DOCSLIB.ORG

A2048-AGES Skeptical

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A2048-AGES Skeptical The Arecibo Galactic Environments Survey (AGES) http://www.naic.edu/~ages/ Report to the skeptical review panel August 1st 2008 Introduction The Arecibo Galactic Environments Survey (AGES) is a proposal to use the Arecibo telescope with its multi-beam instrument ALFA to survey nearby galactic environments and the volumes behind them. The intention of the survey is to reach lower noise levels than ALFALFA and therefore to search for lower mass and lower column density HI objects. We drift scan across the sky with a goal of completing 25 scans across each point, equivalent to a 300s integration. For direct comparison with the ALFALFA survey we have smoothed our data to their spatial and velocity resolution and this gives typically a rms noise level of 0.75 mJy for AGES, compared to the ALFALFA published value of 2.2 mJy. ALFALFA, although covering a larger area is no deeper than previous ‘blind’ Arecibo extra-galactic surveys, while AGES pushes beyond the sensitivity of the previous deepest blind HI surveys. The proposed total sky coverage is 200 sq deg. The original proposal was for 2000 hours with targets spread across the RA range. The proposal was submitted in February 2005 but the start was delayed until late December 2005. It is important to recognize that the E-ALFA collaboration agreed at their meetings that a coordinated strategy was needed to explore the extragalactic Universe at 21cm. That strategy called for three different survey depths, following the classic ‘wedding cake’ design. ALFALFA is the large area shallow survey that will improve on the small number statistics of previous surveys. AGES is the middle level sensitivity survey, which will explore new parameter space at greater sensitivity than previous surveys, but will cover less area. Finally, AUDS will explore much greater depths over a very small area. To date AGES has been allocated about 500 hours of observing time in total; about one quarter of that originally requested. In the period covered by this review, 1st August 2007 to 1st August 2008, AGES was scheduled for 226 hours of telescope time most of which has been quite recent (since January) due to telescope painting. We request a minimum of 500 hours over the next year so that the survey can be completed over a reasonable period of time (hopefully within the next 3 years). Technical issues We now routinely observe remotely from Cardiff, Socorro, Green Bank and University of Massachusetts. We have spent a considerable amount of time developing our data reduction pipeline, assessing data quality (Fig 1), testing source detection methods and quantifying completeness and reliability. During the precursor run (described in a previous report) we showed that we could successfully reduce noise levels by the expected factor of t1/2 by keeping the array at fixed azimuth and elevation while the sky drifts overhead. In order to account for the change in parallactic angle, and thus achieve uniform sky coverage, ALFA is rotated before every scan - all of this is now fully automated in software and is very easy for the observer to use (see http://www.naic.edu/~ages/a2048/AGES_guide.html). In order to attain fully sampled sky coverage each scan is staggered by half the beam separation. With this observing set up every beam covers the same patch of sky averaging out gain variations between beams and reducing the impact of side-lobe contamination. We have adapted the HIPASS software (LIVEDATA and GRIDZILLA) so that it operates on the Arecibo CIMAFITS file format. LIVEDATA performs bandpass estimation (using various user specified algorithms) and removal, Doppler tracking and calibrates and smooths (if required) the residual spectrum. GRIDZILLA is a gridding package that co-adds all the spectra letting the user have full control over beam selection, polarizations, frequency range and image and pixel size. For the AGES datacubes we chose 1 arc min pixels and 5 km/s channels and ALL of the reduced data cubes are publicly available in this format at http://www.naic.edu/~ages/public_data.html. We are currently experimenting with other ways of fitting the bandpass and combining scans to try and extract more extended features (Minchin et al., 2008, Taylor et al. 2008 – NGC7332 and Virgo cluster data) , in the future we intend to make available cubes reduced in different, but well documented ways. Analysis of continuum sources in the NGC 7332 data (Minchin et al. 2007) has shown that the post-processing AGES beam is very close to circular with sidelobes at around the 5% level in the expected position. Deconvolving the beam will be necessary for science objective 8 (below) – investigating the low column-density extent of large galaxies. However this is not necessary for the other objectives of AGES and, with only two large galaxies in the currently completed datasets (NGC 1156 and NGC 7339), the scientific return does not currently justify devoting a large amount of team-members time to this problem at the moment. 