Masers and the Massive Star Formation Process: New Insights Through Infrared Observations

Our mid-infrared and near-infrared surveys over the last five years have helped to strengthen and clarify the relationships between water, methanol, and OH masers and the star formation process. Our surveys show that maser emission seems to be more closely associated with mid-infrared emission than cm radio continuum emission from UC HII regions. We find that masers of all molecular species surveyed trace a wide variety of phenomena and show a proclivity for linear distributions. The vast majority of these linear distributions can be explained by outflows or shocks, and in general do not appear to trace circumstellar disks as was previously thought. Some water and methanol masers that are not associated with radio continuum emission appear to trace infrared-bright hot cores, the earliest observable stage of massive stellar life before the onset of a UC HII region.Comment: 6 pages, 3 figures, to appear in the proceedings of IAU Symposium 227: "Massive Star Birth: A Crossroads of Astrophysics", version with full-resolution images available at http://www.ctio.noao.edu/~debuize

Mid-Infrared Imaging of NGC 6334 I

We present high-resolution (<0.5") mid-infrared Keck II images of individual sources in the central region of NGC 6334 I. We compare these images to images at a variety of other wavelengths from the near infrared to cm radio continuum and speculate on the nature of the NGC 6334 I sources. We assert that the cometary shape of the UCHII region here, NGC 6334 F, is due to a champagne-like flow from a source on the edge of a molecular clump and not a due to a bow shock caused by the supersonic motion of the UCHII region through the interstellar medium. The mid-infrared emission in concentrated into an arc of dust that define the boundary between the UCHII region and the molecular clump. This dust arc contains a majority of the masers in the region. We discuss the nature of the four near-infrared sources associated with IRS-I 1, and suggest that one of the sources, IRS1E, is responsible for the heating and ionizing of the UCHII region and the mid-infrared dust arc. Infrared source IRS-I 2, which has been thought to be a circumstellar disk associated with a linear distribution of methanol masers, is found not to be directly coincident with the masers and elongated at a much different position angle. IRS-I 3 is found to be a extended source of mid-infrared emission coming from a cluster of young dusty sources seen in the near-infrared.Comment: Accepted for publication by the Astrophysical Journal, 27 pages, 9 figure

Glicerina bruta em suplementos para bovinos de corte a pasto no período seco.

O objetivo deste trabalho foi avaliar o efeito da substituição do milho pela glicerina bruta (GB) sobre os parâmetros nutricionais e o desempenho de bovinos de corte em pastagem de Urochloa brizantha 'Marandu', no período seco. Para a avaliação dos parâmetros ruminais, foram utilizados cinco bovinos da raça Nelore não fistulados, com peso corporal (PC) inicial de 331,7±29,6 kg, distribuídos em delineamento em quadrado latino 5x5. Para a avaliação do desempenho, foram utilizados 30 bovinos, com PC médio de 312,4±23,3 kg, distribuídos em delineamento inteiramente casualizado. Avaliaram-se suplementos concentrados (20% de proteína bruta) com 0, 33, 66 e 100% de GB em substituição ao milho, fornecidos na quantidade de 4,0 kg por animal por dia. Os consumos de matéria seca (MS) de suplemento, total e de pasto, bem como o de matéria orgânica (MO) digestível, apresentaram comportamento quadrático frente aos níveis de substituição. As digestibilidades aparentes de MS, MO, fibra em detergente neutro e MO digerida, bem como o ganho médio diário, também apresentaram comportamento quadrático. Em suplementos concentrados fornecidos na quantidade de 10g kg-1 de peso corporal, a substituição total do milho pela glicerina bruta reduz o consumo de suplemento e de matéria orgânica digerida, além do desempenho de bovinos de corte em pastejo.Título em inglês: Crude glycerin in supplements for beef cattle at pasture during the dry season

A Representação do Leitor Modernista Sul-Baiano em Iararana visto sob a Perspectiva da Estética da Recepção

Estudo da representação do leitor modernista sul baiano em Iararana, numa perspectiva da Teoria do Efeito de Wolfgang Iser. Iararana acabou sendo um instrumento que facilitou não somente a instalação das idéias modernistas na Bahia, mas também, a ampliação do leitorado sul baiano, num processo de reconstrução de certos paradigmas existentes naquela época. O trabalho aqui proposto parte da investigação de elementos introjetados no poema em tela que funcionariam como “guias” de leitura. Tais “guias” viabilizariam maneiras de apropriação do texto pelo leito

Predição do fracionamento de carboidratos da cana-de-açúcar com base em componentes fibrosos.

