U.S. PERSPECTIVES ON EAST ASIAN ECONOMIC INTEGRATION

USA only major trade power with equal economic stakes in all regions, and will oppose Asian economic integration if it excludes USA. Charts show relatively declining US role, rising China role as key trade partner for Japan, Korea, ASEAN. Responding to China¡¯s lead, as in its ASEAN trade deals, and shaped by former USTR Zoellick, there is growing US support for bilateral trade agreements, including Korea-US FTA, though most economists oppose bilateral/regional approach as inconsistent with the WTO-multilateral trade format. From US perspective, prognosis for East Asian economic integration not good.Economic Integration, APEC, FTA, ASEAN, Asian Economy, CAFTA, WTO

The Dust-to-Gas Ratio in the Small Magellanic Cloud Tail

The Tail region of the Small Magellanic Cloud (SMC) was imaged using the MIPS instrument on the Spitzer Space Telescope as part of the SAGE-SMC Spitzer Legacy. Diffuse infrared emission from dust was detected in all the MIPS bands. The Tail gas-to-dust ratio was measured to be 1200 +/- 350 using the MIPS observations combined with existing IRAS and HI observations. This gas-to-dust ratio is higher than the expected 500-800 from the known Tail metallicity indicating possible destruction of dust grains. Two cluster regions in the Tail were resolved into multiple sources in the MIPS observations and local gas-to-dust ratios were measured to be ~440 and ~250 suggests dust formation and/or significant amounts of ionized gas in these regions. These results support the interpretation that the SMC Tail is a tidal tail recently stripped from the SMC that includes gas, dust, and young stars.Comment: 6 pages, 3 figures, ApJ Letters, in press, (version with full resolution figures at http://www.stsci.edu/~kgordon/papers/PS_files/sage-smc_taildust_v1.62.pdf

Dust Emission from Evolved and Unevolved HII Regions in the Large Magellanic Cloud

We present a study of the dust properties of 12 classical and superbubble HII regions in the Large Magellanic Cloud. We use infrared photometry from Spitzer (8, 24, 70, and 160 \mum bands), obtained as part of the Surveying the Agents of a Galaxy's Evolution (SAGE) program, along with archival spectroscopic classifications of the ionizing stars to examine the role of stellar sources on dust heating and processing. Our infrared observations show surprisingly little correlation between the emission properties of the dust and the effective temperatures or bolometric magnitudes of stars in the HII regions, suggesting that the HII region evolutionary timescale is not on the order of the dust processing timescale. We find that the infrared emission of superbubbles and classical HII regions shows little differentiation between the two classes, despite the significant differences in age and morphology. We do detect a correlation of the 24 \mum emission from hot dust with the ratio of 70 to 160 \mum flux. This correlation can be modeled as a trend in the temperature of a minority hot dust component, while a majority of the dust remains significantly cooler.Comment: 15 pages, 5 figures. Accepted to Ap

Dust in the bright supernova remnant N49 in the LMC

We investigate the dust associated with the supernova remnant (SNR) N49 in the Large Magellanic Cloud (LMC) as observed with the Herschel Space Observatory. N49 is unusually bright because of an interaction with a molecular cloud along its eastern edge. We have used PACS and SPIRE to measure the far IR flux densities of the entire SNR and of a bright region on the eastern edge of the SNR where the SNR shock is encountering the molecular cloud. Using these fluxes supplemented with archival data at shorter wavelengths, we estimate the dust mass associated with N49 to be about 10 Msun. The bulk of the dust in our simple two-component model has a temperature of 20-30 K, similar to that of nearby molecular clouds. Unfortunately, as a result of the limited angular resolution of Herschel at the wavelengths sampled with SPIRE, the uncertainties are fairly large. Assuming this estimate of the dust mass associated with the SNR is approximately correct, it is probable that most of the dust in the SNR arises from regions where the shock speed is too low to produce significant X-ray emission. The total amount of warm 50-60 K dust is ~0.1 or 0.4 Msun, depending on whether the dust is modeled in terms of carbonaceous or silicate grains. This provides a firm lower limit to the amount of shock heated dust in N49.Comment: accepted by the Astronomy & Astrophysics Lette

Star formation in M33: Spitzer photometry of discrete sources

Combining the relative vicinity of the Local Group spiral galaxy M33 with the Spitzer images, we investigate the properties of infrared (IR) emission sites and assess the reliability of the IR emission as a star formation tracer. The mid- and far-IR emission of M33 was obtained from IRAC and MIPS images from the Spitzer archive. We compared the photometric results for several samples of three known types of discrete sources (HII regions, supernovae remnants and planetary nebulae) with theoretical diagnostic diagrams, and derived the spectral energy distribution (from 3.6 to 24 micron) of each type of object. Moreover, we generated a catalogue of 24 micron sources and inferred their nature from the observed and theoretical colours of the known type sources. We estimated the star formation rate in M33 both globally and locally, from the IR emission and from the Halpha emission line. The colours of the typical IR emissions of HII regions, supernovae remnants and planetary nebulae are continuous among the different samples, with overlapping regions in the diagnostic diagrams. The comparison between the model results and the colours of HII regions indicates a dusty envelope at relatively high temperatures ~600 K, and moderate extinction Av < 10. The 24 micron sources IR colours follow the regions observationally defined by the three classes of known objects but the majority of them represent HII regions. The derived total IR luminosity function is in fact very similar to the HII luminosity function observed in the Milky Way and in other late type spirals. Even though our completeness limit is 5x10^37 ergs s-1, in low density regions we are able to detect sources five times fainter than this, corresponding to the faintest possible HII region. [abridged]Comment: 19 pages, 18 figures (low resolution), accepted for publication by A&A; corrected typo

