Predicting the resolved CO emission of $z=1-3$ star-forming galaxies

Abstract

(Abridged) Resolved observations of the CO emission from $z=1-3$ star-forming galaxies are becoming increasingly common, with new high-resolution surveys on the horizon. We aim to inform the interpretation of this resolved CO emission by creating synthetic observations and testing to what extent routinely observed CO transitions can be used to trace H${}_2$ across galaxy disks. To this end, we extract $z=1-3$ massive star-forming galaxies (on and above the main sequence) from the SIMBA cosmological simulation and predict their spatially resolved CO(1$-$0)-to-CO(5$-$4) emission using the $\text{SLICK}$ pipeline, which combines sub-resolution modeling of the cloud population with the DESPOTIC spectral line calculation code. We find that the CO(1$-$0)-to-H${}_2$ ratio (${\alpha }_{\mathrm{CO}}$) varies significantly within these galaxy disks$-$from values of $\sim 1-5$ ${\mathrm{M}}_{\odot }$ (K km s${}^{-1}$ pc${}^2$)${}^{-1}$ in the central 1-3 kpc of the most massive galaxies to $>100$ ${\mathrm{M}}_{\odot }$ (K km s${}^{-1}$ pc${}^2$)${}^{-1}$ at $\sim$ 15 kpc. Thus, the use of a single ${\alpha }_{\mathrm{CO}}$ to derive the H${}_2$ surface density leads to severe underestimates of the H${}_2$ contribution in its outskirts. As expected, higher-$J$ CO transitions trace molecular gas in the centers at higher densities, whereas CO(1$-$0) better traces the more diffuse, extended molecular gas. We see significant variations in the CO excitation, with CO(3$-$2)/CO(1$-$0) line luminosity ratios of the most massive galaxies at $z\sim 2$ declining from $\sim$ 0.9 in the galaxy centers to $\sim$ 0.1 in the outskirts. On average, line ratios increase substantially toward higher redshifts and lower galaxy stellar masses. We predict that tracing molecular gas with CO beyond 3-5 kpc of cosmic noon galaxies will be challenging with current facilities due to the drastic increase in ${\alpha }_{\mathrm{CO}}$.

