Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago. Genzel, R., Schreiber, N. M. F., Übler, H., Lang, P., Naab, T., Bender, R., Tacconi, L. J., Wisnioski, E., Wuyts, S., Alexander, T., Beifiori, A., Belli, S., Brammer, G., Burkert, A., Carollo, C. M., Chan, J., Davies, R., Fossati, M., Galametz, A., Genel, S., Gerhard, O., Lutz, D., Mendel, J. T., Momcheva, I., Nelson, E. J., Renzini, A., Saglia, R., Sternberg, A., Tacchella, S., Tadaki, K., & Wilman, D. Nature, 543(7645):397–401, March, 2017. arXiv: 1703.04310
Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago [link]Paper  doi  abstract   bibtex   
In cold dark matter cosmology, the baryonic components of galaxies are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark matter halo. In the local Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius. Comparison between the dynamical mass and the sum of stellar and cold gas mass at the peak epoch of galaxy formation, inferred from ancillary data, suggest high baryon factions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (stellar initial mass function, calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of two main factors: first, a large fraction of the massive, high-redshift galaxy population was strongly baryon dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early Universe efficiently condensed at the centres of dark matter halos when gas fractions were high, and dark matter was less concentrated. [Abridged]
@article{genzel_strongly_2017,
	title = {Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago},
	volume = {543},
	issn = {0028-0836, 1476-4687},
	url = {http://arxiv.org/abs/1703.04310},
	doi = {10.1038/nature21685},
	abstract = {In cold dark matter cosmology, the baryonic components of galaxies are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark matter halo. In the local Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius. Comparison between the dynamical mass and the sum of stellar and cold gas mass at the peak epoch of galaxy formation, inferred from ancillary data, suggest high baryon factions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (stellar initial mass function, calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of two main factors: first, a large fraction of the massive, high-redshift galaxy population was strongly baryon dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early Universe efficiently condensed at the centres of dark matter halos when gas fractions were high, and dark matter was less concentrated. [Abridged]},
	number = {7645},
	urldate = {2017-03-15},
	journal = {Nature},
	author = {Genzel, R. and Schreiber, N. M. Förster and Übler, H. and Lang, P. and Naab, T. and Bender, R. and Tacconi, L. J. and Wisnioski, E. and Wuyts, S. and Alexander, T. and Beifiori, A. and Belli, S. and Brammer, G. and Burkert, A. and Carollo, C. M. and Chan, J. and Davies, R. and Fossati, M. and Galametz, A. and Genel, S. and Gerhard, O. and Lutz, D. and Mendel, J. T. and Momcheva, I. and Nelson, E. J. and Renzini, A. and Saglia, R. and Sternberg, A. and Tacchella, S. and Tadaki, K. and Wilman, D.},
	month = mar,
	year = {2017},
	note = {arXiv: 1703.04310},
	keywords = {Astrophysics - Astrophysics of Galaxies},
	pages = {397--401},
}
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