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Automated Measurement of Spatially Resolved Hair-Hair Single Fiber Adhesion.
The adhesion force between individual human hair fibers in a crosshair geometry was measured by observing their natural bending and adhesive jumps out of contact, using optical video microscopy. The hair fibers' natural elastic responses, calibrated by measuring their natural resonant frequencies, were used to measure the forces. Using a custom-designed, automated apparatus to measure thousands of individual hair-hair contacts along millimeter length scales of hair, it was found that a broad, yet characteristic, spatially variant distribution in adhesion force is measured on the 1 to 1000 nN scale for both clean and conditioner-treated hair fibers. Comparison between the measured adhesion forces and adhesion forces modeled from the hairs' surface topography (measured using confocal laser profilometry) shows they have a good order-of-magnitude agreement and have similar breadth and shape. The agreement between the measurements and the model suggests, perhaps unsurprisingly, that hair-hair adhesion is governed, to a first approximation, by the unique surface structure of the hairs' cuticles and, therefore, the large distribution in local mean curvature at the various individual contact points along the hairs' lengths. We posit that haircare products could best control the surface properties (or at least the adhesive properties) between hairs by directly modifying the hair surface microstructure
Bragg spectroscopy with an accelerating Bose-Einstein condensate
We present the results of Bragg spectroscopy performed on an accelerating
Bose-Einstein condensate. The Bose condensate undergoes circular micro-motion
in a magnetic TOP trap and the effect of this motion on the Bragg spectrum is
analyzed. A simple frequency modulation model is used to interpret the observed
complex structure, and broadening effects are considered using numerical
solutions to the Gross-Pitaevskii equation.Comment: 5 pages, 3 figures, to appear in PRA. Minor changes to text and fig
The early spectral evolution of SN 2004dt
Aims. We study the optical spectroscopic properties of Type Ia Supernova (SN
Ia) 2004dt, focusing our attention on the early epochs.
Methods. Observation triggered soon after the SN 2004dt discovery allowed us
to obtain a spectrophotometric coverage from day -10 to almost one year (~353
days) after the B band maximum. Observations carried out on an almost daily
basis allowed us a good sampling of the fast spectroscopic evolution of SN
2004dt in the early stages. To obtain this result, low-resolution, long-slit
spectroscopy was obtained using a number of facilities.
Results. This supernova, which in some absorption lines of its early spectra
showed the highest degree of polarization ever measured in any SN Ia, has a
complex velocity structure in the outer layers of its ejecta. Unburnt oxygen is
present, moving at velocities as high as ~16,700 km/s, with some
intermediate-mass elements (Mg, Si, Ca) moving equally fast. Modeling of the
spectra based on standard density profiles of the ejecta fails to reproduce the
observed features, whereas enhancing the density of outer layers significantly
improves the fit. Our analysis indicates the presence of clumps of
high-velocity, intermediate-mass elements in the outermost layers, which is
also suggested by the spectropolarimetric data.Comment: 13 pages, 15 figures, accepted for pubblication in Astronomy and
Astrophysic
The Spectroscopic Diversity of Type Ia Supernovae
We present 2603 spectra of 462 nearby Type Ia supernovae (SN Ia) obtained
during 1993-2008 through the Center for Astrophysics Supernova Program. Most of
the spectra were obtained with the FAST spectrograph at the FLWO 1.5m telescope
and reduced in a consistent manner, making data set well suited for studies of
SN Ia spectroscopic diversity. We study the spectroscopic and photometric
properties of SN Ia as a function of spectroscopic class using the
classification schemes of Branch et al. and Wang et al. The width-luminosity
relation appears to be steeper for SN Ia with broader lines. Based on the
evolution of the characteristic Si II 6355 line, we propose improved methods
for measuring velocity gradients, revealing a larger range than previously
suspected, from ~0 to ~400 km/s/day considering the instantaneous velocity
decline rate at maximum light. We find a weaker and less significant
correlation between Si II velocity and intrinsic B-V color at maximum light
than reported by Foley et al., owing to a more comprehensive treatment of
uncertainties and host galaxy dust. We study the extent of nuclear burning and
report new detections of C II 6580 in 23 early-time spectra. The frequency of C
II detections is not higher in SN Ia with bluer colors or narrower light
curves, in conflict with the recent results of Thomas et al. Based on nebular
spectra of 27 SN Ia, we find no relation between the FWHM of the iron emission
feature at ~4700 A and Dm15(B) after removing the two low-luminosity SN 1986G
and SN 1991bg, suggesting that the peak luminosity is not strongly dependent on
the kinetic energy of the explosion for most SN Ia. Finally, we confirm the
correlation of velocity shifts in some nebular lines with the intrinsic B-V
color of SN Ia at maximum light, although several outliers suggest a possible
non-monotonic behavior for the largest blueshifts.Comment: 36 pages (emulateapj), 23 figures. Accepted for publication in AJ.
