Suchergebnisse

We take advantage of the Gaia-ESO Survey iDR4 bulge data to search for abundance anomalies that could shed light on the composite nature of the Milky Way bulge. The α-element (Mg, Si, and whenever available, Ca) abundances, and their trends with Fe abundances have been analysed for a total of 776 bulge stars. In addition, the aluminum abundances and their ratio to Fe and Mg have also been examined. Our analysis reveals the existence of low-α element abundance stars with respect to the standard bulge sequence in the [α/ Fe] versus [Fe/H] plane. Eighteen objects present deviations in [α/ Fe] ranging from 2.1 to 5.3σ with respect to the median standard value. Those stars do not show Mg-Al anti-correlation patterns. Incidentally, this sign of the existence of multiple stellar populations is reported firmly for the first time for the bulge globular cluster NGC 6522. The identified low-α abundance stars have chemical patterns that are compatible with those of the thin disc. Their link with massive dwarf galaxies accretion seems unlikely, as larger deviations in α abundance and Al would be expected. The vision of a bulge composite nature and a complex formation process is reinforced by our results. The approach used, which is a multi-method and model-driven analysis of high resolution data, seems crucial to reveal this complexity. © ESO, 2017. ; A.R.B., P.d.L., and V.H. acknowledge financial support form the ANR 14-CE33-014-01. This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541. We acknowledge the support from INAF and Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR) in the form of the grant "Premiale VLT 2012". The results presented here benefit from discussions held during the Gaia-ESO workshops and conferences supported by the ESF (European Science Foundation) through the GREAT Research Network Programme. M. Zoccali gratefully acknowledge support by the Ministry of Economy, Development, and Tourism's Millenium Science Initiative through grant IC120009, awarded to the Millenium Institute of Astrophysics (MAS), by Fondecyt Regular 1150345 and by the BASAL-CATA Center for Astrophysics and Associated Technologies PFB-06.

Full list of authors: Rojas-Arriagada, A.; Recio-Blanco, A.; de Laverny, P.; Mikolaitis, Š.; Matteucci, F.; Spitoni, E.; Schultheis, M.; Hayden, M.; Hill, V.; Zoccali, M.; Minniti, D.; Gonzalez, O. A.; Gilmore, G.; Randich, S.; Feltzing, S.; Alfaro, E. J.; Babusiaux, C.; Bensby, T.; Bragaglia, A.; Flaccomio, E. Koposov, S. E.; Pancino, E.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Donati, P.; Franciosini, E.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Lind, K.; Magrini, L.; Morbidelli, L.; Sacco, G. G.; Worley, C. C.; Zaggia, S. ; Context. As observational evidence steadily accumulates, the nature of the Galactic bulge has proven to be rather complex: the structural, kinematic, and chemical analyses often lead to contradictory conclusions. The nature of the metal-rich bulge - and especially of the metal-poor bulge - and their relation with other Galactic components, still need to be firmly defined on the basis of statistically significant high-quality data samples. Aims. We used the fourth internal data release of the Gaia-ESO survey to characterize the bulge metallicity distribution function (MDF), magnesium abundance, spatial distribution, and correlation of these properties with kinematics. Moreover, the homogeneous sampling of the different Galactic populations provided by the Gaia-ESO survey allowed us to perform a comparison between the bulge, thin disk, and thick disk sequences in the [Mg/Fe] vs. [Fe/H] plane in order to constrain the extent of their eventual chemical similarities. Methods. We obtained spectroscopic data for ∼2500 red clump stars in 11 bulge fields, sampling the area -10° ≥ l ≥ +8° and -10° ≥ b ≥ -4° from the fourth internal data release of the Gaia-ESO survey. A sample of ∼6300 disk stars was also selected for comparison. Spectrophotometric distances computed via isochrone fitting allowed us to define a sample of stars likely located in the bulge region. Results. From a Gaussian mixture models (GMM) analysis, the bulge MDF is confirmed to be bimodal