352 research outputs found
Giant disk galaxies : Where environment trumps mass in galaxy evolution
We identify some of the most HI massive and fastest rotating disk galaxies in
the local universe with the aim of probing the processes that drive the
formation of these extreme disk galaxies. By combining data from the Cosmic
Flows project, which has consistently reanalyzed archival galaxy HI profiles,
and 3.6m photometry obtained with the Spitzer Space Telescope, with which
we can measure stellar mass, we use the baryonic Tully-Fisher (BTF)
relationship to explore whether these massive galaxies are distinct. We discuss
several results, but the most striking is the systematic offset of the
HI-massive sample above the BTF. These galaxies have both more gas and more
stars in their disks than the typical disk galaxy of similar rotational
velocity. The "condensed" baryon fraction, , the fraction of the baryons
in a dark matter halo that settle either as cold gas or stars into the disk, is
twice as high in the HI-massive sample than typical, and almost reaches the
universal baryon fraction in some cases, suggesting that the most extreme of
these galaxies have little in the way of a hot baryonic component or cold
baryons distributed well outside the disk. In contrast, the star formation
efficiency, measured as the ratio of the mass in stars to that in both stars
and gas, shows no difference between the HI-massive sample and the typical disk
galaxies. We conclude that the star formation efficiency is driven by an
internal, self-regulating process, while is affected by external factors.
We also found that the most massive HI detected galaxies are located
preferentially in filaments. We present the first evidence of an environmental
effect on galaxy evolution using a dynamical definition of a filament.Comment: 14 pages, in press MNRA
From Spitzer Galaxy Photometry to Tully-Fisher Distances
This paper involves a data release of the observational campaign: Cosmicflows
with Spitzer (CFS). Surface photometry of the 1270 galaxies constituting the
survey is presented. An additional ~ 400 galaxies from various other Spitzer
surveys are also analyzed. CFS complements the Spitzer Survey of Stellar
Structure in Galaxies, that provides photometry for an additional 2352
galaxies, by extending observations to low galactic latitudes (|b|<30 degrees).
Among these galaxies are calibrators, selected in K band, of the Tully-Fisher
relation. The addition of new calibrators demonstrate the robustness of the
previously released calibration. Our estimate of the Hubble constant using
supernova host galaxies is unchanged, H0 = 75.2 +/- 3.3 km/s/Mpc.
Distance-derived radial peculiar velocities, for the 1935 galaxies with all the
available parameters, will be incorporated into a new data release of the
Cosmicflows project. The size of the previous catalog will be increased by 20%,
including spatial regions close to the Zone of Avoidance.Comment: Accepted for publication in MNRAS, 16 pages, 14 figures, 6 table
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Galaxies are observational probes to study the Large Scale Structure. Their gravitational motions are tracers of the total matter density and therefore of the Large Scale Structure. Besides, studies of structure formation and galaxy evolution rely on numerical cosmological simulations. Still, only one universe observable from a given position, in time and space, is available for comparisons with simulations. The related cosmic variance affects our ability to interpret the results. Simulations constrained by observational data are a perfect remedy to this problem. Achieving such simulations requires the projects Cosmic ows and CLUES. Cosmic ows builds catalogs of accurate distance measurements to map deviations from the expansion. These measures are mainly obtained with the galaxy luminosity-rotation rate correlation. We present the calibration of that relation in the mid-infrared with observational data from Spitzer Space Telescope. Resulting accurate distance estimates will be included in the third catalog of the project. In the meantime, two catalogs up to 30 and 150 h-1 Mpc have been released. We report improvements and applications of the CLUES' method on these two catalogs. The technique is based on the constrained realization algorithm. The cosmic displacement field is computed with the Zel'dovich approximation. This latter is then reversed to relocate reconstructed three-dimensional constraints to their precursors' positions in the initial field. The size of the second catalog (8000 galaxies within 150 h-1 Mpc)highlighted the importance of minimizing the observational biases. By carrying out tests on mock catalogs, built from cosmological simulations, a method