Hα and far-infrared emission within the early type spiral galaxy M81

Nicholas A. Devereux, George Jacoby, Robin Bruce Ciardullo

Research output: Contribution to journalArticle

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Abstract

New Hα imaging observations have revealed the morphology of the emission-line gas and permitted the first measurement of the total Ha luminosity for the early type spiral galaxy M81. The total Hα luminosity of M81 is (1.7±0.5)X107L. The Hα luminosity is dominated by emission from H II regions that are distributed approximately in an elliptical ring with a major axis diameter of 11 arcmin. A significant percentage, ∼17%, of the total Hα emission is associated with a curious feature in the central 3 arcmin of M81 that is best described as a nuclear spiral. A wide variety of sources that may be responsible for ionizing the nuclear spiral are evaluated including massive stars, old post-AGB stars, shocks, planetary nebulae, and x-rays. The Hα image is compared with a high resolution far-infrared image, obtained with the Infrared Astronomical Satellite (IRAS), in order to constrain the contribution of O and B stars to the far-infrared luminosity of M81. The correspondence between the Hα and far-infrared morphology is striking when both images are convolved to a common resolution of 105 arcsec. The far-infrared luminosity, L(FIR), and the Hα luminosity, L(Hα), have been measured at 85 independent locations within M81 and the histogram of L(FIR)/L(Hα) ratios is remarkably similar to that determined for Galactic H II regions. Approximately 75% of the far-infrared luminosity of M81 is radiated by dust with temperatures greater than expected for cirrus, but similar to the temperatures measured by IRAS for Galactic and extragalactic H II regions. The results indicate that the majority, ∼70%, of the far infrared and Hα luminosity of M81 is produced by high mass stars located in the star forming ring. The origin of the remaining 30% of the far-infrared and Hα luminosity, that is co-extensive with the bulge, is ambiguous in that it could be powered equally well by young massive stars or old bulge stars.

Original languageEnglish (US)
Pages (from-to)1115-1128
Number of pages14
JournalAstronomical Journal
Volume110
Issue number3
StatePublished - Sep 1 1995

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spiral galaxies
luminosity
H II regions
astronomical satellites
massive stars
stars
O stars
B stars
asymptotic giant branch stars
rings
planetary nebulae
cirrus
histogram
histograms
dust
temperature
shock
high resolution
gases
gas

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Devereux, Nicholas A. ; Jacoby, George ; Ciardullo, Robin Bruce. / Hα and far-infrared emission within the early type spiral galaxy M81. In: Astronomical Journal. 1995 ; Vol. 110, No. 3. pp. 1115-1128.
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title = "Hα and far-infrared emission within the early type spiral galaxy M81",
abstract = "New Hα imaging observations have revealed the morphology of the emission-line gas and permitted the first measurement of the total Ha luminosity for the early type spiral galaxy M81. The total Hα luminosity of M81 is (1.7±0.5)X107L⊙. The Hα luminosity is dominated by emission from H II regions that are distributed approximately in an elliptical ring with a major axis diameter of 11 arcmin. A significant percentage, ∼17{\%}, of the total Hα emission is associated with a curious feature in the central 3 arcmin of M81 that is best described as a nuclear spiral. A wide variety of sources that may be responsible for ionizing the nuclear spiral are evaluated including massive stars, old post-AGB stars, shocks, planetary nebulae, and x-rays. The Hα image is compared with a high resolution far-infrared image, obtained with the Infrared Astronomical Satellite (IRAS), in order to constrain the contribution of O and B stars to the far-infrared luminosity of M81. The correspondence between the Hα and far-infrared morphology is striking when both images are convolved to a common resolution of 105 arcsec. The far-infrared luminosity, L(FIR), and the Hα luminosity, L(Hα), have been measured at 85 independent locations within M81 and the histogram of L(FIR)/L(Hα) ratios is remarkably similar to that determined for Galactic H II regions. Approximately 75{\%} of the far-infrared luminosity of M81 is radiated by dust with temperatures greater than expected for cirrus, but similar to the temperatures measured by IRAS for Galactic and extragalactic H II regions. The results indicate that the majority, ∼70{\%}, of the far infrared and Hα luminosity of M81 is produced by high mass stars located in the star forming ring. The origin of the remaining 30{\%} of the far-infrared and Hα luminosity, that is co-extensive with the bulge, is ambiguous in that it could be powered equally well by young massive stars or old bulge stars.",
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Hα and far-infrared emission within the early type spiral galaxy M81. / Devereux, Nicholas A.; Jacoby, George; Ciardullo, Robin Bruce.

