Classic papers
in cosmology and astrophysics

Cosmology & extragalactic astronomy group

Institute of theoretical astrophysics

Course description
Course contents
  • The purpose of the course is to become familiar with seminal papers in the field of astrophysics and cosmology — the papers that everybody knows and cites, but never really read in-depth.
  • Note that the course is a so-called "special syllabus"; a maximum of 10 ECTS is allowed for special syllabi plus external courses.

Learning outcome
  • When you have completed the course, you will have a knowledge of the basics of important contributions to astrophysics. The actual chosen papers will depend on the preferences of the attendees, but will focus on galaxies and cosmology. A list of suggestion for papers is found below.
  • As an important part of the course is presenting the papers, as well as receiving feedback, the students will also become comfortable with speaking about topics that are somewhat outside their own studies — something which will be valuable as a future scientist.

  • The course runs over a semester. We will meet bi-weekly for 2 hours. The students will take turns on giving a presentation of the paper, which will then lead to a discussion. All students are expected to participate actively, e.g. by having prepared questions. There may also be small assignments to solve.
  • Compulsory attendance (-ish).

  • When presenting a paper, you can
    • make a full PowerPoint presentation with animations,
    • make a PowerPoint with 1 figure,
    • scroll through the paper and talk,
    • express its contents through miming/dancing,
    • bring another relevant paper or figure,
    i.e. basically whatever you want, as long as you make clear (some of) the following
    • what the paper is about,
    • what physical (and mathematical) assumptions were made,
    • what it's most important conclusion is,
    • what secondary conclusions is has,
    • why the paper is important,
    • what impact it has had / how it changed the field,
    • whether it's still important.
  • Meanwhile, the other attendees should
    • read the paper(s),
    • think about the same points as listed above,
    • think of a question to ask,
    • possibly also bring (or bring up) secondary relevant material.
Formal requirements
Admission and prerequisites
  • Students can sign up for the course by writing directly to me at email.
  • Students must hold a Master's degree in physics or astronomy.

Evaluation and examination
  • The course is passed by
    1. participating actively in all discussions,
    2. presenting a number of papers (depending on how many students are attending the course), and
    3. passing an oral exam.
  • After completion of the course, there will be an oral exam where the student draws a random paper from the course and presents it.
List of classic papers

Click table headers to sort table; click reference to go to paper.

Authors Ref. Citations (July 2019) Key words Description
Bacon, Refregier & Ellis 2000, MNRAS, 318, 625 00445 Cosmology; gravity Detection of weak gravitational lensing
Blumenthal et al. 1984, Nature, 311, 517 01277 Galaxies; dark matter Galaxy formation with dark matter
Bond & Efstathiou 1984, ApJ, 285L, 45 00754 Cosmology; CMB CMB fluctuations in a CDM universe (no Lambda)
Bond & Efstathiou 1987, MNRAS, 226, 655 00613 Cosmology; CMB CMB fluctuations; methods used today
Burbridge et al. 1957, RvMP, 29, 547 02268 Stars Synthesis of the elements in stars
Davis & Lineweaver 2004, PASA, 21, 97 00102 Cosmology; expansion Misconceptions of the expansion of the Universe
Dekel & Silk 1986, ApJ, 303, 39 01656 Galaxy formation Supernova feedback; origin of dwarf galaxies
Dicke et al. 1965, ApJ, 142, 414 00382 Cosmology; CMB Interpretation of the CMB
Dressler 1980, ApJ, 236, 351 02730 Galaxies Galaxy morphology, formation, and evolution
Eggen, Lynden-Bell & Sandage 1962, ApJ, 136, 748 01891 Galaxies Formation of the Galaxy (but sort of wrong)
Eisenstein et al. 2005, ApJ, 633, 560 02961 Structure formation Detection of the baryonic acoustic oscillations
Freeman 1970, ApJ, 160, 811 02129 Galaxies Explanation of the exponential disk of spirals and S0
Gunn & Peterson 1965, ApJ, 142, 1633 01173 Cosmology Erasure of light blueward of the Lyα line
Heckman et al. 1990, ApJS, 74, 833 01091 Galaxies Galactic outflows
Hubble 1925, ApJ, 62, 409 00145 Cosmology Evidence for the extragalacticity of nebulae
Hu 1995, PhD thesis 00032 Cosmology; CMB The origin of the CMB power spectrum peaks
Kennicutt 1998, ApJ, 498, 541 03388 Stars; galaxy evolution Evidence for the Schmidt law
Lynden-Bell 1967, MNRAS, 136, 101 01326 Structure formation Relaxation in stellar systems (and dark matter halos)
Navarro, Frenk, & White 1996, ApJ, 462, 563 05185 Dark matter The NFW profile I
Navarro, Frenk, & White 1997, ApJ, 490, 493 06693 Dark matter The NFW profile II
Oke & Gunn 1983, ApJ, 266, 713 01789 Stars AB magnitude definition
Partridge & Peebles 1967, ApJ, 147, 868 00399 Galaxies The visibility of young galaxies
Penzias & Wilson 1965, ApJ, 142, 419 01145 Cosmology; CMB Discovery of the CMB
Planck Collab. et al. 2018, arXiv:180706205 00136 Cosmology; CMB Latest Planck results
Press & Schechter 1974, ApJ, 187, 425 03689 Structure formation Structure formation in the early Universe
Riess et al. 1998, AJ, 116, 1009 11652 Cosmology; expansion Observational evidence for accelerated expansion
Rees & Ostriker 1977, MNRAS, 179, 541 01641 Galaxy formation Galaxy and cluster masses and radii; gas fragmentation
Sachs & Wolfe 1967, ApJ, 147, 73 01607 Cosmology; CMB CMB fluctuations; Sachs-Wolfe effect
Salpeter 1955, ApJ, 121, 161 06190 Stars The initial mass function
Schechter 1976, ApJ, 203, 297 02606 Galaxies The luminosity function
Schmidt 1959, ApJ, 129, 243 01738 Stars; galaxies The Schmidt relation
Seljak & Zaldarriaga 1996, ApJ, 469, 437 01893 Cosmology; CMB CMB fluctuations; methods used today
Shu, Adams, & Lizano 1987, AR&A, 25, 23 02252 Stars Star formation in molecular clouds
Silk & Rees 1998, A&A, 331, 1L 01641 Galaxy formation AGN feedback
Sunyaev & Zel'dovich 1972, A&A, 20, 189 00342 Galaxy formation; cluster formation Protocluster fragmentation and intergalactic gas heating
Tegmark et al. 1997, ApJ, 474, 1 00643 Galaxy formation; cosmology Minimum galaxy mass as a function of redshift
Telfer et al. 2002, ApJ, 565, 773 00461 Galaxies Quasar template spectrum
Toomre & Toomre 1972, ApJ, 178, 623 02401 Galaxies Theoretical explanation of galaxy tidal tails
White & Rees 1978, MNRAS, 183, 341 02736 Galaxy formation Gas cooling
Wolfe et al. 1986, ApJS, 61, 249 00601 Galaxies Damped Lyman alpha absorbers


