Dark matter and MOND dynamical models of the massive spiral galaxy NGC 2841

Abstract

We study dynamical models of the massive spiral galaxy NGC 2841 using both the Newtonian models with Navarro-Frenk-White (NFW) and isothermal dark haloes, as well as various MOND (MOdified Newtonian Dynamics) models. We use the observations coming from several publicly available data bases: we use radio data, near-infrared photometry as well as spectroscopic observations. In our models, we find that both tested Newtonian dark matter approaches can successfully fit the observed rotational curve of NGC 2841. The three tested MOND models (standard, simple and, for the first time applied to another spiral galaxy than the Milky Way, Bekenstein's toy model) provide fits of the observed rotational curve with various degrees of success: the best result was obtained with the standard MOND model. For both approaches, Newtonian and MOND, the values of the mass-to-light ratios of the bulge are consistent with the predictions from the stellar population synthesis (SPS) based on the Salpeter initial mass function (IMF). Also, for Newtonian and simple and standard MOND models, the estimated stellar mass-to-light ratios of the disc agree with the predictions from the SPS models based on the Kroupa IMF, whereas the toy MOND model provides too low a value of the stellar mass-to-light ratio, incompatible with the predictions of the tested SPS models. In all our MOND models, we vary the distance to NGC 2841, and our best-fitting standard and toy models use the values higher than the Cepheid-based distance to the galaxy NGC 2841, and the best-fitting simple MOND model is based on the lower value of the distance. The best-fitting NFW model is inconsistent with the predictions of the cold dark matter cosmology, because the inferred concentration index is too high for the established virial mass.

Dark matter in massive early-type galaxies: 100 years of the jeans equations

“…We indeed found many signs of recent interactions in the galaxies that were most problematic for MOND. Finally, we briefly discuss the recent findings of Samurović and Vudragović (2019) related to two massive nearby ETGs, NGC 4473 and NGC 4697 26 , both fast rotators. Newtonian (purely baryonic and also models based on the Einasto (1965) DM profile) and MOND models were tested using GCs as tracers of gravitational potential of the galaxies.…”

“…It is important to stress that the contribution of the stellar component was not based on the central parts only but was a function of radius (see Fig. 5 in Samurović and Vudragović 2019): the value of the stellar mass-to-light ratio in the B-band varies between approximately 7 in the inner regions to 3 in the outer regions. Three cases of anisotropies were tested and it was found that in most tested cases Newtonian purely baryonic models for both galaxies could not provide a successful fit of the observed velocity dispersion without the additional dark component and that the introduction of the dark Einasto halo improved the quality of the fits.…”

“…toy models (the remaining six MOND models provided fits of similar quality, see Samurović and Vudragović 2019): the simple models are tangentially anisotropic (β = −0.2) based on the IP13 model with the Kroupa IMF, whereas both standard and toy models are based on the Bruzual and Charlot (2003) model (BC model) with the Salpeter IMF, but the standard model is isotropic and the toy model is made with radially anisotropic orbits.…”