Balmer Break Galaxy Candidates at z ˜ 6: A Potential View on the Star Formation Activity at z ≳ 14
Research output: Contribution to journal › Journal article › Research › peer-review
We search for galaxies with a strong Balmer break (Balmer break
galaxies; BBGs) at z ˜ 6 over a 0.41 deg2 effective
area in the COSMOS field. Based on rich imaging data, including data
obtained with the Atacama Large Millimeter/submillimeter Array (ALMA),
three candidates are identified by their extremely red K–[3.6]
colors, as well as by nondetection in the X-ray, optical, far-infrared,
and radio bands. The nondetection in the deep ALMA observations suggests
that they are not dusty galaxies but BBGs at z ˜ 6, although
contamination from active galactic nuclei at z ˜ 0 cannot be
completely ruled out for the moment. Our spectral energy distribution
analyses reveal that the BBG candidates at z ˜ 6 have stellar
masses of ≈5 × 1010 M⊙ dominated by
old stellar populations with ages of ≳ 700 Myr. Assuming that all
three candidates are real BBGs at z ˜ 6, we estimate the stellar
mass density to be ${2.4}_{-1.3}^{+2.3}\times {10}^{4}\,{M}_{\odot }$
Mpc‑3. This is consistent with an extrapolation from
the lower-redshift measurements. The onset of star formation in the
three BBG candidates is expected to be several hundred million yr before
the observed epoch of z ˜ 6. We estimate the star formation rate
density (SFRD) contributed by progenitors of the BBGs to be 2.4–12
× 10‑5 M⊙ yr‑1
Mpc‑3 at z > 14 (99.7% confidence range). Our result
suggests a smooth evolution of the SFRD beyond z = 8.
Original language | English |
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Article number | 137 |
Journal | Astrophysical Journal |
Volume | 889 |
Issue number | 2 |
Number of pages | 20 |
ISSN | 0004-637X |
DOIs | |
Publication status | Published - 1 Feb 2020 |
Links
- http://arxiv.org/pdf/1912.10954
Submitted manuscript
ID: 236171565