Image: The image of distant galaxies found in the Hubble Ultra Deep Field should
ID: 1517430 • Letter: I
Question
Image:
The image of distant galaxies found in the Hubble Ultra Deep Field should at http://www.nasa.gov/images/content/145969main_hst_galaxies_200604_full.jpg. and review the full press release at:http://www.nasa.gov/images/content/145969main_hst_galaxies_200604_prt.htm.
Cosmological Calculator : http://www.astro.ucla.edu/~wright/CosmoCalc.html
Use them to answer the questions below. Be sure to state your assumptions and be clear on the methods/logic/equations you use to arrive at your answers.
1.Supposing the galaxy in 3. is disk-like and has an angular diameter (as measured from this image) of 4 arcseconds ("). Adopting the values we have been using in class M=0.3, =0.7 and a Hubble constant of 70 km/s/Mpc, and assuming the universe is flat, what is its linear diameter? How does the galaxy's stellar disk compare in size to that of the Milky Way? Please be sure to show your work so that it is clear how you arrive at your answer.
2. Notice the relatively bright yellow-orange spiral galaxy just to the left of the faint galaxy labeled 23 in the large image. Suppose it is Milky Way-like and has an angular extent in the image of 10 arcsec. Use the Cosmo Calculator toguess-timate its redshift; this time use the calculator's default values for H0=69.6, M=0.286, =0.714 and assume a flat universe. Please give your answer with a precision to the nearest 0.1 in z if z > 1.0 (e.g. 1.3, 2.5, 7.1) or to 0.05 if z < 1.0 (e.g. 0.05, 0.40, 0.75), and as usual explain how you arrived at it so you will remember later.
Explanation / Answer
1) galaxy's stellar disk compare in size to that of the Milky Way = 70 * (0.7/0.3) * cos4
= 162.93 times
2) Here, red shift = 69.6 * (0.286/0.714) * tan10
= 4.9
=> z = 4.9