Early Spiral Galaxies (original) (raw)
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The Milky Way has been generally considered to be representative of the numerous spiral galaxies inhabiting the local Universe, thus providing general and perhaps the most detailed constraints on numerical models of galaxy formation. We compare both the Milky Way and M31 galaxies to local external disk galaxies within the same mass range, using their locations in the planes drawn by Vf lat versus MK (the “Tully-Fisher” relation), jdisk (angular momentum) and the average Fe abundance, [Fe/H], of stars in the outskirts of the galaxy. These relations are thought to be the imprints of the dynamical, star-formation, and accretion history of disk galaxies. We compare the best established Tully-Fisher relations and reconcile their slopes and zero points in the plane MK-Vf lat. We then compare the properties of local spirals from a representative sample to those of the Milky Way and M31 considering how these two galaxies would appear if observed at larger distances. We find, for all relationships, that the Milky Way is systematically offset by ∼ 1 σ or more from the distribution of comparable local galaxies: specifically, it shows a too small stellar mass, angular momentum, disk radius and outskirts stars [Fe/H] ratio at a given Vf lat, the latter being taken as a proxy for the total mass. In contrast with the Milky Way, M31 lies well within the mean of the fundamental relationships. On the basis of their locations in the (MK , Vf lat and R d) volume, the fraction of spirals like the Milky Way is 7 ±1%, while M31 appears to be a “typical” spiral. As with M31, the bulk of local spirals show evidence for a formation history shaped mainly by merging. The Milky Way appears to have had an exceptionally quiet formation history and had escaped any significant merger over the last ∼10 Gyrs which may explain why its angular momentum, stellar mass and [Fe/H](outskirts) are two to three times smaller than those of other local spirals. We conclude that the standard scenario of secular evolution driven by the accretion of gas and disk instabilities is generally unable to reproduce the properties of most (if not all) spiral galaxies, which are well represented by M31. However, the relatively recent proposal explaining the evolution of spiral galaxies through merging (the so-called “spiral rebuilding” scenario of Hammer et al. 2005) is consistent with the properties of both distant galaxies (e.g., stellar mass assembly through episodic IR luminous burst phases driven predominately by mergers) as well as to those of their descendants – the local spirals.
The milky way, an exceptionally quiet galaxy: Implications for the formation of spiral galaxies
The Astrophysical …, 2007
The Milky Way has been generally considered to be representative of the numerous spiral galaxies inhabiting the local Universe, thus providing general and perhaps the most detailed constraints on numerical models of galaxy formation. We compare both the Milky Way and M31 galaxies to local external disk galaxies within the same mass range, using their locations in the planes drawn by V f lat versus M K (the "Tully-Fisher" relation), j disk (angular momentum) and the average Fe abundance, [Fe/H], of stars in the outskirts of the galaxy. These relations are thought to be the imprints of the dynamical, star-formation, and accretion history of disk galaxies. We compare the best established Tully-Fisher relations and reconcile their slopes and zero points in the plane M K -V f lat . We then compare the properties of local spirals from a representative sample to those of the Milky Way and M31 considering how these two galaxies would appear if observed at larger distances.
The Onset of Spiral Structure in the Universe
The Astrophysical Journal, 2014
The onset of spiral structure in galaxies appears to occur between redshifts 1.4 and 1.8 when disks have developed a cool stellar component, rotation dominates over turbulent motions in the gas, and massive clumps become less frequent. During the transition from clumpy to spiral disks, two unusual types of spirals are found in the Hubble Ultra Deep Field that are massive, clumpy and irregular like their predecessor clumpy disks, yet spiral-like or sheared like their descendants. One type is "woolly" with massive clumpy arms all over the disk and is brighter than other disk galaxies at the same redshift, while another type has irregular multiple arms with high pitch angles, star formation knots and no inner symmetry like today's multiple-arm galaxies. The common types of spirals seen locally are also present in a redshift range around z ∼ 1, namely grand design with two symmetric arms, multiple arm with symmetry in the inner parts and several long, thin arms in the outer parts, and flocculent, with short, irregular and patchy arms that are mostly from star formation. Normal multiple arm galaxies are found only closer than z ∼ 0.6 in the UDF. Grand design galaxies extend furthest to z ∼ 1.8, presumably because interactions can drive a two-arm spiral in a disk that would otherwise have a more irregular structure. The difference between these types is understandable in terms of the usual stability parameters for gas and stars, and the ratio of the velocity dispersion to rotation speed.
Monthly Notices of the Royal Astronomical Society, 2003
We compare the properties of local spiral galaxies with the predictions of the Cole et al. semi-analytic model of hierarchical galaxy formation, in order to gain insight into the baryonic processes, such as gas cooling and star formation, that were responsible for shaping these galaxies. On the whole, the models reproduce the properties of presentday spirals rather well, including the trend in scale-size with luminosity, the width of the scale-size distribution, the tight gas fraction-surface brightness and gas fractionstar formation history correlations, the metallicity-magnitude correlation, and the present-day star formation rates and stellar mass-to-light ratios. Of special note is our demonstration that, once the effects of dust and variations in stellar populations have been taken into account, published spiral galaxy scale-size distributions derived from optical data (with widths σ ∼ 0.3) can be reconciled with the width (σ ∼ 0.5) of the stellar mass scale-size distribution predicted by the semi-analytic model.
