Overestimated inclinations of Milgromian disc galaxies: the case of the ultradiffuse galaxy AGC 114905

Abstract

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 $0.05a_{{}_0}$, 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.

8 pages, 2 figures, 2 tables. Published in the Monthly Notices of the Royal Astronomical Society in this form. Face-on videos available at https://youtu.be/VkZq2Se0_lU (isolated) and https://youtu.be/3wC3yRkrXnc (including an external field of a_0/20)

References in corpus (16)

• SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves
• The Radial Acceleration Relation in Rotationally Supported Galaxies
• One Law To Rule Them All: The Radial Acceleration Relation of Galaxies
• Galaxies as simple dynamical systems: observational data disfavor dark matter and stochastic star formation
• A combined analysis of the $H_0$ late time direct measurements and the impact on the Dark Energy sector
• THINGS about MOND
• The KBC void and Hubble tension contradict $\Lambda$CDM on a Gpc scale $-$ Milgromian dynamics as a possible solution
• Phantom of RAMSES (POR): A new Milgromian dynamics N-body code
• A massive blow for $\Lambda$CDM $-$ the high redshift, mass, and collision velocity of the interacting galaxy cluster El Gordo contradicts concordance cosmology
• Predictions and Outcomes for the Dynamics of Rotating Galaxies
• RAyMOND: An N-body and hydrodynamics code for MOND
• The formation of exponential disk galaxies in MOND
• 3D hydrodynamic simulations for the formation of the Local Group satellite planes
• The global stability of M33 in MOND
• Barred spiral galaxies in modified gravity theories
• The Phantom of RAMSES user guide for galaxy simulations using Milgromian and Newtonian gravity

Cited by in corpus (7)

• From galactic bars to the Hubble tension: weighing up the astrophysical evidence for Milgromian gravity
• The distribution and morphologies of Fornax Cluster dwarf galaxies suggest they lack dark matter
• Distinguishing Dark Matter, Modified Gravity, and Modified Inertia with the Inner and Outer Parts of Galactic Rotation Curves
• Simulations of star forming main sequence galaxies in Milgromian gravity
• The ultra-diffuse galaxy AGC 114905 needs dark matter
• Broader view of bimetric MOND
• Newtonian Fractional-Dimension Gravity and Galaxies without Dark Matter