitational effective field theory must remain within its derivative expansion and be applied consistently to both the
equilibrium background and tidal perturbations. Simple scale estimates show that coefficients of natural size suppressed by the Planck scale are negligible in
neutron stars. Observable effects consequently constrain model-dependent effective scales or enhanced couplings, not microscopic
quantum gravity directly. The resulting framework is intended to separate robust phenomenological bounds from effects produced by inconsistent implementations or by degeneracies with the high-density equation of state.
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Cosmology and Nongalactic Astrophysics
The impact of the IGM thermal state on the Ly$\alpha$ flux 3D power spectrum from linear to highly non-linear scales
Tomáš Šoltinský, Gabriele Autieri, Vid Iršič et al. (+1 more)
Recently initiated and upcoming spectroscopic surveys, such as DESI and WST, will provide more than $10^6$ high-$z$
quasar spectra, enabling dense sky coverage by the Ly$\alpha$ forest. This is expected to establish the three-dimensional (3D) Ly$\alpha$ forest power spectrum, $P_{\rm 3D,\alpha}$, as a probe of the thermal and ionization history of the intergalactic medium (IGM). To exploit this opportunity, we quantify the imprints of reionization on the post-reionization IGM using high-fidelity numerical models. We use the Sherwood and Sherwood-Relics cosmological hydrodynamical simulations with box sizes up to $160\,h^{-1}\,\rm cMpc$ to investigate the impact of box size, mass resolution, and extracted grid resolution on $P_{\rm 3D,\alpha}$ over $2.4\leq z\leq4.8$. After applying a Zel'dovich control variate correction, simulation volume has a modest impact over most scales and orientations, whereas degrading the mass resolution produces differences of up to $\sim13\%$. Insufficient resolution of the grid used for the optical-depth calculation can artificially enhance small-scale power by up to $\sim35\%$. The timing of $\mathrm{H\,I}$ reionization leaves only a percent-level imprint on $P_{\rm 3D,\alpha}$ at $z=2.4$, whereas varying the photoheating rate by a factor of two changes the large-scale power by $\sim4-8\%$. Our results demonstrate that numerical effects can be comparable to, or exceed, the relic astrophysical signatures encoded in $P_{\rm 3D,\alpha}$, making numerical convergence essential for interpreting precise Ly$\alpha$ forest measurements. The strongest astrophysical imprint arises from spatially inhomogeneous $\mathrm{H\,I}$ reionization, which enhances the large-scale power by up to $\sim70\%$ at $z=4.2$. This highlights the potential of post-reionization Ly$\alpha$ forest measurements as a probe of the thermal history and spatial morphology of
cosmic reionization.
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All authors Tomáš Šoltinský, Gabriele Autieri, Vid Iršič, Matteo Viel
Solar and Stellar Astrophysics
Calculation of Field Line Slippage Rates in Coronal Simulations
Valentin Aslanyan, David MacTaggart, Roger B. Scott et al. (+6 more)
We present the Universal Slippage calculator (USlip), an extension of the Universal Fieldline Tracer (UFiT), that computes
magnetic field line slippage rates from an input
magnetic field defined on a structured grid. The slippage rate provides a local, physically grounded diagnostic of non-ideal
evolution, directly quantifying departures from ideal frozen-in motion. We outline the theoretical formulation and describe an efficient numerical implementation. The method is validated against analytical solutions and applied to simulations using three coronal codes treating varying spatial scales, all of which are standard inputs for USlip. In all the examples considered, the slippage rate not only identifies where
magnetic connectivity changes occur, but also accurately reproduces the observed direction of field-line slippage. The consistency of the results across analytical tests and multiple simulation platforms demonstrates that USlip is a robust and versatile tool for diagnosing three-dimensional reconnection in dynamically evolving systems.
