198 7Apj. . .312L. .11J the Astrophysical Journal, 312:L11-L15

Total Page:16

File Type:pdf, Size:1020Kb

198 7Apj. . .312L. .11J the Astrophysical Journal, 312:L11-L15 .11J The Astrophysical Journal, 312:L11-L15,1987 January 1 .312L. © 1987. The American Astronomical Society. All rights reserved. Printed in U.S.A. 7ApJ. 198 INTERSTELLAR DUST IN SHAPLEY-AMES ELLIPTICAL GALAXIES M. Jura and D. W. Kim Department of Astronomy, University of California, Los Angeles AND G. R. Knapp and P. Guhathakurta Princeton University Observatory Received 1986 August 11; accepted 1986 September 30 ABSTRACT We have co-added the IRAS survey data at the positions of the brightest elliptical galaxies in the Revised Shapley-Ames Catalog to increase the sensitivity over that of the IRAS Point Source Catalog. More than half of 7 8 the galaxies (with Bj< \\ mag) are detected at 100 /xm with flux levels indicating, typically, 10 or 10 M0 of cold interstellar matter. The presence of cold gas in ellipticals thus appears to be the rule rather than the exception. Subject headings: galaxies: general — infrared: sources I. INTRODUCTION infrared emission from the elliptical galaxy in the line of sight. The traditional view of early-type galaxies is that they are Our criteria for a real detection are as follows: essentially free of interstellar matter. However, with advances 1. The optical position of the galaxy and the position of the in instrumental sensitivity, it has become possible to observe IRAS source agree to better than V. (The agreement is usually 21 cm emission (Knapp, Turner, and Cunniffe 1985; Wardle much better than T.) and Knapp 1986), optical dust patches (Sadler and Gerhard 2. The flux is at least 3 times the r.m.s. noise. 1985; Ebneter and Balick 1985; Sparks et al 1985; Hansen, 3. The source is detected in more than one IRAS band. Norgaard-Nielsen, and Jorgensen 1985; Gallagher 1986) and 4. The infrared colors generally resemble those of galaxies thermal X-ray emission (Forman, Jones, and Tucker 1985) (de Jong et al. 1984; Jura 1986a). from some of these galaxies as well as ionized gas that Some of the apparent detections listed in Table 1 are of low produces optical emission Unes (Phillips et al. 1986). Jura weight and may not be the result of the elliptical galaxy in the (1986a) and Tytler (1986) have used the infrared emission observed direction. In order to check for the possibility of given in the IRAS Point Source Catalog to study their dust galactic cirrus (Low et al. 1984) or other contaminating sources content. Currently, we are undertaking an extensive project to in the beam, we have obtained co-added IRAS data for 18 co-add the IRAS data to reach a greater level of sensitivity randomly chosen locations of sky with \b\ > 30°. In this than available with the Point Source Catalog in a comprehen- sample, we find no “detections” at 12 jLim; one “detection” at sive statistical study of dust in early-type galaxies. Because 25 /xm; no “detections” at 60 /xm; and two “detections” at our initial results are so striking, we report here the data for 100 /xm. None of these “sources” appeared in more than one the brightest elliptical galaxies in the Revised Shapley-Ames IRAS band. Therefore, the galaxies that are detected only at Catalog (Sandage and Tammann 1981). Details of the data IRAS