Probing cold gas in a massive, compact star-forming galaxy at z=6

Abstract

Observations of low order CO transitions represent the most direct way to study galaxies' cold molecular gas, the fuel of star formation. Here we present the first detection of CO(2-1) in a galaxy lying on the main-sequence of star-forming galaxies at z>6. Our target, G09-83808 at z=6.03, has a short depletion time-scale of T_dep~50Myr and a relatively low gas fraction of M_gas/M_star=0.30 that contrasts with those measured for lower redshift main-sequence galaxies. We conclude that this galaxy is undergoing a starburst episode with a high star formation efficiency that might be the result of gas compression within its compact rotating disk. Its starburst-like nature is further supported by its high star formation rate surface density, thus favoring the use of the Kennicutt-Schmidt relation as a more precise diagnostic diagram for starbursts. Without further significant gas accretion, this galaxy would become a compact, massive quiescent galaxy at z~5.5. In addition, we find that the calibration for estimating ISM masses from dust continuum emission satisfactorily reproduces the gas mass derived from the CO(2-1) transition (within a factor of ~2). This is in line with previous studies claiming a small redshift evolution in the gas-to-dust ratio of massive, metal-rich galaxies. In the absence of gravitational amplification, this detection would have required of order ~1000h of observing time. The detection of cold molecular gas in unlensed star-forming galaxies at high redshifts is thus prohibitive with current facilities and requires a ten-fold improvement in sensitivity, such as that envisaged for the ngVLA.

arXiv commentAccepted for publication in The Astrophysical Journal

References in corpus (65)

• Planck 2015 results. XIII. Cosmological parameters
• Detailed Structural Decomposition of Galaxy Images
• The CO-to-H2 Conversion Factor
• Simulating Galaxy Formation with the IllustrisTNG Model
• Rotating Nuclear Rings and Extreme Starbursts in Ultraluminous Galaxies
• A simple model to interpret the ultraviolet, optical and infrared emission from galaxies
• GOODS-Herschel: an infrared main sequence for star-forming galaxies
• Cool Gas in High Redshift Galaxies
• A Study of the Gas-Star Formation Relation over Cosmic Time
• The Herschel view of the dominant mode of galaxy growth from z=4 to the present day
• Dusty Star-Forming Galaxies at High Redshift
• Gas-to-Dust mass ratios in local galaxies over a 2 dex metallicity range
• PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions
• Combined CO & Dust Scaling Relations of Depletion Time and Molecular Gas Fractions with Cosmic Time, Specific Star Formation Rate and Stellar Mass
• A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34
• The CO-to-H2 Conversion Factor From Infrared Dust Emission Across the Local Group
• The Evolving Interstellar Medium of Star Forming Galaxies Since z=2 as Probed by Their Infrared Spectral Energy Distributions
• ISM masses and the star formation law at Z = 1 to 6 // ALMA observations of dust continuum in 145 galaxies in the COSMOS survey field
• A survey of molecular gas in luminous sub-millimetre galaxies
• The Evolution of the Star-forming Interstellar Medium across Cosmic Time
• On the effect of the Cosmic Microwave Background in high-redshift (sub-)millimeter observations
• Evolution of Interstellar Medium, Star Formation, and Accretion at High Redshift
• Forming Compact Massive Galaxies
• The SFR-M* Relation and Empirical Star-Formation Histories from ZFOURGE at 0.5 < z < 4
• The contribution of starbursts and normal galaxies to infrared luminosity functions at z < 2
• Validation of the equilibrium model for galaxy evolution to z~3 through molecular gas and dust observations of lensed star-forming galaxies
• Galaxy growth in a massive halo in the first billion years of cosmic history
• The ALPINE-ALMA [CII] Survey: data processing, catalogs, and statistical source properties
• ALMA Imaging and Gravitational Lens Models of South Pole Telescope-Selected Dusty, Star-Forming Galaxies at High Redshifts
• Quiescent galaxies 1.5 billion years after the Big Bang and their progenitors
• The Dust-to-Gas and Dust-to-Metals Ratio in Galaxies from z=0-6
• A survey of the cold molecular gas in gravitationally lensed star-forming galaxies at z>2
• Main sequence of star forming galaxies beyond the Herschel confusion limit
• ISM properties of a Massive Dusty Star-Forming Galaxy discovered at z ~ 7
• The Evolution of the Baryons Associated with Galaxies Averaged over Cosmic Time and Space
• A Theory for the Excitation of CO in Star Forming Galaxies
• Automated Mining of the ALMA Archive in the COSMOS Field (A3COSMOS): II. Cold Molecular Gas Evolution out to Redshift 6
• A Survey of Atomic Carbon [C I] in High-redshift Main-Sequence Galaxies
• The ALPINE-ALMA [CII] survey: Molecular gas budget in the Early Universe as traced by [CII]
• The space density of luminous dusty star-forming galaxies at $z>4$: SCUBA-2 and LABOCA imaging of ultrared galaxies from $Herschel$-ATLAS
• A higher efficiency of converting gas to stars push galaxies at z ~ 1.6 well above the star-forming main sequence
• High-resolution CO and radio imaging of z~2 ULIRGs: extended CO structures, and implications for the universal star formation law
• A dusty star-forming galaxy at z=6 revealed by strong gravitational lensing
• The ALPINE-ALMA [CII] Survey: Obscured Star Formation Rate Density and Main Sequence of star-forming galaxies at z>4
• Turbulent Gas in Lensed Planck-selected Starbursts at redshifts 1-3.5
• Stellar Velocity Dispersion of a Massive Quenching Galaxy at z=4.01
• Hidden in plain sight: a massive, dusty starburst in a galaxy protocluster at z=5.7 in the COSMOS field
• Physical Characterization of an Unlensed Dusty Star-Forming Galaxy at $z=5.85$
• Mapping Obscuration to Reionization with ALMA (MORA): 2mm Efficiently Selects the Highest-Redshift Obscured Galaxies
• The most distant, luminous, dusty star-forming galaxies: redshifts from NOEMA and ALMA spectral scans
• Low Gas Fractions Connect Compact Star-Forming Galaxies to their z ~ 2 Quiescent Descendants
• GOODS-ALMA: The slow downfall of star-formation in $z$ = 2-3 massive galaxies
• The emergence of passive galaxies in the early Universe
• Sub-millimetre compactness as a critical dimension to understand the Main Sequence of star-forming galaxies
• GOODS-ALMA 2.0: Starbursts in the main sequence reveal compact star formation regulating galaxy evolution prequenching
• Stellar masses and star formation rates of lensed dusty star-forming galaxies from the SPT survey
• Molecular Line Observations in Two Dusty Star-Forming Galaxies at z = 6.9
• The Number Densities and Stellar Populations of Massive Galaxies at 3 < z < 6: A Diverse, Rapidly Forming Population in the Early Universe
• The NEWFIRM HETDEX Survey: Photometric Catalog and a Conservative Sample of Massive Quiescent Galaxies at z=3-5 over 17.5 deg^2 in the SHELA Field
• Measuring the average molecular gas content of star-forming galaxies at $z=3-4$
• Detection of nitrogen and oxygen in a galaxy at the end of reionization
• The Physical Drivers of the Luminosity-Weighted Dust Temperatures in High-Redshift Galaxies
• NOEMA confirmation of an optically dark ALMA-AzTEC submillimetre galaxy at $z=5.24$. A late-stage starburst prior to quenching
• The Atacama Large Millimeter/submillimeter Array (ALMA) Band-1 Receiver
• Observed cosmic evolution of galaxy dust properties with metallicity and tensions with models

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