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Register a new userA multi-wavelength model of galaxy formation
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C.G. Lacey
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We present new results from a multi-wavelength model of galaxy formation, which combines a semi-analytical treatment of the formation of galaxies within the CDM framework with a sophisticated treatment of absorption and emission of radiation by dust. We find that the model, which incorporates a top-heavy IMF in bursts, agrees well with the evolution of the rest-frame far-UV luminosity function over the range z=0-6, with the IR number counts in all bands measured by SPITZER, and with the observed evolution of the mid-IR luminosity function for z=0-2.
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We present a new version of the GALFORM semi-analytical model of galaxy formation. This brings together several previous developments of GALFORM into a single unified model, including a different initial mass function (IMF) in quiescent star formation and in starbursts, feedback from active galactic nuclei supressing gas cooling in massive halos, and a new empirical star formation law in galaxy disks based on their molecular gas content. In addition, we have updated the cosmology, introduced a more accurate treatment of dynamical friction acting on satellite galaxies, and updated the stellar population model. The new model is able to simultaneously explain both the observed evolution of the K-band luminosity function and stellar mass function, and the number counts and redshift distribution of sub-mm galaxies selected at 850 mu. This was not previously achieved by a single physical model within the LambdaCDM framework, but requires having an IMF in starbursts that is somewhat top-heavy. The new model is tested against a wide variety of observational data covering wavelengths from the far-UV to sub-mm, and redshifts from z=0 to z=6, and is found to be generally successful. These observations include the optical and near-IR luminosity functions, HI mass function, fraction of early type galaxies, Tully-Fisher, metallicity-luminosity and size-luminosity relations at z=0, as well as far-IR number counts, and far-UV luminosity functions at z ~ 3-6. [abridged]
(Abridged) This paper predicts self-consistent faint galaxy counts from the UV to the submm wavelength range. The STARDUST spectral energy distributions described in Devriendt et al. (1999) are embedded within the explicit cosmological framework of a simple semi-analytic model of galaxy formation and evolution. We build a class of models which capture the luminosity budget of the universe through faint galaxy counts and redshift distributions in the whole wavelength range spanned by our spectra. In contrast with a rather stable behaviour in the optical and even in the far-IR, the submm counts are dramatically sensitive to variations in the cosmological parameters and changes in the star formation history. Faint submm counts are more easily accommodated within an open universe with a low value of $Omega_0$, or a flat universe with a non-zero cosmological constant. This study illustrates the implementation of multi-wavelength spectra into a semi-analytic model. In spite of its simplicity, it already provides fair fits of the current data of faint counts, and a physically motivated way of interpolating and extrapolating these data to other wavelengths and fainter flux levels.
A semi-analytic model is proposed that couples the Press-Schechter formalism for the number of galaxies with a prescription for galaxy-galaxy interactions that enables to follow the evolution of galaxy morphologies along the Hubble sequence. Within this framework, we calculate the chemo-spectrophotometric evolution of galaxies to obtain spectral energy distributions. We find that such an approach is very successful in reproducing the statistical properties of galaxies as well as their time evolution. We are able to make predictions as a function of galaxy type: for clarity, we restrict ourselves to two categories of galaxies: early and late types that are identified with ellipticals and disks. In our model, irregulars are simply an early stage of galaxy formation. In particular, we obtain good matches for the galaxy counts and redshift distributions of sources from UV to submm wavelengths. We also reproduce the observed cosmic star formation history and the diffuse background radiation, and make predictions as to the epoch and wavelength at which the dust-shrouded star formation of spheroids begins to dominate over the star formation that occurs more quiescently in disks. A new prediction of our model is a rise in the FIR luminosity density with increasing redshift, peaking at about $zsim 3$, and with a ratio to the local luminosity density $rho_{L, u} (z = z_{peak})/ rho_{L, u} (z = 0)$ about 10 times higher than that in the blue (B-band) which peaks near $zsim 2$.
We present a multi-epoch analysis of the galaxy populations formed within the cosmological hydrodynamical simulations presented in Vogelsberger et al. (2013). These simulations explore the performance of a recently implemented feedback model which includes primordial and metal line radiative cooling with self-shielding corrections; stellar evolution with associated mass loss and chemical enrichment; feedback by stellar winds; black hole seeding, growth and merging; and AGN quasar- and radio-mode heating with a phenomenological prescription for AGN electro-magnetic feedback. We illustrate the impact of the model parameter choices on the resulting simulated galaxy population properties at high and intermediate redshifts. We demonstrate that our scheme is capable of producing galaxy populations that broadly reproduce the observed galaxy stellar mass function extending from redshift z=0 to z=3. We also characterise the evolving galactic B-band luminosity function, stellar mass to halo mass ratio, star formation main sequence, Tully-Fisher relation, and gas-phase mass-metallicity relation and confront them against recent observational estimates. This detailed comparison allows us to validate elements of our feedback model, while also identifying areas of tension that will be addressed in future work.
We present a multi-wavelength, UV-to-radio analysis for a sample of massive (M$_{ast}$ $sim$ 10$^{10}$ M$_odot$) IRAC- and MIPS 24$mu$m-detected Lyman Break Galaxies (LBGs) with spectroscopic redshifts z$sim$3 in the GOODS-North field (L$_{rm UV}$$>1.8times$L$^{ast}_{z=3}$). For LBGs without individual 24$mu$m detections, we employ stacking techniques at 24$mu$m, 1.1mm and 1.4GHz, to construct the average UV-to-radio spectral energy distribution and find it to be consistent with that of a Luminous Infrared Galaxy (LIRG) with L$rm_{IR}$=4.5$^{+1.1}_{-2.3}$$times 10^{11}$ L$_{odot}$ and a specific star formation rate (SSFR) of 4.3 Gyr$^{-1}$ that corresponds to a mass doubling time $sim$230 Myrs. On the other hand, when considering the 24$mu$m-detected LBGs we find among them galaxies with L$rm_{IR}> 10^{12}$ L$_{odot}$, indicating that the space density of $zsim$3 UV-selected Ultra-luminous Infrared Galaxies (ULIRGs) is $sim$(1.5$pm$0.5)$times 10^{-5}$ Mpc$^{-3}$. We compare measurements of star formation rates (SFRs) from data at different wavelengths and find that there is tight correlation (Kendalls $tau >$ 99.7%) and excellent agreement between the values derived from dust-corrected UV, mid-IR, mm and radio data for the whole range of L$rm_{IR}$ up to L$rm_{IR}$ $sim$ 10$^{13}$ L$_{odot}$. This range is greater than that for which the correlation is known to hold at z$sim$2, possibly due to the lack of significant contribution from PAHs to the 24$mu$m flux at $zsim$3. The fact that this agreement is observed for galaxies with L$rm_{IR}$ $>$ 10$^{12}$ L$_{odot}$ suggests that star-formation in UV-selected ULIRGs, as well as the bulk of star-formation activity at this redshift, is not embedded in optically thick regions as seen in local ULIRGs and submillimeter-selected galaxies at $z=2$.
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