TY - JOUR
T1 - NIHAO XXIV
T2 - rotation- or pressure-supported systems? Simulated Ultra Diffuse Galaxies show a broad distribution in their stellar kinematics
AU - Cardona-Barrero, Salvador
AU - Di Cintio, Arianna
AU - Brook, Christopher B.A.
AU - Ruiz-Lara, Tomas
AU - Beasley, Michael A.
AU - Falcón-Barroso, Jesus
AU - Macciò, Andrea V.
N1 - Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2020/10/1
Y1 - 2020/10/1
N2 - In recent years, a new window on galaxy evolution opened, thanks to the increasing discovery of galaxies with a low-surface brightness, such as Ultra Diffuse Galaxies (UDGs). The formation mechanism of these systems is still a much debated question and so are their kinematical properties. In this work, we address this topic by analysing the stellar kinematics of isolated UDGs formed in the hydrodynamical simulation suite Numerical Investigation of a Hundred Astrophysical Objects (NIHAO). We construct projected line-of-sight velocity and velocity dispersion maps to compute the projected specific angular momentum, λR, to characterize the kinematical support of the stars in these galaxies. We found that UDGs cover a broad distribution, ranging from dispersion to rotation-supported galaxies, with similar abundances in both regimes. The degree of rotation support of simulated UDGs correlates with several properties such as galaxy morphology, higher H i fractions, and larger effective radii with respect to the dispersion-supported group, while the dark matter halo spin and mass accretion history are similar among the two populations. We demonstrate that the alignment of the infalling baryons into the protogalaxy at early z is the principal driver of the z = 0 stellar kinematic state: pressure-supported isolated UDGs form via misaligned gas accretion while rotation-supported ones build up their baryons in an ordered manner. Accounting for random inclination effects, we predict that a comprehensive survey will find nearly half of field UDGs to have rotationally supported stellar discs, when selecting UDGs with effective radius larger than 1 kpc.
AB - In recent years, a new window on galaxy evolution opened, thanks to the increasing discovery of galaxies with a low-surface brightness, such as Ultra Diffuse Galaxies (UDGs). The formation mechanism of these systems is still a much debated question and so are their kinematical properties. In this work, we address this topic by analysing the stellar kinematics of isolated UDGs formed in the hydrodynamical simulation suite Numerical Investigation of a Hundred Astrophysical Objects (NIHAO). We construct projected line-of-sight velocity and velocity dispersion maps to compute the projected specific angular momentum, λR, to characterize the kinematical support of the stars in these galaxies. We found that UDGs cover a broad distribution, ranging from dispersion to rotation-supported galaxies, with similar abundances in both regimes. The degree of rotation support of simulated UDGs correlates with several properties such as galaxy morphology, higher H i fractions, and larger effective radii with respect to the dispersion-supported group, while the dark matter halo spin and mass accretion history are similar among the two populations. We demonstrate that the alignment of the infalling baryons into the protogalaxy at early z is the principal driver of the z = 0 stellar kinematic state: pressure-supported isolated UDGs form via misaligned gas accretion while rotation-supported ones build up their baryons in an ordered manner. Accounting for random inclination effects, we predict that a comprehensive survey will find nearly half of field UDGs to have rotationally supported stellar discs, when selecting UDGs with effective radius larger than 1 kpc.
KW - galaxies: dwarf
KW - galaxies: evolution
KW - galaxies: formation
KW - galaxies: kinematics and dynamics
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U2 - 10.1093/mnras/staa2094
DO - 10.1093/mnras/staa2094
M3 - Article
AN - SCOPUS:85096964610
SN - 0035-8711
VL - 497
SP - 4282
EP - 4292
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -