Pure Luminosity Evolution Model Research Articles

Constraints on cosmic star formation history via a new modeling of the radio luminosity function of star-forming galaxies

Context. Radio wavelengths offer a unique possibility to trace the total star-formation rate (SFR) in galaxies, both obscured and unobscured. To probe the dust-unbiased star-formation history, an accurate measurement of the radio luminosity function (LF) for star-forming galaxies (SFGs) is crucial. Aims. We make use of an SFG sample (5900 sources) from the Very Large Array (VLA) COSMOS 3 GHz data to perform a new modeling of the radio LF. By integrating the analytical LF, we aim to calculate the history of the cosmic SFR density (SFRD) from z ∼ 5 onwards. Methods. For the first time, we use both models of the pure luminosity evolution (PLE) and joint luminosity+density evolution (LADE) to fit the LFs directly to the radio data using a full maximum-likelihood analysis, considering the sample completeness correction. We also incorporate updated observations of local radio LFs and radio source counts into the fitting process to obtain additional constraints. Results. We find that the PLE model cannot be used to describe the evolution of the radio LF at high redshift (z > 2). By construct, our LADE models can successfully fit a large amount of data on radio LFs and source counts of SFGs from recent observations. The Akaike information criterion (AIC) also demonstrates that the LADE model is superior to the PLE model. We therefore conclude that density evolution is genuinely indispensable in modeling the evolution of SFG radio LFs. Our SFRD curve shows a good fit to the SFRD points derived by previous radio estimates. In view of the fact that our radio LFs are not biased, as opposed those of previous studies performed by fitting the 1/Vmax LF points, our SFRD results should be an improvement on these previous estimates. Below z ∼ 1.5, our SFRD matches a published multiwavelength compilation, while our SFRD turns over at a slightly higher redshift (2 < z < 2.5) and falls more rapidly out to high redshift.

A deep radio view of the evolution of the cosmic star formation rate density from a stellar-mass-selected sample in VLA-COSMOS

ABSTRACT We present the 1.4 GHz radio luminosity functions (RLFs) of galaxies in the Cosmic Evolution Survey (COSMOS) field, measured above and below the 5σ detection threshold, using a Bayesian model-fitting technique. The radio flux densities from Very Large Array (VLA)-COSMOS 3-GHz data are extracted at the position of stellar-mass-selected galaxies. We fit a local RLF model, which is a combination of active galactic nuclei and star-forming galaxies (SFGs), in 10 redshift bins with a pure luminosity evolution model. Our RLF exceeds previous determinations at low radio luminosities at z < 1.6 with the same radio data, due to our ability to directly constrain the knee and faint-end slope of the RLF. Beyond z ∼ 2, we find that the SFG part of the RLF exhibits a negative evolution (L* moves to lower luminosities) due to the decrease in low stellar-mass galaxies in our sample at high redshifts. From the RLF for SFGs, we determine the evolution in the cosmic star formation rate density (SFRD), which we find to be consistent with the established behaviour up to z ∼ 1 using far-infrared data, but exceeds that from the previous radio-based work for the reasons highlighted above. Beyond z ∼ 1.5 the cosmic SFRD declines. We note that the relation between radio luminosity and star formation rate is crucial in measuring the cosmic SFRD from radio data at z > 1.5. We investigate the effects of stellar mass on the total RLF by splitting our sample into low (108.5 ≤ M/M⊙ ≤ 1010) and high ($M\gt 10^{10}\, \mathrm{M}_{\odot }$) stellar-mass subsets. We find that the SFRD is dominated by sources in the high stellar masses bin, at all redshifts.

