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We present the observed HI size-mass relation of $204$ galaxies from the MIGHTEE Survey Early Science data. The high sensitivity of MeerKAT allows us to detect galaxies spanning more than 4 orders of magnitude in HI mass, ranging from dwarf galaxies to massive spirals, and including all morphological types. This is the first time the relation has been explored on a blind homogeneous data set which extends over a previously unexplored redshift range of $0 < z < 0.084$, i.e. a period of around one billion years in cosmic time. The sample follows the same tight logarithmic relation derived from previous work, between the diameter ($D_{\rm HI}$) and the mass ($M_{\rm HI}$) of HI discs. We measure a slope of $0.501\pm 0.008$, an intercept of $-3.252^{+0.073}_{-0.074}$, and an observed scatter of $0.057$ dex. For the first time, we quantify the intrinsic scatter of $0.054 \pm 0.003$ dex (${\sim} 10 \%$), which provides a constraint for cosmological simulations of galaxy formation and evolution. We derive the relation as a function of galaxy type and find that their intrinsic scatters and slopes are consistent within the errors. We also calculate the $D_{\rm HI} - M_{\rm HI}$ relation for two redshift bins and do not find any evidence for evolution with redshift. These results suggest that over a period of one billion years in lookback time, galaxy discs have not undergone significant evolution in their gas distribution and mean surface mass density, indicating a lack of dependence on both morphological type and redshift., 10 pages, 5 figures, accepted for publication in MNRAS

