Universe Today Research Articles

Annihilation detector for an in-beam spectroscopy apparatus to measure the ground state hyperfine splitting of antihydrogen

The matter-antimatter asymmetry observed in the universe today still lacks a quantitative explanation. One possible mechanism that could contribute to the observed imbalance is a violation of the combined Charge-, Parity- and Time symmetries (CPT). A test of CPT symmetry using anti-atoms is being carried out by the ASACUSA-CUSP collaboration at the CERN Antiproton Decelerator using a low temperature beam of antihydrogen—the most simple atomic system built only of antiparticles. While hydrogen is the most abundant element in the universe, antihydrogen is produced in very small quantities in a laboratory framework. A detector for in-beam measurements of the ground state hyperfine structure of antihydrogen has to be able to detect very low signal rates within high background. To fulfil this challenging task, a two layer barrel hodoscope detector was developed. It is built of plastic scintillators with double sided readout via Silicon Photomultipliers (SiPMs). The SiPM readout is done using novel, compact and cost efficient electronics that incorporate power supply, amplifier and discriminator on a single board. This contribution will evaluate the performance of the new hodoscope detector.

Reionization during the dark ages from a cosmic axion background

Recently it has been pointed out that a cosmic background of relativistic axion-like particles (ALPs) would be produced by the primordial decays of heavy fields in the post-inflation epoch, contributing to the extra-radiation content in the Universe today. Primordial magnetic fields would trigger conversions of these ALPs into sub-MeV photons during the dark ages. This photon flux would produce an early reionization of the Universe, leaving a significant imprint on the total optical depth to recombination τ. Using the current measurement of τ and the limit on the extra-radiation content Δ Neff by the Planck experiment we put a strong bound on the ALP-photon conversions. Namely we obtain upper limits on the product of the photon-ALP coupling constant gaγ times the magnetic field strength B down to gaγ B ≳ 6 × 10−18 GeV−1 nG for ultralight ALPs.

The effect of interacting dark energy on local measurements of the Hubble constant

In the current state of cosmology, where cosmological parameters are being measured to percent accuracy, it is essential to understand all sources of error to high precision. In this paper we present the results of a study of the local variations in the Hubble constant measured at the distance scale of the Coma Cluster, and test the validity of correcting for the peculiar velocities predicted by gravitational instability theory. The study is based on N-body simulations, and includes models featuring a coupling between dark energy and dark matter, as well as two ΛCDM simulations with different values of σ8. It is found that the variance in the local flows is significantly larger in the coupled models, which increases the uncertainty in the local measurements of the Hubble constant in these scenarios. By comparing the results from the different simulations, it is found that most of the effect is caused by the higher value of σ8 in the coupled cosmologies, though this cannot account for all of the additional variance. Given the discrepancy between different estimates of the Hubble constant in the universe today, cosmological models causing a greater cosmic variance is something that we should be aware of.

Impact of other scalar fields on oscillons after hilltop inflation

Oscillons are spatially localized and relatively stable field fluctuations which can form after inflation under suitable conditions. In order to reheat the universe, the fields which dominate the energy density after inflation have to couple to other degrees of freedom and finally produce the matter particles present in the universe today. In this study, we use lattice simulations in 2+1 dimensions to investigate how such couplings can affect the formation and stability of oscillons. We focus on models of hilltop inflation, where we have recently shown that hill crossing oscillons generically form, and consider the coupling to an additional scalar field which, depending on the value of the coupling parameter, can get resonantly enhanced from the inhomogeneous inflaton field. We find that three cases are realized: without a parametric resonance, the additional scalar field has no effects on the oscillons. For a fast and strong parametric resonance of the other scalar field, oscillons are strongly suppressed. For a delayed parametric resonance, on the other hand, the oscillons get imprinted on the other scalar field and their stability is even enhanced compared to the single-field oscillons.

