Testing adiabatic contraction with Sloan Digital Sky Survey elliptical galaxies

Given a flurry of recent claims for systematic variations in the stellar initial mass function (IMF), we carry out the first inventory of the observational evidence using different approaches. This includes literature results, as well as our own new findings from combined stellar population synthesis (SPS) and Jeans dynamical analyses of data on ∼4500 early-type galaxies (ETGs) from the SPIDER project. We focus on the mass-to-light ratio mismatch relative to the Milky Way IMF, δ IMF , correlated against the central stellar velocity dispersion, σ . We find a strong correlation between δ IMF and σ , for a wide set of dark matter (DM) model profiles. These results are robust if a uniform halo response to baryons is adopted across the sample. The overall normalization of δ IMF and the detailed DM profile are less certain, but the data are consistent with standard cold DM halos and a central DM fraction that is roughly constant with σ . For a variety of related studies in the literature, using SPS, dynamics, and gravitational lensing, similar results are found. Studies based solely on spectroscopic line diagnostics agree on a Salpeter-like IMF at high σ but differ at low σ . Overall, we find that multiple independent lines of evidence appear to be converging on a systematic variation in the IMF, such that high-σ ETGs have an excess of low-mass stars relative to spirals and low-σ ETGs. Robust verification of super-Salpeter IMFs in the highest-σ galaxies will require additional scrutiny of scatter and systematic uncertainties. The implications for the distribution of DM are still inconclusive.

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“…We may then apply this IMF result to the full sample if we assume no additional systematic δ IMF -Σ correlation (cf. Schulz et al 2010).…”

Section: Results: Imf and Dm Fraction Trendsmentioning

confidence: 99%

An Inventory of the Stellar Initial Mass Function in Early-Type Galaxies

Tortora

Romanowsky

Napolitano

2013

ApJ

106

158

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“…iii) Kroupa-IMF stellar mass. According to Schulz et al (2010), within a sphere of radius equal to re, 42% of the total stellar mass is contained.…”

Section: The Stellar Massmentioning

confidence: 99%

Dark matter inside early-type galaxies as function of mass and redshift

Nigoche-Netro¹,

Ramos-Larios²,

Lagos³

et al. 2016

Mon. Not. R. Astron. Soc.

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We study the behaviour of the dynamical and stellar mass inside the effective radius (r e ) of early-type galaxies (ETGs). We use several samples of ETGs -ranging from 19 000 to 98 000 objects-from the ninth data release of the Sloan Digital Sky Survey. We consider Newtonian dynamics, different light profiles and different Initial Mass Functions (IMF) to calculate the dynamical and stellar mass. We assume that any difference between these two masses is due to dark matter and/or a non Universal IMF. The main results for galaxies in the redshift range 0.0024 < z < 0.3500 and in the dynamical mass range 9.5 < log(M) < 12.5 are: i) A significant part of the intrinsic dispersion of the distribution of dynamical vs. stellar mass is due to redshift. ii) The difference between dynamical and stellar mass increases as a function of dynamical mass and decreases as a function of redshift. iii) The difference between dynamical and stellar mass goes from approximately 0% to 70% of the dynamical mass depending on mass and redshift. iv) These differences could be due to dark matter or a non Universal IMF or a combination of both. v) The amount of dark matter inside ETGs would be equal to or less than the difference between dynamical and stellar mass depending on the impact of the IMF on the stellar mass estimation. vi) The previous results go in the same direction of some results of the Fundamental Plane (FP) found in the literature in the sense that they could be interpreted as an increase of dark matter along the FP and a dependence of the FP on redshift.

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“…Interestingly, in an analogous Chandra study of mass profiles in seven elliptical galaxies with either galaxy-scale or group-scale halos (Humphrey et al 2006), the stellar mass-to-K-band luminosity ratio (M /L K ) was found to be consistent with SSP models assuming a Kroupa ( The IMF is also indicated as the most significant source of systematic uncertainty in a recent test of adiabatic contraction using profiles of 75 086 elliptical galaxies from the Sloan Digital Sky Survey (Schulz et al 2009). This study is based on weak lensing observations in the outskirts of the halo and measurements of the stellar velocity dispersion in the inner regions of galaxies for stacked galaxy samples.…”

Section: On the Choice Of Imf And Its Impact On The Best Fitting Massmentioning

confidence: 99%

Testing adiabatic contraction of dark matter in fossil group candidates

Démoclès

Pratt

Pierini

et al. 2010

A&A

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We present deep XMM-Newton observations and ESO WFI optical imaging of two X-ray-selected fossil group candidates, RXC J0216.7-4749 and RXC J2315.7-0222. Using the X-ray data, we derive total mass profiles under the hydrostatic equilibrium assumption. The central regions of RXC J0216.7-4749 are found to be dominated by an X-ray bright AGN, and although we derive a mass profile, uncertainties are large and the constraints are significantly weakened due to the presence of the central source. The total mass profile of RXC J2315.7-0222 is of high quality, being measured in fifteen bins from [0.075−0.75] R 500 and containing three data points interior to 30 kpc, allowing comprehensive investigation of its properties. We investigate several mass models based on the standard NFW profile or on the Sérsic-like model recently suggested by high-resolution N-body simulations. We find that the addition of a stellar component due to the presence of the central galaxy is necessary for a good analytical model fit. In all mass profile models fitted, the mass concentration is not especially high compared to non-fossil systems. In addition, the modification of the dark matter halo by adiabatic contraction slightly improves the fit. However, our result depends critically on the choice of IMF used to convert galaxy luminosity to mass, which leads to a degeneracy between the central slope of the dark matter profile and the normalisation of the stellar component. While we argue on the basis of the range of M * /L R ratios that lower M * /L R ratios are preferred on physical grounds and that adiabatic contraction has thus operated in this system, better theoretical and observational convergence on this problem is needed to make further progess.

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Testing adiabatic contraction with Sloan Digital Sky Survey elliptical galaxies

Cited by 64 publications

References 79 publications

An Inventory of the Stellar Initial Mass Function in Early-Type Galaxies

An Inventory of the Stellar Initial Mass Function in Early-Type Galaxies

Dark matter inside early-type galaxies as function of mass and redshift

Testing adiabatic contraction of dark matter in fossil group candidates

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