Article, 2024
RUBIES: Evolved Stellar Populations with Extended Formation Histories at z ∼ 7–8 in Candidate Massive Galaxies Identified with JWST/NIRSpec
The Astrophysical Journal Letters,
ISSN
2041-8205,
2041-8213,
Volume 969,
1,
Page l13,
10.3847/2041-8213/ad55f7
Contributors
Wang, Bingjie
0000-0001-9269-5046
(Corresponding author)
[1]
Leja, Joel
0000-0001-6755-1315
[1]
De Graaff, Anna
0000-0002-2380-9801
[2]
Brammer, Gabriel B
0000-0003-2680-005X
[3]
Weibel, Andrea
0000-0001-8928-4465
[4]
van Dokkum, Pieter G
[5]
Baggen, Josephine F W
0009-0005-2295-7246
[5]
Suess, Katherine A
0000-0002-1714-1905
[6]
[7]
Greene, Jenny E
0000-0002-5612-3427
[8]
Bezanson, Rachel S
0000-0001-5063-8254
[9]
Cleri, Nikko J
0000-0001-7151-009X
[10]
Hirschmann, Michaela
0000-0002-3301-3321
[11]
Labbé, I F L
0000-0002-2057-5376
[12]
Matthee, Jorryt J A
0000-0003-2871-127X
[13]
Mcconachie, Ian
0000-0002-2446-8770
[14]
Naidu, Rohan Potham
0000-0003-3997-5705
[7]
[15]
Nelson, Erica June
[16]
Oesch, Pascal A
0000-0001-5851-6649
[3]
[4]
Setton, David J
0000-0003-4075-7393
[8]
[17]
Williams, Christina C
[18]
[19]
Affiliations
- [1]
Pennsylvania State University
[NORA names:
United States; America, North; OECD];
- [2]
Max Planck Institute for Astronomy
[NORA names:
Germany; Europe, EU; OECD];
- [3]
University of Copenhagen
[NORA names:
KU University of Copenhagen; University; Denmark; Europe, EU; Nordic; OECD];
- [4]
University of Geneva
[NORA names:
Switzerland; Europe, Non-EU; OECD];
- [5]
Yale University
[NORA names:
United States; America, North; OECD];
(... more)
- [6]
Kavli Institute for Particle Astrophysics and Cosmology
[NORA names:
United States; America, North; OECD];
- [7]
NHFP Hubble Fellow.
- [8]
Princeton University
[NORA names:
United States; America, North; OECD];
- [9]
University of Pittsburgh
[NORA names:
United States; America, North; OECD];
- [10]
Texas A&M University
[NORA names:
United States; America, North; OECD];
- [11]
École Polytechnique Fédérale de Lausanne
[NORA names:
Switzerland; Europe, Non-EU; OECD];
- [12]
Swinburne University of Technology
[NORA names:
Australia; Oceania; OECD];
- [13]
Institute of Science and Technology Austria
[NORA names:
Austria; Europe, EU; OECD];
- [14]
University of California, Riverside
[NORA names:
United States; America, North; OECD];
- [15]
Massachusetts Institute of Technology
[NORA names:
United States; America, North; OECD];
- [16]
University of Colorado Boulder
[NORA names:
United States; America, North; OECD];
- [17]
Brinson Prize Fellow.
- [18]
NOIRLab
[NORA names:
United States; America, North; OECD];
- [19]
University of Arizona
[NORA names:
United States; America, North; OECD]
(less)
Abstract
The identification of red, apparently massive galaxies at z > 7 in early James Webb Space Telescope (JWST) photometry suggests a strongly accelerated time line compared to standard models of galaxy growth. A major uncertainty in the interpretation is whether the red colors are caused by evolved stellar populations, dust, or other effects such as emission lines or active galactic nuclei (AGNs). Here we show that three of the massive galaxy candidates at z = 6.7–8.4 have prominent Balmer breaks in JWST/NIRSpec spectroscopy from the RUBIES program. The Balmer breaks demonstrate unambiguously that stellar emission dominates at λ rest = 0.4 μm and require formation histories extending hundreds of millions of years into the past in galaxies only 600–800 Myr after the big bang. Two of the three galaxies also show broad Balmer lines, with Hβ FWHM > 2500 km s−1, suggesting that dust-reddened AGNs contribute to, or even dominate, the spectral energy distributions of these galaxies at λ rest ≳ 0.6 μm. All three galaxies have relatively narrow [O iii] lines, seemingly ruling out a high-mass interpretation if the lines arise in dynamically relaxed, inclined disks. Yet the inferred masses also remain highly uncertain. We model the high-quality spectra using Prospector to decompose the continuum into stellar and AGN components and explore limiting cases in stellar/AGN contribution. This produces a wide range of possible stellar masses, spanning M ⋆ ∼ 109−1011 M ⊙. Nevertheless, all fits suggest a very early and rapid formation, most of which follow with a truncation in star formation. Potential origins and evolutionary tracks for these objects are discussed, from the cores of massive galaxies to low-mass galaxies with overmassive black holes. Intriguingly, we find all of these explanations to be incomplete; deeper and redder data are needed to understand the physics of these systems.
Keywords
AGN,
AGN component,
Balmer,
Balmer break,
Balmer lines,
Bang,
Big Bang,
Extended,
JWST/NIRSpec,
James,
James Webb Space Telescope,
Ruby programs,
Space Telescope,
black hole,
breaks,
candidates,
cases,
color,
compared to standard models,
components,
continuum,
contribution,
core,
cores of massive galaxies,
data,
disk,
distribution,
dust,
effect,
emission,
emission lines,
energy distribution,
evolutionary tracks,
evolving stellar populations,
formation,
formation history,
galaxies,
galaxy candidates,
galaxy growth,
growth,
high-quality spectra,
history,
holes,
identification,
inferred masses,
interpretation,
lines,
low-mass galaxies,
mass,
massive galaxies,
model,
objective,
origin,
overmassive black holes,
photometry,
physics,
population,
potential origin,
program,
prospectors,
red color,
red data,
ruby,
spectra,
spectral energy distribution,
spectroscopy,
standard model,
star formation,
stars,
stellar emission,
stellar mass,
stellar populations,
stellarator,
system,
telescope,
tracking,
truncation,
uncertainty,
years
Funders
Data Provider: Digital Science