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Published September 11, 2013 | Submitted + Published
Journal Article Open

The build-up of nuclear stellar cusps in extreme starburst galaxies and major mergers


Nuclear stellar cusps are defined as central excess light component in the stellar light profiles of galaxies and are suggested to be stellar relics of intense compact starbursts in the central ∼100–500 pc region of gas-rich major mergers. Here, we probe the build-up of nuclear cusps during the actual starburst phase for a complete sample of luminous infrared galaxy (LIRG) systems (85 LIRGs, with 11.4 < log [LIR/L_⊙] < 12.5) in the Great Observatories All-sky LIRG Survey sample. Cusp properties are derived via 2D fitting of the nuclear stellar light imaged in the near-infrared (NIR) by the Hubble Space Telescope and have been combined with mid-infrared (IR) diagnostics for active galactic nucleus (AGN)/starburst characterization. We find that nuclear stellar cusps are resolved in 76 per cent of LIRGs (merger and non-interacting galaxies). The cusp strength and luminosity increase with far-IR luminosity (excluding AGN) and merger stage, confirming theoretical models that starburst activity is associated with the build-up of nuclear stellar cusps. Evidence for ultracompact nuclear starbursts is found in ∼13 per cent of LIRGs, which have a strong unresolved central NIR light component but no significant contribution of an AGN. The nuclear NIR surface density (measured within 1 kpc radius) increases by a factor of ∼5 towards late merger stages. A careful comparison to local early-type galaxies with comparable masses reveals (a) that local (U)LIRGs have a significantly larger cusp fraction and (b) that the majority of the cusp LIRGs have host galaxy luminosities (H band) similar to core ellipticals which are roughly one order in magnitude larger than those for cusp ellipticals.

Additional Information

© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 June 14. Received 2013 June 13; in original form 2013 March 14. The authors wish to thank Robert Joseph for a careful review of the manuscript and many valuable suggestions to improve this paper. The authors are very grateful to Tod R. Lauer for helpful discussions on the characterization of cusp and cores and the comparison between LIRGs and elliptical galaxies. This research has made use of the NASA/IPAC Extragalactic Database (NED) and the Infrared Science Archive (IRSA) which are operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Support for this work was provided through grant HST GO 11235.01-A by NASA from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. VC would like to acknowledge partial support from the EU FP7 grant PIRSES-GA-2012-316788. LA and DBS acknowledge the hospitality of the Aspen Center for Physics, which is supported by the National Science Foundation grant no. PHY-1066293.

Attached Files

Published - MNRAS-2013-Haan-1264-86.pdf

Submitted - 1306.4337v1.pdf


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August 22, 2023
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