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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 10 February

Earth and Planetary Astrophysics

Cold and eccentric: a high-spectral resolution view of 51 Eri b with VLT/HiRISE

A. Denis, A. Vigan, G. Chauvin et al. (+35 more)

Discovered almost 10 years ago, the giant planet 51 Eridani b is one of the least separated (0.2 arcsec) and faintest (J = 19.74 mag) directly imaged exoplanets known to date. Its atmospheric properties have been thoroughly investigated through low- and medium-resolution spectroscopic observations, enabling robust characterization of the planet's bulk parameters. However, the planet's intrinsically high contrast renders high-resolution spectroscopic observations difficult, despite their potential to yield key measurements essential for a more comprehensive characterization. This study seeks to constrain the planet's radial velocity, enabling a full 3D orbital solution when integrated with previous measurements. We have obtained 4 high-contrast high-resolution (R = 140000) spectroscopic datasets of the planet, collected over a two-year interval with the HiRISE visitor instrument at the VLT to derive the planet's radial velocity. Using self-consistent models of atmosphere, we were able to derive the radial velocity of the planet at each of the 4 epochs. These radial velocity measurements were then used in combination with all existing relative astrometry in order to constrain the orbit of the planet. Our radial velocity measurements allow us to break the degeneracy along the line of sight, making it now possible the unambiguous interpretation of the phase curve of the companion. We further constrain the orbital parameters, particularly the eccentricity, for which we derive e = 0.55 (-0.07, +0.03). The relatively high eccentricity indicates that the system has experienced dynamical interactions induced by an external perturber. We place constraints on the mass and semi-major axis of a hypothetical, unseen outer planet capable of producing the observed high eccentricities.
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All authors A. Denis, A. Vigan, G. Chauvin, A. Lacquement, H. Beust, M. Ravet, J. Costes, A. Radcliffe, S. Martos, W. Balmer, T. Stolker, P. Palma Bifani, B. Rajpoot, A. Simonnin, S. Petrus, T. Forveille, M. Janson, A. Reiners, N. Godoy, D. Cont, L. Nortmann, K. Hoy, A. Zurlo, H. Anwand-Heerwart, Y. Charles, A. Costille, M. El Morsy, J. Garcia, M. Houllé, M. Lopez, G. Murray, E. Muslimov, G.P.P.L. Otten, J. Paufique, M. Phillips, U. Seemann, A. Viret, G. Zins

Earth and Planetary Astrophysics

Long-Term Evolution of Close-in Sub-Neptunes and Outer Planetary Embryos: Atmospheric Mass Loss and Origin of Planets Inside and Outside the Radius Gap

Yaxing He, Masahiro Ogihara and Kangrou Guo

As a byproduct of sub-Neptune formation, planetary embryos with high eccentricity can remain in outer orbits, near 1 au from the star. In this work, we investigate the long-term evolution of systems consisting of close-in sub-Neptunes (SNs) and outer high-eccentricity embryos. Our analysis focuses on collisions between SNs and embryos, particularly their atmospheric mass loss. We performed N-body simulations for various initial eccentricities and numbers of embryos. We analyzed the impact-induced atmospheric loss using post-processing methods, finding that the embryos and SNs collide at high speeds on timescales of several million years, leading to the loss of the SNs' atmospheres. Depending on the embryos' eccentricity and the orbital radius of the SNs, the impact velocity can be quite high, ranging from 2 to 5 times the escape velocity. On average, about 15%-30% of the atmosphere is dissipated per collision, so after 3-6 collisions, the atmospheric mass of an SN is reduced to about 1/3 of its initial value. Collisions between SNs and embryos can thus explain the presence of planets within the radius gap. Depending upon the initial eccentricity and the number of remaining embryos, additional collisions can occur, potentially accounting for the formation of the radius gap. This study also indicates that collisions between remaining embryos and SNs may help to explain the observed rarity of SNs with atmospheric mass fractions greater than 10%, commonly termed the "radius cliff."
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Astrophysics of Galaxies

The S-PLUS Fornax Project (S+FP): An extragalactic catalog covering $\sim$ 5 virial radii around NGC 1399 with galaxy properties

R. F. Haack, A. V. Smith Castelli, L. Sodré Jr. et al. (+22 more)

Observational extragalactic catalogs over wide sky areas are essential for uncovering the large-scale structure of the Universe. They allow, among others, cosmological studies and density analyses that impose strong constraints on models of galaxy formation and evolution. By taking advantage of the wide field images and the 12 optical bands of the Southern Photometric Local Universe Survey (S-PLUS), we aim at providing a catalog of galaxies located, in projection, towards the Fornax galaxy cluster, within $\sim$ 5 virial radii in right ascension (R.A.) and $\sim$ 3 virial radius in declination (Dec) around NGC,1399, the dominant galaxy of the cluster. Such a catalog will allow unprecedented large-scale structure studies in that sky region. Supervised deep learning algorithms have been developed, utilizing neural networks complemented with dimensionality reduction techniques, to classify and separate spurious objects, stars and galaxies in a photometric catalog previously built for the S-PLUS Fornax Project (S+FP). That catalog was built using a combination of SExtractor configurations optimized for galaxy detection and characterization. A catalog of 119,580 galaxies was obtained in the direction of the Fornax cluster containing photometric information in the 12 optical bands of S-PLUS complemented with GALEX (UV), VHS-VISTA (NIR) and AllWISE (MIR) data. We estimate photometric redshifts ({\sigma}_ NMAD $\sim$ 0.0219) with a lower limit of z_ lim $\sim$ 0.03. Stellar masses, star formation rates (SFRs) and D4000_N index estimates were obtained through a machine learning approach, by matching S-PLUS photometric data to SDSS spectroscopic data. The completeness of the catalog (72%) was calculated by comparing with mock catalogs ...
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All authors R. F. Haack, A. V. Smith Castelli, L. Sodré Jr., C. Mendes de Oliveira, A. R. Lopes, L. A. Gutiérrez-Soto, R. Demarco, D. E. Olave-Rojas, E. R. Carrasco, P. K. Humire, J. P. Calderón, F. de Almeida Fernandes, L. Lomelí-Núñez, G. Sepúlveda, C. Lima-Dias, S. Torres Flores, E. Telles, N. M. Cardoso, D. Palma, L. Doubrawa, D. Pallero, M. Marinello, W. Schoenell, T. Ribeiro, A. Kanaan

