We use stellar masses, surface photometry, strong lensing masses, and stellar velocity dispersions (σ e/2 ) to investigate empirical correlations for the definitive sample of 73 early-type galaxies (ETGs) that are strong gravitational lenses from the SLACS survey. The traditional correlations (Fundamental Plane [FP] and its projections) are consistent with those found for non-lens galaxies, supporting the thesis that SLACS lens galaxies are representative of massive ETGs (dimensional mass M dim = 10 11 − 10 12 M ⊙ ). The addition of high-precision strong lensing estimates of the total mass allows us to gain further insights into their internal structure: i) the average slope of the total mass density profile (ρ tot ∝ r −γ ′ ) is γ ′ = 2.078 ± 0.027 with an intrinsic scatter of 0.16 ± 0.02; ii) γ ′ correlates with effective radius (r e ) and central mass density, in the sense that denser galaxies have steeper profiles; iii) the dark matter fraction within r e /2 is a monotonically increasing function of galaxy mass and size (due to a mass-dependent central cold dark matter distribution or to baryonic dark matter -stellar remnants or low mass stars -if the IMF is non-universal and its normalization increases with mass); iv) the dimensional mass M dim ≡ 5r e σ 2 e/2 /G is proportional to the total (lensing) mass M re/2 , and both increase more rapidly than stellar mass M * (M * ∝ M 0.8 re/2 ); v) the Mass Plane (MP), obtained by replacing surface brightness with surface mass density in the FP, is found to be tighter and closer to the virial relation than the FP and the M * P, indicating that the scatter of those relations is dominated by stellar populations effects; vi) we construct the Fundamental Hyper-Plane by adding stellar masses to the MP and find the M * coefficient to be consistent with zero and no residual intrinsic scatter. Our results demonstrate that the dynamical structure of ETGs is not scale invariant and that it is fully specified by M re/2 , r e , and σ e/2 . Although the basic trends can be explained qualitatively in terms of varying star formation efficiency as a function of halo mass and as the result of dry and wet mergers, reproducing quantitatively the observed correlations and their tightness may be a significant challenge for galaxy formation models.

We present the definitive data for the full sample of 131 strong gravitational lens candidates observed with the Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope by the Sloan Lens ACS (SLACS) Survey. All targets were selected for higher redshift emission lines and lower redshift continuum in a single Sloan Digital Sky Survey (SDSS) spectrum. The foreground galaxies are primarily of early-type morphology, with redshifts from z ' 0:05 to 0.5 and velocity dispersions from ' 160 to 400 km s À1 ; the faint background emission-line galaxies have redshifts ranging from z ' 0:2 to 1.2. We confirm 70 systems showing clear evidence of multiple imaging of the background galaxy by the foreground galaxy, as well as an additional 19 systems with probable multiple imaging. For 63 clear lensing systems, we present singular isothermal ellipsoid and light-traces-mass gravitational lens models fitted to the ACS imaging data. These strong-lensing mass measurements are supplemented by magnitudes and effective radii measured from ACS surface brightness photometry and redshifts and velocity dispersions measured from SDSS spectroscopy. These data constitute a unique resource for the quantitative study of the interrelations between mass, light, and kinematics in massive early-type galaxies. We show that the SLACS lens sample is statistically consistent with being drawn at random from a parent sample of SDSS galaxies with comparable spectroscopic parameters and effective radii, suggesting that the results of SLACS analyses can be generalized to the massive early-type population.

A large-scale hydrodynamical cosmological simulation, Horizon-AGN , is used to investigate the alignment between the spin of galaxies and the cosmic filaments above redshift 1.2. The analysis of more than 150 000 galaxies per time step in the redshift range 1.2 < z < 1.8 with morphological diversity shows that the spin of low-mass blue galaxies is preferentially aligned with their neighbouring filaments, while high-mass red galaxies tend to have a perpendicular spin. The reorientation of the spin of massive galaxies is provided by galaxy mergers, which are significant in their mass build-up. We find that the stellar mass transition from alignment to misalignment happens around 3 × 10 10 M ⊙ . Galaxies form in the vorticity-rich neighbourhood of filaments, and migrate towards the nodes of the cosmic web as they convert their orbital angular momentum into spin. The signature of this process can be traced to the properties of galaxies, as measured relative to the cosmic web. We argue that a strong source of feedback such as active galactic nuclei is mandatory to quench in situ star formation in massive galaxies and promote various morphologies. It allows mergers to play their key role by reducing post-merger gas inflows and, therefore, keeping spins misaligned with cosmic filaments.

