DOCSLIB.ORG

Type II Supernovae As Probes of Environment Metallicity: Observations of Host H II Regions J

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Type II Supernovae As Probes of Environment Metallicity: Observations of Host H II Regions J A&A 589, A110 (2016) Astronomy DOI: 10.1051/0004-6361/201527691 & c ESO 2016 Astrophysics Type II supernovae as probes of environment metallicity: observations of host H II regions J. P. Anderson1, C. P. Gutiérrez1; 2; 3, L. Dessart4, M. Hamuy3; 2, L. Galbany2; 3, N. I. Morrell5, M. D. Stritzinger6, M. M. Phillips5, G. Folatelli7, H. M. J. Boffin1, T. de Jaeger2; 3, H. Kuncarayakti2; 3, and J. L. Prieto8; 2 1 European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago, Chile e-mail: [email protected] 2 Millennium Institute of Astrophysics, Casilla 36-D, Santiago, Chile 3 Departamento de Astronomía, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile 4 Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Boulevard de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France 5 Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena, Chile 6 Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark 7 Instituto de Astrofísica de La Plata, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, CONICET, Paseo del Bosque S/N, B1900FWA, La Plata, Argentina 8 Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile Received 3 November 2015 / Accepted 28 January 2016 ABSTRACT Context. Spectral modelling of type II supernova atmospheres indicates a clear dependence of metal line strengths on progenitor metallicity. This dependence motivates further work to evaluate the accuracy with which these supernovae can be used as environment metallicity indicators. Aims. To assess this accuracy we present a sample of type II supernova host H ii-region spectroscopy, from which environment oxygen abundances have been derived. These environment abundances are compared to the observed strength of metal lines in supernova spectra. Methods. Combining our sample with measurements from the literature, we present oxygen abundances of 119 host H ii regions by extracting emission line fluxes and using abundance diagnostics. These abundances are then compared to equivalent widths of Fe ii 5018 Å at various time and colour epochs. Results. Our distribution of inferred type II supernova host H ii-region abundances has a range of ∼0.6 dex. We confirm the dearth of type II supernovae exploding at metallicities lower than those found (on average) in the Large Magellanic Cloud. The equivalent width of Fe ii 5018 Å at 50 days post-explosion shows a statistically significant correlation with host H ii-region oxygen abundance. The strength of this correlation increases if one excludes abundance measurements derived far from supernova explosion sites. The correlation significance also increases if we only analyse a “gold” IIP sample, and if a colour epoch is used in place of time. In addition, no evidence is found of a correlation between progenitor metallicity and supernova light-curve or spectral properties – except for that stated above with respect to Fe ii 5018 Å equivalent widths – suggesting progenitor metallicity is not a driving factor in producing the diversity that is observed in our sample. Conclusions. This study provides observational evidence of the usefulness of type II supernovae as metallicity indicators. We finish with a discussion of the methodology needed to use supernova spectra as independent metallicity diagnostics throughout the Universe. Key words. supernovae: general – HII regions – galaxies: abundances 1. Introduction To determine the rate of chemical enrichment as a function of both time and environment, metallicity indicators throughout A fundamental parameter in our understanding of the evolution the Universe are needed. In nearby galaxies one can use spec- of galaxies is the chemical enrichment of the Universe as a func- tra of individual stars to measure stellar metallicity (see, e.g. tion of time and environment. Stellar evolution and its explosive Kudritzki et al. 2012). However, further afield this becomes im- end drive the processes which enrich the interstellar (and indeed possible and other methods are required. In relatively nearby intergalactic) medium with heavy elements. Galaxy formation galaxies (<70 Mpc) one can observe the stellar light from and evolution, together with the evolution of the complete Uni- clusters to constrain stellar metallicities (see e.g. Gazak et al. verse are controlled by the speed and temporal location of chem- 2014), or gas-phase abundances can be obtained through ob- ical enrichment. This is observed in the strong correlation be- servations of emission lines within H ii regions produced by tween a galaxy’s mass and its gas-phase oxygen abundance (see the ionisation (and subsequent recombination) of the interstel- Tremonti et al. 2004). One also observes significant radial metal- lar medium (ISM) (see e.g. review of various techniques in licity gradients within galaxies (see