The figure below shows the spectra of two galaxies A and B. Relative flux density 3.5 3.0 2.5 2.0 1.0 0.5 A option from mwww 4000 B 4500 5500 Wavelength (Ang.) 5000 6000 6500 7000 1. Which of these galaxies has ongoing star formation? How can you tell? 2. One of these galaxies has Hubble type E3 while the other is SBb. Which is which? What does the 3 E3 tell you about the galaxy? What does the SB in SBb tell you about the galaxy? 3. What effects would dust have on the two spectra? 4. Which galaxy would you expect to have more far-infrared emission? Explain.
The figure below shows the spectra of two galaxies A and B.
1. According to the figure Galaxy A has a high relative flux density which shows it has a dense region that helps in star formation and strong emission lines with high uneven distributed brightness due to the blue color of the galaxy wavelength. This blue color shows that it creates a hot and young star. So, Galaxy A is doing ongoing star formation.
2. An elliptical galaxy is an ellipsoidal-shaped galaxy, each part of which is emitting approximately equal brightness and ranges from 0 to 7. Their size can range from a pure sphere to a very flattened egg and can contain from tens of millions to a trillion stars. Along with lens-like galaxies, elliptical galaxies are one of the three main galaxies categories of the Hubble sequence. Elliptical galaxies contain older stars and their interstellar medium is less dense. The young stars are rarely found in these. So, E3 is the type of elliptical galaxy. So, galaxy B is the type of E3 galaxy because of equal brightness and no young star formation.
A spiral galaxy is a spiral-shaped galaxy, such as our own galaxy, the Milky Way. They consist of a flattened rotating circle containing stars, gas, and dust, and a thick bulge, barred in the center of which is a dense sphere of stars. Spiral galaxies have an abundance of newborn, young stars in the arms, and older stars in the center. Because new stars are hotter, the arms shine brighter than the center. The spiral galaxies are represented by Sa, Sb,SBa, SBb, etc. Galaxy A is spiral barred SBb.
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