Resolved spectroscopy of gravitationally lensed galaxies: Recovering coherent velocity fields in subluminous z ∼ 2-3 galaxies

T. A. Jones, A. M. Swinbank, R. S. Ellis, J. Richard, Daniel P Stark

Research output: Contribution to journalArticle

153 Citations (Scopus)

Abstract

We present spatially resolved dynamics for six strongly lensed star-forming galaxies at z = 1.7-3.1, each enlarged by a linear magnification factor of ∼ ×8. Using the Keck laser guide star AO system and the OH-Suppressing Infra-Red Imaging Spectrograph integral field unit spectrograph, we resolve kinematic and morphological detail in our sample with an unprecedented fidelity, in some cases achieving spatial resolutions of ≃100 pc. With one exception our sources have diameters ranging from 1 to 7 kpc, integrated star formation rates of 2-40 M yr-1 (uncorrected for extinction) and dynamical masses of 109.7-10.3 M. With this exquisite resolution, we find that four of the six galaxies display coherent velocity fields consistent with a simple rotating disc model. Our model fits imply ratios for the systemic to random motion, Vc sin i/σ, ranging from 0.5 to 1.3 and Toomre disc parameters Q < 1. The large fraction of well-ordered velocity fields in our sample is consistent with data analysed for larger, more luminous sources at this redshift. We demonstrate that the apparent contradiction with earlier dynamical results published for unlensed compact sources arises from the considerably improved spatial resolution and sampling uniquely provided by the combination of adaptive optics and strong gravitational lensing. Our high-resolution data further reveal that all six galaxies contain multiple giant star-forming H ii regions whose resolved diameters are in the range 300 pc to 1.0 kpc, consistent with the Jeans length expected in the case of dispersion support. From the kinematic data, we calculate that these regions have dynamical masses of 108.8-9.5 M, also in agreement with local data. However, the density of star formation in these regions is ∼100× higher than observed in local spirals; such high values are only seen in the most luminous local starbursts. The global dynamics and demographics of star formation in these H ii regions suggest that vigorous star formation is primarily governed by gravitational instability in primitive rotating discs. The physical insight provided by the combination of adaptive optics and gravitational lensing suggests it will be highly valuable to locate many more strongly lensed distant galaxies with high star formation rates before the era of the next-generation ground-based telescopes when such observations will become routine.

Original languageEnglish (US)
Pages (from-to)1247-1262
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume404
Issue number3
DOIs
StatePublished - May 2010
Externally publishedYes

Fingerprint

velocity distribution
spectroscopy
galaxies
star formation
rotating disks
star formation rate
adaptive optics
spectrographs
spatial resolution
kinematics
laser guide stars
giant stars
gravitational instability
magnification
extinction
laser
sampling
telescopes
stars
high resolution

Keywords

  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: high-redshift

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Resolved spectroscopy of gravitationally lensed galaxies : Recovering coherent velocity fields in subluminous z ∼ 2-3 galaxies. / Jones, T. A.; Swinbank, A. M.; Ellis, R. S.; Richard, J.; Stark, Daniel P.

In: Monthly Notices of the Royal Astronomical Society, Vol. 404, No. 3, 05.2010, p. 1247-1262.

Research output: Contribution to journalArticle

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T2 - Recovering coherent velocity fields in subluminous z ∼ 2-3 galaxies

AU - Jones, T. A.

AU - Swinbank, A. M.

AU - Ellis, R. S.

AU - Richard, J.

AU - Stark, Daniel P

PY - 2010/5

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N2 - We present spatially resolved dynamics for six strongly lensed star-forming galaxies at z = 1.7-3.1, each enlarged by a linear magnification factor of ∼ ×8. Using the Keck laser guide star AO system and the OH-Suppressing Infra-Red Imaging Spectrograph integral field unit spectrograph, we resolve kinematic and morphological detail in our sample with an unprecedented fidelity, in some cases achieving spatial resolutions of ≃100 pc. With one exception our sources have diameters ranging from 1 to 7 kpc, integrated star formation rates of 2-40 M⊙ yr-1 (uncorrected for extinction) and dynamical masses of 109.7-10.3 M⊙. With this exquisite resolution, we find that four of the six galaxies display coherent velocity fields consistent with a simple rotating disc model. Our model fits imply ratios for the systemic to random motion, Vc sin i/σ, ranging from 0.5 to 1.3 and Toomre disc parameters Q < 1. The large fraction of well-ordered velocity fields in our sample is consistent with data analysed for larger, more luminous sources at this redshift. We demonstrate that the apparent contradiction with earlier dynamical results published for unlensed compact sources arises from the considerably improved spatial resolution and sampling uniquely provided by the combination of adaptive optics and strong gravitational lensing. Our high-resolution data further reveal that all six galaxies contain multiple giant star-forming H ii regions whose resolved diameters are in the range 300 pc to 1.0 kpc, consistent with the Jeans length expected in the case of dispersion support. From the kinematic data, we calculate that these regions have dynamical masses of 108.8-9.5 M⊙, also in agreement with local data. However, the density of star formation in these regions is ∼100× higher than observed in local spirals; such high values are only seen in the most luminous local starbursts. The global dynamics and demographics of star formation in these H ii regions suggest that vigorous star formation is primarily governed by gravitational instability in primitive rotating discs. The physical insight provided by the combination of adaptive optics and gravitational lensing suggests it will be highly valuable to locate many more strongly lensed distant galaxies with high star formation rates before the era of the next-generation ground-based telescopes when such observations will become routine.

AB - We present spatially resolved dynamics for six strongly lensed star-forming galaxies at z = 1.7-3.1, each enlarged by a linear magnification factor of ∼ ×8. Using the Keck laser guide star AO system and the OH-Suppressing Infra-Red Imaging Spectrograph integral field unit spectrograph, we resolve kinematic and morphological detail in our sample with an unprecedented fidelity, in some cases achieving spatial resolutions of ≃100 pc. With one exception our sources have diameters ranging from 1 to 7 kpc, integrated star formation rates of 2-40 M⊙ yr-1 (uncorrected for extinction) and dynamical masses of 109.7-10.3 M⊙. With this exquisite resolution, we find that four of the six galaxies display coherent velocity fields consistent with a simple rotating disc model. Our model fits imply ratios for the systemic to random motion, Vc sin i/σ, ranging from 0.5 to 1.3 and Toomre disc parameters Q < 1. The large fraction of well-ordered velocity fields in our sample is consistent with data analysed for larger, more luminous sources at this redshift. We demonstrate that the apparent contradiction with earlier dynamical results published for unlensed compact sources arises from the considerably improved spatial resolution and sampling uniquely provided by the combination of adaptive optics and strong gravitational lensing. Our high-resolution data further reveal that all six galaxies contain multiple giant star-forming H ii regions whose resolved diameters are in the range 300 pc to 1.0 kpc, consistent with the Jeans length expected in the case of dispersion support. From the kinematic data, we calculate that these regions have dynamical masses of 108.8-9.5 M⊙, also in agreement with local data. However, the density of star formation in these regions is ∼100× higher than observed in local spirals; such high values are only seen in the most luminous local starbursts. The global dynamics and demographics of star formation in these H ii regions suggest that vigorous star formation is primarily governed by gravitational instability in primitive rotating discs. The physical insight provided by the combination of adaptive optics and gravitational lensing suggests it will be highly valuable to locate many more strongly lensed distant galaxies with high star formation rates before the era of the next-generation ground-based telescopes when such observations will become routine.

KW - Galaxies: evolution

KW - Galaxies: formation

KW - Galaxies: high-redshift

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