e.g. Henry & Worthey 1999; Kewley & Ellison 2008). At higher redshifts, the latter emission Sánchez et al. 2014) which provides clues to their past formation line diagnostics become the dominant source of measurements. history and future evolution. Article published by EDP Sciences A110, page 1 of 20 A&A 589, A110 (2016) Emission line diagnostics can be broadly separated into two In D14, a conceptual study of SNe II as environment metal- groups. The first group, so called empirical methods, are those licity indicators was published (following Dessart et al. 2013, in where the ratio of strong emission lines within H ii-region spec- which the impact of various stellar and explosion parameters tra are calibrated against abundance estimations from measure- on the resulting SN radiation was examined). Model progeni- ments of the electron temperature (Te, referred to as a direct tors of increasing metallicity produced spectra with metal-line method and derived from the ratio of faint auroral lines, e.g. equivalent widths (EWs) of increasing strength at a given post- [O iii] 4363 Å and 5007 Å, see Osterbrock & Ferland 2006). explosion time or colour. This is the result of the fact that the Some of the most popular empirical relations are those presented hydrogen-rich envelope – which is the region probed during the in Pettini & Pagel(2004), which use the ratio of H α 6563 Å photospheric phase of SN II evolution – retains its original com- to [N ii] 6583 Å (the N2 diagnostic), or a combination of this position (given that nuclear burning during the stars life or the with the ratio of Hβ 4861 Å to [O iii] 5007 Å (the O3N2 diag- explosion has negligible/weak influence on the hydrogen-rich nostic). These diagnostics were updated in Marino et al.(2013; envelope metal content). Hence, the strength of metal line EWs henceforth M13), and we use the latter for the main analysis measured during the “plateau” phase of SNe II is essentially de- in this paper. The second group of diagnostics are those which pendent on the abundance of heavy elements contained within use the comparison of observed emission line ratios with those that part of the SN ejecta, together with the temperature of the predicted by photoionisation/stellar population-synthesis mod- line forming region. The results of D14 therefore make a predic- els (see e.g. McGaugh 1991; Kewley & Dopita 2002). A major tion that SNe II with lower metal line EWs will be found within issue currently plaguing absolute metallicity determinations is environments of lower metallicity within their host galaxies. The the varying results that are obtained with different line diagnos- goal of the current paper is to test such predictions by observing tics. For example, the photoionisation model methods generally SN II host H ii regions, and compare SN pseudo-EWs (pEWs) give abundances that are systematically higher than those de- to host H ii-region metal abundances. rived through empirical techniques. López-Sánchez et al.(2012) The manuscript is organised in the following way. In the next published a review of the systematics involved between the var- section the data sample is introduced, both of the SNe II, and ious abundance diagnostics. It should also be noted that the ma- of host H ii-region spectroscopy. This is followed by a brief de- jority of these techniques use oxygen abundance as a proxy for scription of spectral models. In Sect. 3 we summarise the anal- metallicity, neglecting elemental variations among metals. ysis methods, and in Sect. 4 the results from that analysis are presented. In Sect. 5 the implications of these results are dis- Given the number of issues with current metallicity di- cussed, together with future directions of this research. Finally, agnostics, any new independent technique is of significant in Sect. 6 we draw our conclusions. value. Dessart et al.(2013) presented type II supernova (SN II) model spectra produced from progenitors with distinct metal- licity. Dessart et al. (2014; hereafter D14) then showed how the 2. Data sample and comparison spectral models strength of metal lines observed within photospheric phase spec- tra are strongly dependent on progenitor metallicity. Here we The data analysed in this publication comprise two distinct types present spectral observations of SNe II in comparison to abun- of observations. The first is of SN II optical spectroscopy ob- dances inferred from host H ii-region emission line spectra. This tained during their photospheric phases, i.e. from discovery to comparison presents observational evidence that these explosive at most ∼100 days post explosion. These data are used to ex- events may indeed be used as metallicity indicators throughout tract absorption line pEW measurements. The second data set is the Universe. emission line spectral observations of host H ii regions of SNe II. SNe II are the most frequent stellar explosion in the Universe These are used to estimate SN II environment oxygen abun- dances, which can be used as metallicity proxies.
