De Lorenzi, Flavio, Gerhard, Ortwin, Saglia, Roberto P., Sambhus, Niranjan, Debattista, Victor P., Pannella, Maurilio, ...
We present a dynamical study of NGC 4697, an almost edge-on, intermediate-luminosity, E4 elliptical galaxy, combining new surface brightness photometry, new as well as published long-slit absorption...
Expansion velocities and core masses of bright planetary nebulae in the Virgo cluster (2008)
Arnaboldi, Magda, Doherty, Michelle, Gerhard, Ortwin, Ciardullo, Robin, Aguerri, J. Alfonso, Feldmeier, John J., ...
The line-of-sight velocities and [OIII] 5007 AA expansion velocities are measured for 11 planetary nebulae (PNs) in the Virgo cluster core, at 15 Mpc distance, with the FLAMES spectrograph on the ESO...
Expansion velocities and core masses of bright planetary nebulae in the Virgo Cluster (2008)
Arnaboldi, Magda, Doherty, Michelle, Gerhard, Ortwin, Ciardullo, Robin, Aguerri, J. Alfonso L., Feldmeier, John J., ...
Rattenbury, Nicholas J., Mao, Shude, Debattista, Victor P., Sumi, Takahiro, Gerhard, Ortwin, De Lorenzi, Flavio
Red clump giants in the Galactic bulge are approximate standard candles and hence they can be used as distance indicators. We compute the proper motion dispersions of RCG stars in the Galactic bulge...
Gerhard, Ortwin, Arnaboldi, Magda, Freeman, Kenneth C., Okamura, Sadanori, Kashikawa, Nobunari, Yasuda, Naoki
The Coma cluster is the richest and most compact of the nearby clusters, yet there is growing evidence that its formation is still on-going. With a new multi-slit imaging spectroscopy technique...
Kinematic Substructures in the Coma Cluster Core as traced by Intracluster Planetary Nebulae (2007)
Arnaboldi, Magda, Gerhard, Ortwin, Freeman, Kenneth C., Kashikawa, Nobunari, Okamura, Sadanori, Yasuda, Naoki
The Coma cluster is the richest and most compact of the nearby clusters, yet there is growing evidence that its formation is still on-going. A sensitive probe of this evolution is the dynamics of...
Planetary Nebulae Surveys Beyond the Local Group (2007)
Distant planetary nebulae (PNe) are used to measure distances through the PN luminosity function, as kinematic tracers in determining the mass distribution in elliptical galaxies, and most recently,...
De Lorenzi, Flavio, Debattista, Victor, Gerhard, Ortwin, Sambhus, Niranjan
We describe a made-to-measure algorithm for constructing N-particle models of stellar systems from observational data (Chi-Squared-M2M), extending earlier ideas by Syer and Tremaine. The algorithm...
Virgo's intracluster globular clusters as seen by the advanced camera for surveys (2007)
Williams, Benjamin F., Ciardullo, Robin, Durrell, Patrick R., Feldmeier, John J., Sigurdsson, Steinn, Vinciguerra, Matt, ...
The metallicity distribution of intracluster stars in Virgo (2007)
Williams, Benjamin F., Ciardullo, Robin, Durrell, Patrick R., Vinciguerra, Matt, Feldmeier, John J., Jacoby, George H., ...
The resolved stellar populations of a dwarf spheroidal galaxy in the Virgo cluster (2007)
Durrell, Patrick R., Williams, Benjamin F., Ciardullo, Robin, Feldmeier, John J., Von Hippel, Ted, Sigurdsson, Steinn, ...
Murante, Guiseppe, Giovalli, Martina, Gerhard, Ortwin, Arnaboldi, Magda, Borgani, Stefano, Dolag, Klaus
Murante, Guiseppe, Giovalli, Martina, Gerhard, Ortwin, Arnaboldi, Magda, Borgani, Stefano, Dolag, Klaus
Arnaboldi, Magda, Gerhard, Ortwin, Okamura, Sadanori, Kashikawa, Nobunari, Yasuda, Naoki, Freeman, Kenneth C.
Rattenbury, Nicholas J., Mao, Shude, Debattista, Victor P., Sumi, Takahiro, Gerhard, Ortwin, De Lorenzi, Flavio
Division VII: galactic system (2007)
Whitelock, Patricia, Sarajedini, Ata, Gerhard, Ortwin, Giersz, Mirek, Meylan, Georges, Nordström, Birgitta, ...
Commission 33: structure and dynamics of the galactic system (2007)
Whitelock, Patricia, Gerhard, Ortwin, Efremov, Yuri, Evans, Wyn, Flynn, Chris, Grindlay, Josh, ...
The Resolved Stellar Populations of a Dwarf Spheroidal Galaxy in the Virgo Cluster (2006)
Durrell, Patrick R., Williams, Benjamin F., Ciardullo, Robin, Feldmeier, John J., Von Hippel, Ted, Sigurdsson, Steinn, ...
