The evolution of the dust and gas content in galaxies (1311.3670v1)

Abstract: We use deep Herschel PACS and SPIRE observations in GOODSS, GOODSN and COSMOS to estimate the average dust mass (Mdust) of galaxies on a redshift-stellar mass (Mstar)-SFR grid. We study the scaling relations between Mdust, Mstar and SFR at z<=2.5. No clear evolution of Mdust is observed at fixed SFR and Mstar. We find a tight correlation between SFR and Mdust, likely a consequence of the Schmidt-Kennicutt (S-K) law. The Mstar-Mdust correlation observed by previous works flattens or sometimes disappears when fixing the SFR. Most of it likely derives from the combination of the Mdust-SFR and Mstar-SFR correlations. We then investigate the gas content as inferred by converting Mdust by assuming that the dust/gas ratio scales linearly with the gas metallicity. All galaxies in the sample follow, within uncertainties, the same SFR-Mgas relation (integrated S-K law), which broadly agrees with CO-based results for the bulk of the population, despite the completely different approaches. The majority of galaxies at z~2 form stars with an efficiency (SFE=SFR/Mgas) ~5 times higher than at z~0. It is not clear what fraction of such variation is an intrinsic redshift evolution and what fraction arises from selection effects. The gas fraction (fgas) decreases with Mstar and increases with SFR, and does not evolve with z at fixed Mstar and SFR. We explain these trends by introducing a universal relation between fgas, Mstar and SFR, non-evolving out to z~2.5. Galaxies move across this relation as their gas content evolves in time. We use the 3D fundamental fgas-Mstar-SFR relation and the redshift evolution of the Main Sequence to estimate the evolution of fgas in the average population of galaxies as a function of z and Mstar, and we find evidence a downsizing scenario.

• The paper demonstrates a strong correlation between dust content and star formation rate across redshifts, driven by the Schmidt-Kennicutt law.
• The paper challenges previous dust-stellar mass correlations by showing most disappear when controlling for the star formation rate.
• The paper introduces an innovative proxy for gas content via dust mass, revealing a non-evolving 3D relation among gas fraction, stellar mass, and SFR.

Insights into the Evolution of Dust and Gas Content in Galaxies

The paper of the dust and gas content in galaxies presents a profound understanding of galaxy evolutionary processes. By harnessing the capabilities of the Herschel Space Observatory's PACS and SPIRE imaging cameras, this paper investigates the intricate relations between dust mass, stellar mass, and star formation rate (SFR) in galaxies from the local universe outwards to a redshift of $z \sim 2.5$. The authors use datasets from the GOODS-S, GOODS-N, and COSMOS fields and augment direct observations with stacking techniques to enable analysis over a broad range of galactic properties.

Dust and Star Formation Rate Correlation

A key finding in this research is the tight correlation between dust content and star formation activity at various stellar masses and across different redshift ranges. The authors attribute this correlation primarily to the Schmidt-Kennicutt (S-K) law, which posits that a power-law relationship exists between the gas mass surface density and the star formation rate surface density. The paper emphasizes that dust is closely linked with the SFR independent of time, highlighting the integral role of dust as an indirect measure of star formation dynamics.

Weak Correlation with Stellar Mass

The paper challenges previous assumptions about the relation between dust and stellar mass by showing that most of the dust-stellar mass correlation observed in previous studies disappears when controlling for SFR. This suggests that prior observed correlations may be secondary effects resulting from the SFR's influence over both physical quantities.

Quantifying Gas Content Through Dust Measurements

The research leverages the dust mass as a proxy for estimating the total gas content, considering that the dust-to-gas ratio scales with metallicity. This alternative method provides an innovative way to paper gas content independent of traditional CO observations. Analyzing this relationship underscores the significant implications for molecular cloud formation and evolution over cosmic time.

Implications of Gas Content and Star Formation Efficiency

Through analysis, the paper demonstrates a redshift-dependent increase in star formation efficiency (SFE), indicating a decrease in gas depletion times from $z \sim 0$ to $z \sim 2.5$. It suggests that the increased SFR observed at higher redshifts could predominantly be due to available gas reservoirs' evolution over cosmic times. Moreover, this could imply a systematic change in gas processing, possibly through inflows and outflows or changes in ISM conditions.

Establishing a Non-evolving Fundamental Relation

The authors present compelling evidence for a fundamental, non-evolving 3D relation among gas fraction, stellar mass, and SFR, persisting across the studied redshift range. This 'fundamental plane' suggests a consistent interplay between these parameters across time, challenging models to accurately reflect the subsequent evolutionary pathways.

Theoretical Implications and Future Prospects

This paper may reshape theoretical models by dictating that they incorporate non-linear gas depletion processes and reinforce the significance of dust in understanding galaxy evolution. Future investigations can expand these insights by integrating this fundamental relation with cosmological simulations and deeper extragalactic datasets, potentially utilizing upcoming observatories with heightened sensitivities.

In summary, the paper elucidates a nuanced view on the interdependence and evolution of cosmic dust and gas linked to star formation across a substantially broad redshift landscape, providing essential guidance for future galaxy evolutionary theories.