A Wide and Deep Exploration of Radio Galaxies with Subaru HSC (WERGS). II. Physical Properties Derived from the SED Fitting with Optical, Infrared, and Radio Data

Abstract

We present physical properties of radio galaxies (RGs) with f 1.4GHz > 1 mJy discovered by Subaru Hyper Supreme-Cam (HSC) and VLA Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey. For 1056 FIRST RGs at 0 < z ≤ 1.7 with HSC counterparts in about 100 deg 2 , we compiled multi-wavelength data of optical, near-infrared (IR), mid-IR, far-IR, and radio (150 MHz). We derived their color excess (E(B − V ) * ), stellar mass, star formation rate (SFR), IR luminosity, the ratio of IR and radio luminosity (q IR ), and radio spectral index (α radio ) that are derived from the SED fitting with CIGALE. We also estimated Eddington ratio based on stellar mass and integration of the best-fit SEDs of AGN component. We found that E(B − V ) * , SFR, and IR luminosity clearly depend on redshift while stellar mass, q IR , and α radio do not significantly depend on redshift. Since optically-faint (i AB ≥ 21.3) RGs that are newly discovered by our RG survey tend to be high redshift, they tend to not only have a large dust extinction and low stellar mass but also have high SFR and AGN luminosity, high IR luminosity, and high Eddington ratio compared to optically-bright ones. The physical properties of a fraction of RGs in our sample seem to differ from a classical view of RGs with massive stellar mass, low SFR, and low Eddington ratio, demonstrating that our RG survey with HSC and FIRST provides us curious RGs among entire RG population.

The eROSITA Final Equatorial-Depth Survey (eFEDS)

“…We employed the new version of the Code Investigating GALaxy Emission (CIGALE; Burgarella et al 2005;Noll et al 2009;Boquien et al 2019) called X-CIGALE 3 (Yang et al 2020), which enables SED fitting in the X-ray-to-radio range. In X-CIGALE, we are able to handle many parameters, such as the star formation history (SFH), single stellar population (SSP), attenuation law, AGN emission, dust emission, radio synchrotron emission, and AGN X-ray emission (see, e.g., Boquien et al 2014Boquien et al , 2016Buat et al 2015;Lo Faro et al 2017;Toba et al 2019bToba et al , 2020c. A brief description of each parameter is provided in Appendix B, and the parameter ranges used in the SED fitting are presented in Table B.1 (see also Boquien et al 2019;Yang et al 2020, and references therein).…”

“…Flux densities in the optical to MIR were corrected for galactic extinction according to Fitzpatrick (1999) and Schlafly & Finkbeiner (2011). The SPIRE FIR flux densities were corrected for flux boosting (see, e.g., Valiante et al 2016;Toba et al 2019b).…”

Search for Optically Dark Infrared Galaxies without Counterparts of Subaru Hyper Suprime-Cam in the AKARI North Ecliptic Pole Wide Survey Field

“…For AGN emission, we used models provided by Fritz et al (2006). In order to avoid a degeneracy of AGN templates in the same manner as in Ciesla et al (2015) and Toba et al (2019b), we fixed certain parameters that determine the number density distribution of the dust within the dust torus, i.e., ratio of the maximum to minimum radii of the torus (R max /R min ), density profile along the radial and the polar distance coordinates parameterized by β and γ (see equation 3 in Fritz et al 2006), and opening angle (θ). We parameterized the optical depth at 9.7 µm (τ 9.7 ) and ψ parameter (an angle between equatorial axis and line of sight) that corresponds to our viewing angle of the torus.…”

“…The typical uncertainty of z photo is about 20% (see also Section 4.6.1). Hereafter, we will focus on a subsample of 112 AKARI galaxies with reduced χ 2 of their SED fitting smaller than 5.0 in the same manner as Toba et al (2019b).…”

“…Finally, we check whether or not the derived physical properties in this work can actually be estimated reliably, given the uncertainty of the photometry. We conduct a mock analysis that is a procedure provided by CIGALE (see e.g., Buat et al 2012Buat et al , 2014Ciesla et al 2015;Lo Faro et al 2017;Boquien et al 2019;Toba et al 2019b, for more detail). Figure 13 shows the differences in z photo , V -band attenuation in the ISM (A V ), stellar mass, SFR, and L IR (AGN) derived from CIGALE in this work and those derived from the mock catalog as a function of redshift.…”