TY - JOUR
T1 - Mapping UV properties throughout the cosmic horseshoe
T2 - Lessons from VLT-MUSE
AU - James, Bethan L.
AU - Auger, Matt
AU - Pettini, Max
AU - Stark, Daniel P.
AU - Belokurov, V.
AU - Carniani, Stefano
N1 - Publisher Copyright:
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
PY - 2018/5/11
Y1 - 2018/5/11
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.
KW - Galaxies: ISM
KW - Galaxies: evolution
KW - Galaxies: star formation
KW - Gravitational lensing: strong
KW - Ultraviolet: galaxies
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U2 - 10.1093/mnras/sty315
DO - 10.1093/mnras/sty315
M3 - Article
AN - SCOPUS:85043580757
SN - 0035-8711
VL - 476
SP - 1726
EP - 1740
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 2
ER -