GHASP: an Hα kinematic survey of spiral and irregular galaxies - V. Dark matter distribution in 36 nearby spiral galaxies

Abstract

The results obtained from a study of the mass distribution of 36 spiral galaxies are presented. The galaxies were observed using Fabry–Perot interferometry as part of the GHASP survey. The main aim of obtaining high‐resolution Hα 2D velocity fields is to define more accurately the rising part of the rotation curves which should allow to better constrain the parameters of the mass distribution. The Hα velocities were combined with low resolution H i data from the literature, when available. Combining the kinematical data with photometric data, mass models were derived from these rotation curves using two different functional forms for the halo: an isothermal sphere (ISO) and a Navarro–Frenk–White (NFW) profile. For the galaxies already modelled by other authors, the results tend to agree. Our results point at the existence of a constant density core in the centre of the dark matter haloes rather than a cuspy core, whatever the type of the galaxy from Sab to Im. This extends to all types the result already obtained by other authors studying dwarf and low surface brightness galaxies but would necessitate a larger sample of galaxies to conclude more strongly. Whatever model is used (ISO or NFW), small core radius haloes have higher central densities, again for all morphological types. We confirm different halo scaling laws, such as the correlations between the core radius and the central density of the halo with the absolute magnitude of a galaxy: low‐luminosity galaxies have small core radius and high central density. We find that the product of the central density with the core radius of the dark matter halo is nearly constant, whatever the model and whatever the absolute magnitude of the galaxy. This suggests that the halo surface density is independent from the galaxy type.

Scaling Laws for Dark Matter Halos in Late-Type and Dwarf Spheroidal Galaxies

“…These correlations were first found by Athanassoula et al (1987, hereafter ABP), by Kormendy (1988Kormendy ( , 1990, and by Kormendy & Freeman (1996). Some of the correlations have been confirmed at least qualitatively by, e. g., Burkert (1995); Persic et al (1996Persic et al ( , 1997; Verheijen (1997); Salucci & Burkert (2000); Borriello & Salucci (2001); Begum & Chengalur (2004); Graham et al (2006); Spano et al (2008); Kuzio de Naray et al (2008);de Blok et al (2008), and Plana et al (2010). The most thorough discussion to date is by Kormendy & Freeman (2004).…”

“…Some authors have tried to "save cusps" by emphasizing systematic uncertainties like beam-smearing in the H I rotation data and non-circular motions in the higher-resolution optical rotation data; these could create the appearance of a core. Over the past decade, rotation curve data and mass modeling have improved, and cores in the DM halos of dwarf and low-surface-brightness galaxies are consistently favored (e. g., Marchesini et al 2002;de Blok & Bosma 2002;de Blok et al 2008;Weldrake et al 2003;Gentile et al 2004Gentile et al , 2009Spano et al 2008;Oh et al 2008Oh et al , 2011aDonato et al 2009;Plana et al 2010, Chen & McGaugh 2010). de Blok (2010 concludes that almost all dwarf disk galaxies that have been studied have cored halos.…”

Analytical properties of Einasto dark matter haloes

“…The surface mass density has an importance in theoretical predictions and observations. On the observational side, based mostly on the mass decomposition of rotation curves using cored haloes, various studies (Kormendy & Freeman 2004;Spano et al 2008;Donato et al 2009;Gentile et al 2009) have shown that the product of the central density ρ 0 and the core radius r 0 is consistent with a universal value, independent of galaxy mass. The product ρ 0 r 0 is directly proportional to the average surface density within r 0 , and to the gravitational acceleration of dark matter at r 0 .…”

GHASP: an Hα kinematic survey of spiral galaxies – X. Surface photometry, decompositions and the Tully–Fisher relation in theRcband

“…Spano et al 2008), but studies on the systematic errors and larger, homogeneous samples, are still needed to confirm these results. This series of papers on the GHASP survey has the goal of imposing tighter constraints on the study of dark matter distributions in spiral galaxies.…”

“…The GHASP sample consists of 203 spiral and irregular galaxies in the local universe for which high-resolution Hα maps have been observed with Fabry-Perot interferometry (Garrido et al 2002(Garrido et al , 2003Garrido, Marcelin, & Amram 2004;Garrido et al 2005;Spano et al 2008;Epinat et al 2010;Torres-Flores et al 2011). The GHASP sample was initially designed to be a subsample of the Westerbork survey (WHISP, van der Hulst, van Albada, & Sancisi 2001) with the goal of providing a local universe reference for kinematics and dynamics of disk-like galaxies.…”