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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 21 January

Cosmology and Nongalactic Astrophysics

The First Upper Bound on the Nano-Hertz Gravitational Waves and Galaxy Cross-Correlation signal using 15-year NANOGrav Data and DESI Galaxy Survey

Mohit Raj Sah and Suvodip Mukherjee

The recent detection of a common-spectrum stochastic signal by multiple pulsar timing array (PTA) collaborations has provided tentative evidence for a nanohertz (nHz) stochastic gravitational-wave background (SGWB). This signal can be widely interpreted as originating from a cosmic population of inspiraling supermassive black hole binaries (SMBHBs). Current PTA analyses primarily constrain the SGWB power spectrum and its auto-angular power spectrum. However, the supermassive black holes will produce an underlying correlation with the large-scale structure of the Universe, which can help in understanding the formation and evolution of the binaries. In this work, we develop a new analysis pipeline PyGxGW-PTA for studying the cross-correlation of nHz GW signal with galaxy surveys ($C^{\rm g\, GW}_\ell$) and obtain the first constraint on the SGWB and galaxy distribution cross-correlation using the NANOGrav 15-year dataset in combination with the DESI galaxy catalog. We find no statistically significant correlation between the SGWB and the large-scale distribution of DESI galaxies and using an optimal estimator we put an upper bound on $C^{\rm g\, GW}_{\ell=8} < 0.0083$ at $95\%$ C.I. This yields the first observational upper limit on the spatial correlation between the nHz SGWB and the large-scale structure of the Universe, establishing the observational groundwork for future multi-tracer analyses that will combine PTA data with next-generation galaxy surveys to unveil the SMBHB-galaxy correlation.
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High Energy Astrophysical Phenomena

Modeling X-ray reflection spectra from disk returning radiation: Application to 4U 1630-47

Kostas Kourmpetis, Shafqat Riaz, Honghui Liu et al. (+6 more)

Returning radiation is thought to play a key role in disk illumination of black-hole X-ray binaries in the high-soft state, yet it has not been fully incorporated into XSPEC reflection models. We present a new table model for reflection spectroscopy that self-consistently accounts for the returning radiation of the thermal component. To isolate this effect, we adopted the standard disk-corona configuration but disabled the corona, allowing the reflection spectrum to be produced solely by the self-irradiation of the disk. We applied our model to three NICER and NuSTAR simultaneous observations of the black-hole X-ray binary 4U 1630-47 during the soft state. The model fits the data well, suggesting that returning radiation from the disk could potentially explain the reflection features observed in this source. Our results suggest a rapidly spinning black hole ($a_* \sim 0.99$), a disk inclination of $i \sim 43^\circ-54^\circ$, a mass accretion rate of $\dot{M}_{\rm BH} \sim (0.13-0.25)\,\dot{M}_{\rm Edd}$, and a source distance of $7.3-11.3 \,\rm{kpc}$, which is in broad agreement with previous studies.
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All authors Kostas Kourmpetis, Shafqat Riaz, Honghui Liu, Temurbek Mirzaev, Cosimo Bambi, Debtroy Das, Jiachen Jiang, Kostas D. Kokkotas, Andrea Santangelo

Cosmology and Nongalactic Astrophysics

Dark Energy Survey Year 6 Results: Weak Lensing and Galaxy Clustering Cosmological Analysis Framework

D. Sanchez-Cid, A. Ferté, J. Blazek et al. (+115 more)

We present the methodology for the weak lensing and galaxy clustering analyses of the Dark Energy Survey (DES) Year 6 data set. In this work, we design and validate the analysis pipeline for the cosmic shear, galaxy clustering plus galaxy$-$galaxy lensing ($2 \times 2$pt), and the joint analysis in the $3 \times 2$pt. Our framework accounts for key theoretical uncertainties, such as baryonic feedback and galaxy bias, incorporating both linear and non-linear models. We apply scale cuts in regimes where theoretical modeling becomes unreliable. The robustness of the pipeline is validated using mock data and simulations, confirming unbiased cosmological constraints and highlighting the importance of posterior projection effects in the validation process. As a result, we deliver robust and validated analysis pipelines for cosmic shear, $2 \times 2$pt, and $3 \times 2$pt in $\Lambda$CDM and $w$CDM scenarios, including a well-defined set of scales suitable for real data analysis, a robust prescription for theoretical systematics, and the theoretical covariance of the signal. This comprehensive methodology also lays the groundwork for future galaxy surveys such as the Vera C. Rubin Observatory Legacy Survey of Space and Time.
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All authors D. Sanchez-Cid, A. Ferté, J. Blazek, S. Samuroff, A. Amon, F. Andrade-Oliveira, J. M. Coloma-Nadal, J. Muir, A. Porredon, J. Prat, N. Weaverdyck, M. Yamamoto, D. Anbajagane, M. R. Becker, P. Carrilho, C. Chang, M. Crocce, G. Giannini, W. d'Assignies, J. DeRose, S. Dodelson, E. Krause, E. Legnani, J. Mena-Fernández, N. MacCrann, A. Pourtsidou, C. Preston, P. Rogozenski, M. Rodriguez-Monroy, R. Rosenfeld, E. Sanchez, I. Sevilla-Noarbe, M. Soares-Santos, C.To, M. A. Troxel, M. Tsedrik, B. Yin, J. Zuntz, T. M. C. Abbott, M. Aguena, S. Allam, O. Alves, S. Avila, D. Bacon, K. Bechtol, E. Bertin, S. Bocquet, D. Brooks, H. Camacho, R. Camilleri, A. Campos, A. Carnero Rosell, J. Carretero, F. J. Castander, R. Cawthon, A. Choi, L. N. da Costa, M. E. da Silva Pereira, T. M. Davis, J. De Vicente, S. Desai, C. Doux, A. Drlica-Wagner, T. Eifler, J. Elvin-Poole, S. Everett, A. E. Evrard, B. Flaugher, P. Fosalba, J. Frieman, J. García-Bellido, M. Gatti, E. Gaztanaga, P. Giles, K. Glazebrook, D. Gruen, G. Gutierrez, I. Harrison, K. Herner, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. Huterer, B. Jain, D. J. James, N. Jeffrey, T. Kacprzak, K. Kuehn, O. Lahav, S. Lee, J. L. Marshall, F. Menanteau, R. Miquel, J. J. Mohr, J. Myles, R. C. Nichol, R. L. C. Ogando, A. Palmese, M. Paterno, W. J. Percival, A. A. Plazas Malagón, M. Raveri, A. Roodman, C. Sánchez, T. Schutt, E. Sheldon, N. Sherman, T. Shin, M. Smith, E. Suchyta, M. E. C. Swanson, M. Tabbutt, G. Tarle, D. Thomas, D. L. Tucker, V. Vikram, A. R. Walker, B. Yanny

Solar and Stellar Astrophysics · Cross-listed from hep-ph

Testing the three massive neutrino paradigm: Constraints on Neutrino Properties and Interactions from Recent Experimental Data

