We present the stellar population and ionized-gas outflow properties of ultraluminous IR galaxies (ULIRGs) at z = 0.1-1.0 that are selected from the AKARI far-IR all-sky survey. We construct a ...catalog of 1077 ULIRGs to examine feedback effects after major mergers. Of the 1077 ULIRGs, 202 are spectroscopically identified by SDSS and Subaru/FOCAS observations. Thanks to the deeper depth and higher resolution of AKARI compared to the previous Infrared Astronomical Satellite (IRAS) survey and reliable identification from the Wide-field Infrared Survey Explorer (WISE) mid-IR pointing, the sample is unique in identifying optically faint (i ∼ 20) IR-bright galaxies, which could be missed in previous surveys. A self-consistent spectrum and broadband spectral energy distribution (SED) decomposition method, which constrains stellar population properties in SED modeling based on spectral fitting results, has been employed for 149 ULIRGs whose optical continua are dominated by host galaxies. They are massive galaxies ( -1012 M ) associated with intense star formation activities (SFR ∼ 200-2000 M yr−1). The sample covers a range of active galactic nucleus (AGN) bolometric luminosity of 1010-1013 L , and the outflow velocity measured from the O iii 5007 line shows a correlation with AGN luminosity. Eight galaxies show extremely fast outflows with velocity up to 1500-2000 km s−1. However, the coexistence of vigorous starbursts and strong outflows suggests the star formation has not been quenched during the ULIRG phase. By deriving the stellar mass and mass fraction of the young stellar population, we find no significant discrepancies between stellar properties of ULIRGs with weak and powerful AGNs. The results are not consistent with the merger-induced evolutionary scenario, which predicts that star formation-dominated ULIRGs will show smaller stellar masses and younger stellar populations compared to AGN-dominated ULIRGs.
Abstract
We study spatially resolved properties (on spatial scales of ∼1–2 kpc out to at least 3 effective radii) of the stars, dust, and gas in 10 nearby spiral galaxies. The properties of the ...stellar population and dust are derived by fitting the spatially resolved spectral energy distribution (SED) with more than 20 photometric bands ranging from far-ultraviolet to far-infrared. Our newly developed software
piXedfit
performs point-spread function matching of images, pixel binning, and models the stellar light, dust attenuation, dust emission, and emission from a dusty torus heated by an active galactic nucleus simultaneously through the energy-balance approach. With this self-consistent analysis, we present the spatially resolved version of the IRX–
β
relation, finding that it is consistent with the relationship from the integrated photometry. We show that the old stellar populations contribute to the dust heating, which causes an overestimation of the star formation rate (SFR) derived from the total ultraviolet and infrared luminosities on kiloparsec scales. With archival high-resolution maps of atomic and molecular gas, we study the radial variation of the properties of the stellar populations (including stellar mass, age, metallicity, and SFR), dust (including dust mass, dust temperature, and abundance of polycyclic aromatic hydrocarbon), and gas, as well as dust-to-stellar mass and dust-to-gas mass ratios. We observe a depletion of the molecular gas mass fraction in the central region of the majority of the galaxies, suggesting that the lack of available fuel is an important factor in suppressing the specific SFR at the center.
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