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Brian Woodall,Mariel Borowitz,Kari Watkins,Maria Costa,Angela Howard,Perrine Kemerait,Michelle Lee,Gavin Rolls,Yuji Takubo,Rachel Titshaw,Maria Winstead,Jessica Zhang,Daisy Zhou 서울시립대학교 도시과학연구원 2024 도시과학국제저널 Vol.28 No.1
The megaregion is viewed as a platform from which to address a variety of issues. Despite agreement that a megaregion is a large, globally connected urban agglomeration, there is no consensus as to how to delineate its boundaries and how it differs from other urban forms. The scholarly literature is dominated by three distinct analytic approaches: interdependent systems, nodal linkages, and satellite data. We assess the utility of each approach in delineating the boundaries of four megaregions – BosWash, Greater Tokyo, the Amsterdam-Brussels-Antwerp region, and a Global South megaregion – and conclude by proposing a sequence of steps to guide future research.
An, Deokkeun,Ramí,rez, Solange V.,Sellgren, Kris,Arendt, Richard G.,Boogert, A. C. Adwin,Robitaille, Thomas P.,Schultheis, Mathias,Cotera, Angela S.,Smith, Howard A.,Stolovy, Susan R. IOP Publishing 2011 The Astrophysical journal Vol.736 No.2
<P>We present results from our spectroscopic study, using the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope, designed to identify massive young stellar objects (YSOs) in the Galactic center (GC). Our sample of 107 YSO candidates was selected based on Infrared Array Camera (IRAC) colors from the high spatial resolution, high sensitivity Spitzer/IRAC images in the Central Molecular Zone, which spans the central similar to 300 pc region of the Milky Way. We obtained IRS spectra over 5-35 mu m using both high- and low-resolution IRS modules. We spectroscopically identify massive YSOs by the presence of a 15.4 mu m shoulder on the absorption profile of 15 mu m CO2 ice, suggestive of CO2 ice mixed with CH3OH ice on grains. This 15.4 mu m shoulder is clearly observed in 16 sources and possibly observed in an additional 19 sources. We show that nine massive YSOs also reveal molecular gas-phase absorption from CO2, C2H2, and/or HCN, which traces warm and dense gas in YSOs. Our results provide the first spectroscopic census of the massive YSO population in the GC. We fit YSO models to the observed spectral energy distributions and find YSO masses of 8-23 M-circle dot, which generally agree with the masses derived from observed radio continuum emission. We find that about 50% of photometrically identified YSOs are confirmed with our spectroscopic study. This implies a preliminary star formation rate of similar to 0.07 M-circle dot yr(-1) at the GC.</P>