1,785 research outputs found
Immigration and the Occupational Choice of Natives: a Factor Proportions Approach
This paper evaluates the impact of immigration on the labor market outcomes of natives in France over the period 1962-1999. Combining large (up to 25%) extracts from six censuses and data from Labor Force Surveys, we exploit the variation in the immigrant share across education/experience cells and over time to identify the impact of immigration. In the Borjas (2003) specification, we find that a 10% increase in immigration increases native wages by 3%. However, as the number of immigrants and the number of natives are positively and strongly correlated across cells, the immigrant share may not be a good measure of the immigration shock. When the log of natives and the log of immigrants are used as regressors instead, the impact of immigration on natives’ wages is still positive but much smaller, and natives’ wages are negatively related to the number of natives. To understand this asymmetry and the positive impact of immigration on wages, we explore the link between immigration and the occupational distribution of natives within education/experience cells. Our results suggest that immigration leads to the reallocation of natives to better-paid occupations within education/experience cells.Immigration, Impact, France.
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The Impact of Immigration on the Local Labor Market Outcomes of Blue Collar Workers: Panel Data Evidence
Using a large administrative French panel data set for 1976-2007, we examine how low- educated immigration affects the wages, employment, occupations and locations of blue-collar native workers. The natives in the sample are initially in occupations heterogeneous in the presence of immigrants, which might reflect a different degree of competition with low-educated immigrants. We first show that larger immigration inflows into locations are accompanied by larger outflows of negatively selected natives from these locations. At the same time, larger immigrant inflows into occupations come with larger outflows of positively selected natives towards occupations with less routine tasks. While we find no negative impact on employment, there is substantial evidence that immigration lowers the median annual wages of natives. The estimated negative effects are also much larger in cross-section than in estimates controlling for composition effect, which is consistent with the idea that endogenous changes in occupation and location attenuate the impact of immigration on natives’ wages. We also find much larger wage decreases for workers initially in non-tradable sectors and more particularly in the construction sector, which are much less likely to upgrade their occupation or change location in response to immigration inflows
The abundance of Bullet-groups in LCDM
We estimate the expected distribution of displacements between the two
dominant dark matter (DM) peaks (DM-DM displacements) and between DM and
gaseous baryon peak (DM-gas displacements) in dark matter halos with masses
larger than Msun/h. We use as a benchmark the observation of SL2S
J08544-0121, which is the lowest mass system ( Msun/h)
observed so far featuring a bi-modal dark matter distribution with a dislocated
gas component. We find that % of the dark matter halos with
circular velocities in the range 300 km/s to 700 km/s (groups) show DM-DM
displacements equal or larger than kpc/h as observed in SL2S
J08544-0121. For dark matter halos with circular velocities larger than 700
km/s (clusters) this fraction rises to 70 10%. Using the same simulation
we estimate the DM-gas displacements and find that 0.1 to 1.0% of the groups
should present separations equal or larger than kpc/h corresponding
to our observational benchmark; for clusters this fraction rises to (7
3)%, consistent with previous studies of dark matter to baryon separations.
Considering both constraints on the DM-DM and DM-gas displacements we find that
the number density of groups similar to SL2S J08544-0121 is Mpc, three times larger than the estimated value for clusters.
These results open up the possibility for a new statistical test of LCDM by
looking for DM-gas displacements in low mass clusters and groups.Comment: 6 pages, 3 figures, accepted for publication in ApJ Letter
Gravitational lensing and dynamics in SL2S\,J02140-0535: Probing the mass out to large radius
We aim to probe the mass of SL2S\,J02140-0535, a galaxy group at = 0.44
from the Strong Lensing Legacy Survey (SL2S). We combine strong lensing
modeling and dynamical constraints. The strong lensing analysis is based on
multi-band HST/ACS observations exhibiting strong lensing features that we have
followed-up spectroscopically with VLT/FORS2. To constrain the scale radius of
an NFW mass profile that cannot be constrained by strong lensing, we propose a
new method by taking advantage of the large-scale dynamical information
provided by VLT/FORS2 and KECK/LRIS spectroscopy of group members. In constrast
to other authors, we show that the observed lensing features in
SL2S\,J02140-0535 belong to different background sources: one at = 1.7
0.1 produces three images, while the other at = 1.023 0.001 has
only a single image. Our unimodal NFW mass model reproduces these images very
well. It is characterized by a concentration parameter = 6.0
0.6, which is slightly greater than the value expected from CDM
simulations for a mass of M 1 10 M_{\sun}.
