Evidence for Merger Remnants in Early-Type Host Galaxies of Low-Redshift QSOs

By N. Bennert, G. Canalizo, B. Jungwiert, A. Stockton, F. Schweizer, C. Peng, M. Lacy. 2008

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We present results from a pilot HST ACS deep imaging study in broadband V of five low-redshift QSO host galaxies classified in the literature as ellipticals. The aim of our study is to determine whether these early-type hosts formed at high redshift and have since evolved passively, or whether they have undergone relatively recent mergers that may be related to the triggering of the nuclear activity. We perform two-dimensional modeling of the light distributions to analyze the host galaxies’ morphology. We find that, while each host galaxy is reasonably well fitted by a de Vaucouleurs profile, the majority of them (4/5) reveal significant fine structure such as shells and tidal tails. These structures contribute between ~5% and 10% to the total V-band luminosity of each host galaxy within a region of r ∼ 3reff and are indicative of merger events that occurred between a few hundred Myr and a Gyr ago. These timescales are comparable to starburst ages in the QSO hosts previously inferred from Keck spectroscopy. Our results thus support a consistent scenario in which most of the QSO host galaxies suffered mergers with accompanying starbursts that likely also triggered the QSO activity in some way, but we are also left with considerable uncertainty on physical mechanisms that might have delayed this triggering for several hundred Myr after the merger.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b45ccd768286c30b419b35387b4b489d05eb198b

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Citations in the corpus

THE BULK OF THE BLACK HOLE GROWTH SINCE z ∼ 1 OCCURS IN A SECULAR UNIVERSE: NO MAJOR MERGER–AGN CONNECTION (2010, background): “At the same time, deeper imaging of AGN host galaxies that were initially classified as undisturbed revealed post-merger features not previously detected, both from space-based (Canalizo et al. 2007; Bennert et al. 2008) and ground-based observations (Ramos Almeida et al. 2010).”
REVERBERATION MAPPING MEASUREMENTS OF BLACK HOLE MASSES IN SIX LOCAL SEYFERT GALAXIES (2010, background): “…and theoretical) that there is a connection between supermassive black hole (BH) growth and galaxy evolution (e.g., Silk & Rees 1998; Kormendy & Gebhardt 2001; Häring & Rix 2004; Di Matteo et al. 2005; Bennert et al. 2008; Somerville et al. 2008; Hopkins & Hernquist 2009; Shankar et al. 2009).”
What drives the growth of black holes (2011, background): “%) and, importantly, is found to be higher than comparably massive distant galaxies (e.g., Bahcall et al., 1997; Canalizo & Stockton, 2001; Dunlop et al., 2003; Guyon et al., 2006; Bennert et al., 2008; Urrutia et al., 2008).”
Galaxy pairs in the Sloan Digital Sky Survey – IX. Merger-induced AGN activity as traced by the Wide-field Infrared Survey Explorer (2014, background): “A number of studie have found evidence for mergers in luminous quasar hosts (e.g., Canalizo & Stockton 2001; Bennert et al. 2008; Urrutia et al. 2008; Foreman, Volonteri & Dotti 2009; Ramos Almeida et al. 2011; Bessiere et al. 2012; Urrutia et al. 2012), where the link to interactions is fairly…”
MERGERS AND BULGE FORMATION IN ΛCDM: WHICH MERGERS MATTER? (2009, background): “Observations have similarly linked mergers to at least some of the quasar population (Sanders et al. 1988; Canalizo & Stockton 2001; Guyon et al. 2006; Dasyra et al. 2007; Bennert et al. 2008).”
CANDELS: CONSTRAINING THE AGN–MERGER CONNECTION WITH HOST MORPHOLOGIES AT z ∼ 2 (2011, background): “At low redshifts luminous quasi-stellar objects (QSOs) have long been tied to ongoing or past merger activity (Stockton 1982; Canalizo & Stockton 2001; Bennert et al. 2008).”
Galaxy Zoo: 'Hanny's Voorwerp', a quasar light echo? (2009, background): “The connection between AGN and mergers suggests that the subsequently triggered AGN episodes last typically for 108 yr (Stockton 1982; Bahcall et al. 1997) and may last for up to 109 yr (Bennert et al. 2008).”
A SEARCH FOR BINARY ACTIVE GALACTIC NUCLEI: DOUBLE-PEAKED [O iii] AGNs IN THE SLOAN DIGITAL SKY SURVEY (2009, background): “While seemingly undisturbed AGNs are observed, high-resolution imaging of quasars shows close companions and features of gravitational interaction in many cases (e.g., Bahcall et al. 1997; Bennert et al. 2008).”
The quasar relation through cosmic time – II. Evidence for evolution from z = 3 to the present age (2009, background): “…may experience episodic rejuvenation, but this only marginally affects the mean age of the stellar content: The stellar shells observed, e.g., by Canalizo et al. (2007) and Bennert et al. (2008) in low-redshift quasar host galaxies account for 5 – 10 per cent of the total stellar population.”
Morphologies of z ∼ 0.7 AGN host galaxies in CANDELS: no trend of merger incidence with AGN luminosity (2014, background): “However, host galaxies of moderately luminous AGN and radio-selected AGN show weak merger features with higher surface brightnesses than found in control galaxies (Bennert et al. 2008; Ramos Almeida et al. 2012).”