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A moon in synchronous rotation has longitudinal librations because of its non-spherical mass distribution and its elliptical orbit around the planet. We study the librations of Titan with periods of 14.7y and 29.5y and include deformation effects and the existence of a subsurface ocean. We take into account the fact that the orbit is not Keplerian and has other periodicities than the main period of orbital motion around Saturn due to perturbations by the Sun, other planets and moons. An orbital theory is used to compute the orbital perturbations due to these other bodies.
We numerically evaluate the amplitude of the long-period librations for many interior structure models of Titan constrained by the mass, radius and gravity field. Measurements of the librations may give constraints on the interior structure of the icy satellites.
We present stellar population gradients of early-type galaxies from the ATLAS3D survey: a complete, volume-limited multi-wavelength survey of 260 early-type galaxies in the local 42 Mpc volume. Using emission-corrected spectra integrated within elliptical annuli we measure line-strength indices and apply single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement as function of radius. For all galaxies we derive basic linear stellar population gradients versus radius logR/Re). These gradients are examined on their own and versus three mass-sensitive parameters: K-band luminosity MK, velocity dispersion within one effective radius log σe, and our dynamical mass MJAM. We find a correlation between positive age gradients (younger centre) and steeper negative metallicity gradients with a Spearman rank correlation coefficient of -0.46 and a significance of 7.65 × 10−15. Furthermore, we find a robustly estimated mean metallicity gradient of Δ[Z/H] = -0.37 ± 0.01 for the sample with a significant trend for more massive galaxies to have shallower profiles. While there is no clear distinction between fast and slow rotators or signs of environmental influence, we do detect a significantly larger range of [Z/H]-gradients towards low mass galaxies.
To extend the molecular gas measurements to typical L* star-forming galaxies (SFGs) at z ∼ 1.5 − 3, we have observed CO emission for five strongly-lensed galaxies selected from the Herschel Lensing Survey. The combined sample of our L* SFGs with CO-detected SFGs at z >1 from the literature shows a large spread in star formation efficiency (SFE). We find that this spread in SFE is due to variations of several physical parameters, primarily the specific star formation rate, but also stellar mass and redshift. An increase of the molecular gas fraction (fgas) is observed from z ∼ 0.2 to z ∼ 1.2, followed by a quasi non-evolution toward higher redshifts, as found in earlier studies. We provide the first measure of fgas of z >1 SFGs at the low-stellar mass end between 109.4 < M∗/M⊙ < 109.9, which shows a clear fgas upturn.
Wolf-Rayet HII galaxies are local metal-poor star-forming galaxies, observed when the most massive stars are evolving from O stars to WR stars, making them template systems to study distant starbursts. We have been performing a program to investigate the interplay between massive stars and gas in WR HII galaxies using IFS. Here, we highlight some results from the first 3D spectroscopic study of Mrk 178, the closest metal-poor WR HII galaxy, focusing on the origin of the nebular HeII emission and the aperture effects on the detection of WR features.
The stability diagrams in the “pericentric distance — eccentricity” plane of initial data are built and analyzed for Kepler-38, Kepler-47, and Kepler-64 (PH1). This completes a survey of stability of the known up to now circumbinary planetary systems, initiated by Popova & Shevchenko (2013), where the analysis was performed for Kepler-16, 34, and 35. In the diagrams, the planets appear to be “embedded” in the fractal chaos border; however, I make an attempt to measure the “distance” to the chaos border in a physically consistent way. The obtained distances are compared to those given by the widely used numerical-experimental criterion by Holman & Wiegert (1999), who employed smooth polynomial approximations to describe the border. I identify the resonance cells, hosting the planets.
