90 research outputs found
Compilation of Mentoring Programs in San Diego and Imperial Counties
This document compiles information on mentoring programs in San Diego and Imperial Counties. The goal is to provide a clear picture what mentoring programs are being implemented and to give basic information about those programs as of June 2021.
The purpose of the document is three-fold. First, as a deliverable under the Project Safe Neighborhoods initiative (PSN), it is designed to provide basic information to the US Attorney’s Office and others involved in the PSN on the range of mentoring programs that exist. Mentoring programs have proven to be an effective program strategy for producing a range of positive youth development outcomes, including reducing violence and recidivism. Therefore, it is useful for those working on PSN to have an understanding of the number and nature of mentoring programs that exist.
Second, and similarly, the compilation is for others working on issues of youth development, violence prevention and reducing recidivism. The goal is to provide a continually-updated compilation of mentoring programs for those who wish to access these programs, those who wish to support these programs, and those who wish to ensure they are working in a complementary instead of a duplicative way. This includes the organization currently working under the Project Safe Neighborhoods initiative, many of which are implementing mentoring programs.
Third, the compilation serves as a foundation for our own and for others’ future research efforts regarding youth development, violence prevention, and reducing recidivism in San Diego. Part of our work under the PSN initiative will be a comprehensive report on youth development as a strategy to reduce violence and recidivism in San Diego and Imperial Counties. This will serve as a foundation for this research and for similar research conducted by others working on these issues.https://digital.sandiego.edu/ipj-research/1004/thumbnail.jp
Search for Extratidal Features Around 17 Globular Clusters in the Sloan Digital Sky Survey
The dynamical evolution of a single globular cluster and also of the entire
Galactic globular cluster system has been studied theoretically in detail. In
particular, simulations show how the 'lost' stars are distributed in tidal
tails emerging from the clusters. We investigate the distribution of Galactic
globular cluster stars on the sky to identify such features like tidal tails.
The Sloan Digital Sky Survey provides consistent photometry of a large part of
the sky to study the projected two dimensional structure of the 17 globular
clusters in its survey area. We use a color-magnitude weighted counting
algorithm to map (potential) cluster member stars on the sky. We recover the
already known tidal tails of Pal 5 and NGC 5466. For NGC 4147 we have found a
two arm morphology. Possible indications of tidal tails are also seen around
NGC 5053 and NGC 7078, supporting earlier suggestions. Moreover, we find
potential tails around NGC 5904 and Pal 14. Especially for the Palomar clusters
than Pal 5, deeper data are needed in order to confirm or to rule out the
existence of tails. For many of the remaining clusters in our sample we observe
a pronounced extratidal halo, which is particularly large for NGC 7006 and Pal
1. In some cases, the extratidal halos may be associated with the stream of the
Sagittarius dwarf spheroidal galaxy (e.g.,NGC 4147, NGC 5024, NGC 5053).Comment: Accepted by A&A, 24 pages, 24 figure
Accreted versus In Situ Milky Way Globular Clusters
Here we examine the Milky Way's GC system to estimate the fraction of
accreted versus in situ formed GCs. We first assemble a high quality database
of ages and metallicities for 93 Milky Way GCs from literature deep
colour-magnitude data. The age-metallicity relation for the Milky Way's GCs
reveals two distinct tracks -- one with near constant old age of ~12.8 Gyr and
the other branches to younger ages. We find that the latter young track is
dominated by globular clusters associated with the Sagittarius and Canis Major
dwarf galaxies. Despite being overly simplistic, its age-metallicity relation
can be well represented by a simple closed box model with continuous star
formation. The inferred chemical enrichment history is similar to that of the
Large Magellanic Cloud, but is more enriched, at a given age, compared to the
Small Magellanic Cloud. After excluding Sagittarius and Canis Major GCs,
several young track GCs remain. Their horizontal branch morphologies are often
red and hence classified as Young Halo objects, however they do not tend to
reveal extended horizontal branches (a possible signature of an accreted
remnant nucleus). Retrograde orbit GCs (a key signature of accretion) are
commonly found in the young track. We also examine GCs that lie close to the
Fornax-Leo-Sculptor great circle defined by several satellite galaxies. We find
that several GCs are consistent with the young track and we speculate that they
may have been accreted along with their host dwarf galaxy, whose nucleus may
survive as a GC. Finally, we suggest that 27-47 GCs (about 1/4 of the entire
system), from 6-8 dwarf galaxies, were accreted to build the Milky Way GC
system we seen today.Comment: 13 pages, 9 figures, MNRAS in pres
A wide-field photometric survey for extratidal tails around five metal-poor globular clusters in the Galactic halo
Wide-field deep gri images obtained with the Megacam of the
Canada-France-Hawaii Telescope (CFHT) are used to investigate the spatial
configuration of stars around five metal-poor globular cluster M15, M30, M53,
NGC 5053, and NGC 5466, in a field-of-view ~3 degree. Applying a mask filtering
algorithm to the color-magnitude diagrams of the observed stars, we sorted
cluster's member star candidates that are used to examine the characteristics
