A study of the central stellar populations of galaxies in SDSS-IV MaNGA: identification of a sub-sample with unusually young and massive stars

Abstract

This paper describes a search for galaxy centers with clear indications of unusual stellar populations with an initial mass function flatter than Salpeter at high stellar masses. Out of a sample of 668 face-on galaxies with stellar masses in the range 10^10- 10^11 M_sol, I identify 15 galaxies with young to intermediate age central stellar populations with unusual stellar population gradients in the inner regions of the galaxy. In these galaxies, the 4000 Angstrom break is either flat or rising towards the center of the galaxy, indicating that the central regions host evolved stars, but the H$\alpha$ equivalent width also rises steeply in the central regions. The ionization parameter [OIII]/[OII] is typically low in these galactic centers, indicating that ionizing sources are stellar rather than AGN. Wolf Rayet features characteristic of hot young stars are often found in the spectra and these also get progressively stronger at smaller galactocentric radii. These outliers are compared to a control sample of galaxies of similar mass with young inner stellar populations, but where the gradients in Halpha equivalent width and 4000 Angstrom break follow each other more closely. The outliers exhibit central Wolf Rayet red bump excesses much more frequently, they have higher central stellar and ionized gas metallicities, and they are also more frequently detected at 20 cm radio wavelengths. I highlight one outlier where the ionized gas is clearly being strongly perturbed and blown out either by massive stars after they explode as supernovae, or by energy injection from matter falling onto a black hole.

arXiv comment16 pages, 16 figures, accepted for publication in MNRAS

References in corpus (47)

• Stellar population synthesis at the resolution of 2003
• On the variation of the Initial Mass Function
• A Fundamental Relation Between Supermassive Black Holes and Their Host Galaxies
• Starburst99: Synthesis Models for Galaxies with Active Star Formation
• The Host Galaxies of AGN
• A Relationship Between Nuclear Black Hole Mass and Galaxy Velocity Dispersion
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• Parametric Recovery of Line-of-Sight Velocity Distributions from Absorption-Line Spectra of Galaxies via Penalized Likelihood
• 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 epochs of early-type galaxy formation as a function of environment
• Sloan Digital Sky Survey IV: Mapping the Milky Way, Nearby Galaxies, and the Distant Universe
• The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey
• Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars
• Differential Galaxy Evolution in Cluster and Field Galaxies at z=0.3
• Present-Day Growth of Black Holes and Bulges: the SDSS Perspective
• The Dust Opacity of Star-Forming Galaxies
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• The runaway growth of intermediate-mass black holes in dense star clusters
• The Stellar Cusp Around the Supermassive Black Hole in the Galactic Center
• UV-extended E-MILES stellar population models: young components in massive early-type galaxies
• Host galaxies, clustering, Eddington ratios, and evolution of radio, X-ray, and infrared-selected AGNs
• The MaNGA Integral Field Unit Fiber Feed System for the Sloan 2.5 m Telescope
• The Data Reduction Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey
• The Effects of Stellar Rotation. II. A Comprehensive Set of Starburst99 Models
• Stellar disk in the galactic center -- a remnant of a dense accretion disk?
• The SDSS-IV MaNGA Sample: Design, Optimization, and Usage Considerations
• Nuclear Star Clusters
• New Models for Wolf-Rayet and O Star Populations in Young Starbursts
• SDSS IV MaNGA - Spatially resolved diagnostic diagrams: A proof that many galaxies are LIERs
• SDSS-IV MaNGA IFS Galaxy Survey --- Survey Design, Execution, and Initial Data Quality
• The Data Analysis Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey: Overview
• Spectral synthesis including massive binaries
• Stellar Populations in the Central 0.5 pc of the Galaxy II: The Initial Mass Function
• Color--Mass-to-Light Ratio Relations for Disk Galaxies
• The Data Analysis Pipeline for the SDSS-IV MaNGA IFU Galaxy Survey: Emission-Line Modeling
• The SINS/zC-SINF survey of z~2 galaxy kinematics: SINFONI adaptive optics-assisted data and kiloparsec-scale emission line properties
• Galaxies with Wolf-Rayet signatures in the low-redshift Universe - A survey using the Sloan Digital Sky Survey
• Firefly (Fitting IteRativEly For Likelihood analYsis): a full spectral fitting code
• A High-Resolution Stellar Library for Evolutionary Population Synthesis
• Stellar Population and Kinematic Profiles in Spiral Bulges & Disks: Population Synthesis of Integrated Spectra
• The Galactic WC and WO stars: The impact of revised distances from Gaia DR2 and their role as massive black hole progenitors
• Colors and color gradients in bulges of galaxies
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• A New Diagnostic to Separate Line Emission from Star Formation, Shocks, and AGN Simultaneously in IFU Data
• Wolf-Rayet galaxies in SDSS-IV MaNGA. I. Catalog construction and sample properties

Cited by in corpus (2)

• A study of outer disk stellar populations of face-on star-forming galaxies in SDSS-IV MaNGA: causes of H$\alpha$ deficiency
• A study of 1000 galaxies with unusually young and massive stars in the SDSS: a search for hidden black holes