In the current ΛCDM cosmological scenario, N-body simulations provide us with a universal mass profile, and consequently a universal equilibrium circular velocity of the virialized objects, as ...galaxies. In this paper we obtain, by combining kinematical data of their inner regions with global observational properties, the universal rotation curve of disc galaxies and the corresponding mass distribution out to their virial radius. This curve extends the results of Paper I, concerning the inner luminous regions of Sb–Im spirals, out to the edge of the galaxy haloes.
We present a theoretical model for the evolution of mass, angular momentum and size of galaxy discs and bulges, and we implement it into the semi-analytic galaxy formation code, Semi-Analytic Galaxy ...Evolution. The model follows both secular and violent evolutionary channels, including smooth accretion, disc instabilities, minor and major mergers. We find that the combination of our recipe with hierarchical clustering produces two distinct populations of bulges: merger-driven bulges, akin to classical bulges and ellipticals, and instability-driven bulges, akin to secular (or pseudo-)bulges. The model mostly reproduces the mass–size relation of gaseous and stellar discs, the evolution of the mass–size relation of ellipticals, the Faber–Jackson relation, and the magnitude–colour diagram of classical and secular bulges. The model predicts only a small overlap of merger-driven and instability-driven components in the same galaxy, and predicts different bulge types as a function of galaxy mass and disc fraction. Bulge type also affects the star formation rate and colour at a given luminosity. The model predicts a population of merger-driven red ellipticals that dominate both the low-mass and high-mass ends of the galaxy population, and span all dynamical ages; merger-driven bulges in disc galaxies are dynamically old and do not interfere with subsequent evolution of the star-forming component. Instability-driven bulges dominate the population at intermediate galaxy masses, especially thriving in massive discs. The model green valley is exclusively populated by instability-driven bulge hosts. Through the present implementation, the mass accretion history is perceivable in the galaxy structure, morphology and colours.
Intensity mapping of the neutral hydrogen (H i) is a new observational tool to efficiently map the large-scale structure over wide redshift ranges. The cross-correlation of intensity maps with galaxy ...surveys is a robust measure of the cosmological power spectrum and the H i content of galaxies which diminishes systematics caused by instrumental effects and foreground removal. We examine the cross-correlation signature at redshift 0.9 using a semi-analytical galaxy formation model in order to model the H i gas of galaxies as well as their optical magnitudes. We determine the scale-dependent clustering of the cross-correlation power for different types of galaxies determined by their colours, which act as a proxy for their star formation activity. We find that the cross-correlation coefficient with H i density for red quiescent galaxies falls off more quickly on smaller scales k > 0.2 h Mpc−1 than for blue star-forming galaxies. Additionally, we create a mock catalogue of highly star-forming galaxies to mimic the WiggleZ Dark Energy Survey, and use this to predict existing and future measurements using data from the Green Bank telescope and Parkes telescope. We find that the cross-power of highly star-forming galaxies shows a higher clustering on small scales than any other galaxy type and that this significantly alters the power spectrum shape on scales k > 0.2 h Mpc−1. We show that the cross-correlation coefficient is not negligible when interpreting the cosmological cross-power spectrum and additionally contains information about the H i content of the optically selected galaxies.
We investigate the relationship between stellar and gas specific angular momentum j, stellar mass M
* and optical morphology for a sample of 488 galaxies extracted from the Sydney-AAO Multi-object ...Integral field Galaxy Survey. We find that j, measured within one effective radius, monotonically increases with M
* and that, for M
* > 109.5 M⊙, the scatter in this relation strongly correlates with optical morphology (i.e. visual classification and Sérsic index). These findings confirm that massive galaxies of all types lie on a plane relating mass, angular momentum and stellar-light distribution, and suggest that the large-scale morphology of a galaxy is regulated by its mass and dynamical state. We show that the significant scatter in the M
*-j relation is accounted for by the fact that, at fixed stellar mass, the contribution of ordered motions to the dynamical support of galaxies varies by at least a factor of 3. Indeed, the stellar spin parameter (quantified via λ
R
) correlates strongly with Sérsic and concentration indices. This correlation is particularly strong once slow rotators are removed from the sample, showing that late-type galaxies and early-type fast rotators form a continuous class of objects in terms of their kinematic properties.
