Eliminating Error in the Chemical Abundance Scale for Extragalactic HII Regions

In an attempt to remove the systematic errors which have plagued the calibration of the HII region abundance sequence, we have theoretically modeled the extragalactic HII region sequence. We then used the theoretical spectra so generated in a double blind experiment to recover the chemical abundances using both the classical electron temperature + ionization correction factor technique, and the technique which depends on the use of strong emission lines (SELs) in the nebular spectrum to estimate the abundance of oxygen. We find a number of systematic trends, and we provide correction formulae which should remove systematic errors in the electron temperature + ionization correction factor technique. We also provide a critical evaluation of the various semi-empirical SEL techniques. Finally, we offer a scheme which should help to eliminate systematic errors in the SEL-derived chemical abundance scale for extragalactic HII regions.Comment: 24 pages, 9 Tables, 13 figures, accepted for publication in MNRAS. Updated considering minor changes during the final edition process and some few missing reference

The dependence of oxygen and nitrogen abundances on stellar mass from the CALIFA survey

We analysed the optical spectra of HII regions extracted from a sample of 350 galaxies of the CALIFA survey. We calculated total O/H abundances and, for the first time, N/O ratios using the semi-empirical routine HII-CHI-mistry, which, according to P\'erez-Montero (2014), is consistent with the direct method and reduces the uncertainty in the O/H derivation using [NII] lines owing to the dispersion in the O/H-N/O relation. Then we performed linear fittings to the abundances as a function of the de-projected galactocentric distances. The analysis of the radial distribution both for O/H and N/O in the non-interacting galaxies reveals that both average slopes are negative, but a non-negligible fraction of objects have a flat or even a positive gradient (at least 10\% for O/H and 4\% for N/O). The slopes normalised to the effective radius appear to have a slight dependence on the total stellar mass and the morphological type, as late low-mass objects tend to have flatter slopes. No clear relation is found, however, to explain the presence of inverted gradients in this sample, and there is no dependence between the average slopes and the presence of a bar. The relation between the resulting O/H and N/O linear fittings at the effective radius is much tighter (correlation coefficient $\rho_s$ = 0.80) than between O/H and N/O slopes ($\rho_s$ = 0.39) or for O/H and N/O in the individual \hii\ regions ($\rho_s$ = 0.37). These O/H and N/O values at the effective radius also correlate very tightly (less than 0.03 dex of dispersion) with total luminosity and stellar mass. The relation with other integrated properties, such as star formation rate, colour, or morphology, can be understood only in light of the found relation with mass.Comment: Accepted for publication in A&A. 20 pages, 19 figure

First survey of Wolf-Rayet star populations over the full extension of nearby galaxies observed with CALIFA

The search of extragalactic regions with conspicuous presence of Wolf-Rayet (WR) stars outside the Local Group is challenging task due to the difficulties in detecting their faint spectral features. In this exploratory work, we develop a methodology to perform an automated search of WR signatures through a pixel-by-pixel analysis of integral field spectroscopy (IFS) data belonging to the Calar Alto Legacy Integral Field Area survey, CALIFA. This technique allowed us to build the first catalogue of Wolf-Rayet rich regions with spatially-resolved information, allowing to study the properties of these complexes in a 2D context. The detection technique is based on the identification of the blue WR bump (around He II 4686 {\AA}, mainly associated to nitrogen-rich WR stars, WN) and the red WR bump (around C IV 5808 {\AA} and associated to carbon-rich WR stars, WC) using a pixel-by-pixel analysis. We identified 44 WR-rich regions with blue bumps distributed in 25 galaxies of a total of 558. The red WR bump was identified only in 5 of those regions. We found that the majority of the galaxies hosting WR populations in our sample are involved in some kind of interaction process. Half of the host galaxies share some properties with gamma-ray burst (GRB) hosts where WR stars, as potential candidates to being the progenitors of GRBs, are found. We also compared the WR properties derived from the CALIFA data with stellar population synthesis models, and confirm that simple star models are generally not able to reproduce the observations. We conclude that other effects, such as the binary star channel (which could extend the WR phase up to 10 Myr), fast rotation or other physical processes that causes the loss of observed Lyman continuum photons, are very likely affecting the derived WR properties, and hence should be considered when modelling the evolution of massive stars.Comment: 33 pages, accepted for publication in A&

