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Register a new userGALICS III: Predicted properties for Lyman Break Galaxies at redshift 3
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This paper illustrates how mock observational samples of high-redshift galaxies with sophisticated selection criteria can be extracted from the predictions of GALICS, a hybrid model of hierarchical galaxy formation that couples the outputs of large cosmological simulations and semi-analytic recipes to describe dark matter collapse and the physics of baryons respectively. As an example of this method, we focus on the properties of Lyman Break Galaxies at redshift 3. With the MOMAF software package described in a companion paper, we generate a mock observational sample with selection criteria as similar as possible to those implied in the actual observations of z = 3 LBGs by Steidel et al.(1995). Our model predictions are in good agreement with the observed number density and 2D correlation function. We investigate the optical/IR luminosity budget as well as several other physical properties of LBGs and find them to be in general agreement with observed values. Looking into the future of these LBGs we predict that 75% of them end up as massive ellipticals today, even though only 35% of all our local ellipticals are predicted to have a LBG progenitor. In spite of some shortcomings, this new mock observation method clearly represents a necessary first step toward a more accurate comparison between hierarchical models of galaxy formation and real observational surveys.
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We present a catalogue of 2135 galaxy redshifts from the VLT LBG Redshift Survey (VLRS), a spectroscopic survey of z ~ 3 galaxies in wide fields centred on background quasi-stellar objects. We have used deep optical imaging to select galaxies via the Lyman-break technique. Spectroscopy of the Lyman-break galaxies (LBGs) was then made using the Visible Multi-Object Spectrograph (VIMOS), giving a mean redshift of z=2.79. We analyse the clustering properties of the VLRS sample and also of the VLRS sample combined with the smaller area Keck-based survey of Steidel et al. From the semiprojected correlation function, wp({sigma}) we find that the results are well fit with a single power-law model, with clustering scale lengths of r0=3.46+-0.41 and 3.83+-0.24 Mpc/h, respectively. We note that the corresponding combined {xi}(r) slope is flatter than for local galaxies at {gamma} = 1.5-1.6 rather than {gamma}=1.8. This flat slope is confirmed by the z-space correlation function, {xi}(s), and in the range 10<s<100 Mpc/h the VLRS shows ~2.5{sigma} excess over the {Lambda} cold dark matter. This excess may be consistent with recent evidence for non-Gaussianity in clustering results at z~1. We then analyse the LBG z-space distortions using the 2D correlation function, {xi}({sigma}, {pi}), finding for the combined sample a large-scale infall parameter of $beta$ = 0.38+-0.19 and a velocity dispersion of 420km/s. Based on our measured {beta}, we are able to determine the gravitational growth rate, finding a value of f(z = 3)=0.99+-0.50 (or f{sigma}8 = 0.26+-0.13), which is the highest redshift measurement of the growth rate via galaxy clustering and is consistent with {Lambda}CDM. Finally, we constrain the mean halo mass for the LBG population, finding that the VLRS and combined sample suggest mean halo masses of log(MDM/Msun) = 11.57+-0.15 and 11.73+-0.07, respectively.
We present the basic data for a large ground-based spectroscopic survey for z~3 ``Lyman break galaxies (LBGs), photometrically selected using rest-UV colors from very deep images in 17 high Galactic latitude fields. The total survey covers an area of 0.38 square degrees, and includes 2347 photometrically-selected candidate LBGs to an apparent R_{AB} magnitude limit of 25.5. Approximately half of these objects have been observed spectroscopically using the Keck telescopes, yielding 940 redshifts with <z> =2.96 +/- 0.29. We discuss the images, photometry, target selection, and the spectroscopic program in some detail, and present catalogs of the photometric and spectroscopic data, made available in electronic form. We discuss the general utility of conducting nearly-volume-limited redshift surveys in prescribed redshift intervals using judicious application of photometric pre-selection.
We report on the status of large surveys of photometrically selected star forming galaxies at z~3 and z~4, with particular emphasis on both the advantages and the limitations of selecting objects using the ``Lyman break technique. Current results on the luminosity functions, luminosity densities, color distribution, star formation rates, clustering properties, and the differential evolution of the population as a function of redshift are summarized.
We explore from a statistical point of view the far-infrared (far-IR) and sub-millimeter (sub-mm) properties of a large sample of LBGs (22,000) at z~3 in the COSMOS field. The large number of galaxies allows us to split it in several bins as a function of UV luminosity, UV slope, and stellar mass to better sample their variety. We perform stacking analysis in PACS (100 and 160 um), SPIRE (250, 350 and 500 um) and AzTEC (1.1 mm) images. Our stacking procedure corrects the biases induced by galaxy clustering and incompleteness of our input catalogue in dense regions. We obtain the full IR spectral energy distributions (SED) of subsamples of LBGs and derive the mean IR luminosity as a function of UV luminosity, UV slope, and stellar mass. The average IRX is roughly constant over the UV luminosity range, with a mean of 7.9 (1.8 mag). However, it is correlated with UV slope, and stellar mass. We investigate using a statistically-controlled stacking analysis as a function of (stellar mass, UV slope) the dispersion of the IRX-UVslope and IRX-M* plane. Our results enable us to study the average relation between star-formation rate (SFR) and stellar mass, and we show that our LBG sample lies on the main sequence of star formation at z~3.
We study the luminosity function and the correlation function of about 1200 z~4 Lyman break galaxies (LBGs) with i<26 that are photometrically selected from deep BRi imaging data of a 618 arcmin^2 area in the Subaru/XMM-Newton Deep Field taken with Subaru Prime Focus Camera. The contamination and completeness of our LBG sample are evaluated, on the basis of the Hubble Deep Field-North (HDF-N) objects, to be 17% and 45%, respectively. We derive the UV (rest 1700A) luminosity functions (LFs) and find a large population of UV-luminous galaxies at z~4. The LFs of the red and blue subsamples imply that the bright LBGs are redder in the UV continuum than the average color of the LBGs. Then we calculate the correlation function over theta = 2-1000 and find that it is fitted fairly well by a power law, omega(theta)=A_omega theta^(-0.8), with A_omega=0.71 +/- 0.26. We estimate the correlation length r_0 (in comoving units) of the two-point spatial correlation function xi(r) = (r/r_0)^(-1.8) to be r_0=2.7 +0.5/-0.6 h^(-1) Mpc (Omega_m=0.3 and Omega_Lambda=0.7). The correlation function shows an excess of omega (theta) on small scales (theta < 5), departing from the power-law fit at > 3 sigma significance level. Interpreting this as being due to galaxy mergers, we evaluate the fraction of galaxies undergoing mergers to be 3.0 +/- 0.9%, which is significantly smaller than those of galaxies at intermediate redshifts.
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