Understanding the morphological and dynamical evolution of galaxies across cosmic time is one of the key goals of modern extragalactic astrophysics. Our current view is that galaxies are objects that evolve secularly and build their stellar mass through star formation which is sustained by cold gas accretion from the cosmic web. However, this picture is not sufficient to explain entirely their evolution. Environmental processes can also affect their morphology, kinematics, or gas content, as well as quench star formation, and can thus be driving mechanisms to explain the transition from high to low redshift. Thus, important recent efforts have been put into probing the effect of the environment on galaxies. In this endeavour, 3D spectroscopy can help because it provides spatially resolved properties across the galaxies’ extent. MUSE is one of the most powerful 3D spectrographs thanks to its large field-of-view and high sensitivity when combined with adaptive optics.During this Thesis, I have used data from the deep MUSE-gAlaxy Groups In Cosmos survey (MAGIC) which targets galaxy groups/clusters in the COSMOS field, as well as foreground and background field galaxies. MAGIC is ideal to probe the impact of the environment at 0.2 ≲ z ≲ 1.5 for a large sample of galaxies with high completeness and down to low stellar masses (M⋆ ≈ 10^9 M⊙ ). From this survey, I modelled the morphology of about 900 galaxies by performing a bulge-disk decomposition to extract key morphological parameters (e.g. bulge-to-disk flux ratio, disk inclination, etc.) and the ionised gas kinematics from the MUSE cubes using the [O ii] doublet as kinematics tracer and taking into account beam-smearing for 600 galaxies. I also integrated a mass modelling where I constrained the kinematics using prior information from the bulge-disk decomposition to recover more precise dark matter fractions.This has allowed me to contribute to a first analysis of the Tully-Fisher relation at z ∼ 0.7, followed by my first paper on the analysis of major scaling relations as a function of environment. From these works, I showed that galaxies are affected by their host structure at z ∼ 0.7 in terms of morphology and star-formation rate but not in terms of their dynamics. I continued with another analysis of the impact of the environment on the galaxies’ stellar angular momentum. The first results suggest that there is a visible impact of the environment on the angular momentum, mostly associated to massive galaxies found in the densest parts of the structures. Because these galaxies also host massive bulges, the current interpretation is that they have probably suffered from a depletion of angular momentum (∼ 20%) by building up their bulge component while reaching the inner parts of the structures. Furthermore, I have also worked on the development of a new methodology that produces resolved stellar mass maps using pixel-per-pixel SED fitting techniques and a corresponding machine learning application that I am currently refining.My Thesis has shown the powerful capabilities of MAGIC to probe the impact of the environment on galaxy evolution. This effort will be pushed forward in the near future thanks to already existing and new MUSE surveys such as the HUDF, MUSE-Wide, MXDF, and MUSCATEL. For the latter, I will be able to produce the galaxies’ stellar mass maps and use them to get better constraints on the galaxies’ ionised gas kinematics and on their dark matter content. Furthermore, these new developments combined with my expertise in morpho-kinematics analyses will also be beneficial for future data from next-generation instruments with the JWST or ERIS-VLT and on the longer term with HARMONI and MOSAIC on the ELT.; Comprendre l’évolution morphologique et dynamique des galaxies au cours du temps cosmique est l’un des objectifs principaux de l’astrophysique extragalactique moderne. Notre compréhension actuelle est que les galaxies sont des objets qui évoluent séculairement et qui assemblent leur masse via la formation stellaire entretenue par l’accrétion de gaz froid de la toile cosmique. Cependant, cette image n’est pas suffisante pour expliquer entièrement leur évolution. Des processus environnementaux peuvent aussi affecter leur morphologie, cinématique et contenu en gaz, ainsi que supprimer leur formation stellaire, et donc jouer un rôle majeur pour expliquer la transition de haut à bas redshift. Ainsi, des efforts importants ont récemment été réalisés pour sonder l’effet de l’environnement sur les galaxies. Dans ce but, la spectroscopie 3D peut aider car elle procure des données spatialement résolues des propriétés physiques des galaxies. MUSE est l’un des spectrographes 3D les plus performants grâce à son grand champs de vue et sa haute sensibilité quand il est combiné avec l’optique adaptative.Durant cette thèse, j’ai utilisé des données issues du relevé profond “MUSE gAlaxy Groups In Cosmos survey (MAGIC)” ciblant des groupes/amas de galaxies dans le champs COSMOS, ainsi que des galaxies d’avant et d’arrière plan. MAGIC est idéal pour sonder l’impact de l’environnement à 0.2 ≲ z ≲ 1.5 pour un grand échantillon de galaxies avec une haute complétude et jusqu’à de faibles masses stellaires (M⋆ ≈ 10^9 M⊙ ). Parmi ces données, j’ai modélisé la morphologie d’environ 900 galaxies en réalisant une décomposition bulbe-disque afin d’extraire les paramètres principaux (ratio de flux bulbe-disque, inclinaison du disque, etc.) et la cinématique du gaz ionisé via les cubes MUSE en utilisant le doublet [Oii] comme traceur cinématique et en prenant en compte l’effet du “beam smearing” pour 600 galaxies. J’ai aussi implémenté une modélisation de masse où j’ai contraint la cinématique en utilisant les informations issues de la décomposition bulbe-disque afin d’obtenir des fractions de matière noire plus précises.Cela m’a permis de contribuer à une première analyse de la relation de Tully-Fisher à z ∼ 0.7, suivie de mon premier papier sur l’analyse de plusieurs relations d’échelles majeures en fonction de l’environnement. A partir de ces travaux, j’ai montré que les galaxies sont affectées par leur structure à z ∼ 0.7 au travers de leur morphologie et de leur formation stellaire mais pas de leur dynamique. J’ai poursuivi avec une autre analyse de l’impact de l’environnement sur le moment angulaire stellaire des galaxies. Les premiers résultats suggèrent qu’il y a un impact visible de l’environnement sur le moment angulaire, associé principalement aux galaxies massives localisées dans les zones les plus denses des structures. Étant donné que ces galaxies possèdent des bulbes massifs, l’interprétation actuelle est qu’elles ont probablement souffert d’une déplétion de leur moment angulaire (∼ 20%) durant le processus de formation du bulbe alors qu’elles atteignaient les parties centrales des structures. Qui plus est, j’ai aussi travaillé au développement d’une nouvelle méthode pour produire des cartes de masse résolues via une technique de “SED fitting” pixel par pixel et via une application de “machine learning” que j’affine actuellement. Ma thèse a montré les capacités de MAGIC pour sonder l’effet de l’environnement sur l’évolution des galaxies. Cet effort se poursuivra dans le future proche grâce à d’autre relevés MUSE existants et à venir comme le HUDF, MUSE-Wide, MXDF et MUSCATEL. Pour ce dernier, j’aurai la possibilité de produire des cartes de masse résolues et de les utiliser pour mieux contraindre la cinématique du gaz ionisé et la fraction de matière noire dans les galaxies. Ces nouveaux développements combinés avec mon expertise dans les analyses morpho-cinématiques seront aussi utiles pour de futures données issues d’instruments de prochaine génération avec le JWST ou ERIS-VLT et sur le plus long terme avec HARMONI et MOSAIC sur l’ELT.

We here-in demonstrate that the proposed hitherto unknown gravitomagnetic dark-force that hypothetically explains the Flat Rotation Curves of Spiral Galaxies — this same force, explains very well, the logarithmic and as-well, the barred spiral shapes of spiral galaxies. That is, much in line with Edward Arthur Milne (1896-1950)’s 1946 ideas — albeit, on a radically and asymptotically different philosophical train of thought, the galactic disk is here assumed to be in a state of free-fall around the central bulge with the hypothetical gravitomagnetic dark-force being the dominant force determining all gravity-related dynamics of the disk, thus leading to logarithmic and barred spiral orbits, hence the shape of spiral galaxies.

