Browsing by Author "Gerhard, Ortwin"

Now showing items 1-6 of 6

    • The Andromeda Galaxy’s Last Major Merger: Constraints from the survey of Planetary Nebulae 

      Bhattacharya, Souradeep; Arnaboldi, Magda; Gerhard, Ortwin; Caldwell, Nelson; Kobayashi, Chiaki; Hammer, Francois; Yang, Yanbin; Freeman, Kenneth C.; Hartke, Johanna; McConnachie, Alan (The International Astronomical Union, 2023-05-04)
      The Andromeda galaxy (M 31) has experienced a tumultuous merger history as evidenced by the many substructures present in its inner halo. We use planetary nebulae (PNe) as chemodynamic tracers to shed light on the recent ...

    • The Milky Way bar/bulge in proper motions: a 3D view from VIRAC & Gaia 

      Clarke, Jonathan P.; Wegg, Christopher; Gerhard, Ortwin; Smith, Leigh C.; Lucas, Philip; Wylie, Shola M. (2019-11)
      We have derived absolute proper motions of the entire Galactic bulge region from VIRAC and Gaia. We present these as both integrated on-sky maps and, after isolating standard candle red clump (RC) stars, as a function of ...

    • On the α /Fe Bimodality of the M31 Disks 

      Kobayashi, Chiaki; Bhattacharya, Souradeep; Arnaboldi, Magda; Gerhard, Ortwin (2023-10-10)
      An outstanding question is whether the α/Fe bimodality exists in disk galaxies other than in the Milky Way. Here we present a bimodality using our state-of-the-art galactic chemical evolution models that can explain various ...

    • Self-consistent modelling of the Milky Way's Nuclear Stellar Disc 

      Sormani, Mattia C.; Sanders, Jason L.; Fritz, Tobias K.; Smith, Leigh C.; Gerhard, Ortwin; Schoedel, Rainer; Magorrian, John; Neumayer, Nadine; Nogueras-Lara, Francisco; Feldmeier-Krause, Anja; Mastrobuono-Battisti, Alessandra; Schultheis, Mathias; Shahzamanian, Banafsheh; Vasiliev, Eugene; Klessen, Ralf S.; Lucas, Philip; Minniti, Dante (2022-03-22)
      The Nuclear Stellar Disc (NSD) is a flattened high-density stellar structure that dominates the gravitational field of the Milky Way at Galactocentric radius $30\lesssim R\lesssim 300$ pc. We construct axisymmetric ...

    • The survey of planetary nebulae in Andromeda (M 31) V. Chemical enrichment of the thin and thicker discs of Andromeda. Oxygen to argon abundance ratios for planetary nebulae and H II regions 

      Arnaboldi, Magda; Bhattacharya, Souradeep; Gerhard, Ortwin; Kobayashi, Chiaki; Freeman, Kenneth C.; Caldwell, Nelson; Hartke, Johanna; McConnachie, Alan; Guhathakurta, Puragra (2022-10-13)
      We use oxygen and argon abundances for planetary nebulae (PNe) with low internal extinction (progenitor ages of (>4.5 Gyr) and high extinction (progenitor ages

    • The survey of planetary nebulae in Andromeda (M31). IV. Radial oxygen and argon abundance gradients of the thin and thicker disc 

      Bhattacharya, Souradeep; Arnaboldi, Magda; Caldwell, Nelson; Gerhard, Ortwin; Kobayashi, Chiaki; Hartke, Johanna; Freeman, Kenneth C.; McConnachie, Alan W.; Guhathakurta, Puragra (2022-12-01)
      We obtain a magnitude-limited sample of Andromeda (M 31) disc PNe with chemical abundance estimated through the direct detection of the [O III] 4363 Å line. This leads to 205 and 200 PNe with oxygen and argon abundances, ...