Planck intermediate results: XXIII. Galactic plane emission components derived from Planck with ancillary data

R.D. Davies, Jussi Varis, Planck Collaboration

Research output: Contribution to journalArticleScientificpeer-review

8 Citations (Scopus)

Abstract

Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300° -> 0° -> 60° wherestar-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1° and 2°, which correspond to FWHM z-widths of 100-200pc at a typical distance of 6kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4-857 GHz) in combination with low-frequency radio data at 0.408-2.3 GHz plus WMAP data at 23-94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20-40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1% of the total 28.4 GHz emission in the longitude range l = 300° -> 0° -> 60°. The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ~ 100pc. The narrow synchrotron component has a low-frequency brightness spectral index ßsynch ~ -2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150pc in 3 * 105yr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of Tdust = 20.4 ± 0.4K, ßFIR = 1.94 ± 0.03 (> 353 GHz), and ßmm = 1.67 ± 0.02 (<353 GHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy.
Original languageEnglish
Article numberA13
Number of pages27
JournalAstronomy and Astrophysics
Volume580
DOIs
Publication statusPublished - 2015
MoE publication typeA1 Journal article-refereed

Fingerprint

synchrotrons
microwave emission
dust
longitude
spectral energy distribution
star formation
brightness
radio
galaxies
low frequencies
Cosmic Background Explorer satellite
ionized gases
Infrared Astronomy Satellite
supernova remnants
cosmic ray
recombination
energy
pulsars
cosmic rays
assembly

Keywords

  • ISM
  • galaxy
  • radiation mechnisms
  • radio continuum: ISM
  • submillimeter: ISM

Cite this

@article{f93151e62a214a5a8e71bf83b2baa5e1,
title = "Planck intermediate results: XXIII. Galactic plane emission components derived from Planck with ancillary data",
abstract = "Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300° -> 0° -> 60° wherestar-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1° and 2°, which correspond to FWHM z-widths of 100-200pc at a typical distance of 6kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4-857 GHz) in combination with low-frequency radio data at 0.408-2.3 GHz plus WMAP data at 23-94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20-40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1{\%} of the total 28.4 GHz emission in the longitude range l = 300° -> 0° -> 60°. The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ~ 100pc. The narrow synchrotron component has a low-frequency brightness spectral index {\ss}synch ~ -2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150pc in 3 * 105yr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of Tdust = 20.4 ± 0.4K, {\ss}FIR = 1.94 ± 0.03 (> 353 GHz), and {\ss}mm = 1.67 ± 0.02 (<353 GHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy.",
keywords = "ISM, galaxy, radiation mechnisms, radio continuum: ISM, submillimeter: ISM",
author = "R.D. Davies and Jussi Varis and {Planck Collaboration}",
year = "2015",
doi = "10.1051/0004-6361/201424434",
language = "English",
volume = "580",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",

}

Planck intermediate results : XXIII. Galactic plane emission components derived from Planck with ancillary data. / Davies, R.D.; Varis, Jussi; Planck Collaboration.

In: Astronomy and Astrophysics, Vol. 580, A13, 2015.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Planck intermediate results

T2 - XXIII. Galactic plane emission components derived from Planck with ancillary data

AU - Davies, R.D.

AU - Varis, Jussi

AU - Planck Collaboration

PY - 2015

Y1 - 2015

N2 - Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300° -> 0° -> 60° wherestar-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1° and 2°, which correspond to FWHM z-widths of 100-200pc at a typical distance of 6kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4-857 GHz) in combination with low-frequency radio data at 0.408-2.3 GHz plus WMAP data at 23-94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20-40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1% of the total 28.4 GHz emission in the longitude range l = 300° -> 0° -> 60°. The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ~ 100pc. The narrow synchrotron component has a low-frequency brightness spectral index ßsynch ~ -2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150pc in 3 * 105yr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of Tdust = 20.4 ± 0.4K, ßFIR = 1.94 ± 0.03 (> 353 GHz), and ßmm = 1.67 ± 0.02 (<353 GHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy.

AB - Planck data when combined with ancillary data provide a unique opportunity to separate the diffuse emission components of the inner Galaxy. The purpose of the paper is to elucidate the morphology of the various emission components in the strong star-formation region lying inside the solar radius and to clarify the relationship between the various components. The region of the Galactic plane covered is l = 300° -> 0° -> 60° wherestar-formation is highest and the emission is strong enough to make meaningful component separation. The latitude widths in this longitude range lie between 1° and 2°, which correspond to FWHM z-widths of 100-200pc at a typical distance of 6kpc. The four emission components studied here are synchrotron, free-free, anomalous microwave emission (AME), and thermal (vibrational) dust emission. These components are identified by constructing spectral energy distributions (SEDs) at positions along the Galactic plane using the wide frequency coverage of Planck (28.4-857 GHz) in combination with low-frequency radio data at 0.408-2.3 GHz plus WMAP data at 23-94 GHz, along with far-infrared (FIR) data from COBE-DIRBE and IRAS. The free-free component is determined from radio recombination line (RRL) data. AME is found to be comparable in brightness to the free-free emission on the Galactic plane in the frequency range 20-40 GHz with a width in latitude similar to that of the thermal dust; it comprises 45 ± 1% of the total 28.4 GHz emission in the longitude range l = 300° -> 0° -> 60°. The free-free component is the narrowest, reflecting the fact that it is produced by current star-formation as traced by the narrow distribution of OB stars. It is the dominant emission on the plane between 60 and 100 GHz. RRLs from this ionized gas are used to assess its distance, leading to a free-free z-width of FWHM ~ 100pc. The narrow synchrotron component has a low-frequency brightness spectral index ßsynch ~ -2.7 that is similar to the broad synchrotron component indicating that they are both populated by the cosmic ray electrons of the same spectral index. The width of this narrow synchrotron component is significantly larger than that of the other three components, suggesting that it is generated in an assembly of older supernova remnants that have expanded to sizes of order 150pc in 3 * 105yr; pulsars of a similar age have a similar spread in latitude. The thermal dust is identified in the SEDs with average parameters of Tdust = 20.4 ± 0.4K, ßFIR = 1.94 ± 0.03 (> 353 GHz), and ßmm = 1.67 ± 0.02 (<353 GHz). The latitude distributions of gamma-rays, CO, and the emission in high-frequency Planck bands have similar widths, showing that they are all indicators of the total gaseous matter on the plane in the inner Galaxy.

KW - ISM

KW - galaxy

KW - radiation mechnisms

KW - radio continuum: ISM

KW - submillimeter: ISM

U2 - 10.1051/0004-6361/201424434

DO - 10.1051/0004-6361/201424434

M3 - Article

VL - 580

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

M1 - A13

ER -