Superdense massive galaxies in the nearby universe

At high-z the most superdense massive galaxies are supposed to be the result of gas-rich mergers resulting in compact remnant (Khochfar & Silk (2006); Naab et al.(2007)). After this, dry mergers are expected to be the mechanism that moves these very massive galaxies towards the current stellar mass size relation. Whitin these merging scenarios, a non-negligible fraction (1-10%) of these galaxies is expected to survive since that epoch retaining their compactness and presenting old stellar populations in the past universe.Using the NYU Value-Added Galaxy Catalog (DR6), we find only a tiny fraction of galaxies (∼0.03%) with re <1.5 kpc and M∗ > 8x1010M_ in the local Universe (z∼ 0.2). Surprisingly, they are relatively young (∼2Gyr) and metal rich ([Z/H]∼0.2) These results have been published in Trujillo et al.(2009)