to minimize observational bias can be derived. Finally, for the frst time, cosmological simulations are constrained solely by peculiar velocities. The process is successful as resulting simulations resemble the Local Universe. The major attractors and voids are simulated at positions approaching observational positions by a few megaparsecs, thus reaching the limit imposed by the linear theory.Les galaxies sont des sondes observationnelles pour l'étude des structures de l'Univers. Leur mouvement gravitationnel permet de tracer la densité totale de matière. Par ailleurs, l'étude de la formation des structures et galaxies s'appuie sur les simulations numériques cosmologiques. Cependant, un seul univers observable à partir d'une position donnée, en temps et espace, est disponible pour comparaison avec les simulations. La variance cosmique associée affecte notre capacité à interpréter les résultats. Les simulations contraintes par les données observationnelles constituent une solution optimale au problème. Réaliser de telles simulations requiert les projets Cosmic ows et CLUES. Cosmic ows construit des catalogues de mesures de distances précises afin d'obtenir les déviations de l'expansion. Ces mesures sont principalement obtenues avec la corrélation entre la luminosité des galaxies et la vitesse de rotation de leur gaz. La calibration de cette relation est présentée dans le mi-infrarouge avec les observations du telescope spatial Spitzer. Les estimations de distances résultantes seront intégrées au troisième catalogue de données du projet. En attendant, deux catalogues de mesures atteignant 30 et 150 h-1 Mpc ont été publiés. Les améliorations et applications de la méthode du projet CLUES sur les deux catalogues sont présentées. La technique est basée sur l'algorithme de réalisation contrainte. L'approximation de Zel'dovich permet de calculer le champ de déplacement cosmique. Son inversion repositionne les contraintes tridimensionnelles reconstruites à l'emplacement de leur précurseur dans le champ initial. La taille inégalée, 8000 galaxies jusqu'à une distance de 150 h-1 Mpc, du second catalogue a mis en évidence l'importance de minimiser les biais observationnels. En réalisant des tests sur des catalogues de similis, issus des simulations cosmologiques, une méthode de minimisation des biais peut être dérivée. Finalement, pour la première fois, des simulations cosmologiques sont contraintes uniquement par des vitesses particulières de galaxies. Le procédé est une réussite car les simulations obtenues ressemblent à l'Univers Local. Les principaux attracteurs et vides sont simulés à des positions approchant de quelques mégaparsecs les positions observationnelles, atteignant ainsi la limite fixée par la théorie linéeaire
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Galaxies are observational probes to study the Large Scale Structure. Their gravitational motions are tracers of the total matter density and therefore of the Large Scale Structure. Besides, studies of structure formation and galaxy evolution rely on numerical cosmological simulations. Still, only one universe observable from a given position, in time and space, is available for comparisons with simulations. The related cosmic variance affects our ability to interpret the results. Simulations constrained by observational data are a perfect remedy to this problem. Achieving such simulations requires the projects Cosmic ows and CLUES. Cosmic ows builds catalogs of accurate distance measurements to map deviations from the expansion. These measures are mainly obtained with the galaxy luminosity-rotation rate correlation. We present the calibration of that relation in the mid-infrared with observational data from Spitzer Space Telescope. Resulting accurate distance estimates will be included in the third catalog of the project. In the meantime, two catalogs up to 30 and 150 h-1 Mpc have been released. We report improvements and applications of the CLUES' method on these two catalogs. The technique is based on the constrained realization algorithm. The cosmic displacement field is computed with the Zel'dovich approximation. This latter is then reversed to relocate reconstructed three-dimensional constraints to their precursors' positions in the initial field. The size of the second catalog (8000 galaxies within 150 h-1 Mpc)highlighted the importance of minimizing the observational biases. By carrying out tests on mock catalogs, built from cosmological simulations, a method to minimize observational bias can be derived. Finally, for the frst time, cosmological simulations are constrained solely by peculiar velocities. The process is successful as resulting simulations resemble the Local Universe. The major attractors and voids are