Cosmic Evolution of Nearby Radio Active Galactic Nuclei

The exact formation mechanism of massive galaxy in the universe still become an open question in modern astrophysics. Radio emission from active galactic nucleus (AGN) is known to be suppressing stellar growth in the most massive galaxies, thus becoming significant ingredient in modeling galaxy formation process. Radio luminosity function across cosmic redshifts (z) is an important tool to constrain the co-evolutionary models of radio AGN and its host galaxy. Therefore, we aim to calculate radio luminosity function at 1.4 GHz frequency for radio AGN in the range of 0.1 ≤ z ≤ 1.3 in this work. The radio data was taken from deep VLA observation of Stripe 82 field at angular resolution of 1.8” and 52 μJy sensitivity. On the other hand, the optical/near-infrared data was taken from Dark Energy Survey DR1 observation in g, r, i, z, Y bands with co-added catalog limiting magnitude of i = 23.44.We estimated the photometric redshift (photo-z) of each sources by using combined two machine learning algorithms: neural networks and boosted regression trees. We successfully performed accurate photo-z measurement with average bias 〈δ〉 = −3.5 × 10−3, scatter 〈σ〉 = 0.15 and outlier fraction 〈f(3σ)〉 = 0.06. By using 1/Vmax method, we calculated the luminosity function, then constrained their evolution with pure density evolution (PDE) or pure luminosity evolution (PLE) model. At median z = {0.31, 0.59, 0.88, 1.10}, we found the power-law index of PDE is αD = {1.29, 1.43, 1.73, 0.94} while for PLE is αL = {2.28, 2.59, 3.19, 1.63}. Our result is consistent with previous studies and gives better constraint to radio AGN luminosity and density evolution power-law indexes due to larger number of sources (6900) and wider covered sky fraction (92 deg2).

The VLA-COSMOS 3 GHz Large Project: Star formation properties and radio luminosity functions of AGN with moderate-to-high radiative luminosities out to z∼ 6

We have studied a sample of 1604 moderate-to-high radiative luminosity active galactic nuclei (HLAGN) selected at 3 GHz within the VLA-COSMOS 3 GHz Large Project. These were classified by combining multiple AGN diagnostics: X-ray data, mid-infrared data and broadband spectral energy distribution fitting. We decomposed the total radio 1.4 GHz luminosity (L1.4 GHz, TOT) into the emission originating from star formation and AGN activity by measuring the excess in L1.4 GHz, TOT relative to the infrared-radio correlation of star-forming galaxies. To quantify the excess, for each source we calculated the AGN fraction (fAGN) defined as the fractional contribution of AGN activity to L1.4 GHz, TOT. The majority of the HLAGN, (68.0 ± 1.5)%, are dominated by star-forming processes (fAGN ≤ 0.5), while (32.0 ± 1.5)% are dominated by AGN-related radio emission (0.5 < fAGN ≤ 1). We used the AGN-related 1.4 GHz emission to derive the 1.4 GHz AGN luminosity functions of HLAGN. By assuming pure density and pure luminosity evolution models we constrained their cosmic evolution out to z ∼ 6, finding Φ*(z)∝(1 + z)(2.64 ± 0.10)+(−0.61 ± 0.04)z and L*(z)∝(1 + z)(3.97 ± 0.15)+(−0.92 ± 0.06)z. These evolutionary laws show that the number and luminosity density of HLAGN increased from higher redshifts (z ∼ 6) up to a maximum in the redshift range 1 < z < 2.5, followed by a decline toward local values. By scaling the 1.4 GHz AGN luminosity to kinetic luminosity using the standard conversion, we estimate the kinetic luminosity density as a function of redshift. We compare our result to the semi-analytic models of radio mode feedback, and find that this feedback could have played an important role in the context of AGN-host co-evolution in HLAGN which shows evidence of AGN-related radio emission (fAGN > 0).

Constraints on submicrojansky radio number counts based on evolving VLA-COSMOS luminosity functions

