Massive Ends Research Articles

Big Galaxies and Big Black Holes: The Massive Ends of the Local Stellar and Black Hole Mass Functions and the Implications for Nanohertz Gravitational Waves

We construct the z = 0 galaxy stellar mass function (GSMF) by combining the GSMF at stellar masses M * ≲ 1011.3 M ⊙ from the census study of Leja et al. and the GSMF of massive galaxies at M * ≳ 1011.5 M ⊙ from the volume-limited MASSIVE galaxy survey. To obtain a robust estimate of M * for local massive galaxies, we use MASSIVE galaxies with M * measured from detailed dynamical modeling or stellar population synthesis modeling (incorporating a bottom-heavy initial mass function) with high-quality spatially resolved spectroscopy. These two independent sets of M * agree to within ∼7%. Our new z = 0 GSMF has a higher amplitude at M * ≳ 1011.5 M ⊙ than previous studies, alleviating prior concerns of a lack of mass growth in massive galaxies between z ∼ 1 and 0. We derive a local black hole mass function (BHMF) from this GSMF and the scaling relation of supermassive black holes (SMBHs) and galaxy masses. The inferred abundance of local SMBHs above ∼1010 M ⊙ is consistent with the number of currently known systems. The predicted amplitude of the nanohertz stochastic gravitational-wave background is also consistent with the levels reported by Pulsar Timing Array teams. Our z = 0 GSMF therefore leads to concordant results in the high-mass regime of the local galaxy and SMBH populations and the gravitational-wave amplitude from merging SMBHs. An exception is that our BHMF yields a z = 0 SMBH mass density that is notably higher than the value estimated from quasars at higher redshifts.

The miniJPAS survey: Evolution of luminosity and stellar mass functions of galaxies up to z~0.7

We aim to develop a robust methodology for constraining the luminosity and stellar mass functions (LMFs) of galaxies by solely using photometric measurements from multi-filter imaging surveys. We test the potential of these techniques for determining the evolution of these functions up to $z 0.7$ in the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS), which will image thousands of square degrees in the northern hemisphere with an unprecedented photometric system that includes $54$ narrow band filters. As J-PAS is still an ongoing survey, we used the miniJPAS dataset (a stripe of $1$ deg$^2$ dictated according to the J-PAS strategy) for determining the LMFs of galaxies at $0.05 z 0.7$. Stellar mass and $B$-band luminosity for each of the miniJPAS galaxies are constrained using an updated version of our fitting code for spectral energy distribution, MUlti-Filter FITting (MUFFIT), whose values are based on non-parametric composite stellar population models and the probability distribution functions of the miniJPAS photometric redshifts. Galaxies are classified according to their star formation activity through the stellar mass versus rest-frame colour diagram corrected for extinction (MCDE) and we assign a probability to each source of being a quiescent or star-forming galaxy. Different stellar mass and luminosity completeness limits are set and parametrised as a function of redshift, for setting the limitations of our flux-limited sample ($r_ SDSS 22$) for the determination of the miniJPAS LMFs. The miniJPAS LMFs are parametrised according to Schechter-like functions via a novel maximum likelihood method accounting for uncertainties, degeneracies, probabilities, completeness, and priors. Overall, our results point to a smooth evolution with redshift ($0.05 z 0.7$) of the miniJPAS LMFs, which is in agreement with previous studies. The LMF evolution of star-forming galaxies mainly involve the bright and massive ends of these functions, whereas the LMFs of quiescent galaxies also exhibit a non-negligible evolution in their faint and less massive ends. The cosmic evolution of the global $B$-band luminosity density decreases by $ 0.1$ dex from $z=0.7$ to $0.05$; whereas for quiescent galaxies, this quantity roughly remains constant. In contrast, the stellar mass density increases by $ dex in the same redshift range, where the evolution is mainly driven by quiescent galaxies, owing to an overall increase in the number of this type of galaxy. In turn, this covers the majority and most massive galaxies, namely, $60$--$100$<!PCT!> of galaxies at $ (M_

