67 research outputs found
An ultra-deep multi-band VLA survey of the faint radio sky (COSMOS-XS): New constraints on the cosmic star formation history
We make use of ultra-deep 3 GHz Karl G. Jansky Very Large Array observations
of the COSMOS field from the multi-band COSMOS-XS survey to infer radio
luminosity functions (LFs) of star-forming galaxies (SFGs). Using 1300
SFGs with redshifts out to , and fixing the faint and bright end
shape of the radio LF to the local values, we find a strong redshift trend that
can be fitted by pure luminosity evolution with the luminosity parameter given
by . We then combine the
ultra-deep COSMOS-XS data-set with the shallower VLA-COSMOS
large project data-set over the wider COSMOS field in order to fit for joint
density+luminosity evolution, finding evidence for significant density
evolution. By comparing the radio LFs to the observed far-infrared (FIR) and
ultraviolet (UV) LFs, we find evidence of a significant underestimation of the
UV LF by at high redshift (,
integrated down to ). We derive the cosmic star
formation rate density (SFRD) by integrating the fitted radio LFs and find that
the SFRD rises up to and then declines more rapidly than
previous radio-based estimates. A direct comparison between the radio SFRD and
a recent UV-based SFRD, where we integrate both LFs down to a consistent limit
(), reveals that the discrepancy between the radio and
UV LFs translates to a significant (1 dex) discrepancy in the derived
SFRD at , even assuming the latest dust corrections and without accounting
for optically dark sources.Comment: Submitted to ApJ; 27 pages, 13 figures, 4 table
The ALMA REBELS survey: the dust content of z ∼7 Lyman break galaxies
We include a fully coupled treatment of metal and dust enrichment into the Delphi semi-analytic model of galaxy formation to explain the dust content of 13 Lyman break galaxies (LBGs) detected by the Atacama Large millimetre Array (ALMA) REBELS Large Program at z ≃ 7. We find that the galaxy dust mass, Md, is regulated by the combination of Type II supernova dust production, astration, shock destruction, and ejection in outflows; grain growth (with a standard time-scale τ0 = 30 Myr) plays a negligible role. The model predicts a dust-to-stellar mass ratio of ~ 0.07-0.1per cent and a UV-to-total star formation rate relation such that log(ψUV) = -0.05 [log(ψ)]2 + 0.86 log(ψ) - 0.05 (implying that 55-80 per cent of the star formation is obscured) for REBELS galaxies with stellar mass M∗ = 109-1010 M⊙. This relation reconciles the intrinsic UV luminosity of LBGs with their observed luminosity function at z = 7. However, 2 out of the 13 systems show dust-to-stellar mass ratios (~0.94-1.1per cent) that are up to 18 times larger than expected from the fiducial relation. Due to the physical coupling between dust and metal enrichment, even decreasing τ0 to very low values (0.3 Myr) only increases the dust-to-stellar mass ratio by a factor of ∼2. Given that grain growth is not a viable explanation for such high observed ratios of the dust-to-stellar mass, we propose alternative solutions
The ALMA REBELS survey: obscured star formation in massive Lyman-break galaxies at z = 4-8 revealed by the IRX- and relations
We investigate the degree of dust obscured star formation in 49 massive
() Lyman-break galaxies (LBGs) at
- observed as part of the ALMA Reionization Era Bright Emission
Line Survey (REBELS) large program. By creating deep stacks of the photometric
data and the REBELS ALMA measurements we determine the average rest-frame UV,
optical and far-infrared (FIR) properties which reveal a significant fraction
(-) of obscured star formation, consistent with
previous studies. From measurements of the rest-frame UV slope, we find that
the brightest LBGs at these redshifts show bluer () colours
than expected from an extrapolation of the colour-magnitude relation found at
fainter magnitudes. Assuming a modified blackbody spectral-energy distribution
(SED) in the FIR (with dust temperature of and
), we find that the REBELS sources are in agreement with
the local ''Calzetti-like'' starburst Infrared-excess (IRX)- relation.
By reanalysing the data available for 108 galaxies at - from the
ALPINE ALMA large program using a consistent methodology and assumed FIR SED,
we show that from -, massive galaxies selected in the rest-frame
UV have no appreciable evolution in their derived IRX- relation. When
comparing the IRX- relation derived from the combined ALPINE and
REBELS sample to relations established at , we find a deficit in the
IRX, indicating that at the proportion of obscured star formation is
lower by a factor of at a given a . Our IRX-
results are in good agreement with the high-redshift predictions of simulations
and semi-analytic models for galaxies with similar stellar masses
and SFRs.Comment: 18 pages, 10 figures, 2 tables (plus 1 figure and 2 tables in the
appendix). Updated to match MNRAS accepted version after minor correction
The ALMA REBELS Survey: Discovery of a massive, highly star-forming and morphologically complex ULIRG at
We present Atacama Large Millimeter/Submillimeter Array (ALMA) [CII] and
continuum observations of REBELS-25, a massive,
morphologically complex ultra-luminous infrared galaxy (ULIRG; L) at , spectroscopically
confirmed by the Reionization Era Bright Emission Line Survey (REBELS) ALMA
Large Programme. REBELS-25 has a significant stellar mass of
M. From dust-continuum and ultraviolet
observations, we determine a total obscured + unobscured star formation rate of
SFR M yr. This is about four times the SFR
estimated from an extrapolated main-sequence. We also infer a [CII]-based
molecular gas mass of ,
implying a molecular gas depletion time of Gyr. We observe a [CII] velocity gradient consistent
with disc rotation, but given the current resolution we cannot rule out a more
complex velocity structure such as a merger. The spectrum exhibits excess [CII]
emission at large positive velocities ( km s), which we
interpret as either a merging companion or an outflow. In the outflow scenario,
we derive a lower limit of the mass outflow rate of 200 M yr,
which is consistent with expectations for a star formation-driven outflow.