We present an investigation of radio luminosity functions (LFs) and number counts based on the Karl G. Jansky Very Large Array-COSMOS 3 GHz Large Project. The radio-selected sample of 7826 galaxies with robust optical/near-infrared counterparts with excellent photometric coverage allows us to construct the total radio LF since z ~ 5.7. Using the Markov chain Monte Carlo algorithm, we fit the redshift dependent pure luminosity evolution model to the data and compare it with previously published VLA-COSMOS LFs obtained on individual populations of radio-selected star-forming galaxies and galaxies hosting active galactic nuclei classified on the basis of presence or absence of a radio excess with respect to the star-formation rates derived from the infrared emission. We find they are in excellent agreement, thus showing the reliability of the radio excess method in selecting these two galaxy populations at radio wavelengths. We study radio number counts down to submicrojansky levels drawn from different models of evolving LFs. We show that our evolving LFs are able to reproduce the observed radio sky brightness, even though we rely on extrapolations toward the faint end. Our results also imply that no new radio-emitting galaxy population is present below 1 μJy. Our work suggests that selecting galaxies with radio flux densities between 0.1 and 10 μJy will yield a star-forming galaxy in 90–95% of the cases with a high percentage of these galaxies existing around a redshift of z ~ 2, thus providing useful constraints for planned surveys with the Square Kilometer Array and its precursors.

THE SDSS-III BARYON OSCILLATION SPECTROSCOPIC SURVEY: THE QUASAR LUMINOSITY FUNCTION FROM DATA RELEASE NINE

We present a new measurement of the optical Quasar Luminosity Function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine (DR9), we select a uniform sample of 22,301 i<=21.8 quasars over an area of 2236 sq. deg with confirmed spectroscopic redshifts between 2.2<z<3.5, filling in a key part of the luminosity-redshift plane for optical quasar studies. We derive the completeness of the survey through simulated quasar photometry, and check this completeness estimate using a sample of quasars selected by their photometric variability within the BOSS footprint. We investigate the level of systematics associated with our quasar sample using the simulations, in the process generating color-redshift relations and a new quasar k-correction. We probe the faint end of the QLF to M_i(z=2.2) = -24.5 and see a clear break in the QLF at all redshifts up to z=3.5. We find that a log-linear relation (in log[Phi*] - M*) for a luminosity and density evolution (LEDE) model adequately describes our data within the range 2.2<z<3.5; across this interval the break luminosity increases by a factor of ~2.3 while Phi* declines by a factor of ~6. At z<2.2 our data is reasonably well fit by a pure luminosity evolution (PLE) model. We see only a weak signature of "AGN downsizing", in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities.

Luminosity function from dedicated SDSS-III and MMT data of quasars in 0.7 &lt;z&lt; 4.0 selected with a new approach

We present a measurement of the quasar luminosity function in the range 0.68<z<4 down to extinction corrected magnitude g_dered=22.5, using a simple and well understood target selection technique based on the time-variability of quasars. The completeness of our sample was derived directly from a control sample of quasars, without requiring complex simulations of quasar light-curves or colors. A total of 1877 quasar spectra were obtained from dedicated programs on the Sloan telescope (as part of the SDSS-III/BOSS survey) and on the Multiple Mirror Telescope. They allowed us to derive the quasar luminosity function. It agrees well with previously published results in the redshift range 0.68<z<2.6. Our deeper data allow us to extend the measurement to z=4. We measured quasar densities to g_dered<22.5, obtaining 30 QSO per deg^2 at z<1, 99 QSO per deg^2 for 1<z<2.15, and 47 QSO per deg^2 at z>2.15. Using pure luminosity evolution models, we fitted our LF measurements, and predicted quasar number counts as a function of redshift and observed magnitude. These predictions are useful inputs for future cosmology surveys such as those relying on the observation of quasars to measure baryon acoustic oscillations.

Extending pure luminosity evolution models into the mid-infrared, far-infrared and submillimetre

Simple pure luminosity evolution (PLE) models, in which galaxies brighten at high redshift due to increased star-formation rates (SFRs), are known to provide a good fit to the colours and number counts of galaxies throughout the optical and near-infrared. We show that optically defined PLE models, where dust reradiates absorbed optical light into infrared spectra composed of local galaxy templates, fit galaxy counts and colours out to 8um and to at least z=2.5. At 24-70um, the model is able to reproduce the observed source counts with reasonable success if 16% of spiral galaxies show an excess in mid-IR flux due to a warmer dust component and a higher SFR, in line with observations of local starburst galaxies. There remains an under-prediction of the number of faint-flux, high-z sources at 24um, so we explore how the evolution may be altered to correct this. At 160um and longer wavelengths, the model fails, with our model of normal galaxies accounting for only a few percent of sources in these bands. However, we show that a PLE model of obscured AGN, which we have previously shown to give a good fit to observations at 850um, also provides a reasonable fit to the Herschel/BLAST number counts and redshift distributions at 250-500um. In the context of a LCDM cosmology, an AGN contribution at 250-870um would remove the need to invoke a top-heavy IMF for high-redshift starburst galaxies, although the excellent fit of the galaxy PLE model at shorter wavelengths would still need to be explained.

