SPARC data for the spiral galaxy NGC 5055. The top panel shows the Spitzer [3.6 micron] luminosity profile. The bottom panel shows the rotation curve (black points) and the gravitational contributions due to stars (dashed line), gas (dotted line), and total baryons (solid line). The discrepancy beyond 10 kpc is typically attributed to dark matter.

The new Spitzer Photometry and Accurate Rotation Curves (SPARC) database is publicly available online. Created by team leaders Federico Lelli and Stacy McGaugh (CWRU Astronomy) and Jim Schombert (UOregon Physics), SPARC is a sample of 175 disk galaxies covering a broad range of morphologies (S0 to Irr), luminosities (10⁷ to 10¹² Lsun), and sizes (0.3 to 15 kpc). For each galaxy, the team collected both HI data and Spitzer images at 3.6 um. The HI data provide the gas distribution and the galaxy rotation curve, tracing the total gravitational potential: these data are the fruits of 30 years of observations from an entire community of radio astronomers. The Spitzer images probe the stellar mass distribution: these data were homogeneously analysed by our group and used to calculate the gravitational contribution of stars. The SPARC dataset is used to study the interplay between visible and dark matter in galaxies, test the LCDM cosmological model, and investigate possible alternatives.

The SPARC database can be accessed at http://astroweb.cwru.edu/SPARC/.