The Spitzer Survey of the Small Magellanic Cloud: Discovery of Embedded Protostars in the HII Region NGC 346

We use Spitzer Space Telescope observations from the Spitzer Survey of the Small Magellanic Cloud (S3MC) to study the young stellar content of N66, the largest and brightest HII region in the SMC. In addition to large numbers of normal stars, we detect a significant population of bright, red infrared sources that we identify as likely to be young stellar objects (YSOs). We use spectral energy distribution (SED) fits to classify objects as ordinary (main sequence or red giant) stars, asymptotic giant branch stars, background galaxies, and YSOs. This represents the first large-scale attempt at blind source classification based on Spitzer SEDs in another galaxy. We firmly identify at least 61 YSOs, with another 50 probable YSOs; only one embedded protostar in the SMC was reported in the literature prior to the S3MC. We present color selection criteria that can be used to identify a relatively clean sample of YSOs with IRAC photometry. Our fitted SEDs indicate that the infrared-bright YSOs in N66 have stellar masses ranging from 2 Msun to 17 Msun, and that approximately half of the objects are Stage II protostars, with the remaining YSOs roughly evenly divided between Stage I and Stage III sources. We find evidence for primordial mass segregation in the HII region, with the most massive YSOs being preferentially closer to the center than lower-mass objects. Despite the low metallicity and dust content of the SMC, the observable properties of the YSOs appear consistent with those in the Milky Way. Although the YSOs are heavily concentrated within the optically bright central region of N66, there is ongoing star formation throughout the complex and we place a lower limit on the star formation rate of 3.2 x 10^-3 Msun/yr over the last ~1 Myr.Comment: 13 pages, 5 figures (3 in color), 2 tables. Accepted for publication in Ap

The Chemical and Dynamical Evolution of Isolated Dwarf Galaxies

Using a suite of simulations (Governato et al. 2010) which successfully produce bulgeless (dwarf) disk galaxies, we provide an analysis of their associated cold interstellar media (ISM) and stellar chemical abundance patterns. A preliminary comparison with observations is undertaken, in order to assess whether the properties of the cold gas and chemistry of the stellar components are recovered successfully. To this end, we have extracted the radial and vertical gas density profiles, neutral hydrogen velocity dispersion, and the power spectrum of structure within the ISM. We complement this analysis of the cold gas with a brief examination of the simulations' metallicity distribution functions and the distribution of alpha-elements-to-iron.Comment: To appear in the proceedings of the JENAM 2010 Symposium "Dwarf Galaxies: Keys to Galaxy Formation and Evolution" (Lisbon, 9-10 September 2010), P. Papaderos, S. Recchi, G. Hensler (eds.), Springer Verlag (2011), in pres

Multi-wavelength analysis of the dust emission in the Small Magellanic Cloud

We present an analysis of dust grain emission in the diffuse interstellar medium of the Small Magellanic Cloud (SMC). This study is motivated by the availability of 170 microns ISOPHOT data covering a large part of the SMC, with a resolution enabling to disentangle the diffuse medium from the star forming regions. After data reduction and subtraction of Galactic foreground emission, we used the ISOPHOT data together with HiRes IRAS data and ATCA/Parkes combined HI column density maps to determine dust properties for the diffuse medium. We found a far infrared emissivity per hydrogen atom 30 times lower than the Solar Neighborhood value. The modeling of the spectral energy distribution of the dust, taking into account the enhanced interstellar radiation field, gives a similar conclusion for the smallest grains (PAHs and very small grains) emitting at shorter wavelength. Assuming Galactic dust composition in the SMC, this result implies a difference in the gas-to-dust ratio (GDR) 3 times larger than the difference in metallicity. This low depletion of heavy elements in dust could be specific of the diffuse ISM and not apply for the whole SMC dust if it results from efficient destruction of dust by supernovae explosions.Comment: 11 pages, 10 figures. Accepted for publication in Astronomy & Astrophysic

Atención en un centro de parto según las recomendaciones de la Organización Mundial de la Salud

