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The Large Deficit of HMXB Emission from Luminous Infrared Galaxies: The Case of the Circumnuclear Starburst Ring in NGC 7552

West, Lacey; Garofali, Kristen; Lehmer, Bret D.; Prestwich, Andrea; Eufrasio, Rafael; Luangtip, Wasutep; Roberts, Timothy P.; Zezas, Andreas

The Large Deficit of HMXB Emission from Luminous Infrared Galaxies: The Case of the Circumnuclear Starburst Ring in NGC 7552 Thumbnail


Authors

Lacey West

Kristen Garofali

Bret D. Lehmer

Andrea Prestwich

Rafael Eufrasio

Andreas Zezas



Abstract

Luminous infrared galaxies (LIRGs), the most extreme star-forming galaxies in the nearby (D < 30 Mpc) universe, show a notable X-ray emission deficiency (up to a factor of ∼10) compared with predictions from scaling relations of galaxy-wide high-mass X-ray binary (HMXB) luminosity with star formation rate. In the nearby (≈20 Mpc) LIRG NGC 7552, the majority of the IR emission originates in a circumnuclear starburst ring, which has been resolved into several discrete knots of star formation. We present results from recent Chandra observations of NGC 7552, which reveal significant deficits in the 2–7 keV X-ray luminosities from two of the most powerful star-forming knots. We hypothesize that the expected luminous HMXB populations in these knots are either (1) obscured by very large column densities or (2) suppressed due to the knots having relatively high metallicity and/or very young ages (≲5 Myr). We distinguish between these possibilities using data from recent NuSTAR observations, whose sensitivity above 10 keV is capable of uncovering heavily obscured HMXB populations, since emission at these energies is more immune to absorption effects. We find no evidence of a heavily obscured HMXB population in the central region of NGC 7552, suggesting suppressed HMXB formation. We further show that metallicity-dependent scaling relations cannot fully account for the observed deficit from the most powerful star-forming knots or the central region as a whole. Thus, we suggest that recent bursts in local star formation activity likely drive the high LIR within these regions on timescales ≲5 Myr, shorter than the timescale required for the formation of HMXBs.

Citation

West, L., Garofali, K., Lehmer, B. D., Prestwich, A., Eufrasio, R., Luangtip, W., …Zezas, A. (2023). The Large Deficit of HMXB Emission from Luminous Infrared Galaxies: The Case of the Circumnuclear Starburst Ring in NGC 7552. Astrophysical Journal, 952(1), Article 22. https://doi.org/10.3847/1538-4357/acd9aa

Journal Article Type Article
Acceptance Date May 26, 2023
Online Publication Date Jul 14, 2023
Publication Date Jul 20, 2023
Deposit Date Feb 21, 2024
Publicly Available Date Feb 21, 2024
Journal The Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 952
Issue 1
Article Number 22
DOI https://doi.org/10.3847/1538-4357/acd9aa
Keywords Space and Planetary Science; Astronomy and Astrophysics
Public URL https://durham-repository.worktribe.com/output/2271861

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Copyright Statement
© 2023. The Author(s). Published by the American Astronomical Society
Original content from this work may be used under the terms
of the Creative Commons Attribution 4.0 licence. Any further
distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.





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