Secular Evolution and the Formation of Pseudobulges in Disk Galaxies
17 Aug 2004-Annual Review of Astronomy and Astrophysics (Annual Reviews)-Vol. 42, Iss: 1, pp 603-683
TL;DR: 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 as mentioned in this paper.
Abstract: ▪ Abstract 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 review discusses 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. The results of numerical simulations correspond closely to the morphology of barred galaxies. In the simulations, gas is transported to small radii, where it reaches high densities and...
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TL;DR: In this paper, supermassive black holes (BHs) have been found in 85 galaxies by dynamical modeling of spatially resolved kinematics, and it has been shown that BHs and bulges coevolve by regulating each other's growth.
Abstract: Supermassive black holes (BHs) have been found in 85 galaxies by dynamical modeling of spatially resolved kinematics. The Hubble Space Telescope revolutionized BH research by advancing the subject from its proof-of-concept phase into quantitative studies of BH demographics. Most influential was the discovery of a tight correlation between BH mass and the velocity dispersion σ of the bulge component of the host galaxy. Together with similar correlations with bulge luminosity and mass, this led to the widespread belief that BHs and bulges coevolve by regulating each other's growth. Conclusions based on one set of correlations from in brightest cluster ellipticals to in the smallest galaxies dominated BH work for more than a decade. New results are now replacing this simple story with a richer and more plausible picture in which BHs correlate differently with different galaxy components. A reasonable aim is to use this progress to refine our understanding of BH-galaxy coevolution. BHs with masses of 105−106M...
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TL;DR: In this paper, the authors review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies.
Abstract: We review progress over the past decade in observations of large-scale star formation, with a focus on the interface between extragalactic and Galactic studies. Methods of measuring gas contents and star-formation rates are discussed, and updated prescriptions for calculating star-formation rates are provided. We review relations between star formation and gas on scales ranging from entire galaxies to individual molecular clouds.
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TL;DR: Kormendy and Ho as mentioned in this paper proposed a method to estimate the BH masses for galaxies with active nuclei (AGNs) based on the observational criteria that are used to classify classical and pseudo bulges.
Abstract: This is the Supplemental Material to Kormendy and Ho 2013, ARAA, 51, 511 (arXiv:1304.7762). Section S1 summarizes indirect methods that are used to estimate black hole (BH) masses for galaxies with active nuclei (AGNs). Section S2 lists the observational criteria that are used to classify classical and pseudo bulges. The (pseudo)bulge classifications used in the main paper are not based on physical interpretation; rather, they are based on these observational criteria. Section S3 supplements the BH database in Section 5 of the main paper and Section S4 here. It discusses corrections to galaxy and BH parameters, most importantly to 2MASS K-band apparent magnitudes. It presents evidence that corrections are needed because 2MASS misses light at large radii when the images of galaxies subtend large angles on the sky or have shallow outer brightness gradients. Section S4 reproduces essentially verbatim the first part of Section 5 in the main paper, the BH database. It includes the list of BH and host-galaxy properties (Tables 2 and 3). Its most important purpose is to provide all of the notes on individual objects.
1,774 citations
University of Michigan1, University of Texas at Austin2, ETH Zurich3, Ludwig Maximilian University of Munich4, Carnegie Institution for Science5, University of California, Santa Cruz6, University of California, Berkeley7, University of Arizona8, Durham University9, Ohio Northern University10, Université libre de Bruxelles11
TL;DR: In this article, improved versions of the relations between supermassive black hole mass (M BH) and host-galaxy bulge velocity dispersion (σ) and luminosity (L; the M-σ and M-L relations), based on 49 M BH measurements and 19 upper limits, were derived.
Abstract: We derive improved versions of the relations between supermassive black hole mass (M BH) and host-galaxy bulge velocity dispersion (σ) and luminosity (L; the M-σ and M-L relations), based on 49 M BH measurements and 19 upper limits. Particular attention is paid to recovery of the intrinsic scatter (e0) in both relations. We find log(M BH/M) = α + βlog(σ/200 km s-1) with (α, β, e0) = (8.12 0.08, 4.24 0.41, 0.44 0.06) for all galaxies and (α, β, e0) = (8.23 0.08, 3.96 0.42, 0.31 0.06) for ellipticals. The results for ellipticals are consistent with previous studies, but the intrinsic scatter recovered for spirals is significantly larger. The scatter inferred reinforces the need for its consideration when calculating local black hole mass function based on the M-σ relation, and further implies that there may be substantial selection bias in studies of the evolution of the M-σ relation. We estimate the M-L relationship as log(M BH/M) = α + βlog(LV /1011 L V) of (α, β, e0) = (8.95 0.11, 1.11 0.18, 0.38 0.09); using only early-type galaxies. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We show that culling the sample according to the resolution of the black hole's sphere of influence biases the relations to larger mean masses, larger slopes, and incorrect intrinsic residuals. © 2009. The American Astronomical Society.
