المؤلفون: Navarete, F, Damineli, A, Steiner, J E, Blum, R D

المصدر: Monthly Notices of the Royal Astronomical Society; May2021, Vol. 503 Issue 1, p270-291, 22p

مصطلحات موضوعية: INTEGRAL field spectroscopy, PRINCIPAL components analysis, PROTOSTARS, CIRCUMSTELLAR matter, TOMOGRAPHY, COMPACT discs

مستخلص: W33A is a well-known example of a high-mass young stellar object showing evidence of a circumstellar disc. We revisited the K -band NIFS/Gemini North observations of the W33A protostar using principal components analysis tomography and additional post-processing routines. Our results indicate the presence of a compact rotating disc based on the kinematics of the CO absorption features. The position–velocity diagram shows that the disc exhibits a rotation curve with velocities that rapidly decrease for radii larger than 0.1 arcsec (∼250 au) from the central source, suggesting a structure about four times more compact than previously reported. We derived a dynamical mass of 10.0 |$^{+4.1}_{-2.2}$|   |$\rm {M}_\odot$| for the 'disc + protostar' system, about ∼33 per cent smaller than previously reported, but still compatible with high-mass protostar status. A relatively compact H2 wind was identified at the base of the large-scale outflow of W33A, with a mean visual extinction of ∼63 mag. By taking advantage of supplementary near-infrared maps, we identified at least two other point-like objects driving extended structures in the vicinity of W33A, suggesting that multiple active protostars are located within the cloud. The closest object (Source B) was also identified in the NIFS field of view as a faint point-like object at a projected distance of ∼7000 au from W33A, powering extended K -band continuum emission detected in the same field. Another source (Source C) is driving a bipolar |$\rm {H}_2$| jet aligned perpendicular to the rotation axis of W33A. [ABSTRACT FROM AUTHOR]

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المؤلفون: Damineli, A., Almeida, L. A., Blum, R. D., Damineli, D. S. C., Navarete, F., Rubinho, M. S., Teodoro, M.

المصدر: Monthly Notices of the Royal Astronomical Society; 12/11/2016, Vol. 463 Issue 3, p2653-2666, 14p

مصطلحات موضوعية: STAR formation, PHOTOMETRY, GALACTIC cosmic rays, REDSHIFT, METAPHYSICAL cosmology

مستخلص: The young stellar cluster Westerlund 1 (Wd 1: l = 339 °..°6, b = -0 °..°4) is one of the most massive in the local Universe, but accurate parameters are pending on better determination of its extinction and distance. Based on our photometry and data collected from other sources, we have derived a reddening law for the cluster line-of-sight representative of the Galactic plane (-5° < b <+5°) in the window 0.4-4.8 μm: The power-law exponent α = 2.13 ± 0.08 is much steeper than those published a decade ago (1.6-1.8) and our index RV = 2.50 ± 0.04 also differs from them, but in very good agreement with recent works based on deep surveys in the inner Galaxy. As a consequence, the total extinction AKs = 0.74 ± 0.08 (AV = 11.40 ± 2.40) is substantially smaller than previous results (0.91-1.13), part of which (AKs = 0.63 or AV = 9.66) is from the interstellar medium. The extinction in front of the cluster spans a range of ΔAV ~8.7 with a gradient increasing from SW to NE across the cluster face, following the same general trend of warm dust distribution. The map of the J - Ks colour index also shows a trend of reddening in this direction. We measured the equivalent width of the diffuse interstellar band at 8620 Å (the 'GAIA DIB') for Wd 1 cluster members and derived the relation AKs = 0.612 EW - 0.191 EW². This extends the Munari et al. relation, valid for EB-V < 1, to the non-linear regime (AV > 4). [ABSTRACT FROM AUTHOR]

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المؤلفون: Navarete, F., Damineli, A., Barbosa, C. L., Blum, R. D.

