The Spectral Results of the Far‐Infrared Absolute Spectrophotometer Instrument on<i>COBE</i>

Fixsen, D. J.; Mather, John C.

doi:10.1086/344402

Cited by 186 publications

(217 citation statements)

References 27 publications

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“…The main contribution is the cosmic microwave background (CMB) whose absolute temperature is taken to be T CBR = 2.725 ± 0.001 K based on the full COBE data set as analyzed by Fixsen & Mather (2002). This model of the microwave background represents the broadband continuum only and does not include the strong emission lines, several of which contain significant power in the far-infrared and (sub-)millimeter part of the spectrum (see, e.g., Fixsen et al 1999).…”

Section: Background Radiation Fieldmentioning

confidence: 99%

A computer program for fast non-LTE analysis of interstellar line spectra

Tak¹,

Black²,

Schöier³

et al. 2007

A&A

1,420

836

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Aims. The large quantity and high quality of modern radio and infrared line observations require efficient modeling techniques to infer physical and chemical parameters such as temperature, density, and molecular abundances. Methods. We present a computer program to calculate the intensities of atomic and molecular lines produced in a uniform medium, based on statistical equilibrium calculations involving collisional and radiative processes and including radiation from background sources. Optical depth effects are treated with an escape probability method. The program is available on the World Wide Web at http://www.sron.rug.nl/∼vdtak/radex/index.shtml. The program makes use of molecular data files maintained in the Leiden Atomic and Molecular Database (LAMDA), which will continue to be improved and expanded. Results. The performance of the program is compared with more approximate and with more sophisticated methods. An Appendix provides diagnostic plots to estimate physical parameters from line intensity ratios of commonly observed molecules. Conclusions. This program should form an important tool in analyzing observations from current and future radio and infrared telescopes.

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Section: Background Radiation Fieldmentioning

confidence: 99%

A computer program for fast non-LTE analysis of interstellar line spectra

Tak¹,

Black²,

Schöier³

et al. 2007

A&A

1,420

836

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“…According to the standard model of cosmology, the cosmic microwave background (CMB) should follow a Planck curve of temperature T CMB = (2.725 ± 0.001) × (1 + z), with 0 ≤ z ≤ 1088 +1 −2 denoting redshift (e.g., Battistelli et al 2002;Fixsen & Mather 2002;Spergel et al 2003). Determining deviations from this relation would be a powerful tool to challenge the standard model of cosmology, highlighting possible mechanisms acting upon the photons of the cosmic microwave background (e.g., Lima et al 2000).…”

Section: Article Published By Edp Sciencesmentioning

confidence: 99%

The density, the cosmic microwave background, and the proton-to-electron mass ratio in a cloud at redshift 0.9

Henkel¹,

Menten²,

Murphy

et al. 2009

A&A

151

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Based on measurements with the Effelsberg 100-m telescope, a multi-line study of molecular species is presented toward the gravitational lens system PKS 1830-211, which is by far the best known target to study dense cool gas in absorption at intermediate redshift.Determining average radial velocities and performing Large Velocity Gradient radiative transfer calculations, the aims of this study are (1) to determine the density of the gas, (2) to constrain the temperature of the cosmic microwave background (CMB), and (3) to evaluate the proton-to-electron mass ratio at redshift z ∼ 0.89. Analyzing data from six rotational HC 3 N transitions (this includes the J = 7 ← 6 line, which is likely detected for the first time in the interstellar medium) we obtain n(H 2 ) ∼ 2600 cm −3 for the gas density of the south-western absorption component, assuming a background source covering factor, which is independent of frequency. With a possibly more realistic frequency dependence proportional to ν 0.5 (the maximal exponent permitted by observational boundary conditions), n(H 2 ) ∼ 1700 cm −3 . Again toward the south-western source, excitation temperatures of molecular species with optically thin lines and higher rotational constants are, on average, consistent with the expected temperature of the cosmic microwave background, T CMB = 5.14 K. However, individually, there is a surprisingly large scatter which far surpasses expected uncertainties. A comparison of CS J = 1 ← 0 and 4 ← 3 optical depths toward the weaker north-western absorption component results in T ex = 11 K and a 1-σ error of 3 K. For the main component, a comparison of velocities determined from ten optically thin NH 3 inversion lines with those from five optically thin rotational transitions of HC 3 N, observed at similar frequencies, constrains potential variations of the proton-to-electron mass ratio μ to Δμ/μ < 1.4 × 10 −6 with 3-σ confidence. Also including optically thin rotational lines from other molecular species, it is emphasized that systematic errors are ΔV < 1 km s −1 , corresponding to Δμ/μ < 1.0 × 10 −6 .

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“…Consequently, the constraints on the energy dissipations at various cosmic times set by the currently available data (Salvaterra and Burigana, 2002) and expected by future experiments (Kogut, 1996, Fixsen and Mather, 2002, Burigana and Salvaterra, 2003, Burigana et al, 2004 can be derived, under quite general assumptions, by considering only Compton scattering, bremsstrahlung, and double Compton, other than, obviously, the considered dissipation process(es).…”

Section: Discussionmentioning

confidence: 99%