419 research outputs found
A comparison of the globular cluster luminosity functions of the inner and outer halo of the Milky Way and M31
We show that the globular cluster luminosity function (GCLF) of the inner
halo of the Milky Way is statistically different from the GCLF of the outer
halo. We also find a similar difference between the inner and outer halo
population of M31. We assert that this difference is evidence for some form of
dynamical evolution of the cluster population and/or a dependence of GCLF shape
on the environment in which the cluster population formed. We also find that
the turnover luminosity of the GCLF is unaffected by these differences and
further assert that this stability of the turnover luminosity affirms its
usefulness as an indicator of cosmic distance.Comment: 3 pages, 2 figures, submitted to MNRA
Pencil-Beam Surveys for Faint Trans-Neptunian Objects
We have conducted pencil-beam searches for outer solar system objects to a
limiting magnitude of R ~ 26. Five new trans-neptunian objects were detected in
these searches. Our combined data set provides an estimate of ~90
trans-neptunian objects per square degree brighter than ~ 25.9. This estimate
is a factor of 3 above the expected number of objects based on an extrapolation
of previous surveys with brighter limits, and appears consistent with the
hypothesis of a single power-law luminosity function for the entire
trans-neptunian region. Maximum likelihood fits to all self-consistent
published surveys with published efficiency functions predicts a cumulative sky
density Sigma(<R) obeying log10(Sigma) = 0.76(R-23.4) objects per square degree
brighter than a given magnitude R.Comment: Accepted by AJ, 18 pages, including 6 figure
Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters
We present new (B,I) photometry for the globular cluster systems in eight
Brightest Cluster Galaxies (BCGs), obtained with the ACS/WFC camera on the
Hubble Space Telescope. In the very rich cluster systems that reside within
these giant galaxies, we find that all have strongly bimodal color
distributions All the BCGs show population gradients, with much higher relative
numbers of red clusters within 5 kpc of their centers, consistent with their
having formed at later times than the blue, metal-poor population. A striking
new feature of the color distributions emerging from our data is that for the
brightest clusters (M_I < -10.5) the color distribution becomes broad and less
obviously bimodal. we suggest that it may be a characteristic of many BCGs.
Furthermore, the blue (metal-poor) clusters become progressively redder with
increasing luminosity, following a mass/metallicity scaling relation Z ~
M^0.55. We argue that these GCS characteristics are consistent with a
hierarchical-merging formation picture in which the metal-poor clusters formed
in protogalactic clouds or dense starburst complexes with gas masses in the
range 10^7 - 10^10 M_Sun, but where the more massive clusters on average formed
in bigger clouds with deeper potential wells where more pre-enrichment could
occur.Comment: 48 pages, 24 Figures, PDF, Submitted to Astrophys.J. and refereed.
For complete pdf file with better figures, see:
http://physwww.mcmaster.ca/%7Eharris/Preprints.htm
GRK6 deficiency is associated with enhanced CXCR4-mediated neutrophil chemotaxis in vitro and impaired responsiveness to G-CSF in vivo
The Canada-France Ecliptic Plane Survey - Full Data Release: The orbital structure of the Kuiper belt
We report the orbital distribution of the trans-neptunian objects (TNOs)
discovered during the Canada-France Ecliptic Plane Survey, whose discovery
phase ran from early 2003 until early 2007. The follow-up observations started
just after the first discoveries and extended until late 2009. We obtained
characterized observations of 321 sq.deg. of sky to depths in the range g ~
23.5--24.4 AB mag. We provide a database of 169 TNOs with high-precision
dynamical classification and known discovery efficiency. Using this database,
we find that the classical belt is a complex region with sub-structures that go
beyond the usual splitting of inner (interior to 3:2 mean-motion resonance
[MMR]), outer (exterior to 2:1 MMR), and main (in between). The main classical
belt (a=40--47 AU) needs to be modeled with at least three components: the
`hot' component with a wide inclination distribution and two `cold' components
(stirred and kernel) with much narrower inclination distributions. The hot
component must have a significantly shallower absolute magnitude (Hg)
distribution than the other two components. With 95% confidence, there are
8000+1800-1600 objects in the main belt with Hg <= 8.0, of which 50% are from
the hot component, 40% from the stirred component and 10% from the kernel; the
hot component's fraction drops rapidly with increasing Hg. Because of this, the
apparent population fractions depend on the depth and ecliptic latitude of a
trans-neptunian survey. The stirred and kernel components are limited to only a
portion of the main belt, while we find that the hot component is consistent
with a smooth extension throughout the inner, main and outer regions of the
classical belt; the inner and outer belts are consistent with containing only
hot-component objects. The Hg <= 8.0 TNO population estimates are 400 for the
inner belt and 10,000 for the outer belt within a factor of two.Comment: 59 pages, 9 figures, 7 table
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