AMI limits on 15-GHz excess emission in northern H ii regions

Scaife, Anna M. M.; Hurley‐Walker, N.; Davies, Matthew; Duffett-Smith, Peter; Feroz, Farhan; Grainge, Keith; Green, David A.; Hobson, M.; Kaneko, T.; Lasenby, A.; Pooley, G. G.; Saunders, Richard D. E.; Scott, Paul F.; Titterington, D.; Waldram, Elizabeth; Zwart, Jonathan T. L.

doi:10.1111/j.1365-2966.2007.12743.x

Cited by 35 publications

(38 citation statements)

References 57 publications

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“…The majority of AME sources are diffuse, including the Perseus and ρ Ophiuchi clouds; Tibbs et al (2010) found that in the Perseus molecular cloud at least 90% of the AME comes from diffuse extended emission. Surveys at higher resolution do not appear to detect strong AME; Scaife et al (2008) found little or no detectable AME from a sample of relatively compact ( 1 ) H ii regions.…”

Section: Statistical Study Of Ame Regionsmentioning

confidence: 88%

“…Although this is a considerable fraction, it is less than what has been observed in the diffuse Galactic foreground at high latitudes, where the dust-correlated AME is the dominant component and accounts for approximately 75% of the total 30 GHz emission (Davies et al 2006;Ghosh et al 2012). On the other hand, other measurements (Dickinson et al 2007;Scaife et al 2008) have found much less or no AME as a fraction of the total flux density. Sources with a smaller AME fraction ( 20%) may be prevalent, but are much more difficult to detect since the other non-AME components must be accurately removed first.…”

Section: Ame Fraction and Ire -H II Or Molecular Dust Clouds?mentioning

confidence: 90%

“…Dickinson et al (2007) observed six southern H ii regions with the Cosmic Background Imager at 31 GHz and found tentative evidence for excess emission from the RCW49 complex. Scaife et al (2008) observed a sample of 16 compact H ii regions at 15 GHz with the Arcminute Microkelvin Imager (AMI) and found no evidence for excess emission; the spectrum was consistent with optically thin freefree emission from warm ionized gas. Todorović et al (2010) surveyed the Galactic plane at longitudes 27…”

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confidence: 99%

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Planckintermediate results. XV. A study of anomalous microwave emission in Galactic clouds

Ade¹,

Aghanim²,

Alves³

et al. 2014

A&A

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Anomalous microwave emission (AME) is believed to be due to electric dipole radiation from small spinning dust grains. The aim of this paper is a statistical study of the basic properties of AME regions and the environment in which they emit. We used WMAP and Planck maps, combined with ancillary radio and IR data, to construct a sample of 98 candidate AME sources, assembling SEDs for each source using aperture photometry on 1• -smoothed maps from 0.408 GHz up to 3000 GHz. Each spectrum is fitted with a simple model of free-free, synchrotron (where necessary), cosmic microwave background (CMB), thermal dust, and spinning dust components. We find that 42 of the 98 sources have significant (>5σ) excess emission at frequencies between 20 and 60 GHz. An analysis of the potential contribution of optically thick free-free emission from ultracompact H ii regions, using IR colour criteria, reduces the significant AME sample to 27 regions. The spectrum of the AME is consistent with model spectra of spinning dust. Peak frequencies are in the range 20−35 GHz except for the California nebula (NGC 1499), which appears to have a high spinning dust peak frequency of (50 ± 17) GHz. The AME regions tend to be more spatially extended than regions with little or no AME. The AME intensity is strongly correlated with the sub-millimetre/IR flux densities and comparable to previous AME detections in the literature. AME emissivity, defined as the ratio of AME to dust optical depth, varies by an order of magnitude for the AME regions. The AME regions tend to be associated with cooler dust in the range 14−20 K and an average emissivity index, β d , of +1.8, while the non-AME regions are typically warmer, at 20−27 K. In agreement with previous studies, the AME emissivity appears to decrease with increasing column density. This supports the idea of AME originating from small grains that are known to be depleted in dense regions, probably due to coagulation onto larger grains. We also find a correlation between the AME emissivity (and to a lesser degree the spinning dust peak frequency) and the intensity of the interstellar radiation field, G 0 . Modelling of this trend suggests that both radiative and collisional excitation are important for the spinning dust emission. The most significant AME regions tend to have relatively less ionized gas (free-free emission), although this could be a selection effect. The infrared excess, a measure of the heating of dust associated with H ii regions, is typically >4 for AME sources, indicating that the dust is not primarily heated by hot OB stars. The AME regions are associated with known dark nebulae and have higher 12 μm/25 μm ratios. The emerging picture is that the bulk of the AME is coming from the polycyclic aromatic hydrocarbons and small dust grains from the colder neutral interstellar medium phase.

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Section: Statistical Study Of Ame Regionsmentioning

confidence: 88%

Section: Ame Fraction and Ire -H II Or Molecular Dust Clouds?mentioning

confidence: 90%

mentioning

confidence: 99%

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Planckintermediate results. XV. A study of anomalous microwave emission in Galactic clouds

Ade¹,

Aghanim²,

Alves³

et al. 2014

A&A

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“…Even though AME has been detected on arcmin scales (Scaife et al 2009;Tibbs et al 2013), the emission appears to be correlated with the strength of the radiation field rather than the column of small grains/PAHs along some sight-lines (Tibbs et al 2011(Tibbs et al , 2012. Also, in some objects (such as compact HII regions), the data have failed to detect AME at all (Scaife et al 2008). The AME could also be due to another mechanism, such as thermal fluctuations in magnetic grains (a.k.a.…”

Section: Introductionmentioning

confidence: 92%

Studies of Anomalous Microwave Emission (AME) with the SKA

Dickinson¹,

Ali-Hamoud²,

Beswick³

et al. 2015

Proceedings of Advancing Astrophysics With the Square Kilometre Array — PoS(AASKA14)

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In this chapter, we will outline the scientific motivation for studying Anomalous Microwave Emission (AME) with the SKA. AME is thought to be due to electric dipole radiation from small spinning dust grains, although thermal fluctuations of magnetic dust grains may also contribute. Studies of this mysterious component would shed light on the emission mechanism, which then opens up a new window onto the interstellar medium (ISM). AME is emitted mostly in the frequency range ∼ 10-100 GHz, and thus the SKA has the potential of measuring the low frequency side of the AME spectrum, particularly in band 5. Science targets include dense molecular clouds in the Milky Way, as well as extragalactic sources. We also discuss the possibility of detecting rotational line emission from Poly-cyclic Aromatic Hydrocarbons (PAHs), which could be the main carriers of AME. Detecting PAH lines of a given spacing would allow for a definitive identification of specific PAH species.

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“…Anomalous emission was first proposed by Draine & Lazarian (1998) to come from rapidly rotating PAHs (Rouan et al 1992), the spinning dust grains. Since, it has been observed in various interstellar environments: dark clouds (Watson et al 2005;Casassus et al 2006;Scaife et al 2009;Dickinson et al 2010); H ii regions Scaife et al 2008); planetary nebulae (Casassus et al 2007) and diffuse ISM (Miville-Deschênes et al 2008). Several processes can excite or damp the grains' rotation: pho- Fig.…”

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

120

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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.

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AMI limits on 15-GHz excess emission in northern H ii regions

Cited by 35 publications

References 57 publications

Planckintermediate results. XV. A study of anomalous microwave emission in Galactic clouds

Planckintermediate results. XV. A study of anomalous microwave emission in Galactic clouds

Studies of Anomalous Microwave Emission (AME) with the SKA

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

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