On the buildup of massive early-type galaxies atz$\la$ 1

<i>Context. <i/>Several studies have tried to ascertain whether the increase in abundance of the early-type galaxies (E-S0a's) with time is mainly due to major mergers, but have reached opposite conclusions.<i>Aims. <i/>We have tested it directly through semi-analytical modelling, quantifying the possible contribution of the observed major mergers to the evolution of the high-mass end of the galaxy luminosity function (LF).<i>Methods. <i/>The model analyses the backwards-in-time evolution of the massive early-type galaxies with log (/) <i>><i/> 11 at <i>z<i/> ~ 0 (mETGs) under the hypothesis that each major merger leads to an early-type galaxy. The model considers only the major mergers strictly reported by observations at each redshift and assumes that gas-rich major mergers experience transitory phases as dust-reddened, star-forming galaxies (DSFs).<i>Results. <i/>The model is able to reproduce the observed evolution of the galaxy LFs at <i>z<i/> 1 simultaneously for different rest-frame bands (<i>B<i/>, <i>I<i/>, and <i>K<i/>) and for different selection criteria on colour and morphology. It also provides a framework in which apparently contradictory results on the recent evolution of the LF of massive red galaxies can be reconciled, just considering that observed samples of red galaxies can be significantly contaminated by DSFs. The model proves that it is feasible to build up ~50–60% of the present-day number density of mETGs at <i>z<i/> 1 through the coordinated action of wet, mixed, and dry major mergers, fulfilling global trends that are in general agreement with mass downsizing. The bulk of this assembly takes place during ~1 Gyr elapsed at 0.8 <i><<i/> <i>z<i/> <i><<i/> 1, providing a straightforward explanation for the observed fact that redshift <i>z<i/> ~ 0.8 is a transition epoch in the formation of mETGs. The gas-rich progenitors of these recently assembled mETGs reproduce the observed excess by a factor of ~4–5 of late-type galaxies at 0.8 <i><<i/> <i>z<i/> <i><<i/> 1 naturally, as compared to pure luminosity evolution (PLE) models.<i>Conclusions. <i/>The model suggests that major mergers have been the main driver for the observed mass migration from the massive end of the blue galaxy cloud to that of the red sequence in the past ~8 Gyr.

Evidence for luminosity evolution of long gamma-ray bursts inSwiftdata

We compute the luminosity function (LF) and the formation rate of long gamma ray bursts (GRBs) by fitting the observed differential peak flux distribution obtained by the BATSE experiment in two different scenarios: i) the GRB luminosity evolves with redshift and ii) GRBs form preferentially in low-metallicity environments. In both cases, model predictions are consistent with the Swift number counts and with the number of detections at z>2.5 and z>3.5. To discriminate between the two evolutionary scenarios, we compare the model results with the number of luminous bursts (i.e. with isotropic peak luminosity in excess of 10^53 erg s^-1) detected by Swift in its first three years of mission. Our sample conservatively contains only bursts with good redshift determination and measured peak energy. We find that pure luminosity evolution models can account for the number of sure identifications. In the case of a pure density evolution scenario, models with Z_th>0.3 Zsun are ruled out with high confidence. For lower metallicity thresholds, the model results are still statistically consistent with available lower limits. However, many factors can increase the discrepancy between model results and data, indicating that some luminosity evolution in the GRB LF may be needed also for such low values of Z_th. Finally, using these new constraints, we derive robust upper limits on the bright-end of the GRB LF, showing that this cannot be steeper than ~2.6.

