Search

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM, We present the VST ATLAS Quasar Survey, consisting of ∼1229 000 quasar (QSO) candidates with 16 < g < 22.5 over ∼4700 deg2. The catalogue is based on VST ATLAS+NEOWISE imaging surveys and aims to reach a QSO sky density of 130 deg-2 for z < 2.2 and ∼30 deg-2 for z > 2.2. To guide our selection, we use X-ray/UV/optical/MIR data in the extended William Herschel Deep Field (WHDF) where we find a g < 22.5 broad-line QSO density of 269 ± 67 deg-2, roughly consistent with the expected ∼196 deg-2. We find that ∼25 per cent of our QSOs are morphologically classed as optically extended. Overall, we find that in these deep data, MIR, UV, and X-ray selections are ∼70-90 per cent complete while X-ray suffers less contamination than MIR and UV. MIR is however more sensitive than X-ray or UV to z > 2.2 QSOs at g < 22.5 and the S_X(0.5-10, keV) > 1× 10-14 ergs cm-2 s-1 limit of eROSITA. We adjust the selection criteria from our previous 2QDES pilot survey and prioritize VST ATLAS candidates that show both UV and MIR excess, also selecting candidates initially classified as extended. We test our selections using data from DESI (which will be released in DR1) and 2dF to estimate the efficiency and completeness, and we use ANNz2 to determine photometric redshifts. Applying over the ∼4700 deg2 ATLAS area gives us ∼ 917000 z < 2.2 QSO candidates of which 472 000 are likely to be z < 2.2 QSOs, implying a sky density of ∼100 deg-2, which our WHDF analysis suggests will rise to at least 130 deg-2 when eROSITA X-ray candidates are included. At z > 2.2, we find ∼310() 000 candidates, of which 169 000 are likely to be QSOs for a sky density of ∼36 deg-2

We investigate the ‘Local Hole’, an anomalous underdensity in the local galaxy environment, by extending our previous galaxy K-band number-redshift and number-magnitude counts to ≈90 per cent of the sky. Our redshift samples are taken from the 2MASS Redshift Survey (2MRS) and the 2M++ catalogues, limited to K < 11.5. We find that both surveys are in good agreement, showing an $\approx 21\!-\!22{{\ \rm per\ cent}}$ underdensity at z < 0.075 when compared to our homogeneous counts model that assumes the same luminosity function (LF) and other parameters as in our earlier papers. Using the Two Micron All Sky Survey (2MASS) for n(K) galaxy counts, we measure an underdensity relative to this model of $20 \pm 2 {{\ \rm per\ cent}}$ at K < 11.5, which is consistent in both form and scale with the observed n(z) underdensity. To examine further the accuracy of the counts model, we compare its prediction for the fainter n(K) counts of the Galaxy and Mass Assembly (GAMA) survey. We further compare these data with a model assuming the parameters of a previous study where little evidence for the Local Hole was found. At 13 < K < 16, we find a significantly better fit for our galaxy counts model, arguing for our higher LF normalization. Although our implied underdensity of $\approx 20{{\ \rm per\ cent}}$ means local measurements of the Hubble Constant have been overestimated by ≈3 per cent, such a scale of underdensity is in tension with a global ΛCDM cosmology at an ≈3σ level.

(ABRIDGED) We present a power spectrum analysis of the 10K catalogue from the 2dF QSO Redshift Survey. We compare the redshift-space power spectra of QSOs to those measured for galaxies and Abell clusters at low redshift and find that they show similar shapes in their overlap range, 50-150h^{-1}Mpc, with P_QSO(k)\propto k^{-1.4}. The amplitude of the QSO power spectrum at z~1.4 is almost comparable to that of galaxies at the present day if Omega_m=0.3 and Omega_Lambda=0.7 (the Lambda cosmology), and a factor of ~3 lower if Omega_m=1 (the EdS cosmology) is assumed. The amplitude of the QSO power spectrum is a factor of ~10 lower than that measured for Abell clusters at the present day. At larger scales, the QSO power spectra continue to rise robustly to ~400 h^{-1}Mpc, implying more power at large scales than in the APM galaxy power spectrum measured by Baugh & Efstathiou. We split the QSO sample into two redshift bins and find little evolution in the amplitude of the power spectrum. The QSO power spectrum may show a spike feature at ~90h^{-1}Mpc assuming the Lambda cosmology or ~65 h^{-1}Mpc assuming an EdS cosmology. Although the spike appears to reproduce in both the North and South strips and in two independent redshift ranges, its statistical significance is still marginal and more data is needed to test further its reality. We compare the QSO power spectra to CDM models to obtain a constraint on the shape parameter, Gamma. For two choices of cosmology (Omega_m=1, Omega_Lambda=0 and Omega_m=0.3, Omega_Lambda=0.7), we find the best fit model has Gamma~0.1 +-0.1., MNRAS Accepted

We describe the scientific motivations, the mission concept and the instrumentation of SPACE, a class-M mission proposed for concept study at the first call of the ESA Cosmic-Vision 2015-2025 planning cycle. SPACE aims to produce the largest three-dimensional evolutionary map of the Universe over the past 10 billion years by taking near-IR spectra and measuring redshifts for more than half a billion galaxies at 0, Comment: 27 pages, Experimental Astronomy, in press. The SPACE team complete list is available at http://urania.bo.astro.it/cimatti/space . The article with full resolution figures is available at http://urania.bo.astro.it/cimatti/space/publications.htm

We have cross-correlated the WMAP data with several surveys of extragalactic sources and find evidence for temperature decrements associated with galaxy clusters and groups detected in the APM Galaxy Survey survey and the ACO catalogue. We interpret this as evidence for the thermal Sunyaev-Zeldovich (SZ) effect from the clusters. Most interestingly, the signal may extend to �1 deg (� 5h −1 Mpc) around both groups and clusters and we suggest that this may be due to hot ‘supercluster’ gas. We have further cross-correlated the WMAP data with clusters identified in the 2MASS galaxy catalogue and also find evidence for temperature decrements there. From the APM group data we estimate the mean Compton parameter as y(z 10 and then could seriously affect the WMAP cosmological fits.

