Activity-dependent refinement of the developing visual system. A comparative study across retinal ganglion cell populations and target nuclei

The formation of the mammalian visual system is a complex process that takes place in several phases and includes neurogenesis, axon guidance, axonal refinement and circuit assembly. The last stage of this process occurs after birth but before eye opening. During this period, axon terminals from retinal ganglion cells (RGCs) first extensively arborize in the different visual nuclei and then refine and establish appropriate connections. It is known that the spontaneous activity generated in the immature retina during perinatal ages plays an important role in this axonal refinement process but it is not clear to what extent such retinal activity differentially influences the refinement of the distinct populations of RGCs when they project to specific visual nuclei. To address this issue we have generated conditional mouse lines to alter spontaneous activity in different populations of RGCs and we have analyzed the projection patterns of RGCs in different visual nuclei in each of these mouse lines. Our results show that the alteration of spontaneous activity in RGCs affects axon refinement in the image-forming nuclei such as the lateral geniculate nucleus and the superior colliculus, supporting previous publications. Interestingly, we also observed that, although to a lesser extent than in the image-forming nuclei, retinal spontaneous activity correlation is important for the refinement of RGC axons in the non-image-forming nuclei such as the pretectal olive nucleus or the suprachiasmatic nucleus

Strong lithium lines in red supergiants at different metallicities

Current models of stellar evolution predict that stars more massive than $\sim6\:$M$_{\odot}$ should have completely depleted all lithium (Li) in their atmospheres by the time when they reach the He core burning phase. Against this, a non-negligible number of red giants with masses $>6\:$M$_{\odot}$ presenting strong Li lines have recently been reported. Motivated by this finding, we have carried out a spectroscopic survey of red supergiants (RSGs) in the Perseus Arm and a selection of young open clusters in the Magellanic Clouds to assess the presence of the Li I $\lambda$6708 doublet line. Based on a sample of >70 objects, close to one third of RSGs in the Perseus Arm display noticeable Li lines, with perhaps a trend towards a lower fraction among more luminous stars. The samples in the Magellanic Clouds are not as large, but hint at a metallicity dependence. Twenty one RSGs in 5 LMC clusters show a very high fraction of Li detection, around 40%. Conversely, 17 RSGs in 5 SMC clusters give only one secure detection. The interpretation of these observational results is not straightforward, but a mechanism for Li production seems most likely. Further characterisation work is ongoing, while theoretical studies into this matter are urgently needed.Comment: Accepted in proceedings for IAU Symposium 361: Massive Stars Near and Far, held in Ballyconnell, Ireland, 9-13 May 2022. N. St-Louis, J. S. Vink & J. Mackey, ed

Contribución al estudio del paisaje vegetal de los Montes de Toledo: los valles del Estena, Chorro y Frío en sus cabeceras.

We comment in tbis paper various associations of Toledo Mountains and pTopound a new community of Fraxinus angustifolia and Osmunda regalis.En este trabajo damos a conocer algunas de las comunidades vegetales más características del Macizo de Rocigalgo (Montes de Toledo). Asimismo, denunciamos la asociación Osmundo-Fraxinetum angustifoliae que proponemos como nueva

NGC 3105: a young open cluster with low metallicity

NGC 3105 is a young open cluster hosting blue, yellow and red supergiants. This rare combination makes it an excellent laboratory to constrain evolutionary models of high-mass stars. It is poorly studied and fundamental parameters such as its age or distance are not well defined. We intend to characterize in an accurate way the cluster as well as its evolved stars, for which we derive for the first time atmospheric parameters and chemical abundances. We identify 126 B-type likely members within a radius of 2.7$\pm$0.6 arcmin, which implies an initial mass, $M_{cl}\approx$4100 M$_{\odot}$. We find a distance of 7.2$\pm$0.7 kpc for NGC 3105, placing it at $R_{GC}$=10.0$\pm$1.2 kpc. Isochrone fitting supports an age of 28$\pm$6 Ma, implying masses around 9.5 M$_{\odot}$ for the supergiants. A high fraction of Be stars ($\approx$25 %) is found at the top of the main sequence down to spectral type b3. From the spectral analysis we estimate for the cluster a $v_{rad}$=+46.9$\pm$0.9 km s$^{-1}$ and a low metallicity, [Fe/H]=-0.29$\pm$0.22. We also have determined, for the first time, chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the evolved stars. The chemical composition of the cluster is consistent with that of the Galactic thin disc. An overabundance of Ba is found, supporting the enhanced $s$-process. NGC 3105 has a low metallicity for its Galactocentric distance, comparable to typical LMC stars. It is a valuable spiral tracer in a very distant region of the Carina-Sagittarius spiral arm, a poorly known part of the Galaxy. As one of the few Galactic clusters containing blue, yellow and red supergiants, it is massive enough to serve as a testbed for theoretical evolutionary models close to the boundary between intermediate and high-mass stars.Comment: 18 pages, 13 figures. Accepted for publication in A&