Spitzer Analysis of HII Region Complexes in the Magellanic Clouds: Determining a Suitable Monochromatic Obscured Star Formation Indicator

HII regions are the birth places of stars, and as such they provide the best measure of current star formation rates (SFRs) in galaxies. The close proximity of the Magellanic Clouds allows us to probe the nature of these star forming regions at small spatial scales. We aim to determine the monochromatic IR band that most accurately traces the bolometric IR flux (TIR), which can then be used to estimate an obscured SFR. We present the spatial analysis, via aperture/annulus photometry, of 16 LMC and 16 SMC HII region complexes using the Spitzer IRAC and MIPS bands. UV rocket data and SHASSA H-alpha data are also included. We find that nearly all of the LMC and SMC HII region SEDs peak around 70um, from ~10 to ~400 pc from the central sources. As a result, the sizes of HII regions as probed by 70um is approximately equal to the sizes as probed by TIR (about 70 pc in radius); the radial profile of the 70um flux, normalized by TIR, is constant at all radii (70um ~ 0.45 TIR); the 1-sigma standard deviation of the 70um fluxes, normalized by TIR, is a lower fraction of the mean (0.05 to 0.12 out to ~220 pc) than the normalized 8, 24, and 160um normalized fluxes (0.12 to 0.52); and these results are invariant between the LMC and SMC. From these results, we argue that 70um is the most suitable IR band to use as a monochromatic obscured star formation indicator because it most accurately reproduces the TIR of HII regions in the LMC and SMC and over large spatial scales. We also explore the general trends of the 8, 24, 70, and 160um bands in the LMC and SMC HII region SEDs, radial surface brightness profiles, sizes, and normalized (by TIR) radial flux profiles. We derive an obscured SFR equation that is modified from the literature to use 70um luminosity, SFR(Mo/yr) = 9.7(0.7)x10^{-44} L(70)(ergs/s), which is applicable from 10 to 300 pc distance from the center of an HII region.Comment: 21 pages, 12 figures, 4 tables. Will be published in ApJ

The CO-to-H2 Conversion Factor From Infrared Dust Emission Across the Local Group

We estimate the conversion factor relating CO emission to H2 mass, alpha_CO, in five Local Group galaxies that span approximately an order of magnitude in metallicity - M31, M 33, the Large Magellanic Cloud (LMC), NGC 6822, and the Small Magellanic Cloud (SMC). We model the dust mass along the line of sight from infrared (IR) emission and then solve for the alpha_CO that best allows a single gas-to-dust ratio (delta_GDR) to describe each system. This approach remains sensitive to CO-dark envelopes of H2 surrounding molecular clouds. In M 31, M 33, and the LMC we find alpha_CO \approx 3-9 M_sun pc^-2 (K km s^-1)^-1, consistent with the Milky Way value within the uncertainties. The two lowest metallicity galaxies in our sample, NGC 6822 and the SMC (12 + log(O/H) \approx 8.2 and 8.0), exhibit a much higher alpha_CO. Our best estimates are \alpha_NGC6822 \approx 30 M_sun/pc^-2 (K km s^-1)^-1 and \alpha_SMC \approx 70 M_sun/pc^-2 (K km s-1)-1. These results are consistent with the conversion factor becoming CO a strong function of metallicity around 12 + log(O/H) \sim 8.4 - 8.2. We favor an interpretation where decreased dust-shielding leads to the dominance of CO-free envelopes around molecular clouds below this metallicity.Comment: Accepted for publication in the Astrophysical Journal, 15 pages, 7 figure

The Anatomy of Star Formation in NGC 300

The Spitzer Space Telescope was used to study the mid-infrared to far-infrared properties of NGC 300, and to compare dust emission to Halpha to elucidate the heating of the ISM and the star formation cycle at scales < 100 pc. The new data allow us to discern clear differences in the spatial distribution of 8 micron dust emission with respect to 24 micron dust and to HII regions traced by the Halpha light. The 8 micron emission highlights the rims of HII regions, and the 24 micron emission is more strongly peaked in star forming regions than at 8 microns. We confirm the existence and approximate amplitude of interstellar dust emission at 4.5 microns, detected statistically in Infrared Space Observatory (ISO) data, and conclude it arises in star forming regions. When averaging over regions larger than ~ 1 kpc, the ratio of Halpha to Aromatic Feature emission in NGC 300 is consistent with the values observed in disks of spiral galaxies. The mid-to-far-infrared spectral energy distribution of dust emission is generally consistent with pre-Spitzer models.Comment: to appear in the ApJS Spitzer special issue (September 2004