Astrophysics of Galaxies
Discovery of Isolated, Quenched Candidate Backsplash Dwarf Galaxies near M101
Julian Shapiro
I report the discovery of three faint, semi-resolved quiescent candidate
dwarf galaxies, which are potential backsplash
galaxies associated with the nearby spiral M101 ($D \sim 6.7 \,\mathrm{Mpc}$). The
galaxies are cataloged as Shapiro DG-I/MAGE1412+5650, Shapiro DG-II, and Shapiro DG-III. Sha DG-I is concurrently discovered in ID-MAGE. The backsplash candidates lie in a magnitude range $M_V\sim-7.3$ to $-8.1$, and half-light radii $r_h\sim110-140\,\mathrm{pc}$. Hydrodynamical simulations suggest a population of backsplash
galaxies that have been environmentally stripped by interactions with a host and ejected from the system, though they have not yet been definitively observed in the local universe. Initial distance estimates are determined using surface brightness fluctuations in Sérsic model-subtracted CFHTLS and HSC archival images. The
galaxies are not detected in GALEX, or H$\alpha$ for Sha DG-I/MAGE1412+5650, providing upper limits on their SFR history. The provisional distances and quiescence of the
dwarf candidates are consistent with a potential backsplash nature, though HST/JWST follow-up are necessary for stronger constraints, and to probabilistically distinguish from
cosmic web stripping. Sha DG-II is alternatively a possible satellite of NGC 5585. Abundance models of satellites based on
halo masses, which can be extended to model backsplash
galaxies, will enable important consistency tests of $\Lambda\mathrm{CDM}$ with upcoming surveys, e.g., LSST. This is briefly explored in the context of the M101 group.
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Cosmology and Nongalactic Astrophysics
FrankenStat I: a New Approach to Pulsar Timing Array Data Combination
David Wright, Kalista Wayt, Jeffrey S. Hazboun et al. (+4 more)
In 2023, after more than two decades of searching,
pulsar timing array (PTA) collaborations around the world announced evidence for a
stochastic gravitational wave background. It was quickly followed by work from the International
Pulsar Timing Array (IPTA), demonstrating that the results of regional collaborations were consistent with each other. The combination of these
datasets is still ongoing and represents a significant investment of time and expertise. In that IPTA comparison, authors of this letter combined the separate
datasets in the standard PTA optimal detection statistic for cross-correlations incoherently, that is, the data was combined without fitting a merged timing model across all PTA
datasets, treating
datasets of the same
pulsar as independent, and neglecting the "same
pulsar, different
datasets" cross-correlations. This work refines that method by extending its core ideas beyond detection statistics and into a full, general data-combination method. We have demonstrated its efficacy and extreme efficiency on simulated data. This new method, FrankenStat, is very similar in sensitivity and parameter-constraining power to traditional data combination methods while completing the full data combination in just a few minutes.
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All authors David Wright, Kalista Wayt, Jeffrey S. Hazboun, Xavier Siemens, Rutger van Haasteren, Levi Schult, Stephen R. Taylor
Instrumentation and Methods for Astrophysics
Finding New Debris Discs at Sub-millimetre Wavelengths
Mark Booth, Patricia Luppe, Sebastian Marino et al. (+9 more)
Debris discs reveal the architectures and dynamical histories of planetary systems. Sub-millimetre observations trace large
dust grains within debris discs, revealing their bulk properties. Debris discs have so far only been detected around ~20% of
stars, representing the bright end of the population. A new facility is required to reach fainter discs, overcoming the confusion limit, with multiwavelength capabilities for characterisation, sensitivity to large-scale emission for nearby targets and a large field of view for surveying distant populations. All of this is made possible with the Atacama Large Aperture Submillimetre
Telescope (AtLAST).
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All authors Mark Booth, Patricia Luppe, Sebastian Marino, Joshua B. Lovell, Jonathan P. Marshall, Gaspard Duchêne, Isabel Rebollido, Mark C. Wyatt, Riouhei Nakatani, Aya E. Higuchi, Miguel Chavez-Dagostino, Hiroshi Kobayashi
Instrumentation and Methods for Astrophysics
Dynamical binary interactions in the 2040s
Nadejda Blagorodnova, Ondřej Pejcha, Tomek Kamiński et al. (+15 more)
Dynamical binary interactions such as common envelope (CE)
evolution or
stellar mergers are a critical phase in the formation of a wide variety of binary phenomena, ranging from blue stragglers to type I
supernovae (of all flavours, a, b and c), $\gamma$-ray bursts to bipolar planetary nebulae, Thorne-Zytkow objects to X-ray binaries. In 2040s, the urgency of resolving long-standing questions regarding the physics behind the dynamical interaction stages and the absolute and relative frequencies of binary evolutionary pathways will only increase owing to rapidly expanding population statistics of gravitational wave events. Here, we argue that multi-wavelength observations (spectroscopy and photometry), linear spectropolarimetry, and interferometry of a large number of Luminous Red Novae, a particular class of transients associated with dynamical binary interactions, will provide unprecedented details about the underlying interaction physics. A breakthrough will be achieved by a tenfold or larger increase in identifications of transient-type events from interacting binaries and their follow-up with instrumentation that provides at least 10 times better angular resolution, 100 times better spectral resolution, and $\sim$100 times higher sensitivity than 2030s facilities.
