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

Title: The cosmic-ray and gas content of the Cygnus region as measured in γ -rays by the Fermi Large Area Telescope

Journal Article · · Astronomy and Astrophysics
 [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States); et al.

Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral Hi emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.) +0.15 -0.84 (syst.)] × 10-26 photons s-1 sr-1 H-atom-1, where the systematic error is dominated by the uncertainty on the Hi opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average XCO = N(H2)/WCO ratio is found to be [1.68 ± 0.05 (stat.) +0.87 -0.10 (Hi opacity)] × 1020 molecules cm-2 (K km s-1)-1, consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ~ 40% of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 +5 -1 × 106M⊙ at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and high masses of the interstellar clouds, the cosmic-ray population in the Cygnus complex averaged over a few hundred parsecs is similar to that of the local interstellar space.

Research Organization:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Organization:
USDOE
Contributing Organization:
Fermi LAT Collaboration
Grant/Contract Number:
AC02-76SF00515
OSTI ID:
1356757
Journal Information:
Astronomy and Astrophysics, Vol. 538; ISSN 0004-6361
Publisher:
EDP SciencesCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 38 works
Citation information provided by
Web of Science

References (62)

The Cygnus superbubble revisited journal May 2001
A Self‐Absorption Census of Cold H i Clouds in the Canadian Galactic Plane Survey journal June 2005
Discovery of TeV Gamma-Ray Emission from the Cygnus Region of the Galaxy journal February 2007
DETECTION OF GAMMA-RAY EMISSION FROM THE STARBURST GALAXIES M82 AND NGC 253 WITH THE LARGE AREA TELESCOPE ON FERMI journal January 2010
Measurement of the Cosmic Ray e + + e Spectrum from 20 GeV to 1 TeV with the Fermi Large Area Telescope journal May 2009
Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds journal June 1998
A survey of interstellar H I from L-alpha absorption measurements. II journal August 1978
Observations of the Large Magellanic Cloud with Fermi journal March 2010
FERMI LARGE AREA TELESCOPE FIRST SOURCE CATALOG journal May 2010
The X-ray superbubble in Cygnus journal May 1980
THE FIRST FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS journal March 2010
PRECISE γ-RAY TIMING AND RADIO OBSERVATIONS OF 17 FERMI γ-RAY PULSARS journal April 2011
THE OUTER DISK OF THE MILKY WAY SEEN IN λ21 cm ABSORPTION journal March 2009
A Study of Cygnus OB2: Pointing the Way toward Finding Our Galaxy’s Super–Star Clusters journal November 2003
Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived from First-Year Fermi Large Area Telescope Data journal March 2010
CONSTRAINTS ON THE COSMIC-RAY DENSITY GRADIENT BEYOND THE SOLAR CIRCLE FROM FERMI γ-RAY OBSERVATIONS OF THE THIRD GALACTIC QUADRANT journal December 2010
Diffuse Gamma-Ray Emission in the Galactic Plane from Cosmic-Ray, Matter, and Photon Interactions journal October 1993
New perspectives on the supernova remnant G78.2+2.1 journal August 2008
C + detection of warm dark gas in diffuse clouds journal October 2010
EGRET Observations of the Diffuse Gamma‐Ray Emission from the Galactic Plane journal May 1997
Inverse Compton Origin of the Hard X‐Ray and Soft Gamma‐Ray Emission from the Galactic Ridge journal July 2008
EIGHT γ-RAY PULSARS DISCOVERED IN BLIND FREQUENCY SEARCHES OF FERMI LAT DATA journal November 2010
FERMI OBSERVATIONS OF CASSIOPEIA AND CEPHEUS: DIFFUSE GAMMA-RAY EMISSION IN THE OUTER GALAXY journal January 2010
A Three‐dimensional Decomposition of the Infrared Emission from Dust in the Milky Way journal May 1997
Planck early results. XIX. All-sky temperature and dust optical depth from Planck and IRAS. Constraints on the “dark gas” in our Galaxy journal December 2011
Propagation of Cosmic‐Ray Nucleons in the Galaxy journal December 1998
A Cocoon of Freshly Accelerated Cosmic Rays Detected by Fermi in the Cygnus Superbubble journal November 2011
The on-orbit calibration of the Fermi Large Area Telescope journal October 2009
Unveiling Extensive Clouds of Dark Gas in the Solar Neighborhood journal February 2005
Characteristics of new star cluster candidates in the Cygnus area journal September 2002
A synthetic view on structure and evolution of the Milky Way journal October 2003
The link between molecular cloud structure and turbulence journal March 2011
The relationship between infrared, optical, and ultraviolet extinction journal October 1989
New $\mathsf{\lambda}$6 cm observations of the Cygnus Loop journal February 2006
A Measurement of the Spatial Distribution of Diffuse TeV Gamma‐Ray Emission from the Galactic Plane with Milagro journal December 2008
FERMI LAT OBSERVATION OF DIFFUSE GAMMA RAYS PRODUCED THROUGH INTERACTIONS BETWEEN LOCAL INTERSTELLAR MATTER AND HIGH-ENERGY COSMIC RAYS journal September 2009
Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3 journal November 2009
THE LARGE AREA TELESCOPE ON THE FERMI GAMMA-RAY SPACE TELESCOPE MISSION journal May 2009
The Canadian Galactic Plane Survey journal June 2003
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
CH, CO, and E ( BV ) as Molecular Gas Tracers in a Translucent Cloud journal April 2003
A Full‐Sky Hα Template for Microwave Foreground Prediction journal June 2003
Diffuse Galactic Continuum Gamma Rays: A Model Compatible with EGRET Data and Cosmic‐Ray Measurements journal October 2004
The total-to-selective extinction ratio determined from near IR photometry of OB stars journal April 2003
THE BALLOON-BORNE LARGE APERTURE SUBMILLIMETER TELESCOPE (BLAST) 2005: A 10 deg 2 SURVEY OF STAR FORMATION IN CYGNUS X journal January 2011
Gamma rays from halos around stars and the Sun journal April 2007
The Two Micron All Sky Survey (2MASS) journal February 2006
SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE ( WMAP ) OBSERVATIONS: GALACTIC FOREGROUND EMISSION journal January 2011
Detection of 16 Gamma-Ray Pulsars Through Blind Frequency Searches Using the Fermi LAT journal July 2009
PULSED GAMMA-RAYS FROM PSR J2021+3651 WITH THE FERMI LARGE AREA TELESCOPE journal July 2009
A radio catalog of Galactic HII regions for applications from decimeter to millimeter wavelengths journal December 2002
New very massive stars in Cygnus OB2 journal June 2008
The dark Molecular gas journal May 2010
The structure of molecular clouds - I. All-sky near-infrared extinction maps journal May 2009
The Milky Way in Molecular Clouds: A New Complete CO Survey journal February 2001
A new view of the Cygnus X region: KOSMA $\mathsf{^{13}}$CO 2 $\to$ 1, 3 $\to$ 2, and $\mathsf{^{12}}$CO 3 $\to$ 2 imaging journal September 2006
The Millennium Arecibo 21 Centimeter Absorption‐Line Survey. II. Properties of the Warm and Cold Neutral Media journal April 2003
FERMI LARGE AREA TELESCOPE OBSERVATIONS OF THE CYGNUS LOOP SUPERNOVA REMNANT journal October 2011
tempo2, a new pulsar-timing package - I. An overview: tempo2, a new pulsar-timing package - I. Overview journal May 2006
Nuclear enhancement factor in calculation of Galactic diffuse gamma-rays: A new estimate with DPMJET-3 journal June 2009
Cosmic-Ray Propagation and Interactions in the Galaxy journal November 2007
Dust energetics in the gas phases of the interstellar medium - The origin of the Galactic large-scale far-infrared emission observed by IRAS journal January 1989

