Hubble's Galaxy NGC 4242 24 July 2017

Total Page：16

File Type：pdf, Size：1020Kb

Image: Hubble's galaxy NGC 4242 24 July 2017 as with much of the Universe, it is still a beautiful and ethereal sight. Provided by NASA Credit: ESA/Hubble & NASA Tucked away in the small northern constellation of Canes Venatici (The Hunting Dogs) is the galaxy NGC 4242, shown here as seen by the NASA/ESA Hubble Space Telescope. The galaxy lies some 30 million light-years from us. At this distance from Earth, actually not all that far on a cosmic scale, NGC 4242 is visible to anyone armed with even a basic telescope, as British astronomer William Herschel found when he discovered the galaxy in 1788. This image shows the galaxy's bright center and the surrounding dimmer and more diffuse "fuzz." Despite appearing to be relatively bright in this image, studies have found that NGC 4242 is actually relatively dim (it has a moderate-to-low surface brightness and low luminosity) and also supports a low rate of star formation. The galaxy also seems to have a weak bar of stars cutting through its asymmetric center, and a very faint and poorly-defined spiral structure throughout its disk. But if NGC 4242 is not all that remarkable, 1 / 2 APA citation: Image: Hubble's galaxy NGC 4242 (2017, July 24) retrieved 25 September 2021 from https://phys.org/news/2017-07-image-hubble-galaxy-ngc.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).

Copy Link

Recommended publications

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]
Structure and Star Formation in Disk Galaxies I. Sample Selection And
Mon. Not. R. Astron. Soc. 000, 1–9 (2003) Printed 31 October 2018 (MN LATEX style file v1.4) Structure and star formation in disk galaxies I. Sample selection and near infrared imaging J. H. Knapen1,2, R. S. de Jong3, S. Stedman1 and D. M. Bramich4 1University of Hertfordshire, Department of Physical Sciences, Hatfield, Herts AL10 9AB 2Isaac Newton Group of Telescopes, Apartado 321, E-38700 Santa Cruz de La Palma, Spain 3Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 4School of Physics and Astronomy, University of St. Andrews, Scotland KY16 9SS Accepted March 2003. Received ; in original form ABSTRACT We present near-infrared imaging of a sample of 57 relatively large, Northern spiral galaxies with low inclination. After describing the selection criteria and some of the basic properties of the sample, we give a detailed description of the data collection and reduction procedures. The Ks λ =2.2µm images cover most of the disk for all galaxies, with a field of view of at least 4.2 arcmin. The spatial resolution is better than an arcsec for most images. We fit bulge and exponential disk components to radial profiles of the light distribution. We then derive the basic parameters of these components, as well as the bulge/disk ratio, and explore correlations of these parameters with several galaxy parameters. Key words: galaxies: spiral – galaxies: structure – infrared: galaxies 1 INTRODUCTION only now starting to be published (e.g., 2MASS: Skrutskie et al. 1997, Jarrett et al. 2003; Seigar & James 1998a, 1998b; Near-infrared (NIR) imaging of galaxies is a better tracer Moriondo et al.
[Show full text]
Classification of Galaxies Using Fractal Dimensions
UNLV Retrospective Theses & Dissertations 1-1-1999 Classification of galaxies using fractal dimensions Sandip G Thanki University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Thanki, Sandip G, "Classification of galaxies using fractal dimensions" (1999). UNLV Retrospective Theses & Dissertations. 1050. http://dx.doi.org/10.25669/8msa-x9b8 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted.
[Show full text]
A Search For" Dwarf" Seyfert Nuclei. VII. a Catalog of Central Stellar
TO APPEAR IN The Astrophysical Journal Supplement Series. Preprint typeset using LATEX style emulateapj v. 26/01/00 A SEARCH FOR “DWARF” SEYFERT NUCLEI. VII. A CATALOG OF CENTRAL STELLAR VELOCITY DISPERSIONS OF NEARBY GALAXIES LUIS C. HO The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 JENNY E. GREENE1 Department of Astrophysical Sciences, Princeton University, Princeton, NJ ALEXEI V. FILIPPENKO Department of Astronomy, University of California, Berkeley, CA 94720-3411 AND WALLACE L. W. SARGENT Palomar Observatory, California Institute of Technology, MS 105-24, Pasadena, CA 91125 To appear in The Astrophysical Journal Supplement Series. ABSTRACT We present new central stellar velocity dispersion measurements for 428 galaxies in the Palomar spectroscopic survey of bright, northern galaxies. Of these, 142 have no previously published measurements, most being rela- −1 tively late-type systems with low velocity dispersions (∼<100kms ). We provide updates to a number of literature dispersions with large uncertainties. Our measurements are based on a direct pixel-ﬁtting technique that can ac- commodate composite stellar populations by calculating an optimal linear combination of input stellar templates. The original Palomar survey data were taken under conditions that are not ideally suited for deriving stellar veloc- ity dispersions for galaxies with a wide range of Hubble types. We describe an effective strategy to circumvent this complication and demonstrate that we can still obtain reliable velocity dispersions for this sample of well-studied nearby galaxies. Subject headings: galaxies: active — galaxies: kinematics and dynamics — galaxies: nuclei — galaxies: Seyfert — galaxies: starburst — surveys 1. INTRODUCTION tors, apertures, observing strategies, and analysis techniques.