المصدر: Monthly Notices of the Royal Astronomical Society; 7/11/2015, Vol. 450 Issue 4, p4364-4398, 35p

مصطلحات موضوعية: HYDROGEN analysis, EMISSIONS (Air pollution), NEAR infrared radiation, ASTRONOMICAL photometry, WAVELENGTHS

مستخلص: We present the results from a survey, designed to investigate the accretion process of massive young stellar objects (MYSOs) through near-infrared narrow-band imaging using the H2 ν=1–0 S(1) transition filter. A sample of 353 MYSO candidates was selected from the Red MSX Source survey using photometric criteria at longer wavelengths (infrared and submillimetre) and chosen with positions throughout the Galactic plane. Our survey was carried out at the Southern Astrophysical Research Telescope Telescope in Chile and Canada–France–Hawaii Telescope in Hawaii covering both hemispheres. The data reveal that extended H2 emission is a good tracer of outflow activity, which is a signpost of accretion process on young massive stars. Almost half of the sample exhibit extended H2 emission and 74 sources (21 per cent) have polar morphology, suggesting collimated outflows. The polar-like structures are more likely to appear on radio-quiet sources, indicating these structures occur during the pre-UCH II phase. We also found an important fraction of sources associated with fluorescent H2 diffuse emission that could be due to a more evolved phase. The images also indicate only ~23 per cent (80) of the sample is associated with extant (young) stellar clusters. These results support the scenario in which massive stars are formed by accretion discs, since the merging of low-mass stars would not produce outflow structures. [ABSTRACT FROM AUTHOR]

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المؤلفون: Navarete, F., Damineli, A., Barbosa, C. L., Blum, R. D., Meynet, Georges, Georgy, Cyril, Groh, José, Stee, Philippe

المصدر: Proceedings of the International Astronomical Union; Jun2014 Supplement, Vol. 9 Issue S307, p431-436, 6p

مستخلص: We present preliminary results from a survey of molecular H2 (2.12 μm) emission in massive young stellar objects (MYSO) candidates selected from the Red MSX Source survey. We observed 354 MYSO candidates through the H2 S(1) 1-0 transition (2.12 μm) and an adjacent continuum narrow-band filters using the Spartan/SOAR and WIRCam/CFHT cameras. The continuum-subtracted H2 maps were analyzed and extended H2 emission was found in 50% of the sample (178 sources), and 38% of them (66) have polar morphology, suggesting collimated outflows. The polar-like structures are more likely to be driven on radio-quiet sources, indicating that these structures occur during the pre-ultra compact H ii phase. We analyzed the continuum images and found that 54% (191) of the sample displayed extended continuum emission and only ~23% (80) were associated to stellar clusters. The extended continuum emission is correlated to the H2 emission and those sources within stellar clusters does display diffuse H2 emission, which may be due to fluorescent H2 emission. These results support the accretion scenario for massive star formation, since the merging of low-mass stars would not produce jet-like structures. Also, the correlation between jet-like structures and radio-quiet sources indicates that higher inflow rates are required to form massive stars in a typical timescale less than 105 years. [ABSTRACT FROM PUBLISHER]

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المؤلفون: Woods, Paul M., Oliveira, J. M., Kemper, F., van Loon, J. Th., Sargent, B. A., Matsuura, M., Szczerba, R., Volk, K., Zijlstra, A. A., Sloan, G. C., Lagadec, E., McDonald, I., Jones, O., Gorjian, V., Kraemer, K. E., Gielen, C., Meixner, M., Blum, R. D., Sewiło, M., Riebel, D.