Objetivando desenvolver e validar modelos de predição do fracionamento de carboidratos da cana-de-açúcar com base em componentes fibrosos, foram realizadas determinações em triplicata da fibra em detergente neutro (FDN), lignina (LIG), fração A+B1, B2 e C dos carboidratos de 15 variedades de cana-de-açúcar (Saccharum spp.), colhidas aos 426, 487 e 549 dias apÓs para compor um banco de dados para ser utilizado no desenvolvimento e validação de equações de predição das frações dos carboidratos. As equações desenvolvidas foram para A+B1 = 101,21052- 1,06067FDN (R2 = 99,13) e para fração C = -16,51672 +O,34406FDN +1,2103L1g (R2 = 99,55). A fração B2 foi obtida por diferença 100- (A+B1+C). Com base nos valores de P observados, pode-se inferir que todas as equações propostas são precisas, pois nelas o intercepto (130) não foi significativamente (P>0,05) diferente de zero e a inclinação (131) não foi significativamente diferente de 1. As equações desenvolvidas para predição das frações A+B1, B2 e C dos carboidratos são precisas e podem ser utilizadas com segurança

Resolved Mid-IR Emission in the Narrow Line Region of NGC 4151

We present subarcsecond resolution mid infrared images of NGC 4151 at 10.8 micron and 18.2 micron. These images were taken with the University of Florida mid-IR camera/spectrometer OSCIR at the Gemini North 8-m telescope. We resolve emission at both 10.8 micron and 18.2 micron extending ~ 3.5" across at a P.A. of ~ 60 degrees. This coincides with the the narrow line region of NGC 4151 as observed in [OIII] by the Hubble Space Telescope. The most likely explanation for this extended mid-IR emission is dust in the narrow line region heated by a central engine. We find no extended emission associated with the proposed torus and place an upper limit on its mid-IR size of less than or equal to ~ 35 pc.Comment: accepted for publication in the Astrophysical Journal, 19 pages including 5 figure

A Search for Mid-Infrared Emission from Hot Molecular Core Candidates

We present here mid-infrared images of seven sites of water maser emission thought to be associated with the hot molecular core (HMC) phase of massive star formation. Observations were obtained at the NASA InfraRed Telescope Facility 3-m, the Gemini 8-m, and Keck II 10-m telescopes. We have detected mid-infrared sources at the locations of two HMC candidates, G11.94-0.62 and G45.07-0.13. We observed G19.61-0.23 and G34.26+0.15, each of which have HMCs previously detected in the mid-infrared. We did not detect mid-infrared emission from either HMC source, and we place new upper limits on the mid-infrared flux densities for these HMCs that are much lower than their previously reported flux densities. We were able to obtain extremely accurate astrometry for our mid-infrared images of G9.62+0.19, and conclude that the mid-infrared emission thought to be coming from the HMC in this field is in fact coming from a different source altogether.Comment: 19 pages, 17 figures, to appear in ApJ. Also available at http://www.ctio.noao.edu/~debuizer

Observations of Massive Star Forming Regions with Water Masers: Mid-Infrared Imaging

We present here a mid-infrared imaging survey of 26 sites of water maser emission. Observations were obtained at the InfraRed Telescope Facility 3-m telescope with the University of Florida mid-infrared imager/spectrometer OSCIR, and the JPL mid-infrared camera MIRLIN. The main purpose of the survey was to explore the relationship between water masers and the massive star formation process. It is generally believed that water masers predominantly trace outflows and embedded massive stellar objects, but may also exist in circumstellar disks around young stars. We investigate each of these possibilities in light of our mid-infrared imaging. We find that mid-infrared emission seems to be more closely associated with water and OH maser emission than cm radio continuum emission from UC HII regions. We also find from the sample of sources in our survey that, like groups of methanol masers, both water and OH masers have a proclivity for grouping into linear or elongated distributions. We conclude that the vast majority of linearly distributed masers are not tracing circumstellar disks, but outflows and shocks instead.Comment: 49 pages; 23 figures; To appear in February 2005 ApJS; To download a version with better quality figures, go to http://www.ctio.noao.edu/~debuizer