Compactness of Cold Gas in High-Redshift Galaxies

Abstract

Galaxies in the early Universe were more compact and contained more molecular gas than today. In this paper, we revisit the relation between these empirical findings, and we quantitatively predict the cosmic evolution of the surface densities of atomic (HI) and molecular (H2) hydrogen in regular galaxies. Our method uses a pressure-based model for the H2/HI-ratio of the Interstellar Medium, applied to ~3*10^7 virtual galaxies in the Millennium Simulation. We predict that, on average, the HI-surface density of these galaxies saturates at Sigma_HI<10 Msun/pc^2 at all redshifts (z), while H2-surface densities evolve dramatically as Sigma_H2(1+z)^2.4. This scaling is dominated by a (1+z)^2 surface brightness scaling originating from the (1+z)^-1 size scaling of galaxies at high z. Current measurements of Sigma_H2 at high z, derived from CO-observations, tend to have even higher values, which can be quantitatively explained by a selection bias towards merging systems. However, despite the consistency between our high-z predictions and the sparse empirical data, we emphasize that the empirical data potentially suffer from serious selection biases and that the semi-analytic models remain in many regards uncertain. As a case study, we investigate the cosmic evolution of simulated galaxies, which resemble the Milky Way at z=0. We explicitly predict their HI- and H2-distribution at z=1.5, corresponding to the CO-detected galaxy BzK-21000, and at z=3, corresponding to the primary science goal of the Atacama Large Millimeter/submillimeter Array (ALMA).

5 pages, 3 figures, 2 tables

References in corpus (12)

• The hierarchical formation of the brightest cluster galaxies
• The Role of Pressure in GMC Formation II: The H_2 - Pressure Relation
• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• Size evolution of the most massive galaxies at 1.7<z<3 from GOODS NICMOS survey imaging
• On the mass-to-light ratio of the local Galactic disc and the optical luminosity of the Galaxy
• Molecular Hydrogen and Global Star Formation Relations in Galaxies
• Vigorous star formation with low efficiency in massive disk galaxies at z=1.5
• Simulation of the Cosmic Evolution of Atomic and Molecular Hydrogen in Galaxies
• GMC formation by agglomeration and self gravity
• Understanding the H2/HI Ratio in Galaxies
• The Cosmic Decline in the H2/HI-Ratio in Galaxies
• CO line emission from Lyman Break Galaxies. Cosmological simulations and predictions for ALMA

Cited by in corpus (13)

• The Morphologies of Massive Galaxies at 1<z<3 in the CANDELS-UDS Field: Compact Bulges, and the Rise and Fall of Massive Disks
• Fundamental Mass-Spin-Morphology Relation of Spiral Galaxies
• Semi-analytic forecasts for JWST -- II. physical properties and scaling relations for galaxies at z = 4-10
• Phylogeny of the Milky Way's inner disk and bulge populations: Implications for gas accretion, (the lack of) inside-out thick disk formation, and quenching
• GOODS-ALMA: The slow downfall of star-formation in $z$ = 2-3 massive galaxies
• GMRT mini-survey to search for 21-cm absorption in Quasar-Galaxy Pairs at z~0.1
• CO observations of high-z radio galaxies MRC 2104-242 and MRC 0943-242: spectral-line performance of the Compact Array Broadband Backend
• Detecting neutral hydrogen in emission at redshift z ~ 1
• Probing AGN triggering mechanisms through the starburstiness of the host galaxies
• Evolution of the Milky Way in Semi-Analytic Models: Detecting Cold Gas at z=3 with ALMA and SKA
• Towards the first detection of strongly lensed HI emission
• The molecular gas in the central region of NGC 7213
• A comparison of ${\text{H}}_2$ formation models at high redshift