DOCSLIB.ORG

Milkomeda's Birthday

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Milkomeda's Birthday . o gahma-ray bursts hold secrets of the infant . ~~How,,astrono.mers? -.$ . .. : are finding out. g:& , g:& a&'" - . ' Bob Berman Master the How to create your on finding art of wide- own astronomy another Earth field imaging '..weather forecast p. 13 p. 66 - ,p. 64 > : I Ii. BILLIONS OF YEARS FROM bJW, ttp night sky will glow with stars, dust,.md psfrom two galaxies: the Milky Way, in ~Mchwe' live, and the *roaching Anqromeda Galaxy (M31). LYNE~TECOOKFOR ASTRONOMY / THE ANDROMEDA GALAXY (M31) is a typical spiral of stars, dust, and gas. Spiral galaxies the Sun's mass. It also suggests the Milky I dominate the night sky in the local universe. Fourteen satellite galaxies accompany / Andromeda, including the two visible in this image: M32 (above Andromeda) and NGC 205 Way and Andromeda \c.ill nialie a close pass : (below). Andromeda is the largest in the Local Group of galaxies. TONYANUDAPHNEHALLAS in about 4 billion years. Kahn and Woltjer inspired a generation and is visible in the northern sky with the effect. In contrast, most galaxies in the uni- of studies that further constrained the mass naked eye. The remaining members of the verse are flying away from the Milky Way. of the Local Group and revealed important Local Group - several dozen - are a bevy characteristics of Andromeda's orbit, such of much smaller satellite galaxies. Timing is everything as its total energy of motion. A galaxy group con~prisestwo or more Nearly 50 years ago, Franz Kahn and But the timing argument does not have relatively close, massive galaxies. The com- Lodewijk Woltjer pioneered the "timing the ability to follow the coniplex dynamics pactness of galaxies that form groups sug- argument." This hypothesis held that the that accompany the merger of extended gests that they are gravitationally bound Milky Way and Andromeda formed close galaxies. Therefore, it cannot predict the and dynamically coupled to each other. to each other, during the dense, early stages future arrangement of the Local Group. For This simply means the galaxies attract each of the universe. processes as conlplex as galaxy mergers, other gravitationally, so a change in one Subsequently, the general expansion of astronomers need more powerfill tools. affects the fate of the other. the universe pulled the two galactic neigh- Evidence of the dynamic connection bors apart. Later, the Milky Way and Simulating the Local Group between the Milky Way and Andromeda Andromeda reversed their out\vard trajec- Numerical simulations are indispensable comes from their relative motions. The gal- tories owing to mutual gravitational attrac- for understanding processes too complex to axies are barreling toward each other at tion. Since then, they have completed solve with pen and paper. In galactic merg- nearly 270,000 mph (190,000 kilometers nearly a full orbit around each other. ers, for example, simple gravity shapes the per hour). We know this because the spec- The timing argument, combined with merged galaxy. But the sheer number of tral lines of Andromeda's light appear to be estimates of the galaxies' relative velocities atoms interacting over time makes it dif- blueshifted - displaced toward the blue and other factors, indicates the Local ficult or impossible to simulate the merger end of the spectrum - by the Doppler Group's total mass is about 3 trillion times without massive computer power. ...............................--------.........~....~~ To simulate the evolution of the Local Abraham Loeb is a professor of astronomy at Harvard University, a visiting professor at the Group, first we create a mathematical model Weizmann lnstitute of Science, and the director of the lnstitute for Theory and Computation describing its present state. This is straight- at the Harvard-Smithsonian Center for Astrophysics. T. J. Cox is a postdoctoral fellow at the forward for the Milky Way and Andromeda. lnstitute for Theory and Computation at the Harvard-Smithsonian Center for Astrophysics. Several decades of observations enable us to 30 Astronomy/// June 08 estimate the quantity gas, stars, and other matter involved. We can determine a plau- sible mass estimate for the Milky Way and Andromeda to well beyond the visible inner portion of each galaxy. However, the combined mass of the Milky Way and Andromeda is still less than nearly every number the timing argument yields. This implies there is additional mass in the Local Group. The missing mass turns out to be the diffuse "intergalactic medium" of atoms, gas, and dust between the galaxies. Galaxies ... ....,, ,. ". _. '...: L - . ,' . :. ,.......... ........ .:I .. - , , . , . are simply the visible peaks of massive ice- .... :. ..\ .,:.. - .... :.. ,.... ............. .'? I.. ....... .... ., . .< :..,,..,. ... '- . .. , <."........ , .- . .... , ,: . ' . .... :, , ........: .. ... bergs of matter. Much of the mass is not ........ ....... ., ...... readily apparent, just as most of an iceberg's bulk lies underneath the water's surface. j FROM EARTH, we see the Milky Way from an insider's perspective. Depending on the time 1 of year, an Earth-bound observer can see 3 or 4 different arms of the spiral. JOHNCHUMACK When galaxies collide Full-scale simulations typically require 2 nucleii (quasars), and transform pinwheel- dynamic impact upon each other owing to weeks of number crunching. This task shaped spiral galaxies into smooth spheroi- their mutual gravitation. As a result, it's requires the power of the equivalent of 16 dal or elliptical galaxies. possible the Sun - and Earth and the other fully loaded desktop computers. One of the distinguishing characteristics planets - will be dragged into a tidal tail. Since the early days of astronomy, merg- of galaxy interactions is the appearance of During this period, an observer would have ing galaxies have remained curiosities long streams of stars and gas that stretch one of the most unique vantage points owing to their complex and irregular from one or both of the participant galax- imaginable. Torn shreds of the Milky Way shapes. But astronomers now appreciate ies. We commonly call these features tidal will fill a large fraction of the night sky as that mergers significantly drive galaxy evo- tails. They result from the powerful gravita- our galaxy experiences its gravitational lution. Galaxy mergers touch off bursts of tional forces at work between merging gal- dance with Andromeda. star formation, give birth to bright galactic axies. As the tails form,.they rip stars and Because only a small fraction of a gal- gas from the host galaxy and hurl it into axy's mass ends up in tidal tails, it is more intergalactic space. likely the Sun will go for a much less dra- As the Local Group evolves, the Milky matic ride. Most of the stars in merging Sextans A Sextans T Way and Andromeda will begin to have a galaxies remain relatively close to their host The IN THE LOCAL GROUP OF GALAXIES, the Milky Way, Andromeda Local Group (M31), and the Pinwheel Galaxy (M33) are the'largest in the group. of galaxies Dozens of smaller satellite galaxies accompany them. The group's members are all bound by mutual gravitational attraction. Its total 'LeOAlfilled space spans 6 million light-years. A~TRONOMZROENKELLY Galaxies larger than 4,000 light-years Satellite galaxies smaller than 4,000 light-years WLM 1 .I. -- L. I GALAXY MERGERS IN CYBERSPACE Astronomers don't simulate galaxy mergers just to create pretty pictures. The images below, sampled from a merger simulation by Harvard astrono- The simulations are serious and time-consuming scientific experiments. mersT. J. Cox and Avi Loeb, depict the merger of the Milky Way and Simulations enable astronomers to test new ideas about the merger pro- Andromeda galaxies.These frames highlight important milestones and .g *- cess and the role of mergers in the evolution of galaxies and the universe. events in the merger process. UNLESS~iRWSENOTEQMERGERIMACESBYTJJCOX~C~A~ 2 billio~ 2.5 billion 4.5 billion years 5.5 billion yc from nc :iom now from no\-. frem now 2 BILLION YEARS from the pres- j IN 2.5 BILLION YEARS, the i IN 4.5 BILLION YEARS, the galax- IN 5.5 BILLION YEARS, Milkon ent, the galaxies swing around galaxies are still moving ! ies loop around another time and / eda is born. Tidal swirls, tails, 5 each other in a close pass. Mutual 1 apart. A ghostly bridge of then finally coalesce into a single and eddies left over from the attraction draws tenuous tidal j gas and stars still connects i mass. Their dense cores, each har- 1 violent merger slowly relax anc tails of stars and gas.Tidal tails [ them. Stars in the bridge, / boring a black hole, gradually j dissipate. Individual stars are hallmarks of mergers in the 1 perhaps some with plan- \ combine into a single nucleus.The ! spread out, forming a more real universe (see image below), j ets, could end up literally j merging galaxies experience a / homogenous elliptical galaxy lost in space as the galaxy j brief pulse of star formation as 1 similar to M32 (right), a satellit bridge dissipates. ! the black holes merge. 5 i1 L___ a*. --.-- i I. ! ' -P -1 S z E 2 II rnZ I 0 Z 0, 1 - _.' "NGC 2207 (lower galaxy) as it / THE BEAUTY of merging galaxies stands out in this simulation of another possible model of the Milky -c, , merges with smaller IC 2163. j Way-Andromeda collision by astronomer John Dubinski.The simulation reveals more detailed structure , , NASNESAMJBBLE HERITAGE TEAM iSTScl1 ,1 . / than Cox and Loeb's images because it includes more than 300 million particles of interacting matter. galaxies. The chance of the Sun being ban- chaotic owing to the rapid fluctuations in ing life span. Currently, our Sun is about ished to the tidal-tail boondocks is rela- gravity induced by the merger. What would halfway through its lifetime and eventually tively small, based on our simulations. this mean for Earth and its residents? will begin to expand.
