A Chandra View of Dark Matter in Early-Type Galaxies

By P. J. Humphrey, D. Buote, F. Gastaldello, L. Zappacosta, James S Bullock, F. Brighenti, W. Mathews. 2006

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We present a Chandra study of mass profiles in seven elliptical galaxies, of which three have galaxy-scale and four have group-scale halos, demarcated at 1013 M☉. These represent the best available data for nearby objects with comparable X-ray luminosities. We measure approximately flat mass-to-light (M/L) profiles within an optical half-light radius (Reff), rising by an order of magnitude at ~10 Reff, which confirms the presence of dark matter (DM). The data indicate hydrostatic equilibrium, which is also supported by agreement with studies of stellar kinematics in elliptical galaxies. The data are well fitted by a model comprising an NFW DM profile and a baryonic component following the optical light. The distribution of DM halo concentration parameters (c) versus Mvir agrees with ΛCDM predictions and our observations of bright groups. Concentrations are slightly higher than expected, which is most likely a selection effect. Omitting the stellar mass drastically increases c, possibly explaining large concentrations found by some past observers. The stellar M/LK agree with population synthesis models, assuming a Kroupa IMF. Allowing adiabatic compression (AC) of the DM halo by baryons made M/L more discrepant, casting some doubt on AC. Our best-fitting models imply total baryon fractions ~0.04-0.09, consistent with models of galaxy formation incorporating strong feedback. The groups exhibit positive temperature gradients, consistent with the "universal" profiles found in other groups and clusters, whereas the galaxies have negative gradients, suggesting a change in the evolutionary history of the systems around Mvir ≃ 1013 M☉.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/68e0a9a3ed149c798069e57e02cb55ed544b0968

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Citations in the corpus

Density profiles of galaxy groups and clusters from SDSS galaxy–galaxy weak lensing (2006, methodology): “Recent X-ray studies have found that the profile is consistent with the NFW model (Vikhlinin et al. 2005; Fukazawa et al. 2006; Humphrey et al. 2006), though with indications for poor groups (consistent in mass with our “faint” sample) of some excess over NFW on small scales (Vikhlinin et al.…”
Hidden charged dark matter (2009, methodology): “[117, 118], we derive the radial velocity dispersion v2 r (r) = (3/2)v 2 0(r) and the dark matter density ρX(r) at a radius ∼ 3 − 10 kpc.”
The Sloan Lens ACS Survey. IV. The Mass Density Profile of Early-Type Galaxies out to 100 Effective Radii (2007, background): “We note however that the rather low values of M∗/LV we find would make it unlikely to have a dark matter halo much steeper than NFW (ρ ∝ r−1 at the center) (see also Borriello et al. 2003; Humphrey et al. 2006).”
Cosmological simulations with self-interacting dark matter – II. Halo shapes versus observations (2012, background): “There are a number of other elliptical galaxies for which high-resolution X-ray data exist (e.g., Humphrey et al. 2006), but they lack the detailed shape measurements of NGC 720.”
Dark Matter Candidates from Particle Physics and Methods of Detection (2010, background): “X-ray observations have established the ellipticity of the dark matter halo of the elliptical galaxy NGC 720 (221; 222), and requiring Γ−1 k > 10 10 Gyr for this system also constrains self-interacting hidden dark matter, as shown in Fig.”
CHANDRA STUDIES OF THE X-RAY GAS PROPERTIES OF GALAXY GROUPS (2008, background): “We follow Humphrey et al. (2006), G07 and V08 to discuss the systematic error budgets in our results.”
Concentration, spin and shape of dark matter haloes as a function of the cosmological model: WMAP1, WMAP3 and WMAP5 results (2008, background): “However, studies which model the radial density profiles of clusters and elliptical galaxies suggest that it is difficult to reconcile models with adiabatic contraction with observations (Zappacosta et al. 2006; Humphrey et al. 2006, Gastaldello et al. 2007).”
Gravitational quenching in massive galaxies and clusters by clumpy accretion (2007, result): “This is indeed comparable to the observed X-ray output of Lx ∼ 1042 erg s−1 from giant ellipticals and groups of virial halo mass in the ball-park of 1013M⊙ (Mathews & Brighenti 2003; Helsdon & Ponman 2003; Humphrey et al. 2006; Fukazawa et al. 2006).”
Mechanical AGN feedback: controlling the thermodynamical evolution of elliptical galaxies (2012, background): “A distinctive characteristic of classic cooling-flow models with CGG is the presence, often observed in real systems, of a relatively broad cool core, in perfect analogy with galaxy clusters (Brighenti & Mathews 1998, 1999; Humphrey et al. 2006; Diehl & Statler 2008b).”
THE INITIAL MASS FUNCTION OF EARLY-TYPE GALAXIES (2010, unknown): “However, Xray observations show that the residual gas is a small fraction of the stellar mass (e.g. Mathews & Brighenti 2003; Humphrey et al. 2006) and therefore most of the gas must be either expelled or recycled into secondary episodes of star formation.”
Dynamical modelling of luminous and dark matter in 17 Coma early-type galaxies (2007, background): “…evidence for extended dark matter haloes around early-type galaxies (e.g. Bertola et al. 1993; Pizzella et al. 1997; Loewenstein & White 1999; Oosterloo et al. 2002; Hoekstra, Yee & Gladders 2004; Fukazawa et al. 2006; Humphrey et al. 2006; Kleinheinrich et al. 2006; Mandelbaum et al. 2006).”
Galaxy Masses: A Review (2013, background): “…such large radii reached by the GC populations, as in NGC 1399, many studies take advantage of the presence of large X-ray halos around specific ETGs to constrain the corresponding radial mass, and make direct comparisons (Humphrey et al. 2006; Schuberth et al. 2010; Das et al. 2011; Gerhard 2013).”
One Law to Rule Them All: The Radial Acceleration Relation of Galaxies (2016, methodology): “Four of these ETGs (NGC 1407, NGC 4261, NGC 4472, and NGC 4649) belong to groups with 10 to 60 known members, thus the outer mass profile may be tracing the group potential instead of the galaxy potential (Humphrey et al. 2006).”
Radiative Feedback from Massive Black Holes in Elliptical Galaxies: AGN Flaring and Central Starburst Fueled by Recycled Gas (2007, background): “…r þ r ð Þ3 : ð2Þ Optical (e.g., Saglia et al. 1993; Bertin et al. 1994; Cappellari et al. 2006; Douglas et al. 2007) and X-ray (e.g., Fabian et al. 1986; Humphrey et al. 2006) based studies typically find that luminous matter dominates the mass distribution inside the effective radius Re ,…”
Globular cluster systems in nearby dwarf galaxies – III. Formation efficiencies of old globular clusters (2010, background): “To avoid problems with hydrostatic equilibrium Humphrey et al. (2006) and O’Sullivan et al. (2007) studied isolated elliptical galaxies for which they obtain MX few times 10 8M , c© 2009 RAS, MNRAS 000, 1–??”