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Register a new userGAMA/G10-COSMOS/3D-HST: The 0<z<5 cosmic star-formation history, stellar- and dust-mass densities
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We use the energy-balance code MAGPHYS to determine stellar and dust masses, and dust corrected star-formation rates for over 200,000 GAMA galaxies, 170,000 G10-COSMOS galaxies and 200,000 3D-HST galaxies. Our values agree well with previously reported measurements and constitute a representative and homogeneous dataset spanning a broad range in stellar mass (10^8---10^12 Msol), dust mass (10^6---10^9 Msol), and star-formation rates (0.01---100 Msol per yr), and over a broad redshift range (0.0 < z < 5.0). We combine these data to measure the cosmic star-formation history (CSFH), the stellar-mass density (SMD), and the dust-mass density (DMD) over a 12 Gyr timeline. The data mostly agree with previous estimates, where they exist, and provide a quasi-homogeneous dataset using consistent mass and star-formation estimators with consistent underlying assumptions over the full time range. As a consequence our formal errors are significantly reduced when compared to the historic literature. Integrating our cosmic star-formation history we precisely reproduce the stellar-mass density with an ISM replenishment factor of 0.50 +/- 0.07, consistent with our choice of Chabrier IMF plus some modest amount of stripped stellar mass. Exploring the cosmic dust density evolution, we find a gradual increase in dust density with lookback time. We build a simple phenomenological model from the CSFH to account for the dust mass evolution, and infer two key conclusions: (1) For every unit of stellar mass which is formed 0.0065---0.004 units of dust mass is also formed; (2) Over the history of the Universe approximately 90 to 95 per cent of all dust formed has been destroyed and/or ejected.
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Using a combined and consistently analysed GAMA, G10-COSMOS, and 3D-HST dataset we explore the evolution of the galaxy stellar-mass function over lookback times $t_{rm L} in left[0.2,12.5right] {rm h^{-1}_{70} Gyr}$. We use a series of volume limited samples to fit Schechter functions in bins of $sim!$constant lookback time and explore the evolution of the best-fit parameters in both single and two-component cases. In all cases, we employ a fitting procedure that is robust to the effects of Eddington bias and sample variance. Surprisingly, when fitting a two-component Schechter function, we find essentially no evidence of temporal evolution in $M_star$, the two $alpha$ slope parameters, or the normalisation of the low-mass component. Instead, our fits suggest that the various shape parameters have been exceptionally stable over cosmic time, as has the normalisation of the low-mass component, and that the evolution of the stellar-mass function is well described by a simple build up of the high-mass component over time. When fitting a single component Schechter function, there is an observed evolution in both $M_star$ and $alpha$, however this is interpreted as being an artefact. Finally, we find that the evolution of the stellar-mass function, and the observed stellar mass density, can be well described by a simple model of constant growth in the high-mass source density over the last $11 {rm h^{-1}_{70} Gyr}$.
We make use of the deep Karl G. Jansky Very Large Array (VLA) COSMOS radio observations at 3 GHz to infer radio luminosity functions of star-forming galaxies up to redshifts of z~5 based on approximately 6000 detections with reliable optical counterparts. This is currently the largest radio-selected sample available out to z~5 across an area of 2 square degrees with a sensitivity of rms=2.3 ujy/beam. By fixing the faint and bright end shape of the radio luminosity function to the local values, we find a strong redshift trend that can be fitted with a pure luminosity evolution L~(1+z)^{(3.16 +- 0.2)-(0.32 +- 0.07) z}. We estimate star formation rates (SFRs) from our radio luminosities using an infrared (IR)-radio correlation that is redshift dependent. By integrating the parametric fits of the evolved luminosity function we calculate the cosmic SFR density (SFRD) history since z~5. Our data suggest that the SFRD history peaks between 2<z<3 and that the ultraluminous infrared galaxies (ULIRGs; 100 Msol/yr<SFR<1000 Msol/yr) contribute up to ~25% to the total SFRD in the same redshift range. Hyperluminous infrared galaxies (HyLIRGs; SFR>1000 Msol/yr) contribute an additional <2% in the entire observed redshift range. We find evidence of a potential underestimation of SFRD based on ultraviolet (UV) rest-frame observations of Lyman break galaxies (LBGs) at high redshifts (z>4) on the order of 15-20%, owing to appreciable star formation in highly dust-obscured galaxies, which might remain undetected in such UV observations.