Lagrangian methods of cosmic web classification

The cosmic web defines the large scale distribution of matter we see in the Universe today. Classifying the cosmic web into voids, sheets, filaments and nodes allows one to explore structure formation and the role environmental factors have on halo and galaxy properties. While existing studies of cosmic web classification concentrate on grid based methods, this work explores a Lagrangian approach where the V-web algorithm proposed by Hoffman et al. (2012) is implemented with techniques borrowed from smoothed particle hydrodynamics. The Lagrangian approach allows one to classify individual objects (e.g. particles or halos) based on properties of their nearest neighbours in an adaptive manner. It can be applied directly to a halo sample which dramatically reduces computational cost and potentially allows an application of this classification scheme to observed galaxy samples. Finally, the Lagrangian nature admits a straight forward inclusion of the Hubble flow negating the necessity of a visually defined threshold value which is commonly employed by grid based classification methods.

Evidence for dark matter interactions in cosmological precision data?

We study a two-parameter extension of the cosmological standard model ΛCDM in which cold dark matter interacts with a new form of dark radiation. The two parameters correspond to the energy density in the dark radiation fluid ΔNfluid and the interaction strength between dark matter and dark radiation. The interactions give rise to a very weak ``dark matter drag'' which damps the growth of matter density perturbations throughout radiation domination, allowing to reconcile the tension between predictions of large scale structure from the CMB and direct measurements of σ8. We perform a precision fit to Planck CMB data, BAO, large scale structure, and direct measurements of the expansion rate of the universe today. Our model lowers the χ-squared relative to ΛCDM by about 12, corresponding to a preference for non-zero dark matter drag by more than 3σ. Particle physics models which naturally produce a dark matter drag of the required form include the recently proposed non-Abelian dark matter model in which the dark radiation corresponds to massless dark gluons.

Space. Astronomers see ashes of the first stars.

Primordial clouds show how giant stars forged the heavy elements that fill today's universe.

THE STRIKINGLY UNIFORM, HIGHLY TURBULENT INTERSTELLAR MEDIUM OF THE MOST LUMINOUS GALAXY IN THE UNIVERSE

ABSTRACT Observed at z = 4.601 and with L bol ?> = 3.5 × 10 14 L ⊙ ?> , W2246–0526 is the most luminous galaxy known in the universe and hosts a deeply buried active galactic nucleus (AGN)/supermassive black hole (SMBH). Discovered using the Wide-field Infrared Survey Explorer, W2246–0526 is classified as a hot dust-obscured galaxy, based on its luminosity and dust temperature. Here, we present spatially resolved ALMA [C ii]157.7 μm observations of W2246–0526, providing unique insight into the kinematics of its interstellar medium (ISM). The measured [C ii] -to-far-infrared ratio is ∼ 2 × 10 − 4 ?> , implying ISM conditions that compare only with the most obscured, compact starbursts and AGNs in the local universe today. The spatially resolved [C ii] line is strikingly uniform and very broad, 500–600 km s−1 wide, extending throughout the entire galaxy over about 2.5 kpc, with modest shear. Such a large, homogeneous velocity dispersion indicates a highly turbulent medium. W2246–0526 is unstable in terms of the energy and momentum that are being injected into the ISM, strongly suggesting that the gas is being blown away from the system isotropically, likely reflecting a cathartic state on its road to becoming an unobscured quasar. W2246–0526 provides an extraordinary laboratory to study and model the properties and kinematics of gas in an extreme environment under strong feedback, at a time when the universe was 1/10 of its current age: a system pushing the limits that can be reached during galaxy formation.

Commercial morals and ethics in modern advertising and sales promotion

In today's universe of ferocious rivalry each association is putting vigorously in publicizing. Promoting is important to make another item famous in the business sector and to build the offers of existing brands. Promoting assumes a critical part in brand building and illuminating open about accessible items so they can settle on educated decision among distinctive items or brands. The paper undertakes and concludes the advertising, publicizing and promotion activities along the lines of commercial morals and ethics.