João Paulo Pinheiro

Neutrino physics offers unique insights into phenomena beyond the Standard Model (BSM). This thesis presents phenomenological investigations organized around three pillars: consolidation of the three-flavor oscillation paradigm, exploration of new physics viability, and precise determination of solar neutrino fluxes. The theoretical framework introduces massive neutrinos, leptonic mixing, and flavor transitions, followed by experimental results emphasizing Borexino and NOvA data analyses. The first pillar establishes the three-flavor framework through global analysis of solar, atmospheric, reactor, and accelerator data, providing updated determinations of mixing angles ($\theta_{12}$, $\theta_{13}$, $\theta_{23}$) and mass-squared differences ($\Delta m^2_{21}$, $\Delta m^2_{31}$), while quantifying ambiguities in mass ordering and $\theta_{23}$ octant. The second pillar investigates Non-Standard Interactions (NSI) with electrons and quarks, combining Borexino data with COHERENT's CE$\nu$NS measurements to establish bounds on propagation and detection couplings, excluding viable NSI parameter regions including potential LMA-D solutions. The third pillar advances solar neutrino physics through precision flux determinations, integrating pp-chain and CNO-cycle measurements. Results show preference for high-metallicity Standard Solar Models and incompatibility between $3+1$ mixing parameters favored by Gallium experiments and solar observations. This synthesis guides future experiments toward resolving mass ordering, CP violation, and dark sector interactions.
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Cosmology and Nongalactic Astrophysics

Dark Energy Survey Year 6 Results: Magnification modeling and its impact on galaxy clustering and galaxy-galaxy lensing cosmology

E. Legnani, J. Elvin-Poole, D. Anbajagane et al. (+72 more)

Gravitational lensing magnification alters the observed spatial distribution of galaxies and must be accounted for to prevent biases in cosmological probes of the large-scale structure. We investigate its effects on the Dark Energy Survey Year 6 galaxy clustering and galaxy-galaxy lensing analyses using the fiducial lens (position tracer) sample MagLim++. Magnification bias is parameterized by a coefficient that describes the response of the number of selected objects per unlensed area element to a change in the lensing convergence. We quantify this coefficient using the Balrog synthetic source injection catalog to account for the complexity of the selection function, and compare these results with simplified estimates. The resulting values of the magnification coefficients for each redshift bin are [3.16 $\pm$ 0.08, 2.76 $\pm$ 0.21, 4.09 $\pm$ 0.15, 4.42 $\pm$ 0.16, 4.90 $\pm$ 0.29, 4.83 $\pm$ 0.25]. Relative to Year 3, this analysis provides more precise and accurate magnification bias estimates through a larger Balrog area and reweighting to better match the data properties. The cosmological results are robust when tested against various magnification parameter prior choices and also when adding cross-clustering between lens redshift bins. Neglecting magnification, however, introduces significant systematic shifts: relative to the fiducial analysis with Gaussian priors centered on the Balrog-derived estimates, we observe shifts of 1.37$\sigma$ in $S_8$ and -0.84$\sigma$ in $\Omega_m$ (with cosmic shear included: -0.61$\sigma$ in $S_8$ and -0.71$\sigma$ in $\Omega_m$), in agreement with findings from simulated data, demonstrating that magnification must be modeled to avoid biases. Freeing the magnification bias in lens bin 2 leads to unphysical negative values, further justifying its exclusion from the fiducial Year 6 analysis.
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All authors E. Legnani, J. Elvin-Poole, D. Anbajagane, D. Sanchez Cid, A. Ferté, N. Weaverdyck, A. Porredon, S. Avila, R. Miquel, J. De Vicente, J. Coloma, S. Samuroff, W. d'Assignies, A. Alarcon, C. Sánchez, J. Muir, J. Prat, N. MacCrann, D. Bacon, M. A. Troxel, C. Chang, M. Crocce, M. R. Becker, J. Blazek, M. Yamamoto, T. Schutt, M. Rodriguez-Monroy, G. Giannini, B. Yin, A. Amon, K. Bechtol, I. Sevilla-Noarbe, T. M. C. Abbott, M. Aguena, S. Allam, O. Alves, F. Andrade-Oliveira, G. M. Bernstein, S. Bocquet, D. Brooks, R. Camilleri, A. Carnero Rosell, J. Carretero, L. N. da Costa, M. E. da Silva Pereira, T. M. Davis, S. Desai, S. Dodelson, P. Doel, C. Doux, J. García-Bellido, D. Gruen, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Honscheid, D. Huterer, D. J. James, K. Kuehn, O. Lahav, S. Lee, J. L. Marshall, J. Mena-Fernández, F. Menanteau, J. J. Mohr, J. Myles, R. L. C. Ogando, M. Paterno, A. A. Plazas Malagón, R. Rosenfeld, E. Sanchez, M. Smith, M. Soares-Santos, E. Suchyta, V. Vikram

High Energy Astrophysical Phenomena

SN 2023zcu: A Type IIP SN with Early Flash Features

Monalisa Dubey, Kuntal Misra, Géza Csörnyei et al. (+51 more)

We present a detailed photometric and spectroscopic analysis of the Type IIP supernova SN~2023zcu, which exploded in the galaxy NGC~2139 (redshift $z$ = 0.006). SN~2023zcu exhibits a well-sampled light curve covering the rise, plateau, and nebular phases. It has an optically thick phase of $100.6 \pm 0.6$ d with a magnitude drop of $\sim$1.7 mag in the V band during the transition between the plateau and the nebular phases. Weak emission features in the early-time spectra indicate a low-level interaction between circumstellar material (CSM) and the SN ejecta. The spectral evolution is well sampled and exhibits a prominent P-Cygni profile of H$\alpha$, a defining characteristic of Type IIP SNe. Signatures of metal-line formation (e.g., \ion{Fe}{2}, \ion{Ca}{2} near-infrared triplet) are also evident in the spectra as the SN evolves. Spectral modeling with the radiative-transfer code TARDIS during the early photospheric phase (8.7–35.5 d since explosion) yields photospheric temperatures decreasing from $\sim$9,000 to $\sim$6,000 K and expansion velocities declining from $\sim$10,000 to $\sim$5,400 km s$^{-1}$. A tailored expanding photosphere method (EPM) fit based on the TARDIS models provides a distance estimate of $27.8 \pm 2.0$ Mpc. Nebular-phase spectra and bolometric light-curve modeling suggest a progenitor mass in the range 12–15 M$_\odot$. This thorough analysis helps to constrain progenitor properties and explosion parameters, thereby strengthening our understanding of Type IIP SNe.
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All authors Monalisa Dubey, Kuntal Misra, Géza Csörnyei, Raya Dastidar, D. Andrew Howell, David J. Sand, Stefano Valenti, WeiKang Zheng, Alexei V. Filippenko, Saurabh Jha, Jesper Sollerman, Peter Brown, Kate D. Alexander, Moira Andrews, Jennifer Andrews, Dre Betz, Emma Born, Kate Bostow, K. Azalee Bostroem, Sea'n J. Brennan, Thomas G. Brink, Collin Christy, Elma Chuang, Yize Dong, Naveen Dukiya, Joseph R. Farah, Noah Franz, Estefania Padilla Gonzalez, Joshua Haislip, Emily Hoang, Griffin Hosseinzadeh, Brian Hsu, Connor Jennings, Vladimir Kouprianov, M.J. Lundquist, Colin Macrie, Curtis McCully, Andrew Mchaty, Darshana Mehta, Katie Mora, Megan Newsome, Jeniveve Pearson, Neil Pichay, Conor Ransome, Aravind P. Ravi, Daniel E. Reichart, Nicolás Meza Retamal, Sophia Risin, Manisha Shrestha, Ajay Kumar Singh, Nathan Smith, Bhagya Subrayan, Giacomo Terreran, William Wu

