1.To what redshift/blueshift could we observe HI if our spectrometer covered a 64.00 MHz band centred on 1.410 GHz. [ What velocities do these correspond to? [ Would this be a sensible place to place the centre frequency of your receiver?
2. You have detected HI (21cm) emission from a nearby galaxy at three locations: -at the galaxy center (C), -10 arcmin to the east of the galaxy center along the galaxy’s major axis (E), and -10 arcmin to the west of the galaxy center (W). The HI emission peaks at 21.190 cm at (C), 21.204 cm at (W), and 21.176 cm at (E). (a) For a Hubble constant of 70 km/sec/Mpc, how far away is this galaxy (in Mpc)? (b) How fast is the galaxy rotating? Assume that the galaxy is seen edge-on. (c) Assuming the gas is on circular orbits, use Newton’s law of gravity to determine the amount of mass in the galaxy interior to 10 arcmin radius. (d) The peak brightness temperature at location (C) is 12K – what is the peak column density of this galaxy at this location?