Galaxy Formation Models — MCQs

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1. The monolithic collapse model of galaxy formation was proposed by?
(A) Eggen, Lynden-Bell, and Sandage
(B) Hubble
(C) Hoyle
(D) Zwicky

2. The hierarchical model of galaxy formation suggests that galaxies formed by?
(A) Rapid collapse of a single cloud
(B) Merging of smaller sub-galactic units
(C) Continuous star formation in isolation
(D) Tidal stripping only

3. Which observation strongly supports hierarchical galaxy formation?
(A) Existence of quasars
(B) Presence of galaxy mergers
(C) Spiral arms in galaxies
(D) Uniform galaxy distribution

4. The monolithic collapse model predicts that elliptical galaxies formed?
(A) From gradual merging of spirals
(B) From a single rapid collapse of gas cloud
(C) From tidal tails
(D) From quasar remnants

5. Which model best explains the presence of stellar streams in galaxies?
(A) Monolithic collapse
(B) Hierarchical merging
(C) Steady-State model
(D) Static model

6. Which process triggers starbursts during galaxy formation?
(A) Supernova feedback
(B) Galaxy mergers
(C) Magnetic fields
(D) Cosmic rays

7. Cold Dark Matter (CDM) models predict galaxy formation through?
(A) Rapid gas collapse
(B) Bottom-up structure formation
(C) Top-down structure formation
(D) Gravitational lensing only

8. Which component plays a crucial role in galaxy formation?
(A) Dark matter halos
(B) Planetary nebulae
(C) Black hole jets
(D) Gamma-ray bursts

9. The presence of old stellar populations in ellipticals supports?
(A) Monolithic collapse
(B) Hierarchical merging
(C) Continuous accretion
(D) Cold streams

10. Which model suggests galaxies formed gradually over time?
(A) Monolithic collapse
(B) Hierarchical merging
(C) Big Bang nucleosynthesis
(D) Quasar model

11. The ΛCDM model combines?
(A) Inflation and steady-state ideas
(B) Dark energy and cold dark matter
(C) Spiral and elliptical formation
(D) Galactic winds and feedback only

12. Which feedback mechanism regulates star formation in galaxies?
(A) Cosmic rays
(B) AGN and supernova feedback
(C) Tidal disruption
(D) Weak nuclear force

13. Which galaxies are often formed through mergers of spirals?
(A) Elliptical galaxies
(B) Dwarf irregulars
(C) Globular clusters
(D) Lenticular galaxies only

14. Galaxy interactions often lead to the formation of?
(A) Spiral arms
(B) Starburst regions
(C) Black hole jets
(D) Dark energy

15. Which type of galaxy is more common in high-density regions like clusters?
(A) Spirals
(B) Ellipticals
(C) Irregulars
(D) Dwarf spheroidals

16. The Tully-Fisher relation connects galaxy luminosity with?
(A) Stellar ages
(B) Rotation velocity
(C) Metallicity
(D) Gas fraction

17. Which process helps explain the thin disks of spiral galaxies?
(A) Violent relaxation
(B) Dissipative collapse of gas
(C) Tidal disruption
(D) Stellar evaporation

18. In hierarchical models, dwarf galaxies are considered?
(A) Remnants of quasars
(B) Building blocks of larger galaxies
(C) Collapsed globular clusters
(D) Failed ellipticals

19. What does the “downsizing” phenomenon in galaxy formation imply?
(A) Large galaxies form later than small ones
(B) Large galaxies formed earlier than small ones
(C) Small galaxies never form stars
(D) Galaxy sizes always shrink

20. Galaxy simulations rely heavily on?
(A) Dark matter and hydrodynamics
(B) Nuclear reaction rates
(C) Solar wind data
(D) Neutrino detection

21. Which galaxies are most gas-rich and still forming stars?
(A) Ellipticals
(B) Dwarf irregulars
(C) Lenticulars
(D) Globular clusters

22. Which observational evidence supports mergers in galaxy evolution?
(A) Stellar streams and tidal tails
(B) Uniform rotation curves
(C) CMB fluctuations
(D) Supernova neutrinos

23. The cosmic star formation rate peaked around?
(A) Present day
(B) Redshift z ≈ 2
(C) Redshift z ≈ 10
(D) During recombination

24. The Fundamental Plane relation applies to?
(A) Spiral disks
(B) Elliptical galaxies
(C) Irregular galaxies
(D) Dwarf spheroidals

25. Which galaxies are thought to evolve into lenticulars in dense environments?
(A) Spirals
(B) Ellipticals
(C) Irregulars
(D) Dwarf spheroidals

