We constrain the spatial gradient of star formation history (SFH) within galaxies using the colour gradients in NUV - u (where NUV stands for near-ultraviolet) and u - i for a local spatially resolved galaxy sample. By splitting each galaxy into an inner and an outer part, we find that most galaxies show negative gradients in these two colours. We first rule out dust extinction gradient and metallicity gradient as the dominant source for the colour gradient. Then using stellar population models, we explore variations in SFH to explain the colour gradients. As shown by our earlier work, a two-phase SFH consisting of an early secular evolution (growth) phase and a subsequent rapid evolution (quenching) phase is necessary to explain the observed colour distributions among galaxies. We explore two different inside-out growth models and two different inside-out quenching models by varying parameters of the SFH between inner and outer regions of galaxies. Two of the models can explain the observed range of colour gradients in NUV - u and u - i colours. We further distinguish them using an additional constraint provided by the u - i colour gradient distribution, under the assumption of constant galaxy formation rate and a common SFH followed by most galaxies. We find the best model is an inside-out growth model in which the inner region has a shorter e-folding time-scale in the growth phase than the outer region. More spatially resolved UV observations are needed to improve the significance of the result.
|Number of pages||10|
|Journal||Monthly Notices of the Royal Astronomical Society|
|State||Published - Dec 1 2017|
Bibliographical noteFunding Information:
GALEX is a NASA Small Explorer, launched in 2003 April. We gratefully acknowledge NASA's support for the construction, operation and scientific analysis for the GALEX mission, developed in cooperation with the Centre National d'Etudes Spatiales of France and the Korean Ministry of Science and Technology. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, theUS Department of Energy, NASA, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web Site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, the Astrophysical Institute Potsdam, the University of Basel, the University of Cambridge, the Case Western Reserve University, the University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), the Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, the University of Pittsburgh, the University of Portsmouth, Princeton University, the United States Naval Observatory and the University of Washington.
© 2017 The Authors.
- Galaxies: evolution
- Galaxies: photometry
- Galaxies: star formation
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science