===================================================================== ==> in this proposal, more time is being requested for fboulang.wismdust ==> this proposal requests an upgrade from priority 3 for fboulang.wismdust ===================================================================== dust grains in low density gas are subjected to sputtering and shattering in fast supernovae shocks. although there has been extensive modelling of the dust destruction, still little is known about the grains which survive. jones et al. (1996) have modeled the effect of the destruction processes on the size distribution of grains. they predict that fast j shocks are efficient in grinding large dust grains into smaller particles. two recent results providing information about dust in low density gas may be confirming this prediction. (1) analysis of dirbe data has brought evidence for a large enhancement of the abundance of very small grains around the nearby star spica. spica is located in a low density region of the ism within the loop i bubble centered on the sco-cen association. with this location it is tentalizing to associate the enhanced abundance with a shock. (2) using isocam we have detected extended emission around a halo star, hd149881, located at a z-height of 1.2 kpc. this detection suggests the presence of pahs in the galactic halo. since matter in the halo must have been expulsed up to high z heights by some energetic events the detection could indicate that pahs can be produced by shock processing of large grains. we propose new observations to complement these results and confirm them on one additonal galactic halo star. we also ask for a time upgrade to extend a statistical search for dust in the galactic halo. the proposed observations should have important implications on the understanding of the dust life-cycle and the evolution of interstellar gas in between the different phases of the interstellar medium.
Instrument
CAM01 , PHT32
Temporal Coverage
1997-01-17T21:07:05Z/1997-01-23T17:55:59Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, BOULANGER et al., 1998, 'VERY SMALL DUST GRAINS IN THE GALACTIC HALO: DUST DESTRUCTION IN SHOCKS', 1.0, European Space Agency, https://doi.org/10.5270/esa-307n340
