1,931 research outputs found
The Aging of the American Workforce
The decades immediately following World War II saw a sharp decline in the labor force participation rates of older Americans, due largely to the ever earlier retirement of men. While older persons in search of work have long faced formidable barriers finding it, during the post-war years, the country was becoming richer and using some of the increased wealth to purchase later-life leisure. About twenty years ago, participation rates at upper ages stopped declining and have been inching upward since then. The coming insolvency of the Social Security system, potential labor and skills shortages, and inadequate retirement savings are among the factors expected to put greater pressure on government to implement policies that foster longer work lives, on employers to expand employment opportunities for older workers, and on workers to remain longer in the workforce. This article provides an overview of the weakening labor force attachment of older Americans in the decades following World War II; speculates on what the future holds and why more work later in life may characterize growing numbers of older persons; and discusses a number of issues—such as labor demand and the quality of work—that must be addressed to ensure a productive aging workforce. Although the population and workforce are aging, substantially higher participation rates on the part of older persons are not inevitable
The Aging of the American Workforce
The decades immediately following World War II saw a sharp decline in the labor force participation rates of older Americans, due largely to the ever earlier retirement of men. While older persons in search of work have long faced formidable barriers finding it, during the post-war years, the country was becoming richer and using some of the increased wealth to purchase later-life leisure. About twenty years ago, participation rates at upper ages stopped declining and have been inching upward since then. The coming insolvency of the Social Security system, potential labor and skills shortages, and inadequate retirement savings are among the factors expected to put greater pressure on government to implement policies that foster longer work lives, on employers to expand employment opportunities for older workers, and on workers to remain longer in the workforce. This article provides an overview of the weakening labor force attachment of older Americans in the decades following World War II; speculates on what the future holds and why more work later in life may characterize growing numbers of older persons; and discusses a number of issues—such as labor demand and the quality of work—that must be addressed to ensure a productive aging workforce. Although the population and workforce are aging, substantially higher participation rates on the part of older persons are not inevitable
Results from the CASTLES Survey of Gravitational Lenses
We show that most gravitational lenses lie on the passively evolving
fundamental plane for early-type galaxies. For burst star formation models (1
Gyr of star formation, then quiescence) in low Omega_0 cosmologies, the stellar
populations of the lens galaxies must have formed at z_f > 2. Typical lens
galaxies contain modest amounts of patchy extinction, with a median
differential extinction for the optical (radio) selected lenses of E(B-V) =
0.04 (0.07) mag. The dust can be used to determine both extinction laws and
lens redshifts. For example, the z_l=0.96 elliptical lens in MG0414+0534 has an
R_V=1.7 +/- 0.1 mean extinction law. Arc and ring images of the quasar and AGN
source host galaxies are commonly seen in NICMOS H band observations. The hosts
are typically blue, L < L_* galaxies.Comment: 12 pages, 10 figures, from Proceedings of the 9th Annual Astrophysics
Conference in Maryland, After the Dark Ages: When Galaxies Were Youn
HST/STIS Spectra of Nuclear Star Clusters in Spiral Galaxies: Dependence of Age and Mass On Hubble Type
(Abridged) We study the nuclear star clusters in spiral galaxies of various
Hubble types using spectra obtained with STIS on-board HST. We observed the
nuclear clusters in 40 galaxies, selected from two previous HST/WFPC2 imaging
surveys. The spectra provide a better separation of cluster light from
underlying galaxy light than is possible with ground-based spectra. To infer
the star formation history, metallicity and dust extinction, we fit weighted
superpositions of single-age stellar population templates to the spectra. The
luminosity-weighted age ranges from 10 Myrs to 10 Gyrs. The stellar populations
of NCs are generally best fit as a mixture of populations of different ages.
This indicates that NCs did not form in a single event, but instead they had
additional star formation long after the oldest stars formed. On average, the
sample clusters in late-type spirals have a younger luminosity-weighted mean
age than those in early-type spirals (log(age/yr) = 8.37+/-0.25 vs.