Spectroscopic data available at
http://www.cfa.harvard.edu/supernova/SNarchive.html . New SNID template set
available at http://marwww.in2p3.fr/~blondin/software/snid/index.html . Minor
changes from v1 to conform to published versio
Prospects of observing a quasar HII region during the Epoch of Reionization with redshifted 21cm
We present a study of the impact of a bright quasar on the redshifted 21cm
signal during the Epoch of Reionization (EoR). Using three different
cosmological radiative transfer simulations, we investigate if quasars are
capable of substantially changing the size and morphology of the H II regions
they are born in. We choose stellar and quasar luminosities in a way that is
favourable to seeing such an effect. We find that even the most luminous of our
quasar models is not able to increase the size of its native H II region
substantially beyond those of large H II regions produced by clustered stellar
sources alone. However, the quasar H II region is found to be more spherical.
We next investigate the prospects of detecting such H II regions in the
redshifted 21cm data from the Low Frequency Array (LOFAR) by means of a matched
filter technique. We find that H II regions with radii ~ 25 comoving Mpc or
larger should have a sufficiently high detection probability for 1200 hours of
integration time. Although the matched filter can in principle distinguish
between more and less spherical regions, we find that when including realistic
system noise this distinction can no longer be made. The strong foregrounds are
found not to pose a problem for the matched filter technique. We also
demonstrate that when the quasar position is known, the redshifted 21cm data
can still be used to set upper limits on the ionizing photon rate of the
quasar. If both the quasar position and its luminosity are known, the
redshifted 21 cm data can set new constrains on quasar lifetimes.Comment: 17 pages, 12 figures, 3 tables, accepted for publication in MNRAS;
changes in introduction and figure
The Intergalactic medium transmission towards z>4 galaxies with VANDELS and the impact of dust attenuation
International audienceAims. Our aim is to estimate the intergalactic medium (IGM) transmission towards UV-selected star-forming galaxies at z ≳ 4 and study the effect of the dust attenuation on these measurements.Methods. The UV spectrum of high-redshift galaxies is a combination of their intrinsic emission and the effect of the IGM absorption along their line of sight. Using data coming from the unprecedentedly deep spectroscopy from the VANDELS ESO public survey carried out with the VIMOS instrument, we compute both the dust extinction and the mean transmission of the IGM as well as its scatter from a set of 281 galaxies at z > 3.87. Because of a degeneracy between the dust content of the galaxy and the IGM, we first estimate the stellar dust extinction parameter E(B − V) and study the result as a function of the dust prescription. Using these measurements as constraint for the spectral fit we estimate the IGM transmission Tr(Lyα). Both photometric and spectroscopic spectral energy distribution fits are performed using the SPectroscopy And photometRy fiTting tool for Astronomical aNalysis which is able to fit the spectral continuum of the galaxies as well as photometric data.Results. Using the classical Calzetti attenuation law we find that E(B − V) goes from 0.11 at z = 3.99 to 0.08 at z = 5.15. These results are in very close agreement with published measurements. We estimate the IGM transmission and find that the transmission is decreasing with increasing redshift from Tr(Lyα) = 0.53 at z = 3.99 to 0.28 at z = 5.15. We also find a large standard deviation around the average transmission that is more than 0.1 at every redshift. Our results are in very good agreement with both previous measurements from AGN studies and with theoretical models.Key words: galaxies: high-redshift / galaxies: general / intergalactic medium⋆ Based on observations made with ESO Telescopes at the La Silla or Paranal Observatories under programme ID(s) 194.A-2003