[Show full text]
Radial Star Formation Histories in Fifteen Nearby Galaxies
RADIAL STAR FORMATION HISTORIES IN FIFTEEN NEARBY GALAXIES Daniel A. Dale1, Gillian D. Beltz-Mohrmann2, Arika A. Egan3, Alan J. Hatlestad1, Laura J. Herzog4, Andrew S. Leung5, Jacob N. McLane5, Christopher Phenicie6, Jareth S. Roberts1, Kate L. Barnes7, Médéric Boquien8, Daniela Calzetti9, David O. Cook1, Henry A. Kobulnicky1, Shawn M. Staudaher1, and Liese van Zee7 ABSTRACT New deep optical and near-infrared imaging is combined with archival ultravi- olet and infrared data for fifteen nearby galaxies mapped in the Spitzer Extended Disk Galaxy Exploration Science survey. These images are particularly deep and thus excellent for studying the low surface brightness outskirts of these disk- 8 11 dominated galaxies with stellar masses ranging between 10 and 10 M⊙. The spectral energy distributions derived from this dataset are modeled to investigate the radial variations in the galaxy colors and star formation histories. Taken as a whole, the sample shows bluer and younger stars for larger radii until reversing near the optical radius, whereafter the trend is for redder and older stars for larger galacto-centric distances. These results are consistent with an inside-out disk formation scenario coupled with an old stellar outer disk population formed through radial migration and/or the cumulative history of minor mergers and ac- cretions of satellite dwarf galaxies. However, these trends are quite modest and the variation from galaxy to galaxy is substantial. Additional data for a larger sample of galaxies are needed to confirm or dismiss
[Show full text]
Lopsided Spiral Galaxies: Evidence for Gas Accretion
A&A 438, 507–520 (2005) Astronomy DOI: 10.1051/0004-6361:20052631 & c ESO 2005 Astrophysics Lopsided spiral galaxies: evidence for gas accretion F. Bournaud1, F. Combes1,C.J.Jog2, and I. Puerari3 1 Observatoire de Paris, LERMA, 61 Av. de l’Observatoire, 75014 Paris, France e-mail: [email protected] 2 Department of Physics, Indian Institute of Science, Bangalore 560012, India 3 Instituto Nacional de Astrofísica, Optica y Electrónica, Calle Luis Enrique Erro 1, 72840 Tonantzintla, Puebla, Mexico Received 3 January 2005 / Accepted 15 March 2005 Abstract. We quantify the degree of lopsidedness for a sample of 149 galaxies observed in the near-infrared from the OSUBGS sample, and try to explain the physical origin of the observed disk lopsidedness. We confirm previous studies, but for a larger sample, that a large fraction of galaxies have significant lopsidedness in their stellar disks, measured as the Fourier amplitude of the m = 1 component normalised to the average or m = 0 component in the surface density. Late-type galaxies are found to be more lopsided, while the presence of m = 2 spiral arms and bars is correlated with disk lopsidedness. We also show that the m = 1 amplitude is uncorrelated with the presence of companions. Numerical simulations were carried out to study the generation of m = 1viadifferent processes: galaxy tidal encounters, galaxy mergers, and external gas accretion with subsequent star formation. These simulations show that galaxy interactions and mergers can trigger strong lopsidedness, but do not explain several independent statistical properties of observed galaxies. To explain all the observational results, it is required that a large fraction of lopsidedness results from cosmological accretion of gas on galactic disks, which can create strongly lopsided disks when this accretion is asymmetrical enough.
