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We present polarization observations of the young supernova remnant (SNR) Cas A using the High-resolution Airborne Wideband Camera-Plus (HAWC+) instrument onboard the Stratospheric Observatory for Infrared Astronomy (SOFIA). The polarization map at 154 microns reveals dust grains with strong polarization fractions (5 - 30 percent), supporting previous measurements made over a smaller region of the remnant at 850 microns. The 154 microns emission and the polarization signal is coincident with a region of cold dust observed in the southeastern shell and in the unshocked central ejecta. The highly polarized far-IR emission implies the grains are large (greater than 0.14 microns) and silicate-dominated. The polarization level varies across the SNR, with an inverse correlation between the polarization degree and the intensity and smaller polarization angle dispersion for brighter SNR emission. Stronger polarization is detected between the bright structures. This may result from a higher collision rate between the gas and dust producing a lower grain alignment efficiency where the gas density is higher. We use the dust emission to provide an estimate of the magnetic field strength in Cas A using the Davis-Chandrasekhar-Fermi method. The high polarization level is direct evidence that grains are highly elongated and strongly aligned with the magnetic field of the SNR. The dust mass from the polarized region is 0.14+-0.04 Msun, a lower limit of the amount of dust present within the ejecta of Cas A. This result strengthens the hypothesis that core-collapse SNe are an important contributor to the dust mass in high redshift galaxies., Comment: MNRAS, accepted (18 pages with 14 figures)

Dust in the interstellar medium (ISM) is critical to the absorption and intensity of emission profiles used widely in astronomical observations, and necessary for star and planet formation. Supernova explosions (SNe) eject dust into the ISM, but potentially destroy much larger quantities already present in the ambient ISM. A major unresolved astrophysical problem exists: theory and prior simulations of dust processing by supernovae in uniform ISM predict much greater dust destruction than is compatible with estimates of dust abundances observed in young starburst galaxies. We simulate dust processing by supernovae within more realistic simulations of ISM dynamics and consider magnetic field effects. We show that the inhomogeneity of the ISM protects dust from blast waves, reducing dust mass destroyed within 1 Myr per SNe from 70 M⊙ to ∼60 M⊙. Magnetic fields protect dust, particularly large grains, from grain-grain collisions, reducing losses to only ∼30 M⊙.

Dust grains form in the clumpy ejecta of core-collapse supernovae where they are subject to the reverse shock, which is able to disrupt the clumps and destroy the grains. Important dust destruction processes include thermal and kinetic sputtering as well as fragmentation and grain vaporization. In the present study, we focus on the effect of magnetic fields on the destruction processes. We have performed magneto-hydrodynamical simulations using AstroBEAR to model a shock wave interacting with an ejecta clump. The dust transport and destruction fractions are computed using our post-processing code Paperboats in which the acceleration of grains due to the magnetic field and a procedure that allows partial grain vaporization have been newly implemented. For the oxygen-rich supernova remnant Cassiopeia A we found a significantly lower dust survival rate when magnetic fields are aligned perpendicular to the shock direction compared to the non-magnetic case. For a parallel field alignment, the destruction is also enhanced but at a lower level. The survival fractions depend sensitively on the gas density contrast between the clump and the ambient medium and on the grain sizes. For a low-density contrast of $100$, e.g., $5\,$nm silicate grains are completely destroyed while the survival fraction of $1\,\mu$m grains is $86\,$per cent. For a high-density contrast of $1000$, $95\,$per cent of the $5\,$nm grains survive while the survival fraction of $1\,\mu$m grains is $26\,$per cent. Alternative clump sizes or dust materials (carbon) have non-negligible effects on the survival rate but have a lower impact compared to density contrast, magnetic field strength, and grain size., Comment: Accepted by MNRAS. Author accepted manuscript. Accepted on 23/01/2023. 24 pages, 21 Figures

Excess near-infrared emission is detected around one fifth of main-sequence stars, but its nature is a mystery. These excesses are interpreted as thermal emission from populations of small, hot dust very close to their stars (`hot exozodis'), but such grains should rapidly sublimate or be blown out of the system. To date, no model has fully explained this phenomenon. One mechanism commonly suggested in the literature is cometary supply, where star-grazing comets deposit dust close to the star, replenishing losses from grain sublimation and blowout. However, we show that this mechanism alone is very unlikely to be responsible for hot exozodis. We model the trajectory and size evolution of dust grains released by star-grazing comets, to establish the dust and comet properties required to reproduce hot-exozodi observations. We find that cometary supply alone can only reproduce observations if dust ejecta has an extremely steep size distribution upon release, and the dust-deposition rate is extraordinarily high. These requirements strongly contradict our current understanding of cometary dust and planetary systems. Cometary supply is therefore unlikely to be solely responsible for hot exozodis, so may need to be combined with some dust-trapping mechanism (such as gas or magnetic trapping) if it is to reproduce observations., 18 pages, 9 figures, accepted for publication in MNRAS

We present 850 $��$m polarimetric observations toward the Serpens Main molecular cloud obtained using the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields In STar-forming Region Observations (BISTRO) survey. These observations probe the magnetic field morphology of the Serpens Main molecular cloud on about 6000 au scales, which consists of cores and six filaments with different physical properties such as density and star formation activity. Using the histogram of relative orientation (HRO) technique, we find that magnetic fields are parallel to filaments in less dense filamentary structures where $N_{H_2} < 0.93\times 10^{22}$ cm$^{-2}$ (magnetic fields perpendicular to density gradients), while being perpendicular to filaments (magnetic fields parallel to density gradients) in dense filamentary structures with star formation activity. Moreover, applying the HRO technique to denser core regions, we find that magnetic field orientations change to become perpendicular to density gradients again at $N_{H_2} \approx 4.6 \times 10^{22}$ cm$^{-2}$. This can be interpreted as a signature of core formation. At $N_{H_2} \approx 16 \times 10^{22}$ cm$^{-2}$ magnetic fields change back to being parallel to density gradients once again, which can be understood to be due to magnetic fields being dragged in by infalling material. In addition, we estimate the magnetic field strengths of the filaments ($B_{POS} = 60-300~��$G)) using the Davis-Chandrasekhar-Fermi method and discuss whether the filaments are gravitationally unstable based on magnetic field and turbulence energy densities., 18 pages, accepted for publication in ApJ

