UC Irvine

There is mounting evidence that compact elliptical galaxies (CEGs) are local analogs of the high-redshift "red nuggets" that are thought to represent progenitors of today's early-type galaxies (ETGs). We report the discovery of extended X-ray emission from a hot interstellar/intragroup medium in two CEGs, Mrk 1216 and PGC 032873, using shallow Chandra observations. We find that PGC 032873 has an average gas temperature of k B T =0.67 ±0.06 keV within a radius of 15 kpc and a luminosity L x =(1.8 ±0.2) ×1041 erg s-1 within a radius of 100 kpc. For Mrk 1216, which is closer and more luminous (L x(<100 kpc) =(12.1 ±1.9) ×1041 erg s-1), we used an entropy-based hydrostatic equilibrium (HE) procedure and obtained a good constraint on the H-band stellar mass-to-light ratio, M stars/L H =1.33 ±0.21 solar, that is in good agreement with stellar dynamical (SD) studies, which supports the HE approximation. We obtain a density slope of 2.22 ±0.08 within R e that is consistent with other CEGs and normal local ETGs, while the dark matter fraction within R e, f DM =0.20 ±0.07 is similar to local ETGs. We constrain the supermasssive black hole mass, M BH =(5 ±4) ×109 M o, with M BH > 1.4 ×1010 M o (90% confidence), which is consistent with a recent SD measurement. We obtain a halo concentration (c 200 =17.5 ±6.7) and mass (M 200 =(9.6 ±3.7) ×1012 M o), where c 200 exceeds the mean ΛCDM value (≈7), which is consistent with a system that formed earlier than the general halo population. We suggest that these galaxies should be classified as fossil groups.