195 research outputs found
Clustering of the AKARI NEP deep field 24<i>Ό</i>m selected galaxies
Aims. We present a method of selection of 24 ÎŒm galaxies from the AKARI north ecliptic pole (NEP) deep field down to 150 ÎŒJy and measurements of their two-point correlation function. We aim to associate various 24 ÎŒm selected galaxy populations with present day galaxies and to investigate the impact of their environment on the direction of their subsequent evolution.
Methods. We discuss using of Support Vector Machines (SVM) algorithm applied to infrared photometric data to perform star-galaxy separation, in which we achieve an accuracy higher than 80%. The photometric redshift information, obtained through the CIGALE code, is used to explore the redshift dependence of the correlation function parameter (r0) as well as the linear bias evolution. This parameter relates galaxy distribution to the one of the underlying dark matter. We connect the investigated sources to their potential local descendants through a simplified model of the clustering evolution without interactions.
Results. We observe two different populations of star-forming galaxies, at zmed ⌠0.25, zmed ⌠0.9. Measurements of total infrared luminosities (LTIR) show that the sample at zmed ⌠0.25 is composed mostly of local star-forming galaxies, while the sample at zmed ⌠0.9 is composed of luminous infrared galaxies (LIRGs) with LTIR ⌠1011.62 Lâš. We find that dark halo mass is not necessarily correlated with the LTIR: for subsamples with LTIR = 1011.15 Lâš at zmed ⌠0.7 we observe a higher clustering length (r0 = 6.21 ± 0.78 [hâ1Mpc]) than for a subsample with mean LTIR = 1011.84 Lâš at zmed ⌠1.1 (r0 = 5.86 ± 0.69 hâ1Mpc). We find that galaxies at zmed ⌠0.9 can be ancestors of present day Lâ early type galaxies, which exhibit a very high r0 ⌠8hâ1 Mpc.</p
VIPERS: An Unprecedented View of Galaxies and Large-Scale Structure Halfway Back in the Life of the Universe
The VIMOS Public Extragalactic Redshift Survey (VIPERS) is an ongoing ESO
Large Programme to map in detail the large-scale distribution of galaxies at
0.5 < z <1.2. With a combination of volume and sampling density that is unique
for these redshifts, it focuses on measuring galaxy clustering and related
cosmological quantities as part of the grand challenge of understanding the
origin of cosmic acceleration. VIPERS has also been designed to guarantee a
broader legacy, allowing detailed investigations of the properties and
evolutionary trends of z~1 galaxies. The survey strategy exploits the specific
advantages of the VIMOS spectrograph at the VLT, aiming at a final sample of
nearly 100,000 galaxy redshifts to iAB = 22.5 mag, which represents the largest
redshift survey ever performed with ESO telescopes. In this introductory
article we describe the survey construction, together with early results based
on a first sample of ~55,000 galaxies.Comment: 6 pages, 8 figures; introductory pape
Posture as Index for Approach-Avoidance Behavior
Approach and avoidance are two behavioral responses that make people tend to approach positive and avoid negative situations. This study examines whether postural behavior is influenced by the affective state of pictures. While standing on the Wiiâą Balance Board, participants viewed pleasant, neutral, and unpleasant pictures (passively viewing phase). Then they had to move their body to the left or the right (lateral movement phase) to make the next picture appear. We recorded movements in the anterior-posterior direction to examine approach and avoidant behavior. During passively viewing, people approached pleasant pictures. They avoided unpleasant ones while they made a lateral movement. These findings provide support for the idea that we tend to approach positive and avoid negative situations
Search for Point Sources of High Energy Neutrinos with AMANDA
This paper describes the search for astronomical sources of high-energy
neutrinos using the AMANDA-B10 detector, an array of 302 photomultiplier tubes,
used for the detection of Cherenkov light from upward traveling
neutrino-induced muons, buried deep in ice at the South Pole. The absolute
pointing accuracy and angular resolution were studied by using coincident
events between the AMANDA detector and two independent telescopes on the
surface, the GASP air Cherenkov telescope and the SPASE extensive air shower
array. Using data collected from April to October of 1997 (130.1 days of
livetime), a general survey of the northern hemisphere revealed no
statistically significant excess of events from any direction. The sensitivity
for a flux of muon neutrinos is based on the effective detection area for
through-going muons. Averaged over the Northern sky, the effective detection
area exceeds 10,000 m^2 for E_{mu} ~ 10 TeV. Neutrinos generated in the
atmosphere by cosmic ray interactions were used to verify the predicted
performance of the detector. For a source with a differential energy spectrum
proportional to E_{nu}^{-2} and declination larger than +40 degrees, we obtain
E^2(dN_{nu}/dE) <= 10^{-6}GeVcm^{-2}s^{-1} for an energy threshold of 10 GeV.Comment: 46 pages, 22 figures, 4 tables, submitted to Ap.