Tao-Chung Ching et al., We present 850 μm dust polarization observations of the massive DR21 filament from the B-fields In STar-forming Region Observations (BISTRO) survey, using the POL-2 polarimeter and the SCUBA-2 camera on the James Clerk Maxwell Telescope. We detect ordered magnetic fields perpendicular to the parsec-scale ridge of the DR21 main filament. In the subfilaments, the magnetic fields are mainly parallel to the filamentary structures and smoothly connect to the magnetic fields of the main filament. We compare the POL-2 and Planck dust polarization observations to study the magnetic field structures of the DR21 filament on 0.1–10 pc scales. The magnetic fields revealed in the Planck data are well-aligned with those of the POL-2 data, indicating a smooth variation of magnetic fields from large to small scales. The plane-of-sky magnetic field strengths derived from angular dispersion functions of dust polarization are 0.6–1.0 mG in the DR21 filament and ∼0.1 mG in the surrounding ambient gas. The mass-to-flux ratios are found to be magnetically supercritical in the filament and slightly subcritical to nearly critical in the ambient gas. The alignment between column density structures and magnetic fields changes from random alignment in the low-density ambient gas probed by Planck to mostly perpendicular in the high-density main filament probed by James Clerk Maxwell Telescope. The magnetic field structures of the DR21 filament are in agreement with MHD simulations of a strongly magnetized medium, suggesting that magnetic fields play an important role in shaping the DR21 main filament and subfilaments., This work is supported by National Natural Science Foundation of China (NSFC) grant Nos. 11988101, U1931117, 11725313, and 12073061 and the CAS International Partnership Program of Chinese Academy of Sciences grant No. 114A11KYSB20160008. T.-C.C. is funded by Chinese Academy of Sciences Taiwan Young Talent Program grant No. 2018TW2JB0002. T.-C.C. and C.E. were supported by Special Funding for Advanced Users, budgeted and administrated by Center for Astronomical Mega-Science (CAMS), Chinese Academy of Sciences. K.P. is a Royal Society University Research Fellow, supported by grant No. URF\R1\211322. D.J. is supported by the National Research Council of Canada and by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant. P.M.K. is supported by the Ministry of Science and Technology (MoST) in Taiwan through grants 109-2112-M-001-022 and 110-2112-M-001-057. C.W.L. is supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF-2019R1A2C1010851), and by the Korea Astronomy and Space Science Institute grant funded by the Korea government (MSIT; Project No. 2022-1-840-05). T.H. is supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) through the Mid-career Research Program (2019R1A2C1087045). W.K. was supported by the NRF grant funded by the MSIT (2021R1F1A1061794). C.E. acknowledges the financial support from grant RJF/2020/000071 as a part of Ramanujan Fellowship awarded by the Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Govt. of India. F.P. acknowledges support from the Spanish State Research Agency (AEI) under grant No. PID2019-105552RB-C43. M.T. is supported by JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. J.K. is supported by JSPS KAKENHI grant No. 19K14775. L.F. and F.K. acknowledge the support by the MoST in Taiwan through grant 107-2119-M-001-031-MY3 and Academia Sinica through grant AS-IA-106-M03. L.F. acknowledges the support by the MoST in Taiwan through grants 111-2811-M-005-007 and 109-2112-M-005-003-MY3. C.L.H.H. acknowledges the support of the NAOJ Fellowship and JSPS KAKENHI grants 18K13586 and 20K14527. F.K. is supported by the Spanish program Unidad de Excelencia María de Maeztu CEX2020-001058-M, financed by MCIN/AEI/10.13039/501100011033. K.Q. is partially supported by National Key R&D Program of China No. 2022YFA1603100, and acknowledges the National Natural Science Foundation of China (NSFC) grant U1731237. S.P.L. acknowledges grants from the Ministry of Science and Technology of Taiwan 106-2119-M-007-021-MY3 and 109-2112-M-007-010-MY3. Y.D. acknowledges the support of JSPS KAKENHI grants 25247016 and 18H01250. Y.S.D. is supported by the National Key R&D Program of China for grant No. 2022YFA1605300, and NSFC grants Nos. 12273051, 11933003.

Hwang et al., We present and analyze observations of polarized dust emission at 850 μm toward the central 1 × 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields in Star-forming Region Observations survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis–Chandrasekhar–Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from Herschel data and the C18O (J = 3 − 2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 ± 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 ± 0.02. Additionally, the mean Alfvén Mach number is 0.35 ± 0.01. This suggests that, in Mon R2, the magnetic fields provide resistance against large-scale gravitational collapse, and the magnetic pressure exceeds the turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically subcritical., J.H. is supported by the University of Science and Technology (UST) Overseas Training Program 2022, funded by the University of Science and Technology, Korea (No. 2022-017). K.P. is a Royal Society University Research Fellow, supported by grant number URF\R1\211322. C.W.L. was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (NRF- 2019R1A2C1010851), and by the Korea Astronomy and Space Science Institute grant funded by the Korea government (MSIT; Project No. 2022-1-840-05). D.J. and J.d.F. are supported by the National Research Council of Canada and by Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants. G.P. is supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF; 2020R1A6A3A01100208) W.K. was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT; NRF-2021R1F1A1061794). M.T. is supported by JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. J.K. is supported by JSPS KAKENHI grant No. 19K14775. M.M. is supported by JSPS KAKENHI grant No. 20K03276. F.P. acknowledges support from the Spanish State Research Agency Agencia Estatal de Investigación (AEI) under grant number PID2019-105552RB-C43. S.P.L., H.Y.D., S.J.L., and M.Z.Y. acknowledge grants from the Ministry of Science and Technology of Taiwan 106-2119-M-007-021-MY3 and 109-2112-M-007-010-MY3. C.E. acknowledges the financial support from grant RJF/2020/000071 as a part of a Ramanujan Fellowship awarded by Science and Engineering Research Board (SERB), Department of Science and Technology (DST), Govt. of India. L.F. and F.K. acknowledge support from the Ministry of Science and Technology of Taiwan, under grant No. MoST107-2119-M-001-031- MY3 and from Academia Sinica under grant No. AS-IA-106-M03. L.F. acknowledges the support by the MoST in Taiwan through grants 111-2811-M-005-007 and 109-2112-M-005-003-MY3. F.K. acknowledges support from the Spanish program Unidad de Excelencia María de Maeztu CEX2020-001058-M, financed by MCIN/AEI/10.13039/501100011033. Y.S.D. would like to acknowledge the support from NSFC grants 12273051 and 10878003. M.R. is supported by the international Gemini Observatory, a program of NSFs NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership of Argentina, Brazil, Canada, Chile, the Republic of Korea, and the United States of America. The JCMT is operated by the East Asian Observatory on behalf of The National Astronomical Observatory of Japan; Academia Sinica Institute of Astronomy and Astrophysics; the Korea Astronomy and Space Science Institute; the Operation, Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments, budgeted from the Ministry of Finance of China. Additional funding support is provided by the Science and Technology Facilities Council of the United Kingdom and participating universities and organizations in the United Kingdom, Canada, and Ireland. Additional funds for the construction of SCUBA-2 were provided by the Canada Foundation for Innovation.

