A mapping survey of the 13CO and 12CO emission in galaxies

Timothy A D Paglione, W. F. Wall, Judith S. Young, Mark H. Heyer, Michael Richard, Michael Goldstein, Zeke Kaufman, Julie Nantais, Gretchen Perry

Resultado de la investigación: Review article

83 Citas (Scopus)

Resumen

We present spectra of the extended 12CO and 13CO J = 1 → 0 emission along the major axes of 17 nearby galaxies. Spatial variations in the ratio of CO and 13CO integrated intensities, ℛ, are found in nearly every galaxy observed. There is an overall variation in ℛ of 20%-40% from the inner 2 kpc to the disk. Roughly one-third of the survey galaxies have such gradients in ℛ detected above the 2 σ confidence level. Though some galaxies show a lower central value of ℛ, on average ℛ inside 2 kpc is 10%-30% higher than ℛ outside of 2 kpc. The average CO/13CO intensity ratio within the central 2 kpc of the survey sources is 11.6 ± 0.4 (based on the noise) ± 1.5 (based on systematic uncertainties estimated from daily variations in CO and 13CO intensities). The 1 σ dispersion in ℛ between galactic nuclei of 4.2 is also quite large. The average value of ℛ outside 2 kpc is 9.8 ± 0.6 ± 1.2 with a standard deviation of 4.5. An increase in the CO/13CO intensity ratio from disk to nucleus may imply that the conversion factor between CO intensity and H2 column density, X, is lower in galactic nuclei. In addition, variations in physical conditions, most notably the gas kinetic temperature, affect both ℛ and X. Abundance variations probably do not cause the gradient in ℛ, though we do not rule out a decrease in effective cloud column densities in galactic nuclei possibly caused by destructive starburst superwinds. A modest rise in temperature (less than a factor of 2 or 3) from outside a 2 kpc radius toward the nucleus can easily account for the observed gradient. These results support previous work implying that X is lower in the center of the Milky Way and probably most galactic nuclei. Therefore, calculating H2 masses using the standard Galactic X-factor, especially within the central few kiloparsecs of galaxies, overestimates the true mass by factors of a few. The standard X-factor still appears to be appropriate for galactic disks.

Idioma originalEnglish
Páginas (desde-hasta)183-200
Número de páginas18
PublicaciónAstrophysical Journal, Supplement Series
Volumen135
N.º2
DOI
EstadoPublished - ago 2001

Huella dactilar

galactic nuclei
galaxies
diurnal variation
spatial variation
temperature
gradients
kinetics
gas
nuclei
confidence
standard deviation
radii
causes
gases
physical conditions

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Citar esto

Paglione, T. A. D., Wall, W. F., Young, J. S., Heyer, M. H., Richard, M., Goldstein, M., ... Perry, G. (2001). A mapping survey of the 13CO and 12CO emission in galaxies. Astrophysical Journal, Supplement Series, 135(2), 183-200. https://doi.org/10.1086/321785
Paglione, Timothy A D ; Wall, W. F. ; Young, Judith S. ; Heyer, Mark H. ; Richard, Michael ; Goldstein, Michael ; Kaufman, Zeke ; Nantais, Julie ; Perry, Gretchen. / A mapping survey of the 13CO and 12CO emission in galaxies. En: Astrophysical Journal, Supplement Series. 2001 ; Vol. 135, N.º 2. pp. 183-200.
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title = "A mapping survey of the 13CO and 12CO emission in galaxies",
abstract = "We present spectra of the extended 12CO and 13CO J = 1 → 0 emission along the major axes of 17 nearby galaxies. Spatial variations in the ratio of CO and 13CO integrated intensities, ℛ, are found in nearly every galaxy observed. There is an overall variation in ℛ of 20{\%}-40{\%} from the inner 2 kpc to the disk. Roughly one-third of the survey galaxies have such gradients in ℛ detected above the 2 σ confidence level. Though some galaxies show a lower central value of ℛ, on average ℛ inside 2 kpc is 10{\%}-30{\%} higher than ℛ outside of 2 kpc. The average CO/13CO intensity ratio within the central 2 kpc of the survey sources is 11.6 ± 0.4 (based on the noise) ± 1.5 (based on systematic uncertainties estimated from daily variations in CO and 13CO intensities). The 1 σ dispersion in ℛ between galactic nuclei of 4.2 is also quite large. The average value of ℛ outside 2 kpc is 9.8 ± 0.6 ± 1.2 with a standard deviation of 4.5. An increase in the CO/13CO intensity ratio from disk to nucleus may imply that the conversion factor between CO intensity and H2 column density, X, is lower in galactic nuclei. In addition, variations in physical conditions, most notably the gas kinetic temperature, affect both ℛ and X. Abundance variations probably do not cause the gradient in ℛ, though we do not rule out a decrease in effective cloud column densities in galactic nuclei possibly caused by destructive starburst superwinds. A modest rise in temperature (less than a factor of 2 or 3) from outside a 2 kpc radius toward the nucleus can easily account for the observed gradient. These results support previous work implying that X is lower in the center of the Milky Way and probably most galactic nuclei. Therefore, calculating H2 masses using the standard Galactic X-factor, especially within the central few kiloparsecs of galaxies, overestimates the true mass by factors of a few. The standard X-factor still appears to be appropriate for galactic disks.",
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Paglione, TAD, Wall, WF, Young, JS, Heyer, MH, Richard, M, Goldstein, M, Kaufman, Z, Nantais, J & Perry, G 2001, 'A mapping survey of the 13CO and 12CO emission in galaxies', Astrophysical Journal, Supplement Series, vol. 135, n.º 2, pp. 183-200. https://doi.org/10.1086/321785

A mapping survey of the 13CO and 12CO emission in galaxies. / Paglione, Timothy A D; Wall, W. F.; Young, Judith S.; Heyer, Mark H.; Richard, Michael; Goldstein, Michael; Kaufman, Zeke; Nantais, Julie; Perry, Gretchen.

