412 research outputs found
Quality control in major abdominal surgery
Cuesta Valentin, M.A. [Promotor]Peet, D.L. van der [Copromotor
A massive, quiescent galaxy at redshift of z=3.717
In the early Universe finding massive galaxies that have stopped forming
stars present an observational challenge as their rest-frame ultraviolet
emission is negligible and they can only be reliably identified by extremely
deep near-infrared surveys. These have revealed the presence of massive,
quiescent early-type galaxies appearing in the universe as early as z2,
an epoch 3 Gyr after the Big Bang. Their age and formation processes have now
been explained by an improved generation of galaxy formation models where they
form rapidly at z3-4, consistent with the typical masses and ages derived
from their observations. Deeper surveys have now reported evidence for
populations of massive, quiescent galaxies at even higher redshifts and earlier
times, however the evidence for their existence, and redshift, has relied
entirely on coarsely sampled photometry. These early massive, quiescent
galaxies are not predicted by the latest generation of theoretical models.
Here, we report the spectroscopic confirmation of one of these galaxies at
redshift z=3.717 with a stellar mass of 1.710 M whose
absorption line spectrum shows no current star-formation and which has a
derived age of nearly half the age of the Universe at this redshift. The
observations demonstrates that the galaxy must have quickly formed the majority
of its stars within the first billion years of cosmic history in an extreme and
short starburst. This ancestral event is similar to those starting to be found
by sub-mm wavelength surveys pointing to a possible connection between these
two populations. Early formation of such massive systems is likely to require
significant revisions to our picture of early galaxy assembly.Comment: 6 pages, 7 figures. This is the final preprint corresponding closely
to the published version. Uploaded 6 months after publication in accordance
with Nature polic
Intimate Partner Violence and COVID-19 in Rural, Remote, and Northern Canada: Relationship, Vulnerability and Risk
In rural, remote, and northern parts of Canada, the pre-existing vulnerability and risk for intimate partner violence has been exacerbated by COVID-19. The purpose of this commentary is to identify the unique impact of COVID-19 on intimate partner violence both in terms of the bearing on those experiencing abuse and on the service sector in rural, remote and northern communities where the rates of intimate partner violence and intimate partner femicide pre-pandemic are higher than in larger cities. The recommendations offered in this paper include enhanced safety planning, alternate housing for victims fleeing violence, and suggestions for service providers. We also offer ways to move forward with further research in the COVID-19 era
Z-FIRE: ISM properties of the z = 2.095 COSMOS Cluster
We investigate the ISM properties of 13 star-forming galaxies within the z~2
COSMOS cluster. We show that the cluster members have [NII]/Ha and [OIII]/Hb
emission-line ratios similar to z~2 field galaxies, yet systematically
different emission-line ratios (by ~0.17 dex) from the majority of local
star-forming galaxies. We find no statistically significant difference in the
[NII]/Ha and [OIII]/Hb line ratios or ISM pressures among the z~2 cluster
galaxies and field galaxies at the same redshift. We show that our cluster
galaxies have significantly larger ionization parameters (by up to an order of
magnitude) than local star-forming galaxies. We hypothesize that these high
ionization parameters may be associated with large specific star formation
rates (i.e. a large star formation rate per unit stellar mass). If this
hypothesis is correct, then this relationship would have important implications
for the geometry and/or the mass of stars contained within individual star
clusters as a function of redshift.Comment: 11 pages, 5 figures, accepted for publication in Ap
IL CONTRATTO A TEMPO INDETERMINATO A TUTELE CRESCENTI
La disciplina del licenziamento nel rapporto di lavoro ha comportato una dinamica evolutiva, che l'ha portata a distaccarsi dal regime disposto dal codice civile, incentrato, per entrambe le parti del rapporto di lavoro, sul principio, di matrice liberale, della libertà di recesso dal contratto di lavoro subordinato a tempo indeterminato. Con la Legge n. 108/1990 è stato portato a compimento una generalizzazione della giustificazione del licenziamento individuale. Una maggiore intensificazione della tutela contro i licenziamenti trova un freno, invece, con la riforma della tutela reale ad opera della Legge n. 92/2012. Questo ridimensionamento, da ultimo, viene confermato ed intensificato dalla disciplina in materia di contratto di lavoro a tempo indeterminato a tutele crescenti, di cui al D.lgs. n. 23/2015
ZFIRE: The Evolution of the Stellar Mass Tully-Fisher Relation to Redshift 2.0 < Z < 2.5 with MOSFIRE
Using observations made with MOSFIRE on Keck I as part of the ZFIRE survey,
we present the stellar mass Tully-Fisher relation at 2.0 < z < 2.5. The sample
was drawn from a stellar mass limited, Ks-band selected catalog from ZFOURGE
over the CANDELS area in the COSMOS field. We model the shear of the Halpha
emission line to derive rotational velocities at 2.2X the scale radius of an
exponential disk (V2.2). We correct for the blurring effect of a
two-dimensional PSF and the fact that the MOSFIRE PSF is better approximated by
a Moffat than a Gaussian, which is more typically assumed for natural seeing.
We find for the Tully-Fisher relation at 2.0 < z < 2.5 that logV2.2 =(2.18 +/-
0.051)+(0.193 +/- 0.108)(logM/Msun - 10) and infer an evolution of the
zeropoint of Delta M/Msun = -0.25 +/- 0.16 dex or Delta M/Msun = -0.39 +/- 0.21
dex compared to z = 0 when adopting a fixed slope of 0.29 or 1/4.5,
respectively. We also derive the alternative kinematic estimator S0.5, with a
best-fit relation logS0.5 =(2.06 +/- 0.032)+(0.211 +/- 0.086)(logM/Msun - 10),
and infer an evolution of Delta M/Msun= -0.45 +/- 0.13 dex compared to z < 1.2
if we adopt a fixed slope. We investigate and review various systematics,
ranging from PSF effects, projection effects, systematics related to stellar
mass derivation, selection biases and slope. We find that discrepancies between
the various literature values are reduced when taking these into account. Our
observations correspond well with the gradual evolution predicted by
semi-analytic models.Comment: 21 pages, 14 figures, 1 appendix. Accepted for publication by Apj,
February 28, 201
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