The DiskMass Survey VII. The distribution of luminous and dark matter in spiral galaxies

By T. Martinsson, Marc A. W. Verheijen, K. Westfall, M. Bershady, D. Andersen, R. Swaters. 2013

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We present dynamically-determined rotation-curve mass decompositions of 30 spiral galaxies, which were carried out to test the maximum-disk hypothesis and to quantify properties of their dark-matter halos. We used measured vertical velocity dispersions of the disk stars to calculate dynamical mass surface densities ({$Sigma$}$_{dyn}$). By subtracting our observed atomic and inferred molecular gas mass surface densities from {$Sigma$}$_{dyn}$, we derived the stellar mass surface densities ({$Sigma$}$_{∗}$), and thus have absolute measurements of all dominant baryonic components of the galaxies. Using K-band surface brightness profiles (I$_K$), we calculated the K-band mass-to-light ratio of the stellar disks ({Upsilon}$_{∗}$ = {$Sigma$}$_{∗}$/I$_K$) and adopted the radial mean (overline${$mls$}$) for each galaxy to extrapolate {$Sigma$}$_{∗}$ beyond the outermost kinematic measurement. The derived overline${$mls$}$ of individual galaxies are consistent with all galaxies in the sample having equal {Upsilon}$_{∗}$. We find a sample average and scatter of mlab overline${$mls$}$mrab = 0.31 {plusmn} 0.07. Rotation curves of the baryonic components were calculated from their deprojected mass surface densities. These were used with circular-speed measurements to derive the structural parameters of the dark-matter halos, modeled as either a pseudo-isothermal sphere (pISO) or a Navarro-Frenk-White (NFW) halo. In addition to our dynamically determined mass decompositions, we also performed alternative rotation-curve decompositions by adopting the traditional maximum-disk hypothesis. However, the galaxies in our sample are submaximal, such that at 2.2 disk scale lengths (h$_R$) the ratios between the baryonic and total rotation curves (F$_b$$^{2.2hR}$) are less than 0.75. We find this ratio to be nearly constant between 1-6h$_R$ within individual galaxies. We find a sample average and scatter of mlab F$_b$$^{2.2hR}$mrab = 0.57 {plusmn} 0.07, with trends of larger F$_b$$^{2.2hR}$ for more luminous and higher-surface-brightness galaxies. To enforce these being maximal, we need to scale {Upsilon}$_{∗}$ by a factor 3.6 on average. In general, the dark-matter rotation curves are marginally better fit by a pISO than by an NFW halo. For the nominal-{Upsilon}$_{∗}$ (submaximal) case, we find that the derived NFW-halo parameters have values consistent with {$Lambda$}CDM N-body simulations, suggesting that the baryonic matter in our sample of galaxies has only had a minor effect on the dark-matter distribution. In contrast, maximum-{Upsilon}$_{∗}$ decompositions yield halo-concentration parameters that are too low compared to the {$Lambda$}CDM simulations. Appendix is available in electronic form at http://www.aanda.org

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/5f6638518528639dc0eaa58d3758765a7b9469bc

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Citations in the corpus

COLOR–MASS-TO-LIGHT-RATIO RELATIONS FOR DISK GALAXIES (2014, background): “However, their normalization is different: Martinsson et al. (2013) find 〈ΥK∗ 〉 = 0.31±0.07.”
THE SMALL SCATTER OF THE BARYONIC TULLY–FISHER RELATION (2015, background): “A small scatter of ∼0.1 dex is consistently found using different approaches: stellar population synthesis models (McGaugh & Schombert 2014; Meidt et al. 2014), resolved stellar populations (Eskew et al. 2012), and the vertical velocity dispersion of galaxy discs (Martinsson et al. 2013).”
Constraining the Galaxy's dark halo with RAVE stars (2014, background): “For this value, we have FR,bary/FR,dm ∼ 0.85. galaxies (Bershady et al. 2011; Martinsson et al. 2013).”
One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (2016, background): “The DiskMass survey, however, reports smaller values of the Υ? in the K-band (Martinsson et al. 2013; Swaters et al. 2014), corresponding to ∼0.2 M /L at [3.6] (see Paper I).”
Cold dark matter haloes in the Planck era: evolution of structural parameters for Einasto and NFW profiles (2014, background): “The black pentagons show observational results for spiral galaxies at redshift z ≃ 0 from the DiskMass project (Bershady et al. 2010; Martinsson et al. 2013).”
SPARC: MASS MODELS FOR 175 DISK GALAXIES WITH SPITZER PHOTOMETRY AND ACCURATE ROTATION CURVES (2016, background): “= 0.2 M /L at [3.6] (∼0.26 M /L in the K-band) is comparable to the results of the DMS (Martinsson et al. 2013; Swaters et al. 2014).”