Hubble Snaps Ghostly Galaxy 24 July 2020

Total Page:16

File Type:pdf, Size:1020Kb

Hubble Snaps Ghostly Galaxy 24 July 2020 Image: Hubble snaps ghostly galaxy 24 July 2020 Provided by NASA's Goddard Space Flight Center Credit: ESA/Hubble & NASA, M. Gregg A notable feature of most spiral galaxies is the multitude of arching spiral arms that seemingly spin out from the galaxy's center. In this image, taken with the NASA/ESA Hubble Space Telescope, the stunning silvery-blue spiral arms of the galaxy NGC 4848 are observed in immense detail. Not only do we see the inner section of the spiral arms containing hundreds of thousands of young, bright, blue stars, but Hubble has also captured the extremely faint, wispy tails of the outer spiral arms. Myriad more distant and delightfully diverse galaxies appear in the background. This wispy barred spiral galaxy was first discovered in 1865 by the German astronomer Heinrich Louis d'Arrest. In his career, Heinrich also notably discovered the asteroid 76 Freia and many other galaxies, and he also contributed to the discovery of Neptune. If you are situated in the Northern Hemisphere with a large telescope, you might just be able to observe the ghost-like appearance of this faint galaxy within the faint constellation of Coma Berenices (Berenice's Hair). 1 / 2 APA citation: Image: Hubble snaps ghostly galaxy (2020, July 24) retrieved 30 September 2021 from https://phys.org/news/2020-07-image-hubble-snaps-ghostly-galaxy.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. 2 / 2 Powered by TCPDF (www.tcpdf.org).
Recommended publications
  • Ubiquitous Ram Pressure Stripping in the Coma Cluster of Galaxies
    Astronomy & Astrophysics manuscript no. 33427˙corr c ESO 2018 August 17, 2018 Ubiquitous ram pressure stripping in the Coma cluster of galaxies⋆ G. Gavazzi1, G. Consolandi1, M. L. Gutierrez2, A. Boselli3, and M. Yoshida4 1 Universit`adegli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy e-mail: [email protected] 2 nstituto de Astronomia, UNAM, Km 107 Carretera Tijuana-Ensenada, Ensenada, B.C., Mexico 22860 3 Aix Marseille Univ, CNRS, CNES LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France 4 Subaru Telescope, National Astronomical Observatory of Japan, National Institutes of Natural Sciences, 650 A’ohoku Place, Hilo, Hawaii 96720, USA Received; accepted ABSTRACT We report the detection of Hα trails behind three new intermediate-mass irregular galaxies in the NW outskirts of the nearby cluster of galaxies Abell 1656 (Coma). Hints that these galaxies possess an extended component were found in earlier, deeper Hα observations carried out with the Subaru telescope. However the lack of a simultaneous r-band exposure, together with the presence of strong stellar ghosts in the Subaru images, prevented us from quantifying the detections. We therefore devoted one full night of Hα observation to each of the three galaxies using the San Pedro Martir 2.1m telescope. One-sided tails of Hα emission of 10-20 kpc projected size were detected, suggesting an ongoing ram pressure stripping event. We added these 3 new sources of extended ionized gas (EIG) added to the 12 found by Yagi et al. (2010), NGC 4848 (Fossati et al. 2012), and NGC 4921 whose ram pressure stripping is certified by HI asymmetry.
    [Show full text]
  • Gas and Star Formation Laws in Galaxies
    Gas and Star Formation laws in galaxies Jonathan Braine Laboratoire d'Astrophysique de Bordeaux University of Bordeaux, France Why link gas and star formation ? Stars form directly from the molecular gas. --- understand the physical conditions in molecular gas --- devise methods to estimate gas mass --- devise methods to measure the star formation rate In most galaxies, the majority of the gas is in the form of atomic Hydrogen, "HI", from which the H2 forms. So an important part of the star formation cycle is also the HI --> H2 transformation. --- Phases of gas in galaxies --- Link between SF and molecular gas and its consequences --- How do we trace star formation ? --- How can we measure the molecular gas mass ? --- HI --> H2 transformation --- Variations in Star Formation Efficiency Gas in Galaxies 3 phases: ionized (H+, HII), atomic (HI), molecular (H2) Ionized gas mass is much smaller that the atomic or molecular gas mass in spirals and star-forming Irregular galaxies. Not necessarily in Elliptical galaxies, particularly large ones. The HI is usually the dominantWhy mass care component of the gas. Not the case for galaxies with very high Star Formation Rates (SFR). Large spirals often have similar HI and H2 masses. As the metallicity (size, generally) decreases, HI becomes more and more dominant, at least in the local universe. The HI is very extended in isolated galaxies but often deficient in cluster galaxies. HI emission has not been detected at high redshift (z > 0.3) Molecular gas is organized in clouds which follow scaling laws, which will be discussed further on. Mol clouds are cool (10-30K).
