A SAURON look at galaxy bulges

Falcón-Barroso, J.; Bacon, Roland; Bureau, Martin; Cappellari, Michele; Davies, Roger L.; Emsellem, Éric; Krajnović, Davor; Küntschner, H.; McDermid, Richard M.; Peletier, Reynier F.; Zeeuw, P. T. de

doi:10.1002/asna.200310182

Cited by 8 publications

(5 citation statements)

References 35 publications

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“…A link between n-body bars and boxy bulges is the observation in both of cylindrical rotation to substantial heights above the equatorial plane (see Bertola & Capaccioli 1977;Kormendy & Illingworth 1982;Jarvis 1990;Shaw, Wilkinson, & Carter 1993a;Shaw 1993a;Bettoni & Galletta 1994;Fisher, Illingworth, & Franx 1994;D'Onofrio et al 1999;and Falcón-Barroso et al 2004 for the observations and Combes et al 1990;Sellwood 1993a;Athanassoula & Misiriotis 2002 for simulations). Classical bulges and ellipticals do not rotate cylindrically, as evident from early long-slit spectroscopy (Illingworth & Schechter 1982;Kormendy & Illingworth 1982;Binney, Davies, & Illingworth 1990) and now beautifully shown by integralfield spectroscopy (de Zeeuw et al 2002;Verolme et al 2002Copin, Cretton, & Emsellem 2004;Falcón-Barroso et al 2004;Krajnović et al 2004). Kuijken & Merrifield (1995) and Merrifield (1996) suggest that a kinematic signature of edge-on bars is a splitting in the gas velocities just interior to corotation because the gas there is depleted by radial transport.…”

Section: Box-shaped Bulgesmentioning

confidence: 98%

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Kormendy¹,

Kennicutt

2004

Annu. Rev. Astron. Astrophys.

1,764

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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Section: Box-shaped Bulgesmentioning

confidence: 98%

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Kormendy¹,

Kennicutt

2004

Annu. Rev. Astron. Astrophys.

1,764

107

2,359

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“…Boxy bulges present a characteristic cylindrical rotation, namely, a nearly constant stellar rotation speed with height above the Galactic plane. Classical bulges rotate more slowly at increasing height (Falcón-Barroso et al 2004). After studies of various probes (K giants, globular clusters, planetary nebulae), the first and recent large data set of systematically collected radial velocities in the Galactic bulge was assembled by the BRAVA project (Rich et al 2007b), and showed indistinguishable rotation curves in strips at b = −4 • , b = −6 • , and b = −8 • (l ± 10).…”

Section: Introductionmentioning

confidence: 99%

TheGaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge

Rojas-Arriagada

Recio–Blanco

Hill

et al. 2014

A&A

145

186

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Aims. Observational studies of the Milky Way bulge are providing increasing evidence of its complex chemo-dynamical patterns and morphology. Our intent is to use the iDR1 Gaia-ESO Survey (GES) data set to provide new constraints on the metallicity and kinematic trends of the Galactic bulge, exploring the viability of the currently proposed formation scenarios. Methods. We analyzed the stellar parameters and radial velocities of ∼1200 stars in five bulge fields wich are located in the region −10 • < l < 7 • and −10 • < b < −4 • . We use VISTA Variables in the Via Lactea (VVV) photometry to verify the internal consistency of the atmospheric parameters recommended by the consortium. As a by-product, we obtained reddening values using a semi-empirical T eff -color calibration. We constructed the metallicity distribution functions and combined them with photometric and radial velocity data to analyze the properties of the stellar populations in the observed fields. Results. From a Gaussian decomposition of the metallicity distribution functions, we unveil a clear bimodality in all fields, with the relative size of components depending of the specific position on the sky. In agreement with some previous studies, we find a mild gradient along the minor axis (−0.05 dex/deg between b = −6 • and b = −10 • ) that arises from the varying proportion of metal-rich and metal-poor components. The number of metal-rich stars fades in favor of the metal-poor stars with increasing b. The K-magnitude distribution of the metal-rich population splits into two peaks for two of the analyzed fields that intersects the near and far branches of the X-shaped bulge structure. In addition, two lateral fields at (l, b) = (7, −9) and (l, b) = (−10, −8) present contrasting characteristics. In the former, the metallicity distribution is dominated by metal-rich stars, while in the latter it presents a mix of a metal-poor population and and a metal-intermediate one, of nearly equal sizes. Finally, we find systematic differences in the velocity dispersion between the metal-rich and the metal-poor components of each field. Conclusions. The iDR1 bulge data show chemo-dynamical distributions that are consistent with varying proportions of stars belonging to (i) a metal-rich boxy/peanut X-shaped component, with bar-like kinematics; and (ii) a metal-poor more extended rotating structure with a higher velocity dispersion that dominates far from the Galactic plane. These first GES data already allow studying the detailed spatial dependence of the Galactic bulge populations, thanks to the analysis of individual fields with relatively high statistics.

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“…Further tests of whether the Galaxy's boxy bulge really is a edge-on bar would therefore be valuable. Classical bulges are observed to rotate more slowly at increasing height above the disk plane, whereas boxy bulges in other galaxies rotate cylindrically, with V (r) essentially independent of height above the disk plane (e. g., Kormendy & Illingworth 1982;Jarvis 1990;Shaw 1993;Falcón-Barroso et al 2004; see Kormendy & Kennicutt 2004 for a review). Supporting the above interpretation, Nbody models of bars also rotate cylindrically when viewed edge-on (Combes et al 1990;Fux 1997Fux , 1999Zhao et al 1996;Athanassoula & Misiriotis 2002;Athanassoula 2005).…”

Section: Introductionmentioning

confidence: 99%

Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation

Howard

Rich

Clarkson

et al. 2009

ApJ

119

126

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We present new results from BRAVA, a large-scale radial velocity survey of the Galactic bulge, using M giant stars selected from the Two Micron All Sky Survey catalog as targets for the Cerro Tololo Inter-American Observatory 4m Hydra multi-object spectrograph. The purpose of this survey is to construct a new generation of self-consistent bar models that conform to these observations. We report the dynamics for fields at the edge of the Galactic bulge at latitudes b = −8 • and compare to the dynamics at b = −4 • . We find that the rotation curve V(r) is the same at b = −8 • as at b = −4 • . That is, the Galactic boxy bulge rotates cylindrically, as do boxy bulges of other galaxies. The summed line of sight velocity distribution at b = −8 • is Gaussian, and the binned longitude-velocity plot shows no evidence for either a (disk) population with cold dynamics or for a (classical bulge) population with hot dynamics. The observed kinematics are well modeled by an edge-on N-body bar, in agreement with published structural evidence. Our kinematic observations indicate that the Galactic bulge is a prototypical product of secular evolution in galaxy disks, in contrast with stellar population results that are most easily understood if major mergers were the dominant formation process.

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A SAURON look at galaxy bulges

Cited by 8 publications

References 35 publications

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

Secular Evolution and the Formation of Pseudobulges in Disk Galaxies

TheGaia-ESO Survey: metallicity and kinematic trends in the Milky Way bulge

Kinematics at the Edge of the Galactic Bulge: Evidence for Cylindrical Rotation

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