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All authors Nadejda Blagorodnova, Ondřej Pejcha, Tomek Kamiński, Yongzhi Cai, Kishalay De, Nancy Elias-Rosa, Jim Fuller, Hongwei Ge, David Jones, Stephen Justham, Viraj Karambelkar, Jakub Klencki, Elena Mason, Brian Metzger, Andrea Pastorello, Andrea Reguitti Friedrich Röpke, Steven Shore, Giorgio Valerin
Instrumentation and Methods for Astrophysics
White Dwarf Binaries: Probes of Future Astrophysics
Anna F. Pala, Roberto Raddi, Alberto Rebassa-Mansergas et al. (+25 more)
White
dwarf binaries are fundamental astrophysical probes. They represent ideal laboratories to test the models of binary
evolution, which also apply to the sources of gravitational waves, whose detection led to the award of the 2017 Nobel Prize in Physics. Moreover, their final fate is intimately linked to Type Ia
Supernovae (SNe Ia), i.e. the thermonuclear explosion of a white
dwarf following the interaction with a companion
star, which have become the fundamental yardsticks on cosmological distance scales and led to the discovery of dark energy and the award of the 2011 Nobel Prize in Physics. Finally, white
dwarf binaries play a crucial role in influencing
star formation and chemical
evolution of the
Galaxy by injecting energy into, and enriching, the interstellar medium with material ejected during nova eruptions and SN Ia explosions. In the next decade, the advent of the Large Synoptic Survey
Telescope (LSST) at the Vera Rubin Observatory will lead to the discovery of hundreds of thousands of white
dwarf binaries. Nonetheless, the intrinsic faintness of the majority of these systems will prevent their spectroscopic characterisation with the instruments available in the 2030s. Hence ESO's Expanding Horizons call is timely for planning a future transformative facility, capable of delivering phase-resolved spectroscopic observations of faint white
dwarf binaries, which are key to advancing our understanding of
stellar and
Galactic evolution and cosmology.
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All authors Anna F. Pala, Roberto Raddi, Alberto Rebassa-Mansergas, Boris T. Gänsicke, Richard I. Anderson, Diogo Belloni, Avraham Binnenfeld, Elmé Breedt, David Buckley, Tim Cunningham, Alessandro Ederoclite, Ana Escorza, Valeriya Korol, Thomas Kupfer, Domitilla de Martino, Jaroslav Merc, Joaquin Meza, Steven Parsons, Ingrid Pelisoli, Nicole Reindl, Pablo Rodríguez-Gil, Alejandro Santos-García, Simone Scaringi, Paula Szkody, Odette Toloza, Santiago Torres, Murat Uzundag, Monica Zorotovic
Instrumentation and Methods for Astrophysics
Why the northern hemisphere needs a 30-40 m telescope and the science at stake: Massive stars in spiral galaxies
J. Maíz Apellániz, S. Simón-Díaz, A. Herrero et al. (+5 more)
This document discusses the three main lines expected to dominate massive-
star research in the 2040s, namely: (1) The role of
metallicity in
stellar evolution, especially in determining the end products such as gravitational-wave progenitors. (2) The initial mass function from the most massive
stars to substellar objects. (3) The role of the environment in the different modes of
star formation from compact
star clusters to born-this-way associations and from massive clusters to small
stellar groups. More specifically, we present the contributions to such science that would be enabled by a 30~m type
telescope in the northern hemisphere studying spiral
galaxies. Those can be grouped in three: our own
Galaxy, the Milky Way; the other two spiral
galaxies in the Local Group, M31 and M33; and other
galaxies within 25 Mpc, such as M101, M51, and NGC~6946. This work is based on the fact that, as of today, no construction of a 30~m
telescope has yet started in the northern hemisphere, so even in the best case scenario of such a hypothetical
telescope, its full operation would not start until the late 2030s or early 2040s. It makes no assumptions about its location but supposes an instrumentation development similar to that of ELT.
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All authors J. Maíz Apellániz, S. Simón-Díaz, A. Herrero, S. R. Berlanas, J. M. Mas Hesse, I. Negueruela, G. Holgado, M. García
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Key Targets of Opportunity on Gas and Ice Giants and their satellites
Ricardo Hueso, Leigh N. Fletcher, Damya Souami et al. (+15 more)
The Extremely Large
Telescope (ELT) will transform our knowledge of the outer
planets and their satellite systems; however the visibility of unique targets of opportunity with high scientific value will be reduced for northern objects. Uranus' declination favors observations from the Northern Hemisphere until 2055, and Neptune will be favored from the Northern Hemisphere from 2027 for the next 90 years. Jupiter and Saturn experience cycles of better observability from either hemisphere on cycles of 10 and 30 years. These
planets and their satellite systems often offer unique opportunities for discovery through time-critical observations. We argue that a 30-m class size
telescope in the Northern Hemisphere with complementary scientific instrumentation to that on the ELT will secure the possibility of observing high-impact unpredictable phenomena in these systems.
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All authors Ricardo Hueso, Leigh N. Fletcher, Damya Souami, Thierry Fouchet, Tristan Guillot, Olivier Mousis, Patrick G. J. Irwin, Michael Roman, Arrate Antuñano, Athena Coustenis, Julia de León, Sonia Fornasier, Emmanuel Lellouch, Alice Lucchetti, Noemí Pinilla-Alonso, Don Pollacco, Agustín Sánchez-Lavega, Daniel Toledo
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Northern Local Star-forming Dwarf Galaxies. Analogues of the First Galaxies and Probes of the Cosmic Metallicity Scale
C. Esteban, J. M. Vilchez, J. García-Rojas et al. (+15 more)
Star-forming
dwarf galaxies in the local Universe, especially extremely metal-poor ones, can be considered analogous to early
galaxies of the Epoch of Reionization (z >= 6). Currently available
telescopes cannot adequately detect and measure heavy element recombination lines and certain faint collisionally excited lines, which are essential for exploring the effects and biases that potential inhomogeneities in electron temperature and density of the ionized gas may have on determining the chemical composition of these
galaxies. On the other hand, the origin of very high-ionization lines (e.g. He II, [Ne V], C IV]) measured in the spectra of an important fraction of these objects remains unknown and a challenge to current
stellar models, suggesting the presence of Population III-like
stars and/or the existence of non-conventional ionizing sources. Obtaining very deep spectra for a selected sample of local
star-forming
dwarf galaxies would provide unprecedented constraints on their nature, ionization and true chemical abundances, and could change the
metallicity scale we assume to understand the chemical
evolution of
galaxies over
cosmic time.
