Star formation in NGC 5194 (M51a)

The panchromatic view from Galex to Spitzer

D. Calzett, R. C. Kennicutt, L. Bianchi, D. A. Thilker, D. A. Dale, C. W. Engelbracht, C. Leitherer, M. J. Meyer, M. L. Sosey, M. Mutchler, M. W. Regan, M. D. Thornley, L. Armus, G. J. Bendo, S. Boissier, A. Boselli, B. T. Draine, K. D. Gordon, G. Helou, D. J. Hollenbach & 15 others L. Kewley, B. F. Madore, D. C. Martin, E. J. Murphy, G. H. Rieke, M. J. Rieke, H. Roussel, K. Sheth, J. D. Smith, F. Walter, B. A. White, Sukyoung Yi, N. Z. Scoville, M. Polletta, D. Lindler

Research output: Contribution to journalArticle

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Abstract

Far-ultraviolet to far-infrared images of the nearby galaxy NGC 5194 (M51a), from a combination of space-based (Spitzer, GALEX, and Hubble Space Telescope) and ground-based data, are used to investigate local and global star formation and the impact of dust extinction. The Spitzer data provide unprecedented spatial detail in the infrared, down to sizes ∼500 pc at the distance of NGC 5194. The multiwavelength set is used to trace the relatively young stellar populations, the ionized gas, and the dust absorption and emission in H II-emitting knots, over 3 orders of magnitude in wavelength range. As is common in spiral galaxies, dust extinction is high in the center of the galaxy (Av ∼ 3.5 mag), but its mean value decreases steadily as a function of galactocentric distance, as derived from both gas emission and stellar continuum properties. In the IR/UV-UV color plane, the NGC 5194 H II knots show the same trend observed for normal star-forming galaxies, having a much larger dispersion (∼ 1 dex peak to peak) than starburst galaxies. We identify the dispersion as due to the UV emission predominantly tracing the evolved, nonionizing stellar population, up to ages ∼50-100 Myr. While in starbursts the UV light traces the current star formation rate (SFR), in NGC 5194 it traces a combination of current and recent past SFRs. Possibly, mechanical feedback from supernovae is less effective at removing dust and gas from the star formation volume in normal star-forming galaxies than in starbursts because of the typically lower SFR densities in the former. The application of the starburst opacity curve for recovering the intrinsic UV emission (and deriving SFRs) in local and distant galaxies appears therefore appropriate only for SFR densities ≳1 M yr-1 kpc-2. Unlike the UV emission, the monochromatic 24 μm luminosity is an accurate local SFR tracer for the 24 μm knots in NGC 5194, with a peak-to-peak dispersion of less than a factor of 3 relative to hydrogen emission line tracers; this suggests that the 24 μm emission carriers are mainly heated by the young, ionizing stars. However, preliminary results show that the ratio of the 24 μm emission to the SFR varies by a factor of a few from galaxy to galaxy; this variation needs to be understood and carefully quantified before the 24 μm luminosity can be used as an SFR tracer for galaxy populations. While also correlated with star formation, the 8 μm emission is not directly proportional to the number of ionizing photons; it is overluminous, by up to a factor of ∼2, relative to the galaxy's average in weakly ionized regions and is underluminous, by up to a factor of ∼3, in strongly ionized regions. This confirms earlier suggestions that the carriers of the 8 μm emission are heated by more than one mechanism.

Original languageEnglish
Pages (from-to)871-893
Number of pages23
JournalAstrophysical Journal
Volume633
Issue number2 I
DOIs
Publication statusPublished - 2005 Nov 10

Fingerprint

star formation
star formation rate
galaxies
dust
tracers
tracer
stars
extinction
luminosity
gas
young population
Space Infrared Telescope Facility
starburst galaxies
ionized gases
spiral galaxies
tracing
opacity
gases
Hubble Space Telescope
suggestion