المصدر: Monthly Notices of the Royal Astronomical Society; Mar2011, Vol. 411 Issue 3, p1597-1627, 31p, 1 Color Photograph, 1 Diagram, 4 Charts, 19 Graphs

مصطلحات موضوعية: COSMIC dust, MAGELLANIC clouds, INFRARED spectra, SPECTROGRAPHS, DECISION trees, SPECTRAL energy distribution, ASTRONOMICAL photometry

مستخلص: We present the classification of 197 point sources observed with the Infrared Spectrograph in the SAGE-Spec Legacy programme on the Spitzer Space Telescope. We introduce a decision-tree method of object classification based on infrared spectral features, continuum and spectral energy distribution shape, bolometric luminosity, cluster membership and variability information, which is used to classify the SAGE-Spec sample of point sources. The decision tree has a broad application to mid-infrared spectroscopic surveys, where supporting photometry and variability information are available. We use these classifications to make deductions about the stellar populations of the Large Magellanic Cloud and the success of photometric classification methods. We find 90 asymptotic giant branch (AGB) stars, 29 young stellar objects, 23 post-AGB objects, 19 red supergiants, eight stellar photospheres, seven background galaxies, seven planetary nebulae, two H regions and 12 other objects, seven of which remain unclassified. [ABSTRACT FROM AUTHOR]

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المؤلفون: Moisés, A. P., Damineli, A., Figuerêdo, E., Blum, R. D., Conti, P. S., Barbosa, C. L.

المصدر: Monthly Notices of the Royal Astronomical Society; Feb2011, Vol. 411 Issue 2, p705-760, 56p

مصطلحات موضوعية: GALAXIES, H II regions (Astrophysics), T Tauri stars, STAR formation, SPECTROPHOTOMETRY, NEAR infrared spectroscopy, ASTRONOMICAL photometry

مستخلص: We present a near-infrared study of the stellar content of 35 H regions in the Galactic plane, 24 of which have been classified as giant H regions. We have selected these optically obscured star-forming regions from the catalogues of Russeil, Conti & Crowther and Bica et al. In this paper, we have used the near-infrared domain J-, H- and K-band colour images to visually inspect the sample. Also, we have used colour-colour and colour-magnitude diagrams to indicate ionizing star candidates, as well as the presence of young stellar objects such as classical T Tauri stars and massive young stellar objects (MYSOs). We have obtained Spitzer Infrared Array Camera images for each region to help further characterize them. Spitzer and near-infrared morphology were used to place each cluster in an evolutionary phase of development. Spitzer photometry was also used to classify the MYSOs. A comparison of the main sequence in the colour-magnitude diagrams for each observed cluster was used to infer whether or not the cluster kinematic distance is consistent with brightnesses of the stellar sources. We find qualitative agreement for a dozen of the regions, but about half the regions have near-infrared photometry that suggests they may be closer than the kinematic distance. A significant fraction of these already have spectrophotometric parallaxes that support smaller distances. These discrepancies between kinematic and spectrophotometric distances are not a result of the spectrophotometric methodologies, as independent non-kinematic measurements are in agreement with the spectrophotometric results. For instance, the trigonometric parallaxes of star-forming regions were collected from the literature and show the same effect of smaller distances when compared to the kinematic results. In our sample of H regions, most of the clusters are evident in the near-infrared images. Finally, it is possible to distinguish among qualitative evolutionary stages for these objects. [ABSTRACT FROM AUTHOR]

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المؤلفون: Furness, J. P., Crowther, P. A., Morris, P. W., Barbosa, C. L., Blum, R. D., Conti, P. S., van Dyk, S. D.

المصدر: Monthly Notices of the Royal Astronomical Society; Apr2010, Vol. 403 Issue 3, p1433-1447, 15p, 1 Diagram, 7 Charts, 12 Graphs

مصطلحات موضوعية: STAR clusters, SPECTRUM analysis, EARLY stars, MILKY Way, NEBULAE