simulated at positions approaching observational positions by a few megaparsecs, thus reaching the limit imposed by the linear theory.Les galaxies sont des sondes observationnelles pour l'étude des structures de l'Univers. Leur mouvement gravitationnel permet de tracer la densité totale de matière. Par ailleurs, l'étude de la formation des structures et galaxies s'appuie sur les simulations numériques cosmologiques. Cependant, un seul univers observable à partir d'une position donnée, en temps et espace, est disponible pour comparaison avec les simulations. La variance cosmique associée affecte notre capacité à interpréter les résultats. Les simulations contraintes par les données observationnelles constituent une solution optimale au problème. Réaliser de telles simulations requiert les projets Cosmic ows et CLUES. Cosmic ows construit des catalogues de mesures de distances précises afin d'obtenir les déviations de l'expansion. Ces mesures sont principalement obtenues avec la corrélation entre la luminosité des galaxies et la vitesse de rotation de leur gaz. La calibration de cette relation est présentée dans le mi-infrarouge avec les observations du telescope spatial Spitzer. Les estimations de distances résultantes seront intégrées au troisième catalogue de données du projet. En attendant, deux catalogues de mesures atteignant 30 et 150 h-1 Mpc ont été publiés. Les améliorations et applications de la méthode du projet CLUES sur les deux catalogues sont présentées. La technique est basée sur l'algorithme de réalisation contrainte. L'approximation de Zel'dovich permet de calculer le champ de déplacement cosmique. Son inversion repositionne les contraintes tridimensionnelles reconstruites à l'emplacement de leur précurseur dans le champ initial. La taille inégalée, 8000 galaxies jusqu'à une distance de 150 h-1 Mpc, du second catalogue a mis en évidence l'importance de minimiser les biais observationnels. En réalisant des tests sur des catalogues de similis, issus des simulations cosmologiques, une méthode de minimisation des biais peut être dérivée. Finalement, pour la première fois, des simulations cosmologiques sont contraintes uniquement par des vitesses particulières de galaxies. Le procédé est une réussite car les simulations obtenues ressemblent à l'Univers Local. Les principaux attracteurs et vides sont simulés à des positions approchant de quelques mégaparsecs les positions observationnelles, atteignant ainsi la limite fixée par la théorie linéeaire
The Calibration of the WISE W1 and W2 Tully-Fisher Relation
In order to explore local large-scale structures and velocity fields,
accurate galaxy distance measures are needed. We now extend the well-tested
recipe for calibrating the correlation between galaxy rotation rates and
luminosities -- capable of providing such distance measures -- to the all-sky,
space-based imaging data from the Wide-field Infrared Survey Explorer (WISE) W1
(m) and W2 (m) filters. We find a linewidth to absolute
magnitude correlation (known as the Tully-Fisher Relation, TFR) of
(0.54
magnitudes rms) and (0.56 magnitudes rms) from 310 galaxies in 13 clusters. We update the
I-band TFR using a sample 9% larger than in Tully & Courtois (2012). We derive
(0.46 magnitudes
rms). The WISE TFRs show evidence of curvature. Quadratic fits give
(0.52 magnitudes rms) and (0.55
magnitudes rms). We apply an I-band -- WISE color correction to lower the
scatter and derive
and (both 0.46
magnitudes rms). Using our three independent TFRs (W1 curved, W2 curved and
I-band), we calibrate the UNION2 supernova Type Ia sample distance scale and
derive (stat) (sys) kms Mpc with 4%
total error.Comment: 22 page, 21 figures, accepted to ApJ, Table 1 data at
http://spartan.srl.caltech.edu/~neill/tfwisecal/table1.tx
Cosmicflows-2: The Data
Cosmicflows-2 is a compilation of distances and peculiar velocities for over
8000 galaxies. Numerically the largest contributions come from the
luminosity-linewidth correlation for spirals, the TFR, and the related
Fundamental Plane relation for E/S0 systems, but over 1000 distances are
contributed by methods that provide more accurate individual distances:
Cepheid, Tip of the Red Giant Branch, Surface Brightness Fluctuation, SNIa, and
several miscellaneous but accurate procedures. Our collaboration is making
important contributions to two of these inputs: Tip of the Red Giant Branch and
TFR. A large body of new distance material is presented. In addition, an effort
is made to assure that all the contributions, our own and those from the
literature, are on the same scale. Overall, the distances are found to be
compatible with a Hubble Constant H_0 = 74.4 +-3.0 km/s/Mpc. The great interest
going forward with this data set will be with velocity field studies.
