PAHs in the Halo of NGC 5529

We present sensitive ISO $\lambda 6.7 \mu$m observations of the edge-on galaxy, NGC 5529, finding an extensive MIR halo around NGC 5529. The emission is dominated by PAHs in this band. The PAH halo has an exponential scale height of 3.7 kpc but can still be detected as far as $\approx 10$ kpc from the plane to the limits of the high dynamic range (1770/1) data. This is the most extensive PAH halo yet detected in a normal galaxy. This halo shows substructure and the PAHs likely originate from some type of disk outflow. PAHs are long-lived in a halo environment and therefore continuous replenishment from the disk is not required (unless halo PAHs are also being destroyed or removed), consistent with the current low SFR of the galaxy. The PAHs correlate spatially with halo H$\alpha$ emission, previously observed by Miller & Veilleux (2003); both components are likely excited/ionized by in-disk photons that are leaking into the halo. The presence of halo gas may be related to the environment of NGC 5529 which contains at least 17 galaxies in a small group of which NGC 5529 is the dominant member. Of these, we have identified two new companions from the SDSS.Comment: 16 pages, 5 gif figures, accepted for publication in A&A, For pdf with higher quality figures, see http://www.astro.queensu.ca/~irwi

Derivatives and Global Capital Flows: Applications to Asia

There are four factors involved in the current financial crisis in Asia that have caused surprise. Since the Latin American debt crisis was thought to have been aggravated by the dominance of syndicated private bank lending, borrowers were encouraged to increase private direct investment flows. The stability of capital flows to Asia was used as an example. Yet, the Asian crisis appears to have been precipitated by the reversal of short-term private bank lending. Second, the flows of capital to Asia have been used as example of the benefits of free international capital markets in directing resources to the most productive uses. Yet, in the aftermath of the crisis it appears that total returns on equity investments in Asia have in fact been lower than in most other regions throughout the 1 990s. Third, it appears that in a number of Asian countries, the majority of the international lending was between foreign and domestic banks. It has been suggested that the major cause of the crisis is unsafe lending practices by the Asian banks permitted by inadequate national prudential supervision. Yet, these economies were the most advanced on the road to market liberalisation. One of the cardinal principles of financial liberalisation, formed in the aftermath of the Chilean crisis, is that the creation of institutional structures ensuring the stability of the financial system should precede financial market liberalisation. Indeed, many countries were following this advice. It is interesting to note that the lending banks were generally large, global banks who employ highly sophisticated risk assessment procedures. Yet, they appear to have continued lending well after the increased risks in the region were generally apparent. This suggests that even the most sophisticated operators in global financial markets have difficulties in assessing risk, and that their regulators were no more successful in imposing prudent limits. Finally, private portfolio and direct investment flows were considered to be preferable to syndicated bank lending because they were thought to segregate the problem of foreign exchange instability from asset market instability. Syndicated lending was denominated in the currency of the lending bank, and the exchange rate risk was borne by the borrower; but direct equity investors purchase foreign financial assets denominated in foreign currency and thus bears the currency risk. It was suggested that in a crisis the foreign investor would suffer first from a fall in asset prices, and second from a decline in the exchange rate, which would discourage him from liquidating the investment and reduce selling pressure in the foreign exchange market. Yet, the linkage between the collapse in exchange rates and equity markets appears to have been even closer in Asia than in other experiences of financial crisis.

Equilibrium Disk-Bulge-Halo Models for the Milky Way and Andromeda Galaxies

We describe a new set of self-consistent, equilibrium disk galaxy models that incorporate an exponential disk, a Hernquist model bulge, an NFW halo and a central supermassive black hole. The models are derived from explicit distribution functions for each component and the large number of parameters permit detailed modeling of actual galaxies. We present techniques that use structural and kinematic data such as radial surface brightness profiles, rotation curves and bulge velocity dispersion profiles to find the best-fit models for the Milky Way and M31. Through N-body realizations of these models we explore their stability against the formation of bars. The models permit the study of a wide range of dynamical phenomenon with a high degree of realism.Comment: 58 pages, 20 figures, submitted to the Astrophysical Journa

A possible radio supernova in the outer part of NGC 3310

As part of an on-going radio supernova monitoring program, we have discovered a variable, compact steep spectrum radio source ~65 arcsec (~4 kpc) from the centre of the starburst galaxy NGC 3310. If the source is at the distance of NGC 3310, then its 5 GHz luminosity is ~3 x 10^{19} WHz^-1. The source luminosity, together with its variability characteristics, compact structure (<17 mas) and its association with a group of HII regions, leads us to propose that it is a previously uncatalogued type II radio supernova. A search of archival data also shows an associated X-ray source with a luminosity similar to known radio supernova.Comment: 5 pages, 3 figures. Accepted by MNRA

Estimating the Dark Halo Mass from the Relative Thickness of Stellar Disks

We analyze the relationship between the mass of a spherical component and the minimum possible thickness of stable stellar disks. This relationship for real galaxies allows the lower limit on the dark halo mass to be estimated (the thinner the stable stellar disk is, the more massive the dark halo must be). In our analysis, we use both theoretical relations and numerical N-body simulations of the dynamical evolution of thin disks in the presence of spherical components with different density profiles and different masses. We conclude that the theoretical relationship between the thickness of disk galaxies and the mass of their spherical components is a lower envelope for the model data points. We recommend using this theoretical relationship to estimate the lower limit for the dark halo mass in galaxies. The estimate obtained turns out to be weak. Even for the thinnest galaxies, the dark halo mass within four exponential disk scale lengths must be more than one stellar disk mass.Comment: 20 pages including 6 figures. To be published in Astronomy Letters (v. 32, No. 10, pp. 649-660, 2006