Load more

Recommended publications
  • Luminous Blue Variables
    Review Luminous Blue Variables Kerstin Weis 1* and Dominik J. Bomans 1,2,3 1 Astronomical Institute, Faculty for Physics and Astronomy, Ruhr University Bochum, 44801 Bochum, Germany 2 Department Plasmas with Complex Interactions, Ruhr University Bochum, 44801 Bochum, Germany 3 Ruhr Astroparticle and Plasma Physics (RAPP) Center, 44801 Bochum, Germany Received: 29 October 2019; Accepted: 18 February 2020; Published: 29 February 2020 Abstract: Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or h Car analogs and the S Dor cycle LBVs.
    [Show full text]
  • Redalyc. Mass Loss from Luminous Blue Variables and Quasi-Periodic
    Revista Mexicana de Astronomía y Astrofísica ISSN: 0185-1101 [email protected] Instituto de Astronomía México Vink, Jorick S.; Kotak, Rubina Mass loss from Luminous Blue Variables and Quasi-periodic Modulations of Radio Supernovae Revista Mexicana de Astronomía y Astrofísica, vol. 30, agosto, 2007, pp. 17-22 Instituto de Astronomía Distrito Federal, México Available in: http://www.redalyc.org/articulo.oa?id=57130005 Abstract Massive stars, supernovae (SNe), and long-duration gamma-ray bursts (GRBs) have a huge impact on their environment. Despite their importance, a comprehensive knowledge of which massive stars produce which SN/GRB is hitherto lacking. We present a brief overview about our knowledge of mass loss in the Hertzsprung- Russell Diagram (HRD) covering evolutionary phases of the OB main sequence, the unstable Luminous Blue Variable (LBV) stage, and the Wolf-Rayet (WR) phase. Despite the fact that metals produced by \selfenrichment" in WR atmospheres exceed the initial { host galaxy { metallicity, by orders of magnitude, a particularly strong dependence of the mass-loss rate on the initial metallicity is found for WR stars at subsolar metallicities (1/10 { 1/100 solar). This provides a signicant boost to the collapsar model for GRBs, as it may present a viable mechanism to prevent the loss of angular momentum by stellar winds at low metallicity, whilst strong Galactic WR winds may inhibit GRBs occurring at solar metallicities. Furthermore, we discuss recently reported quasi-sinusoidal modulations in the radio lightcurves
    [Show full text]
  • The Impact of the Astro2010 Recommendations on Variable Star Science
    The Impact of the Astro2010 Recommendations on Variable Star Science Corresponding Authors Lucianne M. Walkowicz Department of Astronomy, University of California Berkeley [email protected] phone: (510) 642–6931 Andrew C. Becker Department of Astronomy, University of Washington [email protected] phone: (206) 685–0542 Authors Scott F. Anderson, Department of Astronomy, University of Washington Joshua S. Bloom, Department of Astronomy, University of California Berkeley Leonid Georgiev, Universidad Autonoma de Mexico Josh Grindlay, Harvard–Smithsonian Center for Astrophysics Steve Howell, National Optical Astronomy Observatory Knox Long, Space Telescope Science Institute Anjum Mukadam, Department of Astronomy, University of Washington Andrej Prsa,ˇ Villanova University Joshua Pepper, Villanova University Arne Rau, California Institute of Technology Branimir Sesar, Department of Astronomy, University of Washington Nicole Silvestri, Department of Astronomy, University of Washington Nathan Smith, Department of Astronomy, University of California Berkeley Keivan Stassun, Vanderbilt University Paula Szkody, Department of Astronomy, University of Washington Science Frontier Panels: Stars and Stellar Evolution (SSE) February 16, 2009 Abstract The next decade of survey astronomy has the potential to transform our knowledge of variable stars. Stellar variability underpins our knowledge of the cosmological distance ladder, and provides direct tests of stellar formation and evolution theory. Variable stars can also be used to probe the fundamental physics of gravity and degenerate material in ways that are otherwise impossible in the laboratory. The computational and engineering advances of the past decade have made large–scale, time–domain surveys an immediate reality. Some surveys proposed for the next decade promise to gather more data than in the prior cumulative history of astronomy.
