Abstract
Mapping Nearby Galaxies at Apache Point Observatory provides the opportunity to make precise spatially resolved measurements of the IMF slope in galaxies owing to its unique combination of spatial resolution, wavelength coverage, and sample size. We derive radial gradients in age, element abundances, and IMF slope analysing optical and near-infrared absorption features from stacked spectra out to the half-light radius of 366 early-type galaxies with masses 9.9-10.8 logM/M⊙. We find flat gradients in age and [α/Fe] ratio, as well as negative gradients in metallicity, consistent with the literature. We further derive significant negative gradients in the [Na/Fe] ratio with galaxy centres being well enhanced in Na abundance by up to 0.5 dex. Finally, we find a gradient in IMF slope with a bottom-heavy IMF in the centre (typical mass excess factor of 1.5) and a Milky Way-type IMF at the half-light radius. This pattern is mass dependent with the lowest mass galaxies in our sample featuring only a shallow gradient around a MilkyWay IMF. Our results imply the local IMF-σ relation within galaxies to be even steeper than the global relation and hint towards the local metallicity being the dominating factor behind the IMF variations. We also employ different stellar population models in our analysis and show that a radial IMF gradient is found independently of the stellar population model used. A similar analysis of theWing-Ford band provides inconsistent results and further evidence of the difficulty in measuring and modelling this particular feature.
| Original language | English |
|---|---|
| Pages (from-to) | 3954-3982 |
| Number of pages | 29 |
| Journal | Monthly Notices of the Royal Astronomical Society |
| Volume | 477 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jul 1 2018 |
Bibliographical note
Funding Information:TP would like to thank P. Guarnieri and P. Carter for fruitful discussions. The authors are grateful to C. Conroy for providing latest versions of their stellar population models. We are also thankful to the referee for useful comments and suggestions which have improved the paper. This research made use of the PYTHON packages NUMPY (Walt, Colbert & Varoquaux 2011), SCIPY (Jones et al. 2001), MATPLOTLIB (Hunter 2007), and ASTROPY (Astropy Collaboration 2013). This work also made use of MARVIN, a core PYTHON package and web framework for MaNGA data, developed by Brian Cherinka, José Sánchez-Gallego, and Brett Andrews. (MaNGA Collaboration, 2017). TP is funded by a University of Portsmouth PhD bursary. The Science, Technology and Facilities Council is acknowledged for support through the Consolidated Grant Cosmology and Astrophysics at Portsmouth, ST/N000668/1. Numerical computations were performed on the Sciama High Performance Computer cluster which is supported by the Institute of Cosmology of Gravitation, South East Physics Network and the University of Portsmouth. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofísica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut für Astrophysik Potsdam (AIP), Max-Planck-Institut für Astronomie (MPIA Heidelberg), Max-Planck-Institut für Astrophysik (MPA Garching), Max-Planck-Institut für Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatário Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autónoma de México, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University ofWashington, University ofWisconsin, Vanderbilt University, and Yale University.
Funding Information:
TP would like to thank P. Guarnieri and P. Carter for fruitful discussions. The authors are grateful to C. Conroy for providing latest versions of their stellar population models. We are also thankful to the referee for useful comments and suggestions which have improved the paper. This research made use of the PYTHON packages NUMPY (Walt, Colbert & Varoquaux 2011), SCIPY (Jones et al. 2001), MATPLOTLIB (Hunter 2007), and ASTROPY (Astropy Collaboration 2013). This work also made use of MARVIN, a core PYTHON package and web framework for MaNGA data, developed by Brian Cherinka, Jos? S?nchez-Gallego, and Brett Andrews. (MaNGA Collaboration, 2017). TP is funded by a University of Portsmouth PhD bursary. The Science, Technology and Facilities Council is acknowledged for support through the Consolidated Grant Cosmology and Astrophysics at Portsmouth, ST/N000668/1. Numerical computations were performed on the Sciama High Performance Computer cluster which is supported by the Institute of Cosmology of Gravitation, South East Physics Network and the University of Portsmouth. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the University of Utah. The SDSS web site is www.sdss.org. SDSS-IV is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS Collaboration including the Brazilian Participation Group, the Carnegie Institution for Science, Carnegie Mellon University, the Chilean Participation Group, the French Participation Group, Harvard-Smithsonian Center for Astrophysics, Instituto de Astrof?sica de Canarias, The Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, Lawrence Berkeley National Laboratory, Leibniz Institut f?r Astrophysik Potsdam (AIP), Max-Planck-Institut f?r Astronomie (MPIA Heidelberg), Max-Planck-Institut f?r Astrophysik (MPA Garching), Max-Planck-Institut f?r Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observat?rio Nacional/MCTI, The Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Aut?noma de M?xico, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University ofWashington, University ofWisconsin, Vanderbilt University, and Yale University.
Publisher Copyright:
© 2018 The Author(s).
Keywords
- CD
- Galaxies: elliptical and lenticular
- Galaxies: evolution
- Galaxies: formation
- Galaxies: fundamental parameters
- Galaxies: stellar content
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science