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

Abstract

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.

The quantity of dark matter in early-type galaxies and its relation to the environment

“…Indeed we can see a mild shift of the maximum at large redshift, as the maximum is close to 0.4 for nearby galaxies and close to 0.5 for distant galaxies. This result seems to be the opposite to that found in Nigoche-Netro et al (2016) and by other authors, where they found that the difference between virial and stellar mass decreases as a function of redshift. The most plausible explanation of this apparent contradiction is that the dependence of log(M Virial /MSun) -log(MStar/MSun) on mass, reported by different authors, has not been taken into account in the previous analysis.…”

“…The density of galaxies was calculated using the third, fifth, eighth, and tenth nearest neighbours, for both the spectroscopic and photometric samples. Cappellari et al 2013;Nigoche-Netro et al 2016) and redshift (Nigoche-Netro et al 2016). In the following we will analyse the above-mentioned dependencies.…”

“…There are, however, anticorrelations of fDM with mass that have been found by Grillo et al (2009), Grillo (2010, and Grillo & Gobat (2010). These results may indicate that the amount of DM within re correlates with the baryonic mass of a galaxy, however this apparent fDM trend with mass could disappear completely if a non-universal IMF is used (Thomas et al 2011;Tortora et al 2013;Nigoche-Netro et al 2016). It is important to mention that the IMF is the most important source of uncertainty in the calculation of the relative amounts of stellar and DM mass, in the central regions of a galaxy (Tortora et al 2018).…”

“…Observational estimates of the amount of DM within re appear to indicate that DM haloes are cuspy (Thomas et al 2009;) and, independently of the galaxy mass distribution, the DM amount tends to increase with velocity dispersion, size, stellar mass, and luminosity of the galaxy (Ferreras, Saha & Williams 2005;Cappellari et al 2006;Forbes et al 2008;Tortora et al 2009;Auger et al 2010b;Leir et al 2011;Tortora et al 2010;Nigoche-Netro et al 2016), in agreement with theoretical predictions of the DM fraction (fDM ) in central regions of galaxies (Ruszkowski & Springel 2009;Hilz, Naab & Ostriker 2013;Wu et al 2014).…”

The last 6 Gyr of dark matter assembly in massive galaxies from the Kilo Degree Survey

“…But DM rules also the central galaxy regions (Gerhard et al 2001;Padmanabhan et al 2004;Cappellari et al 2006;Thomas et al 2007;Cardone et al 2009; Thomas et al 2009;Hyde & Bernardi 2009b;Tortora et al 2009;Auger et al 2010;Cardone & Tortora 2010;Thomas et al 2011;Cardone et al 2011;Tortora et al 2012;Tortora et al 2014b;Shu et al 2015;Nigoche-Netro et al 2016), in a way substantially consistent with the concordance ΛCDM scenario Napolitano et al 2010;Tortora et al 2012). Different works have shown that the central DM fraction (typically within one effective radius, Re hereafter) is higher in larger and more massive galaxies (e.g.…”