Oxygen lines in solar granulation - I. Testing 3D models against new observations with high spatial and spectral resolution

摘要

Aims. We seek to provide additional tests of theline formationof theoretical 3D solar photosphere models. In particular, we set outto test the spatially-resolved line formation at several viewingangles, from the solar disk-centre to the limb and focusing on atomicoxygen lines. The purpose of these tests is to provide additionalinformation on whether the 3D model is suitable to derive the solaroxygen abundance. We also aim to empirically constrain the NLTE recipesfor neutral hydrogen collisions, using the spatially-resolvedobservations of the OI777nm lines. Methods. Using the Swedish1-m SolarTelescope we obtainedhigh-spatial-resolution observations of five atomic oxygen lines (aswell as several lines for other species, mainly FeI)for five positions on the solar disk. These observations have a highspatial (sub-arcsecond) and spectral resolution, and a continuumintensity contrast up to 9% at 615nm. The theoretical lineprofiles were computed using the 3D model, with a full 3D NLTEtreatment for oxygen and LTE for the other lines. Results. At disk-centre we find an excellentagreement betweenpredicted and observed line shifts, strengths, FWHM and asymmetries. Atother viewing angles the agreement is also good, but the smallercontinuum intensity contrast makes a quantitative comparison harder. Weuse the disk-centre observations we constrain ,the scaling factor for the efficiency of collisions with neutralhydrogen. We find that provides the best match to the observations, although this method isnot as robust as the centre-to-limb line variations to constrain .Conclusions. Overall there is a very good agreementbetweenpredicted and observed line properties over the solar granulation. Thisfurther reinforces the view that the 3D model is realistic and areliable tool to derive the solar oxygen abundance. Key words: Sun: granulation - line: formation -Sun: photosphere - techniques: spectroscopic - techniques: high angularresolution