347 research outputs found
Charting the evolution of the ages and metallicities of massive galaxies since z=0.7
The stellar populations of intermediate-redshift galaxies can shed light onto
the growth of massive galaxies in the last 8 billion years. We perform deep,
multi-object rest-frame optical spectroscopy with IMACS/Magellan of ~70
galaxies in the E-CDFS with redshift 0.6522.7 and
stellar mass >10^{10}Msun. Following the Bayesian approach adopted for previous
low-redshift studies, we constrain the stellar mass, mean stellar age and
stellar metallicity of individual galaxies from stellar absorption features. We
characterize for the first time the dependence of stellar metallicity and age
on stellar mass at z~0.7 for all galaxies and for quiescent and star-forming
galaxies separately. These relations for the whole sample have a similar shape
as the z=0.1 SDSS analog, but are shifted by -0.28 dex in age and by -0.13 dex
in metallicity, at odds with simple passive evolution. We find that no
additional star formation and chemical enrichment are required for z=0.7
quiescent galaxies to evolve into the present-day quiescent population.
However, this must be accompanied by the quenching of a fraction of z=0.7
Mstar>10^{11}Msun star-forming galaxies with metallicities comparable to those
of quiescent galaxies, thus increasing the scatter in age without affecting the
metallicity distribution. However rapid quenching of the entire population of
massive star-forming galaxies at z=0.7 would be inconsistent with the
age/metallicity--mass relation for the population as a whole and with the
metallicity distribution of star-forming galaxies only, which are on average
0.12 dex less metal-rich than their local counterparts. This indicates chemical
enrichment until the present in at least a fraction of the z=0.7 massive
star-forming galaxies.[abridged]Comment: accepted for publication on ApJ, 26 pages, 13 figure
Gravitational lens candidates in the E-CDFS
We report ten lens candidates in the E-CDFS from the GEMS survey. Nine of the
systems are new detections and only one of the candidates is a known lens
system. For the most promising five systems including the known lens system, we
present results from preliminary lens mass modelling, which tests if the
candidates are plausible lens systems. Photometric redshifts of the candidate
lens galaxies are obtained from the COMBO-17 galaxy catalog. Stellar masses of
the candidate lens galaxies within the Einstein radius are obtained by using
the -band luminosity and the color-based stellar mass-to-light ratios.
As expected, the lensing masses are found to be larger than the stellar masses
of the candidate lens galaxies. These candidates have similar dark matter
fractions as compared to lenses in SLACS and COSMOS. They also roughly follow
the halo mass-stellar mass relation predicted by the subhalo abundance matching
technique. One of the candidate lens galaxies qualifies as a LIRG and may not
be a true lens because the arc-like feature in the system is likely to be an
active region of star formation in the candidate lens galaxy. Amongst the five
best candidates, one is a confirmed lens system, one is a likely lens system,
two are less likely to be lenses and the status of one of the candidates is
ambiguous. Spectroscopic follow-up of these systems is still required to
confirm lensing and/or for more accurate determination of the lens masses and
mass density profiles.Comment: 12 pages, 5 figures, 3 tables, ApJ accepte
On the connection between galactic downsizing and the most fundamental galactic scaling relations
In their evolution, star-forming galaxies are known to follow scaling
relations between some fundamental physical quantities, such as the
mass-metallicity and the main sequence relations. We aim at studying the
evolution of galaxies that, at a given redshift, lie simultaneously on the
mass-metallicity and main sequence relations (MZR, MSR). To this aim, we use
the analytical, 'leaky-box' chemical evolution model of Spitoni et al. (2017),
in which galaxy evolution is described by an infall timescale and a wind
efficiency . We provide a detailed analysis of the temporal evolution
of galactic metallicity, stellar mass, mass-weighted age and gas fraction. The
evolution of the galaxies lying on the MZR and MSR at suggests that
the average infall time-scale in two different bins of stellar masses
() decreases
with decreasing redshift. This means that at each redshift, only the youngest
galaxies can be assembled on the shortest timescales and still belong to the
star-forming MSR. In the lowest mass bin, a decrease of the median is
accompanied by an increase of the median value. This implies that
systems which have formed at more recent times will need to eject a larger
amount of mass to keep their metallicity at low values. Another important
result is that galactic downsizing, as traced by the age-mass relation, is
naturally recovered by imposing that local galaxies lie on both the MZR and
MSR. Finally, we study the evolution of the hosts of C -selected
AGN, which at follow a flat MZR, as found by Mignoli et al. (2019).