Solar and Stellar Astrophysics

Linking Solar Magnetism, Extreme Solar Particle Events and Stellar Superflares

Valeriy Vasilyev, Natalie Krivova and Ilya Usoskin

The magnetic field of the Sun drives a wide range of eruptive phenomena, from small-scale nanoflares to large flares and coronal mass ejections (CMEs). While direct observations of solar activity cover only the past few decades, indirect evidence indicates that the Sun can occasionally produce events orders of magnitude stronger than any recorded ones in the modern era. Two complementary lines of evidence exist. First, extreme solar particle events (ESPEs) have been inferred from prominent spikes in cosmogenic isotope concentrations preserved in precisely dated natural archives such as tree rings and ice cores over the past 15 millennia. Second, high-precision space-borne photometry has revealed superflares on thousands of stars similar to the Sun. Whether these solar and stellar extremes are physically related remains an open question. We summarise the present state of understanding and discuss physical mechanisms that may link them. Although superflares and ESPEs are both extremely energetic manifestations of magnetic energy storage and release, their relationship does not appear to be one-to-one. Their occurrence and energetics likely depend on how magnetic flux and topology govern the partitioning of released energy between radiation, mass ejection, and particle acceleration.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Accelerated expansion of the universe purely driven by scalar field fluctuations

Daniel Jiménez-Aguilar

We show that scalar field fluctuations alone can drive cosmic acceleration, provided the universe is spatially closed and the Compton wavelength of the field exceeds the radius of curvature. This mechanism may open new perspectives on inflation and dark energy, which could arise from a gas of sufficiently light bosons in a closed universe.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Gravitational scalar production with a generic reheating scenario

Francesco Costa and Jinsu Kim

Gravitational production of decoupled scalars during inflationary and post-inflationary phases is efficient and can lead to over-production. We study this production with various reheating scenarios such as a generic power-law inflaton potential $V_{\rm inf}\propto \phi^k$ as well as a multi-stage reheating scenario. We derive constraints on the scalar self-interaction coupling $\lambda_s$, the mass $m_s$, and coefficients of quantum gravity-induced operators. We find that the constraints depend sensitively on the reheating dynamics. Our analysis demonstrates that universal gravity effects do not necessarily spoil the predictivity of non-thermal dark matter scenarios with $k < 4$ and low reheating temperatures, as an extended reheating phase dilutes gravitationally-produced relics. For $k > 4$, on the other hand, the relic abundance is enhanced during the reheating phase, leading to stringent constraints on the scalar. In multi-stage reheating, we show that the enhancement/dilution effect of subsequent reheating phases factorises.
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High Energy Astrophysical Phenomena

On the Expected Orbitally-modulated TeV Signatures of Spider Binaries: The Effect of Intrabinary Shock Geometry

Christo Venter, Andreas Kopp, Zorawar Wadiasingh et al. (+2 more)

'Spider' binary systems - black widow and redback compact binaries differentiated by their companion's mass and nature - are an important type of pulsar system exhibiting a rich empirical phenomenology, including radio eclipses, optical light curves from a heated companion, as well as non-thermal X-ray and GeV orbital light curves and spectra. Multi-wavelength observations have now resulted in the detection of >~50 of these systems in which a millisecond pulsar heats and ablates its low-mass companion via its intense pulsar wind. Broadband observations have established the presence of relativistic leptons that have been accelerated in the pulsar magnetosphere and near the intrabinary shock, as well as a hot companion, presenting an ideal environment for the creation of orbitally-modulated inverse Compton fluxes that should be within reach of current and future Cherenkov telescopes. We have included an updated synchrotron kernel, different parametric injection spectral shapes, and several intrabinary shock geometries in our emission code to improve our predictions of the expected TeV signatures from spider binaries. Our updated phase-dependent spectral and energy-dependent light curve outputs may aid in constraining particle energetics, wind properties, shock geometry, and system inclination of several spider binaries.
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All authors Christo Venter, Andreas Kopp, Zorawar Wadiasingh, Alice K Harding, M Baring

Solar and Stellar Astrophysics

The Landscape of Unstable Mass Transfer in Interacting Binaries and Its Imprint on the Population of Luminous Red Novae

Angela A. G. Twum, Alejandro Vigna-Gómez, Morgan MacLeod et al. (+4 more)

A common-envelope (CE) phase occurs when a star engulfs its companion and is widely considered the primary channel for producing Luminous Red Novae (LRNe). In this study, we combine binary-population synthesis with stellar-evolution calculations to systematically estimate the mass, velocity, and launching radius of ejecta produced during coalescence across a range of binary configurations. Our aim is to quantify how unstable mass-transfer dynamics in binaries at various evolutionary stages shape CE outcomes, enabling a predictive framework for modeling the LRN luminosity function. We find a bimodal distribution of plateau luminosities with significant implications for binary mass stability criteria that can be tested with forthcoming LSST observations. This bimodality emerges from differing mass-ejection outcomes during common-envelope interactions, which can lead either to stellar mergers, often accompanied by tidal disruption of the companion, or to successful envelope ejection. Although our predicted plateau luminosities and timescales broadly match existing observations, the models underpredict the number of LRNe with long-duration plateaus ($t_p \gtrsim 100\, \text{d}$) by about a third. We propose that these long-duration events arise from highly extended progenitors whose envelopes are ejected over multiple orbits (i.e., non-impulsively), producing relatively faint, long-lived transients. By constraining ejecta properties and incorporating pre-outburst progenitor imaging, we show how our models can clarify the physical processes that drive unstable mass transfer in these events. Finally, we argue that common-envelope interactions involving white-dwarf accretors can yield exotic outcomes, including red giants containing embedded white dwarfs that resemble Thorne-Żytków objects (TŻOs), along with calcium-rich supernovae that preserve hydrogen envelopes.
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All authors Angela A. G. Twum, Alejandro Vigna-Gómez, Morgan MacLeod, Rosa Wallace Everson, Ricardo Yarza, V. Ashley Villar, Enrico Ramirez-Ruiz

High Energy Astrophysical Phenomena

Evidence for neutrino emission from X-ray Bright Seyfert Galaxies in the Southern Hemisphere using Enhanced Starting Track Events with IceCube