    [Show full text]
  • Deep Silicate Absorption Features in Compton-Thick Active Galactic Nuclei Predominantly Arise Due to Dust in the Host Galaxy
    The Astrophysical Journal, 755:5 (8pp), 2012 August 10 doi:10.1088/0004-637X/755/1/5 C 2012. The American Astronomical Society. All rights reserved. Printed in the U.S.A. DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY A. D. Goulding1, D. M. Alexander2,F.E.Bauer3, W. R. Forman1, R. C. Hickox4, C. Jones1, J. R. Mullaney2,5, and M. Trichas1 1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA; [email protected] 2 Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK 3 Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22, Chile 4 Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA 5 Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service Astrophysique, CEA-Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France Received 2012 February 3; accepted 2012 May 31; published 2012 July 19 ABSTRACT We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z<0.05) bona fide Compton-thick 24 −2 (NH > 1.5×10 cm ) active galactic nuclei (AGNs) with hard energy (E>10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at λ ∼ 9.7 μm in archival low-resolution (R ∼ 57–127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority (≈45%) of nearby Compton-thick AGNs have strong Si-absorption features (S9.7 = ln(fint/f obs) 0.5) which would indicate significant dust attenuation.
    [Show full text]
  • And Ecclesiastical Cosmology
    GSJ: VOLUME 6, ISSUE 3, MARCH 2018 101 GSJ: Volume 6, Issue 3, March 2018, Online: ISSN 2320-9186 www.globalscientificjournal.com DEMOLITION HUBBLE'S LAW, BIG BANG THE BASIS OF "MODERN" AND ECCLESIASTICAL COSMOLOGY Author: Weitter Duckss (Slavko Sedic) Zadar Croatia Pусскй Croatian „If two objects are represented by ball bearings and space-time by the stretching of a rubber sheet, the Doppler effect is caused by the rolling of ball bearings over the rubber sheet in order to achieve a particular motion. A cosmological red shift occurs when ball bearings get stuck on the sheet, which is stretched.“ Wikipedia OK, let's check that on our local group of galaxies (the table from my article „Where did the blue spectral shift inside the universe come from?“) galaxies, local groups Redshift km/s Blueshift km/s Sextans B (4.44 ± 0.23 Mly) 300 ± 0 Sextans A 324 ± 2 NGC 3109 403 ± 1 Tucana Dwarf 130 ± ? Leo I 285 ± 2 NGC 6822 -57 ± 2 Andromeda Galaxy -301 ± 1 Leo II (about 690,000 ly) 79 ± 1 Phoenix Dwarf 60 ± 30 SagDIG -79 ± 1 Aquarius Dwarf -141 ± 2 Wolf–Lundmark–Melotte -122 ± 2 Pisces Dwarf -287 ± 0 Antlia Dwarf 362 ± 0 Leo A 0.000067 (z) Pegasus Dwarf Spheroidal -354 ± 3 IC 10 -348 ± 1 NGC 185 -202 ± 3 Canes Venatici I ~ 31 GSJ© 2018 www.globalscientificjournal.com GSJ: VOLUME 6, ISSUE 3, MARCH 2018 102 Andromeda III -351 ± 9 Andromeda II -188 ± 3 Triangulum Galaxy -179 ± 3 Messier 110 -241 ± 3 NGC 147 (2.53 ± 0.11 Mly) -193 ± 3 Small Magellanic Cloud 0.000527 Large Magellanic Cloud - - M32 -200 ± 6 NGC 205 -241 ± 3 IC 1613 -234 ± 1 Carina Dwarf 230 ± 60 Sextans Dwarf 224 ± 2 Ursa Minor Dwarf (200 ± 30 kly) -247 ± 1 Draco Dwarf -292 ± 21 Cassiopeia Dwarf -307 ± 2 Ursa Major II Dwarf - 116 Leo IV 130 Leo V ( 585 kly) 173 Leo T -60 Bootes II -120 Pegasus Dwarf -183 ± 0 Sculptor Dwarf 110 ± 1 Etc.
