Gas, gas everywhere and every-when

We are bounded in a nutshell of Infinite space: Blog Post #25, Worksheet # 7.2, Problem #5: Gas, gas everywhere and every-when

5. You may also have noticed some weak “dips” (or absorption features) in the spectrum:

(a) Suggest some plausible origins for these features. By way of inspiration, you may want to consider what might occur if the bright light from this quasar’s accretion disk encounters some gaseous material on its way to Earth. That gaseous material will definitely contain hydrogen, and those hydrogen atoms will probably have electrons occupying the lowest allowed energy state.

(b) A spectrum of a different quasar is shown below. Assuming the strongest emission line you see here is due to \(L\gamma\alpha\), what is the approximate red-shift of this object?

(c) What is the most noticeable difference between this spectrum and the spectrum of 3C 273? What conclusion might we draw regarding the incidence of gas in the early Universe as compared to the nearby Universe?

(a) These features could be caused by the way the elements found in the gas of the interstellar medium have the ability, like all atoms, to absorb energy and thus dim the light we receive from the original source. However, if we take these absorption numbers, we can then find the exact composition of the interstellar gas, since only specific wavelengths can be absorbed and used within the internal mechanics of the atom.

(b) As to the Red Shift of this new emission spectrum, the process is almost identical to the process made for problem #4. Knowing the Red Shift Equation, we have:   \[\frac{\lambda_{observed} - \lambda_{emitted}}{\lambda_{emitted}}  = z ,\] which is just a matter of plugging in the emitted wavelength of hydrogen, since the peak of this spectrum is the hydrogen emission (as the problem establishes), which is 1215.67 \(\dot{A}\). The Other value would be the wavelength of the max flux, which is 5625 Angstroms. So the equation is: 
\[\frac{5625 \dot{A}  - 1215.67 \dot{A}}{1215.67 \dot{A}}  = z,  \] \[ z =3.627, \] which is the Red Shift of this emission spectrum.

(c) Considering both the emission spectrum we just analyzed and the spectrum for 3C 273, the one we studied previously, there seems to be a major difference. The emission is shifted for the fact of the Red Shift as a result of the quasar being farther away, therefore faster from our perspective, and thus older. But the clear distinction is how the 3C 273 graph had much fewer dips during the beginning of the spectra, while the new quasar is absolutely full of dips before it rises to the max Flux. This helps to show that this galaxy, being farther away and older than other stars, hints at how the universe was long ago: full of gas, unformed and ready to be turned into the next generations of stars and planets.