New atomic and molecular data for astrophysics by high resolution Fourier Transform Spectroscopy

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Summary: New high resolution spectrographs on both ground and space-based telescopes have allowed astronomers to observe astrophysical spectra of unprecedented quality, and have led to an urgent need for atomic data of sufficient accuracy and completeness to analyse these spectra. Particularly important are the abundant, line rich spectra of the iron group elements (Ti, V, Cr, Mn, Fe, Co, Ni). Atomic data of the doubly ionised iron group spectra are in many cases very old, incomplete, and inaccurate, and in the case of the infra red spectra of neutral and singly ionised species are often missing entirely. Using our unique visible-ultraviolet Fourier Transform (FT) spectrometer at Imperial College and the NIST (National Institute Standards & Technology, USA) FT spectrometer we will study high resolution spectra of these elements. The advantages of using an FT spectrometer are that we can measure the spectrum of a particular species at high resolution over a wide spectral range. We will focus on measurements leading to at least order-of-magnitude improvements in wavelength accuracy, atomic energy levels, oscillator strengths (needed for determining abundances of elements in astrophysical objects), and hyperfine structure. Astronomers use these atomic data in analysing astrophysical spectra. Once measured the atomic data will be used immediately in specific astrophysics projects we are collaborating on, examples include: Low mass stars, brown dwarfs and extra solar planets, hot stars, and chemically peculiar stars. We also plan measurements of accurate wavelengths of lines for use in cosmology applications: in particular in investigations of a possible time variation in the fine structure constant, one of the fundamental constants. All the new laboratory atomic and molecular data we produce is incorporated into databases and model atmosphere codes, benefiting astronomers worldwide in addition to those in the UK. The new laboratory data we provide to the astronomical community means that analyses of expensively obtained modern astrophysical spectra will no longer be limited by the quality and quantity of atomic (or molecular) data used in their analyses. In addition to the program of atomic data measurements, we plan a new project of high resolution molecular spectroscopy of SO2 which involves low temperature measurements in the UV, to yield molecular data urgently needed for studies of volcanically active Io, a moon of Jupiter.