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Using adaptive optics with the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT), the Middle Ages Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey allows us to study the spatially resolved Universe at a crucial time of ~4 Gyr ago ($z$ ~ 0.3) when simulations predict the greatest diversity in evolutionary pathways for galaxies. We investigate the radial trends in the star formation (SF) activity and luminosity-weighted stellar ages as a function of offset from the star-forming main sequence (SFMS) for a total of 294 galaxies. Using both H$\alpha$ emission and the 4000 Angstrom break (i.e., D4000) as star formation rate (SFR) tracers, we find overall flat radial profiles for galaxies lying on and above the SFMS, suggestive of physical processes that enhance/regulate SF throughout the entire galaxy disc. However, for galaxies lying below the SFMS, we find positive gradients in SF suggestive of inside-out quenching. Placing our results in context with results from other redshift regimes suggests an evolution in radial trends at $z$ ~ 0.3 for SF galaxies above the SFMS, from uniformly enhanced SF at $z$ ~ 1 and $z$ ~ 0.3 to centrally enhanced SF at $z$ ~ 0 (when averaged over a wide range of mass). We also capture higher local SFRs for galaxies below the SFMS compared to that of $z$ ~ 0, which can be explained by a larger population of quenched satellites in the local Universe and/or different treatments of limitations set by the D4000-sSFR relation., Comment: 19 pages, 15 figures, 4 tables, accepted for publication in MNRAS

Understanding the behaviors of ecological systems is challenging given their multi-faceted complexity. To proceed, theoretical models such as Lotka-Volterra dynamics with random interactions have been investigated by the dynamical mean-field theory to provide insights into underlying principles such as how biodiversity and stability depend on the randomness in interaction strength. Yet the fully-connected structure assumed in these previous studies is not realistic as revealed by a vast amount of empirical data. We derive a generic formula for the abundance distribution under an arbitrary distribution of degree, the number of interacting neighbors, which leads to degree-dependent abundance patterns of species. Notably, in contrast to the well-mixed system, the number of surviving species can be reduced as the community becomes cooperative in heterogeneous interaction structures. Our study, therefore, demonstrates that properly taking into account heterogeneity in the interspecific interaction structure is indispensable to understanding the diversity in large ecosystems, and our general theoretical framework can apply to a much wider range of interacting many-body systems.

Spiral structures are important drivers of the secular evolution of disc galaxies, however, the origin of spiral arms and their effects on the development of galaxies remain mysterious. In this work, we present two three-armed spiral galaxies at z~0.3 in the Middle Age Galaxy Properties with Integral Field Spectroscopy (MAGPI) survey. Taking advantage of the high spatial resolution (~0.6'') of the Multi-Unit Spectroscopic Unit (MUSE), we investigate the two-dimensional distributions of different spectral parameters: Halpha, gas-phase metallicity, and D4000. We notice significant offsets in Halpha (~0.2 dex) as well as gas-phase metallicities (~0.05 dex) among the spiral arms, downstream and upstream of MAGPI1202197197 (SG1202). This observational signature suggests the spiral structure in SG1202 is consistent with arising from density wave theory. No azimuthal variation in Halpha or gas-phase metallicities is observed in MAGPI1204198199 (SG1204), which can be attributed to the tighter spiral arms in SG1204 than SG1202, coming with stronger mixing effects in the disc. The absence of azimuthal D4000 variation in both galaxies suggests the stars at different ages are well-mixed between the spiral arms and distributed around the disc regions. The different azimuthal distributions in Halpha and D4000 highlight the importance of time scales traced by various spectral parameters when studying 2D distributions in spiral galaxies. This work demonstrates the feasibility of constraining spiral structures by tracing interstellar medium (ISM) and stellar population at z~0.3, with a plan to expand the study to the full MAGPI survey., Comment: 15 pages, 11 figures, 2 tables, accepted for publication in MNRAS

The competitive exclusion principle (CEP) is a fundamental concept in the niche theory, which posits that the number of available resources constrains the coexistence of species. While the CEP offers an intuitive explanation on coexistence, it has been challenged by counterexamples observed in nature. One prominent counterexample is the phytoplankton community, known as the paradox of the plankton. Diverse phytoplankton species coexist in the ocean even though they demand a limited number of resources. To shed light on this remarkable biodiversity in large ecosystems quantitatively, we consider \textit{intraspecific suppression} into the generalized MacArthur's consumer-resource model and study the relative diversity, the number ratio between coexisting consumers and resource kinds. By employing the cavity method and generating functional analysis, we demonstrate that, under intraspecific suppression, the number of consumer species can surpass the available resources. This phenomenon stems from the fact that intraspecific suppression prevents the emergence of dominant species, thereby fostering high biodiversity. Furthermore, our study highlights that the impact of this competition on biodiversity is contingent upon environmental conditions. Our work presents a comprehensive framework that encompasses the CEP and its counterexamples by introducing intraspecific suppression., Comment: 40 pages (including Appendix), 25 figures (5 figures in main, 20 figures in Appendix)

