Question

The GBT has sensitive receivers covering the frequency ranges 18 to 26.5 GHz and 26 to 40 GHz. Show how this frequency coverage is sufficient to detect CO emission from galaxies at any redshift from z = 1.9 to at least z = 10, the estimated redshift at which stars first produced significant amounts of interstellar CO.

Answer 1

Answer on Question 55070, Physics / Astronomy | Astrophysics

The most commonly observed CO emission lines arise either from J = 1–0 or J = 2–1 transition, with rest frequencies of about 115 and about 230 GHz. For the upper limit on the redshift:

$$z = \frac{230 - 18}{18} \approx 11.7$$

For the lower limit on the redshift:

$$z = \frac{115 - 40}{40} \approx 1.9$$

Answer: z = 11.7 and z = 1.9

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