[Show full text]
SAC's 110 Best of the NGC
SAC's 110 Best of the NGC by Paul Dickson Version: 1.4 | March 26, 1997 Copyright °c 1996, by Paul Dickson. All rights reserved If you purchased this book from Paul Dickson directly, please ignore this form. I already have most of this information. Why Should You Register This Book? Please register your copy of this book. I have done two book, SAC's 110 Best of the NGC and the Messier Logbook. In the works for late 1997 is a four volume set for the Herschel 400. q I am a beginner and I bought this book to get start with deep-sky observing. q I am an intermediate observer. I bought this book to observe these objects again. q I am an advance observer. I bought this book to add to my collect and/or re-observe these objects again. The book I'm registering is: q SAC's 110 Best of the NGC q Messier Logbook q I would like to purchase a copy of Herschel 400 book when it becomes available. Club Name: __________________________________________ Your Name: __________________________________________ Address: ____________________________________________ City: __________________ State: ____ Zip Code: _________ Mail this to: or E-mail it to: Paul Dickson 7714 N 36th Ave [email protected] Phoenix, AZ 85051-6401 After Observing the Messier Catalog, Try this Observing List: SAC's 110 Best of the NGC [email protected] http://www.seds.org/pub/info/newsletters/sacnews/html/sac.110.best.ngc.html SAC's 110 Best of the NGC is an observing list of some of the best objects after those in the Messier Catalog.
[Show full text]
A Multi-Wavelength Study of Star Formation in 15 Local Star-Forming Galaxies
MNRAS 000,1–41 (2021) Preprint 31 May 2021 Compiled using MNRAS LATEX style file v3.0 A Multi-Wavelength Study of Star Formation in 15 Local Star-Forming Galaxies Madison V. Smith,1¢ L. van Zee1, S. Salim1, D. Dale2, S. Staudaher 3, T. Wrock 1, A. Maben 1 1Department of Astronomy, Indiana University, Bloomington IN, USA 2Department of Physics & Astronomy, University of Wyoming, Laramie WY, USA 3College of Osteopathic Medicine, Sam Houston State University, Conroe TX, USA Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We have fit the far-ultraviolet (FUV) to mid-infrared (MIR) spectral energy distributions (SEDs) for several nearby galaxies (< 20 Mpc). Global, radial, and local photometric measurements are explored to better understand how SED-derived star formation histories (SFHs) and classic star formation rate (SFR) tracers manifest at different scales. Surface brightness profiles and radial SED fitting provide insight into stellar population gradients in stellar discs and haloes. A double exponential SFH model is used in the SED fitting to better understand the distributions of young vs. old populations throughout these galaxies. Different regions of a galaxy often have undergone very different SFHs, either in strength, rate, timing, or some combination of all these factors. An analysis of individual stellar complexes within these galaxies shows a relationship between the ages of stellar clusters and how these clusters are distributed throughout the galaxy. These star formation properties are presented alongside previously published HI observations to provide a holistic picture of a small sample of nearby star-forming galaxies. The results presented here show that there is a wide variety of star formation gradients and average stellar age distributions that can manifest in a ΛCDM universe.
[Show full text]
Tracing the Local Volume Galaxy Halo-To-Stellar Mass Ratio with Satellite Kinematics
Received 10 July 2020; Revised 23 August 2020; Accepted 23 August 2020 DOI: xxx/xxxx 10.1002/asna.20210018 ORIGINAL ARTICLE Tracing the Local Volume galaxy halo-to-stellar mass ratio with satellite kinematics Igor Karachentsev | Olga Kashibadze Special Astrophysical Observatory, Russian Academy of Sciences, Russia Rapid advance has been made recently in accurate distance measurements for nearby Correspondence (D < 11 Mpc) galaxies based on the magnitude of the tip of red giant branch stars I. D. Karachentsev, SAO RAS, Nizhny Arkhyz, Karachay-Cherkessia, resolved with the Hubble Space Telescope. We use observational properties of galax- 369167 Russia. Email: [email protected] ies presented in the last version of Updated Nearby Galaxy Catalog to derive a halo mass of luminous galaxies via orbital motion of their companions. Our sample con- Funding Information tains 298 assumed satellites with known radial velocities around 25 Milky Way-like Russian Scientiﬁc Foundation, 19– massive galaxies and 65 assumed satellites around 47 fainter dominant galaxies. 02–00145. The average total mass-to-K-band luminosity ratio is 31 , 6M⊙_L⊙ for the lumi- nous galaxies, increasing up to ∼ 200M⊙_L⊙ toward dwarfs. The bulge-dominated luminous galaxies are characterized with êMT _LK ë = 73 , 15M⊙_L⊙, while the disc-dominated spirals have êMT _LK ë = 17:4 , 2:8M⊙_L⊙. We draw attention to a particular subsample of luminous spiral galaxies with signs of declining rotation curve, which have a radial velocity dispersion of satellites less than 55 km/s and a poor dark matter halo with êMT _LK ë = 5:5 , 1:1M⊙_L⊙.
