• Publications of The Korean Astronomical Society
• /
• v.11 no.1
• /
• pp.139-146
• /
• 1996

Galactic open clusters NGC 1907 and NGC 1912 are known as a binary cluster candidate by Subramaniam et al.(1995). With the SNUO 0.6m telescope, UBV CCD photometric observations were performed for 62 stars in NGC 1907 within the area of $8'{\times}8'$ and 203 stars in NGC 1912 within the area of $15'{\times}15'$ area. We obtained C-M and C-C diagrams. Their mean reddenings are E(B-V) = $0.50{\pm}0.03$ for NGC 1907 and $0.27{\pm}0.03$ for NGC 1912. The distance moduli are estimated as $10.9{\pm}0.15$ and $10.4{\pm}0.10$ for NGC 1907 and NGC 1912, respectively. The ages for these clusters are $400{\pm}50Myr$ for NGC 1907 and $150{\pm}30Myr$ for NGC 1912. The distance difference of the two clusters is 300pc and the age difference is 150Myr. These results imply that the two clusters are not physically connected.

• Publications of The Korean Astronomical Society
• /
• v.14 no.1
• /
• pp.1-8
• /
• 1999

We performed VRI CCD surface photometry of three spiral galaxies of HCG10 in order to understand the effect of interactions in the compact group. The morphology of the largest member NGC 536 seems to be normal but its bulge is thought to be of an oblate spheroid. The central surface brightness of the disk of NGC 536 is much fainter than that of disks of nearby spiral galaxies. The morphologies of NGC 531 and NGG 542 appear to be affected by interactions which lead to a warped disk in NGC 531 and a slightly bent disk in NGC 542. NGC 531 have a boxy bulge and a Freeman Type II disk both of which strongly suggest the presence of a bar in the galaxy. There is a break in the slope of the luminosity profile of NGC 542 which is dominated by the disk component.

• Journal of The Korean Astronomical Society
• /
• v.32 no.1
• /
• pp.1-6
• /
• 1999

We have conducted near-infrared (J- and H-band) surface photometry for two early type barred galaxies, NGC 3412 and NGC 3941. The bulges of NGC 3412 and NGC 3941 show isophotal twists which indicate that they are triaxial. NGC 3412 has a very short bar and its bulge is more centrally concentrated than that of NGC 3941. The unusually short bar and the centrally concentrated triaxial bulge of NGC 3412 might be the result of bar dissolution. The colors of the nuclear region of NGC 3941 resemble those of the blue nuclei, implying the presence of young stellar populations.

• The Bulletin of The Korean Astronomical Society
• /
• v.44 no.2
• /
• pp.74.1-74.1
• /
• 2019

We present the distance measurements of two spiral galaxies NGC 4517, NGC 4592, and neighboring dwarf galaxies found in Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) wide field survey data. Distances to NGC 4517 and NGC 4592 are measured by the Tip of the Red Giant Branch method from archival Hubble Space Telescope data; 9.00^+0.094_-0.260 Mpc for NGC 4517 and 8.90^+0.256_-0.060 Mpc for NGC 4592. The spatial distance between NGC 4517 and NGC 4592 is 300 kpc, which is close enough for them to be considered as a group (NGC 4517 group). Using resolved stellar photometry and Surface Brightness Fluctuation (SBF) method with HSC-SSP data, we estimate the distances to three other dwarf galaxies and confirm that they are members of the group. Velocities of three of the galaxies in the NGC 4517 group show that this group is one of the galaxy groups in the near side of the Virgo Cluster infall region.

• Journal of The Korean Astronomical Society
• /
• v.15 no.1
• /
• pp.41-48
• /
• 1982

PDS was used to get the structure of two barred spiral galaxies NGC 1313 and NGC 1365. The result shows that NGC 1365 has both a deep spheroidal component and an exponential disk, but NGC 1313 has only an prominent exponential component. The luminosity profiles indicate that KGC 1313 is in type I and NGC 1365 belongs to type II. The length scales $({\alpha}^{-1})$ were derived from the exponential luminosity distributions as 1.64 kpc for NGC 1313 and 2.49kpc for KGC 1365.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.1
• /
• pp.60.1-60.1
• /
• 2012

