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Seymour N.,CSIRO | Seymour N.,University College London | Altieri B.,European Space Agency | De Breuck C.,European Southern Observatory | And 34 more authors.
Astrophysical Journal | Year: 2012

We present a detailed study of the infrared spectral energy distribution of the high-redshift radio galaxy MRC1138-26 at z = 2.156, also known as the Spiderweb Galaxy. By combining photometry from Spitzer, Herschel, and LABOCA we fit the rest-frame 5-300 μm emission using a two-component, starburst, and active galactic nucleus (AGN) model. The total infrared (8-1000 μm) luminosity of this galaxy is (1.97 ± 0.28) ×1013 L ⊙ with (1.17 ± 0.27) and (0.79 ± 0.09) ×1013 L ⊙ due to the AGN and starburst components, respectively. The high derived AGN accretion rate of 20% Eddington and the measured star formation rate (SFR) of 1390 ± 150 M ⊙yr-1 suggest that this massive system is in a special phase of rapid central black hole and host galaxy growth, likely caused by a gas-rich merger in a dense environment. The accretion rate is sufficient to power both the jets and the previously observed large outflow. The high SFR and strong outflow suggest that this galaxy could potentially exhaust its fuel for stellar growth in a few tens of Myr, although the likely merger of the radio galaxy with nearby satellites suggests that bursts of star formation may recur again on timescales of several hundreds of Myr. The age of the radio lobes implies the jet started after the current burst of star formation, and therefore we are possibly witnessing the transition from a merger-induced starburst phase to a radio-loud AGN phase. We also note tentative evidence for [C II]158 μm emission. This paper marks the first results from the Herschel Galaxy Evolution Project (Project HeRGÉ), a systematic study of the evolutionary state of 71 high-redshift, 1 < z < 5.2, radio galaxies. © 2012. The American Astronomical Society. All rights reserved.

Gyulzadyan M.,Vaambartsumian Byurakan Astrophysical Observatory | McLean B.,US Space Telescope Science Institute | Adibekyan V.Z.,Vaambartsumian Byurakan Astrophysical Observatory | Adibekyan V.Z.,Yerevan State University | And 4 more authors.
Astrophysics | Year: 2011

A database for the entire catalog of the Second Byurakan Survey (SBS) galaxies is presented. It contains new measurements of their optical parameters and additional information taken from the literature and other databases. The measurements were made using Ipg (near-infrared), Fpg (red), and Jpg (blue) band images from photographic sky survey plates obtained by the Palomar Schmidt telescope and extracted from the STScI Digital Sky Survey (DSS). The database provides accurate coordinates, morphological type, spectral and activity classes, apparent magnitudes and diameters, axial ratios and position angles, as well as number counts of neighboring objects in a circle of radius 50 kpc. The total number of individual SBS objects in the database is now 1676. The 188 Markarian galaxies that were re-discovered by SBS are not included in this database. We also include redshifts that are now available for 1576 SBS objects, as well as 2MASS infrared magnitudes for 1117 SBS galaxies. © 2011 Springer Science+Business Media, Inc.

Treister E.,University of Concepción | Schawinski K.,ETH Zurich | Volonteri M.,Paris Institute of Astrophysics | Natarajan P.,Yale Center for Astronomy and Astrophysics | Natarajan P.,Yale University
Astrophysical Journal | Year: 2013

We constrain the total accreted mass density in supermassive black holes at z > 6, inferred via the upper limit derived from the integrated X-ray emission from a sample of photometrically selected galaxy candidates. Studying galaxies obtained from the deepest Hubble Space Telescope images combined with the Chandra 4 Ms observations of the Chandra Deep Field-South, we achieve the most restrictive constraints on total black hole growth in the early universe. We estimate an accreted mass density <1000 M ⊙ Mpc -3 at z ∼ 6, significantly lower than the previous predictions from some existing models of early black hole growth and earlier prior observations. These results place interesting constraints on early black hole growth and mass assembly by accretion and imply one or more of the following: (1) only a fraction of the luminous galaxies at this epoch contain active black holes; (2) most black hole growth at early epochs happens in dusty and/or less massive - as yet undetected - host galaxies; (3) there is a significant fraction of low-z interlopers in the galaxy sample; (4) early black hole growth is radiatively inefficient, heavily obscured, and/or due to black hole mergers as opposed to accretion; or (5) the bulk of the black hole growth occurs at late times. All of these possibilities have important implications for our understanding of high-redshift seed formation models. © 2013. The American Astronomical Society. All rights reserved.

