Jubee Sohn (손 주 비)
HectoMAP
Cluster Survey
HectoMAP is a dense redshift survey enabling a survey of galaxy clusters based on spectroscopy. We test the redMaPPer catalog and we use ROSAT All-Sky Survey (RASS) data to construct X-ray cluster catalog.
-
More than 90% of HectoMAP redMaPPer clusters have at least 10 spectroscopic members.
-
Based on the HectoMAP and RASS data, we find 15 clusters (7 newly discovered) with redshift z ≤ 0.4 to the X-ray flux limit of the RASS (∼ 3 × 10−13 erg s−1 cm−2).
-
We predict that there are ∼ 12000 ± 3000 detectable X-ray clusters in the RASS, comparable to the estimate based on the XXL cluster survey (Pacaud et al. 2016).
X-ray clusters in HectoMAP (Subaru/HSC images)
Velocity
Dispersion
Function
Velocity Dispersion Function (VDF) is a statistical tool for studying the dark halo mass distribution. Central velocity dispersion traces the velocity dispersion of dark matter halos, which may be directly correlated to the dark matter halo mass.
-
VDFs of the quiescent member galaxies of Coma and Abell 2029 are measured, for the first time.
-
Cluster VDFs exceed the field VDF at both high and low dispersion ends.
-
The decreasing field VDF at low dispersion end is caused by the selection effect: the field VDF should be measured from velocity-dispersion limited sample.
(Left) Cluster Velocity Dispersion Function
(Right) Cluster (white) vs. Field (red) VDFs
Compact
groups
of
Galaxies
Compact Groups of Galaxies are the densest known galaxy systems in the universe. In compact groups, member galaxies frequently interact each other and they are expected to form a single elliptical galaxy within a short period (< 2 Gyrs). The fate of compact groups are an intriguing question.
I constructed the largest compact group catalog based on the SDSS DR12 spectroscopic data based on the friend-of-friend algorithm.
SDSS thumbnail images of compact groups