Revealing the cosmic evolution of boxy/peanut-shaped bulges from HST COSMOS and SDSS

Kruk, Sandor; Erwin, Peter; Debattista, Victor P.; Lintott, Chris

doi:10.1093/mnras/stz2877

Cited by 40 publications

(39 citation statements)

References 88 publications

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“…Still, we should expect such shapes to be weaker in galaxies with higher gas fractions. The results presented here are also consistent with the recent finding of Kruk et al (2019) who studied the fraction of galaxies with a boxy/peanut bulge as a function of redshift using data from the Hubble Space Telescope Cosmic Evolution Survey and the Sloan Digital Sky Survey. They find this fraction to strongly decrease with redshift down to zero at a redshift of z = 1.…”

Section: Discussionsupporting

confidence: 91%

The effect of warm gas on the buckling instability in galactic bars

Łokas

2020

A&A

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By using N-body and hydro simulations, we study the formation and evolution of bars in galaxies with significant gas content focusing on the phenomenon of the buckling instability. The galaxies are initially composed of a spherical dark matter halo and only stellar, or stellar and gaseous, disks with parameters that are similar to the Milky Way and are evolved for 10 Gyr. We consider different values of the gas fraction f = 0 − 0.3 and in order to isolate the effect of the gas, we kept the fraction constant during the evolution by not allowing the gas to cool and form stars. The stellar bars that form in simulations with higher gas fractions are weaker and shorter, and they do not form at all for gas fractions that are higher than 0.3. The bar with a gas fraction of 0.1 forms sooner due to initial perturbations in the gas, but despite the longer evolution, it does not become stronger than the one in the collisionless case at the end of evolution. The bars in the gas component are weaker; they reach their maximum strength around 4 Gyr and later decline to transform into spheroidal shapes. The distortion of the stellar bar during the buckling instability is weaker for higher gas fractions and weakens the bar less significantly, but it has a similar structure both in terms of radial profiles and in face-on projections. For f = 0.2, the first buckling lasts significantly longer and the bar does not undergo the secondary buckling event, while for f = 0.3, the buckling does not occur. Despite these differences, all bars develop boxy/peanut shapes in the stellar and gas component by the end of the evolution, although their thickness is smaller for higher gas fractions.

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Section: Discussionsupporting

confidence: 91%

The effect of warm gas on the buckling instability in galactic bars

Łokas

2020

A&A

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“…those with characteristic stellar mass log (M /M ) 10.4) barred galaxies, a fraction which declines rapidly at lower masses . This characteristic mass appears to have remained unchanged since redshift z ∼ 1 (Kruk et al 2019).…”

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confidence: 87%

Predicted trends in Milky Way bulge proper motion rotation curves: future prospects for HST and LSST

Gough-Kelly

Debattista

Clarkson

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We use an N-body+smoothed particle hydrodynamics simulation of an isolated barred galaxy to study the age dependence of bulge longitudinal proper motion (μl) rotation curves. We show that close to the minor axis (|l| ∼ 0○) the relatively young stars rotate more rapidly than the old stars, as found by Hubble Space Telescope in the Milky Way’s bulge. This behaviour would be expected also if the Milky Way were unbarred. At larger |l| a different behaviour emerges. Because younger stars trace a strong bar, their Galactocentric radial motions dominate their μl at |l| ∼ 6○, leading to a reversal in the sign of $\left<{{\mu _l}}\right>$. This results in a rotation curve with forbidden velocities (negative $\left<{{\mu _l}}\right>$ at positive longitudes, and positive $\left<{{\mu _l}}\right>$ at negative longitudes). The old stars, instead, trace a much weaker bar and thus their kinematics are more axisymmetric, resulting in no forbidden velocities. We develop metrics of the difference in the $\left<{{\mu _l}}\right>$ rotation curves of young and old stars, and forbidden velocities. We use these to predict the locations where rotation curve reversals can be observed by HST and the Vera Rubin Telescope. Such measurements would represent support for the amplitude of the bar being a continuous function of age, as predicted by kinematic fractionation, in which the bar strength variations are produced purely by differences in the random motions of stellar populations at bar formation.

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“…Complicating this simple picture is the observation that the fraction of barred galaxies that host B/P bulges rises rapidly at log(M * / M ) 10.4, with no evidence that the (present day) gas fraction matters . Even more puzzling, this transitional mass appears unchanged since redshift z 1 (Kruk et al 2019). Clearly there is still much to learn about B/P bulge formation and more detailed study of stellar populations in the MW, and in external galaxies, may provide clues to a better understanding.…”

Section: A Statistical Mechanical Viewmentioning

confidence: 99%

Box/peanut-shaped bulges in action space

Debattista

Liddicott

Khachaturyants

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We introduce the study of box/peanut (B/P) bulges in the action space of the initial axisymmetric system. We explore where populations with different actions end up once a bar forms and a B/P bulge develops. We find that the density bimodality due to the B/P bulge (the X-shape) is better traced by populations with low radial, $\rm J_{R,0}$, or vertical, $\rm J_{z,0}$, actions, or high azimuthal action, $\rm J_{\phi ,0}$. Generally populations separated by $\rm J_{R,0}$ have a greater variation in bar strength and vertical heating than those separated by $\rm J_{z,0}$. While the bar substantially weakens the initial vertical gradient of $\rm J_{z,0}$, it also drives a strikingly monotonic vertical profile of $\rm J_{R,0}$. We then use these results to guide us in assigning metallicity to star particles in a pure N-body model. Because stellar metallicity in unbarred galaxies depends on age as well as radial and vertical positions, the initial actions are particularly well suited for assigning metallicities. We argue that assigning metallicities based on single actions, or on positions, results in metallicity distributions inconsistent with those observed in real galaxies. We therefore use all three actions to assign metallicity to an N-body model by comparing with the actions of a star-forming, unbarred simulation. The resulting metallicity distribution is pinched on the vertical axis, has a realistic vertical gradient and has a stronger X-shape in metal-rich populations, as found in real galaxies.

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Revealing the cosmic evolution of boxy/peanut-shaped bulges from HST COSMOS and SDSS

Cited by 40 publications

References 88 publications

The effect of warm gas on the buckling instability in galactic bars

The effect of warm gas on the buckling instability in galactic bars

Predicted trends in Milky Way bulge proper motion rotation curves: future prospects for HST and LSST

Box/peanut-shaped bulges in action space

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