ISOCAM observations of the Ursa Major cirrus: Evidence for large abundance variations of small dust grains

Details ISOCAM observations of the Ursa Major cirrus: Evidence for large abundance variations of small dust grains ISOCAM observations of the Ursa Major cirrus: Evidence for large abundance variations of small dust grains

2002-03-12

arxiv.org/abs/astro-ph/0203192v1

Aastronomy and Astrophysics, 2002, 381, 209

Astronomy and Astrophysics

Astrophysics

11 pages, 13 figures, better resolution figures to be found in published version

Scientific paper

10.1051/0004-6361:20011074

We present mid-IR imaging observations of a high Galactic latitude cirrus obtained with the ISO camera ISOCAM at 6" angular resolution. The observations were done with two filters LW2 (5-8.5 microns) and LW3 (12-18 microns) that measure respectively the aromatic carbon bands and the underlying continuum emission from small dust particles. Three 0.05 square degree images sample atomic and molecular sections in the Ursa Major cirrus. These images are compared with Hi, CO and IRAS observations. In such a cloud transparent to stellar light (Av < 0.5) the mid-infrared to 100 microns and the mid-IR emissivity per hydrogen are related to the abundance and the optical properties of small dust particles independently of any modelling of the penetration of the radiation. Within the atomic section of the cloud, the comparison between ISOCAM images and 21 cm interferometric data highlights an enhancement of the mid-IR emitters abundance by a factor ~5 in an Hi filament characterized by a large transverse velocity gradient suggestive of rotation. Furthermore, a drop in the abundance of the same mid-IR emitters is observed at the interface between the atomic and molecular cirrus sections. We propose that these abundance variations of the mid-IR emitters are related to the production of small dust particles by grain shattering in energetic grain-grain collisions generated by turbulent motions within the cirrus and inversely by their disappearance due to coagulation on large grains. At the atomic-molecular interface we also observe a decrease of the Lw2/Lw3 ratio by a factor 2 in the molecular region. This could result from a modification of the dust size distribution or of the intrinsic optical properties of the small dust particles.

Affiliated with

Also associated with

No associations

Rating

ISOCAM observations of the Ursa Major cirrus: Evidence for large abundance variations of small dust grains does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with ISOCAM observations of the Ursa Major cirrus: Evidence for large abundance variations of small dust grains, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and ISOCAM observations of the Ursa Major cirrus: Evidence for large abundance variations of small dust grains will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-252748