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Redshift Range (redshift + range)
Selected AbstractsStructures in the fundamental plane of early-type galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2010D. Fraix-Burnet ABSTRACT The fundamental plane of early-type galaxies is a rather tight three-parameter correlation discovered more than 20 yr ago. It has resisted both a global and precise physical interpretation despite a consequent number of works, observational, theoretical or using numerical simulations. It appears that its precise properties depend on the population of galaxies in study. Instead of selecting a priori these populations, we propose to objectively construct homologous populations from multivariate analyses. We have undertaken multivariate cluster and cladistic analyses of a sample of 56 low-redshift galaxy clusters containing 699 early-type galaxies, using four parameters: effective radius, velocity dispersion, surface brightness averaged over effective radius and Mg2 index. All our analyses are consistent with seven groups that define separate regions on the global fundamental plane, not across its thickness. In fact, each group shows its own fundamental plane, which is more loosely defined for less diversified groups. We conclude that the global fundamental plane is not a bent surface, but made of a collection of several groups characterizing several fundamental planes with different thicknesses and orientations in the parameter space. Our diversification scenario probably indicates that the level of diversity is linked to the number and the nature of transforming events and that the fundamental plane is the result of several transforming events. We also show that our classification, not the fundamental planes, is universal within our redshift range (0.007,0.053). We find that the three groups with the thinnest fundamental planes presumably formed through dissipative (wet) mergers. In one of them, this(ese) merger(s) must have been quite ancient because of the relatively low metallicity of its galaxies, Two of these groups have subsequently undergone dry mergers to increase their masses. In the k-space, the third one clearly occupies the region where bulges (of lenticular or spiral galaxies) lie and might also have formed through minor mergers and accretions. The two least diversified groups probably did not form by major mergers and must have been strongly affected by interactions, some of the gas in the objects of one of these groups having possibly been swept out. The interpretation, based on specific assembly histories of galaxies of our seven groups, shows that they are truly homologous. They were obtained directly from several observables, thus independently of any a priori classification. The diversification scenario relating these groups does not depend on models or numerical simulations, but is objectively provided by the cladistic analysis. Consequently, our classification is more easily compared to models and numerical simulations, and our work can be readily repeated with additional observables. [source] A deep i -selected multiwaveband galaxy catalogue in the COSMOS field,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2008A. Gabasch ABSTRACT In this paper we present a deep and homogeneous i -band-selected multiwaveband catalogue in the COSMOS field covering an area of about 0.7 deg2. Our catalogue with a formal 50 per cent completeness limit for point sources of i, 26.7 comprises about 290 000 galaxies with information in 8 passbands. We combine publicly available u, B, V, r, i, z and K data with proprietary imaging in H band. We discuss in detail the observations, the data reduction, and the photometric properties of the H -band data. We estimate photometric redshifts for all the galaxies in the catalogue. A comparison with 162 spectroscopic redshifts in the redshift range 0 ,z, 3 shows that the achieved accuracy of the photometric redshifts is ,z/(zspec+ 1) , 0.035 with only ,2 per cent outliers. We derive absolute UV magnitudes and investigate the evolution of the luminosity function evaluated in the rest-frame UV (1500 Å). There is a good agreement between the luminosity functions derived here and the luminosity functions derived in the FORS Deep Field. We see a similar brightening of M* and a decrease of ,* with redshift. The catalogue including the photometric redshift information is made publicly available. [source] Reionization bias in high-redshift quasar near-zonesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008J. Stuart B. Wyithe ABSTRACT Absorption spectra of high-redshift quasars exhibit an increasingly thick Ly, forest, suggesting that the fraction of neutral hydrogen in the intergalactic medium (IGM) is increasing towards z, 6. However, the interpretation of these spectra is complicated by the fact that the Ly, optical depth is already large for neutral hydrogen fractions in excess of 10,4, and also