The baryonic Tully-Fisher relation (BTFR) is an important tool for constraining galaxy evolution models. As 21-cm HI emission studies have been largely restricted to low redshifts, the redshift evolution of the BTFR is less studied. The upcoming LADUMA survey (Looking At the Distant Universe with the MeerKAT Array) will address this. As preparation for LADUMA, we use the Simba hydrodynamical galaxy formation simulation from the Simba-hires (25 h$^{-1}$ Mpc)$^{3}$ run to generate rotational velocity measures from galaxy rotation curves ($V_{\rm flat}$) and HI spectral line profile widths ($W_{\rm 50}$ and $W_{\rm 20}$) at three different redshifts ($z$ = 0, 0.5, and 1). Using these measures, together with the dark matter velocity dispersion and halo mass, we consider the redshift evolution of the BTFR of Simba galaxies. We find that LADUMA will be successful in detecting weak redshift evolution of the BTFR, provided that auxiliary data is used to distinguish galaxies with disky morphologies. $W_{\rm 20}$ spectral line widths give lower scatter and more pronounced redshift evolution compared to $W_{\rm 50}$. We also compare these rotational velocity measures to the dark matter velocity dispersion across redshift and galaxy morphology. We find weak redshift evolution between rotational velocity and the dark matter halo mass, and provide fits for estimating a galaxy's dark matter halo mass from HI spectral line widths. This study with Simba showcases the importance of upcoming, deep SKA pathfinder surveys such as LADUMA, and provides predictions to compare with redshift evolution of the BTFR and galaxy dark matter content from HI rotational velocity measures., 19 pages, 10 figures, 4 tables. Accepted for publication to MNRAS

We use an up-to-date compilation of Tully–Fisher data to search for transitions in the evolution of the Tully–Fisher relation. Using an up-to-date data compilation, we find hints at ≈3σ level for a transition at critical distances Dc≃9 Mpc and Dc≃17 Mpc. We split the full sample in two subsamples, according to the measured galaxy distance with respect to splitting distance Dc, and identify the likelihood of the best-fit slope and intercept of one sample with respect to the best-fit corresponding values of the other sample. For Dc≃9 Mpc and Dc≃17 Mpc, we find a tension between the two subsamples at a level of Δχ2&gt, 17(3.5σ). Using Monte Carlo simulations, we demonstrate that this result is robust with respect to random statistical and systematic variations of the galactic distances and is unlikely in the context of a homogeneous dataset constructed using the Tully–Fisher relation. If the tension is interpreted as being due to a gravitational strength transition, it would imply a shift in the effective gravitational constant to lower values for distances larger than Dc by ΔGG≃−0.1. Such a shift is of the anticipated sign and magnitude but at a somewhat lower distance (redshift) than the gravitational transition recently proposed to address the Hubble and growth tensions (ΔGG≃−0.1 at the transition redshift of zt≲0.01 (Dc≲40 Mpc)).

Using a sample of 67 galaxies from the MIGHTEE Survey Early Science data we study the HI-based baryonic Tully-Fisher relation (bTFr), covering a period of $\sim$one billion years ($0 \leq z \leq 0.081 $). We consider the bTFr based on two different rotational velocity measures: the width of the global HI profile and $\rm V_{out}$, measured as the outermost rotational velocity from the resolved HI rotation curves. Both relations exhibit very low intrinsic scatter orthogonal to the best-fit relation ($\sigma_{\perp}=0.07\pm0.01$), comparable to the SPARC sample at $z \simeq 0$. The slopes of the relations are similar and consistent with the $ z \simeq 0$ studies ($3.66^{+0.35}_{-0.29}$ for $\rm W_{50}$ and $3.47^{+0.37}_{-0.30}$ for $\rm V_{out}$). We find no evidence that the bTFr has evolved over the last billion years, and all galaxies in our sample are consistent with the same relation independent of redshift and the rotational velocity measure. Our results set up a reference for all future studies of the HI-based bTFr as a function of redshift that will be conducted with the ongoing deep SKA pathfinders surveys., Comment: 11 pages, 6 figures, accepted for publication in MNRAS

We explore the Baryonic Tully-Fisher Relation in the Local Group. Rotationally supported Local Group galaxies adhere precisely to the relation defined by more distant galaxies. For pressure supported dwarf galaxies, we determine the scaling factor $\beta_c$ that relates their observed velocity dispersion to the equivalent circular velocity of rotationally supported galaxies of the same mass such that $V_o = \beta_c \sigma_*$. For a typical mass-to-light ratio $\Upsilon_* = 2\;\mathrm{M}_{\odot}/\mathrm{L}_{\odot}$ in the $V$-band, we find that $\beta_c = 2$. More generally, $\log \beta_c = 0.25 \log \Upsilon_* +0.226$. This provides a common kinematic scale relating pressure and rotationally supported dwarf galaxies., Comment: 14 pages, 4 figures. Accepted for publication in the Astronomical Journal

We demonstrate that in-principle, one of the five solutions presented in the reading Nyambuya (2015b), i.e., a solution of the Four Poisson-Laplace equation of gravitation [or Nordstrom (1912) equation of gravitation] can be used to explain the anomalous flat rotation curves of spiral galaxies. The proposed solution does not invoke the exotic hypothesis of darkmatter but makes the assumption that our existing Laws of Gravitation need to be amended. Our proposed amendment falls well within the accepted domain of legitimate gravitational field equations.

