Page Text: Authors: Nadav Joseph Outmezguine , Kimberly K. Boddy , Sophia Gad-Nasr , Manoj Kaplinghat , Laura Sagunski
Subjects: Astrophysics of Galaxies (astro-ph.GA); High Energy Physics - Phenomenology (hep-ph)
We study the evolution of isolated self-interacting dark matter (SIDM) halos using spherically-symmetric gravothermal equations allowing for the scattering cross section to be velocity dependent. We focus our attention on the large class of models where the core is in the long mean free path regime for a substantial time. We find that the temporal evolution exhibits an approximate universality that allows velocity-dependent models to be mapped onto velocity-independent models in a well-defined way using the scattering timescale computed when the halo achieves its minimum central density. We show how this timescale depends on the halo parameters and an average cross section computed at the central velocity dispersion when the central density is minimum. The predicted collapse time is fully defined by the scattering timescale, with negligible variation due to the velocity dependence of the cross section. We derive new self-similar solutions that provide an analytic understanding of the numerical results.
[2] arXiv:2204.06569 [ pdf , other ]
Title: Overestimated inclinations of Milgromian disc galaxies: the case of the ultradiffuse galaxy AGC 114905
Authors: Indranil Banik (Saint Andrews), Srikanth Togere Nagesh (Bonn), Hosein Haghi (Bonn, Zanjan), Pavel Kroupa (Bonn, Prague), Hongsheng Zhao (Saint Andrews)
Comments: 8 pages, 2 figures, 2 tables. Accepted for publication in the Monthly Notices of the Royal Astronomical Society in this form
Subjects: Astrophysics of Galaxies (astro-ph.GA)
We present hydrodynamical star-forming simulations in the Milgromian dynamics (MOND) framework of a gas-rich disc galaxy with properties similar to AGC 114905, which has recently been argued to have a rotation curve (RC) that is inconsistent with the MOND prediction. Our first model considers the galaxy in isolation, while our second model includes an external field of $0.05 \, a_{_0}$, the estimated gravitational field from large-scale structure. We show that isophotes in the face-on view can differ from circular at the 50% level. This could mislead observers into overestimating the inclination $i$ between disc and sky planes. Because RCs require a correction factor of $1/\sin i$, the actual RC could be much higher than reported by observers. This plausibly reconciles AGC 114905 with MOND expectations.
[3] arXiv:2204.06572 [ pdf , other ]
Title: Spatially Resolved Gas-phase Metallicity in FIRE-2 Dwarfs: Late-Time Evolution of Metallicity Relations in Simulations with Feedback and Mergers