29 research outputs found
Near-Infrared Photometric Study of the Old Open Cluster Trumpler 5
We present JHK near-infrared photometric study for the old open cluster (OC)
Trumpler 5 (Tr 5), based on the 2MASS data. From the color-magnitude diagrams
of Tr 5, we have located the position of the red giant clump (RGC) stars, and
used the mean magnitude of the RGC stars in K-band to estimate the distance to
Tr 5, d = 3.1 +/- 0.1 kpc ((m-M)_0 = 12.46 +/- 0.04). From fitting the
theoretical isochrones of Padova group, we have estimated the reddening,
metallicity, and age : E(B-V) = 0.64 +/- 0.05, [Fe/H] = -0.4 +/- 0.1 dex, and t
=2.8 +/- 0.2 Gyr (log t=9.45 +/- 0.04), respectively. These parameters
generally agree well with those obtained from the previous studies on Tr 5 and
confirms that this cluster is an old OC with metallicity being metal-poorer
than solar abundance, located in the anti-Galactic center region.Comment: JKAS (J. of the Korean Astron. Soc.) in press (2009 Dec issue), page
numbers will be change
UBVI CCD Photometry of the Old Open Cluster NGC 1193
We present UBVI photometry of the old open cluster NGC 1193. Color-magnitude
diagrams (CMDs) of this cluster show a well defined main sequence and a sparse
red giant branch. For the inner region of r<50 arcsec, three blue straggler
candidates are newly found in addition to the objects Kaluzny (1988) already
found. The color-color diagrams show that the reddening value toward NGC 1193
is E(B-V) =0.19 +/- 0.04. From the ultraviolet excess measurement, we derived
the metallicity to be [Fe/H]=-0.45 +/- 0.12. A distance modulus of (m-M)_0
=13.3 +/- 0.15 is obtained from zero age main sequence fitting with the
empirically calibrated Hyades isochrone of Pinsonneault et al. (2004). CMD
comparison with the Padova isochrones by Bertelli et al. (1994) gives an age of
log t =9.7 +/- 0.1.Comment: JKAS (J. of the Korean Astron. Soc.) in press (Dec 2008 issue
Near-Infrared Photometry of the Star Clusters in the Dwarf Irregular Galaxy IC 5152
We present JHK-band near-infrared photometry of star clusters in the dwarf
irregular galaxy IC 5152. After excluding possible foreground stars, a number
of candidate star clusters are identified in the near-infrared images of IC
5152, which include young populations. Especially, five young star clusters are
identified in the (J-H, H-K) two color diagram and the total extinction values
toward these clusters are estimated to be A_V =2 - 6 from the comparison with
the theoretical values given by the Leitherer et al. (1999)'s theoretical star
cluster model.Comment: Accepted by the Journal of the Korean Astronomical Society, 2006
December issue (Vol. 39, No. 4
Distance and Reddening of the Isolated Dwarf Irregular Galaxy NGC 1156
We present a photometric estimation of the distance and reddening values to
the dwarf irregular galaxy NGC 1156, which is one of the best targets to study
the isolated dwarf galaxies in the nearby universe. We have used the imaging
data sets of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS)
High Resolution Channel (HRC) of the central region of NGC 1156 (26" X 29")
available in the HST archive for this study. From the (U-B, B-V) color-color
diagram, we first estimate the total (foreground + internal) reddening toward
NGC 1156 of E(B-V) =0.35 +/- 0.05 mag, whereas only the foreground reddening
was previously known to be E(B-V)=0.16 mag (Burstein & Heiles) or 0.24 mag
(Schlegel, Finkbeiner, & Davis). Based on the brightest stars method, selecting
the three brightest blue supergiant (BSG) stars with mean B magnitude of
= 21.94 mag and the three brightest red supergiant (RSG) stars with
mean V magnitude of = 22.76 mag, we derive the distance modulus to NGC
1156 to be (m-M)_{0,BSG} = 29.55 mag and (m-M)_{0,RSG} = 29.16 mag. By using
weights of 1 and 1.5 for the distance moduli from using the BSGs and the RSGs,
respectively, we finally obtain the weighted mean distance modulus to NGC 1156
(m-M)_0 = 29.39 +/- 0.20 mag (d = 7.6 +/- 0.7 Mpc), which is in very good
agreement with the previous estimates. Combining the photometry data of this
study with those of Karachentsev et al. gives smaller distance to NGC 1156,
which is discussed together with the limits of the data.Comment: 18 pages, 8 figures, Accepted by PASJ (2012 Apr issue