because quasars are expected to reside in dense regions of the IGM. We present a model for the evolution of the ionization state of the IGM which is applicable to the dense, biased regions around high-redshift quasars as well as more typical regions in the IGM. We employ a cold dark matter based model in which the ionizing photons for reionization are produced by star formation in dark matter haloes spanning a wide range of masses, combined with numerical radiative transfer simulations which model the resulting opacity distribution in quasar absorption spectra. With an appropriate choice for the parameter which controls the star formation efficiency, our model is able to simultaneously reproduce the observed Ly, forest opacity at 4 < z < 6, the ionizing photon mean-free-path at z, 4 and the rapid evolution of highly ionized near-zone sizes around high-redshift quasars at 5.8 < z < 6.4. In our model, reionization extends over a wide redshift range, starting at z, 10 and completing as H ii regions overlap at z, 6,7. We find that within 5 physical Mpc of a high-redshift quasar, the evolution of the ionization state of the IGM precedes that in more typical regions by around 0.3 redshift units. More importantly, when combined with the rapid increase in the ionizing photon mean-free-path expected shortly after overlap, this offset results in an ionizing background near the quasar which exceeds the value in the rest of the IGM by a factor of ,2,3. We further find that in the post-overlap phase of reionization the size of the observed quasar near-zones is not directly sensitive to the neutral hydrogen fraction of the IGM. Instead, these sizes probe the level of the background ionization rate and the temperature of the surrounding IGM. The observed rapid evolution of the quasar near-zone sizes at 5.8 < z < 6.4 can thus be explained by the rapid evolution of the ionizing background, which in our model is caused by the completion of overlap at the end of reionization by 6 ,z, 7. [source] A catalogue of absorption lines in eight Hubble Space Telescope/STIS E230M 1.0 < z < 1.7 quasar spectra,MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2007N. Milutinovi ABSTRACT We have produced a catalogue of line identifications and equivalent width measurements for all absorption features in eight ultraviolet echelle quasar spectra. These spectra were selected as having the highest signal-to-noise ratio among the Hubble Space Telescope/STIS spectra obtained with the E230M grating. We identify 56 metal-line systems towards the eight quasars, and present plots of detected transitions, aligned in velocity space. We found that about 1/4,1/3 of the features in the Ly, forest region, redward of the incidence of the Ly, forest, are metal lines. High-ionization transitions are common. At the redshift range we study, z < 1.7, we see both O vi and C iv in 88,90 per cent of the metal-line systems for which the spectra cover the expected wavelength. Si iii is seen in 58 per cent, while low-ionization absorption in C ii, Si ii and/or Al ii is detected in 50 per cent of the systems for which they are covered. This catalogue will facilitate future studies of the Ly, forest and of metal-line systems of various types. [source] Selection of ThAr lines for wavelength calibration of echelle spectra and implications for variations in the fine-structure constantMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2007M. T. Murphy ABSTRACT Echelle spectrographs currently provide some of the most precise and detailed spectra in astronomy, the interpretation of which sometimes depends on the wavelength calibration accuracy. In some applications, such as constraining cosmological variations in the fundamental constants from quasar absorption lines, the wavelength calibration is crucial. Here we detail an algorithm for selecting thorium,argon (ThAr) emission lines for wavelength calibration which incorporates the properties of both a new laboratory wavelength list and the spectrograph of interest. We apply the algorithm to the Very Large Telescope Ultraviolet and Visual Echelle Spectrograph (UVES) and demonstrate a factor of ,3 improvement in the wavelength calibration residuals (i.e. random errors) alone. It is also found that UVES spectra calibrated using a previous, widely distributed line-list contain systematic ±30 ,75 m s,1 distortions of the wavelength scale over both short and long wavelength ranges. These distortions have important implications for current UVES constraints on cosmological variations in the fine-structure constant. The induced systematic errors are most severe for Mg/Feii quasar absorbers in the redshift range 1.2 ,zabs, 2.3, with individual absorbers studied by recent authors containing systematic errors up to four times larger than quoted statistical errors. [source] The DEEP2 galaxy redshift survey: the evolution of the blue fraction in groups and the fieldMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007Brian