It is well-known that interactions between species determine the population composition in an ecosystem. Conventional studies have focused on fixed population structures to reveal how interactions shape population compositions. However, interaction structures are not fixed, but change over time due to invasions. Thus, invasion and interaction play an important role in shaping communities. Despite its importance, however, the interplay between invasion and interaction has not been well explored. Here, we investigate how invasion affects the population composition with interactions in open evolving systems considering generalized Lotka-Volterra-type dynamics. Our results show that the system has two distinct regimes. One is characterized by low diversity with abrupt changes of dominant species in time, appearing when the interaction between species is strong and invasion slowly occurs. On the other hand, frequent invasions can induce higher diversity with slow changes in abundances despite strong interactions. It is because invasion happens before the system reaches its equilibrium, which drags the system from its equilibrium all the time. All species have similar abundances in this regime, which implies that fast invasion induces regime shift. Therefore, whether invasion or interaction dominates determines the population composition., Comment: 15 pages (including supplementary material), 8 figures (4 figures in main, 4 figures in SI)

We examine the HI gas kinematics of galaxy pairs in two clusters and a group using Australian Square Kilometre Array Pathfinder (ASKAP) WALLABY pilot survey observations. We compare the HI properties of galaxy pair candidates in the Hydra I and Norma clusters, and the NGC 4636 group, with those of non-paired control galaxies selected in the same fields. We perform HI profile decomposition of the sample galaxies using a tool, {\sc baygaud} which allows us to de-blend a line-of-sight velocity profile with an optimal number of Gaussian components. We construct HI super-profiles of the sample galaxies via stacking of their line profiles after aligning the central velocities. We fit a double Gaussian model to the super-profiles and classify them as kinematically narrow and broad components with respect to their velocity dispersions. Additionally, we investigate the gravitational instability of HI gas disks of the sample galaxies using Toomre Q parameters and HI morphological disturbances. We investigate the effect of the cluster environment on the HI properties of galaxy pairs by dividing the cluster environment into three subcluster regions (i.e., outskirts, infalling and central regions). We find that the denser cluster environment (i.e., infalling and central regions) is likely to impact the HI gas properties of galaxies in a way of decreasing the amplitude of the kinematically narrow HI gas ($M_{\rm{narrow}}^{\rm{HI}}$/$M_{\rm{total}}^{\rm{HI}}$), and increasing the Toomre Q values of the infalling and central galaxies. This tendency is likely to be more enhanced for galaxy pairs in the cluster environment., Comment: Accepted for publication in MNRAS, 25 pages, 20 figures. Supplementary material included (20 pages)

The distribution of LIGO black hole binaries (BBH) shows an intermediate-mass range consistent with the Salpeter Initial Mass Function (IMF) in black hole formation by core-collapse supernovae, subject to preserving binary association. They are effectively parameterized by mean mass $\mu$ with Pearson correlation coefficient $r = 0.93\,\pm\,0.06$ of secondary to primary masses with mean mass-ratio $\bar{q}\simeq 0.67$, $q=M_2/M_1$, consistent with the paucity of intermediate-mass X-ray binaries. The mass-function of LIGO BBHs is well-approximated by a broken power-law with a tail $\mu\gtrsim 31.4M_\odot$ {in the mean binary mass $\mu=\left(M_1+M_2\right)/2$}. Its power-law index $\alpha_{B,true}=4.77\pm 0.73$ inferred from the tail of the observed mass-function is found to approach the upper bound $2\alpha_S=4.7$ of the uncorrelated binary initial mass-function, defined by the Salpeter index $\alpha_S=2.35$ of the Initial Mass Function of stars. The observed low scatter in BBH mass ratio $q$ evidences equalizing mass-transfer in binary evolution prior to BBH formation. At the progenitor redshift $z^\prime$, furthermore, the power-law index satisfies $\alpha_B^\prime>\alpha_B$ in a flat $\Lambda$CDM background cosmology. The bound $\alpha_{B,true}^\prime \lesssim 2\alpha_S$ hereby precludes early formation at arbitrarily high redshift $z^\prime \gg1$, that may be made more precise and robust with extended BBH surveys from upcoming LIGO O4-5 observations., Comment: 7 pages, 6 figures

Feature Pyramid Network (FPN) has been an essential module for object detection models to consider various scales of an object. However, average precision (AP) on small objects is relatively lower than AP on medium and large objects. The reason is why the deeper layer of CNN causes information loss as feature extraction level. We propose a new scale sequence (S^2) feature extraction of FPN to strengthen feature information of small objects. We consider FPN structure as scale-space and extract scale sequence (S^2) feature by 3D convolution on the level axis of FPN. It is basically scale invariant feature and is built on high-resolution pyramid feature map for small objects. Furthermore, the proposed S^2 feature can be extended to most object detection models based on FPN. We demonstrate the proposed S2 feature can improve the performance of both one-stage and two-stage detectors on MS COCO dataset. Based on the proposed S2 feature, we achieve upto 1.3% and 1.1% of AP improvement for YOLOv4-P5 and YOLOv4-P6, respectively. For Faster RCNN and Mask R-CNN, we observe upto 2.0% and 1.6% of AP improvement with the suggested S^2 feature, respectively.