The ALHAMBRA survey : B−B-band luminosity function of quiescent and star-forming galaxies at 0.2≤z<10.2 \leq z < 1 by PDF analysis

Our goal is to study the evolution of the $B-$band luminosity function (LF) since $z=1$ using ALHAMBRA data. We used the photometric redshift and the $I-$band selection magnitude probability distribution functions (PDFs) of those ALHAMBRA galaxies with $I\leq24$ mag to compute the posterior LF. We statistically studied quiescent and star-forming galaxies using the template information encoded in the PDFs. The LF covariance matrix in redshift-magnitude-galaxy type space was computed, including the cosmic variance. That was estimated from the intrinsic dispersion of the LF measurements in the 48 ALHAMBRA sub-fields. The uncertainty due to the photometric redshift prior is also included in our analysis. We modelled the LF with a redshift-dependent Schechter function affected by the same selection effects than the data. The measured ALHAMBRA LF at $0.2\leq z<1$ and the evolving Schechter parameters both for quiescent and star-forming galaxies agree with previous results in the literature. The estimated redshift evolution of $M_B^* \propto Qz$ is $Q_{\rm SF}=-1.03\pm0.08$ and $Q_{\rm Q}=-0.80\pm0.08$, and of $\log \phi^* \propto Pz$ is $P_{\rm SF}=-0.01\pm0.03$ and $P_{\rm Q}=-0.41\pm0.05$. The measured faint-end slopes are $\alpha_{\rm SF}=-1.29\pm0.02$ and $\alpha_{\rm Q}=-0.53\pm0.04$. We find a significant population of faint quiescent galaxies, modelled by a second Schechter function with slope $\beta=-1.31\pm0.11$. We find a factor $2.55\pm0.14$ decrease in the luminosity density $j_B$ of star-forming galaxies, and a factor $1.25\pm0.16$ increase in the $j_B$ of quiescent ones since $z=1$, confirming the continuous build-up of the quiescent population with cosmic time. The contribution of the faint quiescent population to $j_B$ increases from 3% at $z=1$ to 6% at $z=0$. The developed methodology will be applied to future multi-filter surveys such as J-PAS.Comment: Accepted for publication in Astronomy and Astrophysics. 25 pages, 20 figures, 7 table

Aperture effects on the oxygen abundance determinations from CALIFA data

This paper aims at providing aperture corrections for emission lines in a sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey (CALIFA) database. In particular, we explore the behavior of the log([OIII]5007/Hbeta)/([NII]6583/Halpha) (O3N2) and log[NII]6583/Halpha (N2) flux ratios since they are closely connected to different empirical calibrations of the oxygen abundances in star forming galaxies. We compute median growth curves of Halpha, Halpha/Hbeta, O3N2 and N2 up to 2.5R_50 and 1.5 disk R_eff. The growth curves simulate the effect of observing galaxies through apertures of varying radii. The median growth curve of the Halpha/Hbeta ratio monotonically decreases from the center towards larger radii, showing for small apertures a maximum value of ~10% larger than the integrated one. The median growth curve of N2 shows a similar behavior, decreasing from the center towards larger radii. No strong dependence is seen with the inclination, morphological type and stellar mass for these growth curves. Finally, the median growth curve of O3N2 increases monotonically with radius. However, at small radii it shows systematically higher values for galaxies of earlier morphological types and for high stellar mass galaxies. Applying our aperture corrections to a sample of galaxies from the SDSS survey at 0.02<=z<=0.3 shows that the average difference between fiber-based and aperture corrected oxygen abundances, for different galaxy stellar mass and redshift ranges, reaches typically to ~11%, depending on the abundance calibration used. This average difference is found to be systematically biased, though still within the typical uncertainties of oxygen abundances derived from empirical calibrations. Caution must be exercised when using observations of galaxies for small radii (e.g. below 0.5R_eff) given the high dispersion shown around the median growth curves.Comment: Accepted for publication in Ap

Prognostic value of multilayer left ventricular global longitudinal strain in patients with ST-segment elevation myocardial infarction with mildly reduced left ventricular ejection fractions