Polarized dust emission is a key tracer in the study of interstellar medium and of star formation. The observed polarization, however, is a product of magnetic field structure, dust grain properties and grain alignment efficiency, as well as their variations in the line of sight, making it difficult to interpret polarization unambiguously. The comparison of polarimetry at multiple wavelengths is a possible way of mitigating this problem. We use data from HAWC+/SOFIA and from SCUBA-2/POL-2 (from the BISTRO survey) to analyse the NGC 2071 molecular cloud at 154, 214 and 850 $\mu$m. The polarization angle changes significantly with wavelength over part of NGC 2071, suggesting a change in magnetic field morphology on the line of sight as each wavelength best traces different dust populations. Other possible explanations are the existence of more than one polarization mechanism in the cloud or scattering from very large grains. The observed change of polarization fraction with wavelength, and the 214-to-154 $\mu$m polarization ratio in particular, are difficult to reproduce with current dust models under the assumption of uniform alignment efficiency. We also show that the standard procedure of using monochromatic intensity as a proxy for column density may produce spurious results at HAWC+ wavelengths. Using both long-wavelength (POL-2, 850 $\mu$m) and short-wavelength (HAWC+, $\lesssim 200\, \mu$m) polarimetry is key in obtaining these results. This study clearly shows the importance of multi-wavelength polarimetry at submillimeter bands to understand the dust properties of molecular clouds and the relationship between magnetic field and star formation., Comment: Main article: 18 pages, 11 figures. Online supplemental material: 2 pages, 3 figures

We present the results of simultaneous 450 $\mu$m and 850 $\mu$m polarization observations toward the massive star forming region NGC 2071IR, a target of the BISTRO (B-fields in Star-Forming Region Observations) Survey, using the POL-2 polarimeter and SCUBA-2 camera mounted on the James Clerk Maxwell Telescope. We find a pinched magnetic field morphology in the central dense core region, which could be due to a rotating toroidal disk-like structure and a bipolar outflow originating from the central young stellar object, IRS 3. Using the modified Davis-Chandrasekhar-Fermi method, we obtain a plane-of-sky magnetic field strength of 563$\pm$421 $\mu$G in the central $\sim$0.12 pc region from 850 $\mu$m polarization data. The corresponding magnetic energy density of 2.04$\times$10$^{-8}$ erg cm$^{-3}$ is comparable to the turbulent and gravitational energy densities in the region. We find that the magnetic field direction is very well aligned with the whole of the IRS 3 bipolar outflow structure. We find that the median value of polarization fractions, 3.0 \%, at 450 $\mu$m in the central 3 arcminute region, which is larger than the median value of 1.2 \% at 850 $\mu$m. The trend could be due to the better alignment of warmer dust in the strong radiation environment. We also find that polarization fractions decrease with intensity at both wavelengths, with slopes, determined by fitting a Rician noise model, of $0.59 \pm 0.03$ at 450 $\mu$m and $0.36 \pm 0.04$ at 850 $\mu$m, respectively. We think that the shallow slope at 850 $\mu$m is due to grain alignment at the center being assisted by strong radiation from the central young stellar objects., Comment: 17 pages, 11 figures, 4 tables

We present the first 850 $\mu$m polarization observations in the most active star-forming site of the Rosette Molecular Cloud (RMC, $d\sim$1.6 kpc) in the wall of the Rosette Nebula, imaged with the SCUBA-2/POL-2 instruments of the JCMT, as part of the B-Fields In Star-Forming Region Observations 2 (BISTRO-2) survey. From the POL-2 data we find that the polarization fraction decreases with the 850 $\mu$m continuum intensity with $\alpha$ = 0.49 $\pm$ 0.08 in the $p \propto I^{\rm -\alpha}$ relation, which suggests that some fraction of the dust grains remain aligned at high densities. The north of our 850 $\mu$m image reveals a "gemstone ring" morphology, which is a $\sim$1 pc-diameter ring-like structure with extended emission in the "head" to the south-west. We hypothesize that it might have been blown by feedback in its interior, while the B-field is parallel to its circumference in most places. In the south of our SCUBA-2 field the clumps are apparently connected with filaments which follow Infrared Dark Clouds (IRDCs). Here, the POL-2 magnetic field orientations appear bimodal with respect to the large-scale Planck field. The mass of our effective mapped area is $\sim$ 174 $M_\odot$ that we calculate from 850 $\mu$m flux densities. We compare our results with masses from large-scale emission-subtracted Herschel 250 $\mu$m data, and find agreement within 30%. We estimate the POS B-field strength in one typical subregion using the Davis-Chandrasekhar-Fermi (DCF) technique and find 80 $\pm$ 30 $\mu$G toward a clump and its outskirts. The estimated mass-to-flux ratio of $\lambda$ = 2.3 $\pm$ 1.0 suggests that the B-field is not sufficiently strong to prevent gravitational collapse in this subregion., Comment: 15 pages (12+3), 9 figures, 1 table. Accepted for publication in the Astrophysical Journal

We have obtained sensitive dust continuum polarization observations at 850 μm in the B213 region of Taurus using POL-2 on SCUBA-2 at the James Clerk Maxwell Telescope as part of the B-fields in STar-forming Region Observations (BISTRO) survey. These observations allow us to probe magnetic field (B-field) at high spatial resolution (∼2000 au or ∼0.01 pc at 140 pc) in two protostellar cores (K04166 and K04169) and one prestellar core (Miz-8b) that lie within the B213 filament. Using the Davis–Chandrasekhar–Fermi method, we estimate the B-field strengths in K04166, K04169, and Miz-8b to be 38 ± 14, 44 ± 16, and 12 ± 5 μG, respectively. These cores show distinct mean B-field orientations. The B-field in K04166 is well ordered and aligned parallel to the orientations of the core minor axis, outflows, core rotation axis, and large-scale uniform B-field, in accordance with magnetically regulated star formation via ambipolar diffusion taking place in K04166. The B-field in K04169 is found to be ordered but oriented nearly perpendicular to the core minor axis and large-scale B-field and not well correlated with other axes. In contrast, Miz-8b exhibits a disordered B-field that shows no preferred alignment with the core minor axis or large-scale field. We found that only one core, K04166, retains a memory of the large-scale uniform B-field. The other two cores, K04169 and Miz-8b, are decoupled from the large-scale field. Such a complex B-field configuration could be caused by gas inflow onto the filament, even in the presence of a substantial magnetic flux.