    [Show full text]
  • Doctor of Philosophy
    BIBLIOGRAPHY 152 Chapter 4 WALLABY Early Science - III. An H I Study of the Spiral Galaxy NGC 1566 ABSTRACT This paper reports on the atomic hydrogen gas (HI) observations of the spiral galaxy NGC 1566 using the newly commissioned Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope. This spiral galaxy is part of the Dorado loose galaxy group, which has a halo mass of 13:5 1 10 M . We measure an integrated HI flux density of 180:2 Jy km s− emanating from this ∼ galaxy, which translates to an HI mass of 1:94 1010 M at an assumed distance of 21:3 Mpc. Our × observations show that NGC 1566 has an asymmetric and mildly warped HI disc. The HI-to-stellar mass fraction (MHI/M ) of NGC 1566 is 0:29, which is high in comparison with galaxies that have ∗ the same stellar mass (1010:8 M ). We also derive the rotation curve of this galaxy to a radius of 50 kpc and fit different mass models to it. The NFW, Burkert and pseudo-isothermal dark matter halo profiles fit the observed rotation curve reasonably well and recover dark matter fractions of 0:62, 0:58 and 0:66, respectively. Down to the column density sensitivity of our observations 19 2 (NHI = 3:7 10 cm ), we detect no HI clouds connected to, or in the nearby vicinity of, the × − HI disc of NGC 1566 nor nearby interacting systems. We conclude that, based on a simple analytic model, ram pressure interactions with the IGM can affect the HI disc of NGC 1566 and is possibly the reason for the asymmetries seen in the HI morphology of NGC 1566.
    [Show full text]
  • Binocular Challenges
    This page intentionally left blank Cosmic Challenge Listing more than 500 sky targets, both near and far, in 187 challenges, this observing guide will test novice astronomers and advanced veterans alike. Its unique mix of Solar System and deep-sky targets will have observers hunting for the Apollo lunar landing sites, searching for satellites orbiting the outermost planets, and exploring hundreds of star clusters, nebulae, distant galaxies, and quasars. Each target object is accompanied by a rating indicating how difficult the object is to find, an in-depth visual description, an illustration showing how the object realistically looks, and a detailed finder chart to help you find each challenge quickly and effectively. The guide introduces objects often overlooked in other observing guides and features targets visible in a variety of conditions, from the inner city to the dark countryside. Challenges are provided for viewing by the naked eye, through binoculars, to the largest backyard telescopes. Philip S. Harrington is the author of eight previous books for the amateur astronomer, including Touring the Universe through Binoculars, Star Ware, and Star Watch. He is also a contributing editor for Astronomy magazine, where he has authored the magazine’s monthly “Binocular Universe” column and “Phil Harrington’s Challenge Objects,” a quarterly online column on Astronomy.com. He is an Adjunct Professor at Dowling College and Suffolk County Community College, New York, where he teaches courses in stellar and planetary astronomy. Cosmic Challenge The Ultimate Observing List for Amateurs PHILIP S. HARRINGTON CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, Sao˜ Paulo, Delhi, Dubai, Tokyo, Mexico City Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521899369 C P.
