Superdense Massive Galaxies in Wings Local Clusters

Abstract

Massive quiescent galaxies at z > 1 have been found to have small physical sizes, and hence to be superdense. Several mechanisms, including minor mergers, have been proposed for increasing galaxy sizes from high-to low-z. We search for superdense massive galaxies in the WIde-field Nearby Galaxy-cluster Survey (WINGS) of X-ray selected galaxy clusters at 0.04 < z < 0.07. We discover a significant population of superdense massive galaxies with masses and sizes comparable to those observed at high redshift. They approximately represent 22% of all cluster galaxies more massive than 3 × 10 10 M , are mostly S0 galaxies, have a median effective radius R e = 1.61 ± 0.29 kpc, a median Sersic index n = 3.0 ± 0.6, and very old stellar populations with a median mass-weighted age of 12.1 ± 1.3 Gyr. We calculate a number density of 2.9 × 10 −2 Mpc −3 for superdense galaxies in local clusters, and a hard lower limit of 1.3 × 10 −5 Mpc −3 in the whole comoving volume between z = 0.04 and z = 0.07. We find a relation between mass, effective radius, and luminosity-weighted age in our cluster galaxies, which can mimic the claimed evolution of the radius with redshift, if not properly taken into account. We compare our data with spectroscopic high-z surveys and find that-when stellar masses are considered-there is consistency with the local WINGS galaxy sizes out to z ∼ 2, while a discrepancy of a factor of 3 exists with the only spectroscopic z > 2 study. In contrast, there is strong evidence for a large evolution in radius for the most massive galaxies with M * > 4 × 10 11 M compared to similarly massive galaxies in WINGS, i.e., the brightest cluster galaxies.

Towards a census of supercompact massive galaxies in the Kilo Degree Survey

“…However, we cannot exclude that galaxy environment, which might be the actual driver of the number density of compact relics at z ∼ 0 (see, e.g. Trujillo et al 2014;Poggianti et al 2013a;Valentinuzzi et al 2010), may be different for galaxies in the KiDS-DR2 and COSMOS areas -an issue that will be addressed in forthcoming extensions of the present work.…”

The fundamental plane of EDisCS galaxies

“…If we add the galaxies with VLT photometry only (entries 3 and 4 of Table 7), we derive larger R c and steeper slopes. Figure 20 shows R c as a function of redshift when we apply a correction for progenitor bias as in Valentinuzzi et al (2010a). The EDisCS galaxies considered here are a sample of spectroscopically selected passive objects.…”

“…In contrast, a morphologically selected local sample of early-type galaxies contains objects with relatively young ages that, when evolved to EDisCS redshifts, would not be recognized as being spectroscopically passive. Valentinuzzi et al (2010a) analyze the WINGS sample of local galaxies and determine their ages by means of a Table 7. The redshift evolution of the mass correlation fits.…”

“…The full lines show the best-fit function to the galaxies with HST photometry (yellow points) R c = R 0 c × (1 + z) −ν without selection weighting (see Table 7, case 1). The open dots show the local sample of Valentinuzzi et al (2010a) evolved at the redshifts 0, 0.25, 0.5, 0.75, and 1, after having applied the progenitor bias correction. The dashed line shows the local value.…”

“…Following the procedure of Valentinuzzi et al (2010a) described above, we construct the local sample of WINGS galaxies with velocity dispersions, trimmed to contain only massive spectroscopically passive galaxies at the redshifts z = 0, 0.25, 0.5, 0.75, and 1, and compute the median σ of massive galaxies. The resulting σ vary as σ = (197±2)+(6±4)z km s −1 , when selecting galaxies with dynamical masses 10 11 < M dyn /M < 3×10 11 , and is constant at (210 ± 1.5) km s −1 when selecting galaxies with stellar masses 10 11 < M * /M < 3 × 10 11 .…”