We compare the directions of molecular outflows of 62 low-mass Class 0 and I protostars in nearby (, 27 pages, 14 figures, Accepted by ApJ

Observing nearby galaxies with submillimeter telescopes on the ground has two major challenges. First, the brightness is significantly reduced at long submillimeter wavelengths compared to the brightness at the peak of the dust emission. Second, it is necessary to use a high-pass spatial filter to remove atmospheric noise on large angular scales, which has the unwelcome by-product of also removing the galaxy's large-scale structure. We have developed a technique for producing high-resolution submillimeter images of galaxies of large angular size by using the telescope on the ground to determine the small-scale structure (the large Fourier components) and a space telescope (Herschel or Planck) to determine the large-scale structure (the small Fourier components). Using this technique, we are carrying out the HARP and SCUBA-2 High Resolution Terahertz Andromeda Galaxy Survey (HASHTAG), an international Large Program on the James Clerk Maxwell Telescope, with one aim being to produce the first high-fidelity high-resolution submillimeter images of Andromeda. In this paper, we describe the survey, the method we have developed for combining the space-based and ground-based data, and present the first HASHTAG images of Andromeda at 450 and 850um. We also have created a method to predict the CO(J=3-2) line flux across M31, which contaminates the 850um band. We find that while normally the contamination is below our sensitivity limit, the contamination can be significant (up to 28%) in a few of the brightest regions of the 10 kpc ring. We therefore also provide images with the predicted line emission removed., Comment: 26 pages, 19 figures. Submitted to ApJS June 2021, Accepted September 2021

We report the first high spatial resolution measurement of magnetic fields surrounding LkH$\alpha$ 101, a part of the Auriga-California molecular cloud. The observations were taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope within the framework of the B-fields In Star-forming Region Observations (BISTRO) survey. Observed polarization of thermal dust emission at 850 $\mu$m is found to be mostly associated with the red-shifted gas component of the cloud. The magnetic field displays a relatively complex morphology. Two variants of the Davis-Chandrasekhar-Fermi method, unsharp masking and structure function, are used to calculate the strength of magnetic fields in the plane of the sky, yielding a similar result of $B_{\rm POS}\sim 115$ $\mathrm{\mu}$G. The mass-to-magnetic-flux ratio in critical value units, $\lambda\sim0.3$, is the smallest among the values obtained for other regions surveyed by POL-2. This implies that the LkH$\alpha$ 101 region is sub-critical and the magnetic field is strong enough to prevent gravitational collapse. The inferred $\delta B/B_0\sim 0.3$ implies that the large scale component of the magnetic field dominates the turbulent one. The variation of the polarization fraction with total emission intensity can be fitted by a power-law with an index of $\alpha=0.82\pm0.03$, which lies in the range previously reported for molecular clouds. We find that the polarization fraction decreases rapidly with proximity to the only early B star (LkH$\alpha$ 101) in the region. The magnetic field tangling and the joint effect of grain alignment and rotational disruption by radiative torques are potential of explaining such a decreasing trend., Comment: 25 pages, 19 figures, Accepted for publication in The Astrophysical Journal

We present 850$\mu$m polarization observations of the L1689 molecular cloud, part of the nearby Ophiuchus molecular cloud complex, taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT). We observe three regions of L1689: the clump L1689N which houses the IRAS 16293-2422 protostellar system, the starless clump SMM-16, and the starless core L1689B. We use the Davis-Chandrasekhar-Fermi method to estimate plane-of-sky field strengths of $366\pm 55$ $\mu$G in L1689N, $284\pm 34$ $\mu$G in SMM-16, and $72\pm 33$ $\mu$G in L1689B, for our fiducial value of dust opacity. These values indicate that all three regions are likely to be magnetically trans-critical with sub-Alfv\'{e}nic turbulence. In all three regions, the inferred mean magnetic field direction is approximately perpendicular to the local filament direction identified in $Herschel$ Space Telescope observations. The core-scale field morphologies for L1689N and L1689B are consistent with the cloud-scale field morphology measured by the $Planck$ Space Observatory, suggesting that material can flow freely from large to small scales for these sources. Based on these magnetic field measurements, we posit that accretion from the cloud onto L1689N and L1689B may be magnetically regulated. However, in SMM-16, the clump-scale field is nearly perpendicular to the field seen on cloud scales by $Planck$, suggesting that it may be unable to efficiently accrete further material from its surroundings., Comment: 29 pages, 9 figures, 4 tables. Accepted for publication in the Astrophysical Journal

We present ALMA Band 7 polarisation observations of the OMC-1 region of the Orion molecular cloud. We find that the polarisation pattern observed in the region is likely to have been significantly altered by the radiation field of the $>10^{4}$ L$_{\odot}$ high-mass protostar Orion Source I. In the protostar's optically thick disc, polarisation is likely to arise from dust self-scattering. In material to the south of Source I - previously identified as a region of 'anomalous' polarisation emission - we observe a polarisation geometry concentric around Source I. We demonstrate that Source I's extreme luminosity may be sufficient to make the radiative precession timescale shorter than the Larmor timescale for moderately large grains ($> 0.005-0.1\,��$m), causing them to precess around the radiation anisotropy vector (k-RATs) rather than the magnetic field direction (B-RATs). This requires relatively unobscured emission from Source I, supporting the hypothesis that emission in this region arises from the cavity wall of the Source I outflow. This is one of the first times that evidence for k-RAT alignment has been found outside of a protostellar disc or AGB star envelope. Alternatively, the grains may remain aligned by B-RATs and trace gas infall onto the Main Ridge. Elsewhere, we largely find the magnetic field geometry to be radial around the BN/KL explosion centre, consistent with previous observations. However, in the Main Ridge, the magnetic field geometry appears to remain consistent with the larger-scale magnetic field, perhaps indicative of the ability of the dense Ridge to resist disruption by the BN/KL explosion., 20 pages, 20 figures, 3 tables, accepted for publication in Monthly Notices of the Royal Astronomical Society (MNRAS)