HIDING IN PLAIN SIGHT: AN ABUNDANCE OF COMPACT MASSIVE SPHEROIDS IN THE LOCAL UNIVERSE

It has been widely remarked that compact, massive, elliptical-like galaxies are abundant at high redshifts but exceedingly rare in the Universe today, implying significant evolution such that their sizes at z ~ 2+/-0.6 have increased by factors of 3 to 6 to become today's massive elliptical galaxies. These claims have been based on studies which measured the half-light radii of galaxies as though they are all single component systems. Here we identify 21 spheroidal stellar systems within 90 Mpc that have half-light, major-axis radii R_e < ~2 kpc, stellar masses 0.7x10^{11} < M_*/M_Sun < 1.4x10^{11}, and Sersic indices typically around a value of n=2 to 3. This abundance of compact, massive spheroids in our own backyard - with a number density of 6.9x10^{-6} / Mpc^3 (or 3.5x10^{-5} / Mpc^3 per unit dex in stellar mass) - and with the same physical properties as the high-redshift galaxies, had been over-looked because they are encased in stellar disks which usually result in `galaxy' sizes notably larger than 2 kpc. Moreover, this number density is a lower limit because it has not come from a volume-limited sample. The actual density may be closer to 10^{-4} / Mpc^3, although further work is required to confirm this. We therefore conclude that not all massive `spheroids' have undergone dramatic structural and size evolution since z ~ 2+/-0.6. Given that the bulges of local early-type disk galaxies are known to consist of predominantly old stars which existed at z ~ 2, it seems likely that some of the observed high redshift spheroids did not increase in size by building (3D) triaxial envelopes as commonly advocated, and that the growth of (2D) disks has also been important over the past 9-11 billion years.

The ATLAS3D Project – XXX. Star formation histories and stellar population scaling relations of early-type galaxies

We present the stellar population content of early-type galaxies from the Atlas3D survey. Using spectra integrated within apertures covering up to one effective radius, we apply two methods: one based on measuring line-strength indices and applying single stellar population (SSP) models to derive SSP-equivalent values of stellar age, metallicity, and alpha enhancement; and one based on spectral fitting to derive non-parametric star-formation histories, mass-weighted average values of age, metallicity, and half-mass formation timescales. Using homogeneously derived effective radii and dynamically-determined galaxy masses, we present the distribution of stellar population parameters on the Mass Plane (M_JAM, Sigma_e, R_maj), showing that at fixed mass, compact early-type galaxies are on average older, more metal-rich, and more alpha-enhanced than their larger counterparts. From non-parametric star-formation histories, we find that the duration of star formation is systematically more extended in lower mass objects. Assuming that our sample represents most of the stellar content of today's local Universe, approximately 50% of all stars formed within the first 2 Gyr following the big bang. Most of these stars reside today in the most massive galaxies (>10^10.5 M_sun), which themselves formed 90% of their stars by z~2. The lower-mass objects, in contrast, have formed barely half their stars in this time interval. Stellar population properties are independent of environment over two orders of magnitude in local density, varying only with galaxy mass. In the highest-density regions of our volume (dominated by the Virgo cluster), galaxies are older, alpha-enhanced and have shorter star-formation histories with respect to lower density regions.

Constraint on a varying proton-electron mass ratio 1.5 billion years after the big bang.

A molecular hydrogen absorber at a lookback time of 12.4 billion years, corresponding to 10% of the age of the Universe today, is analyzed to put a constraint on a varying proton-electron mass ratio, μ. A high resolution spectrum of the J1443+2724 quasar, which was observed with the Very Large Telescope, is used to create an accurate model of 89 Lyman and Werner band transitions whose relative frequencies are sensitive to μ, yielding a limit on the relative deviation from the current laboratory value of Δμ/μ=(-9.5 ± 5.4(stat)± 5.3(syst))×10(-6).

