Found 14 talks width keyword dust
AbstractWe present the results of our systematic search for optically elusive, but intrinsically luminous buried AGNs in >100 nearby (z < 0.3) luminous infrared galaxies with L(IR) > 1011 L⊙, classified optically as non-Seyferts. To disentangle AGNs and stars, we have performed (1) infrared 2.5-35 μ low-resolution (R ~ 100) spectroscopy using Subaru, AKARI, and Spitzer, to estimate the strengths of PAH (polycyclic aromatic hydrocarbon) emission and dust absorption features, (2) high-spatial-resolution infrared 20 micron imaging observations using Subaru and Gemini, to constrain the emission surface brightnesses of energy sources, and (3) millimeter interferometric measurements of molecular gas flux ratios, which reflect the physical and chemical effects from AGNs and stars. Overall, all methods provided consistent pictures. We found that the energetic importance of buried AGNs is relatively higher in galaxies with higher infrared luminosities (where more stars will be formed), suggesting that AGN-starburst connections are luminosity dependent. Our results might be related to the AGN feedback scenario as the possible origin of the galaxy down-sizing phenomenon.
We test the theoretical prediction that the straightest dust lanes in bars are found in strongly barred galaxies, or more specifically, that the degree of curvature of the dust lanes is inversely proportional to the strength of the bar. The test uses archival images of barred galaxies for which a reliable non-axisymmetric torque parameter (Qb) and the radius at which Qb has been measured (r(Qb)) have been published in the literature. Our results confirm the theoretical prediction but show a large spread that cannot be accounted for by measurement errors. We simulate 238 galaxies with different bar and bulge parameters in order to investigate the origin of the spread in the dust lane curvature versus Qb relation. From these simulations, we conclude that the spread is greatly reduced when describing the bar strength as a linear combination of the bar parameters Qb and the quotient of the major and minor axes of the bar, a/b. Thus, we conclude that the dust lane curvature is predominantly determined by the parameters of the bar.
AbstractSpectroscopic observations of novae date back a century, and the fundamental nature of the outburst has been understood for 50 years. Yet, recent observations suggest possible major modifications to the standard nova paradigm. A high-resolution spectroscopic survey of novae has revealed short-lived heavy element absorption systems near maximum light consisting of Fe-peak and s-process elements. The absorbing gas is circumbinary and it must pre-exist the outburst. Its origin appears to be mass ejection from the secondary star, implying large episodic mass transfer events from the secondary that initiate the nova outburst. The spectroscopic evolution of novae is interpreted in terms of two distinct interacting gas systems in which the bright continuum is produced by the outburst ejecta but absorption and emission lines originate in gas ejected by the secondary star in a way that may explain dust formation and X-ray emission from novae.
AbstractMost studies of the stellar and substellar populations of star forming regions rely on the identification of the signatures of accretion, outflows, circumstellar dust, or activity characteristic of the early stages of stellar evolution. However, the decay of these observational signatures with time limits our ability to understand the complete star forming history of young aggregates, and to obtain unbiased samples of young stellar objects at different stages of disk evolution. I will present the results of a wide-area study of the stellar population of selected clouds in the nearby Lupus star forming region, initially defined to complement the data obtained by the Spitzer Space Observatory Legacy Program “From molecular cores to planet-forming disks”. When combined with 2MASS photometry, our data allow us to fit the spectral energy distributions of well over 150,000 sources seen in that direction, and to identify possible new members based on their photospheric fluxes alone, with independence of the display of signposts of youth. In this way we identify a very clear signature of the existence of a surprisingly numerous and thus far unrecognized population of cool members of Lupus 1 and 3, which is absent from Lupus 4.
The approximately 130 new members that we identify show that Lupus 1 and 3 have been forming low mass stars in numbers comparable to, or even exceeding in Lupus 1, those revealed by recent sensitive surveys based on the signposts of youth. We hypothesize on several possibilities for the origin of this population that may account for its puzzling properties of general lack of disks, coevality with the disk-bearing population, and preferential off-cloud location, which hint at a picture more complex and interesting than the quiescent formation inside dense molecular clouds.
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- From Ultra-High Energy Cosmic Rays to the Study of Gamma RaysMr. Patrick CechvalaTuesday June 18, 2019 - 12:30 (Aula)
- Galaxy structure and the galaxy-halo connectionLorenzo ZanisiThursday June 20, 2019 - 10:30 (Aula)