band at either 60 /xm or 100 /xm are quite possibly and analysis will be presented in later papers. spurious, and they are noted as such in Table 1. There are seven such objects out of the 58 that we have measured; this II. DATA ANALYSIS is consistent with a rate of -15% apparent detections found in the randomly chosen positions. The presence of cirrus We have used the one-dimensional co-adding procedure emission is also apparent in several of our observations; the provided by the Infrared Processing and Analysis Center noise in the 100 /xm data is sometimes much higher than the (IPAC) to analyze the IRAS data for all elliptical galaxies instrumental noise. The high value of the r.m.s. noise for the brighter than = 12.0 mag in the Revised Shapley-Ames 100 /xm observations of NGC 185 and NGC 221 Usted in Catalog, except for NGC 3078 and NGC 3608 which are in Table 1 is due to the proximity of M31. portions of the sky not scanned by IRAS. The preliminary fluxes for these 58 galaxies, along with the classifications given by Sandage and Tammann (1981), the fluxes at B converted to mJy, and the distances from the prescription III. RESULTS given by Knapp, Turner, and Cunniffe (1985) with Virgo- The elHptical galaxies Usted in Table 1 are strongest at 12 -1 -1 centric flow and H0 = 100 km s Mpc are given in Table /xm and 100 /xm. At 12 /xm it is likely that the emission 1. The 1 a errors are quoted for all detections; 3 a upper mainly arises both from the photospheres of stars and from limits are given for nondetections. dust in circumstellar envelopes around mass-losing red giants Most of the positive results shown in Table 1 indicate real (Soifer et al 1986; Impey, Wynn-WilUams, and BeckUn 1986). © American Astronomical Society • Provided by the NASA Astrophysics Data System .11J .312L. TABLE 1 Fluxes from Shapley-Ames Ellipticals2 7ApJ. Fv (mJy) M M D FP(B) 1 7 198 Galaxy (Mpc) (mJy) 12 /Ltm 25 /um 60 ¿im 100/un (M0 yr' ) (10 M0) B® < 10.0 mag NGC 147(dE5) . 0.7 460 < 87 < 63 < 135 < 540 2.2(-4) < 0.0042 NGC 185(dE3p) 0.7 570 < 90 < 75 420(24) 1500: (202) 2.3(-4) 0.012 < 255 < 4200 l.l(-3) < 0.033 NGC 221 (E2)... 0.7 1350 450(39) 230(36) a NGC 4486(E0).. 13.5 630 290(34) < 153 330(40) 440(93) 0.27 1.3 10.0 <B^< 11.0 mag < 87 340(82)b 0.077 0.91 NGC 1399(E1) 12.9 214 90(25) < 60 b NGC 1407(E0) 16.4 189 < 69 87 120(30) 480(74) < 0.10 2.1 < 66 180(55)b 0.044 0.25 NGC 1549(E2) 9.3 233 100(20) 60(16) c NGC 3379(EO) 7.6 327 220(42) 153 < 123 < 327 0.065 < 0.30 NGC 4125(E6) 18.9 220 < 117 72 620(44) 1670(69) < 0.22 9.5 < 732 0.14 < 2.1 NGC 4365(E3) 13.5 256 150(35) 147 < 132 b NGC 4374(E1) 115 359 200(38) 190(42) 500(27) 1280(94) 0.19 3.7 NGC 4494(E1) 12.9 224 < 90 123 < 108 < 510 < 0.08 < 1.4 < 141 < 282c 0.18 < 0.82 NGC 4621(E5) 13.5 240 190(44) 129 b NGC 4697(E6) 11.7 401 290(24) 123 330(23) 1240(76) 0.20 2.7 420(37) 1000(76)b < 0.21 9.8 NGC 5322(E4) 24.7 192 < 66 63 b IC 1459(E4)... 14.8 183 170(29) 230(44) 450(31) 1180(103) 0.19 4.1 11.0 < Bj< 12.0 mag NGC 596(E0).. 18.4 79 < 105 < 162 78 < 339 < 0.18 < 1.8 123 < 189c 0.13 < 0.83 NGC 720(E5).. 16.6 154 90(28) < 123 b,c NGC 821 (E6).. 17.5 78 < 99 < 201 123 500(130) < 0.16 2.5 NGC 1275(Ep) 52.5 76 860(34) 3820(39) 5760(63) 7500(200) 12 330 78 390(61)b 0.15 1.5 NGC 1395(E2). 15.7 150 120(28) < 87 b,c NGC 1404(E2). 17.9 167 < 132 < 75 84 290(56) < 0.22 1.5 111 < 147 < 0.062 < 0.52 NGC 1427(E5). 14.9 74 < 54 < 63 b,c NGC 1537(E6). 12.1 105 < 96 < 48 81 280(82) < 0.072 0.66 NGC 1700(E3). 38.3 84 < 111 < 102 < 90 < 654 < 0.84 < 15 NGC 2325(E4). 21.8 86 < 99 < 66 < 159 < 630 < 0.24 < 4.8 NGC 2300(E3) 22.3 71 < 60 90 < 105 < 276 < 0.15 < 2.2 NGC 2974(E4). 22.5 94 < 69 87 420(33) 1900(53) < 0.18 15 NGC 2986(E2). 25.2 82 < 84 90 < 60 < 192 < 0.27 2.0 NGC 3136(E4). 15.8 120 < 75 75 < 168 < 249 < 0.096 < 1.0 NGC 3193(E2). 18.6 82 < 105 144 < 114 < 1083 < 0.19 < 6.0 < 177 < 441 0.82 < 5.9 NGC 3250(E3). 29.0 85 190(56) 120(21) b NGC 3377(E6). 6.0 161 < 105 < 216 170(45) 350(60) < 0.02 0.20 190(46) 750(169)b 0.69 12 NGC 3557(E3). 32.1 143 130(26) < 84 b c NGC 3610(E5). 23.0 107 < 108 < 63 < 93 280(86) ’ < 0.29 2.4 NGC 3613(E6). 25.7 97 < 81 < 99 < 78 < 258 < 0.28 < 2.7 NGC 3640(E2). 12.0 139 < 123 < 129 < 117 < 198 < 0.091 < 0.46 NGC 3706(E4). 31.2 75 < 96 < 135 < 123 < 336 < 0.48 < 5.2 < 168 < 627 < 0.20 < 3.4 NGC 3904(E2) 18.5 82 < 114 < 120 c NGC 3962(E1). 22.3 101 < 108 < 177 280(50) < 903 < 0.28 < 7.2 NGC 4261(E3). 11.7 125 < 174 < 195 < 135 < 585 < 0.12 < 1.3 NGC 4278(E1). 7.9 157 < 129 < 96 590(56) 1930(99) < 0.041 1.9 NGC 4373(E4), 35.1 80 87 < 93 < 138 < 699 < 0.55 < 14 IC 3370(E2p) . 30.5 76 102 < 165 520(35) 1910(119) < 0.49 28 NGC 4473(E5) 13.5 166 144 < 120 < 183 < 321 < 0.14 < 0.94 < 195 < 636 < 0.12 < 1.9 NGC 4564(E6) 13.5 79 132 < 144 b NGC 4589(E2) 24.8 84 96 < 90 200(31) 660(168) < 0.30 6.5 < 144 < 339 < 0.12 < 0.99 NGC 4660(E5) 13.5 79 126 183 b NGC 4696(E3) 30.6 127 105 87 100(27) 770(155) < 0.51 12 NGC 5018(E4) 31.4 97 160(31) 210 1020(40) 2030(96) 0.81 32 NGC 5044(E0) 29.9 79 < 138 291 < 159 < 312 < 0.63 < 4.5 < 102 < 480 0.38 < 4.1 NGC 5061(E0) 23.1 139 140(23) 117 b IC 4296(E0)..
Recommended publications
  • Arxiv:1601.00329V3 [Astro-Ph.CO] 19 Aug 2016 Early Data
    DES 2015-0085 FERMILAB-PUB-16-003-AE Mon. Not. R. Astron. Soc. 000, 1–?? (2002) Printed 22 August 2016 (MN LATEX style file v2.2) The Dark Energy Survey: more than dark energy - an overview Dark Energy Survey Collaboration: T. Abbott1, F. B. Abdalla2, J. Aleksic´47, S. Allam3, A. Amara4, D. Bacon6, E. Balbinot46, M. Banerji7;8, K. Bechtol56;57, A. Benoit-Levy´ 13;2;12, G. M. Bernstein10, E. Bertin12;13, J. Blazek14, C. Bonnett15, S. Bridle16, D. Brooks2, R. J. Brunner41;20, E. Buckley- Geer3, D. L. Burke11;17, G. B. Caminha51;52, D. Capozzi6, J. Carlsen6, A. Carnero-Rosell18;19, M. Carollo54, M. Carrasco-Kind20;21, J. Carretero9;47, F. J. Castander9, L. Clerkin2, T. Collett6, C. Conselice55, M. Crocce9, C. E. Cunha11, C. B. D’Andrea6, L. N. da Costa19;18, T. M. Davis49, S. Desai25;24, H. T. Diehl3, J. P. Dietrich25;24, S. Dodelson3;27;58, P. Doel2, A. Drlica-Wagner3, J. Estrada3, J. Etherington6, A. E. Evrard22;29, J. Fabbri2, D. A. Finley3, B. Flaugher3, R. J. Foley21;41, P. Fosalba9, J. Frieman27;3, J. Garc´ıa-Bellido43, E. Gaztanaga9, D. W. Gerdes22, T. Giannantonio8;7, D. A. Goldstein44;37, D. Gruen17;11, R. A. Gruendl20;21, P. Guarnieri6, G. Gutierrez3, W. Hartley4, K. Honscheid14;32, B. Jain10, D. J. James1, T. Jeltema53, S. Jouvel2, R. Kessler27;58, A. King49, D. Kirk2, R. Kron27, K. Kuehn33, N. Kuropatkin3, O. Lahav2;?, T. S. Li23, M. Lima19;35, H. Lin3, M. A. G. Maia19;18, M. Makler51, M. Manera2, C. Maraston6, J. L.
