arXiv subjects

Narae Hwang

Publications and source records attributed to Narae Hwang.

60 records · Page 4Linked to original sources

arXiv2007

Star Cluster Population of the Interacting Galaxy System M51

We present a star cluster population study in the interacting galaxy system M51 based on HST ACS BVI mosaic images taken by the Hubble Heritage Team to commemorate the HST's 15th anniversary. We have found and classified star clusters in M51 using SExtractor and visual inspection. We have derived the photometry, size, and age of the clusters. It is found that the companion SB0 galaxy NGC 5195 harbors about 50 faint fuzzy clusters and that the age distribution of star clusters appears to be correlated with the epochs of dynamical events in M51 system.

astro-ph↗

arXiv2007

An Optical Source Catalog of the North Ecliptic Pole Region

We present a five (u*,g',r',i',z') band optical photometry catalog of the sources in the North Ecliptic Pole (NEP) region based on deep observations made with MegaCam at CFHT. The source catalog covers about 2 square degree area centered at the NEP and reaches depths of about 26 mag for u*, g', r' bands, about 25 mag for i' band, and about 24 mag for z' band (4 sigma detection over an 1 arcsec aperture). The total number of cataloged sources brighter than r'= 23 mag is about 56,000 including both point sources and extended sources. From the investigation of photometric properties using the color-magnitude diagrams and color-color diagrams, we have found that the colors of extended sources are mostly (u*-r') < 3.0 and (g'-z') > 0.5. This can be used to separate the extended sources from the point sources reliably, even for the faint source domain where typical morphological classification schemes hardly work efficiently. We have derived an empirical color-redshift relation of the red sequence galaxies using the Sloan Digital Sky Survey data. By applying this relation to our photometry catalog and searching for any spatial overdensities, we have found two galaxy clusters and one nearby galaxy group.

astro-ph↗

arXiv2006

Spatial Distribution of Faint Fuzzy Star Clusters in NGC 5195

We present a study of a faint fuzzy star cluster system in the nearby SB0 galaxy NGC 5195 interacting with the famous spiral galaxy NGC 5194 (M51), based on HST ACS BVI mosaic images taken by the Hubble Heritage Team. We have found about 50 faint fuzzy star clusters around NGC 5195 which are larger than typical globular clusters with effective radii r_eff > 7 pc and red with (V-I) > 1.0. They are mostly fainter than M_V ~ 8.3 mag. From the comparison of BVI photometry of these clusters with the simple stellar population models, we find that they are as massive as ~ 10^5 M_sun and older than 1 Gyr. Strikingly, most of these clusters are found to be scattered in an elongated region almost perpendicular to the northern spiral arm of NGC 5194, and the center of the region is slightly north of the NGC 5195 center, while normal compact red clusters of NGC 5195 are located around the bright optical body of the host galaxy. This is in contrast against the cases of NGC 1023 and NGC 3384 where spatial distribution of faint fuzzy clusters shows a ring structure around the host galaxy. We suggest that at least some faint fuzzy clusters are experiencing tidal interactions with the companion galaxy NGC 5194 and must be associated with the tidal debris in the western halo of NGC 5195.

astro-ph↗

arXiv2005

Giant Halos in Dwarf Irregular Galaxies vs. Dwarf Elliptical Galaxies

We present a discovery of a giant stellar halo in NGC 6822, a dwarf irregular galaxy in the Local Group. This halo is mostly made of old red giants, showing striking features: 1) it is several times larger than the main body of the galaxy seen in the optical images, and 2) it is elongated in the direction almost perpendicular to the HI disk of NGC 6822. The structure of this stellar halo looks similar to the shape of dwarf elliptical galaxies, indicating that the halos of dwarf irregular galaxies share the same origin with those of the dwarf elliptical galaxies.

astro-ph↗

arXiv2005

Discovery of Remote Star Clusters in the Halo of the Irregular Galaxy NGC 6822

We report the discovery of three new star clusters in the halo of the Local Group dwarf irregular galaxy NGC 6822. These clusters were found in the deep images taken with the MegaPrime at the CFHT, covering a total field of 2 deg x 2 deg. The most remote cluster is found to be located as far as 79 arcmin away from the center of NGC 6822. This distance is several times larger than the size of the region in NGC 6822 where star clusters were previously found. Morphological structures of the clusters and color-magnitude diagrams of the resolved stars in the clusters show that at least two of these clusters are proabably old globular clusters.

astro-ph↗

arXiv2000

Morphological Number Counts of Galaxies in the Hubble Deep Field South

We present a study of photometric properties of the galaxies in the Hubble Deep Field South (HDFS) based on the released WFPC2 images obtained with the Hubble Space Telescope (HST). We have classified about 340 galaxies with $I<26$ mag in the HDFS as well as about 400 galaxies in the Hubble Deep Field North (HDFN) using the visual classification supplemented by inspection of the surface brightness profiles of the galaxies. Galaxy population statistics and morphological number counts for the HDFS are found to be similar to be those for the HDFN. We have also determined photometrically the redshifts of the galaxies with $I<26$ mag in the HDFS and the HDFN using the empirical training set method. Redshift distribution, color-redshift relation, and magnitude-redshift for each type of galaxies are investigated.

astro-ph↗