9.23+/-0.21). The average cluster masses are smaller in late-type spirals than
in early-type spirals (log(M/Msun) = 6.25+/-0.21 vs. 7.63+/-0.24), and exceed
the masses typical of globular clusters. The cluster mass correlates strongly
with both the Hubble type of the host galaxy and the luminosity of its bulge.
The latter correlation has the same slope as the well-known correlation between
supermassive black hole mass and bulge luminosity. The properties of both
nuclear clusters and black holes are therefore intimately connected to the
properties of the host galaxy.Comment: AJ submitted (original submission Nov 30, 2005, present version
includes changes based on referee recommendations). 69 pages, 16 figures, 7
table
A Young Stellar Cluster in the Nucleus of NGC 4449
We have obtained 1-2 A resolution optical Echellette spectra of the nuclear
star cluster in the nearby starburst galaxy NGC 4449. The light is clearly
dominated by a very young (6-10 Myr) population of stars. For our age dating,
we have used recent population synthesis models to interpret the observed
equivalent width of stellar absorption features such as the HI Balmer series
and the CaII triplet around 8500 A. We also compare the observed spectrum of
the nuclear cluster to synthesized spectra of simple stellar populations of
varying ages. All these approaches yield a consistent cluster age. Metallicity
estimates based on the relative intensities of various ionization lines yield
no evidence for significant enrichment in the center of this low mass galaxy:
the metallicity of the nuclear cluster is about one fourth of the solar value,
in agreement with independent estimates for the disk material of NGC 4449.Comment: 24 pages (incl. 7 figures), accepted by AJ, March 2001 issue revised
version with minor changes and additions, one additional figur
A Search for Planetary Nebulae With the SDSS: the outer regions of M31
We have developed a method to identify planetary nebula (PN) candidates in
imaging data of the Sloan Digital Sky Survey (SDSS). This method exploits the
SDSS' five-band sampling of emission lines in PN spectra, which results in a
color signature distinct from that of other sources. Selection criteria based
on this signature can be applied to nearby galaxies in which PNe appear as
point sources. We applied these criteria to the whole area of M31 as scanned by
the SDSS, selecting 167 PN candidates that are located in the outer regions of
M31. The spectra of 80 selected candidates were then observed with the 2.2m
telescope at Calar Alto Observatory. These observations and cross-checks with
literature data show that our method has a selection rate efficiency of about
90%, but the efficiency is different for the different groups of PNe
candidates.
In the outer regions of M31, PNe trace different well-known morphological
features like the Northern Spur, the NGC205 Loop, the G1 Clump, etc. In
general, the distribution of PNe in the outer region 8<R<20 kpc along the minor
axis shows the "extended disk" - a rotationally supported low surface
brightness structure with an exponential scale length of 3.21+/-0.14 kpc and a
total mass of ~10^10 M_{\sun}, which is equivalent to the mass of M33. We
report the discovery of three PN candidates with projected locations in the
center of Andromeda NE, a very low surface brightness giant stellar structure
in the outer halo of M31. Two of the PNe were spectroscopically confirmed as
genuine PNe. These two PNe are located at projected distances along the major
axis of ~48 Kpc and ~41 Kpc from the center of M31 and are the most distant PNe
in M31 found up to now.Comment: 58 pages, 17 figures, 2 tables, Accepted to Astronomical Journa
Mapping low-latitude stellar substructure with SEGUE photometry
Encircling the Milky Way at low latitudes, the Low Latitude Stream is a large
stellar structure, the origin of which is as yet unknown. As part of the SEGUE
survey, several photometric scans have been obtained that cross the Galactic
plane, spread over a longitude range of 50 to 203 degrees. These data allow a
systematic study of the structure of the Galaxy at low latitudes, where the Low
Latitude Stream resides. We apply colour-magnitude diagram fitting techniques
to map the stellar (sub)structure in these regions, enabling the detection of
overdensities with respect to smooth models. These detections can be used to
distinguish between different models of the Low Latitude Stream, and help to
shed light on the nature of the system.Comment: To appear in the proceedings of IAU Symposium 254 "The Galaxy disk in
a cosmological context", Copenhagen, June 200
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