Massive Dark Matter Halos and Evolution of Early-Type Galaxies to z ≈ 1

By T. Treu, Leon V. E. Koopmans. 2004

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The combination of gravitational lensing and stellar dynamics breaks the mass-anisotropy degeneracy and provides stringent constraints on the distribution of luminous and dark matter in early-type (E/S0) galaxies out to z ≈ 1. We present new observations and models of three lens systems (CFRS 03.1077, HST 14176+5226, HST 15433+5352) and the combined results from the five field E/S0 lens galaxies at z ≈ 0.5-1.0 analyzed as part of the Lenses Structure and Dynamics (LSD) Survey. Our main results are as follows: (1) Constant mass-to-light ratio models are ruled out at greater than 99% CL for all five E/S0 galaxies, consistent with the presence of massive and extended dark matter halos. The range of projected dark matter mass fractions inside the Einstein radius is fDM = 0.37-0.72, or 0.15-0.65 inside the effective radius Re for isotropic models. (2) The average effective power-law slope of the total (luminous plus dark; ρtot ∝ r) mass distribution is ⟨γ′⟩ = 1.75 ± 0.10 (1.57 ± 0.16) for Osipkov-Merritt models with anisotropy radius ri = ∞ (Re) with an rms scatter of 0.2 (0.35), i.e., marginally flatter than isothermal (γ′ = 2). The ratio between the observed central stellar velocity dispersion and that from the best-fit singular isothermal ellipsoid (SIE) lens model is ⟨fSIE⟩ = ⟨σ/σSIE⟩ = 0.87 ± 0.04 with 0.08 rms, consistent with flatter-than-isothermal density profiles. Considering that γ′ > 2 and fSIE > 1 have been reported for other systems (i.e., B1608+656 and PG 1115+080), we conclude that there is a significant intrinsic scatter in the slope of the mass-density profile of lens galaxies (rms ~ 15%), similar to what is found for local E/S0 galaxies. Hence, the isothermal approximation is not sufficiently accurate for applications that depend critically on the slope of the mass-density profile, such as the measurement of the Hubble constant from time delays. (3) The average inner power-law slope γ of the dark matter halo is constrained to be ⟨γ⟩ = 1.3 (68% CL), if the stellar velocity ellipsoid is isotropic (ri = ∞), or an upper limit of γ < 0.6, if the galaxies are radially anisotropic (ri = Re). The observed range of slopes of the inner dark matter distribution is consistent with the results from numerical simulations only for an isotropic velocity ellipsoid and if baryonic collapse and star formation do not steepen dark matter density profiles. (4) The average stellar mass-to-light ratio evolves as d log(M*/LB)/dz = -0.72 ± 0.10, obtained via a fundamental plane analysis. An independent analysis based on lensing and dynamics gives an average ⟨d log(M*/LB)/dz⟩ = -0.75 ± 0.17. Both values indicate that the mass-to-light ratio evolution for our sample of field E/S0 galaxies is slightly faster than those in clusters, consistent with the hypothesis that field E/S0 galaxies experience secondary bursts (~10% in mass) of star formation at z < 1. These findings are consistent with pure luminosity evolution of E/S0 galaxies in the past 8 Gyr and would be hard to reconcile with scenarios involving significant structural and dynamical evolution.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

