Anomalous Microwave Emission (AME) is a component of diffuse Galactic radiation observed at frequencies in the range ≈ 10-60 GHz. AME was first detected in 1996 and recognised as an additional component of emission in 1997. Since then, AME has been observed by a range of experiments and in a variety of environments. AME is spatially correlated with far-IR thermal dust emission but cannot be explained by synchrotron or free-free emission mechanisms, and is far in excess of the emission contributed by thermal dust emission with the power-law opacity consistent with the observed emission at sub-mm wavelengths. Polarization observations have shown that AME is very weakly polarized ( 1 %). The most natural explanation for AME is rotational emission from ultra-small dust grains ("spinning dust"), first postulated in 1957.

Aims. The Herschel survey of the Galactic plane (Hi-GAL) provides a unique opportunity to study star formation over large areas of the sky and different environments in the Milky Way. We use the best-studied Hi-GAL fields to date, two 2 • · 2 • tiles centered on ( , b) = (30 • , 0 • ) and ( , b) = (59 • , 0 • ), to study the star formation activity in these regions of the sky using a large sample of well-selected young stellar objects (YSOs). Methods. We used the science demonstration phase Hi-GAL fields, where a tremendous effort has been made to identify the newly formed stars and to derive their properties as accurately as possible, e.g. distance, bolometric luminosity, envelope mass, and stage of evolution. We estimated the star formation rate (SFR) for these fields using the number of candidate YSOs and their average time scale to reach the zero age main sequence, and compared it with the rate estimated using their integrated luminosity at 70 μm, combined with an extragalactic star formation indicator. Results. We measure an SFR of (9.5 ± 4.3) × 10 −4 M /yr and (1.6 ± 0.7) × 10 −4 M /yr with the source counting method, in = 30 • and = 59 • , respectively. Results with the 70 μm estimator are (2.4 ± 0.4) × 10 −4 M /yr and (2.6 ± 1.1) × 10 −6 M /yr. Since the 70 μm indicator is derived from averaging extragalactic star forming complexes, we extrapolated of these values to the whole Milky Way and obtain SFR MW = (0.71 ± 0.13) M /yr from l = 30 • and SFR MW = (0.10 ± 0.04) M /yr from = 59 • . The estimates in = 30 • agree with the most recent results for Galactic star formation activity. Conclusions. The source-counting method gives results that are only valid for the particular region under consideration. In contrast, the construction of the IR indicator leads to results that can be extrapolated to the whole Galaxy. In particular, when it is applied to the = 30 • field, it provides an SFR that is consistent with previous estimates, indicating that the characteristics of this field are very likely close to those of the star formation-dominated galaxies used for its derivation. Since the sky coverage is limited, this analysis will improve when the full Hi-GAL survey is available. It will cover the whole Galactic plane, sampling almost the totality of Galactic star forming complexes. By means of the candidate YSO-counting method, it will then be possible to calibrate an SFR Galactic indicator and to test the validity of the extragalactic estimators.

We have analyzed a uniform sample of 16 evolved H II regions located in a 2 • ×2 • Galactic field centered at (l,b) = (30 • , 0 • ) and observed as part of the Herschel Hi-GAL survey. The evolutionary stage of these H II regions was established using ancillary radio continuum data. By combining Hi-GAL PACS (70 µm, 160 µm) and SPIRE (250 µm, 350 µm and 500 µm) measurements with MIPSGAL 24 µm data, we built Spectral Energy Distributions (SEDs) of the sources and showed that a 2-component grey-body model is a good representation of the data. In particular, wavelengths > 70 µm appear to trace a cold dust component, for which we estimated an equilibrium temperature of the Big Grains (BGs) in the range 20 -30 K, while for λ < 70 µm, the data indicated the presence of a warm dust component at temperatures of the order of 50 -90 K. This analysis also revealed that dust is present in the interior of H II regions, although likely not in a large amount. In addition, the data appear to corroborate the hypothesis that the main mechanism responsible for the (partial) depletion of dust in H II regions is radiation-pressure-driven drift. In this framework, we speculated that the 24 µm emission which spatially correlates with ionized gas might be associated with either Very Small Grain (VSG) or BG replenishment, as recently proposed for the case of Wind-Blown Bubbles (WBB). Finally, we found that evolved H II regions are characterized by distinctive far-IR and sub-mm colors, which can be used as diagnostics for their identification in unresolved Galactic and extragalactic regions.

The dust complex G159.6–18.5 in the Perseus region has previously been observed with the COSMOSOMAS experiment on angular scales of ≈1°, and was found to exhibit anomalous microwave emission. We present the first high angular resolution observations of this dust complex, performed with the Very Small Array (VSA) at 33 GHz, to help increase the understanding of the nature of this anomalous emission. On the angular scales observed with the VSA (≈10–40 arcmin), G159.6–18.5 consists of five distinct components, all of which are found to exhibit an excess of emission at 33 GHz that is highly correlated with far‐infrared emission. Within the region, we find a range of physical conditions: one of the features, which is associated with the reflection nebula IC 348, has a dust emissivity comparable to that of H ii regions, while the other four features have values in agreement with previous observations of intermediate Galactic latitudes. We provide evidence that all of these compact components have anomalous emission that is consistent with electric dipole emission from very small, rapidly rotating dust grains. We find that these five components contribute ≈10 per cent to the flux density of the diffuse extended emission detected by COSMOSOMAS, implying that the bulk of the anomalous emission in Perseus is diffuse and not concentrated in these compact components.