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We explore a sample of 1492 galaxies with measurements of the mean stellar population properties and the spin parameter proxy, |$\lambda _{R_{\rm {e}}}$|⁠ , drawn from the SAMI Galaxy Survey. We fit a global |$[\alpha /\rm {Fe}]$| –σ relation, finding that |${[\alpha /\rm {Fe}]}=(0.395\pm 0.010)\rm {log}_{10}(\sigma)-(0.627\pm 0.002)$|⁠. We observe an anti-correlation between the residuals |$\Delta [\alpha /\rm {Fe}]$| and the inclination-corrected |$\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}$|⁠ , which can be expressed as |${\Delta [\alpha /\rm {Fe}]}=(-0.057\pm 0.008){\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}+(0.020\pm 0.003)$|⁠. The anti-correlation appears to be driven by star-forming galaxies, with a gradient of |${\Delta [\alpha /\rm {Fe}]}\sim (-0.121\pm 0.015){\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}$|⁠ , although a weak relationship persists for the subsample of galaxies for which star formation has been quenched. We take this to be confirmation that disc-dominated galaxies have an extended duration of star formation. At a reference velocity dispersion of 200 km s−1, we estimate an increase in half-mass formation time from ∼0.5 Gyr to ∼1.2 Gyr from low- to high- |$\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}$| galaxies. Slow rotators do not appear to fit these trends. Their residual α-enhancement is indistinguishable from other galaxies with |${\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}\lessapprox 0.4$|⁠ , despite being both larger and more massive. This result shows that galaxies with |${\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}\lessapprox 0.4$| experience a similar range of star formation histories, despite their different physical structure and angular momentum. [ABSTRACT FROM AUTHOR]

The majority of spiral and elliptical galaxies in the Universe host very dense and compact stellar systems at their centres known as nuclear star clusters (NSC). In this work, we study the stellar populations and star formation histories (SFH) of the NSCs of six nearby galaxies with stellar masses ranging between 2 and $$8\times 10^9\, \rm M_{\odot }$$ (four late-type spirals and two early-types) with high-resolution spectroscopy. Our observations are taken with the X-shooter spectrograph at the VLT. We make use of an empirical simple stellar population (SSP) model grid to fit composite stellar populations to the data and recover the SFHs of the nuclei. We find that the nuclei of all late-type galaxies experienced a prolonged SFH, while the NSCs of the two early-types are consistent with SSPs. The NSCs in the late-type galaxies sample appear to have formed a significant fraction of their stellar mass already more than 10 Gyr ago, while the NSCs in the two early-type galaxies are surprisingly younger. Stars younger than 100 Myr are present in at least two nuclei: NGC 247 & NGC 7793, with some evidence for young star formation in NGC 300's NSC. The NSCs of the spirals NGC 247 and NGC 300 are consistent with prolonged in situ star formation with a gradual metallicity enrichment from ∼−1.5 dex more than 10 Gyr ago, reaching super-Solar values few hundred Myr ago. NGC 3621 appears to be very metal-rich already in the early Universe and NGC 7793 presents us with a very complex SFH, likely dominated by merging of various massive star clusters coming from different environments. [ABSTRACT FROM AUTHOR]

The surface brightness fluctuation (SBF) method measures spatial fluctuations due to the most luminous stars in a galaxy. Besides being useful for distance measurements, it also provides diagnostic power to investigate the contribution of the brightest stars to the underlying unresolved stellar population. We apply the SBF technique to every wavelength layer in integral field spectroscopy data obtained with the MUSE instrument. This yields the first SBF spectrum of a galaxy. SBF spectra combine the sensitivity of SBF to luminous stars with the physical information content of spectra. We show that the SBF spectrum of the S0 galaxy NGC 5102 is dominated by spectra of M-type giants (red giant branch, asymptotic giant branch, and red supergiant stars). We build the first stellar population synthesis tool that predicts SBF spectra. Through comparison of integrated spectra from our new tool with published model spectra, we confirm that it is mathematically correct. We use the integrated spectrum and a bootstrap method to derive an ensemble of (degenerate) star formation histories of NGC 5102. We compute a model SBF spectrum for each star formation history. Given that some models do not reproduce the observed SBF spectrum well, we are able to obtain additional constraints on the star formation history, leading to marginally reduced uncertainties on the mean age and metallicity. This result is confirmed by modelling mock spectra with different star formation histories. [ABSTRACT FROM AUTHOR]