En: Astrophysical Journal, Supplement Series, Vol. 135, N.º 2, 08.2001, p. 183-200.

Resultado de la investigación: Review article

TY - JOUR

T1 - A mapping survey of the 13CO and 12CO emission in galaxies

AU - Paglione, Timothy A D

AU - Wall, W. F.

AU - Young, Judith S.

AU - Heyer, Mark H.

AU - Richard, Michael

AU - Goldstein, Michael

AU - Kaufman, Zeke

AU - Nantais, Julie

AU - Perry, Gretchen

PY - 2001/8

Y1 - 2001/8

N2 - We present spectra of the extended 12CO and 13CO J = 1 → 0 emission along the major axes of 17 nearby galaxies. Spatial variations in the ratio of CO and 13CO integrated intensities, ℛ, are found in nearly every galaxy observed. There is an overall variation in ℛ of 20%-40% from the inner 2 kpc to the disk. Roughly one-third of the survey galaxies have such gradients in ℛ detected above the 2 σ confidence level. Though some galaxies show a lower central value of ℛ, on average ℛ inside 2 kpc is 10%-30% higher than ℛ outside of 2 kpc. The average CO/13CO intensity ratio within the central 2 kpc of the survey sources is 11.6 ± 0.4 (based on the noise) ± 1.5 (based on systematic uncertainties estimated from daily variations in CO and 13CO intensities). The 1 σ dispersion in ℛ between galactic nuclei of 4.2 is also quite large. The average value of ℛ outside 2 kpc is 9.8 ± 0.6 ± 1.2 with a standard deviation of 4.5. An increase in the CO/13CO intensity ratio from disk to nucleus may imply that the conversion factor between CO intensity and H2 column density, X, is lower in galactic nuclei. In addition, variations in physical conditions, most notably the gas kinetic temperature, affect both ℛ and X. Abundance variations probably do not cause the gradient in ℛ, though we do not rule out a decrease in effective cloud column densities in galactic nuclei possibly caused by destructive starburst superwinds. A modest rise in temperature (less than a factor of 2 or 3) from outside a 2 kpc radius toward the nucleus can easily account for the observed gradient. These results support previous work implying that X is lower in the center of the Milky Way and probably most galactic nuclei. Therefore, calculating H2 masses using the standard Galactic X-factor, especially within the central few kiloparsecs of galaxies, overestimates the true mass by factors of a few. The standard X-factor still appears to be appropriate for galactic disks.

AB - We present spectra of the extended 12CO and 13CO J = 1 → 0 emission along the major axes of 17 nearby galaxies. Spatial variations in the ratio of CO and 13CO integrated intensities, ℛ, are found in nearly every galaxy observed. There is an overall variation in ℛ of 20%-40% from the inner 2 kpc to the disk. Roughly one-third of the survey galaxies have such gradients in ℛ detected above the 2 σ confidence level. Though some galaxies show a lower central value of ℛ, on average ℛ inside 2 kpc is 10%-30% higher than ℛ outside of 2 kpc. The average CO/13CO intensity ratio within the central 2 kpc of the survey sources is 11.6 ± 0.4 (based on the noise) ± 1.5 (based on systematic uncertainties estimated from daily variations in CO and 13CO intensities). The 1 σ dispersion in ℛ between galactic nuclei of 4.2 is also quite large. The average value of ℛ outside 2 kpc is 9.8 ± 0.6 ± 1.2 with a standard deviation of 4.5. An increase in the CO/13CO intensity ratio from disk to nucleus may imply that the conversion factor between CO intensity and H2 column density, X, is lower in galactic nuclei. In addition, variations in physical conditions, most notably the gas kinetic temperature, affect both ℛ and X. Abundance variations probably do not cause the gradient in ℛ, though we do not rule out a decrease in effective cloud column densities in galactic nuclei possibly caused by destructive starburst superwinds. A modest rise in temperature (less than a factor of 2 or 3) from outside a 2 kpc radius toward the nucleus can easily account for the observed gradient. These results support previous work implying that X is lower in the center of the Milky Way and probably most galactic nuclei. Therefore, calculating H2 masses using the standard Galactic X-factor, especially within the central few kiloparsecs of galaxies, overestimates the true mass by factors of a few. The standard X-factor still appears to be appropriate for galactic disks.

KW - Galaxies: ISM

KW - Galaxies: starburst

KW - ISM: clouds

KW - ISM: molecules

UR - http://www.scopus.com/inward/record.url?scp=0141485675&partnerID=8YFLogxK

U2 - 10.1086/321785

DO - 10.1086/321785

M3 - Review article

AN - SCOPUS:0141485675

VL - 135

SP - 183

EP - 200

JO - Astrophysical Journal, Supplement Series

JF - Astrophysical Journal, Supplement Series

SN - 0067-0049

IS - 2

ER -

Paglione TAD, Wall WF, Young JS, Heyer MH, Richard M, Goldstein M y otros. A mapping survey of the 13CO and 12CO emission in galaxies. Astrophysical Journal, Supplement Series. 2001 ago;135(2):183-200. https://doi.org/10.1086/321785