We matched the 1.4 GHz local luminosity functions of star-forming galaxies (SFGs) and active galactic nuclei to the 1.4 GHz differential source counts from $0.25 mumathrm{Jy}$ to 25 Jy using combinations of luminosity and density evolution. We present the most robust and complete local far-infrared (FIR)/radio luminosity correlation to date in a volume-limited sample of $approx 4.3 times 10^3$ nearby SFGs, finding that it is very tight but distinctly sub-linear: $L_mathrm{FIR} propto L_mathrm{1.4,GHz}^{0.85}$. If the local FIR/radio correlation does not evolve, the evolving 1.4 GHz luminosity function of SFGs yields the evolving star-formation rate density (SFRD) $psi (M_odot mathrm{year}^{-1} mathrm{Mpc}^{-3}$) as a function of time since the big bang. The SFRD measured at 1.4 GHz grows rapidly at early times, peaks at cosmic noon when $t approx 3 mathrm{Gyr}$ and $z approx 2$, and subsequently decays with an $e$-folding time scale $tau = 3.2 mathrm{Gyr}$. This evolution is similar to, but somewhat stronger than, SFRD evolution estimated from UV and FIR data.
There is a remarkably tight relation between the observationally inferred dust masses and star-formation rates (SFRs) of SDSS galaxies, Mdust $propto$ SFR$^{1.11}$ (Da Cunha et al. 2010). Here we extend the Mdust-SFR relation to the high end and show that it bends over at very large SFRs (i.e., dust masses are lower than predicted for a given SFR). We identify several distinct evolutionary processes in the diagram: (1) A star-bursting phase in which dust builds up rapidly at early times. The maximum attainable dust mass in this process is the cause of the bend-over of the relation. A high dust-formation efficiency, a bottom-light initial mass function, and negligible supernova shock dust destruction are required to produce sufficiently high dust masses. (2) A quiescent star-forming phase in which the subsequent parallel decline in dust mass and SFR gives rise to the Mdust-SFR relation, through astration and dust destruction. The dust-to-gas ratio is approximately constant along the relation. We show that the power-law slope of the Mdust-SFR relation is inversely proportional to the global Schmidt-Kennicutt law exponent (i.e., $sim 0.9$) in simple chemical evolution models. (3) A quenching phase which causes star formation to drop while the dust mass stays roughly constant or drops proportionally. Combined with merging, these processes, as well as the range in total baryonic mass, give rise to a complex population of the diagram which adds significant scatter to the original Mdust-SFR relation. (4) At very high redshifts, a population of galaxies located significantly below the local relation is predicted.
Building galaxy merger trees from a state-of-the-art cosmological hydrodynamics simulation, Horizon-AGN, we perform a statistical study of how mergers and smooth accretion drive galaxy morphologic properties above $z > 1$. More specifically, we investigate how stellar densities, effective radii and shape parameters derived from the inertia tensor depend on mergers of different mass ratios. We find strong evidence that smooth accretion tends to flatten small galaxies over cosmic time, leading to the formation of disks. On the other hand, mergers, and not only the major ones, exhibit a propensity to puff up and destroy stellar disks, confirming the origin of elliptical galaxies. We also find that elliptical galaxies are more susceptible to grow in size through mergers than disc galaxies with a size-mass evolution $r prop M^{1.2}$ instead of $r prop M^{-0.5} - M^{0.5}$ depending on the merger mass ratio. The gas content drive the size-mass evolution due to merger with a faster size growth for gas-poor galaxies $r prop M^2$ than for gas-rich galaxies $r prop M$.
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