The resolved chemical composition of the starburst dwarf galaxy CGCG007-025: Direct method versus photoionization model fitting

This work focuses on the gas chemical composition of CGCG007-025. This compact dwarf is undergoing a galaxy wide star forming burst, whose spatial behaviour has been observed by VLT/MUSE. We present a new line measurement library to treat almost 7800 voxels. The direct method chemical analysis is limited to 484 voxels with good detection of the $[SIII]6312\AA$ temperature diagnostic line. The recombination fluxes are corrected for stellar absorption via a population synthesis. Additionally, we discuss a new algorithm to fit photoionization models via neural networks. The 8 ionic abundances analyzed show a spatial normal distribution with a $\sigma\sim0.1\,dex$, where only half this value can be explained by the uncertainty in the measurements. The oxygen abundance distribution is $12+log(O/H)=7.88\pm0.11$. The $T_{e}[SIII]$ and $ne[SII]$ are also normally distributed. However, in the central and brightest region, the $ne[SII]$ is almost thrice the mean galaxy value. This is also reflected in the extinction measurements. The ionization parameter has a distribution of $log(U) = -2.52^{0.17}_{0.19}$. The parameter spatial behaviour agrees with the $S^{2+}/S^{+}$ map. Finally, the discrepancies between the direct method and the photoionization model fitting are discussed. In the latter technique, we find that mixing lines with uneven uncertainty magnitudes can impact the accuracy of the results. In these fittings, we recommend overestimating the minimum flux uncertainty one order below the maximum line flux uncertainty. This provides a better match with the direct method.Comment: Minor revision of your manuscript is requested before it is reconsidered for publication in MNRA

On the assembly of dwarf galaxies in clusters and their efficient formation of globular clusters

Galaxy clusters contain a large population of low-mass dwarf elliptical galaxies whose exact origin is unclear: their colours, structural properties and kinematics differ substantially from those of dwarf irregulars in the field. We use the Illustris cosmological simulation to study differences in the assembly histories of dwarf galaxies (3 × 10⁸ < M*/M⊙ < 10¹⁰) according to their environment. We find that cluster dwarfs achieve their maximum total and stellar mass on average ∼8 and ∼4.5 Gyr ago (or redshifts z = 1.0 and 0.4, respectively), around the time of infall into the clusters. In contrast, field dwarfs not subjected to environmental stripping reach their maximum mass at z = 0. These different assembly trajectories naturally produce a colour bimodality, with blue isolated dwarfs and redder cluster dwarfs exhibiting negligible star formation today. The cessation of star formation happens over median times 3.5–5 Gyr depending on stellar mass, and shows a large scatter (∼1–8 Gyr), with the lower values associated with starburst events that occur at infall through the virial radius or pericentric passages. We argue that such starbursts together with the early assembly of cluster dwarfs can provide a natural explanation for the higher specific frequency of globular clusters (GCs) in cluster dwarfs, as found observationally. We present a simple model for the formation and stripping of GCs that supports this interpretation. The origin of dwarf ellipticals in clusters is, therefore, consistent with an environmentally driven evolution of field dwarf irregulars. However, the z = 0 field analogues of cluster dwarf progenitors have today stellar masses a factor of ∼3 larger – a difference arising from the early truncation of star formation in cluster dwarfs

A close look at the dwarf AGN of NGC 4395 : optical and near-IR integral field spectroscopy

Intermediate-mass black holes (103–105 M⊙) in the centre of dwarf galaxies are believed to be analogous to growing active galactic nuclei (AGNs) in the early Universe. Their characterization can provide insight about the early galaxies. We present optical and near-infrared integral field spectroscopy of the inner ∼50 pc of the dwarf galaxy NGC 4395, known to harbour an AGN. NGC 4395 is an ideal candidate to investigate the nature of dwarf AGN, as it is nearby (d ≈ 4.4 Mpc) enough to allow a close look at its nucleus. The optical data were obtained with the Gemini GMOS-IFU covering the 4500 –7300 Å spectral range at a spatial resolution of 10 pc. The J and K-band spectra were obtained with the Gemini NIFS at spatial resolutions of ∼5 pc. The gas kinematics show a compact, rotation disc component with a projected velocity amplitude of 25 kms−1. We estimate a mass of 7.7 × 105 M⊙ inside a radius of 10 pc. From the Hα broad-line component, we estimate the AGN bolometric luminosity as Lbol=(9.9±1.4)×1040 erg s−1 and a mass MBH=(2.5+1.0−0.8)×105 M⊙ for the central black hole. The mean surface mass densities for the ionized and molecular gas are in the ranges (1–2) M⊙ pc−2 and (1–4) × 10−3 M⊙ pc−2 and the average ratio between ionized and hot molecular gas masses is ∼500. The emission-line flux distributions reveal an elongated structure at 24 pc west of the nucleus, which is blueshifted relative to the systemic velocity of the galaxy by ≈30 kms−1. We speculate that this structure is originated by the accretion of a gas-rich small satellite or by a low-metallicity cosmic clou

