Browsing by Author "Martin, Nicolas"

Now showing 1 - 5 of 5
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    Detailed study of the Milky Way globular cluster Laevens 3
    (2019) Longeard, Nicolas; Martin, Nicolas; Ibata, Rodrigo A.; Collins, Michelle L. M.; Laevens, Benjamin P. M.; Bell, Eric; Mackey, Dougal
    We present a photometric and spectroscopic study of the Milky Way satellite Laevens 3. UsingMegaCam/Canada-France-Hawaii Telescope g and i photometry andKeck II/DEIMOS multi-object spectroscopy, we refine the structural and stellar properties of the system. The Laevens 3 colour-magnitude diagram shows that it is quite metal-poor, old (13.0 +/- 1.0Gyr), and at a distance of 61.4 +/- 1.0 kpc, partly based on two RR Lyrae stars. The system is faint (M-V = -2.8(-0.3)(+0.2) mag) and compact (r(h) = 11.4 +/- 1.0 pc). From the spectroscopy, we constrain the systemic metallicity ([Fe/H](spectro) = -1.8 +/- 0.1 dex) but the metallicity and velocity dispersions are both unresolved. Using Gaia DR2, we infer a mean proper motion of (mu(alpha)*, mu(delta)) = (0.51 +/- 0.28,-0.83 +/- 0.27) mas yr(-1), which, combined with the system's radial velocity (< v(r)> = -70.2 +/- 0.5km s(-1)), translates into a halo orbit with a pericenter and apocenter of 40.7(-14.7)(+5.6) and 85.6(-5.9)(+17.2) kpc, respectively. Overall, Laevens 3 shares the typical properties of the Milky Way's outer halo globular clusters. Furthermore, we find that this system shows signs of mass segregation that strengthens our conclusion that Laevens 3 is a globular cluster.
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    Nature of a shell of young stars in the outskirts of the Small Magellanic Cloud
    (2019) Martinez-Delgado, David; Katherina Vivas, Anna; Grebel, Eva K.; Gallart, Carme; Pieres, Adriano; Bell, Cameron P. M.; Zivick, Paul; Lemasle, Bertrand; Johnson, Lent Clifton; Carballo-Bello, Julio A.; Noel, Noelia E. D.; Cioni, Maria-Rosa L.; Choi, Yumi; Besla, Gurtina; Schmidt, Judy; Zaritsky, Dennis; Gruendl, Robert A.; Seibert, Mark; Nidever, David; Monteagudo, Laura; Monelli, Mateo; Hubl, Bernhard; van der Marel, Roeland; Ballesteros, Fernando J.; Stringfellow, Guy; Walker, Alistair; Blum, Robert; Bell, Eric F.; Conn, Blair C.; Olsen, Knut; Martin, Nicolas; Chu, You-Hua; Inno, Laura; Boer, Thomas J. L.; Kallivayalil, Nitya; De Leo, Michele; Beletsky, Yuri; Neyer, Fabian; Munoz, Ricardo R.
    Context. Understanding the evolutionary history of the Magellanic Clouds requires an in-depth exploration and characterization of the stellar content in their outer regions, which ultimately are key to tracing the epochs and nature of past interactions.