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All authors Valentin Aslanyan, David MacTaggart, Roger B. Scott, Chloe P. Wilkins, David I. Pontin, Anthony R. Yeates, Peter F. Wyper, Karen A. Meyer, Spiro K. Antiochos
Solar and Stellar Astrophysics
Photospheric index of geomagnetic activity
Ismo Tähtinen, Timo Qvick, Timo Asikainen et al. (+1 more)
Geomagnetic indices quantify the disturbances of the Earth's
magnetic field. They form an important space weather and space
climate record that tracks solar-terrestrial effects on the Earth. Although geomagnetic activity has its origins in the photospheric
magnetic fields, the two have so far not been directly related. We develop a photospheric index of geomagnetic activity (PIGA) that measures the geoeffectiveness of the Sun based on photospheric
magnetic field as presented in synoptic magnetograms. We construct the PIGA from synoptic magnetograms of Wilcox Solar Observatory by relating the equatorial and axial dipole components of the photospheric
magnetic field to the geomagnetic Kp index by means of linear regression. PIGA captures well the
evolution of the geomagnetic activity over the past 50 years at the resolution of solar rotation, having linear correlation of 0.71 with the geomagnetic Kp index. PIGA makes it straightforward to measure the geoeffectiveness of the Sun using the dominant structure of the global solar
magnetic field. PIGA can for example be used to study the geoeffectiveness of the Sun using historical simulations or the predicted solar
magnetic field. PIGA also allows to use observed geomagnetic activity as an additional constraint for the early
magnetic field reconstructions of the solar
magnetic field.
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All authors Ismo Tähtinen, Timo Qvick, Timo Asikainen, Kalevi Mursula
Earth and Planetary Astrophysics
Potential survivable niches for microbial life on the lunar south pole
Prabal Saxena, Stefano Bertone, Heather V. Graham et al. (+5 more)
Most lunar surface conditions are incredibly harsh for microbial survival. High ultraviolet radiation, temperatures, and energetic particle radiation limit survival over most unprotected lunar surfaces, particularly in equatorial regions where all previous crewed exploration occurred. However, whether these harsh conditions are widespread at lunar poles has not been examined considering topographical effects. Here, we show that recent microorganism survivability data and lunar surface remote sensing reveal likely survivable niches in lunar polar regions. Analysis of topography and latitude-driven surface conditions using remote sensing data and high-resolution illumination models indicates the lunar south pole possesses significant regions with persistent low temperatures and ultraviolet flux. Comparing these conditions to survivability data of specific microorganisms, we find significant lunar polar areas likely possess surface conditions amenable to microbial survival. Our findings suggest lunar polar regions may be less hostile to microbial survival than previously assumed. This does not encompass growth likelihood, but survival in a cryptobiotic state where growth would be possible if habitable conditions were present. Potential microbial survivability at lunar poles is particularly significant given many examined microbes will likely be transported to the Moon during crewed lunar south pole exploration planned in numerous near-term missions. Thoughtfully planning exploration and tracking its impact is key to limiting and understanding potential unintended life transfer to the Moon.
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All authors Prabal Saxena, Stefano Bertone, Heather V. Graham, Natalie M. Curran, Aaron B. Regberg, Andrew Needham, D.E. Pugel, Noah E. Petro
Instrumentation and Methods for Astrophysics · Cross-listed from hep-ex
Cosmic muon arrival directions as a source of entropy
Deepak Samuel
We demonstrate, for the first time, that the arrival directions of
cosmic-ray
muons from a
muon telescope provide a measurable source of physical
entropy. Using six months of data collected from a
muon telescope, the local zenith and azimuth angles were used for randomness extraction. The result of this study show that each
cosmic muon track from our detector can generate upto 4 bits with an
entropy of 0.999182 bits/bit with a maximum bit rate of roughly 650 bits/s which can possibly be enhanced by improving the detector size and angular resolution. The suggested technique can be potentially used as a random number generator required for closing the settings-independence loophole in the tests for violations of Bell's inequality. The data acquisition, data reduction, and conditioning
algorithms are discussed in detail.
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