Multilayer (epi-, mid- and endocardium) left ventricular (LV) global longitudinal strain (GLS) reflects the extent of myocardial damage after ST-segment myocardial infarction (STEMI). However, the prognostic implications of multilayer LV GLS remain unclear. We studied the association between multilayer LV GLS and prognosis in patients with mildly reduced or preserved LV ejection fraction (EF) after STEMI. Patients with first STEMI and LVEF>45% were evaluated retrospectively. Baseline multilayer (endocardial, mid-myocardial and epicardial) LV GLS were measured on 2-dimensional speckle tracking echocardiography. Patients were followed up for of all-cause mortality. A total of 569 patients (77% male, 60 +/- 11 years) were included. After a median follow-up of 117 (interquartile range 106-132) months, 95 (17%) patients died. We observed no differences in baseline LVEF and peak troponin levels between survivors and non-survivors. However, non-survivors showed more impaired GLS at all layers (epicardium: -11.9 +/- 2.8% vs. -13.4 +/- 2.8%; mid-myocardium: -14.2 +/- 3.2% vs. -15.6 +/- 3.2%; endocardium: -16.5 +/- 3.7% vs. -17.7 +/- 3.6%, p<0.05, for all). On multivariable analysis, increasing age (hazard ratio 1.095; p<0.001) and impaired LV GLS of the epicardial layer (hazard ratio 1.085; p = 0.047) were independently associated with higher risk of all-cause mortality. In addition, LV GLS at the epicardium had incremental prognostic value for all-cause mortality (chi(2) = 114, p = 0.044). In conclusion, in contemporary STEMI patients with mildly reduced or preserved LVEF, ageing and reduced LV GLS of the epicardium (reflecting transmural scar formation) were independently associated with all-cause mortality after adjusting for clinical and echocardiographic variables. (C) 2021 The Authors. Published by Elsevier Inc.Cardiolog

The O3N2 and N2 abundance indicators revisited: improved calibrations based on CALIFA and Te-based literature data

The use of IFS is since recently allowing to measure the emission line fluxes of an increasingly large number of star-forming galaxies both locally and at high redshift. The main goal of this study is to review the most widely used empirical oxygen calibrations, O3N2 and N2, by using new direct abundance measurements. We pay special attention to the expected uncertainty of these calibrations as a function of the index value or abundance derived and the presence of possible systematic offsets. This is possible thanks to the analysis of the most ambitious compilation of Te-based HII regions to date. This new dataset compiles the Te-based abundances of 603 HII regions extracted from the literature but also includes new measurements from the CALIFA survey. Besides providing new and improved empirical calibrations for the gas abundance, we also present here a comparison between our revisited calibrations with a total of 3423 additional CALIFA HII complexes with abundances derived using the ONS calibration by Pilyugin et al. (2010). The combined analysis of Te-based and ONS abundances allows us to derive their most accurate calibration to date for both the O3N2 and N2 single-ratio indicators, in terms of all statistical significance, quality and coverage of the space of parameters. In particular, we infer that these indicators show shallower abundance dependencies and statistically-significant offsets compared to those of Pettini and Pagel (2004), Nagao et al. (2006) and P\'erez-Montero and Contini (2009). The O3N2 and N2 indicators can be empirically applied to derive oxygen abundances calibrations from either direct abundance determinations with random errors of 0.18 and 0.16, respectively, or from indirect ones (but based on a large amount of data) reaching an average precision of 0.08 and 0.09 dex (random) and 0.02 and 0.08 dex (systematic; compared to the direct estimations),respectively.Comment: 12 pages, 5 figures, accepted for publication in A&

Mapping the ionized gas of the metal-poor HII galaxy PHL 293B with MEGARA

Here we report the first spatially resolved spectroscopic study for the galaxy PHL293B using the high-resolution GTC/MEGARA IFU. PHL293B is a local, extremely metal-poor, high ionization galaxy. This makes PHL 293B an excellent analogue for galaxies in the early Universe. The MEGARA aperture (~12.5''x 11.3'') covers the entire PHL 293B main body and its far-reaching ionized gas. We created and discussed maps of all relevant emission lines, line ratios and physical-chemical properties of the ionized ISM. The narrow emission gas appears to be ionized mainly by massive stars according to the observed diganostic line ratios, regardless of the position across the MEGARA aperture. We detected low intensity broad emission components and blueshifted absorptions in the Balmer lines (H$\alpha$,H$\beta$) which are located in the brightest zone of the galaxy ISM. A chemically homogeneity, across hundreds of parsecs, is observed in O/H. We take the oxygen abundance 12+log(O/H)=7.64 $\pm$ 0.06 derived from the PHL293B integrated spectrum as the representative metallicity for the galaxy. Our IFU data reveal for the first time that the nebular HeII4686 emission from PHL 293B is spatially extended and coincident with the ionizing stellar cluster, and allow us to compute its absolute HeII ionizing photon flux. Wolf-Rayet bumps are not detected excluding therefore Wolf-Rayet stars as the main HeII excitation source. The origin of the nebular HeII4686 is discussed.Comment: 14 pages, 9 Figures, 3 Tables; Accepted for publication in MNRA

ALDH4A1 is an atherosclerosis auto-antigen targeted by protective antibodies

Cardiovascular disease (CVD) is the leading cause of mortality in the world, with most CVD-related deaths resulting from myocardial infarction or stroke. The main underlying cause of thrombosis and cardiovascular events is atherosclerosis, an inflammatory disease that can remain asymptomatic for long periods. There is an urgent need for therapeutic and diagnostic options in this area. Atherosclerotic plaques contain autoantibodies, and there is a connection between atherosclerosis and autoimmunity. However, the immunogenic trigger and the effects of the autoantibody response during atherosclerosis are not well understood. Here we performed high-throughput single-cell analysis of the atherosclerosis-associated antibody repertoire. Antibody gene sequencing of more than 1,700 B cells from atherogenic Ldlr and control mice identified 56 antibodies expressed by in-vivo-expanded clones of B lymphocytes in the context of atherosclerosis. One-third of the expanded antibodies were reactive against atherosclerotic plaques, indicating that various antigens in the lesion can trigger antibody responses. Deep proteomics analysis identified ALDH4A1, a mitochondrial dehydrogenase involved in proline metabolism, as a target antigen of one of these autoantibodies, A12. ALDH4A1 distribution is altered during atherosclerosis, and circulating ALDH4A1 is increased in mice and humans with atherosclerosis, supporting the potential use of ALDH4A1 as a disease biomarker. Infusion of A12 antibodies into Ldlr mice delayed plaque formation and reduced circulating free cholesterol and LDL, suggesting that anti-ALDH4A1 antibodies can protect against atherosclerosis progression and might have therapeutic potential in CVD.Ministerio de Economía y Competitividad (SVP-2014-068289); P.D. was supported by an AECC grant (AIO 2012, Ayudas a Investigadores en Oncología 2012); A.S.-B. is a Juan de la Cierva researcher (IJC2018-035279-I); I.M.-F. was a fellow of the research training program funded by Ministerio de Economía y Competitividad (SVP-2014-068216); and A.R.R. and J.V. are supported by Centro Nacional de Investigaciones Cardiovasculares (CNIC). The project leading to these results has received funding from la Caixa Banking Foundation under the project code HR17-00247 and from SAF2016-75511-R and PID2019-106773RB-I00 grants to A.R.R. (Plan Estatal de Investigación Científica y Técnica y de Innovación 2013–201

In vivo murine model of acquired resistance in myeloma reveals differential mechanisms for lenalidomide and pomalidomide in combination with dexamethasone

The development of resistance to therapy is unavoidable in the history of multiple myeloma patients. Therefore, the study of its characteristics and mechanisms is critical in the search for novel therapeutic approaches to overcome it. This effort is hampered by the absence of appropriate preclinical models, especially those mimicking acquired resistance. Here we present an in vivo model of acquired resistance based on the continuous treatment of mice bearing subcutaneous MM1S plasmacytomas. Xenografts acquired resistance to two generations of immunomodulatory drugs (IMiDs; lenalidomide and pomalidomide) in combination with dexamethasone, that was reversible after a wash-out period. Furthermore, lenalidomide-dexamethasone (LD) or pomalidomide-dexamethasone (PD) did not display cross-resistance, which could be due to the differential requirements of the key target Cereblon and its substrates Aiolos and Ikaros observed in cells resistant to each combination. Differential gene expression profiles of LD and PD could also explain the absence of cross-resistance. Onset of resistance to both combinations was accompanied by upregulation of the mitogen-activated protein kinaseextracellular signal-regulated kinase (ERK) kinase (MEK)ERK pathway and addition of selumetinib, a small-molecule MEK inhibitor, could resensitize resistant cells. Our results provide insights into the mechanisms of acquired resistance to LD and PD combinations and offer possible therapeutic approaches to addressing IMiD resistance in the clinic.Peer Reviewe