High Energy Astrophysical Phenomena

The Supernova Remnant G284.3$-$1.8 and Its Relation to the Gamma-ray Binary 1FGL J1018.6$-$5856

Natsuki Terano, Takaaki Tanaka, Hiromasa Suzuki et al. (+6 more)

G284.3$-$1.8 is a supernova remnant with a radio shell and thermal X-ray emission. Located near its center is the gamma-ray binary 1FGL J1018.6$-$5856, although the physical association between the two systems is not clear yet. Our X-ray spectroscopy with Suzaku reveals that G284.3$-$1.8 and 1FGL J1018.6$-$5856 have compatible absorption column densities of $N_\mathrm{H} = 6\textrm{--}7 \times 10^{21}~\mathrm{cm}^{-2}$, indicating that the two systems have similar distances. The actual distance is determined as $3~\mathrm{kpc}$ using $\mathrm{^{12}CO}$ ($J=1\textrm{--}0$) data obtained with NANTEN. The X-ray spectrum of G284.3$-$1.8 shows a strong K-shell emission line of Mg, confirming that the earlier claim that the SNR is one of the few Mg-rich SNRs. Comparing recent stellar models taking into account the "shell merger" processes, we find that the obtained Mg-to-Ne mass ratio of $M_\mathrm{Mg}/M_\mathrm{Ne} = 0.73^{+0.07}_{-0.03}$ and Si-to-Mg mass ratio of $M_\mathrm{Si}/M_\mathrm{Mg} = 0.44\pm0.03$ suggest a supernova explosion that would have left a neutron star. The characteristics of 1FGL J1018.6$-$5856, on the other hand, are better explained with a model in which its compact object is neutron star. The present results, therefore, would suggest a possible scenario where G284.3$-$1.8 and 1FGL J1018.6$-$5856 are both remnants of a common supernova explosion although further observational tests are necessary.
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All authors Natsuki Terano, Takaaki Tanaka, Hiromasa Suzuki, Rei Enokiya, Hiroyuki Uchida, Kai Matsunaga, Takuto Narita, Yasuo Fukui, Toshiki Sato

Astrophysics of Galaxies

The Intermediate-Mass Black Hole Reverberation Mapping Project: Stable Optical Continuum Lags of an IMBH in the Dwarf Galaxy NGC 4395 Over Years

Yu Pan, Hengxiao Guo, Chenxu Liu et al. (+15 more)

NGC 4395 is a nearby dwarf spiral galaxy hosting an active galactic nucleus (AGN) powered by an intermediate-mass black hole (IMBH, $M_{\rm BH} \sim 10^{4}$–$10^{5}\,M_\odot$). Recent optical continuum reverberation mapping studies have suggested potential lag variations between different epochs, offering important clues to the physical mechanisms governing variability in the vicinity of the central black hole. We present continuous intranight multi-band photometric monitoring of NGC 4395 based on five nights of observations, including three nights from the Faulkes Telescope North (two of which are archival) and two new nights from Mephisto. This represents the first systematic investigation of optical continuum lag stability in a galaxy hosting a robustly confirmed IMBH. By applying difference-imaging techniques to both the new observations and the reprocessed archival data, we detect statistically significant optical inter-band lags of $\sim 5$–15 minutes, which increase monotonically with increasing wavelength. No obvious $u$-band lag excess is observed, implying a negligible fractional contribution from diffuse continuum (DC) emission to the optical continuum, in agreement with our spectral decomposition results. The inter-band lags remain stable over multi-year baselines. We suggest that this long-term lag stability may be related to the minor DC contribution, a relatively steady disk-corona structure, and the unusually high X-ray-to-optical luminosity ratio characteristic of low-luminosity AGNs, which likely allows X-ray reprocessing to dominate over other potential variability mechanisms. Future facilities like Gemini/SCORPIO, with its simultaneous optical-to-near-infrared coverage, will be ideally suited to play an important role in advancing this field.
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All authors Yu Pan, Hengxiao Guo, Chenxu Liu, Xinlei Chen, Yuan Fang, Jinghua Zhang, Wenwen Zuo, Philip G. Edwards, Jamie Stevens, Manqi Fu, Mouyuan Sun, Zhen-yi Cai, Guowang Du, Xingzhu Zou, Tao Wang, Xufeng Zhu, Xiangkun Liu, Xiaowei Liu

Astrophysics of Galaxies

Polarization properties of changing-look active galactic nuclei: NGC 1365 and NGC 2992

D. Hutsemékers, F. Marin, B. Agis González et al. (+2 more)

Changing-look active galactic nuclei (CLAGNs) represent a rare class of AGNs that undergo transitions from type 1 (characterized by the presence of broad emission lines in their spectra) to type 2 (absence of broad emission lines) or vice versa, over timescales ranging from months to years. Since normal type 1 and type 2 AGNs are known to show different polarization properties, detailed investigations of the CLAGN polarization can shed light on the underlying mechanisms responsible for the changing-look phenomenon. We present new (spectro)polarimetric observations of two changing-look AGNs located in the core of the inclined spiral galaxies NGC 1365 and NGC 2992. Both AGNs are radio emitters, thereby enabling a comparison of their polarization to the radio jet axis, which defines the accretion disk geometry. In the case of NGC 1365, the AGN shows polarization characteristics consistent with those observed in type 1 Seyferts, in particular polarization parallel to the radio jet. This intrinsic polarization is modified by the wavelength-dependent dichroic extinction that occurs in the galaxy bar and that rotates the polarization angle at the shortest wavelengths. NGC 2992, on the other hand, is so inclined that dichroic dust extinction in the disk completely dominates the polarization of the AGN, thus overwhelming any polarization due to scattering. Consequently, the polarization properties remain essentially constant between the different AGN states, and the faint broad lines observed in the polarized flux are most likely not scattered light. Differential dilution between the continuum and the narrow-line polarizations can explain the unusually high polarization measured in the emission lines.
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All authors D. Hutsemékers, F. Marin, B. Agis González, J.-A. Acosta Pulido, M. Kokubo

Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det

A SiPM-Based RICH Detector with Timing Capabilities for Isotope Identification

M. N. Mazziotta, L. Congedo, G. De Robertis et al. (+7 more)

In this work, we present a novel compact particle identification (PID) detector concept based on Silicon Photomultipliers (SiPMs) optimized to perform combined Ring-Imaging Cherenkov (RICH) and Time-of-Flight (TOF) measurements using a common photodetector layer. The system consists of a Cherenkov radiator layer separated from a photosensitive surface equipped with SiPMs by an expansion gap. A thin glass slab, acting as a second Cherenkov radiator, is coupled to the SiPMs to perform Cherenkov-based charged particle timing measurements. We assembled a small-scale prototype instrumented with various Hamamatsu SiPM array sensors with pixel pitches ranging from 2 to 3 mm and coupled with 1 mm thick fused silica window. The RICH radiator consisted of a 2 cm thick aerogel tile with a refractive index of 1.03 at 400 nm. The prototype was successfully tested in beam test campaigns at the CERN PS T10 beam line with pions and protons. We measured a single-hit angular resolution of about 4 mrad at the Cherenkov angle saturation value and a time resolution better than 50 ps RMS for charged particles with Z = 1. The present technology makes the proposed SiPM-based PID system particularly attractive for space applications due to the limited detector volumes available. In this work, we present beam test results obtained with the detector prototype and we discuss possible configurations optimized for the identification of ions in space applications.
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All authors M. N. Mazziotta, L. Congedo, G. De Robertis, M. Giliberti, F. Licciulli, A. Liguori, L. Lorusso, N. Nicassio, G. Panzarini, R. Pillera

