CO ro-vibrational lines in HD 100546: A search for disc asymmetries and the role of fluorescence

• Published in: Astronomy and astrophysics (Berlin) 2014-01, Vol.561, p.np-np
• Main Authors: Hein Bertelsen, R P, Kamp, I, Goto, M, van der Plas, G, Thi, W-F, Waters, L B F M, van den Ancker, M E, Woitke, P
• Format: Article
• Language: English
• Subjects: Astrophysics; Asymmetry; Carbon monoxide; Density; Discs; Disks; Emission analysis; Fluorescence; Sciences of the Universe; Very Large Telescope
• ISSN: 0004-6361; 1432-0746; 1432-0756
• DOI: 10.1051/0004-6361/201322574

We have studied the emission of CO ro-vibrational lines in the disc around the Herbig Be star HD 100546 to determine physical properties, disc asymmetries, the CO excitation mechanism, and the spatial extent of the emission, with the final goal of using the CO ro-vibrational lines as a diagnostic to understand inner disc structure in the context of planet formation. High-spectral-resolution infrared spectra of CO ro-vibrational emission at eight different position angles were taken with the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) at the Very Large Telescope (VLT). The observed CO ro-vibrational lines are largely emitted from the inner rim of the outer disc at 10-13 AU. The line shapes are similar for all v levels and line fluxes from all vibrational levels vary only within one order of magnitude. We find that lower gas volume densities at the surface of the inner rim of the outer disc can make the fluorescence pumping more efficient and reproduce the observed band ratios.