From interstellar abundances to grain composition: the major dust constituents Mg, Si and Fe

Details From interstellar abundances to grain composition: the major dust constituents Mg, Si and Fe From interstellar abundances to grain composition: the major dust constituents Mg, Si and Fe

2010-04-06

arxiv.org/abs/1004.0967v2

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

16 pages, 16 figures, accepted for publication in Astronomy and Astrophysics

Scientific paper

We analyse observational correlations for three elements entering into the composition of interstellar silicate and oxide grains. Using current solar abundances (Asplund et al. 2009), we convert the gas-phase abundances into dust-phase abundances for 196 sightlines. We deduce a sharp difference in abundances for sightlines located at low ($|b|<30\degr$) and high ($|b|>30\degr$) galactic latitudes. For high-latitude stars the ratios Mg/Si and Fe/Si in dust are close to 1.5. For disk stars they are reduced to ${\rm Mg/Si} \sim 1.2$ and ${\rm Fe/Si} \sim 1.05$. The derived numbers indicate that 1) the dust grains cannot be the mixture of silicates with olivine and pyroxene composition only and some amount of magnesium or iron (or both) should be in another population and 2) the destruction of Mg-rich grains in the warm medium is more effective than of Fe-rich grains. We reveal a decrease of dust-phase abundances and correspondingly an increase of gas-phase abundances with distance $D$ for stars with $D\ga 400$\,pc. We attribute this fact to an observational selection effect: a systematic trend toward smaller observed hydrogen column density for distant stars. We find differences in abundances for disk stars with low ($E({\rm B-V}) \la 0.2$) and high ($E({\rm B-V}) \ga 0.2$) reddenings which reflect the distinction between the sightlines passing through diffuse and translucent interstellar clouds. For Scorpius-Ophiuchus we detect an uniform increase of dust-phase abundances of Mg and Si with an increase of the ratio of total to selective extinction $R_{\rm V}$ and a decrease of the strength of the far-UV extinction. This is the first evidence for a growth of Mg-Si grains due to accretion in the interstellar medium.

Affiliated with

Also associated with

No associations

Rating

From interstellar abundances to grain composition: the major dust constituents Mg, Si and Fe 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 From interstellar abundances to grain composition: the major dust constituents Mg, Si and Fe, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and From interstellar abundances to grain composition: the major dust constituents Mg, Si and Fe will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-396219