Dissipation and Extra Light in Galactic Nuclei: III. 'Core' Ellipticals and 'Missing' Light

Abstract

We investigate how 'extra' central light in the surface brightness profiles of cusp ellipticals relates to the profiles of ellipticals with cores. Cusp elliptical envelopes are formed by violent relaxation in mergers acting on stars in progenitor disks, while their centers are structured by dissipational starbursts. Core ellipticals are formed by subsequent merging of (now gas-poor) cusp ellipticals, with the fossil starburst components combining to preserve a compact component in the remnant (although the 'transition' is smoothed). Comparing hydrodynamical simulations and observed profiles, we show how to observationally isolate the relic starburst components in core ellipticals. We demonstrate that these survive re-mergers and reliably trace the dissipation in the initial gas-rich merger(s). The typical degree of dissipation is a strong function of stellar mass, tracing observed disk gas fractions. We find a correlation between dissipation and effective radius: systems with more dissipation are more compact. The survival of this component and scattering of stars into the envelope naturally explain high-Sersic index profiles characteristic of massive core ellipticals. This is also closely related to the kinematics and isophotal shapes: only systems with matched starburst components from their profile fits also reproduce the observed kinematics of boxy/core ellipticals. We show that it is critical to adopt physically motivated profiles when attempting to quantify how much mass has been 'scoured' or scattered out of the inner regions by binary black holes. Estimates of scoured mass ignoring multi-component structure can be strongly biased, potentially explaining observed systems with large inferred core masses in apparent conflict with core-scouring models.

48 pages, 37 figures, accepted to ApJ (revised to match accepted version; added comparison of kinematics and isophotal shapes)

References in corpus (14)

• A Semi-Analytic Model for the Co-evolution of Galaxies, Black Holes, and Active Galactic Nuclei
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• Galaxy Evolution from Halo Occupation Distribution Modeling of DEEP2 and SDSS Galaxy Clustering
• The SAURON project -- X. The orbital anisotropy of elliptical and lenticular galaxies: revisiting the (V/sigma,epsilon) diagram with integral-field stellar kinematics
• The SAURON project - XII. Kinematic substructures in early-type galaxies: evidence for disks in fast rotators
• Spatially resolved spectroscopy of early-type galaxies over a range in mass
• Dissipation and Extra Light in Galactic Nuclei: I. Gas-Rich Merger Remnants
• Dissipationless Mergers of Elliptical Galaxies and the Evolution of the Fundamental Plane
• The Radical Consequences of Realistic Satellite Orbits for the Heating and Implied Merger Histories of Galactic Disks
• Host dynamics and origin of Palomar-Green QSOs
• The Co-Formation of Spheroids and Quasars Traced in their Clustering
• Dissipation and the Fundamental Plane: Observational Tests
• The growth of luminous red galaxies by merging
• The spatially resolved stellar populations of isolated early-type galaxies

Cited by in corpus (4)

• An ultra-deep near-infrared spectrum of a compact quiescent galaxy at z=2.2
• Quasars Are Not Light-Bulbs: Testing Models of Quasar Lifetimes with the Observed Eddington Ratio Distribution
• Feedback from central black holes in elliptical galaxies. I: models with either radiative or mechanical feedback but not both
• The SAURON Project - XIV. No escape from V${}_{\mathrm{esc}}$: a global and local parameter in early-type galaxy evolution