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Where Stars Form: Inside-out Growth and Coherent Star Formation from HST Hα Maps of 3200 Galaxies across the Main Sequence at 0.7 < z < 1.5

Nelson, Erica June and van Dokkum, Pieter G. and Förster Schreiber, Natascha M. and Franx, Marijn and Brammer, Gabriel B. and Momcheva, Ivelina G. and Wuyts, Stijn and Whitaker, Katherine E. and Skelton, Rosalind E. and Fumagalli, Mattia and Hayward, Christopher C. and Kriek, Mariska and Labbé, Ivo and Leja, Joel and Rix, Hans-Walter and Tacconi, Linda J. and van der Wel, Arjen and van den Bosch, Frank C. and Oesch, Pascal A. and Dickey, Claire and Lange, Johannes Ulf (2016) Where Stars Form: Inside-out Growth and Coherent Star Formation from HST Hα Maps of 3200 Galaxies across the Main Sequence at 0.7 < z < 1.5. Astrophysical Journal, 828 (1). Art. No. 27. ISSN 0004-637X.

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We present Hα maps at 1 kpc spatial resolution for star-forming galaxies at z ~ 1, made possible by the Wide Field Camera 3 grism on Hubble Space Telescope (HST). Employing this capability over all five 3D-HST/CANDELS fields provides a sample of 3200 galaxies enabling a division into subsamples based on stellar mass and star formation rate (SFR). By creating deep stacked Hα images, we reach surface brightness limits of 1 × 10^(−18) erg s^(−1) cm^(−2) arcsec^(−2), allowing us to map the distribution of ionized gas to ~10 kpc for typical L* galaxies at this epoch. We find that the spatial extent of the Hα distribution increases with stellar mass as r_(Hα) = 1.5(M⋆/10^(10) M⊙)^(0.23) kpc. The Hα emission is more extended than the stellar continuum emission, consistent with inside-out assembly of galactic disks. This effect grows stronger with mass as r_(Hα)/r⋆ = 1.1 (M⋆/10^(10) M⊙)^(0.054). We map the Hα distribution as a function of SFR(IR+UV) and find evidence for "coherent star formation" across the SFR–M * plane: above the main sequence (MS), Hα is enhanced at all radii; below the MS, Hα is depressed at all radii. This suggests that at all masses the physical processes driving the enhancement or suppression of star formation act throughout the disks of galaxies. At high masses (10^(10.5) < M⋆/M⊙ < 10^(11)), above the MS, Hα is particularly enhanced in the center, potentially building bulges and/or supermassive black holes. Below the MS, a strong central dip in the EW(Hα), as well as the inferred specific SFR, appears. Importantly, though, across the entirety of the SFR–M* plane, the absolute SFR as traced by Hα is always centrally peaked, even in galaxies below the MS.

Item Type:Article
Related URLs:
URLURL TypeDescription
Nelson, Erica June0000-0002-7524-374X
van Dokkum, Pieter G.0000-0002-8282-9888
Franx, Marijn0000-0002-8871-3026
Brammer, Gabriel B.0000-0003-2680-005X
Whitaker, Katherine E.0000-0001-7160-3632
Fumagalli, Mattia0000-0001-6676-3842
Hayward, Christopher C.0000-0003-4073-3236
Kriek, Mariska0000-0002-7613-9872
Labbé, Ivo0000-0002-2057-5376
Leja, Joel0000-0001-6755-1315
Rix, Hans-Walter0000-0003-4996-9069
Tacconi, Linda J.0000-0002-1485-9401
Oesch, Pascal A.0000-0001-5851-6649
Additional Information:© 2016 The American Astronomical Society. Received 2015 July 10; revised 2016 May 30; accepted 2016 June 9; published 2016 August 25. We thank the referee for their thoughtful report, which improved the paper. This work is based on observations taken by the 3D-HST Treasury Program (GO 12177 and 12328) with the NASA/ESA HST, which is operated by the Associations of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. E.J.N. gratefully acknowledges support from the National Science Foundation Graduate Research Fellowship.
Funding AgencyGrant Number
NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:galaxies: evolution – galaxies: formation – galaxies: high-redshift – galaxies: star formation – galaxies: structure
Issue or Number:1
Record Number:CaltechAUTHORS:20160829-084930693
Persistent URL:
Official Citation:Erica June Nelson et al 2016 ApJ 828 27
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69984
Deposited By: Tony Diaz
Deposited On:29 Aug 2016 17:25
Last Modified:09 Mar 2020 13:18

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