High Energy Astrophysical Phenomena

Evidence of mutually exclusive outflow forms from a black hole X-ray binary

Zuobin Zhang, Jiachen Jiang, Francesco Carotenuto et al. (+13 more)

Accretion onto black holes often leads to the launch of outflows that significantly influence their surrounding environments. The two primary forms of these outflows are X-ray disk winds-hot, ionized gases ejected from the accretion disk-and relativistic jets, which are collimated streams of particles often expelled along the rotational axis of the black hole. While previous studies have revealed a general association between spectral states and different types of outflows, the physical mechanisms governing wind and jet formation remain debated. Here, using coordinated NICER and MeerKAT observations of the recurrent black hole X-ray binary 4U 1630-472, we identify a clear anti-correlation between X-ray disk winds and jets: during three recent outbursts, only one type of outflow is detected at a time. Notably, this apparent exclusivity occurs even as the overall accretion luminosity remains within the range expected for a standard thin disk, characteristic of the canonical soft state. These results suggest a competition between outflow channels that may depend on how the accretion energy is partitioned between the disk and the corona. Our findings provide new observational constraints on jet and wind formation in X-ray binaries and offer a fresh perspective on the interplay between different modes of accretion-driven feedback.
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All authors Zuobin Zhang, Jiachen Jiang, Francesco Carotenuto, Honghui Liu, Cosimo Bambi, Rob P. Fender, Andrew J. Young, Jakob van den Eijnden, Christopher S. Reynolds, Andrew C. Fabian, Julien N. Girard, Joey Neilsen, James F. Steiner, John A. Tomsick, Stéphane Corbel, Andrew K. Hughes

High Energy Astrophysical Phenomena

The puzzle of composition of cosmic rays with energies (2-12.5) EeV according to muon detectors data of the Yakutsk EAS array

A.V. Glushkov, L.T. Ksenofontov, K.G. Lebedev et al. (+1 more)

The results of a study of the cosmic ray composition in individual events in the energy range (2-12.5) EeV using the muon correlation method is presented. The considered sample included showers with zenith angles less than 60 degrees recorded in the period 1974-2018. The existence of four separate groups of primary particles with different origins is confirmed. The obtained results have potential importance for understanding the composition of cosmic rays in the specified primary energy range.
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All authors A.V. Glushkov, L.T. Ksenofontov, K.G. Lebedev, A.V. Sabourov

Cosmology and Nongalactic Astrophysics

Cosmological Constraints on f(T,B) Gravity from Observations of Early and Late Universe

Yahia Al-Omar, Majida Nahili and Nidal Chamoun

We present a unified framework that combines early- and late-Universe observations to constrain three functional realizations of f(T,B) gravity: the linear, quadratic, and general power-law models. First, constraints on deviations from the standard weak interaction freeze-out temperature are derived using the most recent measurements of the primordial helium-4 mass fraction. Second, we perform a joint analysis incorporating five priors: Type Ia supernovae, baryon acoustic oscillations, cosmic chronometers, Big Bang Nucleosynthesis, and Cosmic Microwave Background in order to place bounds on the model parameters. The joint likelihood analysis significantly tightens the constraints compared to individual datasets. Third, we test the null, strong, and dominant energy conditions to evaluate the physical viability of the best-fit solutions across the cosmic redshift range. Our results show that all three f(T,B) models are consistent with current observations and exhibit stable behavior under the energy-condition criteria, supporting torsion-boundary modified gravity as a robust and viable alternative to General Relativity.
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Solar and Stellar Astrophysics

Closed-Form Statistical Relations Between Projected Separation, Semimajor Axis, Companion Mass, and Host Acceleration

Timothy D Brandt

I derive the statistical relationship between a radial velocity or astrometric acceleration (a trend), a companion's mass, and the projected separation of the companion. These relationships, expressed as probability density functions, are analytic and independent of all Keplerian orbital elements so long as orbits are randomly oriented in space. I also derive a closed-form expression for the probability distribution of the ratio of the projected separation to the semimajor axis at fixed eccentricity. This expression can be numerically integrated over eccentricity for an arbitrary distribution of eccentricities. I verify my results with empirical comparisons to equivalent but more complex expressions in the literature based on the equations of Keplerian orbits. The closed-formed expressions derived here would be especially useful for any calculation that requires derivatives, e.g., Hamiltonian Monte Carlo. I also provide a Jupyter notebook including all figures and calculations.
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Astrophysics of Galaxies

Detailed lens modeling and kinematics of the submillimeter galaxy G09v1.97. An analysis of CO, H2O, H2O+, and dust continuum emission

K. Kade, C. Yang, M. Yttergren et al. (+14 more)

The formation mechanisms of intensely starbursting galaxies at high redshift remain unknown. One possible mechanism for triggering these starbursts is mergers and interactions, but detecting these at high redshift remains a challenge. Observations of high-redshift gravitationally lensed galaxies enable studies of the interstellar medium and environment of these extreme starbursts in detail. We used high angular resolution observations of dust continuum, CO(6-5), H2O(211-202), and H2O+(202-111) emission to constrain the ongoing processes in the z = 3.63 gravitationally lensed submillimeter galaxy H-ATLAS J083051.0+013224 (G09v1.97). We used PyAutoLens to create a de-magnified source plane CO(6-5) emission line cube and performed kinematic modeling using 3DBarolo. Additionally, we investigated the properties of the continuum and molecular line emission in the source plane. We find that the regions of CO(6-5) and H2O(211-202) emission match closely in the source plane but that the dust continuum emission is more compact. We find that our lens modeling results do not require more than one source, contrary to what has been found in previous studies. Instead, we find that G09v1.97 resembles a rotating disk with Vmax/sigma = 2.8 +/- 0.4 with evidence for residual emission indicative of non-circular motions such as outflows, tidal tails, or an additional background galaxy. We suggest that the origin of the non-circular motions may be associated with a bi-conical outflow, a tidal tail from an interaction, or indicate the possible presence of an additional galaxy. We calculate the dynamical mass, gas mass, star-formation rate, and depletion time for G09v1.97 and find a high star-formation rate and low gas depletion time. In combination, this suggests that G09v1.97 has recently undergone an interaction, triggering intense star formation, and is in the process of settling into a disk.
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All authors K. Kade, C. Yang, M. Yttergren, K. K. Knudsen, S. König, A. Amvrosiadis, S. Dye, J. Nightingale, L. Zhang, Z. Zhang, A. Cooray, P. Cox, R. Gavazzi, E. Ibar, M. J. Michałowski, P. van der Werf, R. Xue

