The KLEVER Survey: spatially resolved metallicity maps and gradients in a sample of 1.2 < z < 2.5 lensed galaxies

Abstract

We present near-infrared observations of 42 gravitationally lensed galaxies obtained in the framework of the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey, a programme aimed at investigating the spatially resolved properties of the ionized gas in 1.2 < z < 2.5 galaxies by means of a full coverage of the YJ, H, and K near-infrared bands. Detailed metallicity maps and gradients are derived for a subsample of 28 galaxies from reconstructed source-plane emission-line maps, exploiting the variety of different emission-line diagnostics provided by the broad wavelength coverage of the survey. About $85 {{\, per\ cent}}$ of these galaxies are characterized by metallicity gradients shallower than $0.05\ \rm dex\, kpc^{-1}$ and $89{{\ \rm per\ cent}}$ are consistent with a flat slope within 3σ ($67{{\ \rm per\ cent}}$ within 1σ), 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. Three galaxies with significantly (>3σ) ‘inverted’ gradients are also found, showing an anticorrelation between metallicity and star formation rate density on local scales, possibly suggesting recent episodes of pristine gas accretion or strong radial flows in place. Nevertheless, the individual metallicity maps are characterized by a variety of different morphologies, with flat radial gradients sometimes hiding non-axisymmetric variations on kpc scales, which are washed out by azimuthal averages, especially in interacting systems or in those undergoing local episodes of recent star formation.

Super

“…3. The light blue vertical area denotes the w 80 value from a stacked spectrum of mass-matched and redshift-matched galaxies from the KLEVER survey (Curti et al 2020), a high-redshift survey targeting star forming galaxies. The stellar mass of the overall SUPER sample has been used to mass-match the comparison samples, as most of the Type 1 AGN do not have reliable stellar mass measurements (Circosta et al 2018).…”

“…The Type 1 sample used in this paper has a median hard X-ray luminosity of 10 44.8 erg s −1 and the redshift-matched KASHz targets have a median X-ray luminosity of 10 43.9 erg s −1 . The blue histogram shows the w 80 distribution of massmatched low redshift star forming sample fromWylezalek et al (2020), while the ocean-blue vertical bar shows the w 80 value from the redshift and mass-matched star forming sample from the KLEVER survey (334 ± 35 km s −1 ,Curti et al 2020). The dashed black-line at 600 km s −1 corresponds to the w 80 value used in this work to define if a target hosts an AGN-driven outflow.…”

L-GALAXIES 2020: The evolution of radial metallicity profiles and global metallicities in disc galaxies

“…There have also been a number of observational studies of metallicity profiles at higher redshift recently (e.g. Troncoso et al 2014;Stott et al 2014;Leethochawalit et al 2016;Curti et al 2020b;Wang et al 2020;Gillman et al 2021). In general, these studies suggest that (a) profiles are rather flat at all redshifts back to ∼ 2.5, albeit with a wide spread in Δ( g ) (see Hemler et al 2020), and (b) strong, metal-rich galactic outflows are required in order to explain this.…”

A Census of Sub-kiloparsec Resolution Metallicity Gradients in Star-forming Galaxies at Cosmic Noon from HST Slitless Spectroscopy

“…All individual ground-based measurements at similar resolution (kpc scale) are represented by magenta squares. Recently, Curti et al (2020) analyzed the KMOS observations in the field of RX J2248 and measured metallicity gradients in 12 background galaxies lensed by RX J2248, of which three are in overlap with our sample (i.e., ID 00206, ID 00428, and ID 01205). We verified that the gradient results measured from both works are compatible at a 1σ confidence level.…”

“…Lensing is thus essential for resolving the lowest-mass galaxies at high redshifts. Recently, Curti et al (2020) derived metallicity maps and radial gradients in a sample of 28 lensed galaxies with stellar masses as low as 10 9  M . In this work, we measure radial gradients of metallicity in 76 star-forming galaxies at 1.2z2.3 gravitationally lensed by foreground galaxy clusters, further extending to even lower stellar masses.…”