The Sloan Lens ACS Survey. II. Stellar Populations and Internal Structure of Early-Type Lens Galaxies (2005, background): “Based on the limited amount of information available so far, no significant difference has been found between the structural properties (e.g. Treu & Koopmans 2004) of lens and non-lens galaxies, supporting the hypothesis that E/S0 lenses are representative of the whole E/S0 population.”
The Time Delays of Gravitational Lens HE 0435–1223: An Early-Type Galaxy with a Rising Rotation Curve (2005, background): “…galaxies have nearly flat rotation curves (isothermal lens models) extending from the inner regions (see, e.g., Gerhard et al. 2001; Rusin & Kochanek 2005; Winn et al. 2004; Treu & Koopmans 2004), but there are some interesting counterexamples (e.g., Romanowsky et al. 2003; Treu & Koopmans 2002).”
Gravitational lensing (2010, background): “It is agreed in [478] that the density profiles are nearly isothermal, but find a somewhat larger scatter.”
Formation of Early-Type Galaxies from Cosmological Initial Conditions (2005, result): “This is consistent with most findings based on observations and dynamical modeling that early-type galaxies are dominated by luminous matter in their inner parts (Efstathiou et al. 1982; Rix et al. 1997; Romanowsky et al. 2003; Treu & Koopmans 2004; Thomas et al. 2005b).”
TWO ACCURATE TIME-DELAY DISTANCES FROM STRONG LENSING: IMPLICATIONS FOR COSMOLOGY (2012, background): “(7) Two practical approaches to overcome this degeneracy are (1) to use the stellar kinematics of the lens galaxy (e.g., Treu & Koopmans 2002, 2004; Koopmans & Treu 2003; Barnabè et al. 2009; Auger et al. 2010; Suyu et al. 2010; Sonnenfeld et al. 2012) to make an independent estimate of the lens…”
TDCOSMO. I. An exploration of systematic uncertainties in the inference of $H_0$ from time-delay cosmography (2019, background): “As we see below, this is likely due to the “bulge-halo” conspiracy (Treu & Koopmans 2004; Dutton & Treu 2014).”
H0LiCOW – I. H0 Lenses in COSMOGRAIL's wellspring: program overview (2016, background): “…of dark matter in the lens galaxies by combining lensing and kinematics data, and also infer the stellar mass of the lens galaxies (e.g., Treu & Koopmans 2004; Barnabè et al. 2011; 10 with spectroscopic observations of HE 1104−1805 pending for lens velocity dispersion measurement MNRAS…”
The Evolution and Structure of Early-Type Field Galaxies: A Combined Statistical Analysis of Gravitational Lenses (2004, background): “Note, however, that Treu & Koopmans (2004) favor models with systematically shallower profiles, while Romanowsky et al. (2003) favor significantly more concentrated models.”
The SAURON project – X. The orbital anisotropy of elliptical and lenticular galaxies: revisiting the (V/σ, ɛ) diagram with integral‐field stellar kinematics (2007, background): “Evidencefrom dynamical modelling (e.g. Gerhard et al. 2001; Cappellari et al. 2006) and gravitational lensing (e.g. Treu & Koopmans 2004; Rusin & Kochanek 2005; Koopmans al.”
Detection of a dark substructure through gravitational imaging (2009, background): “Gravitational lensing, especially in combination with other ⋆ E-mail: vegetti@astro.rug.nl techniques, provides an invaluable and sometimes unique insight in answering these questions (e.g. Rusin & Kochanek 2005; Treu & Koopmans 2004; Koopmans et al. 2009, and references therein).”
HerMES: CANDIDATE GRAVITATIONALLY LENSED GALAXIES AND LENSING STATISTICS AT SUBMILLIMETER WAVELENGTHS (2012, methodology): “In combination with dynamical studies, lensing mass reconstruction allows one to obtain the density profile of the dark matter in individual lensing galaxies down to ∼ 10 kpc scales (e.g. Miralda-Escude 1995; Dalal & Kochanek 2002; Metcalf & Zhao 2002; Rusin & Kochanek 2005; Treu & Koopmans 2004).”
The Sloan Lens ACS Survey. IV. The Mass Density Profile of Early-Type Galaxies out to 100 Effective Radii (2007, background): “It is now a well established from SLACS (paper III) and earlier strong lensing studies (e.g. Treu & Koopmans 2002; Rusin et al. 2003; Rusin & Kochanek 2005; Treu & Koopmans 2004) that the total mass profile of lens galaxies is close to isothermal (ρ ∝ r−2) within Reff .”
Gravitational Lens Time Delays: A Statistical Assessment of Lens Model Dependences and Implications for the Global Hubble Constant (2006, background): “However, we note that the result of Treu & Koopmans (2004) was drawn from only five lensed quasar systems, and therefore, the scatter should be large.”
THE SLOAN LENS ACS SURVEY. X. STELLAR, DYNAMICAL, AND TOTAL MASS CORRELATIONS OF MASSIVE EARLY-TYPE GALAXIES (2010, methodology): “The mass distributions are defined as in Treu & Koopmans (2004) and Koopmans et al. (2006, 2009), with ρ ∝ r−γ ′ , and these models are constrained using the mass within the Einstein radius, the SDSS stellar velocity dispersion, and de Vaucouleurs fits to the stellar light distribution.”
The total mass of the Large Magellanic Cloud from its perturbation on the Orphan stream (2018, background): “…which rely on either the availability of kinematic tracers (e.g. Wilkinson & Evans 1999; Cappellari et al. 2006; Xue et al. 2008) or the presence of a gravitational lensing signal (e.g. Kochanek, Keeton & McLeod 2001), or both (e.g. Sand, Treu & Ellis 2002; Treu & Koopmans 2004; Auger et al. 2010).”
Two-dimensional kinematics of SLACS lenses – III. Mass structure and dynamics of early-type lens galaxies beyond z ≃ 0.1 (2011, result): “As highlighted by these studies, as well as by a number of other works (see Treu & Koopmans 2002, Koopmans & Treu 2003, Treu & Koopmans 2004, Rusin & Kochanek 2005, Jiang & Kochanek 2007, Grillo et al. 2008, Koopmans et al. 2009, Trott et al. 2010, van de Ven et al. 2010, Dutton et al. 2011,…”
THE INITIAL MASS FUNCTION OF EARLY-TYPE GALAXIES (2010, unknown): “The degeneracy is best reduced by spatially resolved velocity dispersion measurements (e.g., Treu & Koopmans 2004).”
COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA (2013, background): “This “bulge-halo conspiracy” has already been noted in earlier studies (e.g., Treu & Koopmans 2004; Koopmans et al. 2009; van de Ven et al. 2009) and is reproduced by some numerical simulations including baryonic physics (Remus et al. 2013).”
Probing the Coevolution of Supermassive Black Holes and Galaxies Using Gravitationally Lensed Quasar Hosts (2006, background): “…statistical properties of lens samples (e.g. Chae et al. 2002, Zhang 2004, Chen 2005, Rusin & Kochanek 2005), and dynamical studies (Rix et al. 1997, Treu & Koopmans 2004, Treu et al. 2006), that the typical lens has a radial density distribution that is reasonably well modeled by an SIE in the…”