Schwarzschild orbit-based dynamical models are widely used to uncover the internal dynamics of early-type galaxies and globular clusters. Here we present for the first time the Schwarzschild models of late-type galaxies: an SBb galaxy NGC4210 and an S0 galaxy NGC6278 from the Calar Alto Legacy Integral Field Area (CALIFA) survey. The mass profiles within 2Re are constrained well with 1σ statistical error of ~10 per cent. The luminous and dark mass can be disentangled with uncertainties of ~20 and ~50 per cent, respectively. From Re to 2Re, the dark matter fraction increases from 14 ± 10 to 18 ± 10 per cent for NGC4210 and from 15 ± 10 to 30 ± 20 per cent for NGC6278. The velocity anisotropy profiles of both σr/σt and σz/σR are well constrained. The inferred internal orbital distributions reveal clear substructures. The orbits are naturally separated into three components: a cold component with near circular orbits; a hot component with near radial orbits and a warm component in between. The photometrically identified exponential discs are predominantly made up of cold orbits only beyond ~1Re, while they are constructed mainly with the warm orbits inside. Our dynamical hot components are concentrated in the inner regions, similar to the photometrically identified bulges. The reliability of the results, especially the orbit distribution, is verified by applying the model to mock data. [ABSTRACT FROM AUTHOR]

The kinematics and stellar populations of the low-mass nearby S0 galaxyNGC5102 are studied from integral field spectra taken with the Multi-Unit Spectroscopic Explorer. The kinematic maps reveal for the first time that NGC 5102 has the characteristic 2s peaks indicative of galaxies with counter-rotating discs. This interpretation is quantitatively confirmed by fitting two kinematic components to the observed spectra. Through stellar population analysis, we confirm the known young stellar population in the centre and find steep age and metallicity gradients. We construct axisymmetric Jeans anisotropic models of the stellar dynamics to investigate the initial mass function (IMF) and the dark matter halo of the galaxy. The models show that this galaxy is quite different from all galaxies previously studied with a similar approach: even within the half-light radius, it cannot be approximated with the self-consistent mass-follows-light assumption. Including a Navarro, Frenk & White dark matter halo, we need a heavy IMF and a dark matter fraction of 0.37 ± 0.04 within a sphere of one Re radius to describe the stellar kinematics. The more general model with a free slope of the dark matter halo shows that slope and IMF are degenerate, but indicates that a light weight IMF (Chabrierlike) and a higher dark matter fraction, with a steeper (contracted) halo, fit the data better. Regardless of the assumptions about the halo profile, we measure the slope of the total mass density to be -1.75 ± 0.04. This is shallower than the slope of -2 of an isothermal halo and shallower than published slopes for more massive early-type galaxies. [ABSTRACT FROM AUTHOR]

We study the sources of biases and systematics in the derivation of galaxy properties from observational studies, focusing on stellar masses, star formation rates, gas and stellar metallicities, stellar ages, magnitudes and colours. We use hydrodynamical cosmological simulations of galaxy formation, for which the real quantities are known, and apply observational techniques to derive the observables. We also analyse biases that are relevant for a proper comparison between simulations and observations. For our study, we post-process the simulation outputs to calculate the galaxies' spectral energy distributions (SEDs) using stellar population synthesis models and also generate the fully consistent far-UV-submillimetre wavelength SEDs with the radiative transfer code SUNRISE. We compared the direct results of simulations with the observationally derived quantities obtained in various ways, and found that systematic differences in all studied galaxy properties appear, which are caused by: (1) purely observational biases, (2) the use of mass-weighted and luminosity-weighted quantities, with preferential sampling of more massive and luminous regions, (3) the different ways of constructing the template of models when a fit to the spectra is performed, and (4) variations due to different calibrations, most notably for gas metallicities and star formation rates. Our results show that large differences can appear depending on the technique used to derive galaxy properties. Understanding these differences is of primary importance both for simulators, to allow a better judgement of similarities and differences with observations, and for observers, to allow a proper interpretation of the data. [ABSTRACT FROM AUTHOR]