[Show full text]
Enhancement Classification of Galaxy Images
See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/275963346 Enhancement Classiﬁcation of Galaxy Images Thesis · December 2014 DOI: 10.13140/RG.2.1.4152.4641 CITATIONS READS 0 493 1 author: John Jenkinson University of Texas at San Antonio 5 PUBLICATIONS 53 CITATIONS SEE PROFILE All content following this page was uploaded by John Jenkinson on 07 May 2015. The user has requested enhancement of the downloaded file. ENHANCEMENT CLASSIFICATION OF GALAXY IMAGES APPROVED BY SUPERVISING COMMITTEE: Arytom Grigoryan, Ph.D., Chair Walter Richardson, Ph.D. David Akopian, Ph.D. Accepted: Dean, Graduate School Copyright 2014 John Jenkinson All rights reserved. DEDICATION To my family. ENHANCEMENT CLASSIFICATION OF GALAXY IMAGES by JOHN JENKINSON, M.S. DISSERTATION Presented to the Graduate Faculty of The University of Texas at San Antonio In Partial Fulﬁllment Of the Requirements For the Degree of MASTER OF SCIENCE IN ELECTRICAL ENGINEERING THE UNIVERSITY OF TEXAS AT SAN ANTONIO College of Engineering Department of Electrical and Computer Engineering December 2014 UMI Number: 1572687 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. UMI 1572687 Published by ProQuest LLC (2015). 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.
[Show full text]
A Composite H II Region Luminosity Function in Hα of Unprecedented Statistical Weight,
A&A 459, L13–L16 (2006) Astronomy DOI: 10.1051/0004-6361:20066151 & c ESO 2006 Astrophysics L E A composite H II region luminosity function in Hα of unprecedented statistical weight, T. R. Bradley1,2, J. H. Knapen2, J. E. Beckman3,4, and S. L. Folkes2 1 Centre for Astrophysics, University of Central Lancashire, Preston PR1 2HE, UK 2 Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB, UK e-mail: [email protected] 3 Instituto de Astrofísica de Canarias, 38200 La Laguna, Spain 4 Consejo Superior de Investigaciones Científicas, Spain Received 31 July 2006 / Accepted 15 September 2006 ABSTRACT Context. Statistical properties of H region populations in disk galaxies yield important clues to the physics of massive star formation. Aims. We present a set of H region catalogues and luminosity functions for a sample of 56 spiral galaxies in order to derive the most general form of their luminosity function. Methods. H region luminosity functions are derived for individual galaxies which, after photometric calibration, are summed to form a total luminosity function comprising 17 797 H regions from 53 galaxies. Results. The total luminosity function, above its lower limit of completeness, is clearly best fitted by a double power law with a significantly steeper slope for the high luminosity portion of the function. This change of slope has been reported in the literature for individual galaxies, and occurs at a luminosity of log L = 38.6 ± 0.1(L in erg s−1) which has been termed the Strömgren luminosity. A steep fall off in the luminosity function above log L = 40 is also noted, and is related to an upper limit to the luminosities of underlying massive stellar clusters.
[Show full text]
RADIAL STAR FORMATION HISTORIES in FIFTEEN NEARBY GALAXIES Daniel A
RADIAL STAR FORMATION HISTORIES IN FIFTEEN NEARBY GALAXIES Daniel A. Dale1, Gillian D. Beltz-Mohrmann2, Arika A. Egan3 Alan J. Hatlestad1, Laura J. Herzog4, Andrew S. Leung5, Jacob N. McLane6 Christopher Phenicie7, Jareth S. Roberts1, Kate L. Barnes8, Médéric Boquien9, Daniela Calzetti10, David O. Cook1, and Henry A. Kobulnicky1, Shawn M. Staudaher1, and Liese van Zee8 ABSTRACT New deep optical imaging is combined with archival ultraviolet and infrared data for fifteen nearby galaxies mapped in the Spitzer Extended Disk Galaxy Ex- ploration Science survey. These images are particularly deep and thus excellent for studying the low surface brightness outskirts of these disk dominated galaxies 8 11 with stellar masses ranging between 10 and 10 M⊙. The spectral energy distri- butions derived from this dataset are modeled to investigate the radial variations in the galaxy colors and star formation histories. Though there is substantial variation from galaxy to galaxy, taken as a whole the sample shows bluer and younger stars for larger radii until reversing near the optical radius, whereafter the trend is for redder and older stars for larger galacto-centric distances. These results are consistent with an inside-out disk formation scenario coupled with an old stellar outer disk population formed through radial migration and/or the cumulative history of minor mergers and accretions of satellite dwarf galaxies. Subject headings: galaxies: star formation — galaxies: halos — galaxies: forma- tion — galaxies: photometry 1Department of Physics
[Show full text]