Staffing:

In order to examine the SEDs for AGN host galaxies, I use model SEDs, which are made by combining a stellar population, optical-UV emission from AGN BBB, hot dust emission from AGN torus, and IR starburst templates to match the broadband photometry SEDs of AGN sample. The nuclear emission contributes significantly to the UV-to-optical parts of the spectra of unobscured (Type 1) AGNs (e.g. Elvis et al. 2012; Hao et al. 2013), while in obscured (Type 2) AGNs, the nuclear emission dominates the SED only in the X-ray band and at other wavelengths, the light is mainly due to the galaxy emission combined with

Table 4.1. Detection Fraction for Each Photometry Band Photometry Band Detection fraction

GALEX NUV 13%(466/3701) CFHT U 68%(2519/3701) Subaru B 76%(2819/3701) Subaru V 77%(2845/3701) Subaru r 84%(3104/3701) Subaru i 85%(3137/3701) Subaru z+ _{87%(3213/3701)} UltraVista Y 73%(2720/3701) UltraVista J 75%(2783/3701) UltraVista H 78%(2878/3701) UltraVista Ks 80%(2944/3701) Spitzer 3.6µm 92%(3390/3701) Spitzer 4.5µm 92%(3391/3701) Spitzer 5.8µm 86%(3169/3701) Spitzer 8.0µm 78%(2888/3701)

reprocessed nuclear emission in the NIR and MIR. While nuclear emission, reprocessed by dust, could significantly contribute to the MIR luminosity, the FIR luminosity is known to be dominated by galaxy emission produced by star-formation activity (e.g., Kirkpatrick et al. 2012). Although a recent study by Symeonidis (2017) pointed out that the most powerful unobscured quasars could dominate the FIR luminosity, I only consider the far-IR luminosity produced by starburst activity for this sample of moderate-luminosity AGNs.

The optical SED of a galaxy represents the integrated light of the stellar populations. I have generated a set of synthetic spectra from the stellar population synthesis models of Bruzual & Charlot (2003). The solar metallicity and the Chabrier (2003) initial mass function (IMF) have been used. I have built 10 exponentially decaying star-formation histories (SFH), where the optical star-formation rate is defined as SFR ∝ et/τ_{, with}

characteristic times ranging from τ = 0.1 to 30 Gyr, and a model with constant star formation. For each SFH, the SEDs are generated by models with 15 grids of ages (tage)

ranging from 0.1 to 10 Gyr, with the additional constraint on each component that the age should be smaller than the age of the universe at the redshift of the source. The library

of stellar population models is composed of 165 templates. Since the stellar light can be affected by dust extinction, I take into account the reddening effect using the Calzetti et al. (2000) law. I have considered E(B − V ) values in the range between 0 and 0.5 with steps of 0.05, and the range between 0.5 and 1 with a step of 0.1. I show some examples of stellar population templates with various combinations of τ =[0.1, 1, 3], and tage=[50 Myr, 2 Gyr]

with E(B − V )=[0.0, 0.3] in Figure 4.1 (green curves).

The UV-to-optical part of the SED of unobscured (Type 1) AGN is dominated by the nuclear emission from the BBB. The BBB template is taken from Richards et al. (2006). This template is reddened according to the Prevot et al. (1984) reddening law for the Small Magellanic Clouds (SMC, which seems to be appropriate for Type 1 AGNs; Hopkins et al. 2004; Salvato et al. 2009). The E(B − V )AGNvalues range between 0 and 1 with a variable

step (∆E(B−V )AGN= 0.01 for E(B−V )AGNbetween 0 and 0.1, and ∆E(B−V )AGN= 0.05

for E(B − V )AGN between 0.1 and 1) for a total of 29 templates. A subsample of BBB

templates with different reddening levels E(B −V )=[0.00, 0.03, 0.10, 0.50, 0.90] is presented in Figure 4.1 (blue curves).

In general, the SED of an obscured (Type 2) AGN is characterized by the NIR bump that is a result of the absorption of intrinsic nuclear radiation by dust clouds in the proximity of the central region (so-called torus) on parsec scales, which subsequently re-radiate at infrared frequencies (Barvainis 1987). The dust torus SED templates are taken from Silva et al. (2004), as constructed from the study of a large sample of Seyfert galaxies for which clear signatures of non-stellar nuclear emission were detected in the NIR and MIR, and also using the radiative transfer code GRASIL (Silva et al. 1998). There are four different templates depending on the amount of nuclear obscuration in terms of hydrogen column density, NH< 1022 cm−2 for Seyfert 1, and 1022< NH< 1023 cm−2, 1023< NH< 1024 cm−2, and

NH> 1024 cm−2 for Seyfert 2. The four templates of AGN dust torus are plotted in

Figure 4.1 with yellow curves. The larger the column density, the higher is the nuclear contribution to the IR emission. Although the X-ray data for this AGN sample contains

Figure 4.1 Examples of model templates used in the multi-component SED fitting. Blue curves indicate subsamples of BBB templates with different reddening levels E(B − V )=[0.00,0.03,0.10,0.50,0.90]. Green curves indicate some examples of host galaxy templates with various combinations of τ =[0.1, 1, 3], and tage=[50 Myr, 2 Gyr] with

E(B −V )=[0.0, 0.3]. Yellow curves correspond to four AGN dust torus templates depending on the hydrogen column density, NH. Red curves correspond to the subset of starburst

templates.

some information on the NHtoward each source (see Marchesi et al. 2016), I chose to allow

NH to be a free parameter in the SED fitting.

For the starburst component in the far/mid-IR region, I adopted 169 starburst templates (105 from Chary & Elbaz 2001 and 64 from Dale & Helou 2002) for fitting the cold dust emission (i.e. far-IR emission). It has been shown that measuring the FIR luminosity from fitting the FIR region to libraries of SED (Chary & Elbaz 2001; Dale & Helou 2002) gives roughly the same results as the modified blackbody plus power-law model (Casey 2012; U et al. 2012; Lee et al. 2013). The Chary & Elbaz (2001) templates are generated based on the SEDs of four prototypical starburst galaxies (Arp220, ULIRG; NGC 6090, LIRG; M82, starburst; and M51, normal star-forming galaxy). The Dale & Helou (2002) templates are based on 69 normal star-forming galaxies, representing a wide range of SED shapes and IR

luminosities, complementing each other. A small subset of starburst templates are shown in Figure 4.1 as red curves.