Podcast
Questions and Answers
What is the main difference in the environments where elliptical galaxies and spiral galaxies are typically found?
What is the main difference in the environments where elliptical galaxies and spiral galaxies are typically found?
What phenomenon causes active galaxies to emit a non-stellar component in their spectral energy distribution?
What phenomenon causes active galaxies to emit a non-stellar component in their spectral energy distribution?
How does redshift relate to the distance of galaxies?
How does redshift relate to the distance of galaxies?
What do high-redshift galaxies represent in terms of galaxy evolution?
What do high-redshift galaxies represent in terms of galaxy evolution?
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What is believed to cause the morphology–density relation observed in galaxies?
What is believed to cause the morphology–density relation observed in galaxies?
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What recently advanced tools allow researchers to observe galaxies at high redshifts?
What recently advanced tools allow researchers to observe galaxies at high redshifts?
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What aspect of galaxy properties can studying changes in number density with redshift reveal?
What aspect of galaxy properties can studying changes in number density with redshift reveal?
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During galaxy formation and evolution, which aspect is considered crucial in understanding the processes involved?
During galaxy formation and evolution, which aspect is considered crucial in understanding the processes involved?
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What does the flow chart of galaxy formation illustrate?
What does the flow chart of galaxy formation illustrate?
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What is a primary assumption of modern cosmology?
What is a primary assumption of modern cosmology?
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Which of the following is NOT specified by modern cosmology?
Which of the following is NOT specified by modern cosmology?
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What is one consequence of the cosmological principle and general relativity?
What is one consequence of the cosmological principle and general relativity?
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What may happen as our understanding of galaxy formation evolves?
What may happen as our understanding of galaxy formation evolves?
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What does the term 'scale factor, a(t)' represent in cosmology?
What does the term 'scale factor, a(t)' represent in cosmology?
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Why might cold gas not settle into a gaseous disk before a merger occurs?
Why might cold gas not settle into a gaseous disk before a merger occurs?
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What represents a key task in cosmology according to the content?
What represents a key task in cosmology according to the content?
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What is the outcome of merging two galaxies of roughly equal mass?
What is the outcome of merging two galaxies of roughly equal mass?
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What happens when gas cools onto a merger remnant with significant angular momentum?
What happens when gas cools onto a merger remnant with significant angular momentum?
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What is tidal stripping?
What is tidal stripping?
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What role do dynamical processes play in galaxy evolution within clusters?
What role do dynamical processes play in galaxy evolution within clusters?
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What can large scale instabilities in a galaxy cause?
What can large scale instabilities in a galaxy cause?
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What is the result of the bar-instability in disk galaxies?
What is the result of the bar-instability in disk galaxies?
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What triggers ram-pressure stripping in satellite galaxies?
What triggers ram-pressure stripping in satellite galaxies?
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Which of the following is a prominent feature of a barred spiral galaxy?
Which of the following is a prominent feature of a barred spiral galaxy?
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What is the term used for the evolution processes that occur in galaxies after their initial formation?
What is the term used for the evolution processes that occur in galaxies after their initial formation?
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Which process is NOT mentioned as a potential contributor to the formation of galaxy bulges?
Which process is NOT mentioned as a potential contributor to the formation of galaxy bulges?
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What defines the metallicity of a baryonic component in astronomy?
What defines the metallicity of a baryonic component in astronomy?
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Which elements were produced during the primordial nucleosynthesis epoch primarily?
Which elements were produced during the primordial nucleosynthesis epoch primarily?
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How do massive stars influence the interstellar medium (ISM)?
How do massive stars influence the interstellar medium (ISM)?
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What effect does increased metallicity have on the cooling efficiency of gas?
What effect does increased metallicity have on the cooling efficiency of gas?
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What role do dust grains play in the interstellar medium?
What role do dust grains play in the interstellar medium?
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What influences the mass and chemical composition of material ejected by a stellar population?
What influences the mass and chemical composition of material ejected by a stellar population?
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What distinguishes warm dark matter (WDM) from cold dark matter (CDM)?
What distinguishes warm dark matter (WDM) from cold dark matter (CDM)?
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Why did the shortcomings of hot dark matter (HDM) models prompt the exploration of other scenarios?
Why did the shortcomings of hot dark matter (HDM) models prompt the exploration of other scenarios?
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What aspect of dark matter particles enhances the growth of density fluctuations?
What aspect of dark matter particles enhances the growth of density fluctuations?
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What does the 'standard' CDM model prefer regarding the mass density of dark matter?
What does the 'standard' CDM model prefer regarding the mass density of dark matter?