Given its large stellar mass, SFR and molecular gas reservoir Myr
after the Big Bang, we explore the future evolution of REBELS-25. Considering a
simple, conservative model assuming an exponentially declining star formation
history, constant star formation efficiency, and no additional gas inflow, we
find that REBELS-25 has the potential to evolve into a galaxy consistent with
the properties of high-mass quiescent galaxies recently observed at .Comment: Accepted for publication in MNRAS. 21 pages, 8 figure
The ALMA REBELS Survey : Average [CII] 158μm Sizes of Star-forming Galaxies from z~7 to z~4
We present the average [C II] 158 μm emission line sizes of UV-bright star-forming galaxies at z ~ 7. Our results are derived from a stacking analysis of [C II] 158 μm emission lines and dust continua observed by the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of the large program Reionization Era Bright Emission Line Survey. We find that the average [C II] emission at z ~ 7 has an effective radius re of 2.2 ± 0.2 kpc. It is ≥2× larger than the dust continuum and the rest-frame UV emission, in agreement with recently reported measurements for z ≤ 6 galaxies. Additionally, we compared the average [C II] size with 4 < z < 6 galaxies observed by the ALMA Large Program to INvestigate [C II] at Early times (ALPINE). By analyzing [C II] sizes of 4 < z < 6 galaxies in two redshift bins, we find an average [C II] size of re = 2.2 ± 0.2 kpc and re = 2.5 ± 0.2 kpc for z ~ 5.5 and z ~ 4.5 galaxies, respectively. These measurements show that star-forming galaxies, on average, show no evolution in the size of the [C II] 158 μm emitting regions at redshift between z ~ 7 and z ~ 4. This finding suggests that the star-forming galaxies could be morphologically dominated by gas over a wide redshift range
The ALMA-ALPINE [CII] survey: Kennicutt-Schmidt relation in four massive main-sequence galaxies at <i>z</i> ∼ 4.5
Aims. The Kennicutt-Schmidt (KS) relation between the gas and the star formation rate (SFR) surface density (Σ − Σ) is essential to understand star formation processes in galaxies. To date, it has been measured up to z ∼ 2.5 in main-sequence galaxies. In this Letter our aim is to put constraints at z ∼ 4.5 using a sample of four massive main-sequence galaxies observed by ALMA at high resolution.
Methods. We obtained ∼0.3″-resolution [CII] and continuum maps of our objects, which we then converted into gas and obscured SFR surface density maps. In addition, we produced unobscured SFR surface density maps by convolving Hubble ancillary data in the rest-frame UV. We then derived the average Σ in various Σ bins, and estimated the uncertainties using a Monte Carlo sampling.
