A search for high-redshift direct-collapse black hole candidates in the PEARLS north ecliptic pole field

¹ Observational Astrophysics, Department of Physics and Astronomy, Uppsala University, Box 516 751 20 Uppsala, Sweden
e-mail: armin.nabizade@gmail.com
² Center for Astrophysics | Harvard & Smithsonian, 60 Garden St., Cambridge, MA 02138, USA
³ School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404, USA
⁴ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁵ Association of Universities for Research in Astronomy (AURA) for the European Space Agency (ESA), STScI, Baltimore, MD 21218, USA
⁶ Department of Physics, 366 Physics North MC 7300, University of California, Berkeley, CA 94720, USA
⁷ Jodrell Bank Centre for Astrophysics, Alan Turing Building, University of Manchester, Oxford Road, Manchester M13 9PL, UK
⁸ International Centre for Radio Astronomy Research (ICRAR) and the International Space Centre (ISC), The University of Western Australia, M468, 35 Stirling Highway, Crawley, WA 6009, Australia
⁹ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia
¹⁰ Department of Astronomy/Steward Observatory, University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721-0009, USA
¹¹ National Research Council of Canada, Herzberg Astronomy & Astrophysics Research Centre, 5071 West Saanich Road, Victoria, BC V9E 2E7, Canada
¹² INAF – Osservatorio Astronomico di Trieste, Via Bazzoni 2, 34124 Trieste, Italy
¹³ Minnesota State University-Mankato, Telescope Science Institute, TN141, Mankato, MN 56001, USA
¹⁴ Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211, USA
¹⁵ Instituto de Física de Cantabria, Edificio Juan Jordá, Avenida de los Castros s/n, 39005 Santander, Cantabria, Spain
¹⁶ Instituto de Física de Cantabria (CSIC-UC), Avenida Los Castros s/n, 39005 Santander, Spain
¹⁷ Chinese Academy of Sciences, National Astronomical Observatories, CAS, Beijing 100101, PR China
¹⁸ Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712, USA
¹⁹ Physics Department, Ben-Gurion University of the Negev, PO Box 653 Beer-Sheva 8410501, Israel
²⁰ European Space Agency (ESA), European Space Astronomy Centre (ESAC), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
²¹ Department of Physics, Montana State University, PO Box 173840 Bozeman, MT 59717, USA
²² Swedish Collegium for Advanced Study, Linneanum Thunbergsvägen 2, 752 38 Uppsala, Sweden
²³ Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, TX 77843, USA
²⁴ NASA Marshall Space Flight Center, Huntsville, AL 35812, USA

Received: 14 August 2023
Accepted: 12 December 2023

Abstract

Direct-collapse black holes (DCBHs) of mass ∼10⁴ − 10⁵ M_⊙ that form in HI-cooling halos in the early Universe are promising progenitors of the ≳10⁹ M_⊙ supermassive black holes that fuel observed z ≳ 7 quasars. Efficient accretion of the surrounding gas onto such DCBH seeds may render them sufficiently bright for detection with the JWST up to z ≈ 20. Additionally, the very steep and red spectral slope predicted across the ≈1 − 5 μm wavelength range of the JWST/NIRSpec instrument during their initial growth phase should make them photometrically identifiable up to very high redshifts. In this work, we present a search for such DCBH candidates across the 34 arcmin² in the first two spokes of the JWST cycle-1 PEARLS survey of the north ecliptic pole time-domain field covering eight NIRCam filters down to a maximum depth of ∼29 AB mag. We identify two objects with spectral energy distributions consistent with theoretical DCBH models. However, we also note that even with data in eight NIRCam filters, objects of this type remain degenerate with dusty galaxies and obscured active galactic nuclei over a wide range of redshifts. Follow-up spectroscopy would be required to pin down the nature of these objects. Based on our sample of DCBH candidates and assumptions on the typical duration of the DCBH steep-slope state, we set a conservative upper limit of ≲5 × 10⁻⁴ comoving Mpc⁻³ (cMpc⁻³) on the comoving density of host halos capable of hosting DCBHs with spectral energy distributions similar to the theoretical models at z ≈ 6 − 14.