2006/09/01 by C. Quireza, Cintia Quireza, R. T. Rood +6 · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Electron #Electron temperature #Galactic Center #Line (geometry) #Milky Way #RADIUS #Stellar, planetary, and galactic studies #Temperature gradient #Velocity gradient #astro-ph
paper · pdf · doi:10.1086/508803
published as Astrophys.J.653:1226-1240,2006 · 43 pages, 9 figures (accepted for publication in the ApJ)
arxiv created 2006/09/01 · openalex publication_date 2006/12/13 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We derive the electron temperature gradient in the Galactic disk, using a sample of H ii regions that spans Galacto-centric distances of 0 Y17 kpc. The electron temperature was calculated using high-precision radio recombination line and continuum observations for more than 100 H ii regions. Nebular Galactocentric distances were calculated in a consistent manner, using the radial velocities measured by our radio recombination line survey. The large number of nebulae widely distributed over the Galactic disk, together with the uniformity of our data, provide a secure estimate of the present electron temperature gradient in the Milky Way. Because metals are the main coolants in the photo-ionized gas, the electron temperature along theGalactic disk should be directly related to the distribution of heavy ele-ments in theMilkyWay. Our best estimate of the electron temperature gradient is derived from a sample of 76 sources for which we have the highest quality data. The present gradient in electron temperature has a minimum at the Galactic center and rises at a rate of 287 46 K kpc1. There are no significant variations in the value of the gradient as a function of Galactocentric radius or azimuth. The scatter we find in the H ii region electron temperatures at a given Galactocentric radius is not due to observational error, but rather to intrinsic fluctuations in these temperatures, which are almost certainly due to fluctuations in the nebular heavy-element abundances. Comparing the H ii region gradient with the much steeper gradient found for planetary nebulae suggests that the electron temperature gradient evolves with time, becoming flatter as a consequence of the chemical evolution of the Milky Way’s disk.