1 Fig. 1 Comparison (A1367 field) of the HI fluxes (left) and velocity widths (right) measured by AGES, L- wide and past literature. Filled circles indicate the 22 sources confirmed during L-wide follow-up observations, empty circles show the 18 galaxies already known from the literature. The dotted lines indicate the one to one correlation. One of the challenges facing the extragalactic HI surveys is developing a method for detecting galaxies that is both well defined and complete. To achieve this goal we have been experimenting with different detection methods. Currently we search each data cube by eye (independently by two people) and also use two automated finders (POLYFIND) developed by Davies and Minchin and DUCHAMP developed by Matthew Whiting in Australia. We have also obtained follow up observations of low signal to noise detections to check on the reliability of our methods. In Fig. 2, as an example, we show the peak signal to noise of sources plotted against their W20 velocity width. In Auld (2007) we show that this is the best plane to carry out the selection cut (dashed line Fig. 2) giving us 75% reliability to 4σ. Fig 2: Reliability selection criteria for 265 detections from the NGC 1156, Abell 1367 and NGC 628 regions. Black represents detections that have either been followed up or strong signals confirmed by 3 independent methods. Red represents sources that were not confirmed by follow up observations. Stars represent sources that were detected by all three methods, circles by two methods and triangles by one method. Marked on the plot are reliability contours empirically derived from the data. 2 Current status The originally proposed survey fields are shown in Fig. 3. Fig. 3. The originally proposed survey fields are marked in blue. Those that have been completed have been circled in red. Current field status is: Field Status NGC7332 5 sq deg requested and completed Virgo2 5 sq deg requested and completed A1367 20 sq deg requested 5 sq deg completed NGC1156 5 sq deg requested and completed NGC628 Precursor field completed Voids Not started NGC7448 20 sq deg requested 5 sq deg completed Virgo1 20 sq deg requested 5 sq deg completed and 5 sq deg to two thirds depth Leo1 Not started NGC3193 20 sq deg requested, one complete scan completed NGC2577 Not started M33 Not started UGC2082 Not started Our total observed area to full depth amounts to 30 sq deg or just 15% of the total area request in the original proposal and only 10 sq deg more than at this time last year.1 Survey Science The scientific goals of the survey as given in the original proposal are listed below: 1. The HI mass function in different environments - around large galaxies, in groups, clusters and beyond the Local Supercluster - comparison with galaxy evolution models. 2. Given the excellent correlation between star-formation-rate and 20cm continuum emission, we will use the continuum emission to measure the star formation rates of a large number of galaxies selected by their gaseous rather than their optical or far infrared properties. 3. The contribution of neutral gas to the baryonic mass density - the 'missing' baryonic matter problem. 4. The nature of and possible link between HVCs and dwarf galaxies - a possible solution of the CDM sub-structure problem ? 5. The identification of gaseous tidal features as signatures of galaxy interactions and mergers - the importance of mergers as a mechanism for the assembly of galaxies, gas removal mechanisms in clusters and groups. 6. The velocity dispersions of galaxies in groups and clusters - dark matter. 7. The dynamical masses of galaxies - galaxy rotation curves - dark matter. 8. The low-column-density extent of large galaxies - ionisation by the metagalactic radiation field. 9. The identification of isolated neutral gas clouds - remnants or precursors of the galaxy formation process ? 10. A comparison of the atomic hydrogen detected by QSO-absorption-line and 21cm observations - consistency between different observations that measure the same thing. 11. The spatial distribution of HI selected galaxies. 12. A comparison with numerical models of galaxy formation - providing input and tests of the simulations. 1 Note both Virgo1 and NGC193 have incomplete scan data. 3 13. Serendipitous findings - with a survey like this, covering large areas to low mass-limits and column-densities, we might hope to make new and unexpected discoveries. In the rest of this section we will discuss science results not yet published. These are somewhat limited compared to last year as by far the majority of the observations have been obtained since January (due to telescope painting), a number of scans are incomplete and the Virgo fields are part of Rhys Taylor’s PHD project.
