A multiwavelength consensus on the main sequence of star-forming galaxies at z similar to 2

We compare various star formation rate (SFR) indicators for star-forming galaxies at 1.4 < z < 2.5 in the COSMOS field. The main focus is on the SFRs from the far-IR (PACS-Herschel data) with those from the ultraviolet, for galaxies selected according to the BzK criterion. FIR-selected samples lead to a vastly different slope of the SFR-stellar mass (M-*) relation, compared to that of the dominant main-sequence population as measured from the UV, since the FIR selection picks predominantly only a minority of outliers. However, there is overall agreement between the main sequences derived with the two SFR indicators, when stacking on the PACS maps the BzK-selected galaxies. The resulting logarithmic slope of the SFR-M-* relation is similar to 0.8-0.9, in agreement with that derived from the dust-corrected UV luminosity. Exploiting deeper 24 mu m Spitzer data, we have characterized a subsample of galaxies with reddening and SFRs poorly constrained, as they are very faint in the B band. The combination of Herschel with Spitzer data has allowed us to largely break the age/reddening degeneracy for these intriguing sources, by distinguishing whether a galaxy is very red in B-z because of being heavily dust reddened, or whether because star formation has been (or is being) quenched. Finally, we have compared our SFR(UV) to the SFRs derived by stacking the radio data and to those derived from the H alpha luminosity of a sample of star-forming galaxies at 1.4 < z < 1.7. The two sets of SFRs are broadly consistent as they are with the SFRs derived from the UV and by stacking the corresponding PACS data in various mass bins

Ensembles of Convolutional Neural Networks models for pediatric pneumonia diagnosis

Pneumonia is a lung infection that causes 15% of childhood mortality, over 800,000 children under five every year, all over the world. This pathology is mainly caused by viruses or bacteria. X-rays imaging analysis is one of the most used methods for pneumonia diagnosis. These clinical images can be analyzed using machine learning methods such as convolutional neural networks (CNN), which learn to extract critical features for the classification. However, the usability of these systems is limited in medicine due to the lack of interpretability, because of these models cannot be used to generate an understandable explanation (from a human-based perspective), about how they have reached those results. Another problem that difficults the impact of this technology is the limited amount of labeled data in many medicine domains. The main contributions of this work are two fold: the first one is the design of a new explainable artificial intelligence (XAI) technique based on combining the individual heatmaps obtained from each model in the ensemble. This allows to overcome the explainability and interpretability problems of the CNN "black boxes", highlighting those areas of the image which are more relevant to generate the classification. The second one is the development of new ensemble deep learning models to classify chest X-rays that allow highly competitive results using small datasets for training. We tested our ensemble model using a small dataset of pediatric X-rays (950 samples) with low quality and anatomical variability (which represents one of the biggest challenges). We also tested other strategies such as single CNNs trained from scratch and transfer learning using CheXNet. Our results show that our ensemble model outperforms these strategies obtaining highly competitive results. Finally, we confirmed the robustness of our approach using another pneumonia diagnosis dataset [1]

La flora de Guinea Ecuatorial como herramienta para la conservación vegetal en los trópicos

Depto. de Biodiversidad, Ecología y EvoluciónFac. de Ciencias BiológicasTRUEpu

SHARDS: constraints on the dust attenuation law of star-forming galaxies at z∼2

We make use of the Survey of High-z Absorption Red and Dead Sources, an ultradeep (<26.5AB) galaxy survey that provides optical photospectra at resolution R similar to 50, via medium-band filters (FWHM similar to 150 angstrom). This data set is combined with ancillary optical and NIR fluxes to constrain the dust attenuation law in the rest-frame NUV region of star-forming galaxies within the redshift window 1.5 < z < 3. We focus on the NUV bump strength (B) and the total-to-selective extinction ratio (R-V), targeting a sample of 1753 galaxies. By comparing the data with a set of population synthesis models coupled to a parametric dust attenuation law, we constrain R-V and B, as well as the colour excess, E(B - V). We find a correlation between R-V and B, which can be interpreted either as a result of the grain size distribution, or a variation of the dust geometry among galaxies. According to the former, small dust grains are associated with a stronger NUV bump. The latter would lead to a range of clumpiness in the distribution of dust within the interstellar medium of star-forming galaxies. The observed wide range of NUV bump strengths can lead to a systematic in the interpretation of the UV slope beta typically used to characterize the dust content. In this study, we quantify these variations, concluding that the effects are Delta beta similar to 0.4

