The long-wavelength emission of interstellar PAHs: characterizing the spinning dust contribution

Ysard, N.; Verstraete, L.

doi:10.1051/0004-6361/200912708

Cited by 89 publications

(62 citation statements)

References 45 publications

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“…We have not included the near-IR bands between 1 and 2 μm, which have little effect on the emission. We added the far-IR bands defined by Ysard & Verstraete (2010) from the Malloci database. The PAHs are assumed to be disk-like and their size, a, is defined to be that of an equivalent sphere of the same mass, assuming a density of ρ = 2.24 g/cm 3 .…”

Section: Appendix A: Dust Propertiesmentioning

confidence: 99%

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

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Verstraete

Jones

et al. 2010

A&A

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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: Appendix A: Dust Propertiesmentioning

confidence: 99%

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

Compiègne

Verstraete

Jones

et al. 2010

A&A

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“…Unlike the excess in the Magellanic clouds, Galactic excess peaks between 20 and 40 GHz. However, models predict that the peak frequency of spinning dust emission shifts with radiation field intensity, interstellar gas physical parameters 2 , grain size distribution, and electric dipole moment (Ali-Haïmoud et al 2009;Ysard & Verstraete 2010).…”

Section: Spinning Dust Emission?mentioning

confidence: 99%

“…Anomalous dust emission remains poorly constrained by observations (in particular its variations with the environment). Theoretical models predict that the peak frequency of spinning dust emission should shift with grain size or density (Ali-Haïmoud et al 2009;Ysard & Verstraete 2010). What is the influence of spinning dust emission on submillimeter to radio spectral energy distribution of galaxies?…”

Section: Introductionmentioning

confidence: 99%

Submillimeter to centimeter excess emission from the Magellanic Clouds

Bot

Ysard

Paradis

et al. 2010

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Context. Dust emission at sub-millimeter to centimeter wavelengths is often simply the Rayleigh-Jeans tail of dust particles at thermal equilibrium and is used as a cold mass tracer in various environments, including nearby galaxies. However, well-sampled spectral energy distributions of the nearby, star-forming Magellanic Clouds have a pronounced (sub-)millimeter excess. Aims. This study attempts to confirm the existence of this millimeter excess above expected dust, free-free and synchrotron emission and to explore different possibilities for its origin. Methods. We model near-infrared to radio spectral energy distributions of the Magellanic Clouds with dust, free-free, and synchrotron emission. A millimeter excess emission is confirmed above these components and its spectral shape and intensity are analyzed in light of different scenarios: very cold dust, cosmic microwave background (CMB) fluctuations, a change of the dust spectral index and spinning dust emission. Results. We show that very cold dust or CMB fluctuations are very unlikely explanations for the observed excess in these two galaxies. The excess in the Large Magellanic Cloud can be satisfactorily explained either by a change of the spectral index related to intrinsic properties of amorphous grains, or by spinning dust emission. In the Small Magellanic Cloud, however, the excess is larger and the dust grain model including TLS/DCD effects cannot reproduce the observed emission in a simple way. A possible solution was achieved with spinning dust emission, but many assumptions on the physical state of the interstellar medium had to be made. Conclusions. Further studies, with higher resolution data from Planck and Herschel are needed to probe the origin of this observed submillimeter-centimeter excess more definitely. Our study shows that the different possible origins will be best distinguished where the excess is the highest, as is the case in the Small Magellanic Cloud.

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“…Studies by Anderson & Watson (1993), Draine & Lazarian (1998), Hoang et al (2010), Silsbee et al (2011) or the recent Planck results (Planck Collaboration 2011a) aimed to characterise this component which explains most of the 10−100 GHz emission, also called the anomalous foreground. Ysard & Verstraete (2010) recently suggested that their peak frequency could depend on different parameters (radiation field intensity, size distribution of the dust species, dipole moment distribution, physical parameters of the gas phases etc.) and thus that spinning dust emission could be responsible for the excess at submm wavelengths observed in some galaxies, as recently suggested by Bot et al (2010) for the Large Magellanic Cloud.…”

Section: Introductionmentioning

confidence: 99%

Probing the dust properties of galaxies up to submillimetre wavelengths

Galametz

Madden

Galliano

et al. 2011

A&A

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Aims. We are studying the effects of submm observations on the total dust mass and thus dust-to-gas mass ratio measurements. Methods. We gather a wide sample of galaxies that have been observed at submillimeter (submm) wavelengths to model their spectral energy distributions using submm observations (>160 μm) and then without submm observational constraints in order to quantify the error on the dust mass when submm data are not available. Our model does not make strong assumptions on the dust temperature distribution to precisely avoid submm biaises in the study. Our sample includes 52 galaxies observed at submm wavelengths. Out of these, 9 galaxies show an excess in submm which is not accounted for in our fiducial model, most of these galaxies being lowmetallicity dwarfs. We chose to add an independant very cold dust component (T = 10 K) to account for this excess. Results. We find that metal-rich galaxies modelled with submm data often show lower dust masses than when modelled without submm data. Indeed, these galaxies usually have dust SEDs that peaks at longer wavelengths and require constraints above 160 μm to correctly position the peak and sample the submillimeter slope of their SEDs and thus correctly cover the dust temperature distribution. On the other hand, some metal-poor dwarf galaxies modelled with submm data show higher dust masses than when modelled without submm data. Using submm constraints for the dust mass estimates, we find a tightened correlation of the dust-to-gas mass ratio with the metallicity of the galaxies. We also often find that when there is a submm excess present, it occurs preferentially in low-metallicity galaxies. We analyse the conditions for the presence of this excess and find a relation between the 160/850 μm ratio and the submm excess.

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The long-wavelength emission of interstellar PAHs: characterizing the spinning dust contribution

Cited by 89 publications

References 45 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

Submillimeter to centimeter excess emission from the Magellanic Clouds

Probing the dust properties of galaxies up to submillimetre wavelengths

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