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We examine the evolution induced by secular processes of an initial, cosmologically motivated, radial chemical distribution, in a barred and an unbarred disk.
We report on first molecular gas observations in the Lyman Alpha Reference Sample (LARS; Hayes et al.2013, 2014, Östlin et al.2014), which were performed using the 45m telescope at the Nobeyama Radio Observatory (NRO). The beamsize at the observed 12CO (1–0) emission is ≈ 15” corresponding to ≈ 12kpc at the given redshift of z ≈ 0.04. We detected strong 12CO emission in LARS 3 (Arp 238), marginally detected LARS 8 (SDSS 1250+0734) and derived an upper limit for LARS 9 (IRAS 08208+2816).
The combination of strong gravitational lensing and stellar kinematics provides a powerful and robust method to investigate the mass and dynamical structure of early-type galaxies. We demonstrate this approach by analysing two massive ellipticals from the XLENS Survey for which both high-resolution HST imaging and X-Shooter spectroscopic observations are available. We adopt a flexible axisymmetric two-component mass model for the lens galaxies, consisting of a generalised NFW dark halo and a realistic self-gravitating stellar mass distribution. For both systems, we put constraints on the dark halo inner structure and flattening, and we find that they are dominated by the luminous component within one effective radius. By comparing the tight inferences on the stellar mass from the combined lensing and dynamics analysis with the values obtained from stellar population studies, we conclude that both galaxies are characterised by a Salpeter-like stellar initial mass function.
Spatially resolved spectroscopy is even more powerful when combined with magnification by gravitational lensing. I discuss observations of lensed galaxies at z≃2 with spatial resolution reaching 100 parsecs. Near-IR integral field spectroscopy reveals the kinematics, distribution and physical properties of star forming regions, and gas-phase metallicity gradients. Roughly two thirds of observed galaxies are isolated systems with coherent velocity fields, large velocity dispersion, multiple giant star-forming regions, and negative gas-phase metallicity gradients, suggestive of inside-out growth in gravitationally unstable disks. The remainder are undergoing mergers and have shallower metallicity gradients, indicating mixing of the interstellar gas via gravitational interaction. The metallicity gradients in isolated galaxies are consistent with simulations using standard feedback prescriptions, whereas simulations with enhanced feedback predict shallower gradients. These measurements therefore constrain the growth of galaxies from mergers and star formation as well as the regulatory feedback.
We introduce a pilot project to measure metallicitiy gradients for a sample of twenty nearby galaxies drawn from the Herschel Reference Survey (HRS), representative of normal, star-forming spiral galaxies. We have obtained optical spectroscopic observations using the Very Large Telescope with the FORS2 instrument in multi-object mode, targeting individual Hii and star-forming regions across the galaxy discs (P. I.: L. Cortese). From the ratios of the strong emission lines, we estimate the local gas-phase oxygen abundance and construct metallicity gradients. Combining these new data with Herschel PACS/SPIRE far-infrared photometric observations and Hi 21 cm line maps, to trace the cold dust and gas respectively, will allow the study of the relationships between stars, gas, dust and metals on sub-kiloparsec scales.
A large number of observed exoplanets are part of multiple planet systems. Most of these systems are sufficiently close-in to be tidally evolving. In such systems, there is a competition between the excitation caused by planet-planet interactions and tidal damping. Using as an example two multiple planet systems, which host planets in the surface liquid water habitable zone (HZ): Kepler-62 and Kepler-186, we show the importance and effect of both planetary and stellar tides on the dynamical evolution of planets and on the climate of the HZ planets.
By studying the individual star-formation histories of the bulges and discs of lenticular (S0) galaxies, it is possible to build up a sequence of events that leads to the cessation of star formation and the consequent transformation from the progenitor spiral. In order to separate the bulge and disc stellar populations, we spectroscopically decomposed long-slit spectra of Virgo Cluster S0s into bulge and disc components. Analysis of the decomposed spectra shows that the most recent star formation activity in these galaxies occurred within the bulge regions, having been fuelled by residual gas from the disc. These results point towards a scenario where the star formation in the discs of spiral galaxies are quenched, followed by a final episode of star formation in the central regions from the gas that has been funnelled inwards through the disc.