F. Gerke ABSTRACT We explore the behaviour of the blue galaxy fraction over the redshift range 0.75 ,z, 1.3 in the DEEP2 Survey, both for field galaxies and for galaxies in groups. The primary aim is to determine the role that groups play in driving the evolution of galaxy colour at high z. In pursuing this aim, it is essential to define a galaxy sample that does not suffer from redshift-dependent selection effects in colour,magnitude space. We develop four such samples for this study: at all redshifts considered, each one is complete in colour,magnitude space, and the selection also accounts for evolution in the galaxy luminosity function. These samples will also be useful for future evolutionary studies in DEEP2. The colour segregation observed between local group and field samples is already in place at z, 1: DEEP2 groups have a significantly lower blue fraction than the field. At fixed z, there is also a correlation between blue fraction and galaxy magnitude, such that brighter galaxies are more likely to be red, both in groups and in the field. In addition, there is a negative correlation between blue fraction and group richness. In terms of evolution, the blue fraction in groups and the field remains roughly constant from z= 0.75 to 1, but beyond this redshift the blue fraction in groups rises rapidly with z, and the group and field blue fractions become indistinguishable at z, 1.3. Careful tests indicate that this effect does not arise from known systematic or selection effects. To further ensure the robustness of this result, we build on previous mock DEEP2 catalogues to develop mock catalogues that reproduce the colour,overdensity relation observed in DEEP2 and use these to test our methods. The convergence between the group and field blue fractions at z, 1.3 implies that DEEP2 galaxy groups only became efficient at quenching star formation at z, 2; this result is broadly consistent with other recent observations and with current models of galaxy evolution and hierarchical structure growth. [source] Cosmological simulations of intergalactic medium enrichment from galactic outflowsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Benjamin D. Oppenheimer ABSTRACT We investigate models of self-consistent chemical enrichment of the intergalactic medium (IGM) from z= 6.0 , 1.5, based on hydrodynamic simulations of structure formation that explicitly incorporate outflows from star-forming galaxies. Our main result is that outflow parametrizations derived from observations of local starburst galaxies, in particular momentum-driven wind scenarios, provide the best agreement with observations of C iv absorption at z, 2,5. Such models sufficiently enrich the high- z IGM to produce a global mass density of C iv absorbers that is relatively invariant from z= 5.5 , 1.5, in agreement with observations. This occurs despite continual IGM enrichment causing an increase in volume-averaged metallicity by ,× 5,10 over this redshift range, because energy input accompanying the enriching outflows causes a drop in the global ionization fraction of C iv. Comparisons to observed C iv column density and linewidth distributions and C iv -based pixel optical depth ratios provide significant constraints on wind models. Our best-fitting outflow models show mean IGM temperatures only slightly above our no-outflow case, metal filling factors of just a few per cent with volume-weighted metallicities around 10,3 at z, 3, significant amounts of collisionally ionized C iv absorption and a metallicity,density relationship that rises rapidly at low overdensities and flattens at higher ones. In general, we find that outflow speeds must be high enough to enrich the low-density IGM at early times but low enough not to overheat it, and concurrently must significantly suppress early star formation while still producing enough early metals. It is therefore non-trivial that locally calibrated momentum-driven wind scenarios naturally yield the desired strength and evolution of outflows, and suggest that such models represent a significant step towards understanding the impact of galactic outflows on galaxies and the IGM across cosmic time. [source] The properties of Ly, emitting galaxies in hierarchical galaxy formation modelsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2006M. Le Delliou ABSTRACT We present detailed predictions for the properties of Ly,-emitting galaxies in the framework of the , cold dark matter cosmology, calculated using the semi-analytical galaxy formation model galform. We explore a model that assumes a top-heavy initial mass function in starbursts and that has previously been shown to explain the sub-millimetre number counts and the luminosity function of Lyman-break galaxies at high redshift. We show that this model, with the simple assumption that a fixed fraction of Ly, photons escape from each galaxy, is remarkably successful at explaining