Self-consistent predictions for LIER-like emission lines from post-AGB stars

Abstract

Early type galaxies (ETGs) frequently show emission from warm ionized gas. These Low Ionization Emission Regions (LIERs) were originally attributed to a central, low-luminosity active galactic nuclei. However, the recent discovery of spatially-extended LIER emission suggests ionization by both a central source and an extended component that follows a stellar-like radial distribution. For passively-evolving galaxies with old stellar populations, hot post-Asymptotic Giant Branch (AGB) stars are the only viable extended source of ionizing photons. In this work, we present the first prediction of LIER-like emission from post-AGB stars that is based on fully self-consistent stellar evolution and photoionization models. We show that models where post-AGB stars are the dominant source of ionizing photons reproduce the nebular emission signatures observed in ETGs, including LIER-like emission line ratios in standard optical diagnostic diagrams and H$\alpha$ equivalent widths of order 0.1-3 angstroms. We test the sensitivity of LIER-like emission to the details of post-AGB models, including the mass loss efficiency and convective mixing efficiency, and show that line strengths are relatively insensitive to post-AGB timescale variations. Finally, we examine the UV-optical colors of the models and the stellar populations responsible for the UV-excess observed in some ETGs. We find that allowing as little as 3% of the HB population to be uniformly distributed to very hot temperatures (30,000 K) produces realistic UV colors for old, quiescent ETGs.

ApJ accepted. 20 pages, 8 figures

References in corpus (18)

• Modules for Experiments in Stellar Astrophysics (MESA)
• The Host Galaxies and Classification of Active Galactic Nuclei
• The propagation of uncertainties in stellar population synthesis modeling I: The relevance of uncertain aspects of stellar evolution and the IMF to the derived physical properties of galaxies
• Overview of the SDSS-IV MaNGA Survey: Mapping Nearby Galaxies at Apache Point Observatory
• The MAPPINGS III Library of Fast Radiative Shock Models
• The Assembly Histories of Quiescent Galaxies Since z=0.7 from Absorption Line Spectroscopy
• Mass loss on the red giant branch: the value and metallicity dependence of Reimers' η in globular clusters
• SDSS IV MaNGA - The spatially resolved transition from star formation to quiescence
• Synthetic nebular emission from massive galaxies I: origin of the cosmic evolution of optical emission-line ratios
• Evolution of Thermally Pulsing Asymptotic Giant Branch Stars IV. Constraining Mass-Loss & Lifetimes of Low Mass, Low Metallicity AGB Stars
• Origin and Dynamical Support of Ionized Gas in Galaxy Bulges
• The Dearth of UV-Bright Stars in M32: Implications for Stellar Evolution Theory
• Diffuse Gas in Retired Galaxies: Nebular Emission Templates and Constraints on the Sources of Ionization
• On the Production of He, C and N by Low and Intermediate Mass Stars: A Comparison of Observed and Model-Predicted Planetary Nebula Abundances
• The MASSIVE Survey VI: The Spatial Distribution and Kinematics of Warm Ionized Gas in the Most Massive Local Early-type Galaxies
• Binary stars and the UVX in early type galaxies
• Discovery of kpc-scale line emission in barred galaxies, not linked to AGN or star formation
• An Extensive Grid of Models Producing Extreme Horizontal Branch Stars

Cited by in corpus (10)

• The contribution from stars stripped in binaries to cosmic reionization of hydrogen and helium
• The diffuse ionized gas (DIG) in star-forming galaxies: the influence of aperture effects on local HII regions
• Delayed Photons from Binary Evolution Help Reionize the Universe
• Star formation in outer rings of S0 galaxies. II. NGC 4513 -- a multi-spin ringed S0 galaxy
• Brackett-$\gamma$ as a Gold-standard Test of Star Formation Rates Derived from SED Fitting
• Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas
• Diffuse LINER-type emission from extended disc regions of barred galaxies
• Star formation in outer rings of S0 galaxies. III. UGC 5936 -- an S0 with currently accreted satellite matter
• Linking the properties of accreting white dwarfs with the ionization state of their ambient medium
• Broadband photometry of asteroid 6478 Gault: activity and morphology