Origin of 60Fe nuclei in cosmic rays: the contribution of local OB associations

ABSTRACT The presence of live 60Fe nuclei (lifetime of 3.8 Myr) in cosmic rays detected by the Advanced Composition Explorer/Cosmic Ray Isotope Spectrometer instrument suggests a nearby nucleosynthesis source. 60Fe is primarily produced in core-collapse supernovae, and we aim to clarify whether the detected 60Fe nuclei can be associated with a particular local supernova. We consider 25 OB associations and subgroups located within 1 kpc of the Solar system based on recent Gaia census. A model is developed that combines stellar population synthesis within these OB associations, cosmic ray acceleration within associated superbubbles, and cosmic ray transport to the Solar system. The most critical model parameter impacting 60Fe cosmic ray production is the explodability criterion, which determines if a massive star ends its life as a supernova. Our study points to the Scorpius–Centaurus (Sco–Cen) OB association as the most probable origin of the observed 60Fe nuclei, particularly suggesting they were accelerated in the Sco–Cen superbubble by a young supernova aged ≤500 kyr with a progenitor mass of approximately 13–20 M⊙. A less likely source is the supernova at the origin of the Geminga pulsar 342 kyr ago, if the progenitor originated in the Orion OB1 association. The contribution of local OB associations to the cosmic ray density of stable 56Fe is estimated to be around 20 per cent, with some sensitivity to cosmic ray acceleration efficiency and diffusion coefficient. These findings shed light on the origins of cosmic ray nuclei, connecting them to nucleosynthesis events within our local cosmic neighbourhood.

An endogenous intelligent architecture for wireless communication networks

AbstractThe challenges posed by the future wireless communication network, which will be a huge system with more complex structures, diverse functions, and massive communication ends, will be addressed by intelligent wireless communication technologies. These technologies are playing an increasingly important role in network architecture, computing architecture, resource allocation algorithm design, etc., thanks to the rapid development of artificial intelligence technologies, particularly the deep learning technologies, and their extensive application in various domains. In this paper, an endogenous intelligent architecture is developed to effectively clarify and understand in-depth the relationship among the factors by constructing wireless knowledge graph for the air interface transmission, the core network, as well as the network environment, and so on. Furthermore, the knowledge graph simultaneously reveals the structure and operation mechanism of the whole wireless communication networks. Cause tracing, intelligent optimization, and performance evaluation are sequentially implemented based on the knowledge graph, thus forming a complete closed-loop for endogenous intelligent wireless communication networks.

What Happens When a Massive Ecological Rehabilitation Program Ends? Evidence from China Using a Quasi-Natural Experiment

What Happens When a Massive Ecological Rehabilitation Program Ends? Evidence from China Using a Quasi-Natural Experiment

Galaxy and mass assembly: luminosity and stellar mass functions in GAMA groups

ABSTRACT How do galaxy properties (such as stellar mass, luminosity, star formation rate, and morphology) and their evolution depend on the mass of their host dark matter halo? Using the Galaxy and Mass Assembly group catalogue, we address this question by exploring the dependence on host halo mass of the luminosity function (LF) and stellar mass function (SMF) for grouped galaxies subdivided by colour, morphology, and central/satellite. We find that spheroidal galaxies in particular dominate the bright and massive ends of the LF and SMF, respectively. More massive haloes host more massive and more luminous central galaxies. The satellites LF and SMF, respectively, show a systematic brightening of characteristic magnitude, and increase in characteristic mass, with increasing halo mass. In contrast to some previous results, the faint-end and low-mass slopes show little systematic dependence on halo mass. Semi-analytic models and simulations show similar or enhanced dependence of central mass and luminosity on halo mass. Faint and low-mass simulated satellite galaxies are remarkably independent of halo mass, but the most massive satellites are more common in more massive groups. In the first investigation of low-redshift LF and SMF evolution in group environments, we find that the red/blue ratio of galaxies in groups has increased since redshift z ≈ 0.3 relative to the field population. This observation strongly suggests that quenching of star formation in galaxies as they are accreted into galaxy groups is a significant and ongoing process.