Gamma-ray luminosity function of blazars and the cosmic gamma-ray background: evidence for the luminosity-dependent density evolution

We present a comprehensive study of the gamma-ray luminosity function (GLF) of blazars and their contribution to the extragalactic diffuse gamma-ray background (EGRB). Radio and gamma-ray luminosity correlation is introduced with a modest dispersion, consistent with observations, to take into account the radio detectability, which is important for blazar identification. Previous studies considered only pure luminosity evolution (PLE) or pure density evolution, but here we introduce the luminosity-dependent density evolution (LDDE) model, which is favored on the basis of the evolution of the X-ray luminosity function (XLF) of AGNs. The model parameters are constrained by likelihood analyses of the observed redshift and gamma-ray flux distributions of the EGRET blazars. Interestingly, we find that the LDDE model gives a better fit to the observed distributions than the PLE model, indicating that the LDDE model is also appropriate for gamma-ray blazars and that the jet activity is universally correlated with the accretion history of AGNs. We then find that only 25–50% of the EGRB can be explained by unresolved blazars with the best-fit LDDE parameters. Unresolved blazars can account for all the EGRB only with a steeper index of the faint-end slope of the GLF, which is marginally consistent with the EGRET data but inconsistent with XLF data. Therefore, unresolved AGNs cannot be the dominant source of the EGRB, unless there is a new population of gamma-ray emitting AGNs that evolves differently from the XLF of AGNs. Predictions for the GLAST mission are made, and we find that the best-fit LDDE model predicts about 3000 blazars in the entire sky, which is considerably fewer (by a factor of more than 3) than a previous estimate.

SWAN: galaxy morphology and evolution from adaptive optics-assisted imaging

Morphology is among the most appropriate ways to characterize the properties of galaxies. Indeed, we will reach a complete understanding of galaxies only by deriving the mechanisms responsible for their structures. However, disentangling these processes in nearby systems is already extremely difficult, and the challenge is even greater at higher redshift, where sources are compact (∼ 0.1− 0.3”) and larger galaxies are rare. In this context, the study of galaxy size, and of the evolution of other galaxy properties according to morphological type (disk or spheroid galaxy), have made use mainly of the classification derived from deep optical Hubble Space Telescope (HST) imaging. This is because of the higher angular resolution achievable at optical wavelengths with space-based observations using HST. However, near-infrared (NIR) surveys provide one of the best opportunities to investigate the cosmic evolution of galaxies and their mass assembly. In particular, at these wavelengths we gain direct sensitivity to the galaxy stellar mass rather than to ongoing or recent star formation, and we see smaller dust extinction effects. The use of adaptive optics (AO) systems allows groundbased telescopes to operate at or near the diffraction limit in the NIR (∼0.07” in the K band for an 8m telescope, a resolution comparable with optical HST observations), correcting for the blurring introduced by the atmosphere. The advantages of NIR AO observations for studying how galaxies form and evolve in the early universe are clear. However, until now there have been only a few attempts using natural guide star sensing.1–3 This is because of the very small number of known extragalactic sources lying at distances ∆θ ≤ 30” from the bright (V ≤ 13) stars needed to correct the wavefront for AO guiding, and also because of problems arising from the space variance of the shape of the point spread function (PSF) in Figure 1. The upper panel shows a comparison of the effective radius (Re) distribution as a function of magnitude for late-type (left) and early-type (right) galaxies with the pure luminosity evolution model (solid line) and hierarchical model (dashed line) predictions. The error bars are the standard error on the mean; no error bar is drawn for a bin with one galaxy. The lower panel shows a comparison of the SWAN (Survey of a Wide Area with NACO) completeness corrected counts for late-type (left) and early-type (right) galaxies with the predictions of the two galaxy evolution models.