of the spatial stellar distribution surrounding the target clusters. The
smoothed surface density maps and the overlaid isodensity contours indicate
that all of the five metal-poor globular clusters exhibit strong evidence of
extratidal overdensity features over their tidal radii, in the form of extended
tidal tails around the clusters. The orientations of the observed extratidal
features show signatures of tidal tails tracing the clusters' orbits, inferred
from their proper motions, and effects of dynamical interactions with the
Galaxy. Our findings include detections of a tidal bridge-like feature and an
envelope structure around the pair of globular clusters M53 and NGC 5053. The
observed radial surface density profiles of target clusters have a deviation
from theoretical King models, for which the profiles show a break at
0.5~0.7r_t, extending the overdensity features out to 1.5~2r_t. Both radial
surface density profiles for different angular sections and azimuthal number
density profiles confirm the overdensity features of tidal tails around the
five metal-poor globular clusters. Our results add further observational
evidence that the observed metal-poor halo globular clusters originate from an
accreted satellite system, indicative of the merging scenario of the formation
of the Galactic halo.Comment: 69 pages, 21 figures, accepted for publication in the Astronomical
Journa
Outer density profiles of 19 Galactic globular clusters from deep and wide-field imaging
Using deep photometric data from WFC@INT and [email protected] we measure the outer
number density profiles of 19 stellar clusters located in the inner region of
the Milky Way halo (within a Galactocentric distance range of 10-30 kpc) in
order to assess the impact of internal and external dynamical processes on the
spatial distribution of stars. Adopting power-law fitting templates, with index
in the outer region, we find that the clusters in our sample can be
divided in two groups: a group of massive clusters ( M_sun) that
has relatively flat profiles with and a group of low-mass
clusters ( M_sun), with steep profiles () and clear
signatures of interaction with the Galactic tidal field. We refer to these two
groups as 'tidally unaffected' and 'tidally affected', respectively. Our
results also show a clear trend between the slope of the outer parts and the
half-mass density of these systems, which suggests that the outer density
profiles may retain key information on the dominant processes driving the
dynamical evolution of Globular Clusters.Comment: 17 pages, 14 figures, 2 tables; accepted for publication in MNRA
The VPOS: a vast polar structure of satellite galaxies, globular clusters and streams around the Milky Way
It has been known for a long time that the satellite galaxies of the Milky
Way (MW) show a significant amount of phase-space correlation, they are
distributed in a highly inclined Disc of Satellites (DoS). We have extended the
previous studies on the DoS by analysing for the first time the orientations of
streams of stars and gas, and the distributions of globular clusters within the
halo of the MW. It is shown that the spatial distribution of MW globular
clusters classified as young halo clusters (YH GC) is very similar to the DoS,
while 7 of the 14 analysed streams align with the DoS. The probability to find
the observed clustering of streams is only 0.3 per cent when assuming isotropy.
The MW thus is surrounded by a vast polar structure (VPOS) of subsystems
(satellite galaxies, globular clusters and streams), spreading from
Galactocentric distances as small as 10 kpc out to 250 kpc. These findings
demonstrate that a near-isotropic infall of cosmological sub-structure
components onto the MW is essentially ruled out because a large number of
infalling objects would have had to be highly correlated, to a degree not
natural for dark matter sub-structures. The majority of satellites, streams and
YH GCs had to be formed as a correlated population. This is possible in tidal
tails consisting of material expelled from interacting galaxies. We discuss the
tidal scenario for the formation of the VPOS, including successes and possible
challenges. The potential consequences of the MW satellites being tidal dwarf
galaxies are severe. If all the satellite galaxies and YH GCs have been formed
in an encounter between the young MW and another gas-rich galaxy about 10-11
Gyr ago, then the MW does not have any luminous dark-matter substructures and
the missing satellites problem becomes a catastrophic failure of the standard
cosmological model.Comment: 21 pages, 8 figures, 2 tables. Accepted for publication in MNRAS. An
animation of Figure 5 can be found at http://youtu.be/nUwxv-WGfH
A 500 Parsec Halo Surrounding the Galactic Globular NGC 1851
Using imaging that shows four magnitudes of main sequence stars, we have
discovered that the Galactic globular cluster NGC 1851 is surrounded by a halo
that is visible from the tidal radius of 700 arcsec (41 pc) to more than 4500
arcsec (>250 pc). This halo is symmetric and falls in density as a power law of
. It contains approximately 0.1% of the dynamical mass of NGC 1851.
There is no evidence for tidal tails. Current models of globular cluster
evolution do not explain this feature, although simulations of tidal influences
on dwarf spheroidal galaxies qualitatively mimic these results. Given the state
of published models it is not possible to decide between creation of this halo
from isolated cluster evaporation, or from tidal or disk shocking, or from
destruction of a dwarf galaxy in which this object may have once been embedded.Comment: Version with higher-resolution figures is at
http://adansonia.as.arizona.edu/~edo/1851_paper/paper_aug11.ps.g
Alien Registration- Lauchner, Gilbert H. (Upton, Oxford County)
https://digitalmaine.com/alien_docs/13982/thumbnail.jp
- …