Load more

Recommended publications
  • CO Multi-Line Imaging of Nearby Galaxies (COMING) IV. Overview Of
    Publ. Astron. Soc. Japan (2018) 00(0), 1–33 1 doi: 10.1093/pasj/xxx000 CO Multi-line Imaging of Nearby Galaxies (COMING) IV. Overview of the Project Kazuo SORAI1, 2, 3, 4, 5, Nario KUNO4, 5, Kazuyuki MURAOKA6, Yusuke MIYAMOTO7, 8, Hiroyuki KANEKO7, Hiroyuki NAKANISHI9 , Naomasa NAKAI4, 5, 10, Kazuki YANAGITANI6 , Takahiro TANAKA4, Yuya SATO4, Dragan SALAK10, Michiko UMEI2 , Kana MOROKUMA-MATSUI7, 8, 11, 12, Naoko MATSUMOTO13, 14, Saeko UENO9, Hsi-An PAN15, Yuto NOMA10, Tsutomu, T. TAKEUCHI16 , Moe YODA16, Mayu KURODA6, Atsushi YASUDA4 , Yoshiyuki YAJIMA2 , Nagisa OI17, Shugo SHIBATA2, Masumichi SETA10, Yoshimasa WATANABE4, 5, 18, Shoichiro KITA4, Ryusei KOMATSUZAKI4 , Ayumi KAJIKAWA2, 3, Yu YASHIMA2, 3, Suchetha COORAY16 , Hiroyuki BAJI6 , Yoko SEGAWA2 , Takami TASHIRO2 , Miho TAKEDA6, Nozomi KISHIDA2 , Takuya HATAKEYAMA4 , Yuto TOMIYASU4 and Chey SAITA9 1Department of Physics, Faculty of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan 2Department of Cosmosciences, Graduate School of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan 3Department of Physics, School of Science, Hokkaido University, Kita 10 Nishi 8, Kita-ku, Sapporo 060-0810, Japan 4Division of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan 5Tomonaga Center for the History of the Universe (TCHoU), University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan 6Department of Physical Science, Osaka Prefecture University, Gakuen 1-1,
    [Show full text]
  • The Applicability of Far-Infrared Fine-Structure Lines As Star Formation
    A&A 568, A62 (2014) Astronomy DOI: 10.1051/0004-6361/201322489 & c ESO 2014 Astrophysics The applicability of far-infrared fine-structure lines as star formation rate tracers over wide ranges of metallicities and galaxy types? Ilse De Looze1, Diane Cormier2, Vianney Lebouteiller3, Suzanne Madden3, Maarten Baes1, George J. Bendo4, Médéric Boquien5, Alessandro Boselli6, David L. Clements7, Luca Cortese8;9, Asantha Cooray10;11, Maud Galametz8, Frédéric Galliano3, Javier Graciá-Carpio12, Kate Isaak13, Oskar Ł. Karczewski14, Tara J. Parkin15, Eric W. Pellegrini16, Aurélie Rémy-Ruyer3, Luigi Spinoglio17, Matthew W. L. Smith18, and Eckhard Sturm12 1 Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, Belgium e-mail: [email protected] 2 Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle Str. 2, 69120 Heidelberg, Germany 3 Laboratoire AIM, CEA, Université Paris VII, IRFU/Service d0Astrophysique, Bat. 709, 91191 Gif-sur-Yvette, France 4 UK ALMA Regional Centre Node, Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK 5 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 6 Laboratoire d0Astrophysique de Marseille − LAM, Université Aix-Marseille & CNRS, UMR7326, 38 rue F. Joliot-Curie, 13388 Marseille CEDEX 13, France 7 Astrophysics Group, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UK 8 European Southern Observatory, Karl
    [Show full text]
  • Physical Conditions of the Molecular Gas in Metal-Poor Galaxies? L
