Frank C. van den Bosch
 Home CV Research Publications Preprints Presentations Teaching Astronomy Dept Physics Dept Yale University

 I am an associate professor at the Astronomy Department of Yale University. My research focusses on various theoretical aspects of cosmology, large scale structure, and galaxy formation. In particular, I'm involved in ongoing projects to study the structure and formation of dark matter haloes, the formation of disk galaxies, the galaxy occupation statistics of dark matter haloes, galaxy-galaxy lensing, preheating of the IGM by pancake formation, and on the bias of galaxies and dark matter haloes. For more details please consult the research page.

 Our New Graduate Text Book on Galaxy Formation & Evolution Together with Houjun Mo and Simon White I have written an 840 page graduate text book on galaxy formation and evolution, which has been published by Cambridge University Press (winner 2010 PROSE Award) For more information, or to order your copy, click here
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February 3, 2010: Our book wins 2010 PROSE award

Our book Galaxy Formation and Evolution has been awarded the 2010 PROSE Award in the category Cosmology and Astronomy. The PROSE Awards, the American Publishers Awards for Professional and Scholarly Excellence, annually recognize the very best in professional and scholarly publishing by bringing attention to distinguished books, journals, and electronic content in over 40 categories. Judged by peer publishers, librarians, and medical professionals since 1976, the PROSE Awards are extraordinary for their breadth and depth.

April 19, 2010: Surhud More awarded Otto-Hahn Medal

Surhud More has been awarded the 2009 Otto-Hahn Medal by the president of the Max-Planck Society for his PhD thesis work on satellite kinematics.

Recent Publications

October 11, 2011: Cross identification between X-ray and Optical Clusters of Galaxies in the SDSS DR7 Field
We use the ROSAT all sky survey X-ray cluster catalogs and the optical SDSS DR7 galaxy and group catalogs to cross-identify X-ray clusters with their optical counterparts, resulting in a sample of 201 X-ray clusters in the sky coverage of SDSS DR7. We investigate various correlations between the optical and X-ray properties of these X-ray clusters. We obtain an unbiased fundamental plane relation between the X-ray luminosity, the central galaxy stellar mass and the characteristic satellite stellar mass as ${\log L_X} = -4.894 + 2.108 \log (M_{\ast, c} + 0.506 M_{\rm sat})$ with relatively small scatter of $\sim 0.42$dex. Comparing the properties of the groups of similar mass and redshift that are X-ray luminous or under-luminous, we find that X-ray luminous groups, have more faint satellite galaxies and the red fraction in their satellite galaxies is also enhanced.

October 10, 2011: Evolution of the Galaxy - Dark Matter Connection and the Assembly of Galaxies in Dark Matter Halos
We present a new model to describe the galaxy-dark matter connection across cosmic time, which unlike the popular subhalo abundance matching technique is self-consistent in that it takes account of the facts that (i) subhalos are accreted at different times, and (ii) the properties of satellite galaxies may evolve after accretion. Using observations of galaxy stellar mass functions out to $z \sim 4$, the conditional stellar mass function at $z\sim 0.1$ obtained from SDSS galaxy group catalogues, and the two-point correlation function (2PCF) of galaxies at $z \sim 0.1$ as function of stellar mass, we constrain the relation between galaxies and dark matter halos over the entire cosmic history from $z \sim 4$ to the present. This relation is then used to predict the median assembly histories of different stellar mass components within dark matter halos (central galaxies, satellite galaxies, and halo stars).

August 5, 2011: Mass Growth & Mergers: Direct Observations of the Luminosity Function of LRG Satellite Galaxies out to z=0.7 from SDSS and BOSS Images
We present a statistical study of the luminosity functions of galaxies surrounding luminous red galaxies (LRGs) at average redshifts =0.34 and =0.65. The luminosity functions are derived by extracting source photometry around the LRGs and subtracting foreground and background contamination using randomly selected control fields. We utilize a two-component fit of a Schechter function plus a log-normal distribution to demonstrate that LRGs are typically brighter than their most luminous satellite by roughly 1.3 magnitudes. This luminosity gap implies that interactions within LRG environments are typically restricted to minor mergers with mass ratios of 1:4 or lower. The luminosity functions further imply that roughly 35% of the mass in the environment is locked in the LRG itself, supporting the idea that mass growth through major mergers within the environment is unlikely.

