Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

Feng, James Q.; Gallo, C. F.

doi:10.1088/1674-4527/11/12/005

Cited by 22 publications

(42 citation statements)

References 33 publications

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“…The rotational velocity v(r) with a maximum rotation velocity V max can have several functional forms: it can be an arctan velocity profile (e.g. Puech et al 2008), an inverted exponential (Feng & Gallo 2011), or a hyperbolic tanh profile (e.g. Andersen & Bershady 2013) :…”

Section: A Parametric Galaxy Model In Three Dimensionsmentioning

confidence: 99%

GalPaK^3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA

et al. 2015

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We present a method to constrain galaxy parameters directly from three-dimensional data cubes. The algorithm compares directly the data with a parametric model mapped in x, y, λ coordinates. It uses the spectral line-spread function (LSF) and the spatial point-spread function (PSF) to generate a 3-dimensional kernel whose characteristics are instrument specific or user generated. The algorithm returns the intrinsic modeled properties along with both an 'intrinsic' model data cube and the modeled galaxy convolved with the 3D-kernel. The algorithm uses a Markov Chain Monte Carlo (MCMC) approach with a nontraditional proposal distribution in order to efficiently probe the parameter space. We demonstrate the robustness of the algorithm using 1728 mock galaxies and galaxies generated from hydrodynamical simulations in various seeing conditions from 0. 6 to 1. 2. We find that the algorithm can recover the morphological parameters (inclination, position angle) to within 10% and the kinematic parameters (maximum rotation velocity) to within 20%, irrespectively of the PSF in seeing (up to 1. 2) provided that the maximum signal-to-noise ratio (SNR) is greater than ∼ 3 pixel −1 and that ratio of galaxy half-light radius to seeing radius is greater than about 1.5. One can use such an algorithm to constrain simultaneously the kinematics and morphological parameters of (nonmerging) galaxies observed in nonoptimal seeing conditions. The algorithm can also be used on adaptive-optics (AO) data or on high-quality, high-S/N data to look for nonaxisymmetric structures in the residuals.

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Section: A Parametric Galaxy Model In Three Dimensionsmentioning

confidence: 99%

GalPaK^3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA

et al. 2015

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“…It was proved long time ago (Kuzmin 1952(Kuzmin , 1955 that there is no evidence for the presence of large amounts dark matter in the disk of the Galaxy from observations in the solar neighborhood, and this is still confirmed today (Garbari et al 2012), but one might investigate whether amounts of dark matter in the outer disk are possible. From the theoretical point of view at least, it is a general solution A128, page 8 of 9 for the observed rotation curves : Feng & Gallo (2011) showed that some mass distributions of the disk alone might mimic the flat rotation curves of a galaxy (Mestel's disk), without dark matter halos, although these distributions are not realistic compared with the observed stellar distribution (exponential).…”

