Turning back the clock: Inferring the history of the eight O'clock arc

Steven L. Finkelstein, Casey Papovich, Gregory Rudnick, Eiichi Egami, Emeric Le Floc'H, Marcia J Rieke, Jane R. Rigby, Christopher N A Willmer

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

We present the results from an optical and near-infrared (NIR) spectroscopic study of the ultraviolet-luminous z = 2.73 galaxy, the 8 o'clock arc. Due to gravitational lensing, this galaxy is magnified by a factor of μ > 10, allowing in-depth measurements which are usually unfeasible at such redshifts. In the optical spectra, we measured the systemic redshift of the galaxy, z = 2.7322 ± 0.0012, using stellar photospheric lines. This differs from the redshift of absorption lines in the interstellar medium, z = 2.7302 ± 0.0006, implying gas outflows on the order of 160 km s -1. With H- and K-band NIR spectra, we have measured nebular emission lines of Hα,Hβ,Hλ ,[NII], and [O III], which have a redshift z = 2.7333 ± 0.0001, consistent with the derived systemic redshift. From the Balmer decrement, we measured the dust extinction in this galaxy to be A5500 = 1.17 ± 36 mag. Correcting the Hα line flux for dust extinction as well as the assumed lensing factor, we measure a star formation rate (SFR) of ∼270 M⊙ yr-1, which is higher than ∼85% of star-forming galaxies at z ∼ 2-3. Using combinations of all detected emission lines, we find that the 8 o'clock arc has a gas-phase metallicity of ∼0.8 Z⊙, showing that enrichment at high redshift is not rare, even in blue, star-forming galaxies. Studying spectra from two of the arc components separately, we find that one component dominates both the dust extinction and SFR, although the metallicities between the two components are similar. We derive the mass via stellar population modeling, and find that the arc has a total stellar mass of ∼4.2 x 1011 M⊙, which falls on the mass-metallicity relation at z ∼ 2. Finally, we estimate the total gas mass, and find it to be only ∼12% of the stellar mass, implying that the 8 o'clock arc is likely nearing the end of a starburst.

Original languageEnglish (US)
Pages (from-to)376-386
Number of pages11
JournalAstrophysical Journal
Volume700
Issue number1 PART 2
DOIs
StatePublished - 2009

Fingerprint

clocks
arcs
histories
galaxies
history
stellar mass
extinction
metallicity
dust
star formation rate
near infrared
gas
population modeling
H lines
depth measurement
blue stars
extremely high frequencies
gases
outflow
optical spectrum

Keywords

  • Galaxies: high-redshift
  • Galaxies: ISM
  • Galaxies: starburst
  • Online-only material: color figures

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Finkelstein, S. L., Papovich, C., Rudnick, G., Egami, E., Le Floc'H, E., Rieke, M. J., ... Willmer, C. N. A. (2009). Turning back the clock: Inferring the history of the eight O'clock arc. Astrophysical Journal, 700(1 PART 2), 376-386. https://doi.org/10.1088/0004-637X/700/1/376

Turning back the clock : Inferring the history of the eight O'clock arc. / Finkelstein, Steven L.; Papovich, Casey; Rudnick, Gregory; Egami, Eiichi; Le Floc'H, Emeric; Rieke, Marcia J; Rigby, Jane R.; Willmer, Christopher N A.

In: Astrophysical Journal, Vol. 700, No. 1 PART 2, 2009, p. 376-386.

Research output: Contribution to journalArticle

Finkelstein, SL, Papovich, C, Rudnick, G, Egami, E, Le Floc'H, E, Rieke, MJ, Rigby, JR & Willmer, CNA 2009, 'Turning back the clock: Inferring the history of the eight O'clock arc', Astrophysical Journal, vol. 700, no. 1 PART 2, pp. 376-386. https://doi.org/10.1088/0004-637X/700/1/376
Finkelstein SL, Papovich C, Rudnick G, Egami E, Le Floc'H E, Rieke MJ et al. Turning back the clock: Inferring the history of the eight O'clock arc. Astrophysical Journal. 2009;700(1 PART 2):376-386. https://doi.org/10.1088/0004-637X/700/1/376
Finkelstein, Steven L. ; Papovich, Casey ; Rudnick, Gregory ; Egami, Eiichi ; Le Floc'H, Emeric ; Rieke, Marcia J ; Rigby, Jane R. ; Willmer, Christopher N A. / Turning back the clock : Inferring the history of the eight O'clock arc. In: Astrophysical Journal. 2009 ; Vol. 700, No. 1 PART 2. pp. 376-386.
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