Load more

Recommended publications
  • The Dynamical State of the Coma Cluster with XMM-Newton?
    A&A 400, 811–821 (2003) Astronomy DOI: 10.1051/0004-6361:20021911 & c ESO 2003 Astrophysics The dynamical state of the Coma cluster with XMM-Newton? D. M. Neumann1,D.H.Lumb2,G.W.Pratt1, and U. G. Briel3 1 CEA/DSM/DAPNIA Saclay, Service d’Astrophysique, L’Orme des Merisiers, Bˆat. 709, 91191 Gif-sur-Yvette, France 2 Science Payloads Technology Division, Research and Science Support Dept., ESTEC, Postbus 299 Keplerlaan 1, 2200AG Noordwijk, The Netherlands 3 Max-Planck Institut f¨ur extraterrestrische Physik, Giessenbachstr., 85740 Garching, Germany Received 19 June 2002 / Accepted 13 December 2002 Abstract. We present in this paper a substructure and spectroimaging study of the Coma cluster of galaxies based on XMM- Newton data. XMM-Newton performed a mosaic of observations of Coma to ensure a large coverage of the cluster. We add the different pointings together and fit elliptical beta-models to the data. We subtract the cluster models from the data and look for residuals, which can be interpreted as substructure. We find several significant structures: the well-known subgroup connected to NGC 4839 in the South-West of the cluster, and another substructure located between NGC 4839 and the centre of the Coma cluster. Constructing a hardness ratio image, which can be used as a temperature map, we see that in front of this new structure the temperature is significantly increased (higher or equal 10 keV). We interpret this temperature enhancement as the result of heating as this structure falls onto the Coma cluster. We furthermore reconfirm the filament-like structure South-East of the cluster centre.
    [Show full text]
  • Identification and Study of Systems of Galaxies in The
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/41708749 Identification and study of systems of galaxies in the Shapley supercluster Article in Astronomy and Astrophysics · January 2006 DOI: 10.1051/0004-6361:20053623 CITATIONS READS 11 41 5 authors, including: Andreas Reisenegger Hernan Quintana Pontifical Catholic University of Chile Pontifical Catholic University of Chile 111 PUBLICATIONS 1,691 CITATIONS 226 PUBLICATIONS 5,059 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Abell and Group Galaxy Studies View project PUC Astronomy Group - Cluster of galaxies View project All content following this page was uploaded by Hernan Quintana on 20 July 2014. The user has requested enhancement of the downloaded file. A&A 445, 819–825 (2006) Astronomy DOI: 10.1051/0004-6361:20053623 & c ESO 2006 Astrophysics Identification and study of systems of galaxies in the Shapley supercluster C. J. Ragone1,2, H. Muriel1,2, D. Proust3, A. Reisenegger4, and H. Quintana4 1 Grupo de Investigaciones en Astronomía Teórica y Experimental, IATE, Observatorio Astronómico, Laprida 854, Córdoba, Argentina 2 Consejo de Investigaciones Científicas y Técnicas de la República Argentina e-mail: [cin;hernan]@oac.uncor.edu 3 GEPI, Observatoire de Paris-Meudon, 92195 Meudon Cedex, France e-mail: [email protected] 4 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile e-mail: [areisene;hquintana]@astro.puc.cl Received 13 June 2005 / Accepted 7 September 2005 ABSTRACT Based on the largest compilation of galaxies with redshift in the region of the Shapley Supercluster (Proust et al.