R. Abbasi, M. Ackermann, J. Adams et al. (+428 more)

IceCube recently reported the observation of TeV neutrinos from the nearby Seyfert galaxy NGC~1068, and the corresponding neutrino flux is significantly higher than the upper limit implied by observations of GeV-TeV gamma rays. This suggests that neutrinos are produced near the supermassive black hole, where the radiation density is high enough to obscure gamma rays. We use a set of muon neutrinos with interaction vertices inside the detector, which have good sensitivity to sources in the Southern sky, from IceCube data recorded between 2011 and 2021. We then search for individual and collective neutrino signals from 14 Seyfert galaxies in the Southern Sky selected from the Swift Burst Alert Telescope (BAT) AGN Spectroscopic Survey. Using the correlations between keV X-rays and TeV neutrinos predicted by disk-corona models, and assuming production characteristics similar to NGC~1068, a collective neutrino signal search reveals an excess of $6.7_{-3.2}^{+4.0}$ events, which is inconsistent with background expectations at the 3$\sigma$ level of significance. In this paper, we present new independent evidence that Seyfert galaxies contribute to the extragalactic flux of high-energy neutrinos.
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All authors R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, J. Baines-Holmes, A. Balagopal V., S. W. Barwick, S. Bash, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, I. Bodo, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, M. A. Campana, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Z. Chen, D. Chirkin, S. Choi, B. A. Clark, P. Coleman, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, L. Fischer, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, G. Garg, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, C. Haack, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Ha Minh, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, M. Karl, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, H. Kimku, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, J. Krishnamoorthi, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, N. Lad, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, J. Madsen, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, S. Mechbal, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, M. Moulai, D. Mousadi, E. Moyaux, T. Mukherjee, R. Naab, M. Nakos, U. Naumann, J. Necker, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, M. Plum, A. Pontén, V. Poojyam, Y. Popovych, M. Prado Rodriguez, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, S. Reusch, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, P. Schaile, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. G. Schröder, L. Schumacher, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, S. Tilav, K. Tollefson, S. Toscano, D. Tosi, A. Trettin, A. K. Upadhyay, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, M. Wolf, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman

Instrumentation and Methods for Astrophysics

Optimizing Deep Learning Photometric Redshifts for the Roman Space Telescope with HST/CANDELS

Ashod Khederlarian, Brett H. Andrews, Jeffrey A. Newman et al. (+2 more)

Photometric redshifts (photo-$z$'s) will be crucial for studies of galaxy evolution, large-scale structure, and transients with the Nancy Grace Roman Space Telescope. Deep learning methods leverage pixel-level information from ground-based images to achieve the best photo-$z$'s for low-redshift galaxies, but their efficacy at higher redshifts with deep, space-based imaging remains largely untested. We used Hubble Space Telescope CANDELS optical and near-infrared imaging to evaluate fully-supervised, self-supervised, and semi-supervised deep learning photo-$z$ algorithms out to $z\sim3$. Compared to template-based and classical machine learning photometry methods, the fully-supervised and semi-supervised models achieved better performance. Our new semi-supervised model, PITA (Photo-$z$ Inference with a Triple-task Algorithm), outperformed all others by learning from unlabeled and labeled data through a three-part loss function that incorporates images and colors for all objects as well as redshifts when available. PITA produces a latent space that varies smoothly in magnitude, color, and redshift, resulting in the best photo-$z$ performance even when the redshift training set was significantly reduced. In contrast, the self-supervised approach produced a latent space with significant color and redshift fluctuations that hindered photo-$z$ inference. Looking forward to Roman, we recommend using semi supervised deep learning to take full advantage of the information contained in the hundreds of millions of high-resolution images and color measurements, together with the limited redshift measurements available, to achieve the most accurate photo-$z$ estimates for both faint and bright sources.
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All authors Ashod Khederlarian, Brett H. Andrews, Jeffrey A. Newman, Tianqing Zhang, Biprateep Dey

Astrophysics of Galaxies

The Keck/DEIMOS Stellar Archive: II. Dynamical Masses and Metallicities for a Uniform Sample of Milky Way Satellites

Marla Geha

Population-level studies of Milky Way satellites used to constrain dark matter or the threshold of galaxy formation often rely on velocity dispersions and metallicities derived from heterogeneous spectroscopic analyses. Systematic differences between data reduction pipelines and membership criteria can masquerade as astrophysical signals, or obscure real trends. Here, we present the largest self-consistent sample of spectroscopically-derived quantities for Milky Way satellite galaxies and globular clusters based on a homogeneous re-analysis of individual stars observed with the Keck/DEIMOS spectrograph. We determine enclosed dynamical masses, mean [Fe/H] metallicities, and metallicity dispersions for 67 systems with 10 or more member stars. At a given stellar mass, systems classified as satellite galaxies are well separated from globular clusters in their dynamical mass and mass-to-light ratios. The average enclosed mass densities of satellite galaxies agree with semi-analytic CDM model predictions. For satellite galaxies, we observe a break in the stellar mass-metallicity relation near log M*/Msun = 4 (M_V ~ -4.5). Above this stellar mass, satellite galaxies show the well-known tight trend (0.16 dex scatter in [Fe/H]) of decreasing metallicity with stellar mass; below log M*/Msun = 4, the mass-metallicity relation flattens and/or increases in scatter. Satellite galaxies have internal metallicity scatter between 0.3-0.4 dex across our stellar mass range. These uniform measurements will enable tighter constraints on the stellar mass-halo mass relation, improved J-factor estimates for dark matter searches, and lay a foundation for interpreting the flood of new Milky Way satellites expected in the LSST/Roman/Euclid era.
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Astrophysics of Galaxies

The Keck/DEIMOS Stellar Archive: I. Uniform Velocities and Metallicities for 78 Milky Way Dwarf Galaxies and Globular Clusters

Marla Geha, Debora Pelliccia, J.Xavier Prochaska et al. (+5 more)