The spectroscopic analysis of group members also reveals a unimodal structure
that exhibits no evidence of merging. We compare our dynamic mass estimate with
an independent weak-lensing based mass estimate finding that both are
consistent. Our combined lensing and dynamical analysis of SL2S\,J02140-0535
demonstrates the importance of spectroscopic information in reliably
identifying the lensing features. Our findings argue that the system is a
relaxed, massive galaxy group where mass is traced by light. This work shows a
potentially useful method for constraining large-scale properties inaccessible
to strong lensing, such as the scale radius of the NFW profile.Comment: Accepted for publication in A&
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Moving up or down? Immigration and the selection of natives across occupations and locations
Exploiting a large French panel for 1976-2007, we examine the impact of low-educated immigration on the labour market outcomes of blue-collar natives initially in jobs where immigrants became overrepresented in the last decades. Immigrant inflows generate substantial reallocations of natives across locations and occupations. Location movers are negatively selected while occupation movers are positively selected and move towards better paid-jobs characterised by less routine tasks. As a result, controlling for composition effects has an important quantitative impact on the estimated effects of immigration. Low-educated immigration generally lowers the wages of blue-collar workers, but its impact is heterogeneous across sectors
Multiple introductions, polyploidy and mixed reproductive strategies are linked to genetic diversity and structure in the most widespread invasive plant across Southern Ocean archipelagos
This work received support
from the Swiss Polar Institute and Ferring Pharmaceuticals through
the Antarctic Circumnavigation Expedition (“ACE”). Additional fi-
nancial and logistical support was provided by the South African
National Research Foundation (NRF) and by the South African
National Antarctic Programme (SANAP). MM and CH were also
supported by the National Research Foundation (grant 89967).
We thank Tasmanian Parks and Wildlife Service for granting ac-
cess and collection permits for Macquarie Island and the Australian
Antarctic Program for logistical support. We thank Institut polaire
français Paul- Émile Victor for logistical support for sampling on Iles
Kerguelen and Ile de la Possession. We thank wintering staff for sam-
ple collection on Ile de la Possession. We thank the Department of
Conservation for granting access and collection permits for the New
Zealand islands. We thank Heritage Expeditions for providing logis-
tics and voyage support. Collections were undertaken on the ACE
expedition under permits granted to the expedition and its research-
ers. Collections at the Prince Edward Islands, and at the Tristan da
Cunha and Gough islands were permitted through the South African
National Antarctic Program, notably via the Prince Edward Islands
Management Committee for the former and the Tristan da Cunha
Conservation Department for the latter.Biological invasions in remote areas that experience low human activity provide unique opportunities to elucidate processes responsible for invasion success. Here we study the most widespread invasive plant species across the isolated islands of the Southern Ocean, the annual bluegrass, Poa annua. To analyse geographical variation in genome size, genetic diversity and reproductive strategies, we sampled all major sub-Antarctic archipelagos in this region and generated microsatellite data for 470 individual plants representing 31 populations. We also estimated genome sizes for a subset of individuals using flow cytometry. Occasional events of island colonization are expected to result in high genetic structure among islands, overall low genetic diversity and increased self-fertilization, but we show that this is not the case for P. annua. Microsatellite data indicated low population genetic structure and lack of isolation by distance among the sub-Antarctic archipelagos we sampled, but high population structure within each archipelago. We identified high levels of genetic diversity, low clonality and low selfing rates in sub-Antarctic P. annua populations (contrary to rates typical of continental populations). In turn, estimates of selfing declined in populations as genetic diversity increased. Additionally, we