P. T. de Zeeuw

The discovery of a galaxy-wide superwind from a young massive galaxy at redshift z ≈ 3

High-velocity galactic outflows, driven by intense bursts of star formation and black hole accretion, are processes invoked by current theories of galaxy formation to terminate star formation in the most massive galaxies and to deposit heavy elements in the intergalactic medium. From existing observational evidence (for high-redshift galaxies) it is unclear whether such outflows are localized to regions of intense star formation just a few kiloparsecs in extent, or whether they instead have a significant impact on the entire galaxy and its surroundings. Here we present two-dimensional spectroscopy of a star-forming galaxy at redshift z = 3.09 (seen 11.5u2009gigayears ago, when the Universe was 20 per cent of its current age): its spatially extended Lyα line emission appears to be absorbed by Hu2009i in a foreground screen covering the entire galaxy, with a lateral extent of at least 100u2009kpc and remarkable velocity coherence. This screen was ejected from the galaxy during a starburst several 108 years earlier and has subsequently swept up gas from the surrounding intergalactic medium and cooled. This demonstrates the galaxy-wide impact of high-redshift superwinds.

Recovery of the internal orbital structure of galaxies

We construct axisymmetric and triaxial galaxy models with a phase-space distribution function that depends on linear combinations of the three exact integrals of motion for a separable potential. These Abel models, first introduced by Dejonghe & Laurent and subsequently extended by Mathieu & Dejonghe, are the axisymmetric and triaxial generalizations of the well-known spherical Osipkov-Merritt models. We show that the density and higher order velocity moments, as well as the line-of-sight velocity distribution of these models can be calculated efficiently and that they capture much of the rich internal dynamics of early-type galaxies. We build a triaxial and oblate axisymmetric galaxy model with projected kinematics that mimic the two-dimensional kinematic observations that are obtained with integral-field spectrographs such as SAURON. We fit the simulated observations with axisymmetric and triaxial dynamical models constructed with our numerical implementation of Schwarzschild orbit-superposition method. We find that Schwarzschild method is able to recover the internal dynamics and three-integral distribution function of realistic models of early-type galaxies.

Indication for an intermediate-mass black hole in the globular cluster NGC 5286 from kinematics

Context. Intermediate-mass black holes (IMBHs) fill the gap between stellar-mass black holes and supermassive black holes (SMBHs). The existence of the latter is widely accepted, but there are only few detections of intermediate-mass black holes (10-10M ) so far. Simulations have shown that intermediate-mass black holes may form in dense star clusters, and therefore may still be present in these smaller stellar systems. Also, extrapolating the M- σ scaling relation to lower masses predicts intermediate-mass black holes in systems with σ ∼ 10-20 km s such as globular clusters. Aims. We investigate the Galactic globular cluster NGC 5286 for indications of a central intermediate-mass black hole using spectroscopic data from VLT/FLAMES*, velocity measurements from the Rutgers Fabry Perot at CTIO, and photometric data from HST/ACS. Methods. We compute the photometric center, a surface brightness profile, and a velocity-dispersion profile. We run analytic spherical and axisymmetric Jeans models with different central black-hole masses, anisotropy, mass-to-light ratio, and inclination. Further, we compare the data to a grid of N-body simulations without tidal field. Additionally, we use one N-body simulation to check the results of the spherical Jeans models for the total cluster mass. Results. Both the Jeans models and the N-body simulations favor the presence of a central black hole in NGC 5286 and our detection is at the 1-to 1.5-σ level. From the spherical Jeans models we obtain a best fit with black-hole mass M = (1.5 ± 1.0) × 10 M. The error is the 68% confidence limit from Monte Carlo simulations. Axisymmetric models give a consistent result. The best fitting N-body model is found with a black hole of 0.9% of the total cluster mass (4.38 ± 0.18) × 10 M , which results in an IMBH mass of M = (3.9 ± 2.0) × 10 M. Jeans models give values for the total cluster mass that are lower by up to 34% due to a lower value of M/L. Our test of the Jeans models with N-body simulation data shows that the discrepancy in the total cluster mass has two reasons: The influence of a radially varying M/L profile, and underestimation of the velocity dispersion as the measurements are limited to bright stars, which have lower velocities than fainter stars. We conclude that detection of IMBHs in Galactic globular clusters remains a challenging task unless their mass fractions are above those found for SMBHs in nearby galaxies.

Supermassive black holes from OASIS and SAURON integral-field kinematics

Supermassive black holes are a key element in our understanding of how galaxies form. Most of the progress in this very active field of research is based on just � 30 determi- nations of black hole mass, accumulated over the past decade. We illustrate how integral-field spectroscopy, and in particular our OASIS modeling effort, can help improve the current situation.

