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 - Funding Information:
We are grateful to the European Southern Observatory time assignment committee who awarded time to this programme and to the staff astronomers at Paranal who conducted the observations. We also extend our thanks to the reviewer, Johan Richard, for his insightful and valuable comments on our manuscript. The authors are sincerely grateful to Danielle Berg for discussions concerning electron density diagnostics, along with Jane Rigby and Jason Tumlinson for discussions on spatially resolving outflows. BLJ thanks support from the European Space Agency (ESA) and SC acknowledges financial support from the Science and Technology Facilities Council (STFC). The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement no. 308024.
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
VL - 476
SP - 1726
EP - 1740
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -