CFHTLenS: higher order galaxy-mass correlations probed by galaxy-galaxy-galaxy lensing (original) (raw)
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Astronomy and Astrophysics, 2009
Context. The Strong Lensing Legacy Survey (SL2S) provides a sample of strong lensing events associated with massive distant galaxies, some of which lie in the outskirts of galaxy groups and clusters. Aims. We investigate the internal structure of early-type galaxies in overdense environments, where tidal forces are expected to alter dark matter halos of infalling galaxies. Methods. SL2SJ02176-0513 is a remarkable lens for the presence of two multiply-imaged systems at different redshifts lensed by a foreground massive galaxy at z lens = 0.656: a bright cusp arc at z arc = 1.847 and an additional double-image system at an estimated redshift of z dbl ∼ 2.9 based on photometry and lensing geometry. The system is located about 400 kpc away from the center of a massive group of galaxies. Mass estimates for the group are available from X-ray observations and satellite kinematics. Multicolor photometry provides an estimate of the stellar mass of the main lens galaxy. The lensing galaxy is modeled with two components (stars and dark matter), and we include the perturbing effect of the group environment, and all available constraints. Results. We find that classic lensing degeneracies, e.g. between external convergence and mass density slope, are significantly reduced with respect to standard systems and infer tight constraints on the mass density profile: (i) the dark matter content of the main lens galaxy is in line with that of typical galaxies f dm (< R e ) = 0.41 +0.09 −0.06 ; (ii) the required mass associated with the dark matter halo of the nearby group is consistent with X-ray and weak-lensing estimates (σ grp = 550 +130 −240 ); (iii) accounting for the group contribution in the form of an external convergence, the slope of the mass density profile of the main lens galaxy alone is found to be α = −1.03 +0.22 −0.16 , consistent with the isothermal (α = −1) slope. Conclusions. We demonstrate that multiple source plane systems together with good ancillary dataset can be used to disentangle local and environmental effects.
The Galaxy-Mass Correlation Function Measured from Weak Lensing in the Sloan Digital Sky Survey
The Astronomical Journal, 2004
We present galaxy-galaxy lensing measurements over scales 0.025 to 10 h −1 Mpc in the Sloan Digital Sky Survey. Using a flux-limited sample of 127,001 lens galaxies with spectroscopic redshifts and mean luminosity L ∼ L * and 9,020,388 source galaxies with photometric redshifts, we invert the lensing signal to obtain the galaxy-mass correlation function ξ gm . We find ξ gm is consistent with a power-law, ξ gm = (r/r 0 ) −γ , with best-fit parameters γ = 1.79 ± 0.06 and r 0 = (5.4 ± 0.7)(0.27/Ω m ) 1/γ h −1 Mpc. At fixed separation, the ratio ξ gg /ξ gm = b/r where b is the bias and r is the correlation coefficient. Comparing to the galaxy auto-correlation function for a similarly selected sample of SDSS galaxies, we find that b/r is approximately scale independent over scales 0.2 − 6.7h −1 Mpc, with mean b/r = (1.3 ± 0.2)(Ω m /0.27). We also find no scale dependence in b/r for a volume limited sample of luminous galaxies (−23.0 < M r < −21.5). The mean b/r for this sample is b/r V lim = (2.0 ± 0.7)(Ω m /0.27). We split the lens galaxy sample into subsets based on luminosity, color, spectral type, and velocity dispersion, and see clear trends of the lensing signal with each of these parameters. The amplitude and logarithmic slope of ξ gm increases with galaxy luminosity. For high luminosities (L ∼ 5L * ), ξ gm deviates significantly from a power law. These trends with luminosity also appear in the subsample of red galaxies, which are more strongly clustered than blue galaxies. Subject headings: cosmology:observations -dark matter -gravitational lensing -large-scale structure of the universe
Monthly Notices of the Royal Astronomical Society, 2012
We construct a fully self-consistent mass model for the lens galaxy SDSS J2141 at redshift 0.14, and use it to improve on previous studies by modelling its gravitational lensing effect, gas rotation curve and stellar kinematics simultaneously. We adopt a very flexible axisymmetric mass model constituted by a generalized NFW dark matter halo and a stellar mass distribution obtained by deprojecting the multi-Gaussian expansion (MGE) fit to the highresolution K'-band Laser Guide Star Adaptive Optics (LGSAO) imaging data of the galaxy, with the (spatially constant) mass-to-light ratio as a free parameter. We model the stellar kinematics by solving the anisotropic Jeans equations. We find that the inner logarithmic slope of the dark halo is weakly constrained, i.e. γ = 0.82 +0.65 −0.54 , and consistent with an unmodified NFW profile; we can conclude, however, that steep profiles (γ 1.5) are disfavoured (< 14% posterior probability). We marginalize over this parameter to infer the galaxy to have (i) a dark matter fraction within 2.2 disk radii of 0.28 +0.15 −0.10 , independent of the galaxy stellar population, implying a maximal disk for SDSS J2141; (ii) an apparently uncontracted dark matter halo, with concentration c −2 = 7.7 +4.2 −2.5 and virial velocity v vir = 242 +44 −39 km s −1 , consistent with ΛCDM predictions; (iii) a slightly oblate halo (q h = 0.75 +0.27 −0.16), consistent with predictions from baryon-affected models. Comparing the tightly constrained gravitational stellar mass inferred from the combined analysis (log 10 M ⋆ /M ⊙ = 11.12 +0.05 −0.09) with that inferred from stellar populations modelling of the galaxies colours, and accounting for an expected cold gas fraction of 20 ± 10 per cent, we determine a preference for a Chabrier IMF over Salpeter IMF by a Bayes factor of 5.7 (corresponding to substantial evidence). We infer a value β z ≡ 1 − σ 2 z /σ 2 R = 0.43 +0.08 −0.11 for the orbital anisotropy parameter in the meridional plane, in agreement with most studies of local disk galaxies, and ruling out at 99 per cent confidence level that the dynamics of this system can be described by a two-integral distribution function.
The Astrophysical Journal, 2007
We present a weak gravitational lensing analysis of 22 early-type (strong) lens galaxies, based on deep Hubble Space Telescope images obtained as part of the Sloan Lens ACS Survey. Using advanced techniques to control systematic uncertainties related to the variable point spread function and charge transfer efficiency of the Advanced Camera for Surveys (ACS), we show that weak lensing signal is detected out to the edge of the Wide Field Camera ( 300 h −1 kpc at the mean lens redshift z = 0.2). We analyze blank control fields from the COSMOS survey 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. ρ ∝ r −2 ) over two decades in radius (3-300 h −1 kpc, approximately 1-100 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 component "conspire" to form an isothermal mass distribution. In order to disentangle the contributions of luminous and dark matter, we fit a twocomponent mass model (de Vaucouleurs + Navarro Frenk & White) to the weak and strong lensing constraints. It provides a good fit to the data with only two free parameters; i) the average stellar mass-to-light ratio M * /L V = 4.48±0.46 hM ⊙ /L ⊙ (at z = 0.2), in agreement with that expected for an old stellar population; ii) the average virial mass-to-light ratio M vir /L V = 246 +101 −87 hM ⊙ /L ⊙ . Taking into account the scatter in the mass-luminosity relation, this latter result is in good agreement with semi-analytical models of massive galaxies formation. The dark matter fraction inside the sphere of radius the effective radius is found to be 27±4%. Our results are consistent with galaxy-galaxy lensing studies of early-type galaxies that are not strong lenses, in the region of overlap (30-300 h −1 kpc). Thus, within the uncertainties, our results are representative of early-type galaxies in general.
The Astrophysical Journal, 2013
We present optical and near infrared spectroscopy obtained at Keck, VLT, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part of the SL2S survey. The deflectors are massive early-type galaxies in the redshift range z d = 0.2 − 0.8, while the lensed sources are at z s = 1 − 3.5. We combine this data with photometric and lensing measurements presented in the companion paper III and with lenses from the SLACS and LSD surveys to investigate the cosmic evolution of the internal structure of massive early-type galaxies over half the age of the universe. We study the dependence of the slope of the total mass density profile γ ′ (ρ(r) ∝ r −γ ′) on stellar mass, size, and redshift. We find that two parameters are sufficent to determine γ ′ with less than 6% residual scatter. At fixed redshift, γ ′ depends solely on the surface stellar mass density ∂γ ′ /∂Σ * = 0.38 ± 0.07, i.e. galaxies with denser stars also have steeper slopes. At fixed M * and R eff , γ ′ depends on redshift, in the sense that galaxies at a lower redshift have steeper slopes (∂γ ′ /∂z = −0.31 ± 0.10). However, the mean redshift evolution of γ ′ for an individual galaxy is consistent with zero dγ ′ /dz = −0.10 ± 0.12. This result is obtained by combining our measured dependencies of γ ′ on z, M * ,R eff with the evolution of the R eff-M * taken from the literature, and is broadly consistent with current models of the formation and evolution of massive early-type galaxies. Detailed quantitative comparisons of our results with theory will provide qualitatively new information on the detailed physical processes at work.
