Dust-correlated cm wavelength continuum emission from translucent clouds ζ Oph and LDN 1780

Vidal, M.; Casassus, S.; Dickinson, C.; Witt, A. N.; Castellanos, Patricia Cruz; Davies, R. D.; Davis, R. J.; Cabrera, Guillermo; Cleary, Kieran; Allison, J. R.; Bond, J. R.; Bronfman, L.; Bustos, R.; Jones, Michael E.; Paladini, R.; Pearson, T. J.; Readhead, A. C. S.; Reeves, R.; Sievers, Jonathan; Taylor, Angela C.

doi:10.1111/j.1365-2966.2011.18562.x

Cited by 35 publications

(46 citation statements)

References 61 publications

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“…For the ISM density we adopted a value of n a ∼ 10 cm −3 ; since ζ Oph is embedded in a cirrus cloud region, the density and ambient temperature might be higher than average (e.g. Vidal et al 2011). These parameters yield R 0 ∼ 0.3 pc, which agrees well with the upper limit measured by Peri et al (2011).…”

Section: Bowshock Shapesupporting

confidence: 73%

Non-thermal processes in bowshocks of runaway stars

Valle¹,

Romero²

2012

A&A

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Context. Runaway massive stars are O-and B-type stars with high spatial velocities with respect to the interstellar medium. These stars can produce bowshocks in the surrounding gas. Bowshocks develop as arc-shaped structures, with bows pointing to the same direction as the stellar velocity, while the star moves supersonically through the interstellar gas. The piled-up shocked matter emits thermal radiation and a population of locally accelerated relativistic particles is expected to produce non-thermal emission over a wide range of energies. Aims. We aim to model the non-thermal radiation produced in these sources. Methods. Under some assumptions, we computed the non-thermal emission produced by the relativistic particles and the thermal radiation caused by free-free interactions, for O4I and O9I stars. We applied our model to ζ Oph (HD 149757), an intensively studied massive star seen from the northern hemisphere. This star has spectral type O9.5V and is a well-known runaway. Results. Spectral energy distributions of massive runaways are predicted for the whole electromagnetic spectrum. Conclusions. We conclude that the non-thermal radiation might be detectable at various energy bands for relatively nearby runaway stars, especially at high-energy gamma rays. Inverse Compton scattering with photons from the heated dust gives the most important contribution to the high-energy spectrum. This emission approaches Fermi sensitivities in the case of ζ Oph.

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Section: Bowshock Shapesupporting

confidence: 73%

Non-thermal processes in bowshocks of runaway stars

Valle¹,

Romero²

2012

A&A

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“…These values show that the Pleiades reflection nebula constitutes indeed a more diffuse medium than others where AME has been usually studied, such as the Perseus and ρ Ophiuchus molecular clouds, where N H = 117×10 20 cm −2 and 171×10 20 cm −2 , respectively (Planck Collaboration et al 2011). This also becomes evident from the reddening measurements in this region, E B−V = 0.1 mag (see Section 3.1), which are typical of diffuse clouds, and lower than the respective values in the Perseus and ρ Ophiuchus molecular clouds, and even lower than the reddening of the translucent cloud LDN 1780, E B−V ∼ 0.6, where Vidal et al (2011) have recently found AME. Our fitted values for the hydrogen column densities are also of the same order of those derived by applying the scaling relation of Bohlin et al (1978), (N H + N H2 )/E B−V = 5.8 × 10 21 cm −2 mag −1 , and taking for the reddening E B−V = 0.1 mag.…”

Section: Notesmentioning

confidence: 68%

“…It is also interesting to compare our results with those presented in Figure 13 of Vidal et al (2011), where they plot emissivity at 31 GHz (intensity at 31 GHz divided by hydrogen column density) versus hydrogen column density. Dividing the total flux at 33 GHz for case B by the solid angle of the aperture and by the corresponding fitted column density we get 33 = (2.55 ± 0.28) × 10 −24 MJy sr −1 cm 2 .…”

Section: Notesmentioning

confidence: 78%

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

Génova-Santos

Rebolo

Rubiño-Martín

et al. 2011

ApJ

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We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe and from the COSMOSOMAS (Cosmological Structures on Medium Angular Scales) experiment. The flux integrated in a 1• radius around R.A. = 56.• 24, decl. = 23.• 78 (J2000) is 2.15 ± 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow one to set upper limits of 0.94 and 1.58 Jy (99.7% confidence level), respectively, at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected Hα template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz, the residual flux, associated with AME, is 2.12 ± 0.12 Jy (17.7σ ). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100 μm data, is found to be 4.36 ± 0.17 μK (MJy sr −1 ) −1 , a value considerably lower than in typical AME clouds, which present emissivities of ∼20 μK (MJy sr −1 ) −1 , although higher than the 0.2 μK (MJy sr −1 ) −1 of the translucent cloud LDN 1780, where AME has recently been claimed. The physical properties of the Pleiades nebula, in particular its low extinction A V ∼ 0.4, indicate that this is indeed a much less opaque object than those where AME has usually been studied. This fact, together with the broad knowledge of the stellar content of this region, provides an excellent testbed for AME characterization in physical conditions different from those generally explored up to now.

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“…In general, we find little or no correlation with most parameters. Previous works (Lagache 2003;Vidal et al 2011) found Fig. 21.…”

Section: Ghz Residmentioning

confidence: 76%

“…The nanoscale dust particles (PAHs and VSGs) are proportional to G 0 (Sellgren et al 1985) when G 0 10. Previous studies (e.g., Vidal et al 2011) have found that a better correlation can be obtained with the infrared by dividing far-infrared flux density by G 0 .…”

Section: Dust Correlationsmentioning

confidence: 98%

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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Dust-correlated cm wavelength continuum emission from translucent clouds ζ Oph and LDN 1780

Cited by 35 publications

References 61 publications

Non-thermal processes in bowshocks of runaway stars

Non-thermal processes in bowshocks of runaway stars

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

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

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