the observed luminosity function of Ly, emitters (LAEs) over the redshift range 3 < z < 6.6. We also examine the distribution of Ly, equivalent widths and the broad-band continuum magnitudes of emitters, which are in good agreement with the available observations. We look more deeply into the nature of LAEs, presenting predictions for fundamental properties such as the stellar mass and radius of the emitting galaxy and the mass of the host dark matter halo. The model predicts that the clustering of LAEs at high redshifts should be strongly biased relative to the dark matter, in agreement with observational estimates. We also present predictions for the luminosity function of LAEs at z > 7, a redshift range that is starting to be be probed by near-infrared surveys and using new instruments such as the Dark Ages Z Lyman Explorer (DAzLE). [source] The sources of intergalactic metalsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2006E. Scannapieco ABSTRACT We study the clustering properties of metals in the intergalactic medium (IGM) as traced by 619 C iv and 81 Si iv absorption components with N, 1012 cm,2 and 316 Mg ii and 82 Fe ii absorption components with N, 1011.5 cm,2 in 19 high signal-to-noise ratio (60,100 pixel,1), high-resolution (R= 45 000) quasar spectra. C iv and Si iv trace each other closely and their line-of-sight correlation functions ,(v) exhibit a steep decline at large separations and a flatter profile below ,150 km s,1, with a large overall bias. These features do not depend on absorber column densities, although there are hints that the overall amplitude of ,C iv (v) increases with time over the redshift range detected (1.5,3). Carrying out a detailed smoothed particle hydrodynamic simulation (2 × 3203, 57 Mpc3 comoving), we show that the C iv correlation function cannot be reproduced by models in which the IGM metallicity is constant or a local function of overdensity (Z,,2/3). However, the properties of ,C iv(v) are generally consistent with a model in which metals are confined within bubbles with a typical radius Rs about sources of mass ,Ms. We derive best-fitting values of Rs, 2 comoving Mpc and Ms, 1012 M, at z= 3. Our lower-redshift (0.5,2) measurements of the Mg ii and Fe ii correlation functions also uncover a steep decline at large separations and a flatter profile at small separations, but the clustering is even higher than in the z= 1.5,3 measurements, and the turnover is shifted to somewhat smaller distances, ,75 km s,1. Again, these features do not change with column density, but there are hints that the amplitudes of ,Mg ii(v) and ,Fe ii(v) increase with time. We describe an analytic ,bubble' model for these species, which come from regions that are too compact to be accurately simulated numerically, deriving best-fitting values of Rs, 2.4 Mpc and Ms, 1012 M,. Equally good analytic fits to all four species are found in a similarly biased high-redshift enrichment model in which metals are placed within 2.4 comoving Mpc of Ms, 3 × 109 sources at z= 7.5. [source] The 2dF QSO Redshift Survey , XIV.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005Structure, evolution from the two-point correlation function ABSTRACT In this paper we present a clustering analysis of quasi-stellar objects (QSOs) using over 20 000 objects from the final catalogue of the 2dF QSO Redshift Survey (2QZ), measuring the redshift-space two-point correlation function, ,(s). When averaged over the redshift range 0.3 < z < 2.2 we find that ,(s) is flat on small scales, steepening on scales above ,25 h,1 Mpc. In a WMAP/2dF cosmology (,m= 0.27, ,,= 0.73) we find a best-fitting power law with s0= 5.48+0.42,0.48 h,1 Mpc and ,= 1.20 ± 0.10 on scales s= 1 to 25 h,1 Mpc. We demonstrate that non-linear redshift-space distortions have a significant effect on the QSO ,(s) at scales less than ,10 h,1 Mpc. A cold dark matter model assuming WMAP/2dF cosmological parameters is a good description of the QSO ,(s) after accounting for non-linear clustering and redshift-space distortions, and allowing for a linear bias at the mean redshift of bQ(z= 1.35) = 2.02 ± 0.07. We subdivide the 2QZ into 10 redshift intervals with effective redshifts from z= 0.53 to 2.48. We find a significant increase in clustering amplitude at high redshift in the WMAP/2dF cosmology. The QSO clustering amplitude increases with redshift such that the integrated correlation function, , within 20 h,1 Mpc is and . We derive the QSO bias and find it to be a strong function of redshift with bQ(z= 0.53) = 1.13 ± 0.18 and bQ(z= 2.48) = 4.24 ± 0.53. We use these bias values to derive the mean dark matter halo (DMH) mass occupied by the QSOs. At all redshifts 2QZ QSOs inhabit approximately the same mass DMHs with MDH= (3.0 ± 1.6) × 1012 h,1 M,, which is close to the characteristic mass in the Press,Schechter mass function, M*, at z= 0. These results imply that L*Q QSOs at z, 0 should be largely unbiased. If the