Doherty PAs for 5G Massive MIMO: Energy-Efficient Integrated DPA MMICs for Sub-6-GHz and mm-Wave 5G Massive MIMO Systems

To accommodate growing user demand for faster data rates and extensive connectivity, modern wireless communication systems must evolve to support a sharply increasing number of subscribers, all requesting service at the same time. This trend encourages the broad application of multiple input/multiple output (MIMO) systems. In fact, MIMO techniques can increase data rates, coverage of service areas, and communication reliability without additional RFs. In recent proposals for 5G systems, the required separate RF chains in massive MIMO RF front ends can reach up to 256, with bandwidths of up to 800 MHz per RF chain [1], [2]. Massive MIMO is a critical technology that helps significantly in increasing network capacity and spectral efficiency, while reducing wireless network interference, ultimately improving the end-user experience.

Interstellar ^{60}Fe on the Surface of the Moon.

A dying massive star ends in a supernova explosion ejecting a large fraction of its mass into the interstellar medium. If this happens nearby, part of the ejecta might end on Solar System bodies and, in fact, radioactive ^{60}Fe has been detected on the Pacific ocean floor in about 2Ma old layers. Here, we report on the detection of this isotope also in lunar samples, originating presumably from the same event. The concentration of the cosmic ray produced isotope ^{53}Mn, measured in the same samples, proves the supernova origin of the ^{60}Fe. From the ^{60}Fe concentrations found we deduce a reliable value for the local interstellar fluence in the range of 1×10^{8} at/cm^{2}. Thus, we obtain constraints on the recent and nearby supernova(e).

String models and Regge trajectories for baryons

The string with massive ends may be considered as the model q-q of a meson or as the quark-diquark model q-qq of a baryon. Rotational states (planar uniform rotations) of this string demonstrate quasilinear dependence between an- gular momentum and square of energy of a state. Such a behavior was used for describing light, strange, charmed, bottom mesons on Regge trajectories. In this paper we choose the quark-diquark string baryon model because of its stability and true Regge slope and use this model with two types of spin-orbit correction for describing N , ∆, Σ, Λ and Λc baryons on Regge trajectories.

Compact object formation and the supernova explosion engine

When a massive star ends its life, its core collapses, forming a neutron star or black hole and producing some of the most energetic explosions in the universe. Core-collapse supernovae and long-duration gamma-ray bursts are the violent signatures of compact remnant formation. As such, both fields are intertwined and, coupled with theory, observations of transients can help us better understand compact remnants just as neutron star and black hole observations can constrain the supernova and gamma-ray burst engine. We review these ties in this paper.

Perturbed States of a Rotating Relativistic String

We investigate arbitrary small perturbations of the uniform rotation of a rectilinear relativistic string with massive ends. Two classes of such perturbations with different spectra of eigenfrequencies have the form of stationary waves and correspond to string oscillations in the rotation plane and in the orthogonal direction. These states are represented by the Fourier series used to quantize string excitations in the linear neighborhood of the classical rotation. These string oscillations can be used to describe daughter Regge trajectories in the framework of the considered model.

Instability of the Y string baryon model within classical dynamics

For the three-string baryon model (Y configuration), the known exact solution to the classical equations of motion that describes the rotational motion of the system at a constant speed is investigated for stability. In the spectrum of small perturbations of this solution, modes growing exponentially with time are found, whereby the instability of rotational motion is proven for the Y configuration. This result is confirmed within an alternative approach that makes it possible to determine the classical motion of the system from a specific initial position and initial velocities of string points. A comparison of the Y configuration with the model of a relativistic string with massive ends, in which case rotational motion is stable in the linear approximation, aids in revealing the most adequate string model from the point of view of describing baryon excitations on Regge trajectories.

Disturbances of rotational motions for string models of hadrons and the stability problem

Slight disturbances of a classical rotational motion (uniform rotation of a system) are considered for a relativistic string with massive ends and for the q-q-q and Y baryon string models. It is shown that for a string with massive ends this motion is stable in the linear approximation and the slight perturbations are representable by a series each term of which describes a standing wave of certain frequency. These modes make it possible to simulate various excited states of hadrons. At the same time, for the q-q-q and Y baryon string models the instability of rotational motions has been proved: exponentially growing modes have been detected in their perturbation spectra.

