The VIMOS Public Extragalactic Redshift Survey (VIPERS)

Abstract

We use the final data from the VIPERS redshift survey to extract an unparalleled sample of more than 2000 massive M ≥1011 M ⊙ passive galaxies (MPGs) at redshift 0.5 ≤ z ≤ 1.0, based on their NUVrK colours. This enables us to investigate how the population of these objects was built up over cosmic time. We find that the evolution of the number density depends on the galaxy mean surface stellar mass density, Σ. In particular, dense (Σ ≥ 2000 M ⊙ pc −2 ) MPGs show a constant comoving number density over this redshift range, whilst this increases by a factor ∼ 4 for the least dense objects, defined as having Σ < 1000 M ⊙ pc −2 . We estimate stellar ages for the MPG population both fitting the Spectral Energy Distribution (SED) and through the D4000 n index, obtaining results in good agreement. Our findings are consistent with passive ageing of the stellar content of dense MPGs. We show that at any redshift the less dense MPGs are younger than dense ones and that their stellar populations evolve at a slower rate than predicted by passive evolution. This points to a scenario in which the overall population of MPGs was built up over the cosmic time by continuous addition of less dense galaxies: on top of an initial population of dense objects that passively evolves, new, larger, and younger MPGs continuously join the population at later epochs. Finally, we demonstrate that the observed increase in the number density of MPGs is totally accounted for by the observed decrease in the number density of correspondingly massive star forming galaxies (i.e. all the nonpassive M ≥10 11 M ⊙ objects). Such systems observed at z ≃ 1 in VIPERS, therefore, represent the most plausible progenitors of the subsequent emerging class of larger MPGs.

The evolution of sizes and specific angular momenta in hierarchical models of galaxy formation and evolution

“…When considering the mass thresholds adopted by Cassata et al (2013), our model Q number density is in agreement with the corresponding observational estimates. When considering the mass thresholds adopted by van Dokkum et al (2015) and Gargiulo et al (2017), model predictions are offset low with respect to observational estimates, at all cosmic epochs. If we consider the uncertainty in the stellar mass measurement, adding Gaussian random error to log 10 (M * ) with a standard deviation of σ * = 0.25 dex, the resulting number density evolution changes significantly, in particular at high redshift, as shown in the bottom panel of figure 4.…”

“…To have a fair comparison with observations, we select Q galaxies adopting different stellar mass thresholds. Solid, dotted and dash-dotted lines show predictions corresponding to M * > 10 10 M (as in Cassata et al 2013), M * > 10 10.6 M (as in van Dokkum et al 2015), and M * > 10 11 M (as in Gargiulo et al 2017). van Dokkum et al (2015) selected galaxies from the 3D-HST project (Brammer et al 2012), according to their position in the U − V versus V − J diagram (the considered size is the circularized half-light radius re).…”

“…van Dokkum et al (2015) selected galaxies from the 3D-HST project (Brammer et al 2012), according to their position in the U − V versus V − J diagram (the considered size is the circularized half-light radius re). In Gargiulo et al (2017), ET galaxies are from the VIPERS project (Scodeggio et al 2018), with spectroscopic redshift 0.5 < z < 1. Their galaxies are selected according to the rest-frame NUV-r vs r-K diagram.…”

“…model galaxies with respect to observational estimates for tH > 5 Gyr. Gargiulo et al (2016) argue that the difference between estimates by van der Wel et al (2014) and Gargiulo et al (2017) can be largely ascribed to the different definition of galaxy sizes. The different selections may also play a role.…”

A few StePS forward in unveiling the complexity of galaxy evolution: light-weighted stellar ages of intermediate-redshift galaxies with WEAVE

“…In this context, the intermediate redshift range (0.3 z 0.7) offers an interesting niche of investigation: the span in cosmic time covered up to z ∼ 0.7 is nearly half the age of the Universe, enabling the direct observation of galaxies over a significant and continuous interval of their evolutionary life. In this redshift range, a coarse estimate of the morphological type is possible with data from ground-based telescopes ; the fraction of galaxies located in structures like groups progressively rises as expected in a hierarchical structure formation scenario (Knobel et al 2009), and the increase of number of red massive passive galaxies is significant down to z ∼ 0.5 (Gargiulo et al 2017;Haines et al 2017).…”