The Astrophysical Journal Letters (Jan 2024)
Not-so-little Red Dots: Two Massive and Dusty Starbursts at z ∼ 5–7 Pushing the Limits of Star Formation Discovered by JWST in the COSMOS-Web Survey
- Fabrizio Gentile,
- Caitlin M. Casey,
- Hollis B. Akins,
- Maximilien Franco,
- Jed McKinney,
- Edward Berman,
- Olivia R. Cooper,
- Nicole E. Drakos,
- Michaela Hirschmann,
- Arianna S. Long,
- Georgios Magdis,
- Anton M. Koekemoer,
- Vasily Kokorev,
- Marko Shuntov,
- Margherita Talia,
- Natalie Allen,
- Santosh Harish,
- Olivier Ilbert,
- Henry Joy McCracken,
- Jeyhan S. Kartaltepe,
- Daizhong Liu,
- Louise Paquereau,
- Jason Rhodes,
- Michael R. Rich,
- Brant E. Robertson,
- Sune Toft,
- Ghassem Gozaliasl
Affiliations
- Fabrizio Gentile
- ORCiD
- University of Bologna , Department of Physics and Astronomy (DIFA), Via Gobetti 93/2, I-40129, Bologna, Italy ; [email protected]; INAF—Osservatorio di Astrofisica e Scienza dello Spazio , via Gobetti 93/3-40129, Bologna, Italy
- Caitlin M. Casey
- ORCiD
- The University of Texas at Austin , 2515 Speedway Boulevard Stop C1400, Austin, TX 78712, USA
- Hollis B. Akins
- ORCiD
- The University of Texas at Austin , 2515 Speedway Boulevard Stop C1400, Austin, TX 78712, USA
- Maximilien Franco
- ORCiD
- The University of Texas at Austin , 2515 Speedway Boulevard Stop C1400, Austin, TX 78712, USA
- Jed McKinney
- ORCiD
- The University of Texas at Austin , 2515 Speedway Boulevard Stop C1400, Austin, TX 78712, USA
- Edward Berman
- ORCiD
- Department of Physics, Northeastern University , 360 Huntington Ave., Boston, MA, USA
- Olivia R. Cooper
- ORCiD
- The University of Texas at Austin , 2515 Speedway Boulevard Stop C1400, Austin, TX 78712, USA
- Nicole E. Drakos
- ORCiD
- Department of Physics and Astronomy, University of Hawaii , Hilo, 200 W Kawili St., Hilo, HI 96720, USA
- Michaela Hirschmann
- ORCiD
- Institute of Physics , GalSpec, Ecole Polytechnique Federale de Lausanne, Observatoire de Sauverny, Chemin Pegasi 51, 1290 Versoix, Switzerland; INAF, Astronomical Observatory of Trieste , Via Tiepolo 11, 34131 Trieste, Italy
- Arianna S. Long
- ORCiD
- The University of Texas at Austin , 2515 Speedway Boulevard Stop C1400, Austin, TX 78712, USA
- Georgios Magdis
- ORCiD
- Cosmic Dawn Center (DAWN) , Denmark; DTU-Space, Technical University of Denmark , Elektrovej 327, 2800, Kgs. Lyngby, Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200, Copenhagen, Denmark
- Anton M. Koekemoer
- ORCiD
- Space Telescope Science Institute , 3700 San Martin Dr., Baltimore, MD 21218, USA
- Vasily Kokorev
- ORCiD
- Kapteyn Astronomical Institute, University of Groningen , PO Box 800, 9700 AV Groningen, The Netherlands
- Marko Shuntov
- ORCiD
- Cosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200, Copenhagen, Denmark
- Margherita Talia
- ORCiD
- University of Bologna , Department of Physics and Astronomy (DIFA), Via Gobetti 93/2, I-40129, Bologna, Italy ; [email protected]; INAF—Osservatorio di Astrofisica e Scienza dello Spazio , via Gobetti 93/3-40129, Bologna, Italy
- Natalie Allen
- ORCiD
- Cosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200, Copenhagen, Denmark
- Santosh Harish
- ORCiD
- Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology , 84 Lomb Memorial Dr., Rochester, NY 14623, USA
- Olivier Ilbert
- ORCiD
- Aix Marseille Univ , CNRS, CNES, LAM, Marseille, France
- Henry Joy McCracken
- ORCiD
- Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université , 98 bis boulevard Arago, F-75014 Paris, France
- Jeyhan S. Kartaltepe
- ORCiD
- Laboratory for Multiwavelength Astrophysics, School of Physics and Astronomy, Rochester Institute of Technology , 84 Lomb Memorial Dr., Rochester, NY 14623, USA
- Daizhong Liu
- ORCiD
- Purple Mountain Observatory, Chinese Academy of Sciences , 10 Yuanhua Road, Nanjing 210023, People’s Republic of China
- Louise Paquereau
- ORCiD
- Institut d’Astrophysique de Paris, UMR 7095, CNRS, and Sorbonne Université , 98 bis boulevard Arago, F-75014 Paris, France
- Jason Rhodes
- ORCiD
- Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Dr., Pasadena, CA 91001, USA
- Michael R. Rich
- ORCiD
- Department of Physics and Astronomy, UCLA , PAB 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547, USA
- Brant E. Robertson
- ORCiD
- Department of Astronomy and Astrophysics, University of California , Santa Cruz, 1156 High St., Santa Cruz, CA 95064, USA
- Sune Toft
- ORCiD
- Cosmic Dawn Center (DAWN) , Denmark; Niels Bohr Institute, University of Copenhagen , Jagtvej 128, DK-2200, Copenhagen, Denmark
- Ghassem Gozaliasl
- ORCiD
- Department of Computer Science, Aalto University , PO Box 15400, Espoo, FI-00 076, Finland; Department of Physics, P.O. Box 64, 00014 University of Helsinki , Finland
- DOI
- https://doi.org/10.3847/2041-8213/ad738a
- Journal volume & issue
-
Vol. 973,
no. 1
p. L2
Abstract
We present the properties of two candidate massive ( M _⋆ ∼ 10 ^11 M _⊙ ) and dusty ( A _v > 2.5 mag) galaxies at z = 5–7 in the first 0.28 deg ^2 of the COSMOS-Web survey. One object is spectroscopically confirmed at z _spec = 5.051, while the other has a robust z _phot = 6.7 ± 0.3. Thanks to their extremely red colors (F277W–F444W ∼ 1.7 mag), these galaxies satisfy the nominal color selection for the widely studied “little red dot” (LRD) population with the exception of their spatially resolved morphologies. The morphology of our targets allows us to conclude that their red continuum is dominated by highly obscured stellar emission and not by reddened nuclear activity. Using a variety of spectral energy distribution fitting tools and star formation histories, we estimate the stellar masses to be $\mathrm{log}({M}_{\star })={11.32}_{-0.15}^{+0.07}\,{M}_{\odot }$ and $\mathrm{log}({M}_{\star })={11.2}_{-0.2}^{+0.1}\,{M}_{\odot }$ , respectively, with a red continuum emission dominated by a recent episode of star formation. We then compare their number density to the halo mass function to infer stellar baryon fractions of ϵ _⋆ ∼ 0.25 and ϵ _⋆ ∼ 0.5. Both are significantly higher than what is commonly observed in lower- z galaxies or more dust-obscured galaxies at similar redshifts. With very bright ultra-high- z Lyman-Break Galaxies and some non-AGN-dominated LRDs, such “extended” LRDs represent another population that may require very efficient star formation at early times.
Keywords