    A&A 606, A99 (2017) Astronomy DOI: 10.1051/0004-6361/201731000 & c ESO 2017 Astrophysics Physical conditions of the molecular gas in metal-poor galaxies? L. K. Hunt1, A. Weiß2, C. Henkel2; 3, F. Combes4, S. García-Burillo5, V. Casasola1, P. Caselli6, A. Lundgren9, R. Maiolino7, K. M. Menten2, and L. Testi1; 8 1 INAF–Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125 Firenze, Italy e-mail: [email protected] 2 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 3 Astronomy Department, King Abdulaziz University, PO Box 80203, Jeddah, Saudia Arabia 4 Observatoire de Paris, LERMA, Collège de France, CNRS, PSL, Sorbonne University UPMC, 75014 Paris, France 5 Observatorio Astronómico Nacional (OAN)-Observatorio de Madrid, Alfonso XII, 3, 28014 Madrid, Spain 6 Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany 7 Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Avenue, Cambridge CB3 0HE, UK 8 ESO, Karl Schwarzschild str. 2, 85748 Garching bei München, Germany 9 Vittja 64, 74793 Alunda, Sweden Received 18 April 2017 / Accepted 8 August 2017 ABSTRACT Studying the molecular component of the interstellar medium (ISM) in metal-poor galaxies has been challenging because of the faint- ness of carbon monoxide emission, the most common proxy of H2. Here we present new detections of molecular gas at low metal- licities, and assess the physical conditions in the gas through various CO transitions for 8 galaxies. For one, NGC 1140 (Z=Z ∼ 0.3), two detections of 13CO isotopologues and atomic carbon, [Ci](1–0) and an upper limit for HCN(1–0) are also reported.
    [Show full text]
  • Modelling Ionised and Photodissociated Regions
    Modelling ionised and photodissociated regions Magda Vasta Thesis submitted for the Degree of Doctor of Philosophy of University College London Department of Physics & Astronomy UNIVERSITY COLLEGE LONDON March 2010 I, Magda Vasta, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. To my parents, my brother and my husband, who always supported and encouraged me no matter what. I tell people I am too stupid to know what is impossible. I have ridiculously large dreams, and half the time they come true. — Thomas D. ACKNOWLEDGEMENTS Some people come into our lives and quickly go. Some stay for a while and leave footprints on our hearts. And we are never, ever the same. I made it, I still cannot believe it, but I finally made it. However, it would have been almost impossible to reach this target without the constant scientific support from some people. My first big THANKS go to my supervisor Serena Viti. Thanks for being the supportive person you are, for giving me the possibility to be independent in my research, but being always present when I needed you. Thanks for all the times that you did not talk to me in Italian, for encouraging me to not give up and for being the lovely person you are. Thanks to Mike Barlow for the amazing scientific suggestions and for tolerating ALL my silly questions (most of them grammatically incorrect!). Thanks to Barbara Ercolano for her patience when answering my emails “HELP, PLEASE!!” about MOCASSIN.