Cosmicflows-2 is characterized by a great density and high accuracy of distance
measures locally, falling to sparse and coarse sampling extending to z=0.1.Comment: To be published in Astronomical Journal. Two extensive tables to be
available on-line. Table 1 available at http://edd.ifa.hawaii.edu select
catalog `Cosmicflows-2 Distances
Uncertainty analysis technique for OMEGA Dante measurements
The Dante is an 18 channel X-ray filtered diode array which records the spectrally and temporally resolved radiation flux from various targets (e.g. hohlraums, etc.) at X-ray energies between 50 eV to 10 keV. It is a main diagnostics installed on the OMEGA laser facility at the Laboratory for Laser Energetics, University of Rochester. The absolute flux is determined from the photometric calibration of the X-ray diodes, filters and mirrors and an unfold algorithm. Understanding the errors on this absolute measurement is critical for understanding hohlraum energetic physics. We present a new method for quantifying the uncertainties on the determined flux using a Monte-Carlo parameter variation technique. This technique combines the uncertainties in both the unfold algorithm and the error from the absolute calibration of each channel into a one sigma Gaussian error function. One thousand test voltage sets are created using these error functions and processed by the unfold algorithm to produce individual spectra and fluxes. Statistical methods are applied to the resultant set of fluxes to estimate error bars on the measurements
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Thomson scattering techniques in laser produced plasmas
Thomson scattering has been shown to be a valuable technique for measuring the plasma conditions in laser produced plasmas. Measurement techniques are discussed that use the ion-acoustic frequency measured from the collective Thomson-scattering spectrum to extract the electron temperature, ion temperature, plasma flow, and electron density in a laser produced plasma. In a recent study, they demonstrated a novel Thomson-scattering technique to measure the dispersion of ion-acoustic fluctuations that employing multiple color Thomson-scattering diagnostics. They obtained frequency-resolved Thomson-scattering spectra of the two separate thermal ion-acoustic fluctuations with significantly different wave vectors. This new technique allows a simultaneous time resolved local measurement of electron density and temperature. The plasma fluctuations are shown to become dispersive with increasing electron temperature. Furthermore, a Thomson-scattering technique to measure the electron temperature profile is presented where recent experiments have measured a large electron temperature gradient (Te = 1.4 keV to Te = 3.2 keV over 1.5-mm) along the axis of a 2-mm long hohlraum when heated asymmetrically
Generation Gap and the Impact of the Web on Goods Quality Perceptions
This study explores how age and general online shopping experience affect consumer perceptions on product quality uncertainty. Using the survey data collected from 549 consumers, we investigated how they perceive the uncertainty of product quality on six search, experience and credence goods. The ANOVA results show that age and the Web shopping experience of consumers are significant factors. A generation gap is indeed seen for all but one experience good. Web shopping experience is not a significant factor for search goods but is for experience and credence goods. There is an interaction effect between age and Web shopping experience for one credence good. Implications of these results are discussed
The baryonic tully-fisher relationship for S4G galaxies and the "condensed" baryon fraction of galaxies
We combine data from the Spitzer Survey for Stellar Structure in Galaxies, a recently calibrated empirical stellar mass estimator from Eskew et al., and an extensive database of H I spectral line profiles to examine the baryonic Tully-Fisher (BTF) relation. We find (1) that the BTF has lower scatter than the classic Tully-Fisher (TF) relation and is better described as a linear relationship, confirming similar previous results, (2) that the inclusion of a radial scale in the BTF decreases the scatter but only modestly, as seen previously for the TF relation, and (3) that the slope of the BTF, which we find to be 3.5 ± 0.2 (Δlog M v ), implies that on average a nearly constant fraction (0.4) of all baryons expected to be in a halo are "condensed" onto the central region of rotationally supported galaxies. The condensed baryon fraction, M , is, to our measurement precision, nearly independent of galaxy circular velocity (our sample spans circular velocities, v , between 60 and 250 km s, but is extended to v 10 km s using data from the literature). The observed galaxy-to-galaxy scatter in this fraction is generally ≤ a factor of 2 despite fairly liberal selection criteria. These results imply that cooling and heating processes, such as cold versus hot accretion, mass loss due to stellar winds, and active galactic nucleus driven feedback, to the degree that they affect the global galactic properties involved in the BTF, are independent of halo mass for galaxies with 10 < v < 250 km s and typically introduce no more than a factor of two range in the resulting M . Recent simulations by Aumer et al. of a small sample of disk galaxies are in excellent agreement with our data, suggesting that current simulations are capable of reproducing the global properties of individual disk galaxies. More detailed comparison to models using the BTF holds great promise, but awaits improved determinations of the stellar masses. © 2014. The American Astronomical Society. All rights reserved.</p
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