5,530 research outputs found
A 12 μm ISOCAM survey of the ESO-Sculptor field
We present a detailed reduction of a mid-infrared 12 μm (LW10 filter) ISOCAM open time observation performed on the ESOSculptor
Survey field (Arnouts et al. 1997, A&AS, 124, 163). A complete catalogue of 142 sources (120 galaxies and 22 stars),
detected with high significance (equivalent to 5σ), is presented above an integrated flux density of 0.24 mJy. Star/galaxy separation
is performed by a detailed study of colour-colour diagrams. The catalogue is complete to 1 mJy and, below this flux density, the
incompleteness is corrected using two independent methods. The first method uses stars and the second uses optical counterparts of
the ISOCAM galaxies; these methods yield consistent results. We also apply an empirical flux density calibration using stars in the
field. For each star, the 12 μm flux density is derived by fitting optical colours from a multi-band χ^2 to stellar templates (BaSel-2.0)
and using empirical optical-IR colour-colour relations. This article is a companion analysis to our 2007 paper (Rocca-Volmerange
et al. 2007, A&A, 475, 801) where the 12 μm faint galaxy counts are presented and analysed per galaxy type with the evolutionary
code PÉGASE.3
The 12 μm ISO-ESO-Sculptor and 24 μm Spitzer faint counts reveal a population of ULIRGs as dusty massive ellipticals: Evolution by types and cosmic star formation
Context. Multi-wavelength galaxy number counts provide clues to the nature of galaxy evolution. The interpretation per galaxy type of
the mid-IR faint counts obtained with ISO and Spitzer, consistent with the analysis of deep UV-optical-near IR galaxy counts, provide
new constraints on the dust and stellar emission. Discovering the nature of new populations, such as high redshift ultra-luminous
(≥10^(12) L_⊙) infrared galaxies (ULIRGs), is also crucial for understanding galaxy evolution at high redshifts.
Aims. We first present the faint galaxy counts at 12 μm from the catalogue of the ISO-ESO-Sculptor Survey (ISO-ESS) published in a
companion article (Seymour et al. 2007a, A&A, 475, 791). They go down to 0.31 mJy after corrections for incompleteness. We verify
the consistency with the existing ISO number counts at 15 μm. Then we analyse the 12 μm (ISO-ESS) and the 24 μm (Spitzer) faint
counts, to constrain the nature of ULIRGs, the cosmic star formation history and time scales for mass buildup.
Methods. We show that the “normal” scenarios in our evolutionary code PÉGASE, which had previously fitted the deep UV-opticalnear
IR counts, are unsuccessful at 12 μm and 24 μm. We thus propose a new ULIRG scenario adjusted to the observed cumulative
and differential 12 μm and 24 μm counts and based on observed 12 μm and 25 μm IRAS luminosity functions and evolutionary
optical/mid-IR colours from PÉGASE.
Results. We succeed in simultaneously modelling the typical excess observed at 12 μm, 15 μm (ISO), and 24 μm (Spitzer) in the
cumulative and differential counts by only changing 9% of normal galaxies (1/3 of the ellipticals) into ultra-bright dusty galaxies
evolving as ellipticals, and interpreted as distant ULIRGs. These objects present similarities with the population of radio-galaxy hosts
at high redshift. No number density evolution is included in our models even if minor starbursts due to galaxy interactions remain
compatible with our results.
Conclusions. Higher spectral and spatial resolution in the mid-IR, together with submillimeter observations using the future Herschel
observatory, will be useful to confirm these results
The 12 μm ISO-ESO-Sculptor and 24 μm Spitzer faint counts reveal a population of ULIRGs as dusty massive ellipticals: Evolution by types and cosmic star formation
Context. Multi-wavelength galaxy number counts provide clues to the nature of galaxy evolution. The interpretation per galaxy type of
the mid-IR faint counts obtained with ISO and Spitzer, consistent with the analysis of deep UV-optical-near IR galaxy counts, provide
new constraints on the dust and stellar emission. Discovering the nature of new populations, such as high redshift ultra-luminous
(≥10^(12) L_⊙) infrared galaxies (ULIRGs), is also crucial for understanding galaxy evolution at high redshifts.
Aims. We first present the faint galaxy counts at 12 μm from the catalogue of the ISO-ESO-Sculptor Survey (ISO-ESS) published in a
companion article (Seymour et al. 2007a, A&A, 475, 791). They go down to 0.31 mJy after corrections for incompleteness. We verify
the consistency with the existing ISO number counts at 15 μm. Then we analyse the 12 μm (ISO-ESS) and the 24 μm (Spitzer) faint
counts, to constrain the nature of ULIRGs, the cosmic star formation history and time scales for mass buildup.