International audienceMassive present-day early-type (elliptical and lenticular) galaxies probably gained the bulk of their stellar mass and heavy elements through intense, dust-enshrouded starbursts--that is, increased rates of star formation--in the most massive dark-matter haloes at early epochs. However, it remains unknown how soon after the Big Bang massive starburst progenitors exist. The measured redshift (z) distribution of dusty, massive starbursts has long been suspected to be biased low in z owing to selection effects, as confirmed by recent findings of systems with redshifts as high as ~5 (refs 2-4). Here we report the identification of a massive starburst galaxy at z = 6.34 through a submillimetre colour-selection technique. We unambiguously determined the redshift from a suite of molecular and atomic fine-structure cooling lines. These measurements reveal a hundred billion solar masses of highly excited, chemically evolved interstellar medium in this galaxy, which constitutes at least 40 per cent of the baryonic mass. A 'maximum starburst' converts the gas into stars at a rate more than 2,000 times that of the Milky Way, a rate among the highest observed at any epoch. Despite the overall downturn in cosmic star formation towards the highest redshifts, it seems that environments mature enough to form the most massive, intense starbursts existed at least as early as 880 million years after the Big Ban

We determine an absolute calibration of the initial mass function (IMF) of early-type galaxies, by studying a sample of 56 gravitational lenses identified by the SLACS Survey. Under the assumption of standard Navarro, Frenk & White dark matter halos, a combination of lensing, dynamical, and stellar population synthesis models is used to disentangle the stellar and dark matter contribution for each lens. We define an "IMF mismatch" parameter α ≡M LD * ,Ein /M SPS * ,Ein as the ratio of stellar mass inferred by a joint lensing and dynamical models (M LD * ,Ein ) to the current stellar mass inferred from stellar populations synthesis models (M SPS * ,Ein ). We find that a Salpeter IMF provides stellar masses in agreement with those inferred by lensing and dynamical models ( log α = 0.00 ± 0.03 ± 0.02), while a Chabrier IMF underestimates them ( log α = 0.25 ± 0.03 ± 0.02). A tentative trend is found, in the sense that α appears to increase with galaxy velocity dispersion. Taken at face value, this result would imply a non universal IMF, perhaps dependent on metallicity, age, or abundance ratios of the stellar populations. Alternatively, the observed trend may imply non-universal dark matter halos with inner density slope increasing with velocity dispersion. While the degeneracy between the two interpretations cannot be broken without additional information, the data imply that massive early-type galaxies cannot have both a universal IMF and universal dark matter halos.

We present a weak-lensing analysis of 22 early-type (strong) lens galaxies, based on deep HST images obtained as part of the Sloan Lens ACS Survey. Using advanced techniques to control systematic uncertainties, we show that weak-lensing signal is detected out to $300 h À1 kpc (at the mean lens redshift z ¼ 0:2). We analyze blank control fields from COSMOS in the same manner, inferring that the residual systematic uncertainty in the tangential shear is less than 0.3%. A joint strong-and weak-lensing analysis shows that the average total mass density profile is consistent with isothermal (i.e., / r À2 ) over two decades in radius (3Y300 h À1 kpc, approximately 1Y100 effective radii). This finding extends by over an order of magnitude in radius previous results, based on strong lensing and/or stellar dynamics, that luminous and dark components ''conspire'' to form an isothermal mass distribution. In order to disentangle the contributions of luminous and dark matter, we fit a two-component mass model (de Vaucouleurs+NFW) to the weak-and strong-lensing constraints. It provides a good fit to the data with only two free parameters: (1) the average stellar mass-to-light ratio M Ã /L V ¼ 4:48 AE 0:46 h M L À1 (at z ¼ 0:2), in agreement with that expected for an old stellar population; (2) the average virial mass-to-light ratio M vir /L V ¼ 246 þ101 À87 h M L À1 . Taking into account the scatter in the mass-luminosity relation, the latter result is in good agreement with semianalytical models of massive galaxy formation. The dark matter fraction inside the sphere of radius, the effective radius, is found to be 27% AE 4%. Our results are consistent with galaxy-galaxy lensing studies of early-type galaxies that are not strong lenses, in the 30Y 300 h À1 kpc radius range. Thus, within the uncertainties, our results are representative of early-type galaxies in general.

