Superdense massive galaxies in the Nearby Universe

Understand

Superdense massive galaxies (r_e~1 kpc; M~10^{11} Msun) were common in the early universe (z>1.5).

• Within some hierarchical 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 present universe.
• Using the NYU Value-Added Galaxy Catalog from the SDSS Data Release 6 we find only a tiny fraction of galaxies (~0.03%) with r_e<1.5 kpc and M_*>8x10^{10} Msun in the local Universe (z<0.2).
• Surprinsingly, they are relatively young (~2 Gyr) and metal-rich ([Z/H]~0.2).