A5012749486- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Scientific Research and Discoveries
- Gamma-ray bursts and supernovae
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- CCD and CMOS Imaging Sensors
- Remote Sensing in Agriculture
- Black Holes and Theoretical Physics
- Dark Matter and Cosmic Phenomena
- Advanced Vision and Imaging
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Computational Physics and Python Applications
- History and Developments in Astronomy
- Solar and Space Plasma Dynamics
- Impact of Light on Environment and Health
- Gaussian Processes and Bayesian Inference
- Plant Water Relations and Carbon Dynamics
- Spectroscopy and Laser Applications
Durham University
2015-2024
European Space Astronomy Centre
2024
Indiana Cancer Consortium
2005-2022
Max Planck Institute for Astrophysics
2010
Durham Technical Community College
1997-2006
United Nations Industrial Development Organization
2003
Sheffield Children's Hospital
2000
University of Oxford
1993-1995
Recent observations of the distant Universe suggest that much stellar mass bright galaxies was already in place at z > 1. This presents a challenge for models galaxy formation because massive haloes are assembled late hierarchical clustering process intrinsic to cold dark matter (CDM) cosmology. In this paper, we discuss new implementation Durham semi-analytic model which feedback due active galactic nuclei (AGN) is assumed quench cooling flows haloes. mechanism naturally creates break local...
We present a power-spectrum analysis of the final 2dF Galaxy Redshift Survey (2dFGRS), employing direct Fourier method. The sample used comprises 221 414 galaxies with measured redshifts. investigate in detail modelling selection, improving on previous treatments number respects. A new angular mask is derived, based revisions to photometric calibration. redshift selection function determined by dividing survey according rest-frame colour, and deducing self-consistent treatment k-corrections...
We describe the GALFORM semi-analytic model for calculating formation and evolution of galaxies in hierarchical clustering cosmologies. It improves upon, extends, earlier scheme developed by Cole et al. The employs a new Monte Carlo algorithm to follow merging dark matter haloes with arbitrary mass resolution. incorporates realistic descriptions density profiles gas they contain; it follows chemical stars, associated production dust; includes detailed calculation sizes discs spheroids....
We combine the Two Micron All Sky Survey (2MASS) Extended Source Catalogue and 2dF Galaxy Redshift to produce an infrared selected galaxy catalogue with 17 173 measured redshifts. use this extensive data set estimate luminosity functions in J- KS-bands. The are fairly well fitted by Schechter parameters MJ*−5 log h = −22.36±0.02, αJ −0.93±0.04, ΦJ* 0.0104±0.0016 h3 Mpc−3 J-band MKS*−5 −23.44±0.03, αKS −0.96±0.05, ΦKS* 0.0108±0.0016 KS-band (2MASS Kron magnitudes). These derived assuming a...
We investigate the physical mechanisms that shape luminosity function of galaxies in hierarchical clustering models. Beginning with mass dark matter halos ΛCDM (Λ cold matter) cosmology, we show, incremental steps, how gas cooling, photoionization at high redshift, feedback processes, galaxy merging, and thermal conduction affect function. consider three processes whereby supernovae stellar wind energy can forming galaxy: (1) reheating disk to halo temperature; (2) expansion hot, diffuse...
The 2dF Galaxy Redshift Survey has now measured in excess of 160-000 galaxy redshifts. This paper presents the power spectrum distribution, calculated using a direct Fourier transform based technique. We argue that, within k-space region , shape this should be close to that linear density perturbations convolved with window function survey. and its convolving effect on estimate are analysed detail. By model spectra, we able fit power-spectrum data provide measure matter content Universe. Our...
The halo occupation distribution (HOD) describes the relation between galaxies and dark matter at level of individual halos. properties residing centers halos differ from those satellite because differences in their formation histories. Using a smoothed particle hydrodynamics (SPH) simulation semi-analytic (SA) galaxy model, we examine separate contributions central to HOD, more specifically probability P(N|M) that virial mass M contains N particular class. In agreement with earlier results...
We present a detailed analysis of the two-point correlation function, ξ(σ, π), from 2dF Galaxy Redshift Survey (2dFGRS). The large size catalogue, which contains ∼220 000 redshifts, allows us to make high-precision measurements various properties galaxy clustering pattern. effective redshift at our estimates are made is zs≈ 0.15, and similarly luminosity, Ls≈ 1.4L*. estimate redshift-space ξ(s), we measure length, s0= 6.82 ± 0.28 h−1 Mpc. also projected Ξ(σ), real-space ξ(r), can be fit by...
We present predictions for the abundance of submillimetre galaxies (SMGs) and Lyman-break (LBGs) in Λ cold dark matter cosmology. A key feature our model is self-consistent calculation absorption emission radiation by dust. The new successfully matches LBG luminosity function, as well reproducing properties local galaxy population optical infrared. can also explain observed number counts at 850 μm, but only if we assume a top-heavy initial mass function stars formed bursts. predicted...
We compute the bispectrum of 2dF Galaxy Redshift Survey (2dFGRS) and use it to measure bias parameter galaxies. This quantifies strength clustering galaxies relative mass in Universe. By analysing 80 × 106 triangle configurations wavenumber range 0.1 < k 0.5 h Mpc−1 (i.e. on scales roughly between 5 30 h−1 Mpc) we find that linear is consistent with unity: b1= 1.04 ± 0.11, quadratic (non-linear) zero: b2=−0.054 0.08. Thus, at least large scales, optically selected do indeed trace underlying...
