PILOT: a balloon-borne experiment to measure the polarized FIR emission of dust grains in the interstellar medium

Bernard, J.-P.; Ade, Peter A. R.; André, Y.; Aumont, J.; Bautista, Linda; Bray, Nicolas; Bernardis, P. de; Boulade, O.; Bousquet, F.; Bouzit, M.; Buttice, V.; Caillat, A.; Charra, M.; Chaigneau, M.; Crane, B.; Crussaire, J. P.; Douchin, F.; Doumayrou, E.; Dubois, Jean‐Pierre; Engel, C.; Etcheto, Pierre; Gélot, P.; Griffin, Matthew Joseph; Foenard, G.; Grabarnik, S.; Hargrave, Peter Charles; Hughes, Annie; Laureijs, R. J.; Lepennec, Y.; Leriche, B.; Longval, Y.; Maestre, S.; Maffei, B.; Martignac, J.; Marty, C.; Marty, W.; Masi, S.; Mirc, F.; Misawa, R.; Montel, Johan; Montier, L.; Mot, B.; Narbonne, J.; Nicot, J. M.; Pajot, F.; Parot, G.; Pérot, Etienne; Pimentão, João; Pisano, G.; Ponthieu, N.; Ristorcelli, I.; Rodriguez, L.; Roudil, G.; Salatino, Maria; Savini, G.; Simonella, O.; Saccoccio, M.; Tapie, P.; Tauber, J. A.; Torre, J. P.; Tucker, C.

doi:10.1007/s10686-016-9506-1

Cited by 25 publications

(33 citation statements)

References 35 publications

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“…PILOT observations of the GC region were obtained during the second flight of the PILOT balloon experiment, which took place from Alice Springs, Australia, as part of the 2017 French Space Agency (CNES) balloon campaign. A complete description of the PILOT instrument is presented in Bernard et al (2016), while the performance of the PILOT instrument during the Alice Springs flight is described in Mangilli et al (2018).…”

Section: Pilot Observationsmentioning

confidence: 99%

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The geometry of the magnetic field in the central molecular zone measured by PILOT

Mangilli

Aumont

Bernard

et al. 2019

A&A

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We present the first far infrared (FIR) dust emission polarization map covering the full extent Milky Way's Central molecular zone (CMZ). The data, obtained with the PILOT balloon-borne experiment, covers the Galactic Center region −2 • < < 2 • , −4 • < b < 3 • at a wavelength of 240 µm and an angular resolution 2.2 . From our measured dust polarization angles, we infer a magnetic field orientation projected onto the plane of the sky that is remarkably ordered over the full extent of the CMZ, with an average tilt angle of 22 • clockwise with respect to the Galactic plane. Our results confirm previous claims that the field traced by dust polarized emission is oriented nearly orthogonal to the field traced by GHz radio synchrotron emission in the Galactic Center region. The observed field structure is globally compatible with the latest Planck polarization data at 353 GHz and 217 GHz. Upon subtraction of the extended emission in our data, the mean field orientation that we obtain shows good agreement with the mean field orientation measured at higher angular resolution by the JCMT within the 20 km/s and 50 km/s molecular clouds. We find no evidence that the magnetic field orientation is related to the 100 pc twisted ring structure within the CMZ. We propose that the low polarization fraction in the Galactic Center region and the highly ordered projected field orientation can be reconciled if the field is strong, with a 3D geometry that is is mostly oriented 15 • with respect to the line-of-sight towards the Galactic center. Assuming equipartition between the magnetic pressure and ram pressure, we obtain magnetic field strengths estimates as high as a few mG for several CMZ molecular clouds.

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Section: Pilot Observationsmentioning

confidence: 99%

“…A preliminary version of the PILOT focal plane geometry was obtained during ground calibration of the instrument (Bernard et al 2016). Here, we used all parameters of this determination including the pixel size and array rotation values.…”

Section: Pointing Reconstructionmentioning

confidence: 99%

The geometry of the magnetic field in the central molecular zone measured by PILOT

Mangilli

Aumont

Bernard

et al. 2019

A&A

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“…3.3.1) were associated with some decrease in S POS . In Mangilli et al (2019), similar effect was seen in PILOT balloon-borne telescope (Bernard et al 2016) observations of low Galactic latitudes and interpreted as averaging over many turbulent cells, which recovers the mean Galactic field orientation. In our simulations, the effect is also strong because of the relatively uniform mean-field direction.…”

Section: Clump Polarisationmentioning

confidence: 55%

Synthetic observations of dust emission and polarisation of Galactic cold clumps

Juvela

Padoan

Ristorcelli

et al. 2019

A&A

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Context. The Planck Catalogue of Galactic Cold Clumps (PGCC) contains over 13000 sources that are detected based on their cold dust signature. They are believed to consist of a mixture of quiescent, pre-stellar, and already star-forming objects within molecular clouds. Aims. We extracted PGCC-type objects from cloud simulations and examined their physical and polarisation properties. The comparison with the PGCC catalogue helps to characterise the properties of this large sample of Galactic objects and, conversely, provides valuable tests for numerical simulations of large volumes of the interstellar medium and the evolution towards pre-stellar cores. Methods. We used several magnetohydrodynamical (MHD) simulation snapshots to define the density field of our model clouds. Sub-millimetre images of the surface brightness and polarised signal were obtained with radiative transfer calculations. We examined the statistics of synthetic cold clump catalogues extracted with methods similar to the PGCC. We also examined the variations of the polarisation fraction p in the clumps. Results. The clump sizes, aspect ratios, and temperatures in the synthetic catalogue are similar to the PGCC. The fluxes and column densities of synthetic clumps are smaller by a factor of a few. Rather than with an increased dust opacity, this could be explained by increasing the average column density of the model by a factor of two to three, close to N(H) = 10 22 cm 2 . When the line of sight is parallel to the mean magnetic field, the polarisation fraction tends to increase towards the clump centres, which is contrary to observations. When the field is perpendicular, the polarisation fraction tends to decrease towards the clumps, but the drop in p is small (e.g. from p ∼8% to p ∼7%). Conclusions. Magnetic field geometry reduces the polarisation fraction in the simulated clumps by only ∆p ∼1% on average. The larger drop seen towards the actual PGCC clumps therefore suggests some loss of grain alignment in the dense medium, such as predicted by the radiative torque mechanism. The statistical study is not able to quantify dust opacity changes at the scale of the PGCC clumps.

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“…The second objective is the characterization of polarized emission from dust grains: it will be helpful for foreground subtraction (in the frame of CMB future analysis), but also for the study of the interstellar grains physical properties ( [1], [2]). …”

Section: A Scientific Objectivesmentioning

confidence: 99%

Pilot, a balloon borne experiment underground tests

Engel¹,

Marty²,

Mot³

et al. 2017

International Conference on Space Optics — ICSO 2010

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PILOT: a balloon-borne experiment to measure the polarized FIR emission of dust grains in the interstellar medium

Cited by 25 publications

References 35 publications

The geometry of the magnetic field in the central molecular zone measured by PILOT

The geometry of the magnetic field in the central molecular zone measured by PILOT

Synthetic observations of dust emission and polarisation of Galactic cold clumps

Pilot, a balloon borne experiment underground tests

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