Article
Astronomy & Astrophysics
Kerwann Tep, Jean-Baptiste Fouvry, Christophe Pichon, Gernot Heissel, Thibaut Paumard, Guy Perrin, Frederic Vincent
Summary: Supermassive black holes at the center of galaxies play a significant role in shaping the orbits of surrounding stellar clusters. Stars in these dense environments experience relaxation of their eccentricities through resonant and non-resonant processes, which can be explored using resonant diffusion coefficients. By studying the S-cluster around SgrA* and employing this framework, researchers can estimate the properties of intermediate-mass black holes and dark clusters, contributing to the understanding of supermassive black hole formation scenarios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Uddipan Banik, Frank C. van den Bosch
Summary: The study focuses on impulsive encounters between astrophysical objects, finding that the distant tide approximation method often overpredicts the energy change caused by impulses when the impact parameter is small, and is not suitable for the most interesting close encounters. To address these issues, a comprehensive, non-perturbative treatment of impulsive encounters is proposed, which is valid for any impact parameter and not hampered by divergence issues.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
C. T. Mpetha, C. A. Collins, N. Clerc, A. Finoguenov, J. A. Peacock, J. Comparat, D. Schneider, R. Capasso, S. Damsted, K. Furnell, A. Merloni, N. D. Padilla, A. Saro
Summary: Data from the SPIDERS was used to detect gravitational redshifting of light from approximately 20,000 galaxies in around 2500 galaxy clusters, with results showing a clear detection of the effect. The BCG centroid was identified as the most robust method for analysis, with no strong preference for one gravity theory over another. Future studies will require a larger sample of galaxies and could potentially be achieved with upcoming observatories like the Vera C. Rubin Observatory, Euclid, and eROSITA.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Shohei Saga, Atsushi Taruya, Stephane Colombi
Summary: This study explores the structure around the shell-crossing time of cold dark matter protohaloes seeded by two or three crossed sine waves of various relative initial amplitudes by comparing Lagrangian perturbation theory up to the tenth order with high-resolution cosmological simulations. The results show that high-order LPT predictions match the exact solution well in the generic case, but convergence slows down in axial-symmetric configurations, especially when velocity-related quantities are considered.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Nicholas Pavanel, Jeremy J. Webb
Summary: This study investigates how perturbations from a distribution of Lambda CDM dark matter subhalos affect the orbits of star clusters. The findings show that subhalos with masses less than 10^8 solar masses have negligible effects on test particle orbits, while perturbations lead to orbital deviations only in environments with substructure fractions greater than or equal to 1%. Additionally, perturbations from denser subhalos produce larger orbital deviations, and subhalo perturbations that are strong relative to the background tidal field lead to larger orbital deviations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
F. G. Ramon-Fox, I. A. Bonnell
Summary: Star formation occurs on the smallest scales within molecular clouds, likely initiated by large-scale flows driven by galactic dynamics. Local shocks induced by arms and the increase in kinetic energy are crucial elements in forming molecular clouds and driving star formation.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
T. Mistele, S. McGaugh, S. Hossenfelder
Summary: This study made rotation curve fits using the superfluid dark matter model and evaluated the relationship between the fits, stellar mass-to-light ratios, and the resemblance to MOND. The results showed that the mass-to-light ratios obtained with superfluid dark matter are generally reasonable, but they exhibit an unnatural dependence on galaxy size. Additionally, when the fits were forced to resemble MOND, there was tension between the total dark matter mass and gravitational lensing data.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Chris Hamilton
Summary: The unshielded nature of gravity leads to inherent inhomogeneity in stellar systems, requiring the use of angle-action variables in kinetic theory. Collective interactions and polarization effects can enhance or suppress the relaxation of star clusters and galaxies. A recent angle-action generalization of the Balescu-Lenard equation accounts for both inhomogeneity and collective effects, providing a simpler derivation using Rostoker's superposition principle, which connects the BL picture to classical two-body relaxation theory.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Review
Multidisciplinary Sciences
Indranil Banik, Hongsheng Zhao
Summary: Astronomical observations reveal a major deficiency in our understanding of physics, which may be explained by Milgromian dynamics (MOND) theory. We review the MOND theory and test its predictions using evidence from galaxies and the universe. We find that MOND is well-supported by data across different scales. The article also discusses future testing directions.