In: Astronomical Journal, Vol. 110, No. 3, 01.09.1995, p. 1115-1128.

Research output: Contribution to journalArticle

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T1 - Hα and far-infrared emission within the early type spiral galaxy M81

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AU - Ciardullo, Robin Bruce

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N2 - New Hα imaging observations have revealed the morphology of the emission-line gas and permitted the first measurement of the total Ha luminosity for the early type spiral galaxy M81. The total Hα luminosity of M81 is (1.7±0.5)X107L⊙. The Hα luminosity is dominated by emission from H II regions that are distributed approximately in an elliptical ring with a major axis diameter of 11 arcmin. A significant percentage, ∼17%, of the total Hα emission is associated with a curious feature in the central 3 arcmin of M81 that is best described as a nuclear spiral. A wide variety of sources that may be responsible for ionizing the nuclear spiral are evaluated including massive stars, old post-AGB stars, shocks, planetary nebulae, and x-rays. The Hα image is compared with a high resolution far-infrared image, obtained with the Infrared Astronomical Satellite (IRAS), in order to constrain the contribution of O and B stars to the far-infrared luminosity of M81. The correspondence between the Hα and far-infrared morphology is striking when both images are convolved to a common resolution of 105 arcsec. The far-infrared luminosity, L(FIR), and the Hα luminosity, L(Hα), have been measured at 85 independent locations within M81 and the histogram of L(FIR)/L(Hα) ratios is remarkably similar to that determined for Galactic H II regions. Approximately 75% of the far-infrared luminosity of M81 is radiated by dust with temperatures greater than expected for cirrus, but similar to the temperatures measured by IRAS for Galactic and extragalactic H II regions. The results indicate that the majority, ∼70%, of the far infrared and Hα luminosity of M81 is produced by high mass stars located in the star forming ring. The origin of the remaining 30% of the far-infrared and Hα luminosity, that is co-extensive with the bulge, is ambiguous in that it could be powered equally well by young massive stars or old bulge stars.

AB - New Hα imaging observations have revealed the morphology of the emission-line gas and permitted the first measurement of the total Ha luminosity for the early type spiral galaxy M81. The total Hα luminosity of M81 is (1.7±0.5)X107L⊙. The Hα luminosity is dominated by emission from H II regions that are distributed approximately in an elliptical ring with a major axis diameter of 11 arcmin. A significant percentage, ∼17%, of the total Hα emission is associated with a curious feature in the central 3 arcmin of M81 that is best described as a nuclear spiral. A wide variety of sources that may be responsible for ionizing the nuclear spiral are evaluated including massive stars, old post-AGB stars, shocks, planetary nebulae, and x-rays. The Hα image is compared with a high resolution far-infrared image, obtained with the Infrared Astronomical Satellite (IRAS), in order to constrain the contribution of O and B stars to the far-infrared luminosity of M81. The correspondence between the Hα and far-infrared morphology is striking when both images are convolved to a common resolution of 105 arcsec. The far-infrared luminosity, L(FIR), and the Hα luminosity, L(Hα), have been measured at 85 independent locations within M81 and the histogram of L(FIR)/L(Hα) ratios is remarkably similar to that determined for Galactic H II regions. Approximately 75% of the far-infrared luminosity of M81 is radiated by dust with temperatures greater than expected for cirrus, but similar to the temperatures measured by IRAS for Galactic and extragalactic H II regions. The results indicate that the majority, ∼70%, of the far infrared and Hα luminosity of M81 is produced by high mass stars located in the star forming ring. The origin of the remaining 30% of the far-infrared and Hα luminosity, that is co-extensive with the bulge, is ambiguous in that it could be powered equally well by young massive stars or old bulge stars.

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