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Calzett, D., Kennicutt, R. C., Bianchi, L., Thilker, D. A., Dale, D. A., Engelbracht, C. W., ... Lindler, D. (2005). Star formation in NGC 5194 (M51a): The panchromatic view from Galex to Spitzer. Astrophysical Journal, 633(2 I), 871-893. https://doi.org/10.1086/466518
Calzett, D. ; Kennicutt, R. C. ; Bianchi, L. ; Thilker, D. A. ; Dale, D. A. ; Engelbracht, C. W. ; Leitherer, C. ; Meyer, M. J. ; Sosey, M. L. ; Mutchler, M. ; Regan, M. W. ; Thornley, M. D. ; Armus, L. ; Bendo, G. J. ; Boissier, S. ; Boselli, A. ; Draine, B. T. ; Gordon, K. D. ; Helou, G. ; Hollenbach, D. J. ; Kewley, L. ; Madore, B. F. ; Martin, D. C. ; Murphy, E. J. ; Rieke, G. H. ; Rieke, M. J. ; Roussel, H. ; Sheth, K. ; Smith, J. D. ; Walter, F. ; White, B. A. ; Yi, Sukyoung ; Scoville, N. Z. ; Polletta, M. ; Lindler, D. / Star formation in NGC 5194 (M51a) : The panchromatic view from Galex to Spitzer. In: Astrophysical Journal. 2005 ; Vol. 633, No. 2 I. pp. 871-893.
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abstract = "Far-ultraviolet to far-infrared images of the nearby galaxy NGC 5194 (M51a), from a combination of space-based (Spitzer, GALEX, and Hubble Space Telescope) and ground-based data, are used to investigate local and global star formation and the impact of dust extinction. The Spitzer data provide unprecedented spatial detail in the infrared, down to sizes ∼500 pc at the distance of NGC 5194. The multiwavelength set is used to trace the relatively young stellar populations, the ionized gas, and the dust absorption and emission in H II-emitting knots, over 3 orders of magnitude in wavelength range. As is common in spiral galaxies, dust extinction is high in the center of the galaxy (Av ∼ 3.5 mag), but its mean value decreases steadily as a function of galactocentric distance, as derived from both gas emission and stellar continuum properties. In the IR/UV-UV color plane, the NGC 5194 H II knots show the same trend observed for normal star-forming galaxies, having a much larger dispersion (∼ 1 dex peak to peak) than starburst galaxies. We identify the dispersion as due to the UV emission predominantly tracing the evolved, nonionizing stellar population, up to ages ∼50-100 Myr. While in starbursts the UV light traces the current star formation rate (SFR), in NGC 5194 it traces a combination of current and recent past SFRs. Possibly, mechanical feedback from supernovae is less effective at removing dust and gas from the star formation volume in normal star-forming galaxies than in starbursts because of the typically lower SFR densities in the former. The application of the starburst opacity curve for recovering the intrinsic UV emission (and deriving SFRs) in local and distant galaxies appears therefore appropriate only for SFR densities ≳1 M⊙ yr-1 kpc-2. Unlike the UV emission, the monochromatic 24 μm luminosity is an accurate local SFR tracer for the 24 μm knots in NGC 5194, with a peak-to-peak dispersion of less than a factor of 3 relative to hydrogen emission line tracers; this suggests that the 24 μm emission carriers are mainly heated by the young, ionizing stars. However, preliminary results show that the ratio of the 24 μm emission to the SFR varies by a factor of a few from galaxy to galaxy; this variation needs to be understood and carefully quantified before the 24 μm luminosity can be used as an SFR tracer for galaxy populations. While also correlated with star formation, the 8 μm emission is not directly proportional to the number of ionizing photons; it is overluminous, by up to a factor of ∼2, relative to the galaxy's average in weakly ionized regions and is underluminous, by up to a factor of ∼3, in strongly ionized regions. This confirms earlier suggestions that the carriers of the 8 μm emission are heated by more than one mechanism.",
author = "D. Calzett and Kennicutt, {R. C.} and L. Bianchi and Thilker, {D. A.} and Dale, {D. A.} and Engelbracht, {C. W.} and C. Leitherer and Meyer, {M. J.} and Sosey, {M. L.} and M. Mutchler and Regan, {M. W.} and Thornley, {M. D.} and L. Armus and Bendo, {G. J.} and S. Boissier and A. Boselli and Draine, {B. T.} and Gordon, {K. D.} and G. Helou and Hollenbach, {D. J.} and L. Kewley and Madore, {B. F.} and Martin, {D. C.} and Murphy, {E. J.} and Rieke, {G. H.} and Rieke, {M. J.} and H. Roussel and K. Sheth and Smith, {J. D.} and F. Walter and White, {B. A.} and Sukyoung Yi and Scoville, {N. Z.} and M. Polletta and D. Lindler",
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Calzett, D, Kennicutt, RC, Bianchi, L, Thilker, DA, Dale, DA, Engelbracht, CW, Leitherer, C, Meyer, MJ, Sosey, ML, Mutchler, M, Regan, MW, Thornley, MD, Armus, L, Bendo, GJ, Boissier, S, Boselli, A, Draine, BT, Gordon, KD, Helou, G, Hollenbach, DJ, Kewley, L, Madore, BF, Martin, DC, Murphy, EJ, Rieke, GH, Rieke, MJ, Roussel, H, Sheth, K, Smith, JD, Walter, F, White, BA, Yi, S, Scoville, NZ, Polletta, M & Lindler, D 2005, 'Star formation in NGC 5194 (M51a): The panchromatic view from Galex to Spitzer', Astrophysical Journal, vol. 633, no. 2 I, pp. 871-893. https://doi.org/10.1086/466518