Based on 58 SLACS strong-lens early-type galaxies with direct total-mass and stellar-velocity dispersion measurements, we find that inside one effective radius massive elliptical galaxies with M eff 3 · 10 10 M ⊙ are well-approximated by a power-law ellipsoid with an average logaritmic density slope of γ ′ LD ≡ −d log(ρ tot )/d log(r) = 2.085 +0.025 −0.018 (random error on mean) for isotropic orbits with β r = 0, ±0.1 (syst.) and σ γ ′ 0.20 +0.04 −0.02 intrinsic scatter (all errors indicate the 68% CL). We find no correlation of γ ′ LD with galaxy mass (M eff ), rescaled radius (i.e. R einst /R eff ) or redshift, despite intrinsic differences in density-slope between galaxies. Based on scaling relations, the average logarithmic density slope can be derived in an alternative manner, fully independent from dynamics, yielding γ ′ SR = 1.959 ± 0.077. Agreement between the two values is reached for β r = 0.45 ± 0.25, consistent with mild radial anisotropy. This agreement supports the robustness of our results, despite the increase in mass-to-light ratio with total galaxy mass: M eff ∝ L 1.363±0.056 V,eff. We conclude that massive early-type galaxies are structurally close-to homologous with close-to isothermal total density profiles ( 10% intrinsic scatter) and have at most some mild radial anisotropy. Our results provide new observational limits on galaxy formation and evolution scenarios, covering four Gyr look-back time.

We present the current photometric dataset for the Sloan Lens ACS (SLACS) Survey, including HST photometry from ACS, WFPC2, and NICMOS. These data have enabled the confirmation of an additional 15 grade 'A' (certain) lens systems, bringing the number of SLACS grade 'A' lenses to 85; including 13 grade 'B' (likely) systems, SLACS has identified nearly 100 lenses and lens candidates. Approximately 80% of the grade 'A' systems have elliptical morphologies while ∼10% show spiral structure; the remaining lenses have lenticular morphologies. Spectroscopic redshifts for the lens and source are available for every system, making SLACS the largest homogeneous dataset of galaxy-scale lenses to date. We have created lens models using singular isothermal ellipsoid mass distributions for the 11 new systems that are dominated by a single mass component and where the multiple images are detected with sufficient signal-to-noise; these models give a high precision measurement of the mass within the Einstein radius of each lens. We have developed a novel Bayesian stellar population analysis code to determine robust stellar masses with accurate error estimates. We apply this code to deep, high-resolution HST imaging and determine stellar masses with typical statistical errors of 0.1 dex; we find that these stellar masses are unbiased compared to estimates obtained using SDSS photometry, provided that informative priors are used. The stellar masses range from 10 10.5 to 10 11.8 M ⊙ and the typical stellar mass fraction within the Einstein radius is 0.4, assuming a Chabrier IMF. The ensemble properties of the SLACS lens galaxies, e.g. stellar masses and projected ellipticities, appear to be indistinguishable from other SDSS galaxies with similar stellar velocity dispersions. This further supports that SLACS lenses are representative of the overall population of massive early-type galaxies with M * 10 11 M ⊙ , and are therefore an ideal dataset to investigate the kpc-scale distribution of luminous and dark matter in galaxies out to z ∼ 0.5.