Click a paper entry to view notes about that paper; click a name to view that person's presentation times.

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week 3819 Sep 2019
Topic: Expansion of the Universe
Stian9:30 - 10:30

Riess et al. (1998, AJ, 116, 1009)

Observational Evidence From Supernovae For An Accelerating Universe And A Cosmological Constant

Stian's notes (as .pdf)

  • What is the paper about?
    • The paper is about the observational evidence from luminosity distance measurements of SNe Ia for a positive non-zero cosmological constant and the accelerated expansion of the universe.
  • What are the physical assumptions made?
    • The paper assumes a universe with (positive) matter energy density and a cosmological constant.
  • What is the most important conclusion?
    • The most important conclusion is the existence of a non-zero and positive cosmological constant, and the accelerated expansion of the universe.
  • What is the secondary conclusion?
    • The secondary conclusion is the estimate of the age of the universe to be about 14.2Gyr, and that the flat universe with only matter is ruled out at very high sigma. It also found a value for the Hubble parameter.
  • What has the impact of the paper on the field been?
    • The paper showed that contrary to the current belief that the expansion of the universe was slowing down, it was actually accelerating, and provided evidence for the existence of a dark energy.
  • Is the work still important?
    • It is still important in the sense that it laid the observational foundation for research into the nature of dark energy which is still ongoing.
Other notes
  • Used SNe Ia because they are believed to be very regular in their characteristics. This is because they are exploding white dwarfs that exceeds the Chandrasekar mass-limit through accretion, so the initial state will be very similar for all such SNe.
  • Used two methods to determine the absolute magnitude of observed SN Ia, a template fitting based on nearby SN, and a so-called “linear estimation algorithm”, or the “MLCS” method. There was also a third method (so-called “snapshot” method) used on four SN that were too sparsely sampled for the above two methods to be applicable.
  • The dominant source of statistical uncertainty is from the excitation measurements.
  • The paper makes several different analysis: They include and exclude in different combinations SN data that for some reason could be bad (e.g. nearby SN that could be inside a local void, or SN data that could be another type of SN than SN Ia). They use various prior, such as assuming a flat space, zero cosmological constant. Despite this they always get that a non-zero and positive cosmological constant is preferred.
  • The confidence intervals are very elliptical (see fig 7), and lie approximately along the lines of equal age for the universe (see fig 9), so that even though the constraints on Omega_m0 and Omega_Lambda0 separately are weak, the age of the universe could still be determined quite well.
  • The age of the universe from the paper is consistent with stellar theory and radioactive dating.
Systematic uncertainties considered
  • Evolution
    • The local sample of SN show a weak correlation between light curve shape and host galaxy type, and there are observations that could indicate an evolution of SNe Ia with progenitor age. Since the early-times and late-time galaxy types differ there could be a difference in the SN they host. However, it was not found to change the result of a positive non-zero cosmological constant.
  • Extinction
    • Extinction is a major source of error in the distance uncertainties. It could be that the size of the dust grains vary from early-times to late-times, causing a redshift-dependent extinction that was not considered. Or it could induce a dispersion in the derived distances. However, both effects were concluded to not be plausible explanations for the observed faintness of high-redshift SNe Ia.
  • Selection Bias
    • Sample selection bias could distort the comparison between nearby and distant SNe. Examples of selection biasas are that the SN searched preferentially detect intrinsically luminous SNe, or “brighter-than-usual” SNe for a particular light curve shape, and that different types of searches select SNe Ia with different parameters or environments, so that a comparison is affected. It is concluded that more work is needed and that they must continue to be wary of subtle biases that affect the comparisons of neaby and distant SNe Ia.