Discovery of an overdensity of Lyman alpha emitters around a z ∼ 4 QSO with the Large Binocular Telescope

Measurements of QSO clustering in the SDSS show that $\mathrm{z}>4$ QSOs are some of the most highly biased objects in the universe. Their large correlation lengths of $r_0 \sim 20h^{-1}$Mpc are comparable to the most massive clusters of galaxies in the universe today and suggest that these QSOs may mark the locations of massive cluster progenitors at high redshift. We report the discovery of an overdensity of LBGs around QSO SDSSJ114514.18+394715.9 as part of our survey to identify Lyman-Break galaxies (LBGs) around luminous $\mathrm{z}\sim4$ QSOs. In this field three of the eight LBGs with secure redshifts are consistent with the redshift of the QSO. We find that the likelihood that this is merely an apparent overdensity due to the chance selection of field galaxies is only 0.02%, based on comparisons to simulations and our modeled selection efficiency. Overall, our survey finds four of the 15 LBGs with secure redshifts are consistent with the redshifts of their respective QSOs, which is consistent with luminous QSOs residing in larger haloes.

Big-bang nucleosynthesis and gamma-ray constraints on cosmic strings with a large Higgs condensate

We consider constraints on cosmic strings from their emission of Higgs particles, in the case that the strings have a Higgs condensate with amplitude of order the string mass scale, assuming that a fraction of the energy of condensate can be turned into radiation near cusps. The injection of energy by the decaying Higgs particles affects the light element abundances predicted by standard Big-Bang Nucleosynthesis (BBN), and also contributes to the Diffuse Gamma-Ray Background (DGRB) in the universe today. We examine the two main string scenarios (Nambu-Goto and field theory), and find that the primordial Helium abundance strongly constrains the string tension and the efficiency of the emission process in the NG scenario, while the strongest BBN constraint in the FT scenario comes from the Deuterium abundance. The Fermi-LAT measurement of the DGRB constrains the field theory scenario even more strongly than previously estimated from EGRET data, requiring that the product of the string tension {\mu} and Newton's constant G is bounded by G{\mu} < 2.7x10^{-11}{\beta}_{ft}^{-2}, where {\beta}_{ft}^2 is the fraction of the strings' energy going into Higgs particles.

Astrophysics: Monster star found hiding in plain sight.

Massive stars are rare, but they are sources of some of the most energetic phenomena seen in the Universe today. A high-mass candidate has now been found in a star-forming region that has been observed for more than 50 years.

Annual modulation of cosmic relic neutrinos

The cosmic neutrino background (CvB), produced about one second after the Big Bang, permeates the Universe today. New technological advancements make neutrino capture on beta-decaying nuclei (NCB) a clear path forward towards the detection of the CvB. We show that gravitational focusing by the Sun causes the expected neutrino capture rate to modulate annually. The amplitude and phase of the modulation depend on the phase-space distribution of the local neutrino background, which is perturbed by structure formation. These results also apply to searches for sterile neutrinos at NCB experiments. Gravitational focusing is the only source of modulation for neutrino capture experiments, in contrast to dark-matter direct-detection searches where the Earth's time-dependent velocity relative to the Sun also plays a role.

Dark matter interacts with variable vacuum energy

We investigate a spatially flat Friedmann-Robertson-Walker (FRW) scenario with two interacting components, dark matter and variable vacuum energy (VVE) densities, plus two decoupled components, one is a baryon term while the other behaves as a radiation component. We consider a linear interaction in the derivative dark component density. We apply the $\chi^2$ method to the observational Hubble data for constraining the cosmological parameters and analyze the amount of dark energy in the radiation era for the model. It turns out that our model fulfills the severe bound of $\Omega_{x}(z\simeq 1100)<0.009$ at $2\sigma$ level, so is consistent with the recent analysis that includes cosmic microwave background anisotropy measurements from Planck survey, the future constraints achievable by Euclid and CMBPol experiments, reported for the behavior of the dark energy at early times, and fulfills the stringent bound $\Omega_{x}(z\simeq 10^{10})<0.04$ at $2\sigma$ level in the big-bang nucleosynthesis epoch. We also examine the cosmic age problem at high redshift associated with the old quasar APM 08279+5255 and estimate the age of the universe today.

