2003/08/21 by D. Pierini, C. S. Möller, C. S. Moeller · 5 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Attenuation #Circumstellar dust #Cosmic dust #Galaxies: Formation, Evolution, Phenomena #Luminosity #Photometry (optics) #Star formation #Stellar population #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2003.07126.x
published in Monthly Notices of the Royal Astronomical Society 346(3), 818-824 (Oxford University Press) · 8 pages, 2 figures, accepted for publication in MNRAS
arxiv created 2003/08/21 · openalex publication_date 2003/12/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We investigate whether dust emission in the far-infrared (far-IR) continuum provides a robust estimate of the star formation rate (SFR) for a nearby, normal late-type galaxy. We focus on the ratio of the 40–1000 μm luminosity (Ldust) to the far-ultraviolet (far-UV) (0.165 μm) luminosity, which is connected to recent episodes of star formation. Available total photometry at 0.165, 60, 100 and 170 μm limits the statistics to 30 galaxies, which, however, span a large range in observed (and, thus, attenuated by dust) K-band (2.2 μm) luminosity, morphology and inclination (i). This sample shows that the ratio of Ldust to the observed far-UV luminosity depends not only on i, as expected, but also on morphology and, in a tighter way, on observed K-band luminosity. We find that Ldust/LFUV∝ eLK0.62, where LFUV and LK are the unattenuated stellar luminosities in far-UV and K, respectively, and α is the ratio of the attenuation optical depths at 0.165 μm (τFUV) and 2.2 μm (τK). This relation is to zeroth order independent of i and morphology. It may be further expressed as Ldust/LFUV∝LδK, where δ= 0.61 − 0.02α, under the observationally motivated assumption that, for an average inclination, e∝L−0.02K. We adopt calculations of two different models of attenuation of stellar light by internal dust to derive solid-angle-averaged values of α. We find that δ is positive and decreases towards 0 from the more luminous to the less luminous galaxies. This means that there is no universal ratio of far-IR luminosity to unattenuated far-UV luminosity for nearby, normal late-type galaxies. The far-IR luminosity systematically overestimates SFR in more luminous, earlier-type spirals, owing to the increased fractional contribution to dust heating of optical/near-IR photons in these objects. Conversely, it systematically underestimates SFR in fainter, later-type galaxies, the τFUV of which is reduced. The limited statistics and the uncertainty affecting the previous scaling relations do not allow us to establish quantitative conclusions, but an analogous analysis making use of larger data sets, available in the near future (e.g. from GALEX, ASTRO-F and SIRTF), and of more advanced models will allow a quantitative test of our conclusions.