    [Show full text]
  • Jsolated Stars of Low Metallicity
    galaxies Article Jsolated Stars of Low Metallicity Efrat Sabach Department of Physics, Technion—Israel Institute of Technology, Haifa 32000, Israel; [email protected] Received: 15 July 2018; Accepted: 9 August 2018; Published: 15 August 2018 Abstract: We study the effects of a reduced mass-loss rate on the evolution of low metallicity Jsolated stars, following our earlier classification for angular momentum (J) isolated stars. By using the stellar evolution code MESA we study the evolution with different mass-loss rate efficiencies for stars with low metallicities of Z = 0.001 and Z = 0.004, and compare with the evolution with solar metallicity, Z = 0.02. We further study the possibility for late asymptomatic giant branch (AGB)—planet interaction and its possible effects on the properties of the planetary nebula (PN). We find for all metallicities that only with a reduced mass-loss rate an interaction with a low mass companion might take place during the AGB phase of the star. The interaction will most likely shape an elliptical PN. The maximum post-AGB luminosities obtained, both for solar metallicity and low metallicities, reach high values corresponding to the enigmatic finding of the PN luminosity function. Keywords: late stage stellar evolution; planetary nebulae; binarity; stellar evolution 1. Introduction Jsolated stars are stars that do not gain much angular momentum along their post main sequence evolution from a companion, either stellar or substellar, thus resulting with a lower mass-loss rate compared to non-Jsolated stars [1]. As previously stated in Sabach and Soker [1,2], the fitting formulae of the mass-loss rates for red giant branch (RGB) and asymptotic giant branch (AGB) single stars are set empirically by contaminated samples of stars that are classified as “single stars” but underwent an interaction with a companion early on, increasing the mass-loss rate to the observed rates.
    [Show full text]
  • 1987Apj. . .320. .2383 the Astrophysical Journal, 320:238-257
    .2383 The Astrophysical Journal, 320:238-257,1987 September 1 © 1987. The American Astronomical Society. AU rights reserved. Printed in U.S.A. .320. 1987ApJ. THE IRÁS BRIGHT GALAXY SAMPLE. II. THE SAMPLE AND LUMINOSITY FUNCTION B. T. Soifer, 1 D. B. Sanders,1 B. F. Madore,1,2,3 G. Neugebauer,1 G. E. Danielson,4 J. H. Elias,1 Carol J. Lonsdale,5 and W. L. Rice5 Received 1986 December 1 ; accepted 1987 February 13 ABSTRACT A complete sample of 324 extragalactic objects with 60 /mi flux densities greater than 5.4 Jy has been select- ed from the IRAS catalogs. Only one of these objects can be classified morphologically as a Seyfert nucleus; the others are all galaxies. The median distance of the galaxies in the sample is ~ 30 Mpc, and the median 10 luminosity vLv(60 /mi) is ~2 x 10 L0. This infrared selected sample is much more “infrared active” than optically selected galaxy samples. 8 12 The range in far-infrared luminosities of the galaxies in the sample is 10 LQ-2 x 10 L©. The far-infrared luminosities of the sample galaxies appear to be independent of the optical luminosities, suggesting a separate luminosity component. As previously found, a correlation exists between 60 /¿m/100 /¿m flux density ratio and far-infrared luminosity. The mass of interstellar dust required to produce the far-infrared radiation corre- 8 10 sponds to a mass of gas of 10 -10 M0 for normal gas to dust ratios. This is comparable to the mass of the interstellar medium in most galaxies.
    [Show full text]
  • A Search For" Dwarf" Seyfert Nuclei. VII. a Catalog of Central Stellar
    TO APPEAR IN The Astrophysical Journal Supplement Series. Preprint typeset using LATEX style emulateapj v. 26/01/00 A SEARCH FOR “DWARF” SEYFERT NUCLEI. VII. A CATALOG OF CENTRAL STELLAR VELOCITY DISPERSIONS OF NEARBY GALAXIES LUIS C. HO The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 JENNY E. GREENE1 Department of Astrophysical Sciences, Princeton University, Princeton, NJ ALEXEI V. FILIPPENKO Department of Astronomy, University of California, Berkeley, CA 94720-3411 AND WALLACE L. W. SARGENT Palomar Observatory, California Institute of Technology, MS 105-24, Pasadena, CA 91125 To appear in The Astrophysical Journal Supplement Series. ABSTRACT We present new central stellar velocity dispersion measurements for 428 galaxies in the Palomar spectroscopic survey of bright, northern galaxies. Of these, 142 have no previously published measurements, most being rela- −1 tively late-type systems with low velocity dispersions (∼<100kms ). We provide updates to a number of literature dispersions with large uncertainties. Our measurements are based on a direct pixel-fitting technique that can ac- commodate composite stellar populations by calculating an optimal linear combination of input stellar templates. The original Palomar survey data were taken under conditions that are not ideally suited for deriving stellar veloc- ity dispersions for galaxies with a wide range of Hubble types. We describe an effective strategy to circumvent this complication and demonstrate that we can still obtain reliable velocity dispersions for this sample of well-studied nearby galaxies. Subject headings: galaxies: active — galaxies: kinematics and dynamics — galaxies: nuclei — galaxies: Seyfert — galaxies: starburst — surveys 1. INTRODUCTION tors, apertures, observing strategies, and analysis techniques.
