| Authors | Garcia-Barreto, J. A.; Downes, D.; Combes, F.; Gerin, M.; Magri, C.; Carrasco, L.; Cruz-Gonzalez, I. |
| Abstract | We present new observations of the barred spiral galaxy NGC 4314 in the CO (1-0) and (2-1) lines, the 21 cm HI line, the radio continuum, the visible and the near infrared. The CO observations, made with the IRAM 30 m telescope, show abundant molecular gas in the center of this galaxy, probably in the 12" circumnuclear ring, in the middle of the strong bar. Even more remarkable is the extreme HI deficiency, as shown by our HI detection with the Arecibo telescope: in NGC 4314, the H_2_/HI mass ratio is 60-to-1! VLA maps at 2, 6 and 20 cm show several radio continuum sources in a 12" ring around the optical nucleus. No radio continuum emission was detected from the nucleus itself, the bar or the outer spiral arms. The radio continuum emission has a shallow spectral index of -0.4, and may be a mixture of free-free and synchrotron radiation. Short exposure optical images of the galaxy also show bright spots in a ring around the nucleus, coinciding with the radio continuum structures. Near-infrared photometry of the inner region suggests that the mass-to-2μm luminosity ratio within a radius of 9 arcsec (450 pc) of the nucleus is 3 M_sun_/L_sun_, as in the center of our Galaxy. However, in this region, the H_2_ mass is 3 10^8^M_sun_, a large fraction of the total mass. Presumably the bar has driven gas into the inner region where it has formed molecular clouds. These clouds produce the O stars ionizing the HII regions seen in the visible and the thermal radio continuum, and supernovae giving rise to the nonthermal radio emission. |