We report on the discovery of a faint (M_V ~ -10.6 +/- 0.2) dwarf spheroidal galaxy on deep F606W and F814W Hubble Space Telescope images of a Virgo intracluster field. The galaxy is easily resolved...
The Metallicity Distribution of Intracluster Stars in Virgo (2006)
Williams, Benjamin F., Ciardullo, Robin, Durrell, Patrick R., Vinciguerra, Matt, Feldmeier, John J., Jacoby, George H., ...
We have used the Hubble Space Telescope's Advanced Camera for Surveys (ACS) to detect and measure ~5300 stars in a single intracluster field in the Virgo Cluster. By performing F606W and F814W...
Virgo's Intracluster Globular Clusters as Seen by the Advanced Camera for Surveys (2006)
Williams, Benjamin F., Ciardullo, Robin, Durrell, Patrick R., Feldmeier, John J., Sigurdsson, Steinn, Vinciguerra, Matt, ...
We report the discovery of 4 candidate intracluster globular clusters (IGCs) in a single deep HST ACS field of the Virgo Cluster. We show that each cluster is roughly spherical, has a magnitude near...
Mass Distribution and Bulge Formation in the Milky Way Galaxy (2006)
In its first part, this paper summarizes recent work on the mass and shape of the Galactic dark halo. The second part presents a review of the large-scale structure of the Milky Way, and of the...
Kinematic substructures in the coma cluster core as traced by intracluster planetary nebulae (2006)
Arnaboldi, Magda, Gerhard, Ortwin, Freeman, Kenneth C., Kashikawa, Nobunari, Okamura, Sadanori, Yasuda, Naoki
The radial velocity experiment (RAVE) : first data release (2006)
Steinmetz, Matthias, Zwitter, Tomaz, Siebert, Arnaud, Watson, Fred G., Freeman, Kenneth C., Munari, Ulisse, ...
We present the first data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity,...
The radial velocity experiment (RAVE) : first data release (2006)
Steinmetz, Matthias, Zwitter, Tomaz, Siebert, Arnaud, Watson, Fred G., Freeman, Kenneth C., Munari, Ulisse, ...
We present the first data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity,...
The radial velocity experiment (RAVE) : first data release (2006)
Steinmetz, Matthias, Zwitter, Tomaz, Siebert, Arnaud, Watson, Fred G., Freeman, Kenneth C., Munari, Ulisse, ...
We present the first data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity,...
The radial velocity experiment (RAVE) : first data release (2006)
Steinmetz, Matthias, Zwitter, Tomaz, Siebert, Arnaud, Watson, Fred G., Freeman, Kenneth C., Munari, Ulisse, ...
We present the first data release of the Radial Velocity Experiment (RAVE), an ambitious spectroscopic survey to measure radial velocities and stellar atmosphere parameters (temperature, metallicity,...
Sambhus, Niranjan, Gerhard, Ortwin, Mendez, Roberto H.
We have analysed the magnitudes, kinematics and positions of a complete sample of 320 PNs in the elliptical galaxy NGC 4697. We show (i) that the PNs in NGC 4697 do not constitute a single population...
Arnaboldi, Magda, Gerhard, Ortwin, Aguerri, J. Alfonso L., Freeman, Kenneth C., Napolitano, Nicola R., Okamura, Sadanori, ...
Radial velocities of 40 intracluster planetary nebulae (ICPNe) in the Virgo cluster were obtained with the new multi-fiber FLAMES spectrograph on UT2 at VLT. For the first time, the lambda 4959 AA...
Detection of Intracluster Planetary Nebulae in the Coma Cluster (2005)
Gerhard, Ortwin, Arnaboldi, Magda, Freeman, Kenneth C., Kashikawa, Nobunari, Okamura, Sadanori, Yasuda, Naoki
[OIII] lambda 5007AA emission lines of 16 intracluster planetary nebulae candidates in the Coma cluster were detected with a Multi-Slit Imaging Spectroscopy (MSIS) technique using FOCAS on the Subaru...
Sub-Galactic Clumps at High Redshift: A Fragmentation Origin? (2004)
Immeli, Andreas, Samland, Markus, Westera, Pieter, Gerhard, Ortwin
We investigate the origin of the clumpy structures observed at high redshift, like the chain galaxies. We use a three dimensional chemodynamical simulation describing the dynamics of stars and a...
Bissantz, Nicolai, Debattista, Victor P., Gerhard, Ortwin
We build a stellar-dynamical model of the Milky Way barred bulge and disk, using a newly implemented adaptive particle method. The underlying mass model has been previously shown to match the...
