Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. T.P. acknowledges support from NASA under the Swift GI grant 1619152, the Tess GI grant G03267, from the NYU Center for Cosmology and Particle Physics, from a 19 Washington Square North Award awarded to M.M, and in part by a grant from the New York University Research Challenge FundProgram. M.M. and the SNYU group have been supported by the NSF CAREER award AST-1352405, by the NSF award AST1413260, and by a Humboldt Faculty Fellowship. M.M. is grateful for her sabbatical stay supported by the Center for Computational Astrophysics at the Flatiron institute and for the hospitality of the Max-Planck Institute for Astronomy, Heidelberg, during which some of this work was accomplished. K.B. acknowledges financial support from the Ministerio de Economia y Competitividad through the Spanish grant BES2014-069767. K.B., C.T. and A.d.U.P. acknowledge support from the Spanish research project AYA2017-89384-P. C.T. acknowledges support from funding associated to a Ramon y Cajal fellowship RyC-2012-09984. A.d.U.P. acknowledges support from funding associated to a Ramon y Cajal fellowship RyC-2012-09975. L.I. acknowledges support from funding associated to a Juan de la Cierva Incorporacion fellowship IJCI-2016-30940. D.A.K. acknowledges support from the Spanish research projects AYA 2014-58381-P, AYA201789384-P, from Juan de la Cierva Incorporacion fellowship IJCI-2015-26153, and from Spanish National Project research project RTI2018-098104-J-I00 (GRBPhot). J.V. and his research group at Konkoly Observatory is supported by the "Transient Astrophysical Objects" GINOP 2.3.2-15-2016-00033 project of the National Research, Development and Innovation Office (NKFIH), Hungary, funded by the European Union. K.V. and L.K. thank the financial support from the National Research, Development and Innovation Office (NKFIH), Hungary, under grants NKFI-K-131508 and NKFI-KH-130526. A.B. and K.V. are supported by the Lendulet program grant LP2018-7/2019 of the Hungarian Academy of Sciences. T.N.D. also acknowledges the support of the Hungarian OTKA grant No. 119993. The work of X.W. was funded by the National Science Foundation of China (NSFC grants 12033003, 11633002, and 11761141001), the Major State Basic Research Development Program (grant No. 2016YFA0400803), and the Scholar Program of Beijing Academy of Science and Technology (DZ:BS202002). L.G. was funded by the European Union's Horizon 2020 research and innovation program under the Marie SklodowskaCurie grant agreement No. 839090. This work has been partially supported by the Spanish grant PGC2018-095317-BC21 within the European Funds for Regional Development (FEDER). R.G.B. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through grant AYA2016-77846-P and from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award to the Instituto de Astrofisica de Andalucia (SEV-2017-0709). These observations made use of the LCO network. D.A.H., C.P., D.H., and J.B. are supported by NSF Grant AST-1911225 and NASA Grant 80NSSC19k1639. ; In the last decade a number of rapidly evolving transients have been discovered that are not easily explained by traditional supernova models. We present optical and UV data on one such object, SN 2018gep, that displayed a fast rise with a mostly featureless blue continuum around peak, and evolved to develop broad features typical of an SN Ic-bl while retaining significant amounts of blue flux throughout its observations. This blue excess is most evident in its near-UV flux, which is over 4 mag brighter than other stripped-envelope supernovae, and is still visible in optical g-r colors. Its fast rise time of t (rise,V ) = 5.6 +/- 0.5 days puts it squarely in the emerging class of Fast Evolving Luminous Transients, or Fast Blue Optical Transients. With a peak absolute magnitude of M ( v ) = -19.53 +/- 0.23 mag it is on the extreme end of both the rise time and peak magnitude distribution for SNe Ic-bl. These observations are consistent with a simple SN Ic-bl model that has an additional form of energy injection at early times that drives the observed rapid, blue rise. We show that SN 2018gep and the literature SN iPTF16asu have similar photometric and spectroscopic properties and that they overall share many similarities with both SNe Ic-bl and Fast Evolving