skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Fermi observations of Cassiopeia and Cepheus: Diffuse gamma-ray emission in the outer galaxy

Abstract

Here, we present the analysis of the interstellar γ-ray emission measured by the Fermi Large Area Telescope toward a region in the second Galactic quadrant at 100° ≤ l ≤ 145° and –15° ≤ b ≤ +30°. This region encompasses the prominent Gould Belt clouds of Cassiopeia, Cepheus, and the Polaris flare, as well as atomic and molecular complexes at larger distances, like that associated with NGC 7538 in the Perseus arm. The good kinematic separation in velocity between the local, Perseus, and outer arms, and the presence of massive complexes in each of them, make this region well suited to probe cosmic rays (CRs) and the interstellar medium beyond the solar circle. Furthermore, the γ-ray emissivity spectrum of the gas in the Gould Belt is consistent with expectations based on the locally measured CR spectra. The γ-ray emissivity decreases from the Gould Belt to the Perseus arm, but the measured gradient is flatter than expectations for CR sources peaking in the inner Galaxy as suggested by pulsars. The X CO = N(H2)/W CO conversion factor is found to increase from (0.87 ± 0.05) × 1020 cm–2 (K km s–1)–1 in the Gould Belt to (1.9 ± 0.2) × 1020more » cm–2 (K km s–1)–1 in the Perseus arm. We also derive masses for the molecular clouds under study. Dark gas, not properly traced by radio and microwave surveys, is detected in the Gould Belt through a correlated excess of dust and γ-ray emission: its mass amounts to ~50% of the CO-traced mass.« less

Authors:
 [1]
  1. Naval Research Lab. (NRL), Washington, DC (United States); National Academy of Sciences, Washington, DC (United States); et al.
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
Fermi LAT Collaboration
OSTI Identifier:
1357581
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 710; Journal Issue: 1; Journal ID: ISSN 0004-637X
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; cosmic rays; gamma rays: diffuse background; ISM: clouds

Citation Formats

Abdo, A. A. Fermi observations of Cassiopeia and Cepheus: Diffuse gamma-ray emission in the outer galaxy. United States: N. p., 2010. Web. doi:10.1088/0004-637X/710/1/133.
Abdo, A. A. Fermi observations of Cassiopeia and Cepheus: Diffuse gamma-ray emission in the outer galaxy. United States. doi:10.1088/0004-637X/710/1/133.
Abdo, A. A. Fri . "Fermi observations of Cassiopeia and Cepheus: Diffuse gamma-ray emission in the outer galaxy". United States. doi:10.1088/0004-637X/710/1/133. https://www.osti.gov/servlets/purl/1357581.
@article{osti_1357581,
title = {Fermi observations of Cassiopeia and Cepheus: Diffuse gamma-ray emission in the outer galaxy},
author = {Abdo, A. A.},
abstractNote = {Here, we present the analysis of the interstellar γ-ray emission measured by the Fermi Large Area Telescope toward a region in the second Galactic quadrant at 100° ≤ l ≤ 145° and –15° ≤ b ≤ +30°. This region encompasses the prominent Gould Belt clouds of Cassiopeia, Cepheus, and the Polaris flare, as well as atomic and molecular complexes at larger distances, like that associated with NGC 7538 in the Perseus arm. The good kinematic separation in velocity between the local, Perseus, and outer arms, and the presence of massive complexes in each of them, make this region well suited to probe cosmic rays (CRs) and the interstellar medium beyond the solar circle. Furthermore, the γ-ray emissivity spectrum of the gas in the Gould Belt is consistent with expectations based on the locally measured CR spectra. The γ-ray emissivity decreases from the Gould Belt to the Perseus arm, but the measured gradient is flatter than expectations for CR sources peaking in the inner Galaxy as suggested by pulsars. The X CO = N(H2)/W CO conversion factor is found to increase from (0.87 ± 0.05) × 1020 cm–2 (K km s–1)–1 in the Gould Belt to (1.9 ± 0.2) × 1020 cm–2 (K km s–1)–1 in the Perseus arm. We also derive masses for the molecular clouds under study. Dark gas, not properly traced by radio and microwave surveys, is detected in the Gould Belt through a correlated excess of dust and γ-ray emission: its mass amounts to ~50% of the CO-traced mass.},
doi = {10.1088/0004-637X/710/1/133},
journal = {Astrophysical Journal},
number = 1,
volume = 710,
place = {United States},
year = {2010},
month = {1}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Citation Metrics:
Cited by: 116 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Measurement of the Cosmic Ray e + + e Spectrum from 20 GeV to 1 TeV with the Fermi Large Area Telescope
journal, May 2009


