Studies of dynamically close pairs of galaxies can serve as a powerful probe of the galaxy merger rate and its evolution. Here we present a large sample of dynamically close pairs of galaxies selected in the K-band from the UKIDSS LAS. These data span ~ 175 deg2 on the sky in the 2dFGRS equatorial region (10h < RA < 14h). Combining the 2dFGRS redshifts with those from the SDSS, our K-band selected catalog is > 90% spectroscopically complete at KAB < 16.4. In this study, we focus on quantifying the relative contributions of wet, dry, and mixed mergers to the stellar mass buildup of galaxies over the past 1-2 Gyr.

This work investigates the density of in-falling prominence material following the 7th June 2011 eruption. Both the evolution and the distribution of the density is analysed in five discreet “blobs” of material. The density appears to be remarkably uniform, both spatially within the blobs, and temporally over the course of the descent of each, although a slight concentration of material towards the leading edge is noted in some cases. Online material is available at bit.ly/jackblob

We present the preliminary analysis of clustering of a sample of 1157 radio-identified galaxies from Machalski & Condon (1999). We found that for separations 2–15 h−1 Mpc their redshift space autocorrelation function ξ(s) can be approximated by the power law with the correlation length ~3.75h−1 Mpc and slope γ ~ 1.8. The correlation length for radiogalaxies is found to be lower and the slope steeper than the corresponding parameters of the control sample of optically observed galaxies. Analysis the projected correlation function Ξ(r) displays possible differences in the clustering properties between active galactic nuclei (AGN) and starburst (SB) galaxies.

We have investigated the flow pattern that arises past (proto)planets embedded in the nebula disk during its formation. We consider the regime where the planet mass is large enough to gravitationally perturb the gas (≳0.01 Earth masses), but not too large to open a gap or accrete unlimited amounts of gas from the disk. We consider both inviscid and viscid flows and aim to understand the flow pattern on the scales of the Bondi radius. Having described the flow pattern of the gas, we integrate trajectories of small, solid particles. In agreement with previous findings, we show that the ensuing accretion rates can be high—although, due to radial drift motions, pebble accretion is not necessarily an efficient mechanism.

Past investigations have shown a connection between the properties of Type Ia supernovae (SNe Ia) and their host galaxies. We refine these studies using ultraviolet through mid-infrared observations of both nearby and distant SN Ia hosts. We present new results showing that the properties of SNe Ia, both intrinsic and with respect to their use as distance indicators, appear to depend on a combination of metallicity, stellar age, and star-formation rate of the host. We suggest that the stellar population age and location of the supernova progenitor all can play a roll in using SNe Ia as precision distance indicators, and advocate that a multiwavelength approach is one way to disentangle the different influences, resulting in an improvement of 8% in distance measurements.

We observed with the Submillimeter Array and IRAM 30 m telescope three high-mass star-forming regions in different evolutionary stages in the W3 high-mass star formation complex. These regions, i.e. W3 SMS1 (W3 IRS5), SMS2 (W3 IRS4) and SMS3, are located within the same large-scale environment, which allows us to study rotation and outflows as well as chemical properties in an evolutionary sense. While we find multiple mm continuum sources toward all regions, these three subregions exhibit different dynamical and chemical properties, which indicates that they are in different evolutionary stages. Even within each sub-region, massive cores of different ages are found, e.g. in SMS2, sub-sources from the most evolved UCHii region to potential starless cores exist within 30 000 AU (left panel, Fig. 1). Outflows and rotational structures are found in SMS1 and SMS2. Evidence for interactions between the molecular cloud and the HII regions is found in the 13CO channel maps (right panel, Fig. 1), which may indicate triggered star formation.

We present VLBI maps of the 6.7 GHz methanol maser emission in 32 sources obtained using the Japanese VLBI Network (JVN) and the East-Asian VLBI Network (EAVN). All of the observed sources provide new VLBI maps, and the spatial morphologies have been classified into five categories similar to the results obtained from European VLBI Network observations (Bartkiewicz et al. 2009). The 32 methanol sources are being monitored to measure the relative proper motions of the methanol maser spots.

Lyman-α and extreme-ultraviolet radiation from exoplanet host stars are critically important for evaluating the phototchemistry of planetary atmospheres, but these emissions are largely or completely absorbed by hydrogen in the interstellar medium. We describe a new technique for estimating the intrinsic Lyman-α and EUV fluxes of F, G, K, and M stars using correlations with observable emission lines.

The helicity of cellular convective flows in a horizontal layer of compressible fluid (gas) heated from below and rotating about a vertical axis is studied using finite-difference numerical simulations. The medium is assumed to be polytropically stratified. An initial thermal perturbation is introduced so as to produce a system of Bénard-type hexagonal convection cells. The flow gradually becomes less ordered, and the mean helicity grows initially and decreases sharply after the substantial chaotisation of the flow. Given the Rayleigh and Prandtl numbers, the maximum value reached by the mean helicity increases with the decrease of the polytrope index and has a maximum at a certain rotational velocity of the layer.

