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Abstract
The HI and CO components of the interstellar medium (ISM) are usually used to derive the dynamical mass M-dyn of nearby galaxies. Both components become too faint to be used as a tracer in observations of high-redshift galaxies. In those cases, the 158 mu m line of atomic carbon ([CII]) may be the only way to derive M-dyn. As the distribution and kinematics of the ISM tracer affects the determination of M-dyn, it is important to quantify the relative distributions of HI, CO, and [CII]. HI and CO are well-characterized observationally, however, for [CII] only very few measurements exist. Here we compare observations of CO, HI, and [CII] emission of a sample of nearby galaxies, drawn from the HERACLES, THINGS, and KINGFISH surveys. We find that within R-25, the average [CII] exponential radial profile is slightly shallower than that of the CO, but much steeper than the HI distribution. This is also reflected in the integrated spectrum ("global profile"), where the [CII] spectrum looks more like that of the CO than that of the HI. For one galaxy, a spectrally resolved comparison of integrated spectra was possible; other comparisons were limited by the intrinsic line-widths of the galaxies and the coarse velocity resolution of the [CII] data. Using high-spectral-resolution SOFIA [CII] data of a number of star forming regions in two nearby galaxies, we find that their [CII] linewidths agree better with those of the CO than the HI. As the radial extent of a given ISM tracer is a key input in deriving M-dyn from spatially unresolved data, we conclude that the relevant length-scale to use in determining M-dyn based on [CII] data, is that of the well-characterized CO distribution. This length scale is similar to that of the optical disk.
Keywords
TULLY-FISHER RELATION, STAR-FORMING GALAXIES, ROTATION CURVES, HIGH-REDSHIFT, RADIAL-DISTRIBUTION, SPIRAL GALAXIES, DWARF GALAXIES, EARLY UNIVERSE, DISK GALAXIES, FORMATION LAW, galaxies: fundamental parameters, galaxies: ISM, galaxies: kinematics, and dynamics, radio lines: galaxies, submillimeter: galaxies

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MLA
de Blok, W. J. G. et al. “Comparing [cii], Hi, and Co Dynamics of Nearby Galaxies.” ASTRONOMICAL JOURNAL 152.2 (2016): n. pag. Print.
APA
de Blok, W. J. G., Walter, F., Smith, J.-D. T., Herrera-Camus, R., Bolatto, A. D., Requena-Torres, M. A., Crocker, A. F., et al. (2016). COMPARING [CII], HI, AND CO DYNAMICS OF NEARBY GALAXIES. ASTRONOMICAL JOURNAL, 152(2).
Chicago author-date
de Blok, W. J. G., F. Walter, J. -D. T. Smith, R. Herrera-Camus, A. D. Bolatto, M. A. Requena-Torres, A. F. Crocker, et al. 2016. “Comparing [cii], Hi, and Co Dynamics of Nearby Galaxies.” Astronomical Journal 152 (2).
Chicago author-date (all authors)
de Blok, W. J. G., F. Walter, J. -D. T. Smith, R. Herrera-Camus, A. D. Bolatto, M. A. Requena-Torres, A. F. Crocker, K. V. Croxall, R. C. Kennicutt, J. Koda, L. Armus, M. Boquien, D. Dale, K. Kreckel, and Sharon Meidt van der Wel. 2016. “Comparing [cii], Hi, and Co Dynamics of Nearby Galaxies.” Astronomical Journal 152 (2).
Vancouver
1.
de Blok WJG, Walter F, Smith J-DT, Herrera-Camus R, Bolatto AD, Requena-Torres MA, et al. COMPARING [CII], HI, AND CO DYNAMICS OF NEARBY GALAXIES. ASTRONOMICAL JOURNAL. Bristol: Iop Publishing Ltd; 2016;152(2).
IEEE
[1]
W. J. G. de Blok et al., “COMPARING [CII], HI, AND CO DYNAMICS OF NEARBY GALAXIES,” ASTRONOMICAL JOURNAL, vol. 152, no. 2, 2016.
@article{8622250,
  abstract     = {The HI and CO components of the interstellar medium (ISM) are usually used to derive the dynamical mass M-dyn of nearby galaxies. Both components become too faint to be used as a tracer in observations of high-redshift galaxies. In those cases, the 158 mu m line of atomic carbon ([CII]) may be the only way to derive M-dyn. As the distribution and kinematics of the ISM tracer affects the determination of M-dyn, it is important to quantify the relative distributions of HI, CO, and [CII]. HI and CO are well-characterized observationally, however, for [CII] only very few measurements exist. Here we compare observations of CO, HI, and [CII] emission of a sample of nearby galaxies, drawn from the HERACLES, THINGS, and KINGFISH surveys. We find that within R-25, the average [CII] exponential radial profile is slightly shallower than that of the CO, but much steeper than the HI distribution. This is also reflected in the integrated spectrum ("global profile"), where the [CII] spectrum looks more like that of the CO than that of the HI. For one galaxy, a spectrally resolved comparison of integrated spectra was possible; other comparisons were limited by the intrinsic line-widths of the galaxies and the coarse velocity resolution of the [CII] data. Using high-spectral-resolution SOFIA [CII] data of a number of star forming regions in two nearby galaxies, we find that their [CII] linewidths agree better with those of the CO than the HI. As the radial extent of a given ISM tracer is a key input in deriving M-dyn from spatially unresolved data, we conclude that the relevant length-scale to use in determining M-dyn based on [CII] data, is that of the well-characterized CO distribution. This length scale is similar to that of the optical disk.},
  articleno    = {51},
  author       = {de Blok, W. J. G. and Walter, F. and Smith, J. -D. T. and Herrera-Camus, R. and Bolatto, A. D. and Requena-Torres, M. A. and Crocker, A. F. and Croxall, K. V. and Kennicutt, R. C. and Koda, J. and Armus, L. and Boquien, M. and Dale, D. and Kreckel, K. and van der Wel, Sharon Meidt},
  issn         = {0004-6256},
  journal      = {ASTRONOMICAL JOURNAL},
  keywords     = {TULLY-FISHER RELATION,STAR-FORMING GALAXIES,ROTATION CURVES,HIGH-REDSHIFT,RADIAL-DISTRIBUTION,SPIRAL GALAXIES,DWARF GALAXIES,EARLY UNIVERSE,DISK GALAXIES,FORMATION LAW,galaxies: fundamental parameters,galaxies: ISM,galaxies: kinematics,and dynamics,radio lines: galaxies,submillimeter: galaxies},
  language     = {eng},
  number       = {2},
  pages        = {10},
  publisher    = {Iop Publishing Ltd},
  title        = {COMPARING [CII], HI, AND CO DYNAMICS OF NEARBY GALAXIES},
  url          = {http://dx.doi.org/10.3847/0004-6256/152/2/51},
  volume       = {152},
  year         = {2016},
}

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