We present a homogeneous spectroscopic dataset of 22,339 stars in 78 Milky Way dwarf galaxy satellites and globular clusters. All data were taken with the Keck II telescope and Deep Extragalactic Imaging Multiobject Spectrograph (DEIMOS) spectrograph using the 1200G grating (spectral resolution R~6000). Based on a uniform data reduction of 411 DEIMOS masks, we present a catalog of individual stellar radial velocities, equivalent width-based [Fe/H] metallicities, and membership estimates. The Milky Way satellites range from M_V = 2 to -14 (M* = 10^1.5 to 10^7.5 Msun); the majority of individual stars presented in these systems have magnitudes 17 > r > 22. The data were reduced to 1D spectra using PypeIt, which provides near Poisson statistics-level sky subtraction. Radial velocities were determined via dmost, a forward modeling method first presented here, which combines both synthetic telluric and stellar templates to determine stellar radial velocities. We assess the accuracy and precision our method via comparison to thousands of repeat measurements and literature values. We determine a velocity error floor of 1.1 km/s and a CaII triplet-based metallicity error floor of 0.1 dex. We calculate internal velocity dispersions and compare to literature values, demonstrating 20-50% improved precision over the literature in most cases. In a companion paper, we use our homogeneous catalogs to explore properties of these Milky Way satellites, including previously unpublished measurements in several systems including Bootes II and Draco II. We provide full access to the data catalogs to enable further studies.
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All authors Marla Geha, Debora Pelliccia, J.Xavier Prochaska, William Cerny, Frederick B. Davies, Joseph Hennawi, Brad Holden Dusty Reichwein, Kyle B. Westfall

High Energy Astrophysical Phenomena

New Deep Radio Continuum Imaging Still Indicates a Large Reservoir of Undiscovered Millisecond Pulsars in Terzan 5

Ryan Urquhart, Jay Strader, Laura Chomiuk et al. (+4 more)

We present the deepest and highest-resolution radio continuum imaging of the Galactic globular cluster Terzan 5, one of the most crowded locations in the radio sky. In these new 2$-$4 GHz Karl G. Jansky Very Large Array images, we detect 38 of the 49 confirmed pulsars, including extensive multi-frequency eclipse mapping of the luminous redback Ter5A. Nonetheless, there is still a large amount of diffuse residual flux from pulsars that are fainter than our 2.5 GHz continuum detection limit of $\sim 11\,\mu$Jy. Using a range of approaches including image-based simulations, we model the fluxes of the detected pulsars together with the residual flux. We find a minimum total population of $N\sim250$ detectable pulsars in Terzan 5 and perhaps substantially more, though the luminosity function remains very uncertain. Consideration of the $\gamma$-ray properties of the cluster, though also not unambiguous to interpret, leads to consistent conclusions. These pulsar population estimates are larger than inferred from previous work and highlight Terzan 5 as a keystone target for next-generation radio facilities.
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All authors Ryan Urquhart, Jay Strader, Laura Chomiuk, Scott M. Ransom, Craig O. Heinke, Arash Bahramian, Thomas J. Maccarone

Earth and Planetary Astrophysics

Keck Observations in the INfrared of Taurus and $\rho$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU) II: Two Young Bound Companions to Ophiuchus Stars

Samuel Walker, Michael C. Liu, Dimitri Mawet et al. (+4 more)

We present the second set of discoveries from Keck Observations in the INfrared of Taurus and $\rho$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU), an adaptive optics survey of young stars in the Taurus and $\rho$ Oph star-forming regions using Keck/NIRC2 in conjunction with the Keck infrared pyramid wavefront sensor. We have discovered two faint comoving companions to young stars ISO-Oph 96 and 2MASS J16262785-2625152. The companion to ISO-Oph 96, KOINTREAU-3b, is at a projected separation of 340 au (2.49"). Using our NIRC2 photometry and evolutionary models, and assuming that the companion has the same extinction as its host star, we infer that KOINTREAU-3b has a mass of $3.4\pm0.7$ M$_{\rm Jup}$. The companion to 2MASS J16262785-2625152, KOINTREAU-4b, has a projected separation of 180 au (1.25") and could have a mass of either $11.5^{+1.2}_{-1.6}$ M$_{\rm Jup}$ or $15.3^{+0.7}_{-0.8}$ M$_{\rm Jup}$, depending on whether the host star is a member of $\rho$ Oph or Upper Sco.
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All authors Samuel Walker, Michael C. Liu, Dimitri Mawet, Mark W. Phillips, Aniket Sanghi, Bin B. Ren, Taichi Uyama

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Pushing the Limits of Atomic Dark Matter: First-Principles Recombination Rates and Cosmological Constraints

Jared Barron, Rouven Essig, Megan H. McDuffie et al. (+2 more)

Minimal atomic dark matter with its distinctive cooling mechanisms offers an instructive framework for understanding the potential impact of dark matter on small-scale structure formation and early cosmology. The model consists of two fermions with opposite charges under a hidden Abelian gauge symmetry $U(1)_{D}$ and masses $m_{p_{D}}$ and $m_{e_{D}}$, respectively. Analogous to hydrogen in the Standard Model, these fermions interact via their own electromagnetic-like force, with a dark fine structure constant denoted by $\alpha_{D}$, and can bind into neutral atomic (and molecular) dark states. Previous work has largely focused on the benchmark scenario where the dark sector mirrors ordinary matter, with $m_{e_{D}}$ near the electron mass, $m_{p_{D}}$ near the proton mass, and $\alpha_{D}\sim 1/137$. We extend this analysis by investigating dark recombination and cooling physics across the full parameter space of masses and couplings. Combining Cosmic Microwave Background (CMB) measurements from Planck and ACT with BAO and Pantheon+ data, we place new constraints on the atomic dark matter parameter space, identifying regions where acoustic damping and recombination dynamics leave observable imprints on the CMB.
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All authors Jared Barron, Rouven Essig, Megan H. McDuffie, Jesús Pérez-Ríos, Gregory Suczewski

Astrophysics of Galaxies

The stellar-to-halo mass relation of central galaxies across three orders of halo mass

Victoria Toptun, Paola Popesso, Ilaria Marini et al. (+9 more)