across the whole sampled area. The relative ratio between the two modes of the MDF changes as a function of b, with metal-poor stars dominating at high latitudes. The metal-rich stars exhibit bar-like kinematics and display a bimodality in their magnitude distribution, a feature which is tightly associated with the X-shape bulge. They overlap with the metal-rich end of the thin disk sequence in the [Mg/Fe] vs. [Fe/H] plane. On the other hand, metal-poor bulge stars have a more isotropic hot kinematics and do not participate in the X-shape bulge. Their Mg enhancement level and general shape in the [Mg/Fe] vs. [Fe/H] plane is comparable to that of the thick disk sequence. The position at which [Mg/Fe] starts to decrease with [Fe/H], called the "knee", is observed in the metal-poor bulge at [Fe/H] = -0:37 ± 0:09, being 0.06 dex higher than that of the thick disk. Although this difference is inside the error bars, it suggest a higher star formation rate (SFR) for the bulge than for the thick disk. We estimate an upper limit for this difference of Δ[Fe/H] = 0:24 dex. Finally, we present a chemical evolution model that suitably fits the whole bulge sequence by assuming a fast (<1 Gyr) intense burst of stellar formation that takes place at early epochs. Conclusions.We associate metal-rich stars with the bar boxy/peanut bulge formed as the product of secular evolution of the early thin disk. On the other hand, the metal-poor subpopulation might be the product of an early prompt dissipative collapse dominated by massive stars. Nevertheless, our results do not allow us to firmly rule out the possibility that these stars come from the secular evolution of the early thick disk. This is the first time that an analysis of the bulge MDF and α-abundances has been performed in a large area on the basis of a homogeneous, fully spectroscopic analysis of high-resolution, high S/N data. © ESO 2017. ; This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541. We acknowledge the support from INAF and the Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR) in the form of the grant "Premiale VLT 2012". The results presented here benefited from discussions held during the Gaia-ESO workshops and conferences supported by the ESF (European Science Foundation) through the GREAT Research Network Programme. A. Recio-Blanco, P. de Laverny, and V. Hill acknowledge the Programme National de Cosmologie et Galaxies (PNCG) of CNRS/INSU, France, for financial support. A. Recio-Blanco, P. de Laverny, and V. Hill acknowledge financial support form the ANR 14-CE33-014-01. M. Zoccali gratefully acknowledges support from the Ministry of Economy, Development, and Tourism's Millenium Science Initiative through grant IC120009, awarded to the Millenium Institute of Astrophysics (MAS), by Fondecyt Regular 1150345 and by the BASAL-CATA Center for Astrophysics and Associated Technologies PFB-06.

Context. The study of the inner region of the Milky Way bulge is hampered by high interstellar extinction and extreme source crowding. Sensitive high angular resolution near-infrared imaging is needed to study stellar populations and their characteristics in such a dense and complex environment. Aims. We aim at investigating the stellar population in the innermost Galactic bulge, to study the star formation history in this region of the Galaxy. Methods. We used the 0.2″ angular resolution JHK data from the GALACTICNUCLEUS survey to study the stellar population within two 8.0′×3.4′ fields, about 0.6° and 0.4° to the Galactic north of the Milky Way centre and to compare it with the one in the immediate surroundings of Sagittarius A∗. We also characterise the absolute extinction and the extinction curve of the two fields. Results. The average interstellar extinction to the outer and the inner field is A ∼ 1.20 ± 0.08 mag and ∼1.48 ± 0.10 mag, respectively. We present K luminosity functions that are complete down to at least two magnitudes below the red clump (RC). We detect a feature in the luminosity functions that is fainter than the RC by 0.80 ± 0.03 and 0.79 ± 0.02 mag, respectively, in the K band. It runs parallel to the reddening vector. We identify the feature as the red giant branch