1,528 citations
University of Michigan1, University of Texas at Austin2, ETH Zurich3, Ludwig Maximilian University of Munich4, Carnegie Institution for Science5, University of California, Santa Cruz6, University of California, Berkeley7, University of Arizona8, Durham University9, Ohio Northern University10, Université libre de Bruxelles11
TL;DR: This article derived improved versions of the relations between supermassive black hole mass and host-galaxy bulge velocity dispersion (sigma) and luminosity (L) (the M-sigma and M-L relations), based on 49 M_BH measurements and 19 upper limits.
Abstract: We derive improved versions of the relations between supermassive black hole mass (M_BH) and host-galaxy bulge velocity dispersion (sigma) and luminosity (L) (the M-sigma and M-L relations), based on 49 M_BH measurements and 19 upper limits. Particular attention is paid to recovery of the intrinsic scatter (epsilon_0) in both relations. We find log(M_BH / M_sun) = alpha + beta * log(sigma / 200 km/s) with (alpha, beta, epsilon_0) = (8.12 +/- 0.08, 4.24 +/- 0.41, 0.44 +/- 0.06) for all galaxies and (alpha, beta, epsilon_0) = (8.23 +/- 0.08, 3.96 +/- 0.42, 0.31 +/- 0.06) for ellipticals. The results for ellipticals are consistent with previous studies, but the intrinsic scatter recovered for spirals is significantly larger. The scatter inferred reinforces the need for its consideration when calculating local black hole mass function based on the M-sigma relation, and further implies that there may be substantial selection bias in studies of the evolution of the M-sigma relation. We estimate the M-L relationship as log(M_BH / M_sun) = alpha + beta * log(L_V / 10^11 L_sun,V) of (alpha, beta, epsilon_0) = (8.95 +/- 0.11, 1.11 +/- 0.18, 0.38 +/- 0.09); using only early-type galaxies. These results appear to be insensitive to a wide range of assumptions about the measurement errors and the distribution of intrinsic scatter. We show that culling the sample according to the resolution of the black hole's sphere of influence biases the relations to larger mean masses, larger slopes, and incorrect intrinsic residuals.
1,522 citations
Cites methods from "Secular Evolution and the Formation..."
...Our fits only use BH masses from elliptical galaxies or from galaxies with classical bulges or pseudobulges (Kormendy & Kennicutt 2004)....
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References
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TL;DR: In this article, the authors used high-resolution N-body simulations to study the equilibrium density profiles of dark matter halos in hierarchically clustering universes, and they found that all such profiles have the same shape, independent of the halo mass, the initial density fluctuation spectrum, and the values of the cosmological parameters.
Abstract: We use high-resolution N-body simulations to study the equilibrium density profiles of dark matter halos in hierarchically clustering universes. We find that all such profiles have the same shape, independent of the halo mass, the initial density fluctuation spectrum, and the values of the cosmological parameters. Spherically averaged equilibrium profiles are well fitted over two decades in radius by a simple formula originally proposed to describe the structure of galaxy clusters in a cold dark matter universe. In any particular cosmology, the two scale parameters of the fit, the halo mass and its characteristic density, are strongly correlated. Low-mass halos are significantly denser than more massive systems, a correlation that reflects the higher collapse redshift of small halos. The characteristic density of an equilibrium halo is proportional to the density of the universe at the time it was assembled. A suitable definition of this assembly time allows the same proportionality constant to be used for all the cosmologies that we have tested. We compare our results with previous work on halo density profiles and show that there is good agreement. We also provide a step-by-step analytic procedure, based on the Press-Schechter formalism, that allows accurate equilibrium profiles to be calculated as a function of mass in any hierarchical model.
9,729 citations
TL;DR: In this article, high-resolution N-body simulations show that the density profiles of dark matter halos formed in the standard CDM cosmogony can be fit accurately by scaling a simple universal profile.
Abstract: High resolution N-body simulations show that the density profiles of dark matter halos formed in the standard CDM cosmogony can be fit accurately by scaling a simple “universal” profile. Regardless of their mass, halos are nearly isothermal over a large range in radius, but significantly shallower than r -2 near the center and steeper than r -2 in the outer regions. The characteristic overdensity of a halo correlates strongly with halo mass in a manner consistent with the mass dependence of the epoch of halo formation. Matching the shape of the rotation curves of disk galaxies with this halo structure requires (i) disk mass-to-light ratios to increase systematically with luminosity, (ii) halo circular velocities to be systematically lower than the disk rotation speed, and (iii) that the masses of halos surrounding bright galaxies depend only weakly on galaxy luminosity. This offers an attractive explanation for the puzzling lack of correlation between luminosity and dynamics in observed samples of binary galaxies and of satellite companions of bright spiral galaxies, suggesting that the structure of dark matter halos surrounding bright spirals is similar to that of cold dark matter halos.