Three open clusters containing Cepheids: NGC 6649, NGC 6664, and Berkeley 55

Classical Cepheids in open clusters play an important role in benchmarking stellar evolution models, in addition to anchoring the cosmic distance scale and invariably securing the Hubble constant. Three pertinent clusters hosting classical Cepheids and red (super)giants are: NGC 6649, NGC 6664, and Berkeley 55. These clusters form the basis of analysis to assess newly acquired spectra (≈50), archival photometry, and Gaia DR2 data. Importantly, for the first time chemical abundances were determined for the evolved members of NGC 6649 and NGC 6664. We find that they are slightly metal-poor relative to the mean Galactic gradient. Also, an overabundance of Ba is observed. These two clusters likely belong to the thin disc and the latter finding supports the “s-enhanced” scenario of D’Orazi et al. (2009). NGC 6664 and Berkeley 55 exhibit radial velocities consistent with Galactic rotation, while NGC 6649 displays a peculiar velocity. The resulting age estimates for the clusters (≈70 Ma) imply masses of ≈6 M⊙ for the (super)giant demographic. Lastly, the observed yellow-to-red (super)giant ratio is lower than expected and the overall differences that are relative to the models reflect the outstanding theoretical uncertainties.This research is partially supported by the Spanish Ministerio de Ciencia e Innovación under grants AYA2015-68012-C2-2-P and PGC2018-093741-BC21/C22 (MICI/AEI/FEDER, UE). The authors acknowledge financial support from the FCT – Fundação para aCiência e a Tecnologia through national funds (PTDC/FIS-AST/28953/2017) and by FEDER – Fundo Europeu de Desenvolvimento Regional through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI-01-0145-FEDER-028953)

NGC 6067: A young and massive open cluster with high metallicity

© 2017 The Authors. NGC6067 is a young open cluster hosting the largest population of evolved stars among known Milky Way clusters in the 50-150 Ma age range. It thus represents the best laboratory in our Galaxy to constrain the evolutionary tracks of 5-7M⊙ stars. We have used high-resolution spectra of a large sample of bright cluster members (45), combined with archival photometry, to obtain accurate parameters for the cluster as well as stellar atmospheric parameters.We derive a distance of 1.78 ± 0.12 kpc, an age of 90 ± 20 Ma and a tidal radius of 14.8 -3.2+6.8 arcmin. We estimate an initial mass above 5700M⊙, for a present-day evolved population of two Cepheids, two A supergiants and 12 red giants with masses ≈6M⊙. We also determine chemical abundances of Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y and Ba for the red clump stars. We find a supersolar metallicity, [Fe/H]=+0.19 ± 0.05, and a homogeneous chemical composition, consistent with the Galactic metallicity gradient. The presence of a Li-rich red giant, star 276 with A(Li)=2.41, is also detected. An overabundance of Ba is found, supporting the enhanced s-process. The ratio of yellow to red giants is much smaller than 1, in agreement with models with moderate overshooting, but the properties of the cluster Cepheids do not seem consistent with current Padova models for supersolar metallicity

A comprehensive study of NGC 2345, a young open cluster with a low metallicity

Context. NGC 2345 is a young open cluster that hosts seven blue and red supergiants, low metallicity, and a high fraction of Be stars, which makes it a privileged laboratory to study stellar evolution. Aims. We aim to improve the determination of the cluster parameters and study the Be phenomenon. Our objective is also to characterise the seven evolved stars found in NGC 2345 by deriving their atmospheric parameters and chemical abundances. Methods. We performed a complete analysis combining for the first time ubvy photometry with spectroscopy as well as the Gaia Data Release 2. We obtained spectra with classification purposes for 76 stars and high-resolution spectroscopy for an in-depth analysis of the blue and red evolved stars. Results. We identify a new red supergiant and 145 B-type likely members within a radius of 18.7 ± 1.2 arcmin, which implies an initial mass, Mcl ≈ 5200 M⊙. We find a distance of 2.5 ± 0.2 kpc for NGC 2345, placing it at RGC = 10.2 ± 0.2 kpc. Isochrone fitting supports an age of 56 ± 13 Ma, implying masses around 6.5 M⊙ for the supergiants. A high fraction of Be stars (≈10%) is found. From the spectral analysis we estimate an average vrad = +58.6 ± 0.5 km s−1 and a low metallicity, [Fe/H] = −0.28 ± 0.07, for the cluster. We also determine chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the evolved stars. The chemical composition of the cluster is consistent with that of the Galactic thin disc. One of the K supergiants, S50, is a Li-rich star, presenting an A(Li) ≈ 2.1. An overabundance of Ba is found, supporting the enhanced s-process. Conclusions. NGC 2345 has a low metallicity for its Galactocentric distance, which is comparable to typical Large Magellanic Cloud stars. It is massive enough to serve as a test bed for theoretical evolutionary models for massive intermediate-mass stars.This research is partially supported by the Spanish Government under grants AYA2015-68012-C2-2-P and PGC2018-093741-B-C21 (MICIU/AEI/FEDER, UE)