bump. Fitting α-enhanced BaSTI luminosity functions to our data, we find that a single old stellar population of ∼12.8 ± 0.6 Gyr and Z = 0.040 ± 0.003 provides the best fit. Our findings thus show that the stellar population in the innermost bulge is old, similar to the one at larger distances from the Galactic plane, and that its metallicity is about twice solar at distances as short as about 60 pc from the centre of the Milky Way, similar to what is observed at about 500 pc from the Galactic Centre. Comparing the obtained metallicity with previous known values at larger latitudes (|b| > 2°), our results favour a flattening of the gradient at |b| < 2°. As a secondary result we obtain that the extinction index in the studied regions agrees within the uncertainties with our previous value of α = 2.30 ± 0.08 that was derived for the very Galactic centre.© ESO 2018. ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement no [614922]. F. N.-L. acknowledges financial support from a MECD pre-doctoral contract, code FPU14/01700. F. N. acknowledges financial support through Spanish grants ESP2015-65597-C4-1-R and ESP2017-86582-C4-1-R (MINECO/FEDER). ; Peer Reviewed

The catalogues described in this paper and specified in Table 1 are only at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/631/A20. The catalogues follow the structure presented in Table 2. ; Context. The high extinction and extreme source crowding of the central regions of the Milky Way are serious obstacles to the study of the structure and stellar population of the Galactic centre (GC). Existing surveys that cover the GC region (2MASS, UKIDSS, VVV, SIRIUS) do not have the necessary high angular resolution. Therefore, a high-angular-resolution survey in the near infrared is crucial to improve the state of the art. Aims. Here, we present the GALACTICNUCLEUS catalogue, a near infrared JHKs high-angular-resolution (0.2″) survey of the nuclear bulge of the Milky Way. Methods. We explain in detail the data reduction, data analysis, calibration, and uncertainty estimation of the GALACTICNUCLEUS survey. We assess the data quality comparing our results with previous surveys. Results. We obtained accurate JHKs photometry for ∼3.3 × 106 stars in the GC detecting around 20% in J, 65% in H, and 90% in Ks. The survey covers a total area of ∼0.3 deg2, which corresponds to ∼6000 pc2. The GALACTICNUCLEUS survey reaches 5σ detections for J ∼ 22 mag, H ∼ 21 mag, and Ks ∼ 21 mag. The uncertainties are below 0.05 mag at J ∼ 21 mag, H ∼ 19 mag, and Ks ∼ 18 mag. The zero point systematic uncertainty is ≲0.04 mag in all three bands. We present colour–magnitude diagrams for the different regions covered by the survey.© ESO 2019 ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013)/ERC grant agreement n° [614922]. This work is based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes IDs 195.B-0283 and 091.B-0418. We thank the staff of ESO for their great efforts and helpfulness. We acknowledge financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). F.N.-L. acknowledges financial support from a MECD pre-doctoral contract, code FPU14/01700. R.S., A.T.G.-C., B.S. acknnowledge financial support from the national grant PGC2018-095049-B-C21 (MCIU/AEI/FEDER, UE). F.N. acknowledges financial support through Spanish grants ESP2015-65597-C4-1-R and ESP2017-86582-C4-1-R (MINECO/FEDER). N.N. acknowledges support by Sonderforschungsbereich SFB 881 "The Milky Way System" (subproject B8) of the German Research Foundation (DFG). ; Peer reviewed

Lenticular galaxy NGC3 has been chosen to study the surface photometry using griz filter. The data where obtained from the seventh Sloan Digital Sky Survey (SDSS) Data Release seven (DR7), and main the image reduction was done by the pipeline of SDSS. The work was achieved by the ELLIPS task from the STSDAS ISOPHOTE package in the Image Reduction and Analysis Facility (IRAF).The overall structure of the galaxy (a bulge, a bar, isophotal contour maps, together with a bulge to disk decomposition of the galaxy images where achieved, Also, the photometric properties (the disk position angle, ellipticity, B4 and inclination of the galaxy) where estimated.