A set of 29 low order secular resonance relations in the near-Earth satellite dynamics has been obtained and their influence on dynamic evolution of objects has been investigated on time intervals of 100 years. The analysis of the results shows that secular resonances are very common phenomena in the near-Earth orbital space. Sharp resonances are concentrated in the orbital space areas where the semi-major axes a ⩾ 20000 km and the inclinations i ⩾ 50○. In some areas objects have several secular resonances. The superposition of several secular resonances or orbital and secular resonances are the source of randomness in the motion of objects.
We present Magneticum Pathfinder, a new set of hydrodynamical cosmological simulations covering a large range of cosmological scales. Among the important physical processes included in the simulations are the chemical and thermodynamical evolution of the diffuse gas as well as the evolution of stars and black holes and the corresponding feedback channels. In the high resolution boxes aimed at studies of galaxy formation and evolution, populations of both disk and spheroidal galaxies are self-consistently reproduced. These galaxy populations match the observed stellar mass function and show the same trends for disks and spheroids in the mass–size relation as observations from the SDSS. Additionally, we demonstrate that the simulated galaxies successfully reproduce the observed specific angular-momentum–mass relations for the two different morphological types of galaxies. In summary, the Magneticum Pathfinder simulations are a valuable tool for studying the assembly of cosmic and galactic structures in the universe.
In Marino et al. (2013) we provide revisited empirical calibrations for the oxygen abundances in HII regions based on the O3N2 and N2 indicators. This work is based on the most comprehensive compilation of both Te-based and multiple strong-line (ONS-based) ionized-gas abundance measurements in external galaxies to date in terms of all statistical significance, quality, and coverage of the parameters space. Our dataset compiles the Te-based abundances of 603 HII regions extracted from the literature but also includes new measurements from the CALIFA survey. We also present a comparison between our revisited calibrations with a total of 3423 additional CALIFA HII complexes with abundances derived using the ONS calibration. The O3N2 and N2 indicators can be empirically applied to derive oxygen abundances calibrations from either direct-abundance determinations with random errors of 0.18 and 0.16, respectively, and they show shallower abundance dependencies and statistically significant offsets compared to the classical calibrations (as the one of Pettini & Pagel (2004)).
Fabry-Perot data of compact group galaxies have been used to show that the Tully-Fisher relation in any photometric band, for galaxies with vmax > 100 km/s, is very similar to that for galaxies in other less dense environments. In the low-luminosity end, however, a few compact group galaxies fall above the relation apparently because they are too bright for their mass. Here we show that if the mass is properly computed from spectral energy distribution fitting or mass modelling, for the low-luminosity galaxies, their positions in the stellar-mass or baryonic Tully-Fisher relation are what is expected for a normal Tully-Fisher relation and the outlying positions observed in the B and K Tully-Fisher relation could be explained by brightening of the low-luminosity interacting galaxies due to strong star formation or AGN activity.
The relative distribution of matter in galaxies ought to be one of the most definitive predictions of galaxy formation models yet its validation is challenged by numerous observational, theoretical, and operational challenges. All galaxies are believed to be dominated by an invisible matter component in their outskirts. A debate has however been blazing for the last two decades regarding the relative fraction of baryons and dark matter in the inner parts of galaxies: whether galaxies are centrally dominated by baryons (“maximal disk”) is of issue. Some of those debates have been misconstrued on account of operational confusion, such as dark matter fractions being measured and compared at different radii. All galaxies are typically baryon-dominated (maximal) at the center and dark-matter dominated (sub-maximal) in their outskirts; for low-mass galaxies (Vtot ≲ 200 km s− 1), the mass of the dark halo equals the stellar mass at least within 2 disk scale lengths, the transition occurs at larger effective radii for more massive galaxies. An ultimate goal for galaxy structure studies is to achieve accurate data-model comparisons for the relative fractions of baryonic to total matter at any radius.
