The unusual box-shaped elliptical (?) galaxy IC 3370

Jarvis, B. J.

doi:10.1086/114444

Cited by 18 publications

(14 citation statements)

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“…Galaxy mergers probably create a minority of boxy bulges (Jarvis 1987). Also, Patsis et al (2002) illustrate a simulation that makes a boxy-bulgelike structure in the absence of a bar.…”

Section: Box-shaped Bulgesmentioning

confidence: 99%

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Kormendy¹,

Kennicutt

2004

Annu. Rev. Astron. Astrophys.

1,739

107

2,359

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The Universe is in transition. At early times, galactic evolution was dominated by hierarchical clustering and merging, processes that are violent and rapid. In the far future, evolution will mostly be secular: the slow rearrangement of energy and mass that results from interactions involving collective phenomena such as bars, oval disks, spiral structure, and triaxial dark halos. Both processes are important now. This paper reviews internal secular evolution, concentrating on one important consequence, the buildup of dense central components in disk galaxies that look like classical, merger-built bulges but that were made slowly out of disk gas. We call these pseudobulges.We begin with an "existence proof" -a review of how bars rearrange disk gas into outer rings, inner rings, and stuff dumped onto the center. Simulation results correspond closely to the morphology of barred galaxies. In the simulations, gas transported to small radii reaches high densities that plausibly feed star formation. In the observations, many SB and oval galaxies have dense central concentrations of gas and star formation. Optical colors and spectra often imply young stellar populations. So the formation of pseudobulges is well supported by theory and observations. It is embedded in a broader evolution picture that accounts for much of the richness observed in galaxy structure.If secular processes built dense central components that masquerade as bulges, how can we distinguish them from merger-built bulges? Observations show that pseudobulges retain a memory of their disky origin. 2That is, they have one or more characteristics of disks: (1) flatter shapes than those of classical bulges, (2) correspondingly large ratios of ordered to random velocities indicative of disk dynamics, (3) small velocity dispersions σ with respect to the Faber-Jackson correlation between σ and bulge luminosity, (4) spiral structure or nuclear bars in the "bulge" part of the light profile, (5) nearly exponential brightness profiles, and (6) starbursts. These structures occur preferentially in barred and oval galaxies in which secular evolution should be most rapid. So the cleanest examples of pseudobulges are recognizable.Are their formation timescales plausible? We use measurements of central gas densities and star formation rates to show that pseudobulges of the observed densities form on reasonable timescales of a few billion years.Thus a large variety of observational and theoretical results contribute to a new picture of galaxy evolution that complements hierarchical clustering and merging. Secular evolution consists of more than the aging of stellar populations. Every galaxy is dynamically evolving.

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“…Galaxy mergers probably create a minority of boxy bulges (Jarvis 1987). Also, Patsis et al (2002) illustrate a simulation that makes a boxy-bulgelike structure in the absence of a bar.…”

Section: Box-shaped Bulgesmentioning

confidence: 99%

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Kormendy¹,

Kennicutt

2004

Annu. Rev. Astron. Astrophys.

1,739

107

2,359

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“…Existing stellar kinematic studies of B/ PS bulges are limited to a few objects and have largely focused on the issue of cylindrical rotation, using slits offset from the major axis or perpendicular to it (e.g., Bertola & Capaccioli 1977;Kormendy & Illingworth 1982;Rowley 1986;Jarvis 1987;Shaw 1993a;Shaw, Wilkinson, & Carter 1993). As noted above, however, this is consistent with both axisymmetric and barred configurations, and so does not discriminate between the two dominant formation scenarios.…”

Section: Introductionmentioning

confidence: 99%

Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks

2004

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Long-slit stellar kinematic observations were obtained along the major axis of 30 edge-on spiral galaxies, 24 with a boxy or peanut-shaped (B/PS) bulge and six with other bulge types for comparison. Such B/ PS bulges are identified in at least 45% of highly inclined systems, and a growing body of theoretical and observational work suggests that they are the edge-on projection of thickened bars. Profiles of the mean stellar velocity V, the velocity dispersion , as well as the asymmetric (h 3 ) and symmetric (h 4 ) deviations from a pure Gaussian are presented for all objects. Comparing these profiles with stellar kinematic bar diagnostics developed from N-body simulations, we find bar signatures in 24 of our sample galaxies (80%). Galaxies with a B/ PS bulge typically show a double-humped rotation curve with an intermediate dip or plateau. They also frequently show a rather flat central velocity dispersion profile accompanied by a secondary peak or plateau, and numerous galaxies have a local central minimum (k40%). The h 3 profiles display up to three slope reversals. Most importantly, h 3 is normally correlated with V over the presumed bar length, contrary to expectations from axisymmetric disks. These characteristic bar signatures strengthen the case for a close relationship between B/ PS bulges and bars and leave little room for other explanations of the bulges' shape. We also find that h 3 is anticorrelated with V in the very center of most galaxies (k60%), indicating that these objects additionally harbor cold and dense decoupled (quasi-) axisymmetric central stellar disks, which may be related to the central light peaks. These central disks coincide with previously identified star-forming ionized-gas disks (nuclear spirals) in gas-rich systems, and we argue that they formed out of gas accumulated by the bar at its center through inflow. As suggested by N-body models, the asymmetry of the velocity profile (h 3 ) appears to be a reliable tracer of asymmetries in disks, allowing us to discriminate between axisymmetric and barred disks seen in projection. B/ PS bulges (and thus a large fraction of all bulges) appear to be made up mostly of disk material, which has acquired a large vertical extent through bar-driven vertical instabilities. Their formation is thus probably dominated by secular evolution processes rather than merging.

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“…The kinematic signature of a bar in the observations is very evident. erences of cylindrical rotation in other galaxies are rather scarce in the literature: IC 3370 (Jarvis, 1987), NGC 1055 (Shaw, 1993), NGC 3079 (Shaw et al, 1993), NGC 5266 (Varnas et al, 1987), NGC 7332 (Fisher et al, 1994). This lack of cases is likely due to: (1) inclinations effects.…”

Section: Relating Bars and Bulgesmentioning

confidence: 99%

The Stellar Kinematics of Extragalactic Bulges

Falcón-Barroso

2016

Astrophysics and Space Science Library

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Galactic bulges are complex systems. Once thought to be small-scale versions of elliptical galaxies, advances in astronomical instrumentation (spectroscopy in particular) has revealed a wealth of photometric and kinematic substructure in otherwise simple-looking components. This review provides an overview of how our perspective on galactic bulges has changed over the years. While it is mainly focused on aspects related to the dynamical state of their stars, there will be natural connections to other properties (e.g. morphology, stellar populations) discussed in other reviews in this volume.

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The unusual box-shaped elliptical (?) galaxy IC 3370

Cited by 18 publications

References 0 publications

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Stellar Kinematics of Boxy Bulges: Large-Scale Bars and Inner Disks

The Stellar Kinematics of Extragalactic Bulges

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