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Register a new userQuantifying the effect of field variance on the H$alpha$ luminosity function with the New Numerical Galaxy Catalogue ($ u^2$GC)
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We construct a model of H$alpha$ emitters (HAEs) based on a semi-analytic galaxy formation model, the New Numerical Galaxy Catalog ($ u^2$GC). In this paper, we report our estimate for the field variance of the HAE distribution. By calculating the H$alpha$ luminosity from the star-formation rate of galaxies, our model well reproduces the observed H$alpha$ luminosity function (LF) at $z=0.4$. The large volume of the $ u^2$GC makes it possible to examine the spatial distribution of HAEs over a region of (411.8 Mpc)$^3$ in the comoving scale. The surface number density of $z=0.4$ HAEs with $L_{rm Halpha} geq 10^{40}$ erg s$^{-1}$ is 308.9 deg$^{-2}$. We have confirmed that the HAE is a useful tracer for the large-scale structure of the Universe because of their significant overdensity ($>$ 5$sigma$) at clusters and the filamentary structures. The H$alpha$ LFs within a survey area of $sim$2 deg$^2$ (typical for previous observational studies) show a significant field variance up to $sim$1 dex. Based on our model, one can estimate the variance on the H$alpha$ LFs within given survey areas.
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We present the latest results of a semi-analytic model of galaxy formation, New Numerical Galaxy Catalogue, which is combined with large cosmological N-body simulations. This model can reproduce statistical properties of galaxies at z < 6.0. We focus on the properties of active galactic nuclei (AGNs) and supermassive black holes, especially on the accretion timescale onto black holes. We find that the number density of AGNs at z < 1.5 and at hard X-ray luminosity 10^{ 44 }< erg/s is underestimated compared with recent observational estimates when we assume the exponentially decreasing accretion rate and the accretion timescale which is proportional to the dynamical time of the host halo or the bulge, as is often assumed in semi-analytic models. We show that to solve this discrepancy, the accretion timescale of such less luminous AGNs instead should be a function of the black hole mass and the accreted gas mass. This timescale can be obtained from a phenomenological modelling of the gas angular momentum loss in the circumnuclear torus and/or the accretion disc. Such models predict a longer accretion timescale for less luminous AGNs at z < 1.0 than bright QSOs whose accretion timescale would be 10^{ 7-8 } yr. With this newly introduced accretion timescale, our model can explain the observed luminosity functions of AGNs at z < 6.0.
We present a new cosmological galaxy formation model, $ u^2$GC, as an updated version of our previous model $ u$GC. We adopt the so-called semi-analytic approach, in which the formation history of dark matter halos is computed by ${it N}$-body simulations, while the baryon physics such as gas cooling, star formation and supernova feedback are simply modeled by phenomenological equations. Major updates of the model are as follows: (1) the merger trees of dark matter halos are constructed in state-of-the-art ${it N}$-body simulations, (2) we introduce the formation and evolution process of supermassive black holes and the suppression of gas cooling due to active galactic nucleus (AGN) activity, (3) we include heating of the intergalactic gas by the cosmic UV background, and (4) we tune some free parameters related to the astrophysical processes using a Markov chain Monte Carlo method. Our ${it N}$-body simulations of dark matter halos have unprecedented box size and mass resolution (the largest simulation contains 550 billion particles in a 1.12 Gpc/h box), enabling the study of much smaller and rarer objects. The model was tuned to fit the luminosity functions of local galaxies and mass function of neutral hydrogen. Local observations, such as the Tully-Fisher relation, size-magnitude relation of spiral galaxies and scaling relation between the bulge mass and black hole mass were well reproduced by the model. Moreover, the model also well reproduced the cosmic star formation history and the redshift evolution of rest-frame ${it K}$-band luminosity functions. The numerical catalog of the simulated galaxies and AGNs is publicly available on the web.
