Morphological Analysis of the Centimeter‐Wave Continuum in the Dark Cloud LDN 1622

Casassus, S.; Cabrera, Guillermo; Förster, F.; Pearson, T. J.; Readhead, A. C. S.; Dickinson, C.

doi:10.1086/499517

Cited by 119 publications

(172 citation statements)

References 36 publications

Supporting

Mentioning

164

Contrasting

Order By: Relevance

“…Indications of an improved correlation with these data have been seen on smaller scales by e.g., Casassus et al (2006). However, these data are considerably contaminated by zodiacal light and other systematics; as such, we have masked the ecliptic plane (|β| < 20 • ) before fitting these data.…”

Section: All-sky Correlationsmentioning

confidence: 90%

Planck2015 results

Ade

Aghanim

Alves

et al. 2016

A&A

Self Cite

165

View full text Add to dashboard Cite

We discuss the Galactic foreground emission between 20 and 100 GHz based on observations by Planck and WMAP. The total intensity in this part of the spectrum is dominated by free-free and spinning dust emission, whereas the polarized intensity is dominated by synchrotron emission. The Commander component-separation tool has been used to separate the various astrophysical processes in total intensity. Comparison with radio recombination line templates verifies the recovery of the free-free emission along the Galactic plane. Comparison of the high-latitude Hα emission with our free-free map shows residuals that correlate with dust optical depth, consistent with a fraction (≈30%) of Hα having been scattered by high-latitude dust. We highlight a number of diffuse spinning dust morphological features at high latitude. There is substantial spatial variation in the spinning dust spectrum, with the emission peak (in I ν ) ranging from below 20 GHz to more than 50 GHz. There is a strong tendency for the spinning dust component near many prominent H ii regions to have a higher peak frequency, suggesting that this increase in peak frequency is associated with dust in the photo-dissociation regions around the nebulae. The emissivity of spinning dust in these diffuse regions is of the same order as previous detections in the literature. Over the entire sky, the Commander solution finds more anomalous microwave emission (AME) than the WMAP component maps, at the expense of synchrotron and free-free emission. This can be explained by the difficulty in separating multiple broadband components with a limited number of frequency maps. Future surveys, particularly at 5-20 GHz, will greatly improve the separation by constraining the synchrotron spectrum. We combine Planck and WMAP data to make the highest signal-to-noise ratio maps yet of the intensity of the all-sky polarized synchrotron emission at frequencies above a few GHz. Most of the high-latitude polarized emission is associated with distinct large-scale loops and spurs, and we re-discuss their structure. We argue that nearly all the emission at 40 • > l > −90 • is part of the Loop I structure, and show that the emission extends much further in to the southern Galactic hemisphere than previously recognised, giving Loop I an ovoid rather than circular outline. However, it does not continue as far as the "Fermi bubble/microwave haze", making it less probable that these are part of the same structure. We identify a number of new faint features in the polarized sky, including a dearth of polarized synchrotron emission directly correlated with a narrow, roughly 20 • long filament seen in Hα at high Galactic latitude. Finally, we look for evidence of polarized AME, however many AME regions are significantly contaminated by polarized synchrotron emission, and we find a 2σ upper limit of 1.6% in the Perseus region.

show abstract

Section: All-sky Correlationsmentioning

confidence: 90%

Planck2015 results

Ade

Aghanim

Alves

et al. 2016

A&A

Self Cite

165

View full text Add to dashboard Cite

show abstract

“…Draine & Lazarian 1998a;Lagache 2003;de Oliveira-Costa et al 2004;Finkbeiner et al 2004;Casassus et al 2006;Miville-Deschênes et al 2008;Dobler & Finkbeiner 2008). This excess is best explained by small rotating dust grains ("spinning dust" Draine & Lazarian 1998b).…”

Section: Introductionmentioning

confidence: 99%

Submillimeter to centimeter excess emission from the Magellanic Clouds

Bot

Ysard

Paradis

et al. 2010

A&A

115

140

View full text Add to dashboard Cite

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.

show abstract

“…Indeed it is too bright to be free-free emission, and it is not polarised as thermal dust or synchrotron emissions would be. However, it is correlated with dust IR emission and especially with the interstellar PAH and very-small-grain (VSG) emission in the mid-IR (Casassus et al 2006;Scaife et al 2010). Anomalous emission was first proposed by Draine & Lazarian (1998) to come from rapidly rotating PAHs (Rouan et al 1992), the spinning dust grains.…”

Section: Anomalous Microwave Emissionmentioning

confidence: 99%

Planckearly results. XXI. Properties of the interstellar medium in the Galactic plane

Abergel¹,

Ade²,

Aghanim³

et al. 2011

A&A

Self Cite

121

View full text Add to dashboard Cite

Planck has observed the entire sky from 30 GHz to 857 GHz. The observed foreground emission contains contributions from different phases of the interstellar medium (ISM). We have separated the observed Galactic emission into the different gaseous components (atomic, molecular and ionised) in each of a number of Galactocentric rings. This technique provides the necessary information to study dust properties (emissivity, temperature, etc.), as well as other emission mechanisms as a function of Galactic radius. Templates are created for various Galactocentric radii using velocity information from atomic (neutral hydrogen) and molecular ( 12 CO) observations. The ionised template is assumed to be traced by free-free emission as observed by WMAP, while 408 MHz emission is used to trace the synchrotron component. Gas emission not traced by the above templates, namely "dark gas", as evidenced using Planck data, is included as an additional template, the first time such a component has been used in this way. These templates are then correlated with each of the Planck frequency bands, as well as with higher frequency data from IRAS and DIRBE along with radio data at 1.4 GHz. The emission per column density of the gas templates allows us to create distinct spectral energy distributions (SEDs) per Galactocentric ring and in each of the gaseous tracers from 1.4 GHz to 25 THz (12 μm). The resulting SEDs allow us to explore the contribution of various emission mechanisms to the Planck signal. Apart from the thermal dust and free-free emission, we have probed the Galaxy for anomalous (e.g., spinning) dust as well as synchrotron emission. We find the dust opacity in the solar neighbourhood, τ/N H = 0.92 ± 0.05 × 10 −25 cm 2 at 250 μm, with no significant variation with Galactic radius, even though the dust temperature is seen to vary from over 25 K to under 14 K. Furthermore, we show that anomalous dust emission is present in the atomic, molecular and dark gas phases throughout the Galactic disk. Anomalous emission is not clearly detected in the ionised phase, as free-free emission is seen to dominate. The derived dust propeties associated with the dark gas phase are derived but do not allow us to reveal the nature of this phase. For all environments, the anomalous emission is consistent with rotation from polycyclic aromatic hydrocarbons (PAHs) and, according to our simple model, accounts for (25 ± 5)% (statistical) of the total emission at 30 GHz.

show abstract

Morphological Analysis of the Centimeter‐Wave Continuum in the Dark Cloud LDN 1622

Cited by 119 publications

References 36 publications

Planck2015 results

Planck2015 results

Submillimeter to centimeter excess emission from the Magellanic Clouds

Planckearly results. XXI. Properties of the interstellar medium in the Galactic plane

Contact Info

Product

Resources

About