26. Which process explains the quenching of star formation in massive galaxies?
(A) Supernova explosions only
(B) AGN feedback heating the gas
(C) Cosmic ray pressure
(D) Planetary nebula winds

27. The Sersic index is used to describe?
(A) Star formation rate
(B) Galaxy surface brightness profiles
(C) Dark matter halo density
(D) Globular cluster counts

28. Which model better explains the diversity of galaxy morphologies?
(A) Monolithic collapse
(B) Hierarchical merging
(C) Steady-State model
(D) Big Crunch model

29. Which evidence indicates gas accretion in galaxy formation?
(A) Cold gas streams feeding galaxies
(B) Presence of planetary nebulae
(C) Spiral arm star clusters
(D) Pulsar wind nebulae

30. Galaxy harassment refers to?
(A) Rapid star formation
(B) Repeated tidal encounters in clusters
(C) Supernova feedback
(D) AGN heating

31. The morphology-density relation shows that?
(A) Spirals dominate in dense regions
(B) Ellipticals dominate in dense regions
(C) Irregulars dominate in all regions
(D) Dwarfs dominate in voids only

32. Which galaxies are the oldest and most metal-poor?
(A) Dwarf irregulars
(B) Globular clusters within galaxies
(C) Ellipticals
(D) Spirals

33. Disk instabilities in galaxies can lead to formation of?
(A) Bars and spiral arms
(B) Stellar halos
(C) Black hole jets
(D) Tidal tails

34. Violent relaxation occurs during?
(A) Star formation in nebulae
(B) Rapid collapse of a self-gravitating system
(C) Supernova explosions
(D) Galactic disk settling

35. Which type of galaxy is considered a “fossil” of early formation?
(A) Dwarf spheroidals
(B) Spiral galaxies
(C) Lenticular galaxies
(D) Elliptical galaxies

36. The main driver of structure formation in ΛCDM cosmology is?
(A) Dark matter gravity
(B) Dark energy pressure
(C) Stellar winds
(D) Magnetic turbulence

37. Which galaxy component forms first in most models?
(A) Disk
(B) Halo
(C) Bulge
(D) Spiral arms

38. The bulge of spiral galaxies may form through?
(A) Bar instabilities or mergers
(B) Star formation in disks only
(C) Planetary nebula collapse
(D) Tidal stripping only

39. Which feature of galaxies is best explained by hierarchical merging?
(A) Smooth disk structure
(B) Multiple stellar populations
(C) Constant metallicity
(D) No gas reservoirs

40. Feedback processes in galaxy formation are important to?
(A) Stop gravitational collapse entirely
(B) Regulate star formation efficiency
(C) Increase galaxy metallicity only
(D) Reduce dark matter density directly

41. Which observational tool is most important in galaxy formation studies?
(A) CMB anisotropy measurements
(B) Stellar evolution tracks
(C) Supernova light curves
(D) Solar neutrino detection

42. Which galaxies show evidence of secular evolution?
(A) Ellipticals only
(B) Spirals with bars and rings
(C) Dwarf spheroidals only
(D) Irregular galaxies

43. The concept of “galactic downsizing” contradicts?
(A) Monolithic collapse predictions
(B) Hierarchical merging expectations
(C) Both A and B
(D) Neither A nor B

44. Which model best explains massive galaxies at high redshift?
(A) Pure monolithic collapse
(B) Mergers combined with gas accretion
(C) Steady-State cosmology
(D) Only secular evolution

45. In simulations, feedback prevents?
(A) Gas cooling too efficiently
(B) Dark matter clustering
(C) Tidal stripping of galaxies
(D) Planet formation

46. The existence of ultra-compact dwarfs suggests?
(A) Failed quasars
(B) Remnants of stripped galaxies
(C) Large globular clusters
(D) Irregular starbursts

47. Gas outflows from galaxies are primarily driven by?
(A) Stellar winds and supernovae
(B) Planetary nebulae
(C) Cosmic rays only
(D) Gravitational lensing

48. The Hubble sequence classifies galaxies by?
(A) Size
(B) Morphology
(C) Metallicity
(D) Star formation rate only

49. In cold dark matter models, small structures form?
(A) Later than large ones
(B) Earlier than large ones
(C) Simultaneously with large ones
(D) Never form

50. Which process explains intracluster light in galaxy clusters?
(A) Tidal stripping of stars during galaxy interactions
(B) Star formation from hot gas
(C) Black hole activity
(D) Neutrino emission

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