August 4, 2011: Reconstructing the Cosmic Velocity and Tidal Fields with Galaxy Groups Selected from the Sloan Digital Sky Survey
We present a new method to reconstruct the cosmic velocity and tidal fields from a catalogue of galaxy groups in the SDSS Survey Volume. Detailed mock catalogues are used to test the reliability of our method against uncertainties arising from redshift distortions, survey boundaries, and false identifications of groups by our group finder. We find that both the velocity and tidal fields, smoothed on a scale of ~2Mpc/h, can be reliably reconstructed in the inner region (~66%) of the survey volume. The reconstructed tidal field is used to split the cosmic web into clusters, filaments, sheets, and voids, depending on the sign of the eigenvalues of tidal tensor. We use the reconstructed velocity field and the Zel'dovich approximation to predict the mass density field in the SDSS volume as function of redshift. The velocity, tidal and density fields in the SDSS volume, specified on a Cartesian grid with a spatial resolution of ~700kpc/h, are available from the authors upon request.

August 3, 2011: The Angular Momentum of Disk Galaxies: Implications for Gas Accretion, Outflows and Dynamical Friction
We combine constraints on the galaxy-dark matter connection with structural and dynamical scaling relations to investigate the angular momentum content of disk galaxies. We find that average ratio between the specific angular momenta of disk galaxies and their host dark matter haloes is R_j = 0.61. This calls into question a standard assumption made in the majority of all (semi-analytical) models for (disk) galaxy formation, namely that R_j = 1.0. Using simple disk formation models we show that it is particularly challenging to understand why R_j is independent of halo mass, while the galaxy formation efficiency (e_{gf}, proportional to the ratio of galaxy mass to halo mass) reveals a strong halo mass dependence. We conclude that the angular momentum build-up of galactic disks remains poorly understood.

April 10, 2011: An Analytical Model for the Accretion of Dark Matter Subhalos
We develop a new analytical model for the mass function of cold dark matter subhalos at the time of accretion and for the distribution of their accretion times. Our model is simple, and can be used to predict the un-evolved subhalo mass function, the mass function of subhalos accreted at a given time, the accretion-time distribution of subhalos of a given initial mass, and the frequency of major mergers as a function of time. We test our model using high-resolution cosmological N-body simulations, and find that our model predictions match the simulation results remarkably well.

2009

December 20, 2010: Dark Halo Response and the Stellar Initial Mass Function in Early-type and Late-type Galaxies
We investigate the origin of the relations between stellar mass and optical circular velocity for early-type (ETG) and late-type (LTG) galaxies. We combine measurements of dark halo masses and the distribution of baryons in galaxies with constraints on dark halo structure from cosmological simulations. The principle unknowns are the halo response to galaxy formation and the stellar initial mass function (IMF). Models with a universal IMF and universal halo response cannot simultaneously reproduce the zero points of both the TF and FJ relations. For a model with a universal Chabrier IMF, LTGs require halo expansion, while ETGs require halo contraction. We speculate that the presence of a major merger may be responsible for the contraction in ETGs while clumpy accreting streams and/or feedback leads to expansion in LTGs.

July 1, 2010: An Improved Model for the Dynamical Evolution of Dark Matter Subhaloes
Using an analytical model, we study the evolution of subhaloes, including their mass, angular momentum and merging time-scale. This model considers the dominant processes governing subhalo evolution, such as dynamical friction, tidal stripping and tidal heating. We find that in order to best match the evolution of angular momentum measured from N-body simulation, mass stripping by tidal force should become inefficient after subhaloes have experienced a few pericentric passages. It is also found that the often used Coulomb logarithm $\ln M/m$ has to be revised to best fit the merging time-scales from simulation.

June 29, 2010: The dependence of AGN activity on stellar and halo mass in Semi-Analytic Models
In the current theoretical paradigm of galaxy formation, AGN feedback is believed to play a crucial role in regulating the levels of activity in galaxies, in relatively massive halos at low redshift. In recent years, detailed statistical information on the dependence of galaxy activity on stellar mass, parent halo mass and hierarchy has become available. In this paper, we compare the fractions of galaxies belonging to different activity classes (star-forming, AGN and radio active) with predictions from four different and independently developed semi-analytical models. As we show, model predictions differ from observational measurements in a number of ways.

