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Grain growth by accretion of gas-phase metals is a common assumption in models of dust evolution, but in dense gas, where the timescale is short enough for accretion to be effective, material is accreted in the form of ice mantles rather…

Astrophysics of Galaxies · Physics 2021-01-20 F. D. Priestley , I. De Looze , M. J. Barlow

Theoretical studies have revealed that dust grains are usually moving fast through the turbulent interstellar gas, which could have significant effects upon interstellar chemistry by modifying grain accretion. This effect is investigated in…

Astrophysics of Galaxies · Physics 2015-12-09 J. X. Ge , J. H. He , H. R. Yan

Paramagnetic alignment of fractal suprathermally rotating grains is discussed. It is shown that if the concentration of H$_{2}$formation sites is low and resurfacing is active, fractal structure of grains enhances their alignment. Studying…

Astrophysics · Physics 2007-05-23 A. Lazarian

Multiwavelength dust continuum and polarization observations arising from self-scattering have been used to investigate grain sizes in young disks. However, the polarization by self-scattering is low in face-on optically thick disks and…

Solar and Stellar Astrophysics · Physics 2023-11-07 Joaquin Zamponi , María José Maureira , Hauyu Baobab Liu , Bo Zhao , Dominique Segura-Cox , Chia-Lin Ko , Paola Caselli

How and when in the star formation sequence do dust grains start to grow into pebbles is a cornerstone question to both star and planet formation. We compute the polarized radiative transfer from a model solar-type protostellar core, using…

Context. We investigate the grain opacity k_gr in the atmosphere of protoplanets. This is important for the planetary mass-radius relation since k_gr affects the H/He envelope mass of low-mass planets and the critical core mass of giant…

Earth and Planetary Astrophysics · Physics 2014-12-10 C. Mordasini

Maps of estimated dust column density in molecular clouds are usually assumed to reliably trace the total gas column density structure. In this work we present results showing a clear discrepancy between the dust and the gas distribution in…

The results of a near-infrared (J H K LP) imaging linear polarimetry survey of 20 young stellar objects (YSOs) in rho Ophiuchi are presented. The majority of the sources are unresolved, with K-band polarizations, P_K < 6 per cent. Several…

Astrophysics · Physics 2009-11-13 A. F. Beckford , P. W. Lucas , A. C. Chrysostomou , T. M. Gledhill

This paper provides a quantitative account of a recently introduced mechanism of mechanical alignment of suprathermally rotating grains. These rapidly rotating grains are essentially not susceptible to random torques arising from gas-grain…

Astrophysics · Physics 2009-10-28 Alex Lazarian , Michael Efroimsky

We present a study of the polarizing power of the dust in cold dense regions (dark clouds) compared to that of dust in the general interstellar medium (ISM). Our study uses new polarimetric, optical, and spectral classification data for 36…

Astrophysics · Physics 2009-10-30 Hector G. Arce , Alyssa A. Goodman , Pierre Bastien , Nadine Manset , Mathew Sumner

Dust polarization observations at optical wavelengths help to understand the dust grain properties and trace the plane-of-the-sky component of the magnetic field. In this study, we make use of the $I$-band polarization data acquired from…

Astrophysics of Galaxies · Physics 2022-08-09 N. Bijas , Chakali Eswaraiah , Jia-Wei Wang , Jessy Jose , Wen-Ping Chen , Di Li , Shih-Ping Lai , D. K. Ojha

The mechanisms causing millimeter-wave polarization in protoplanetary disks are under debate. To disentangle the polarization mechanisms, we observe the protoplanetary disk around HL Tau at 3.1 mm with the Atacama Large…

Earth and Planetary Astrophysics · Physics 2017-07-26 Akimasa Kataoka , Takashi Tsukagoshi , Adriana Pohl , Takayuki Muto , Hiroshi Nagai , Ian W. Stephens , Kohji Tomisaka , Munetake Momose

Dust grains play a major role in many astrophysical contexts. They affect the chemical, magnetic, dynamical, and optical properties of their environment, from galaxies down to the interstellar medium, star-forming regions, and…

Astrophysics of Galaxies · Physics 2021-05-18 Pierre Marchand , Vincent Guillet , Ugo Lebreuilly , Mordecai-Mark Mac Low

Context: Fast surface conversion between ortho- and para-H2 has been observed in laboratory studies, and this mechanism has been proposed to play a role in the control of the ortho-para ratio in the interstellar medium. Observations of…

Astrophysics of Galaxies · Physics 2016-03-16 Emeric Bron , Franck Le Petit , Jacques Le Bourlot

Atomic species in the interstellar medium (ISM) transition out of their gas phase mainly by depletion onto dust. In this study, we examine if there is any change to the spectral line ratio predictions from a photoionization model of the…

Astrophysics of Galaxies · Physics 2022-04-01 Chamani Gunasekera , Xihan Ji , Marios Chatzikos , Renbin Yan , Gary Ferland

Recent observations in emission, extinction, and polarisation have at least partially invalidated most of the astronomical standard grain models for the diffuse ISM. Moreover, lab measurements on interstellar silicate analogues have shown…

Calculations are performed for the linear polarization of starlight due to extinction by aligned dust grains when the starlight traverses a medium with irregular magnetic fields. This medium is intended to represent the optically thick…

Astrophysics · Physics 2009-10-31 D. S. Wiebe , W. D. Watson

We present a method to include the evolution of the grain size and grain opacity $\kappa_\mathrm{gr}$ in the equations describing the structure of protoplanetary atmospheres. The key assumption of this method is that a single grain size…

Earth and Planetary Astrophysics · Physics 2015-06-22 Chris W. Ormel

The dust emission polarization spectrum -- how the polarization percentage changes with wavelength -- serves as a probe of dust grain properties in star-forming regions. In this paper, we present 89 $\mu$m - 214 $\mu$m polarization spectrum…

Solar and Stellar Astrophysics · Physics 2025-09-18 Erin G. Cox , Giles Novak , David T. Chuss , Dennis Lee , Marc Berthoud , Kaitlyn Karpovich , Joseph M. Michail , Zhi-Yun Li , Peter C. Ashton

The polarization of the cosmic microwave background (CMB) can be used to search for parity-violating processes like that predicted by a Chern-Simons coupling to a light pseudoscalar field. Such an interaction rotates $E$ modes into $B$…

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