Cosmology and Nongalactic Astrophysics

CSST Strong Lensing Preparation: Cosmological constraints from double-source-plane strong lensing systems in era of CSST

Bei-Chen Wu, Xiaoyue Cao, Nan Li et al. (+5 more)

Double source plane strong lensing (DSPL) systems offer a robust, independent probe of cosmological parameters. The Chinese Space Station Telescope (CSST) is expected to discover hundreds of DSPLs, yet the survey modes and system configurations that best enable cosmological inference remain uncertain. To investigate the impact of varying signal-to-noise ratios (SNR) and Einstein radius ratios of DSPLs (denoted as $\beta^{-1}$ parameters) on cosmographic inference under different CSST survey modes (Wide Field (WF), Deep Field (DF), and Ultra-Deep Field (UDF)), we simulate and model mock lenses with Singular Isothermal Ellipsoid (SIE) mass profiles and Sérsic sources whose image properties are tailored to CSST specifications. Assuming a flat $w$CDM universe with fiducial values $\Omega_{\rm m} = 0.30966$ and $w = -1$, and uniform priors of $\Omega_{\rm m} \in [0, 1]$ and $w \in [-2, -1/3$), we find that the constraining power on cosmological parameters for a given DSPL system increases significantly with survey depth. For a representative DSPL system with two prominent arcs and a moderate $\beta^{-1}=1.17$, the constraints on ($w, \Omega_{\rm m}$) improve from ($-1.28_{-1.00}^{+0.64}, 0.50_{-0.32}^{+0.28}$) in the WF to ($-1.59_{-0.32}^{+0.63}, 0.42_{-0.06}^{+0.15}$) in the UDF. Furthermore, we find that systems with smaller $\beta$ values yield tighter cosmographic constraints. We conclude that DSPL systems identified in UDF observations, particularly those with small $\beta$, are the most promising candidates for early-stage cosmological studies with CSST.
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All authors Bei-Chen Wu, Xiaoyue Cao, Nan Li, Yan Gong, Shenzhe Cui, Di Wu, Tong Zhao, Junhui Yan

Astrophysics of Galaxies

Decomposing the growth mechanisms of galaxies over the last 10 billion years

Luke J. M. Davies, Annagrazia Puglisi, Marcella Longhetti et al. (+10 more)

Determining how galaxies accumulate stellar mass is paramount to understanding the Universe. Two primary mechanisms drive this process: star-formation (SF) & mergers. Our understanding of star formation, and to some degree the processes that influence the baryon cycle (environment, gas supply, feedback, etc), are either relatively well constrained or will develop significantly over the coming decades via upcoming facilities (i.e. through their imprint on galaxy properties measured with deep multi-wavelength and spectroscopic data). However, the same can not be said for mergers. It is telling that we indirectly know hierarchical assembly through mergers is one of the most crucial processes that shape our Universe, but the robust observational measurement of mergers is almost non-existent outside of the local Universe - let alone how these mergers impact galaxy properties. This is not likely to significantly change in the coming decades as existing or approved facilities/surveys are inadequate in charactering mergers in the distant Universe. Motivated by this, we discuss an ambitious study to first explore mergers, and then the co-dependent astrophysical process that govern the accumulation of stellar mass over the last ~10billion years, and highlight the essential need for a 10m+ class multi-object spectroscopic facility.
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All authors Luke J. M. Davies, Annagrazia Puglisi, Marcella Longhetti, Mark Sargent, Simon P. Driver, Aaron S. G. Robotham, Sabine Bellstedt, Fabio Rosario Ditrani, Anna R. Gallazzi, Laura Scholz Díaz, Stefania Barsanti, Stefano Zibetti, Sabine Thater

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Covariant interpretation of proper infall times in Kerr spacetime

Erick Pasten, Claudia Alvarez and Norman Cruz

We investigate proper infall times in the Schwarzschild and Kerr spacetimes from a covariant perspective, focusing on the role of black–hole rotation in the focusing properties of timelike geodesic congruences.To perform a geometrically consistent comparison between rotating and non–rotating black holes, we analyse infall trajectories between surfaces of equal circumferential radius in the equatorial plane. Using equatorial timelike geodesics in the test–particle limit, we compute and compare the corresponding proper infall times for different values of the specific energy $E$, specific angular momentum $L$, and black–hole spin parameter $a$. Within the equal circumferential-radius prescription adopted here, we show that Kerr angular momentum $a$ can produce longer or shorter integrated proper infall times relative to the Schwarzschild case, depending on the orbital configuration and energy regime considered. We then interpret these results within the covariant $1+3$ formalism of general relativity, in terms of the expansion, shear, and Raychaudhuri evolution of timelike congruences. Our analysis shows that the Kerr–Schwarzschild differences in proper infall times are encoded in the corresponding Raychaudhuri time integrand, which reflects a competition between the radial evolution of the expansion and the nonlinear focusing contribution driven by expansion and shear. Black–hole rotation modifies both effects in a systematic way, leading to distinct behaviours for prograde and retrograde infall configurations.
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High Energy Astrophysical Phenomena

Constraints on Axion-Like Particles from Ultra-High-Energy Observations of 3HWC J1908+063 with HAWC

R. Alfaro, C. Alvarez, A. Andres et al. (+92 more)

Axion-like particles (ALPs) are hypothetical particles and compelling candidates for cold dark matter. Their existence could be probed through their conversions into photons in the presence of magnetic fields. In this work, we explore the effect of these photon-ALP conversions by searching for an attenuation in the observed gamma ray spectra of galactic sources that emit at energies of hundreds of TeV. We analyze data from the High-Altitude Water Cherenkov (HAWC) Observatory for the source 3HWC J1908+063. No evidence of photon-ALP conversions was found, and we set constraints on the ALP parameter space. Specifically, we derive exclusion limits for ALPs with masses in the range $10^{-8}~\mathrm{eV} \leq m_a \leq 10^{-6}~\mathrm{eV}$ and photon-ALP couplings in the range $10^{-12}~\mathrm{GeV}^{-1} \leq g_{a\gamma} \leq 10^{-10}~\mathrm{GeV}^{-1}$, based on HAWC observations.
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All authors R. Alfaro, C. Alvarez, A. Andres, E. Anita-Rangel, M. Araya, J.C. Arteaga-Velazquez, D. Avila Rojas, H.A. Ayala Solares, R. Babu, P. Bangale, E. Belmont-Moreno, A. Bernal, K.S. Caballero-Mora, T. Capistran, A. Carraminana, F. Carreon, S. Casanova, U. Cotti, J. Cotzomi, E. De la Fuente, P. Desiati, N. Di Lalla, R. Diaz Hernandez, M.A. DuVernois, J.C. Diaz-Velez, T. Ergin, C. Espinoza, N. Fraija, S. Fraija, J.A. Garcia-Gonzalez, F. Garfias, N. Ghosh, A. Gonzalez Munoz, M.M. Gonzalez, J.A. Gonzalez, J.A. Goodman, J. Gyeong, J.P. Harding, S. Hernandez-Cadena, I. Herzog, D. Huang, F. Hueyotl-Zahuantitla, A. Iriarte, S. Kaufmann, D. Kieda, A. Lara, W.H. Lee, J. Lee, H. Leon Vargas, A.L. Longinotti, G. Luis-Raya, K. Malone, O. Martinez, J. Martinez-Castro, H. Martinez-Huerta, J.A. Matthews, P. Miranda-Romagnoli, P.E. Miron-Enriquez, J.A. Morales-Soto, E. Moreno, M. Mostafa, M. Najafi, A. Nayerhoda, L. Nellen, M.U. Nisa, R. Noriega-Papaqui, N. Omodei, E. Ponce, Y. Perez Araujo, E.G. Perez-Perez, A. Pratts, C.D. Rho, A. Rodriguez Parra, D. Rosa-Gonzalez, M. Roth, A. Sandoval, M. Schneider, J. Serna-Franco, A.J. Smith, Y. Son, R.W. Springer, O. Tibolla, K. Tollefson, I. Torres, R. Torres-Escobedo, E. Varela, L. Villasenor, X. Wang, Z. Wang, I.J. Watson, H. Wu, S. Yu, X. Zhang, H. Zhou, C. de Leon