    [Show full text]
  • Ngc Catalogue Ngc Catalogue
    NGC CATALOGUE NGC CATALOGUE 1 NGC CATALOGUE Object # Common Name Type Constellation Magnitude RA Dec NGC 1 - Galaxy Pegasus 12.9 00:07:16 27:42:32 NGC 2 - Galaxy Pegasus 14.2 00:07:17 27:40:43 NGC 3 - Galaxy Pisces 13.3 00:07:17 08:18:05 NGC 4 - Galaxy Pisces 15.8 00:07:24 08:22:26 NGC 5 - Galaxy Andromeda 13.3 00:07:49 35:21:46 NGC 6 NGC 20 Galaxy Andromeda 13.1 00:09:33 33:18:32 NGC 7 - Galaxy Sculptor 13.9 00:08:21 -29:54:59 NGC 8 - Double Star Pegasus - 00:08:45 23:50:19 NGC 9 - Galaxy Pegasus 13.5 00:08:54 23:49:04 NGC 10 - Galaxy Sculptor 12.5 00:08:34 -33:51:28 NGC 11 - Galaxy Andromeda 13.7 00:08:42 37:26:53 NGC 12 - Galaxy Pisces 13.1 00:08:45 04:36:44 NGC 13 - Galaxy Andromeda 13.2 00:08:48 33:25:59 NGC 14 - Galaxy Pegasus 12.1 00:08:46 15:48:57 NGC 15 - Galaxy Pegasus 13.8 00:09:02 21:37:30 NGC 16 - Galaxy Pegasus 12.0 00:09:04 27:43:48 NGC 17 NGC 34 Galaxy Cetus 14.4 00:11:07 -12:06:28 NGC 18 - Double Star Pegasus - 00:09:23 27:43:56 NGC 19 - Galaxy Andromeda 13.3 00:10:41 32:58:58 NGC 20 See NGC 6 Galaxy Andromeda 13.1 00:09:33 33:18:32 NGC 21 NGC 29 Galaxy Andromeda 12.7 00:10:47 33:21:07 NGC 22 - Galaxy Pegasus 13.6 00:09:48 27:49:58 NGC 23 - Galaxy Pegasus 12.0 00:09:53 25:55:26 NGC 24 - Galaxy Sculptor 11.6 00:09:56 -24:57:52 NGC 25 - Galaxy Phoenix 13.0 00:09:59 -57:01:13 NGC 26 - Galaxy Pegasus 12.9 00:10:26 25:49:56 NGC 27 - Galaxy Andromeda 13.5 00:10:33 28:59:49 NGC 28 - Galaxy Phoenix 13.8 00:10:25 -56:59:20 NGC 29 See NGC 21 Galaxy Andromeda 12.7 00:10:47 33:21:07 NGC 30 - Double Star Pegasus - 00:10:51 21:58:39
    [Show full text]
  • Galaxy / Cluster Ecosystem
    Galaxy / Cluster Ecosystem Ming Sun (University of Alabama in Huntsville)‏ P. Jachym (AIAS, Czech Republic); S. Sivanandam (U. of Toronto); J. Scharwaechter, F. Combes, P. Salome (LERMA); P. Nulsen, W. Forman, C. Jones, A. Vikhlinin, B. Zhang (CfA); M. Fumagalli (Durham); J. Sanders, M. Fossati (MPE); M. Donahue, M. Voit (MSU); C. Sarazin (UVa); A. Fabian (Cambridge); R. Canning, N. Werner (Stanford); E. Roediger (Hamburg); D. Vir Lal (NCRA); L. Cortese (Swinburne); J. Kenney (Yale) Why study galaxy / cluster ecosystem ? 1) Galaxies inject energy into the intracluster medium (ICM), with AGN outflows, galactic winds, galaxy motion etc. 2) Galaxies also dump heavy elements and magnetic field in the ICM. 3) Clusters also change galaxies, e.g., density - morphology (or SFR) relation, with e.g., ram pressure stripping and harassment. 4) Great examples to study transport processes (conductivity and viscosity) Summary Ram pressure Stripping Environment stripped tails Conduction UMBHs B Draping (multi-phase Radio AGN Turbulence gas and SF) You have heard a lot of discussions on thermal coronae of early-type galaxies in this workshop. What about early-type galaxies‏in‏clusters?‏Are‏they‏“naked”‏without‏gas?‏‏--- No firm detections of coronae in hot clusters before Chandra ! You have heard a lot of discussions on thermal coronae of early-type galaxies in this workshop. What about early-type galaxies‏in‏clusters?‏Are‏they‏“naked”‏without‏gas?‏‏--- No firm detections of coronae in hot clusters before Chandra ! Vikhlinin + 2001 You have heard a lot of discussions on thermal coronae of early-type galaxies in this workshop. What about early-type galaxies‏in‏clusters?‏Are‏they‏“naked”‏without‏gas?‏‏--- No firm detections of coronae in hot clusters before Chandra ! Vikhlinin + 2001 Later more embedded coronae discovered (Yamasaki+2002; Sun+2002, 2005, 2006) and the first sample in Sun+2007 You have heard a lot of discussions on thermal coronae of early-type galaxies in this workshop.
