Dust production 680-850 million years after the Big Bang

Dust plays an important role in our understanding of the Universe, but it is not obvious yet how the dust in the distant universe was formed. I derived the dust yields per asymptotic giant branch (AGB) star and per supernova (SN) required to explain dust masses of galaxies at z=6.3-7.5 (680-850 million years after the Big Bang) for which dust emission has been detected (HFLS3 at z=6.34, ULAS J1120+0641 at z=7.085, and A1689-zD1 at z=7.5), or unsuccessfully searched for. I found very high required yields, implying that AGB stars could not contribute substantially to dust production at these redshifts, and that SNe could explain these dust masses, but only if they do not destroy most of the dust they form (which is unlikely given the upper limits on the SN dust yields derived for galaxies where dust is not detected). This suggests that the grain growth in the interstellar medium is likely required at these early epochs.Comment: Accepted to A&A. 6 pages, 1 figure, 2 tables. V2: minor changes to match the published versio

Spectral energy distributions of submm/radio bright gamma-ray burst host galaxies

We present optical to radio spectral energy distribution fitting of the host galaxies of four long gamma-ray bursts: 980703, 000210, 000418 and 010222, which were detected at submillimetre and/or radio wavelengths. We find that only very young starburst galaxy models are consistent with the data having both blue optical colors and a pronounced submm emission. For each host we are able to construct a model consistent with the short- and long-wavelength parts of the spectra. We find galaxy ages ranging from 0.09 to 2.0 Gyrs and star formation rates ranging from 138 to 380 MSun/yr.Comment: 6 pages, 1 figure, Proceedings of the Conference "The Multicoloured Landscape of Compact Objects and their Explosive Origins" (Cefalu, Sicily, 2006 June 11-24). Eds. L. Burderi et al. (New York: AIP), in press, for SED templates, see http://archive.dark-cosmology.dk

Dust production scenarios in galaxies at z ~ 6-8.3

The mechanism of dust formation in galaxies at high redshift is still unknown. Asymptotic giant branch (AGB) stars and explosions of supernovae (SNe) are possible dust producers, and non-stellar processes may substantially contribute to dust production, for example grain growth in the interstellar medium (ISM). Our aim is to determine the contribution to dust production of AGB stars and SNe in nine galaxies at z ~ 6-8.3, for which observations of dust have been recently attempted. In order to determine the origin of the observed dust we have determined dust yields per AGB star and SN required to explain the total amounts of dust in these galaxies. We find that AGB stars were not able to produce the amounts of dust observed in the galaxies in our sample. In order to explain these dust masses, SNe would have to have maximum efficiency and not destroy the dust which they formed. Therefore, the observed amounts of dust in the galaxies in the early universe were formed either by efficient supernovae or by a non-stellar mechanism, for instance the grain growth in the interstellar medium.Comment: Accepted for publication in A&A, 5 pages, 1 figur

Shaping the dust mass - star-formation rate relation

There is a remarkably tight relation between the observationally inferred dust masses and star-formation rates (SFRs) of SDSS galaxies, Mdust $\propto$ SFR$^{1.11}$ (Da Cunha et al. 2010). Here we extend the Mdust-SFR relation to the high end and show that it bends over at very large SFRs (i.e., dust masses are lower than predicted for a given SFR). We identify several distinct evolutionary processes in the diagram: (1) A star-bursting phase in which dust builds up rapidly at early times. The maximum attainable dust mass in this process is the cause of the bend-over of the relation. A high dust-formation efficiency, a bottom-light initial mass function, and negligible supernova shock dust destruction are required to produce sufficiently high dust masses. (2) A quiescent star-forming phase in which the subsequent parallel decline in dust mass and SFR gives rise to the Mdust-SFR relation, through astration and dust destruction. The dust-to-gas ratio is approximately constant along the relation. We show that the power-law slope of the Mdust-SFR relation is inversely proportional to the global Schmidt-Kennicutt law exponent (i.e., $\sim 0.9$) in simple chemical evolution models. (3) A quenching phase which causes star formation to drop while the dust mass stays roughly constant or drops proportionally. Combined with merging, these processes, as well as the range in total baryonic mass, give rise to a complex population of the diagram which adds significant scatter to the original Mdust-SFR relation. (4) At very high redshifts, a population of galaxies located significantly below the local relation is predicted.Comment: 5 pages, 1 figure, ApJL, in pres

„Miejsce cieniem kryte” w domu nr 4 z Kościelisk, pow. Olesno, woj. Opolskie (próba rekonstrukcji) - problem budownictwa podcieniowego w kulturze przeworskiej

The article brings about another attempt to reconstruct the shape of house No. 4 from Kościeliska, Olesno district (Hedwigstein, Kr. Rosenberg) within the context of arcaded houses noticed at the Przeworsk culture settlements. The undertaken analysis makes possible a reinterpretation of the already published materials and proposes a new research strategy that addresses this issue more efficiently. This makes it possible to prove the existence of comer arcades in the architecture of the Przeworsk culture.The article brings about another attempt to reconstruct the shape of house No. 4 from Kościeliska, Olesno district (Hedwigstein, Kr. Rosenberg) within the context of arcaded houses noticed at the Przeworsk culture settlements. The undertaken analysis makes possible a reinterpretation of the already published materials and proposes a new research strategy that addresses this issue more efficiently. This makes it possible to prove the existence of comer arcades in the architecture of the Przeworsk culture