The little-studied cluster Berkeley 90 I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Context. It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find owing to their low numbers throughout the Galaxy and the implied large distances and extinctions. Aims. We want to study LS III +46 11, identified in this paper as a very massive binary; another nearby massive system, LS III +46 12; and the surrounding stellar cluster, Berkeley 90. Methods. Most of the data used in this paper are multi-epoch high S/N optical spectra, although we also use Lucky Imaging and archival photometry. The spectra are reduced with dedicated pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results. LS III +46 11 is identified as a new very early O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 11 and derive minimum masses of 38.80 ± 0.83 M⊙ and 35.60 ± 0.77 M⊙ for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system where the companion is currently undetected.J.M.A. and A.S. acknowledge support from [a] the Spanish Government Ministerio de Economía y Competitividad (MINECO) through grants AYA2010-15 081, AYA2010-17 631, and AYA2013-40 611-P and [b] the Consejería de Educación of the Junta de Andalucía through grant P08-TIC-4075. J.M.A. was also supported by the George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy and he is grateful to the Department of Physics and Astronomy at Texas A&M University for their hospitality during some of the time this work was carried out. I.N., A.M., J.A., and J.L. acknowledge support from [a] the Spanish Government Ministerio de Economía y Competitividad (MINECO) through grant AYA2012-39 364-C02-01/02, [b] the European Union, and [c] the Generalitat Valenciana through grant ACOMP/2014/129. R.H.B. acknowledges support from FONDECYT Project 1 140 076. S.S.-D. acknowledges funding by [a] the Spanish Government Ministerio de Economía y Competitividad (MINECO) through grants AYA2010-21 697-C05-04, AYA2012-39 364-C02-01, and Severo Ochoa SEV-2011-0187 and [b] the Canary Islands Government under grant PID2 010 119. J.S.-B. acknowledges support by the JAE-PreDoc program of the Spanish Consejo Superior de Investigaciones Científicas (CSIC). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555

The little-studied cluster Berkeley 90 : I. LS III +46 11: a very massive O3.5 If* + O3.5 If* binary

Context. It appears that most (if not all) massive stars are born in multiple systems. At the same time, the most massive binaries are hard to find owing to their low numbers throughout the Galaxy and the implied large distances and extinctions. Aims. We want to study LS III +46 11, identified in this paper as a very massive binary; another nearby massive system, LS III +46 12; and the surrounding stellar cluster, Berkeley 90. Methods. Most of the data used in this paper are multi-epoch high S/N optical spectra, although we also use Lucky Imaging and archival photometry. The spectra are reduced with dedicated pipelines and processed with our own software, such as a spectroscopic-orbit code, CHORIZOS, and MGB. Results. LS III +46 11 is identified as a new very early O-type spectroscopic binary [O3.5 If* + O3.5 If*] and LS III +46 12 as another early O-type system [O4.5 V((f))]. We measure a 97.2-day period for LS III +46 11 and derive minimum masses of 38.80 ± 0.83 M⊙ and 35.60 ± 0.77 M⊙ for its two stars. We measure the extinction to both stars, estimate the distance, search for optical companions, and study the surrounding cluster. In doing so, a variable extinction is found as well as discrepant results for the distance. We discuss possible explanations and suggest that LS III +46 12 may be a hidden binary system where the companion is currently undetected.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

A Retino-retinal Projection Guided by Unc5c Emerged in Species with Retinal Waves

We thank D Baeza and M Herrera for mouse breeding, genotyping and help in in utero electroporation experiments and E Llorens and J Mullet for technical help in experiments involving ferrets. We also thank A Barco for discussion and comments on the manuscript. The laboratory of EH is funded with the following grants: (BFU2016-77605 from the National Grant Research Program, PROMETEO Program (2016/026) from Generalitat Valenciana, (PCIN2015-192-C02-02 from ERA-Net Program) and (ERC282329 from the European Research Council). Work in the laboratory of LMM and SS was supported by the National Grant Research Program (Grant BFU2014-58776-r), cofinanced by the European Regional Development Fund (ERDF). VMB holds a postdoctoral contract from the Regional Government. AJV is the recipient of a FPI fellowship from the National Grant Research Program. We also acknowledge the financial support received from the “Severo Ochoa” Program for Centers of Excellence in R&D (SEV-2013-0317). AK was supported by the Canadian Institutes for Health Research Operating Grants MOP-77556 and MOP-97758, as well as Brain Canada, Canadian Foundation for Innovation, and the W. Garfield Weston Foundation.Peer reviewedPublisher PD