36 research outputs found
Interacting galaxies on FIRE-2: The connection between enhanced star formation and interstellar gas content
We present a comprehensive suite of high-resolution (parsec-scale), idealised
(non-cosmological) galaxy merger simulations (24 runs, stellar mass ratio
~2.5:1) to investigate the connection between interaction-induced star
formation and the evolution of the interstellar medium (ISM) in various
temperature-density regimes. We use the GIZMO code and the second version of
the 'Feedback in Realistic Environments' model (FIRE-2), which captures the
multi-phase structure of the ISM. Our simulations are designed to represent
galaxy mergers in the local Universe. In this work, we focus on the
'galaxy-pair period' between first and second pericentric passage. We split the
ISM into four regimes: hot, warm, cool and cold-dense, motivated by the hot,
ionised, atomic and molecular gas phases observed in real galaxies. We find
that, on average, interactions enhance the star formation rate of the pair
(~30%, merger-suite sample average) and elevate their cold-dense gas content
(~18%). This is accompanied by a decrease in warm gas (~11%), a negligible
change in cool gas (~4% increase), and a substantial increase in hot gas
(~400%). The amount of cold-dense gas with densities above 1000 cm^3 (the cold
ultra-dense regime) is elevated significantly (~240%), but only accounts for
0.15% (on average) of the cold-dense gas budget.Comment: 21 pages, 17 figures, accepted by MNRA
Interacting galaxies on FIRE-2: the connection between enhanced star formation and interstellar gas content
We present a comprehensive suite of high-resolution (parsec-scale), idealized (non-cosmological) galaxy merger simulations (24 runs, stellar mass ratio âŒ2.5:1) to investigate the connection between interaction-induced star formation and the evolution of the interstellar medium (ISM) in various temperatureâdensity regimes. We use the GIZMO code and the second version of the âFeedback in Realistic Environmentsâ model (FIRE-2), which captures the multiphase structure of the ISM. Our simulations are designed to represent galaxy mergers in the local Universe. In this work, we focus on the âgalaxy-pair periodâ between first and second pericentric passage. We split the ISM into four regimes: hot, warm, cool, and cold-dense, motivated by the hot, ionized, atomic and molecular gas phases observed in real galaxies. We find that, on average, interactions enhance the star formation rate of the pair (â âŒ30 per cent, merger-suite sample average) and elevate their cold-dense gas content (â âŒ18 per centâ ). This is accompanied by a decrease in warm gas (â âŒ11 per cent), a negligible change in cool gas (â âŒ4 per cent increase), and a substantial increase in hot gas (â âŒ400 per centâ ). The amount of cold-dense gas with densities above 1000 cm^(â3) (the cold ultra-dense regime) is elevated significantly (â âŒ240 per centâ ), but only accounts for âŒ0.15 per cent (on average) of the cold-dense gas budget
Different higher order kinematics between star-forming and quiescent galaxies based on the SAMI, MAGPI, and LEGA-C surveys
We present the first statistical study of spatially integrated non-Gaussian stellar kinematics spanning 7 Gyr in cosmic time. We use deep, rest-frame optical spectroscopy of massive galaxies (stellar mass â ) at redshifts z = 0.05, 0.3, and 0.8 from the SAMI, MAGPI, and LEGA-C surveys, to measure the excess kurtosis h4 of the stellar velocity distribution, the latter parametrized as a GaussâHermite series. We find that at all redshifts where we have large enough samples, h4 anticorrelates with the ratio between rotation and dispersion, highlighting the physical connection between these two kinematic observables. In addition, and independently from the anticorrelation with rotation-to-dispersion ratio, we also find a correlation between h4 and Mâ, potentially connected to the assembly history of galaxies. In contrast, after controlling for mass, we find no evidence of independent correlation between h4 and aperture velocity dispersion or galaxy size. These results hold for both star-forming and quiescent galaxies. For quiescent galaxies, h4 also correlates with projected shape, even after controlling for the rotation-to-dispersion ratio. At any given redshift, star-forming galaxies have lower h4 compared to quiescent galaxies, highlighting the link between kinematic structure and star-forming activity
Evolution in the orbital structure of quiescent galaxies from MAGPI, LEGA-C, and SAMI surveys: direct evidence for merger-driven growth over the last 7 Gyr
We present the first study of spatially integrated higher-order stellar kinematics over cosmic time. We use deep rest-frame optical spectroscopy of quiescent galaxies at redshifts z = 0.05, 0.3, and 0.8 from the SAMI, MAGPI, and LEGA-C surveys to measure the excess kurtosis h4 of the stellar velocity distribution, the latter parametrized as a Gauss-Hermite series. Conservatively using a redshift-independent cut in stellar mass (â â ) and matching the stellar-mass distributions of our samples, we find 7Ï evidence of h4 increasing with cosmic time, from a median value of 0.019 ± 0.002 at z = 0.8 to 0.059 ± 0.004 at z = 0.06. Alternatively, we use a physically motivated sample selection based on the mass distribution of the progenitors of local quiescent galaxies as inferred from numerical simulations; in this case, we find 10Ï evidence. This evolution suggests that, over the last 7 Gyr, there has been a gradual decrease in the rotation-to-dispersion ratio and an increase in the radial anisotropy of the stellar velocity distribution, qualitatively consistent with accretion of gas-poor satellites. These findings demonstrate that massive galaxies continue to accrete mass and increase their dispersion support after becoming quiescent