    [Show full text]
  • Galaxies Through Cosmic Time Illuminated by Gamma-Ray Bursts and Quasars
    Galaxies through Cosmic Time Illuminated by Gamma-Ray Bursts and Quasars Kasper Elm Heintz arXiv:1910.09849v1 [astro-ph.GA] 22 Oct 2019 Faculty of Physical Sciences University of Iceland 2019 Galaxies through Cosmic Time Illuminated by Gamma-Ray Bursts and Quasars Kasper Elm Heintz Dissertation submitted in partial fulfillment of a Philosophiae Doctor degree in Physics PhD Committee Prof. Páll Jakobsson (supervisor) Assoc. Prof. Jesús Zavala Prof. Emeritus Einar H. Guðmundsson Opponents Prof. J. Xavier Prochaska Dr. Valentina D’Odorico Faculty of Physical Sciences School of Engineering and Natural Sciences University of Iceland Reykjavik, July 2019 Galaxies through Cosmic Time Illuminated by Gamma-Ray Bursts and Quasars Dissertation submitted in partial fulfillment of a Philosophiae Doctor degree in Physics Copyright © Kasper Elm Heintz 2019 All rights reserved Faculty of Physical Sciences School of Engineering and Natural Sciences University of Iceland Dunhagi 107, Reykjavik Iceland Telephone: 525-4000 Bibliographic information: Kasper Elm Heintz, 2019, Galaxies through Cosmic Time Illuminated by Gamma-Ray Bursts and Quasars, PhD disserta- tion, Faculty of Physical Sciences, University of Iceland, 71 pp. ISBN 978-9935-9473-3-8 Printing: Háskólaprent Reykjavik, Iceland, July 2019 Contents Abstract v Útdráttur vii Acknowledgments ix 1 Introduction 1 1.1 The nature of GRBs and quasars 1 1.1.1 GRB optical afterglows...................................2 1.1.2 Late-stage emission components associated with GRBs..............3 1.1.3 Quasar classification and selection............................4 1.1.4 GRBs and quasars as cosmic probes..........................5 1.2 Damped Lyman-α absorbers 7 1.2.1 Gas-phase abundances and kinematics........................ 10 1.2.2 The effect of dust.....................................
    [Show full text]
  • Groups of Galaxies in the Nearby Universe Held in Santiago De Chile, 5–9 December 2006
    Report on the Conference on Groups of Galaxies in the Nearby Universe held in Santiago de Chile, 5–9 December 2006 Ivo Saviane, Valentin D. Ivanov, Jura Borissova (ESO) n Bi r 10 For every galaxy in the field or in clusters, pe p there are about three galaxies in groups. ou Therefore, the evolution of most galax- Gr r ies actually happens in groups. The Milky pe Way resides in a group, and groups can be found at high redshift. The current xies 1 generation of 10-m-class telescopes and Gala space facilities allows us to study mem- of bers of nearby groups with exquisite de- tail, and their properties can be corre- –1 Number L < 41.7 Log (erg s ) lated with the global properties of their x L > 41.7 Log (erg s–1) host group. Finally, groups are relevant x for cosmology, since they trace large- scale structures better than clusters, and –22 –20 –18 –16 –14 Absolute Magnitude (M ) the evolution of groups and clusters may B be related. Figure 1: Cumulative B-band luminosity function of Strangely, there are three times fewer pa- 25 GEMS groups of galaxies grouped into X-ray- bright and X-ray-faint categories, fitted with one or pers on groups of galaxies than on clus- two Schechter functions, respectively (Miles et ters of galaxies, as revealed by an ADS al. 2004, MNRAS 355, 785; presented by Raychaud- search. Organising this conference was a hury). Mergers could explain the bimodality of the way to focus the attention of the com- luminosity function of X-ray-faint groups.
    [Show full text]
  • Galaxy Group and Cluster Astronomy at RIT
    Galaxy Group and Cluster Astronomy at RIT 23 Spitzer,)HST,)GALEX,)&)Chandra)Image) Green Bank 100M Hershel 3.5M Credit:)NRAO) Credit:)Chicago)University) Hubble Space Telescope (HST) Sloan Digital 2.4M Sky Survey 2.5M Credit:) Hubblesite ) In Space On Earth Astronomers at RIT want to learn about galaxy groups and clusters. They use a variety of ground- and space-based telescopes. 24 YOU ARE HERE Milky Way galaxy Artist’s representation Here’s where the sun lives! We are on the outskirts of the Milky Way. It takes the sun 200 million years to travel once around the galaxy. Credit:)NASA/JPLJCaltech/R) 25 Sometimes galaxies run past each other or even combine! ZOOM Antennae Galaxies This can jumpstart star formation and make irregularly shaped galaxies like the ones shown here. 26 Credit:)HubbleSite) Living as a group of galaxies, the Milky Way has neighbors: the larger Andromeda and the smaller Tr i a n g u l u m . The Milky Way s Home The Local Group Andromeda Galaxy This is an artist’s interpretation. NGC185 Not drawn to scale. NGC147 M32 Tr i a n g u l u m Galaxy NGC205 Pegasus Milky Way Galaxy IC1613 Draco Fornax WLM Ursa Minor Sculptor LEo I Leo II Sextans NGC6822 SMC LMC Carina Artist’s representation of the Local Group Around each larger galaxy there are dozens of dwarf galaxies. It takes light 2.5 million years to get to Earth from Andromeda. 27 Hundreds, or even thousands, of galaxies can live together in a cluster. A crowded neighborhood Abell 1689 shown here has over 2000 galaxies living far, far away from Earth.
    [Show full text]
  • Collapse, Connectivity, and Galaxy Populations in Supercluster Cocoons: the Case of A2142
    COLLAPSE, CONNECTIVITY, AND GALAXY POPULATIONS IN SUPERCLUSTER COCOONS: THE CASE OF A21421 Maret Einasto Tartu Observatory, Tartu University, Observatooriumi 1, 61602 T˜oravere, Estonia Abstract The largest galaxy systems in the cosmic web are superclusters, overdensity regions of galaxies, groups, clusters, and filaments. Low-density regions around superclusters are called basins of attraction or cocoons. In my talk I discuss the properties of galaxies, groups, and filaments in the A2142 supercluster and its cocoon at redshift z ≈ 0.09. Cocoon boundaries are determined by the lowest density regions around the supercluster. We analyse the structure, dynamical state, connectivity, and galaxy content of the supercluster, and its high density core with the cluster A2142. We show that the main body of the supercluster is collapsing, and long filaments which surround the supercluster are detached from it. Galaxies with very old stellar populations lie not only in the central parts of clusters and groups in the supercluster, but also in the poorest groups in the cocoon. Keywords: galaxies: clusters: general – galaxies: groups: general – large- scale structure of Universe arXiv:2012.05843v1 [astro-ph.CO] 10 Dec 2020 1Paper presented at the Fourth Zeldovich meeting, an international conference in honor of Ya. B. Zel- dovich held in Minsk, Belarus on September 7–11, 2020. Published by the recommendation of the special editors: S. Ya. Kilin, R. Ruffini and G. V. Vereshchagin. 1 1 Introduction The large-scale distribution of galaxies can be described as the supercluster-void network or the cosmic web. The cosmic web consists of galaxies, galaxy groups, and clusters connected by filaments and separated by voids [1].
    [Show full text]
  • MULTI-WAVELENGTH STRONG LENSING STUDY of LOW REDSHIFT CLUSTER CORES By
    MULTI-WAVELENGTH STRONG LENSING STUDY OF LOW REDSHIFT CLUSTER CORES by PAUL EDWARD MAY A thesis submitted to The University of Birmingham for the degree of DOCTOR OF PHILOSOPHY Astrophysics and Space Research Group School of Physics & Astronomy The University of Birmingham Sept 2012 Abstract This thesis covers initial work to increase the total number of galaxy clusters with strong lensing features and, therefore, lensing derived masses. These clusters also possess other multi-wavelength measurements that can be, and were, used for comparison. The work included an investigation into what additional information Dressler Shectman analysis of the incomplete redshift cluster member galaxy samples produced as a result of prioritising mask slit placement on potential strong lensing images. With the test blind on areas centred around the BCG, only a qualitative link was found, providing possible assistance with mass model parametisation. From the sample of eight clusters reduced, five had strong lensing features, of which, A 3084 had an unusual and rare lensing configuration. Analysis of A 3084 with relatively shallow survey data revealed a cluster with the largest cluster-scale halo centred on the intra-cluster gas and not the BCG: these two were offset from one another. The BCG had a compact DM halo coincident with it, yielding a high substructure fraction of fsub= 0.73 0.13 which, along with smooth X-ray surface brightness contours, bi-modal cluster ± galaxy redshift histogram and luminosity map, provided evidence that the interpretation of the cluster had suffered a cluster-cluster merger. From the redshift reduction, five new strong lensing models were produced following similar methods to the ones used for A 3084.
