Mathematics – Logic
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...429..153s&link_type=abstract
The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 429, no. 1, p. 153-171
Mathematics
Logic
44
Faint Objects, Far Infrared Radiation, Galactic Evolution, Hubble Diagram, Interstellar Matter, Cosmic Dust, Elliptical Galaxies, Interstellar Extinction, Metallicity, Spectral Energy Distribution
Scientific paper
The far infrared (FIR) properties of normal, non-infrared-bright galaxies along the Hubble sequence are studied as a function of their morphological type, using a complete sample of galaxies in the magnitude-limited (mZwicky less than or equal to 14.5) Center for Astrophysics (CfA) sample detected in the Faint Source Survey, a total of 1544 galaxies. We find that the short-wavelength FIR emission is best explained as having mainly an interstellar origin, and not as coming mostly from nonthermal sources or from circumstellar or photospheric emission from evolved stars. The (FIR) colors of galaxies from type-E-SO to type Sbs, are mainly controlled by the spatial distribution of the dust relative to the stars. The dust in elliptical galaxies is as hot as in Magellanic irregulars, because it is concentrated in their central regions (r approximately less than 1 kpc) where the UV energy density from post Asympotic Giant Branch (AGB) stars is the highest. The dust in Sbc galaxies is the coolest because it is most spread out in the disk where the UV energy density is the lowest. From type Sbc to type Sdm, the FIR colors are controlled by an increasing star formation efficiency, modulated by a change in dust composition. The metallicity decreases in Sdm galaxies leads to a deficiency of small grains relative to large grains and reduction of the dust and H2 masses relative to the H I masses. Conversely, in elliptical galaxies, the larger metallicity may increase the abundance of small grains relative to large grains. Most of the FIR color trends as a function of galaxian morphological type can be reproduced by dust models with three components Polyclic Aromatic Hydrocarbons ((PAHs), intermediate-size grains, and large grains), combined with the appropriate dust heating spectral energy distribution.
Sauvage Marc
Thuan Trinh Xuan
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