Hygienisation, gentrification and urban displacement in Brazil

This article engages recent debates over gentrification and urban displacement in the global South. While researchers increasingly suggest that gentrification is becoming widespread in “Southern” cities, others argue that such analyses overlook important differences in empirical context and privilege EuroAmerican theoretical frameworks. To respond to this debate, in this article, we outline the concept of higieniza\ue7\ue3o (hygienisation), arguing that it captures important contextual factors missed by gentrification. Hygienisation is a Brazilian term that describes a particular form of urban displacement, and is directly informed by legacies of colonialism, racial and class stigma, informality, and state violence. Our objective is to show how “Southern” concepts like hygienisation help urban researchers gain better insight into processes of urban displacement, while also responding to recent calls to decentre and provincialise urban theory

A "Post-Third World City" or a neoliberal "City of Exception"? Rio de Janeiro in the Olympic era

This article considers processes of urban development within the context of mega-event preparations in Rio de Janeiro. We begin with a brief overview of these development processes, highlighting their connections to political and economic change in recent years. Proponents of these mega-event-led initiatives argue that Rio is undergoing a period of inclusive growth and integration: a perspective we call here a ‘post-Third-World city’ narrative of urban renewal. Critics, however, contend that urban officials are harnessing mega-events (e.g. the 2014 World Cup and the 2016 Olympic Games) to push forward a neoliberal agenda of socially unjust policies benefiting the interests of capital and marginalizing the city’s poor and especially its favelas (i.e. the ‘city-of-exception’ thesis). In this article we explore the insights of these two perspectives and consider why they have grown popular in recent years. Though we side generally with the city-of-exception thesis, we argue that important geographic and historical particularities must also be accounted for. Without carefully situating analytical perspectives empirically—in particular, cases in which theoretical models are drawn from European and North American contexts—urban researchers risk concealing more than they reveal in analyses of rapidly developing countries like Brazil

The Lyman-Continuum Fluxes and Stellar Parameters of O and Early B-Type Stars

Using the results of the most recent stellar atmosphere models applied to a sample of hot stars, we construct calibrations of effective temperature (T(sub eff)), and gravity (log(sub g)) with a spectral type and luminosity class for Galactic 0-type and early B-type stars. From the model results we also derive an empirical relation between the bolometric correction and T(sub eff) and log g. Using a sample of stars with known distances located in OB associations in the Galaxy and the Large Magellanic Cloud, we derive a new calibration of M(sub v) with spectral class. With these new calibrations and the stellar atmosphere models of Kurucz, we calculate the physical parameters and ionizing photon luminosities in the H(0) and He(0) continua for O and early B-type stars. We find substantial differences between our values of the Lyman- continuum luminosity and those reported in the literature. We also discuss the systematic discrepancy between O-type stellar masses derived from spectroscopic models and those derived from evolutionary tracks. Most likely, the cause of this 'mass discrepancy' lies primarily in the atmospheric models, which are plane parallel and hydrostatic and therefore do not account for an extended atmosphere and the velocity fields in a stellar wind. Finally, we present a new computation of the Lyman-continuum luminosity from 429 known O stars located within 2.5 kpc of the Sun. We find the total ionizing luminosity from this population ((Q(sub 0)(sup T(sub ot))) = 7.0 x 10(exp 51) photons/s) to be 47% larger than that determined using the Lyman continuum values tabulated by Panagia

Radial abundance gradients in the outer Galactic disk as traced by main-sequence OB stars

Using a sample of 31 main-sequence OB stars located between galactocentric distances 8.4 - 15.6 kpc, we aim to probe the present-day radial abundance gradients of the Galactic disk. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5-m telescope on Las Campanas. We used a non-NLTE analysis in a self-consistent semi-automatic routine based on TLUSTY and SYNSPEC to determine atmospheric parameters and chemical abundances. Stellar parameters (effective temperature, surface gravity, projected rotational velocity, microturbulence, and macroturbulence) and silicon and oxygen abundances are presented for 28 stars located beyond 9 kpc from the Galactic centre plus three stars in the solar neighborhood. The stars of our sample are mostly on the main-sequence, with effective temperatures between 20800 - 31300 K, and surface gravities between 3.23 - 4.45 dex. The radial oxygen and silicon abundance gradients are negative and have slopes of -0.07 dex/kpc and -0.09 dex/kpc, respectively, in the region $8.4 \leq R_G \leq 15.6$\,kpc. The obtained gradients are compatible with the present-day oxygen and silicon abundances measured in the solar neighborhood and are consistent with radial metallicity gradients predicted by chemodynamical models of Galaxy Evolution for a subsample of young stars located close to the Galactic plane.Comment: Accepted for publication in the A&

