217 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
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
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Very-high-growth-factor Planar Ablative Rayleigh Taylor Experiments
The Rayleigh-Taylor (RT) instability is an important factor in bounding the performance envelope of ignition targets. This paper describes an experiment for ablative RT instability that for the first time achieves growth factors close to those expected to occur in ignition targets at the National Ignition Facility (NIF). The large growth allows small seed perturbations to be detected and can be used to place an upper bound on perturbation growth at the ablation front resulting from microstructure in the preferred Be ablator. The experiments were performed on the Omega laser using a halfraum 1.2 mm long by 2 mm diameter with a 75% laser entrance hole. The halfraum was filled with {approx} 1 atm of neopentane to delay gold plasma from closing the diagnostic line of sight down the axis of the halfraum. The ablator was mounted at the base of the halfraum, and was accelerated by a two stepped X-ray pulse consisting of an early time section {approx} 100 eV to emulate the NIF foot followed by an approximately constant {approx} 150 eV drive sustained over an additional 5-7ns. It is this long pulse duration and late time observation that distinguishes the present work from previous experiments, and is responsible for the large growth that is achieved. The growth of a 2D sinusoidal perturbation machined on the drive side of the ablator was measured using face-on radiography. The diagnostic view remained open until {approx} 11 ns with maximum growth factors measured to be {approx} 200. The trajectory of the ablator was measured using streaked backlit radiography. The design and analysis of the experiments is described, and implications for experiments on ignition target ablators are discussed
Upward intergenerational influences on parents' innovativeness and innovation adoption: A comparative study of single‐ and multiple‐child families
4MOST Scientific Operations
The 4MOST instrument is a multi-object spectrograph that will address
Galactic and extragalactic science cases simultaneously by observing targets
from a large number of different surveys within each science exposure. This
parallel mode of operation and the survey nature of 4MOST require some distinct
4MOST-specific operational features within the overall operations model of ESO.
The main feature is that the 4MOST Consortium will deliver, not only the
instrument, but also contractual services to the user community, which is why
4MOST is also described as a facility. This white paper concentrates on
information particularly useful to answering the forthcoming Call for Letters
of Intent.Comment: Part of the 4MOST issue of The Messenger, published in preparation of
4MOST Community Workshop, see http://www.eso.org/sci/meetings/2019/4MOST.htm
NADPH oxidase elevations in pyramidal neurons drive psychosocial stress-induced neuropathology
Oxidative stress is thought to be involved in the development of behavioral and histopathological alterations in animal models of psychosis. Here we investigate the causal contribution of reactive oxygen species generation by the phagocyte NADPH oxidase NOX2 to neuropathological alterations in a rat model of chronic psychosocial stress. In rats exposed to social isolation, the earliest neuropathological alterations were signs of oxidative stress and appearance of NOX2. Alterations in behavior, increase in glutamate levels and loss of parvalbumin were detectable after 4 weeks of social isolation. The expression of the NOX2 subunit p47phox was markedly increased in pyramidal neurons of isolated rats, but below detection threshold in GABAergic neurons, astrocytes and microglia. Rats with a loss of function mutation in the NOX2 subunit p47phox were protected from behavioral and neuropathological alterations induced by social isolation. To test reversibility, we applied the antioxidant/NOX inhibitor apocynin after initiation of social isolation for a time period of 3 weeks. Apocynin reversed behavioral alterations fully when applied after 4 weeks of social isolation, but only partially after 7 weeks. Our results demonstrate that social isolation induces rapid elevations of the NOX2 complex in the brain. Expression of the enzyme complex was strongest in pyramidal neurons and a loss of function mutation prevented neuropathology induced by social isolation. Finally, at least at early stages, pharmacological targeting of NOX2 activity might reverse behavioral alterations
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Demonstartion of density dependence of x-ray flux in a laser-driven hohlraum
Experiments have been conducted using laser-driven cylindrical hohlraums whose walls are machined from Ta{sub 2}O{sub 5} foams of 100 mg/cc and 4 g/cc densities. Measurements of the radiation temperature demonstrate that the lower density walls produce higher radiation temperatures than the high density walls. This is the first experimental demonstration of the prediction that this would occur [M. D. Rosen and J. H. Hammer, Phys. Rev. E 72, 056403 (2005)]. For high density walls, the radiation front propagates subsonically, and part of the absorbed energy is wasted by the flow kinetic energy. For the lower wall density, the front velocity is supersonic and can devote almost all of the absorbed energy to heating the wall
The Three Hundred project: a large catalogue of theoretically modelled galaxy clusters for cosmological and astrophysical applications
We introduce the The Three Hundred project, an endeavour to model 324 large galaxy clusters with full-physics hydrodynamical re-simulations. Here we present the dataset and study the differences to observations for fundamental galaxy cluster properties and scaling relations. We find that the modelled galaxy clusters are generally in reasonable agreement with observations with respect to baryonic fractions and gas scaling relations at redshift z = 0. However, there are still some (model-dependent) differences, such as central galaxies being too massive, and galaxy colours (g − r) being bluer (about 0.2 dex lower at the peak position) than in observations. The agreement in gas scaling relations down to 1013 h−1M⊙ between the simulations indicates that particulars of the sub-grid modelling of the baryonic physics only has a weak influence on these relations. We also include – where appropriate – a comparison to three semi-analytical galaxy formation models as applied to the same underlying dark matter only simulation. All simulations and derived data products are publicly available
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