Limits on diffuse fluxes of high energy extraterrestrial neutrinos with the AMANDA-B10 detector
Data from the AMANDA-B10 detector taken during the austral winter of 1997
have been searched for a diffuse flux of high energy extraterrestrial
muon-neutrinos, as predicted from, e.g., the sum of all active galaxies in the
universe. This search yielded no excess events above those expected from the
background atmospheric neutrinos, leading to upper limits on the
extraterrestrial neutrino flux. For an assumed E^-2 spectrum, a 90% classical
confidence level upper limit has been placed at a level E^2 Phi(E) = 8.4 x
10^-7 GeV cm^-2 s^-1 sr^-1 (for a predominant neutrino energy range 6-1000 TeV)
which is the most restrictive bound placed by any neutrino detector. When
specific predicted spectral forms are considered, it is found that some are
excluded.Comment: Submitted to Physical Review Letter
Muon Track Reconstruction and Data Selection Techniques in AMANDA
The Antarctic Muon And Neutrino Detector Array (AMANDA) is a high-energy
neutrino telescope operating at the geographic South Pole. It is a lattice of
photo-multiplier tubes buried deep in the polar ice between 1500m and 2000m.
The primary goal of this detector is to discover astrophysical sources of high
energy neutrinos. A high-energy muon neutrino coming through the earth from the
Northern Hemisphere can be identified by the secondary muon moving upward
through the detector. The muon tracks are reconstructed with a maximum
likelihood method. It models the arrival times and amplitudes of Cherenkov
photons registered by the photo-multipliers. This paper describes the different
methods of reconstruction, which have been successfully implemented within
AMANDA. Strategies for optimizing the reconstruction performance and rejecting
background are presented. For a typical analysis procedure the direction of
tracks are reconstructed with about 2 degree accuracy.Comment: 40 pages, 16 Postscript figures, uses elsart.st
The IceCube Neutrino Observatory: Instrumentation and Online Systems
The IceCube Neutrino Observatory is a cubic-kilometer-scale high-energy
neutrino detector built into the ice at the South Pole. Construction of
IceCube, the largest neutrino detector built to date, was completed in 2011 and
enabled the discovery of high-energy astrophysical neutrinos. We describe here
the design, production, and calibration of the IceCube digital optical module
(DOM), the cable systems, computing hardware, and our methodology for drilling
and deployment. We also describe the online triggering and data filtering
systems that select candidate neutrino and cosmic ray events for analysis. Due
to a rigorous pre-deployment protocol, 98.4% of the DOMs in the deep ice are
operating and collecting data. IceCube routinely achieves a detector uptime of
99% by emphasizing software stability and monitoring. Detector operations have
been stable since construction was completed, and the detector is expected to
operate at least until the end of the next decade.Comment: 83 pages, 50 figures; updated with minor changes from journal review
and proofin
Limits to the muon flux from WIMP annihilation in the center of the Earth with the AMANDA detector
A search for nearly vertical up-going muon-neutrinos from neutralino
annihilations in the center of the Earth has been performed with the AMANDA-B10
neutrino detector. The data sample collected in 130.1 days of live-time in
1997, ~10^9 events, has been analyzed for this search. No excess over the
expected atmospheric neutrino background is oberved. An upper limit at 90%
confidence level on the annihilation rate of neutralinos in the center of the
Earth is obtained as a function of the neutralino mass in the range 100
GeV-5000 GeV, as well as the corresponding muon flux limit.Comment: 14 pages, 11 figures. Version accepted for publication in Physical
Review
IceCube - the next generation neutrino telescope at the South Pole
IceCube is a large neutrino telescope of the next generation to be
constructed in the Antarctic Ice Sheet near the South Pole. We present the
conceptual design and the sensitivity of the IceCube detector to predicted
fluxes of neutrinos, both atmospheric and extra-terrestrial. A complete
simulation of the detector design has been used to study the detector's
capability to search for neutrinos from sources such as active galaxies, and
gamma-ray bursts.Comment: 8 pages, to be published with the proceedings of the XXth
International Conference on Neutrino Physics and Astrophysics, Munich 200
Approach and Avoidance Tendencies in Spider Fearful Children: The Approach-Avoidance Task
Fear in children is associated with the tendency to avoid situations related to the fear. In this study, the Approach-Avoidance Task (AAT) was evaluated as a test of automatic behavioral avoidance tendencies in children. A sample of 195 children aged between 9 and 12Â years completed an AAT, a Behavioral Assessment Task (BAT), and two spider fear questionnaires. The results indicate that all children showed an automatic avoidance tendency in response to spider pictures, but not pictures of butterflies or neutral pictures. Girls who reported more fear of spiders on the self-reports and behaved more anxiously during the BAT also showed a greater avoidance tendency in the AAT. These relationships were absent in boys
- âŠ