The stellar content of galaxies is tightly connected to the mass and growth of their host dark matter halos. Observational constraints on this relation remain limited, particularly for low-mass groups, leaving uncertainties in how galaxies assemble their stars across halo mass scales. Accurately measuring the brightest central galaxy (BCG) stellar-to-halo mass relation (SHMR) over a wide mass range is therefore crucial for understanding galaxy formation and the role of feedback processes. Here we present the SHMR spanning $M_{\rm halo} \sim 10^{12}$-$10^{15}\,M_\odot$, using halo masses derived from eROSITA eRASS1 X-ray data and BCG stellar masses based on SDSS photometry. By stacking X-ray spectra of optically selected groups, we recover robust average halo gas temperatures for each bin, which are then converted to halo masses via the $M$-$T_X$ relation. We find that the SHMR peaks near $M_{\rm halo} \sim 10^{12}\,M_\odot$, with a declining stellar fraction at higher masses. This trend reflects a combination of processes that reduce the efficiency of stellar mass growth in massive halos, such as AGN feedback, reduced cooling efficiency, and the increasing dominance of ex-situ assembly, while halos continue to grow through mergers and accretion. Our measurements are consistent over the full mass range with previous observational studies, including weak lensing, X-ray analyses of individual clusters, and kinematical and dynamical methods. Comparisons with hydrodynamical simulations show good agreement at low masses but reveal significant discrepancies in the normalization at cluster scales, highlighting the sensitivity of BCG stellar growth to feedback prescriptions and halo assembly history. These results provide the first X-ray-based observational SHMR covering three orders of magnitude in halo mass, establish a robust benchmark for testing galaxy formation models.
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All authors Victoria Toptun, Paola Popesso, Ilaria Marini, Stephan Vladutescu-Zopp, Klaus Dolag, Peter Behroozi, Lorenzo Lovisari, Stefano Ettori, Veronica Biffi, Xiaohu Yang, Natanael de Isídio, Daudi T. Mazengo

Astrophysics of Galaxies

Forged by Feedback: Stellar Properties of Brightest Group Galaxies in Cosmological Simulations

Ruxin Barré, Arif Babul, Ghassem Gozaliasl et al. (+7 more)

We investigate how different galaxy formation models impact the stellar properties of brightest group galaxies (BGGs) in four cosmological simulations: ROMULUS, SIMBA, SIMBA-C, and OBSIDIAN. The stellar masses, specific star formation rates, and mass-weighted stellar ages of the simulated BGGs are analysed alongside those of observed BGGs from X-ray-selected galaxy groups in the COSMOS field. We find that the global properties and underlying evolutionary pathways of simulated BGG populations are strongly impacted by the strength and mechanism of their respective active galactic nucleus (AGN) feedback models, which play a critical role in regulating the growth of massive galaxies. OBSIDIAN's sophisticated three-regime AGN feedback model achieves the highest overall agreement with COSMOS observations, matching stellar property distributions, quenched fractions, and the evolution of star formation in increasingly massive systems. We find evidence suggesting that BGG populations of OBSIDIAN and COSMOS undergo a gradual decline in star formation with stellar mass, in contrast to SIMBA and SIMBA-C, which display rapid quenching linked to the onset of powerful AGN jet feedback. By comparison, ROMULUS produces highly star-forming, under-quenched BGGs due to the inefficiency of its thermal AGN feedback in preventing cooling flows from fuelling BGG growth. The success of the OBSIDIAN simulation demonstrates the importance of physically motivated subgrid prescriptions for realistically capturing the processes that shape BGGs and their dynamic group environments.
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All authors Ruxin Barré, Arif Babul, Ghassem Gozaliasl, Alexis Finoguenov, Romeel Davé, Aviv Padawer-Blatt, Douglas Rennehan, Vida Saeedzadeh, Renier T. Hough, Thomas R. Quinn

High Energy Astrophysical Phenomena

Machine Learning Methods for Stellar Collisions. I. Predicting Outcomes of SPH Simulations

Elena González Prieto, James C. Lombardi, Jr. et al. (+8 more)

Stellar collisions can occur frequently in dense cluster environments, and play a crucial role in producing exotic phenomena from blue stragglers in globular clusters to high-energy transients in galactic nuclei. Successive collisions and mergers of massive stars could also lead to the formation of massive black holes, serving as seeds for supermassive black hole in the early universe. While analytic fitting formulae exist for predicting collision outcomes, they do not generalize across different energy scales or stellar evolutionary phases. Smoothed particle hydrodynamics (SPH) simulations are often used to compute the outcomes of stellar collisions, but, even at low resolution, their computational cost makes running on-the-fly calculations during an $N$-body simulation quite challenging. Here we present a new grid of $27,720$ SPH calculations of main-sequence star collisions, spanning a wide range of masses, ages, relative velocities, and impact parameters. Using this grid, we train machine learning models to predict both collision outcomes (merger vs disruption, or flyby) and final remnant masses. We compare the performance of nearest neighbors, support vector machines, and neural networks, achieving classification balanced accuracy of $98.4\%$, and regression relative errors as low as $0.11\%$ and $0.15\%$ for the final stars $1$ and $2$, respectively. We make our trained models publicly available as part of the package collAIder, enabling rapid predictions of stellar collision outcomes in $N$-body models of dense star cluster dynamics.
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All authors Elena González Prieto, James C. Lombardi, Jr., Sanaea C. Rose, Charles F.A. Gibson, Christopher E. O'Connor, Tjitske Starkenburg, Fulya K{\i}roğlu, Kyle Kremer, Tristan C. Parmerlee, Frederic A. Rasio

Solar and Stellar Astrophysics

Modern tidal interaction models for rapid binary population synthesis: I. Methods

Veome Kapil, Ilya Mandel, Evgeni Grishin et al. (+3 more)

In this work, we present an updated prescription of contemporary tidal dissipation theory adapted for rapid binary population synthesis. Our simplified expressions encode the dependence of tidal dissipation on stellar structure, stratification, and tidal forcing frequency, while remaining computationally efficient. We implement these prescriptions in the rapid population synthesis code COMPAS, and demonstrate the self-consistent coupling of tides with stellar evolution and binary properties such as orbital periods, spins, and eccentricities for several representative binary systems. When compared with commonly used tidal prescriptions, our equilibrium tidal dissipation efficiencies can be stronger by 1-2 orders of magnitude for low mass main sequence and giant type stars, and dynamical tides can be stronger by 1-7 orders of magnitude due to the explicit dependence on internal stellar structure and the presence of inertial wave dissipation. Despite our simplistic approach, our models agree with detailed stellar simulations to within an order of magnitude across tidal dissipation mechanisms.
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All authors Veome Kapil, Ilya Mandel, Evgeni Grishin, Jim Fuller, Jeff Riley, Emanuele Berti