This work has made use of BaSTI web tools. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n◦ [614922]. This work is based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes IDs 195.B-0283 and 091.B-0418. We thank the staff of ESO for their great efforts and helpfulness. F N-L acknowledges financial support from a MECD pre-doctoral contract, code FPU14/01700. We acknowledge support from the State Agency for Research of the Spanish MCIU through the Centre of Excellence Severo Ochoa Award of the Instituto de Astrofísica de Andalucía (CSIC) (SEV-2017-0709). ; The centre of the Milky Way is a fundamental astrophysical target since it is the closest galaxy nucleus (∼ 8 kpc from Earth) and the only one where we can study individual stars with high angular resolution. It is an extreme environment characterised by extreme conditions such as: very high stellar densities (∼ 105−7 pc−3, Launhardt et al., 2002; Schödel et al., 2007, 2018), a tidal field so intense that even massive, young clusters dissolve into the background in less than 10 Myr (Portegies Zwart et al., 2002), high turbulence and temperature of the interstellar medium (Morris & Serabyn, 1996), a strong magnetic field (Crocker, 2012), and intense UV radiation (Launhardt et al., 2002). Despite, or possibly because of these extreme properties, the Galactic centre (GC) is the Galaxy's most prolific massive star forming environment (Mauerhan et al., 2010b; Schödel et al., 2007; Yusef-Zadeh et al., 2009). Moreover, it possesses a supermassive black hole, SgrA*, in its centre. Therefore, it is a unique laboratory to improve our understanding about the inner regions of the galaxies. Nevertheless, in spite of its importance only ∼ 1% of its total area has been studied with the sufficient wavelength coverage and high angular resolution to analyse its stellar structure and population. In addition, the high extinction (and its strong variation on arc second scales) and the extreme source crowding of the central regions of the Milky Way pose great difficulties to the study of the GC. In this way, all the existing surveys that contain the GC (2MASS, UKIDSS, VVV, SIRIUS) fail at covering adequately the GC area. This thesis aims at improving the state of the art in order to enable us to perform a detailed study of the stellar population of the GC. For this, we carried out the GALACTICNUCLEUS survey during this PhD thesis. This is a high angular near infrared (NIR) survey (JHKs bands) with the HAWK-I instrument located at the VLT UT4 (ESO, Paranal-Chile). In this dissertation, I explain the whole process to perform the survey from the observing strategy to the first data release of the catalogue. The development of the data reduction (highly non standard) pipeline and the analysis of the data to obtain accurate photometry and astrometry, lie at the heart of this thesis. To achieve the necessary high angular resolution to analyse the stellar population of the GC, we use the speckle holographic technique described in Schödel et al. (2013), which has been optimised for crowded fields. To assess the data quality, we compare GALACTICNUCLEUS with the up-to-now best surveys for the GC: VVV, SIRIUS and NICMOS (HST) data. ; El centro de la Vía Láctea constituye un objetivo fundamental para la astrofísica, puesto que es el núcleo galáctico más cercano (∼ 8 kpc desde la Tierra) y el único donde es posible estudiar las estrellas individuales con alta resolución angular. Es un entorno extremo caracterizado por condiciones límite como: densidades estelares muy elevadas (∼105−7 pc−3, Launhardt et al., 2002; Schödel et al., 2007, 2018), un campo de marea tan intenso que incluso los cúmulos jóvenes y masivos se disuelven en menos de 10 Myr entre la población estelar circundante (Portegies Zwart et al., 2002), alta turbulencia y temperatura del medio interestelar, un fuerte campo magnético (Crocker, 