557 research outputs found
Two distinct red giant branch populations in the globular cluster NGC 2419 as tracers of a merger event in the Milky Way
Recent spectroscopic observations of the outer halo globular cluster (GC) NGC
2419 show that it is unique among GCs, in terms of chemical abundance patterns,
and some suggest that it was originated in the nucleus of a dwarf galaxy. Here
we show, from the Subaru narrow-band photometry employing a calcium filter,
that the red giant-branch (RGB) of this GC is split into two distinct
subpopulations. Comparison with spectroscopy has confirmed that the redder RGB
stars in the [=(Ca] index are enhanced in [Ca/H] by 0.2
dex compared to the bluer RGB stars. Our population model further indicates
that the calcium-rich second generation stars are also enhanced in helium
abundance by a large amount (Y = 0.19). Our photometry, together with
the results for other massive GCs (e.g., Cen, M22, and NGC 1851),
suggests that the discrete distribution of RGB stars in the index might be
a universal characteristic of this growing group of peculiar GCs. The planned
narrow-band calcium photometry for the Local Group dwarf galaxies would help to
establish an empirical connection between these GCs and the primordial building
blocks in the hierarchical merging paradigm of galaxy formation.Comment: 4 pages, 4 figures, 1 table, accepted for the publication in ApJ
Recommended from our members
Evaluation of the On-Campus Dining Service Using Importance-Performance Analysis
University foodservice is one of the largest sectors of the foodservice industry, and the college-student market is getting larger. Therefore, it is important that university foodservice needs to be monitored periodically and improved comprehensively in order to retain students as satisfied customers for on-campus foodservice. The objectives of the current study were to explore the importance and performance/satisfaction of on-campus dining service consumers, to investigate the importance-performance difference between patron and non-patron customers, and to examine the difference between gender groups. The study compared the respondents’ perceived importance and performance ratings of the dining service quality attributes using IPA. The IPA grid illustrated that food quality and sanitation fell into the Quadrant II (Keep up the Work); price into the Quadrant III (Low Priority); and service and environment into the Quadrant IV (Possible Overkill). However, according to IPA of comparison of patron versus non-patron groups and gender groups, the service attribute was allocated differently
The Presence of Two Distinct Red Giant Branches in the Globular Cluster NGC 1851
There is a growing body of evidence for the presence of multiple stellar
populations in some globular clusters, including NGC 1851. For most of these
peculiar globular clusters, however, the evidence for the multiple red
giant-branches (RGBs) having different heavy elemental abundances as observed
in Omega Centauri is hitherto lacking, although spreads in some lighter
elements are reported. It is therefore not clear whether they also share the
suggested dwarf galaxy origin of Omega Cen or not. Here we show from the CTIO
4m UVI photometry of the globular cluster NGC 1851 that its RGB is clearly
split into two in the U - I color. The two distinct RGB populations are also
clearly separated in the abundance of heavy elements as traced by Calcium,
suggesting that the type II supernovae enrichment is also responsible, in
addition to the pollutions of lighter elements by intermediate mass asymptotic
giant branch stars or fast-rotating massive stars. The RGB split, however, is
not shown in the V - I color, as indicated by previous observations. Our
stellar population models show that this and the presence of bimodal
horizontal-branch distribution in NGC 1851 can be naturally reproduced if the
metal-rich second generation stars are also enhanced in helium.Comment: 13 pages, 4 figures, accepted for publication in the Astrophysical
Journal Letter
Permanent Pacemaker for Syncope after Heart Transplantation with Bicaval Technique
Sinus node dysfunction occurs occasionally after heart transplantation and may be caused by surgical trauma, ischemia to the sinus node, rejection, drug therapy, and increasing donor age. However, the timing and indication of permanent pacemaker insertion due to sinus node dysfunction following heart transplantation is contentious. Here, we report a case of a permanent pacemaker insertion for syncope due to sinus arrest after heart transplantation, even with a bicaval technique, which has been known to associate with few incidences of sinus node dysfunction
Solution-processed germanium nanowire-positioned Schottky solar cells
Germanium nanowire (GeNW)-positioned Schottky solar cell was fabricated by a solution process. A GeNW-containing solution was spread out onto asymmetric metal electrodes to produce a rectifying current flow. Under one-sun illumination, the GeNW-positioned Schottky solar cell yields an open-circuit voltage of 177 mV and a short-circuit current of 19.2 nA. Schottky and ohmic contacts between a single GeNW and different metal electrodes were systematically investigated. This solution process may provide a route to the cost-effective nanostructure solar architecture
- …