Solar and Stellar Astrophysics

A method for constructing the joint mass function of binary stars

Amery Gration, Robert G. Izzard and Payel Das

The initial mass function (IMF) describes the distribution of stellar masses in a population of newly born stars and is amongst the most fundamental concepts in astrophysics. It is not only the direct result of the star formation process but it also explains the evolution of galaxies' luminosities, metal yields, star-formation efficiencies, and supernova production rates. Because most stars exist in binary systems, however, a full statistical account of stellar mass requires not the IMF but rather the joint distribution of a binary population's primary- and secondary-star masses. This joint distribution must respect the IMF of the stars from which the population has been assembled as well as the distribution of mass ratios that results from the assembly mechanism. Despite its importance, this joint distribution is known only in the case of random pairing. Here we present a method for constructing it in the general case. We also illustrate the use of our method by recovering the known result for random pairing and by finding the previously unknown result for uniform pairing.
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Instrumentation and Methods for Astrophysics

Why do we do astrophysics?

David W. Hogg

At time of writing, large language models (LLMs) are beginning to obtain the ability to design, execute, write up, and referee scientific projects on the data-science side of astrophysics. What implications does this have for our profession? In this white paper, I list - and argue for - a set of facts or "points of agreement" about what astrophysics is, or should be; these include considerations of novelty, people-centrism, trust, and (the lack of) clinical value. I then list and discuss every possible benefit that astrophysics can be seen as bringing to us, and to science, and to universities, and to the world; these include considerations of love, weaponry, and personal (and personnel) development. I conclude with a discussion of two possible (extreme and bad) policy recommendations related to the use of LLMs in astrophysics, dubbed "let-them-cook" and "ban-and-punish." I argue strongly against both of these; it is not going to be easy to develop or adopt good moderate policies.
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High Energy Astrophysical Phenomena

TDE 2025abcr: A Tidal Disruption Event in the Outskirts of a Massive Galaxy

Robert Stein, Jonathan Carney, Charlotte Ward et al. (+27 more)

Tidal disruption events (TDEs) have traditionally been discovered in optical sky surveys through targeted searches of nuclear transients. However, it is expected that some TDEs will occur outside the galaxy nucleus, arising from wandering black holes originating in galaxy mergers. Here we present observations of TDE 2025abcr, the first optical TDE discovered in the outskirts of a host galaxy. The TDE was identified by a custom 'off-nuclear' implementation of the ML classifier $\texttt{tdescore}$, which classifies new ZTF transients based on their lightcurves. Follow-up observations confirm that TDE 2025abcr is a TDE-H+He, occurring 9.5$"$ (9.3 kpc projected distance) from the nucleus of a massive galaxy ($\mathrm{M}_{\star}$ = $10^{11.18 \pm 0.03}\mathrm{M}_{\odot}$) with a central black hole mass of $10^{8.82 \pm 0.65}\mathrm{M}_{\odot}$. TDE 2025abcr itself was likely disrupted by a much lighter black hole ($10^{6.09\pm0.53}\mathrm{M}_{\odot}$, as estimated with peak luminosity scaling relations). The black hole was either dynamically ejected from the nucleus or lies at the center of a very faint tidally-stripped dwarf galaxy undergoing a minor merger. Late-time observations of TDE 2025abcr could confirm the origin of this apparent 'wandering' black hole. The rate of highly offset ($\gtrsim$3 kpc) TDEs can be constrained to $<$10% of the nuclear TDE rate, but our discovery implies that many dozens of similar sources will be detected by the Vera C. Rubin each year with resolvable offsets.
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All authors Robert Stein, Jonathan Carney, Charlotte Ward, Raffaella Margutti, Xander J. Hall, Itai Sfaradi, Igor Andreoni, Ryan Chornock, Suvi Gezari, Geoffrey Mo, Yuhan Yao, Eric C. Bellm, Joshua S. Bloom, Malte Busmann, Ilaria Caiazzo, S. Bradley Cenko, Matthew J. Graham, Steven L. Groom, Daniel Gruen, Erica Hammerstein, Mansi M. Kasliwal, Brendan O'Connor, Antonella Palmese, Josiah Purdum, Jillian C. Rastinejad, Reed Riddle, Ben Rusholme, Jesper Sollerman, Jean J. Somalwar, Sylvain Veilleux

Cosmology and Nongalactic Astrophysics

Statistical isotropy of the universe and the look-elsewhere effect

Alan H. Guth and Mohammad Hossein Namjoo

Recently, Jones et al. [arXiv:2310.12859] claimed strong evidence for the statistical anisotropy of the universe. The claim is based on a joint analysis of four different anomaly tests of the cosmic microwave background data, each of which is known to be anomalous, with a lower level of significance. They reported a combined $p$-value of about $3\times 10^{-8}$, which is more than a $5\sigma$ level of significance. We observe that statistical anisotropy is not even relevant for two of the four considered tests, which seems sufficient to invalidate the authors' claim. Furthermore, even if one reinterprets the claim as evidence against $\Lambda$CDM rather than statistical anisotropy, we argue that this result significantly suffers from the look-elsewhere effect. Assuming a set of independent (i.e., uncorrelated) tests, we show that if the four tests with the smallest $p$-values are cherry-picked from 10 independent tests, the $p$-value reported by Jones et al. corresponds to only $3\sigma$ significance. If there are 27 independent tests, the significance falls to $2\sigma$. These numbers, however, overstate our argument, since the four tests used by Jones et al. are slightly correlated. Determining the correlation of Jones et al.'s tests by comparing their joint $p$-value with the product of the four separate $p$-values, we find that about 16 or 50 tests are sufficient to reduce the significance of Jones et al.'s results to 3$\sigma$ or 2$\sigma$ significance, respectively. We also provide a list of anomaly tests discussed in the literature (and propose a few generalizations), suggesting that very plausibly 16 (or even 50) independent tests have been published, and possibly many more have been considered but not published. We conclude that the current data is consistent with the $\Lambda$CDM model and, in particular, with statistical isotropy.
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Instrumentation and Methods for Astrophysics