Galaxy morphology and evolution from SWAN adaptive optics imaging

We present the results from adaptive optics (AO) assisted imaging in the Ks band of an area of 15 arcmin^2 for SWAN (Survey of a Wide Area with NACO). We derive the high resolution near-IR morphology of ~400 galaxies up to Ks~23.5 in the first 21 SWAN fields around bright guide stars, carefully taking into account the survey selection effects and using an accurate treatment of the anisoplanatic AO PSF. The detected galaxies are sorted into two morphological classes according to their Sersic index. The extracted morphological properties and number counts of the galaxies are compared with the predictions of different galaxy formation and evolution models, both for the whole galaxy population and separately for late-type and early-type galaxies. This is one of the first times such a comparison has been done in the near-IR, as AO observations and accurate PSF modeling are needed to obtain reliable morphological classification of faint field galaxies at these wavelengths. For early-type galaxies we find that a pure luminosity evolution model, without evidence for relevant number and size evolution, better reproduces the observed properties of our Ks-selected sample than current semi-analytic models based on the hierarchical picture of galaxy formation. In particular, we find that the observed flattening of elliptical galaxy counts at Ks~20 is quantitatively in good agreement with the prediction of the pure luminosity evolution model that was calculated prior to the observation. For late-type galaxies, while both models are able to reproduce the number counts, we find some hints of a possible size growth. These results demonstrate the unique power of AO observations to derive high resolution details of faint galaxies' morphology in the near-IR and drive studies of galaxy evolution.

Galaxy number counts - VI. An H-band survey of the Herschel Deep Field

We present H-band infrared (IR) galaxy data to a 3σ limit of H∼ 22.9 and optical–IR colours of galaxies on the William Herschel Deep Field (WHDF). These data were taken from a 7 × 7 arcmin2 area observed for 14 h with the Ω Prime camera on the 3.5-m Calar Alto telescope. We also present counts derived from the Hubble Deep Field-South (HDF-S) NICMOS camera to the limit of H∼ 29 mag over a 0.95 × 0.95 arcmin2 area. Following previous papers, we derive H-band number counts, colour–magnitude diagrams and colour histograms for the whole H-selected sample. We review our Pure Luminosity Evolution (PLE) galaxy count models based on the spectral synthesis models of Bruzual & Charlot. We find that our previously assumed forms for the luminosity function (LF) agree well with those recently derived from 2dF Galaxy Redshift Survey (2dFGRS)/Two-Micron All-Sky Survey (2MASS) at B and K, except that the 2dFGRS K LF has an unexpectedly flat slope which, if correct, could affect our interpretation of the faintest H and K counts. We find that these PLE models give an excellent fit to the WHDF H-band count data to H < 22.5 and HDF count data to H < 28. However, if we use the flat 2dFGRS/2MASS near-infrared (NIR) LF, then the predicted count is too flat at H > 21. We confirm that PLE models that assume a Salpeter initial mass function (IMF) for early-type galaxies overestimate the average galaxy redshift in K < 20 galaxy redshift surveys. Models that assume a steep x= 3 IMF continue to give better agreement with the N(z) data than even models based on a Scalo IMF, although they do show an unobserved peak in B−H and I−H colour distributions at faint H magnitudes corresponding to z > 1 early-type galaxies. But this feature may simply reflect a larger scatter in optical–IR colours than in the optical B−R colour of early-type galaxies at this redshift. This scatter is obvious in optical–IR colour–colour diagrams and may be explained by ongoing star formation in an intermediate subpopulation of early-type galaxies. The numbers of EROs detected are a factor of 2–3 lower than predicted by the early-type models that assume the Salpeter IMF and in better agreement with those that assume the x= 3 IMF. The tight sequence of early-type galaxies also shows a subclass which is simultaneously redder in IR bands and bluer in the bluer bands than the classical, passive early-type galaxy; this subclass appears at relatively low redshifts and may constitute an intermediate-age, early-type population. Finally, we have also detected a candidate z > 1 galaxy cluster using our panoramic H-band observations of the WHDF.