    [Show full text]
  • ISOCAM Observations of Normal Star-Forming Galaxies: the Key Project Sample’
    ISOCAM Observations of Normal Star-Forming Galaxies: The Key Project Sample’ D.A. Dale,2 N.A. Silbermann,2 G. Heloq2 E. Valjaveq2 S. Malhotra,2 C.A. Beichman,2 J. Brauher,2 A. Contursi,2H. Diner~tein,~D. H~llenbach,~D. Hunter,s S. Kolhatkar,2 K.Y. LO,^ S. Lord,2 N.Y. Lu,~R. Rubiq4 G. Stacey,? H. Thronson, Jr.,’ M. Werner,g H. Corwin2 ABSTRACT We present mid-infrared maps and preliminary analysis for 61 galaxies observed with the Infrared Space Observatory. Many of the general features of galaxies observed at optical wavelengths-spiral arms, disks, rings, and bright knots of emission-are also seen in the mid-infrared, except the prominent optical bulges are absent at 6.75 and 15 pm. In addition, the maps are quite similar at 6.75 and 15 pm, except for a few cases where a central starburst leads to lower !dS3~4ratios in the inner region. kVe also present infrared flux densities and mid-infrared sizes for these galasies. The mid-infrared color Iu(6.Zpm) Iu(l.5pm) shows a distincttrend with the far-infrared color m.The quiescent galasies in our sample 1, (60~)g 0.6) show unity,near ( I,( 1OOpm) whereas this ratio drops significantly for galaxies with higher global heating intensity levels. Azimuthally-averaged surface brightness profiles indicate the extent to which the mid-infrared flux is centrally concerltratecl, a,rltl provide information on the radial dependence of mid-infrared colors. The galaxies are mostly well resolved in these maps: almost half of them have < 10% of their flux in the central resolution element.
    [Show full text]
  • 190 Index of Names
    Index of names Ancora Leonis 389 NGC 3664, Arp 005 Andriscus Centauri 879 IC 3290 Anemodes Ceti 85 NGC 0864 Name CMG Identification Angelica Canum Venaticorum 659 NGC 5377 Accola Leonis 367 NGC 3489 Angulatus Ursae Majoris 247 NGC 2654 Acer Leonis 411 NGC 3832 Angulosus Virginis 450 NGC 4123, Mrk 1466 Acritobrachius Camelopardalis 833 IC 0356, Arp 213 Angusticlavia Ceti 102 NGC 1032 Actenista Apodis 891 IC 4633 Anomalus Piscis 804 NGC 7603, Arp 092, Mrk 0530 Actuosus Arietis 95 NGC 0972 Ansatus Antliae 303 NGC 3084 Aculeatus Canum Venaticorum 460 NGC 4183 Antarctica Mensae 865 IC 2051 Aculeus Piscium 9 NGC 0100 Antenna Australis Corvi 437 NGC 4039, Caldwell 61, Antennae, Arp 244 Acutifolium Canum Venaticorum 650 NGC 5297 Antenna Borealis Corvi 436 NGC 4038, Caldwell 60, Antennae, Arp 244 Adelus Ursae Majoris 668 NGC 5473 Anthemodes Cassiopeiae 34 NGC 0278 Adversus Comae Berenices 484 NGC 4298 Anticampe Centauri 550 NGC 4622 Aeluropus Lyncis 231 NGC 2445, Arp 143 Antirrhopus Virginis 532 NGC 4550 Aeola Canum Venaticorum 469 NGC 4220 Anulifera Carinae 226 NGC 2381 Aequanimus Draconis 705 NGC 5905 Anulus Grahamianus Volantis 955 ESO 034-IG011, AM0644-741, Graham's Ring Aequilibrata Eridani 122 NGC 1172 Aphenges Virginis 654 NGC 5334, IC 4338 Affinis Canum Venaticorum 449 NGC 4111 Apostrophus Fornac 159 NGC 1406 Agiton Aquarii 812 NGC 7721 Aquilops Gruis 911 IC 5267 Aglaea Comae Berenices 489 NGC 4314 Araneosus Camelopardalis 223 NGC 2336 Agrius Virginis 975 MCG -01-30-033, Arp 248, Wild's Triplet Aratrum Leonis 323 NGC 3239, Arp 263 Ahenea
    [Show full text]
  • Making a Sky Atlas
    Appendix A Making a Sky Atlas Although a number of very advanced sky atlases are now available in print, none is likely to be ideal for any given task. Published atlases will probably have too few or too many guide stars, too few or too many deep-sky objects plotted in them, wrong- size charts, etc. I found that with MegaStar I could design and make, specifically for my survey, a “just right” personalized atlas. My atlas consists of 108 charts, each about twenty square degrees in size, with guide stars down to magnitude 8.9. I used only the northernmost 78 charts, since I observed the sky only down to –35°. On the charts I plotted only the objects I wanted to observe. In addition