If we impose that these systems lie on the MSR, at lower redshifts we find an
'inverted' MZR, meaning that some additional processes must be at play in their
evolution.Comment: Accepted for publication in Astronomy and Astrophysics (A&A), 20
pages, 26 figure
Continuous central venous saturation monitoring in critically ill patients
Table 1 (abstract P39). Patients\u2019 variables according to ScvO2 range
ScvO2 75
Patients 15/37 36/37 36/37
SpO2 (%) 95.8 \ub1 3.0 95.0 \ub1 3.3 96.4 \ub1 2.3
HR (bpm) 90.6 \ub1 16.1 90.5 \ub1 18.1 90.7 \ub1 16.5
MAP (mmHg) 82.5 \ub1 10.6 83.4 \ub1 12.7 82.2 \ub1 11.7
CVP (mmHg) 18.3 \ub1 4.6 20.2 \ub1 8.2 19.2 \ub1 5.
The cosmic evolution of the spatially-resolved star formation rate and stellar mass of the CALIFA survey
We investigate the cosmic evolution of the absolute and specific star
formation rate (SFR, sSFR) of galaxies as derived from a spatially-resolved
study of the stellar populations in a set of 366 nearby galaxies from the
CALIFA survey. The analysis combines GALEX and SDSS images with the 4000 break,
H_beta, and [MgFe] indices measured from the datacubes, to constrain parametric
models for the SFH, which are then used to study the cosmic evolution of the
star formation rate density (SFRD), the sSFR, the main sequence of star
formation (MSSF), and the stellar mass density (SMD). A delayed-tau model,
provides the best results, in good agreement with those obtained from
cosmological surveys. Our main results from this model are: a) The time since
the onset of the star formation is larger in the inner regions than in the
outer ones, while tau is similar or smaller in the inner than in the outer
regions. b) The sSFR declines rapidly as the Universe evolves, and faster for
early than for late type galaxies, and for the inner than for the outer regions
of galaxies. c) SFRD and SMD agree well with results from cosmological surveys.
At z< 0.5, most star formation takes place in the outer regions of late spiral
galaxies, while at z>2 the inner regions of the progenitors of the current E
and S0 are the major contributors to SFRD. d) The inner regions of galaxies are
the major contributor to SMD at z> 0.5, growing their mass faster than the
outer regions, with a lookback time at 50% SMD of 9 and 6 Gyr for the inner and
outer regions. e) The MSSF follows a power-law at high redshift, with the slope
evolving with time, but always being sub-linear. f) In agreement with galaxy
surveys at different redshifts, the average SFH of CALIFA galaxies indicates
that galaxies grow their mass mainly in a mode that is well represented by a
delayed-tau model, with the peak at z~2 and an e-folding time of 3.9 Gyr.Comment: 23 pages, 16 figures, 6 tables, accepted for publication in Astronomy
& Astrophysics. *Abridged abstract
Multicentric, multifocal, and recurrent osteoid osteoma of the hip : first case report
BACKGROUND:
Osteoid osteoma is a benign bone-forming tumour, which very unfrequently has multifocal or multicentric presentation. We report the first known case of a multicentric, multifocal and recurrent osteoid osteoma treated using radiofrequency ablation.