  • Effect of a Local Void
    • In another work (Zehavi et al 1998) it was noted that the local expansion is greater than that measured for more distant objects. This could be because we are in a local void, i.e. lower mean matter density than the global mean. Since the paper is probing the global expansion, this local effect could give a false impression of a non-zero positive cosmological constant. They test the effect of a local void on the cosmological parameters by excluding the nearby SNe Ia in this possible local void and find that the effect is relatively small, and doesn’t change the conclusion.
  • Weak Gravitational Lensing
    • It is expected that SNe light will on average be demagnified, or dimmed, by 0.5% at z=0.5 and 1% at z=1 due to gravitational lensing. While this effect could give a false impression of a cosmological constant, it is far too small to affect the analysis. They also considered if matter was clumped in stars and DM MACHOs, which would give a larger microlensing, but it would still be too small to explain the observed SNe distances without a cosmological constant.
  • Light Curve Fitting Method
    • While they find a few differences with the two methods, such as a small difference in distances and scatter, which results in slightly different confidence intervals (see figs 6, 7, 8 and Table 8), both methods favor the existence of a non-zero positive cosmological constant and accelerated expansion.
  • Sample Contamination
    • It could be that SN types that are not Ia contaminated the data-set, which would make some of the distance measurements incorrect and could result in an incorrect conclusion. The classification of a SN is determined from the presence or absence of specific characteristics in the spectrum. But for SNe at high redshift some of these characteristics are shift out of the observer’s frequency range, and there are low signal-to-noise ratio cases. In the paper they do their analysis both with and without two of the most likely SN samples to be a contamination to see its effect on the result, which was found to be very small. However, they note that contamination of future samples is a concern.
Renate10:30 - 11:30

Davis & Lineweaver (2004, PASA, 21, 97)

Expanding Confusion: Common Misconceptions of Cosmological Horizons and the Superluminal Expansion of the Universe

Renate's notes (as .pdf)
week 4030 Sep 2019
Topic: Galaxy formation
Robert14:00 - 15:00

Dressler et al. (1980, ApJ, 236, 351)

Galaxy morphology in rich clusters - Implications for the formation and evolution of galaxies

Here Robert will add his notes

Isabel15:00 - 16:00

Dekel & Silk (1986, ApJ, 303, 39)

The origin of dwarf galaxies, cold dark matter, and biased galaxy formation

Isabel's notes (as .pdf)

week 4217 Oct 2019
Topic: More galaxies…
Renate9:30 - 10:30

Partridge & Peebles (1967, ApJ, 147, 868)

Are Young Galaxies Visible?

Renate's notes (as .pdf)
Isabel10:30 - 11:30

Salpeter (1955, ApJ, 121, 161)

The Luminosity Function and Stellar Evolution

Isabel's notes (as .pdf)

week 4431 Oct 2019
Topic: Cosmology
Håvard9:30 - 10:30

Press & Schechter (1974, ApJ, 187, 425)

Formation of Galaxies and Clusters of Galaxies by Self-Similar Gravitational Condensation

Håvard's notes (as .jpg)
Slađa10:30 - 11:30

Planck Collaboration (2018, arXiv:1807.06205)

Planck 2018 results. VI. Cosmological parameters

Here Slađa will add her notes

week 4614 Nov 2019
Topic: Dark matter halo profiles
Stian9:30 - 10:30

Navarro et al. (1996, ApJ, 462, 563)

The Structure of Cold Dark Matter Halos

Here Stian will add his notes

Robert10:30 - 11:30

Navarro et al (1997, ApJ, 490, 493)

A Universal Density Profile from Hierarchical Clustering

Here Robert will add his notes

week 4828 Nov 2019
Topic: The discovery of the CMB
Slađa9:30 - 10:30

Penzias & Wilson (1965, ApJ, 142, 419)

A Measurement of Excess Antenna Temperature at 4080 Mc/s

Here Slađa will add her notes

Håvard10:30 - 11:30

Dicke et al. (1965, ApJ, 142, 414)

Cosmic Black-Body Radiation

Here Håvard will add his notes