I made enlargements of small, overcrowded areas (“quad charts”) as well as separate large-scale charts for the Virgo Galaxy Cluster, the latter with guide stars down to magnitude 11.4. I put the charts in plastic sheet protectors in a three-ring binder, taking them out and plac- ing them on my telescope mount’s clipboard as needed. To find an object I would use the 35 mm finder (except in the Virgo Cluster, where I used the 60 mm as the finder) to point the ensemble of telescopes at the indicated spot among the guide stars. If the object was not seen in the 35 mm, as it usually was not, I would then look in the larger telescopes. If the object was not immediately visible even in the primary telescope – a not uncommon occur- rence due to inexact initial pointing – I would then scan around for it.
    [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]
  • A Search for Dark Galaxies Through the AGES
    A search for dark galaxies through the AGES by Robbie Richard Auld A thesis submitted to Cardiff University for the degree of Doctor of Philosophy May 2007 UMI Number: U584983 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI U584983 Published by ProQuest LLC 2013. Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 DECLARATION This work has not previously been, accepted in substance for any degree and is not being coi ' * ndidature for any degree. Signed Date STATEMENT 1 The work presented in this thesis is all my own work carried out under the joint supervision of Dr. J. I. Davies and Dr. W. J. G. de Blok, with the exception of the following: I did not take the optical, NIR, Ha, or HI observations for Chapter 2, although all subsequent data reduction and analysis is my own. The optical, NIR, and Ha data were kindly made available by Dr. Eric Bell. Dr. W. J. G. de Blok took the HI observations. The optical spectroscopy data from Loiano, presented ced by Dr. L. Cortese. STATEMENT 2 I hereby give consent for my thesis, if accepted, to be available for photocopying and for inter-library loan, and for the title and summary to be made available to outside organisations.
    [Show full text]
  • 1985Apjs...58..533H the Astrophysical Journal Supplement Series, 58:533-560, 1985 August © 1985. the American Astronomical Soci
    The Astrophysical Journal Supplement Series, 58:533-560, 1985 August © 1985. The American Astronomical Society. All rights reserved. Printed in U.S.A. STAR-FORMING PROPERTIES AND HISTORIES OF DWARF IRREGULAR GALAXIES: 1985ApJS...58..533H DOWN BUT NOT OUT Deidre A. Hunter and John S. Gallagher III Kitt Peak National Observatory, National Optical Astronomy Observatories1 Received 1984 October 31; accepted 1985 January 28 ABSTRACT Star formation processes and their relationships to other galactic properties are investigated in a sample of low optical surface brightness dwarf irregular galaxies. New observations made for this study include B and R images taken with a CCD detector; flux-calibrated, Ha, narrow-band digital imagery; large-aperture spectropho- tometry; and spectrophotometry of individual H n regions. These data provide the basis for several measure- ments of star-forming characteristics of dwarf irregular galaxies: (1) Total current star formation rates are deduced from Ha luminosities. (2) Properties of typical star-forming centers are derived from the sizes, luminosities, and surface brightnesses of H ii regions. (3) Star formation histories are estimated from the ratio of Ha to blue luminosities and from the stellar content models. (4) The metallicity of the gas comes from oxygen emission lines. (5) Images provide information on the optical light distributions. 10 1 2 The dwarf irregulars in our sample have low stellar production rates of -10“ M0 yr“ pc“ and have formed stars at approximately constant rates over the last few Gyr. Because of their large H i gas contents, dwarf irregulars potentially can sustain constant star formation rates for very long times ( > 100 Gyr in some cases).