relation between black hole (BH) mass and MDH or host velocity dispersion does not evolve, then we find that the accretion efficiency (L/LEdd) for L*Q QSOs is approximately constant with redshift. Thus the fading of the QSO population from z, 2 to ,0 appears to be due to less massive BHs being active at low redshift. We apply different methods to estimate, tQ, the active lifetime of QSOs and constrain tQ to be in the range 4 × 106,6 × 108 yr at z, 2. We test for any luminosity dependence of QSO clustering by measuring ,(s) as a function of apparent magnitude (equivalent to luminosity relative to L*Q). However, we find no significant evidence of luminosity-dependent clustering from this data set. [source] The mass function of the stellar component of galaxies in the Sloan Digital Sky SurveyMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2004Benjamin Panter ABSTRACT Using the moped algorithm, we determine non-parametrically the stellar mass function of 96 545 galaxies from the Sloan Digital Sky Survey Data Release One. By using the reconstructed spectrum due to starlight, we can eliminate contamination from either emission lines or active galactic nuclei components. Our results give excellent agreement with previous works, but extend their range by more than two decades in mass to 107.5,Ms/h,2 M,, 1012. We present both a standard Schechter fit and a fit modified to include an extra, high-mass contribution, possibly from cluster central dominant galaxies. The Schechter fit parameters are ,,= (7.8 ± 0.1) × 10,3 h3 Mpc,3, M,= (7.64 ± 0.09) × 1010 h,2 M, and ,=,1.159 ± 0.008. Our sample also yields an estimate for the contribution from baryons in stars to the critical density of ,b*h= (2.39 ± 0.08) × 10,3, in good agreement with other indicators. Error bars are statistical and a Salpeter initial mass function is assumed throughout. We find no evolution of the mass function in the redshift range 0.05 < z < 0.34, indicating that almost all stars were already formed at z, 0.34 with little or no star formation activity since then and that the evolution seen in the luminosity function must be largely due to stellar fading. [source] Probing the dark ages with redshift distribution of gamma-ray burstsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2002T. Roy Choudhury Abstract In this article, we explore the possibility of using the properties of gamma-ray bursts (GRBs) to probe the physical conditions in the epochs prior to reionization. The redshift distribution of GRBs is modelled using the Press,Schechter formalism with an assumption that they follow the cosmic star formation history. We reproduce the observed star formation rate obtained from galaxies in the redshift range 0 < z < 5, as well as the redshift distribution of the GRBs inferred from the luminosity,variability correlation of the burst light curve. We show that the fraction of GRBs at high redshifts, the afterglows of which cannot be observed in the R and I bands owing to H i Gunn,Peterson optical depth can, at the most, account for one third of the dark GRBs. The observed redshift distribution of GRBs, with much less scatter than the one available today, can put stringent constraints on the epoch of reionization and the nature of gas cooling in the epochs prior to reionization. [source] Hubble Space Telescope Wide Field Planetary Camera 2 observations of hyperluminous infrared galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2002D. Farrah We present Hubble Space Telescope Wide Field Planetary Camera 2 I -band imaging for a sample of nine hyperluminous infrared galaxies (HLIRGs) spanning a redshift range . Three of the sample have morphologies showing evidence for interactions and six are quasi-stellar objects (QSOs). Host galaxies in the QSOs are detected reliably out to . The detected QSO host galaxies have an elliptical morphology with scalelengths spanning and absolute k -corrected magnitudes spanning There is no clear correlation between the infrared (IR) power source and the optical morphology. None of the sources in the sample, including F15307+3252, shows any evidence for gravitational lensing. We infer that the IR luminosities are thus real. Based on these results, and previous studies of HLIRGs, we conclude that this class of object is broadly consistent with being a simple extrapolation of the ULIRG population to higher luminosities; ULIRGs being mainly violently interacting systems powered by starbursts and/or active galactic nuclei. Only a small number of sources, the infrared luminosities of which exceed 1013 L,, are intrinsically less luminous objects that have been boosted by gravitational lensing. [source] Setting new constraints on the age of the UniverseMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001Ignacio Ferreras There are three independent techniques for determining the age of the Universe: via cosmochronology of long-lived radioactive nuclei, via stellar modelling and