Composition and radiative properties of grains in molecular clouds and accretion disks

Pollack, James B.; Hollenbach, D. J.; Beckwith, S.; Simonelli, D. P.; Roush, T. L.; Fong, W.

doi:10.1086/173677

Cited by 975 publications

(1,041 citation statements)

References 0 publications

Supporting

Mentioning

1,005

Contrasting

Order By: Relevance

“…The opacities have a composition that is 40% astronomical silicate, 30% organics, and 30% water ice, roughly following the recipe from Pollack et al (1994) but adjusted to match the dense protostellar core opacities from Ossenkopf & Henning (1994) (see Sheehan & Eisner 2014, for a more thorough discussion). We use a gain size distribution with µ -n a p with p=3.5 (Mathis et al 1977), and dust grains ranging from 0.005 μm to a max .…”

Section: Dustmentioning

confidence: 99%

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Sheehan

Eisner

2017

ApJ

View full text Add to dashboard Cite

Class I protostars are thought to represent an early stage in the lifetime of protoplanetary disks, when they are still embedded in their natal envelope. Here we measure the disk masses of 10 Class I protostars in the Taurus Molecular Cloud to constrain the initial mass budget for forming planets in disks. We use radiative transfer modeling to produce synthetic protostar observations and fit the models to a multi-wavelength data set using a Markov Chain Monte Carlo fitting procedure. We fit these models simultaneously to our new Combined Array for Research in Millimeter-wave Astronomy 1.3 mm observations that are sensitive to the wide range of spatial scales that are expected from protostellar disks and envelopes so as to be able to distinguish each component, as well as broadband spectral energy distributions compiled from the literature. We find a median disk mass of  M 0.018 on average, more massive than the Taurus Class II disks, which have median disk mass of~ M 0.0025 . This decrease in disk mass can be explained if dust grains have grown by a factor of 75 in grain size, indicating that by the Class II stage, at a few Myr, a significant amount of dust grain processing has occurred. However, there is evidence that significant dust processing has occurred even during the Class I stage, so it is likely that the initial mass budget is higher than the value quoted here.

show abstract

Section: Dustmentioning

confidence: 99%

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Sheehan

Eisner

2017

ApJ

View full text Add to dashboard Cite

show abstract

“…8.7. Left panel: the dust absorption opacity as a function of wavelength (Isella et al 2010) for standard interstellar grain composition (12% silicates, 27% organics, and 61% water ice; Pollack et al 1994), and size distribution n(a) ∝ a −3.5 from 0.01 to 1 µm radius. The absorption coefficient is normalised relative to that at visual wavelength (6060Å, κ V = 2.3 × 10 4 gr −1 ) -for a standard gasto-dust abundance (∼100 in mass) with N H+2H2 = 2 × 10 21 cm −2 per mag of visual extinction (A V ).…”

Section: Infrared Emissionmentioning

confidence: 99%

Evolution of star formation and gas

Scoville¹

2013

Secular Evolution of Galaxies

View full text Add to dashboard Cite

In these lectures I review observations of star-forming molecular clouds in our Galaxy and nearby galaxies to develop a physical intuition for understanding star formation in the local and high-redshift Universe. A lot of this material is drawn from early work in the field since much of the work was done two decades ago and this background is not generally available in the present literature. I also attempt to synthesise our welldeveloped understanding of star formation in low-redshift galaxies with constraints from theory and observations at high redshift to develop an intuitive model for the evolution of galaxy mass and luminosity functions in the early Universe.The overall goal of this contribution is to provide students with background helpful for analysis of far-infrared (FIR) observations from Herschel and millimetre/submillimetre (mm/submm) imaging with ALMA (the Atacama Large Millimetre/submillimetre Array).These two instruments will revolutionise our understanding of the interstellar medium (ISM) and associated star formation and galaxy evolution, both locally and in the distant Universe. To facilitate interpreting the FIR spectra of Galactic star-forming regions and high-redshift sources, I develop a model for the dust heating and radiative transfer in order to elucidate the observed infrared (IR) emissions. I do this because I am not aware of a similar coherent discussion in the literature. Star-forming molecular cloudsHere, I provide an overview of the observations and physics of star-forming molecular clouds in the Galaxy and nearby normal galaxies. The motivation is to develop the intuitive background for analysis of observations at high 1 arXiv:1210.6990v2 [astro-ph.CO] 1 Nov 2012

show abstract

“…In addition, even at some of the envelopes of protostars, the opacity index is indicated to be as low as the later stage of protoplanetary disks, which suggests that the dust grains are grown to a millimeter in size even in the early phase of the protoplanetary disks (Miotello et al 2014) although the modeling contains large uncertainties. However, the low opacity index can also be explained with optically thick disks (e.g., Ricci et al 2012), irregularly shaped grains (e.g., Min et al 2005Min et al , 2007, or different chemical composition of the grains (e.g., Pollack et al 1994;Mennella et al 1998;Jones 2012). Therefore, there are still large uncertainties of constraints on the grain size in protoplanetary disks.…”

Section: Introductionmentioning

confidence: 99%

Grain Size Constraints on Hl Tau With Polarization Signature

Kataoka

Muto

Momose

et al. 2016

ApJ

119

147

View full text Add to dashboard Cite

The millimeter-wave polarization of the protoplanetary disk around HL Tau has been interpreted as the emission from elongated dust grains aligned with the magnetic field in the disk. However, the self-scattering of thermal dust emission may also explain the observed millimeter-wave polarization. In this paper, we report a modeling of the millimeter-wave polarization of the HL Tau disk with the self-polarization. Dust grains are assumed to be spherical and to have a power-law size distribution. We change the maximum grain size with a fixed dust composition in a fixed disk model to find the grain size to reproduce the observed signature. We find that the direction of the polarization vectors and the polarization degree can be explained with the self-scattering. Moreover, the polarization degree can be explained only if the maximum grain size is ∼150 μm. The obtained grain size from the polarization is different from that which has been previously expected from the spectral index of the dust opacity coefficient (a millimeter or larger) if the emission is optically thin. We discuss that porous dust aggregates may solve the inconsistency of the maximum grain size between the two constraints.

show abstract

Composition and radiative properties of grains in molecular clouds and accretion disks

Cited by 975 publications

References 0 publications

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Disk Masses for Embedded Class I Protostars in the Taurus Molecular Cloud

Evolution of star formation and gas

Grain Size Constraints on Hl Tau With Polarization Signature

Contact Info

Product

Resources

About