    [Show full text]
  • The DEEP2 Galaxy Redshift Survey: Environments of Post-Starburst Galaxies at Z 0.1 and 0.8 ∼ ∼ Renbin Yan,1! Jeffrey A
    Mon. Not. R. Astron. Soc. 398, 735–753 (2009) doi:10.1111/j.1365-2966.2009.15192.x The DEEP2 Galaxy Redshift Survey: environments of post-starburst galaxies at z 0.1 and 0.8 ∼ ∼ Renbin Yan,1! Jeffrey A. Newman,2 S. M. Faber,3 Alison L. Coil,4,5 Michael C. Cooper,4 Marc Davis,6,7 Benjamin J. Weiner,4 Brian F.† Gerke8 and David C. Koo3 ‡ 1Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4, Canada 2Department of Physics and Astronomy, University of Pittsburgh, 401-C Allen Hall, 3941 O’Hara Street, Pittsburgh, PA 15620, USA 3UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064, USA 4Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA 5Department of Physics and Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093, USA 6Department of Astronomy, University of California, Berkeley, CA 94720, USA 7Department of Physics, University of California, Berkeley, CA 94720, USA 8Kavli Institute for Particle Astrophysics and Cosmology, Stanford Linear Accelerator Center, 2575 Sand Hill Rd., M/S 29, Menlo Park, CA 94025, USA Accepted 2009 June 3. Received 2009 May 29; in original form 2009 March 8 ABSTRACT Post-starburst (also known as K A) galaxies exhibit spectroscopic signatures indicating that + their star formation was recently quenched; they are candidates for galaxies in transition from astar-formingphasetoapassivelyevolvingphase.Wehavespectroscopicallyidentifiedlarge samples of post-starburst galaxies both in the Sloan Digital Sky Survey (SDSS) at z 0.1 and ∼ in the DEEP2 Galaxy Redshift Survey at z 0.8, using a uniform and robust selection method ∼ based on a cut in Hβ line emission rather than the more problematic [O II] λ3727.
    [Show full text]
  • 65 Kpc of Ionized Gas Trailing Behind NGC 4848 During Its First Crossing Of
    A&A 544, A128 (2012) Astronomy DOI: 10.1051/0004-6361/201219933 & c ESO 2012 Astrophysics 65 kpc of ionized gas trailing behind NGC 4848 during its first crossing of the Coma cluster Matteo Fossati1, Giuseppe Gavazzi1, Alessandro Boselli2, and Michele Fumagalli3 1 Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy e-mail: [matteo.fossati;giuseppe.gavazzi]@mib.infn.it 2 Laboratoire d’Astrophysique de Marseille, UMR 6110 CNRS, 38 rue F. Joliot-Curie, 13388 Marseille, France e-mail: [email protected] 3 Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064, USA e-mail: [email protected] Received 2 July 2012 / Accepted 18 July 2012 ABSTRACT In a five hour Hα exposure of the northwest region of the Coma cluster with the 2.1 m telescope at San Pedro Martir (Mx), we discovered a 65 kpc cometary emission of ionized gas trailing behind the SBab galaxy NGC 4848. The tail points in the opposite direction of the cluster center, in the same direction where stripped HI had been detected in previous observations. The galaxy shows −1 bright HII regions in an inner ring-like pattern, where the star formation takes place at the prodigious rate of ∼8.9 M yr .Fromthe morphologies of the galaxy and the trailing material, we infer that the galaxy is suffering from ram pressure due to its high velocity 9 motion through the intergalactic medium. We estimate that ∼4 × 10 M of gas is swept out from the galaxy forming the tail.