We present a multiwavelength study of the AGN-host starburst galaxy PKS 0529-549 at z similar or equal to 2.6. We use (1) new ALMA observations of the dust continuum and of the [CI] 370 mu m line, tracing molecular gas, (2) SINFONI spectroscopy of the [OIII] 5007 angstrom line, tracing ionized gas, and (3) ATCA radio continuum images, tracing synchrotron emission. Both [CI] and [O III] show regular velocity gradients, but their systemic velocities and position angles differ by similar to 300 km s(-1) and similar to 30 degrees, respectively. The [CI] is consistent with a rotating disc, aligned with the dust and stellar continuum, while the [OIII] likely traces an outflow, aligned with two AGN-driven radio lobes. We model the [CI] cube using 3D disc models, which give best-fitting rotation velocities V-rot similar or equal to 310 km s(-1) and velocity dispersions sigma(V) less than or similar to 30 km s(-1). Hence, the [CI] disc has V-rot/sigma(V) greater than or similar to 10 and is not particularly turbulent, similar to local galaxy discs. The dynamical mass (similar to 10(11) M-circle dot) is comparable to the baryonic mass within the errors. This suggests that baryons dominate the inner galaxy dynamics, similar to massive galaxies at z similar or equal to 0. Remarkably, PKS 0529-549 lies on the local baryonic Tully-Fisher relation, indicating that at least some massive galaxies are already in place and kinematically relaxed at z similar or equal to 2.6. This work highlights the potential of the [CI] line to trace galaxy dynamics at high z, as well as the importance of multiwavelength data to interpret gas kinematics.

Aims. We present new gas kinematic observations with the OSIRIS instrument at the GTC for galaxies in the Cl1604 cluster system at z ∼ 0.9. These observations together with a collection of other cluster samples at different epochs analyzed by our group are used to study the evolution of the Tully-Fisher, velocity-size, and specific angular momentum-stellar mass relations in dense environments over cosmic time. Methods. We used 2D and 3D spectroscopy to analyze the kinematics of our cluster galaxies and extract their maximum rotation velocities (Vmax), which were used as the common parameter in all scaling relations under scrutiny. We determined the structural parameters of our objects by fitting surface brightness profiles to the images of our objects, while stellar-mass values were computed by fitting the spectral energy distribution by making use of extensive archival optical to near-IR photometry. Our methods were consistently applied to all our cluster samples. This makes them ideal for an evolutionary comparison. Results. Up to redshift one, our cluster samples show evolutionary trends compatible with previous observational results in the field and in accordance with semianalytical models and hydrodynamical simulations concerning the Tully-Fisher and velocity-size relations. However, we find a drop of a factor ∼3 in disk sizes and an average B-band luminosity enhancement ⟨ΔMB⟩∼2 mag by z ∼ 1.5. We discuss the role that different cluster-specific interactions may play in producing this observational result. In addition, we find that our intermediate-to-high redshift cluster galaxies follow parallel sequences with respect to the local specific angular momentum to stellar mass relation, although they display lower specific angular momentum values than field samples at similar redshifts. This may be explained by the stronger interacting nature of dense environments in comparison with the field.

We present a novel 2D flux density model for observed HI emission lines combined with a Bayesian stacking technique to measure the baryonic Tully-Fisher relation below the nominal detection threshold. We simulate a galaxy catalogue, which includes HI lines described either with Gaussian or busy function profiles, and HI data cubes with a range of noise and survey areas similar to the MeerKAT International Giga-Hertz Tiered Extragalactic Exploration (MIGHTEE) survey. With prior knowledge of redshifts, stellar masses and inclinations of spiral galaxies, we find that our model can reconstruct the input baryonic Tully-Fisher parameters (slope and zero point) most accurately in a relatively broad redshift range from the local Universe to $z = 0.3$ for all the considered levels of noise and survey areas, and up to $z = 0.55$ for a nominal noise of $90\,\mu$Jy/channel over 5 deg$^{2}$. Our model can also determine the $M_{\rm HI} - M_{\star}$ relation for spiral galaxies beyond the local Universe, and account for the detailed shape of the HI emission line, which is crucial for understanding the dynamics of spiral galaxies. Thus, we have developed a Bayesian stacking technique for measuring the baryonic Tully-Fisher relation for galaxies at low stellar and/or HI masses and/or those at high redshift, where the direct detection of HI requires prohibitive exposure times., Comment: 13 pages, 9 figures. Accepted for publication in MNRAS

