The Pristine Inner Galaxy Survey (PIGS) I: Tracing the kinematics of metal-poor stars in the Galactic bulge. (arXiv:1910.06337v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Arentsen_A/0/1/0/all/0/1">Anke Arentsen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Starkenburg_E/0/1/0/all/0/1">Else Starkenburg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Martin_N/0/1/0/all/0/1">Nicolas F. Martin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hill_V/0/1/0/all/0/1">Vanessa Hill</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ibata_R/0/1/0/all/0/1">Rodrigo Ibata</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kunder_A/0/1/0/all/0/1">Andrea Kunder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schultheis_M/0/1/0/all/0/1">Mathias Schultheis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Venn_K/0/1/0/all/0/1">Kim A. Venn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zucker_D/0/1/0/all/0/1">Daniel B. Zucker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aguado_D/0/1/0/all/0/1">David Aguado</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Carlberg_R/0/1/0/all/0/1">Ray Carlberg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hernandez_J/0/1/0/all/0/1">Jonay I. González Hernández</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lardo_C/0/1/0/all/0/1">Carmela Lardo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Longeard_N/0/1/0/all/0/1">Nicolas Longeard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malhan_K/0/1/0/all/0/1">Khyati Malhan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Navarro_J/0/1/0/all/0/1">Julio F. Navarro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_Janssen_R/0/1/0/all/0/1">Ruben Sánchez-Janssen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sestito_F/0/1/0/all/0/1">Federico Sestito</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Thomas_G/0/1/0/all/0/1">Guillaume Thomas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Youakim_K/0/1/0/all/0/1">Kris Youakim</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lewis_G/0/1/0/all/0/1">Geraint F. Lewis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Simpson_J/0/1/0/all/0/1">Jeffrey D. Simpson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wan_Z/0/1/0/all/0/1">Zhen Wan</a>
Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the
importance of a classical, pressure-supported component within the central part
of the Milky Way is still being debated. It should be most visible at low
metallicity, a regime that has not yet been studied in detail. Using
metallicity-sensitive narrow-band photometry, the Pristine Inner Galaxy Survey
(PIGS) has collected a large sample of metal-poor ([Fe/H] < -1.0) stars in the
inner Galaxy to address this open question. We use PIGS to trace the metal-poor
inner Galaxy kinematics as function of metallicity for the first time. We find
that the rotational signal decreases with decreasing [Fe/H], until it becomes
negligible for the most metal-poor stars. Additionally, the velocity dispersion
increases with decreasing metallicity for -3.0 < [Fe/H] < -0.5, with a gradient
of -44 $pm$ 4 km$,$s$^{-1},$dex$^{-1}$. These observations may signal a
transition between Galactic components of different metallicities and
kinematics, a different mapping onto the boxy/peanut-shaped bulge for former
disk stars of different metallicities and/or the secular dynamical and
gravitational influence of the bar on the pressure-supported component. Our
results provide strong constraints on models that attempt to explain the
properties of the inner Galaxy.
Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the
importance of a classical, pressure-supported component within the central part
of the Milky Way is still being debated. It should be most visible at low
metallicity, a regime that has not yet been studied in detail. Using
metallicity-sensitive narrow-band photometry, the Pristine Inner Galaxy Survey
(PIGS) has collected a large sample of metal-poor ([Fe/H] < -1.0) stars in the
inner Galaxy to address this open question. We use PIGS to trace the metal-poor
inner Galaxy kinematics as function of metallicity for the first time. We find
that the rotational signal decreases with decreasing [Fe/H], until it becomes
negligible for the most metal-poor stars. Additionally, the velocity dispersion
increases with decreasing metallicity for -3.0 < [Fe/H] < -0.5, with a gradient
of -44 $pm$ 4 km$,$s$^{-1},$dex$^{-1}$. These observations may signal a
transition between Galactic components of different metallicities and
kinematics, a different mapping onto the boxy/peanut-shaped bulge for former
disk stars of different metallicities and/or the secular dynamical and
gravitational influence of the bar on the pressure-supported component. Our
results provide strong constraints on models that attempt to explain the
properties of the inner Galaxy.
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