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All authors C. Esteban, J. M. Vilchez, J. García-Rojas, R. Amorín, K. Z. Arellano-Córdova, L. Carigi, F. Cullen, O. V. Egorov, S. R. Flury, J. Iglesias-Páramo, C. Kehrig, K. Kreckel, J. E. Méndez-Delgado, E. Pérez-Montero, F. F. Rosales-Ortega, D. Scholte, T. M. Stanton, E. Villaver
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Galactic Archaeology from the Northern Sky
Borja Anguiano, David Valls-Gabaud, Guillaume F. Thomas et al. (+7 more)
By the 2040s–50s, facilities such as
Gaia, WEAVE, 4MOST, Rubin, Euclid, Roman, and the ESO ELT will have transformed our global view of the Milky Way. Yet key questions will remain incompletely resolved: a detailed reconstruction of the
Galaxy's assembly from its earliest building blocks, and robust tests of dark matter granularity using the fine structure of the
stellar halo and outer disk – particularly in the
Galactic anticenter. Addressing these questions requires high-resolution spectroscopy of faint main-sequence
stars (typically 1–2 mag below the turnoff) and turnoff
stars ($r \sim 21$–23) in low-surface-brightness structures:
halo streams and shells, ultra-faint
dwarf galaxies, the warped and flared outer disk, and anticenter substructures. We argue that addressing this science case requires a 30\,m-class
telescope in the northern hemisphere, equipped with wide-field, highly multiplexed, high-resolution spectroscopic capabilities. Such a facility would enable (i) a Northern
Halo Deep Survey of $\sim 10^{5}$–$10^{6}$ faint main-sequence and turnoff
stars out to $\sim 150$–200\,kpc, (ii) chemodynamical mapping of dozens of streams to measure perturbations from dark matter subhalos, and (iii) tomographic studies of the anticenter and outer disk to disentangle perturbed disk material from accreted debris. A northern 30\,m
telescope would provide the essential complement to ESO's southern ELT, enabling genuinely all-sky Milky Way archaeology and delivering stringent constraints on the small-scale structure of dark matter.
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All authors Borja Anguiano, David Valls-Gabaud, Guillaume F. Thomas, David Martínez Delgado, Alberto M. Martínez-García, Andrés del Pino, Ivan Minchev, Patricia Sanchez-Blazquez, Carme Gallart, Teresa Antoja
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Resolved Stellar Populations Studies in M31 and its Satellites
C. Gallart, E. Fernández-Alvar, A. B. A. Queiroz et al. (+48 more)
A 30 m class optical/near-IR
telescope in the Northern Hemisphere, equipped for diffraction-limited imaging and high-resolution, multi-object spectroscopy of faint
stars, would enable a transformational investigation of the formation and
evolution of M31 and its satellite system - on par with what
Gaia, the HST, and other major photometric and spectroscopic facilities have achieved for the Milky Way (MW) and its satellites. The unprecedented detail obtained for our home system has reshaped our understanding of the assembly of the MW disk,
halo, and bulge, and that of its satellites, which now serve as a
benchmark for
galaxy formation and
evolution models. Extending this level of insight to the M31 system - that of the nearest massive spiral and the only one for which such a comprehensive, resolved
stellar population study is feasible - will allow us to address a fundamental question: how representative is the MW and its satellite system within the broader context of
galaxy evolution?
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All authors C. Gallart, E. Fernández-Alvar, A. B. A. Queiroz, A. Aparicio, B. Anguiano, G. Battaglia, M. Beasley, T. Bensby, G. Bono, V. Braga, L. Carigi, L. Casamiquela, S. Cassisi, C. Chiappini, V. P. Debattista, A. del Pino, I. Escala, A. M. N. Ferguson, G. Fiorentino, K. M. Gilbert, P. Guhathakurta, R. Ibata, E. N. Kirby, K. Kuijken, S. Larsen, D. Martínez-Delgado, C. Martínez-Vázquez, D. Massari, I. Minchev, M. Monelli, J. F. Navarro, M. Ness, S. Okamoto, K. Olsen, S. Ortolani, P. A. Palicio, I. Pérez, F. Pinna, A. Prieto, J. Read, A. Recio-Blanco, M. Rejkuba, A. Renzini, R. M. Rich, T. Ruiz-Lara, M. Schultheis, M. Tantalo, G. F. Thomas, A. Vazdekis, E. Villaver, M. Zoccali
Instrumentation and Methods for Astrophysics
Science Enabled by a 30-Meter-Class Telescope in the Northern Hemisphere: Massive Stars at Low Metallicity
Miriam Garcia, Artemio Herrero, Ignacio Negueruela et al. (+11 more)
Massive
stars are at the core of our observations of the Universe up to the reionization epoch, both through their intense ionizing fluxes and through the energetic end products that release fresh elements into the interstellar medium. Our interpretation of very high
redshift galaxies and transient phenomena depends on knowledge derived from massive
star populations in the Milky Way and nearby
galaxies, with characteristics that only remotely resemble the conditions in the early Universe. However, the models supporting these interpretations have been tested in a narrow range of environments and carry significant uncertainties when extrapolated. Advancing in our understanding of the Universe beyond the Local Volume therefore requires extending massive
star studies to conditions representative of the early Universe. The next generation of
telescopes has the potential to accomplish this goal.