Astrophysics of Galaxies

A New Framework for Multi-Line Analysis Combined Kernel PCA and Kernel SHAP: A Case of NGC 1068 ALMA Band 3 Data

Hiroma Okubo, Tsutomu T. Takeuchi, Shotaro Akaho et al. (+7 more)

We present a new framework for multi-line analysis that combines kernel principal component analysis (Kernel PCA), an unsupervised machine-learning method, and Kernel SHapley Additive exPlanations (Kernel SHAP), an explainable artificial intelligence (XAI) technique. To enable a comparison with PCA-based studies, which have been widely used in multi-line analyses, we apply our framework to integrated intensity maps of 13 molecular lines from Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 archival data of the nearby galaxy NGC 1068. Previous PCA-based studies of NGC 1068 reported that physically meaningful structures are mainly captured up to the second component. In contrast, our framework can interpret physically meaningful features up to the fourth component. Furthermore, by comparing the results obtained from our framework with molecular column densities derived from local thermodynamical equilibrium (LTE) analysis, we suggest that the abundance of HCO+ is relatively enhanced in the molecular outflow region extending to a radius of about 400 pc from the galactic center, likely due to the effects of ultraviolet radiation and highly dense gas. These results show that our framework can provide data-driven insights into physical and chemical features that have not been clearly identified in previous studies. It also provides an efficient tool for interpreting the rapidly increasing amount of multi-line observational data.
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All authors Hiroma Okubo, Tsutomu T. Takeuchi, Shotaro Akaho, Toshiki Saito, Yasuhiko Igarashi, Nario Kuno, Nanase Harada, Akio Taniguchi, Shuro Takano, Taku Nakajima

Solar and Stellar Astrophysics

SETI Observations of k-Hz Periodic Radio Signals from Five Nearby Stars with FAST at L Band

Yu Hu, Bo-Lun Huang, Vishal Gajjar et al. (+3 more)

We report a radio SETI search for periodic, kHz-wide signals from five of the nearest stars observable with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). Using the 19-beam L-band receiver (1.05-1.45 GHz), we obtained 1200 s tracking observations of Groombridge 34 A/B, Ross 248, 61 Cygni B, and Ross 128. Dynamic spectra from all beams and both linear polarisations were searched channel by channel with a fast-folding algorithm sensitive to periods between 1.1 and 300 s. A multi-layer RFI-mitigation pipeline exploits multi-beam occupancy, cross-target bad-channel statistics, XX/YY polarisation coincidence, broad frequency masks, and narrow site-specific RFI exclusion zones, followed by clustering in period-frequency space. The pipeline is validated on FAST observations of PSR B0329+54, where we recover the known 0.714 s spin period and harmonic structure in the expected beam. For the stellar sample, successive cuts reduce the raw FFA hit lists (> 10^6 hits per target) to a small number of cluster-level candidates, all of which exhibit clear radio-frequency interference signatures in phase-time and phase-frequency diagnostics. We therefore report no convincing detections of periodic transmitters in our searched parameter space. Using the radiometer equation with our adopted detection threshold (S/N = 25) and assuming a duty cycle delta = 0.1, we obtain upper limits of approximately (7-9) x 10^9 W on the isotropic-equivalent EIRP of kHz-wide periodic beacons at these stars, among the most stringent constraints to date on periodic radio emission from nearby stellar systems.
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All authors Yu Hu, Bo-Lun Huang, Vishal Gajjar, Xiao-Hang Luan, Zhen-Zhao Tao, Tong-Jie Zhang

Cosmology and Nongalactic Astrophysics

A JWST Paschen-alpha Calibration of the Radio Luminosity-Star Formation Rate Relation at z~1.3

Nick Seymour, Catherine Hale, Imogen Whittam et al. (+17 more)

As radio emission from normal galaxies is a dust-free tracer of star formation, tracing the star formation history of the Universe is a key goal of the SKA and ngVLA. In order to investigate how well radio luminosity traces star formation rate (SFR) in the early Universe, we have examined the radio properties of a JWST Paschen-alpha sample of galaxies at 1.0<=z<=1.8. In the GOODS-S field, we cross-matched a sample of 506 FRESCO Paschen-alpha emitters with the 1.23 GHz radio continuum data from the MeerKAT MIGHTEE survey finding 47 detections. After filtering for AGN (via X-ray detections, hot mid-infrared dust and extended radio emission), as well as blended sources, we obtained a sample of SFGs comprising: 11 cataloged radio detections, 18 non-cataloged detections (at ~3-5sigma) and 298 undetected sources. Stacking the 298 undetected sources we obtain a 3.3sigma detection in the radio. This sample, along with a local sample of Paschen-alpha emitters, lies along previous radio luminosity/SFR relations from local (z<0.2) to high redshift (z~1). Fitting the FRESCO data at 1.0<=z<=1.8 we find log(L_1.4GHz) = (1.31+/-0.17) x log(SFR_Pa-alpha) + (21.36+/-0.17) which is consistent with other literature relations. We can explain some of the observed scatter in the L_1.4GHz/SFR_Pa-alpha correlation by a toy model in which the synchrotron emission is a delayed/averaged tracer of the instantaneous Paschen-alpha SFR by ~10/75 Myr.
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All authors Nick Seymour, Catherine Hale, Imogen Whittam, Pascal Oesch, Alba Covelo-Paz, Stijn Wuyts, Jose Afonso, Rebecca Bowler, Joe A. Grundy, Ravi Jaiswar, Matt Jarvis, Allison Matthews, Romain A. Meyer, Chloe Neufeld, Naveen A. Reddy, Irene Shivaei, Dan Smith, Rohan Varadaraj, Michael A. Wozniak, Lyla Jung

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Higher Harmonics of Double White Dwarfs in the Centihertz Band: Linking LISA and DECIGO

Naoki Seto

We investigate the detectability of post-Newtonian higher harmonics from Galactic double white dwarfs in the centihertz band ($\sim 0.01$ Hz). Using a synthetic population, we show that, unlike the quadrupole mode, higher harmonics remain undetectable with LISA except for rare nearby systems. In contrast, planned mid-band (decihertz) observatories such as DECIGO and BBO will be able to detect the third harmonic for about 10% of inspiral binaries above $\sim 5$ mHz, enabling statistical constraints on mass ratios. These results highlight the successive roles of LISA and future decihertz missions in establishing a coherent strategy for space-based gravitational-wave astronomy.
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Solar and Stellar Astrophysics