Cosmo3DFlow: Wavelet Flow Matching for Spatial-to-Spectral Compression in Reconstructing the Early Universe

Md. Khairul Islam, Zeyu Xia, Ryan Goudjil et al. (+3 more)

Reconstructing the early universe from the evolved present-day universe is a challenging and computationally demanding problem in modern astrophysics. We devise a novel generative framework, Cosmo3DFlow, designed to address dimensionality and sparsity, the critical bottlenecks inherent in current state-of-the-art methods for cosmological inference. By integrating 3D Discrete Wavelet Transform (DWT) with flow matching, we effectively represent high-dimensional cosmological structures. The Wavelet Transform addresses the “void problem” by translating spatial emptiness into spectral sparsity. It decouples high-frequency details from low-frequency structures, and wavelet-space velocity fields facilitate stable ordinary differential equation (ODE) solvers with large step sizes. Using large-scale cosmological $N$-body simulations at $128^3$ resolution, we achieve up to $46\times$ faster sampling than diffusion models. Our results enable initial conditions to be sampled in seconds, compared to minutes for previous methods.
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All authors Md. Khairul Islam, Zeyu Xia, Ryan Goudjil, Jialu Wang, Arya Farahi, Judy Fox

Instrumentation and Methods for Astrophysics

Observing solar vortices with existing and future instrumentation. Solar Physics International Network for Swirls (SPINS) white paper (Helio)

Suzana S.A. Silva, Viktor Fedun, Gary Verth et al. (+13 more)

Solar vortices are fundamental components of solar atmospheric dynamics, serving as natural laboratories for magnetic field twisting, energy concentration and transport, wave guidance, and plasma coupling across atmospheric layers. Numerical and observational studies show that solar vortices are intimately connected to key physical processes including magnetic reconnection, atmospheric heating, turbulence, and wave generation. This white paper, prepared for the UK Space Frontiers 2035 call, outline five high-priority scientific questions addressing vortex generation mechanisms, cross-layer coupling, magnetic restructuring, collective wave-guidance structures, and their role in triggering explosive events and modulating the solar wind. Key observations and capabilities required to make significant advancements over the coming decade are identified. The UK solar physics community has established world-leading expertise in vortex dynamics, combining strengths in high-resolution observations, MHD turbulence theory, numerical modelling, and space instrumentation. UK researchers have made foundational contributions to Solar Orbiter, delivered critical systems for DKIST, and maintain active involvement in MUSE and SOLAR-C EUVST missions. Our technical approach centres on developing next-generation instrumentation: a multi-band, space-qualified system employing four tunable Fabry-Pérot Interferometers providing diffraction-limited, high-cadence spectropolarimetric coverage from the deep photosphere to the low corona. This capability will be validated through a staged mission architecture beginning with balloon-borne demonstrators. Continuing this effort over the coming decade is vital to maintain UK leadership in this field and achieve the goals of roadmap for solar system research.
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All authors Suzana S.A. Silva, Viktor Fedun, Gary Verth, Istvan Ballai, Eamon Scullion, Malcolm Druett, Kostas Tziotziou, Alex Pietrow, Nitin Yadav, Ioannis Dakanalis, Elena Khomenko, Hidetaka Kuniyoshi, Shivdev Turkay, Matias Koll Pistarini, Robertus Erdelyi, Luiz Augusto Camargo Aranha Schiavo

Instrumentation and Methods for Astrophysics

The indiscriminate adoption of AI threatens the foundations of academia

Roberto Trotta

Artificial intelligence offers much promise, but its use in scientific research should be restrained so that the primary aim of academia – advancing knowledge for humans – is safeguarded.

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Minimal Freeze-in Dark Matter: Reviving electroweak doublet dark matter with Boltzmann suppressed freeze-in

Nicolás Bernal, Sagnik Mukherjee and James Unwin

Dark matter communicating with the Standard Model solely via electroweak interactions provides a compelling picture. However, thermal freeze-out of electroweak doublet dark matter is generically strongly excluded by direct detection. We show that SU(2)${}_L$ doublet fermion dark matter evades direct detection if its mass exceeds $10^{10}$ GeV. If the neutral Dirac fermion is split into a pseudo-Dirac pair (via high dimension operator) this limit can be relaxed to 300 GeV. Provided the dark matter mass is above the reheat temperature of the Universe, the production rate never exceeds the Hubble rate in cases of interest, thus the dark matter never thermalizes. We apply constraints from direct detection (e.g. LZ) and consider the discovery potential of Darwin. This scenario presents the most minimal model of freeze-in dark matter, and is both elegant and highly predictive.
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Cosmology and Nongalactic Astrophysics

Measurement of the Full Shape of the Thermal Sunyaev-Zeldovich Power Spectrum from South Pole Telescope and Herschel-SPIRE Observations