Pathways to quiescence: SHARDS view on the star formation histories of massive quiescent galaxies at 1.0 < z < 1.5

et al.We present star formation histories (SFHs) for a sample of 104 massive (stellar massM> 1010 M) quiescent galaxies (MQGs) at z = 1.0-1.5 from the analysis of spectrophotometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) and HST/WFC3 G102 and G141 surveys of the GOODS-North field, jointly with broad-band observations from ultraviolet (UV) to far-infrared (far-IR). The sample is constructed on the basis of restframe UVJ colours and specific star formation rates (sSFRs = SFR/Mass). The spectral energy distributions (SEDs) of each galaxy are compared to models assuming a delayed exponentially declining SFH. A Monte Carlo algorithm characterizes the degeneracies, which we are able to break taking advantage of the SHARDS data resolution, by measuring indices such as MgUV and D4000. The population of MQGs shows a duality in their properties. The sample is dominated (85 per cent) by galaxies with young mass-weighted ages, t 1.0, when our galaxies were 0.5-1.0 Gyr old. According to these SFHs, all the MQGs experienced a luminous infrared galaxy phase that lasts for ~500 Myr, and half of them an ultraluminous infrared galaxy phase for ~100 Myr. We find that the MQG population is almost assembled at z ~ 1, and continues evolving passively with few additions to the population.We acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2012-31277. NCL acknowledges financial support from AYA2013-46724-P. AAH and AHC acknowledge support from the Spanish Programa Nacional de Astronomía y Astrofísica under grant AYA2012-31447, which is partly funded by the Fondo Europeo de Desarrollo Regional programme. The work of AC is supported by the STARFORM Sinergia Project funded by the Swiss National Science Foundation. SC acknowledges support from the ERC via an Advanced Grant under grant agreement no. 321323-NEOGAL. DC thanks AYA2012-32295. GB acknowledges support for this work from the National Autonomous University of México (UNAM), through grant PAPIIT IG100115.Peer Reviewe

Optically-faint massive Balmer Break Galaxies at z>3 in the CANDELS/GOODS fields

We present a sample of 33 Balmer Break Galaxies (BBGs) selected as HST/F160W dropouts in the deepest CANDELS/GOODS fields ($H\gtrsim27.3$~mag) but relatively bright in {\it Spitzer}/IRAC ($[3.6],[4.5]<24.5$~mag), implying red colors (median and quartiles: $\langle H-[3.6]\rangle=3.1^{3.4}_{2.8}$\,mag). Half of these BBGs are newly identified sources. Our BBGs are massive ($\langle \log(\rm{M}/\rm{M}_\odot)\rangle=10.8$) high redshift ($\langle z\rangle=4.8$) dusty ($\langle \rm{A(V)}\rangle=2.0$~mag) galaxies. The SEDs of half of our sample indicate that they are star-forming galaxies with typical specific SFRs 0.5-1.0~Gyr$^{-1}$, qualifying them as main sequence (MS) galaxies at $3<z<6$. One third of those SEDs indicates the presence of prominent emission lines (H$\beta$+$[OIII]$, H$\alpha$$+$[NII]) boosting the IRAC fluxes and red colors. Approximately 20\% of the BBGs are very dusty ($\rm{A(V)}\sim2.5$~mag) starbursts with strong mid-to-far infrared detections and extreme SFRs ($\rm{SFR}>10^{3}\,\rm{M}_\odot/yr$) that place them above the MS. The rest, 30\%, are post-starbursts or quiescent galaxies located $>2\sigma$ below the MS with mass-weighted ages older than 700~Myr. Only 2 of the 33 galaxies are X-ray detected AGN with optical/near-infrared SEDs dominated by stellar emission, but the presence of obscured AGN in the rest of sources cannot be discarded. Our sample accounts for 8\% of the total number density of $\log(\rm{M}/\rm{M}_\odot)>10$ galaxies at $z>3$, but it is a significant contributor (30\%) to the general population of red $\log(\rm{M}/\rm{M}_\odot)>11$ galaxies at $4<z<6$. Finally, our results point out that 1 of every 30 massive $\log(\rm{M}/\rm{M}_\odot)>11$ galaxies in the local Universe was assembled in the first 1.5~Gyr after the Big Bang, a fraction that is not reproduced by state-of-the-art galaxy formation simulations.Comment: 38 pages, 18 figures, Accepted for publication in The Astrophysical Journal 26/03/201