We present H I gas kinematics and star formation activities of NGC 6822, a dwarf galaxy located in the Local Group at a distance of ~ 490 kpc. We perform profile decomposition of line-of-sight velocity profiles of the H I data cube (42.4" x 12.0" spatial, corresponding to ~ 100 pc; 1.6 km s$^{-1}$ spectral) taken with the Australia Telescope Compact Array (ATCA). For this, we use a new tool, the so-called BAYGAUD which is based on Bayesian analysis techniques, allowing us to decompose a line-of-sight velocity profile into an optimal number of Gaussian components in a quantitative manner. We classify the decomposed H I gas components of NGC 6822 into cool-bulk, warm-bulk, cool-non-bulk and warm-non-bulk motions with respect to their centroid velocities and velocity dispersions. We correlate their gas surface densities with corresponding star formation rate densities derived using both the GALEX far-ultraviolet and WISE 22 $\mu$m data to examine the resolved Kennicutt-Schmidt (K-S) law for NGC 6822. Of the decomposed H I gas components, the cool-bulk component is likely to better follow the linear extension of the K-S law for molecular hydrogen (H$_2$) at low gas surface densities where H I is not saturated., Comment: 20 pages, 11 figures, 4 tables, accepted for publication in AJ

We present a method to determine sodium-abundance ratios ([Na/Fe]) using the Na I D doublet lines in low-resolution ($R \sim$ 2000) stellar spectra. As stellar Na I D lines are blended with those produced by the interstellar medium (ISM), we developed a technique for removing the interstellar Na I D lines using the relationship between extinction, which is proportional to $E(B-V)$, and the equivalent width (EW) of the interstellar Na I D absorption lines. When measuring [Na/Fe], we also considered corrections for non-local thermodynamic equilibrium (NLTE) effects. Comparisons with data from high-resolution spectroscopic surveys suggest that the expected precision of [Na/Fe] from low-resolution spectra is better than 0.3 dex for stars with [Fe/H] $>$ $-$3.0. We also present a simple application employing the estimated [Na/Fe] values for a large number of stellar spectra from the Sloan Digital Sky Survey (SDSS). After classifying the SDSS stars into Na-normal, Na-high, and Na-extreme, we explore their relation to stars in Galactic globular clusters (GCs). We find that, while the Na-high SDSS stars exhibit a similar metallicity distribution function (MDF) to that of the GCs, indicating that the majority of such stars may have originated from GC debris, the MDF of the Na-normal SDSS stars follows that of typical disk and halo stars. As there is a high fraction of carbon-enhanced metal-poor stars among the Na-extreme stars, they may have a non-GC origin, perhaps due to mass-transfer events from evolved binary companions., Comment: 13 pages, 9 figures, submitted to ApJ

Cooperators forgo their interest to benefit others. Thus cooperation should not be favored by natural selection. It challenges the evolutionists, since cooperation is widespread. As one of the resolutions, information spreading has been revealed to play a key role in the emergence of cooperation. Individuals, however, are typically assumed to be passive in the information spreading. Here we assume that individuals are active to spread the information via self-recommendation. Individuals with higher intensities of self-recommendation are likely to have more neighbors. We find that i) eloquent cooperators are necessary to promote cooperation; ii) individuals need to be open to the self-recommendation to enhance cooperation level; iii) the cost-to-benefit ratio should be smaller than one minus the ratio between self-recommendation intensities of defector and cooperator, which qualitatively measures the viscosity of the population. Our results highlight the importance of active information spreading on cooperation., Comment: 14 pages, 4 figures

The gravity model (GM) analogous to Newton's law of universal gravitation has successfully described the flow between different spatial regions, such as human migration, traffic flows, international economic trades, etc. This simple but powerful approach relies only on the 'mass' factor represented by the scale of the regions and the 'geometrical' factor represented by the geographical distance. However, when the population has a subpopulation structure distinguished by different attributes, the estimation of the flow solely from the coarse-grained geographical factors in the GM causes the loss of differential geographical information for each attribute. To exploit the full information contained in the geographical information of subpopulation structure, we generalize the GM for population flow by explicitly harnessing the subpopulation properties characterized by both attributes and geography. As a concrete example, we examine the marriage patterns between the bride and the groom clans of Korea in the past. By exploiting more refined geographical and clan information, our generalized GM properly describes the real data, a part of which could not be explained by the conventional GM. Therefore, we would like to emphasize the necessity of using our generalized version of the GM, when the information on such nongeographical subpopulation structures is available., Comment: 14 pages, 6 figures, 2 tables

Deterministic evolutionary game dynamics can lead to stable coexistences of different types. Stochasticity, however, drives the loss of such coexistences. This extinction is usually accompanied by population size fluctuations. We investigate the most probable extinction trajectory under such fluctuations by mapping a stochastic evolutionary model to a problem of classical mechanics using the Wentzel-Kramers-Brillouin (WKB) approximation. Our results show that more abundant types in a coexistence can be more likely to go extinct first well agreed with previous results, and also the distance between the coexistence and extinction point is not a good predictor of extinction. Instead, the WKB method correctly predicts the type going extinct first.