2017/11/01 by R. Scott Barrows, Julia M. Comerford, Nadia L. Zakamska +1 · 2 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Galaxy merger #Gamma-ray bursts and supernovae #Intergalactic star #Luminosity #Star formation #Supermassive black hole #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aa93de
17 pages, 10 figures, accepted for publication in The Astrophysical Journal
arxiv created 2017/11/01 · openalex created_date 2017/11/10 · openalex publication_date 2017/11/14 · arxiv updated 2017/11/29 · openalex updated_date 2026/08/06
Abstract Galaxy mergers are capable of triggering both star formation and active galactic nuclei (AGNs) and therefore may represent an important pathway in the co-evolution of galaxies and supermassive black holes (SMBHs). However, correlated enhancements of merger-induced star formation and AGN triggering may be hidden by the variable conditions and timescales during which they occur. In Paper I, we presented evidence of merger-triggered AGN in a sample of six late-stage galaxy mergers ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2</mml:mn> <mml:mo>–</mml:mo> <mml:mn>8</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>kpc</mml:mi> </mml:math> nuclear separations). In this follow-up work, we use multi-wavelength Hubble Space Telescope imaging and additional archival data to examine their star-forming properties to test for merger-triggered star formation and if it is correlated with SMBH growth. We find that the morphological asymmetries are correlated with enhanced specific star formation rates, indicating the presence of merger-triggered star formation. Additionally, the stellar populations become younger with increasing radius from the nucleus, indicating that the merger-induced star formation primarily occurs on global scales. However, we also find that the star formation rate enhancements are consistent with or lower than those of larger separation galaxy pair samples. This result is consistent with simulations predicting a decline of the global star formation rates in late-stage galaxy mergers with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo><</mml:mo> <mml:mn>10</mml:mn> <mml:mspace width="0.25em"/> <mml:mi>kpc</mml:mi> </mml:math> nuclear separations. Finally, we find that enhancements in specific star formation rate and AGN luminosity are positively correlated, but that an average temporal delay of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mo>≳</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>8</mml:mn> </mml:mrow> </mml:msup> </mml:math> years likely exists between the peak of global star formation and the onset of AGN triggering in 80% of the systems.