Less and more IGM-transmitted galaxies from z ∼2.7 to z ∼6 from VANDELS and VUDS
Aims. Our aim is to analyze the variance of the intergalactic medium (IGM) transmission by studying this parameter in the rest-frame UV spectra of a large sample of high-redshift galaxies. Methods. We made use of the VIMOS Ultra Deep Survey and the VANDELS public survey to gain insight into the far UV spectrum of 2.7 < z < 6 galaxies. Using the SPARTAN fitting software, we estimated the IGM toward individual galaxies and then divided them into two sub-samples characterized by a transmission above or below the theoretical prescription. We created average spectra of combined VUDS and VANDELS data for each set of galaxies in seven redshift bins. Results. The resulting spectra clearly exhibit the variance of the IGM transmission that can be seen directly from high-redshift galaxy observations. Computing the optical depth based on the IGM transmission, we find an excellent agreement with results for quasi-stellar objects. In addition, our measurements appear to suggest that there is a large dispersion of redshift where a complete Gunn-Peterson Trough occurs, depending on the line of sight
The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
The Sloan Digital Sky Survey III (SDSS-III) presents the first spectroscopic
data from the Baryon Oscillation Spectroscopic Survey (BOSS). This ninth data
release (DR9) of the SDSS project includes 535,995 new galaxy spectra (median
z=0.52), 102,100 new quasar spectra (median z=2.32), and 90,897 new stellar
spectra, along with the data presented in previous data releases. These spectra
were obtained with the new BOSS spectrograph and were taken between 2009
December and 2011 July. In addition, the stellar parameters pipeline, which
determines radial velocities, surface temperatures, surface gravities, and
metallicities of stars, has been updated and refined with improvements in
temperature estimates for stars with T_eff<5000 K and in metallicity estimates
for stars with [Fe/H]>-0.5. DR9 includes new stellar parameters for all stars
presented in DR8, including stars from SDSS-I and II, as well as those observed
as part of the SDSS-III Sloan Extension for Galactic Understanding and
Exploration-2 (SEGUE-2).
The astrometry error introduced in the DR8 imaging catalogs has been
corrected in the DR9 data products. The next data release for SDSS-III will be
in Summer 2013, which will present the first data from the Apache Point
Observatory Galactic Evolution Experiment (APOGEE) along with another year of
data from BOSS, followed by the final SDSS-III data release in December 2014.Comment: 9 figures; 2 tables. Submitted to ApJS. DR9 is available at
http://www.sdss3.org/dr
The VANDELS ESO public spectroscopic survey : Final Data Release of 2087 spectra and spectroscopic measurements
© ESO 2021. The original publication is available at https://doi.org/10.1051/0004-6361/202040059VANDELS is an ESO Public Spectroscopic Survey designed to build a sample of high signal to noise, medium resolution spectra of galaxies at redshift between 1 and 6.5. Here we present the final Public Data Release of the VANDELS Survey, comprising 2087 redshift measurements. We give a detailed description of sample selection, observations and data reduction procedures. The final catalogue reaches a target selection completeness of 40% at iAB = 25. The high Signal to Noise ratio of the spectra (above 7 in 80% of the spectra) and the dispersion of 2.5{\AA} allowed us to measure redshifts with high precision, the redshift measurement success rate reaching almost 100%. Together with the redshift catalogue and the reduced spectra, we also provide optical mid-IR photometry and physical parameters derived through SED fitting. The observed galaxy sample comprises both passive and star forming galaxies covering a stellar mass range 8.3<Log(M*/Msolar)Peer reviewe
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