English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Compact elliptical galaxies (CEGs) are candidates for local analogs of thehigh-redshift "red nuggets" thought to represent the progenitors of today'searly-type galaxies (ETGs). To address whether the structure of the dark matter(DM) halo in a CEG also reflects the extremely quiescent and isolated evolutionof its stars, we use a new $\approx 122$ ks Chandra observation together with ashallow $\approx 13$ ks archival observation of the CEG Mrk 1216 to perform ahydrostatic equilibrium analysis of the luminous and relaxed X-ray plasmaemission extending out to a radius $0.85r_{2500}$. We examine several DM modelprofiles and in every case obtain a halo concentration $(c_{200})$ that is alarge positive outlier in the theoretical $\Lambda$CDM $c_{200}-M_{200}$relation; i.e., ranging from $3.4\,\sigma - 6.3\, \sigma$ above the median$\Lambda$CDM relation in terms of the intrinsic scatter. The high value of$c_{200}$ we measure implies an unusually early formation time that firmlyestablishes the relic nature of the DM halo in Mrk 1216. The highlyconcentrated DM halo leads to a higher DM fraction and smaller total mass slopeat $1R_e$ compared to nearby normal ETGs. In addition, the highly concentratedtotal mass profile of Mrk 1216 cannot be described by MOND without adding DM,and it deviates substantially from the Radial Acceleration Relation. Mrk 1216contains $\approx 80\%$ of the cosmic baryon fraction within $r_{200}$. Theradial profile of the ratio of cooling time to free-fall time varies within anarrow range $(t_c/t_{\rm ff}\approx 14-19)$ over a large central region ($r\le10$ kpc) suggesting "precipitation-regulated AGN feedback" for a multiphaseplasma, though presently there is little evidence for cool gas in Mrk 1216. Theproperties of Mrk 1216 are remarkably similar to those of the nearby fossilgroup NGC 6482.

The Extremely High Dark Matter Halo Concentration of the Relic Compact Elliptical Galaxy Mrk 1216