We have measured the equivalent width of Hα emission line for 11 006 galaxies brighter than Mb=−19 (ΩΛ= 0.7, Ωm= 0.3, H0= 70 km s−1 Mpc−1) at 0.05 < z 0.1 in 2dF Galaxy Redshift Survey (2dFGRS), fields 17 known galaxy clusters. The limited redshift range ensures that our results are insensitive to aperture bias, and residuals from night sky lines. use these measurements trace μ*, star formation rate normalized L*, as a function distance cluster centre, local projected density. find...
We investigate the dependence of galaxy clustering on luminosity and spectral type using 2dF Galaxy Redshift Survey (2dFGRS). Spectral types are assigned principal-component analysis Madgwick et al. divide sample into two broad classes: galaxies with strong emission lines ('late types') more quiescent ('early types'). measure in real space, free from any distortion pattern owing to peculiar velocities, for a series volume-limited samples. The projected correlation functions both well...
We have used a combination of high resolution cosmological N-body simulations and semi-analytic modelling galaxy formation to investigate the processes that determine spatial distribution galaxies in cold dark matter (CDM) models its relation matter. The depends sensitively on efficiency with which form haloes different mass. In small mass haloes, is inhibited by reheating cooled gas feedback processes, whereas large it long cooling time gas. As result, mass-to-light ratio has deep minimum...
We investigate the dependence of strength galaxy clustering on intrinsic luminosity using Anglo-Australian two degree field redshift survey (2dFGRS). The 2dFGRS is over an order magnitude larger than previous surveys used to address this issue. measure projected two-point correlation function galaxies in a series volume-limited samples. free from any distortion pattern induced by peculiar motions and well described power law pair separation range . real space well-fitted length power-law...
Recent observational and theoretical breakthroughs make this an exciting time to be working towards understanding the physics of galaxy formation. The goal review is principles behind hierarchical paradigm accessible a wide audience by providing pedagogical introduction modern theories I outline ingredients powerful approach called semi-analytical modelling contrast method with numerical simulations gas dynamics baryons. Semi-analytical models have enjoyed many successes, but it observations...
We analyse the observed correlation between galaxy environment and H-alpha emission line strength, using volume-limited samples group catalogues of 24968 galaxies drawn from 2dF Galaxy Redshift Survey (Mb<-19.5) Sloan Digital Sky (Mr<-20.6). characterise by 1) Sigma_5, surface number density determined projected distance to 5th nearest neighbour; 2) rho1.1 rho5.5, three-dimensional estimates obtained convolving distribution with Gaussian kernels dispersion 1.1 Mpc 5.5 Mpc, respectively. find...
We use more than 110500 galaxies from the 2dF galaxy redshift survey (2dFGRS) to estimate b_J-band luminosity function at z=0, taking account of evolution, distribution magnitude measurement errors and small corrections for incompletenessin catalogue. Throughout interval -16.5>M- 5log h>-22, is accurately described by a Schechter with M* -5log h =-19.66+/-0.07, alpha=-1.21+/-0.03 phistar=(1.61+/-0.08) 10^{-2} h^3/Mpc^3, giving an integrated density rho_L=(1.82+/-0.17) 10^8 L_sol/Mpc^3...
We present a new version of the GALFORM semi-analytical model galaxy formation. This brings together several previous developments into single unified model, including different initial mass function (IMF) in quiescent star formation and starbursts, feedback from active galactic nuclei supressing gas cooling massive halos, empirical law disks based on their molecular content. In addition, we have updated cosmology, introduced more accurate treatment dynamical friction acting satellite...
We present a very large high-resolution cosmological N-body simulation, the Millennium-XXL or MXXL, which uses 303 billion particles to represent formation of dark matter structures throughout 4.1Gpc box in LambdaCDM cosmology. create sky maps and identify samples galaxy clusters using surrogates for four different observables: richness estimated from surveys, X-ray luminosity, integrated Sunyaev-Zeldovich signal, lensing mass. The unprecedented combination volume resolution allows us...
We present a test of different error estimators for 2-point clustering statistics, appropriate and future large galaxy redshift surveys. Using an ensemble very dark matter LambdaCDM N-body simulations, we compare internal (jackknife bootstrap) to external ones (Monte-Carlo realizations). For 3-dimensional find that none the methods investigated are able reproduce neither accurately nor robustly errors on 1 25 Mpc/h scales. The standard bootstrap overestimates variance xi(s) by ~40% all...
Current models of galaxy formation predict satellite galaxies in groups and clusters that are redder than observed. We investigate the effect on colours produced by ram pressure stripping their hot gaseous atmospheres as satellites orbit within parent halo. incorporate a model process based detailed hydrodynamic simulations Durham semi-analytic formation. The show environment is less aggressive previously assumed. main uncertainty treatment gas expelled supernovae. With reasonable...
We study the evolution of cold gas content galaxies by splitting interstellar medium into its atomic and molecular hydrogen components, using galaxy formation model GALFORM in LCDM framework. calculate molecular-to-atomic mass ratio, H2/HI, each two different approaches; pressure-based empirical relation Blitz & Rosolowsky theoretical Krumholz, McKeee Tumlinson, apply them to consistently star rates galaxies. find that based on law predicts an HI function, CO(1-0) luminosity correlations...