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All authors Miriam Garcia, Artemio Herrero, Ignacio Negueruela, Norberto Castro, Sara R. Berlanas, Miguel Cerviño, Gonzalo Holgado, Jorge Iglesias-Páramo, Carolina Kehrig, Jesús Maíz Apellániz, J. Miguel Mas-Hesse, Francisco Najarro, Sergio Simón-Díaz, José M. Vílchez
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Mapping formation pathways of nuclear star clusters across galaxies
Francesca Pinna, Isabel Pérez, Anna Ferré-Mateu et al. (+21 more)
Nuclear star clusters (NSCs) are dense, compact
stellar systems only a few parsecs across, located at
galaxy centers. Their small sizes make them difficult to resolve spatially. NSCs often coexist with massive black holes, and both trace the dynamical state and
evolution of their host
galaxies. Dense
stellar environments such as NSCs are also ideal sites for forming intermediate-mass black holes (IMBHs). To date, spatially resolved NSC properties, crucial for reconstructing dynamical and
star-formation histories, have only been obtained for
galaxies within 5 Mpc, using the highest-resolution instruments on the current class of very large
telescopes. This severely limits spectroscopic studies, and a systematic, unbiased survey has never been accomplished. Because the vast majority of known NSCs are located in the Northern Hemisphere, only a 30-m-class
telescope in the North can provide the statistical power needed to study their physical properties and measure the mass of coexisting central black holes. We propose leveraging the capabilities of a 30-m-class Northern
telescope to obtain the first comprehensive, spatially resolved survey of NSCs, finally allowing us to unveil their formation pathways and their yet unknown connection with central massive black holes.
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All authors Francesca Pinna, Isabel Pérez, Anna Ferré-Mateu, Begoña García Lorenzo, Alessandra Mastrobuono Battisti, Abbas Askar, Michael Beasley, Bahar Bidaran, Ana L. Chies-Santos, Sébastien Comerón, Kristen C. Dage, Adriana de Lorenzo-Cáceres, Katja Fahrion, Jesús Falcón Barroso, Anja Feldmeier-Krause, Emma Fernández Alvar, Nils Hoyer, Rubén García Benito, Rosa M. Gonzalez Delgado, Ignacio Martín Navarro, Cristina Ramos Almeida, Patricia Sánchez Blázquez, Rubén Sánchez Janssen, Alexandre Vazdekis
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40m Telescope and the Science at Stake: from Interstellar Visitors to Planetary Defence
J. de León, N. Pinilla-Alonso, P. Tanga et al. (+49 more)
Small
Solar system Objects (SSOs) preserve the physical, chemical, and dynamical signatures of the Sun's protoplanetary disk. Upcoming surveys will discover vast numbers of new objects, yet their scientific value will depend on follow-up observations requiring far greater sensitivity and resolution than those currently available. A 30-m class
telescope like the Extremely Large
Telescope (ELT) will be transformative, but its Southern location will leave significant regions of the sky poorly covered or even non accessible. A Northern 30-40m
telescope is therefore essential to achieve full-sky coverage and fully exploit the small body discoveries of the 2030-2050 era, in particular for targets of opportunity or unexpected discoveries, like those of interstellar objects and potentially hazardous asteroids, as well as for distant trans-Neptunian objects and space mission targets.
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All authors J. de León, N. Pinilla-Alonso, P. Tanga, D. Souami, Z. Gray, A. Alvarez-Candal, B. Carry, R. de la Fuente Marcos, A. Delsanti, F. La Forgia, A. Migliorini, T. Müller, A. Penttilä, M. Popescu, C. Snodgrass, D. Oszkiewicz, C. Opitom, A. Campo-Bagatin, J. Licandro, R. Hueso, M. Lazzarin, S. Fornasier, R. Brunetto, J. A. de Abol Brasón, J. de Cos Juez, J. DeMartini, A. Donaldson, R. Dorsey, R. Duffard, J. Fernández Díaz, F. García de Leániz, R. Hevia Díaz, J. M. Gómez-Limón, O. Groussin, S. Iglesias Álvarez, T. Kohout, M. Kretlow, T. Le Pivert-Jolivet, M. Montero-Vega, N. Morales, K. Muinonen, J. L. Ortiz, G. P. Prodan, J. L. Rizos, J. E. Robinson, S. Rodríguez Cabo, J. Rodríguez Rodríguez, A. Rozek, P. Santos-Sanz, E. Tatsumi, F. Tinaut-Ruano, E. Villaver
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: A Low Surface Brightness Science Case
Mireia Montes, Ignacio Trujillo, David Martínez Delgado et al. (+27 more)
The Extragalactic Low Surface Brightness (LSB, $\mu_V\gtrsim 27$ mag/arcsec$^2$) Universe represents a crucial, yet largely unseen, frontier in modern astrophysics. This faint realm holds the keys to completing our understanding of
galaxy evolution, hierarchical assembly, and even the fundamental nature of dark matter. Our current theoretical models are inherently incomplete, largely mirroring the properties of the brightest, most easily observed objects. To overcome this critical bias and unlock the secrets of this realm, a transformative leap in observational capability is required. A 30 to 40m class
telescope, leveraging unprecedented sensitivity and spatial resolution, especially with adaptive optics, is the essential tool to fundamentally probe these faint, low-density
stellar regimes. This white paper details the transformative LSB science that such a facility, strategically positioned in the Northern Hemisphere (NH) to access crucial nearby structures and rich environments, can achieve.
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All authors Mireia Montes, Ignacio Trujillo, David Martínez Delgado, Borja Anguiano, Magda Arnaboldi, Michael A. Beasley, Fernando Buitrago, Michele Cantiello, Andrés del Pino, Amandine Doliva-Dolinsky, Helena Domínguez-Sánchez, Mauro D'Onofrio, Pierre-Alain Duc, Katja Fahrion, Anna Ferré-Mateu, Carme Gallart, Nina Hatch, Enrica Iodice, Yolanda Jiménez-Teja, Francine Marleau, Chris Mihos, Nicola Napolitano, Agnieszka Pollo, Javier Román, Joanna Sakowska, Jorge Sánchez Almeida, Patricia Sánchez-Blázquez, Marilena Spavone, Guillaume Thomas, Eva Villaver
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40m Telescope and the Science at Stake: Ultra-Low-Mass Dwarf Galaxies Across the Boreal Cosmic Web
J. Alfonso L. Aguerri, Jesús Falcón-Barroso, María Argudo-Fernández et al. (+22 more)
Dwarf galaxies dominate the
galaxy population in the nearby Universe and occupy the regime where feedback, reionization, and environment exert their strongest influence on
galaxy formation. Despite their importance, detailed spectroscopic constraints on the faintest
dwarfs are currently limited to a handful of systems in the Local Volume, leaving the role of large-scale environment essentially unexplored at ultra-low
stellar masses. A northern 30-40m class
telescope equipped with a multiplexed optical integral-field spectrograph will enable a systematic, spatially resolved spectroscopic census of
dwarf galaxies with $M_\star \sim 10^{5}-10^{7} M_\odot$ across a wide range of environments. A deep survey of the Coma Cluster, combined with targeted observations of
dwarfs in clusters, groups, filaments, and low-density regions, will map
star formation histories, chemical enrichment, and internal kinematics at unprecedented depth. This program will directly test models of dark-matter physics, early-Universe feedback, and environmental quenching in the lowest-mass
galaxies, establishing
dwarf galaxies as precision probes of both
galaxy formation and fundamental physics.
