Suchergebnisse

We investigate radiation hardness within a representative sample of 67 nearby (0.02 ≤ z ≤ 0.06) star-forming (SF) galaxies using the integral field spectroscopic data from the MaNGA survey. The softness parameter η = O+/O2+S+/S2+ is sensitive to the spectral energy distribution of the ionizing radiation. We study η via the observable quantity η' (=[O II]/[O III] [S II][S III] ). We analyze the relation between radiation hardness (traced by η and η') and diagnostics sensitive to gas-phase metallicity, electron temperature, density, ionization parameter, effective temperature, and age of ionizing populations. It is evident that low metallicity is accompanied by low log η', i.e. hard radiation field. No direct relation is found between radiation hardness and other nebular parameters though such relations cannot be ruled out. We provide empirical relations between log η and strong emission line ratios N2, O3N2, and Ar3O3, which will allow future studies of radiation hardness in SF galaxies where weak auroral lines are undetected. We compare the variation of [OIII]/[O II] and [S III]/[S II] for MaNGA data with SF galaxies and HII regions within spiral galaxies from literature and find that the similarity and differences between different data set are mainly due to the metallicity. We find that predictions from photoionization models considering young and evolved stellar populations as ionizing sources in good agreement with the MaNGA data. This comparison also suggests that hard radiation fields from hot and old low-mass stars within or around SF regions might significantly contribute to the observed η values. © 2021 The Author(s). ; NK acknowledges financial support from the Schlumberger Foundation, which facilitated her stay at the KICC during which a majority of work was carried out. RA acknowledges support from FONDECYT (Fondo Nacional de Desarrollo Científico y Tecnológico) regular grant 1202007. RM acknowledges ERC (European Research Council) advanced grant 695671 'QUENCH' and support by the Science and Technology Facilities Council (STFC). This project makes use of the MaNGA-Pipe3D data products. We thank the IA-UNAM MaNGA team for creating this catalogue, and the ConaCyt-180125 project for supporting them (Sánchez et al. 2016b). This research made use of Marvin, a core PYTHON package and web framework for MaNGA data, developed by Brian Cherinka, José Sánchez-Gallego, Brett Andrews, and Joel Brownstein (Cherinka et al. 2019); SAOImage DS9, developed by Smithsonian Astrophysical Observatory; and Astropy, a community-developed core PYTHON package for astronomy (Astropy Collaboration 2013). ; With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709. ; Peer reviewed

We present an overview of a new integral field spectroscopic survey called MaNGA (Mapping Nearby Galaxies at Apache Point Observatory), one of three core programs in the fourth-generation Sloan Digital Sky Survey (SDSS-IV) that began on 2014 July 1. MaNGA will investigate the internal kinematic structure and composition of gas and stars in an unprecedented sample of 10,000 nearby galaxies. We summarize essential characteristics of the instrument and survey design in the context of MaNGA's key science goals and present prototype observations to demonstrate MaNGA's scientific potential. MaNGA employs dithered observations with 17 fiber-bundle integral field units that vary in diameter from 12 '' (19 fibers) to 32 '' (127 fibers). Two dual-channel spectrographs provide simultaneous wavelength coverage over 3600-10300 angstrom at R similar to 2000. With a typical integration time of 3 hr, MaNGA reaches a target r-band signal-to-noise ratio of 4-8 (angstrom(-1) per 2 '' fiber) at 23 AB mag arcsec(-2), which is typical for the outskirts of MaNGA galaxies. Targets are selected with M* greater than or similar to 10(9) M-circle dot using SDSS-I redshifts and i-band luminosity to achieve uniform radial coverage in terms of the effective radius, an approximately flat distribution in stellar mass, and a sample spanning a wide range of environments. Analysis of our prototype observations demonstrates MaNGA's ability to probe gas ionization, shed light on recent star formation and quenching, enable dynamical modeling, decompose constituent components, and map the composition of stellar populations. MaNGA's spatially resolved spectra will enable an unprecedented study of the astrophysics of nearby galaxies in the coming 6 yr. ; Alfred P. Sloan Foundation ; National Science Foundation ; U.S. Department of Energy Office of Science ; Carnegie Mellon University ; Colorado University ; Boulder ; Harvard-Smithsonian Center for Astrophysics Participation Group ; Johns Hopkins University ; Kavli Institute for the Physics and Mathematics of the Universe ; Max-Planck-Institut fuer Astrophysik (MPA Garching) ; Max-Planck-Institut fuer Extraterrestrische Physik (MPE) ; Max-Planck-Institut fuer Astronomic (MPIA Heidelberg) ; National Astronomical Observatories of China ; New Mexico State University ; New York University ; Ohio State University ; Penn State University ; Shanghai Astronomical Observatory ; United Kingdom Participation Group ; University of Portsmouth ; University of Utah ; University of Wisconsin ; Yale University ; World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan ; People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7 under REA PITN-GA-2011-289313 ; Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences Xdb09000000 ; National Natural Science Foundation of China (NSFC) 11333003 ; Royal Society University Research Fellowship ; Sloan Foundation ; Packard Foundation ; Grainger Foundation ; McDonald Observatory