population synthesis of the oldest stellar populations, and, most recently, via the precision cosmology that has become feasible with the mapping of the acoustic peaks in the cosmic microwave background. We demonstrate that all three methods give completely consistent results, and enable us to set rigorous bounds on the maximum and minimum ages that are allowed for the Universe. We present new constraints on the age of the Universe by performing a multiband colour analysis of bright cluster ellipticals over a large redshift range , which allows us to infer the ages of their stellar populations over a wide range of possible formation redshifts and metallicities. Applying a prior to Hubble's constant of we find the age of the Universe to be (1,), in agreement with the estimates from Type Ia supernovae, as well as with the latest uranium decay estimates, which yield an age for the Milky Way of . If we combine the results from cluster ellipticals with the analysis of the angular power spectrum of the cosmic microwave background and with the observations of Type Ia supernovae at high redshift, we find a similar age: . Without the assumption of any priors, universes older than 18 Gyr are ruled out by the data at the 90 per cent confidence level. [source] Possible evidence for a variable fine-structure constant from QSO absorption lines: systematic errorsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001M.T. Murphy Comparison of quasar (QSO) absorption spectra with laboratory spectra allows us to probe possible variations in the fundamental constants over cosmological time-scales. In a companion paper we present an analysis of Keck/HIRES spectra and report possible evidence suggesting that the fine-structure constant, ,, may have been smaller in the past: over the redshift range . In this paper we describe a comprehensive investigation into possible systematic effects. Most of these do not significantly influence our results. When we correct for those which do produce a significant systematic effect in the data, the deviation of from zero becomes more significant. We are led increasingly to the interpretation that , was slightly smaller in the past. [source] A weak lensing estimate from GEMS of the virial to stellar mass ratio in massive galaxies to z, 0.8MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2006Catherine Heymans ABSTRACT We present constraints on the evolution of the virial to stellar mass ratio of galaxies with high stellar masses in the redshift range 0.2 < z < 0.8, by comparing weak lensing measurements of virial mass Mvir with estimates of stellar mass Mstar. For a complete sample of galaxies with log (Mstar/M,) > 10.5, where the majority show an early-type morphology, we find that the virial mass to stellar mass ratio is given by Mvir/Mstar= 53+13,16. Assuming a baryon fraction from the concordance cosmology, this corresponds to a stellar fraction of baryons in massive galaxies of ,*b/,b= 0.10 ± 0.03. Analysing the galaxy sample in different redshift slices, we find little or no evolution in the virial to stellar mass ratio, and place an upper limit of ,2.5 on the growth of massive galaxies through the conversion of gas into stars from z= 0.8 to the present day. [source] Photometric properties and scaling relations of early-type Brightest Cluster GalaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008F. S. Liu ABSTRACT We investigate the photometric properties of the early-type Brightest Cluster Galaxies (BCGs) using a carefully selected sample of 85 BCGs from the C4 cluster catalogue with a redshift of less than 0.1. We perform accurate background subtractions and surface photometry for these BCGs to 25 mag arcsec,2 in the Sloan r band. By quantitatively analysing the gradient of the Petrosian profiles of BCGs, we find that a large fraction of BCGs have extended stellar envelopes in their outskirts; more luminous BCGs tend to have more extended stellar haloes that are likely to be connected with mergers. A comparison sample of elliptical galaxies was chosen with similar apparent magnitude and redshift ranges, for which the same photometric analysis procedure is applied. We find that BCGs have steeper size,luminosity (R,L,) and Faber,Jackson (L,,,) relations than the bulk of early-type galaxies. Furthermore, the power-law indices (, and ,) in these relations increase as the isophotal limits become deeper. For isophotal limits from 22 to 25 mag arcsec,2, BCGs are usually larger than the bulk of early-type galaxies, and a large fraction (,49 per cent) of BCGs have discy isophotal shapes. The differences in the scaling relations are consistent with a scenario where the dynamical structure and formation route of BCGs may be different from the bulk of early-type galaxies; in particular dry (dissipationless) mergers may play a more important role in their formation. We highlight several possible dry merger candidates in our sample. [source] | ||||||||||