2011A&A...533A..16W


Query : 2011A&A...533A..16W

2011A&A...533A..16W - Astronomy and Astrophysics, volume 533A, 16-16 (2011/9-1)

The galactic dust-to-metals ratio and metallicity using gamma-ray bursts.

WATSON D.

Abstract (from CDS):

The metallicity and dust-to-metals ratio of the Galaxy are fundamental parameters in understanding the interstellar medium (ISM). Currently, there is still some uncertainty surrounding these parameters. In this paper, the dust-to-metals ratio in the Galaxy is determined using the photoelectric absorption of the soft X-ray afterglows of a large sample of several hundred gamma-ray bursts (GRBs) to determine the metal column density in combination with Galactic dust maps to determine the line-of-sight dust extinction through the Galaxy in the direction of the GRB. GRB afterglows often have large extragalactic soft X-ray absorptions and therefore the GRB sample's upper-bound will define the Galactic dust-to-metals relation. Using a two-dimensional two-sample Kolmogorov-Smirnoff test, we determine this upper-bound and so derive the dust-to-metals ratio of the Galaxy. We find NH=2.2+0.3–0.4x1021cm–2AV as- assuming solar, Anders & Grevesse (1989, Geochim. Cosmochim. Acta, 53, 197), metallicity. This result is consistent with previous findings using bright X-ray sources in the Galaxy. Using the same technique but substituting the HI maps from the Leiden-Argentine-Bonn survey for the dust maps, allows us to place a limit on the metallicity in the Galaxy. We find a metallicity consistent with the Anders & Grevesse (1989) solar values often used in X-ray fitting. Based on this and previous studies, we suggest that the metallicity of a typical ISM sightline through the Galaxy is ∼0.25dex higher than the current best estimate of the solar metallicity. We further show that the dust-to-gas ratio seems to be correlated with the total gas column density, and that this may be due to the metallicity gradient observed toward the Galactic centre. Based on the non-constant nature of the dust-to-gas ratio, we propose that the dust column density, at NH= 2.2x1021cm–2AV, represents a better proxy for the soft X-ray absorption column density than HI maps.

Abstract Copyright:

Journal keyword(s): ISM: abundances - dust, extinction - Galaxy: abundances - X-rays: ISM - gamma-ray burst: general

Simbad objects: 4

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Number of rows : 4
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 GRB 101030A gB 11 05 34.0 -16 23 11           ~ 28 0
2 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3199 1
3 NAME Galactic Center gam 17 45 39.60213 -29 00 22.0000           ~ 12317 0
4 NAME Sgr A East Rad 17 45 41 -29 00.8           ~ 459 2

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2021.08.03-08:43:50

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