Cited By (8)

Cosmic rays, gas and dust in nearby anticentre clouds: I. CO-to-H journal May 2017
FERMI LARGE AREA TELESCOPE SECOND SOURCE CATALOG journal March 2012
On the radial distribution of Galactic cosmic rays journal July 2016
Gamma-ray puzzle in Cygnus X: Implications for high-energy neutrinos journal August 2017
Cosmic Rays in Superbubbles journal July 2019
The Structure of Dark Molecular Gas in the Galaxy. II. Physical State of “CO-dark” Gas in the Perseus Arm journal September 2019
Study of the diffuse gamma-ray emission from the Galactic plane with ARGO-YBJ text January 2015
On the radial distribution of Galactic cosmic rays text January 2016

Similar Records

Planck intermediate results: XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck $\star$
Journal Article · Wed Sep 30 00:00:00 EDT 2015 · Astronomy and Astrophysics · OSTI ID:1356757

QUANTIFYING THE INTERSTELLAR MEDIUM AND COSMIC RAYS IN THE MBM 53, 54, AND 55 MOLECULAR CLOUDS AND THE PEGASUS LOOP USING FERMI -LAT GAMMA-RAY OBSERVATIONS
Journal Article · Tue Dec 20 00:00:00 EST 2016 · The Astrophysical Journal (Online) · OSTI ID:1356757

Detection of the Small Magellanic Cloud in gamma-rays with  Fermi /LAT
Journal Article · Mon Nov 01 00:00:00 EDT 2010 · Astronomy and Astrophysics · OSTI ID:1356757