Detalles de publicación
PP 019099
Kinematic and metallicity properties od the Aquarius dwarf galaxy from FORS2 MXU spectroscopy
1 Instituto de Astrofísica de Andalucía - CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
2 Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
3 Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife, Spain
4 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
5 European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching, Germany
6 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
7 School of Natural Sciences, University of Tasmania, Private Bag 37 Hobart, Tasmania 7001, Australia
8 Institute of Physics, Laboratory of Astrophysics, École Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny,
Switzerland
9 GEPI, CNRS UMR 8111, Observatoire de Paris, PSL Research University, F-92125, Meudon, Cedex, France
10 National Research Council, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7,
Canada
11 Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
12 Kapteyn Astronomical Institute, University of Groningen, 9700AV Groningen, The Netherlands
Dwarf galaxies found in isolation in the Local Group (LG) are unlikely to
have interacted with the large LG spirals, and therefore environmental effects
should not be the main drivers of their evolution. We aim to provide insight
into the internal mechanisms shaping LG dwarf galaxies by increasing our
knowledge of the internal properties of isolated systems. We focus on the
evolved stellar component of the Aquarius dwarf, whose kinematic and
metallicity properties have only recently started to be explored. We have
obtained spectroscopic data in the the near-infrared CaII triplet lines region
with FORS2 at the Very Large Telescope for 53 red giant branch (RGB) stars, to
derive line-of-sight velocities and [Fe/H] of the individual RGB stars. We have
derived a systemic velocity of $-142.2^{+1.8}_{-1.8}$ km s$^{-1}$, in agreement
with previous measurements from both the HI gas and stars. The internal
kinematics of Aquarius appears to be best modelled by a combination of random
motions (l.o.s. velocity dispersion of $10.3^{+1.6}_{-1.3}$ km s$^{-1}$) and
linear rotation (with a gradient $-5.0^{+1.6}_{-1.9}$ km s$^{-1}$
arcmin$^{-1}$) along a P.A.=$139_{-27}^{+17}$ deg, consistent with the optical
projected major axis. This rotation signal is significantly misaligned or even
counter-rotating to that derived from the HI gas. We also find the tentative
presence of a mild negative metallicity gradient and indications that the
metal-rich stars have a colder velocity dispersion than the metal-poor ones.
This work represents a significant improvement with respect to previous
measurements of the RGB stars of Aquarius, as it doubles the number of member
stars studied in the literature. We speculate that the misaligned rotation
between the HI gas and evolved stellar component might have been the result of
recent accretion of HI gas or re-accretion after gas-loss due to internal
stellar feedback.
have interacted with the large LG spirals, and therefore environmental effects
should not be the main drivers of their evolution. We aim to provide insight
into the internal mechanisms shaping LG dwarf galaxies by increasing our
knowledge of the internal properties of isolated systems. We focus on the
evolved stellar component of the Aquarius dwarf, whose kinematic and
metallicity properties have only recently started to be explored. We have
obtained spectroscopic data in the the near-infrared CaII triplet lines region
with FORS2 at the Very Large Telescope for 53 red giant branch (RGB) stars, to
derive line-of-sight velocities and [Fe/H] of the individual RGB stars. We have
derived a systemic velocity of $-142.2^{+1.8}_{-1.8}$ km s$^{-1}$, in agreement
with previous measurements from both the HI gas and stars. The internal
kinematics of Aquarius appears to be best modelled by a combination of random
motions (l.o.s. velocity dispersion of $10.3^{+1.6}_{-1.3}$ km s$^{-1}$) and
linear rotation (with a gradient $-5.0^{+1.6}_{-1.9}$ km s$^{-1}$
arcmin$^{-1}$) along a P.A.=$139_{-27}^{+17}$ deg, consistent with the optical
projected major axis. This rotation signal is significantly misaligned or even
counter-rotating to that derived from the HI gas. We also find the tentative
presence of a mild negative metallicity gradient and indications that the
metal-rich stars have a colder velocity dispersion than the metal-poor ones.
This work represents a significant improvement with respect to previous
measurements of the RGB stars of Aquarius, as it doubles the number of member
stars studied in the literature. We speculate that the misaligned rotation
between the HI gas and evolved stellar component might have been the result of
recent accretion of HI gas or re-accretion after gas-loss due to internal
stellar feedback.