    [Show full text]
  • Stripped Elliptical Galaxies As Probes of Icm Physics. Ii
    The Astrophysical Journal, 806:104 (15pp), 2015 June 10 doi:10.1088/0004-637X/806/1/104 © 2015. The American Astronomical Society. All rights reserved. STRIPPED ELLIPTICAL GALAXIES AS PROBES OF ICM PHYSICS. II. STIRRED, BUT MIXED? VISCOUS AND INVISCID GAS STRIPPING OF THE VIRGO ELLIPTICAL M89 E. Roediger1,2,5, R. P. Kraft2, P. E. J. Nulsen2, W. R. Forman2, M. Machacek2, S. Randall2, C. Jones2, E. Churazov3, and R. Kokotanekova4 1 Hamburger Sternwarte, Universität Hamburg, Gojensbergsweg 112, D-21029 Hamburg, Germany; [email protected] 2 Harvard/Smithsonian Center for Astrophysics, 60 Garden Street MS-4, Cambridge, MA 02138, USA 3 MPI für Astrophysik, Karl-Schwarzschild-Str. 1, Garching D-85741, Germany 4 AstroMundus Master Programme, University of Innsbruck, Technikerstr. 25/8, 6020 Innsbruck, Austria Received 2014 September 18; accepted 2015 March 29; published 2015 June 10 ABSTRACT Elliptical galaxies moving through the intracluster medium (ICM) are progressively stripped of their gaseous atmospheres. X-ray observations reveal the structure of galactic tails, wakes, and the interface between the galactic gas and the ICM. This fine-structure depends on dynamic conditions (galaxy potential, initial gas contents, orbit in the host cluster), orbital stage (early infall, pre-/post-pericenter passage), as well as on the still ill-constrained ICM plasma properties (thermal conductivity, viscosity, magnetic field structure). Paper I describes flow patterns and stages of inviscid gas stripping. Here we study the effect of a Spitzer-like temperature dependent viscosity corresponding to Reynolds numbers, Re, of 50–5000 with respect to the ICM flow around the remnant atmosphere. Global flow patterns are independent of viscosity in this Reynolds number range.
    [Show full text]
  • 1. Introduction
    THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 122:109È150, 1999 May ( 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A. GALAXY STRUCTURAL PARAMETERS: STAR FORMATION RATE AND EVOLUTION WITH REDSHIFT M. TAKAMIYA1,2 Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637; and Gemini 8 m Telescopes Project, 670 North Aohoku Place, Hilo, HI 96720 Received 1998 August 4; accepted 1998 December 21 ABSTRACT The evolution of the structure of galaxies as a function of redshift is investigated using two param- eters: the metric radius of the galaxy(Rg) and the power at high spatial frequencies in the disk of the galaxy (s). A direct comparison is made between nearby (z D 0) and distant(0.2 [ z [ 1) galaxies by following a Ðxed range in rest frame wavelengths. The data of the nearby galaxies comprise 136 broad- band images at D4500A observed with the 0.9 m telescope at Kitt Peak National Observatory (23 galaxies) and selected from the catalog of digital images of Frei et al. (113 galaxies). The high-redshift sample comprises 94 galaxies selected from the Hubble Deep Field (HDF) observations with the Hubble Space Telescope using the Wide Field Planetary Camera 2 in four broad bands that range between D3000 and D9000A (Williams et al.). The radius is measured from the intensity proÐle of the galaxy using the formulation of Petrosian, and it is argued to be a metric radius that should not depend very strongly on the angular resolution and limiting surface brightness level of the imaging data. It is found that the metric radii of nearby and distant galaxies are comparable to each other.
    [Show full text]
  • Radio Sources in Low-Luminosity Active Galactic Nuclei
    A&A 392, 53–82 (2002) Astronomy DOI: 10.1051/0004-6361:20020874 & c ESO 2002 Astrophysics Radio sources in low-luminosity active galactic nuclei III. “AGNs” in a distance-limited sample of “LLAGNs” N. M. Nagar1, H. Falcke2,A.S.Wilson3, and J. S. Ulvestad4 1 Arcetri Observatory, Largo E. Fermi 5, Florence 50125, Italy 2 Max-Planck-Institut f¨ur Radioastronomie, Auf dem H¨ugel 69, 53121 Bonn, Germany e-mail: [email protected] 3 Department of Astronomy, University of Maryland, College Park, MD 20742, USA Adjunct Astronomer, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: [email protected] 4 National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA e-mail: [email protected] Received 23 January 2002 / Accepted 6 June 2002 Abstract. This paper presents the results of a high resolution radio imaging survey of all known (96) low-luminosity active galactic nuclei (LLAGNs) at D ≤ 19 Mpc. We first report new 2 cm (150 mas resolution using the VLA) and 6 cm (2 mas resolution using the VLBA) radio observations of the previously unobserved nuclei in our samples and then present results on the complete survey. We find that almost half of all LINERs and low-luminosity Seyferts have flat-spectrum radio cores when observed at 150 mas resolution. Higher (2 mas) resolution observations of a flux-limited subsample have provided a 100% (16 of 16) detection rate of pc-scale radio cores, with implied brightness temperatures ∼>108 K. The five LLAGNs with the highest core radio fluxes also have pc-scale “jets”.
    [Show full text]
  • The Globular Cluster System of NGC 1399
    Astronomy & Astrophysics manuscript no. sch1399 c ESO 2018 August 28, 2018 The globular cluster system of NGC 1399 ⋆,⋆⋆ V. dynamics of the cluster system out to 80 kpc Y. Schuberth1,2, T. Richtler2, M. Hilker3, B. Dirsch2, L. P. Bassino4, A. J. Romanowsky5,2, and L. Infante6 1 Argelander-Institut f¨ur Astronomie, Universit¨at Bonn, Auf dem H¨ugel 71, D-53121 Bonn, Germany 2 Universidad de Concepci´on, Departamento de Astronomia, Casilla 160-C, Concepci´on, Chile 3 European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany 4 Facultad de Ciencias Astron´omicas y Geof´ısicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900–La Plata, Argentina; and Instituto de Astrof´ısica de La Plata (CCT La Plata – CONICET – UNLP) 5 UCO/Lick Observatory, University of California, Santa Cruz, CA 95064, USA 6 Departamento de Astronom´ıa y Astrof´ısica, Pontificia Universidad Cat´olica de Chile, Casilla 306, Santiago 22, Chile Received 14 May, 2009; accepted 16 October, 2009 ABSTRACT Globular clusters (GCs) are tracers of the gravitational potential of their host galaxies. Moreover, their kinematic properties may provide clues for understanding the formation of GC systems and their host galaxies. We use the largest set of GC velocities obtained so far of any elliptical galaxy to revise and extend the previous investigations (Richtler et al. 2004) of the dynamics of NGC 1399, the central dominant galaxy of the nearby Fornax cluster of galaxies. The GC velocities are used to study the kinematics, their relation with population properties, and the dark matter halo of NGC 1399.
    [Show full text]
  • Long-Period Variables in NGC 147 and NGC 185⋆
    A&A 532, A78 (2011) Astronomy DOI: 10.1051/0004-6361/201116951 & c ESO 2011 Astrophysics Long-period variables in NGC 147 and NGC 185 D. Lorenz1, T. Lebzelter1,W.Nowotny1, J. Telting2, F. Kerschbaum1,H.Olofsson3,4, and H. E. Schwarz 1 University of Vienna, Department of Astronomy, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: [email protected] 2 Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain 3 Department of Astronomy, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden 4 Onsala Space Observatory, 43992 Onsala, Sweden Received 24 March 2011 / Accepted 25 May 2011 ABSTRACT Context. Previous studies on the stellar content of the two nearby dwarf galaxies NGC 147 and NGC 185 reveal a rich population of late-type giants in both systems, including a large number of carbon-rich objects. These stars are known to show pronounced photo- metric variability, which can be used for a more detailed characterisation of these highly evolved stars. Owing to their well-studied parameters, these Local Group members are ideal candidates for comparative studies. Aims. Through photometric monitoring, we attempt to provide a catalogue of long-period variables (LPVs), including Mira variables, semi-regular variables, and even irregular variables in NGC 147 and NGC 185. We investigate the light variations and compare the characteristics of these two LPV populations with the results found for other galaxies, such as the LMC. Methods. We carried out time-series photometry in the i-band of the two target galaxies with the Nordic Optical Telescope (NOT), covering a time span of ≈2.5 years.
    [Show full text]
  • New Insights from HST Studies of Globular Cluster Systems I: Colors, Distancesprovided by CERN and Document Server Specific Frequencies of 28 Elliptical Galaxies 1
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE New Insights from HST Studies of Globular Cluster Systems I: Colors, Distancesprovided by CERN and Document Server Specific Frequencies of 28 Elliptical Galaxies 1 Arunav Kundu 2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 Electronic Mail: [email protected] and Dept of Astronomy, University of Maryland, College Park, MD 20742-2421 Bradley C. Whitmore Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 Electronic Mail: [email protected] Received ; accepted 1Based on observations with the NASA/ESA Hubble Space Telescope, obtained from the data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Re- search in Astronomy, Inc., under NASA contract NAS5-26555 1Present address: Astronomy Department, Yale University, 260 Whitney Av., New Haven, CT 06511 ABSTRACT We present an analysis of the globular cluster systems of 28 elliptical galaxies using archival WFPC2 images in the V and I-bands. The V-I color distributions of at least 50% of the galaxies appear to be bimodal at the present level of photometric accuracy.Weargue that this is indicative of multiple epochs of cluster formation early in the history of these galaxies, possibly due to mergers. We also present the first evidence of bimodality in low luminosity galaxies and discuss its implication on formation scenarios. The mean color of the 28 cluster systems studied by us is V-I = 1.04 0.04 (0.01) mag corresponding to a mean metallicity of Fe/H = -1.0 0.19 (0.04).
    [Show full text]
  • Astronomy Magazine Special Issue
    γ ι ζ γ δ α κ β κ ε γ β ρ ε ζ υ α φ ψ ω χ α π χ φ γ ω ο ι δ κ α ξ υ λ τ μ β α σ θ ε β σ δ γ ψ λ ω σ η ν θ Aι must-have for all stargazers η δ μ NEW EDITION! ζ λ β ε η κ NGC 6664 NGC 6539 ε τ μ NGC 6712 α υ δ ζ M26 ν NGC 6649 ψ Struve 2325 ζ ξ ATLAS χ α NGC 6604 ξ ο ν ν SCUTUM M16 of the γ SERP β NGC 6605 γ V450 ξ η υ η NGC 6645 M17 φ θ M18 ζ ρ ρ1 π Barnard 92 ο χ σ M25 M24 STARS M23 ν β κ All-in-one introduction ALL NEW MAPS WITH: to the night sky 42,000 more stars (87,000 plotted down to magnitude 8.5) AND 150+ more deep-sky objects (more than 1,200 total) The Eagle Nebula (M16) combines a dark nebula and a star cluster. In 100+ this intense region of star formation, “pillars” form at the boundaries spectacular between hot and cold gas. You’ll find this object on Map 14, a celestial portion of which lies above. photos PLUS: How to observe star clusters, nebulae, and galaxies AS2-CV0610.indd 1 6/10/10 4:17 PM NEW EDITION! AtlAs Tour the night sky of the The staff of Astronomy magazine decided to This atlas presents produce its first star atlas in 2006.
    [Show full text]
  • Measurements of Variability of Low Mass X-Ray Binary Candidates In
    DRAFT VERSION NOVEMBER 5, 2018 Preprint typeset using LATEX style emulateapj v. 10/09/06 MEASUREMENTS OF VARIABILITY OF LOW MASS X-RAY BINARY CANDIDATES IN THE EARLY-TYPE GALAXY NGC 4697 FROM MULTI-EPOCH CHANDRA X-RAY OBSERVATIONS GREGORY R. SIVAKOFF1,2 ,ANDRÉS JORDÁN3,4 ,ADRIENNE M. JUETT5,CRAIG L. SARAZIN1, JIMMY A. IRWIN6 Draft version November 5, 2018 ABSTRACT Multi-epoch Chandra X-ray observations of nearby massive early-type galaxies open up the study of an im- portant regime of low-mass X-ray binary (LMXB) behavior — long term variability. In a companion paper, we report on the detection of 158 X-ray sources down to a detection/completeness limit of 0.6/1.4 × 1037 ergss−1 using five Chandra observations of NGC 4697, one of the nearest (11.3Mpc), optically luminous (MB < −20), elliptical (E6) galaxy. In this paper, we report on the variability of LMXB candidates measured on timescales from seconds to years. At timescales of seconds to hours, we detect five sources with significant variability. Approximately 7% of sources show variability between any two observations, and 16 ± 4% of sources do not have a constant luminosity over all five observations. Among variable sources, we identify eleven transient candidates, with which we estimate that if all LMXBs in NGC 4697 are long-term transients then they are on for ∼ 100yr and have a 7% duty cycle. These numbers are consistent with those found for brighter LMXBs in M87 and NGC 1399, which suggests that there does not appear to be a measurable difference between the outburst durations of long-term transient neutron star LMXBs and black hole LMXBs.