مستخلص: We present near-infrared Very Large Telescope/Infrared Spectrograph and Array Camera and mid-infrared (mid-IR) Spitzer/Infrared Spectrograph spectroscopy of the young massive cluster in the W31 star-forming region. H-band spectroscopy provides refined classifications for four cluster member O stars with respect to Blum et al. In addition, photospheric features are detected in the massive young stellar object (massive YSO) #26. Spectroscopy permits estimates of stellar temperatures and masses, from which a cluster age of ∼0.6 Myr and distance of 3.3 kpc are obtained, in excellent agreement with Blum et al. IRS spectroscopy reveals mid-IR fine structure line fluxes of [Ne ii–iii] and [S iii–iv] for four O stars and five massive YSOs. In common with previous studies, stellar temperatures of individual stars are severely underestimated from the observed ratios of fine-structure lines, despite the use of contemporary stellar atmosphere and photoionization models. We construct empirical temperature calibrations based upon the W31 cluster stars of known spectral type, supplemented by two inner Milky Way ultracompact (UC) H ii regions whose ionizing star properties are established. Calibrations involving [Ne iii] 15.5 μm/[Ne ii] 12.8 μm, [S iv] 10.5 μm/[Ne ii] 12.8 μm or [Ar iii] 9.0 μm/[Ne ii] 12.8 μm have application in deducing the spectral types of early to mid O stars for other inner Milky Way compact and UC H ii regions. Finally, evolutionary phases and time-scales for the massive stellar content in W31 are discussed, due to the presence of numerous young massive stars at different formation phases in a ‘coeval’ cluster. [ABSTRACT FROM AUTHOR]

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المؤلفون: Gordon, Karl D., Meixner, M., Blum, R. D., Reach, W., Whitney, B. A., Harris, J., Indebetouw, R., Bolatto, A. D., Bernard, J.-P., Sewilo, M., Babler, B. L., Block, M., Bot, C., Bracker, S., Carlson, L., Churchwell, E., Clayton, G. C., Cohen, M., Engelbracht, C. W., Fukui, Y.

المصدر: Proceedings of the International Astronomical Union; 07/02/2008, Vol. 4 Issue S256, p184-188, 5p

مستخلص: Early results from the SAGE-SMC (Surveying the Agents of Galaxy Evolution in the tidally-disrupted, low-metallicity Small Magellanic Cloud) Spitzer legacy program are presented. These early results concentrate on the SAGE-SMC MIPS observations of the SMC Tail region. This region is the high H i column density portion of the Magellanic Bridge adjacent to the SMC Wing. We detect infrared dust emission and measure the gas-to-dust ratio in the SMC Tail and find it similar to that of the SMC Body. In addition, we find two embedded cluster regions that are resolved into multiple sources at all MIPS wavelengths. [ABSTRACT FROM PUBLISHER]

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المؤلفون: Cunha, Katia, Smith, V. V., Sellgren, K., Blum, R. D., Ramírez, S. V., Terndrup, D. M.

المصدر: Proceedings of the International Astronomical Union; 07/02/2007, Vol. 3 Issue S245, p339-342, 4p

مستخلص: We discuss oxygen and iron abundance patterns in K and M red-giant members of the Galactic bulge and in the young and massive M-type stars inhabiting the very center of the Milky Way. The abundance results from the different bulge studies in the literature, both in the optical and the infrared, indicate that the [O/Fe]-[Fe/H] relation in the bulge does not follow the disk relation, with [O/Fe] values falling above those of the disk. Based on these elevated values of [O/Fe] extending to large Fe abundances, it is suggested that the bulge underwent a rapid chemical enrichment with perhaps a top-heavy initial mass function. The Galactic Center stars reveal a nearly uniform and slightly elevated (relative to solar) iron abundance for a studied sample which is composed of 10 red giants and supergiants. Perhaps of more significance is the fact that the young Galactic Center M-type stars show abundance patterns that are reminiscent of those observed for the bulge population and contain enhanced abundance ratios of α-elements relative to either the Sun or Milky Way disk at near-solar metallicities. [ABSTRACT FROM PUBLISHER]

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المؤلفون: Blum, R. D., Mould, J. R., Olsen, K. A., Frogel, J. A., Werner, M., Meixner, M., Markwick-Kemper, F., Indebetouw, R., Whitney, B., Meade, M., Babler, B., Churchwell, E. B., Gordon, K., Engelbracht, C., For, B.-Q., Misselt, K., Vijh, U., Leitherer, C., Volk, K., Points, S.

المصدر: Astronomical Journal; Nov2006, Vol. 132 Issue 5, p2034-2045, 12p