We present a study of the nature of the blue early-type galaxies found in the HST/ACS images of the GOODS north and south fields.

The role of primordial CH molecules in the first structures formation epoch is considered. We discuss the plausibility of observing protostructures in the Dark Age epoch of the Universe by studying the rotational structure of the CH molecule. It is stressed that considerable abundances of this molecule could be formed for different Inhomogeneous BBN models, which could lead to observable spectral-spatial fluctuations in the CMBR spectrum. The calculation is carried out for the Lambda-CDM cosmology and for typical first structures physical conditions. The chemical evolution of the structures is followed numerically, and the optical depth for the most important ground rotational transitions of the CH molecule are proposed. It is shown that under reasonable conditions the primordial CH molecule can be observed with mm-telescopes under construction.

The stellar mass-metallicity relations of star-forming galaxies at intermediate-z (0.4<z<1) and high-z (z≥2) are compared with the local SDSS galaxies. It shows obvious evolutionary effect, i.e., at a given stellar mass, the intermediate-z galaxies show about 0.3 dex lower metallicity, and the high-z galaxies show about 0.56 dex more metal-deficient than the local ones. These distant galaxies will produce these important parts of their metals during the consequent evolutionary process. A close-box model can explain this evolutionary process generally.

The debate regarding the number of dust-reddened quasars has been ongoing for several years. Selecting quasars based on a UV excess will exclude any quasar that has an SED that departs from the standard power-law or is experiencing obscuration from dust. As longer wavelengths are less affected by dust attenuation, it is advantageous to select quasar candidates in the NIR, but until now, there did not exist a dataset of sufficient depth and coverage suitable for undertaking such an experiment.

We present results on the properties and evolution of moderately ionized gas in the Universe based on intervening CIV absorption-line systems. We have compiled a database of CIV systems from the SDSS, and we find evidence for evolution in the incidence of CIV absorbers.

We present preliminary results of Hα near-infrared (NIR) spectroscopy of 16 galaxies with redshifts in the range 0.8 ≤ z ≤ 1.0 drawn from the DEEP2 Galaxy Redshift Survey. The spectra were taken using the multi-slit mode of LIRIS (Long-slit Intermediate Resolution Infrared Spectrograph), installed at the 4.2-m WHT. Twelve out of 16 spectra yield robust (>5σ) Hα detections. We compare star formation rates (SFRs) from Hα luminosities to those derived from DEEP2 rest-frame UV measurements. This study is part of a larger program to obtain accurate Hα luminosities of about 50 star-forming galaxies at z ~ 1 in the Extended Groth Strip. Our scientific goals are the measurement of SFRs from Hα, and the comparison and calibration of Hα and other SFR tracers at z ~ 1. The study will be complemented with galaxy stellar masses, reddening estimates, galaxy morphologies and metallicities.

Classifying Object by Medium-Band Observations in 17 filters (COMBO-17) has already produced a very accurate picture of galaxy evolution since z~1 based on 25000 galaxies in 17 medium optical bands. We now extend the range of reliable multi-color redshifts with COMBO-17+4, a deep optical-NIR survey which will combine the existing optical data set of COMBO-17 with near infrared observation in three medium bands: Y(λ/Δλ = 1040/80nm), J1(1190/130nm) and J2(1320/130nm) and one broad band H(1650/300nm). The NIR bands extend the photometric redshift range to z~2.1. COMBO 17+4 will provide the first large sample of galaxies (>5000) at 1<z<2 with a redshifts accuracy of Δz<0.03(1+z). Three fields are observed: Abell 901, Abell 226 and the COMBO 11h-field, for a total coverage of 0.77□2 of the sky. Each COMBO 17+4 field measures 31 × 30 sqarcmin. The NIR bands are observed with the Omega2000 camera at Calar Alto Observatory in Spain.

The scientific goals for this study are multiple. COMBO-17+4 will enable us to establish the luminosity function for the red sequence and blue galaxies in the redshift range 1<z<2. Also it will be possible to determine the formation history at z=2 by analyzing the width of the red sequence galaxies. Moreover this survey will provide several thousand of individual galaxy masses (with an accuracy <30%) obtained with Spectral Energy Distribution (SED) template fitting. Once the masses are obtained the mass function will provide a useful tool to test the hierarchical model of evolution of galaxies by checking whether the massive red sequence galaxies (logM>10.5) are already in place at z>1.5 (9Gyr).

We present first results from the full 21 bands photometry in half of the Abell 901 field. It allows us to study not only z>1 galaxies but also the stellar content of several hundred cluster galaxies.

We use a set of hydrodynamical, self consistent simulations operating in the context of a concordance cosmological model where relaxed elliptical-like objects (ELOs) were identified at different redshifts. ELOs at different redshift are well described by the Sérsic (1968) function. We also obtain a good comparison with observational scaling relations. These results indicate that ELOs conform a homogeneous population at any redshift, except that high z ELOs tend to be more compact that their lower z counterparts. Also, scaling relations point to the rupture of the structural homology.

Photometric redshifts technique and red sequence technique are used in order to analyze the clustering of galaxies in the environments of 4 radio galaxies with redshifts z>0.6.

