We present the results of a detailed optical and near-IR study of the nearby star-forming dwarf galaxy NGC 4214. We discuss the stellar content, drawing particular attention to the intermediate-age and/or old field stars, which are used as a distance indicator. On images obtained with the Hubble Space Telescope Wide Field Planetary Camera 2 and Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) instruments in the equivalents of the V, R, I, J and H bands, the galaxy is well resolved into stars. We achieve limiting magnitudes of F814W approximate to 27 in the WF chips and F110W approximate to 25 in the NICMOS 2 camera. The optical and near-infrared color-magnitude diagrams confirm a core-halo galaxy morphology: an inner, high surface brightness, young population within similar to 1.'5 (similar to1 kpc) from the center of the galaxy, where the stars are concentrated in bright complexes along a barlike structure, and a relatively low surface brightness, field star population extending out to at least 8' (7 kpc). The color-magnitude diagrams of the core region show evidence of blue and red supergiants, main-sequence stars, asymptotic giant branch stars, and blue loop stars. We identify some candidate carbon stars from their extreme near-IR color. The field-star population is dominated by the "red tangle," which contains the red giant branch. We use the I-band luminosity function to determine the distance based on the tip of the red giant branch method: 2.7 +/- 0.3 Mpc. This is much closer than the values usually assumed in the literature, and we provide revised distance-dependent parameters such as physical size, luminosity, H I mass, and star formation rate. From the mean color of the red giant branch in V and I, we estimate the mean metal abundance of this population to be Fe/H similar or equal to -1.7 dex, with a large internal abundance spread characterized by sigma(int) (Fe/H) approximate to1 dex. References: 62
展开▼