    [Show full text]
  • A Basic Requirement for Studying the Heavens Is Determining Where In
    Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun­ damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short).
    [Show full text]
  • 115 Abell Galaxy Cluster # 373
    WINTER Medium-scope challenges 271 # # 115 Abell Galaxy Cluster # 373 Target Type RA Dec. Constellation Magnitude Size Chart AGCS 373 Galaxy cluster 03 38.5 –35 27.0 Fornax – 180 ′ 5.22 Chart 5.22 Abell Galaxy Cluster (South) 373 272 Cosmic Challenge WINTER Nestled in the southeast corner of the dim early winter western suburbs. Deep photographs reveal that NGC constellation Fornax, adjacent to the distinctive triangle 1316 contains many dust clouds and is surrounded by a formed by 6th-magnitude Chi-1 ( ␹ 1), Chi-2 ( ␹ 2), and complex envelope of faint material, several loops of Chi-3 ( ␹ 3) Fornacis, is an attractive cluster of galaxies which appear to engulf a smaller galaxy, NGC 1317, 6 ′ known as Abell Galaxy Cluster – Southern Supplement to the north. Astronomers consider this to be a case of (AGCS) 373. In addition to his research that led to the galactic cannibalism, with the larger NGC 1316 discovery of more than 80 new planetary nebulae in the devouring its smaller companion. The merger is further 1950s, George Abell also examined the overall structure signaled by strong radio emissions being telegraphed of the universe. He did so by studying and cataloging from the scene. 2,712 galaxy clusters that had been captured on the In my 8-inch reflector, NGC 1316 appears as a then-new National Geographic Society–Palomar bright, slightly oval disk with a distinctly brighter Observatory Sky Survey taken with the 48-inch Samuel nucleus. NGC 1317, about 12th magnitude and 2 ′ Oschin Schmidt camera at Palomar Observatory. In across, is visible in a 6-inch scope, although averted 1958, he published the results of his study as a paper vision may be needed to pick it out.
    [Show full text]
  • Spectral Properties of Xrbs in Dusty Early-Type Galaxies
    Spectral properties of XRBs in dusty early-type galaxies N. D. Vagshette, M. B. Pandge, M.K. Patil∗ School of Physical Sciences, S.R.T.M. University, Nanded-431 606 (MS), India Tel.+91-2462-229242; +91-9405938449/Fax:+91-2462-229245 Abstract We present spectral properties of a total of 996 discrete X-ray sources resolved in a sample of 23 dusty early-type galaxies selected from different environments. The combined X-ray luminosity function of all the 996 sources within the optical D25 of the sample galaxies is well described by a broken power law with a break at 2.71 1038erg s−1 and is close to × the Eddington limit for a 1.4M⊙ neutron star. Out of the 996, about 63% of the sources have their X-ray luminosities in the range between few 1037to 2.0 1039erg s−1and are like × × normal LMXBs; about 15-20% with luminosities < few 1037 erg s−1 are either super- × soft or very-soft sources; while the remainder represents ULXs, HMXBs or unrelated heavily absorbed harder sources. More XRBs have been detected in the galaxies from isolated regions while those from rich groups and clusters host very few sources. The X-ray color-color plot for these sources has enabled us to classify them as SNRs, LMXBs, HMXBs and heavily absorbed AGNs. The composite X-ray spectra of the resolved sources within D25 region of each of the galaxies are best represented by a power law with the average photon spectral index close to 1.65. The contribution of the resolved sources to the total X-ray luminosity of their host is found to vary greatly, in the sense that, in galaxies like NGC 3379 the XRB contribution is about 81% while for NGC 5846 it is only 2%.
    [Show full text]