Abstract
We describe the selection of galaxies targeted in eight low-redshift clusters (APMCC0917, A168, A4038, EDCC442, A3880, A2399, A119 and A85; 0.029 < z < 0.058) as part of the Sydney-AAO ...Multi-Object Integral field spectrograph Galaxy Survey (SAMI-GS). We have conducted a redshift survey of these clusters using the AAOmega multi-object spectrograph on the 3.9-m Anglo-Australian Telescope. The redshift survey is used to determine cluster membership and to characterize the dynamical properties of the clusters. In combination with existing data, the survey resulted in 21 257 reliable redshift measurements and 2899 confirmed cluster member galaxies. Our redshift catalogue has a high spectroscopic completeness (∼94 per cent) for rpetro ≤ 19.4 and cluster-centric distances R < 2R200. We use the confirmed cluster member positions and redshifts to determine cluster velocity dispersion, R200, virial and caustic masses, as well as cluster structure. The clusters have virial masses 14.25 ≤ log(M200/M⊙) ≤ 15.19. The cluster sample exhibits a range of dynamical states, from relatively relaxed-appearing systems, to clusters with strong indications of merger-related substructure. Aperture- and point spread function matched photometry are derived from Sloan Digital Sky Survey and VLT Survey Telescope/ATLAS imaging and used to estimate stellar masses. These estimates, in combination with the redshifts, are used to define the input target catalogue for the cluster portion of the SAMI-GS. The primary SAMI-GS cluster targets have R <R200, velocities |vpec| < 3.5σ200 and stellar masses $9.5 \le {\rm log({\it M}}^*_{{\rm approx}}/$M⊙)≤12. Finally, we give an update on the SAMI-GS progress for the cluster regions.
We propose that angular momentum transfer from the baryons to the dark matter (DM) during the early stages of galaxy formation can flatten the halo inner density profile and modify the halo dynamics. ...We compute the phase-space distribution function of DM halos that corresponds to the density and anisotropy profiles obtained from TV-body simulations in the concordance cosmology. We then describe an injection of angular momentum into the halo by modifying the distribution function and show that the system evolves into a new equilibrium configuration; the latter features a constant central density and a tangentially dominated anisotropy profile in the inner regions, while the structure is nearly unchanged beyond 10% of the virial radius. Then we propose a toy model to account for such a halo evolution, based on the angular momentum exchange due to dynamical friction; at the epoch of galaxy formation this is efficiently exerted by the DM onto the gas clouds spiralling down the potential well. The comparison between the angular momentum profile gained by the halo through dynamical friction and that provided by the perturbed distribution function reveals a surprising similarity, hinting at the reliability of the process.
Abstract
Using the stellar kinematic maps and ancillary imaging data from the Sydney AAO Multi Integral field (SAMI) Galaxy Survey, the intrinsic shape of kinematically selected samples of galaxies ...is inferred. We implement an efficient and optimized algorithm to fit the intrinsic shape of galaxies using an established method to simultaneously invert the distributions of apparent ellipticities and kinematic misalignments. The algorithm output compares favourably with previous studies of the intrinsic shape of galaxies based on imaging alone and our re-analysis of the ATLAS3D data. Our results indicate that most galaxies are oblate axisymmetric. We show empirically that the intrinsic shape of galaxies varies as a function of their rotational support as measured by the ‘spin’ parameter proxy
$\lambda _{R_e}$
. In particular, low-spin systems have a higher occurrence of triaxiality, while high-spin systems are more intrinsically flattened and axisymmetric. The intrinsic shape of galaxies is linked to their formation and merger histories. Galaxies with high-spin values have intrinsic shapes consistent with dissipational minor mergers, while the intrinsic shape of low-spin systems is consistent with dissipationless multimerger assembly histories. This range in assembly histories inferred from intrinsic shapes is broadly consistent with expectations from cosmological simulations.
We present a methodology for the regularization and combination of sparse sampled and irregularly gridded observations from fibre-optic multiobject integral field spectroscopy. The approach minimizes ...interpolation and retains image resolution on combining subpixel dithered data. We discuss the methodology in the context of the Sydney-AAO multiobject integral field spectrograph (SAMI) Galaxy Survey underway at the Anglo-Australian Telescope. The SAMI instrument uses 13 fibre bundles to perform high-multiplex integral field spectroscopy across a 1° diameter field of view. The SAMI Galaxy Survey is targeting ~3000 galaxies drawn from the full range of galaxy environments. We demonstrate the subcritical sampling of the seeing and incomplete fill factor for the integral field bundles results in only a 10 per cent degradation in the final image resolution recovered. We also implement a new methodology for tracking covariance between elements of the resulting data cubes which retains 90 per cent of the covariance information while incurring only a modest increase in the survey data volume.
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