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    Pristine dwarf galaxy survey - I. A detailed photometric and spectroscopic study of the very metal-poor Draco II satellite
    (2018) Longeard, Nicolas; Martin, Nicolas; Starkenburg, Else; Ibata, Rodrigo A.; Collins, Michelle L. M.; Geha, Marla; Laevens, Benjamin P. M.; Rich, R. Michael; Aguado, David S.; Arentsen, Anke; Carlberg, Raymond G.; Cote, Patrick; Hill, Vanessa; Jablonka, Pascale; Gonzalez Hernandez, Jonay I.; Navarro, Julio F.; Sanchez-Janssen, Ruben; Tolstoy, Eline; Venn, Kim A.; Youakim, Kris
    We present a detailed study of the faint Milky Way satellite Draco II (Dra II) from deep CFHT/MegaCam broad-band g and i photometry and narrow-band metallicity-sensitive CaliK observations, along with follow-up Keck II/DEIMOS multi-object spectroscopy. Forward modelling of the deep photometry allows us to refine the structural and photometric properties of Dra II: the distribution of stars in colour-magnitude space implies Dra II is old (13.5 +/- 0.5 Gyr), very metal-poor, very faint (L-v = 180(-72)(+124) L-circle dot), and at a distance d = 21.5 +/- 0.4 kpc. The narrow-band, metallicity-sensitive Cal-IK Pristine photometry confirms this very low metallicity ([Fe/H] = -2.7 +/- 0.1 dex). Even though our study benefits from a doubling of the spectroscopic sample size compared to previous investigations, the velocity dispersion of the system is still only marginally resolved (sigma(vr) < 5.9 km s(-1) at the 95 per cent confidence level) and confirms that Dra II is a dynamically cold stellar system with a large recessional velocity (< v(r)> = -342.5(-1.2)(+1.1)km s(-)1). We further show that the spectroscopically confirmed members of Dra II have a mean proper motion of (mu(alpha)*, mu(delta)) = (1.26 +/- 0.27, 0.94 +/- 0.28) mas/yr in the Gaia DR2 data, which translates to an orbit with a pericentre and an apocentre of 21.3(-1.0)(+0.7) and 153.8(-34.7)(+56.7) kpc, respectively. Taken altogether, these properties favour the scenario of Dra II being a potentially disrupting dwarf galaxy. The low-significance extra-tidal features we map around the satellite tentatively support this scenario.
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    The large-scale structure of the halo of the andromeda galaxy. II. Hierarchical structure in the pan-andromeda archaeological survey
    (2018) McConnachie, Alan W.; Ibata, Rodrigo; Martin, Nicolas; Ferguson, Annette M.N.; Collins, Michelle; Gwyn, Stephen; Irwin, Mike; Lewis, Geraint F.; Dougal Mackey, A.; Puzia, Thomas H.
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    The Pristine Dwarf-Galaxy survey - II. In-depth observational study of the faint Milky Way satellite Sagittarius II
    (2020) Longeard, Nicolas; Martin, Nicolas; Starkenburg, Else; Ibata, Rodrigo A.; Collins, Michelle L. M.; Laevens, Benjamin P. M.; Mackey, Dougal; Rich, R. Michael; Aguado, David S.; Arentsen, Anke; Jablonka, Pascale; Hernandez, Jonay I. Gonzalez; Navarro, Julio F.; Sanchez-Janssen, Ruben
    We present an extensive study of the Sagittarius II (Sgr II) stellar system using MegaCam g and i photometry, narrow-band, metallicity-sensitive calcium H&K doublet photometry and Keck II/DEIMOS multiobject spectroscopy. We derive and refine the Sgr II structural and stellar properties inferred at the time of its discovery. The colour-magnitude diagram implies Sgr II is old (12.0 +/- 0.5 Gyr) and metal poor. The CaHK photometry confirms the metal-poor nature of the satellite ([Fe/H](CaHK) = -2.32 +/- 0.04 dex) and suggests that Sgr II hosts more than one single stellar population (sigma(CaHK)([FeH]) = 0.11(-0.03)(+0.05) dex). Using the Ca infrared triplet measured from our highest signal-to-noise spectra, we confirm the metallicity and dispersion inferred from the Pristine photometric metallicities ([Fe/H](spectro) = -2.23 +/- 0.05 dex, sigma(spectro)([Fe/H]) = 0.10(-0.04)(+0.06) dex). The velocity dispersion of the system is found to be sigma(v) = 2.7(-1.0)(+1.3) km s(-1) after excluding two potential binary stars. Sgr II's metallicity and absolute magnitude (M-V = -5.7 +/- 0.1 mag) place the system on the luminosity-metallicity relation of the Milky Way dwarf galaxies despite its small size. The low but resolved metallicity and velocity dispersions paint the picture of a slightly dark-matter-dominated satellite (M/L = 23.0(-23.0)(+32.8) M-circle dot L-circle dot(-1)). Furthermore, using the Gaia Data Release 2, we constrain the orbit of the satellite and find an apocentre of 118.4(-23.7)(+28.4) kpc and a pericentre of 54.8(-6.1)(+3.3) kpc. The orbit of Sgr II is consistent with the trailing arm of the Sgr stream and indicates that it is possibly a satellite of the Sgr dSph that was tidally stripped from the dwarf's influence.