    [Show full text]
  • DSO List V2 Current
    7000 DSO List (sorted by name) 7000 DSO List (sorted by name) - from SAC 7.7 database NAME OTHER TYPE CON MAG S.B. SIZE RA DEC U2K Class ns bs Dist SAC NOTES M 1 NGC 1952 SN Rem TAU 8.4 11 8' 05 34.5 +22 01 135 6.3k Crab Nebula; filaments;pulsar 16m;3C144 M 2 NGC 7089 Glob CL AQR 6.5 11 11.7' 21 33.5 -00 49 255 II 36k Lord Rosse-Dark area near core;* mags 13... M 3 NGC 5272 Glob CL CVN 6.3 11 18.6' 13 42.2 +28 23 110 VI 31k Lord Rosse-sev dark marks within 5' of center M 4 NGC 6121 Glob CL SCO 5.4 12 26.3' 16 23.6 -26 32 336 IX 7k Look for central bar structure M 5 NGC 5904 Glob CL SER 5.7 11 19.9' 15 18.6 +02 05 244 V 23k st mags 11...;superb cluster M 6 NGC 6405 Opn CL SCO 4.2 10 20' 17 40.3 -32 15 377 III 2 p 80 6.2 2k Butterfly cluster;51 members to 10.5 mag incl var* BM Sco M 7 NGC 6475 Opn CL SCO 3.3 12 80' 17 53.9 -34 48 377 II 2 r 80 5.6 1k 80 members to 10th mag; Ptolemy's cluster M 8 NGC 6523 CL+Neb SGR 5 13 45' 18 03.7 -24 23 339 E 6.5k Lagoon Nebula;NGC 6530 invl;dark lane crosses M 9 NGC 6333 Glob CL OPH 7.9 11 5.5' 17 19.2 -18 31 337 VIII 26k Dark neb B64 prominent to west M 10 NGC 6254 Glob CL OPH 6.6 12 12.2' 16 57.1 -04 06 247 VII 13k Lord Rosse reported dark lane in cluster M 11 NGC 6705 Opn CL SCT 5.8 9 14' 18 51.1 -06 16 295 I 2 r 500 8 6k 500 stars to 14th mag;Wild duck cluster M 12 NGC 6218 Glob CL OPH 6.1 12 14.5' 16 47.2 -01 57 246 IX 18k Somewhat loose structure M 13 NGC 6205 Glob CL HER 5.8 12 23.2' 16 41.7 +36 28 114 V 22k Hercules cluster;Messier said nebula, no stars M 14 NGC 6402 Glob CL OPH 7.6 12 6.7' 17 37.6 -03 15 248 VIII 27k Many vF stars 14..
    [Show full text]
  • Université De Montréal Et Université De Provence Cinématique Et
    Université de Montréal et Université de Provence Cinématique et dynamique des galaxies spirales barrées par Olivier Hernandez Thèse effectuée en cotutelle au Département de Physique Faculté des arts et des sciences Université de Montréal et au Laboratoire d’Astrophysique de Marseille Université de Provence Thèse présentée à la Faculté des études supérieures de l’Université de Montréal en vue de l’obtention du grade de Phi1osophi Doctor (Ph.D.) en Physique et à l’Université de Provence en vue de l’obtention du grade de Docteur de l’Université de Provence Décembre, 2004 ©Olivier Hernandez, 2004 Oc u 5 P005 ,e10 Université dl1 de Montréal Direction des bibliothèques AVIS L’auteur a autorisé l’Université de Montréal à reproduire et diffuser, en totalité ou en partie, par quelque moyen que ce soit et sur quelque support que ce soit, et exclusivement à des fins non lucratives d’enseignement et de recherche, des copies de ce mémoire ou de cette thèse. L’auteur et les coauteurs le cas échéant conservent la propriété du droit d’auteur et des droits moraux qui protègent ce document. Ni la thèse ou le mémoire, ni des extraits substantiels de ce document, ne doivent être imprimés ou autrement reproduits sans l’autorisation de l’auteur. Afin de se conformer à la Loi canadienne sur la protection des renseignements personnels, quelques formulaires secondaires, coordonnées ou signatures intégrées au texte ont pu être enlevés de ce document. Bien que cela ait pu affecter la pagination, il n’y a aucun contenu manquant. NOTICE The author of this thesis or dissertation has granted a nonexclusive license allowing Université de Montréal to reproduce and publish the document, in part or in whole, and in any format, solely for noncommercial educational and research purposes.
