Abstract
ABSTRACT We present the results of an integral field spectroscopy survey of a sample of dusty (ultra) luminous infrared galaxies (U/LIRGs) at 2 < z < 2.5 using KMOS on the Very Large Telescope. The sample has been drawn from Herschel deep field surveys and benefits from ancillary multiwavelength data. Our goal is to investigate the physical characteristics, kinematics, and the drivers of star formation in the galaxies whose contribution dominates the peak of the cosmic star formation density. Two-thirds of the sample are main-sequence galaxies in contrast to the starburst nature of local U/LIRGs. Our kinematic study, unique in its focus on z ∼ 2 dusty star-forming galaxies, uses the H α emission line to find that ∼40 per cent appear to be isolated discs based on the ratio of rotational velocity to the velocity dispersion, suggesting steady-state mechanisms are sufficient to power the large star formation rates (SFRs). The ratio of obscured to unobscured star formation indicates the sample of galaxies experiences less dust obscuration compared to intermediate and local counterparts, while also hosting cooler dust than local U/LIRGs. In addition to H α we detect [N ii] 6583 Å in our targets and show the gas-phase metallicities do not exhibit the metal deficiency of local U/LIRGs. These results indicate that, despite their extreme IR luminosity, the underlying mechanisms driving the massive SFRs found at cosmic noon are due to scaled up disc galaxies as opposed to mergers.
Highlights
(Ultra) Luminous infrared galaxies (U/LIRGs) are amongst the most powerful star-forming galaxies in the Universe
We present the results of an integral field spectroscopy survey of a sample of dusty luminous infrared galaxies (U/LIRGs) at 2 < z < 2.5 using K-band Multi Object Spectrograph (KMOS) on the Very Large Telescope
GalPak3D’s model galaxy has 10 free parameters: x, y, and z centroid position, flux, half-light radius, turnover radius, position angle, inclination, maximum rotational velocity, and the one-dimensional intrinsic velocity dispersion. The emission from this model galaxy is subsequently convolved with a point-spread function (PSF), specified by the user, and the best fit to the observed data is found via a Bayesian Markov Chain Monte Carlo (MCMC) approach
Summary
(Ultra) Luminous infrared galaxies (U/LIRGs) are amongst the most powerful star-forming galaxies in the Universe. It appears that MS galaxies are responsible for up to 90 per cent of the cosmic SFRD (e.g. Rodighiero et al 2011; Sargent et al 2012) and the density of large dust-obscured galaxies increasing with redshift (e.g. Floc’h et al 2005) This is suggestive that a substantial fraction of high-z luminous IR galaxies should be scaled up versions of local star-forming disc galaxies with their increased SFRs due to the comparatively larger reservoirs of molecular gas at high redshift (e.g. Daddi et al 2010a; Tacconi et al 2013; Combes 2018). When required the initial mass function (IMF) was assumed to be a Chabrier (2003) form
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