윤석진 교수

The colors of globular clusters in most large elliptical galaxies are bimodal. This is generally taken as evidence for the presence of two cluster subpopulations that have different geneses. However, here we find that, because of the nonlinear nature of the metallicity-to-color transformation, a coeval group of old clusters with a unimodal metallicity spread can exhibit color bimodality. The models of cluster colors indicate that horizontal-branch stars are the main drivers behind the empirical

The industrial clusters literature has shaped contemporary thinking on the potential of small firms to become globally competitive through agglomeration gains and collective action. However, clusters often generate negative environmental externalities. The industrial ecology framework suggests that producer agglomerations can spawn closed loop production arrangements that reduce environmental diseconomies. To date there has been little engagement between the industrial cluster and industrial eco

One of the conundrums in extragalactic astronomy is the discrepancy in observed metallicity distribution functions (MDFs) between the two prime stellar components of early-type galaxies-globular clusters (GCs) and halo field stars. This is generally taken as evidence of highly decoupled evolutionary histories between GC systems and their parent galaxies. Here we show, however, that new developments in linking the observed GC colors to their intrinsic metallicities suggest nonlinear color-to-meta

One of the long-standing problems in modern astronomy is the curious division of Galactic globular clusters, the "Oosterhoff dichotomy," according to the properties of their RR Lyrae stars. Here, we find that most of the lowest metallicity ([Fe/H] < -2.0) clusters, which are essential to an understanding of this phenomenon, display a planar alignment in the outer halo. This alignment, combined with evidence from kinematics and stellar population, indicates a captured origin from a satellite gala

ABSTRACT The dynamical formation of black hole binaries in globular clusters that merge due to gravitational waves occurs more frequently in higher stellar density. Meanwhile, the probability to form intermediate mass black holes (IMBHs) also increases with the density. To explore the impact of the formation and growth of IMBHs on the population of stellar mass black hole binaries from globular clusters, we analyse the existing large survey of Monte Carlo globular cluster simulation data (mocca-

Abstract Galaxies in pairs show enhanced star formation (SF) compared to their counterparts in isolation, which is often explained by the tidal effect of neighboring galaxies. Recent observations, however, reported that galaxies paired with early-type neighbors do not undergo the SF enhancement. Here we revisit the influence of neighbors using a large sample of paired galaxies from the Sloan Digital Sky Survey and a carefully constructed control sample of isolated counterparts. We find that star

Abstract We present a statistical analysis of the flybys of dark matter halos compared to mergers, using cosmological N -body simulations. We mainly focus on gravitationally interacting target halos with mass of 10 10.8 –10 13.0 h −1 M ⊙ , and their neighbors are counted only when the mass ratio is 1:3–3:1 and the distance is less than the sum of the virial radii of target and neighbor. The neighbors are divided into the flyby or merger samples if the pair’s total energy is greater or smaller, r

Abstract We present an extensive catalog of 5405 early-type dwarf (dE) galaxies located in the various environments, i.e., clusters, groups, and fields, of the local universe ( z &lt; 0.01). The dEs are selected through visual inspection of the Legacy survey’s g – r – z combined tricolor images. The inspected area, covering a total sky area of 7643 deg 2 , encompasses two local clusters (Virgo and Fornax), 265 groups, and the regions around 586 field galaxies of M K &lt; −21 mag. The catalog aim

Abstract We study a low-mass spiral galaxy NGC 2750 (∼5 times less massive than the Milky Way), located ∼40 Mpc away in a sparse region that hosts seven satellite galaxies within a projected distance of 150 Kpc. Among them six are star-forming dwarfs with stellar masses of &gt;≈10 7 M ⊙ and one is an early-type dwarf with a stellar mass of 2.6 × 10 6 M ⊙ . The star-forming dwarfs are gas rich, with gas mass fractions as high as Log( M H i / M * ) = 1.2 and their star formation rates vary between

The color distributions of globular clusters (GCs) in individual early-type galaxies show great diversity in their morphology. Based on the conventional "linear" relationship between the colors and metallicities of GCs, the GC metallicity distributions inferred from colors and in turn their formation histories, should be as diverse as they appear. In contrast, here we show that an alternative scenario rooted in the "nonlinear" nature of the metallicity-to-color transformation points to a simpler

Abstract Recent observations revealed a coherence between the spin vector of a galaxy and the orbital motion of its neighbors. We refer to the phenomenon as “the spin–orbit alignment (SOA)” and explore its physical origin via the IllustrisTNG simulation. This is the first study to utilize a cosmological hydrodynamic simulation to investigate the SOA of galaxy pairs. In particular, we identify paired galaxies at z = 0 having the nearest neighbor with mass ratios from 1/10 to 10 and calculate the

Abstract We aim to unravel the interplay between bars, star formation (SF), and active galactic nuclei (AGNs) in barred galaxies. To this end, we utilize the SDSS DR12 to select a sample of nearby (0.02 &lt; z &lt; 0.06) disk galaxies that are suitable for bar examination ( M r &lt; −20.12 and inclination ≲53°). We identify 3662 barred galaxies and measure the length and axis ratio of each bar. We invent new bar parameters that mitigate the stellar and bulge mass biases and show, for the first t

Abstract Warped disk galaxies are classified into two morphologies: S and U types. Conventional theories routinely attribute both types to galactic tidal interaction and/or gas accretion, but reproducing U types in simulations is extremely challenging. Here we investigate whether both types are governed by the same mechanisms using the most extensive sample of ∼8000 nearby (0.02 &lt; z &lt; 0.06) massive ( M * / M ⊙ &gt; 10 9 ) edge-on disks from the Sloan Digital Sky Survey. We find that U type

Abstract A numerical detection of the mass-dependent spin transition of the galaxies is presented. Analyzing a sample of the galaxies with stellar masses in the range of 10 9 &lt; ( M ⋆ / M ⊙ ) ≤ 10 11 from the IllustrisTNG300-1 simulations, we explore the alignment tendency between the galaxy baryon spins and the three eigenvectors of the linearly reconstructed tidal field as a function of M ⋆ and its evolution in the redshift range of 0 ≤ z ≤ 1.5. Detecting a significant signal of the occurren