5.1 Spectral Energy Distribution

Since it was found by Lee et al. (2013) that the UV continuum is an important component of the ionizing flux, we employed a similar methodology here to generate radio, infrared, UV, and X-ray components of the ionizing SED for the photoionization modeling of the warm absorber in PG1211+143 . Although the combined UV and X-ray continua are expected to be the main source of the ionizing radiation, we have used the entire ranges from radio to X-ray to construct the SED (see Figure4). The archival UV data taken with the HST-FOS in April 1991 (G130H, G190H, and G270H), together with our HST-COS time-averaged FUV spectrum (G140L) observed simultaneously with Chandra in April 2015, were used to construct the SED. We utilized our Chandra  MEG and HEG data to make X-ray continuum regions (0.5-8keV) of the ionizing SED. The soft X-ray continuum was extrapolated as a power law at energies below 0.5 keV to the point at which it meets the high-energy extrapolation of the UV powerlaw. We also used the radio fluxes at 20cm (1.5GHz), $S_{\nu}=2$ mJy, measured with the VLA (§ 2.3), the near-infrared (NIR) measurements (JHKs) from the Two Micron All Sky Survey (2MASS), the mid-infrared (MIR) measurements at 3.4, 4.6, 12, and 22 $\mu$m from the Wide-field Infrared Survey Explorer (WISE), and the far-infrared (FIR) measurements at 70, 100, 160, 250, 350, and 500 $\mu$m from the ESA Herschel Space Observatory  (Petric et al., 2015). Similarly, the radio, NIR, MIR, and FIR band points were connected to each other. However, the ionizing SED is mainly characterized by the UV and X-ray spectra without the emission and absorption lines. The IR, optical and UV data were first dereddened using $R_{\rm V}= 3.1$ and $E({\rm B-V})= 0.035$ (Schlafly & Finkbeiner, 2011), and placed in the rest frame. The X-ray data were also corrected for the foreground Galactic absorption.

The resulting intrinsic SED is shown in Figure 4 with associated bands (points) and composite spectra, connecting the IR, UV and X-rays regions (solid line). The intrinsic SED is then used to generate grids of photoionization models that are fitted to the X-ray absorption lines. To obtain the ionizing luminosity, we integrate the interpolated baseline SED between $\nu=3.29 \times 10^{15}$ and $3.29 \times 10^{18}$ Hz (i.e., 1-1000 Ryd), finding $\int F_{\nu}\,d\nu = 1.035 \times 10^{-10}$ ergcm$^{-2}$s$^{-1}$, which yields $L_{\rm ion} =1.587 \times 10^{45}$ ergs$^{-1}$ at the luminosity distance of 358Mpc ($H_{0}= 73$kms$^{-1}$Mpc$^{-1}$, $\Omega_{m} = 0.27$, and $\Lambda_{0} = 0.73$; $z=0.082$ corrected to the microwave background radiation reference frame). Previously, the ionizing luminosity (1-1000 Ryd) of $3.8 \times 10^{45}$ ergs$^{-1}$ was estimated from XMM-Newton observation (Pounds et al., 2016b).