For the first time we observed the emission of hot exozodiacal dust in L band. We used the new instrument MATISSE at the Very Large Telescope Interferometer to detect the hot dust around $\kappa$ Tuc with a significance of 3$\sigma$ to 6$\sigma$ at wavelengths between 3.37 and 3.85 $\mu$m and a dust-to-star flux ratio of 5 to 7 %. We modelled the spectral energy distribution based on the new L band data alone and in combination with H band data published previously. In all cases we find 0.58 $\mu$m grains of amorphous carbon to fit the $\kappa$ Tuc observations the best, however, also nanometre or micrometre grains and other carbons or silicates reproduce the observations well. Since the H band data revealed a temporal variability, while our L band data were taken at a different epoch, we combine them in different ways. Depending on the approach, the best fits are obtained for a narrow dust ring at a stellar distance in the 0.1 to 0.29 au range and thus with a temperature between 940 and 1430 K. Within the 1$\sigma$ uncertainty dust location and temperature are confined to 0.032 - 1.18 au and 600 - 2000 K., Comment: Accepted by MNRAS Letters. Author accepted manuscript. Accepted on 04/09/2020. Deposited on 04/09/2020. 6 pages, 4 figures

[Abridged] Filaments and hubs have received special attention recently thanks to studies showing their role in star formation. While the column density and velocity structures of both filaments and hubs have been studied, their magnetic fields (B-field) are not yet characterized. We aim to understand the role of the B-field in the dynamical evolution of the NGC 6334 hub-filament network. We present new observations of the dust polarized emission at 850$\mu$m towards NGC 6334 obtained with the JCMT/POL-2. We study the distribution and dispersion of the polarized intensity ($PI$), the polarization fraction ($PF$), and the B-field angle ($\theta_{B}$). We derive the power spectrum of the intensity and $\theta_{B}$ along the ridge crest. Our analyses show a complex B-field structure when observed over the whole region ($\sim10$ pc), however, at smaller scales ($\sim1$ pc), $\theta_{B}$ varies coherently along the filaments. The observed power spectrum of $\theta_{B}$ can be well represented with a power law function with a slope $-1.33\pm0.23$, which is $\sim20\%$ shallower than that of $I$. This result is compatible with the properties of simulated filaments and may indicate the processes at play in the formation of filaments. $\theta_{B}$ rotates from being mostly perpendicular to the filament crests to mostly parallel as they merge with the hubs. This variation of $\theta_{B}$ may be tracing local velocity flows of matter in-falling onto the hubs. Our analysis suggests a variation of the energy balance along the crests of these filaments, from magnetically critical/supercritical at their far ends to magnetically subcritical near the hubs. We detect an increase of $PF$ towards the high-column density star cluster-forming hubs that may result from the increase of grain alignment efficiency due to stellar radiation from the newborn stars., Comment: Accepted for publication in Astronomy & Astrophysics

International audience; We discuss science cases to support the development of sub-au imaging capabilities to image forming planets in the terrestrial region of nearby proto-planetary disks.

ALMA observations revealed recently polarised radiation of several protoplanetary disks in the (sub-)millimetre wavelength range. Besides self-scattering of large particles, thermal emission by elongated grains is a potential source for the detected polarisation signal. We calculate the wavelength dependent absorption and intrinsic polarisation of spheroidally shaped, micrometre and sub-millimetre sized dust grains using the discrete dipole approximation. In particular, we analyse the impact of dust grain porosity which appears to be present in disks when small grains coagulate to form larger aggregates. For the first time our results show that (a) the intrinsic polarisation decreases for increasing grain porosity and (b) the polarisation orientation flips by 90 degree for certain ratios of wavelength to grain size. We present a new method to constrain grain porosity and the grain size in protoplanetary disks using multi-wavelength polarisation observations in the far-infrared to millimetre wavelengths. Finally, we find that moderate grain porosities ($\mathcal{P}\lesssim0.7$) potentially explain the observed polarisation fraction in the system HD 142527 while highly porous grains ($\mathcal{P}>0.7$) fail unless the grain's axis ratio is extraordinarily large., 10 pages, 10 figures

Context: Since circumstellar dust in debris disks is short-lived, dust-replenishing requires the presence of a reservoir of planetesimals. These planetesimals in the parent belt of debris disks orbit their host star and continuously supply the disk with fine dust through their mutual collisions. Aims: We aim to understand effects of different collisional parameters on the observational appearance of eccentric debris disks. Methods: The collisional evolution of selected debris disk configurations was simulated with the numerical code ACE. Subsequently, selected observable quantities are simulated with our newly developed code DMS. The impact of the eccentricity, dynamical excitation, and the material strength is discussed with respect to the grain size distribution, the spectral energy distribution, and spatially resolved images of debris disk systems. Results: The most recognizable features in different collisional evolutions are as follows. First, both the increase of dynamical excitation in the eccentric belt of the debris disk system and the decrease of the material strength of dust particles result in a higher production rate of smaller particles. This reduces the surface brightness differences between the periastron and the apastron sides of the disks. For very low material strengths, the "pericenter glow" phenomenon is reduced and eventually even replaced by the opposite effect, the "apocenter glow". Second, it is possible to constrain the level of collisional activity from the appearance of the disk, for example, the wavelength-dependent apocenter-to-pericenter flux ratio. Within the considered parameter space, the impact of the material strength on the appearance of the disk is stronger than that of dynamical excitation of the system. Finally, we find that the impact of the collisional parameters on the net spectral energy distribution is weak., Accepted for publication in A&A, 15 pages, 17 figures

Plasmas growing or containing nanometric dust particles are widely used and proposed in plasma technological applications for production of nano-crystals and surface deposition. Here, we give a compact review of in situ methods for the diagnostics of nanodust and nanodusty plasmas, which have been developed in the framework of the SFB-TR24 to fully characterize these systems. The methods include kinetic Mie ellipsometry, angular-resolved Mie scattering, and 2D imaging Mie ellipsometry to get information about particle growth processes, particle sizes and particle size distributions. There, also the role of multiple scattering events is analyzed using radiative transfer simulations. Computed tomography and Abel inversion techniques to get the 3D dust density profiles of the particle cloud will be presented. Diagnostics of the dust dynamics yields fundamental dust and plasma properties like particle charges and electron and ion densities. Since nanodusty plasmas usually form dense dust clouds electron depletion (Havnes effect) is found to be significant.