Section: Dynamical Consequencesmentioning

confidence: 99%

Milky Way rotation curve from proper motions of red clump giants

López-Corredoira

2014

A&A

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Aims. We derive the stellar rotation curve of the Galaxy in the range of Galactocentric radii of R = 4−16 kpc at different vertical heights from the Galactic plane of z between -2 and +2 kpc. With this we reach high Galactocentric distances in which the kinematics is poorly known due mainly to uncertainties in the distances to the sources. Methods. We used the PPMXL survey, which contains the USNO-B1 proper motions catalog cross-correlated with the astrometry and near-infrared photometry of the 2MASS Point Source Catalog. To improve the accuracy of the proper motions, we calculated the average proper motions of quasars to know their systematic shift from zero in this PPMXL survey, and we applied the corresponding correction to the proper motions of the whole survey, which reduces the systematic error. We selected from the color-magnitude diagram K vs. (J − K) the standard candles corresponding to red clump giants and used the information of their proper motions to build a map of the rotation speed of our Galaxy. Results. We obtain an almost flat rotation curve with a slight decrease for higher values of R or |z|. The most puzzling result is obtained for the farthest removed and most off-plane regions, that is, at R ≈ 16 kpc and |z| ≈ 2 kpc, where a significant deviation from a null average proper motion (∼4 mas/yr) in the Galactic longitude direction for the anticenter regions can be directly translated into a rotation speed much lower than at the solar Galactocentric radius. In particular, we obtain an average speed of 82 ± 5(stat.) ± 58(syst.) km s −1 (assuming a solar Galactocentric distance of 8 kpc, and a circular/azimuthal velocity of 250 km s −1 for the Sun and of 238 km s −1 for the Local Standard of Rest), where the high systematic error bar is due mainly to the highest possible contamination of non-red clump giants and the proper motion systematic uncertainty. Conclusions. A scenario with a rotation speed lower than 150 km s −1 in these farthest removed and most off-plane regions of our explored zone is intriguing, and invites one to reconsider different possibilities for the dark matter distribution. However, given the high systematic errors, we cannot conclude about this. Hence, more measurements of the proper motions at high R and |z| are necessary to validate the exotic scenario that would arise if this low speed were confirmed.

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“…where V (r) is measured in units of a characteristic rotational velocity V 0 . As shown in our previous publications (Gallo and Feng, 2009, Feng and Gallo, 2011, 2014, equating (3) and (4) with slight algebraic arrangements yields a force-balance equation,…”

Section: Mass In a Galaxymentioning

confidence: 88%

Deficient Reasoning for Dark Matter in Galaxies

Feng¹,

Gallo²

2015

Physics International

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In this universe, not all of the matter around us can be readily seen. The further an object is away from us and the less luminous it is, the less visible it becomes. Just by looking at an object is usually difficult, if not impossible, to tell the amount of mass it contains. But astronomers have been using the measured luminosity to estimate the luminous mass of stars, based on empirically established mass-to-light ratio which seems to be only applicable to a special class of stars-the main-sequence stars-with still considerable uncertainties. Another basic tool for astronomers to determine the mass of a system of stars or galaxies comes from the study of their motion, as Newton demonstrated with his law of gravitation, which yields the gravitational mass. Because the luminous mass can at best only represent a portion of the gravitational mass, finding the luminous mass to be different or less than the gravitational mass should not be surprising. Using such an apparent discrepancy as compelling evidence for the so-called dark matter, which has been believed to possess mysterious nonbaryonic properties having a dominant amount in galaxies and the universe, seems to be too far a stretch when seriously examining the facts and uncertainties in the measurement techniques. In our opinion, a galaxy with star type distribution varying from its center to edge may have a mass-to-light ratio varying accordingly. With the thin-disk model computations based on measured rotation curves, we found that most galaxies have a typical mass density profile that peaks at the galactic center and decreases rapidly within ∼ 5% of the cut-off radius, and then declines nearly exponentially toward the edge. The predicted mass density in the Galactic disk is reasonably within the reported range of that observed in interstellar medium. This leads us to believe that ordinary baryonic matter can be sufficient for supporting the observed galactic rotation curves; speculation of large amount of non-baryonic matter may be based on an ill-conceived discrepancy between gravitational mass and luminous mass which appears to be unjustified.

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Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

Cited by 22 publications

References 33 publications

GalPaK^3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA

GalPaK^3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA

Milky Way rotation curve from proper motions of red clump giants

Deficient Reasoning for Dark Matter in Galaxies

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Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

Cited by 22 publications

References 33 publications

GalPaK3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA

GalPaK3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA

Milky Way rotation curve from proper motions of red clump giants

Deficient Reasoning for Dark Matter in Galaxies

Contact Info

Product

Resources

About

GalPaK^3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA

GalPaK^3D: A BAYESIAN PARAMETRIC TOOL FOR EXTRACTING MORPHOKINEMATICS OF GALAXIES FROM 3D DATA