Transients. Based on our SN 2018gep host galaxy data we derive a number of properties, and we show that the derived host galaxy properties for both SN 2018gep and iPTF16asu are consistent with the SNe Ic-bl and gamma-ray burst/supernova sample while being on the extreme edge of the observed Fast Evolving Transient sample. ; W.M. Keck Foundation ; NASA under the Swift GI grant 1619152 ; Tess GI grant G03267 ; NYU Center for Cosmology and Particle Physics ; New York University Research Challenge FundProgram ; National Science Foundation (NSF) NSF - Office of the Director (OD) AST-1352405 National Science Foundation (NSF) AST-1911225 AST-1413260 ; Humboldt Faculty Fellowship ; Center for Computational Astrophysics at the Flatiron institute ; Spanish Government BES2014-069767 RyC-2012-09975 RyC-2012-09984 ; Juan de la Cierva Incorporacion fellowship IJCI-2015-26153 IJCI-2016-30940 ; "Transient Astrophysical Objects" project of the National Research, Development and Innovation Office (NKFIH), Hungary - European Union GINOP 2.3.2-15-2016-00033 ; National Research, Development & Innovation Office (NRDIO) - Hungary NKFI-K-131508 NKFI-KH-130526 ; Hungarian Academy of Sciences LP2018-7/2019 ; Orszagos Tudomanyos Kutatasi Alapprogramok (OTKA) 119993 ; National Natural Science Foundation of China (NSFC) 12033003 11633002 11761141001 ; National Basic Research Program of China 2016YFA0400803 ; Scholar Program of Beijing Academy of Science and Technology DZ:BS202002 ; European Commission 839090 PGC2018-095317-BC21 ; Spanish Ministry of Economy and Competitiveness AYA2016-77846-P ; State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award SEV-2017-0709 ; National Aeronautics & Space Administration (NASA) 80NSSC19k1639 ; 19 Washington Square North Award AYA 2014-58381-P AYA201789384-P RTI2018-098104-J-I00 AYA2017-89384-P
We measured the gas abundance profiles in a sample of 122 face-on spiral galaxies observed by the CALIFA survey and included all spaxels whose line emission was consistent with star formation. This type of analysis allowed us to improve the statistics with respect to previous studies, and to properly estimate the oxygen distribution across the entire disc to a distance of up to 3-4 disc effective radii (r). We confirm the results obtained from classical H ii region analysis. In addition to the general negative gradient, an outer flattening can be observed in the oxygen abundance radial profile. An inner drop is also found in some cases. There is a common abundance gradient between 0.5 and 2.0 r of α =-0.075 dex/r with a scatter of σ = 0.016 dex/r when normalising the distances to the disc effective radius. By performing a set of Kolmogorov-Smirnov tests, we determined that this slope is independent of other galaxy properties, such as morphology, absolute magnitude, and the presence or absence of bars. In particular, barred galaxies do not seem to display shallower gradients, as predicted by numerical simulations. Interestingly, we find that most of thegalaxies in the sample with reliable oxygen abundance values beyond ~2 effective radii (57 galaxies) present a flattening of the abundance gradient in these outer regions. This flattening is not associated with any morphological feature, which suggests that it is a common property of disc galaxies. Finally, we detect a drop or truncation of the abundance in the inner regions of 27 galaxies in the sample; this is only visible for the most massive galaxies. ; We acknowledge financial support from the Spanish Ministerio de Economia y Competitividad (MINECO) via grant AYA2012-31935, and from the >Junta de Andalucia> local government through the FQM-108 project. We also acknowledge support to the ConaCyt funding program 180125. Y.A. acknowledges finantial support from the Ramon y Cajal programme (RyC-2011-09461). Y.A. and A.I.D. acknowledge support from the project AYA2013-47742-C4-3-P from the Spanish MINECO, as well as the >Study of Emission-Line Galaxies with Integral-Field Spectroscopy> (SELGIFS) programme, funded by the EU (FP7-PEOPLE-2013-IRSES-612701). Support for L.G. is provided by the Ministry of Economy, Development, and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics, MAS. LG acknowledges support by CONICYT through FONDECYT grant 3140566. R.M.G.D. acknowledges support from the Spanish grant AYA2014-57490-P, and from the >Junta de Andalucia> P12-FQM2828 project. RAM thanks the Spanish program of International Campus of Excellence Moncloa (CEI). IM and A.d.O. acknowledge support from the Spanish MINECO grant AYA2013-42227P. JMA acknowledges support from the European Research Council Starting Grant (SEDmorph, P.I. V. Wild). Support for MM has been provided by DGICYT grant AYA2013-47742-C4-4-P. PSB acknowledges support from the Ramon y Cajal programme, grant ATA2010-21322-C03-02 from the Spanish MINECO. CJW acknowledges support through the Marie Curie Career Grant Integration 303912. ; Peer Reviewed