Nanoparticles grown in reactive plasmas and nanodusty plasmas gain high interest from basic science and technology. One of the great challenges of nanodusty plasmas is the in-situ diagnostic of the nanoparticle size and refractive index. The analysis of scattered light by means of the Mie solution of the Maxwell equations was proposed and used as an in-situ size diagnostic during the past two decades. Today, imaging ellipsometry techniques and the investigation of dense, i. e. optically thick nanoparticle clouds demand for analysis methods to take multiple scattering into account. We present the first 3D Monte-Carlo polarized radiative transfer simulations of the scattered light in a dense nanodusty plasma. This technique extends the existing diagnostic methods for the in-situ analysis of the properties of nanoparticles to systems where multiple scattering can not be neglected., 5 pages, 5 figures

Recent interferometric surveys of nearby main-sequence stars show a faint but significant near-infrared excess in roughly two dozen systems, i.$\,$e. around $10\,\%$ to $30\,\%$ of stars surveyed. This excess is attributed to dust located in the immediate vicinity of the star, the origin of which is highly debated. We used previously published interferometric observations to constrain the properties and distribution of this hot dust. Considering both scattered radiation and thermal reemission, we modelled the observed excess in nine of these systems. We find that grains have to be sufficiently absorbing to be consistent with the observed excess, while dielectric grains with pure silicate compositions fail to reproduce the observations. The dust should be located within $\sim\,0.01-1\,au$ from the star depending on its luminosity. Furthermore, we find a significant trend for the disc radius to increase with the stellar luminosity. The dust grains are determined to be below $0.2-0.5\,\mu\textrm{m}$, but above $0.02-0.15\,\mu\textrm{m}$ in radius. The dust masses amount to $(0.2-3.5)\times10^{-9}\,M_\oplus$. The near-infrared excess is probably dominated by thermal reemission, though a contribution of scattered light up to $35\,\%$ cannot be completely excluded. The polarisation degree predicted by our models is always below $5\,\%$, and for grains smaller than $\sim0.2\,\mu\textrm{m}$ even below $1\,\%$. We also modelled the observed near-infrared excess of another ten systems with poorer data in the mid-infrared. The basic results for these systems appear qualitatively similar, yet the constraints on the dust location and the grain sizes are weaker., Comment: 14 pages, 11 figures

We present new data of the protoplanetary disc surrounding the Herbig Ae/Be star HD 169142 obtained in the very broad-band (VBB) with the Zurich imaging polarimeter (ZIMPOL), a sub-system of the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) at the Very Large Telescope (VLT). Our Polarimetric Differential Imaging (PDI) observations probe the disc as close as 0.03" (3.5au) to the star and are able to trace the disc out to ~1.08" (~126au). We find an inner hole, a bright ring bearing substructures around 0.18" (21au), and an elliptically shaped gap stretching from 0.25" to 0.47" (29-55au). Outside of 0.47", the surface brightness drops off, discontinued only by a narrow annular brightness minimum at ~0.63"-0.74" (74-87au). These observations confirm features found in less-well resolved data as well as reveal yet undetected indications for planet-disc interactions, such as small-scale structures, star-disk offsets, and potentially moving shadows., Comment: Accepted for publication in MNRAS

Hot exozodiacal dust emission was detected in recent surveys around two dozen main sequence stars at distances of less than $1\,\text{au}$ using H and K band interferometry. Due to the high contrast as well as the small angular distance between the circumstellar dust and the star, direct observation of this dust component is challenging. An alternative way to explore the hot exozodiacal dust is provided by mid-infrared interferometry. We analyze the L, M and N band interferometric signature of this emission in order to find stronger constraints for the properties and the origin of the hot exozodiacal dust. Considering the parameters of nine debris disc systems derived previously, we model the discs in each of these bands. We find that the M band possesses the best conditions to detect hot dust emission, closely followed by L and N bands. The hot dust in three systems - HD 22484 (10 Tau), HD 102647 ($\beta$ Leo) and HD 177724 ($\zeta$ Aql) - shows a strong signal in the visibility functions which may even allow one to constrain the dust location. In particular, observations in the mid-infrared could help to determine whether the dust piles up at the sublimation radius or is located at radii up to $1\,\text{au}$. In addition, we explore observations of the hot exozodiacal dust with the upcoming mid-infrared interferometer MATISSE at the Very Large Telescope Interferometer (VLTI)., Comment: 6 pages, 4 figures, 3 tables, accepted for publication in MNRAS

Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their solar system's counterparts are the asteroid and Edgeworth-Kuiper belts. The aim of this paper is to provide robust numbers for the incidence of debris discs around FGK stars in the solar neighbourhood. The full sample of 177 FGK stars with d, 31 pages, 15 figures, 10 tables, 2 appendices

Protoplanetary disks are a byproduct of the star formation process. In the dense mid-plane of these disks, planetesimals and planets are expected to form. The first step in planet formation is the growth of dust particles from submicrometer-sized grains to macroscopic mm-sized aggregates. The grain growth is accompanied by radial drift and vertical segregation of the particles within the disk. To understand this essential evolutionary step, spatially resolved multi-wavelength observations as well as photometric data are necessary which reflect the properties of both disk and dust. We present the first spatially resolved image obtained with NACO at the VLT in the L$_\text{p}$ band of the near edge-on protoplanetary disk FS Tau B. Based on this new image, a previously published Hubble image in H band and the spectral energy distribution from optical to millimeter wavelengths, we derive constraints on the spatial dust distribution and the progress of grain growth. For this purpose we perform a disk modeling using the radiative transfer code MC3D. Radial drift and vertical sedimentation of the dust are not considered. We find a best-fit model which features a disk extending from $2\,\text{AU}$ to several hundreds AU with a moderately decreasing surface density and $M_\text{disk}=2.8\,\times\,10^{-2}\,\text{M}_\odot$. The inclination amounts to $i=80^\circ$. Our findings indicate that substantial dust grain growth has taken place and that grains of a size equal to or larger than $1\,\text{mm}$ are present in the disk. In conclusion, the parameters describing the vertical density distribution are better constrained than those describing the radial disk structure., 10 pages, 9 figures, 2 tables

Many debris discs reveal a two-component structure, with an outer Kuiper-belt analogue and a warm inner component whose origin is still a matter of debate. One possibility is that warm emission stems from an "asteroid belt" closer in to the star. We consider a scenario in which a set of giant planets is formed in an initially extended planetesimal disc. These planets carve a broad gap around their orbits, splitting up the disc into the outer and the inner belts. After the gas dispersal, both belts undergo collisional evolution in a steady-state regime. This scenario is explored with detailed collisional simulations involving realistic physics to describe a long-term collisional depletion of the two-component disc. We find that the inner disc may be able to retain larger amounts of material at older ages than thought before on the basis of simplified analytic models. We show that the proposed scenario is consistent with a suite of thermal emission and scattered light observational data for a bright two-temperature debris disc around a nearby solar-type star q$^1$ Eridani. This implies a Solar System-like architecture of the system, with an outer massive "Kuiper belt", an inner "asteroid belt", and a few Neptune- to Jupiter-mass planets in between., accepted for publication in Monthly Notices of the Royal Astronomical Society Main Journal, 9 pages, 3 figures