We have recently proposed a new approach to the asteroid family classification by combining the classical HCM method with an automated procedure to add newly discovered members to existing families. This approach is specifically intended to cope with ever increasing asteroid data sets, and consists of several steps to segment the problem and handle the very large amount of data in an efficient and accurate manner. We briefly present all these steps and show the results from three subsequent updates making use of only the automated step of attributing the newly numbered asteroids to the known families. We describe the changes of the individual families membership, as well as the evolution of the classification due to the newly added intersections between the families, resolved candidate family mergers, and emergence of the new candidates for the mergers. We thus demonstrate how by the new approach the asteroid family classification becomes stable in general terms (converging towards a permanent list of confirmed families), and in the same time evolving in details (to account for the newly discovered asteroids) at each update.
We study the secular dynamics of extrasolar planetary systems by extending the Lagrange-Laplace theory to high order and by including the relativistic effects. We investigate the long-term evolution of the planetary eccentricities via normal form and we find an excellent agreement with direct numerical integrations. Finally we set up a simple analytic criterion that allows to evaluate the impact of the relativistic effects in the long-time evolution.
In this paper we consider the special case of the planar circular restricted three-body problem by the example of the problem of the Earth, the Moon and a point mass, where the gravitational potentials of the Earth and the Moon are given as the Kislik potential. The Kislik potential takes into account the flattening of a celestial body on the poles. We find the relative equilibria solutions for a point mass and analyze their stability. We describe the difference between the obtained points and the classical solution of the three-body problem.
We present optical properties of the 26 most massive galaxy clusters in the South Pole Telescope 2500 sq-deg footprint. We find a general consistency between our results and results found in the literature on samples built with different selection techniques. Most interesting, we find a preference for an evolution in the slope of the Schechter function, α, with its value increasing at higher redshift.
Using the imaging Fourier transform spectrograph (FTS) SpIOMM we study 7 nearby spiral galaxies. The large database of spectra obtained around Hα and Hβ is ideal to study the star forming regions and warm ionized medium (WIM) with a high spatial resolution (∼ 50-150 pc).
We present results of ALMA (Cycle-0) observations of the CO (6-5) line emission and the 435μm continuum of two nearby luminous infrared galaxies (LIRGs) NGC 34 (a major merger with an AGN) and NGC 1614 (a minor merger with a circum-nuclear starburst). Using receivers in the highest frequency ALMA band available (Band-9), these observations achieved the best angular resolutions (∼0″.25) for ALMA Cycle-0 observations and resolved for the first time distributions of warm dense molecular gas (n > 105 cm−3, T > 100 K) in LIRGs with spatial resolutions better than 100 pc. Our ALMA data show a very tight correlation between the CO (6-5) line emission and the 435μm dust continuum emission, suggesting the warm dense molecular gas dominates the ISM in the central kpc of LIRGs, and gas heating and dust heating in the warm dense gas cores are strongly coupled. On the other hand, we saw very different spatial distributions and kinematic properties of warm dense gas in the two LIRGs, indicating that physical conditions in the ISM can be very different in different LIRGs.
Using data from the SAMI Galaxy Survey we measure azimuthally averaged stellar age and metallicity profiles for ∼ 500 galaxies, using both luminosity-weighted Lick indices and mass-weighted full spectral fitting. We find a weak trend for steeper (i.e. more negative) metallicity gradients in more massive galaxies, however, below stellar masses ∼ 1010.5 M⊙, the scatter in metallicity gradient increases dramatically.
We investigate the existence of a Kennicutt-Schmidt type relation between ΣSFR and Σgas, atomic in the HI dominated regions of nearby spirals and dwarf irregulars.