FERMI /LARGE AREA TELESCOPE BRIGHT GAMMA-RAY SOURCE LIST
journal, June 2009

  • Abdo, A. A.; Ackermann, M.; Ajello, M.
  • The Astrophysical Journal Supplement Series, Vol. 183, Issue 1
  • DOI: 10.1088/0067-0049/183/1/46

FERMI LAT OBSERVATION OF DIFFUSE GAMMA RAYS PRODUCED THROUGH INTERACTIONS BETWEEN LOCAL INTERSTELLAR MATTER AND HIGH-ENERGY COSMIC RAYS
journal, September 2009


FERMI LAT DISCOVERY OF EXTENDED GAMMA-RAY EMISSION IN THE DIRECTION OF SUPERNOVA REMNANT W51C
journal, October 2009


Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes
journal, December 2009


Observation of Extended very high Energy Emission from the Supernova Remnant ic 443 with Veritas
journal, June 2009


New Measurement of the Antiproton-to-Proton Flux Ratio up to 100 GeV in the Cosmic Radiation
journal, February 2009


Discovery of very high energy gamma-ray emission coincident with molecular clouds in the W 28 (G6.4-0.1) field
journal, January 2008

  • Aharonian, F.; Akhperjanian, A. G.; Bazer-Bachi, A. R.
  • Astronomy & Astrophysics, Vol. 481, Issue 2
  • DOI: 10.1051/0004-6361:20077765

Discovery of Very High Energy Gamma Radiation from IC 443 with the MAGIC Telescope
journal, July 2007

  • Albert, J.; Aliu, E.; Anderhub, H.
  • The Astrophysical Journal, Vol. 664, Issue 2
  • DOI: 10.1086/520957

Protons in near earth orbit
journal, January 2000


CO-to-H 2 Conversion Factor in Galaxies
journal, April 1996

  • Arimoto, Nobuo; Sofue, Yoshiaki; Tsujimoto, Takuji
  • Publications of the Astronomical Society of Japan, Vol. 48, Issue 2
  • DOI: 10.1093/pasj/48.2.275

THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION
journal, May 2009


Diffuse Galactic Gamma-Ray Emission
journal, September 1989


Millimeter dust continuum emission revealing the true mass of giant molecular clouds in the Small Magellanic Cloud
journal, June 2007


A New Σ‐ D Relation and Its Application to the Galactic Supernova Remnant Distribution
journal, September 1998

  • Case, Gary L.; Bhattacharya, Dipen
  • The Astrophysical Journal, Vol. 504, Issue 2
  • DOI: 10.1086/306089

The Milky Way in Molecular Clouds: A New Complete CO Survey
journal, February 2001

  • Dame, T. M.; Hartmann, Dap; Thaddeus, P.
  • The Astrophysical Journal, Vol. 547, Issue 2
  • DOI: 10.1086/318388

Binary collision rates of relativistic thermal plasmas. II - Spectra
journal, August 1986

  • Dermer, C. D.
  • The Astrophysical Journal, Vol. 307
  • DOI: 10.1086/164391

THE OUTER DISK OF THE MILKY WAY SEEN IN λ21 cm ABSORPTION
journal, March 2009


Giant molecular clouds in the outer arm of the galaxy
journal, July 1990

  • Digel, Seth; Thaddeus, Patrick; Bally, John
  • The Astrophysical Journal, Vol. 357
  • DOI: 10.1086/185759