Context: High-resolution images of circumstellar debris discs reveal off-centred rings that indicate past or ongoing perturbation, possibly caused by secular gravitational interaction with unseen stellar or substellar companions. The purely dynamical aspects of this departure from radial symmetry are well understood. However, the observed dust is subject to additional forces and effects, most notably collisions and drag. Aims: To complement the studies of dynamics, we therefore aim to understand how new asymmetries are created by the addition of collisional evolution and drag forces, and existing ones strengthened or overridden. Methods: We augmented our existing numerical code "Analysis of Collisional Evolution" (ACE) by an azimuthal dimension, the longitude of periapse. A set of fiducial discs with global eccentricities ranging from 0 to 0.4 is evolved over giga-year timescales. Size distribution and spatial variation of dust are analysed and interpreted. The basic impact of belt eccentricity on spectral energy distributions (SEDs) and images is discussed. Results: We find features imposed on characteristic timescales. First, radiation pressure defines size cutoffs that differ between periapse and apoapse, resulting in an asymmetric halo. The differences in size distribution make the observable asymmetry of the halo depend on wavelength. Second, collisional equilibrium prefers smaller grains on the apastron side of the parent belt, reducing the effect of pericentre glow and the overall asymmetry. Third, Poynting-Robertson drag fills the region interior to an eccentric belt such that the apastron side is more tenuous. Interpretation and prediction of the appearance in scattered light is problematic when spatial and size distribution are coupled., Comment: Accepted for publication in A&A, 14 pages, 16 figures

When modeling the density and grain size distribution in debris disks, the minimum particle size is often significantly larger than the corresponding blowout size. While the dust particles are usually modeled as compact, homogenous spheres, we instead investigate the impact of porosity. The optical properties of porous particles are determined, and the influences of porosity on the blowout size and dust temperatures investigated. Using the method of discrete dipole approximation, we calculate the scattering and absorption cross sections of porous particles and derive the blowout size and the behavior of the dust temperature. We investigate the influence on the beta-ratio. Blowout sizes are calculated for various stellar luminosities and porosities, and an approximation equation is derived to estimate the blowout size as a function of these parameters. Furthermore, we investigate the influence of the porosity on the dust equilibrium temperature. The blowout size increases with the particle porosity and stellar luminosity. The dust temperature of porous particles is lower than the one of the compact spheres, in particular the temperature of blowout grains decreases for porous particles., 10 pages, 18 figures

Astronomy and Astrophysics 561 (2014): A114 reproduced with permission from Astronomy & Astrophysics, Context. The dust observed in debris disks is produced through collisions of larger bodies left over from the planet/planetesimal formation process. Spatially resolving these disks permits to constrain their architecture and thus that of the underlying planetary/planetesimal system. Aims. Our Herschel open time key program DUNES aims at detecting and characterizing debris disks around nearby, sun-like stars. In addition to the statistical analysis of the data, the detailed study of single objects through spatially resolving the disk and detailed modeling of the data is a main goal of the project. Methods. We obtained the first observations spatially resolving the debris disk around the sun-like star HIP 17439 (HD 23484) using the instruments PACS and SPIRE on board the Herschel Space Observatory. Simultaneous multi-wavelength modeling of these data together with ancillary data from the literature is presented. Results. A standard single component disk model fails to reproduce the major axis radial profiles at 70 μm, 100 μm, and 160 μm simultaneously. Moreover, the best-fit parameters derived from such a model suggest a very broad disk extending from few au up to few hundreds of au from the star with a nearly constant surface density which seems physically unlikely. However, the constraints from both the data and our limited theoretical investigation are not strong enough to completely rule out this model. An alternative, more plausible, and better fitting model of the system consists of two rings of dust at approx. 30 au and 90 au, respectively, while the constraints on the parameters of this model are weak due to its complexity and intrinsic degeneracies. Conclusions. The disk is probably composed of at least two components with different spatial locations (but not necessarily detached), while a single, broad disk is possible, but less likely. The two spatially well-separated rings of dust in our best-fit model suggest the presence of at least one high mass planet or several low-mass planets clearing the region between the two rings from planetesimals and dust, S. Ertel and J.-C. Augereau thank the French National Research Agency (ANR, contract ANR-2010 BLAN-0505-01, EXOZODI) and PNP-CNES for financial support. C. Eiroa, J. Maldonado, J. P. Marshall, and B. Montesinos are partially supported by Spanish grant AYA 2011-26202. A. V. Krivov acknowledges support from the DFG, grant Kr 2164/10-1. T. Löhne acknowledges support from the DFG, grant Lo 1715/1-1. R. Liseau acknowledges the continued support by the Swedish National Space Board (SNSB)

Cool debris discs are a relic of the planetesimal formation process around their host star, analogous to the solar system's Edgeworth-Kuiper belt. As such, they can be used as a proxy to probe the origin and formation of planetary systems like our own. The Herschel Open Time Key Programmes "DUst around NEarby Stars" (DUNES) and "Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre" (DEBRIS) observed many nearby, sun-like stars at far-infrared wavelengths seeking to detect and characterize the emission from their circumstellar dust. Excess emission attributable to the presence of dust was identified from around $\sim$ 20% of stars. Herschel's high angular resolution ($\sim$ 7" FWHM at 100 $\mu$m) provided the capacity for resolving debris belts around nearby stars with radial extents comparable to the solar system (50 to 100 au). As part of the DUNES and DEBRIS surveys, we obtained observations of three debris disc stars, HIP 22263 (HD 30495), HIP 62207 (HD 110897), and HIP 72848 (HD 131511), at far-infrared wavelengths with the Herschel PACS instrument. Combining these new images and photometry with ancilliary data from the literature, we undertook simultaneous multi-wavelength modelling of the discs' radial profiles and spectral energy distributions using three different methodologies: single annulus, modified black body, and a radiative transfer code. We present the first far-infrared spatially resolved images of these discs and new single-component debris disc models. We characterize the capacity of the models to reproduce the disc parameters based on marginally resolved emission through analysis of two sets of simulated systems (based on the HIP 22263 and HIP 62207 data) with the noise levels typical of the Herschel images. We find that the input parameter values are recovered well at noise levels attained in the observations presented here., Comment: 13 pages, 5 figures, 5 tables, accepted for publication in A&A

