Towards a free-free template for CMB foregrounds

Dickinson, C.; Davies, R. D.; Davis, R. J.

doi:10.1046/j.1365-8711.2003.06439.x

Cited by 223 publications

(351 citation statements)

References 56 publications

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“…For WMAP, we used the seven-year temperature maps (Jarosik et al 2010), and subtracted the cosmic microwave background (CMB) using the map obtained with the internal linear combination method (Gold et al 2010). The free-free contribution to the emission was subtracted using the model of Dickinson et al (2003).…”

Section: The Observablesmentioning

confidence: 99%

The global dust SED: tracing the nature and evolution of dust with DustEM

Compiègne

Verstraete

Jones

et al. 2010

A&A

411

724

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The Planck and Herschel missions are currently measuring the far-infrared to millimeter emission of dust, which combined with existing IR data, will for the first time provide the full spectral energy distribution (SED) of the galactic interstellar medium dust emission, from the mid-IR to the mm range, with an unprecedented sensitivity and down to spatial scales ∼30 . Such a global SED will allow a systematic study of the dust evolution processes (e.g. grain growth or fragmentation) that directly affect the SED because they redistribute the dust mass among the observed grain sizes. The dust SED is also affected by variations of the radiation field intensity. Here we present a versatile numerical tool, DustEM, that predicts the emission and extinction of dust grains given their size distribution and their optical and thermal properties. In order to model dust evolution, DustEM has been designed to deal with a variety of grain types, structures and size distributions and to be able to easily include new dust physics. We use DustEM to model the dust SED and extinction in the diffuse interstellar medium at high-galactic latitude (DHGL), a natural reference SED that will allow us to study dust evolution. We present a coherent set of observations for the DHGL SED, which has been obtained by correlating the IR and HI-21 cm data. The dust components in our DHGL model are (i) polycyclic aromatic hydrocarbons; (ii) amorphous carbon and (iii) amorphous silicates. We use amorphous carbon dust, rather than graphite, because it better explains the observed high abundances of gas-phase carbon in shocked regions of the interstellar medium. Using the DustEM model, we illustrate how, in the optically thin limit, the IRAS/Planck HFI (and likewise Spitzer/Herschel for smaller spatial scales) photometric band ratios of the dust SED can disentangle the influence of the exciting radiation field intensity and constrain the abundance of small grains (a < ∼ 10 nm) relative to the larger grains. We also discuss the contributions of the different grain populations to the IRAS, Planck (and similarly to Herschel) channels. Such information is required to enable a study of the evolution of dust as well as to systematically extract the dust thermal emission from CMB data and to analyze the emission in the Planck polarized channels. The DustEM code described in this paper is publically available.

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Section: The Observablesmentioning

confidence: 99%

The global dust SED: tracing the nature and evolution of dust with DustEM

Compiègne

Verstraete

Jones

et al. 2010

A&A

411

724

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“…Theoretical calculations of free-free emission in an electrically medium consisting of ions and electrons give the brightness temperature at frequency ν as (Dickinson et al 2003)…”

Section: Free-free Radiationmentioning

confidence: 99%

Extracting H i cosmological signal with generalized needlet internal linear combination

Olivari¹,

Remazeilles²,

Dickinson³

2015

Mon. Not. R. Astron. Soc.

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HI intensity mapping is a new observational technique to map fluctuations in the large-scale structure of matter using the 21 cm emission line of atomic hydrogen (HI). Sensitive HI intensity mapping experiments have the potential to detect Baryon Acoustic Oscillations (BAO) at low redshifts (z 1) in order to constrain the properties of dark energy. Observations of the HI signal will be contaminated by instrumental noise and, more significantly, by astrophysical foregrounds, such as Galactic synchrotron emission, which is at least four orders of magnitude brighter than the HI signal. Foreground cleaning is recognised as one of the key challenges for future radio astronomy surveys. We study the ability of the Generalized Needlet Internal Linear Combination (GNILC) method to subtract radio foregrounds and to recover the cosmological HI signal for a general HI intensity mapping experiment. The GNILC method is a new technique that uses both frequency and spatial information to separate the components of the observed data. Our results show that the method is robust to the complexity of the foregrounds. For simulated radio observations including HI emission, Galactic synchrotron, Galactic free-free, radio sources and 0.05 mK thermal noise, we find that the GNILC method can reconstruct the HI power spectrum for multipoles 30 < < 150 with 6% accuracy on 50% of the sky for a redshift z ∼ 0.25.

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“…Dickinson et al 2003;Tabatabaei et al 2007b). The brightest recombination line data available, the Hα line emission, is used for both galaxies.…”

Section: Free-free and Synchrotron Emissionmentioning

confidence: 99%

“…with a 1 (Dickinson et al 2003). The factor (1 + 0.08) takes the contribution from singly ionized He into account.…”

mentioning

confidence: 99%

Multi-scale radio-infrared correlations in M 31 and M 33: The role of magnetic fields and star formation

Tabatabaei

Berkhuijsen

Frick

et al. 2013

A&A

101

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Interstellar magnetic fields and the propagation of cosmic ray electrons have an important impact on the radio-infrared (IR) correlation in galaxies. This becomes evident when studying different spatial scales within galaxies. We investigate the correlation between the IR and free-free/synchrotron radio continuum emission at 20 cm from the two local group galaxies M 31 and M 33 on spatial scales between 0.4 and 10 kpc. The multi-scale radio-IR correlations have been carried out using a wavelet analysis. The free-free and IR emission are correlated on all scales, but on some scales the synchrotron emission is only marginally correlated with the IR emission. The synchrotron-IR correlation is stronger in M 33 than in M 31 on small scales (<1 kpc), but it is weaker than in M 31 on larger scales. Taking the smallest scale on which the synchrotron-IR correlation exists as the propagation length of cosmic ray electrons, we show that the difference on small scales can be explained by the smaller propagation length in M 33 than in M 31. On large scales, the difference is due to the thick disk/halo in M 33, which is absent in M 31. A comparison of our data with data on NGC 6946, the LMC and M 51 suggests that the propagation length is determined by the ratio of ordered-to-turbulent magnetic field strength, which is consistent with diffusion of CR electrons in the ISM. As the diffusion length of CR electrons influences the radio-IR correlation, this dependence is a direct observational evidence of the importance of magnetic fields for the radio-IR correlation within galaxies. The star-formation rate per surface area only indirectly influences the diffusion length as it increases the strength of the turbulent magnetic field.

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Towards a free-free template for CMB foregrounds

Cited by 223 publications

References 56 publications

The global dust SED: tracing the nature and evolution of dust with DustEM

The global dust SED: tracing the nature and evolution of dust with DustEM

Extracting H i cosmological signal with generalized needlet internal linear combination

Multi-scale radio-infrared correlations in M 31 and M 33: The role of magnetic fields and star formation

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