Optical BVI imaging and H I synthesis observations of the dwarf irregular Galaxy ESO 364-G029

As part of an effort to enlarge the number of well-studied Magellanic-type galaxies, we obtained broadband optical imaging and neutral hydrogen radio synthesis observations of the dwarf irregular galaxy ESO 364-G 029. The optical morphology characteristically shows a bar-like main body with a one-sided spiral arm, an approximately exponential light distribution, and offset photometric and kinematic centers. The HI distribution is mildly asymmetric and, although slightly offset from the photometric center, roughly follows the optical brightness distribution, extending to over 1.2 Holmberg radii (where mu_B = 26.5 mag/arcsec^2). In particular, the highest HI column densities closely follow the bar, one-arm spiral, and a third optical extension. The rotation is solid-body in the inner parts but flattens outside of the optical extent. The total HI flux F_HI = 23.1 pm 1.2 Jy km/s, yielding a total HI mass M_HI= (6.4 pm 1.7) x 10^8 Msun (for a distance D = 10.8 pm 1.4 Mpc) and a total HI mass-to-blue-luminosity ratio M_HI/L_B = (0.96 pm 0.14) Msun / Lsun,B (distance independent). The HI data suggest a very complex small-scale HI structure, with evidence of large shells and/or holes, but deeper observations are required for a detailed study. Follow-up observations are also desirable for a proper comparison with the Large Magellanic Cloud, where despite an optical morphology very similar to ESO 364-G 029 the HI bears little resemblance to the optical.

The continuing formation of early‐type galaxies: an H I survey

A deep H I survey of nearby early‐type galaxies carried out with the Westerbork Radio Synthesis Telescope has shown that, contrary to expectation, neutral hydrogen is a significant constituent of the ISM in this type of objects located in low density environment. The studied galaxies are part of a representative sample of nearby E and SO for which integral‐field spectroscopy using the SAURON spectrograph is available. We present preliminary results on the comparison of the characteristics of the H I with those of the molecular and ionised gas as well as the stellar dynamics and population.

Mapping young stellar populations toward Orion with Gaia DR1

In this work we use the first data release of the Gaia mission to explore the three-dimensional arrangement and age ordering of the many stellar groups toward the Orion OB association, aiming at a new classification and characterization of the stellar population not embedded in the Orion A and B molecular clouds. We make use of the parallaxes and proper motions provided in the Tycho Gaia Astrometric Solution (TGAS) subset of the Gaia Data Release 1 (DR1) catalog and of the combination of Gaia DR1 and 2MASS photometry. In TGAS, we find evidence for the presence of a young population at a parallax ϖ ~ 2.65 mas, which is loosely distributed around the following known clusters: 25 Ori, ϵ Ori, and σ Ori, and NGC 1980 ( ι Ori) and the Orion Nebula Cluster (ONC). The low mass counterpart of this population is visible in the color magnitude diagrams constructed by combining Gaia DR1 G -band photometry and 2MASS. We study the density distribution of the young sources in the sky using a kernel density estimation (KDE). We find the same groups as in TGAS and also some other density enhancements that might be related to the recently discovered Orion X group, Orion dust ring, and λ Ori complex. The maps also suggest that the 25 Ori group presents a northern elongation. We estimated the ages of this population using a Bayesian isochronal fitting procedure assuming a unique parallax value for all the sources, and we inferred the presence of an age gradient going from 25 Ori (13−15 Myr) to the ONC (1−2 Myr). We confirmed this age ordering by repeating the Bayesian fit using the Pan-STARRS1 data. Intriguingly, the estimated ages toward the NGC 1980 cluster span a broad range of values. This can either be due to the presence of two populations coming from two different episodes of star formation or to a large spread along the line of sight of the same population. Some confusion might arise from the presence of unresolved binaries, which are not modeled in the fit, and usually mimic a younger population. Finally, we provisionally relate the stellar groups to the gas and dust features in Orion. Our results form the first step toward using Gaia data to unravel the complex star formation history of the Orion region in terms of the various star formation episodes, their duration, and their effects on the surrounding interstellar medium.

The stellar structure of early-type galaxies: a wide-field Mitchell Spectrograph view

N. F. Boardman1†, A. Weijmans1, R. C. E. van den Bosch2, L. Zhu2, A. Yildirim2, G. van de Ven2, M. Cappellari3, P. T. de Zeeuw4,5, E. Emsellem4, D. Krajnović6 and T. Naab7 School of Physics and Astronomy, University of St Andrews, KY16 9SS UK Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany Sub-department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany Sterrewacht Leiden, Leiden University, Postbus 9513, 2300 RA, Leiden, The Netherlands Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany

Formation of slowly rotating elliptical galaxies in major mergers - a resolution study

We study resolution effects in numerical simulations of gas‐rich (20% of the total baryonic mass) major mergers, and show that the formation of slowly‐rotating elliptical galaxies requires a resolution that is beyond the present‐day standards to be properly modelled. Our findings show that a high‐enough resolution is required to accurately model the global properties of merger remnants and the evolution of their angular momentum. The role of wet mergers of spiral galaxies in the formation of slow‐rotating ellipticals may therefore have been underestimated.

Stellar populations of early-type galaxies in the ATLAS3D sample

ATLAS3D is a multi‐wavelength, volume‐limited survey of 263 morphologically‐selected early‐type galaxies within a distance of 42 Mpc and complete to MK⩽−21.5. Here we present the ATLAS3D project and our first results on the stellar populations of galaxies in the ATLAS3D sample based on SAURON integral‐field spectroscopy. We show relations between integrated line‐strength indices and stellar velocity dispersion σ in the range 55⩽σ(km/s)⩽350. We derive simple‐stellar‐population‐equivalent age, metallicity and α/Fe abundance ratio and discuss their relation to stellar velocity dispersion, environment and galaxy internal kinematics. These preliminary results indicate that slow rotators tend to be older and have less variation in age than fast rotators. We also find that galaxies in lower density environments are on average younger than those in denser environments, as found by other authors.