Constraints on the Inner Mass Profiles of Lensing Galaxies from Missing Odd Images
The Astrophysical Journal, 2001
Most gravitational lens systems consist of two or four observable images. The absence of detectable odd images allows us to place a lower limit on the power-law slope of the inner mass profile of lensing galaxies. Using a sample of six two-image radio-loud lens systems and assuming a singular power-law surface density (Σ ∝ r −β ) for the inner several kpc of the mass distribution, we find that there is less than a 10% probability that the data are consistent with profile slopes β < 0.80. Furthermore, individual mass modeling yields β > 0.85 for B0739+366 and β > 0.91 for B1030+074. Modeling central black holes as additional point masses changes the constraints in these systems to β > 0.84 and β > 0.83, respectively. The inner mass profiles of lensing galaxies are therefore not much shallower than isothermal.
The SWELLS survey - I. A large spectroscopically selected sample of edge-on late-type lens galaxies
Monthly Notices of the Royal Astronomical Society, 2011
The relative contribution of baryons and dark matter to the inner regions of spiral galaxies provides critical clues to their formation and evolution, but it is generally difficult to determine. For spiral galaxies that are strong gravitational lenses, however, the combination of lensing and kinematic observations can be used to break the diskhalo degeneracy. In turn, such data constrain fundamental parameters such as i) the mass density profile slope and axis ratio of the dark matter halo, and by comparison with dark matter-only numerical simulations the modifications imposed by baryons; ii) the mass in stars and therefore the overall star formation efficiency, and the amount of feedback; iii) by comparison with stellar population synthesis models, the normalization of the stellar initial mass function. In this first paper of a series, we present a sample of 16 secure, 1 probable, and 6 possible strong lensing spiral galaxies, for which multi-band high-resolution images and rotation curves were obtained using the Hubble Space Telescope and Keck-II Telescope as part of the Sloan WFC Edge-on Late-type Lens Survey (SWELLS). The sample includes 8 newly discovered secure systems. We characterize the sample of deflector galaxies in terms of their morphologies, structural parameters, and stellar masses. We find that the SWELLS sample of secure lenses spans a broad range of morphologies (from lenticular to late-type spiral), spectral types (quantified by Hα emission), and bulge to total stellar mass ratio (0.22-0.85), while being limited to M * > 10 10.5 M ⊙ . The SWELLS sample is thus well-suited for exploring the relationship between dark and luminous matter in a broad range of galaxies. We find that the deflector galaxies obey the same size-mass relation as that of a comparison sample of elongated non-lens galaxies selected from the SDSS survey. We conclude that the SWELLS sample is consistent with being representative of the overall population of high-mass high-inclination disky galaxies.
Astronomical Journal, 2000
We present measurements of galaxy-galaxy weak lensing from 225 deg2 of early commissioning imaging data from the Sloan Digital Sky Survey (SDSS). We measure a mean tangential shear around a stacked sample of foreground galaxies in three bandpasses (g@, r@, and i@) out to angular radii of 600@@, detecting the shear signal at very high statistical signiÐcance. The shear proÐle is well described by a power law with best-Ðt slope of g \ 0.7È1.1 (95% conÐdence). In the range h \ 10@@È600@@, c T \ c T0 (1@/h)g, the mean tangential shear is approximately 6^1 ] 10~4 in all three bands. A variety of rigorous tests demonstrate the reality of the gravitational lensing signal and conÐrm the uncertainty estimates. In particular, we obtain shear measurements consistent with zero when we rotate the background galaxies by 45¡, replace foreground galaxies with random points, or replace foreground galaxies with bright stars. We interpret our results by assuming that all matter correlated with galaxies belongs to the galaxies. We model the mass distributions of the foreground galaxies, which have a mean luminosity SL (h \ 5@@)T \ 8.7^0.7 ] 109 h~2 1.4^0.12 ] 1010 h~2 1.8^0.14 ] 1010 h~2 as L g{_ , L r{_ , L i{_ , approximately isothermal spheres characterized by a velocity dispersion and a truncation radius s. p v The velocity dispersion is constrained to be km s~1 at 95% conÐdence (145È195 km s~1 p v \ 150È190 including systematic uncertainties), consistent with previous determinations but with smaller error bars. Our detection of shear at large angular radii sets a 95% conÐdence lower limit s [ 140@@, corresponding to a physical radius of 260 h~1 kpc, implying that the dark halos of typical luminous galaxies extend to very large radii. However, it is likely that this is being systematically biased to large value by di †use matter in the halos of groups and clusters of galaxies. We also present a preliminary determination of the galaxy-mass correlation function, Ðnding a correlation length similar to the galaxy autocorrelation function and consistency with a low matter density universe with modest bias.