    [Show full text]
  • The AIMSS Project – I. Bridging the Star Cluster–Galaxy Divide †‡§¶
    MNRAS 443, 1151–1172 (2014) doi:10.1093/mnras/stu1186 ? The AIMSS Project – I. Bridging the star cluster–galaxy divide †‡§¶ Mark A. Norris,1,2k Sheila J. Kannappan,2 Duncan A. Forbes,3 Aaron J. Romanowsky,4,5 Jean P. Brodie,5 Favio Raul´ Faifer,6,7 Avon Huxor,8 Claudia Maraston,9 Amanda J. Moffett,2 Samantha J. Penny,10 Vincenzo Pota,3 Anal´ıa Smith-Castelli,6,7 Jay Strader,11 David Bradley,2 Kathleen D. Eckert,2 Dora Fohring,12,13 JoEllen McBride,2 David V. Stark2 and Ovidiu Vaduvescu12 Downloaded from https://academic.oup.com/mnras/article-abstract/443/2/1151/1058316 by guest on 04 September 2019 Affiliations are listed at the end of the paper Accepted 2014 June 16. Received 2014 May 13; in original form 2014 January 27 ABSTRACT We describe the structural and kinematic properties of the first compact stellar systems dis- covered by the Archive of Intermediate Mass Stellar Systems project. These spectroscopically 6 confirmed objects have sizes (∼6 < Re [pc] < 500) and masses (∼2 × 10 < M∗/M¯ < 6 × 109) spanning the range of massive globular clusters, ultracompact dwarfs (UCDs) and compact elliptical galaxies (cEs), completely filling the gap between star clusters and galax- ies. Several objects are close analogues to the prototypical cE, M32. These objects, which are more massive than previously discovered UCDs of the same size, further call into question the existence of a tight mass–size trend for compact stellar systems, while simultaneously strengthening the case for a universal ‘zone of avoidance’ for dynamically hot stellar systems in the mass–size plane.
    [Show full text]
  • ALFALFA HI OBSERVATIONS of the NGC 5846 GALAXY GROUP Ana Mikler1, Katelyn O'brien1, Sreynoch Chin1, Rebecca A
    ALFALFA HI OBSERVATIONS OF THE NGC 5846 GALAXY GROUP Ana Mikler1, Katelyn O'Brien1, SreyNoch Chin1, Rebecca A. Koopmann1,Jessica Rossenberg2, ALFALFA Team3 1Union College , 2 George Mason University, 3PI: Riccardo Giovanelli, Cornell University ABSTRACT The intermediate density NGC 5846 group of galaxies has one of the highest fractions of early-type galaxies in the local Universe. Based on Arecibo Legacy Fast ALFA (ALFALFA) observations, the Union College group has shown that NGC 5846 contains few galaxies with detectable HI. We compare the gas and stellar properties of gas-poor galaxies in the group by measuring upper limits for the HI content of galaxies not detected using the ALFALFA survey, based on a list of group members constructed from the Sloan Digital Sky Survey (SDSS). We present contour maps of HI emission in member galaxies. This project is part of the Undergraduate ALFALFA Team Groups project whose general goal is to measure and compare HI and multi-wavelength observations for groups with different properties. This work is supported by NSF grants AST-0724918 and AST-0725380. NGC 5846 GROUP OF GALAXIES HI RESULTS • HI MASS • Well-defined, relatively isolated group in Local Supercluster. • 4.8 X 8° region covering NGC5846 group center • Distance = 26.1 Mpc. All • 26 galaxies detected by ALFALFA • High density, intermediate mass system, • The HI mass in a galaxy is calculated from: Spirals > 300 members, 4 with L > L* 5 2 MHI = 2.36 x 10 D FHI Mʘ • Early- type rich population. • Velocity: 1749 km/s with a velocity dispersion of 322 km/s. where F is the corrected HI flux density integrated over HI • X-ray emission; possible intragroup medium.
