• 천문학회보
• /
• 제24권1호
• /
• pp.48-48
• /
• 1999

• 천문학회지
• /
• 제13권1호
• /
• pp.45-62
• /
• 1980

Defining a metal parameter $(Sp)_c$, which is related to the morphological parameters of C-M diagrams, we have estimated metal abundances for 97 globular clusters in our Galaxy. A correlation between absolute magnitude of the horizontal branch and metal abundance is derived, which is used for the determining distances to globular clusters whose visual magnitudes of the horizontal branch are known. The space distribution of globular clusters and the chemical evolution of the halo are examined. Our analysis suggests an initial mean gradient of metallicity to be d[Fe/H]/$dr_G$ = -0.06 $kpc^{-1}$ for the halo in galactocentric distance, $r_G$<20 kpc. Our findings also imply a slow collapse of protogalaxy.

• 천문학회보
• /
• 제24권1호
• /
• pp.47-47
• /
• 1999

• 천문학회보
• /
• 제24권1호
• /
• pp.49-49
• /
• 1999

• 천문학회보
• /
• 제36권2호
• /
• pp.68.2-68.2
• /
• 2011

We present the detailed image decomposition of Hubble Space Telescope archival images for 235 nearby (z < 0.35) unobscured type 1 AGNs. It allows us to perform robust measurements of host galaxy properties and AGN luminosity contribution. We examine how the host properties correlate with AGN properties. Broad line type 1 and radio-loud AGNs are hosted preferentially by early type galaxies. Narrow line type 1 AGNs show a low fraction of tidal interaction, that might suggest the secular evolution may play an important role for triggering AGN activity, while the fraction of merging hosts is rather higher in luminous AGNs. We compare the nucleus luminosity and bulge luminosity and find that either our sample might have a smaller zero point in the M(BH)-L(bulge) relation (i.e. less massive black hole at a given bulge luminosity) relation compared to the normal galaxies or Eddington ratio of our sample could be systematically overestimated.

• 천문학회보
• /
• 제36권2호
• /
• pp.73.1-73.1
• /
• 2011

An understanding of the ultraviolet (UV) properties of nearby galaxies is essential for interpreting images of high redshift systems. In this respect, the prediction of optical-band morphologies at high redshifts requires UV images of local galaxies with various morphologies. We present the simulated optical images of galaxies at high redshifts using diverse and high-quality UV images of nearby galaxies obtained through the Galaxy Evolution Explorer (GALEX). We measured CAS (concentration, asymmetry, clumpiness) as well as Gini/M20 parameters of galaxies at near-ultraviolet (NUV) and simulated optical images to quantify effects of redshift on the appearance of distant stellar systems. We also discuss the change of morphological parameters with redshift.

• 천문학회보
• /
• 제41권1호
• /
• pp.69.3-70
• /
• 2016

We study the orbital histories of Virgo galaxies undergoing different HI gas stripping stages using phase-space diagrams. Based on the HI properties of galaxies, we find that location of galaxies is in good agreement with ram-pressure stripping predicted by numerical simulations with different infall time. For example, galaxies experiencing active gas stripping are mostly found in the first infall region showing high velocity with respect to the cluster center. Meanwhile, most galaxies that are likely to have lost gas a while ago are found in the cluster outskirts with low orbital velocities. We also discuss the cases where observational properties of galaxies and their locations in the phase-space do not well agree. In addition, we probe the phase-space of filaments and subgroups around or within Virgo. Our results strongly suggest that substructures can play important roles in galaxy evolution while galaxies are falling to the cluster.

• 천문학회지
• /
• 제36권3호
• /
• pp.249-260
• /
• 2003

ASTRO-F is the next generation Japanese infrared space mission of the Institute of Space and Astronautical Science. ASTRO-F will be dedicated to an All Sky Survey in the far-infrared in 4 bands from 50-200microns with 2 additional mid-infrared bands at 9microns and 20microns. This will be the first all sky survey in the infrared since the ground breaking IRAS mission almost 20 years ago and the first ever survey at 170microns. The All Sky Survey should detect 10's of millions of sources in the far-infrared bands most of which will be dusty luminous and ultra-luminous star forming galaxies, with as many as half lying at redshifts greater than unity. In this contribution, the ASTRO-F mission and its objectives are reviewed and many of the mission expectations are discussed.

• 천문학논총
• /
• 제30권2호
• /
• pp.289-292
• /
• 2015

Most of the stars in the Galaxy are in binary systems. Binaries should be possible as the hosting stars of planets. Searching for planetary companions to binaries, especially evolved close binary stars, can provide insight into the formation and the ultimate fate of circumbinary planets and shed light on the late evolution of binary stars. In order to do this, we have chosen some post common envelope binaries including sdB-type eclipsing binaries and detached WD+dM eclipsing binaries as our targets and monitored them for several years. In this paper, we will present some of our new observations and results for three targets, NSVS 07826147, NSVS14256825 and RR Cae.

• 천문학회보
• /
• 제43권2호
• /
• pp.38.2-38.2
• /
• 2018

To understand the assembly of the galaxy population in clusters today, it is important to first understand preprocessing, the impact of environments prior to cluster infall. We use 15 cluster samples from YZiCS, a hydrodynamic cluster zoom-in simulation to determine the significance of preprocessing, and focus on the tidal mass loss of dark matter halos. We find ~48% of the cluster member halos were once satellites of another host. The preprocessed fraction depends on each cluster's recent mass growth history. Also, we find that the total mass loss is a clear function of the time spent in a host. However, two factors can increase the mass loss rate considerably. First, if the satellite mass is approaching the mass of its host. Second, when the halo suffers tidal mass loss at a higher redshift. Being in hosts before cluster infall enables halos to experience tidal mass loss for an extended period of time.