    [Show full text]
  • VLA HI Imaging of the Brightest Spiral Galaxies in Coma
    CORE Metadata, citation and similar papers at core.ac.uk Provided by CERN Document Server VLA HI imaging of the brightest spiral galaxies in Coma H. Bravo-Alfaro Observatoire de Paris DAEC, and UMR 8631, associ´eauCNRSet`a l'Universit´e Paris 7, 92195 Meudon Cedex, France. Departamento de Astronom´ıa, Universidad de Guanajuato. Apdo. Postal 144 Guanajuato 36000. M´exico. V.Cayatte Observatoire de Paris DAEC, and UMR 8631, associ´eauCNRSet`a l'Universit´e Paris 7, 92195 Meudon Cedex, France. J. H. van Gorkom Department of Astronomy, Columbia University, New York, New York 10027. and C. Balkowski Observatoire de Paris DAEC, and UMR 8631, associ´eauCNRSet`a l'Universit´e Paris 7, 92195 Meudon Cedex, France. ABSTRACT We have obtained 21 cm images of 19 spiral galaxies in the Coma clus- ter, using the VLA in its C and D configurations. The sample selection was based on morphology, brightness, and optical diameters of galaxies within one Abell radius (1.2◦). The Hi detected, yet deficient galaxies show a strong correlation in their Hi properties with projected distance from the cluster center. The most strongly Hi deficient (DefHI>0.4) galaxies are located inside a radius of 300 ( 0.6 Mpc) from the center of ∼ 1 Coma, roughly the extent of the central X-ray emission. These central galaxies show clear asymmetries in their Hi distribution and/or shifts between the optical and 21 cm positions. Another 12 spirals were not detected in Hi with typical Hi mass upper limits of 108 M . Seven out of the twelve non detections are located in the central region of Coma, roughly within 300 from the center.
    [Show full text]
  • The Astrophysical Journal, 388:310-327,1992 April 1
    .310K The Astrophysical Journal, 388:310-327,1992 April 1 © 1992. The American Astronomical Society. All rights reserved. Printed in U.S.A. .388. 1992ApJ. THE INTEGRATED SPECTRA OF NEARBY GALAXIES: GENERAL PROPERTIES AND EMISSION-LINE SPECTRA Robert C. Kennicutt, Jr.1 Steward Observatory, University of Arizona, Tucson, AZ 85721 Received 1991 July 29; accepted 1991 September 11 ABSTRACT This paper presents the first results from a survey of the integrated spectra of 90 nearby galaxies. Intermediate- and low-resolution spectrophotometry over the 3650-7000 Á range has been used to compile a spectral atlas of galaxies (published in a companion paper) and to investigate the systematic behavior of the emission-line spectra in normal and peculiar galaxies. The data are especially useful as a comparison sample for spectroscopic surveys of more distant galaxies. The integrated absorption- and emission-line spectra show a smooth progression with Hubble type. Most spiral and irregular galaxies exhibit detectable emission lines of Ha, [O n], [N n], [S n], and sometimes H/l and [O in]. The Ha line is the strongest emission line and is most reliable quantitative tracer of the massive star formation rate, but the [O n] line provides a good substitute in high-redshift galaxies, where Ha is inac- cessible. The H/? and [O m] lines are unsatisfactory as star formation tracers in all but the strongest emission- line galaxies, due to variations in stellar absorption and excitation, respectively. Methods for distinguishing between distant starburst galaxies and active nuclei are discussed. The new data are used to examine the statistical properties of the [O n] emission in galaxies, and to cali- brate a mean relation between [O n] luminosity and the total star formation rate.
    [Show full text]