Diffuse interstellar bands in damped Lyman-alpha and starburst galaxies.

摘要

I present a study of diffuse interstellar bands (DIBs) in seven moderate redshift HI-selected damped Lyalpha galaxies and 18 low to moderate redshift NaI-selected starbursts. I have developed a spectral analysis method for finding and calculating limits for the weak DIB absorption profiles. The spectral analysis is optimized for both resolved and unresolved features and also assesses the accuracy of equivalent width limits by calculating the effects caused by errors in the DIB intrinsic rest wavelength, DIB rest FWHM, instrumental resolution, and continuum placement. This spectral analysis technique is used to calculate robust equivalent width limit in the HI-selected DLA sample. The DIBs in DLAs are weaker than expected, based on Galactic observations and the large abundance of H I. The DIB limits put constraints on the DLA reddening and gas-to-dust ratios. Four of the seven DLAs have sufficiently good limits to constrain DLA reddenings to less than 0.08. I constrain the DLA gas-to-dust ratios as being comparable to the Magellanic Clouds for the four DLAs with the best limits. I detect DIBs in 14 of the 18 NaI-selected starbursts. The lambda5780 DIB is especially prevalent in the starburst sample. I perform Kendall tau correlation tests on the DIB equivalent widths and velocities with the NaI outflow properties and the intrinsic starburst properties. The lambda5780 DIB is weakly to moderately correlated with the column densities and velocities of the NaI outflow gas, but not with galaxy properties. The lambda5780 DIB velocity is moderately correlated with the NaI outflow velocity, but it is also moderately correlated with velocity separation from the NaI outflow gas. As the Na I outflow velocity increases, so does the velocity separation between the DIB absorbing gas and the NaI outflow gas. The lambda5780 DIB shows a weak anti-correlation with the column density of NaI outflow gas, which is opposite of what is observed in the Galaxy. I argue that the correlation tests indicate that the lambda5780 DIB absorbing gas is influenced by the NaI gas abundance and kinematics, but the DIB absorbing gas is not entrained in the largest N(Na I) outflow gas.