Space & astronomy · the experiment
Recover the Black Pearl's bump
Webb's spectrum hides a dust dip. Bring it back to where NIRSpec saw it, fit the authors' profile to it, then put its shift to the test.
1 · Stretch the light all the way to Webb
At rest, the Black Pearl's dip sits at 2,132 Å, in the ultraviolet. NIRSpec observes from 0.6 to 5.3 µm.
Beginner
Why is it an infrared instrument, NIRSpec, that sees this ultraviolet dip?
Hydrogen and oxygen lines place the galaxy at z = 9.3335. Raise the redshift until the dip lands on the one in the NIRSpec spectrum.
2 · Fit the Drude profile
The plot below divides the spectrum by its continuum, as in equation (1): A = −2.5 log₁₀(F / F_cont).
Intermediate
At the bottom of the dip, dust dims the light by A_max = 0.21 magnitudes. What share of the starlight is missing?
Your template starts at the Milky Way's position, narrow and shallow. Adjust its position, width and depth until it falls within the authors' error bars.
3 · Place the other bumps
Intermediate
Your bump is at 2,132 ± 17 Å; the Milky Way's is near 2,175 Å. How many sigma is that shift?
Place the Milky Way and the two bumps known around z ≈ 7 on the ruler.
4 · Put the redshift to the test
Expert
A sceptic argues: "The z is slightly off; really, the bump is at 2,175 Å, just like ours." How does the objection hold up?
The dip stays where NIRSpec saw it. Lower the assumed z until the bump is back at 2,175 Å, to within one ångström.
5 · Read the second fit
The full model of the galaxy, with the bump's position and width left free, gives 2,147 (+51 / −59) Å or 2,168 (+77 / −73) Å depending on the star-formation history.
Expert
On their own, what do these two values say about the blueshift?
Bump recovered
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