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TL;DR: In this article, the authors focus on the broad patterns in the star formation properties of galaxies along the Hubble sequence and their implications for understanding galaxy evolution and the physical processes that drive the evolution.
Abstract: Observations of star formation rates (SFRs) in galaxies provide vital clues to the physical nature of the Hubble sequence and are key probes of the evolutionary histories of galaxies. The focus of this review is on the broad patterns in the star formation properties of galaxies along the Hubble sequence and their implications for understanding galaxy evolution and the physical processes that drive the evolution. Star formation in the disks and nuclear regions of galaxies are reviewed separately, then discussed within a common interpretive framework. The diagnostic methods used to measure SFRs are also reviewed, and a self-consistent set of SFR calibrations is presented as an aid to workers in the field. One of the most recognizable features of galaxies along the Hubble sequence is the wide range in young stellar content and star formation activity. This variation in stellar content is part of the basis of the Hubble classification itself (Hubble 1926), and understanding its physical nature and origins is fundamental to understanding galaxy evolution in its broader context. This review deals with the global star formation properties of galaxies, the systematics of those properties along the Hubble sequence, and their implications for galactic evolution. I interpret “Hubble sequence” in this context very loosely, to encompass not only morphological type but other properties such as gas content, mass, bar structure, and dynamical environment, which can strongly influence the largescale star formation rate (SFR).
6,640 citations
TL;DR: In this paper, the Schmidt law was used to model the global star formation law over the full range of gas densities and star formation rates observed in galaxies, and the results showed that the SFR scales with the ratio of the gas density to the average orbital timescale.
Abstract: Measurements of Hα, H I, and CO distributions in 61 normal spiral galaxies are combined with published far-infrared and CO observations of 36 infrared-selected starburst galaxies, in order to study the form of the global star formation law over the full range of gas densities and star formation rates (SFRs) observed in galaxies. The disk-averaged SFRs and gas densities for the combined sample are well represented by a Schmidt law with index N = 1.4 ± 0.15. The Schmidt law provides a surprisingly tight parametrization of the global star formation law, extending over several orders of magnitude in SFR and gas density. An alternative formulation of the star formation law, in which the SFR is presumed to scale with the ratio of the gas density to the average orbital timescale, also fits the data very well. Both descriptions provide potentially useful "recipes" for modeling the SFR in numerical simulations of galaxy formation and evolution.
5,299 citations
"Secular Evolution and the Formation..." refers background or methods in this paper
...SFRs of 0.1 – 2 M⊙ yr −1 are modest compared to the total SFRs in giant spiral galaxies, which typically range from 0.1 – 1 M⊙ yr −1 in normal Sa galaxies to 1 – 10 M⊙ yr −1 in Sb–Sc galaxies (Kennicutt 1983, 1998a)....
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...Kennicutt (1994, 1998a) provides reviews, contrasting the global star formation in barred galaxies, which is indistinduishable from that in unbarred galaxies, with the nuclear star formation, which is enhanced over that in unbarred galaxies....
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...Current SFRs in these regions can be estimated from Hα or Paα measurements converted using the SFR calibrations of Kennicutt (1998a)....
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...It approaches the SFR densities seen in some infrared starburst galaxies (Kennicutt 1998a, b)....
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TL;DR: In this paper, the Schmidt law was used to model the global star formation law, over the full range of gas densities and star formation rates (SFRs) observed in galaxies.
Abstract: Measurements of H-alpha, HI, and CO distributions in 61 normal spiral galaxies are combined with published far-infrared and CO observations of 36 infrared-selected starburst galaxies, in order to study the form of the global star formation law, over the full range of gas densities and star formation rates (SFRs) observed in galaxies. The disk-averaged SFRs and gas densities for the combined sample are well represented by a Schmidt law with index N = 1.4+-0.15. The Schmidt law provides a surprisingly tight parametrization of the global star formation law, extending over several orders of magnitude in SFR and gas density. An alternative formulation of the star formation law, in which the SFR is presumed to scale with the ratio of the gas density to the average orbital timescale, also fits the data very well. Both descriptions provide potentially useful "recipes" for modelling the SFR in numerical simulations of galaxy formation and evolution.
4,770 citations