Diffuse High-Energy Gamma-Ray Emission beyond the Solar Circle: The Cepheus and Polaris Flares and the Perseus Arm
journal, May 1996

  • Digel, S. W.; Grenier, I. A.; Heithausen, A.
  • The Astrophysical Journal, Vol. 463
  • DOI: 10.1086/177275

EGRET Observations of Monoceros: Diffuse Gamma‐Ray Emission in the Outer Galaxy
journal, July 2001

  • Digel, S. W.; Grenier, I. A.; Hunter, S. D.
  • The Astrophysical Journal, Vol. 555, Issue 1
  • DOI: 10.1086/321446

Gamma rays from molecular clouds
journal, April 2007

  • Gabici, Stefano; Aharonian, Felix A.; Blasi, Pasquale
  • Astrophysics and Space Science, Vol. 309, Issue 1-4
  • DOI: 10.1007/s10509-007-9427-6

A Self‐Absorption Census of Cold H i Clouds in the Canadian Galactic Plane Survey
journal, June 2005

  • Gibson, Steven J.; Taylor, A. Russell; Higgs, Lloyd A.
  • The Astrophysical Journal, Vol. 626, Issue 1
  • DOI: 10.1086/429870

Unveiling Extensive Clouds of Dark Gas in the Solar Neighborhood
journal, February 2005


CO observations of the Cepheus flare. I - Molecular clouds associated with a nearby bubble
journal, December 1989

  • Grenier, I. A.; Lebrun, F.; Arnaud, M.
  • The Astrophysical Journal, Vol. 347
  • DOI: 10.1086/168112

The Polaris Flare - Extensive molecular gas near the north celestial pole
journal, April 1990

  • Heithausen, Andreas; Thaddeus, Patrick
  • The Astrophysical Journal, Vol. 353
  • DOI: 10.1086/185705

New calculation of the atmospheric neutrino flux in a three-dimensional scheme
journal, August 2004


The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI: Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections
journal, September 2005


Parameterization of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\gamma ,\, e^{\pm }$ \end{document} , and Neutrino Spectra Produced by p‐p Interaction in Astronomical Environments
journal, August 2006

  • Kamae, Tuneyoshi; Karlsson, Niklas; Mizuno, Tsunefumi
  • The Astrophysical Journal, Vol. 647, Issue 1
  • DOI: 10.1086/505189

Gamma-rays from atomic and molecular gas in the first galactic quadrant
journal, November 1983

  • Lebrun, F.; Bennett, K.; Bignami, G. F.
  • The Astrophysical Journal, Vol. 274
  • DOI: 10.1086/161440

Trigonometric Parallaxes of Massive Star-Forming Regions. ii. cep a and ngc 7538
journal, March 2009


Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: II. The Molecular Gas Disk
journal, October 2006

  • Nakanishi, Hiroyuki; Sofue, Yoshiaki
  • Publications of the Astronomical Society of Japan, Vol. 58, Issue 5
  • DOI: 10.1093/pasj/58.5.847

3D dynamical evolution of the interstellar gas in the Gould Belt
journal, June 2003


Inverse Compton Origin of the Hard X‐Ray and Soft Gamma‐Ray Emission from the Galactic Ridge
journal, July 2008

  • Porter, Troy A.; Moskalenko, Igor V.; Strong, Andrew W.
  • The Astrophysical Journal, Vol. 682, Issue 1
  • DOI: 10.1086/589615

Submillimeter Continuum Observations of NGC 7538
journal, January 2004

  • Sandell, Goran; Sievers, Albrecht
  • The Astrophysical Journal, Vol. 600, Issue 1
  • DOI: 10.1086/379646

Precise Measurement of Cosmic‐Ray Proton and Helium Spectra with the BESS Spectrometer
journal, December 2000

  • Sanuki, T.; Motoki, M.; Matsumoto, H.
  • The Astrophysical Journal, Vol. 545, Issue 2
  • DOI: 10.1086/317873