A deep probe of the galaxy stellar mass functions at z˜ 1-3 with the GOODS NICMOS Survey
Monthly Notices of The Royal Astronomical Society, 2011
We use a sample of 8298 galaxies observed in the HST GOODS NICMOS Survey (GNS) to construct the galaxy stellar mass function as a function of both redshift and stellar mass up to z=3.5 and down to masses of Mstar=10^8.5 Msun at z~1. We discover that a significant fraction of all massive Mstar>10^11 Msun galaxies are in place up to the highest redshifts we probe, with a decreasing fraction of lower mass galaxies present at all redshifts. This is an example of `galaxy mass downsizing', and is the result of massive galaxies forming before lower mass ones, and not just simply ending their star formation earlier as in traditional downsizing scenarios. We find that the faint end slope is significantly steeper than what is found in previous investigations. We demonstrate that this steeper mass function better matches the stellar mass added due to star formation, thereby alleviating some of the mismatch between these two measures of the evolution of galaxy mass. We furthermore examine the stellar mass function divided into blue/red systems, as well as for star forming and non-star forming galaxies. We find a similar mass downsizing present for both blue/red and star-forming/non-star forming galaxies, and that the low mass galaxies are mostly all blue, and are therefore creating the steep mass functions. We furthermore show that, although there is a downsizing such that high mass galaxies are nearer their z=0 values at high redshift, this turns over at masses Mstar~10^10 Msun, such that the lowest mass galaxies are more common than galaxies at slight higher masses, creating a `dip' in the observed galaxy mass function. We argue that the galaxy assembly process may be driven by different mechanisms at low and high masses, and that the efficiency of the galaxy formation process is lowest at masses Mstar~10^10 Msun at 1<z<3. (Abridged)
Stellar mass estimates in early-type galaxies from lensing+dynamical and photometric measurements
Astronomy & Astrophysics, 2007
Aims. Our purpose is to compare two different diagnostics for estimating stellar masses in early-type galaxies and to establish their level of reliability. In particular, we consider the well-studied sample of 15 field elliptical galaxies selected from the Sloan Lens ACS (SLACS) Survey (z = 0.06-0.33). We examine here the correlation between the stellar mass values, enclosed inside the Einstein radius (R Ein) of each lens, based on analyses of lensing and stellar dynamics combined and based on multiwavelength photometry spectral template fitting. Methods. The lensing+dynamics stellar mass M * len+dyn (≤R Ein) is obtained from the published SLACS Survey results, assuming a twocomponent density distribution model and a prior from the fundamental plane on the mass-to-light ratio for the lens galaxies. The photometric stellar mass M * phot (≤R Ein) is measured by fitting the observed spectral energy distribution of the galaxies (from the SDSS multi-band photometry over 354-913 nm) with composite stellar population templates, under the assumption that light traces stellar mass. Results. The two methods are completely independent. They rely on several different assumptions, and so, in principle, both can have significant biases. Based on our sample of massive galaxies (log M * phot (≤R Ein) [10.3, 11.5]), we find consistency between the values of M * len+dyn (≤R Ein) and M * phot (≤R Ein). We obtain a Pearson linear correlation coefficient of 0.94 and a median value of the ratio between the former and the latter mass measurements of 1.1 ± 0.1. This suggests that both methods can separately yield reliable stellar masses of early-type galaxies, and confirms that photometric mass estimates are accurate, as long as optical/near-IR rest frame photometry is available.