found that most P. annua individuals are probably tetraploid and that only slight variation exists in genome size across the Southern Ocean. Our findings suggest multiple independent introductions of P. annua into the sub-Antarctic, which promoted the establishment of genetically diverse populations. Despite multiple introductions, the adoption of convergent reproductive strategies (outcrossing) happened independently in each major archipelago. The combination of polyploidy and a mixed reproductive strategy probably benefited P. annua in the Southern Ocean by increasing genetic diversity and its ability to cope with the novel environmental conditions.National Research Foundation
89967Antarctic Circumnavigation Expedition “ACE”South African
National Research Foundation (NRF)South African
National Antarctic Programme (SANAP
Kinematics of disk galaxies in (proto-)clusters at z=1.5
We observed star-forming galaxies at z~1.5 selected from the HyperSuprimeCam
Subaru Strategic Program. The galaxies are part of two significant
overdensities of [OII] emitters identified via narrow-band imaging and
photometric redshifts from grizy photometry. We used VLT/KMOS to carry out
Halpha integral field spectroscopy of 46 galaxies in total. Ionized gas maps,
star formation rates and velocity fields were derived from the Halpha emission
line. We quantified morphological and kinematical asymmetries to test for
potential gravitational (e.g. galaxy-galaxy) or hydrodynamical (e.g.
ram-pressure) interactions. Halpha emission was detected in 36 targets. 34 of
the galaxies are members of two (proto-)clusters at z=1.47, confirming our
selection strategy to be highly efficient. By fitting model velocity fields to
the observed ones, we determined the intrinsic maximum rotation velocity Vmax
of 14 galaxies. Utilizing the luminosity-velocity (Tully-Fisher) relation, we
find that these galaxies are more luminous than their local counterparts of
similar mass by up to ~4 mag in the rest-frame B-band. In contrast to field
galaxies at z<1, the offsets of the z~1.5 (proto-)cluster galaxies from the
local Tully-Fisher relation are not correlated with their star formation rates
but with the ratio between Vmax and gas velocity dispersion sigma_g. This
probably reflects that, as is observed in the field at similar redshifts, fewer
disks have settled to purely rotational kinematics and high Vmax/sigma_g
ratios. Due to relatively low galaxy velocity dispersions (sigma_v < 400 km/s)
of the (proto-)clusters, gravitational interactions likely are more efficient,
resulting in higher kinematical asymmetries, than in present-day clusters.
(abbr.)Comment: Accepted for publication in A&A. 11 pages, 8 figures, 1 tabl
Multiwavelength Study of NGC 281 Region
We present a multiwavelength study of the NGC 281 complex which contains the
young cluster IC 1590 at the center, using deep wide-field optical UBVI_c
photometry, slitless spectroscopy along with archival data sets in the
near-infrared (NIR) and X-ray. The extent of IC 1590 is estimated to be ~6.5
pc. The cluster region shows a relatively small amount of differential
reddening. The majority of the identified young stellar objects (YSOs) are low
mass PMS stars having age <1-2 Myr and mass 0.5-3.5 M_\odot. The slope (\Gamma)
of the mass function for IC 1590, in the mass range 2 < M/M_\odot \le 54, is
found to be -1.11+-0.15. The slope of the K-band luminosity function
(0.37+-0.07) is similar to the average value (~0.4) reported for young
clusters. The distribution of gas and dust obtained from the IRAS, CO and radio
maps indicates clumpy structures around the central cluster. The radial
distribution of the young stellar objects, their ages, \Delta(H-K) NIR-excess,
and the fraction of classical T Tauri stars suggest triggered star formation at
the periphery of the cluster region. However, deeper optical, NIR and MIR
observations are needed to have a conclusive view of star formation scenario in
the region. The properties of the Class 0/I and Class II sources detected by
using the Spitzer mid-infrared observations indicate that a majority of the
Class II sources are X-ray emitting stars, whereas X-ray emission is absent
from the Class 0/I sources. The spatial distribution of Class 0/I and Class II
sources reveals the presence of three sub-clusters in the NGC 281 West region.Comment: 29 pages, 21 figures and 11 tables, Accepted for the publication in
PAS
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