Various programs aimed at exploring the still largely unknown low surface brightness Universe with deep imaging optical surveys have recently started. They open a new window for studies of galaxy evolution, pushing the technique of galactic archeology outside the Local Group (LG). The method, based on the detection and analysis of the diffuse light emitted by collisional debris or extended stellar halos (rather than on stellar counts as done for LG systems), faces however a number of technical difficulties, like the contamination of the images by reflection halos and Galactic cirrus. I review here the on-going efforts to address them and highlight the preliminary promising results obtained with a systematic survey with MegaCam on the CFHT of nearby massive early-type galaxies done as part of the ATLAS3D, NGVS and MATLAS collaborations.
We propose a strategy to attack the problems of orbit determination arising from the large number of short arcs. The method uses a solution of the linkage problem depending on the first integrals of the Keplerian motion.
The luminosity function is an important quantity for analysis of large scale structure statistics, interpretation of galaxy counts (Lin & Kirshner 1996). We investigate the luminosity function of galaxy clusters. This is performed by counting the brightness of galaxies belonging to clusters in PF Catalogue. The obtained luminosity function is significantly different than that obtained both for optical and radiogalaxies (Machalski & Godowski 2000). The implications of this result for theories of galaxy formation are discussed as well.
The late-type spiral NGC 2770 hosted 3 Type Ib supernovae (SNe) in or next to star-forming regions in its outer spiral arms. We study the properties of the SN sites and the galaxy at different spatial resolutions to infer propeties of the SN progenitors and the SF history of the galaxy. Several 3D techniques are used and, for the first time, we present images of metallicity, shocks and stellar population ages from OSIRIS/GTC imaging with tunable narrowband filters.
The problem of the origin of asteroids residing in the Jovian first-order mean motion resonances is still open. Is the observed population survivors of a much larger population formed in the resonance in primordial times? Here, we study the evolution of 182 long-lived asteroids in the 2:1 Mean Motion Resonance, identified in Brož & Vokrouhlické (2008). We numerically integrate their trajectories in two different dynamical models of the solar system: (a) accounting for the gravitational effects of the four giant planets (i.e. 4-pl) and (b) adding the terrestrial planets from Venus to Mars (i.e. 7-pl). We also include an approximate treatment of the Yarkovksy effect (as in Tsiganis et al.2003), assuming appropriate values for the asteroid diameters.
We present an overview of the HALOGAS (Hydrogen Accretion in LOcal GAlaxieS) Survey, which is the deepest systematic investigation of cold gas accretion in nearby spiral galaxies to date. Using the deep H i data that form the core of the survey, we are able to detect neutral hydrogen down to a typical column density limit of about 1019 cm−2 and thereby characterize the low surface brightness extra-planar and anomalous-velocity neutral gas in nearby galaxies with excellent spatial and velocity resolution. Through comparison with sophisticated kinematic modeling, our 3D HALOGAS data also allow us to investigate the disk structure and dynamics in unprecedented detail for a sample of this size. Key scientific results from HALOGAS include new insight into the connection between the star formation properties of galaxies and their extended gaseous media, while the developing HALOGAS catalogue of cold gas clouds and streams provides important insight into the accretion history of nearby spirals. We conclude by motivating some of the unresolved questions to be addressed using forthcoming 3D surveys with the modern generation of radio telescopes.
In the standard model of core accretion, the cores of the giant planets form by the accretion of planetesimals. In this scenario, the evolution of the planetesimal population plays an important role in the formation of massive cores. Recently, we studied the role of planetesimal fragmentation in the in situ formation of a giant planet. However, the exchange of angular momentum between the planet and the gaseous disk causes the migration of the planet in the disk. In this new work, we incorporate the migration of the planet and study the role of planet migration in the formation of a massive core when the population of planetesimals evolves by planet accretion, migration, and fragmentation.