Astronomy and Astrophysics 559 (2013): A114 reproduced with permission from Astronomy and Astrophysics ; The use of integral field spectroscopy 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. Many studies have used these fluxes to derive the gas-phase metallicity of the galaxies by applying the so-called strong-line methods. However, the metallicity indicators that these datasets use were empirically calibrated using few direct abundance data points (Te-based measurements). Furthermore, a precise determination of the prediction intervals of these indicators is commonly lacking in these calibrations. Such limitations might lead to systematic errors in determining the gas-phase metallicity, especially at high redshift, which might have a strong impact on our understanding of the chemical evolution of the Universe. The main goal of this study is to review the most widely used empirical oxygen calibrations, O3N2 and N2, by using newdirect abundance measurements. We pay special attention to (1) the expected uncertainty of these calibrations as a function of the index value or abundance derived and (2) the presence of possible systematic offsets. This is possible thanks to the analysis of the most ambitious compilation of Te-based H ii regions to date. This new dataset compiles the Te-based abundances of 603 H ii 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 a comparison between our revisited calibrations with a total of 3423 additional CALIFA H ii complexes with abundances derived using the ONS calibration from the literature. The combined analysis of T e-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 parameters space. In particular, we infer that these indicators show shallower abundance dependencies and statistically significant offsets compared to others'. 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 ; R.A. Marino is funded by the Spanish program of International Campus of Excellence Moncloa (CEI). D. Mast thank the Plan Nacional de Investigación y Desarrollo funding programs, AYA2012-31935 of the Spanish Ministerio de Economía y Competitividad, for the support given to this project. S.F.S thanks the the Ramón y Cajal project RyC-2011-07590 of the spanish Ministerio de Economía y Competitividad, for the support giving to this project. F.F.R.O. acknowledges the Mexican National Council for Science and Technology (CONACYT) for financial support under the program Estancias Postdoctorales y Sabáticas al Extranjero para la Consolidación de Grupos de Investigación, 2010-2012. We acknowledge financial support for the ESTALLIDOS collaboration by the Spanish Ministerio de Ciencia e Innovación under grant AYA2010- 21887-C04-03. BG-L also acknowledges support from the Spanish Ministerio de Economía y Competitividad (MINECO) under grant AYA2012- 39408-C02-02. J.F.-B. acknowledges financial support from the Ramón y Cajal Program and grant AYA2010-21322-C03-02 from the Spanish Ministry of Economy and Competitiveness (MINECO), as well as to the DAGAL network from the People's Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/ under REA grant agreement number PITN-GA-2011-289313. CK has been funded by project AYA2010-21887 from the Spanish PNAYA. P.P. acknowledges support by the Fundação para a Ciência e a Tecnologia (FCT) under project FCOMP-01-0124-FEDER-029170 (Reference FCT PTDC/FIS-AST/3214/2012), funded by FCT-MEC (PIDDAC) and FEDER (COMPETE). R.M.G.D. and R.G.B. also acknowledge support from the Spanish Ministerio de Economía y Competitividad (MINECO) under grant AyA2010-15081. V.S., L.G., and A.M.M. acknowledge financial support from the Fundação para a Ciência e a Tecnologia (FCT) under program Ciência 2008 and the research grant PTDC/CTE-AST/112582/2009