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All authors J. Alfonso L. Aguerri, Jesús Falcón-Barroso, María Argudo-Fernández, Yago Ascasibar, Marc Balcells, Bahar Bidaran, Virginia Cuomo, David Fernández-Arenas, Anna Ferré-Mateu, Rubén García-Benito, Rosa María González Delgado, Marcella Longhetti, Pavel Mancera-Piña, Antonino Marasco, Lorenzo Morelli, Reynier F. Peletier, Isabel Pérez Martín, Francesca Pinna, Daniel Rosa González, Marc Sarzi, Alexandre Vazdekis, Marc Verheijen, Pedro Villalba González, Anne-Marie Weijmans, Stefano Zarattini
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake. How do Planetary Systems Form?
I. Mendigutía, N. Huélamo, I. Jiménez-Serra et al. (+32 more)
The detection and characterization of protoplanets in protoplanetary disks around young
stars is emerging as a transformative field that will redefine our understanding of how planetary systems form. While current facilities have revealed the diversity of mature
exoplanets and the complex structures of disks, we still lack the crucial observational link between them: a statistically meaningful census of
planets caught in the act of formation. This white paper argues that such a breakthrough requires access to the nearest and most informative
star-forming regions, roughly half of which are poorly accessible or entirely unreachable from Cerro Armazones. Although the ELT alone will strongly impact our knowledge of
planet formation, its location prevents Europe from fully exploiting the necessary parameter space. A 30-40 m
telescope in the northern hemisphere is therefore essential for obtaining diffraction-limited imaging of protoplanets and disks across the entire sky, enabling robust demographics, exploiting synergies with ngVLA,
Gaia, and other facilities covering the north, and ensuring that Europe remains at the forefront of the
planet-formation revolution in the coming decades.
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All authors I. Mendigutía, N. Huélamo, I. Jiménez-Serra, E. Villaver, O. Balsalobre-Ruza, D. Barrado, M. Benisty, A. Boccaletti, H. Bouy, G. Chauvin, G. Cugno, R. Fedriani, M. Fernández, A. Fuente, S. Haffert, M. Kama, J. Lillo-Box, G. Meeus, N. Miret-Roig, B. Montesinos, M. Osorio, R.D. Oudmaijer, A.F. Placinta-Mitrea, D. Pollacco, I. Rebollido, M. Reggiani, A. Ribas, P. Rivière-Marichalar, A. Sicilia-Aguilar, C. Toci, R. van Boekel, N. van der Marel, M. Vioque, E. Whelan, A. Zurlo
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40 m Telescope and the Science at Stake: Cosmology and High-z Universe
Pablo G. Pérez-González, Roberto Maiolino, Pascal A. Oesch et al. (+16 more)
Full sky coverage with 30-40 meter-class
telescopes is essential to answer fundamental questions in Astrophysics, Cosmology, and Physics, such as the composition of the Universe and the formation of the first
stars and supermassive black holes. An ELT/TMT-like
telescope in the Northern Hemisphere is a fundamental and necessary facility to provide multiplexing of observing power, diversity of instrumentation, rapid response, and statistical power required to address the questions and the problems, current and future, unveiled by full sky observatories such as JWST, Euclid, or Roman space
telescopes. The Northern ELT/TMT will expedite the study of unique, extreme, rare, transient, and/or high-energy events which will give the most information about fundamental Physics problems in the era of multi-messenger and time-domain Astronomy.
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All authors Pablo G. Pérez-González, Roberto Maiolino, Pascal A. Oesch, Alvio Renzini, Tommaso Treu, Cristina Ramos Almeida, Sandra Faber, Luis Colina, Almudena Alonso-Herrero, Santiago Arribas, Guillermo Barro, Helmut Dannerbauer, Mark Dickinson, Mauro Giavalisco, Marc Huertas-Company, Göran Östlin, Giulia Rodighiero, Patricia Sánchez-Blázquez, Elisa Toloba
Instrumentation and Methods for Astrophysics
Why the Northern Hemisphere Needs a 30-40m Telescope and the Science at Stake: Shaping Galaxies and Their Stars with Stellar Population Gradients, IMF Variations and Environmental Drivers in Cluster Early-Type Galaxies
A. Vazdekis, P. Sánchez-Blázquez, A. Ferré-Mateu et al. (+23 more)
This white paper highlights how
stellar population gradients, chemical abundance patterns,
stellar initial mass function (IMF) variations, and structural signatures in early-type
galaxies (ETGs), measured at faint and large galactocentric radii, out to $\sim4R_e$, provide powerful diagnostics of their formation and evolutionary histories. These observables encode the combined effects of early dissipative
star formation, subsequent
accretion and mergers, and internal feedback processes. Achieving such measurements requires high-signal-to-noise, spatially resolved U-band–optical–near-IR spectroscopy at large radii, with enough spatial resolution to study the variation of these properties on $\sim$kpc scales. These capabilities can only be delivered by a 30\,m-class
telescope. Disentangling these internal processes from environmental influences further demands observations of
galaxies across clusters spanning a wide range of evolutionary stages and local environments. The nearby Virgo, Perseus, and Coma clusters, without any comparable nearby counterparts in the Southern Hemisphere, offer ideal laboratories for this work. Such observations will place stringent constraints on the formation mechanism of ETGs, connecting local cluster ETGs to their high-
redshift progenitors. This white paper outlines several key science cases enabled by such a facility: (1) mapping
stellar population gradients across environments; (2) tracing IMF variations as a function of evolutionary stage and environment; (3) reconstructing the three-dimensional structure of
galaxies through deep integral-field spectroscopy and imaging; and (4) identifying and studying compact and relic systems as progenitors of present-day ETGs.