    [Show full text]
  • Celebrating the Wonder of the Night Sky
    Celebrating the Wonder of the Night Sky The heavens proclaim the glory of God. The skies display his craftsmanship. Psalm 19:1 NLT Celebrating the Wonder of the Night Sky Light Year Calculation: Simple! [Speed] 300 000 km/s [Time] x 60 s x 60 m x 24 h x 365.25 d [Distance] ≈ 10 000 000 000 000 km ≈ 63 000 AU Celebrating the Wonder of the Night Sky Milkyway Galaxy Hyades Star Cluster = 151 ly Barnard 68 Nebula = 400 ly Pleiades Star Cluster = 444 ly Coalsack Nebula = 600 ly Betelgeuse Star = 643 ly Helix Nebula = 700 ly Helix Nebula = 700 ly Witch Head Nebula = 900 ly Spirograph Nebula = 1 100 ly Orion Nebula = 1 344 ly Dumbbell Nebula = 1 360 ly Dumbbell Nebula = 1 360 ly Flame Nebula = 1 400 ly Flame Nebula = 1 400 ly Veil Nebula = 1 470 ly Horsehead Nebula = 1 500 ly Horsehead Nebula = 1 500 ly Sh2-106 Nebula = 2 000 ly Twin Jet Nebula = 2 100 ly Ring Nebula = 2 300 ly Ring Nebula = 2 300 ly NGC 2264 Nebula = 2 700 ly Cone Nebula = 2 700 ly Eskimo Nebula = 2 870 ly Sh2-71 Nebula = 3 200 ly Cat’s Eye Nebula = 3 300 ly Cat’s Eye Nebula = 3 300 ly IRAS 23166+1655 Nebula = 3 400 ly IRAS 23166+1655 Nebula = 3 400 ly Butterfly Nebula = 3 800 ly Lagoon Nebula = 4 100 ly Rotten Egg Nebula = 4 200 ly Trifid Nebula = 5 200 ly Monkey Head Nebula = 5 200 ly Lobster Nebula = 5 500 ly Pismis 24 Star Cluster = 5 500 ly Omega Nebula = 6 000 ly Crab Nebula = 6 500 ly RS Puppis Variable Star = 6 500 ly Eagle Nebula = 7 000 ly Eagle Nebula ‘Pillars of Creation’ = 7 000 ly SN1006 Supernova = 7 200 ly Red Spider Nebula = 8 000 ly Engraved Hourglass Nebula
    [Show full text]
  • Arxiv:Astro-Ph/9902377V1 26 Feb 1999 Sus Uha H Omcxrybcgon.Ide,Tedis the Indeed, Background
    The distribution of absorbing column densities among Seyfert 2 galaxies G. Risaliti Dipartimento di Astronomia e Scienza dello Spazio, Univerit`adi Firenze, L. E. Fermi 5, I-50125, Firenze, Italy R. Maiolino and M. Salvati Osservatorio Astrofisico di Arcetri, L. E. Fermi 5, I-50125 Firenze, Italy ABSTRACT We use hard X-ray data for an “optimal” sample of Seyfert 2 galaxies to derive the distribution of the gaseous absorbing column densities among obscured active nuclei in the local Universe. Of all Seyfert 2 galaxies in the sample, 75% are heavily obscured 23 −2 24 −2 (NH > 10 cm ) and about half are Compton thick (NH > 10 cm ). Intermediate type 1.8–1.9 Seyferts are characterized by an average NH much lower than “strict” Seyfert 2s. No correlation is found between NH and the intrinsic luminosity of the nuclear source. This NH distribution has important consequences for the synthesis of the cosmic X-ray background. Also, the large fraction of Compton thick objects implies that most of the obscuring gas is located within a radius of a few 10 pc from the nucleus. Subject headings: Galaxies: active — Galaxies: nuclei — Galaxies: Seyfert — X-rays: galaxies arXiv:astro-ph/9902377v1 26 Feb 1999 1. Introduction According to the so-called unified model (Antonucci 1993) the same engine is at work in all Active Galactic Nuclei (AGNs). The differences between type 1 and type 2 AGNs are ascribed solely to orientation effects: our line of sight to the nucleus may (type 2) or may not (type 1) be obstructed by optically thick material, perhaps distributed in a toroidal geometry.