Article
Astronomy & Astrophysics
Jonathan Freundlich, Benoit Famaey, Pierre-Antoine Oria, Michal Bilek, Oliver Mueller, Rodrigo Ibata
Summary: Research shows that ultra-diffuse galaxies (UDGs) in galaxy clusters exhibit a tight radial acceleration relation (RAR) and velocity dispersion profiles consistent with modified Newtonian dynamics (MOND), but the strong equivalence principle (SEP) is broken by the external field effect (EFE). Possible explanations within the MOND framework include tidal heating and higher baryonic masses, and it is speculated that the EFE may be screened in cluster UDGs.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
M. J. M. Marcha, I. W. A. Browne
Summary: Evidence for large-scale clustering is found among Fermi-selected BL Lac objects, but not among Fermi-selected FSRQs. High-latitude Fermi sources as a whole show a significant clustering signal on scales up to 30 degrees, while this signal may be washed out in FSRQs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Carlos R. Melo-Carneiro, Cristina Furlanetto, Ana L. Chies-Santos
Summary: In this work, the eta PPN parameter of the SDP.81 lens galaxy is investigated using mass measurements from gravitational lensing and galactic dynamics. The result shows that eta(PPN) = 1.13(+0.03)(-0.03)+/- 0.20(sys), which is consistent with the predictions of General Relativity. Better spectroscopy data are required to reduce the systematic uncertainties and improve the accuracy.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Chris Hamilton, Roman R. Rafikov
Summary: This study explores the secular evolution of binary systems driven by external (tidal) forces, focusing on the impact of general relativity (GR) precession on tidal evolution and discovering new phase space morphologies. The results provide important insights into understanding binary orbital evolution, particularly in various astrophysical systems. This research also sheds light on how the GR precession affects the secular evolution of binary orbital elements, especially in high eccentricity scenarios, with implications for tide-driven compact object mergers in LIGO/Virgo gravitational wave sources.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jean-Baptiste Fouvry, Chris Hamilton, Simon Rozier, Christophe Pichon
Summary: Globular clusters with a finite number of stars undergo secular evolution driven by local deflections and resonant couplings, known as non-resonant relaxation and resonant relaxation. A study comparing both relaxation theories found that they predict the correct morphology of the cluster's distribution function evolution, with non-resonant relaxation overestimating the relaxation rate by a factor of 2.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Jean-Baptiste Fouvry, Simon Prunet
Summary: The study focuses on the amplification of perturbations and the response matrix in stellar clusters, presenting a generic method for calculating damped modes in spherically symmetric stellar clusters. Through testing predictions with direct N-body simulations, a low-frequency weakly damped mode was discovered.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Mattia Mina, David F. Mota, Hans A. Winther
Summary: In this study, we present the results of a cosmological simulation using the new code SCALAR to study the formation and evolution of fuzzy dark matter. Despite limitations on large-scale resolution, the study provides detailed analysis of the formation and evolution of central solitonic cores. The results indicate a shallower halo mass function in the low-mass end due to the quantum nature of the scalar field.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Ryan J. Farber, Max Gronke
Summary: Recent progress has been made in understanding gas phases in the circumgalactic medium and galactic wind, particularly in relation to the origin and survival of the cold molecular phase, as well as the role of dust in the acceleration process.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Siddhartha Gurung-Lopez, Max Gronke, Shun Saito, Silvia Bonoli, Alvaro A. Orsi
Summary: zELDA is an open source code for fitting Lyman alpha line profiles, which allows for the analysis of Ly alpha emitting galaxies. By training a neural network, zELDA can accurately predict model parameters and provides a faster alternative to existing methods. Through fitting observed data, zELDA demonstrates good accuracy and potential in determining Ly alpha wavelengths and identifying possible trends.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Max Gronke, S. Peng Oh, Suoqing Ji, Colin Norman
Summary: This work investigates the survival and growth of cold gas in turbulent, multiphase astrophysical gases using three-dimensional hydrodynamical simulations. The results show that the survival of cold gas depends on the cooling time and the Kelvin-Helmholtz time of the mixed gas. In a turbulent flow, the cold gas fragments and its surface area enhances, leading to exponential mass growth. The study has important implications for larger scale simulations and observations of the circumgalactic medium.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Zhihui Li, Max Gronke
Summary: The Lyman-alpha emission line plays a crucial role in understanding the gaseous medium in the Universe. However, the resonant nature of the line complicates the modeling process. This study revisits the modeling problem and establishes a connection between the more physically realistic multiphase, clumpy model and the commonly used shell model. By breaking the intrinsic degeneracies and utilizing additional observations, the study provides a viable solution to the discrepancies reported in previous literature.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Zhihui Li, Charles C. Steidel, Max Gronke, Yuguang Chen, Yuichi Matsuda
Summary: This study presents new spectroscopic observations of Ly alpha Blob 2, revealing extended Ly alpha emission and the presence of a high surface brightness center far from known continuum sources. Radiative transfer models are used to explain the diverse Ly alpha morphologies, indicating outflow-dominated kinematics and a significant correlation between parameter pairs. The results support the scenario of Ly alpha photons being generated by a central powering source and scattering with outflowing H i gas.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Chad Bustard, Max Gronke
Summary: We analyze the interaction between the Magellanic Stream and the circumgalactic medium of the Milky Way and present new insights. Contrary to previous expectations, we predict that the clouds in the Leading Arm and Trailing Stream should survive and even gain mass. Our findings also have broader implications for extragalactic phenomena, such as galactic winds.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Danielle A. Berg, Bethan L. James, Teagan King, Meaghan McDonald, Zuyi Chen, John Chisholm, Timothy Heckman, Crystal L. Martin, Dan P. Stark, Alessandra Aloisi, Ricardo O. Amorin, Karla Z. Arellano-Cordova, Matthew Bayliss, Rongmon Bordoloi, Jarle Brinchmann, Stephane Charlot, Jacopo Chevallard, Ilyse Clark, Dawn K. Erb, Anna Feltre, Max Gronke, Matthew Hayes, Alaina Henry, Svea Hernandez, Anne Jaskot, Tucker Jones, Lisa J. Kewley, Nimisha Kumari, Claus Leitherer, Mario Llerena, Michael Maseda, Matilde Mingozzi, Themiya Nanayakkara, Masami Ouchi, Adele Plat, Richard W. Pogge, Swara Ravindranath, Jane R. Rigby, Ryan Sanders, Claudia Scarlata, Peter Senchyna, Evan D. Skillman, Charles C. Steidel, Allison L. Strom, Yuma Sugahara, Stephen M. Wilkins, Aida Wofford, Xinfeng Xu
Summary: Far-ultraviolet (FUV) spectra play a crucial role in understanding star-forming galaxies. The launch of the James Webb Space Telescope will advance our knowledge of FUV spectroscopy. This study presents the Cosmic Origins Spectrograph Legacy Spectroscopic Survey (CLASSY) and its high-quality FUV spectral database of nearby star-forming galaxies.
