Question

5x105 0.01 0.015 0.02 4000 4500 Angstrom 5000 5500 6000 0 2x10-5 4x108 6x10" 8x10-5 Angstrom 4110 41204130 41404150 41604170 4100 4190 4200 4210

Q.) The left panel shows the optical spectrum of a quasar between 4000–6000 angstroms. The right panel shows a zoom of the same spectrum in the 4110–4210 angstrom region.

(a)If the brightest emission feature in the spectrum was identified as a redshifted Lyman-α line, then what is redshift (z) of the quasar?

(b) When the light that reached our telescopes today (and allowed us to take this spectrum) had started its journey from the quasar, the size of the universe at that time was what fraction of the size of the present universe? You can assume that the universe has been uniformly expanding throughtout the time the photons were traveling from the quasar to us.

(c)Looking at the right panel: what object, and at what redshift, might have caused the narrow absorption line near 4127 angstroms?

Answer 1

Sole (a) The given optical spectrum of a quasar between 4000-6000 angstroms and also sadlh is measured at the difference in wavelength emitted mincy and wavelength, divided by the emitted wavelength The redshif enpression to the . 2. Pobso-demit 0 rennid. As per the lyman-alpha speetra, the weweleryth d 12164, by observed in a wisered Spectra of Lyman alpha wavelength is around 4600 A, the given valus in images, the redshift d. the Quassar is . so that by submitting the given valey in ea - uboo-1216 2- 1916. 1698 846 423 Sub क्या 104 304 ..) 433 -9782 This is the redshift of the Quasar il 2.782

@ The gren Lighti that reached our telescopy today @ had started its journey from the questas, the relation between redshif and seale facter of the universes then the expression is 1+2=anow . O aten .. by submitting the given valuy in exprenion & theni Yt 2-782= 3.782 a here, the radius of our universe at present is then 1 3.782 factar more than the unverse this is the universe has been uniformely empinding throughtond the time. the photons were travelling from the Quasar tous. C. Now the given the narrow absorption line near ulat angstroms, then the redshift is zo we can get the value of 2 by submitting the given valing. 2 u127 1218 2909 . 12 16 2,39399 Tu #26 : -) This is the 2.399 required solution for the giren data