Dust growth in the interstellar medium: how do accretion and coagulation interplay?
Article first published online: 1 MAR 2012
© 2012 The Author Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 422, Issue 2, pages 1263–1271, May 2012
How to Cite
Hirashita, H. (2012), Dust growth in the interstellar medium: how do accretion and coagulation interplay?. Monthly Notices of the Royal Astronomical Society, 422: 1263–1271. doi: 10.1111/j.1365-2966.2012.20702.x
- Issue published online: 25 APR 2012
- Article first published online: 1 MAR 2012
- Accepted 2012 February 5. Received 2012 February 2; in original form 2011 December 12
- ISM: clouds;
- dust, extinction;
- ISM: evolution;
- galaxies: evolution;
- galaxies: ISM
Dust grains grow in interstellar clouds by accretion and coagulation. In this paper, we focus on these two grain growth processes and numerically investigate how they interplay to increase the grain radii. We show that accretion efficiently depletes grains with radii on a time-scale of 10 Myr in solar-metallicity molecular clouds. Coagulation also occurs on a similar time-scale, but accretion is more efficient in producing a large bump in the grain size distribution. Coagulation further pushes the grains to larger sizes after a major part of the gas-phase metals are used up. Similar grain sizes are achieved by coagulation regardless of whether accretion takes place or not; in this sense, accretion and coagulation modify the grain size distribution independently. The increase of the total dust mass in a cloud is also investigated. We show that coagulation slightly ‘suppresses’ dust mass growth by accretion but that this effect is slight enough to be neglected in considering the grain mass budget in galaxies. Finally, we examine how accretion and coagulation affect the extinction curve: the ultraviolet slope and the carbon bump are enhanced by accretion, while they are flattened by coagulation.