Stars were born in significantly denser regions in the early Universe

Abstract

The density of the warm ionized gas in high-redshift galaxies is known to be higher than what is typical in local galaxies on similar scales. At the same time, the mean global properties of the high- and low-redshift galaxies are quite different. Here, we present a detailed differential analysis of the ionization parameters of 14 star-forming galaxies at redshift 2.6-3.4, compiled from the literature. For each of those high-redshift galaxies, we construct a comparison sample of low-redshift galaxies closely matched in specific star formation rate (sSFR) and stellar mass, thus ensuring that their global physical conditions are similar to the high-redshift galaxy. We find that the median log [OIII] 5007/ [OII] 3727 line ratio of the high-redshift galaxies is 0.5 dex higher than their local counterparts. We construct a new calibration between the [OIII] 5007/ [OII] 3727 emission line ratio and ionization parameter to estimate the difference between the ionization parameters in the high and low-redshift samples. Using this, we show that the typical density of the warm ionized gas in star-forming regions decreases by a median factor of $7.1_{-5.4}^{+10.2}$ from z ~ 3.3 to z ~ 0 at fixed mass and sSFR. We show that metallicity differences cannot explain the observed density differences. Because the high- and low-redshift samples are comparable in size, we infer that the relationship between star formation rate density and gas density must have been significantly less efficient at z ~2-3 than what is observed in nearby galaxies with similar levels of star formation activity.

16 pages, 6 figures, accepted for publication in ApJ

References in corpus (17)

• Star Formation in AEGIS Field Galaxies since z=1.1 : The Dominance of Gradually Declining Star Formation, and the Main Sequence of Star-Forming Galaxies
• UV Star Formation Rates in the Local Universe
• Theoretical Evolution of Optical Strong Lines across Cosmic Time
• The Cosmic BPT Diagram: Confronting Theory with Observations
• New insights into the stellar content and physical conditions of star-forming galaxies at z = 2-3 from spectral modelling
• Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey
• Clumpy Galaxies in GOODS and GEMS: Massive Analogs of Local Dwarf Irregulars
• Metallicities and Physical Conditions in Star-forming Galaxies at z~1.0-1.5
• Observations of Thick Disks in the Hubble Space Telescope Ultra Deep Field
• The cycle of interstellar dust in galaxies of different morphological types
• Modelling the Pan-Spectral Energy Distribution of Starburst Galaxies: II. Control of the \HII Region Parameters
• Shocked Superwinds from the z~2 Clumpy Star-forming Galaxy, ZC406690
• On the self-regulation of intense star-formation in galaxies at z=1-3
• Nebular Excitation in z~2 Star-forming Galaxies from the SINS and LUCI Surveys: The Influence of Shocks and AGN
• Estimating gas masses and dust-to-gas ratios from optical spectroscopy
• A Magnified View of the Kinematics and Morphology of RCSGA 032727-132609: Zooming in on a Merger at z=1.7
• The physical nature of the 8 o'clock arc based on near-IR IFU spectroscopy with SINFONI

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