Constraining non standard recombination: A worked example

Abstract

We fit the BOOMERANG, MAXIMA and COBE/DMR measurements of the cosmic microwave background anisotropy in spatially flat cosmological models where departures from standard recombination of the primeval plasma are parametrized through a change in the fine structure constant $\alpha$ compared to its present value. In addition to $\alpha$ we vary the baryon and dark matter densities, the spectral index of scalar fluctuations, and the Hubble constant. Within the class of models considered, the lack of a prominent second acoustic peak in the measured spectrum can be accomodated either by a relatively large baryon density, by a tilt towards the red in the spectrum of density fluctuations, or by a delay in the time at which neutral hydrogen formed. The ratio between the second and first peak decreases by around 25% either if the baryon density ${\Omega }_b{h}^2$ is increased or the spectral index $n$ decreased by a comparable amount, or if neutral hydrogen formed at a redshift $z_{\ast }$ about 15% smaller than its standard value. We find that the present data is best fitted by a delay in recombination, with a lower baryon density than the best fit if recombination is standard. Our best fit model has $z_{\ast }=900$, ${\Omega }_b{h}^2=0.024$, ${\Omega }_m{h}^2=0.14$, $H_0=49$ and $n=1.02$. Compatible with present data at 95% confidence level $780<z_{\ast }<1150$, $0.018<{\Omega }_b{h}^2<0.036$, $0.07<{\Omega }_m{h}^2<0.3$ and $0.9<n<1.2$.

9 pages, 6 figs. Version accepted for publication in Phys.Rev.D

References in corpus (11)

• A Flat Universe from High-Resolution Maps of the Cosmic Microwave Background Radiation
• MAXIMA-1: A Measurement of the Cosmic Microwave Background Anisotropy on angular scales of 10 arcminutes to 5 degrees
• First Estimations of Cosmological Parameters From BOOMERANG
• Review of Big Bang Nucleosynthesis and Primordial Abundances
• Current cosmological constraints from a 10 parameter CMB analysis
• New CMB constraints on the cosmic matter budget: trouble for nucleosynthesis?
• Looking for a varying $\alpha$ in the Cosmic Microwave Background
• Photoproduction of Charmonia and Total Charmonium-Proton Cross Sections
• Delayed Recombination
• VSL theories and the Doppler peak
• Boomerang returns unexpectedly

Cited by in corpus (29)

• The fundamental constants and their variation: observational status and theoretical motivations
• Varying constants, Gravitation and Cosmology
• New varying speed of light theories
• Changing alpha With Time: Implications For Fifth-Force-Type Experiments And Quintessence
• E/B decomposition of finite pixelized CMB maps
• Models of quintessence coupled to the electromagnetic field and the cosmological evolution of alpha
• Probing the Friedmann equation during recombination with future CMB experiments
• Planck intermediate results. XXIV. Constraints on variation of fundamental constants
• Probing variations in fundamental constants with radio and optical quasar absorption-line observations
• Varying Constants
• Cosmology with varying fundamental constants from hyperlight, coupled scalars
• Early Universe Constraints on Time Variation of Fundamental Constants
• Testing theories that predict time variation of fundamental constants
• CMB constraints on the fine structure constant
• Model Independent Primordial Power Spectrum from Maxima, Boomerang, and DASI Data
• Recombining WMAP: constraints on ionizing and resonance radiation at recombination
• Varying Couplings in Electroweak Theory
• Varying-Alpha Cosmologies with Potentials
• Delayed Recombination and Cosmic Parameters
• Time Evolution of the Fine Structure Constant in a Two-Field Quintessence Model
• Cosmological constraints in the presence of ionizing and resonance radiation at recombination
• Delayed Recombination and Standard Rulers
• Dimensionless cosmology
• Variation of the fine structure constant in the light of recent helium abundance measurement
• Recent CMB Observations and the Ionization History of the Universe
• Time varying $\alpha$ in N=8 extended Supergravity
• Manifestations of dark matter and variations of fundamental constants in atoms and astrophysical phenomena
• Variations of the Fine Structure Constant in Space and Time
• Cosmological Constraints on Radion Evolution in the Universal Extra Dimension Model