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All authors A. Vazdekis, P. Sánchez-Blázquez, A. Ferré-Mateu, I. Martín-Navarro, M. A. Beasley, J.A.L. Aguerri, A. Camps-Fariña, A. de Lorenzo-Cáceres, E. Eftekhari, J. Falcón-Barroso, I. Ferreras, F. La Barbera, R. García-Benito, R. M. González Delgado, M. Longhetti, C. Maraston, I. Pérez, F. Pinna, V. Quilis, R. F. Peletier, S. F. Sánchez-Sánchez, A. Sansom, L. Scholz-Díaz, C. Spiniello, D. Thomas, E. Villaver
Instrumentation and Methods for Astrophysics
Sub-millimeter wavelength protostellar accretion rate monitoring with AtLAST
Thomas Stanke, Verena Wolf, Bringfried Stecklum et al. (+5 more)
How a
star forms is a fundamental question in astrophysics. In the earliest stages of protostellar
evolution high extinction prevents a direct study of the
accretion processes and their temporal
evolution. Monitoring the variations of the
accretion luminosity in a large protostar sample over decades is needed to reveal how protostars accrete – in major bursts or in a quasi-steady fashion. We here argue that a large ground based sub-millimeter single-dish facility with a wide FoV is required to fulfill this task.
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All authors Thomas Stanke, Verena Wolf, Bringfried Stecklum, Doug Johnstone, Jochen Eislöffel, Gregory J. Herczeg, S. Tom Megeath, Karri I. I. Koljonen
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Analytical model of the photon ring with finite thickness
S.V. Chernov
An analytical model of a thick asymmetric Gaussian ring is presented for which the visibility function is calculated in two perpendicular directions for baselines up to 6 of the Earth's diameter.
Instrumentation and Methods for Astrophysics
The Future of Evolved Planetary Systems
Roberto Raddi, Anna F. Pala, Alberto Rebassa-Mansergas et al. (+19 more)
Understanding the formation,
evolution, and chemical diversity of
exoplanets are now central areas of astrophysics research. White
dwarfs provide a uniquely sensitive laboratory for studying the end stages of planetary-system
evolution and for probing the bulk composition of both rocky and volatile-rich exoplanetary material. In the 2030s new facilities will transform our ability to carry out “industrial-scale” astrophysics, leading to fundamental results and new challenges for the next decade. By combining the volume of data surveyed by the ESA
Gaia mission and Vera C. Rubin Observatory with the next-generation of spectroscopic facilities, the European Southern Observatory (ESO) community will be in a position to obtain an unbiased census of evolved planetary systems, constrain the composition of thousands of disrupted planetesimals, and connect these signatures to
Galactic populations and
stellar birth environments. Thus, it is now the time for assessing those challenges and preparing for the future. This white paper outlines key science opportunities arising in the next decade and the technological requirements of future ESO facilities in enabling transformative discoveries in the 2040s. These future facilities will have to combine a number of features that are crucial for studying evolved planetary systems at white
dwarfs, such as broad optical to near-infrared coverage, a high sensitivity at blue wavelengths, multi-resolution capability, massive multi-plexing, and time-domain reactivity.
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All authors Roberto Raddi, Anna F. Pala, Alberto Rebassa-Mansergas, Boris T. Gänsicke, Lientur Celedon, Tim Cunningham, Camila Damia Rincón, Aina Ferrer i Burjachs, Enrique García-Zamora, Nicola Pietro Gentile Fusillo, Joaquim Meza, Evelyn Puebla, Pablo Rodríguez-Gil, Snehalata Sahu, Alejandro Santos-García, Odette Toloza, Santiago Torres, Pier-Emmanuel Tremblay, Jan van Roestel, Murat Uzundag, Dimitri Veras, Jamie Williams
Astrophysics of Galaxies · Cross-listed from gr-qc
Achromatic, spin-odd Kerr EVPA as a null Frenet-Serret torsion integral on the photon ring
M. Baran Ökten
We compute the achromatic gravitational imprint that Kerr spacetime leaves on linear polarization at the
photon ring. Recasting parallel transport in a null Frenet–Serret frame yields a single scalar
evolution law for the electric-vector position angle. On the observer's screen, the Kerr-minus-Schwarzschild pattern on the direct critical curve is nonzero, strictly odd under
spin reversal after a half-turn azimuth relabelling, and tightly confined to a thin annulus. Using backward-shot, Carter-separated geodesics with midpoint RK2 transport, we achieve second-order convergence and degree-scale amplitudes that grow monotonically with
spin and inclination (RMS $\simeq 0.5$–$2^\circ$ for $a/M\gtrsim 0.8$, $i\gtrsim 60^\circ$). Three independent constructions – Frenet–Serret line integral, explicit Levi–Civita transport of the polarization vector, and the phase of the Walker–Penrose constant – agree ray by ray. We then define a parity-odd ring
estimator that is intrinsically achromatic after standard wavelength-squared regression,
symmetry-protected against common even-parity systematics, and compressed into low azimuthal modes. This yields a minimal two-parameter template (
spin and inclination) for mm/sub-mm polarimetry of horizon-scale rings in sources such as M87$^\ast$ and Sgr~A$^\ast$. The pipeline enables either a detection of the strong-field parallel-transport phase induced by frame dragging or informative upper limits.