    [Show full text]
  • April 2016 BRAS Newsletter
    April 2016 Issue th Next Meeting: Monday, April 11 at 7PM at HRPO (2nd Mondays, Highland Road Park Observatory) April 6th through April 10th is our annual Hodges Gardens Star Party. You can pre-register using the form on the BRAS website. If you have never attended this star party, make plans to attend this one. What's In This Issue? President’s Message Photos: BRAS Telescope donated to EBRP Library Secretary's Summary of March Meeting Recent BRAS Forum Entries 20/20 Vision Campaign Message from the HRPO Astro Short: Stellar Dinosaurs? International Astronomy Day Observing Notes: Leo The Lion, by John Nagle Newsletter of the Baton Rouge Astronomical Society April 2016 Page 2 President’s Message There were 478 people who stopped by the BRAS display at the March 19th ―Rockin at the Swamp‖ event at the Bluebonnet Swamp and Nature Center. I give thanks to all our volunteers for our success in this outreach event. April 6th through April 10th is our annual Hodges Gardens Star Party. You can pre-register on the BRAS website, or register when you arrive (directions are on the BRAS website). If you have never attended a star party, of if you are an old veteran star partier; make plans to attend this one. Our Guest Speaker for the BRAS meeting on April 11th will be Dr. Joseph Giaime, Observatory Head, LIGO Livingston (Caltech), Professor of Physics and Astronomy (LSU). Yes, he will be talking about gravity waves and the extraordinary discovery LIGO has made. We need volunteers to help at our display on Earth Day on Sunday, April 17th.
    [Show full text]
  • Identification and Study of Systems Of
    A&A 445, 819–825 (2006) Astronomy DOI: 10.1051/0004-6361:20053623 & c ESO 2006 Astrophysics Identification and study of systems of galaxies in the Shapley supercluster C. J. Ragone1,2, H. Muriel1,2, D. Proust3, A. Reisenegger4, and H. Quintana4 1 Grupo de Investigaciones en Astronomía Teórica y Experimental, IATE, Observatorio Astronómico, Laprida 854, Córdoba, Argentina 2 Consejo de Investigaciones Científicas y Técnicas de la República Argentina e-mail: [cin;hernan]@oac.uncor.edu 3 GEPI, Observatoire de Paris-Meudon, 92195 Meudon Cedex, France e-mail: [email protected] 4 Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile e-mail: [areisene;hquintana]@astro.puc.cl Received 13 June 2005 / Accepted 7 September 2005 ABSTRACT Based on the largest compilation of galaxies with redshift in the region of the Shapley Supercluster (Proust et al. 2004, P2004), we identified 122 galaxy systems, 60 of which are new systems. Using the SuperCOSMOS catalogue, we have assigned b j magnitudes to each galaxy in our 13 15 −1 compilation. The sample of galaxy systems was used to estimate the mass function of systems in the range 10 to 10 M h . We computed a lower value to the total mass in the region of the Shapley Supercluster with this mass function. Using 15 mock catalogues we derived the mean mass that these kinds of systems have before comparing it with that obtained from the real data. Key words. galaxies: clusters: general 1. Introduction representing an overdensity range ρ/ρc ∼ 3−20. In this work we explore an alternative way to estimate a lower limit to the to- The Shapley Supercluster (hereafter SSC) has the highest con- tal mass of the SSC.
    [Show full text]
  • MACHINE LEARNING in GALAXY GROUPS DETECTION By
    MACHINE LEARNING IN GALAXY GROUPS DETECTION by RAFEE TARIQ IBRAHEM A thesis submitted to The University of Birmingham for the degree of DOCTOR OF PHILOSOPHY School of Computer Science College of Engineering and Physical Sciences The University of Birmingham May 2017 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract The detection of galaxy groups and clusters is of great importance in the field of astrophysics. In particular astrophysicists are interested in the evolution and formation of these systems, as well as the interactions that occur within galaxy groups and clusters. In this thesis, we developed a probabilistic model capa- ble of detecting galaxy groups and clusters based on the Hough transform. We called this approach probabilistic Hough transform based on adaptive local ker- nel (PHTALK). PHTALK was tested on a 3D realistic galaxy and mass assembly (GAMA) mock data catalogue (at close redshift z < 0:1)(mock data: contains information related to galaxies’ position, redshift and other properties). We com- pared the performance of our PHTALK method with the performance of two ver- sions of the standard friends-of-friends (FoF) method.
    [Show full text]