The Effects of Radially Varying Diffusivities on Stellar Convection Zone Dynamics

Brandon J. Lazard, Nicholas A. Featherstone and Jonathan M. Aurnou

Convection is ubiquitous in stellar and planetary interiors where it likely plays an integral role in the generation of magnetic fields. As the interiors of these objects remain hidden from direct observation, numerical models of convection are an important tool in the study of astrophysical dynamos. In such models, unrealistic large values of the viscous ($\nu$) and thermal ($\kappa$) diffusivity are routinely used as an ad-hoc representation of the effects of subgrid scale turbulence which is otherwise too small-scale to resolve numerically. However, the functional forms of these diffusion coefficients can vary greatly between studies, complicating efforts to compare between results and against observations. We explore this issue by considering a series of non-rotating, non-magnetic, solar-like convection models with varying radial functions for the diffusivities and differing boundary conditions. We find that the bulk kinetic energy scales similarly regardless of the diffusivity parameterization. This scaling is consistent with a free-fall scaling, wherein viscosity plays a subdominant role in the force balance. We do not, however, observe such diffusion-free behavior in the convective heat transport. Our results also indicate that the functional form adopted for the diffusion coefficients can impact the distribution of turbulence within the convective shell. These results suggest that some care should be taken when comparing solar convection models directly against helioseismic observations.
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Astrophysics of Galaxies

Signatures of a Tidally Induced Spiral Arm at the Anticenter of the Milky Way and a Kinematically Extended Anticenter Stream Using DESI DR2

Mika Lambert, Constance M. Rockosi, Sergey E. Koposov et al. (+46 more)

Using the Dark Energy Spectroscopic Instrument Milky Way Survey (DESI MWS), we examine the 6D space of the anticenter region of the stellar disk (150$^\circ$ $<$ Galactic longitude $<$ 220$^\circ$) using 61,883 main-sequence turnoff stars. We focus on two well-known stellar overdensities in the anticenter, the Monoceros Ring (MRi) and Anticenter Stream (ACS). We find that the MRi overdensity has kinematics consistent with a tidally induced spiral arm, a type of dynamic spiral arm created by an interaction with a satellite galaxy, most likely the Sagittarius dwarf spheroidal galaxy (Sgr). We use the kinematics of the MRi to calculate the two most recent passage times of Sgr are 0.25 $\pm$ 0.09 Gyrs and 1.10 $\pm$ 0.23 Gyrs from the present day. We validate that the ACS is kinematically decoupled from the MRi because they are moving in opposite radial and vertical directions. We find that the kinematics associated with the ACS are not confined to our defined overdensity. The features we see in the ACS region are likely part of a broader distribution of stars with the same kinematic signature as detected in other places, like the vertical wave in the outer disk and phase spiral.
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All authors Mika Lambert, Constance M. Rockosi, Sergey E. Koposov, Ting S. Li, Monica Valluri, Leandro Beraldo e Silva, Songting Li, Joaõ A. S. Amarante, Amanda Byström, Gustavo E. Medina, Nathan R. Sandford, Joan Najita, Namitha Kizhuprakkat, Jessica N. Aguilar, Steven Ahlen, Davide Bianchi, David Brooks, Todd Claybaugh, Kyle Dawson, Axel de la Macorra, Peter Doel, Jaime E. Forero-Romero, Enrique Gaztañaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Dick Joyce, Anthony Kremin, Claire Lamman, Martin Landriau, Laurent Le Guillou, Marc Manera, Aaron Meisner, Ramon Miquel, John Moustakas, Adam Myers, Seshadri Nadathur, Will Percival, Francisco Prada, Ignasi Perez-Rafols, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Joseph H. Silber, David Sprayberry, Gregory Tarle, Benjamin A. Weaver, Rongpu Zhou, Hu Zou

Cosmology and Nongalactic Astrophysics

Dark Energy Survey Year 6 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing

DES Collaboration: T. M. C. Abbott, M. Adamow, M. Aguena et al. (+168 more)

We present cosmology results combining galaxy clustering and weak gravitational lensing measured in the full six years (Y6) of observations by the Dark Energy Survey (DES) covering $\sim$5000 deg$^2$. We perform a large-scale structure analysis using three two-point correlation functions (3$\times$2pt): (i) cosmic shear from 140 million source galaxy shapes, (ii) galaxy clustering of 9 million lens galaxy positions, and (iii) galaxy-galaxy lensing from their cross-correlation. We model the data in flat $\Lambda$CDM and $w$CDM cosmologies. The combined analysis yields $S_8\equiv \sigma_8 (\Omega_{\rm m}/0.3)^{0.5} = 0.789^{+0.012}_{-0.012}$ and matter density $\Omega_{\rm m} = 0.333^{+0.023}_{-0.028}$ in $\Lambda$CDM (68% CL), where $\sigma_8$ is the clustering amplitude. These constraints show a (full-space) parameter difference of 1.8$\sigma$ from a combination of cosmic microwave background (CMB) primary anisotropy datasets from Planck 2018, ACT-DR6, and SPT-3G DR1. Projected only into $S_8$ the difference is $2.6\sigma$. In $w$CDM the Y6 3$\times$2pt results yield $S_8 = 0.782^{+0.021}_{-0.020}$, $\Omega_{\rm m} = 0.325^{+0.032}_{-0.035}$, and dark energy equation-of-state parameter $w = -1.12^{+0.26}_{-0.20}$. For the first time, we combine all DES dark-energy probes: 3$\times$2pt, SNe Ia, BAO and Clusters. In $\Lambda$CDM this combination yields a $2.8\sigma$ parameter difference from the CMB. When combining DES 3$\times$2pt with other low-redshift datasets (DESI DR2 BAO, DES SNe Ia, SPT clusters), we find a 2.3$\sigma$ parameter difference with CMB. A joint fit of Y6 3$\times$2pt, CMB, and those low-redshift datasets produces the tightest $\Lambda$CDM constraints to date: $S_8 = 0.806^{+0.006}_{-0.007}$, $\Omega_{\rm m} = 0.302^{+0.003}_{-0.003}$, $h = 0.683^{+0.003}_{-0.002}$, and $\sum m_\nu < 0.14$ eV (95% CL). In $w$CDM, this combination yields $w = -0.981^{+0.021}_{-0.022}$.
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All authors DES Collaboration: T. M. C. Abbott, M. Adamow, M. Aguena, A. Alarcon, S. S. Allam, O. Alves, A. Amon, D. Anbajagane, F. Andrade-Oliveira, S. Avila, D. Bacon, E. J. Baxter, J. Beas-Gonzalez, K. Bechtol, M. R. Becker, G. M. Bernstein, E. Bertin, J. Blazek, S. Bocquet, D. Brooks, D. Brout, H. Camacho, G. Camacho-Ciurana, R. Camilleri, G. Campailla, A. Campos, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, P. Carrilho, F. J. Castander, R. Cawthon, C. Chang, A. Choi, J. M. Coloma-Nadal, M. Costanzi, M. Crocce, W. d'Assignies, L. N. da Costa, M. E. da Silva Pereira, T. M. Davis, J. De Vicente, J. DeRose, H. T. Diehl, S. Dodelson, P. Doel, C. Doux, A. Drlica-Wagner, T. F. Eifler, J. Elvin-Poole, J. Estrada, S. Everett, A. E. Evrard, J. Fang, A. Farahi, A. Ferté, B. Flaugher, P. Fosalba, J. Frieman, J. García-Bellido, M. Gatti, E. Gaztanaga, G. Giannini, P. Giles, K. Glazebrook, M. Gorsuch, D. Gruen, R. A. Gruendl, J. Gschwend, G. Gutierrez, I. Harrison, W. G. Hartley, E. Henning, K. Herner, S. R. Hinton, D. L. Hollowood, K. Honscheid, E. M. Huff, D. Huterer, B. Jain, D. J. James, M. Jarvis, N. Jeffrey, T. Jeltema, T. Kacprzak, S. Kent, A. Kovacs, E. Krause, R. Kron, K. Kuehn, O. Lahav, S. Lee, E. Legnani, C. Lidman, H. Lin, N. MacCrann, M. Manera, T. Manning, J. L. Marshall, S. Mau, J. McCullough, J. Mena-Fernández, F. Menanteau, R. Miquel, J. J. Mohr, J. Muir, J. Myles, R. C. Nichol, B. Nord, J. H. O'Donnell, R. L. C. Ogando, A. Palmese, M. Paterno, J. Peoples, W. J. Percival, D. Petravick, A. Pieres, A. A. Plazas Malagón, A. Porredon, A. Pourtsidou, J. Prat, C. Preston, M. Raveri, W. Riquelme, M. Rodriguez-Monroy, P. Rogozenski, A. K. Romer, A. Roodman, R. Rosenfeld, A. J. Ross, E. Rozo, E. S. Rykoff, S. Samuroff, C. Sánchez, E. Sanchez, D. Sanchez Cid, T. Schutt, I. Sevilla-Noarbe, E. Sheldon, N. Sherman, T. Shin, M. Smith, M. Soares-Santos, E. Suchyta, M. E. C. Swanson, M. Tabbutt, G. Tarle, D. Thomas, C. To, A. Tong, L. Toribio San Cipriano, M. A. Troxel, M. Tsedrik, D. L. Tucker, V. Vikram, A. R. Walker, N. Weaverdyck, R. H. Wechsler, D. H. Weinberg, J. Weller, V. Wetzell, A. Whyley, R.D. Wilkinson, P. Wiseman, H.-Y. Wu, M. Yamamoto, B. Yanny, B. Yin, G. Zacharegkas, Y. Zhang, J. Zuntz