On the assembly of dwarf galaxies in clusters and their efficient formation of globular clusters

Galaxy clusters contain a large population of low-mass dwarf elliptical galaxies whose exact origin is unclear: their colours, structural properties and kinematics differ substantially from those of dwarf irregulars in the field. We use the Illustris cosmological simulation to study differences in the assembly histories of dwarf galaxies (3 × 108 < M*/M⊙ < 1010) according to their environment. We find that cluster dwarfs achieve their maximum total and stellar mass on average ∼8 and ∼4.5 Gyr ago (or redshifts z = 1.0 and 0.4, respectively), around the time of infall into the clusters. In contrast, field dwarfs not subjected to environmental stripping reach their maximum mass at z = 0. These different assembly trajectories naturally produce a colour bimodality, with blue isolated dwarfs and redder cluster dwarfs exhibiting negligible star formation today. The cessation of star formation happens over median times 3.5–5 Gyr depending on stellar mass, and shows a large scatter (∼1–8 Gyr), with the lower values associated with starburst events that occur at infall through the virial radius or pericentric passages. We argue that such starbursts together with the early assembly of cluster dwarfs can provide a natural explanation for the higher specific frequency of globular clusters (GCs) in cluster dwarfs, as found observationally. We present a simple model for the formation and stripping of GCs that supports this interpretation. The origin of dwarf ellipticals in clusters is, therefore, consistent with an environmentally driven evolution of field dwarf irregulars. However, the z = 0 field analogues of cluster dwarf progenitors have today stellar masses a factor of ∼3 larger – a difference arising from the early truncation of star formation in cluster dwarfs.Astronom

A close look at the dwarf AGN of NGC 4395 : optical and near-IR integral field spectroscopy

Intermediate-mass black holes (103–105 M⊙) in the centre of dwarf galaxies are believed to be analogous to growing active galactic nuclei (AGNs) in the early Universe. Their characterization can provide insight about the early galaxies. We present optical and near-infrared integral field spectroscopy of the inner ∼50 pc of the dwarf galaxy NGC 4395, known to harbour an AGN. NGC 4395 is an ideal candidate to investigate the nature of dwarf AGN, as it is nearby (d ≈ 4.4 Mpc) enough to allow a close look at its nucleus. The optical data were obtained with the Gemini GMOS-IFU covering the 4500 –7300 Å spectral range at a spatial resolution of 10 pc. The J and K-band spectra were obtained with the Gemini NIFS at spatial resolutions of ∼5 pc. The gas kinematics show a compact, rotation disc component with a projected velocity amplitude of 25 kms−1. We estimate a mass of 7.7 × 105 M⊙ inside a radius of 10 pc. From the Hα broad-line component, we estimate the AGN bolometric luminosity as Lbol=(9.9±1.4)×1040 erg s−1 and a mass MBH=(2.5+1.0−0.8)×105 M⊙ for the central black hole. The mean surface mass densities for the ionized and molecular gas are in the ranges (1–2) M⊙ pc−2 and (1–4) × 10−3 M⊙ pc−2 and the average ratio between ionized and hot molecular gas masses is ∼500. The emission-line flux distributions reveal an elongated structure at 24 pc west of the nucleus, which is blueshifted relative to the systemic velocity of the galaxy by ≈30 kms−1. We speculate that this structure is originated by the accretion of a gas-rich small satellite or by a low-metallicity cosmic clou

Association between convalescent plasma treatment and mortality in COVID-19: a collaborative systematic review and meta-analysis of randomized clinical trials