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
(2022)
Article
Astronomy & Astrophysics
S. T. H. Hartman, H. A. Winther, D. F. Mota
Summary: This study performs fully 3D cosmological simulations of scalar field dark matter with self-interactions, also known as Bose-Einstein condensate dark matter. The simulations are based on a set of effective hydrodynamic equations derived from the non-linear Schrodinger equation. The results show that the formed dark matter halos have Navarro-Frenk-White envelopes and cored centers due to fluid pressures. The core radii are largely determined by the self-interaction Jeans' length, while the effective thermal energy becomes important as structures collapse. Comparisons with observations of Milky Way dwarf spheroidals and nearby galaxies suggest that the simulated population of halos does not match well but performs better compared to simulations of fuzzy dark matter-only.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Alex Woodfinden, Seshadri Nadathur, Will J. Percival, Sladana Radinovic, Elena Massara, Hans A. Winther
Summary: This study presents measurements of the anisotropic cross-correlation of galaxies and cosmic voids in SDSS data, achieving higher precision than traditional analyses and confirming expectations of the Λ cold dark matter model. The results on the growth rate of structure and comoving angular diameter distance provide valuable insights for modern observational cosmology and complement other cosmological probes.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Brent Tan, S. Peng Oh, Max Gronke
Summary: Understanding the survival, growth, and dynamics of cold gas is essential for galaxy formation. This study focuses on the infall of cold gas under gravity, which is different from wind simulations. The survival criterion for infalling gas requires cloud growth to be faster than destruction, and a critical pressure of P ~ 3000 k(B) K cm(-3) is determined for Milky Way-like conditions.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Max Gronke, S. Peng Oh
Summary: This study investigates the multiphase structures of astrophysical gases, such as interstellar and circumgalactic mediums. Through hydrodynamical simulations, it is found that pulsations in perturbed cold gas clouds lead to mass growth and coagulation with hot gas and cold droplets. The attractive force between cold gas droplets resembles gravity, where the 'monopole' is in terms of surface area. A simple analytic model is developed to validate the numerical findings.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ryan J. Farber, Max Gronke
Summary: Recent observations suggest that galaxies may have a molecular component in their circumgalactic medium. However, the structure and dynamics of the molecular circumgalactic medium are still poorly understood. This study uses simulations to explore the process of fragmentation and shattering of molecular clouds, finding that larger clouds can shatter into tiny droplets, and cold clouds can undergo a process of splintering. These findings have implications for understanding the molecular phase of the circumgalactic medium in observations and cosmological simulations.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Shahab Joudaki, Pedro G. Ferreira, Nelson A. Lima, Hans A. Winther
Summary: We provide a comprehensive exploration of a distinct modified gravitational theory in Jordan-Brans-Dicke (JBD) gravity, covering analytical and numerical descriptions of background expansion, linear perturbations, and nonlinear regimes. The JBD coupling constant is constrained through various cosmological probes, showing agreement with the standard model expectations. The lower bound on the coupling constant strengthens when fixing the sum of neutrino masses. Additionally, a positive shift in the effective gravitational constant impacts the CMB damping tail. No substantial preference for JBD gravity over ?CDM is found in model selection.
Article
Astronomy & Astrophysics
Brent Tan, S. Peng Oh, Max Gronke
Summary: Radiative mixing layers arise from the presence of multiphase gas, shear, and radiative cooling. Thermal advection from the hot phase balances radiative cooling in steady state, but many features remain puzzling, such as the characteristic velocity and scaling of hot gas heat flux. By exploiting parallels with turbulent combustion, a deeper physical understanding of radiative fronts can be achieved, shedding light on the structure and survival of cold gas in various scenarios.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)