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Instrumentation and Methods for Astrophysics
The Emergence of Prebiotic Chemistry in the ISM
Izaskun Jimenez-Serra, Giuliana Cosentino, Francisco Montenegro-Montes et al. (+22 more)
Contrary to popular belief, the interstellar medium (ISM) is not empty; it is filled with atoms,
dust particles, and molecules. Some of these molecules may have been the very building blocks of life that, delivered to Earth via comets and meteorites, could have given rise to Life itself. A large-area single-dish
telescope with superb sensitivity, field-of-view and multi-band instruments will allow us to explore the limits of chemical complexity in the interstellar medium, across our
Galaxy and in external
galaxies, determining whether amino acids, sugars, or RNA/DNA nucleobases can form in space.
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All authors Izaskun Jimenez-Serra, Giuliana Cosentino, Francisco Montenegro-Montes, Laura Colzi, Victor M. Rivilla, Miguel Sanz-Novo, Marta Rey-Montejo, David San Andres, Sergio Martin, Shaoshan Zeng, Amelie Godard Palluet, Miguel A. Requena-Torres, German Molpeceres, Pamela Klassen, Doug Johnston, Francesco Fontani, Silvia Spezzano, Elena Redaelli, Juris Kalvans, Yuri Aikawa, Belen Tercero, Pablo de Vicente, Serena Viti, Emilio J. Cocinero, Aran Insausti
Instrumentation and Methods for Astrophysics
White Dwarfs in Wide Binary Systems as Reliable Age Calibrators
Alberto Rebassa-Mansergas, Roberto Raddi, Anna F. Pala et al. (+13 more)
Deriving precise
stellar ages is a challenging task. Consequently, age-dependent relations - such as the age-
metallicity and age-velocity dispersion relations of the Milky Way, or the age-rotation-activity relation of low-mass
stars - are subject to potentially large uncertainties, despite the well-defined trends observed at the population level. White
dwarfs, the most common
stellar remnants, follow a relatively simple and well-understood cooling process. When found in wide binary systems with main-sequence companions, they can therefore provide the much-needed precise age estimates. The total age of such systems depends not only on the white
dwarf cooling time but also on the lifetime of the main-sequence progenitor. Estimating this lifetime requires knowledge of the progenitor mass, which is typically inferred by adopting an initial-to-final mass relation. However, the observational constraints on this relation are still poorly defined, introducing a source of uncertainty in white
dwarf age determinations. To mitigate this issue, we focus on a large sample of massive white
dwarfs (>~0.7 Msun), for which the main-sequence progenitor lifetime is negligible. These white
dwarfs are intrinsically faint and therefore require specialized facilities for adequate follow-up observations. In this white paper, we outline the instrumentation requirements needed to observe the forthcoming population of massive white
dwarfs in our
Galaxy.
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All authors Alberto Rebassa-Mansergas, Roberto Raddi, Anna F. Pala, Alejandro Santos-García, Santiago Torres, Leandro Althaus, Diogo Belloni, Maria Camisassa, Tim Cunningham, Camila Damia Rincón, Aina Ferrer i Burjachs, Enrique García-Zamora, JJ Hermes, Adam Moss, Steven G. Parsons, Odette Toloza
Instrumentation and Methods for Astrophysics
Serendipitous and targeted mm/sub-mm transient searches with wide-FOV telescope
Karri Koljonen, Claudio Ricci, Thomas Stanke et al. (+4 more)
The millimeter/sub-millimeter (mm/sub-mm) sky remains a rich but under-explored frontier for transient and variable phenomena. A wide-field, high-sensitivity instrument with a large aperture and degree-scale field of view would open this regime, enabling both systematic survey monitoring and rapid-response follow-up. Key science opportunities include
Galactic Plane monitoring and surveys to discover and characterize time-variable emission from young
stellar objects, magnetically active and flaring
stars, compact binaries, and explosive events, as well as
prompt responses to multi-messenger alerts with large localization regions (e.g., gravitational-wave triggers). Multi-band capability, rapid slewing, and high sensitivity are essential to probe energetic processes such as jet launching, relativistic shocks and
accretion flows in unprecedented detail. While long-term monitoring is well established at
radio and optical/infrared wavelengths, mm/sub-mm observations uniquely bridge the spectral gap between these regimes, directly probing obscured environments that are inaccessible elsewhere. Large-scale monitoring programs will yield legacy
datasets crucial for population studies through the 2040s and beyond.
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All authors Karri Koljonen, Claudio Ricci, Thomas Stanke, Doug Johnstone, Atul Mohan, Francisco Montenegro-Montes, John Orlowski-Scherer
Astrophysics of Galaxies
JWST Observations of the Double Nucleus in NGC 4486B: Possible Evidence for a Recent Binary SMBH Merger and Recoil
Behzad Tahmasebzadeh, Monica Valluri, Shashank Dattathri et al. (+19 more)
A recent study of the compact elliptical
galaxy NGC 4486B using JWST-NIRSpec IFU kinematics confirmed a supermassive black hole (SMBH) of mass $M_{BH}=3.6\pm0.7\times10^8$ (~8% of the
stellar mass). In addition to its double
nucleus, the
nuclear kinematics show pronounced asymmetries: a velocity-dispersion peak displaced by 6 pc from the
galaxy center and a ~16 km/s offset in the mean
stellar line-of-sight velocity near the SMBH. We examine the origin of the 12 pc double
nucleus and these asymmetries and show that the observations favor an SMBH surrounded by an eccentric
nuclear disk (END). END formation models require the SMBH to experience a gravitational wave (GW)
recoil following a binary SMBH merger. Our orbit-superposition models contain ~50% retrograde
stars at the edge of the
nuclear region, in striking agreement with END-formation simulations. We infer a pre-merger mass ratio q>0.15 and a
recoil kick of ~340 km/s. Our N-body simulations show that with such a kick, the SMBH returns to the center within ~30 Myr. Its flat central core is also consistent with earlier binary black hole scouring. We test two alternative mechanisms-buoyancy-driven oscillations and a pre-merger SMBH binary-but neither reproduces the observed offsets, favoring the GW-kick scenario. Our direct N-body simulations further show that a prograde SMBH binary in a rotating host can stall in a corotation resonance, delaying coalescence. Thus, although NGC 4486B is an old, relaxed
galaxy near the Virgo cluster center, its SMBH appears to have merged only recently, making its
nucleus a rare nearby laboratory for studying post-merger SMBH dynamics.
