57 research outputs found
Discovery of a redshift 6.13 quasar in the UKIRT infrared deep sky survey
Original article can be found at: http://www.aanda.org/ Copyright The European Southern Observatory (ESO) DOI: 10.1051/0004-6361/200811161Optical and near-infrared (NIR) spectra are presented for ULAS J131911.29+095051.4â(hereafter ULAS J1319+0950), a new redshift z = 6.127 0.004 quasar discovered in the Third Data Release (DR3) of the UKIRT Infrared Deep Sky Survey (UKIDSS). The source has = 19.10 0.03, corresponding to = -27.12, which is comparable to the absolute magnitudes of the z 6 quasars discovered in the Sloan Digital Sky Survey (SDSS). ULAS J1319+0950âwas, in fact, registered by SDSS as a faint source with = 20.13 0.12, just below the signal-to-noise ratio limit of the SDSS high-redshift quasar survey. The faint z-band magnitude is a consequence of the weak Lyâ/NâVâemission line, which has a rest-frame equivalent width of ~20Ă
âand provides only a small boost to the z-band flux. Nevertheless, there is no evidence of a significant new population of high-redshift quasars with weak emission lines from this UKIDSS-based search. The Lyââoptical depth to ULAS J1319+0950âis consistent with that measured towards similarly distant SDSS quasars, implying that results from optical- and NIR-selected quasars may be combined in studies of cosmological reionization. Also presented is a new NIR-spectrum of the previously discovered UKIDSS quasar ULAS J020332.38+001229.2, which reveals the object to be a broad absorption line quasar. The new spectrum shows that the emission line initially identified as Lyââis actually NâV, leading to a revised redshift of z = 5.72, rather than z = 5.86 as previously estimatedPeer reviewe
Harmonic E/B decomposition for CMB polarization maps
The full sky cosmic microwave background polarization field can be decomposed
into 'electric' (E) and 'magnetic' (B) components that are signatures of
distinct physical processes. We give a general construction that achieves
separation of E and B modes on arbitrary sections of the sky at the expense of
increasing the noise. When E modes are present on all scales the separation of
all of the B signal is no longer possible: there are inevitably ambiguous modes
that cannot be separated. We discuss the practicality of performing E/B
decomposition on large scales with realistic non-symmetric sky-cuts, and show
that separation on large scales is possible by retaining only the well
supported modes. The large scale modes potentially contain a great deal of
useful information, and E/B separation at the level of the map is essential for
clean detection of B without confusion from cosmic variance due to the E
signal. We give simple matrix manipulations for creating pure E and B maps of
the large scale signal for general sky cuts. We demonstrate that the method
works well in a realistic case and give estimates of the performance with data
from the Planck satellite. In the appendix we discuss the simple analytic case
of an azimuthally symmetric cut, and show that exact E/B separation is possible
on an azimuthally symmetric cut with a finite number of non-intersecting
circular cuts around foreground sources.Comment: Fixed numerical bug in tensor C_l: Planck detection probability
results updated (supersedes PRD version). Sample code and additional examples
available at http://cosmologist.info/polar
The scientific potential of space-based gravitational wave detectors
The millihertz gravitational wave band can only be accessed with a
space-based interferometer, but it is one of the richest in potential sources.