Gamma‐Ray Luminosity Function of Blazars and the Cosmic Gamma‐Ray Background: Evidence for the Luminosity‐Dependent Density Evolution

We present a comprehensive study for the gamma-ray luminosity function (GLF) of blazars and their contribution to the extragalactic diffuse gamma-ray background (EGRB). Radio and gamma-ray luminosity correlation is introduced to take into account the radio detectability which is important for the blazar identification. Previous studies considered only pure luminosity evolution (PLE) or pure density evolution, but we introduce the luminosity dependent density evolution (LDDE) model, which is favored from the evolution of X-ray luminosity function (XLF) of AGNs. The model parameters are constrained by likelihood analyses about the observed redshift and gamma-ray flux distributions of the EGRET blazars. We find that the LDDE model gives a better fit to the observed distributions than the PLE model, indicating that the LDDE model is also appropriate for gamma-ray blazars, and that the jet activity is universally correlated with the accretion history of AGNs. The normalization between the GLF and XLF is consistent with the unified picture of AGNs, when the beaming and a reasonable duty cycle of jet activity are taken into account. We then find that only 25--50% of the EGRB can be explained by unresolved blazars with the best-fit LDDE parameters. Unresolved blazars can account for all the EGRB only with a steeper index of the faint-end slope of the GLF, which is marginally consistent with the EGRET data but inconsistent with that of the XLF. Therefore unresolved AGNs cannot be the dominant source of the EGRB, unless there is a new population of gamma-ray emitting AGNs that evolves differently from the XLF of AGNs. Predictions for the GLAST mission are made, and we find that the best-fit LDDE model predicts about 3000 blazars in the entire sky, which is considerably fewer than a previous estimate.

Pure luminosity evolution models: too few massive galaxies at intermediate and high redshift

We compare pure luminosity evolution (PLE) models with recent data at low and high redshift. These models assume that massive galaxies were assembled and formed most of their stars at high redshift (z > 3) and have evolved without merging or substantial dust obscuration since then. Our models span the full range of plausible metallicities, initial mass functions (IMF's) and star formation histories. We require them to reproduce the abundance of galaxies by colour and luminosity in the Sloan Digital Sky Survey and we investigate whether they can simultaneously fit (i) the observed galaxy counts as a function of redshift in magnitude limited surveys with K < 20, and (ii) the colour and M/L ratio evolution of red sequence galaxies in clusters. All models that are consistent with (ii) predict galaxy counts at 1.5 < z < 3 which lie above the observations. Models with an IMF slope similar to the Salpeter value lie far above the data. We conclude that the majority of massive galaxies were either assembled relatively late in this redshift interval or were substantially obscured by dust at these redshifts.

The HELLAS2XMM Survey. VII. The Hard X‐Ray Luminosity Function of AGNs up toz= 4: More Absorbed AGNs at Low Luminosities and High Redshifts

We have determined the cosmological evolution of the density of active galactic nuclei (AGNs) and of their NH distribution as a function of the unabsorbed 2-10 keV luminosity up to redshift 4. We used the HELLAS2XMM sample combined with other published catalogs, yielding a total of 508 AGNs. Our best fit is obtained with a luminosity-dependent density evolution (LDDE) model where low-luminosity (LX ~ 1043 ergs s-1) AGNs peak at z ~ 0.7, while high-luminosity AGNs (LX > 1045 ergs s-1) peak at z ~ 2.0. A pure luminosity evolution model (PLE) can instead be rejected. There is evidence that the fraction of absorbed (NH > 1022 cm-2) AGNs decreases with the intrinsic X-ray luminosity and increases with the redshift. Our best-fit solution provides a good fit to the observed counts, the cosmic X-ray background, and to the observed fraction of absorbed AGNs as a function of the flux in the 10-15 ergs cm-2 s-1 < S2-10 < 10-10 ergs cm-2 s-1 range. We find that the absorbed, high-luminosity (LX > 1044 ergs s-1) AGNs have a density of 267 deg-2 at fluxes S2-10 > 10-15 ergs cm-2 s-1. Using these results, we estimate a density of supermassive black holes in the local universe of ρBH = 3.2 h × 105 M☉ Mpc-3, which is consistent with the recent measurements of the black hole mass function in the local galaxies.