Kakazu Y.,California Institute of Technology | Kakazu Y.,Paris Institute of Astrophysics | Hu E.M.,University of Hawaii at Manoa | Liu M.C.,University of Hawaii at Manoa | And 3 more authors.
Astrophysical Journal | Year: 2010

The Hawaii Quasar and T dwarf survey (HQT Survey) is a wide-field, red optical survey carried out with the Suprime-Cam mosaic CCD camera on the 8.2 m Subaru telescope. The HQT survey is designed to search for low-luminosity (MAB1450 < -23) quasars at high redshift (z > 5.7) as well as T dwarfs, both of which are selected by their very red I - z′ colors. We use an optical narrowband filter NB816 to break a well-known I - z′ color degeneracy between high-z quasars and foreground M and L dwarfs, which are more numerous than quasars. This paper is the first in a series of papers from the HQT survey and we report on the discovery of six faint (19 ≤ J ≤ 20) ultracool dwarfs found over a ∼ 9.3 deg2 area with a limiting magnitude of z′AB ≤ 23.3. These dwarfs were confirmed by near-IR imaging and/or spectroscopy conducted at various facilities on Mauna Kea. With estimated distances of 60-170 pc, these are among the most distant spectroscopically confirmed field brown dwarfs to date. Limits on the proper motions of these ultracool dwarfs suggest that they are old members of the Galactic disk, though future follow-up observations are necessary to minimize errors. Our finding rate of ultracool dwarfs is within model predictions of Liu et al. However, the large brightening amplitude (∼ 1 mag) previously reported for the L/T transition objects appears to overpredict the numbers. We also examine how the survey field latitude affects the survey sensitivity to the vertical scale height of ultracool dwarfs. © 2010. The American Astronomical Society.

Weniger C.,Max Planck Institute for Physics | Bringmann T.,University of Hamburg | Calore F.,University of Hamburg | Vertongen G.,Paris Institute of Astrophysics
Journal of Physics: Conference Series | Year: 2012

Indirect searches for dark matter annihilation or decay products in the cosmic-ray spectrum are plagued by the question of how to disentangle a dark matter signal from the omnipresent astrophysical background. One of the practically background-free smoking-gun signatures for dark matter would be the observation of a sharp cutoff or a pronounced bump in the gamma-ray energy spectrum. Such features are generically produced in many dark matter models by internal Bremsstrahlung, and they can be treated in a similar manner as the traditionally looked-for gamma-ray lines. Here, we discuss prospects for seeing such features with present and future Atmospheric Cherenkov Telescopes.

Brandenberger R.H.,McGill University | Martin J.,Paris Institute of Astrophysics
Classical and Quantum Gravity | Year: 2013

The accelerated expansion of space during the cosmological inflation period leads to trans-Planckian issues which need to be addressed. Most importantly, the physical wavelength of fluctuations which are studied at the present time by means of cosmological observations may well originate with a wavelength smaller than the Planck length at the beginning of the inflationary phase. Thus, questions arise as to whether the usual predictions of inflationary cosmology are robust considering our ignorance of physics on trans-Planckian scales, and whether the imprints of Planck-scale physics are at the present time observable. These and other related questions are reviewed in this paper. © 2013 IOP Publishing Ltd.

Bellovary J.,Vanderbilt University | Brooks A.,University of Wisconsin - Madison | Volonteri M.,Paris Institute of Astrophysics | Governato F.,University of Washington | And 2 more authors.
Astrophysical Journal | Year: 2013

Using a set of zoomed-in cosmological simulations of high-redshift progenitors of massive galaxies, we isolate and trace the history of gas that is accreted by central supermassive black holes. We determine the origins of the accreted gas, in terms of whether it entered the galaxy during a merger event or was smoothly accreted. Furthermore, we designate whether the smoothly accreted gas is accreted via a cold flow or is shocked upon entry into the halo. For moderate-mass (106-107 M⊙) black holes at z ∼ 4, there is a preference to accrete cold flow gas as opposed to gas of shocked or merger origin. However, this result is a consequence of the fact that the entire galaxy has a higher fraction of gas from cold flows. In general, each black hole tends to accrete the same fractions of smooth- and merger-accreted gas as is contained in its host galaxy, suggesting that once gas enters a halo it becomes well-mixed, and its origins are erased. We find that the angular momentum of the gas upon halo entry is a more important factor; black holes preferentially accrete gas that had low angular momentum when it entered the galaxy, regardless of whether it was accreted smoothly or through mergers. © 2013. The American Astronomical Society. All rights reserved.

Kuroyanagi S.,University of Tokyo | Miyamoto K.,University of Tokyo | Sekiguchi T.,Nagoya University | Takahashi K.,Kumamoto University | And 2 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study future observational constraints on cosmic string parameters from various types of next-generation experiments: direct detection of gravitational waves (GWs), pulsar timing array, and the cosmic microwave background. We consider both GW burst and stochastic GW background searches by ground- and space-based interferometers as well as GW background detection in pulsar timing experiments. We also consider cosmic string contributions to the cosmic microwave background temperature and polarization anisotropies. These different types of observations offer independent probes of cosmic strings and may enable us to investigate cosmic string properties if the signature is detected. In this paper, we evaluate the power of future experiments to constrain cosmic string parameters, such as string tension Gμ, initial loop size α, and reconnection probability p, by performing Fisher information matrix calculations. We find that combining the information from the different types of observations breaks parameter degeneracies and provides more stringent constraints on the parameters. We also find future space-borne interferometers independently provide a highly precise determination of the parameters. © 2013 American Physical Society.

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