2012), y una intensa radiación ultravioleta (Launhardt et al., 2002). A pesar de estas condiciones, o precisamente debido a ellas, el centro Galáctico (CG) es el entorno estelar más prolífico en nuestra galaxia para la formación de estrellas masivas (Mauerhan et al., 2010b; Schödel et al., 2007; Yusef-Zadeh et al., 2009). Además, su centro está ocupado por un agujero negro supermasivo, SgrA*. Por lo tanto, es un laboratorio único para mejorar nuestro conocimiento sobre las regiones internas de las galaxias. Sin embargo, a pesar de su extraordinaria importancia, solo ∼ 1% de su área total ha sido estudiada con la suficiente resolución angular y cobertura en diferentes longitudes de onda para analizar su estructura y población estelar. Además, la alta extinción (y su fuerte variación en escalas de segundos de arco) y la extrema densidad de fuentes de las regiones centrales de la Vía Láctea, constituyen serios obstáculos para su estudio. De esta forma, todos los catálogos existentes que contienen el CG (2MASS, UKIDSS, VVV, SIRIUS) fracasan al cubrir este área en detalle. El objetivo fundamental de esta tesis es contribuir a la mejora del estado del arte, para permitir un estudio detallado de la población estelar del bulbo nuclear de la Vía Láctea. Para ello, hemos desarrollado un nuevo catálogo, GALACTICNUCLEUS, durante esta tesis doctoral. Este catálogo se caracteriza por estar diseñado especialmente para la observación del CG en el infrarrojo cercano (bandas JHKs) con alta resolución angular. Los datos fueron tomados con el instrumento HAWK-I situado en el UT4 del VLT (ESO, Paranal-Chile). En esta disertación, se trata detalladamente el proceso completo desde la elaboración de la estrategia de observación hasta la primera publicación de los datos del catálogo. El desarrollo de un procedimiento para la reducción de los datos (altamente no estándar) y el análisis de los mismos para obtener fotometría y astrometría precisas constituyen una parte fundamental de la tesis. Para conseguir la resolución angular necesaria para analizar la población estelar del CG, utilizamos la técnica de holografía descrita en Schödel et al. (2013), que ha sido optimizada para campos con altas densidades estelares. Para comprobar la calidad de los datos, llevamos a cabo una comparación de GALACTICNUCLEUS con los mejores catálogos existentes hasta la fecha para el CG: VVV, SIRIUS y NICMOS (HST). ; Tesis Univ. Granada. ; European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n◦ [614922] ; MECD pre-doctoral contract, code FPU14/01700 ; State Agency for Research of the Spanish MCIU through the Centre of Excellence Severo Ochoa Award of the Instituto de Astrofísica de Andalucía (CSIC) (SEV-2017-0709)

The protagonists of the last great phase transition of the universe – cosmic reionization – remain elusive. Galaxies at z~2 are already mature: bulges have already formed in the cores of these galaxies. The high stellar mass densities in these systems require a high star-formation rate surface density at earlier times; providing possible candidates of galaxies that drive reionization. Using an empirical model for galaxy evolution at z>4, we constrain the escape fraction by leveraging latest constraints on the reionization timeline, such as the Ly-alpha damping of quasars and galaxies at z>7. Inspired by the emergent sample of Lyman Continuum (LyC) leakers spanning z=0-6.6 that overwhelmingly displays higher-than-average star-formation surface density, we propose a physically motivated model relating f_esc to star-formation surface density. Within this model, strikingly, 8 (the "oligarchs") account for >80% of the reionization budget – a stark departure from the canonical "democratic" reionization led by copious faint sources. We predict that the drivers of reionization do not lie hidden across the faint-end of the luminosity function, but are already known to us.

JMA acknowledge support from the Spanish Ministerio de Economia y Competitividad (MINECO) by the grant AYA2017-83204-P and the Programa Operativo FEDER Andalucia 2014-2020 in collaboration with the Andalucian Office for Economy and Knowledge. AdLC acknowledges financial support from the Spanish Ministry of Economy and Competitiveness (MINECO) under grants AYA201677237-C3-1-P and RTI2018-096188-B-I00, the latter is partly funded by the European Regional Development Fund (ERDF). SFS thanks the projects ConaCyt CB-285080, FC-2016-01-1916, and PAPIIT IN100519. This paper is based on data from the Calar Alto Legacy Integral Field Area Survey, CALIFA, funded by the Spanish Ministry of Science under grant ICTS-2009-10, and the Centro Astronomico Hispano-Aleman. This paper is based on observations collected at the Centro Astronomico Hispano Aleman (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut fur Astronomie and the Instituto de Astrofisica de Andalucia. ; This series of papers aims at understanding the formation and evolution of non-barred disc galaxies. We use the new spectro-photometric decomposition code, C2D, to separate the spectral information of bulges and discs of a statistically representative sample of galaxies from the CALIFA survey. Then, we study their stellar population properties analysing the structure-independent datacubes with the PIPE3D algorithm. We find a correlation between the bulge-to-total (B/T) luminosity (and mass) ratio and galaxy stellar mass. The B/T mass ratio has only a mild evolution with redshift, but the bulge-to-disc (B/D) mass ratio shows a clear increase of the disc component since redshift z 10.5). The relation holds for bulges but not for discs when using their individual stellar masses. We find a negligible evolution of the mass-size relation for both the most massive (log(M-star,M-b,M-d/M-circle dot) > 10) bulges and discs. For lower masses, discs show a larger variation than bulges. We also find a correlation between the Sersic index of bulges and both galaxy and bulge stellar mass, which does not hold for the disc mass. Our results support an inside-out formation of nearby non-barred galaxies, and they suggest that (i) bulges formed early-on and (ii) they have not evolved much through cosmic time. However, we find that the early properties of bulges drive the future evolution of the galaxy as a whole, and particularly the properties of the discs that eventually form around them. ; Spanish Government AYA2017-83204-P ; Programa Operativo FEDER Andalucia 2014-2020 ; Andalucian Office for Economy and Knowledge ; European Commission ; Consejo Nacional de Ciencia y Tecnologia (CONACyT) CB-285080 ; Spanish Government ICTS-2009-10 ; Centro Astronomico Hispano-Aleman ; Programa de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT) IN100519 ; Spanish Government AYA201677237-C3-1-P RTI2018-096188-B-I00 FC-2016-01-1916

Galaxies with stellar masses near M* contain the majority of stellar mass in the universe, and are therefore of special interest in the study of galaxy evolution. The Milky Way (MW) and Andromeda (M31) have present-day stellar masses near M*, at 5 x 10(10) M-circle dot (defined here to be MW-mass) and 10(11) M-circle dot (defined to be M31-mass). We study the typical progenitors of these galaxies using the FOURSTAR Galaxy Evolution Survey (ZFOURGE). ZFOURGE is a deep medium-band near-IR imaging survey, which is sensitive to the progenitors of these galaxies out to z similar to 3. We use abundance-matching techniques to identify the main progenitors of these galaxies at higher redshifts. We measure the evolution in the stellar mass, rest-frame colors, morphologies, far-IR luminosities, and star formation rates, combining our deep multiwavelength imaging with near-IR Hubble Space Telescope imaging from Cosmic Near-IR Deep Extragalactic Legacy Survey (CANDELS), and Spitzer and Herschel far-IR imaging from Great Observatories Origins Deep Survey-Herschel and CANDELS-Herschel. The typical MW-mass and M31-mass progenitors passed through the same evolution stages, evolving from blue, star-forming disk galaxies at the earliest stages to redder dust-obscured IR-luminous galaxies in intermediate stages and to red, more quiescent galaxies at their latest stages. The progenitors of the MW-mass galaxies reached each evolutionary stage at later times (lower redshifts) and with stellar masses that are a factor of two to three lower than the progenitors of the M31-mass galaxies. The process driving this evolution, including the suppression of star formation in present-day M* galaxies, requires an evolving stellar-mass/halo-mass ratio and/or evolving halo-mass threshold for quiescent galaxies. The effective size and SFRs imply that the baryonic cold-gas fractions drop as galaxies evolve from high redshift to z similar to 0 and are strongly anticorrelated with an increase in the Sersic index. Therefore, the growth of galaxy bulges in M* galaxies corresponds to a rapid decline in the galaxy gas fractions and/or a decrease in the star formation efficiency. ; National Science Foundation AST-1009707, AST-0808133 ; ERC HIGHZ 227749 ; NL-NWO Spinoza ; NASA NAS5-26555 ; HST program GO-12060 ; National Collaborative Research Infrastructure Strategy of the Australian Federal Government ; Texas A&M University ; George P. and Cynthia Woods Institute for Fundamental Physics and Astronomy ; Astronomy