Embedded Stellar Clusters in the W3/W4/W5 Molecular Cloud Complex

We analyze the embedded stellar content in the vicinity of the W3/W4/W5 HII regions using the FCRAO Outer Galaxy 12CO(J=1-0) Survey, the IRAS Point Source Catalog, published radio continuum surveys, and new near-infrared and molecular line observations. Thirty-four IRAS Point Sources are identified that have far-infrared colors characteristic of embedded star forming regions, and we have obtained K' mosaics and 13CO(J=1-0) maps for 32 of them. Ten of the IRAS sources are associated with an OB star and 19 with a stellar cluster, although three OB stars are not identified with a cluster. Half of the embedded stellar population identified in the K' images is found in just the 5 richest clusters, and 61% is contained in IRAS sources associated with an embedded OB star. Thus rich clusters around OB stars contribute substantially to the stellar population currently forming in the W3/W4/W5 region. Approximately 39% of the cluster population is embedded in small clouds with an average mass of ~130 Mo that are located as far as 100 pc from the W3/W4/W5 cloud complex. We speculate that these small clouds are fragments of a cloud complex dispersed by previous episodes of massive star formation. Finally, we find that 4 of the 5 known embedded massive star forming sites in the W3 molecular cloud are found along the interface with the W4 HII region despite the fact that most of the molecular mass is contained in the interior regions of the cloud. These observations are consistent with the classical notion that the W4 HII region has triggered massive star formation along the eastern edge of the W3 molecular cloud.Comment: to appear in ApJS, see http://astro.caltech.edu/~jmc/papers/w

Clumpy outer Galaxy molecular clouds and the steepening of the IMF

We report the results of high-resolution (~0.2 pc) CO(1-0) and CS(2-1) observations of the central regions of three star-forming molecular clouds in the far-outer Galaxy (~16 kpc from the Galactic Center): WB89 85 (Sh 2-127), WB89 380, and WB89 437. We used the BIMA array in combination with IRAM 30-m and NRAO 12-m observations. The GMC's in which the regions are embedded were studied by means of KOSMA 3-m CO(2-1) observations. The properties the CO and CS clumps are analyzed and compared with newly derived results of previously published single-dish measurements of local clouds (OrionB South and Rosette). We find that the slopes of the clump mass distributions (-1.28 and -1.49, for WB89 85 and WB89 380, respectively) are somewhat less steep than found for most local clouds, but similar to those of clouds which have been analyzed with the same clumpfind program. We investigate the clump stability by using the virial theorem, including all possible contributions (gravity, turbulence, magnetic fields, and pressure due to the interclump gas). It appears that under reasonable assumptions a combination of these forces would render most clumps stable. Comparing only gravity and turbulence, we find that in the far-outer Galaxy clouds, these forces are in equilibium (virial parameter alpha~1) for clumps down to the lowest masses found (a few Msol). For clumps in the local clouds alpha~1 only for clumps with masses larger than a few tens of Msol. Thus it appears that in these outer Galaxy clumps gravity is the dominant force down to a much lower mass than in local clouds, implying that gravitational collapse and star formation may occur more readily even in the smallest clumps. Although there are some caveats, due to the inhomogeneity of the data used, this might explain the apparently steeper IMF found in the outer Galaxy.Comment: 29 pages, including 9 tables, 21 figures. Accepted for Astron. Astrop

The ionising cluster of 30 Doradus.IV. Stellar kinematics

On the basis of multislit spectroscopy of 180 stars in the ionising cluster of 30 Doradus we present reliable radial velocities for 55 stars. We calculate a radial velocity dispersion of ~35 km/s for the cluster and we analyse the possible influence of spectroscopic binaries in this rather large velocity dispersion. We use numerical simulations to show that the observations are consistent with the hypothesis that all the stars in the cluster are binaries, and the total mass of the cluster is ~5E+5 solar masses. A simple test shows only marginal evidence for dynamical mass segregation which if present is most likely not due to dynamical relaxation.Comment: accepted for publication in Astronomy and Astrophysic