Open AccessFar‐infrared dust properties in the Galaxy and the Magellanic Clouds
Author(s) -
Hirashita Hiroyuki,
Hibi Yasunori,
Shibai Hiroshi
Publication year - 2007
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2007.11745.x
Subject(s) - physics , galaxy , astrophysics , emissivity , large magellanic cloud , cosmic dust , astronomy , infrared , interstellar medium , optics
A recent data analysis of the far‐infrared (FIR) map of the Galaxy and the Magellanic Clouds has shown that there is a tight correlation between two FIR colours: the 60–100 and 100–140 μm colours. This FIR colour relation called ‘main correlation’ can be interpreted as indicative of a sequence of various interstellar radiation fields with a common FIR optical property of grains. In this paper, we constrain the FIR optical properties of grains by comparing the calculated FIR colours with the observational main correlation. We show that neither of the ‘standard’ grain species (i.e. astronomical silicate and graphite grains) reproduces the main correlation. However, if the emissivity index at 100 ≲λ≲ 200 μm is changed to ≃1–1.5 (not ≃2 as the above two species), the main correlation can be successfully explained. Thus, we propose that the FIR emissivity index is ≃1–1.5 for the dust in the Galaxy and the Magellanic Clouds at 100 ≲λ≲ 200 μm . We also consider the origin of the minor correlation called ‘subcorrelation’, which can be used to estimate the Galactic star formation rate.