Quasirotational motions and stability problem in the dynamics of string hadron models

For the relativistic string with massive ends (the meson model) and four various string baryon models (q-qq, q-q-q, Y and $\Delta$) we consider the classical quasirotational motions, which are small disturbances of the planar uniform rotations of these systems. For the string meson model the two types of these solutions are obtained. They describe oscillatory motions in the form of stationary waves in the rotational plane and in the orthogonal direction. This approach and the suggested method of determining an arbitrary motion of the system on the base of initial data let us solve the stability problem for the rotational motions for all mentioned string configurations. It is shown that the classic rotational motions are {\it stable} for the string meson model (or its analog q-qq) and for the $\Delta$ baryon configuration, but they are {\it unstable} for the string baryon models Y and q-q-q. For the latter two systems any small asymmetric disturbances grow with growing time. The motion of the q-q-q configuration become more complicated and quasiperiodic but quarks do not merge. In the case of Y model the evolution of disturbances results in falling a quark into the junction. These features of the classic behavior are important for describing the hadron states on the Regge trajectories and for choosing and developing the most adequate QCD-based string hadron models.

Remark on the computation of mode sums

The computation of mode sums of the types encountered in basic quantum field theoretic applications is addressed with an emphasis on their expansions into functions of distance that can be interpreted as potentials. We show how to regularize and calculate the Casimir energy for the continuum Nambu-Goto string with massive ends as well as for the discrete Isgur-Paton non-relativistic string with massive ends. As an additional example, we examine the effect on the interquark potential of a constant Kalb-Ramond field strength interacting with a QCD string.

Integrals of periodic motion for classical equations of relativistic string with masses at ends

Boundary equations for the relativistic string with masses at ends are formulated in terms of geometrical invariants of world trajectories of masses at the string ends. In the three-dimensional Minkowski space , there are two invariants of that sort, the curvature K and torsion . Curvatures of trajectories of the string massive ends are always constant, , whereas torsions are the functions of and obey a system of differential equations of second order with deviating arguments. For periodic torsions , where l is the string length in the plane of parameters and , these equations result in constant of motion.

On the calculation of the interquark potential generated by a string with massive ends

The variational equations, defining the stationary point of the effective action of the Nambu-Goto string with massive ends, are solved numerically by making use of an iterative procedure. The obtained solution enables one to evaluate the string functional integral. Proceeding from this, the interquark potential generated by a string with massive ends is derived. Calculations show that the higher iterative corrections turn out to be small, and the zero approximation fairly well reproduces the interquark potential generated by the Nambu-Goto string with massive ends.

Critical temperature in the Nambu-Goto string with massive ends

In the one-string approximation, it is shown that the critical (or deconfinement) temperature for the Nambu-Goto string connecting the point-like masses (quarks) does not depend on the value of these masses. This temperature turns out to be the same as that in the case of string with fixed ends (infinitely heavy immobile quarks).

Quark mass correction to the string potential.

A consistent method for calculating the interquark potential generated by the relativistic string with massive ends is proposed. In this approach the interquark potential in the model of the Nambu--Goto string with point--like masses at its ends is calculated. At first the calculation is done in the one--loop approximation and then the variational estimation is performed. The quark mass correction results in decreasing the critical distance (deconfinement radius). When quark mass decreases the critical distance also decreases. For obtaining a finite result under summation over eigenfrequencies of the Nambu--Goto string with massive ends a suitable mode--by--mode subtraction is proposed. This renormalization procedure proves to be completely unique. In the framework of the developed approach the one--loop interquark potential in the model of the relativistic string with rigidity is also calculated.

Classification of motions admitting linearization of boundary conditions for the relativistic string with massive ends

For the relativistic string with masses at its ends, a classification of motions (world surfaces) admitting a parametrization under which the equations of motion and the boundary conditions are linear (due to the fact that the parameter for the trajectories of the string ends is proportional to the natural parameter) is carried out. These motions can be represented as Fourier series with respect to the eigenfunctions of a generalized Sturm-Liouville problem. The completeness of the family of these eigenfunctions in class C is proved. It is shown that in Minkowski spaces of dimensions2+1 and3+1, the motions in question reduce to a uniform rotation of one or several (spatially coincident) rectilinear strings (the world surface is a helicoid). In spaces of higher dimensions, some other nontrivial motions of this type are also possible.