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According to simulations by M. Davis et al. (1985), what is necessary for the CDM model to match observed galaxy clustering?
According to simulations by M. Davis et al. (1985), what is necessary for the CDM model to match observed galaxy clustering?
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What is the primary contribution of the APM galaxy survey in the context of the standard CDM model?
What is the primary contribution of the APM galaxy survey in the context of the standard CDM model?
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In the mixed dark matter (MDM) model, what percentage of the cosmic mass density is attributed to cold dark matter?
In the mixed dark matter (MDM) model, what percentage of the cosmic mass density is attributed to cold dark matter?
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What particle type is indicated as a candidate for dark matter due to its larger mass and smaller initial velocities?
What particle type is indicated as a candidate for dark matter due to its larger mass and smaller initial velocities?
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What major discovery in 1965 provided strong support for the Hot Big Bang model?
What major discovery in 1965 provided strong support for the Hot Big Bang model?
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Which isotopes were suggested to be explained by primordial nucleosynthesis according to Wagoner et al. (1967)?
Which isotopes were suggested to be explained by primordial nucleosynthesis according to Wagoner et al. (1967)?
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What observation pointed out an issue regarding the uniformity of the Universe at large scales in the context of the standard cosmology?
What observation pointed out an issue regarding the uniformity of the Universe at large scales in the context of the standard cosmology?
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What does the standard model suggest about the spatial geometry of the Universe?
What does the standard model suggest about the spatial geometry of the Universe?
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What was one of the significant shortcomings of the standard cosmology recognized in the 1960s and 1970s?
What was one of the significant shortcomings of the standard cosmology recognized in the 1960s and 1970s?
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What aspect of the early Universe's evolution raised questions about the time scales of physical processes?
What aspect of the early Universe's evolution raised questions about the time scales of physical processes?
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Who first published calculations that linked helium abundance to the Hot Big Bang?
Who first published calculations that linked helium abundance to the Hot Big Bang?
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What is indicated by the isotropic nature of the cosmic microwave background?
What is indicated by the isotropic nature of the cosmic microwave background?
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Study Notes
Introduction
- This book examines the physical processes behind galaxy formation and evolution.
- A galaxy is a gravitationally bound system of stars.
- Typical bright galaxies, like the Milky Way, contain billions of stars.
- Galaxy sizes are much smaller than the average distance between galaxies.
- Galaxy densities are much higher than the average density of stars in the universe.
- The goal of this text is to explain how physics can be used to understand galaxy formation and evolution.
- This study will consider initial and boundary conditions, as well as physical processes driving evolution.
Parts of the Study
- Cosmology: Understanding the space-time structure on large scales within the cosmological framework.
- Initial conditions: Understanding the physical processes in the early universe (beyond our current observation capabilities).
- Physical processes: Including general relativity, hydrodynamics, the behaviour of collisionless systems, plasma physics, thermodynamics, atomic, nuclear and particle physics, and radiation processes.
Diversity of Galaxy Populations
- Galaxies are diverse objects. A multitude of parameters needs to be considered in order to describe any particular galaxy; they are correlated.
- Morphology: The most significant observable property of a galaxy, with major types being spirals and ellipticals.
- Ellipticals are usually spheroidal or slightly oblate, dominated by random star movement.
- Spirals usually have flattened disks with a dominant rotational component.
- Luminosity and Stellar Mass:
- Galaxies vary significantly in luminosity.
- Luminosity is correlated to the total number of stars and, thus, the total stellar mass.
- Stellar populations of different ages have different luminosities relative to mass.
- Size and Surface Brightness:
- Galaxies lack clear boundaries, so multiple definitions for their size exist.
- Brighter galaxies are generally larger.
- Gas Mass Fraction:
- The ratio of cold gas mass to total mass of the galaxy.
- Spiral galaxies often have larger gas mass fractions (relative to total mass) than other types.
- Color:
- Color is a ratio of luminosities in different photometric passbands.
- Redder colours correlate with age and/or metallicity, although dust absorption can obscure that.
Basic Elements of Galaxy Formation
- Cosmology: The study of the large-scale properties of the universe.
- Initial conditions: The starting conditions of the universe.
- Gravitational instability: Perturbations in the density will grow over time in an expanding universe.
- The size of perturbations increase over time.
- Feedback processes: Mechanisms where energy and matter are transferred from/to the galaxy.
- Mergers: When systems join together, re-shaping its structure.
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Description
This quiz explores the physical processes involved in galaxy formation and evolution, including the roles of initial conditions and cosmology. It delves into the gravitational dynamics that govern galaxy structures and their interactions over time. Test your knowledge on the complex physics that shapes the universe's galaxies.
