545 research outputs found
Development and testing of a mouse simulated space flight model
The development and testing of a mouse model for simulating some aspects of weightlessness that occur during space flight, and the carrying out of immunological flight experiments on animals was discussed. The mouse model is an antiorthostatic, hypokinetic, hypodynamic suspension model similar to the one used with rats. It is shown that this murine model yield similar results to the rat model of antiorthostatic suspension for simulating some aspects of weightlessness. It is also shown that mice suspended in this model have decreased interferon-alpha/beta production as compared to control, nonsuspended mice or to orthostatically suspended mice. It is suggested that the conditions occuring during space flight could possibly affect interferon production. The regulatory role of interferon in nonviral diseases is demonstrated including several bacterial and protozoan infections indicating the great significance of interferon in resistance to many types of infectious diseases
The inner dark matter distribution of the Cosmic Horseshoe (J1148+1930) with gravitational lensing and dynamics
We present a detailed analysis of the inner mass structure of the Cosmic
Horseshoe (J1148+1930) strong gravitational lens system observed with the
Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3). In addition to the
spectacular Einstein ring, this systems shows a radial arc. We obtained the
redshift of the radial arc counter image from
Gemini observations. To disentangle the dark and luminous matter, we consider
three different profiles for the dark matter distribution: a power-law profile,
the NFW, and a generalized version of the NFW profile. For the luminous matter
distribution, we base it on the observed light distribution that is fitted with
three components: a point mass for the central light component resembling an
active galactic nucleus, and the remaining two extended light components scaled
by a constant M/L. To constrain the model further, we include published
velocity dispersion measurements of the lens galaxy and perform a
self-consistent lensing and axisymmetric Jeans dynamical modeling. Our model
fits well to the observations including the radial arc, independent of the dark
matter profile. Depending on the dark matter profile, we get a dark matter
fraction between 60 % and 70 %. With our composite mass model we find that the
radial arc helps to constrain the inner dark matter distribution of the Cosmic
Hoseshoe independently of the dark matter profile.Comment: 19 pages, 14 figures, 8 tables, submitted to A&
Experiment K-6-23. Effect of spaceflight on levels and function of immune cells
Two different immunology experiments were performed on samples received from rats flown on Cosmos 1887. In the first experiment, rat bone marrow cells were examined in Moscow for their response to colony stimulating factor-M. In the second experiment, rat spleen and bone marrow cells were stained in Moscow with a variety of antibodies directed against cell surface antigenic markers. These cells were preserved and shipped to the United States where they were subjected to analysis on a flow cytometer. The results of the studies indicate that bone marrow cells from flown rats showed a decreased response to colony stimulating factor than did bone marrow cells from control rats. There was a higher percentage of spleen cells from flown rats staining positively for pan-T-cell, suppressor-T-cell and innate interleukin-2 receptor antigens than from control animals. In addition, a higher percentage of cells that appeared to be part of the myelogenous population of bone marrow cells from flown rats stained positively for surface immunoglobulin than did equivalent cells from control rats
Direct measurement of the magnification produced by galaxy clusters as gravitational lenses
Context. Weak lensing is one of the most readily available diagnostic tools to measure the total density profiles of distant clusters of galaxies. Unfortunately, it suffers from the well-known mass-sheet degeneracy, so that weak lensing analyses cannot lead to fully reliable determinations of the total mass of the clusters. One possible way to set the relevant scale of the density profile would be to make a direct measurement of the magnification produced by the clusters as gravitational lenses; in the past, this objective has been addressed in a number of ways, but with no significant success.
Aims. We revisit a suggestion made a few years ago for this general purpose, based on the use of the fundamental plane as a standard rod for early-type galaxies. Here we move one step further, beyond the simple outline of the idea given earlier, and quantify some statistical properties of this innovative diagnostic tool, with the final goal of identifying clear guidelines for a future observational test of concrete cases, which turns out to be well within the current instrument capabilities.
Methods. The study is carried out by discussing the statistical properties of fundamental plane measurements for a sample of early-type source galaxies behind a massive cluster, for which a weak lensing analysis is assumed to be available. Some general results are first obtained analytically and then tested and extended by means of dedicated simulations.
Results. We proceed with determining the optimal way of using fundamental plane measurements to determine the mass scale of a given cluster, which we find to be the study of a sample of early-type galaxies behind the cluster distributed approximately uniformly on the sky. We discuss the role of the redshift distribution of the source galaxies, in relation to the redshift of the lensing cluster and to the limitations of fundamental plane measurements. Simple simulations are carried out for clusters with intrinsic properties similar to those of the Coma cluster. We also show that, within a realistic cosmological scenario, substructures do not contribute much to the magnification signal that we are looking for, but add only a modest amount of scatter.
Conclusions. We find that for a massive cluster (M-200 > 10(15) M-circle dot) located at redshift 0.3 +/- 0.1, a set of about 20 fundamental plane measurements, combined with a robust weak lensing analysis, should be able to lead to a mass determination with a precision of 20% or better
The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. II. Results
The spectral absorption lines in early-type galaxies contain a wealth of
information regarding the detailed abundance pattern, star formation history,
and stellar initial mass function (IMF) of the underlying stellar population.
Using our new population synthesis model that accounts for the effect of
variable abundance ratios of 11 elements, we analyze very high quality
absorption line spectra of 38 early-type galaxies and the nuclear bulge of M31.
These data extend to 1um and they therefore include the IMF-sensitive spectral
features NaI, CaII, and FeH at 0.82um, 0.86um and 0.99um, respectively. The
models fit the data well, with typical rms residuals ~1%. Strong constraints on
the IMF and therefore the stellar mass-to-light ratio, (M/L)_stars, are derived
for individual galaxies. We find that the IMF becomes increasingly bottom-heavy
with increasing velocity dispersion and [Mg/Fe]. At the lowest dispersions and
[Mg/Fe] values the derived IMF is consistent with the Milky Way IMF, while at
the highest dispersions and [Mg/Fe] values the derived IMF contains more
low-mass stars (is more bottom-heavy) than even a Salpeter IMF. Our best-fit
(M/L)_stars values do not exceed dynamically-based M/L values. We also apply
our models to stacked spectra of four metal-rich globular clusters in M31 and
find an (M/L)_stars that implies fewer low-mass stars than a Milky Way IMF,
again agreeing with dynamical constraints. We discuss other possible
explanations for the observed trends and conclude that variation in the IMF is
the simplest and most plausible.Comment: 16 pages, 13 figures, ApJ accepte
The Drosophila tango gene encodes a bHLH-PAS protein that is orthologous to mammalian Arnt and controls CNS midline and tracheal development
The Drosophila single-minded and trachealess bHLH-PAS genes control transcription and development of the CNS midline cell lineage and tracheal tubules, respectively. We show that Single-minded and Trachealess activate transcription by forming dimers with the Drosophila Tango protein that is an orthologue of the mammalian Arnt protein. Both cell culture and in vivo studies show that a DNA enhancer element acts as a binding site for both Single-minded::Tango and Trachealess::Tango heterodimers and functions in controlling CNS midline and tracheal transcription. Isolation and analysis of tango mutants reveal CNS midline and tracheal defects, and gene dosage studies demonstrate in vivo interactions between single-minded::tango and trachealess::tango. These experiments support the existence of an evolutionarily conserved, functionally diverse bHLH-PAS protein regulatory system
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H0LiCOW X: Spectroscopic/imaging survey and galaxy-group identification around the strong gravitational lens system WFI2033-4723
Galaxies and galaxy groups located along the line of sight towards
gravitationally lensed quasars produce high-order perturbations of the
gravitational potential at the lens position. When these perturbation are too
large, they can induce a systematic error on of a few-percent if the lens
system is used for cosmological inference and the perturbers are not explicitly
accounted for in the lens model. In this work, we present a detailed
characterization of the environment of the lens system WFI2033-4723 (, = 0.6575), one of the core targets of the H0LICOW
project for which we present cosmological inferences in a companion paper (Rusu
et al. 2019). We use the Gemini and ESO-Very Large telescopes to measure the
spectroscopic redshifts of the brightest galaxies towards the lens, and use the
ESO-MUSE integral field spectrograph to measure the velocity-dispersion of the
lens ( km/s) and of several nearby
galaxies. In addition, we measure photometric redshifts and stellar masses of
all galaxies down to mag, mainly based on Dark Energy Survey imaging
(DR1). Our new catalog, complemented with literature data, more than doubles
the number of known galaxy spectroscopic redshifts in the direct vicinity of
the lens, expanding to 116 (64) the number of spectroscopic redshifts for
galaxies separated by less than 3 arcmin (2 arcmin) from the lens. Using the
flexion-shift as a measure of the amplitude of the gravitational perturbation,
we identify 2 galaxy groups and 3 galaxies that require specific attention in
the lens models. The ESO MUSE data enable us to measure the
velocity-dispersions of three of these galaxies. These results are essential
for the cosmological inference analysis presented in Rusu et al. (2019).Comment: Matches the version accepted for publication by MNRAS. Note that this
paper previously appeared as H0LICOW X
The Lick AGN Monitoring Project 2011: Reverberation Mapping of Markarian 50
The Lick AGN Monitoring Project 2011 observing campaign was carried out over
the course of 11 weeks in Spring 2011. Here we present the first results from
this program, a measurement of the broad-line reverberation lag in the Seyfert
1 galaxy Mrk 50. Combining our data with supplemental observations obtained
prior to the start of the main observing campaign, our dataset covers a total
duration of 4.5 months. During this time, Mrk 50 was highly variable,
exhibiting a maximum variability amplitude of a factor of 4 in the U-band
continuum and a factor of 2 in the H-beta line. Using standard
cross-correlation techniques, we find that H-beta and H-gamma lag the V-band
continuum by tau_cen = 10.64(-0.93,+0.82) and 8.43(-1.28,+1.30) days,
respectively, while the lag of He II 4686 is unresolved. The H-beta line
exhibits a symmetric velocity-resolved reverberation signature with shorter
lags in the high-velocity wings than in the line core, consistent with an
origin in a broad-line region dominated by orbital motion rather than infall or
outflow. Assuming a virial normalization factor of f=5.25, the virial estimate
of the black hole mass is (3.2+-0.5)*10^7 solar masses. These observations
demonstrate that Mrk 50 is among the most promising nearby active galaxies for
detailed investigations of broad-line region structure and dynamics.Comment: Accepted for publication in ApJ Letters. 6 pages, 4 figure
The Sloan Digital Sky Survey Quasar Lens Search. VI. Constraints on Dark Energy and the Evolution of Massive Galaxies
We present a statistical analysis of the final lens sample from the Sloan
Digital Sky Survey Quasar Lens Search (SQLS). The number distribution of a
complete subsample of 19 lensed quasars selected from 50,836 source quasars is
compared with theoretical expectations, with particular attention to the
selection function. Assuming that the velocity function of galaxies does not
evolve with redshift, the SQLS sample constrains the cosmological constant to
\Omega_\Lambda=0.79^{+0.06}_{-0.07}(stat.)^{+0.06}_{-0.06}(syst.) for a flat
universe. The dark energy equation of state is found to be consistent with w=-1
when the SQLS is combined with constraints from baryon acoustic oscillation
(BAO) measurements or results from the Wilkinson Microwave Anisotropy Probe
(WMAP). We also obtain simultaneous constraints on cosmological parameters and
redshift evolution of the galaxy velocity function, finding no evidence for
redshift evolution at z<1 in any combinations of constraints. For instance,
number density evolution quantified as \nu_n=d\ln\phi_*/d\ln(1+z) and the
velocity dispersion evolution \nu_\sigma=d\ln\sigma_*/d\ln(1+z) are constrained
to \nu_n=1.06^{+1.36}_{-1.39}(stat.)^{+0.33}_{-0.64}(syst.) and
\nu_\sigma=-0.05^{+0.19}_{-0.16}(stat.)^{+0.03}_{-0.03}(syst.) respectively
when the SQLS result is combined with BAO and WMAP for flat models with a
cosmological constant. We find that a significant amount of dark energy is
preferred even after fully marginalizing over the galaxy evolution parameters.
Thus the statistics of lensed quasars robustly confirm the accelerated cosmic
expansion.Comment: 44 pages, 12 figures, 4 tables, accepted for publication in A
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