Observations in this band have amazing scientific potential. The mergers
between massive black holes with mass in the range 10 thousand to 10 million
solar masses, which are expected to occur following the mergers of their host
galaxies, produce strong millihertz gravitational radiation. Observations of
these systems will trace the hierarchical assembly of structure in the Universe
in a mass range that is very difficult to probe electromagnetically. Stellar
mass compact objects falling into such black holes in the centres of galaxies
generate detectable gravitational radiation for several years prior to the
final plunge and merger with the central black hole. Measurements of these
systems offer an unprecedented opportunity to probe the predictions of general
relativity in the strong-field and dynamical regime. Millihertz gravitational
waves are also generated by millions of ultra-compact binaries in the Milky
Way, providing a new way to probe galactic stellar populations. ESA has
recognised this great scientific potential by selecting The Gravitational
Universe as its theme for the L3 large satellite mission, scheduled for launch
in ~2034. In this article we will review the likely sources for millihertz
gravitational wave detectors and describe the wide applications that
observations of these sources could have for astrophysics, cosmology and
fundamental physics.Comment: 18 pages, 2 figures, contribution to Gravitational Wave Astrophysics,
the proceedings of the 2014 Sant Cugat Forum on Astrophysics; v2 includes one
additional referenc
Neutrino Interferometry In Curved Spacetime
Gravitational lensing introduces the possibility of multiple (macroscopic)
paths from an astrophysical neutrino source to a detector. Such a multiplicity
of paths can allow for quantum mechanical interference to take place that is
qualitatively different to neutrino oscillations in flat space. After an
illustrative example clarifying some under-appreciated subtleties of the phase
calculation, we derive the form of the quantum mechanical phase for a neutrino
mass eigenstate propagating non-radially through a Schwarzschild metric. We
subsequently determine the form of the interference pattern seen at a detector.
We show that the neutrino signal from a supernova could exhibit the
interference effects we discuss were it lensed by an object in a suitable mass
range. We finally conclude, however, that -- given current neutrino detector
technology -- the probability of such lensing occurring for a
(neutrino-detectable) supernova is tiny in the immediate future.Comment: 25 pages, 1 .eps figure. Updated version -- with simplified notation
-- accepted for publication in Phys.Rev.D. Extra author adde
The VANDELS ESO public spectroscopic survey
VANDELS is a uniquely deep spectroscopic survey of high-redshift galaxies with the VIMOS spectrograph on ESOâs Very Large Telescope (VLT). The survey has obtained ultradeep optical (0.48 < λ < 1.0 ÎŒ m) spectroscopy of â2100 galaxies within the redshift interval 1.0 †z †7.0, over a total area of â0.2 deg2 centred on the CANDELS Ultra Deep Survey and Chandra Deep Field South fields. Based on accurate photometric redshift pre-selection, 85âperâcent of the galaxies targeted by VANDELS were selected to be at z â„ 3. Exploiting the red sensitivity of the refurbished VIMOS spectrograph, the fundamental aim of the survey is to provide the high-signal-to-noise ratio spectra necessary to measure key physical properties such as stellar population ages, masses, metallicities, and outflow velocities from detailed absorption-line studies. Using integration times calculated to produce an approximately constant signal-to-noise ratio (20 < tint< 80 h), the VANDELS survey targeted: (a) bright star-forming galaxies at 2.4 †z †5.5, (b) massive quiescent galaxies at 1.0 †z †2.5, (c) fainter star-forming galaxies at 3.0 †z †7.0, and (d) X-ray/Spitzer-selected active galactic nuclei and Herschel-detected galaxies. By targeting two extragalactic survey fields with superb multiwavelength imaging data, VANDELS will produce a unique legacy data set for exploring the physics underpinning high-redshift galaxy evolution. In this paper, we provide an overview of the VANDELS survey designed to support the science exploitation of the first ESO public data release, focusing on the scientific motivation, survey design, and target selection
Planck intermediate results V : Pressure profiles of galaxy clusters from the Sunyaev-Zeldovich effect
This article has an erratum: http://dx.doi.org/10.1051/0004-6361/201220040ePeer reviewe
Planck early results. VI. The High Frequency Instrument data processing
We describe the processing of the 336 billion raw data samples from the High Frequency Instrument (HFI) which we performed to produce six
temperature maps from the first 295 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143,
217, 353, 545 and 857GHz with an angular resolution ranging from 9.9 to 4.4 . The white noise level is around 1.5 ÎŒK degree or less in the 3 main
CMB channels (100â217 GHz). The photometric accuracy is better than 2% at frequencies between 100 and 353 GHz and around 7% at the two
highest frequencies. The maps created by the HFI Data Processing Centre reach our goals in terms of sensitivity, resolution, and photometric
accuracy. They are already sufficiently accurate and well-characterised to allow scientific analyses which are presented in an accompanying series
of early papers. At this stage, HFI data appears to be of high quality and we expect that with further refinements of the data processing we should
be able to achieve, or exceed, the science goals of the Planck project
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