Quantum gravity is the solution ascribed to rendering the geometric description of classical gravity, in any dimensions, completely consistent with principles of quantum theory. The serendipitous theoretical discovery that black holes are thermodynamical objects that must participate in the second law has led to these purely gravitational objects to be dubbed, `the hydrogen atom for quantum gravity', analogous to the atomic spectrum of hydrogen, effectively used by Neils Bohr and his contemporaries to successfully formulate quantum mechanics in the early 20th century. Here, we employ the temperature and entropy formulae describing Schwarzschild black holes to consider the emergence of Einstein Field Equations from a complex-Hermitian structure, [Ricci tensor $\pm \sqrt{-1}$ Yang-Mills field strength], where the gravitational degrees of freedom are the SU($N$) colors with $N \in \mathbb{Z} \geq 0$ and a condensate comprising color pairs, $k = N/2$, appropriately coupled to the Yang-Mills gauge field. The foundations of our approach reveal the complex-Hermitian structure is analogous to Cayley-Dickson algebras, which aids in formulating the appropriate action principle for our formalism. The SU($N$) gauge group is broken into an effective SU($4$) $\rightarrow$ SO($4$) $\leftrightarrow$ SO($1,3$) field theory on the tangent space with two terms: the Einstein-Hilbert action and a Gauss-Bonnet topological term. Moreover, since topologically classifying all $n = 4$ (dimensional) Riemannian manifolds is not a clear-cut endeavor, we only consider the Euclidean path integral as the sum over manifolds with distinct topologies, $h \in \mathbb{Z} \geq 0$ homeomorphic to connected sums of an arbitrary number of $n = 4$-spheres and $h$ number of $n = 4$-tori. Consequently, the partition function adopts a reminiscent form of the sum of the vacuum Feynman diagrams for a large $\mathcal{N} = \exp(\beta M/2)$ theory, provided $\mathcal{S} = \beta M/2 = \pi N$ is the Schwarzschild black hole entropy, $\beta = 8\pi GM$ is the inverse temperature, $G$ is gravitational constant, $M$ is the black hole mass and horizon area, $\mathcal{A} = 2G\beta M = 4\pi GN$ is pixelated in units of $4\pi G$. This leads us to conclude that the partition function for quantum gravity is equivalent to the vacuum Feynman diagrams of a yet unidentified large $\mathcal{N}$ theory in $n = 4$ dimensions. Our approach also sheds new light on the asymptotic behavior of dark matter-dominated galaxy rotation curves (the empirical baryonic Tully-Fisher relation) and emergent gravity in condensed matter systems with defects such as layered materials with cationic vacancies as topological defects.

Galaxies in dense environments are subject to interactions and mechanisms which directly affect their evolution by lowering their gas fractions and reducing their star-forming capacity earlier than their isolated counterparts. The aim of our project is to get new insights about the role of environment on the stellar and baryonic content of galaxies using a kinematic approach, through the study of the Tully-Fisher relation (TFR). We study a sample of galaxies in 8 groups spanning a redshift range of $0.5, Comment: Accepted for publication in Astronomy & Astrophysics

Square–torsion gravity is applied to the long standing dark matter problem. In this context the theory reduces to General Relativity complemented by a dark stress–energy tensor due to the torsion of spacetime and is studied under the simplifying assumption of spherical symmetry. The dark stress–energy tensor satisfies an anisotropic structure equation. In vacuum this is equivalent to a wave equation with sources. A natural class of exact solutions is found which explicitly perturbs any seed spacetime metric by a conformal factor. This leads to the concept of dark coating. Static solutions are then used to construct structures that model dark matter halos surrounding baryonic bodies. In the Newtonian régime the baryonic mass $$m_b$$ m b and the flat rotation curve velocity $$v_f$$ v f are related by the baryonic Tully–Fisher relation$$m_b\propto v_f^4$$ m b ∝ v f 4 , a hitherto purely empirical result. The example of a dark halo on the Schwarzschild geometry is made as a toy model for a galaxy. Qualitative an quantitative features of galactic rotation curves are recovered. In this setting, a boundary of staticity is found, called torsion sphere, placed between the photon sphere and the event horizon. The phenomenon of dark radiation is briefly exposed.

We explore the use of the baryonic Tully-Fisher relation (bTFR) as a new distance indicator. Advances in near-IR imaging and stellar population models, plus precise rotation curves, have reduced the scatter in the bTFR such that distance is the dominant source of uncertainty. Using 50 galaxies with accurate distances from Cepheids or tip magnitude of the red giant branch, we calibrate the bTFR on a scale independent of $H_o$. We then apply this calibrated bTFR to 95 independent galaxies from the SPARC sample, using CosmicFlows-3 velocities, to deduce the local value of $H_o$. We find $H_o$ = 75.1 +/- 2.3 (stat) +/- 1.5 (sys) km s$^{-1}$ Mpc$^{-1}$., 21 pages, 3 figures, accepted by AJ

The relation between early type galaxy size, surface brightness and velocity dispersion, "the fundamental plane", has long been understood as resulting from equilibrium in their largely pressure supported stellar dynamics. The dissipation and feedback involved in reaching such an equilibrium through merger formation of these galaxies over cosmic time can be responsible for the orientation of the plane. We see a correlation between surface brightness enhancement and youth in the 6dF Galaxy Survey. Correlations of this `tilt' with stellar mass, age, concentration, shape and metallicity now point the direction for further work on the resolved kinematics and structure of these nearby galaxies and on their initial mass function and dark matter component. On the face of it, the Tully Fisher relation is a simpler one dimensional scaling relation. However, as late type galaxies have bulges as well as disks, and, as the surface density of disks is only standard for the more massive galaxies, additional parameters are involved., For publication in Frontiers in Astronomy and Space Sciences

We investigate the Baryonic Tully-Fisher Relation (BTFR) in the $(100\,h^{-1}{\rm Mpc})^3$ Simba hydrodynamical galaxy formation simulation together with a higher-resolution $(25\,h^{-1}{\rm Mpc})^3$ Simba run, for over $10,000$ disk-dominated, HI-rich galaxies. We generate simulated galaxy rotation curves from the mass distribution, which we show yields similar results to using the gas rotational velocities. From this we measure the galaxy rotation velocity $V_{\rm circ}$ using four metrics: $V_{\rm max}, V_{\rm flat}, V_{2R_e},$ and $V_{\rm polyex}$. We compare the predicted BTFR to the SPARC observational sample and find broad agreement. In detail, however, Simba is biased towards higher $V_{\rm circ}$ by up to 0.1 dex. We find evidence for the flattening of the BTFR in $V_{\rm circ}>300$ km s$^{-1}$ galaxies, in agreement with recent observational findings. Simba's rotation curves are more peaked for lower mass galaxies, in contrast with observations, suggesting overly bulge-dominated dwarf galaxies in our sample. We investigate for residuals around the BTFR versus HI mass, stellar mass, gas fraction, and specific star formation rate, which provide testable predictions for upcoming BTFR surveys. Simba's BTFR shows sub-optimal resolution convergence, with the higher-resolution run lowering $V$ in better agreement with data., 18 pages, 11 figures. Accepted for publication in MNRAS

In a recent paper McGaugh, Lelli, and Schombert showed that in an empirical plot of the observed centripetal accelerations in spiral galaxies against those predicted by the Newtonian gravity of the luminous matter in those galaxies the data points occupied a remarkably narrow band. While one could summarize the mean properties of the band by drawing a single mean curve through it, by fitting the band with the illustrative conformal gravity theory with fits that fill out the width of the band we show here that the width of the band is just as physically significant. We show that at very low luminous Newtonian accelerations the plot can become independent of the luminous Newtonian contribution altogether, but still be non-trivial due to the contribution of matter outside of the galaxies (viz. the rest of the visible universe). We present a new empirical plot of the difference between the observed centripetal accelerations and the luminous Newtonian expectations as a function of distance from the centers of galaxies, and show that at distances greater than 10 kpc the plot also occupies a remarkably narrow band, one even close to constant. Using the conformal gravity theory we provide a first principles derivation of the empirical Tully-Fisher relation., Comment: 6 pages, 15 figures. The paper is a comment on S. S. McGaugh, F. Lelli, and J. M. Schombert, Phys. Rev. Lett. 117, 201101 (2016). Updated to include a first principles derivation of the Tully-Fisher relation using the conformal gravity theory. Submitted to Physics Letters B

In this paper we investigate the statistical properties of the Tully-Fisher relation for a sample of 32 galaxies with measured distances from the Cepheid period-luminosity relation and/or TRGB stars. We take advantage of panchromatic photometry in 12 bands (from FUV to 4.5 $\mu$m) and of spatially resolved HI kinematics. We use these data together with three kinematic measures ($W^{i}_{50}$, $V_{max}$ and $V_{flat}$) extracted from the global HI profiles or HI rotation curves, so as to construct 36 correlations allowing us to select the one with the least scatter. We introduce a tightness parameter $\sigma_{\perp}$ of the TFr, in order to obtain a slope-independent measure of the goodness of fit. We find that the tightest correlation occurs when we select the 3.6 $\mu$m photometric band together with the $V_{flat}$ parameter extracted from the HI rotation curve., Comment: 16 pages, 16 figures, accepted for publication in MNRAS, minor changes due to proof corrections