Methods. We show that the “normal” scenarios in our evolutionary code PÉGASE, which had previously fitted the deep UV-opticalnear
IR counts, are unsuccessful at 12 μm and 24 μm. We thus propose a new ULIRG scenario adjusted to the observed cumulative
and differential 12 μm and 24 μm counts and based on observed 12 μm and 25 μm IRAS luminosity functions and evolutionary
optical/mid-IR colours from PÉGASE.
Results. We succeed in simultaneously modelling the typical excess observed at 12 μm, 15 μm (ISO), and 24 μm (Spitzer) in the
cumulative and differential counts by only changing 9% of normal galaxies (1/3 of the ellipticals) into ultra-bright dusty galaxies
evolving as ellipticals, and interpreted as distant ULIRGs. These objects present similarities with the population of radio-galaxy hosts
at high redshift. No number density evolution is included in our models even if minor starbursts due to galaxy interactions remain
compatible with our results.
Conclusions. Higher spectral and spatial resolution in the mid-IR, together with submillimeter observations using the future Herschel
observatory, will be useful to confirm these results
Gamma Ray Burst Host Galaxies Have `Normal' Luminosities
The galactic environment of Gamma Ray Bursts can provide good evidence about
the nature of the progenitor system, with two old arguments implying that the
burst host galaxies are significantly subluminous. New data and new analysis
have now reversed this picture: (A) Even though the first two known host
galaxies are indeed greatly subluminous, the next eight hosts have absolute
magnitudes typical for a population of field galaxies. A detailed analysis of
the 16 known hosts (ten with red shifts) shows them to be consistent with a
Schechter luminosity function with as expected for
normal galaxies. (B) Bright bursts from the Interplanetary Network are
typically 18 times brighter than the faint bursts with red shifts, however the
bright bursts do not have galaxies inside their error boxes to limits deeper
than expected based on the luminosities for the two samples being identical. A
new solution to this dilemma is that a broad burst luminosity function along
with a burst number density varying as the star formation rate will require the
average luminosity of the bright sample (
or ) to be much greater than the
average luminosity of the faint sample ( or ). This places the bright bursts at distances
for which host galaxies with a normal luminosity will not violate the observed
limits. In conclusion, all current evidence points to GRB host galaxies being
normal in luminosity.Comment: 18 pages, 3 figures, Submitted to ApJLet
Deepest Near-IR Surface Photometry of Galaxies in the Local Sphere of Influence
We present near-IR, deep (4 mag deeper than 2MASS) imaging of 56 Local Volume
galaxies. Global parameters such as total magnitudes and stellar masses have
been derived and the new near-IR data combined with existing 21cm and optical
B-band data. We present multiwavelength relations such as the HI mass-to-light
ratio and investigate the maximum total baryonic mass a galaxy can have.Comment: 4 pages, 3 figures, To be published in the proceedings of "Galaxies
in the Local Volume", ed. B. Koribalski, H. Jerje
Human brain distinctiveness based on EEG spectral coherence connectivity
The use of EEG biometrics, for the purpose of automatic people recognition,
has received increasing attention in the recent years. Most of current analysis
rely on the extraction of features characterizing the activity of single brain
regions, like power-spectrum estimates, thus neglecting possible temporal
dependencies between the generated EEG signals. However, important
physiological information can be extracted from the way different brain regions
are functionally coupled. In this study, we propose a novel approach that fuses
spectral coherencebased connectivity between different brain regions as a
possibly viable biometric feature. The proposed approach is tested on a large
dataset of subjects (N=108) during eyes-closed (EC) and eyes-open (EO) resting
state conditions. The obtained recognition performances show that using brain
connectivity leads to higher distinctiveness with respect to power-spectrum
measurements, in both the experimental conditions. Notably, a 100% recognition
accuracy is obtained in EC and EO when integrating functional connectivity
between regions in the frontal lobe, while a lower 97.41% is obtained in EC
(96.26% in EO) when fusing power spectrum information from centro-parietal
regions. Taken together, these results suggest that functional connectivity
patterns represent effective features for improving EEG-based biometric
systems.Comment: Key words: EEG, Resting state, Biometrics, Spectral coherence, Match
score fusio
Measurement of the current-phase relation of superconducting atomic contacts
We have probed the current-phase relation of an atomic contact placed with a
tunnel junction in a small superconducting loop. The measurements are in
quantitative agreement with the predictions of a resistively shunted SQUID
model in which the Josephson coupling of the contact is calculated using the
independently determined transmissions of its conduction channels.Comment: to be published in Physical Review Letter
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