(c) Show that the signal-to-noise ratio (S/N) of background-limited CCD observations scales as the square root of the ex

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C Show That The Signal To Noise Ratio S N Of Background Limited Ccd Observations Scales As The Square Root Of The Ex 1 (84.57 KiB) Viewed 80 times

(c) Show that the signal-to-noise ratio (S/N) of background-limited CCD observations scales as the square root of the exposure time. Explain why it is important to obtain background-limited data when stacking images of faint galaxies. (d) A CCD detector on a 4 m telescope requires an integration time of 100 s to reach S/N = 10 for a particular target. Calculate the exposure time required to reach S/N = 10 on an 8 m telescope with the same CCD detector, assuming both observations are back- ground limited and experience the same observing conditions. For this S/N, calculate the uncertainty on the target magnitude. (e) A galaxy has an observed flux density per unit wavelength of fx = 7.71 x 10-11 Wm-3 at a wavelength of 7500 Å. Calculate the equivalent flux density per unit frequency and thereby calculate the galaxy's apparent magnitude in the AB system. [Note: the AB zero point is 3631 Jy and 1 Jy = 1 x 10-26 Wm-?Hz-1]