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All authors Behzad Tahmasebzadeh, Monica Valluri, Shashank Dattathri, Tatsuya Akiba, Fazeel Mahmood Khan, Matthew A. Taylor, Haruka Yoshino, Solveig Thompson, Ann-Marie Madigan, Frank C. van den Bosch, Kelly holley-bockelmann, Patrick Côté, Laura Ferrarese, Michael J. Drinkwater, Holger Baumgardt, Misty C. Bentz, Kristen Dage, Eric W. Peng, Somya Jha, Andrea V. Macciò, Chengze Liu, Tyrone E. Woods
Cosmology and Nongalactic Astrophysics
Cosmic Strings Gravitational Wave Probe of Leptogenesis: Thermal, Non-thermal, Near-resonant and Flavourful
Anish Ghoshal, Angus Spalding and Graham White
Breaking a global or local $U(1)_{\rm B-L}$
symmetry at high scales simultaneously generates Majorana masses for heavy right-handed
neutrinos and produces a network of
cosmic strings. The
evolution and decay of these strings source a
stochastic gravitational-wave background that may be probed by current and future gravitational-wave experiments, while the decays of the resulting massive right-handed
neutrinos can generate the
baryon asymmetry of the Universe via leptogenesis. We derive analytical bounds for successful leptogenesis with a global and a local $U(1)_{B-L}$
symmetry, separately finding an absolute lower bound on the lightest right-handed
neutrino mass $M_1 > 1.74 \times 10^{8}\,\mathrm{GeV}$ for thermal initial conditions and $M_1 > \mathcal{O}(10^{6})\,\mathrm{GeV}$ for non-thermal initial conditions. Allowing for near-resonant leptogenesis relaxes these bounds to TeV scale in both cases making it a viable target at
collider searches complementing the GW signals. Full flavour effects are included, and crucially, we determine the region where successful leptogenesis can be probed through gravitational-wave observations in upcoming experiments such as LISA and Einstein
Telescope. Importantly, we find that flavour effects rescue regions of the parameter space that are ruled out due to current CMB or gravitational wave measurements.
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Cosmology and Nongalactic Astrophysics
Clustering with Light (but Massive) Relics
Jason Kumar, Pearl Sandick and Shuting Xu
We consider the effect of Light (but Massive) Relics (LiMRs) on the clustering of matter in the early Universe. We account for the fact that LiMRs which are massive enough may cluster on large length scales at early times, and may thus impact weak
lensing of the
cosmic microwave background (CMB) even on small angular scales. In particular, we find that LiMRs in the $\gtrsim$ eV mass range (and even $> 10$ eV), can constitute a non-negligible component of dark matter. This opens up a class of scenarios in which energy is injected as dark radiation, but begins to
redshift as matter before recombination, thus avoiding constraints on $\Delta N_{eff}$ while providing an eV-range dark matter component.
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Cosmology and Nongalactic Astrophysics
A universal scaling law for gravitational waves induced during inflation
Martin Teuscher, Ruth Durrer, Killian Martineau et al. (+1 more)
We consider the
stochastic gravitational wave background induced by arbitrary source fields that are amplified during cosmological inflation. The associated tensor spectral index is shown to be given, under minimal assumptions, by a simple formula easy to apply in most situations of accelerated expansion. For slow-roll inflation, the induced spectrum is nearly scale invariant, with an index deviating from the standard outcome of
vacuum generated gravitational waves. Remarkably, we demonstrate that scale invariance remains true regardless of the original spectrum of the source. We show how this generic approach reproduces the literature on specific models of gravitational wave
primordial sources, and discuss its limitations. It provides a very practical estimation of the tensor spectral index for future models, to which subleading corrections can then be added.
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All authors Martin Teuscher, Ruth Durrer, Killian Martineau, Aurélien Barrau
Astrophysics of Galaxies
1D stellar mergers: entropy sorting and PyMMAMS
Max Heller, Fabian R. N. Schneider, Jan Henneco et al. (+2 more)
Stellar multiple systems are the norm, not the exception, with many systems undergoing interaction phases during their lifetimes. A subset of these interactions can lead to
stellar mergers, where the two components of a
stellar binary system come close enough to coalesce into a single
star. Accurately modeling
stellar mergers requires computationally expensive 3D methods, which are not suited for exploring large parameter spaces as required e.g., by population synthesis studies. In this work, we compare two 1D prescriptions based on the concept of
entropy sorting to their 3D counterparts. We employ a basic
entropy sorting method ('ES'), which builds the merger remnant by sorting the progenitor
stars' shells by increasing
entropy, and a Python version of the 'Make Me A Massive
Star' code ('PM'), which additionally applies a shock-heating prescription calibrated on SPH simulations of
stellar head-on collisions. Comparing to a set of 39 more recent SPH head-on collisions different from the ones used for PM calibration, we find that PM reproduces the outcome of these mergers a lot better than ES in terms of thermal and composition structure post-merger. Both 1D methods produce remnants that are rejuvenated more strongly than expected for massive
stars, indicating that increased amounts of hydrogen are being mixed into the core. In an effort to further improve PM, we introduce a scaling factor for the shock-heating. We compare 1D models with both down- and up-scaled heating to a 3D MHD $9 + 8\,\mathrm{M_\odot}$ merger of main-sequence
stars. Decreasing the shock-heating improves the agreement in terms of the
entropy profile, but has only a minor impact on the subsequent
stellar evolution of the remnant. We find that 1D methods are able to approximate 3D
stellar merger simulations well, and that shock-heating has to be considered to properly predict the post-merger structures.
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All authors Max Heller, Fabian R. N. Schneider, Jan Henneco, Vincent A. Bronner, Mike Y. M. Lau