A relation between the stellar mass M and the gas-phase metallicity Z of galaxies, the MZR, is observed up to higher redshifts. It is a matter of debate, however, if the SFR is a second parameter in the MZR. To explore this issue at z > 1, we used VLT-SINFONI near-infrared (NIR) spectroscopy of eight zCOSMOS galaxies at 1.3 < z < 1.4 to measure the strengths of four emission lines: Hβ, [OIII]λ5007, Hα, and [NII]λ6584, additional to [OII]λ3727 measured from VIMOS. We derive reliable O/H metallicities based on five lines, and also SFRs from extinction corrected Hα measurements. We find that the MZR of these star-forming galaxies at z ≈ 1.4 is lower than the local SDSS MZR by a factor of three to five, a larger change than reported in the literature using [NII]/Hα-based metallicities from individual and stacked spectra. Correcting N2-based O/Hs using recent results by Newman et al. (2014), also the larger FMOS sample at z ∼ 1.4 of Zahid et al. (2014) shows a similar evolution of the MZR like the zCOSMOS objects. These observations seem also in agreement with a non-evolving FMR using the physically motivated formulation of the FMR from Lilly et al. (2013).
We apply two new state-of-the-art methods that model the distribution of observed tracers in projected phase space to lift the mass / velocity anisotropy (VA) degeneracy and deduce constraints on the mass profiles of galaxies, as well as their VA. We first show how a distribution function based method applied to the satellite kinematics of otherwise isolated SDSS galaxies shows convincing observational evidence of age matching: red galaxies have more concentrated dark matter (DM) halos than blue galaxies of the same stellar or halo mass. Then, applying the MAMPOSSt technique to M87 (traced by its red and blue globular clusters) we find that very cuspy DM is favored, unless we release priors on DM concentration or stellar mass (leading to unconstrained slope). For the Fornax dwarf spheroidal (traced by its metal-rich and metal-poor stars), the inner DM slope is unconstrained, with weak evidence for a core if the stellar mass is fixed. This highlights how priors are crucial for DM modeling. Finally, we find that blue GCs around M87 and metal-rich stars in Fornax have tangential outer VA.
My contribution to Roger's celebration symposium focuses on the treatment of late stellar evolutionary phases in stellar population models, reviewing the state of art and discussing some very recent developments, ranging from local stellar clusters up to distant galaxies at high redshift. I shall focus in particular on the Thermally Pulsating Asymptotic Giant Branch, about which a vivid discussion has been ongoing since a few years. I shall present renewed evidence in favour of a sizable contribution from this phase for matching the observed spectral energy distribution of distant massive galaxies. I shall also discuss the possible reasons why such a conclusion has been controversial in the recent literature. Stellar population models are the magic tool to shape the physics of galaxies out of their observed light, and enter virtually all papers presented at this symposium. In a collective effort to properly treat all relevant aspects of the modelling, we split the discussion into six contributions given by experts in the field, as our present to Roger and his outstanding career.
The presence of a co-orbital companion induces the splitting of the well known Keplerian spin-orbit resonances. It leads to chaotic rotation when those resonances overlap.
We present ALMA cycle 0 observations of the luminous merger VV 114. One of the main goals is to investigate mechanisms of molecular line ratio enhancement. Regions with the high 12CO (1–0)/13CO (1–0) and 12CO (3–2)/12CO (1–0) is located at a central filamentary structure (∼6 kpc) in VV 114. The filament consists of the eastern nucleus and the overlap region, where the galaxy disks are colliding. We also investigate these molecular line ratios on the Kennicutt-Schmidt law. VV 114 fills a gap between the “starburst” sequence and the “normal disk” sequence, and regions with the high ratios show the high ΣSFR and ΣH2. We suggest that the high ratios in VV 114 are due to star-forming activities in the both progenitor's nuclei and the merger-induced overlap region.
The formation of planetesimals and large bodies in circumstellar discs can be referred to the stage of massive unstable disc emerging due to the gravitational collapse in the molecular cloud. We have simulated the dynamics of gas and boulder clumps in such systems. The features of instability development in massive disc is discussed. Unlike medium-massive discs the massive disc can provide conditions for simultaneous formation of several clumps as a result of overdensity ring fragmentation. We found regimes where 3, 2 or 1 overdensity ring appear in the disc and then fragment into clumps collecting about a half of the disc mass.