We present the evolution of dark matter halos in six large cosmological N-body simulations, called the $ u^2$GC (New Numerical Galaxy Catalog) simulations on the basis of the LCDM cosmology consistent with observational results obtained by the Planck satellite. The largest simulation consists of $8192^3$ (550 billion) dark matter particles in a box of $1.12 , h^{-1} rm Gpc$ (a mass resolution of $2.20 times 10^{8} , h^{-1} M_{odot}$). Among simulations utilizing boxes larger than $1 , h^{-1} rm Gpc$, our simulation yields the highest resolution simulation that has ever been achieved. A $ u^2$GC simulation with the smallest box consists of eight billions particles in a box of $70 , h^{-1} rm Mpc$ (a mass resolution of $3.44 times 10^{6} , h^{-1} M_{odot}$). These simulations can follow the evolution of halos over masses of eight orders of magnitude, from small dwarf galaxies to massive clusters. Using the unprecedentedly high resolution and powerful statistics of the $ u^2$GC simulations, we provide statistical results of the halo mass function, mass accretion rate, formation redshift, and merger statistics, and present accurate fitting functions for the Planck cosmology. By combining the $ u^2$GC simulations with our new semi-analytic galaxy formation model, we are able to prepare mock catalogs of galaxies and active galactic nuclei, which will be made publicly available in the near future.
We take advantage of the capability of the OTELO survey to obtain the H$alpha$ luminosity function (LF) at ${rm z}sim0.40$. Because of the deepest coverage of OTELO, we are able to determine the faint end of the LF, and thus better constrain the star formation rate and the number of galaxies at low luminosities. The AGN contribution to this LF is estimated as well. We make use of the multi-wavelength catalogue of objects in the field compiled by the OTELO survey, which is unique in terms of minimum flux and equivalent width. We also take advantage of the pseudo-spectra built for each source, which allow the identification of emission lines and the discrimination of different types of objects. The H$alpha$ luminosity function at $zsim0.40$ is obtained, which extends the current faint end by almost 1 dex, reaching minimal luminosities of $log_{10}L_{rm lim}=38.5$ erg s$^{-1}$ (or $sim0.002, text{M}_odottext{ yr}^{-1})$. The AGN contribution to the total H$alpha$ luminosity is estimated. We find that no AGN should be expected below a luminosity of $log_{10}L=38.6$ erg s$^{-1}$. From the sample of non-AGN (presumably, pure SFG) at $zsim0.40$ we estimated a star formation rate density of $rho_{rm SFR}=0.012pm0.005 {rm text{M}_{odot} yr^{-1} Mpc^{-3}}$.
We have re-examined the nature of the cluster galaxy luminosity function using the data from the Edinburgh-Durham Southern Galaxy Catalogue and the Edinburgh-Milano Redshift Survey. We derive a best fit luminosity function over the range M(bj)=-18 to -21, for a composite sample of 22 of the richer clusters that has M*=-20.16+/-0.02 and alpha=-1.22+/-0.04. The dominant error in these values results from the choice of background subtraction method. From extensive simulations we can show that when the LF is fitted over this narrow range, it is difficult to discriminate against bright values of M*in the single cluster fits, but that faint values provide a strong test of the universality of the luminosity function. We find that all the individual cluster data are well fit by a Schechter function with alpha fixed at -1.25, and that <=10% of these have fitted values of M* that disagree from the average at the 99% confidence level. We further show that fitting only a single parameter Schechter function to composite subsets of the data can give erroneous results for the derived M*. By considering two parameter fits, the results of Monte-Carlo simulations and direct two-sample chi-squared tests we conclude that there is only weak evidence for differences between the data when broken down into subsets based on physical properties (Bautz-Morgan class, richness, velocity dispersion): from our simulations, only the evidence for a difference between subsets based on velocity dispersion may in fact be significant. We find no evidence at all that a Schechter function is not a good model for the intrinsic cluster luminosity function over this absolute magnitude range. Models that invoke strong evolution of galaxy luminosity of all galaxies within clusters are inconsistent with our results.
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