We study the rest-frame optical mass–size relation of bulges and discs from z ∼ 2 to z ∼ 0 for a complete sample of massive galaxies in the CANDELS fields using two-component Sérsic models. Discs and star-forming galaxies follow similar mass–size relations. The mass–size relation of bulges is less steep than the one of quiescent galaxies (best-fitting slope of 0.7 for quiescent galaxies against 0.4 for bulges). We find little dependence of the structural properties of massive bulges and discs with the global morphology of galaxies (disc versus bulge dominated) and the star formation activity (star-forming versus quiescent). This result suggests similar bulge formation mechanisms for most massive galaxies and also that the formation of the bulge component does not significantly affect the disc structure. Our results pose a challenge to current cosmological models that predict distinct structural properties for stellar bulges arising from mergers and disc instabilities. ; This work has been essentially funded by to a French national PhD scholarship. MHC is also thankful to Google for their unrestricted gift to explore deep-learning techniques for galaxy evolution. PGP-G acknowledges support from the Spanish Government grant AYA2015-63650-P. FS acknowledges partial support from a Leverhulme Trust Research Fellowship. ; Peer reviewed

Context. VISTA Variables in the Vía Láctea (VVV) is one of six ESO Public Surveys using the 4 meter Visible and Infrared Survey Telescope for Astronomy (VISTA). The VVV survey covers the Milky Way bulge and an adjacent section of the disk, and one of the principal objectives is to search for new star clusters within previously unreachable obscured parts of the Galaxy. Aims. The primary motivation behind this work is to discover and analyze obscured star clusters in the direction of the inner Galactic disk and bulge. Methods. Regions of the inner disk and bulge covered by the VVV survey were visually inspected using composite JHKS color images to select new cluster candidates on the basis of apparent overdensities. DR1, DR2, CASU, and point spread function photometry of 10 × 10 arcmin fields centered on each candidate cluster were used to construct color–magnitude and color–color diagrams. Follow-up spectroscopy of the brightest members of several cluster candidates was obtained in order to clarify their nature. Results. We report the discovery of 58 new infrared cluster candidates. Fundamental parameters such as age, distance, and metallicity were determined for 20 of the most populous clusters. ; I.N. and A.M. acknowledge support for this work by the Spanish Government Ministerio de Ciencia e Innovación (MICINN) through grant AYA2012-39364-C02-02.

The Galactic Archaeology with HERMES (GALAH) survey is amassive observational project to trace the MilkyWay's history of star formation, chemical enrichment, stellar migration and minor mergers. Using high-resolution (R ≃ 28 000) spectra, taken with the High Efficiency and Resolution Multi-Element Spectrograph (HERMES) instrument at the Anglo-Australian Telescope, GALAH will determine stellar parameters and abundances of up to 29 elements for up to one million stars. Selecting targets from a colour-unbiased catalogue built from 2MASS, APASS and UCAC4 data, we expect to observe dwarfs at 0.3-3 kpc and giants at 1-10 kpc. This enables a thorough local chemical inventory of the Galactic thin and thick discs, and also captures smaller samples of the bulge and halo. In this paper, we present the plan, process and progress as of early 2016 for GALAH survey observations. In our first two years of survey observing we have accumulated the largest high-quality spectroscopic data set at this resolution, over 200 000 stars. We also present the first public GALAH data catalogue: stellar parameters (Teff, log(g), [Fe/H], [α/Fe]), radial velocity, distance modulus and reddening for 10 680 observations of 9860 Tycho-2 stars, 7894 of which are included in the first Gaia data release. ; SLM and DBZ acknowledge support from Australian Research Council grants DE140100598 and FT110100743. JPM is supported by a UNSW Vice-Chancellor's Research Fellowship. KL and SB acknowledge funds from the Alexander von Humboldt Foundation in the framework of the Sofja Kovalevskaja Award endowed by the Federal Ministry of Education and Research as well as funds from the Swedish Research Council (Grant no. 2015-00415_3) and Marie Sklodowska Curie Actions (Cofund Project INCA 600398). This work was partly supported by the European Union FP7 programme through ERG grant number 320360.