Evolution of structure in late-type spiral galaxies
Astronomy and Astrophysics, 2007
Aims. We study two dimensional Fabry-Perot interferometric observations of the nearby face-on late-type spiral galaxy, NGC 628, in order to analyse the ionized gas component of the interstellar medium. Covering the galaxy out to a radius larger than 12 kpc, and with a spatial sampling of 1. ′′ 6, we aim to investigate the large-scale dynamics as well as feedback from individual H regions into their surrounding medium. Methods. The observed Hα emission distribution and kinematics are compared with auxiliary data from molecular and atomic gas observations, which display many similarities. We decompose the observed line-of-sight velocities into rotational and higher-order harmonic components, and study the role of gravitational perturbations along with that of external triggers which can disturb the kinematics and morphology of NGC 628. We calculate radial profiles of the emission-line velocity dispersion which we use to study the role of feedback from individual H regions. Results. We verify the presence of an inner rapidly rotating disc-like component in NGC 628, which we interpret as caused by slow secular evolution of the large-scale spiral arms and oval structure. In combination with auxiliary data, we find indication for that gas is falling in from the outer parts towards the central regions, where a nuclear ring has formed at the location of the inner Lindblad resonance radius of an an m = 2 perturbation. Complementary continuum subtracted narrow band images in Hα have been used to identify 376 H regions with calibrated luminosities ⋆. The mean velocity dispersion for the ionized gas (even when excluding pixels belonging to H regions) is almost constant out to 12 kpc, although it varies from 14 to 20 km s −1 , with a steady decline in the outer parts. Conclusions. We have found kinematic signatures of radial motions caused by an m = 2 perturbation. Such a perturbation may well be responsible for the inflow of material forming the nuclear ring and the inner rapidly rotating disc-like structure. The latter, in turn, could help build a pseudo-bulge in NGC 628. The current paper demonstrates a number of tools that we have developed for building a solid frame work for studying the evolution of structure in spiral galaxies using two dimensional kinematic observations.
Early Formation and Evolution of Galaxies
The Evolution of Galaxies, 2003
I review success and failure of the hierarchical galaxy formation model. In this scenario, the morphology of galaxies is regulated by the mode of gas accretion and intimately linked to discrete accretion events. Some of the common misconceptions about hierarchical clustering are discussed. The need of a self-consistent approach that incorporates the chemical and dynamical evolution on small scales simultaneously with the cosmological framework of structure formation on large scales is emphasized.
Using the latest sample of 48 spiral galaxies having a directly measured supermassive black hole mass, M BH , we determine how the maximum disk rotational velocity, v max (and the implied dark matter halo mass, M DM ), correlates with the (i) black hole mass, (ii) central velocity dispersion, σ 0 , and (iii) spiral-arm pitch angle, φ. We find that M BH ∝ v 10.62±1.37 max ∝ M 4.35±0.66 DM , significantly steeper than previously reported, and with a total root mean square scatter (0.58 dex) similar to that about the M BH -σ 0 relation for spiral galaxies-in stark disagreement with claims that M BH does not correlate with disks. Moreover, this M BH -v max relation is consistent with the unification of the Tully-Fisher relation (involving the total stellar mass, M * ,tot ) and the steep M BH ∝ M 3.05±0.53 * ,tot relation observed in spiral galaxies. We also find that
Chemical Evidence for Morphological Evolution of Spiral Galaxies
The Astrophysical Journal, 1999
Using the methods of spectrophotometric imagery and multislit spectroscopy, we have derived the radial abundance proÐles from O/H measurements in 549 H II regions of eight early-type spiral galaxies. We then compared the characteristic abundance levels and radial distributions of this group of spirals with those of late-type galaxies. The early-type galaxies of our sample display gradients that are Ñatter and overall levels of O/H abundances that are higher than those of normal late-type galaxies. Early-type galaxies show an identical trend in the behavior of extrapolated central abundance versus morphological type to that shown by late-type galaxies with strong bars, even in the absence of a bar. On a diagram showing extrapolated central abundances versus morphological types, two clearly separated sequences appear : late-type barred galaxies and early-type (barred or unbarred) galaxies clearly fall on a sequence D0.5 dex in abundance below that of normal late-type galaxies. This behavior is consistent with a scenario of morphological evolution of disk galaxies by the formation and dissolution of a bar over a period of a few 109 yr, where later type galaxies (Sd, Sc, Sbc) evolve into earlier-type disk galaxies (Sb, Sa) through transitory SBc and SBb phases.
Kinematic and Structural Evolution of Field and Cluster Spiral Galaxies
Arxiv preprint arXiv: …, 2009
Abstract: To understand the processes that build up galaxies we investigate the stellar structure and gas kinematics of spiral and irregular galaxies out to redshift 1. We target 92 galaxies in four cluster (z= 0.3 & 0.5) fields to study the environmental influence. Their ...
Spiral structure and the dynamics of galaxies
Physics Reports, 1976
Conten ts: 1. General characteristics of spiral galaxies 317 5. Stabilization of density waves by the gas 364 1.1. A brief review of two centuries of observations 317 5.1. Introduction 364 1.2. Theories of spiral structure 321 5.2. Stabilization mechanism 1.3. Outline of the present study 324 5.3. Discussion 2. Mathematical tools 326 6. Quasi-linear theory 3. Dynamical properties of flat stellar systems 328 6.1. Introduction 3.1. Introduction 328 6.2. Derivation of the diffusion equation 3.2. Stellar orbits 328 6.3. Diffusion coefficients 3.3. Distribution functions 341 6.4. The persistence of spiral structure 4. Stability of slightly perturbed disks 346 7. Conclusions and summary 4.1. Introduction 346 Acknowledgements 4.2. Mathematical formulation 347 Appendix 4.3. Instabilities 354 References 4.3.1. The rate of change of angular momentum 354 4.3.2. Growing waves 356 4.3.3. Damped waves 358 4.3.4. Physical significance of the growth rate y 359 4.3.5. Astronomical implications 361