LUCIFER@LBT view of star-forming galaxies in the cluster 7C 1756+6520 at z~1.4

Galaxy clusters are key places to study the contribution of {\it nature} (i.e. mass, morphology) and {\it nurture} (i.e.environment) in the formation and evolution of galaxies. Recently, a number of clusters at z$>$1, i.e. corresponding to the first epochs of the cluster formation, has been discovered and confirmed spectroscopically. We present new observations obtained with the {\sc LUCIFER} spectrograph at Large Binocular Telescope (LBT) of a sample of star-forming galaxies associated with a large scale structure around the radio galaxy 7C1756+6520 at z=1.42. Combining our spectroscopic data and the literature photometric data, we derived some of the properties of these galaxies: star formation rate, metallicity and stellar mass. With the aim of analyzing the effect of the cluster environment on galaxy evolution, we have located the galaxies in the plane of the so-called Fundamental Metallically Relation (FMR), which is known not to evolve with redshift up to z$=2.5$ for field galaxies, but it is still unexplored in rich environments at low and high redshift. We found that the properties of the galaxies in the cluster 7C 1756+6520 are compatible with the FMR which suggests that the effect of the environment on galaxy metallicity at this early epoch of cluster formation is marginal. As a side study, we also report the spectroscopic analysis of a bright AGN, belonging to the cluster, which shows a significant outflow of gas.Comment: Accepted for publication by MNRAS, 10 pages, 6 figures, 3 table

Star forming galaxies in the Hercules cluster: Halpha imaging of A2151

This paper presents the first results of an Halpha imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in Halpha. The morphologies of the 43 H$\alpha$ selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalactic HII regions, spanning a range of magnitudes of -21 <= MB <= -12.5 mag. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(Halpha) lower than expected for their MB, a consecuence of the cluster environment. This fact results in differences in the L(Halpha) vs. EW(Halpha) and L(H\alpha) distributions of the clusters with respect to the field, and in cluster to cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. Overall, we conclude that both, the global cluster environment as well as the cluster merging history play a non negligible role in the integral star formation properties of clusters of galaxies.Comment: 38 pages, 11 figures. Accepted for publication in Astronomical Journa

Energetic Particles of Cosmic Accelerators II: Active Galactic Nuclei and Gamma-ray Bursts

The high-energy universe has revealed that energetic particles are ubiquitous in the cosmos and play a vital role in the cultivation of cosmic environments on all scales. Though they play a key role in cultivating the cosmological environment and/or enabling our studies of it, there is still much we do not know about AGNs and GRBs, particularly the avenue in which and through which they supply radiation and energetic particles, namely their jets. This White Paper is the second of a two-part series highlighting the most well-known high-energy cosmic accelerators and contributions that MeV gamma-ray astronomy will bring to understanding their energetic particle phenomena. The focus of this white paper is active galactic nuclei and gamma-ray bursts.Comment: 11 pages (including references), 2 figures; Submitted to the Astro2020 call for science white paper

The chemical history of star-forming galaxies in nearby clusters

The aim of this thesis is to investigate the influence of environment on the chemical history of star-forming galaxies in a sample of local Universe clusters. We have achieved this goal through the study of the fundamental relations between the metallicity of galaxies and their main physical properties, such as stellar mass, luminosity, gas content, star formation activity and structure. In order to carry out this study, we have obtained new optical long-slit spectroscopy of the A2151 cluster with the telescopes INT2.5m and WHT4.2m at the ORM. Additionally an extensive spectroscopic database has been extracted from the SDSS DR8, for a large sample of 781 low-mass star-forming galaxies in the clusters: A1656 (Coma), A1367, A779 A634 as well as in A2147, A2151, A2152 of the Hercules supercluster. We have derived the chemical abundances of the ionized interstellar medium of our sample galaxies, for which we have studied the behavior of the MZR and LZR as a function of their environment. The environment has been quantified as a function of cluster-centric distance and also as a function of the local density of galaxies. Overall, our sample of star-forming galaxies exhibits well defined sequences of stellar mass and metallicity (as parametrized by O/H, and the N/O ratio), following the well known general behavior for star-forming galaxies. Notably outside the cores of more massive clusters, the derived slope of the MZR is in agreement with the predictions of state-of-the-art hydrodynamic models. Besides this global behavior, we have found that dwarf/irregular galaxies populating the densest regions in the A2151 cluster show higher metallicity for their mass and crowd the upper part of the MZR and N/O versus stellar mass relations. Furthermore, low-mass star-forming galaxies located at cluster-centric distances R< R200 in Coma (especially) and A1367, appear preferentially located at the upper side of the derived MZR global relations of O/H and N/O versus mass. This observed enhancement in metallicity appears to be dependent of galaxy stellar mass, being higher for the lower mass bins, thus flattening the MZR slope in the core of these massive clusters. This observed behavior reveals that the imprint of the cluster environment shows up in a mass-dependent way, being both, galaxy mass and cluster mass, relevant parameters. This result suggests the important role that intra-cluster medium properties could play in the chemical evolution of cluster galaxies. A physical scenario has been proposed to explain the metal enhancement of low-mass star-forming galaxies in clusters, in the light of the predictions of recent hydrodynamic simulations for galaxy evolution in clusters. Within this framework, this thesis aims at motivating further efforts in theoretical modelling of chemical evolution in dense environments. Additionally to these main conclusions, in the present thesis we have reached other relevant results. We found that star-forming spiral galaxies in A2151 present oxygen abundances close to solar and shallow oxygen abundance gradients, a result suggesting possible gas infall at their centers. For the N/O ratio, even oversolar values have been obtained for the central parts of some galaxies and a significant spatial variation has been observed. A clear trend was found for the gas-phase metallicity of A2151 galaxies, gradually approaching the stellar metallicity as the latter increases from Zsun/2 to Zsun. The outliers of this trend (less chemically evolved systems with approximately equal gas-phase and stellar metallicity) are identifiable with ``newcomers'' in the cluster environment. An overall positive trend has been found in the gas-phase oxygen abundance versus the mass-weighted stellar age, which becomes more prominent in the case of the N/O ratio. The 2D color g-i and EW(Ha) maps of A2151 cluster have revealed the presence of a filament, mainly of low-mass galaxies, to the North of A2151, that reaches down to the cluster core. The g-i and EW(Ha) maps of A2152 ans A2147 indicate more virialized structures; nonetheless, a filamentary structure dominated by blue low-mass star-forming galaxies has been identified entering in A2147 R200 region from South-East. The LZR and N/O ratio vs. stellar mass relation of the HSC low-mass star-forming galaxies have been found to show an intrinsic dispersion that correlates with galaxy color. In the clusters with available HI measurements we have found that most of the dwarf galaxies with available HI mass are either located outside the cluster core or have been recently accreted to the cluster environment and appear consistent with the predictions of the ``closed box'' model. In the cores of these clusters HI detections are scarce, thus star-forming dwarf galaxies there should have suffered an important ram-pressure stripping. The metal enhancement of star-forming dwarfs in the cluster core has been found to be more important when considering the R200 region of the most massive cluster Coma (Mstar~10^{15} Msun. Despite the general good relation of local galaxy density with cluster-centric distance, this effect appears diluted in terms of local galaxy density, suggesting that the relevant parameter able to affect the chemical evolution of star-forming dwarf galaxies should be the presence of an intra-cluster medium. Finally, for the aims of this thesis we performed a study of the morphological and structural properties of the star-forming galaxies in A2151 cluster. This work allowed a careful spectroscopic follow-up of these galaxies with long-slit spectroscopy. For this specific sample of cluster galaxies we derived galaxy stellar masses using SED fitting on SDSS broadband photometry. The fundamental parameters of the underlying stellar component, such as mean metallicity and age were derived via spectral fitting using the population synthesis code STARLIGHT.Tesis Univ. Granada. Departamento de Física Teórica y del Cosmos

Two cases of severe sepsis caused by Bacillus pumilus in neonatal infants

Bacillus pumilus is an environmental contaminant that has been rarely associated with clinical infections. Here, two cases of severe sepsis caused by B. pumilus are described in two full-term neonates; one in a female infant with no factors predisposing her to infection and the other in a male infant requiring mechanical ventilation and an intravenous catheter. In both cases, the microorganism was recovered from repeated blood cultures and was identified using biochemical assays and 16S rRNA gene sequencing. Both infants were successfully treated with vancomycin. This report reveals the potential role of B. pumilus as a bloodstream pathogen during infancy

Spectroscopic observations of the bilobate potentially hazardous asteroid 2014 JO25 from the Asiago 1.22-m telescope

The potentially hazardous asteroid (PHA) 2014 JO25 made a close approach to Earth on 19 April 2017 at the distance of 0.0118 AU, giving the opportunity to study its nature with large spatial resolution from ground-based observatories. Radar observations revealed an object with a clear bilobate shape. We aimed at the characterization of the surface properties of the object, the determination of its spectral class and the search for possible surface heterogeneities, possibly linked to the two lobes, during different rotational phases. Fourteen low-resolution spectra were acquired with the Boller & Chivens optical spectrograph mounted on the 1.22-m Asiago telescope. The spectra covered an entire rotation period of the asteroid. Data were reduced using IRAF and analyzed with the M4AST tool to infer the best fit Bus-Demeo taxonomy type. We found the asteroid belonging to the S/Q complex of silicaceous asteroids, complex comprising the vast majority of NEAs. This is the tenth bilobate NEA to be taxonomically classified and only the seventh bilobate PHA. We found no clear proof of surface heterogeneity, but there is an interestingvariation in the best spectral match which appears to be synchronous with the rotation period of the object