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122 results on '"Da Costa, Gary S."'

101. COMMISSION 37: STAR CLUSTERS AND ASSOCIATIONS

Author

Hatzidimitriou, Despina, primary, Lada, Charles J., additional, Sarajedini, Ata, additional, Cannon, Russell D., additional, Cudworth, Kyle McC., additional, Da Costa, Gary S., additional, Deng, LiCai, additional, Lee, Young-Wook, additional, and Tosi, Monica, additional

Published
2008
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103. COMMISSION 37: STAR CLUSTERS AND ASSOCIATIONS

Author

Sarajedini, Ata, primary, Spurzem, Rainer, additional, Meylan, Georges, additional, Cannon, Russell D., additional, Castellani, Vittorio, additional, Da Costa, Gary S., additional, Cudworth, Kyle McC., additional, Deng, Licai, additional, Giersz, Miroslav, additional, Hatzidimitriou, Despina, additional, and Lada, Charles J., additional

Published
2007
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115. THE GLOBULAR CLUSTER SYSTEM OF THE MILKY WAY: ACCRETION IN A COSMOLOGICAL CONTEXT.

Author

Keller, Stefan C., MacKey, Dougal, and Da Costa, Gary S.

Subjects
MILKY Way, GLOBULAR clusters, GALAXIES, SIMULATION methods & models, ASTRONOMICAL observations
Abstract

We examine the significance of a planar arrangement in the spatial distribution of the Milky Way (MW) globular clusters (GCs). We find that, when separated on the basis of horizontal branch morphology and metallicity, the outermost canonical young halo (YH) GC sample (at galactocentric radii in excess of 10 kpc) exhibits an anisotropic distribution that may be equated to a plane (24 ± 4) kpc thick (rms) and inclined at 8° ± 5° to the polar axis of the MW disk. To quantify the significance of this plane we determine the fraction of times that an isotropic distribution replicates the observed distribution in Monte Carlo trials. The plane is found to remain significant at the >95% level outside a galactocentric radius of 10 kpc, inside this radius the spatial distribution is apparently isotropic. In contrast, the spatial distribution of the old halo sample outside 10 kpc is well matched by an isotropic distribution. The plane described by the outer YH GCs is indistinguishable in orientation from that presented by the satellite galaxies of the MW. Simulations have shown that the planar arrangement of satellites can arise as filaments of the surrounding large-scale structure feed into the MW's potential. We therefore propose that our results are direct observational evidence for the accreted origin of the outer YH GC population. This conclusion confirms numerous lines of evidence that have similarly indicated an accreted origin for this set of clusters from the inferred cluster properties. [ABSTRACT FROM AUTHOR]

Published
2012
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116. A spectroscopy-based Age-Metallicity Relation of the SMC

Author

Kayser, Andrea, Grebel, Eva K., Harbeck, Daniel R., Cole, Andrew A., Koch, Andreas, Glatt, Katharina, Gallagher, John S., Da Costa, Gary S., Kayser, Andrea, Grebel, Eva K., Harbeck, Daniel R., Cole, Andrew A., Koch, Andreas, Glatt, Katharina, Gallagher, John S., and Da Costa, Gary S.

Abstract

The Small Magellanic Cloud (SMC) is the only dwarf galaxy in the Local Group that is known to have formed and preserved populous star clusters continuously over the past 12 Gyr. Due to its proximity (≈ 60 kpc), stars can be resolved well below the oldest main sequence turnoff points. This facilitates accurate age and metallicity determinations without suffering from the age-metallicity degeneracy. Therefore, the SMC star clusters provide a unique closely spaced set of single-age, single-metallicity tracers to derive a well-sampled age-metallicity relation required for the understanding of the star formation history of this satellite galaxy. Up to date spectroscopically based metallicity estimates exist only for the small number of 7 clusters (Da Costa & Hatzidimitriou 1998). Our project now more than doubles the available data set by the observation of 10 additional clusters

121. Low Light Level Detectors in Astronomy (Book).

Author

Da Costa, Gary S.

Subjects
LOW Light Level Detectors in Astronomy (Book), ECCLES, M. J., SIM, M. Elizabeth, TRITTON, K. P.
Abstract

Reviews the book 'Low Light Level Detectors in Astronomy,' by M.J. Eccles, M. Elizabeth Sim, K.P. Tritton.

Published
1984

122. Measuring the Mass of the Large Magellanic Cloud with Stellar Streams Observed by

Author

Shipp, N, Erkal, D, Drlica-Wagner, A, Li, TS, Pace, AB, Koposov, SE, Cullinane, LR, Da Costa, GS, Ji, AP, Kuehn, K, Lewis, GF, Mackey, D, Simpson, JD, Wan, Z, Zucker, DB, Bland-Hawthorn, J, Ferguson, PS, Lilleengen, S, Shipp, Nora [0000-0003-2497-091X], Drlica-Wagner, Alex [0000-0001-8251-933X], Li, Ting S [0000-0002-9110-6163], Pace, Andrew B [0000-0002-6021-8760], Koposov, Sergey E [0000-0003-2644-135X], Cullinane, Lara R [0000-0001-8536-0547], Da Costa, Gary S [0000-0001-7019-649X], Ji, Alexander P [0000-0002-4863-8842], Kuehn, Kyler [0000-0003-0120-0808], Lewis, Geraint F [0000-0003-3081-9319], Mackey, Dougal [0000-0002-6529-8093], Simpson, Jeffrey D [0000-0002-8165-2507], Wan, Zhen [0000-0002-3105-3821], Zucker, Daniel B [0000-0003-1124-8477], Bland-Hawthorn, Joss [0000-0001-7516-4016], Ferguson, Peter S [0000-0001-6957-1627], and Apollo - University of Cambridge Repository

Subjects
5109 Space Sciences, 51 Physical Sciences
Abstract

Stellar streams are excellent probes of the underlying gravitational potential in which they evolve. In this work, we fit dynamical models to five streams in the Southern Galactic hemisphere, combining observations from the Southern Stellar Stream Spectroscopic Survey (S 5), Gaia EDR3, and the Dark Energy Survey, to measure the mass of the Large Magellanic Cloud (LMC). With an ensemble of streams, we find a mass of the LMC ranging from ∼14–19 × 1010 M ⊙, probed over a range of closest approach times and distances. With the most constraining stream (Orphan–Chenab), we measure an LMC mass of 18.8 − 4.0 + 3.5 × 10 10 M ⊙ , probed at a closest approach time of 310 Myr and a closest approach distance of 25.4 kpc. This mass is compatible with previous measurements, showing that a consistent picture is emerging of the LMC’s influence on structures in the Milky Way. Using this sample of streams, we find that the LMC’s effect depends on the relative orientation of the stream and LMC at their point of closest approach. To better understand this, we present a simple model based on the impulse approximation and we show that the LMC’s effect depends both on the magnitude of the velocity kick imparted to the stream and the direction of this kick.

Published
2021

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