Subaru Super Deep Field with Adaptive Optics. I. Observations and First Implications

We present a deep K'-band (2.12 μm) imaging of the 1' × 1' Subaru Super Deep Field (SSDF) taken with the Subaru adaptive optics (AO) system. Total integration time of 26.8 hr results in the limiting magnitude of K' ~ 24.7 (5 σ, 02 aperture) for point sources and K' ~ 23.5 (5 σ, 06 aperture) for galaxies, which is the deepest limit ever achieved in the K' band. The average stellar full width at half-maximum (FWHM) of the co-added image is 018. Based on the photometric measurements of detected galaxies, we obtained the differential galaxy number counts, for the first time, down to K' ~ 25, which is more than 0.5 mag deeper than the previous data. We found that the number count slope d log N/dm is about 0.15 at 22 < K' < 25, which is flatter than the previous data. Therefore, detected galaxies in the SSDF have only negligible contribution to the near-infrared extragalactic background light (EBL), and the discrepancy claimed so far between the diffuse EBL measurements and the estimated EBL from galaxy count integration has become more serious. The size distribution of detected galaxies was obtained down to the area size of less than 0.1 arcsec2, which is less than half of that of the previous data in the K' band. We compared the observed size-magnitude relation with a simple pure luminosity evolution model allowing for intrinsic size evolution and found that a model with no size evolution gives the best fit to the data. It implies that the surface brightness of galaxies at high redshift is not much different from that expected from the size-luminosity relation of present-day galaxies.

Modeling the Evolution of Infrared Luminous Galaxies: The Influence of the Luminosity‐Temperature Distribution

The evolution of the luminous infrared galaxy population is explored using a pure luminosity evolution model that incorporates the locally observed luminosity-temperature distribution for IRAS galaxies. Pure luminosity evolution models in a fixed ΛCDM cosmology are fitted to submillimeter and infrared counts and backgrounds. We find that the differences between the locally determined bivariate model and the single-variable luminosity function (LF) do not manifest themselves in the observed counts but rather are primarily apparent in the dust temperatures of sources in flux-limited surveys. Statistically significant differences in the redshift distributions are also observed. The bivariate model is used to predict the counts, redshifts, and temperature distributions of galaxies detectable by the Spitzer Space Telescope. The best-fitting model is compared to the high-redshift submillimeter galaxy population, revealing a median redshift for the total submillimeter population of z = 1.8, in good agreement with recent spectroscopic studies of submillimeter galaxies. The temperature distribution for the submillimeter galaxies is modeled to predict the radio/submillimeter indices of the submillimeter galaxies, revealing that submillimeter galaxies exhibit a broader spread in spectral energy distributions than seen in the local IRAS galaxies.

Radio source contamination of the Sunyaev-Zeldovich effect in galaxy clusters

By cross-correlating the 1.4 GHz FIRST catalog of radio sources with the Abell cluster catalog we have found an excess surface density by a factor � 5 of radio sources within a projected distance, rp, of 0.1 Mpc (for h = 0.65) from the cluster center. The profile of the excess density can be described, for rp > 0. 1M pc, by aβ-model with a core radius of � 0.70 Mpc and β = 1.65. The luminosity function of cluster sources does not show hints of cosmological evolution over the redshift range (z < 0.4) covered by our cluster sample. The mean luminosity function is in excellent agreement with the recent determination by Reddy & Yun (2003) for 7 nearby clusters and extends it by two orders of magnitude to higher luminosities. Its shape is very similar to that of the local luminosity function of field galaxies, but the space density is about 3000 times higher. When extrapolated to 30 GHz, our luminosity function compares very favourably with an estimate obtained directly from the 30 GHz observations by Cooray et al. (1998). The antenna temperature contributed by radio sources within the nominal cluster radius of 1.7 Mpc is estimated to be � 13.5 µK at 30 GHz for clusters at z � 0 and decreases to � 3.4 µ Ka tz � 0.5, in the absence of cosmological evolution; it increases by a factor of � 1.5 within 0.25 Mpc from the cluster center. If the pure luminosity evolution models by Dunlop & Peacock (1990) are adopted, the radio source antenna temperature turns out to be essentially independent of redshift.