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Aims.Because of their limited angular resolution, far-infrared telescopes are usually affected by the confusion phenomenon. Since several galaxies can be located in the same instrumental beam, only the brightest objects emerge from the fluctuations caused by fainter sources. The PRobe far-Infrared Mission for Astrophysics imager (PRIMAger) will observe the mid- and far-infrared (25–235 μm) sky both in intensity and polarization. We aim to provide predictions of the confusion level and its consequences for future surveys. Methods.We produced simulated PRIMAger maps affected only by the confusion noise using the simulated infrared extragalactic sky (SIDES) semi-empirical simulation. We then estimated the confusion limit in these maps and extracted the sources using a basic blind extractor. By comparing the input galaxy catalog and the extracted source catalog, we derived various performance metrics as completeness, purity, and the accuracy of various measurements (e.g., the flux density in intensity and polarization or the polarization angle). Results.In intensity maps, we predict that the confusion limit increases rapidly with increasing wavelength (from 21 μJy at 25 μm to 46 mJy at 235 μm). The confusion limit in polarization maps is more than two orders of magnitude lower (from 0.03 mJy at 96 μm to 0.25 mJy at 235 μm). Both in intensity and polarization maps, the measured (polarized) flux density is dominated by the brightest galaxy in the beam, but other objects also contribute in intensity maps at longer wavelengths (∼30% at 235 μm). We also show that galaxy clustering has a mild impact on confusion in intensity maps (up to 25%), while it is negligible in polarization maps. In intensity maps, a basic blind extraction will be sufficient to detect galaxies at the knee of the luminosity function up toz ∼ 3 and 10¹¹M_⊙main-sequence galaxies up toz ∼ 5. In polarization for the most conservative sensitivity forecast (payload requirements), ∼200 galaxies can be detected up toz = 1.5 in two 1500 h surveys covering 1 deg²and 10 deg². For a conservative sensitivity estimate, we expect ∼8000 detections up toz = 2.5, opening a totally new window on the high-zdust polarization. Finally, we show that intensity surveys at short wavelengths and polarization surveys at long wavelengths tend to reach confusion at similar depth. There is thus a strong synergy between them. 

Abstract High-energy neutrinos are detected by the IceCube Observatory in the direction of NGC 1068, the archetypical type II Seyfert galaxy. The neutrino flux, surprisingly, is more than an order of magnitude higher than theγ-ray upper limits at measured TeV energy, posing tight constraints on the physical conditions of a neutrino production site. We report an analysis of the submillimeter, mid-infrared, and ultraviolet observations of the central 50 pc of NGC 1068 and suggest that the inner dusty torus and the region where the jet interacts with the surrounding interstellar medium (ISM) may be a potential neutrino production site. Based on radiation and magnetic field properties derived from observations, we calculate the electromagnetic cascade of theγ-rays accompanying the neutrinos. When injecting protons with a hard spectrum, our model may explain the observed neutrino flux above ∼10 TeV. It predicts a unique sub-TeVγ-ray component, which could be identified by a future observation. Jet–ISM interactions are commonly observed in the proximity of jets of both supermassive and stellar-mass black holes. Our results imply that such interaction regions could beγ-ray-obscured neutrino production sites, which are needed to explain the IceCube diffuse neutrino flux. 

Abstract Located in the Large Magellanic Cloud and mostly irradiated by the massive star cluster R136, 30 Doradus is an ideal target to test the leading theory of grain alignment and rotational disruption by RAdiative Torques (RATs). Here, we use publicly available polarized thermal dust emission observations of 30 Doradus at 89, 154, and 214 μ m using SOFIA/HAWC+. We analyze the variation of the dust polarization degree ( p ) with the total emission intensity ( I ), the dust temperature ( T d ), and the gas column density ( N H ) constructed from Herschel data. The 30 Doradus complex is divided into two main regions relative to R136, namely North and South. In the North, we find that the polarization degree first decreases and then increases before decreasing again when the dust temperature increases toward the irradiating cluster R136. The first depolarization likely arises from the decrease in grain alignment efficiency toward the dense medium due to the attenuation of the interstellar radiation field and the increase in the gas density. The second trend (the increase of p with T d ) is consistent with the RAT alignment theory. The final trend (the decrease of p with T d ) is consistent with the RAT alignment theory only when the grain rotational disruption by RATs is taken into account. In the South, we find that the polarization degree is nearly independent of the dust temperature, while the grain alignment efficiency is higher around the peak of the gas column density and decreases toward the radiation source. The latter feature is also consistent with the prediction of rotational disruption by RATs. 

Abstract Dust-induced polarization in the interstellar medium (ISM) is due to asymmetric grains aligned with an external reference direction, usually the magnetic field. For both the leading alignment theories, the alignment of the grain’s angular momentum with one of its principal axes and the coupling with the magnetic field requires the grain to be paramagnetic. Of the two main components of interstellar dust, silicates are paramagnetic, while carbon dust is diamagnetic. Hence, carbon grains are not expected to align in the ISM. To probe the physics of carbon grain alignment, we have acquired Stratospheric Observatory for Infrared Astronomy/Higch-resolution Airborne Wideband Camera-plus far-infrared photometry and polarimetry of the carbon-rich circumstellar envelope (CSE) of the asymptotic giant branch star IRC+10° 216. The dust in such CSEs are fully carbonaceous and thus provide unique laboratories for probing carbon grain alignment. We find a centrosymmetric, radial, polarization pattern, where the polarization fraction is well correlated with the dust temperature. Together with estimates of a low fractional polarization from optical polarization of background stars, we interpret these results to be due to a second-order, direct radiative external alignment of grains without internal alignment. Our results indicate that (pure) carbon dust does not contribute significantly to the observed ISM polarization, consistent with the nondetection of polarization in the 3.4μm feature due to aliphatic CH bonds on the grain surface.