S. Raghunathan, P. A. R. Ade, D. Anbajagane et al. (+139 more)

We present a measurement of the full shape of the power spectrum of the thermal Sunyaev-Zeldovich (tSZ) effect down to arcminute scales using cosmic microwave background (CMB) data from the South Pole Telescope (SPT) over roughly 100 ${\rm deg}^{2}$ field. The analysis incorporates data from the 2019/20 seasons of the SPT-3G survey in bands centered at 95, 150, and 220 GHz; from the full SPTpol dataset at 150 GHz; and from Herschel-SPIRE survey in bands centered at 600 and 857 GHz. We combine data from all the above bands using linear combination (LC) techniques to produce a tSZ or Compton-$y$ map. We modify the LC weights to produce multiple versions of the Compton-$y$ map, including minimum-variance (MV) and foreground-minimized (-min) maps. We measure the auto- and cross-spectra of a subset of these maps in the range $\ell \in [500, 5000]$. While this power spectrum includes contributions from signals other than tSZ, we present numerous checks to show that the most challenging foreground signal, the cosmic infrared background (CIB) is much lower than the desired tSZ signal in the scales of interest in this work. The final tSZ power spectrum is measured at $9.3\sigma$ with both the MV and CIB-min maps. Our results are consistent with those reported in other CMB surveys across the literature. Using the difference in the tSZ power spectrum from MV and CIB-min maps, we reconstruct the scale-dependent tSZ-CIB cross-correlation $\rho_{\ell}^{\rm tSZ \times CIB}$, finding $3.1\sigma$ evidence for a nonzero correlation coefficient that is positive on large scales and approaches zero for $\ell > 2500$. This result represents the deepest tSZ maps ever produced and provides new constraints that can help refine astrophysical feedback mechanisms and models of the intracluster medium.
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All authors S. Raghunathan, P. A. R. Ade, D. Anbajagane, A. J. Anderson, B. Ansarinejad, M. Archipley, J. E. Austermann, L. Balkenhol, D. R. Barron, P. S. Barry, J. A. Beall, K. Benabed, A. N. Bender, B. A. Benson, F. Bianchini, L. E. Bleem, J. Bock, S. Bocquet, F. R. Bouchet, L. Bryant, E. Camphuis, M. G. Campitiello, J. E. Carlstrom, J. Carron, C. L. Chang, P. Chaubal, H. C. Chiang, P. M. Chichura, A. Chokshi, T.-L. Chou, R. Citron, A. Coerver, C. Corbett Moran, T. M. Crawford, A. T. Crites, C. Daley, T. de Haan, K. R. Dibert, M. A. Dobbs, M. Doohan, A. Doussot, D. Dutcher, W. Everett, C. Feng, K. R. Ferguson, N. C. Ferree, K. Fichman, A. Foster, S. Galli, J. Gallicchio, A. E. Gambrel, A. K. Gao, R. W. Gardner, F. Ge, E. M. George, N. Goeckner-Wald, R. Gualtieri, F. Guidi, S. Guns, N. Gupta, N. W. Halverson, E. Hivon, A. Y. Q. Ho, G. P. Holder, W. L. Holzapfel, J. C. Hood, J. D. Hrubes, A. Hryciuk, N. Huang, J. Hubmayr, K. D. Irwin, T. Jhaveri, F. Kéruzoré, A. R. Khalife, L. Knox, M. Korman, K. Kornoelje, C.-L. Kuo, A. T. Lee, K. Levy, Y. Li, D. Li, A. E. Lowitz, A. Lowitz, C. Lu, G. P. Lynch, T. J. Maccarone, A. S. Maniyar, E. S. Martsen, J. J. McMahon, F. Menanteau, M. Millea, J. Montgomery, Y. Nakato, T. Natoli, J. P. Nibarger, G. I. Noble, V. Novosad, Y. Omori, A. Ouellette, S. Padin, Z. Pan, P. Paschos, S. Patil, K. A. Phadke, A. W. Pollak, K. Prabhu, C. Pryke, W. Quan, M. Rahimi, A. Rahlin, C. L. Reichardt, M. Rouble, J. E. Ruhl, B. R. Saliwanchik, K. K. Schaffer, E. Schiappucci, C. Sievers, A. C. Silva Oliveira, A. Simpson, G. Smecher, J. A. Sobrin, A. A. Stark, J. Stephen, C. Tandoi, B. Thorne, C. Trendafilova, C. Tucker, C. Umilta, T. Veach, J. D. Vieira, A. G. Vieregg, M. P. Viero, A. Vitrier, Y. Wan, G. Wang, N. Whitehorn, W. L. K. Wu, V. Yefremenko, M. R. Young, J. A. Zebrowski, M. Zemcov

Solar and Stellar Astrophysics

Narrow absorption lines from intervening material in supernovae. IV. Type Ia supernovae: Na I D line strength relating to external material and intrinsic properties

Santiago González-Gaitán, Claudia P. Gutiérrez, João Duarte et al. (+4 more)

Type Ia supernovae (SNe Ia) are thermonuclear runaways of some white dwarfs in binary systems. They have been extensively studied, yet their progenitor and explosion mechanisms remain poorly understood. We study a large sample of SNe Ia comparing the narrow interstellar absorption features in their spectra with various photometric and spectroscopic supernova properties, as well as environmental characteristics. The sodium absorption is significantly stronger in younger, more star-forming and more centrally located SNe Ia, as expected. However, we also show that there is a relation with intrinsic properties that is independent of the environment. In fact, there is substantial evidence for two environmental SN Ia populations, an old and a young one, with the young population showing significantly different distributions of sodium strength when divided according to the Si II ejecta velocity, nebular velocity, extinction, E(B-V), and reddening curve, RV. Performing a clustering of the SNe Ia, we recover an old population of SNe with low extinction and normal ejecta velocity, while the young population can be indeed subdivided into a group of highly-extincted, high-velocity SNe Ia with much stronger blueshifted sodium absorption, and another of low-extincted, normal-velocity objects with little sodium absorption. We interpret this relation of intervening material with intrinsic properties as evidence for the young SN Ia population, occurring in young and star-forming environments, to have asymmetric radiation that interacts with nearby material, and whose observables depend thus on the viewing angle. Finally, we show that the cosmological mass-step is consistent with these populations.
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All authors Santiago González-Gaitán, Claudia P. Gutiérrez, João Duarte, Rita Santos, Gonçalo Martins, Joseph P. Anderson, Lluís Galbany

Astrophysics of Galaxies

Effects of Numerical Resolution on Simulated Cloud-Wind Interactions

Hannah Leary, Helena M. Richie and Evan Schneider

Mixing by hydrodynamical instabilities plays a key role in cloud-wind interactions, causing cloud destruction in the adiabatic limit and facilitating cloud survival with efficient radiative cooling. However, the rate of mixing in numerical simulations is sensitive to the smallest resolved scale, and the relationship between resolution and cloud evolution is under-explored. Using a set of cloud-crushing simulations, we investigate the effects of numerical resolution on cloud survival and acceleration. Modeling both adiabatic and radiative cases, in a subsonic and supersonic wind, we find that cloud survival and velocity does depend on the numerical resolution, however, no single resolution requirement can be applied to all scenarios. In the radiative subsonic case, we find that mass growth and acceleration appear converged at only 4 cells per cloud radius. Conversely, in the supersonic regime, we see a clear dependence of cloud destruction and velocity on resolution that is not converged even at 48 cells per cloud radius, implying that accurately capturing cloud destruction may require higher resolution than capturing growth. We also present a simple model illustrating how ram pressure accelerates cool clouds at early times before mixing kicks in as an acceleration mechanism.
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