Baryonic distributions in the dark matter halo of NGC 5005

Abstract

We present results from multiwavelength observations of the galaxy NGC 5005. We use new neutral hydrogen (H I) observations from the Very Large Array to examine the neutral gas morphology and kinematics. We find an HI disc with a well-behaved flat rotation curve in the radial range 20-140 arcsec. Ionized gas observations from the SparsePak integral field unit on the WIYN 3.5 m telescope provide kinematics for the central 70 arcsec. We use both the SparsePak and HI velocity fields to derive a rotation curve for NGC 5005. Deep 3.6 μm observations from the Spitzer Space Telescope probe the faint extended stellar population of NGC 5005. The images reveal a large stellar disc with a high surface brightness component that transitions to a low surface brightness component at a radius nearly 1.6 times farther than the extent of the gas disc detected in HI. The 3.6 μm image is also decomposed into bulge and disc components to account for the stellar light distribution. Optical broad-band B and R and narrowband Hα from the WIYN 0.9 m telescope complement the 3.6 μm data by providing information about the dominant stellar population and current star formation activity. The neutral and ionized gas rotation curve is used along with the stellar bulge and disc light profiles to decompose the mass distributions in NGC 5005 and determine a dark matter halo model. The maximum stellar disc contribution to the total rotation curve is only about 70 per cent, suggesting that dark matter makes a significant contribution to the dynamics at all radii.