Year: 2017
Type: dissertation
Abstract: Diffuse Galactic Light (DGL) is the scattered starlight by interstellar dust grains in the Galaxy.DGL gives us crucial information on optical properties especially size of interstellar dust grains, because the scattering phenomena is the most efficient where its size is comparable to the wavelength of scattered light.To date, measurements of DGL were mostly carried out only in optical wavelength range, however they are insufficient to understand the optical properties of interstellar dust grains.In this study, we have conducted near-infrared observations of diffuse clouds in high Galactic latitude (|b| ∼ 40 • ) at I-band (1.1 µm) and H-band (1.6 µm), and obtained high quality photometric data with a wide-field imager (∼ 3.67 × 3.67 deg 2 ) onboard Korean space telescope so-called Multi-purpose Infra-Red Imaging System (MIRIS), with the best accuracy sufficient to discuss on size of interstellar dust grains.Since the starlight is not only scattered but also absorbed by interstellar dust and re-emitted in the far-infrared, the near-infrared brightness correlates well with the farinfrared one.Thus, the DGL brightness was derived by correlating the near-infrared brightness with the far-infrared brightness observed with IRAS and DIRBE/COBE in a wide density range from blank field to dense dust cloud.In addition, by correlating the near-infrared brightness with the optical brightness taken from existing optical images, we derived an optical to near-infrared spectrum of DGL.The derived DGL at 1.1 µm and 1.6 µm are different among the three observed field, which means the scattering property of interstellar dust grains is different even in similar Galactic latitude.To investigate the size of interstellar dust grains in detail, we firstly compared our result with model spectra of DGL which is generated by applying the conventional interstellar dust models incorporating sub-micrometer sized grains.However, the model spectra shows significantly bluer color than the measured DGL's even though anisotropic effect on scattering is taken into account.iii
Authors: 大西, 陽介, Onishi, Yosuke
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7145019533
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