arXiv comment17 pages, 13 figures ; accepted by A&A ; Key plots: Figs. 3-6,8

References in corpus (88)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Planck 2015 results. XIII. Cosmological parameters
• The CO-to-H2 Conversion Factor
• GIZMO: A New Class of Accurate, Mesh-Free Hydrodynamic Simulation Methods
• Simba: Cosmological Simulations with Black Hole Growth and Feedback
• Gas-to-Dust mass ratios in local galaxies over a 2 dex metallicity range
• The CO-to-H2 Conversion Factor and Dust-to-Gas Ratio on Kiloparsec Scales in Nearby Galaxies
• A Molecular Star Formation Law in the Atomic Gas Dominated Regime in Nearby Galaxies
• The Resolved Properties of Extragalactic Giant Molecular Clouds
• Diagnostics of irradiated dense gas in galaxy nuclei. II. A grid of XDR and PDR models
• A General Model for the CO-H2 Conversion Factor in Galaxies with Applications to the Star Formation Law
• Grackle: a Chemistry and Cooling Library for Astrophysics
• Black hole accretion and star formation as drivers of gas excitation and chemistry in Mrk231
• A Comparison of Methods for Determining the Molecular Content of Model Galaxies
• The Magellanic Mopra Assessment (MAGMA). I. The Molecular Cloud Population of the Large Magellanic Cloud
• The ISM in distant star-forming galaxies: Turbulent pressure, fragmentation and cloud scaling relations in a dense gas disk at z=2.3
• The molecular gas in Luminous Infrared Galaxies I: CO lines, extreme physical conditions, and their drivers
• The Dust-to-Gas and Dust-to-Metals Ratio in Galaxies from z=0-6
• The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
• Tracing the total molecular gas in galaxies: [CII] and the CO-dark gas
• The CO-H2 Conversion Factor in Disc Galaxies and Mergers
• Star Formation in Extreme Environments: The Effects of Cosmic Rays and Mechanical Heating
• Extended Cold Molecular Gas Reservoirs in z~3.4 Submillimeter Galaxies
• Predictions for the CO emission of galaxies from a coupled simulation of galaxy formation and photon dominated regions
• A Theory for the Excitation of CO in Star Forming Galaxies
• Resolving the ISM at the peak of cosmic star formation with ALMA - The distribution of CO and dust continuum in z~2.5 sub-millimetre galaxies
• Galaxy Cold Gas Contents in Modern Cosmological Hydrodynamic Simulations
• The ALMA Spectroscopic Survey in the HUDF: CO Excitation and Atomic Carbon in Star-Forming Galaxies at $z=1-3$
• ALMA Long Baseline Observations of the Strongly Lensed Submillimeter Galaxy HATLAS J090311.6+003906 at z=3.042
• A Simple and Accurate Network for Hydrogen and Carbon Chemistry in the ISM
• Low-J CO Line Ratios From Single Dish CO Mapping Surveys and PHANGS-ALMA
• A spatially resolved study of cold dust, molecular gas, HII regions, and stars in the $z=2.12$ submillimeter galaxy ALESS67.1
• Resolved Giant Molecular Clouds in Nearby Spiral Galaxies: Insights from the CANON CO (1-0) Survey
• Turbulent Gas in Lensed Planck-selected Starbursts at redshifts 1-3.5
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy
• The Star-Forming Molecular Gas in High Redshift Submillimeter Galaxies
• DESPOTIC -- A New Software Library to Derive the Energetics and SPectra of Optically Thick Interstellar Clouds
• Predictions for the spatial distribution of the dust continuum emission in 1<z<5 star-forming galaxies
• Rotating starburst cores in massive galaxies at z=2.5
• The art of modeling CO, [CI], and [CII] in cosmological galaxy formation models
• CO line emission from galaxies in the Epoch of Reionization
• Warm gas in central regions of nearby galaxies. Extended mapping of CO(3-2) emission
• Modelling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies
• CO(1-0) line imaging of massive star-forming disc galaxies at z=1.5-2.2
• The dust-continuum size of TNG50 galaxies at $z=1-5$: a comparison with the distribution of stellar light, stars, dust and H${}_2$
• Sub-mm Emission Line Deep Fields: CO and [CII] Luminosity Functions out to z = 6
• The Main Sequence at $z\sim 1.3$ contains a sizable fraction of galaxies with compact star formation sizes: a new population of early post-starbursts?
• A physical model for the [CII]-FIR deficit in luminous galaxies
• Constraining the star formation rate in the Solar neighbourhood with star clusters
• CO emission in distant galaxies on and above the main sequence
• The effects of metallicity, UV radiation and non-equilibrium chemistry in high-resolution simulations of galaxies
• Sub-kiloparsec Imaging of Cool Molecular Gas in Two Strongly Lensed Dusty, Star-Forming Galaxies
• High Resolution Imaging of PHIBSS z~2 Main Sequence Galaxies in CO J=1-0
• The ALMA-ALPAKA survey I: high-resolution CO and [CI] kinematics of star-forming galaxies at z = 0.5-3.5
• VLA Mapping of the CO(1-0) Line in SMM J14011+0252
• ASTE CO(3-2) Observations of the Barred Spiral Galaxy M 83: I. Correlation between CO(3-2)/CO(1-0) Ratios and Star Formation Efficiencies
• Resolved Measurements of Xco in NGC 6946
• Chemical Analysis of a Diffuse Cloud along a Line of Sight Toward W51: Molecular Fraction and Cosmic-Ray Ionization Rate
• Impact of X-rays on CO emission from high-z galaxies
• Full of Orions: a 200-pc mapping of the interstellar medium in the redshift-3 lensed dusty star-forming galaxy SDP.81
• The nature of the ISM in galaxies during the star-formation activity peak of the Universe
• Sub-millimetre compactness as a critical dimension to understand the Main Sequence of star-forming galaxies
• Cold gas disks in main-sequence galaxies at cosmic noon: Low turbulence, flat rotation curves, and disk-halo degeneracy
• Giant molecular clouds in the non-grand design spiral galaxy NGC 6946
• A Comparison of the Stellar, CO and Dust-Continuum Emission from Three, Star-Forming HUDF Galaxies at $z\sim 2$
• The Influence of Far-Ultraviolet Radiation on the Properties of Molecular Clouds in the 30 Dor Region of the Large Magellanic Cloud
• Quenching and the UVJ diagram in the SIMBA cosmological simulation
• Spatially resolved CO SLED of the Luminous Merger Remnant NGC 1614 with ALMA
• Warm and Cold Molecular Gas Conditions Modeled in 87 Galaxies Observed by the Herschel SPIRE Fourier Transform Spectrometer
• Resolved Molecular Gas and Star Formation Properties of the Strongly Lensed z=2.26 Galaxy SDSS J0901+1814
• PDFchem: A new fast method to determine ISM properties and infer environmental parameters using probability distributions
• VLA Legacy Survey of Molecular Gas in Massive Star-forming Galaxies at High Redshift
• High resolution modeling of [CII], [CI], [OIII] and CO line emission from the ISM and CGM of a star forming galaxy at z ~ 6.5
• High-resolution ALMA study of CO (2-1) line and dust continuum emissions in cluster galaxies at z = 1.46
• Molecular Cloud Properties and CO Line Emission in z >~ 6 Galaxies
• Reproducing the CO-to-H${}_2$ conversion factor in cosmological simulations of Milky Way-mass galaxies
• The cosmic ray ionisation and $\gamma$-ray budgets of star-forming galaxies
• CO line emission from Lyman Break Galaxies. Cosmological simulations and predictions for ALMA
• SImulator of GAlaxy Millimetre/submillimetre Emission (SIGAME): CO emission from massive z=2 main-sequence galaxies
• Resolved CO(1-0) emission and gas properties in luminous dusty star forming galaxies at z=2-4
• The effects of local stellar radiation and dust depletion on non-equilibrium interstellar chemistry
• CO(J=3-2) On-the-fly Mapping of the Nearby Spiral Galaxies NGC 628 and NGC 7793: Spatially-resolved CO(J=3-2) Star-formation Law
• CO Multi-line Imaging of Nearby Galaxies (COMING). XII. CO-to-H${}_2$ Conversion Factor and Dust-to-Gas Ratio
• Cosmic Sands: The Origin of Dusty, Star-forming Galaxies in the Epoch of Reionization
• The CO universe: Modelling CO emission and H${}_2$ abundance in cosmological galaxy formation simulations
• Gas, dust, and the CO-to-molecular gas conversion factor in low-metallicity starbursts
• ALMA resolves the molecular gas in a young low-metallicity starburst galaxy at z=1.7
• $\text{slick}$: Modeling a Universe of Molecular Line Luminosities in Hydrodynamical Simulations