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Hot dust in normal star-forming galaxies: J H K L^' photometry of the ISO Key Project sample

Hunt, L. K. and Giovanardi, C. and Helou, G. (2002) Hot dust in normal star-forming galaxies: J H K L^' photometry of the ISO Key Project sample. Astronomy & Astrophysics, 394 (3). pp. 873-882. ISSN 0004-6361. doi:10.1051/0004-6361:20021335.

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We present JHK and 3.8 μm (L^') photometry of 26 galaxies in the Infrared Space Observatory (ISO) Normal Galaxy Key Project (KP) sample and of seven normal ellipticals with the aim of investigating the origin of the 4 μm emission. The majority of the KP galaxies, and all the ellipticals, have K - L ≾ 1.0, consistent with stellar photospheres plus moderate dust extinction. Ten of the 26 KP galaxies have K - L ≳ 1.0, corresponding to a flat or rising 4 μm continuum, consistent with significant emission from hot dust at 600–1000 K. K -L is anticorrelated with ISO flux ratio F_(6.75)/F15, weakly correlated with line ratio [O i]/[C ii], but not with [C ii]/FIR or IRAS ratio F_(60)/F_(100). Photodissociation-region models for these galaxies show that the hot dust responsible for red K - L resides in regions of high pressure and intense far-ultraviolet radiation field. Taken together, these results suggest that star formation in normal star-forming galaxies can assume two basic forms: an “active”, relatively rare, mode characterized by hot dust, suppressed Aromatic Features in Emission (AFEs), high pressure, and intense radiation field; and the more common “passive” mode that occurs under more quiescent physical conditions, with AFEs, and without hot dust. The occurrence of these modes appears to only weakly depend on the star-formation rate per unit area. Passive star formation over large scales makes up the bulk of star-forming activity locally, while the “active” regime may dominate at high redshifts.

Item Type:Article
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URLURL TypeDescription Paper
Hunt, L. K.0000-0001-9162-2371
Helou, G.0000-0003-3367-3415
Additional Information:© 2002 ESO. Received: 13 August 2002. Accepted: 12 September 2002. The TIRGO staff was instrumental in the success of these observations. We are grateful to Giovanni Moriondo who valiantly attempted to observe for this project, and to the TIRGO Time Allocation Committee for generous time allocations. We gladly acknowledge enlightening discussions with Marc Sauvage, and would like to thank an anonymous referee for several insightful comments.
Subject Keywords:galaxies: spiral - galaxies: starbursts - galaxies: ISM - ISM: dust
Issue or Number:3
Record Number:CaltechAUTHORS:20180228-100722335
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Official Citation:Hot dust in normal star-forming galaxies: Formula Formula photometry of the ISO Key Project sample L. K. Hunt, C. Giovanardi and G. Helou A&A, 394 3 (2002) 873-882 DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85003
Deposited By: Ruth Sustaita
Deposited On:28 Feb 2018 20:08
Last Modified:15 Nov 2021 20:24

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