KLEVER (Kmos LEnsed Velocity and Emission line Review) is a Large Programme of the European Southern Observatory exploiting the multi-IFU near-IR spectrograph KMOS at ESO's Very Large Telescope. The goal is to obtain 3D spectra (i.e. spatially resolved spectroscopy) of a sample of about 140 galaxies, in the redshift range z~1-2.5, in all three primary near-IR bands (J, H, K) so to map all of the primary optical nebular lines redshifted into the near-IR bands ([OII], [NeIII], He II, Hβ, [OIII], Hα, [NII], [SII], [SIII]). The combination of these multiple lines will enable the detailed investigation of the spatially resolved physical properties of the ISM in galaxies (excitation mechanism, chemical enrichment, ionization parameter, density, etc...) with an accuracy that has not been possible in previous large surveys (due to the lack of appropriate diagnostics), spatially resolved and with a statistically sound sample.
The sample consists of spectroscopically confirmed galaxies at z~1-2.5, specifically selected to have the primary nebular lines redshifted into the main near-IR bands. Half of the sample consists of galaxies in GOODS-South and in COSMOS, while half of the sample consists of gravitationally lensed galaxies in six lensing clusters from the CLASH survey (these will enable to achieve a higher projected spatial resolution and to access fainter, low-mass galaxies).
Co-PIs: Michele Cirasuolo and Roberto Maiolino
Co-Is: Mirko Curti, Matt Bothwell, Giovanni Cresci, Max Pettini, Filippo Mannucci, Alessandro Marconi, Massimo Meneghetti, Tohru Nagao, Paulina Troncoso, Yingjie Peng, James Dunlop, Ross McLure, Italo Balestra, Simon Lilly, Claudia Cicone, Piero Rosati, Rob Ivison, Michele Cappellari, Mark Swinbank, Fergus Cullen, Owen Turner, Kazuaki Ota
Early results with data from the first two lensing clusters have enabled us to trace the evolution of metallicity gradients across the cosmic epochs.
We found that most of the galaxies at z~1.5-2.5 are consistent with a shallow metallicity gradients, suggesting a mild evolution with cosmic time.
In the context of cosmological simulations and chemical evolution models, the presence of efficient feedback mechanisms and/or extended star formation profiles on top of the classical "inside-out" scenario of mass assembly is generally required to reproduce the observed flatness of the metallicity gradients beyond z~1.
We also find a few fagalaxies with "inverted" metallicity gradients, showing an anti-correlation between metallicity and star formation rate density on local scales, suggesting recent episodes of pristine gas accretion or strong radial flows in place.