Centros de parto constituem modelo que\ud adota tecnologia apropriada na assistência\ud à parturiente. O objetivo foi caracterizar\ud a assistência intraparto em um centro de\ud parto extra-hospitalar quanto às práticas\ud recomendadas pela Organização Mundial\ud da Saúde (OMS). Estudo descritivo sobre\ud 1.079 partos assistidos de 2006 a 2009 na\ud Casa do Parto de Sapopemba, São Paulo,\ud Brasil. Os resultados mostraram ausculta\ud intermitente (média=7 controles); posição\ud materna no expulsivo semissentada\ud (82,3%), lateral (16,0%), outras (1,7%);\ud aceitação da dieta (95,6%); acompanhante\ud (93,3%); até três exames vaginais (85,4%);\ud banho de aspersão (84,0%), deambulação\ud (68,0%), massagem (60,1%), exercícios\ud com bola suíça (51,7%); amniotomia\ud (53,4%); ocitocina na dilatação (31,0%),\ud banho de imersão (29,3%), ocitocina no\ud expulsivo (25,8%) e episiotomia (14,1%).\ud Concluiu-se que os profissionais do centro\ud de parto utilizam práticas recomendadas\ud pela OMS, contudo existem práticas cujo\ud uso pode ser reduzido, tais como amniotomia,\ud administração de ocitocina, episiotomia\ud e posição semissentada no expulsivoBirth centers are maternal care models\ud that use appropriate technology when\ud providing care to birthing women. This\ud descriptive study aimed to characterize intrapartum\ud care in a freestanding birth center,\ud in light of the practices recommended\ud by the World Health Organization (WHO),\ud with 1,079 assisted births from 2006 to\ud 2009 in the Sapopemba Birth Center, São\ud Paulo, Brazil. Results included the use of\ud intermittent auscultation (mean=7 controls);\ud maternal positions during delivery:\ud semi-sitting (82.3%), side-lying (16.0%),\ud other positions (1.7%), oral intake (95.6%);\ud companionship (93.3%); exposure to up\ud to three vaginal examinations (85.4%),\ud shower bathing (84.0%), walking (68.0%),\ud massage (60.1%), exercising with a Swiss\ud ball (51.7%); amniotomy (53.4%), oxytocin\ud use during the first (31.0%) and second\ud stages of labor (25.8%), bath immersion\ud (29.3%) and episiotomy (14.1%). In this\ud birth center, care providers used practices\ud recommended by the WHO, although\ud some practices might have been applied\ud less frequentlyCentros de parto constituyen un modelo\ud que adopta la tecnología apropiada en la\ud atención a la parturienta. El objetivo fue caracterizar\ud la atención intraparto en un centro\ud de parto extra-hospitalario en relación a las\ud prácticas recomendadas por la Organización\ud Mundial de la Salud (OMS). Estudio descriptivo\ud sobre 1.079 partos atendidos del 2006 al\ud 2009 en la Casa de Parto de Sapopemba, São\ud Paulo, Brasil. Los resultados mostraron: auscultación\ud intermitente (media=7 controles);\ud posición materna en el expulsivo - semisentada\ud (82,3%), lateral (16,0%), otras (1,7%);\ud aceptación de dieta (95,6%); acompañante\ud (93,3%); hasta tres exámenes vaginales\ud (85,4%); baño en ducha (84,0%), deambulación\ud (68,0%), masaje (60,1%), ejercicios con\ud pelota suiza (51,7%); amniotomía (53,4%);\ud oxitocina durante la dilatación (31,0%), baño\ud de inmersión (29,3%), oxitocina durante el\ud expulsivo (25,8%) y episiotomía (14,1%). Se\ud concluyó que los profesionales del centro de\ud parto utilizan prácticas recomendadas por\ud la OMS, pero existen algunas prácticas cuyo\ud uso puede reducirse, tales como la amniotomía,\ud administración de oxitocina, episiotomía\ud y posición semisentada en el período\ud expulsivoCNPqPIBIC 115521/2008-

Discovery of a new Transient X-ray Pulsar in the Small Magellanic Cloud

Rossi X-Ray Timing Explorer observations of the Small Magellanic Cloud have revealed a previously unknown transient X-ray pulsar with a pulse period of 95s. Provisionally designated XTE SMC95, the pulsar was detected in three Proportional Counter Array observations during an outburst spanning 4 weeks in March/April 1999. The pulse profile is double peaked reaching a pulse fraction \~0.8. The source is proposed as a Be/neutron star system on the basis of its pulsations, transient nature and characteristically hard X-ray spectrum. The 2-10 keV X-ray luminosity implied by our observations is > 2x10^37 erg/s which is consistent with that of normal outbursts seen in Galactic systems. This discovery adds to the emerging picture of the SMC as containing an extremely dense population of transient high mass X-ray binaries.Comment: Accepted by A&A. 7 pages, 6 figure

The XMM-Newton survey of the Small Magellanic Cloud: XMMUJ005011.2-730026 = SXP214, a Be/X-ray binary pulsar

In the course of the XMM-Newton survey of the Small Magellanic Cloud (SMC), a region to the east of the emission nebula N19 was observed in November 2009. To search for new candidates for high mass X-ray binaries the EPIC PN and MOS data of the detected point sources were investigated and their spectral and temporal characteristics identified. A new transient (XMMUJ005011.2-730026= SXP214) with a pulse period of 214.05 s was discovered; the source had a hard X-ray spectrum with power-law index of ~0.65. The accurate X-ray source location permits the identification of the X-ray source with a ~15th magnitude Be star, thereby confirming this system as a new Be/X-ray binary.Comment: 8 pages 11 figures. Accepted for publication in MNRA

Lumpy Structures in Self-Gravitating Disks

Following Toomre & Kalnajs (1991), local models of slightly dissipative self-gravitating disks show how inhomogeneous structures can be maintained over several galaxy rotations. Their basic physical ingredients are self-gravity, dissipation and differential rotation. In order to explore the structures resulting from these processes on the kpc scale, local simulation of self-gravitating disks are performed in this paper in 2D as well as in 3D. The third dimension becomes a priori important as soon as matter clumping causes a tight coupling of the 3D equations of motion. The physically simple and general framework of the model permits to make conclusions beyond the here considered scales. A time dependent affine coordinate system is used, allowing to calculate the gravitational forces via a particle-mesh FFT-method, increasing the performance with respect to previous direct force calculations. Persistent patterns, formed by transient structures, whose intensity and morphological characteristic depend on the dissipation rate are obtained and described. Some of our simulations reveal first signs of mass-size and velocity dispersion-size power-law relations, but a clear scale invariant behavior will require more powerful computer techniques.Comment: 28 pages, 32 figures. Accepted for publication in A&A. Full resolution paper available at http://obswww.unige.ch/Preprints/dyn_art.htm