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Title: INTERSTELLAR DUST PROPERTIES OF M51 FROM AKARI MID-INFRARED IMAGES

Using mid-infrared (MIR) images of four photometric bands of the Infrared Camera on board the AKARI satellite, S7 (7 μm), S11 (11 μm), L15 (15 μm), and L24 (24 μm), we investigate the interstellar dust properties of the nearby pair of galaxies M51 with respect to their spiral arm structure. The arm and interarm regions are defined based on a spatially filtered stellar component model image and we measure the arm/interarm contrast for each band. The contrast is lowest in the S11 image, which we interpret as meaning that among the four AKARI MIR bands, the S11 image best correlates with the spatial distribution of dust grains including colder components. On the other hand, the L24 image, with the highest contrast, traces warmer dust heated by star forming activity. The surface brightness ratio between the bands, i.e., color, is measured over the disk of the main galaxy, M51a, at 300 pc resolution. We find that the distribution of S7/S11 is smooth and traces the global spiral arm pattern well while L15/S11 and L24/S11 peak at individual H II regions. This result indicates that the ionization state of polycyclic aromatic hydrocarbons (PAHs) is related to the spiral structure. Comparison with observationalmore » data and dust models also supports the importance of the variation in the PAH ionization state within the M51a disk. However, the mechanism driving this variation is not yet clear from the currently available datasets. Another suggestion from the comparison with the models is that the PAH fraction in the total dust mass is higher than previously estimated.« less
Authors:
; ; ;  [1] ; ;  [2]
  1. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Kanagawa 252-5210 (Japan)
  2. Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan)
Publication Date:
OSTI Identifier:
22270534
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 778; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; BRIGHTNESS; CAMERAS; COMPARATIVE EVALUATIONS; COSMIC DUST; GALAXIES; H2 REGIONS; IMAGES; INTERMEDIATE INFRARED RADIATION; INTERSTELLAR GRAINS; IONIZATION; PHOTOMETRY; POLYCYCLIC AROMATIC HYDROCARBONS; RESOLUTION; SPATIAL DISTRIBUTION; STARS