CASE PRESENTATION:
A 39-year-old man with two-year history of left hip pain was admitted at our Institution. The pain was more intense during the night and partially relieved by salicylates. Pelvis CT demonstrated two lytic lesions (8 and 7\u2009mm, respectively) with surrounding sclerotic reactive bone, both with a central focal area of high attenuation, located in the femoral neck and along the anterior portion of the acetabulum, respectively. Both lesions had clinical and imaging findings consistent with multicentric osteoid osteoma. Thus, the two lesions were biopsied - with pathologic confirmation of osteoid osteoma - and treated using radiofrequency ablation. Hip pain decreased but did not disappear, actually increasing a few months after treatment. CT and MRI were performed showing a smaller lesion (5\u2009mm) with the same imaging features, surrounded by marrow oedema, along the posterior column of the acetabulum. The lesion was considered suspicious for osteoid osteoma, overlooked on previous examinations. Therefore, a diagnosis of multicentric and multifocal osteoid osteoma was established. The new lesion was again treated with radiofrequency ablation with symptom disappearance. However, hip pain relapsed after 18\u2009months, and CT and MRI showed an osteoid osteoma recurrence on the posterior column of the acetabulum, which was biopsied and successfully treated using radiofrequency ablation.
CONCLUSIONS:
To our knowledge, this is the first reported case of multicentric, multifocal, recurrent osteoid osteoma. Our case report highlights the importance of considering a diagnosis of multifocal osteoid osteoma when dealing with multifocal lytic lesions of the bone and with pain persistence after treatment. It also emphasises the combined role of CT and MRI in this setting
The MAGNUM survey: Positive feedback in the nuclear region of NGC 5643 suggested by MUSE
We study the ionization and kinematics of the ionized gas in the nuclear
region of the barred Seyfert 2 galaxy NGC~5643 using MUSE integral field
observations in the framework of the MAGNUM (Measuring Active Galactic Nuclei
Under MUSE Microscope) survey. The data were used to identify regions with
different ionization conditions and to map the gas density and the dust
extinction. We find evidence for a double sided ionization cone, possibly
collimated by a dusty structure surrounding the nucleus. At the center of the
ionization cone, outflowing ionized gas is revealed as a blueshifted,
asymmetric wing of the [OIII] emission line, up to projected velocity
v(10)~-450 km/s. The outflow is also seen as a diffuse, low luminosity radio
and X-ray jet, with similar extension. The outflowing material points in the
direction of two clumps characterized by prominent line emission with spectra
typical of HII regions, located at the edge of the dust lane of the bar. We
propose that the star formation in the clumps is due to `positive feedback'
induced by gas compression by the nuclear outflow, providing the first
candidate for outflow induced star formation in a Seyfert-like radio quiet AGN.
This suggests that positive feedback may be a relevant mechanism in shaping the
black hole-host galaxy coevolution.Comment: 9 pages, 7 figures, accepted for publication in A&
Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies
Superluminous supernovae (SLSNe) are very bright explosions that were only
discovered recently and that show a preference for occurring in faint dwarf
galaxies. Understanding why stellar evolution yields different types of stellar
explosions in these environments is fundamental in order to both uncover the
elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In
this paper, we present the first results of our project to study SUperluminous
Supernova Host galaxIES, focusing on the sample for which we have obtained
spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen-poor) often (~50% in
our sample) occur in a class of galaxies that is known as Extreme Emission Line
Galaxies (EELGs). The probability of this happening by chance is negligible and
we therefore conclude that the extreme environmental conditions and the SLSN
phenomenon are related. In contrast, SLSNe-II (hydrogen-rich) occur in more
massive, more metal-rich galaxies with softer radiation fields. Therefore, if
SLSNe-II constitute a uniform class, their progenitor systems are likely
different from those of H-poor SLSNe. Gamma-ray bursts (GRBs) are, on average,
not found in as extreme environments as H-poor SLSNe. We propose that H-poor
SLSNe result from the very first stars exploding in a starburst, even earlier
than GRBs. This might indicate a bottom-light initial mass function in these
systems. SLSNe present a novel method of selecting candidate EELGs independent
of their luminosity.Comment: Published version, matches proofs. Accepted 2015 February 13. 23
pages, 8 figures, 4 tables. Minor changes with respect to previous versio
A radiological visual scale to predict the potentially recruitable lung in ALI/ARDS patients
Introduction In ALI/ARDS patients the amount of potentially
recruitable lung is extremely variable and it is poorly predictable by
the changes of oxygenation, carbon dioxide or compliance during a
PEEP trial [1]. At the present time the gold standard to compute the
lung recruitability is the quantitative lung CT scan, in which each lung image, after being manually drawn, is analyzed by dedicated software.
