Browsing by Author "Duffau, S."

Now showing 1 - 12 of 12
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    Chemical abundances of giant stars in NGC 5053 and NGC 5634, two globular clusters associated with the Sagittarius dwarf spheroidal galaxy?
    (EDP SCIENCES S A, 2015) Sbordone, L.; Monaco, L.; Moni Bidin, C.; Bonifacio, P.; Villanova, S.; Bellazzini, M.; Ibata, R.; Chiba, M.; Geisler, D.; Caffau, E.; Duffau, S.
    Context. The tidal disruption of the Sagittarius dwarf spheroidal galaxy (Sgr dSph) is producing the most prominent substructure in the Milky Way (MW) halo, the Sagittarius Stream. Aside from field stars, it is suspected that the Sgr dSph has lost a number of globular clusters (GC). Many Galactic GC are thought to have originated in the Sgr dSph. While for some candidates an origin in the Sgr dSph has been confirmed owing to chemical similarities, others exist whose chemical composition has never been investigated.
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    Detailed chemical abundances of distant RR Lyrae stars in the Virgo Stellar Stream
    (2016) Duffau, S.; Sbordone, L.; Vivas, A. K.; Hansen, C. J.; Zoccali, M.; Catelan, Márcio; Minniti, D.; Grebel, E. K.
    We present the first detailed chemical abundances for distant RR Lyrae stars members of the Virgo Stellar Stream (VSS), derived from X- Shooter medium-resolution spectra. Sixteen elements from carbon to barium have been measured in six VSS RR Lyrae stars, sampling all main nucleosynthetic channels. For the first time we will be able to compare in detail the chemical evolution of the VSS progenitor with those of Local Group dwarf spheroidal galaxies (LG dSph) as well as the one of the smooth halo....
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    Discovery of a thin stellar stream in the SLAMS survey
    (2018) Jethwa, P.; Torrealba, G.; Navarrete, C.; Carballo-Bello, J. A.; de Boer, T.; Erkal, D.; Koposov, S. E.; Duffau, S.; Geisler, D.; Catelan, Márcio; Belokurov, V.
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    Mapping the Milky Way Halo Substructures Using RR Lyrae Stars
    (2018) Carballo-Bello, J. A.; Duffau, S.; Vivas, A. K.; Navarrete, C.; Catelan, Márcio
    The Galactic halo is well populated by tidal streams and overdensities, showing its heterogeneus origin and providing important clues about its formation history. RR Lyrae stars have proven to be excellent tracers of halo substructures, due to the quality of the distances that can be derived from them, and the relatively straightforward methods that lead to their clean identification. In this work, we present our observational efforts to unveil and characterize the hypothetical accreted systems in areas of the sky with an evident excess of RR Lyrae stars. In particular, we have focused in the southern hemisphere, where some of these substructures seem to be connected with other northern stellar halo substructures....
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    Near-Field Cosmology with RR Lyrae Variable Stars: a first view of substructure in the southern sky
    (2016) Navarrete, C.; Duffau, S.; Vivas, A. K.; Catelan, Márcio; Hajdu, G.; Torrealba, G.; Cortés, C.; Belokurov, V.; Koposov, S.; Drake, A. J.
    We present the current status of the spectroscopic follow-up of a large number of RR Lyrae (RRL) halo overdensity candidates recently found by Torrealba et al. (2015) using southern-hemisphere data from the Catalina Real-time Transient Survey (CRTS). Characterizing the individual RRL stars in these overdensities is crucial to confirm them as real halo substructures. Low-resolution spectra have been obtained for RRL stars in 11 different overdensities, using the SOAR and Magellan telescopes. Radial velocities and metallicities have been derived so far for 123 and 99 RRL stars, respectively....
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    Stellar streams around the Magellanic Clouds in 4D
    (OUP, 2018) Navarrete Silva, Camila Andrea; Belokurov, V.; Catelan, Márcio; Jethwa, P.; Koposov, S. E.; Carballo-Bello, J. A.; Jofré, P.; Erkal, D.; Duffau, S.; Corral-Santan, J. M.
    We carried out a spectroscopic follow-up programme of the four new stellar stream candidates detected by Belokurov & Koposov in the outskirts of the Large Magellanic Cloud (LMC) using FORS2 (VLT). The medium-resolution spectra were used to measure the line-of-sight velocities, estimate stellar metallicities, and classify stars into Blue Horizontal Branch (BHB) and Blue Straggler (BS) stars. Using the 4-D phase-space information, we attribute approximately one half of our sample to the Magellanic Clouds, while the rest is part of the Galactic foreground. Only two of the four stream candidates are confirmed kinematically. While it is impossible to estimate the exact levels of MW contamination, the phase-space distribution of the entire sample of our Magellanic stars matches the expected velocity gradient for the LMC halo and extends as far as 33 deg (angular separation) or 29 kpc from the LMC centre. Our detections reinforce the idea that the halo of the LMC seems to be larger than previously expected, and its debris can be spread in the sky out to very large separations from the LMC centre. Finally, we provide some kinematic evidence that many of the stars analysed here have likely come from the Small Magellanic Cloud.
