A spatially resolved map of the kinematics, star formation and stellar mass assembly in a star-forming galaxy at z = 4.9
Abstract
We present a detailed study of the spatially resolved kinematics, star formation and stellar mass in a highly amplified galaxy at z = 4.92 behind the lensing cluster MS 1358+62. We use the observed optical, near- and mid-infrared imaging from Hubble Space Telescope ACS & NICMOS and Spitzer IRAC to derive the stellar mass and the Gemini/NIFS IFU to investigate the velocity structure of the galaxy from the nebular [O II]λλ3726.8,3728.9 emission. Using a detailed gravitational lens model, we account for lensing amplification factor 12.5 ± 2.0 and find that this intrinsically L^* galaxy has a stellar mass of M_★= 7 ± 2 × 10^8 M_⊙, a dynamical mass of M_(dyn)= 3 ± 1 × 10^(9)csc^2(i) M_⊙ (within of 2 kpc) and a star formation rate of 42 ± 8 M_⊙ yr^(−1). The source-plane UV/optical morphology of this galaxy is dominated by five discrete star-forming regions. Exploiting the dynamical information we derive masses for individual star-forming regions of M_(cl)~ 10^(8−9) M_⊙ with sizes of ~200 pc. We find that, at a fixed size, the star formation rate density within these H ii regions is approximately two orders of magnitude greater than those observed in local spiral/starburst galaxies, but consistent with the most massive H II regions in the local Universe such as 30 Doradus. Finally, we compare the spatially resolved nebular emission-line velocity with the Lyα and UV interstellar medium (ISM) lines and find that this galaxy is surrounded by a galactic scale outflow in which the Lyα appears redshifted by ~150 km s^(−1) and the UV-ISM lines blueshifted by ~−200 km s^(−1) from the (systemic) nebular emission. The velocity structure of the outflow mirrors that of the nebular emission suggesting the outflow is young (≲15 Myr), and has yet to burst out of the system. Taken together, these results suggest that this young galaxy is undergoing its first major epoch of mass assembly.
Additional Information
© 2009 The Authors. Journal compilation © 2009 RAS. Accepted 2009 August 26. Received 2009 August 24; in original form 2009 May 22. We gratefully acknowledge an anonymous referee for a very constructive report which significantly improved the content and clarity of this paper. We also gratefully acknowledge the Gemini staff for granting SV time for these observations. We would like to thank Janice Lee for very useful discussions and for allowing us to use the 11HUGS narrow-band imaging prior to the publication and Marijn Franx for useful discussions and providing us with the restframe UV spectroscopy. AMS gratefully acknowledges a Sir Norman Lockyer Royal Astronomical Society Fellowship and a Royal Society travel grant and DPS acknowledges an STFC fellowship.Attached Files
Published - Swinbank2009p6648Mon_Not_R_Astron_Soc.pdf
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Additional details
- Eprint ID
- 17082
- Resolver ID
- CaltechAUTHORS:20100106-135111636
- Royal Astronomical Society
- Royal Society
- Science and Technology Facilities Council (STFC)
- Created
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2010-01-07Created from EPrint's datestamp field
- Updated
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2021-11-08Created from EPrint's last_modified field