June 24, 2010: Probing Hot Gas in Galaxy Groups through the Sunyaev-Zeldovich Effect
We investigate the potential of exploiting the Sunyaev-Zeldovich effect (SZE) to study the properties of hot gas in galaxy groups. It is shown that, with upcoming SZE surveys, one can stack SZE maps around galaxy groups of similar halo masses selected from large galaxy redshift surveys to study the hot gas in halos represented by galaxy groups. We also explore the idea of using the cross correlation between hot gas and galaxies of different luminosity to probe the hot gas in dark matter halos without identifying galaxy groups to represent dark halos.

June 17, 2010: On the Evolution of the Velocity-Mass-Size Relations of Disk-Dominated Galaxies over the Past 10 Billion Years
We study the evolution of the scaling relations between maximum circular velocity, stellar mass and optical half-light radius of star-forming disk-dominated galaxies in the context of LCDM-based galaxy formation models. Using data from the literature combined with new data from the DEEP2 and AEGIS surveys we show that there is a consistent observational and theoretical picture for the evolution of these scaling relations from z\sim 2 to z=0.

April 30, 2010: Equilibrium Initialization and Stability of Three-Dimensional Gas Disks
We present a new method for setting up three dimensional gaseous disks in hydrodynamic equilibrium, and use this method to study the stability of gaseous disks embedded in dark matter haloes using the adaptive mesh refinement (AMR) hydrodynamics code RAMSES.

April 27, 2010: The Kinematic Connection Between Galaxies and Dark Matter Haloes
Using estimates of dark halo masses from satellite kinematics, weak gravitational lensing, and halo abundance matching, combined with the Tully-Fisher and Faber-Jackson relations, we derive the mean relation between the optical, V_opt, and virial, V_200, circular velocities of early- and late-type galaxies at redshift z~0. We discuss implications for galaxy formation and evolution.

April 19, 2010: Mergers in Lambda-CDM: Uncertainties in Theoretical Predictions and Interpretations of the Merger Rate
We examine and quantify the dominant uncertainties in predicted galaxy merger rates. We demonstrate that the dominant differences are due to uncertainties related to baryonic physics, in particular those associated with the satellite over-quenching problem.

March 16, 2010: Satellite Kinematics III: Halo Masses of Central Galaxies in SDSS
We use the kinematics of satellite galaxies to investigate the halo mass-luminosity relation (MLR) and the halo mass-stellar mass relation (MSR) of central galaxies in the SDSS. In particular, we focus on the dependence of these scaling relations on the colour of the central galaxy.

January 27, 2010: Are Brightest Halo Galaxies Central Galaxies?
Using a large galaxy group catalogue we rule out the central galaxy paradigm (CGP) according to which the central galaxy in a dark matter halo, that is, the galaxy with the lowest specific potential energy, is also the brightest halo galaxy (BHG), and that it resides at rest at the centre of the dark matter potential well. Rather, the data indicates that in a significant fraction of all haloes the BHG is a satellite rather than a central. We discuss various implications of this finding.

2009

December 14, 2009: The Galaxy Star-Formation-Rate Sequence: Evolution and Scatter
We use a semi-analytic model for disk galaxies to explore the origin of the time evolution and small scatter of the galaxy SFR sequence; the tight correlation between star-formation rate and stellar mass.

December 11, 2009: Stellar Ages and Metallicities of Central and Satellite Galaxies
Using our SDSS galaxy group catalogue, we study how the stellar ages and metallicities of central and satellite galaxies depend on stellar mass and halo mass. We find that satellites are older and metal-richer than centrals of the same stellar mass. In addition, the average age and metallicity of low mass satellite galaxies increase with the mass of the halo in which they reside. We compare these results to the semi-analytical model of Wang et al. and conclude that the model needs to (i) modify the recipes of both supernova feedback and AGN feedback, (ii) use a more realistic description of strangulation, and (iii) include a proper treatment of the tidal stripping, heating and destruction of satellite galaxies.

December 7, 2009: The Stellar Mass Components of Galaxies
We compare the stellar masses of central and satellite galaxies predicted by three independent semianalytical models with observational results obtained from our SDSS galaxy group catalogue. The semi-analytical models only predict the correct stellar masses of central galaxies within a limited mass range and all models fail to reproduce the sharp decline of stellar mass with decreasing halo mass observed at the low mass end. In addition, all models over-predict the number of satellite galaxies by roughly a factor of two. We conclude that current galaxy formation models still have serious problems in modeling star formation in low-mass halos.

November 2, 2009: The Substructure Hierarchy in Dark Matter Haloes
We present a new algorithm for identifying the substructure within simulated dark matter haloes. Our new algorithm identifies substructures at all levels of this hierarchy, and we use it to determine the mass function of all substructure (counting sub-haloes, sub-subhaloes, etc.). We provide analytic fits to the subhalo mass function which should be useful in halo model analyses which equate galaxies with halo substructure when interpreting clustering in large sky surveys.

March 27, 2009: The Size and Comoving Mass Density Evolution of Early-Type Galaxies
We present a simple, empirically motivated model that simultaneously predicts the evolution of the mean size and the comoving mass density of massive early-type galaxies from z=2 to the present. We conclude that the recently measured, substantial size evolution of early-type galaxies can be explained by the combined effect of the continuous emergence of galaxies as early types and their subsequent growth through dry merging.

January 9, 2009: Structural Properties of Central Galaxies in Groups and Clusters
Using a representative sample of 911 central galaxies from our the SDSS group catalogue, we study how the structure of the most massive members in groups and clusters depend on (1) galaxy stellar mass, (2) dark matter halo mass, and (3) halo-centric position. We conclude that stellar mass is the most fundamental property determining the basic structure of a galaxy.

2008

December 19, 2008: The nature of red dwarf galaxies
Using our SDSS galaxy group catalogue we find that about 1/4 of all dwarf galaxies (r-band magn > -17) that are central galaxies in their own halo are not blue and star forming, as expected in standard models of galaxy formation, but are red. We suggest that this population of dwarf galaxies are hosted by low-mass halos that have passed through their massive neighbors, and that the same environmental effects that cause satellite galaxies to become red are also responsible for the red colors of this population of galaxies.

October 28, 2008: The Impact of Feedback on Disk Galaxy Scaling Relations
We use a disk galaxy evolution model to investigate the impact of mass outflows (a.k.a. feedback) on disk galaxy scaling relations. Feedback preferentially ejects low angular momentum material because star formation is more efficient at smaller galactic radii. This effect helps to resolve the discrepancy between the high spin parameters observed for dwarf galaxies with the low spin parameters predicted from LCDM.

October 17, 2008: New Constraints on Star Formation Quenching
We investigate the correlation of star formation quenching with internal galaxy properties and large scale environment (halo mass) in empirical data and theoretical models. For central galaxies, we find that the fractions of red'' and passive'' galaxies in the observational group catalogs are a strong function of halo mass at fixed stellar mass, and a weak function of stellar mass at fixed halo mass. For satellite galaxies, a nearly equally strong dependence on halo mass and stellar mass is seen. A comparison with five different semi-analytic models shows that models with AGN feedback can reproduce the trends of central galaxies, but not for satellite galaxies, which are too red/passivein the models. This satellite overquenching problem is caused by the too-rapid stripping of the satellites' hot gas halos, which leads to rapid strangulation of star formation.

September 13, 2008: Environmental Effects on Satellite Galaxies
Using our SDSS group catalogue, we compare the sizes, concentrations, colour gradients and surface brightness profiles of central and satellite galaxies as fixed stellar mass. We find that at fixed stellar mass, late type satellite galaxies have smaller radii and larger concentrations than late type central galaxies. No such differences are found for early-type galaxies. Late-type satellite galaxies have a lower surface brightness and redder colours than late-type central galaxies. All these differences between satellite and central galaxies can be explained by a simple fading model, in which the star formation in the disk decreases over timescales of 2-3 Gyr after a galaxy becomes a satellite.

August 19, 2008: The Subhalo - Satellite Connection
We use the conditional stellar mass functions of satellite galaxies obtained from our SDSS galaxy group catalogue together with models of the subhalo mass functions to explore the fraction and fate of stars stripped from satellites in galaxy groups and clusters of different masses. The majority of the stripped stars in massive halos are predicted to end up as intra-cluster stars, and the predicted amounts of the intra-cluster component as a function halo mass are in good agreement with direct observational constraints.

August 6, 2008: Luminosity and Stellar Mass Functions of Galaxies
Using our SDSS galaxy group catalogue, we investigate the luminosity and stellar mass functions for different populations of galaxies and for groups themselves. We also determine the conditional stellar mass function, which describes the stellar distribution of galaxies in halos of a given mass. We use the observed stellar mass function of central galaxies to constrain the stellar mass - halo mass relation for low mass halos, and obtain that M_* \propto M_{halo}^{4.9}

August 1, 2008: Galaxy-Galaxy Lensing with the CLF
We use the abundance and clustering properties of galaxies in the SDSS in order to constrain the conditional luminosity function (CLF), which describes the link between galaxies and dark matter haloes. The resulting CLF model is then used to predict the galaxy-galaxy lensing signal. We show that the predicted lensing signal is in agreement with the data for a cosmology with Omega_m=0.238 and sigma_8=0.734, but not for a cosmology with Omega_m=0.3 and sigma_8=0.9.

August 1, 2008: Galaxy-Galaxy Lensing with a Group Catalogue
We use a large galaxy group catalogue to predict the galaxy-galaxy lensing signal, which we compare to data from the SDSS. In agreement with our CLF study we only find a good match to the data if we assume a cosmology with relatively low Omega_m and sigma_8.

July 30, 2008: Satellite Kinematics II: Results
Using the method outlined in Paper I we determine both the mean and the scatter of the mass-luminosity relation of central galaxies in the SDSS. We find that the scatter in halo masses for centrals of a given luminosity increases with increasing luminosity, and discuss the implications for the amount of stochasticity in galaxy formation.

July 30, 2008: Satellite Kinematics I: Methodology
We present a new method that uses satellite kinematics to constrain both the mean and the scatter of the mass-luminosity relation of central galaxies.

July 29, 2008: The Rise and Fall of Galaxy Acticity in Dark Matter Haloes
Using a large SDSS galaxy group catalogue, we study the dependence of galaxy activity on stellar mass, halo mass, and group hierarchy (centrals vs. satellites). We split our galaxy sample in star-forming galaxies, galaxies with optical AGN activity and radio sources. Among others, we find a smooth transition in halo mass as the activity of central galaxies changes from star formation to optical AGN activity to radio emission.

May 12, 2008: Halo Properties as Function of Halo Mass and Cosmology
Using a large suite of numerical simulations, we study the concentrations of dark matter haloes as function of halo mass and cosmology. Our simulations cover 5 order of magnitude in halo mass, and three different cosmological models. We present a new model to compute the average concentration as function of halo mass which accuretely fits our simulation results. We also compare our simulation results to constraints from various observational techniques.

May 1, 2008: Satellite Ecology: The Dearth of Environment Dependence
We study the dependence of the colors and concentrations of satellite galaxies on their stellar mass, their halo mass, and their halo-centric distance. We find that the properties of satellite galaxies are almost entirely determined by their stellar mass, with no significant environment dependence. This has important implications for the physical processes responsible for transforming satellite galaxies.

March 11, 2008: Reconstructing the Cosmic Density Field
We present a new method to reconstruct the cosmic density field from the distribution of dark matter haloes extracted from a large galaxy group catalogue. We demonstrate that our method works remarkably well using haloes (groups) with masses down to 10^12 Msun, even in redshift space. We discuss a number of potentially powerful applications.

January 11, 2008: Constraining Satellite Strangulation Processes
Using semi-analytical models for galaxy formation, and data from the SDSSS we constrain the efficiency with which satellite galaxies are stripped of hot gas, and tidally disrupted by the potential of their host halo.

January 9, 2008: The Dark Matter Halo of the Milky Way
Using a set of halo stars extracted from the SDSS as kinematic tracers, we derive new constraints on the mass of the Milky Way's dark matter halo. Our results indicate a halo virial mass of M$_{\rm vir}=1.1\pm 0.2 \times 10^{12}$M$_\odot$. This implies that nearly 40% of the baryons within the virial radius of the Milky Way's dark matter halo reside in the stellar components of our Galaxy.
 CONTACT INFORMATION Astronomy Department Phone: +1-203-432-0196 Yale University Fax:     +1-203-432-5048 P.O. Box 208101 E-mail: frank.vandenbosch@yale.edu New Haven, CT 06520-8101