SHARDS: A global view of the star formation activity at z∼ 0.84 and z∼ 1.23

et al.In this paper, we present a comprehensive analysis of star-forming galaxies (SFGs) at intermediate redshifts (z ∼ 1). We combine the ultra-deep optical spectro-photometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field. Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we select [O ii] emission line galaxies at z ∼ 0.84 and z ∼ 1.23 and characterize their physical properties. Their rest-frame equivalent widths (EW([O ii])), line fluxes, luminosities, star formation rates (SFRs), and dust attenuation properties are investigated. The evolution of EW([O ii]) closely follows the SFR density evolution of the universe, with a trend of EW([O ii]) (1 + z) up to redshift z ≃ 1, followed by a possible flattening. The SF properties of the galaxies selected on the basis of their [O ii] emission are compared with complementary samples of SFGs selected by their MIR and FIR emission, and also with a general mass-selected sample of galaxies at the same redshifts. We demonstrate observationally that the UVJ diagram (or, similarly, a cut in the specific SFR) is only partially able to distinguish the quiescent galaxies from the SFGs. The SFR-M relation is investigated for the different samples, yielding a logarithmic slope ∼1, in good agreement with previous results. The dust attenuations derived from different SFR indicators (UV(1600), UV(2800), [O ii], IR) are compared and show clear trends with respect to both the stellar mass and total SFR, with more massive and highly star-forming galaxies being affected by stronger dust attenuation.The work of A.C. is supported by the STARFORM Sinergia Project funded by the Swiss National Science Foundation, and also benefited from a MERAC Funding and Travel Award. P.G.P.-G. acknowledges support from the Spanish Programa Nacional de Astronomía y Astrofísica under grants AYA2012-31277. A.V.G. acknowledges support from the ERC via an Advanced Grant under grant agreement no. 321323-NEOGAL. N.C. acknowledges support from the Spanish Ministry of Economy and Competitiveness under grant AYA2013-46724-P. A.A.H. and A.H.C. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2012-31447, which is partly funded by the FEDER program. A.J.C. is a Ramón y Cajal Fellow of the Spanish Ministry of Science and Innovation and acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2012-30789, partly funded by the FEDER program.Peer Reviewe

SHARDS: A global view of the star formation activity at z~0.84 and z~1.23

In this paper, we present a comprehensive analysis of star-forming galaxies (SFGs) at intermediate redshifts (z~1). We combine the ultra-deep optical spectro-photometric data from the Survey for High-z Absorption Red and Dead Sources (SHARDS) with deep UV-to-FIR observations in the GOODS-N field. Exploiting two of the 25 SHARDS medium-band filters, F687W17 and F823W17, we select [OII] emission line galaxies at z~0.84 and z~1.23 and characterize their physical properties. Their rest-frame equivalent widths (EW$_{\mathrm{rf}}$([OII])), line fluxes, luminosities, star formation rates (SFRs) and dust attenuation properties are investigated. The evolution of the EW$_{\mathrm{rf}}$([OII]) closely follows the SFR density evolution of the universe, with a trend of EW$_{\mathrm{rf}}$([OII])$\propto$(1+z)$^3$ up to redshift z~1, followed by a possible flattening. The SF properties of the galaxies selected on the basis of their [OII] emission are compared with complementary samples of SFGs selected by their MIR and FIR emission, and also with a general mass-selected sample of galaxies at the same redshifts. We demonstrate observationally that the UVJ diagram (or, similarly, a cut in the specific SFR) is only partially able to distinguish the quiescent galaxies from the SFGs. The SFR-M$_*$ relation is investigated for the different samples, yelding a logarithmic slope ~1, in good agreement with previous results. The dust attenuations derived from different SFR indicators (UV(1600), UV(2800), [OII], IR) are compared and show clear trends with respect to both the stellar mass and total SFR, with more massive and highly star-forming galaxies being affected by stronger dust attenuation.Comment: Replaced to match the accepted version (24 pages, 1 table, 17 figures). Published in ApJ, 812, 155 (2015): http://stacks.iop.org/0004-637X/812/15

SDSS-IV MaNGA: drivers of stellar metallicity in nearby galaxies

The distribution of stellar metallicities within and across galaxies is an excellent relic of the chemical evolution across cosmic time. We present a detailed analysis of spatially resolved stellar populations based on >2.6 million spatial bins from 7439 nearby galaxies in the Sloan Digital Sky Survey-IV (SDSS-IV) Mapping Nearby Galaxies at APO (MaNGA) survey. To account for accurate inclination corrections, we derive an equation for morphology-dependent determination of galaxy inclinations. Our study goes beyond the well-known global mass-metallicity relation and radial metallicity gradients by providing a statistically sound exploration of local relations between stellar metallicity [Z/H], stellar surface mass density Σ∗, and galactocentric distance in the global mass-morphology plane. We find a significant resolved mass density-metallicity relation Σ ZR for galaxies of all types and masses above 109.8 M⊙. Different radial distances make an important contribution to the spread of the relation. Particularly, in low- and intermediate-mass galaxies, we find that at fixed Σ∗ metallicity increases with radius independently of morphology. For high masses, this radial dependence is only observed in high Σ∗ regions of spiral galaxies. This result calls for a driver of metallicity, in addition to Σ∗ that promotes chemical enrichment in the outer parts of galaxies more strongly than in the inner parts. We discuss gas accretion, outflows, recycling, and radial migration as possible scenarios.The Science and Technology Facilities Council is acknowledged for support through the Consolidated Grant Cosmology and Astrophysics at Portsmouth, ST/S000550/1. JL is supported by the National Science Foundation under Grant No. 2009993. JKB-B acknowledges support from the grant IA-100420 (DGAPA-PAPIIT, UNAM), and funding from the CONACYT grants CF 19-39578, CB-285080, and FC-2016-01-1916