DENSE CORES IN GALAXIES OUT TOz= 2.5 IN SDSS, UltraVISTA, AND THE FIVE 3D-HST/CANDELS FIELDS

The dense interiors of massive galaxies are among the most intriguing environments in the Universe. In this paper we ask when these dense cores were formed and determine how galaxies gradually assembled around them. We select galaxies that have a stellar mass >3x10^10 Msun inside r=1 kpc out to z=2.5, using the 3D-HST survey and data at low redshift. Remarkably, the number density of galaxies with dense cores appears to have decreased from z=2.5 to the present. This decrease is probably mostly due to stellar mass loss and the resulting adiabatic expansion, with some contribution from merging. We infer that dense cores were mostly formed at z>2.5, consistent with their largely quiescent stellar populations. While the cores appear to form early, the galaxies in which they reside show strong evolution: their total masses increase by a factor of 2-3 from z=2.5 to z=0 and their effective radii increase by a factor of 5-6. As a result, the contribution of dense cores to the total mass of the galaxies in which they reside decreases from ~50% at z=2.5 to ~15% at z=0. Because of their early formation, the contribution of dense cores to the total stellar mass budget of the Universe is a strong function of redshift. The stars in cores with M_1kpc>3x10^10 Msun make up ~0.1% of the stellar mass density of the Universe today but 10%-20% at z~2, depending on their IMF. The formation of these cores required the conversion of ~10^11 Msun of gas into stars within ~1 kpc, while preventing significant star formation at larger radii.

Supersonic relative velocity between dark matter and baryons: A review

Our understanding of astrophysical and cosmological phenomena in recent years has improved enormously, thanks to precision measurements of various cosmic signals such as Cosmic Microwave Background radiation, emission of galaxies and dust, spectral lines attributed to various elements, etc. Despite this, our knowledge at intermediate redshifts (10 &lt; z &lt; 1100) remains fragmentary and incomplete, and as a consequence, various physical processes happening between the epochs of hydrogen recombination and reionization remain still highly unconstrained. Moreover, some important fragments of the theoretical description that are less decisive for the universe today, but that had an important impact at intermediate redshifts, have been omitted in some of the studies concerning the universe at high redshifts. One such neglected phenomenon, which is the central topic of this review, is the fact that after hydrogen recombination the large-scale baryons and dark matter fluctuations had supersonic relative velocities. The relative velocities between dark matter and baryons formally introduce a second-order effect on the standard results and thus have been neglected in the framework of linear theory. However, when properly considered, the velocities yield a nonperturbative contribution to the growth of structures which is then inherited by the majority of cosmic signals coming from redshifts above z ~ 10, and in certain cases may even propagate to various low-redshift observables such as the Baryon Acoustic Oscillations measured from the distribution of galaxies. At higher redshifts, the supersonic velocities have thus strong impact affecting the abundance of M ~ 106M⊙halos in an inhomogeneous way, hindering the formation of first stars, leaving traces in the redshifted 21-cm signal of neutral hydrogen, as well as having other important contributions at high redshifts all of which we review in this manuscript.

Enhancement of upper basin distillate output by attachment of vacuum tubes with double-basin solar still

Generally, the distillate output of a solar still is low; hence it is not practicable for the solution of drinkable water in the universe today. Here, a new concept is utilized to increase distillate output of a solar still in use, the double-basin solar still integrated with vacuum tubes. In this research paper, an analysis of the top basin of present solar still with different energy absorbing materials like calcium stones, black granite gravel and pebbles for enhanced surface area of water is performed. Numerous experiments have been conducted in climate conditions of Mehsana (23.6000° N, 72.4000° E) Gujarat, from April to September 2013 with a constant depth of 2 cm inside top basin. Six months’ result shows that, the distillate output of basing material with calcium stones found were more when compared with black granite gravel and pebbles.