We theoretically analyze protoplanetary disks consisting of porous dust grains. In the analysis of observations of protoplanetary disks the dust phase is often assumed to consist of spherical grains, allowing one to apply the Mie scattering formalism. However, in reality, the shape of dust grains is expected to deviate strongly from that of a sphere. We investigate the influence of porous dust grains on the temperature distribution and observable appearance of protoplanetary disks for dust grain porosities of up to 60 %. We performed radiative transfer modeling to simulate the temperature distribution, spectral energy distribution, and spatially resolved intensity and polarization maps. The optical properties of porous grains were calculated using the method of discrete dipole approximation. We find that the flux in the optical wavelength range is for porous grains higher than for compact, spherical grains. The profile of the silicate peak at 9.7 um strongly depends on the degree of grain porosity. The temperature distribution shows significant changes in the direction perpendicular to the midplane. Moreover, simulated polarization maps reveal an increase of the polarization degree by a factor of about four when porous grains are considered, regardless of the disk inclination. The polarization direction is reversed in selected disk regions, depending on the wavelength, grain porosity, and disk inclination. We discuss several possible explanations of this effect and find that multiple scattering explains the effect best. Porosity influences the observable appearance of protoplanetary disks. In particular, the polarization reversal shows a dependence on grain porosity. The physical conditions within the disk are altered by porosity, which might have an effect on the processes of grain growth and disk evolution., Comment: 12 pages, 18 figures

Quantifying the efficiency of dust destruction in the interstellar medium (ISM) due to supernovae (SNe) is crucial for the understanding of galactic dust evolution. We present 3D hydrodynamic simulations of an SN blast wave propagating through the ISM. The interaction between the forward shock of the remnant and the surrounding ISM leads to destruction of ISM dust by the shock-heated gas. We consider the dust processing due to ion sputtering, accretion of atoms/molecules, and grain–grain collisions. Using 2D slices from the simulation time series, we apply post-processing calculations using the paperboats code. We find that efficiency of dust destruction depends strongly on the rate of grain shattering due to grain–grain collisions. The effective dust destruction is similar to previous theoretical estimates when grain–grain collisions are omitted, but with grain shattering included, the net destruction efficiency is roughly one order of magnitude higher. This result indicates that the dust-destruction rate in the ISM may have been severely underestimated in previous work, which only exacerbates the dust-budget crises seen in galaxies at high redshifts.

Supernova remnants (SNRs) are well-recognized dust producers, but their net dust production rate remains elusive due to uncertainties in grain properties that propagate into observed dust mass uncertainties, and determine how efficiently these grains are processed by reverse shocks. In this paper, we present a detection of polarized dust emission in the Crab pulsar wind nebula, the second SNR with confirmed polarized dust emission after Cassiopeia A. We constrain the bulk composition of the dust with new SOFIA/HAWC+ polarimetric data in band C 89 mu m and band D 154 mu m. After correcting for synchrotron polarization, we report dust polarization fractions ranging between 3.7-9.6 per cent and 2.7-7.6 per cent in three individual dusty filaments at 89 and 154 mu m, respectively. The detected polarized signal suggests the presence of large (greater than or similar to 0.05-0.1 mu m) grains in the Crab Nebula. With the observed polarization, and polarized and total fluxes, we constrain the temperatures and masses of carbonaceous and silicate grains. We find that the carbon-rich grain mass fraction varies between 12 and 70 per cent, demonstrating that carbonaceous and silicate grains co-exist in this SNR. Temperatures range from similar to 40 to similar to 70 K and from similar to 30 to similar to 50 K for carbonaceous and silicate grains, respectively. Dust masses range from similar to 10(-4) to similar to 10(-2) M-circle dot for carbonaceous grains and to similar to 10(-1) M-circle dot for silicate grains, in three individual regions., European Research Council (ERC) European Commission 851622, MCIN/AEI PID2020114414GB-100, National Aeronautics & Space Administration (NASA) NNA17BF53C, Deutsches SOFIA Institut (DSI) under DLR 50 OK 0901 URF\R1\211322

The reverse shock in the ejecta of core-collapse supernovae is potentially able to destroy newly formed dust material. In order to determine dust survival rates, we have performed a set of hydrodynamic simulations using the grid-based code AstroBEAR in order to model a shock wave interacting with clumpy supernova ejecta. Dust motions and destruction rates were computed using our newly developed external, post-processing code Paperboats, which includes gas drag, grain charging, sputtering and grain-grain collisions. We have determined dust destruction rates for the oxygen-rich supernova remnant Cassiopeia A as a function of initial grain sizes and clump gas density. We found that up to 30 % of the carbon dust mass is able to survive the passage of the reverse shock if the initial grain size distribution is narrow with radii around ~10 - 50 nm for high gas densities, or with radii around ~0.5 - 1.5 ${\mu}$m for low and medium gas densities. Silicate grains with initial radii around 10 - 30 nm show survival rates of up to 40 % for medium and high density contrasts, while silicate material with micron sized distributions is mostly destroyed. For both materials, the surviving dust mass is rearranged into a new size distribution that can be approximated by two components: a power-law distribution of small grains and a log-normal distribution of grains having the same size range as the initial distribution. Our results show that grain-grain collisions and sputtering are synergistic and that grain-grain collisions can play a crucial role in determining the surviving dust budget in supernova remnants., Comment: Accepted by MNRAS. Author accepted manuscript. Accepted on 28/08/2019. Deposited on 28/08/19. 34 pages

Core-collapse supernovae can condense large masses of dust post-explosion. However, sputtering and grain-grain collisions during the subsequent passage of the dust through the reverse shock can potentially destroy a significant fraction of the newly formed dust before it can reach the interstellar medium. Here we show that in oxygen-rich supernova remnants like Cassiopeia A the penetration and trapping within silicate grains of the same impinging ions of oxygen, silicon and magnesium that are responsible for grain surface sputtering can significantly reduce the net loss of grain material. We model conditions representative of dusty clumps (density contrast $\chi=100$) passing through the reverse shock in the oxygen-rich Cassiopeia A remnant and find that, compared to cases where the effect is neglected, as well as facilitating the formation of grains larger than those that had originally condensed, ion trapping increases the surviving masses of silicate dust by factors of up to two to four, depending on initial grain radii. For higher density contrasts ($\chi\gtrsim180$), we find that the effect of gas accretion on the surface of dust grains surpasses ion trapping, and the survival rate increases to ${\sim}55 \%$ of the initial dust mass for $\chi=256$., Comment: Accepted by ApJ. Author accepted manuscript. Accepted on 06/03/2020. Deposited on 06/03/2020. 11 pages