The Recent Burstiness of Star Formation in Galaxies at z ~ 4.5 from Hα Measurements
Abstract
The redshift range z = 4–6 marks a transition phase between primordial and mature galaxy formation in which galaxies considerably increase their stellar mass, metallicity, and dust content. The study of galaxies in this redshift range is therefore important to understanding early galaxy formation and the fate of galaxies at later times. Here, we investigate the burstiness of the recent star formation history (SFH) of 221z ~ 4.5 main-sequence galaxies at log(M/M⊙) > 9.7 by comparing their ultra-violet (UV) continuum, Hα luminosity, and Hα equivalent-width (EW). The Hα properties are derived from the Spitzer [3.6 μm]−[4.5 μm] broadband color, thereby properly taking into account model and photometric uncertainties. We find a significant scatter between Hα- and UV-derived luminosities and star formation rates (SFRs). About half of the galaxies show a significant excess in Hα compared to expectations from a constant smooth SFH. We also find a tentative anticorrelation between Hα EW and stellar mass, ranging from 1000 Å at log(M/M⊙) < 10 to below 100 Å at log(M/M⊙) > 11. Consulting models suggests that most z ~ 4.5 galaxies had a burst of star formation within the last 50 Myr, increasing their SFRs by a factor of >5. The most massive galaxies on the other hand might decrease their SFRs and may be transitioning to a quiescent stage by z = 4. We identify differential dust attenuation (f) between stars and nebular regions as the main contributor to the uncertainty. With local galaxies selected by increasing Hα EW (reaching values similar to high-z galaxies), we predict that f approaches unity at z > 4, consistent with the extrapolation of measurements out to z = 2.
Additional Information
© 2019 The American Astronomical Society. Received 2019 July 12; revised 2019 September 4; accepted 2019 September 5; published 2019 October 18. We thank the referee for their valuable comments that improved this paper. We also thank J. Kartaltepe, S. Toft, and N. Scoville for useful and fruitful discussions. N.E. acknowledges support from Program No. 13905 provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. S.T. is supported by the Smithsonian Astrophysical Observatory through the CfA Fellowship. This work is based on observations and archival data made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA, along with archival data from the NASA/ESA Hubble Space Telescope. This research made also use of the NASA/IPAC Infrared Science Archive (IRSA), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. In parts based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under ESO programme ID 179.A-2005 and on data products produced by TERAPIX and the Cambridge Astronomy Survey Unit on behalf of the UltraVISTA consortium. Based on data obtained with the European Southern Observatory Very Large Telescope, Paranal, Chile, under Large Program 185.A-0791, and made available by the VUDS team at the CESAM data center, Laboratoire d'Astrophysique de Marseille, France. Furthermore, this work is based on data from the W.M. Keck Observatory and the Canada–France–Hawaii Telescope, as well as collected at the Subaru Telescope and retrieved from the HSC data archive system, which is operated by the Subaru Telescope and Astronomy Data Center at the National Astronomical Observatory of Japan. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Finally, we would also like to recognize the contributions from all of the members of the COSMOS Team who helped in obtaining and reducing the large amount of multi-wavelength data that are now publicly available through IRSA at http://irsa.ipac.caltech.edu/Missions/cosmos.html.Attached Files
Published - Faisst_2019_ApJ_884_133.pdf
Submitted - 1909.03076.pdf
Files
| Name | Size | Download all |
|---|---|---|
|
md5:13e76413bbc4643728427f56e223980b
|
4.8 MB | Preview Download |
|
md5:2727c4222af6e430786cf6a6f7b93955
|
5.6 MB | Preview Download |
Additional details
- Eprint ID
- 99019
- Resolver ID
- CaltechAUTHORS:20191002-112756901
- NAS5-26555
- NASA
- Smithsonian Astrophysical Observatory
- NASA/JPL/Caltech
- Created
-
2019-10-02Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- Infrared Processing and Analysis Center (IPAC)