We use Virtual Observatory methods to investigate the association between radio and X-ray emission at high redshifts. Fifty-five of the 92 HDF(N) sources resolved by combining MERLIN+VLA data were detected by Chandra, of which 18 are hard enough and bright enough to be obscured AGN. The high-z population of μJy radio sources is dominated by starbursts an order of magnitude more active and more extended than any found at z < 1 and at least a quarter of these simultaneously host highly X-ray-luminous obscured AGN.

Molecular gas has now been detected in 15 z>2 QSOs. These detections are commonly obtained by observing high–J CO transitions due to their relatively high peak fluxes and observing frequencies in the millimeter atmospheric windows. However, only observations of the CO ground-state transition, CO(1–0), have the potential to trace the molecular gas at lower excitations, which may give a better estimate of the total molecular gas mass of high–z QSOs. Here we present first z>4 CO(1–0) observations obtained with the NRAO Green Bank Telescope and the MPIfR Effelsberg telescope (Riechers et al. 2006). With these two 100m telescopes, we detect the CO(1–0) transition in the high–redshift QSOs BR 1202-0725 (z = 4.7), PSS J2322+1944 (z = 4.1), and APM 08279+5255 (z = 3.9). We find that the CO/FIR luminosity ratios of these high-z sources follow the same trend as seen for low-z galaxies. Utilizing large velocity gradient (LVG) models based on previous results for higher–J CO transitions, we derive that all CO emission can be described by a single gas component and that all molecular gas appears to be concentrated in a compact nuclear region. We thus find no evidence for luminous, extended CO(1–0) components in the molecular gas reservoirs around our target quasars.

Using the Very Large Array (VLA), we have detected the HCO+(1–0) emission line towards the Cloverleaf quasar (z = 2.56; Riechers et al. 2006). This is the first detection of ionized molecular gas emission at high redshift (z>2). HCO+ emission is a star formation indicator similar to HCN, tracing dense molecular hydrogen gas within star-forming molecular clouds. We find a HCO+/CO luminosity ratio of 0.08 and a HCO+/HCN luminosity ratio of 0.8 for the Cloverleaf. These ratios fall within the scatter of the same relationships found for low–z star–forming galaxies. However, a HCO+/HCN luminosity ratio close to unity would not be expected for the Cloverleaf if the recently suggested relation between this ratio and the far–infrared luminosity (Graciá–Carpio et al. 2006) were to hold. We conclude that a ratio between HCO+ and HCN luminosity close to 1 is likely due to the fact that the emission from both lines is optically thick and thermalized and emerges from dense regions of similar volumes. We conclude that HCO+ is potentially a good tracer for dense molecular gas at high redshift.

Following up on the detailed results from our searches for z~ 6–10 galaxies using gravitional lensing clusters descrived in Richard et al. (2006), we have obtained new observations, which are presented here. For a general overview of the project see Schaerer et al. (2006). First, deep HST/ACS observations in the z-band confirm 17 out of 18 high redshift candidates as optical drop-out objects; the remaining object appears faint and star-like. Second, Spitzer/IRAC images at 3.6, 4.5, 5.8 and 8.0 μm have been obtained. 11 out of 18 candidates are in “free”, uncominated regions. These 11 high-z candidates are undetected, with upper limits which are compatible with their SED if these objects are blue star-forming galaxies at high redshift (see Fig. 1). In conclusion, our new observations corroborate so far the high-z nature of the majority of the candidates.

We present results from our on-going study of the distribution and evolution of high-z galaxies. We exploited the large area coverage (~1.3 deg2) of the Subaru / XMM-Newton Deep Survey field (SXDF) to search for Lyman-break galaxies (LBGs) and Lyα Emitters (LAEs) at 3 <z< 7. We have found filamentary large scale structures, which are made of LAEs, with ~10 to 40 Mpc (in commoving units) scale voids as early as at z = 5.7. Galaxies at this redshift show clustering of ~1 Mpc in diameter (in physical unit). The inferred star formation rate density of these clustering is ~130 times the mean of the whole area, indicates burst of star formation activities. Combined with the UKIDSS/UDS photometry, the optical+near-IR SED fitting provides the estimate of masses for some of these high-z galaxies. Preliminary results indicate a number of galaxies at z >5 have already grown up to ~1011 solar mass.

We present the results of a comprehensive Spitzer survey of 70 radio galaxies across 1 < z < 5.2. Using IRAC (3.6–8.0μm), IRS (16 μm) and MIPS (24–160 μm) imaging, we decompose the rest-frame optical to infrared spectral energy distributions into stellar, AGN, and dust components and determine the contribution of host galaxy stellar emission at rest-frame 1.6 μm (H-band). We find that the fraction of emitted light at rest-frame 1.6 μm from stars is >80% for over half the high redshift radio galaxies. The other radio galaxies have 1.6 μm stellar fractions spanning the range 20–80%. The resultant stellar luminosities imply stellar masses of 1011−12M⊙, independent of redshift, indicating that radio galaxies are amoungst the most massive galaxies observed over this redshift range. Powerful radio galaxies tend to lie in a similar region of mid-IR color-color space as unobscured AGN, despite the inferred stellar contribution to their shorter-wavelength, mid-IR SEDs. The stellar fraction of the rest-frame 1.6 μm luminosity has no correlation with redshift, radio luminosity, or rest-frame mid-IR (5 μm) luminosity. The bolometric energy output of these sources is dominated by the infrared, and the mid-IR luminosities are found to be similar to that of lower redshift (z < 1) radio galaxies. As expected, these exceptionally high mid-IR luminosities are consistent with an obscured, highly-accreting AGN. A weak, but significant, correlation of stellar mass with radio luminosity is found, consistent with earlier results.