We present new upper limits for black hole masses in extremely late type spiral galaxies. We confirm that this class of galaxies has black holes with masses less than 106M☉, if any. We also derive new upper limits for nuclear star cluster masses in massive galaxies with previously determined black hole masses. We use the newly derived upper limits and a literature compilation to study the low mass end of the global-to-nucleus relations. We find the following. (1) The MBH-σ relation cannot flatten at low masses, but may steepen. (2) The MBH-Mbulge relation may well flatten in contrast. (3) The MBH-Sersic n relation is able to account for the large scatter in black hole masses in low-mass disk galaxies. Outliers in the MBH-Sersic n relation seem to be dwarf elliptical galaxies. When plotting MBH versus MNC we find three different regimes: (a) nuclear cluster dominated nuclei, (b) a transition region, and (c) black hole-dominated nuclei. This is consistent with the picture, in which black holes form inside nuclear clusters with a very low-mass fraction. They subsequently grow much faster than the nuclear cluster, destroying it when the ratio MBH/MNC grows above 100. Nuclear star clusters may thus be the precursors of massive black holes in galaxy nuclei. [ABSTRACT FROM AUTHOR]

Supernova (SN) explosions inject a considerable amount of energy into the interstellar medium (ISM) in regions with high-to-moderate star formation rates. In order to assess whether the driving of turbulence by supernovae is also important in the outer Galactic disc, where the star formation rates are lower, we study the spatial distribution of molecular cloud (MC) inclinations with respect to the Galactic plane. The latter contains important information on the nature of the mechanism of energy injection into the ISM. We analyse the spatial correlations between the position angles (PAs) of a selected sample of MCs (the largest clouds in the catalogue of the outer Galaxy published by Heyer et al). Our results show that when the PAs of the clouds are all mapped to values into the interval, there is a significant degree of spatial correlation between the PAs on spatial scales in the range of 100–800 pc. These scales are of the order of the sizes of individual SN shells in low-density environments such as those prevailing in the outer Galaxy and where the metallicity of the ambient gas is of the order of the solar value or smaller. These findings suggest that individual SN explosions, occurring in the outer regions of the Galaxy and in likewise spiral galaxies, albeit at lower rates, continue to play an important role in shaping the structure and dynamics of the ISM in those regions. The SN explosions we postulate here are likely associated with the existence of young stellar clusters in the far outer regions of the Galaxy and the ultraviolet emission and low levels of star formation observed with the Galaxy Evolution Explorer (GALEX) satellite in the outer regions of local galaxies. [ABSTRACT FROM AUTHOR]

Understanding the details of how the red sequence is built is a key question in galaxy evolution. What are the relative roles of gas-rich vs. dry mergers, major vs. minor mergers or galaxy mergers vs. gas accretion? In a recent paper (Wild et al. 2009), we compare hydrodynamic simulations with observations to show how gas-rich major mergers result in galaxies with strong post-starburst spectral features, a population of galaxies easily identified in the real Universe using optical spectra. Using spectra from the VVDS deep survey with = 0.7, and a principal component analysis technique to provide indices with high enough SNR, we find that 40% of the mass flux onto the red-sequence could enter through a strong post-starburst phase, and thus through gas-rich major mergers. The deeper samples provided by next generation galaxy redshift surveys will allow us to observe the primary physical processes responsible for the shut-down in starformation and build-up of the red sequence. [ABSTRACT FROM PUBLISHER]

From the VIMOS VLT Deep Survey (VVDS), we select a sample of 16 galaxies with spectra which identify them as having recently undergone a strong starburst and subsequent fast quenching of star formation. These post-starburst galaxies lie in the redshift range with masses . They have a number density of , almost two orders of magnitude sparser than the full galaxy population with the same mass limit. We compare with simulations to show that the galaxies are consistent with being the descendants of gas-rich major mergers. Starburst mass fractions must be larger than per cent and decay times shorter than for post-starburst (PSB) spectral signatures to be observed in the simulations. We find that the presence of black hole feedback does not greatly affect the evolution of the simulated merger remnants through the PSB phase. The multiwavelength spectral energy distributions of the PSB galaxies show that 5/16 have completely ceased the formation of new stars. These five galaxies correspond to a mass flux entering the red-sequence of , assuming the defining spectroscopic features are detectable for 0.35 Gyr. If the galaxies subsequently remain on the red sequence, this accounts for per cent of the growth rate of the red sequence. Finally, we compare our high-redshift results with a sample of galaxies with observed in the Sloan Digital Sky Survey and United Kingdom Infrared Telescope Infrared Deep Survey. We find a very strong redshift evolution: the mass density of strong PSB galaxies is 230 times lower at than at . [ABSTRACT FROM AUTHOR]