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    The Gaia-ESO Survey: Extracting diffuse interstellar bands from cool star spectra DIB-based interstellar medium line-of-sight structures at the kpc scale
    (EDP SCIENCES S A, 2015) Puspitarini, L.; Lallement, R.; Babusiaux, C.; Chen, H. C.; Bonifacio, P.; Sbordone, L.; Caffau, E.; Duffau, S.; Hill, V.; Monreal Ibero, A.; Royer, F.; Arenou, F.; Peralta, R.; Drew, J. E.; Bonito, R.; Lopez Santiago, J.; Alfaro, E. J.; Bensby, T.; Bragaglia, A.; Flaccomio, E.; Lanzafame, A. C.; Pancino, E.; Recio Blanco, A.; Smiljanic, R.; Costado, M. T.; Lardo, C.; de Laverny, P.; Zwitter, T.
    Aims. We study how diffuse interstellar bands (DIBs) measured toward distance-distributed target stars can be used to locate dense interstellar (IS) clouds in the Galaxy and probe a line-of-sight (LOS) kinematical structure, a potentially useful tool when gaseous absorption lines are saturated or not available in the spectral range. Cool target stars are numerous enough for this purpose.
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    The Gaia-ESO Survey: Galactic evolution of sulphur and zinc
    (EDP SCIENCES S A, 2017) Duffau, S.; Caffau, E.; Sbordone, L.; Bonifacio, P.; Andrievsky, S.; Korotin, S.; Babusiaux, C.; Salvadori, S.; Monaco, L.; Francois, P.; Skuladottir, A.; Bragaglia, A.; Donati, P.; Spina, L.; Gallagher, A. J.; Ludwig, H. G.; Christlieb, N.; Hansen, C. J.; Mott, A.; Steffen, M.; Zaggia, S.; Blanco Cuaresma, S.; Calura, F.; Friel, E.; Jimenez Esteban, F. M.; Koch, A.; Magrini, L.; Pancino, E.; Tang, B.; Tautvaisiene, G.; Vallenari, A.; Hawkins, K.; Gilmore, G.; Randich, S.; Feltzing, S.; Bensby, T.; Flaccomio, E.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Hourihane, A.; Jofre, P.; Lardo, C.; Lewis, J.; Morbidelli, L.; Sousa, S. G.; Worley, C. C.
    Context. Due to their volatile nature, when sulphur and zinc are observed in external galaxies, their determined abundances represent the gas-phase abundances in the interstellar medium. This implies that they can be used as tracers of the chemical enrichment of matter in the Universe at high redshift. Comparable observations in stars are more difficult and, until recently, plagued by small number statistics.
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    The Gaia-ESO Survey: radial distribution of abundances in the Galactic disc from open clusters and young-field stars
    (EDP SCIENCES S A, 2017) Magrini, L.; Randich, S.; Kordopatis, G.; Prantzos, N.; Romano, D.; Ffi, A. Chie; Limongi, M.; Francois, P.; Pancino, E.; Friel, E.; Bragaglia, A.; Tautvaisiene, G.; Spina, L.; Overbeek, J.; Cantat Gaudin, T.; Donati, P.; Vallenari, A.; Sordo, R.; Jimenez Esteban, F. M.; Tang, B.; Drazdauskas, A.; Sousa, S.; Duffau, S.; Jofre, P.; Gilmore, G.; Feltzing, S.; Alfaro, E.; Bensby, T.; Flaccomio, E.; Koposov, S.; Lanzafame, A.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Hourihane, A.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G.; Sbordone, L.; Worley, C. C.; Zaggia, S.
    Context. The spatial distribution of elemental abundances in the disc of our Galaxy gives insights both on its assembly process and subsequent evolution, and on the stellar nucleogenesis of the different elements. Gradients can be traced using several types of objects as, for instance, (young and old) stars, open clusters, HII regions, planetary nebulae.
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    The globular cluster NGC7492 and the Sagittarius tidal stream : Together but unmixed
    (2018) Carballo Bello, J.A.; Corral Santana, J.M.; Catelan, Márcio; Martínez Delgado, D.; Muñoz, R.R.; Sollima, A.; Navarrete, C.; Duffau, S.; Coté, P.; Mora, M.D.
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    The southern leading and trailing wraps of the Sagittarius tidal stream around the globular cluster Whiting 1
    (2017) Carballo Bello, J. A.; Corral Santana, J. M.; Martínez Delgado, D.; Sollima, A.; Muñoz, R. R.; Côté, P.; Duffau, S.; Catelan, Márcio; Grebel, E. K.
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    Using classical cepheids to study the far side of the milky way disk : I. Spectroscopic classification and the metallicity gradient
    (2020) Minniti, Javier Horacio; Sbordone, L.; Rojas Arriagada, A.; Zoccali, Manuela; Contreras Ramos, Rodrigo Andrés; Minniti, D.; Marconi, M.; Braga, V. F.; Catelan, Márcio; Duffau, S.; Gieren Waiblinger, Wolfgang Paul; Valcarce Bravo, Aldo Alfonso Raúl