Using the multi-wavelength COSMOS survey (Scoville et al. 2006), we develop a method based on purely photometric data to separate the faint VLA-COSMOS radio population into star-forming (SF) galaxies and active-galactic nuclei (AGN). Based on this classification method we select SF galaxies within our sample and present first results on the cosmic (dust-obscured) star-formation history based on VLA-COSMOS (Schinnerer et al. 2006) radio data.

We study the submillimetre (submm) properties of the following near-infrared (NIR)-selected massive galaxies at high redshifts: BzK-selected star-forming galaxies (BzKs), distant red galaxies (DRGs) and extremely red objects (EROs). We used the SCUBA HAlf Degree Extragalactic Survey (SHADES), the largest uniform submm survey to date. Since BzKs are expected to include obscured star-forming galaxies at 1.4 < z < 2.5, it is possible that the submm galaxies are a sub-group of BzKs. We identified 4 BzKs as submm galaxies within 93 arcmin2 by using high resolution radio images. This indicates that only ~20% of submm galaxies are BzKs. However, this fraction is consistent with the assumption that the most of submm galaxies at 1.4 < z < 2.5 are BzKs, considering the redshift distribution, radio-detection rate and observed K-band magnitudes of submm galaxies. We found no submm detections for EROs which are clearly non-BzKs. We identify two submm-bright NIR-selected galaxies, which satisfy all the selection criteria we adopt; i.e. they belong to the BzK-DRG-ERO overlapping population, or ‘extremely red’ BzKs. Although these extremely red BzKs are rare (0.25 arcmin−2), about 10% of this population could be submm galaxies. With a stacking analysis, we detected the 850-μm flux of submm-faint BzKs and EROs in our SCUBA maps. While the contribution from BzKs at z ~ 2 to submm background is about 10–15% and similar to that from EROs typically at z ~ 1, BzKs have a higher fraction (~30%) of submm flux in resolved sources than EROs and submm sources as a whole do. Therefore, submm flux of BzKs seems to be biased high. From the SED fitting using an evolutionary model of starbursts with radiative transfer, submm-bright BzKs are found to have the stellar mass of >5 × 1010M⊙ with the luminosity of >3 × 1012L⊙. From an average SED of submm-faint BzKs having similar B − z and z − K colours to submm-bright ones, we suggest that submm-bright BzKs are more massive than submm-faint ones.

We present a new diagnosis method for determining physical properties of star-forming gas in high-z galaxies. In this method, we employed three key observational quantities, [CI], CO, and FIR luminosities, including our new detections of CO J = 4–3 emission from the pure-starburst (non-AGN) submm galaxy SMM J14011+0252 (z = 2.6) and the type-2 AGN IRAS FSC 10214+4724 (z = 2.3) obtained with the Nobeyama Millimeter Array (NMA) at the Nobeyama Radio Observatory. These two sources have extremely high star formation rate, and exhibit strong emission of CO and [CI] 609 μm lines. We determined ISM physical conditions for the two objects and another three high-z quasars in order to investigate the relationship between their ISM and power sources (i.e., massive star formation or AGN). A new PDR analysis (Wolfire et al. 2005, private communication) using CO, [CI], and FIR on five high-z sources provides new evidence that AGN host galaxies harbor denser (log nH ~ 5–6) ISM exposed to stronger far-UV fluxes of log G0 ~ 3.5–4 than the non-AGN submm galaxy. Volume filling factors of the star-forming dense gas in the AGN hosts are an order of magnitude smaller than that of the pure-starburst submm galaxy. This suggests that, in these AGN hosts, dense molecular clouds are dominating the central kpc around AGN, triggering extensive circumnuclear starbursts, and possibly feeding their central supermassive black hole simultaneously.

The investigations of the ultra steep spectrum radio source RC J0311+0507 (4C+04.11) in radio (RATAN-600, VLA) and optics (6-m telescope SAO RAS) are presented. The identification of a strong line at 6703 Å with Lyα gives a redshift z=4.514. The object belongs to the group of extremely distant radio galaxies of ultrahigh radio luminosity (P1400 = 1.3 × 1029WHz−1).

We present a new K-band survey covering 623 arcmin2 in the VVDS 0226-0430 deep field down to a limiting magnitude KVega ≤ 20.5. We use the spectroscopic sample extracted from this new K-band catalogue to assess the effectiveness of optical-near infrared color selections in identifying extreme classes of objects at high redshift.