Local and Global Optical, Far-Infrared (FIR) and X-ray Properties of the FIR Quiescent Sc Galaxy NGC 247

Abstract

We present an Optical, FIR and X-ray study of the low LFIR Sc galaxy, NGC 247. Global correlations (ie. B or X vs. Radio or FIR) in late-type spirals suggest that some luminosities do not scale linearly. We describe first results of a program to study emission in late-type spirals on local (kpc) scales to investigate this non-linear behaviour. Our data includes B, I, Hα+[Nii] CCD, IRAS 60, 100μm (Rice 1993), and ROSAT PSPC, (0.1-2.4keV) images. Since abstract submission we have added H I (Carignan and Puche 1990) and 1.49 GHz continuum (Condon 1987). The Hα+[Nii] is generally coextensive with the IRAS emission and H I. The brightest Hα+[Nii] region (log LHα~38.6 ergs s−1) in a region of low FIR flux, may possess a locally warm 60/100μm ratio suggesting a similarity with more luminous galaxies that have warm 60/100μm ratios globally. 1.49 GHz sources are not cospatial with bright X-ray sources, nor with Hα+[Nii]. Three extended 1.49 GHz sources are cospatial with very faint, soft X-ray emission, suggesting a SNR origin. We cannot rule out a direct 1.49 GHz/X-ray or 1.49 GHz/ H ii origin due to relativistic e− propagation. ROSAT PSPC results suggest 4 4σ (0.1-2.4 keV) X-ray sources are intrinsic. Their LX range of 1036–37 ergs s−1 is consistent with X-ray binaries, whilst the total LX = 3.0×1037 ergs s−1 is underluminous by ~3, compared to previous regression fits. A faint soft, LX ~ 1×1036 ergs s−1 nuclear X-ray feature may be a SNR outflow, and similar to plumes/outflows seen in starbursts, but 104 less luminous.