Dark and Luminous Matter Connections from Smoothed Particle Hydrodynamic Simulations of Isolated Triaxial Collapsing Systems

Murante³

2008

A&A

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Context. This is the third in a series of papers presenting the first attempt to analyse the growth of the bar instability in a consistent cosmological scenario. In the previous two articles, we explored the role of the cosmology on stellar disks and the impact of the gaseous component on a disk embedded in a cosmological dark matter halo. Aims. The aim of this paper is to point out the impact of the star formation on the bar instability inside disks having different gas fractions. Methods. We performed cosmological simulations of the same disk-to-halo mass systems as in the previous works where the star formation was not triggered. We compared the results of the new simulations with the previous ones to investigate the effect of the star formation by analysing the morphology of the stellar components, the bar strength, the behaviour of the pattern speed. We followed the gas and the central mass concentration during the evolution and their impact on the bar strength. Results. A stellar bar, lasting 10 Gyr, is still living at z = 0 in all our cosmological simulations. The central mass concentration of gas and of the new stars has a mild effect on the ellipticity of the bar but is not able to destroy it, and at z = 0 the stellar bar strength is enhanced by the star formation. The bar pattern speed decreases with the disk evolution.

Section: Introductionmentioning

confidence: 99%

Star formation and bar instability in cosmological halos

Curir¹,

Murante³

2008

A&A

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“…Robertson et al (2004) claim to have overcome most problems, however the bar Appendix is only available in electronic form at http://www.edpsciences.org instability has not yet been analysed in a cosmological framework. Furthermore, the high CPU cost of such simulations does not yet allow us to explore the role of several parameters related to the phenomenological treatment of the star formation rate and feedback, and the morphologies of the generated galaxies (Mazzei & Curir 2003;Mazzei 2003).…”

Section: Introductionmentioning

confidence: 99%

Bar instability in cosmological halos

Curir¹,

Murante³

2006

A&A

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Aims. We investigate the growth of bar instability in stellar disks embedded in a dark matter halo evolving in a fully consistent cosmological framework. Methods. We perform seven cosmological simulations to emphasise the role of both the disk-to-halo mass ratio and of the Toomre parameter, Q, on the evolution of the disk.We also compare our fully cosmological cases with corresponding isolated simulations where the same halo is extracted from the cosmological scenario and evolved in physical coordinates. Results. A long living bar, lasting about 10 Gyr, appears in all our simulations. In particular, disks expected to be stable according to classical criteria form weak bars. We argue that such a result is due to the dynamical properties of our cosmological halo which is far from stability and isotropy, typical of the classical halos used in the literature; it is dynamically active, has substructures and undergoes infall. Conclusions. At least for mild self-gravitating disks, the study of the bar instability using isolated isotropic halos in gravitational equilibrium can lead to misleading results. Furthermore, the cosmological framework is needed to quantitatively investigate such an instability.

“…Two halos of initial equal masses, each of 10 11 M , are still approaching. The interaction modifies the halo potentials so that the evolution of each system differs from the same in the isolated case (Mazzei & Curir 2003), and induces the galaxy distortion we observe.…”

Section: Discussionmentioning

confidence: 87%

“…We point out that the resulting SFR, the driver of the evolution of the global properties of the simulated galaxies, converges when the initial particle number is about 10 4 (Figure 1 of Mazzei & Curir 2003;Christensen et al 2010Christensen et al , 2012.…”

Section: Comparison With Simulationsmentioning

confidence: 81%

Galaxy evolution in groups

Marino

Rampazzo

et al. 2018

A&A

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Context. Local Group Analogs are galaxy associations dominated by few bright Spirals reminiscent of the Local Group. The NGC 3447/NGC 3447A system is a member of the LGG 225 group, a nearby Local Group Analog. This system is considered a physical pair composed of an intermediate luminosity late type spiral, NGC 3447 itself, and an irregular companion, NGC 3447A, linked by a faint, short filament of matter. A ring-like structure in the NGC 3447 outskirts has been emphasised by GALEX observations. Aims. This work aims to contribute to the study of galaxy evolution in low density environments, favourable habitat to highly effective encounters, shedding light on the evolution of this system. Methods. We performed a multi-λ analysis of the surface photometry of this system to derive its spectral energy distribution and structural properties using UV, Swift-UVOT, and optical, SDSS images complemented with available far-IR observations. We also characterised the velocity field of the pair using 2D Hα kinematical observations of the system obtained with PUMA@2.2mSPM. All these data are used to constrain smooth particle hydrodynamic simulations with chemo-photometric implementation to shed light on the evolution of this system. Results. The luminosity profiles, from UV to optical wavelengths, are all consistent with the presence of a disc extending and including NGC 3447A. The overall velocity field does not emphasise any significant rotation pattern, rather a small velocity gradient between NGC 3447 and NGC 3447A. Our simulation, detached from a large grid explored to best-fit the global properties of the system, suggests that this arises from an encounter between two halos of equal mass. Conclusions. NGC 3447 and NGC 3447A belong to the same halo, NGC 3447A being a substructure of the same disk including NGC 3447. The halo gravitational instability, enhanced by the encounter, fuels a long lived instability in this dark matter dominated disk, driving the observed morphology. The NGC 3447/NGC 3447A system may warn about a new class of "false pairs" and the potential danger of a misunderstanding of such objects in pair surveys that could produce a severe underestimate of the total mass of the system.