However, this is both a laborious and time-consuming technique. The
aim of this study was to evaluate the ability of a visual radiological scale
compared with lung CT scan analysis to predict the lung recruitability
in ALI/ARDS patients.
Methods A whole lung CT scan was performed at 5 and 45 cmH2O
airway pressure. For CT scan analysis each lung image was manually
outlined and analyzed by a dedicated software. The potentially
recruitable lung was defi ned as the proportion of the nonaerated
lung tissue in which aeration was restored [1]. For radiological visual
scale analysis, two radiologists performed a blinded evaluation of the
consolidation/collapsed areas in each lobe by visual inspection [2]. The
overall lung change in consolidation/collapsed was obtained by the
sum of each lobe and computed as the diff erence between the two
conditions.
Results Twenty-four ALI/ARDS patients (age 59 \ub1 15 years, BMI
26 \ub1 4 kg/m2, PaO2/FiO2 170 \ub1 60, PEEP 10 \ub1 2 cmH2O) were enrolled.
The percentage of potentially recruitable lung was 16.2 \ub1 7.1% and
14.7 \ub1 7.0%, computed by CT scan and by the visual radiological scale,
respectively. The mean diff erence between CT scan analysis and visual
radiological analysis was 3.3 \ub1 4.6% (median: 2.91, interquartile range:
0.38 to 6.56). The error of the visual method was lower than 5% in 14
patients (58.3%), between 5% and 10% in eight patients (33.3%) and
between 10% and 15% in two patients (8.3%).
Conclusions The application of a radiological visual scale is able to
predict the amount of potentially recruitable lung similarly to those
obtained by a dedicated software avoiding the need of manually
drawing each lung image.
References
1. Gattinoni L, et al.: N Engl J Med 2006, 354:1775-1786.
2. Pierce RJ, et al.: Thorax 1980, 35:773-780
Constraining the low-mass end of the Initial Mass Function with Gravitational Lensing
The low-mass end of the stellar Initial Mass Function (IMF) is constrained by
focusing on the baryon-dominated central regions of strong lensing galaxies. We
study in this letter the Einstein Cross (Q2237+0305), a z=0.04 barred galaxy
whose bulge acts as lens on a background quasar. The positions of the four
quasar images constrain the surface mass density on the lens plane, whereas the
surface brightness (H-band NICMOS/HST imaging) along with deep spectroscopy of
the lens (VLT/FORS1) allow us to constrain the stellar mass content, for a
range of IMFs. We find that a classical single power law (Salpeter IMF)
predicts more stellar mass than the observed lensing estimates. This result is
confirmed at the 99% confidence level, and is robust to systematic effects due
to the choice of population synthesis models, the presence of dust, or the
complex disk/bulge population mix. Our non-parametric methodology is more
robust than kinematic estimates, as we do not need to make any assumptions
about the dynamical state of the galaxy or its decomposition into bulge and
disk. Over a range of low-mass power law slopes (with Salpeter being
Gamma=+1.35) we find that at a 90% confidence level, slopes with Gamma>0 are
ruled out.Comment: 5 pages, 6 figures. Accepted for publication in MNRAS Letter
- âŠ