A measurement of the mass density of the universe

Loh, E. D.; Spillar, Earl J.

doi:10.1086/184717

Cited by 127 publications

(45 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Current cosmological observations suggest that the Hubble constant is restricted to lie in the range 50 -100 km s −1 Mpc −1 (e.g., Riess, Press, & Kirshner, 1995), and hence the time scale H −1 0 is restricted to be greater than ∼ 10 Gyr. Additional observations (e.g., Loh & Spillar, 1986) suggest that Ω 0 < 2. Using these results, we thus obtain a lower bound on the total lifetime of the universe,…”

Section: A Future Expansion Of a Closed Universementioning

confidence: 87%

A dying universe: the long-term fate and evolutionof astrophysical objects

1997

View full text Add to dashboard Cite

This paper outlines astrophysical issues related to the long term fate of the universe. We consider the evolution of planets, stars, stellar populations, galaxies, and the universe itself over time scales which greatly exceed the current age of the universe. Our discussion starts with new stellar evolution calculations which follow the future evolution of the low mass (M type) stars that dominate the stellar mass function. We derive scaling relations which describe how the range of stellar masses and lifetimes depend on forthcoming increases in metallicity. We then proceed to determine the ultimate mass distribution of stellar remnants, i.e., the neutron stars, white dwarfs, and brown dwarfs remaining at the end of stellar evolution; this aggregate of remnants defines the "final stellar mass function". At times exceeding ∼1-10 trillion years, the supply of interstellar gas will be exhausted, yet star formation will continue at a highly attenuated level via collisions between brown dwarfs. This process tails off as the galaxy gradually depletes its stars by ejecting the majority, and driving a minority toward eventual accretion onto massive black holes. As the galaxy disperses, stellar remnants provide a mechanism for converting the halo dark matter into radiative energy. Posited weakly interacting massive particles are accreted by white dwarfs, where they subsequently annihilate with each other. Thermalization of the decay products keeps the old white dwarfs much warmer than they would otherwise be. After accounting for the destruction of the galaxy, we consider the fate of the expelled degenerate objects (planets, white dwarfs, and neutron stars) within the explicit assumption that proton decay is a viable process. The evolution and eventual sublimation of these objects is dictated by the decay of their constituent nucleons, and this evolutionary scenario is developed in some detail. After white dwarfs and neutron stars have disappeared, galactic black holes slowly lose their mass as they emit Hawking radiation. This review finishes with an evaluation of cosmological issues that arise in connection with the long-term evolution of the universe. We devote special attention to the relation between future density fluctuations and the prospects for continued large-scale expansion. We compute the evolution of the background radiation fields of the universe. After several trillion years, the current cosmic microwave background will have redshifted into insignificance; the dominant contribution to the radiation background will arise from other sources, including stars, dark matter annihilation, proton decay, and black holes. Finally, we consider the dramatic possible effects of a non-zero vacuum energy density.

show abstract

Section: A Future Expansion Of a Closed Universementioning

confidence: 87%

A dying universe: the long-term fate and evolutionof astrophysical objects

1997

View full text Add to dashboard Cite

show abstract

“…Sandage (1961a) and Brown and Tinsley (1974) showed that with the technology then available galaxy counts are not a very sensitive probe of the cosmological parameters. Loh and Spillar (1986) opened the modern exploration of the galaxy count-redshift relation at redshifts near unity, where the predicted counts are quite different in models with and without a cosmological constant (as illustrated in Figure 13.8 in .…”

Section: Galaxy Countsmentioning

confidence: 99%

The cosmological constant and dark energy

2003

View full text Add to dashboard Cite

Physics invites the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, Λ; nowadays the concept is termed dark energy or quintessence. Physics also suggests the dark energy could be dynamical, allowing the arguably appealing picture that the dark energy density is evolving to its natural value, zero, and is small now because the expanding universe is old. This alleviates the classical problem of the curious energy scale of order a millielectronvolt associated with a constant Λ. Dark energy may have been detected by recent advances in the cosmological tests. The tests establish a good scientific case for the context, in the relativistic Friedmann-Lemaître model, including the gravitational inverse square law applied to the scales of cosmology. We have well-checked evidence that the mean mass density is not much more than one quarter of the critical Einstein-de Sitter value. The case for detection of dark energy is serious but not yet as convincing; we await more checks that may come out of work in progress. Planned observations might be capable of detecting evolution of the dark energy density; a positive result would be a considerable stimulus to attempts to understand the microphysics of dark energy. This review presents the basic physics and astronomy of the subject, reviews the history of ideas, assesses the state of the observational evidence, and comments on recent developments in the search for a fundamental theory.

show abstract

“…This classical technique determines the evolution of the cosmic volume element by measuring the redshift distribution of a tracer whose number density is known, providing constraints on fundamental cosmological parameters. In the past, the abundance of galaxies was used to perform this test under the assumption that the total comoving number density of galaxies integrated over all luminosities is independent of redshift (with further assumptions about the luminosity function ; see, e.g., Loh & Spillar 1986). Such assumptions may be suspect, but improving upon them would require a reliable, comprehensive theory of galaxy formation and evolution.…”

Section: Introductionmentioning

confidence: 99%

Measuring the Cosmic Equation of State with Counts of Galaxies. II. Error Budget for the DEEP2 Redshift Survey

Newman

Davis

2002

ApJ

View full text Add to dashboard Cite

In a previous paper, we described a new variant on the classical "" dN/dz ÏÏ test that could be performed using data from the next generation of redshift surveys. By studying the apparent abundance of galaxies as a function of their circular velocity or velocity dispersion rather than luminosity, it is possible to avoid many of the uncertainties of galaxy evolution while using quantities that may be measured directly. In that work, we assumed that counting statistics would dominate the resulting errors. Here we present the results of including cosmic variance and determine the impact of systematic e †ects on attempts to perform the test with the upcoming DEEP2 Redshift Survey. For the DEEP2 survey geometry, cosmic variance yields errors roughly twice those predicted from Poisson statistics. Through Monte Carlo simulations we Ðnd that if the functional form, but not the strength, of any of the major systematic e †ects (baryonic infall, velocity errors, and incompleteness) is known, the free parameter may be determined from the observed velocity function. The systematic may then be corrected for, leaving a much smaller residual error. The total uncertainty from systematics is comparable to that from cosmic variance but is correlated among redshift bins. Based on these analyses, we present error budgets for a dN/dz measurement with DEEP2 and determine the resulting constraints on cosmological parameters. We Ðnd that the uncertainty in the cosmic equation of state parameter w are D2 times higher than previously derived, providing a measurement much stronger than any available today but weaker than some other proposed tests.

show abstract

A measurement of the mass density of the universe

Cited by 127 publications

References 0 publications

A dying universe: the long-term fate and evolutionof astrophysical objects

A dying universe: the long-term fate and evolutionof astrophysical objects

The cosmological constant and dark energy

Measuring the Cosmic Equation of State with Counts of Galaxies. II. Error Budget for the DEEP2 Redshift Survey

Contact Info

Product

Resources

About