Cosmology and Nongalactic Astrophysics

IRMaGiC: Extending Luminous Red Galaxy Selection into the Infrared with Joint Rubin Observatory's Large Survey of Space Time and Roman's High Latitude Imaging Survey

Zhiyuan Guo, Chris. W. Walter and Eli S. Rykoff

We introduce IRMaGiC, an algorithm built based on RedMaGiC desgined to enhance the selection of Luminous Red Galaxies (LRGs) across the redshift range $1 \leq z \leq 2$. We show that this method extends the capabilities of the redMaGiC algorithm by applying it to simulated photometric data from the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) and the Nancy Grace Roman Space Telescope's High Latitude Wide Area Survey (HLWAS). By integrating infrared band coverage from Roman HLWAS with LSST's optical bands, IRMaGiC enables red-sequence calibration at higher redshifts. We demonstrate that IRMaGiC reduces scatter and bias in photometric redshift estimates for LRGs at higher redshift, providing more accurate redshift assessments compared to existing methods. Our findings suggest that incorporating infrared data can considerably improve the selection and redshift estimation of LRGs at higher redshift, offering substantial benefits for future cosmological surveys.
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Tuesday 20 January

Instrumentation and Methods for Astrophysics · Cross-listed from physics.class-ph

Visualisation of spherical harmonics in Peirce's quincuncial projection

Bjoern Malte Schaefer

The spherical harmonics $Y_{\ell m}(\theta,\varphi)$ are complex-valued functions on the surface of a sphere, and have found widespread application in physics and astronomy. Every physics students knows them from quantum mechanics and electromagnetic theory, where they form the basis of hydrogen orbitals and of the multipole expansion, respectively. More advanced applications include the physics of the cosmic microwave background, gravitational lensing, and gravitational waves. In this paper I aim to contrast their usual $3d$ visualisation with Peirce's quincuncial projection, a conformal projection of the sphere onto a $2d$ unfolded square dihedron, where the projection respects the fundamental rotational symmetries and preserves angles. With this mapping, I guide the reader through the properties of the spherical harmonics in a pedagogical way and show that many of their mathematical relations have an intuitive visualisation on Peirce's $2d$ map, which might be useful for people challenged by processing $3d$ shapes, or which people might appreciate aesthetically.
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Cosmology and Nongalactic Astrophysics

Calibration-independent consistency test of BAO and SNIa data: update

Bikash R. Dinda, Roy Maartens and Chris Clarkson

In a recent paper, arXiv:2509.19899, we presented a new method to test the consistency between uncalibrated BAO and SNIa data through a common parameter, the Alcock-Paczynski variable. Using Gaussian Processes, we can determine if various datasets are consistent, independently of dark energy or modified gravity models, and of the sound horizon and SNIa peak magnitude. We found that the DES-Y5 SNIa data showed non-negligible tension with other datasets. However, the recent update DES-Dovekie removes this tension. We find that all uncalibrated data from DESI DR2 BAO and three SNIa datasets, Union3, Pantheon+, and DES-Dovekie, are consistent with each other within $\sim 1\sigma$.
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Astrophysics of Galaxies

New techniques to investigate the AGN-SF connection with integral field spectroscopy

Aman Chopra, Henry R. M. Zovaro and Rebecca L. Davies

Understanding the connection between active galactic nuclei and star-formation (the AGN-SF connection) is one of the longest standing problems in modern astrophysics. In the age of large Integral Field Unit (IFU) surveys, studies of the AGN-SF connection greatly benefit from spatially resolving AGN and SF contributions to study the two processes independently. Using IFU data for 54 local active galaxies from the S7 sample, we present a new method to separate emission from AGN activity and SF using mixing sequences observed in the [NII]$\lambda 6584$/H$\alpha$ vs. [OIII]$\lambda 5007$/H$\beta$ Baldwin-Phillips-Terlevich (BPT) diagram. We use the new decomposition method to calculate the H$\alpha$ star-formation rate and AGN [OIII] luminosity for the galaxies. Our new method is robust to outliers in the line-ratio distribution and can be applied to large galaxy samples with little manual intervention. We infer star-formation histories (SFHs) using pPXF, conducting detailed recovery tests to determine the quantities that can be considered robust. We test the correlation between the AGN Eddington ratio, using the proxy L[OIII]/$\sigma_*^4$, and star-formation properties. We find a moderately strong correlation between the Eddington ratio and the star-formation rate (SFR). We also observe marginally significant correlations between the AGN Eddington ratio and the light-weighted stellar age under 100 Myr. Our results point to higher AGN accretion being associated with young nuclear star formation under 100 Myr, consistent with timelines presented in previous studies. The correlations found in this paper are relatively weak; extending our methods to larger samples, including radio-quiet galaxies, will help better constrain the physical mechanisms and timescales of the AGN-SF connection.
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