Publications by James Binney

Local kinematics and the local standard of rest

Monthly Notices of the Royal Astronomical Society 403 (2010) 1829-1833

R Schönrich, J Binney, W Dehnen

We re-examine the stellar kinematics of the solar neighbourhood in terms of the velocity υ⊙ of the Sun with respect to the local standard of rest. We show that the classical determination of its component V⊙ in the direction of Galactic rotation via Strömberg's relation is undermined by the metallicity gradient in the disc, which introduces a correlation between the colour of a group of stars and the radial gradients of its properties. Comparing the local stellar kinematics to a chemodynamical model which accounts for these effects, we obtain (U, V, W)⊙ = (11.1+0.69-0.75, 12.24+0.47-0.47, 7.25+0.37-0.36) km s-1, with additional systematic uncertainties ∼(1, 2, 0.5) km s-1. In particular, V⊙ is 7 km s-1 larger than previously estimated. The new values of (U, V, W)⊙ are extremely insensitive to the metallicity gradient within the disc. © 2010 The Authors. Journal compilation © 2010 RAS.

Distance determination for RAVE stars using stellar models


MA Breddels, MC Smith, A Helmi, O Bienayme, J Binney, J Bland-Hawthorn, C Boeche, BCM Burnett, R Campbell, KC Freeman, B Gibson, G Gilmore, EK Grebel, U Munari, JF Navarro, QA Parker, GM Seabroke, A Siebert, A Siviero, M Steinmetz, FG Watson, M Williams, RFG Wyse, T Zwitter

Distribution functions for the Milky Way

Monthly Notices of the Royal Astronomical Society 401 (2010) 2318-2330

J Binney

Analytic distribution functions (DFs) for the Galactic disc are discussed. The DFs depend on action variables and their predictions for observable quantities are explored under the assumption that the motion perpendicular to the Galactic plane is adiabatically invariant during motion within the plane. A promising family of DFs is defined that has several adjustable parameters. A standard DF is identified by adjusting these parameters to optimize fits to the stellar density in the column above the Sun, and to the velocity distribution of nearby stars and stars ∼1 kpc above the Sun. The optimum parameters imply a radial structure for the disc which is consistent with photometric studies of the Milky Way and similar galaxies, and that 20 per cent of the disc's luminosity comes from thick disc. The fits suggest that the value of the V component of the Sun's peculiar velocity should be revised upwards from 5.2 to ∼11 km s-1. It is argued that the standard DF provides a significantly more reliable way to divide solar-neighbourhood stars into members of the thin and thick discs than is currently used. The standard DF provides predictions for surveys of stars observed at any distance from the Sun. It is anticipated that DFs of the type discussed here will provide useful starting points for much more sophisticated chemo-dynamical models of the Milky Way. © 2009 RAS.

Modelling the Galaxy with orbital tori

HIGHLIGHTS OF ASTRONOMY, VOL 15 15 (2010) 194-195

J Binney

Joint Discussion 5 Modelling the Milky Way in the Era of Gaia

HIGHLIGHTS OF ASTRONOMY, VOL 15 15 (2010) 173-173

JJ Binney

Origin and structure of the Galactic disc(s)

Monthly Notices of the Royal Astronomical Society 399 (2009) 1145-1156

R Schönrich, J Binney

We examine the chemical and dynamical structure in the solar neighbourhood of a model Galaxy that is the endpoint of a simulation of the chemical evolution of the Milky Way in the presence of radial mixing of stars and gas. Although the simulation's star formation rate declines monotonically from its unique peak and no merger or tidal event ever takes place, the model replicates all known properties of a thick disc, as well as matching special features of the local stellar population such as a metal-poor extension of the thin disc that has high rotational velocity. We divide the disc by chemistry and relate this dissection to observationally more convenient kinematic selection criteria. We conclude that the observed chemistry of the Galactic disc does not provide convincing evidence for a violent origin of the thick disc, as has been widely claimed. © 2009 RAS.

Do high-velocity clouds form by thermal instability?

Monthly Notices of the Royal Astronomical Society 397 (2009) 1804-1815

J Binney, C Nipoti, F Fraternali

We examine the proposal that the H i 'high-velocity' clouds (HVCs) surrounding the Milky Way and other disc galaxies form by condensation of the hot galactic corona via thermal instability. Under the assumption that the galactic corona is well represented by a non-rotating, stratified atmosphere, we find that for this formation mechanism to work the corona must have an almost perfectly flat entropy profile. In all other cases, the growth of thermal perturbations is suppressed by a combination of buoyancy and thermal conduction. Even if the entropy profile were nearly flat, cold clouds with sizes smaller than 10 kpc could form in the corona of the Milky Way only at radii larger than 100 kpc, in contradiction with the determined distances of the largest HVC complexes. Clouds with sizes of a few kpc can form in the inner halo only in low-mass systems. We conclude that unless even slow rotation qualitatively changes the dynamics of a corona, thermal instability is unlikely to be a viable mechanism for formation of cold clouds around disc galaxies. © 2009 The Authors. Journal compilation © 2009 RAS.

Virtual experiences, physical behaviors: The effect of presence on imitation of an eating avatar

Presence: Teleoperators and Virtual Environments 18 (2009) 294-303

J Fox, J Bailenson, J Binney

In this study, the role of presence in the imitation of a virtual model was examined. Immersive virtual environment technology (IVET) was used to create photorealistic virtual representations of the self that were depicted eating food in a virtual world. Changes in the virtual environment (via a changing or unchanging body) were incorporated to create variance in perceived subjective presence. Based on previous research, presence was hypothesized to affect the relationship between the environmental manipulations and the behavioral outcome of imitating the avatar's eating behavior. Here we show that presence did indeed affect imitation, but that the effects varied for men and women in accordance with previous research on sex differences in eating behavior. Men who experienced high presence were more likely than low presence men to imitate the virtual model and eat candy, whereas women who experienced high presence were more likely than low presence women to suppress the behavior and not eat candy. © 2009 by the Massachusetts Institute of Technology.

RAVE spectroscopy of luminous blue variables in the Large Magellanic Cloud

Astronomy and Astrophysics 503 (2009) 511-520

U Munari, A Siviero, O Bienaymé, J Binney, J Bland-Hawthorn, R Campbell, KC Freeman, JP Fulbright, BK Gibson, G Gilmore, EK Grebel, A Helmi, JF Navarro, QA Parker, W Reid, GM Seabroke, A Siebert, M Steinmetz, FG Watson, M Williams, RFG Wyse, T Zwitter

Context. The RAVE spectroscopic survey for galactic structure and evolution obtains 8400-8800 Å spectra at 7500 resolving power at the UK Schmidt Telescope using the 6dF multi-fiber positioner. More than 300 000 9 ≤ I C ≤ 12 and |b|≥ 25° southern stars have been observed to date. Aims. This paper presents the first intrinsic examination of stellar spectra from the RAVE survey, aimed at evaluating their diagnostic potential for peculiar stars and at contributing to the general understanding of luminous blue variables (LBVs). Methods. We used the multi-epoch spectra for all seven LBVs observed, between 2005 and 2008, in the Large Magellanic Cloud (LMC) by the RAVE survey. Results. We demonstrate that RAVE spectra possess significant diagnostic potential when applied to peculiar stars and, in particular, LBVs. The behaviour of the radial velocities for both emission and absorption lines, and the spectral changes between outburst and quiescence states are described and found to agree with evidence gathered at more conventional wavelengths. The wind outflow signatures and their variability are investigated, with multi-components detected in S Doradus. Photoionisation modelling of the rich emission line spectrum of R 127 shows evidence of a massive detached ionised shell that was ejected during the 1982-2000 outburst. Surface inhomogeneities in the nuclear-processed material, brought to the surface by heavy mass loss, could have been observed in S Doradus, even if alternative explanations are possible. We also detect the transition from quiescence to outburst state in R 71. Finally, our spectrum of R 84 offers one of the clearest views of its cool companion. © ESO 2009.

The role of black holes in galaxy formation and evolution

Nature 460 (2009) 213-219

A Cattaneo, SM Faber, J Binney, A Dekel, J Kormendy, R Mushotzky, A Babul, PN Best, M Brüggen, AC Fabian, CS Frenk, A Khalatyan, H Netzer, A Mahdavi, J Silk, M Steinmetz, L Wisotzki

Virtually all massive galaxies, including our own, host central black holes ranging in mass from millions to billions of solar masses. The growth of these black holes releases vast amounts of energy that powers quasars and other weaker active galactic nuclei. A tiny fraction of this energy, if absorbed by the host galaxy, could halt star formation by heating and ejecting ambient gas. A central question in galaxy evolution is the degree to which this process has caused the decline of star formation in large elliptical galaxies, which typically have little cold gas and few young stars, unlike spiral galaxies. © 2009 Macmillan Publishers Limited. All rights reserved.

Chemical evolution with radial mixing

Monthly Notices of the Royal Astronomical Society 396 (2009) 203-222

R Schönrich, J Binney

Models of the chemical evolution of our Galaxy are extended to include radial migration of stars and flow of gas through the disc. The models track the production of both iron and α-elements. A model is chosen that provides an excellent fit to the metallicity distribution of stars in the Geneva-Copenhagen survey (GCS) of the solar neighbourhood and a good fit to the local Hess diagram. The model provides a good fit to the distribution of GCS stars in the age-metallicity plane, although this plane was not used in the fitting process. Although this model's star formation rate is monotonically declining, its disc naturally splits into an α-enhanced thick disc and a normal thin disc. In particular, the model's distribution of stars in the ([O/Fe], [Fe/H]) plane resembles that of Galactic stars in displaying a ridge line for each disc. The thin-disc's ridge line is entirely due to stellar migration, and there is the characteristic variation of stellar angular momentum along it that has been noted by Haywood in survey data. Radial mixing of stellar populations with high σz from inner regions of the disc to the solar neighbourhood provides a natural explanation of why measurements yield a steeper increase of σz with age than predicted by theory. The metallicity gradient in the interstellar medium is predicted to be steeper than in earlier models, but appears to be in good agreement with data for both our Galaxy and external galaxies. The models are inconsistent with a cut-off in the star formation rate at low gas surface densities. The absolute magnitude of the disc is given as a function of time in several photometric bands, and radial colour profiles are plotted for representative times. © 2009 RAS.

The Bulge-disc connection in the Milky Way


J Binney

AGN jet and thermal conduction in cooling flow clusters

International Journal of Modern Physics D 17 (2008) 1953-1959

FA Bibi, J Binney

We consider the effect of thermal conduction along with AGN jet feedback on the intracluster medium (ICM) in cooling flow clusters. A series of three-dimensional AMR hydrodynamic simulations has been carried out to analyze the dynamic of such interaction. We show the limit of applicability of the Spitzer thermal conduction during jet/ICM interaction. © 2008 World Scientific Publishing Company.

Galactic kinematics with RAVE data

Astronomy and Astrophysics 480 (2008) 753-765

L Veltz, O Bienaymé, KC Freeman, J Binney, J Bland-Hawthorn, BK Gibson, G Gilmore, EK Grebel, A Helmi, U Munari, JF Navarro, QA Parker, GM Seabroke, A Siebert, M Steinmetz, FG Watson, M Williams, RFG Wyse, T Zwitter

We analyze the distribution of G and K type stars towards the Galactic poles using RAVE and ELODIE radial velocities, 2MASS photometric star counts, and UCAC2 proper motions. The combination of photometric and 3D kinematic data allows us to disentangle and describe the vertical distribution of dwarfs, sub-giants and giants and their kinematics. We identify discontinuities within the kinematics and magnitude counts that separate the thin disk, thick disk and a hotter component. The respective scale heights of the thin disk and thick disk are 225 ± 10 pc and 1048 ± 36 pc. We also constrain the luminosity function and the kinematic distribution function. The existence of a kinematic gap between the thin and thick disks is incompatible with the thick disk having formed from the thin disk by a continuous process, such as scattering of stars by spiral arms or molecular clouds. Other mechanisms of formation of the thick disk such as "created on the spot" or smoothly "accreted" remain compatible with our findings. © 2008 ESO.

Galactic dynamics

Princeton Univ Pr, 2008

J Binney, S Tremaine

Papahurihia, Pukerenga, te atua wera and te Nākahi: How many prophets?

Journal of the Polynesian Society 116 (2007) 309-320

J Binney

Symposium summary: Dynamics

Proceedings of the International Astronomical Union 3 (2007) 455-458

J Binney

Pseudobulges form from unstable disks, while classical bulges form in violent episodes of star formation when a merger sweeps cold gas to a galactic centre. It seems unlikely that smashed disks contribute much to classical bulges. During mergers central black holes make cusps shallower and inflate kinematically decoupled cores. The abundance of galaxies with no detected classical bulge can perhaps be understood if galaxies exchange gas with the IGM more freely than is often supposed. © 2008 International Astronomical Union.

Gaseous haloes: Linking galaxies to the IGM

New Astronomy Reviews 51 (2007) 95-98

F Fraternali, J Binney, T Oosterloo, R Sancisi

In recent years, evidence has accumulated that nearby spiral galaxies are surrounded by massive haloes of neutral and ionised gas. These gaseous haloes rotate more slowly than the disks and show inflow motions. They are clearly analogous to the High Velocity Clouds of the Milky Way. We show that these haloes cannot be produced by a galactic fountain process (supernova outflows from the disk) where the fountain gas conserves its angular momentum. Making this gas interact with a pre-existing hot corona does not solve the problem. These results point at the need for a substantial accretion of low angular momentum material from the IGM. © 2006 Elsevier B.V. All rights reserved.

The radial velocity experiment (RAVE): First data release

Astronomical Journal 132 (2006) 1645-1668

M Steinmetz, T Zwitter, A Siebert, FG Watson, KC Freeman, U Munari, R Campbell, M Williams, GM Seabroke, RFG Wyse, QA Parker, O Bienaymé, S Roeser, BK Gibson, G Gilmore, EK Grebel, A Helmi, JF Navarro, D Burton, CJP Cass, JA Dawe, K Fiegert, M Hartley, KS Russell, W Saunders, H Enke, J Bailin, J Binney, J Bland-Hawthorn, C Boeche, W Dehnen, DJ Eisenstein, NW Evans, M Fiorucci, JP Fulbright, O Gerhard, U Jauregi, A Kelz, L Mijovic, I Minchev, G Parmentier, J Peñarrubia, AC Quillen, MA Read, G Ruchti, RD Scholz, A Siviero, MC Smith, R Sordo, L Veltz, S Vidrih, R Von Berlepsch, BJ Boyle, E Schilbach

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, and surface gravity) of up to one million stars using the Six Degree Field multiobject spectrograph on the 1.2 m UK Schmidt Telescope of the Anglo-Australian Observatory. The RAVE program started in 2003, obtaining medium-resolution spectra (median R = 7500) in the Ca-triplet region (8410-8795 Å) for southern hemisphere stars drawn from the Tycho-2 and SuperCOSMOS catalogs, in the magnitude range 9 < I < 12. The first data release is described in this paper and contains radial velocities for 24,748 individual stars (25,274 measurements when including reobservations). Those data were obtained on 67 nights between 2003 April 11 and 2004 April 3. The total sky coverage within this data release is ∼4760 deg 2. The average signal-to-noise ratio of the observed spectra is 29.5, and 80% of the radial velocities have uncertainties better than 3.4 km s -1. Combining internal errors and zero-point errors, the mode is found to be 2 km s -1. Repeat observations are used to assess the stability of our radial velocity solution, resulting in a variance of 2.8 km s -1. We demonstrate that the radial velocities derived for the first data set do not show any systematic trend with color or signal-to-noise ratio. The RAVE radial velocities are complemented in the data release with proper motions from Starnet 2.0, Tycho-2, and SuperCOSMOS, in addition to photometric data from the major optical and infrared catalogs (Tycho-2, USNO-B, DENIS, and the Two Micron All Sky Survey). The data release can be accessed via the RAVE Web site. © 2006. The American Astronomical Society. All rights reserved.

Testing the mond formula in the Galaxy

EAS Publications Series 20 (2006) 277-278

B Famaey, J Binney

The inner Galaxy is completely dominated by baryons, contrary to the predictions of CDM cosmology, whilst the observations are compatible with MOND if the local circular speed is smaller than 220 kms-1 and the asymptotic circular velocity close to 170 km s-1. © EAS, EDP Sciences 2006.