Galaxy formation and evolution

Abstract:

Abstract JWST/NIRCam slitless spectroscopy enables dynamical mass measurements for typical star-forming galaxies only a billion years after the Big Bang. We model the Hα morpho-kinematics of 163 galaxies at redshift z ≈ 4-6 from FRESCO and CONGRESS (with JADES imaging), using the $\texttt {geko}$ code, and infer rotational velocities and dispersions within re. Our sample spans log M⋆ ≈ 7-10 and log Mdyn ≈ 9-11. Gas masses are inferred from empirical scaling relations and combined with stellar masses to yield baryonic masses. The resulting median inferred gas-to-baryonic mass fraction is 〈fgas〉 = 0.77. Using these baryonic masses together with the dynamical masses, we derive dark-matter fractions fDM(r < re) within the Hα half-light radius, and find a high median value of 〈fDM〉 = 0.73, where fDM is defined relative to the total (DM+baryonic) mass. About two-thirds of systems are DM-dominated within re ∼ 0.5–1 kpc. We find that fDM decreases with stellar mass, consistent with predictions from simulations. The stellar Tully-Fisher relation shows a tentative offset to higher vcirc at fixed M⋆ and substantial intrinsic scatter, suggesting that the relation is only beginning to emerge at z ∼ 5. We measure a negative correlation between fDM and baryonic surface density Σbar, weaker but broadly consistent with trends at cosmic noon and at z ∼ 0. Qualitatively comparing with modified NFW profiles coupled to an empirical stellar-to-halo mass relation suggests that the lowest fDM (≲ 0.4) require cored inner DM profiles, while the highest fractions favour cuspier profiles, potentially reflecting adiabatic contraction. Overall, the elevated fgas and fDM at z ≳ 4 are compatible with progenitors of baryon-dominated systems at z ∼ 2 and naturally anticipate overmassive black holes at fixed M⋆.

Abstract:

The interaction of gravitational waves (GWs) with matter is thought to be typically negligible in the Universe. We identify an exception in the case of resonant interactions, where GWs emitted by a background binary system, such as an inspiraling supermassive black hole (SMBH) binary, cause a resonant response in a stellar-mass foreground binary and the frequencies of the two systems become, and remain, synchronized. We point out that this previously unexplored dynamical phenomenon is not only possible, but can lead to $\mathcal{O}(30)$ binary systems becoming resonantly locked in the host galaxy of merging SMBHs of mass ${10}^{8.5-11}{M}_{\odot }$ , each of which has a significantly reduced merger time. We predict $\mathcal{O}({10}^{10})$ binary systems have been locked in the Universe’s history. Resonant locking could be detected through anomalous inspiral of binary systems.

Abstract:

The origin of cosmic rays (CRs) from outside the Solar system is unknown, as they are deflected by the interstellar magnetic field. Supernova remnants are the main candidate for CRs up to PeV energies but due to lack of evidence, they cannot be concluded as the sources of the most energetic Galactic CRs. We investigate discrete ejecta produced in state transitions of black hole X-ray binary systems as a potential source of CRs, motivated by recent TeV -ray detections by LHAASO. Starting from MAXI J1820+070, we examine the multi-wavelength observations and find that efficient particle acceleration may take place (i.e. into a robust power law), up to eV, where is the ratio of particle energy to magnetic energy. From these calculations, we estimate the global contribution of ejecta to the entire Galactic spectrum to be , with the CR contribution rising to at PeV energies, assuming roughly equal energy in non-thermal protons, non-thermal electrons, and magnetic fields. In addition, we calculate associated -ray and neutrino spectra of the MAXI J1820+070 ejecta to investigate new detection methods with CTAO, which provide strong constraints on initial ejecta size of order Schwarzschild radii ( pc) assuming a period of adiabatic expansion.