Gas Physics, Disk Fragmentation, and Bulge Formation in Young Galaxies (2003)
Immeli, Andreas, Samland, Markus, Gerhard, Ortwin, Westera, Pieter
We investigate the evolution of star-forming gas-rich disks, using a 3D chemodynamical model including a dark halo, stars, and a two-phase interstellar medium with feedback processes from the stars....
Formation of the Galactic Halo (2003)
Recent observational and theoretical work suggests that the formation of the Galactic stellar halo involved both dissipative processes and the accretion of subfragments. With present data, the...
Castro-Rodriguez, Nieves, Aguerri, J. Alfonso L., Arnaboldi, Magda, Gerhard, Ortwin, Freeman, Kenneth C., Napolitano, Nicola R., ...
We have observed emission line objects located in a 0.26 deg^2 field in the M96 (Leo) group, coincident with the intergalactic HI cloud. The emission line objects were selected using the same...
Zwart, Simon Portegies, McMillan, Steve, Gerhard, Ortwin
We use direct N-body simulations to study the inspiral and internal evolution of dense star clusters near the Galactic center. These clusters sink toward the center due to dynamical friction with the...
The Formation of a Disk Galaxy within a Growing Dark Halo (2003)
Samland, Markus, Gerhard, Ortwin
We present a dynamical model for the formation and evolution of a massive disk galaxy, within a growing dark halo whose mass evolves according to cosmological simulations of structure formation. The...
Napolitano, Nicola R., Pannella, Maurilio, Arnaboldi, Magda, Gerhard, Ortwin, Aguerri, J. Alfonso L., Freeman, Kenneth C., ...
Gas Dynamics in the Milky Way: Second Pattern Speed and Large-Scale Morphology (2002)
Bissantz, Nicolai, Englmaier, Peter, Gerhard, Ortwin
We present new gas flow models for the Milky Way inside the solar circle. To this end we use SPH simulations in gravitational potentials determined from the NIR luminosity distribution (including...
Isolated Star Formation: A Compact HII Region in the Virgo Cluster (2002)
Gerhard, Ortwin, Arnaboldi, Magda, Freeman, Kenneth C., Okamura, Sadanori
We report on the discovery of an isolated, compact HII region in the Virgo cluster. The object is located in the diffuse outer halo of NGC 4388, or could possibly be in intracluster space. Star...
The Pattern Speed of the OH/IR Stars in the Milky Way (2002)
Debattista, Victor P., Gerhard, Ortwin, Sevenster, Maartje N.
We show how the continuity equation can be used to determine pattern speeds in the Milky Way Galaxy (MWG). This method, first discussed by Tremaine & Weinberg in the context of external galaxies,...
A Pattern Speed in the Galaxy's OH/IR Stars (2002)
Debattista, Victor P., Gerhard, Ortwin, Sevenster, M. N.
We use the Tremaine-Weinberg method, adapted to the Milky Way, to measure a pattern speed in OH/IR stars located in the inner MW.
Colour Evolution of Disk Galaxy Models from z=4 to z=0 (2002)
Westera, Pieter, Samland, Markus, Buser, Roland, Gerhard, Ortwin
We calculate synthetic UBVRIJHKLM images, integrated spectra and colours for the disk galaxy formation models of Samland & Gerhard (2002), from redshift z=4 to z=0. Two models are considered, an...
Dynamical Masses of Elliptical Galaxies (2002)
Recent progress in the dynamical analysis of elliptical galaxy kinematics is reviewed. Results reported briefly include (i) the surprisingly uniform anisotropy structure of luminous ellipticals, (ii)...
The Milky Way has a barred bulge. This article summarizes the current understanding of the main structural parameters and pattern speed of the bar, and compares predicted values for the microlensing...
Mass distribution in our Galaxy (2002)
This article summarizes recent work on the luminosity and mass distribution of the Galactic bulge and disk, and on the mass of the Milky Way's dark halo. A new luminosity model consistent with the...
Spiral arms, bar shape and bulge microlensing in the Milky Way (2001)
Bissantz, Nicolai, Gerhard, Ortwin
A new model for the luminosity distribution in the inner Milky Way is found, using a non-parametric penalized maximum-likelihood algorithm to deproject a dereddened COBE/DIRBE L-band map of the inner...
Dynamical family properties and dark halo scaling relations of giant elliptical galaxies (2000)
Gerhard, Ortwin, Kronawitter, Andi, Saglia, R. P., Bender, Ralf
Based on a uniform dynamical analysis of line-profile shapes for 21 luminous round elliptical galaxies, we have investigated the dynamical family relations of ellipticals: (i) The circular velocity...
Structure and Mass Distribution of the Milky Way Bulge and Disk (2000)
This article summarizes the structural parameters of the Galactic bulge and disk, and discusses the interpretation of the bulge microlensing observations and the determination of the Milky Way's...
