KMOS LENsing Survey (KLENS): Morpho-kinematic analysis of star-forming galaxies at z ~ 2

Abstract

We present results from the KMOS lensing survey (KLENS), which is exploiting gravitational lensing to study the kinematics of 24 star forming galaxies at 1.4 < z < 3.5 with a median mass of log(M /M ) = 9.6 and median star formation rate (SFR) of 7.5 M yr −1 . We find that 25% of these low-mass/low-SFR galaxies are rotation dominated, while the majority of our sample shows no velocity gradient. When combining our data with other surveys, we find that the fraction of rotation dominated galaxies increases with the stellar mass, and decreases for galaxies with a positive offset from the main sequence (higher specific star formation rate). We also investigate the evolution of the intrinsic velocity dispersion, σ 0 , as a function of the redshift, z, and stellar mass, M , assuming galaxies in quasi-equilibrium (Toomre Q parameter equal to 1). From the z − σ 0 relation, we find that the redshift evolution of the velocity dispersion is mostly expected for massive galaxies (log(M /M ) > 10). We derive a M − σ 0 relation, using the Tully-Fisher relation, which highlights that a different evolution of the velocity dispersion is expected depending on the stellar mass, with lower velocity dispersions for lower masses, and an increase for higher masses, stronger at higher redshift. The observed velocity dispersions from this work and from comparison samples spanning 0 < z < 3.5 appear to follow this relation, except at higher redshift (z > 2), where we observe higher velocity dispersions for low masses (log(M /M ) ∼ 9.6) and lower velocity dispersions for high masses (log(M /M ) ∼ 10.9) than expected. This discrepancy could, for instance, suggest that galaxies at high redshift do not satisfy the stability criterion, or that the adopted parametrisation of the specific star formation rate and molecular properties fail at high redshift.

First results from the TNG50 simulation: the evolution of stellar and gaseous discs across cosmic time

“…However, even by allowing Qcrit > 1, the proposed models cannot justify the continuous increase in velocity dispersion at z 1 − 2, in agreement with the conclusions by Girard et al (2018): for TNG50, this is the case for the intrinsic simulated velocity dispersions, i.e. without accounting for thermal motions.…”

“…More recently, Swinbank et al (2017) have extended the gas kinematic analysis of star-forming galaxies throughout the z = 0.3 − 1.7 range and down to galaxies of 10 8 M thanks to MUSE observations. Finally, Girard et al (2018) have further extended the investigated mass range down to ∼ 4 × 10 9 M galaxies at 1.4 < z < 3.5 thanks to gravitational lensing.…”

The ALPINE-ALMA [C II] survey

“…In addition to the average stellar mass growth of SFGs along the MS, simulations suggest SFGs oscillate up and down in sSFR across the MS dispersion, owing to feedback effects that alter the gas accretion rate; internal gas transport; and compaction events (Tacchella et al 2016;Orr et al 2019). The bathtub model agrees with most of the scaling relations observed for MS SFGs, such as the Kennicutt-Schmidt (KS) star-formation law (Kennicutt 1998a;Tacconi et al 2013) and the mass-metallicity relation (e.g., Erb et al 2006;Maiolino et al 2008;Mannucci et al 2010;Ginolfi et al 2020a), and with the dynamically more turbulent galactic disks at high-redshift (e.g., Förster Schreiber et al 2009;Wisnioski et al 2015;Molina et al 2017;Girard et al 2018).…”

First constraints on the stellar mass function of star-forming clumps at the peak of cosmic star formation

“…First, it is successfully reproduced by numerical simulations (e.g., Ceverino et al 2012;Bournaud et al 2014;Tamburello et al 2015;Behrendt et al 2016;Mandelker et al 2017). Second, observational support in favor of rotation-dominated, highly turbulent, strongly star-forming, gasrich, and marginally stable disks at high redshift is now well established (e.g., Förster Schreiber et al 2009;Tacconi et al 2013;Wisnioski et al 2015;Dessauges-Zavadsky et al 2015, 2017bHarrison et al 2017;Turner et al 2017;Girard et al 2018).…”