A UNIFORM CONTRIBUTION OF CORE-COLLAPSE AND TYPE Ia SUPERNOVAE TO THE CHEMICAL ENRICHMENT PATTERN IN THE OUTSKIRTS OF THE VIRGO CLUSTER

Abstract

We present the first measurements of the abundances of α-elements (Mg, Si, and S) extending out to beyond the virial radius of a cluster of galaxies. Our results, based on Suzaku Key Project observations of the Virgo Cluster, show that the chemical composition of the intra-cluster medium is consistent with being constant on large scales, with a flat distribution of the Si/Fe, S/Fe, and Mg/Fe ratios as a function of radius and azimuth out to 1.4 Mpc (1.3 r 200 ). Chemical enrichment of the intergalactic medium due solely to core collapse supernovae (SNcc) is excluded with very high significance; instead, the measured metal abundance ratios are generally consistent with the Solar value. The uniform metal abundance ratios observed today are likely the result of an early phase of enrichment and mixing, with both SNcc and type Ia supernovae (SN Ia) contributing to the metal budget during the period of peak star formation activity at redshifts of 2-3. We estimate the ratio between the number of SN Ia and the total number of supernovae enriching the intergalactic medium to be between 12-37%, broadly consistent with the metal abundance patterns in our own Galaxy or with the SN Ia contribution estimated for the cluster cores.

Radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals

“…Although the scatter (and, by extension, the other systematic uncertainties) prevents us from excluding sudden changes in the outskirts, our observations suggest, on average, a remarkably uniform f SNIa distribution out to, at least, 0.5r 500 . This result contrasts with the dramatic increase of SNcc contribution in the outskirts inferred by Rasmussen & Ponman (2009), but is consistent with more recent measurements (Simionescu et al 2015;Ezer et al 2016) and simulations (Fabjan et al 2010;Planelles et al 2014;Biffi et al 2017). This suggests that the major fraction of the SNIa and SNcc enriching the ICM may share the same origins and may have both exploded before mixing and diffusion processes played a significant role in spreading out the metals.…”

“…Comparison of the measured average radial Si/Fe profile ( Fig. 5) with previous observations for galaxy groups (Rasmussen & Ponman 2007) and Virgo (Simionescu et al 2010(Simionescu et al , 2015, and with the AGN simulation set of Planelles et al (2014). contrary, this trend is consistent with the peaked O profiles found in, for example A S1101 (de Plaa et al 2006), A 3526 (Sanders & Fabian 2006a), Hydra A (Simionescu et al 2009), A 3112 (Bulbul et al 2012b), A 4059 (Mernier et al 2015), and 5 cool-core clusters Lovisari et al (2011).…”

“…In a companion paper (Rasmussen & Ponman 2009), the same authors interpret this increase as a dominant enriching fraction of SNcc products in group outskirts, in agreement with the increasing O/Fe and/or Mg/Fe profiles observed in other studies (see above). Taking advantage of the low instrumental background of Suzaku XIS, Simionescu et al (2015, four outermost green circles) reported a flat Si/Fe radial distribution in the outskirts of the Virgo cluster, in agreement with the Si/Fe ratios measured at smaller radii (Simionescu et al 2010, two innermost green circles). Our flat Si/Fe profile is in agreement with the results of Simionescu et al (2010Simionescu et al ( , 2015 and contradicts the results of Rasmussen & Ponman (2007).…”

“…Tamura et al 2001;Matsushita et al 2003;Tamura et al 2004;Werner et al 2006a). As for Fe, there are also indications of a positive and uniform Mg (and other SNcc products) enrichment out to r 200 (Simionescu et al 2015;Ezer et al 2016). This apparent flat distribution of SNcc products, contrasting with the enhanced central enrichment from SNIa products, has led to the picture of an early ICM enrichment by SNcc (and prompt SNIa, see above), when galaxies underwent important episodes of star formation.…”

Suzaku X-Ray Observations of the Nearest Non-Cool Core Cluster, Antlia: Dynamically Young but With Remarkably Relaxed Outskirts

“…A direct comparison to the nearest clusters with different physical properties in our neighborhood is certainly important to understand the cluster outskirts. For example, the nearby massive cool core cluster, Perseus ) mentioned above, has also been mapped out to R 200 (Urban et al 2011;Simionescu et al 2015). Low mass galaxy groups are also very important to cosmological studies.…”