It is shown with a particle simulation that the outer gap can be reproduced under a few simple assumptions. The simulation includes just the first principles, namely Maxwell's equations, a relativistic equation of motion with radiation drag, and electron-positron pair creation. We also suggest that the Y-point (the open-close boundary in the equator) is likely to be a place of heating and acceleration of plasma, and therefore it would cause high-energy emission. The dead zone along the separatrix of the oppositely directed current is found in the middle latitude region, which separates the outer gap and the polar cap accelerators.

Herbig Ae/Be objects, like their lower mass counterparts T Tauri stars, are seen to form a stable circumstellar disk which is initially gas-rich and could ultimately form a planetary system. We present Herschel SPIRE 460–1540 GHz spectra of five targets out of a sample of 13 young disk sources, showing line detections mainly due to warm CO gas.

We identified 132,684 clusters in the redshift range of 0.05 < z < 0.8 from SDSS DR8. The spectroscopic redshifts of 52,683 clusters have been included in the catalog using SDSS DR9 data. We found that BCGs are more luminous in richer clusters and at higher redshifts.

The inductive electric field is unjustifiably neglected in most models for pulsar electrodynamics; it cannot be screened by the magnetospheric plasma, and it is not small in comparison with the corotation electric field. The perpendicular component of the inductive electric field implies a drift motion that is inconsistent with corotation at any angular velocity. Some implications of the inductive electric field and the associated drift motion are discussed.

In response to the large number of exoplanet detections, the characterization of these planets has become a major focus of exoplanet science. Transiting planets are of particular interest as they allow us to investigate the transmission of their atmospheres. Our group uses ground-based facilities like the ESO/VLT to probe the atmosphere of hot Jupiters with the technique of spectrophotometry. In our preliminary results for the hot Jupiters WASP-17b and WASP-31b we find the reachable precision to be limited by instrumental systematic noise rather than photon noise. We discuss the source of the noise and suggest two approaches to correct it.

Several recent surveys (HERACLES, NGLS, KINGFISH, VNGS) have provided us with sensitive high-resolution observations of the molecular gas and dust content in spiral galaxies within 25 Mpc. I review recent results on the molecular gas content and its relation to star formation, as well as on the gas to dust ratio and the dust heating in spiral galaxies. I also present new results on the effect of environment on the molecular gas content of spiral galaxies.

Convection is simulated numerically based on two-dimensional Boussinesq equations for a fluid layer with a specially chosen stratification such that the convective instability is much stronger in a thin subsurface sublayer than in the remaining part of the layer. The developing convective flow has a small-scale component superposed onto a basic large-scale roll flow.

Population synthesis modeling of Type Ia supernova (SN Ia) progenitors suggests that multiple binary evolution channels may give rise to SNe Ia. Independently of the ignition mechanism, the type of progenitor system involved affects the circumstellar environment into which the explosion propagates, as well as the amount of solid angle blocked by the companion (for single-degenerate models). Using three-dimensional adaptive-mesh simulations of SNe Ia in binary systems, we discuss the effects of the progenitor system on the observable characteristics of SNe Ia and the impact of these effects on systematic errors in the use of SNe Ia as cosmic distance indicators.

The optical variability of a sample of 44 FSRQs and 18 SSRQs in the SDSS stripe 82 region is investigated by using the multi-epoch data covering nine years. The variabilities are clearly detected in each source with the amplitude in r band, from 0.18 to 3.46 mag. Twenty-five of 44 FSRQs show a bluer-when-brighter trend (BWB), while only one FSRQ shows a redder-when-brighter trend, which is in contrast to our previous results. Eight of 18 SSRQs display a BWB. We found an anti-correlation between the Eddington ratio and the variability amplitude in r band for SSRQs, which is similar to that in radio-quiet AGNs. This implies that the thermal emission from the accretion disk may be responsible for the variability in SSRQs.

Using the multi-wavelength data from AIA/SDO, we report a failed filament eruption, which was associated with an X1.9 flare, but without any distinct CME, coronal dimming or EUV wave. Some magnetic arches above the filament was observed distinctly in EUV channels, especially in 94 Å and 131 Å, before and during the filament eruption. Our results show that the overlying arcades expanded along with the ascent of the filament at first until they reached a projected height of about 49 Mm above the Suns surface, where they stopped. The following filament material was observed to be confined by the stopped EUV arches and not to escape from the Sun. These results support that the overlying arcades play an important role in preventing the filament to erupt outward successfully.