Absolute Proper Motions of H 2 O Masers Away from the Galactic Plane Measured with VERA in the “Superbubble” Region NGC 281
journal, August 2007

  • Sato, Mayumi; Hirota, Tomoya; Honma, Mareki
  • Publications of the Astronomical Society of Japan, Vol. 59, Issue 4
  • DOI: 10.1093/pasj/59.4.743

Measurements of 0.2–20GeV/n cosmic-ray proton and helium spectra from 1997 through 2002 with the BESS spectrometer
journal, September 2007


Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds
journal, June 1998

  • Schlegel, David J.; Finkbeiner, Douglas P.; Davis, Marc
  • The Astrophysical Journal, Vol. 500, Issue 2
  • DOI: 10.1086/305772

The Ratio of H 2 Column Density to 12CO Intensity in the Vicinity of the Galactic Center
journal, October 1995

  • Sodroski, T. J.; Odegard, N.; Dwek, E.
  • The Astrophysical Journal, Vol. 452
  • DOI: 10.1086/176297

A Three‐dimensional Decomposition of the Infrared Emission from Dust in the Milky Way
journal, May 1997

  • Sodroski, T. J.; Odegard, N.; Arendt, R. G.
  • The Astrophysical Journal, Vol. 480, Issue 1
  • DOI: 10.1086/303961

Propagation of Cosmic‐Ray Nucleons in the Galaxy
journal, December 1998

  • Strong, Andrew W.; Moskalenko, Igor V.
  • The Astrophysical Journal, Vol. 509, Issue 1
  • DOI: 10.1086/306470

Cosmic-Ray Propagation and Interactions in the Galaxy
journal, November 2007


Diffuse Continuum Gamma Rays from the Galaxy
journal, July 2000

  • Strong, Andrew W.; Moskalenko, Igor V.; Reimer, Olaf
  • The Astrophysical Journal, Vol. 537, Issue 2
  • DOI: 10.1086/309038

Diffuse Galactic Continuum Gamma Rays: A Model Compatible with EGRET Data and Cosmic‐Ray Measurements
journal, October 2004

  • Strong, Andrew W.; Moskalenko, Igor V.; Reimer, Olaf
  • The Astrophysical Journal, Vol. 613, Issue 2
  • DOI: 10.1086/423193

The distribution of cosmic-ray sources in the Galaxy, γ-rays and the gradient in the CO-to-H 2 relation
journal, July 2004


Spatial origin of Galactic cosmic rays in diffusion models: I. Standard sources in the Galactic disk
journal, April 2003


A CO Survey of Giant Molecular Clouds near Cassiopeia A and NGC 7538
journal, July 2000

  • Ungerechts, H.; Umbanhowar, P.; Thaddeus, P.
  • The Astrophysical Journal, Vol. 537, Issue 1
  • DOI: 10.1086/308992

    Works referencing / citing this record:

    Gas dynamics in tidal dwarf galaxies: Disc formation at z = 0
    journal, December 2015


    Molecular gas in AzTEC/C159: a star-forming disk galaxy 1.3 Gyr after the Big Bang
    journal, July 2018


    Low co Luminosities in Dwarf Galaxies
    journal, May 2012


    Herschel Observations of the w3 gmc: Clues to the Formation of Clusters of High-Mass Stars
    journal, March 2013


    Main physics results of the ARGO-YBJ experiment
    journal, August 2014


    Gas dynamics in tidal dwarf galaxies: Disc formation at z = 0
    journal, December 2015


    Molecular gas in AzTEC/C159: a star-forming disk galaxy 1.3 Gyr after the Big Bang
    journal, July 2018


    Low co Luminosities in Dwarf Galaxies
    journal, May 2012


    Herschel Observations of the w3 gmc: Clues to the Formation of Clusters of High-Mass Stars
    journal, March 2013


    Main physics results of the ARGO-YBJ experiment
    journal, August 2014