Results. Our galaxy sample follows the KS relation measured in main-sequence galaxies at lower redshift, and is slightly lower than the predictions from simulations. Our data points probe the high end both in terms of Σ and Σ, and gas depletion timescales (285–843 Myr) remain similar to z ∼ 2 objects. However, three of our objects are clearly morphologically disturbed, and we could have expected shorter gas depletion timescales (≲100 Myr) similar to merger-driven starbursts at lower redshifts. This suggests that the mechanisms triggering starbursts at high redshift may be different than in the low- and intermediate-z Universe
Effect of surgical volume on short-term outcomes of cytoreductive surgery for advanced-stage ovarian cancer:A population-based study from the Dutch Gynecological Oncology Audit
Objective: Despite lacking clinical data, the Dutch government is considering increasing the minimum annual surgical volume per center from twenty to fifty cytoreductive surgeries (CRS) for advanced-stage ovarian cancer (OC). This study aims to evaluate whether this increase is warranted. Methods: This population-based study included all CRS for FIGO-stage IIB-IVB OC registered in eighteen Dutch hospitals between 2019 and 2022. Short-term outcomes included result of CRS, length of stay, severe complications, 30-day mortality, time to adjuvant chemotherapy, and textbook outcome. Patients were stratified by annual volume: low-volume (nine hospitals, <25), medium-volume (four hospitals, 29–37), and high-volume (five hospitals, 54–84). Descriptive statistics and multilevel logistic regressions were used to assess the (case-mix adjusted) associations of surgical volume and outcomes. Results: A total of 1646 interval CRS (iCRS) and 789 primary CRS (pCRS) were included. No associations were found between surgical volume and different outcomes in the iCRS cohort. In the pCRS cohort, high-volume was associated with increased complete CRS rates (aOR 1.9, 95%-CI 1.2–3.1, p = 0.010). Furthermore, high-volume was associated with increased severe complication rates (aOR 2.3, 1.1–4.6, 95%-CI 1.3–4.2, p = 0.022) and prolonged length of stay (aOR 2.3, 95%-CI 1.3–4.2, p = 0.005). 30-day mortality, time to adjuvant chemotherapy, and textbook outcome were not associated with surgical volume in the pCRS cohort. Subgroup analyses (FIGO-stage IIIC-IVB) showed similar results. Various case-mix factors significantly impacted outcomes, warranting case-mix adjustment. Conclusions: Our analyses do not support further centralization of iCRS for advanced-stage OC. High-volume was associated with higher complete pCRS, suggesting either a more accurate selection in these hospitals or a more aggressive approach. The higher completeness rates were at the expense of higher severe complications and prolonged admissions.</p
The infrared-radio correlation of star-forming galaxies is strongly M⋆-dependent but nearly redshift-invariant since z ∼ 4
Over the past decade, several works have used the ratio between total (rest 8‒1000 μm) infrared and radio (rest 1.4 GHz) luminosity in star-forming galaxies (qIR), often referred to as the infrared-radio correlation (IRRC), to calibrate the radio emission as a star formation rate (SFR) indicator. Previous studies constrained the evolution of qIR with redshift, finding a mild but significant decline that is yet to be understood. Here, for the first time, we calibrate qIR as a function of both stellar mass (M⋆) and redshift, starting from an M⋆-selected sample of > 400 000 star-forming galaxies in the COSMOS field, identified via (NUV ‒ r)/(r ‒ J) colours, at redshifts of 0.1 < z < 4.5. Within each (M⋆,z) bin, we stacked the deepest available infrared/sub-mm and radio images. We fit the stacked IR spectral energy distributions with typical star-forming galaxy and IR-AGN templates. We then carefully removed the radio AGN candidates via a recursive approach. We find that the IRRC evolves primarily with M⋆, with more massive galaxies displaying a systematically lower qIR. A secondary, weaker dependence on redshift is also observed. The best-fit analytical expression is the following: qIR(M⋆, z) = (2.646 ± 0.024) × (1 + z)( ‒ 0.023 ± 0.008)-(0.148 ± 0.013) × (log M⋆/M⊙ ‒ 10). Adding the UV dust-uncorrected contribution to the IR as a proxy for the total SFR would further steepen the qIR dependence on M⋆. We interpret the apparent redshift decline reported in previous works as due to low-M⋆ galaxies being progressively under-represented at high redshift, as a consequence of binning only in redshift and using either infrared or radio-detected samples. The lower IR/radio ratios seen in more massive galaxies are well described by their higher observed SFR surface densities. Our findings highlight the fact that using radio-synchrotron emission as a proxy for SFR requires novel M⋆-dependent recipes that will enable us to convert detections from future ultra-deep radio surveys into accurate SFR measurements down to low-M⋆ galaxies with low SFR
Prognostication using SpO(2)/FiO(2) in invasively ventilated ICU patients with ARDS due to COVID-19-Insights from the PRoVENT-COVID study
Background: The SpO(2)/FiO(2) is a useful oxygenation parameter with prognostic capacity in patients with ARDS. We investigated the prognostic capacity of SpO(2)/FiO(2) for mortality in patients with ARDS due to COVID-19. Methods: This was a post-hoc analysis of a national multicenter cohort study in invasively ventilated patients with ARDS due to COVID-19. The primary endpoint was 28-day mortality. Results: In 869 invasively ventilated patients, 28-day mortality was 30.1%. The SpO(2)/FiO(2) on day 1 had no prognostic value. The SpO(2)/FiO(2) on day 2 and day 3 had prognostic capacity for death, with the best cut-offs being 179 and 199, respectively. Both SpO(2)/FiO(2) on day 2 (OR, 0.66 [95%-CI 0.46-0.96]) and on day 3 (OR, 0.70 [95%-CI 0.51-0.96]) were associated with 28-day mortality in a model corrected for age, pH, lactate levels and kidney dysfunction (AUROC 0.78 [0.76-0.79]). The measured PaO2/FiO(2) and the PaO2/FiO(2) calculated from SpO(2)/FiO(2) were strongly correlated (Spearman's r = 0.79). Conclusions: In this cohort of patients with ARDS due to COVID-19, the SpO(2)/FiO(2) on day 2 and day 3 are independently associated with and have prognostic capacity for 28-day mortality. The SpO(2)/FiO(2) is a useful metric for risk stratification in invasively ventilated COVID-19 patients. (C) 2021 The Authors. Published by Elsevier Inc
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