구경 3.6m의 캐나다-프랑스-하와이 망원경(Canada-France-Hawaii Telescope, CFHT)의 주 초점에 설치된 CFH12K CCD 카메라를 이용하여 늙은 산개성단 NGC 1245와 NGC 2506에 대한 V와 I필터를 이용한 CCD측광을 수행하였다. 관측된 영역은 NGC 1245는 84'${\times}$82', NGC 2506은 42'${\times}$81'이고, 한계등급 V ${\approx}$ 23등급까지 관측하였다. 이론적인 등연령곡선을 사용하여 NGC 1245와 NGC 2506에 대해 각각 물리량 E(B-V) = 0.2, 0.03, (V-M_V)_0 = 12.5, 12.5, log(age) = 9.0, 9.3으로 구하였다. 이로부터 MV ${\approx}$ 10등급까지의 광도함수와 질량함수를 구하였다. NGC 1245와 NGC 2506의 질량함수의 기울기를 각각 ${\Gamma}$ = -1.26${\pm}$0.04, ${\Gamma}$ = -1.27${\pm}$0.07로 얻었고, 이들의 기울기는 태양부근의 낱별의 질량함수의 기울기에 비해 완만하다. 이는 성단에서 질량이 작은 별들의 질량 증발에 의한 역학적 진화의 효과로 보인다. 본 발표에서는 관측 내용과 그 결과를 소개하고자 한다.

• Publications of The Korean Astronomical Society
• /
• v.30 no.2
• /
• pp.169-171
• /
• 2015

NGC147 and NGC185, paired satellites of the Andromeda galaxy, possess the same order of mass and analogous structures, but they show different star formation and different amounts of interstellar gas and dust. Therefore, we present the first reconstruction of the star formation history of NGC147 and NGC185. Asymptotic Giant Branch stars are highly evolved stars that are brightest in K-band. This maximum K-band magnitude is related to the birth mass of stars. As a result, we have found a 9.9 Gyr old single star formation epoch for NGC185 followed by relatively continuous star formation. NGC147, however, has passed through two star formation episodes; one is as old as ~6 Gyr and the other is as recent as ~850 Myr. Asymptotic Giant Branch stars are also important dust factories; by fitting Spectral Energy Distributions to observed near and mid infrared data for each star, we were able to measure the dust production rates of individual stars; on order of $10^{-5}M_{\odot}yr^{-1}$. Hence, we estimate the total mass entering the interstellar medium to be $1.06{\times}10^{-4}M_{\odot}yr^{-1}$ and $2.89{\times}10^{-4}M_{\odot}yr^{-1}$ for NGC147 and NGC185.

• Journal of The Korean Astronomical Society
• /
• v.26 no.1
• /
• pp.13-32
• /
• 1993

We have conducted BVI photographic surface photometry of four spiral galaxies NGC1087, NGC2715, NGC2844 and NGC3593, by making use of the Kiso Schmidt plates. Detailed examination of the morphological properties of the galaxies using isophotal maps and luminosity profiles showed that all the program galaxies have some peculiarities in their luminosity distributions. NGC1087 and NGC2715 have extremely small nuclei with inner rings which contain several bright HII regions. NGC2844 has a very large bulge whose luminosity dominates over the disk luminosity in all the radii. The I-band luminosity profile of NGC3593 shows shallower gradient than B- and V-band profiles. We were able to successfully decompose the luminosity profile into a bulge following de Vaucouleurs $\gamma^{1/4}-law$ and an exponential disk only for NGC 3953. Other galaxies have more complicated luminosit profiles.

• Journal of The Korean Astronomical Society
• /
• v.34 no.2
• /
• pp.99-109
• /
• 2001

In the present study we have determined the distance moduli for seven globular clusters M2, M3, Ml0, M12, NGC 2808, NGC 6229, and NGC 6752, whose metallicities are in the range -1.54 < [Fe/H] < -1.10. We have derived distances for them by the main-sequence fitting method using a sample of local subdwarfs, whose accurate parallaxes are taken from the Hipparcos Catalog. The derived distance moduli are 15.52 for M2, 14.98 for M3, 14.23 for Ml0, 14.03 for M12, 15.56 for NGC 2808, 17.34 for NGC 6229, and 13.29 for NGC 6752.

• Journal of The Korean Astronomical Society
• /
• v.31 no.1
• /
• pp.51-65
• /
• 1998

We present B VRI CCD surface photometry for the central $(6'.35\times6'.35)$ regions of the dwarf elliptical galaxies NGC 185 and NGC 205 in the Local Group. Surface brightness profiles of NGC 185 (R<225') and NGC 205 (R<186') show excess components in the central regions. The colors of NGC 185 get bluer inward at R<25', while they remain constant at $R\geq25'$. The colors of NGC 205 get bluer inward at 1'$\approx10^5\; L_\bigodot$. Distributions of dust clouds in the central regions of the two galaxies are also investigated.