Dynamical masses, time-scales, and evolution of star clusters (2000)
This review discusses (i) dynamical methods for determining the masses of Galactic and extragalactic star clusters, (ii) dynamical processes and their time-scales for the evolution of clusters,...
The Galactic Center He I Stars: Remains of a Dissolved Young Cluster? (2000)
A massive young star cluster, initially embedded in its parent molecular cloud, will spiral into the Galactic Center from $\lta 30m_6^{1/2}\pc$ during the life-time of its most massive stars, if the...
Is Galactic Structure Compatible with Microlensing Data? (2000)
Binney, James, Bissantz, Nicolai, Gerhard, Ortwin
We generalize to elliptical models the argument of Kuijken (1997), which connects the microlensing optical depth towards the Galactic bulge to the Galactic rotation curve. When applied to the latest...
The orbital structure and potential of NGC 1399 (1999)
Saglia, R. P., Kronawitter, Andi, Gerhard, Ortwin, Bender, Ralf
Accurate and radially extended stellar kinematic data reaching R=97'' from the center are presented for the cD galaxy of Fornax, NGC 1399. The stellar rotation is small (
Dynamics of the Boxy Elliptical Galaxy NGC 1600 (1999)
Matthias, Michael, Gerhard, Ortwin
We use three--integral models to infer the distribution function (DF) of the boxy E3-E4 galaxy NGC 1600 from surface brightness and line profile data on the minor and major axes. We assume...
Gas Dynamics and Large-Scale Morphology of the Milky Way Galaxy (1998)
Englmaier, Peter, Gerhard, Ortwin
We present a new model for the gas dynamics in the galactic disk inside the Sun's orbit. Quasi-equilibrium flow solutions are determined in the gravitational potential of the deprojected COBE NIR bar...
Dynamical Mass Determination for Elliptical Galaxies (1998)
Gerhard, Ortwin, Jeske, Gunther, Saglia, R. P., Bender, Ralf
The mass and anisotropy of an elliptical galaxy can be simultaneously determined from velocity dispersion and line profile shape measurements. We describe the principles, techniques, and limitations...
Gerhard, Ortwin, Binney, James, Zhao, HongSheng
We summarize recent work on the structure and dynamics of the Galactic bar and inner disk. Current work focusses on constructing a quantitative model which integrates NIR photometry, source count...
Breaking the degeneracy between anisotropy and mass: The dark halo of the E0 galaxy NGC 6703 (1997)
Gerhard, Ortwin, Jeske, Gunther, Saglia, R. P., Bender, Ralf
(abridged) We have measured line-of-sight velocity profiles (VPs) in the E0 galaxy NGC 6703 out to 2.6 R_e. From these data we constrain the mass distribution and the anisotropy of the stellar orbits...
Baryonic Dark Halos: A Model With Machos And Cold Gas Globules (1997)
. The dark matter in the halos of galaxies may well be baryonic, and much of the mass within them could be in the form of clusters of substellar objects within which are embedded cold gas globules....
Two modes of gas flow in a single barred galaxy (1996)
Englmaier, Peter, Gerhard, Ortwin
We investigate stationary gas flows in a fixed, rotating barred potential. The gas is assumed to be isothermal with an effective sound speed c_s, and the equations of motion are solved with smoothed...
The photometric structure of the inner Galaxy (1996)
Binney, James, Gerhard, Ortwin, Spergel, David
The light distribution in the inner few kiloparsecs of the Milky Way is recovered non-parametrically from a dust-corrected near-infrared COBE/DIRBE surface brightness map of the inner Galaxy. The...
The photometric structure of the inner Galaxy (1996)
The light distribution in the inner few kiloparsecs of the Milky Way is recovered nonparametrically from a dust-corrected near-infrared COBE/DIRBE surface brightness map of the inner Galaxy. The best...
Dynamics of the Bar at the Galactic Centre (1996)
The now substantial evidence for a rotating bar in the inner Galaxy and its dynamical implications are reviewed.
Baryonic Dark Halos: A Model with MACHOS and Cold Gas Globules (1995)
The dark matter in the halos of galaxies may well be baryonic, and much of the mass within them could be in the form of clusters of substellar objects within which are embedded cold gas globules....
Baryonic Dark Halos: Machos and Cold Gas? (1995)
We consider the possibility that the dark matter in the halos of galaxies may be in the form of clusters of \macho s within which are embedded cold, dense gas clouds. Microlensing experiments have...
On the deprojection of the Galactic bulge (1995)
Binney, James, Gerhard, Ortwin
An algorithm is developed and tested for the problem posed by photometric observations of the bulge of the Milky Way. The latter subtends a non-trivial solid angle on the sky, and we show that this...
On the deprojection of axisymmetric bodies (1995)
Gerhard, Ortwin, Binney, James
Axisymmetric density distributions are constructed which are invisible when viewed from a range of inclination angles $i$. By adding such distributions to a model galaxy, it can be made either disky...