Mapping UV properties throughout the cosmic horseshoe: Lessons from VLT-MUSE

Bethan L. James, Matt Auger, Max Pettini, Daniel P Stark, V. Belokurov, Stefano Carniani

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

We present the first spatially resolved rest-frame ultraviolet (UV) study of the gravitationally lensed galaxy, the 'Cosmic Horseshoe' (J1148+1930) at z = 2.38. Our gravitational lens model shows that the system is made up of four star-forming regions, each ~4-8 kpc2 in size, from which we extract four spatially exclusive regional spectra. We study the interstellar and wind absorption lines, along with C III] doublet emission lines, in each region to investigate any variation in emission/absorption line properties. Themapped C III] emission shows distinct kinematical structure, with velocity offsets of ~±50 km s-1 between regions suggestive of a merging system, and a variation in equivalent width that indicates a change in ionization parameter and/or metallicity between the regions. Absorption line velocities reveal a range of outflow strengths, with gas outflowing in the range -200 ≲ v (km s-1) ≲ -50 relative to the systemic velocity of that region. Interestingly, the strongest gas outflow appears to emanate from the most diffuse star-forming region. The star formation rates remain relatively constant (~8-16M yr-1), mostly due to large uncertainties in reddening estimates. As such, the outflows appear to be 'global' rather than 'locally' sourced.We measure electron densities with a range of log (Ne)= 3.92-4.36 cm-3, and point out that such high densities may be common when measured using the CIII] doublet due to its large critical density. Overall, our observations demonstrate that while it is possible to trace variations in large-scale gas kinematics, detecting inhomogeneities in physical gas properties and their effects on the outflowing gas may be more difficult. This study provides important lessons for the spatially resolved rest-frame UV studies expected with future observatories, such as James Webb Space Telescope.

Original languageEnglish (US)
Pages (from-to)1726-1740
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume476
Issue number2
DOIs
StatePublished - May 11 2018

Fingerprint

gases
gas
outflow
stars
James Webb Space Telescope
gravitational lenses
star formation rate
metallicity
observatories
inhomogeneity
kinematics
electron density
galaxies
ionization
observatory
estimates

Keywords

  • Galaxies: evolution
  • Galaxies: ISM
  • Galaxies: star formation
  • Gravitational lensing: strong
  • Ultraviolet: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Mapping UV properties throughout the cosmic horseshoe : Lessons from VLT-MUSE. / James, Bethan L.; Auger, Matt; Pettini, Max; Stark, Daniel P; Belokurov, V.; Carniani, Stefano.

In: Monthly Notices of the Royal Astronomical Society, Vol. 476, No. 2, 11.05.2018, p. 1726-1740.

Research output: Contribution to journalArticle

James, Bethan L. ; Auger, Matt ; Pettini, Max ; Stark, Daniel P ; Belokurov, V. ; Carniani, Stefano. / Mapping UV properties throughout the cosmic horseshoe : Lessons from VLT-MUSE. In: Monthly Notices of the Royal Astronomical Society. 2018 ; Vol. 476, No. 2. pp. 1726-1740.
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AU - James, Bethan L.

AU - Auger, Matt

AU - Pettini, Max

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AU - Belokurov, V.

AU - Carniani, Stefano

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N2 - We present the first spatially resolved rest-frame ultraviolet (UV) study of the gravitationally lensed galaxy, the 'Cosmic Horseshoe' (J1148+1930) at z = 2.38. Our gravitational lens model shows that the system is made up of four star-forming regions, each ~4-8 kpc2 in size, from which we extract four spatially exclusive regional spectra. We study the interstellar and wind absorption lines, along with C III] doublet emission lines, in each region to investigate any variation in emission/absorption line properties. Themapped C III] emission shows distinct kinematical structure, with velocity offsets of ~±50 km s-1 between regions suggestive of a merging system, and a variation in equivalent width that indicates a change in ionization parameter and/or metallicity between the regions. Absorption line velocities reveal a range of outflow strengths, with gas outflowing in the range -200 ≲ v (km s-1) ≲ -50 relative to the systemic velocity of that region. Interestingly, the strongest gas outflow appears to emanate from the most diffuse star-forming region. The star formation rates remain relatively constant (~8-16M⊙ yr-1), mostly due to large uncertainties in reddening estimates. As such, the outflows appear to be 'global' rather than 'locally' sourced.We measure electron densities with a range of log (Ne)= 3.92-4.36 cm-3, and point out that such high densities may be common when measured using the CIII] doublet due to its large critical density. Overall, our observations demonstrate that while it is possible to trace variations in large-scale gas kinematics, detecting inhomogeneities in physical gas properties and their effects on the outflowing gas may be more difficult. This study provides important lessons for the spatially resolved rest-frame UV studies expected with future observatories, such as James Webb Space Telescope.

AB - We present the first spatially resolved rest-frame ultraviolet (UV) study of the gravitationally lensed galaxy, the 'Cosmic Horseshoe' (J1148+1930) at z = 2.38. Our gravitational lens model shows that the system is made up of four star-forming regions, each ~4-8 kpc2 in size, from which we extract four spatially exclusive regional spectra. We study the interstellar and wind absorption lines, along with C III] doublet emission lines, in each region to investigate any variation in emission/absorption line properties. Themapped C III] emission shows distinct kinematical structure, with velocity offsets of ~±50 km s-1 between regions suggestive of a merging system, and a variation in equivalent width that indicates a change in ionization parameter and/or metallicity between the regions. Absorption line velocities reveal a range of outflow strengths, with gas outflowing in the range -200 ≲ v (km s-1) ≲ -50 relative to the systemic velocity of that region. Interestingly, the strongest gas outflow appears to emanate from the most diffuse star-forming region. The star formation rates remain relatively constant (~8-16M⊙ yr-1), mostly due to large uncertainties in reddening estimates. As such, the outflows appear to be 'global' rather than 'locally' sourced.We measure electron densities with a range of log (Ne)= 3.92-4.36 cm-3, and point out that such high densities may be common when measured using the CIII] doublet due to its large critical density. Overall, our observations demonstrate that while it is possible to trace variations in large-scale gas kinematics, detecting inhomogeneities in physical gas properties and their effects on the outflowing gas may be more difficult. This study provides important lessons for the spatially resolved rest-frame UV studies expected with future observatories, such as James Webb Space Telescope.

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KW - Gravitational lensing: strong

KW - Ultraviolet: galaxies

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