The evolutionary sequence of active galactic nuclei and galaxy formation revealed

Today, almost every galaxy spheroid contains a massive black hole: a remnant of, and testament to, a period in its evolution when it contained an active galactic nucleus (AGN). However, the sequence and timescales of the formation of the black hole and surrounding spheroid of stars are completely unknown, leaving a large gap in our knowledge of how the universe attained its present appearance. Here we present submillimeter observations of matched samples of X-ray absorbed and unabsorbed AGNs that have luminosities and redshifts characteristic of the sources responsible for most of the mass in present-day black holes. Strong submillimeter emission, an isotropic signature of copious star formation, is found only in the X-ray–absorbed sample, ruling out orientation effects as the cause of the absorption. The space density and luminosity range of the X-ray–absorbed AGNs indicate that they are undergoing the transition between a hidden growth phase and an unabsorbed AGN phase and imply that the X-ray–absorbed period in the AGN's evolution coincides with the formation of the galaxy spheroid

Field notes on the breeding biology and diet of ferruginous pygmy-owl (Glaucidium brasilianum) in the dry chaco of Argentina

Fil:Fernández, F.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Cosmological constraints from the cluster contribution to the power spectrum of the soft X-ray background. New evidence for a low sigma_8

We use the X-ray power spectrum of the ROSAT all-sky survey in the R6 band (approximately 0.9-1.3 keV) to set an upper limit on the galaxy cluster power spectrum. The cluster power spectrum is modelled with a minimum number of robust assumptions regarding the structure of the clusters. The power spectrum of ROSAT sets an upper limit on the Omega_m-sigma_8 plane which excludes all the models with sigma_8 above sigma_8 = 0.5/(Omega_m^0.38) in a flat LCDM universe. We discuss the possible sources of systematic errors in our conclusions, mainly dominated by the assumed L_x-T relation. Alternatively, this relation could be constrained by using the X-ray power spectrum, if the cosmological model is known. Our conclusions suggest that only models with a low value of sigma_8 (sigma_8 < 0.8 for Omega_m = 0.3) may be compatible with our upper limit. We also find that models predicting lower luminosities in galaxy clusters are favoured. Reconciling our cosmological constraints with these arising by other methods might require either a high entropy floor or wide-spread presence of cooling flows in the low-redshift clusters.Comment: 14 pages, 19 plots (2 as gif files). MNRAS submitte

By-catch of cold-water corals from an Experimental Trawl Survey in three seamounts within NAFO Regulatory Area (Divs. 6EFG) during year 2004

By-catch of cold-water corals from a Trawl Experimental Survey developed during 2004 in three NAFO seamounts was examined. Three hauls were carried out over two peaks located in Divs. 6EF. In this area, catches of commercial resources were negligible and by-catch of corals was recorded (degraded pieces of dead Enallopsammia sp and Keratoisis sp and few alive corals like Solenosmilia variabilis, Metallogorgia melanotrichos, Paragorgia johnsoni, etc.), showing some interaction between fishing and vulnerable habitats and that trawl fishing in the area is unfeasible. Ninety-two hauls were carried out over one peak located in Div. 6G, with big catches of alfonsino (Beryx splendens), but only six hauls showing coral records (Enallopsamia rostrata, Solenosmilia variabilis, Madrepora oculata, Acanella eburnea and Placogorgia terceira) and in less quantities in comparison with Divs. 6EF. The low by-catch of corals in the Div. 6G peak could be related with their less rough bottom feature and with the previous alteration of sessile epifauna due to intense fishing activity developed during the last decades of XX Century. The results of the Experimental Survey indicate that the impact of trawling on seamounts could be important and that the closed area agreed in 2007 to protect the bottom habitats of the seamounts within NAFO Regulatory Area (Divs. 6EFG) should be maintained and improved

The XMM deep survey in the CDFS: XI. X-ray spectral properties of 185 bright sources

We present the X-ray spectra of 185 bright sources detected in the XMM-Newton deep survey of the Chandra Deep Field South with the three EPIC cameras combined. The 2\u201310 keV flux limit of the sample is 2\u2005 7\u200510 1215 erg s 121 cm 122. The sources are distributed over a redshift range of z\u2004=\u20040.1 123.8, with 11 new X-ray redshift measurements included. A spectral analysis was performed using a simple model to obtain absorbing column densities, rest-frame 2\u201310 keV luminosities, and Fe K line properties of 180 sources at z\u2004&gt; \u20040.4. Obscured AGN are found to be more abundant toward higher redshifts. Using the XMM-Newton data alone, seven Compton-thick AGN candidates were identified, which set the Compton-thick AGN fraction at 434%. An exploratory spectral inspection method with two rest-frame X-ray colours and an Fe line strength indicator was introduced and tested against the results from spectral fitting. This method works reasonably well to characterise a spectral shape and can be useful for a pre-selection of Compton-thick AGN candidates. We found six objects exhibiting broad Fe K lines out of 21 unobscured AGN of best data quality, implying a detection rate of 3c30%. Five redshift spikes, each with more than six sources, are identified in the redshift distribution of the X-ray sources. Contrary to the overall trend, the sources at the two higher redshift spikes, at z\u2004=\u20041.61 and z\u2004=\u20042.57, exhibit a puzzlingly low obscuration

A systematic cross-search for radio/infrared counterparts of XMM-Newton sources

We present a catalog of cross-correlated radio, infrared and X-ray sources using a very restrictive selection criteria with an IDL-based code developed by us. The significance of the observed coincidences was evaluated through Monte Carlo simulations of synthetic sources following a well-tested protocol. We found 3320 coincident radio/X-ray sources with a high statistical significance characterized by the sum of error-weighted coordinate differences. For 997 of them, 2MASS counterparts were found. The percentage of chance coincidences is less than 1%. X-ray hardness ratios of well-known populations of objects were used to provide a crude representation of their X-ray spectrum and to make a preliminary diagnosis of the possible nature of unidentified X-ray sources. The results support the fact that the X-ray sky is largely dominated by Active Galactic Nuclei at high galactic latitudes (|b| >= 10^\circ). At low galactic latitudes (|b| <= 10^\circ) most of unidentified X-ray sources (~94%) lie at |b| <= 2^\circ. This result suggests that most of the unidentified sources found toward the Milky Way plane are galactic objects. Well-known and unidentified sources were classified in different tables with their corresponding radio/infrared and X-ray properties. These tables are intended as a useful tool for researchers interested in particular identifications.Comment: Accepted for publication in Ap&SS. 47 pages, 10 figures. On-line material: figures and table

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters