Introduction

The nearby (z=0.057; Clements 1983) radio galaxy 3C445 has an FRII radio morphology (Kronberg et al. 1986), with a linear extension up to 10 arcmin (Schilizzi & McAdam 1975). With a steep radio spectrum between 2.7 and 4.8 GHz ( =0.7) and a core to lobe intensity ratio R=0.039 (Morganti, Killeen, & Tadhunter 1993), the source is clearly lobe-dominated. Because of the broad, single-peaked Balmer lines emitted in the optical spectra (Eracleous & Halpern 1994; Crenshaw, Peterson, & Wagner 1988; Antonucci 1984a), 3C445 has been classified as a Broad Line Radio Galaxy (BLRG).

Optical and IR observations of 3C445 show that the emission at these wavelengths comes from a very compact core, with little contribution from the host galaxy (Zirbel 1996; Kotilainen & Ward 1994; Yee & Oke 1978). The IR-to-optical spectrum is steep, (Kotilainen, Ward, & Williger 1992; Elvis et al. 1984), and the IR colors are indicative of an Active Galactic Nucleus (Spinoglio et al. 1995) with a luminosity L erg s (Hes, Barthel, & Hoekstra 1995). The spectrum steepens dramatically at UV energies (Crenshaw et al. 1988). It has been suggested that the large IR emission is the result of the reprocessing of the optical and UV emission by circumnuclear dust (Elvis et al. 1984). Indeed, the polarization of the continuum (Brindle et al. 1990), with a trend of decreasing polarization degree with increasing wavelength (Rudy et al. 1983; but see Antonucci 1984b), provide evidence for the presence of dust in 3C445. The broad H line is also polarized (Kay et al. 1996). The amount of reddening, derived from the large Balmer decrement (H /H ; Crenshaw et al. 1988; Osterbrock, Koski, & Phillips 1976) and by the large Pa /H ratio ( 5.6; Rudy & Tokunaga 1982), is E(B-V) 1 mag. For a standard dust-to-gas conversion ratio, E(B-V)= cm mag (Shull & Van Steenberg 1985), an intrinsic absorbing column density N cm is derived. This is one order of magnitude larger than the Galactic column density in the direction to the source, N cm , derived from 21 cm measurements (Murphy et al. 1997).

Thus, 3C445 appears to host an obscured AGN. Further support to this conclusion is provided by the luminosity of the broad and narrow emission lines. After the reddening correction, the luminosity of the broad H line is L ergs s , while the narrow O[III]  Å emission has L ergs s (Tadhunter et al. 1993). Such high luminosities are the trademark of a powerful compact source of ionizing radiation (e.g., Mulchaey et al. 1994).

X-ray observations at medium-hard energies allow in principle the detection of the primary nuclear emission which can penetrate the layer of obscuring material at these wavelengths. An earlier HEAO-1/A2 detection with a 2-10 keV flux of erg cm s was reported for the source H2216-027, identified with 3C445 (Marshall et al. 1979). However, the large error box of the HEAO-1 detection includes another likely counterpart, the nearby (at 0.5 degrees) cluster of galaxies A2440 (z=0.094). The first X-ray spectrum of 3C445 was obtained with the EXOSAT ME (1-10 keV) experiment. The ME data are consistent with a poorly constrained continuum photon index ( ), a column density N cm , and an intrinsic 2-10 keV luminosity of L ergs s (Turner & Pounds 1989).

GINGA observations of 3C445 yielded a better constrained spectrum, although at the low angular resolution of the LAC, confusion with the nearby cluster was not negligible, the latter dominating the GINGA data below 3 keV. After accounting for the cluster thermal emission, Pounds (1990) finds for 3C445 a continuum with slope , absorbed by a column density N cm and with L ergs s . An iron line was also detected by GINGA around 6 keV, with equivalent width EW 100-150 eV and rest-frame energy 6.4 keV, consistent with an origin by fluorescence in cold material (Pounds 1990).

In this paper we present the first higher-resolution X-ray spectrum of 3C445 obtained with ASCA in 0.6-10 keV. The better angular resolution of ASCA compared to GINGA allows an unambiguous study of the high-energy continuum of the radio galaxy, free from contamination from the nearby cluster. The ASCA data confirm the detection of the Fe K line from the AGN and show a complex X-ray spectrum, with a soft excess below 1.5 keV and an observed flat continuum. A preliminary account of the ASCA data was given by Yamashita & Inoue (1996), with consistent results.

The paper is structured as follows. In § 2 the data analysis is described, while § 3 presents the results of the spectral fits. Our findings are summarized and discussed in § 4, with the conclusions following in § 5. Throughout this paper, H km s Mpc and q =0.5 are assumed.