Near-Infrared Surface Photometry of Bulges and Disks of Spiral Galaxies. The Data

We present optical and near-infrared (NIR) surface brightness and colour profiles,in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 degrees. We describe in detail the observations and the determination of colour parameters. Calibrated monochromatic and real-colour images are presented, as well as colour index maps. This data set, tailored for the study of the population characteristics of galaxy bulges, provides useful information on the colours of inner disks as well. In related papers, we have used them to quantify colour gradients in bulges, and age differentials between bulge and inner disk.Comment: 18 pages Latex with 2 postscript figures. Accepted for New Astronomy. This is an electronic paper; a complete preprint, including all of the tables and figures can be found at ftp://www.astro.rug.nl/peletier/newast/newast.htm

The kinematics and morphology of NGC 520: One, two, or three galaxies

The peculiar galaxy NGC 520 (Arp 157) is often interpreted as an interacting pair of galaxies. The identification of the two bulges and overall morphology of the two galaxies has long been a puzzle which the authors attempt to solve here. New longslit optical spectroscopy and near-infrared images of NGC 520 are presented. These data suggest that the northwest peak is the bulge of one of two galaxies in the system. The other larger bulge is clearly evident in the K band image in the middle of the dust lane. The stellar radial velocity profile in the central 10 seconds of the larger bulge is consistent with counterrotation seen in the molecular gas component. This kinematic subsystem could be the remains of a merged gas-rich irregular

Line-of-sight velocity distributions of elliptical galaxies from collisionless mergers

We analyse the skewness of the line-of-sight velocity distributions in model elliptical galaxies built through collisionless galaxy mergers. We build the models using large N-body simulations of mergers between either two spiral or two elliptical galaxies. Our aim is to investigate whether the observed ranges of skewness coefficient (h3) and the rotational support (V/sigma), as well as the anticorrelation between h3 and V, may be reproduced through collisionless mergers. Previous attempts using N-body simulations failed to reach V/sigma ~ 1-2 and corresponding high h3 values, which suggested that gas dynamics and ensuing star formation might be needed in order to explain the skewness properties of ellipticals through mergers. Here we show that high V/sigma and high h3 are reproduced in collisionless spiral-spiral mergers whenever a central bulge allows the discs to retain some of their original angular momentum during the merger. We also show that elliptical-elliptical mergers, unless merging from a high-angular momentum orbit, reproduce the strong skewness observed in non-rotating, giant, boxy ellipticals. The behaviour of the h3 coefficient therefore associates rapidly-rotating disky ellipticals to disc-disc mergers, and associates boxy, slowly-rotating giant ellipticals to elliptical-elliptical mergers, a framework generally consistent with the expectations of hierarchical galaxy formation.Comment: 5 pages, 4 figures, MNRAS Letters, in pres

Reality Meets Fiction

The development of a film rooted in family conflicts and an exploration of the nature of authorship

Cationic ordering control of magnetization in Sr2FeMoO6 double perovskite

The role of the synthesis conditions on the cationic Fe/Mo ordering in Sr2FeMoO6 double perovskite is addressed. It is shown that this ordering can be controlled and varied systematically. The Fe/Mo ordering has a profound impact on the saturation magnetization of the material. Using the appropriate synthesis protocol a record value of 3.7muB/f.u. has been obtained. Mossbauer analysis reveals the existence of two distinguishable Fe sites in agreement with the P4/mmm symmetry and a charge density at the Fe(m+) ions significantly larger than (+3) suggesting a Fe contribution to the spin-down conduction band. The implications of these findings for the synthesis of Sr2FeMoO6 having optimal magnetoresistance response are discussed.Comment: 9 pages, 4 figure

The shell elliptical NGC2865: evolutionary population synthesis of a kinematically distinct core

We report on the discovery of a rapidly co-rotating stellar and gas component in the nucleus of the shell elliptical NGC2865. The stellar component extends ~ 0.51/h100 kpc along the major axis, and shows depressed velocity dispersion and absorption line profiles skewed in the opposite sense to the mean velocity. Associated with it is a young stellar population with enhanced \hbeta, lowered Mg and same Fe indices relative to the underlying elliptical. Its recent star formation history is constrained by considering ``bulge+burst'' models under 4 physically motivated scenarios, using evolutionary population synthesis. Scenarios in which the nuclear component is formed over a Hubble time or recently from continuous gas inflow are ruled out. Our results argue for a gas-rich accretion or merger origin for the shells and kinematic subcomponent in NGC2865. Arguments based on stellar populations and gas dynamics suggest that one of the progenitors is likely a Sb or Sc spiral. We demonstrate that despite the age and metallicity degeneracy of the underlying elliptical, the age and metallicity of the kinematic subcomponent can be constrained. This work strengthens the link between KDCs and shells, and demonstrates that a KDC can be formed from a late merger.Comment: 26 pages, accepted for publication in MNRA