Abstract Background Convalescent plasma has been widely used to treat COVID-19 and is under investigation in numerous randomized clinical trials, but results are publicly available only for a small number of trials. The objective of this study was to assess the benefits of convalescent plasma treatment compared to placebo or no treatment and all-cause mortality in patients with COVID-19, using data from all available randomized clinical trials, including unpublished and ongoing trials (Open Science Framework, https://doi.org/10.17605/OSF.IO/GEHFX ). Methods In this collaborative systematic review and meta-analysis, clinical trial registries (ClinicalTrials.gov, WHO International Clinical Trials Registry Platform), the Cochrane COVID-19 register, the LOVE database, and PubMed were searched until April 8, 2021. Investigators of trials registered by March 1, 2021, without published results were contacted via email. Eligible were ongoing, discontinued and completed randomized clinical trials that compared convalescent plasma with placebo or no treatment in COVID-19 patients, regardless of setting or treatment schedule. Aggregated mortality data were extracted from publications or provided by investigators of unpublished trials and combined using the Hartung–Knapp–Sidik–Jonkman random effects model. We investigated the contribution of unpublished trials to the overall evidence. Results A total of 16,477 patients were included in 33 trials (20 unpublished with 3190 patients, 13 published with 13,287 patients). 32 trials enrolled only hospitalized patients (including 3 with only intensive care unit patients). Risk of bias was low for 29/33 trials. Of 8495 patients who received convalescent plasma, 1997 died (23%), and of 7982 control patients, 1952 died (24%). The combined risk ratio for all-cause mortality was 0.97 (95% confidence interval: 0.92; 1.02) with between-study heterogeneity not beyond chance (I2 = 0%). The RECOVERY trial had 69.8% and the unpublished evidence 25.3% of the weight in the meta-analysis. Conclusions Convalescent plasma treatment of patients with COVID-19 did not reduce all-cause mortality. These results provide strong evidence that convalescent plasma treatment for patients with COVID-19 should not be used outside of randomized trials. Evidence synthesis from collaborations among trial investigators can inform both evidence generation and evidence application in patient care

Association between convalescent plasma treatment and mortality in COVID-19: a collaborative systematic review and meta-analysis of randomized clinical trials

Abstract Background Convalescent plasma has been widely used to treat COVID-19 and is under investigation in numerous randomized clinical trials, but results are publicly available only for a small number of trials. The objective of this study was to assess the benefits of convalescent plasma treatment compared to placebo or no treatment and all-cause mortality in patients with COVID-19, using data from all available randomized clinical trials, including unpublished and ongoing trials (Open Science Framework, https://doi.org/10.17605/OSF.IO/GEHFX ). Methods In this collaborative systematic review and meta-analysis, clinical trial registries (ClinicalTrials.gov, WHO International Clinical Trials Registry Platform), the Cochrane COVID-19 register, the LOVE database, and PubMed were searched until April 8, 2021. Investigators of trials registered by March 1, 2021, without published results were contacted via email. Eligible were ongoing, discontinued and completed randomized clinical trials that compared convalescent plasma with placebo or no treatment in COVID-19 patients, regardless of setting or treatment schedule. Aggregated mortality data were extracted from publications or provided by investigators of unpublished trials and combined using the Hartung–Knapp–Sidik–Jonkman random effects model. We investigated the contribution of unpublished trials to the overall evidence. Results A total of 16,477 patients were included in 33 trials (20 unpublished with 3190 patients, 13 published with 13,287 patients). 32 trials enrolled only hospitalized patients (including 3 with only intensive care unit patients). Risk of bias was low for 29/33 trials. Of 8495 patients who received convalescent plasma, 1997 died (23%), and of 7982 control patients, 1952 died (24%). The combined risk ratio for all-cause mortality was 0.97 (95% confidence interval: 0.92; 1.02) with between-study heterogeneity not beyond chance (I2 = 0%). The RECOVERY trial had 69.8% and the unpublished evidence 25.3% of the weight in the meta-analysis. Conclusions Convalescent plasma treatment of patients with COVID-19 did not reduce all-cause mortality. These results provide strong evidence that convalescent plasma treatment for patients with COVID-19 should not be used outside of randomized trials. Evidence synthesis from collaborations among trial investigators can inform both evidence generation and evidence application in patient care