Effects of Light Pollution on Observation of Galaxies and Spectrophotometry

Light pollution, artificial light which is far too much and misplaced at night has become an extremely serious inhibitor to ground-based astronomical observation. This paper measures the effect of urban skyglow on the observation and spectral properties of the low-surface-brightness galaxies with an example of M101 (The Pinwheel Galaxy). We created artificial observational data of three sites, a dark-sky site (Bortle Class 1), a rural site (Bortle Class 4), and an urban suburb site (Bortle Class 8). We measured the major parameters in surface brightness, apparent magnitude, SNR of g and r bands, and capacity to detect the emission lines of H-alpha which would prove very important in studying the process of star formation using synthetic photometry and spectroscopy. Findings show that there is a strong degradation in the quality of data as the level of light pollution increases. Urban values of the apparent, and effective, surface brightness of M101 were artificially enhanced by a factor of 0.8 mag, the spectral features SNR diminished by a factor of more than 80 and the effective surface brightness more than 22 mag/arcsec2. The H-alpha was not visible in the urban simulation. This study shows conclusively that light pollution does not only render celestial objects visible faint, but it also causes considerable systematic errors in photometric and spectroscopic observations, threating the accuracy of science. Some protections of dark-sky preferred and instrumented form of mitigation are desperately required.