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Jeffrey M. La Fortune

Publications and source records attributed to Jeffrey M. La Fortune.

7 recordsLinked to original sources

Reframing the Galaxy and Cluster Mass Discrepancy Problem: A Consequence of Virial Equilibrium and Other Energy Considerations

Galaxy and galaxy clusters exhibit tight robust physical scaling relations between baryons and system dynamics. One such phenomenon is mass discrepancy with two leading solution spaces occupied by LCDM and MOND. Here, we propose an alternative solution to this puzzling problem exclusively based on application of the scalar virial theorem. For these dynamically equilibrated systems, we demonstrate there is ample virially-induced kinetic energy available to modify bulk structure dynamics in apparent violation of Newtonian law. We propose the ubiquitous Baryonic Tully-Fisher Relation represents the preferred dynamic configuration that best assures long-term survivability for these thermodynamic quasi-equilibrated systems. We compare total mass estimates guided by the empirical evidence to those obtained from NFW dark matter halo fits ranging from small dwarf galaxies to massive galaxy clusters.

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The Global Escape Velocity Profile and Virial Mass Estimate of The Milky Way Galaxy from Gaia Observations

Gaia HyperVelocity Star (HVS) kinematic observations favor a local escape velocity of ~700 km/s, nearly forty-percent greater than conventional estimates. Combining HVS and dwarf galaxy satellite data reveal the global escape velocity profile for the Galaxy smoothly traces an unbroken Keplerian decline from the central bar to the most remote satellite galaxy. We reveal a robust upper bound in baryonic mass discrepancy (maximal relative accelerations) linked to the virial theorem and obtain a fundamental and universal mass discrepancy-acceleration relation for virialized compact cosmic objects.

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On a Generalized Mass-Velocity Relation for Disk Galaxies and Galaxy Clusters

We consolidate the BFJ and BTF (MVD) relations into a generalized Scaling Mass Velocity Relation applicable to both pressure-supported galaxy clusters and rotation-supported galaxies. Unlike MOND inspired relations containing a characteristic acceleration scale and its normalization factor, our proposal is dependent on observed dynamic surface mass densities and discrepancies. We perform the same analysis for a sample of HIFLUGCS galaxy clusters (Tian et al, 2021) found in prior work with SPARC galaxies (arXiv: 2101.01537). For this galaxy cluster sample, we find little evidence for a universal acceleration constant as previously recognized for galaxies. We finish with an examination of the virial energies for the combined sample recovering a mass-energy relation consistent with the phenomenology.

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Mining the SPARC Galaxy Database: Finding "Hidden Variables" in the Baryonic Tully-Fisher Relation

The Baryonic Tully-Fisher Relation (BTFR) links baryonic mass of rotationally supported galaxies to their flat disk velocities. A popular form of the BTFR linked to MOND is based on an empirically determined characteristic acceleration, a0 that serves as the constant of proportionality. In this work, we propose an alternative, parametric form of the BTFR employing individual galactic properties from the SPARC galaxy database. Based on this data we find that a precise mass-velocity correlation is possible taking into account galactic disk radius and two dynamical related properties; mass discrepancy and disk surface density. We find no need to invoke a characteristic acceleration constant although its ansatz can be extracted and compared to several recent analyses also arguing against the MOND interpretation of a0. This improved BTFR finding has ramifications for the Radial Acceleration Relation (RAR) as well. Rather than a universal relation that describes the dynamics of all rotationally-supported galaxies, we find the RAR consists of a statistically distributed family of curves, reflecting the unique properties attributed to individual galaxies.

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A Physical Interpretation of Milky Way Galaxy Dynamics from Precision Astrometrics

The dynamical and virial mass of the Milky Way galaxy is estimated using latest high precision stellar halo and dwarf galaxy satellite kinematics. The new data suggest the Galaxy is a highly compact, classically thermalized object. Kinematics exhibit significant velocity-spatial substructure, distinctive dynamic partitions, and strong Keplerian signatures that run counter to popular notions of featureless and massively extended dark matter halos. The effective local escape velocity profile of the Galaxy is quantified in terms of distribution and kinematics to reveal the physics responsible for the Mass Discrepancy-Acceleration (MDAR) and Radial Acceleration (RAR) relations.

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A Dimensional Analysis of the Galactic Baryonic Tully-Fisher Relation with Comparison to MOND and Dark Matter Halo Dynamics

Most rotationally-supported galaxies strictly follow the Baryonic Tully-Fisher Relation (BFTR) linking circular velocity with baryon content. This firmly established empirical relationship is currently thought to have origins in either modified gravity or dark matter halo effects. In this work, we construct a physically-based version of the BFTR founded on known scaling relations, disk dynamics (acceleration, jerk and snap) that also reveals the foundational elements responsible for this phenomenology. We employ the Milky Way galaxy as an exemplar to quantitatively compare the two leading theories against this improved version. Additionally, a dimensionless variant of the BFTR is also provided which may permit its use as an analytic tool to aid in the understanding of galactic dynamics.

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The Phenomenological Scaling Relations of Disk Galaxies

A conservative scaling model based on Newton's law of circular motion and the virial theorem is proposed. Employing dimensionless scaling relations, a physical solution to the Baryonic Tully-Fisher Relation (BTFR) is obtained and the origin of the Radial Acceleration Relation (RAR) is provided. A simple model of the Milky Way's dynamics reveals excellent agreement with recent Gaia DR2 kinematical results.

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