Very Small Array observations of the anomalous microwave emission in the Perseus region

Abstract

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.

Planck2015 results

“…The brightest AME regions in the ring are mostly located adjacent to bright thermal dust features, although the brightest AME region does not have a bright thermal dust counterpart. AME has been seen in PDRs around other H ii regions at higher resolution, e.g., in ρ Ophiuchus (Casassus et al 2008) and Perseus (Tibbs et al 2010). λ Orionis has a particularly high emissivity against 545 GHz and τ 353 , but the emissivity against 100 µm is comparable to the average; this indicates that the AME is connected to the colder dust in this region.…”

Planckintermediate results

“…The most compelling evidence for spinning dust grains comes from dedicated observations covering frequencies ranging from the gigahertz radio bands (e.g., COSMOSOMAS, Cosmic Background Imager, Very Small Array) through the millimetre bands of WMAP and Planck to the FIR of IRAS and COBE-DIRBE. The best-studied examples at present are the Perseus molecular cloud (Watson et al 2005;Tibbs et al 2010;Planck Collaboration XX 2011) and the ρ Ophiuchi photo-dissociation region (Casassus et al 2008;Planck Collaboration XX 2011); in these cases the peak is at 25-30 GHz. AME has also been detected in dust clouds associated with H  regions although with a range of emissivities (Todorović et al 2010;Planck Collaboration XX 2011;Planck Collaboration Int.…”

DETECTION OF ANOMALOUS MICROWAVE EMISSION IN THE PLEIADES REFLECTION NEBULA WITHWILKINSON MICROWAVE ANISOTROPY PROBEAND THE COSMOSOMAS EXPERIMENT

“…These observations motivated a search for similar signals in individual regions (Finkbeiner et al 2002), which led to unambiguous detections in several molecular clouds with different experiments, such as COSMOSOMAS (Cosmological Structures on Medium Angular Scales; Watson et al 2005), AMI (Ami Consortium et al 2009a, 2009b, CBI (Casassus et al 2006;Castellanos et al 2011), VSA (Tibbs et al 2010), or Planck (Planck Collaboration et al 2011. These studies led to the idea that this dust-correlated signal, which was thenceforth referred to as "anomalous microwave emission" (AME), was indeed an additional diffuse foreground component, originated by an emission mechanism different from the well-known synchrotron, free-free and thermal dust emissions.…”