X-ray luminous narrow emision-line galaxies (NELG) have been previously identified and proposed as an important class of extragalactic X-ray sources, with a potentially significant contribution to the total extragalactic X-ray flux at energies below $\sim$ 10 keV. In order to investigate and clarify this possibility, we have used a sample of NELG found in 5 deep ROSAT fields and similar samples belonging to the Cambridge-Cambridge ROSAT Serendipity Survey and to the {\it Einstein} Observatory Extended Medium Sensitivity Survey sample. The principal results of this investigation are as follows: a) for a given optical luminosity, the typical X-ray luminosity of NELGs is about one or two orders of magnitude higher than that of normal galaxies; b) the ratio of the surface density of NELGs compared with BLAGN increases from about 0.04 at fx >= 6 x 10^{-13} erg cm^{-2} s^{-1} to about 0.1 at fx >= 10^{-14} erg cm^{-2} s^{-1}, suggesting that the surface density of NL galaxies might be very close to that of BLAGN at fx ~ 10^{-15} erg cm^{-2} s^{-1}; c) we find that these objects are described by a cosmological evolution rate similar to that of soft X-ray selected BLAGN; d) the de-evolved (z=0) XLF of NELGs in the luminosity range 10^{41} - 5 x 10^{43} erg s^{-1} is steeper than the BLAGN (z=0) XLF in the same luminosity interval. Their spatial density is significantly lower than the spatial density of X-ray selected BLAGN at Lx(z=0) ~ 5 x 10^{43} erg s^{-1}, but this difference decreases at lower luminosities such that at Lx(z=0) < 10^{42} erg s^{-1} the spatial density of NELGs is very close to that of BLAGN. The implications of these results for the contribution of this class of objects to the cosmic X-ray background are discussed., To be published in M.N.R.A.S., 10 pages, 2 Tables. Figures are available in the anonymous ftp account on ftp://mds.pha.jhu.edu/pub/nl_paper

We present results from two new near-infrared imaging surveys. One survey covers 47.2 arcmin2 to K(3σ) = 20 mag whilst a second, deeper catalogue covers a subarea of 1.8 arcmin2 to K(3σ) = 22.75 mag. Over the entire area we have extremely deep optical photometry in four bandpasses (UBRI), allowing us to track the colour evolution of galaxies to very faint magnitude limits. Our K-band number counts are consistent with the predictions of non-evolving models with 0 ≤ q0 ≤ 0.5. The K-selected (B - K) galaxy colour distributions from our surveys move sharply bluewards fainter than K∼20. At brighter magnitudes (K < 20 mag) our K-selected (B - K) distributions indicate a deficiency of red, early-type galaxies at z ∼ 1 compared with the predictions of passively evolving models, which implies either a pure luminosity evolution (PLE) model, where star formation continues at a low level after an initial burst, or dynamical merging. At fainter magnitudes, the continuing bluewards trend observed in (B - K) can be explained purely in terms of passively evolving PLE models. We detect 0.5 ± 0.1 galaxy arcmin-2 with (I - K) > 4 and 19 < K < 20 mag. Although this is a factor of ∼3 (2σ) more objects than in the recent survey of Berger et al., this is still lower than the predictions of standard passively evolving models and more consistent with PLE models containing small amounts of ongoing star formation. Our observed numbers of (I - K) > 4 galaxies at K ∼ 20 are lower than the predictions of passively evolving models or PLE models with a low level of continuing star formation, suggesting that at least part of the larger deficiency observed in (B - K) at K ∼ 20 may be caused by star formation rather than dynamical merging. As we and others have noted, the number redshift distribution at 18 < K < 19 of recent, deep K-selected redshift surveys is well fitted by non-evolving models, and passively evolving models with a Salpeter or Scalo initial mass functions predict too many galaxies with z > 1. Dynamical merging is one possible solution to reduce the numbers of these galaxies but (as we have suggested previously) a dwarf-dominated initial mass function for early-type galaxies could offer an alternative explanation; we show here that such a model reproduces well the optical-infrared colour distributions and K-band galaxy counts.

Recent results from studies of galaxy clustering in galaxy redshift surveys have tentatively suggested the existence of ‘spike’ features in the galaxy 2-point correlation function at large spatial scales. These features are most straightforwardly predicted in a dense, baryon dominated world model with initial adiabatic fluctuations. Here we discuss the prospects for such a model assuming a Friedmann cosmology with the density parameter, Ω , equal to the critical value of unity. We conclude that the lower the value of Hubble's constant, H 0 , the more likely it is that the above model may be consistent with the current observational constraints.

A search for intermediate-redshift quasars has been carried out with slitless spectroscopy in the central 21.07 deg2 of the SA 94, where the existence of a large database of objects for which slit spectroscopy was already available provided a valuable opportunity of testing the properties of our selection technique. Fifty candidates have been observed with slit spectroscopy, confirming 34 quasars and two H II galaxies. The completeness of this survey as a function of magnitude and redshift has been analysed, and an effective area of 16.9 deg2 has been evaluated. The estimated quasar surface density for QSOs with 1.8 < z < 3.2 and B < 19.4 is 1.4 +/- 0.3 deg-2, in agreement with other surveys in the literature. A brief analysis of the evolution of the volume density of quasars with - 27.35 < M(B) < - 28.5 is carried out, finding no evidence for a decrease at intermediate-large redshifts.