The KMOS galaxy evolution survey (KGES): the angular momentum of star-forming galaxies over the last ≈10 Gyr

Abstract

We present the KMOS Galaxy Evolution Survey (KGES), a K-band Multi-Object Spectrograph (KMOS) study of the Hα and [N ii] emission from 288 K band-selected galaxies at 1.2 ≲ z ≲ 1.8, with stellar masses in the range $\log _{10}(M_{*}/\rm {M}_{\odot })\approx 9$ – 11.5. In this paper, we describe the survey design, present the sample, and discuss the key properties of the KGES galaxies. We combine KGES with appropriately matched samples at lower redshifts from the KMOS Redshift One Spectroscopic Survey (KROSS) and the SAMI Galaxy Survey. Accounting for the effects of sample selection, data quality, and analysis techniques between surveys, we examine the kinematic characteristics and angular momentum content of star-forming galaxies at z ≈ 1.5, ≈1 and ≈0. We find that stellar mass, rather than redshift, most strongly correlates with the disc fraction amongst star-forming galaxies at z ≲ 1.5, observing only a modest increase in the prevalence of discs between z ≈ 1.5 and z ≈ 0.04 at fixed stellar mass. Furthermore, typical star-forming galaxies follow the same median relation between specific angular momentum and stellar mass, regardless of their redshift, with the normalization of the relation depending more strongly on how disc-like a galaxy’s kinematics are. This suggests that massive star-forming discs form in a very similar manner across the ≈ 10 Gyr encompassed by our study and that the inferred link between the angular momentum of galaxies and their haloes does not change significantly across the stellar mass and redshift ranges probed in this work.

The resolved chemical abundance properties within the interstellar medium of star-forming galaxies at z≈ 1.5

“…The majority of galaxies (20/22) have previously been observed as part of the KMOS Galaxy Evolution Surv e y (KGES; Gillman et al 2019 ;Tiley et al 2021 ) with two galaxies (KURVS 21 and 22) selected from the KMOS 3D surv e y (Wisnioski et al 2019 ). The KURVS galaxies lie within the Cosmic Assembly Near-infrared Deep Extragalactic Le gac y Surv e y (CANDELS; Grogin et al 2011 ) HST fields.…”

“…To determine the presence of AGN in the KURVS sample, we first utilize the AGN identification scheme employed by Tiley et al ( 2021 ) for the full KGES sample. In short AGN are identified in our sample by criteria placed on their integrated [N II ]/H α ratio, emissionline width and infrared colours following the Donley et al ( 2012 ) and Stern et al ( 2012 ) colour selection (see Tiley et al ( 2021 ) for full details). We also exclude galaxies with bright X-ray counterparts by cross-matching our sample with the CDFS 7 Ms Source Catalog (Luo et al 2017 ).…”

Morpheus Reveals Distant Disk Galaxy Morphologies with JWST: The First AI/ML Analysis of JWST Images

“…Large, star-forming disk galaxies at redshifts z ∼ 1 − 3 can be baryon-dominated, with relatively little dark matter contributing to their rotation curves (Wuyts et al 2016;Genzel et al 2017Genzel et al , 2020Übler et al 2018;Price et al 2020). The structure of early disks can be distinct from dynamically colder disk galaxies at the present, perhaps reflecting a transition between disks heavily influenced by the hierarchical mass assembly process to more ordered rotation at lower redshifts (e.g., Kassin et al 2012;Simons et al 2017;Tiley et al 2021). This transition may mirror the evolution of observed axis ratios, as observations with the Hubble Space Telescope (HST) have established a smaller fraction of disk galaxies at earlier cosmic times (e.g., Law et al 2012;van der Wel et al 2014;Zhang et al 2019).…”

KAOSS: turbulent, but disc-like kinematics in dust-obscured star-forming galaxies at $z\sim$1.3-2.6

“…One of the most promising routes to test these competing theories is through integral field spectroscopy (IFS) in the rest-frame optical, which enables two-dimensional (2-D) mapping of the spatially resolved kinematics via nebular emission lines such as H𝛼 (e.g. Cresci et al 2009;Förster Schreiber et al 2009;Alaghband-Zadeh et al 2012;Wisnioski et al 2015Wisnioski et al , 2019Tiley et al 2021). These maps can then be used to measure the rotational velocity 𝑣 rot and intrinsic velocity dispersion 𝜎 0 (e.g.…”

“…However, dynamical analyses with KMOS at this epoch are challenging because of the seeinglimited spatial resolution -KMOS achieves a resolution of ∼ 0.6 (FWHM), which corresponds to a physical size of ∼ 5 kpc at 𝑧 = 2 (although finer spatial scales can be sampled if the sources exhibit velocity gradients). Additionally the 𝐻 band, which covers the redshifted H𝛼 emission from galaxies at 𝑧 ∼ 1.2-1.8, suffers from strong sky contamination (Soto et al 2016;Tiley et al 2021) that can be challenging to robustly model and remove.…”