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Register a new userNew insight into the relation between star formation activity and dust content in galaxies
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Elisabete da Cunha
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(Abridged) We assemble a sample of 3258 low-redshift galaxies from the SDSS DR6 with complementary photometric observations by GALEX, 2MASS and IRAS at far-ultraviolet and infrared wavelengths. We use a recent, simple but physically motivated model to interpret the observed spectral energy distributions of the galaxies in this sample in terms of statistical constraints on physical parameters describing the star formation history and dust content. The focus on a subsample of 1658 galaxies with highest S/N observations enables us to investigate most clearly several strong correlations between various derived physical properties of galaxies. We find that the typical dust mass of a star-forming correlates remarkably well with the star formation rate (SFR). We also find that the dust-to-stellar mass ratio, the ratio of dust mass to star formation rate and the fraction of dust luminosity contributed by the diffuse interstellar medium all correlate strongly with specific SFR. A comparison with recent models of chemical and dust evolution of galaxies suggests that these correlations could arise, at least in part, from an evolutionary sequence. As galaxies form stars, their ISM becomes enriched in dust, while the drop in gas supply makes the specific SFR decrease. Interestingly, as a result, a young, actively star-forming galaxy with low dust-to-gas ratio may still be highly dusty because it contains large amounts of interstellar gas. This may be important for the interpretation of the infrared emission from young, gas-rich star-forming galaxies at high redshift. Our study provides a useful local reference for future statistical studies of the star formation and dust properties of galaxies at high redshifts.
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We present far-infrared (FIR) analysis of 68 Brightest Cluster Galaxies (BCGs) at 0.08 < z < 1.0. Deriving total infrared luminosities directly from Spitzer and Herschel photometry spanning the peak of the dust component (24-500um), we calculate the obscured star formation rate (SFR). 22(+6.2,-5.3)% of the BCGs are detected in the far-infrared, with SFR= 1-150 M_sun/yr. The infrared luminosity is highly correlated with cluster X-ray gas cooling times for cool-core clusters (gas cooling time <1 Gyr), strongly suggesting that the star formation in these BCGs is influenced by the cluster-scale cooling process. The occurrence of the molecular gas tracing Ha emission is also correlated with obscured star formation. For all but the most luminous BCGs (L_TIR > 2x10^11 L_sun), only a small (<0.4 mag) reddening correction is required for SFR(Ha) to agree with SFR_FIR. The relatively low Ha extinction (dust obscuration), compared to values reported for the general star-forming population, lends further weight to an alternate (external) origin for the cold gas. Finally, we use a stacking analysis of non-cool-core clusters to show that the majority of the fuel for star formation in the FIR-bright BCGs is unlikely to originate form normal stellar mass loss.
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The enormous amounts of infrared (IR) radiation emitted by luminous infrared galaxies (LIRGs, L_IR=10^11-10^12Lsun) and ultraluminous infrared galaxies (ULIRGs, L_IR>10^12Lsun) are produced by dust heated by intense star formation (SF) activity and/or an active galactic nucleus (AGN). The elevated star formation rates and high AGN incidence in (U)LIRGs make them ideal candidates to study the interplay between SF and AGN activity in the local universe. In this paper I review recent results on the physical extent of the SF activity, the AGN detection rate (including buried AGN), the AGN bolometric contribution to the luminosity of the systems, as well as the evolution of local LIRGs and ULIRGs. The main emphasis of this review is on recent results from IR observations.
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