Star formation in NGC 5194 (M51a) : The panchromatic view from Galex to Spitzer. / Calzett, D.; Kennicutt, R. C.; Bianchi, L.; Thilker, D. A.; Dale, D. A.; Engelbracht, C. W.; Leitherer, C.; Meyer, M. J.; Sosey, M. L.; Mutchler, M.; Regan, M. W.; Thornley, M. D.; Armus, L.; Bendo, G. J.; Boissier, S.; Boselli, A.; Draine, B. T.; Gordon, K. D.; Helou, G.; Hollenbach, D. J.; Kewley, L.; Madore, B. F.; Martin, D. C.; Murphy, E. J.; Rieke, G. H.; Rieke, M. J.; Roussel, H.; Sheth, K.; Smith, J. D.; Walter, F.; White, B. A.; Yi, Sukyoung; Scoville, N. Z.; Polletta, M.; Lindler, D.

In: Astrophysical Journal, Vol. 633, No. 2 I, 10.11.2005, p. 871-893.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Star formation in NGC 5194 (M51a)

T2 - The panchromatic view from Galex to Spitzer

AU - Calzett, D.

AU - Kennicutt, R. C.

AU - Bianchi, L.

AU - Thilker, D. A.

AU - Dale, D. A.

AU - Engelbracht, C. W.

AU - Leitherer, C.

AU - Meyer, M. J.

AU - Sosey, M. L.

AU - Mutchler, M.

AU - Regan, M. W.

AU - Thornley, M. D.

AU - Armus, L.

AU - Bendo, G. J.

AU - Boissier, S.

AU - Boselli, A.

AU - Draine, B. T.

AU - Gordon, K. D.

AU - Helou, G.

AU - Hollenbach, D. J.

AU - Kewley, L.

AU - Madore, B. F.

AU - Martin, D. C.

AU - Murphy, E. J.

AU - Rieke, G. H.

AU - Rieke, M. J.

AU - Roussel, H.

AU - Sheth, K.

AU - Smith, J. D.

AU - Walter, F.

AU - White, B. A.

AU - Yi, Sukyoung

AU - Scoville, N. Z.

AU - Polletta, M.

AU - Lindler, D.