The dearth of dwarf galaxies in the local universe is hard to reconcile with the large number of low mass haloes expected within the concordance $\Lambda$CDM paradigm. In this paper we perform a systematic evaluation of the uncertainties affecting the measurement of DM halo abundance using galaxy kinematics. Using a large sample of dwarf galaxies with spatially resolved kinematic data we derive a correction to obtain the observed abundance of galaxies as a function of their halo maximum circular velocity from the line-of-sight velocity function in the Local Volume. This estimate provides a direct means of comparing the predictions of theoretical models and simulations (including nonstandard cosmologies and novel galaxy formation physics) to the observational constraints. The new "galactic $V_{max}$" function is steeper than the line-of-sight velocity function but still shallower than the theoretical CDM expectation, showing that some unaccounted physical process is necessary to reduce the abundance of galaxies and/or drastically modify their density profiles compared to CDM haloes. Using this new galactic $V_{max}$ function, we investigate the viability of baryonic solutions such as feedback-powered outflows and photoevaporation of gas from an ionising radiation background. At the 3-$\sigma$ confidence level neither energetic feedback nor photoevaporation are effective enough to reconcile the disagreement. In the case of maximum baryonic effects, the theoretical estimate still deviates significantly from the observations for $V_{max} < 60$ km/s. CDM predicts at least 1.8 times more galaxies with $V_{max} = 50$ km/s and 2.5 times more than observed at $30$ km/s. Recent hydrodynamic simulations seem to resolve the discrepancy but disagree with the properties of observed galaxies with resolved kinematics. (abridged), Comment: 17 pages, 22 figures; major revisions include clarification of the method, expanded comparison with simulations with a new figure, analysis of uncertainties in model as well as pressure support corrections, and a new table with nomenclature

We use a sample of 83 high-resolution cosmological zoom-in simulations and a semi-analytic model (SAM) to study the stochasticity of galaxy formation in haloes ranging from dwarf to Milky Way masses. Our simulated galaxies reproduce the observed inefficiency of galaxy formation as expressed through the stellar, gas and baryonic Tully-Fisher relations. For HI velocities in the range (70 less than or similar to V less than or similar to 220 km s(-1)), the scatter is just 0.08 to 0.14 dex, consistent with the observed intrinsic scatter at these scales. At low velocities (20 less than or similar to V less than or similar to 70 km s(-1)), the simulated scatter is 0.2-0.25 dex, which could be tested with future observations. The scatter in the stellar mass versus dark halo velocity relation is constant for 30 less than or similar to V less than or similar to 180 km s(-1), and smaller (similar or equal to 0.17 dex) when using the maximum circular velocity of the dark-matter-only simulation, V-max(DMO), compared to the virial velocity (V-200 or V-200(DMO)). The scatter in stellar mass is correlated with halo concentration, and is minimized when using a circular velocity at a fixed fraction of the virial radius similar or equal to 0.4R(200) or with V-alpha = V-200(DMO)(V-max(DMO) / V-200(DMO))(alpha) with alpha similar or equal to 0.7, consistent with constraints from halo clustering. Using the SAM we show the correlation between halo formation time and concentration is essential in order to reproduce this result. This uniformity in galaxy formation efficiency we see in our hydrodynamical simulations and an SAM proves the simplicity and self-regulating nature of galaxy formation in a Lambda cold dark matter (Lambda CDM) universe.

We use the 2MFGC catalogue for investigation of large-scale flows on the basis of the Tully-Fisher relation (TFR). The catalogue contains 18020 galaxies selected from the extended sources of the infrared sky survey 2MASS XSC. The majority of galaxies in the catalogue are spiral galaxies of late morphological types whose discs are visible almost from the edge. For more than a decade of the catalogue usage, the number of galaxies in HyperLEDA database with the measured radial velocities and rotational velocities (that are necessary to construct the TFR) has been increased by about 17%. In this paper, an updated working sample of 2MFGC galaxies is presented and earlier results are revised taking into account new data. We have confined ourselves to comparison of only the "old" and "new" parameters of the dipole component of the velocity field. The dipole bulk motion of galaxies of this sample with respect to cosmic microwave radiation is characterised by a velocity of V=264±36 km/s in the direction l=308°±8°, b=-16°±6°.

The Baryonic Tully-Fisher relation was extended to clusters hypothesizing that a0, the characteristic acceleration of the Modified Newtonian Dynamics (MOND), depends on the mass of the system. Circular speeds were calculated for systems with mass up to 1021 M☉. The relativistic impact on super massive systems was considered using the extended Newtonian theory for gravitational bound systems. The impact was an increase of the circular velocity for systems with mass beyond ~1019 M☉.