    [Show full text]
  • Synapses of Active Galactic Nuclei: Comparing X-Ray and Optical Classifications Using Artificial Neural Networks?
    A&A 567, A92 (2014) Astronomy DOI: 10.1051/0004-6361/201322592 & c ESO 2014 Astrophysics Synapses of active galactic nuclei: Comparing X-ray and optical classifications using artificial neural networks? O. González-Martín1;2;??, D. Díaz-González3, J. A. Acosta-Pulido1;2, J. Masegosa4, I. E. Papadakis5;6, J. M. Rodríguez-Espinosa1;2, I. Márquez4, and L. Hernández-García4 1 Instituto de Astrofísica de Canarias (IAC), C/Vía Láctea s/n, 38205 La Laguna, Spain e-mail: [email protected] 2 Departamento de Astrofísica, Universidad de La Laguna (ULL), 38205 La Laguna, Spain 3 Shidix Technologies, 38320, La Laguna, Spain 4 Instituto de Astrofísica de Andalucía, CSIC, C/ Glorieta de la Astronomía s/n, 18005 Granada, Spain 5 Physics Department, University of Crete, PO Box 2208, 710 03 Heraklion, Crete, Greece 6 IESL, Foundation for Research and Technology, 711 10 Heraklion, Crete, Greece Received 2 September 2013 / Accepted 3 April 2014 ABSTRACT Context. Many classes of active galactic nuclei (AGN) have been defined entirely through optical wavelengths, while the X-ray spectra have been very useful to investigate their inner regions. However, optical and X-ray results show many discrepancies that have not been fully understood yet. Aims. The main purpose of the present paper is to study the synapses (i.e., connections) between X-ray and optical AGN classifications. Methods. For the first time, the newly implemented efluxer task allowed us to analyse broad band X-ray spectra of a sample of emission-line nuclei without any prior spectral fitting. Our sample comprises 162 spectra observed with XMM-Newton/pn of 90 lo- cal emission line nuclei in the Palomar sample.
    [Show full text]
  • April 14 2018 7:00Pm at the April 2018 Herrett Center for Arts & Science College of Southern Idaho
    Snake River Skies The Newsletter of the Magic Valley Astronomical Society www.mvastro.org Membership Meeting President’s Message Tim Frazier Saturday, April 14th 2018 April 2018 7:00pm at the Herrett Center for Arts & Science College of Southern Idaho. It really is beginning to feel like spring. The weather is more moderate and there will be, hopefully, clearer skies. (I write this with some trepidation as I don’t want to jinx Public Star Party Follows at the it in a manner similar to buying new equipment will ensure at least two weeks of Centennial Observatory cloudy weather.) Along with the season comes some great spring viewing. Leo is high overhead in the early evening with its compliment of galaxies as is Coma Club Officers Berenices and Virgo with that dense cluster of extragalactic objects. Tim Frazier, President One of my first forays into the Coma-Virgo cluster was in the early 1960’s with my [email protected] new 4 ¼ inch f/10 reflector and my first star chart, the epoch 1960 version of Norton’s Star Atlas. I figured from the maps I couldn’t miss seeing something since Robert Mayer, Vice President there were so many so closely packed. That became the real problem as they all [email protected] appeared as fuzzy spots and the maps were not detailed enough to distinguish one galaxy from another. I still have that atlas as it was a precious Christmas gift from Gary Leavitt, Secretary my grandparents but now I use better maps, larger scopes and GOTO to make sure [email protected] it is M84 or M86.
    [Show full text]