Morphology of luminous IRAS galaxies: Summary talk

The author discusses the morphology of luminous Infrared Astronomy Satellite (IRAS) galaxies. A few comments are made about the direction to be taken in future observations of luminous IRAS galaxies

Infrared observations of possible protostars

Energy distribution measurements on infrared objects located in H2 and gaseous nebulae region

Spitzer IRAC Observations of White Dwarfs. I. Warm Dust at Metal-Rich Degenerates

This paper presents the results of a Spitzer IRAC 3-8 micron photometric search for warm dust orbiting 17 nearby, metal-rich white dwarfs, 15 of which apparently have hydrogen dominated atmospheres (type DAZ). G166-58, G29-38, and GD 362 manifest excess emission in their IRAC fluxes and the latter two are known to harbor dust grains warm enough to radiate detectable emission at near-infrared wavelengths as short as 2 micron. Their IRAC fluxes display differences compatible with a relatively larger amount of cooler dust at GD 362. G166-58 is presently unique in that it appears to exhibit excess flux only at wavelengths longer than about 5 micron. Evidence is presented that this mid-infrared emission is most likely associated with the white dwarf, indicating that G166-58 bears circumstellar dust no warmer than T~400 K. The remaining 14 targets reveal no reliable mid-infrared excess, indicating the majority of DAZ stars do not have warm debris disks sufficiently opaque to be detected by IRAC.Comment: Accepted to ApJ, 10 figures, 6 table

Hadamard Well-Posedness for two Nonlinear Structure Acoustic Models

This dissertation focuses on the Hadamard well-posedness of two nonlinear structure acoustic models, each consisting of a semilinear wave equation defined on a smooth bounded domain $\Omega\subset\mathbb{R}^3$ strongly coupled with a Berger plate equation acting only on a flat portion of the boundary of $\Omega$. In each case, the PDE is of the following form: \begin{align*} \begin{cases} u_{tt}-\Delta u +g_1(u_t)=f(u) &\text{ in } \Omega \times (0,T),\\[1mm] w_{tt}+\Delta^2w+g_2(w_t)+u_t|_{\Gamma}=h(w)&\text{ in }\Gamma\times(0,T),\\[1mm] u=0&\text{ on }\Gamma_0\times(0,T),\\[1mm] \partial_\nu u=w_t&\text{ on }\Gamma\times(0,T),\\[1mm] w=\partial_{\nu_\Gamma}w=0&\text{ on }\partial\Gamma\times(0,T),\\[1mm] (u(0),u_t(0))=(u_0,u_1),\hspace{5mm}(w(0),w_t(0))=(w_0,w_1), \end{cases} \end{align*} where the initial data reside in the finite energy space, i.e., $$(u_0, u_1)\in H^1_{\Gamma_0}(\Omega) \times L^2(\Omega) \, \text{ and }(w_0, w_1)\in H^2_0(\Gamma)\times L^2(\Gamma).$$ The chief assumption of the first model is in taking $f(u)=-u|u|^{p-1}$, i.e., $f$ is a restoring source, where $p\geq 1$ is arbitrary. A standard Galerkin approximation scheme is used to establish a rigorous proof of the existence of local weak solutions. In addition, under some conditions on the parameters in the system, it is shown that such solutions exist globally in time and depend continuously on the initial data. For the second model, $f$ is taken to be an energy building source, and in particular it is allowed to have a \emph{supercritical} exponent, in the sense that its associated Nemytskii operators is not locally Lipschitz from $H^1_{\Gamma_0}(\Omega)$ into $L^2(\Omega)$. By employing nonlinear semigroups and the theory of monotone operators, several results on the existence of local and global weak solutions are obtained. Moreover, it is proven that such solutions depend continuously on the initial data, and uniqueness is obtained in two different scenarios. Adviser: Mohammad A. Rammah

Ground-based 1- to 32-microns observations of ARP 220: Evidence for a dust-embedded AGN?

New observations of the 10 and 20 micron size of the emission region in Arp 220 are presented. Also given are ground based photometry from 1 to 32 micron including measurements of the strength of the silicate feature at 10 micron. The results show that the 20 micron size of Arp is smaller than 1.5 arcsec (500 pc); comparison of IRAS and ground based observations show that IRAS 12 micron flux measured with a large arcmin beam is the same as that seen from the ground with a 3 arcsec aperture. At 10 micron a deep silicate absorption feature is seen that corresponds to a visual extinction of about 50 mag. These results suggest that a very significant portion of the 10 to the 12th power L sub 0 infrared luminosity from Arp 220 comes from a region less than or of the order of 500 pc in diameter. When these results are combined with recent measurement of a broad Brackett alpha line by DePoy and an unresolved 2.2 micron source by Neugebauer, Matthews and Scoville, a very attractive possibility for the primary luminosity source Arp 220 is a dust embedded compact Seyfert type nucleus