PY - 2005/11/10

Y1 - 2005/11/10

N2 - Far-ultraviolet to far-infrared images of the nearby galaxy NGC 5194 (M51a), from a combination of space-based (Spitzer, GALEX, and Hubble Space Telescope) and ground-based data, are used to investigate local and global star formation and the impact of dust extinction. The Spitzer data provide unprecedented spatial detail in the infrared, down to sizes ∼500 pc at the distance of NGC 5194. The multiwavelength set is used to trace the relatively young stellar populations, the ionized gas, and the dust absorption and emission in H II-emitting knots, over 3 orders of magnitude in wavelength range. As is common in spiral galaxies, dust extinction is high in the center of the galaxy (Av ∼ 3.5 mag), but its mean value decreases steadily as a function of galactocentric distance, as derived from both gas emission and stellar continuum properties. In the IR/UV-UV color plane, the NGC 5194 H II knots show the same trend observed for normal star-forming galaxies, having a much larger dispersion (∼ 1 dex peak to peak) than starburst galaxies. We identify the dispersion as due to the UV emission predominantly tracing the evolved, nonionizing stellar population, up to ages ∼50-100 Myr. While in starbursts the UV light traces the current star formation rate (SFR), in NGC 5194 it traces a combination of current and recent past SFRs. Possibly, mechanical feedback from supernovae is less effective at removing dust and gas from the star formation volume in normal star-forming galaxies than in starbursts because of the typically lower SFR densities in the former. The application of the starburst opacity curve for recovering the intrinsic UV emission (and deriving SFRs) in local and distant galaxies appears therefore appropriate only for SFR densities ≳1 M⊙ yr-1 kpc-2. Unlike the UV emission, the monochromatic 24 μm luminosity is an accurate local SFR tracer for the 24 μm knots in NGC 5194, with a peak-to-peak dispersion of less than a factor of 3 relative to hydrogen emission line tracers; this suggests that the 24 μm emission carriers are mainly heated by the young, ionizing stars. However, preliminary results show that the ratio of the 24 μm emission to the SFR varies by a factor of a few from galaxy to galaxy; this variation needs to be understood and carefully quantified before the 24 μm luminosity can be used as an SFR tracer for galaxy populations. While also correlated with star formation, the 8 μm emission is not directly proportional to the number of ionizing photons; it is overluminous, by up to a factor of ∼2, relative to the galaxy's average in weakly ionized regions and is underluminous, by up to a factor of ∼3, in strongly ionized regions. This confirms earlier suggestions that the carriers of the 8 μm emission are heated by more than one mechanism.

AB - Far-ultraviolet to far-infrared images of the nearby galaxy NGC 5194 (M51a), from a combination of space-based (Spitzer, GALEX, and Hubble Space Telescope) and ground-based data, are used to investigate local and global star formation and the impact of dust extinction. The Spitzer data provide unprecedented spatial detail in the infrared, down to sizes ∼500 pc at the distance of NGC 5194. The multiwavelength set is used to trace the relatively young stellar populations, the ionized gas, and the dust absorption and emission in H II-emitting knots, over 3 orders of magnitude in wavelength range. As is common in spiral galaxies, dust extinction is high in the center of the galaxy (Av ∼ 3.5 mag), but its mean value decreases steadily as a function of galactocentric distance, as derived from both gas emission and stellar continuum properties. In the IR/UV-UV color plane, the NGC 5194 H II knots show the same trend observed for normal star-forming galaxies, having a much larger dispersion (∼ 1 dex peak to peak) than starburst galaxies. We identify the dispersion as due to the UV emission predominantly tracing the evolved, nonionizing stellar population, up to ages ∼50-100 Myr. While in starbursts the UV light traces the current star formation rate (SFR), in NGC 5194 it traces a combination of current and recent past SFRs. Possibly, mechanical feedback from supernovae is less effective at removing dust and gas from the star formation volume in normal star-forming galaxies than in starbursts because of the typically lower SFR densities in the former. The application of the starburst opacity curve for recovering the intrinsic UV emission (and deriving SFRs) in local and distant galaxies appears therefore appropriate only for SFR densities ≳1 M⊙ yr-1 kpc-2. Unlike the UV emission, the monochromatic 24 μm luminosity is an accurate local SFR tracer for the 24 μm knots in NGC 5194, with a peak-to-peak dispersion of less than a factor of 3 relative to hydrogen emission line tracers; this suggests that the 24 μm emission carriers are mainly heated by the young, ionizing stars. However, preliminary results show that the ratio of the 24 μm emission to the SFR varies by a factor of a few from galaxy to galaxy; this variation needs to be understood and carefully quantified before the 24 μm luminosity can be used as an SFR tracer for galaxy populations. While also correlated with star formation, the 8 μm emission is not directly proportional to the number of ionizing photons; it is overluminous, by up to a factor of ∼2, relative to the galaxy's average in weakly ionized regions and is underluminous, by up to a factor of ∼3, in strongly ionized regions. This confirms earlier suggestions that the carriers of the 8 μm emission are heated by more than one mechanism.

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Calzett D, Kennicutt RC, Bianchi L, Thilker DA, Dale DA, Engelbracht CW et al. Star formation in NGC 5194 (M51a): The panchromatic view from Galex to Spitzer. Astrophysical Journal. 2005 Nov 10;633(2 I):871-893. https://doi.org/10.1086/466518