We present ALFALFA HI observations of a well studied region of the Leo Cloud, which includes the NGC 3227 group and the NGC 3190 group. We detect optically dark HI tails and plumes with extents potentially exceeding 600 kpc, well beyond the field of view of previous observations. These HI features contain approximately 40% of the total HI mass in the NGC~3227 group and 10% in the NGC~3190 group. We also present WSRT maps which show the complex morphology of the extended emission in the NGC~3227 group. We comment on previously proposed models of the interactions in these groups and the implications for the scale of group processing through interactions. Motivated by the extent of the HI plumes, we place the HI observations in the context of the larger loose group, demonstrating the need for future sensitive, wide field HI surveys to understand the role of group processing in galaxy evolution., 17 pages, 9 figures, accepted for publication in MNRAS

In $\Lambda$CDM cosmology, to first order, galaxies form out of the cooling of baryons within the virial radius of their dark matter halo. The fractions of mass and angular momentum retained in the baryonic and stellar components of disc galaxies put strong constraints on our understanding of galaxy formation. In this work, we derive the fraction of angular momentum retained in the stellar component of spirals, $f_j$, the global star formation efficiency $f_M$, and the ratio of the asymptotic circular velocity ($V_{\rm flat}$) to the virial velocity $f_V$, and their scatter, by fitting simultaneously the observed stellar mass-velocity (Tully-Fisher), size-mass, and mass-angular momentum (Fall) relations. We compare the goodness of fit of three models: (i) where the logarithm of $f_j$, $f_M$, and $f_V$ vary linearly with the logarithm of the observable $V_{\rm flat}$; (ii) where these values vary as a double power law; and (iii) where these values also vary as a double power law but with a prior imposed on $f_M$ such that it follows the expectations from widely used abundance matching models. We conclude that the scatter in these fractions is particularly small ($\sim 0.07$ dex) and that the linear model is by far statistically preferred to that with abundance matching priors. This indicates that the fundamental galaxy formation parameters are small-scatter single-slope monotonic functions of mass, instead of being complicated non-monotonic functions. This incidentally confirms that the most massive spiral galaxies should have turned nearly all the baryons associated with their haloes into stars. We call this the failed feedback problem., Comment: A&A in press (17 pages, 3 appendices)

As an alternative to dark matter models we use generalized Jordan-Brans-Dicke scalar-vector-tensor (JBD-SVT) gravity model to study the behavior of the rotational velocities of test particles moving around galaxies. To do so we consider an interaction potential $U(\phi,N_{\mu})$ between the Brans-Dicke scalar field $\phi$ and time like dynamical four-vector field $N_\mu$ which plays as four velocity of a preferred reference frame. We show that at in weak field limits metric solution of the galaxy under consideration reaches to a modified Schwarzschild-de Sitter space in which mass of the vector field plays as an effective cosmological constant. In fact the present work proposes modification on the formulation of Newton's gravitational acceleration. This is used to explain circular velocity of galaxies without postulating dark matter. We also check our theoretical results with empirical baryonic Tully Fisher relation which states a linear relations between the rotational speed of galaxies and their mass. Mathematical calculation predict a good correspondence between our theoretical results and experimental observations for a set of 12 spiral galaxies., Comment: 28 pages, 2 figure and 1 table

Observations of evolution in the dust-to-metal ratio allow us to constrain the dominant dust processing mechanisms. In this work, we present a study of the dust-to-metal and dust-to-gas ratios in a sub-sample of ~500 DustPedia galaxies. Using literature and MUSE emission line fluxes, we derived gas-phase metallicities (oxygen abundances) for over 10000 individual regions and determine characteristic metallicities for each galaxy. We study how the relative dust, gas, and metal contents of galaxies evolve by using metallicity and gas fraction as proxies for evolutionary state. The global oxygen abundance and nitrogen-to-oxygen ratio are found to increase monotonically as galaxies evolve. Additionally, unevolved galaxies (gas fraction > 60%, metallicity 12 + log(O/H) < 8.2) have dust-to-metal ratios that are about a factor of 2.1 lower (a factor of six lower for galaxies with gas fraction > 80%) than the typical dust-to-metal ratio (Md/MZ ~ 0.214) for more evolved sources. However, for high gas fractions, the scatter is larger due to larger observational uncertainties as well as a potential dependence of the dust grain growth timescale and supernova dust yield on local conditions and star formation histories. We find chemical evolution models with a strong contribution from dust grain growth describe these observations reasonably well. The dust-to-metal ratio is also found to be lower for low stellar masses and high specific star formation rates (with the exception of some sources undergoing a starburst). Finally, the metallicity gradient correlates weakly with the HI-to-stellar mass ratio, the effective radius and the dust-to-stellar mass ratio, but not with stellar mass., 24 pages, 15 figures, published in A&A, bibref: 2019A&A...623A...5D, This Version 2 has increased accuracy in Table B1 in appendix B