Lunch Talk (2013)

Polycyclic aromatic hydrocarbons (PAHs) are one of the major dust components in the interstellar medium (ISM). We present our evolution models for the abundance of PAHs in the ISM on a galaxy-evolution timescale. We consider shattering of carbona- ceous dust grains as the formation mechanism of PAHs while PAHs can be reduced by coagulation onto dust grains, destruction by supernova shocks, or injection into star formation. We implement these processes in a one-zone chemical evolution model to obtain the evolution of the PAH abundance in a galaxy. We find that while the de- struction by supernova shocks is the primary destruction mechanism in the metal-poor environment, the coagulation governs the destruction of PAHs in the metal-rich envi- ronment. We compare the calculated PAH abundances with the observed abundances in galaxies of various types. We discuss the physical properties that play a key role in the evolution of PAH abundance.

Evolved objects such as red supergiants (RSGs) and asymptotic giant branch (AGB) stars inject metal-rich material in the form of gas molecules and solid dust particles into the interstellar medium (ISM) of their host galaxies, where they may seed and be incorporated into the next generation of stars. This mass loss from AGB and RSG stars thus drives galactic chemical evolution, and the total dust production rate from these stars is an important parameter that can be used to constrain evolutionary models. In order to quickly compute the total dust budget for large photometric datasets, we have constructed a Grid of RSG and AGB ModelS (GRAMS, Sargent et al. 2011, Srinivasan et al. 2011) for the dusty shells around these stars. The models, when fit to the observed data, provide reliable estimates of the luminosities and dust production rates (DPRs). We have already used our models to study the AGB/RSG population in the Magellanic Clouds (Riebel et al. 2012, Srinivasan et al. in prep), for which we had photometry and spectra as part of the SAGE (Surveying the Agents of Galaxy Evolution, Meixner et al. 2016), SAGE-SMC (Gordon et al. 2011) and SAGE-Spec (Kemper et al. 2010) programs, and we are now extending our work to other galaxies in our neighbourhood. In this talk, I will describe our model grid and present our results for the Magellanic Clouds as well as for the galaxy M33. Our method provides a quick way of estimating the dust budget for entire galaxies, which will allow us to probe the dependence of this mass loss on properties of the host galaxies.

The Subaru prime focus spectrograph (PFS) is a multi-fiber spectrograph that can provide an field of view (FOV) of 1.3 deg on the sky, covering optical to part of NIR wavebands (0.38 - 1.26 microns) with 2400 fibers and an averaging spectral resolving power of ~3000. Compared with other optical multi-fiber spectrographs, PFS offers a combination of large FOV and large number of fibers on a 8-m class telescope. Science targets of PFS are cosmology, Galactic archaeology and galaxy/AGN evolution. PFS is composed of four main components: prime focus instrument (PFI), fiber connector/cables, spectrographs and the metrology camera system. ASIAA is in charge of part of PFI and the entire metrology camera system. I will briefly introduce the metrology camera system, including its requirements, optical design and the progresses we have made so far

A circumplanetary disk (CPD) may play a key role in the process of planet formation in many aspects, for instance, the gas accretion rate, formation of satellites as well as the long-term averaged torque exerting on protoplanets. We performed 2D and 3D global simulations to study the properties of CPDs that are embedded in an isothermal viscous protoplanetary disk. Without introducing a softening length to the protoplanetary potential, the structure and the gas dynamics of CPDs are properly resolved by using the technique of nested mesh refinement. Our 3D isothermal calculations show that prominent CPDs can form around low-mass protoplanets. Since these CPDs are constantly disturbed by the surroundings, CPD+protoplanet is not an isolated system as usually assumed in the literature for planet migration. The asymmetry of the CPD with respect to protoplanets may have significant impact on planet migration, especially for the low-mass protoplanets. In this series of work, detailed study on the properties of CPDs is first explored with 2D calculations. The dynamical role of CPDs as well as the effects of viscosity are systematically investigated. From our 2D results, we conclude that torques from CPDs exerting on protoplanets are significant compared to that outside of the Hill radii. The effect of viscosity is to reduce the mass accretion rate onto CPDs in the high-mass models.

Otoliths, which are calcium carbonate structures in the inner ears of teleostean fish, function as balance and auditory organs. The acellular and metabolically inert otoliths grow continuously throughout the life of a fish and record the biological events and environmental characteristics e.g., temperature and salinity experienced by the fish. Examination of otolith microstructure and chemical compositions have extensive applications, such as for biologists to reveal life history events of the fishes as well as for geologists to reconstruct paleoclimate