    [Show full text]
  • Wide-Field Survey of Dwarf Satellite Systems Around 10 Hosts in the Local Volume
    Draft version February 12, 2020 Typeset using LATEX twocolumn style in AASTeX62 Wide-Field Survey of Dwarf Satellite Systems Around 10 Hosts in the Local Volume Scott G. Carlsten,1 Johnny P. Greco,2, ∗ Rachael L. Beaton,1, 3, y and Jenny E. Greene1 1Department of Astrophysical Sciences, 4 Ivy Lane, Princeton University, Princeton, NJ 08544 2Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University, Columbus, OH 43210, USA 3The Observatories of the Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (Accepted February 12, 2020) Submitted to ApJ ABSTRACT We present the results of an extensive search for dwarf satellite galaxies around 10 primary host galaxies in the Local Volume (LV, D<12 Mpc) using archival CFHT/MegaCam imaging data. The hosts span a wide range in properties, with stellar masses ranging from that of the LMC to 3 times ∼ that of the Milky Way (MW). The surveyed hosts are: NGC 1023, NGC 1156, NGC 2903, NGC 4258, NGC 4565, NGC 4631, NGC 5023, M51, M64, and M104. We detect satellite candidates using a consistent semi-automated detection algorithm that is optimized for the detection of low surface brightness objects. Depending on the host, our completeness limit is Mg 8 to 10 (assuming the ∼ − − −2 distance of the host). We detect objects with surface brightness down to µ0;g 26 mag arcsec at ∼ & 90% completeness. The survey areas of the six best-surveyed hosts cover most of the inner projected R < 150 kpc area, which will roughly double the number of massive LV hosts surveyed at this level of area and luminosity completeness, once distances are measured for the candidates.
    [Show full text]
  • Publications Ofthe Astronomical Society Ofthe Pacific 98:5-28, January 1986
    Publications ofthe Astronomical Society ofthe Pacific 98:5-28, January 1986 PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF THE PACIFIC Vol. 98 January 1986 No. 599 STELLAR POPULATIONS AND STAR FORMATION IN IRREGULAR GALAXIES* DEIDRE A. HUNTER Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, D.C. 20015 AND JOHN S. GALLAGHER III Kitt Peak National Observatory, National Optiçal Astronomy Observatories,t P.O. Box 26732, Tucson, Arizona 85726 Received 1985 October 18 ABSTRACT We review and intercompare data on various morphologically-chosen groups of irregular galaxies in order to understand the underlying physical mechanisms that differentiate these systems. We particularly discuss the observational clues to the stellar content, star-formation processes, and star-formation histories of these galaxies, with an emphasis on the uncertainties and the many unanswered questions. Key words : irregular galaxies-star-formation rates-morphology of galaxies-stellar populations I. Introduction hydrogen gas and the moderately low metallicities of the A perusal of the Hubble Atlas of Galaxies (Sandage gas suggest that Irr's are less evolved than most spiral 1961) can convince one that, even within the great family galaxies. The Irr's therefore, provide a different sort of of normal spiral galaxies, there is a large variety of struc- system in which to investigate processes of galaxian evolu- tures. As you glance from the Sa-type spirals to Sb to Sc, tion. In addition, the lack of arms of organized star forma- you can see the nucleus becoming less pronounced and tion which so typify the spirals makes the Irr s much from the S c to S m galaxies the spiral arms become increas- simpler systems in which to study the processes of star ingly ratty until eventually you reach the group of irregu- formation and the relationship of star formation to other lar galaxies which Hubble (1926) described as "lack[ing] properties ofthe galaxies (cf.
    [Show full text]