In:
The Astrophysical Journal, American Astronomical Society, Vol. 924, No. 2 ( 2022-01-01), p. 138-
Abstract:
Dust permeates the interstellar medium, reddening and polarizing background starlight, but dust properties vary with local environment. In order to characterize dust in a highly irradiated diffuse cloud, we measure the reddening and optical polarization toward 27 stars surrounding the midlatitude b = +24° O9.2IV star ζ Ophiuchi, using new optical spectroscopy and polarimetry. We incrementally deredden and depolarize with distance, allowing us to distinguish dust components along these sight lines. The data indicate three distinct dust populations: a foreground component characteristic of average Milky Way dust ( R V ≈ 3.1, d ≲ 180 pc), a highly polarizing mid-distance component in the vicinity of ζ Oph ( R V ≈ 2.4, 200 pc 〈 d 〈 300 pc), and a nonpolarizing distant component ( R V ≈ 3.6, 600 pc 〈 d 〈 2000 pc). Prominent 8 μ m infrared striations spanning the field of view likely have high polycyclic aromatic hydrocarbon content and are illuminated by ζ Oph. Foreground-subtracted polarizations roughly align with these striations, which, we argue, lie immediately behind ζ Oph and constitute the highly polarizing mid-distance dust. This component polarizes very efficiently ( P V 〉 9.1 E ( B − V )), implying a high degree of grain alignment and suggesting that the bulk of the polarization occurs in a small fraction of the volume. The large R V in the distant component reveals that dust above the Galactic plane ( z 〉 250 pc) may contain a greater fraction of large grains than the Milky Way average.
Type of Medium:
Online Resource
ISSN:
0004-637X
,
1538-4357
DOI:
10.3847/1538-4357/ac36d8
Language:
Unknown
Publisher:
American Astronomical Society
Publication Date:
2022
detail.hit.zdb_id:
2207648-7
detail.hit.zdb_id:
1473835-1
SSG:
16,12
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