|Figure 6: Distribution of galaxy magnitudes. Distances are from Table 1. Where photometric distances were unavailable, the radial velocities were used with|
On individual galaxies:
UGC 6541: small galaxy, with a light excess close to the center as compared to an exponential profile. As can be seen on the image, this can be a star-forming region or a superimposed star. The color profile shows no deviation in the region concerned by the bright object, so its nature is difficult to assess. The color gradient of this galaxy is steep, and in the sense of the center being bluer.
UGC 6565: possesses a bright central light excess above a pure exponential. This central part also has a knotty structure, and is also much bluer than the rest of the galaxy. This probably suggests ongoing star formation. The outer part of the galaxy seems smooth. The isophotes look boxy, although we haven't quantified this feature in this work.
UGC 6572: irregular structure, with a slightly offset bright region. The color profile is steep, but the brighter spot doesn't seem to be of a different color than its immediate surroundings.
UGC 6817: has a low central surface brightness and a large scale length. The SBP is close to a pure exponential, and the color gradient is smooth, showing a reddening with increasing radius. The aspect of the galaxy is peculiar, with a knotty irregular surface, and a tail extending to the south-west. It could have been disrupted by supernova events. The isophotes also seem twisted, although not examined in detail in this work.
UGC 7047: irregular with a knotty structure, and a light excess over an exponential profile towards the center. This part of the galaxy also shows a flatter color index, whereas the outer parts of the galaxy tend to get redder with increasing radius.
UGC 7165: has a SBP that is close to an exponential, and also has a bright nuclear part. The color is almost constant over the whole radius range, apparently including the central part. But the resolution of our data is insufficient to discuss the center in any detail. The galaxy as a whole has a smooth elliptical appearance.
UGC 7199: knotty irregular with a central blue light excess. Exponential outer SBP shape, with a flat color profile outside the blue center.
UGCA 276: small galaxy with a faint central surface brightness. The central part is slightly deficient compared to an exponential. The color profile is flat.
UGC 7298: apparently small irregular galaxy with a knotty surface. Its color profile seems steep, being redder at large radius, but suffers from poor resolution and large error bars.
UGC 7335: elongated irregular galaxy with a bright central lane. The shape of the galaxy as a whole is elongated and elliptical. Its SBP is close to a pure exponential. The color profile is shallow, getting slightly redder with radius, and showing a bluing close to the center.
UGC 7356: classical nucleated dwarf elliptical. It has a published heliocentric radial velocity suggesting it is close-by (but it is close in projection to NGC 4258). The brightest stars were not resolved by Makarova et al. (1998), confirming the dwarf elliptical nature. Its color profile is flat, with a slightly bluer nucleus.
UGC 7369: is a smooth, elliptically shaped galaxy, with a bright nucleus. It has a shallow color profile, becoming redder with radius, and a slightly blue nucleus. It is classified in the RC3 as an elliptical, but at vhel=333 km s-1 it could be a dwarf elliptical. Its SBP is close to exponential.
UGC 7559: irregular with a knotty face. Also seems disrupted, although not as severely as UGC 6817. We only have a R frame. SBP close to an exponential, with a flat central part.
UGC 7599: apparently small irregular with a large central light excess above an exponential fit to the outer regions. Only a B frame was available.
UGC 7639: irregular with a slight excess above an exponential in the inner part of its SBP. Knotty inner surface, and a slight luminosity excess to the north-west. Smooth color profile, showing a reddening with increasing radius.
Many authors report that color profiles show small gradients or are flat in dwarf galaxies (Bremnes et al. 1998; Patterson & Thuan 1996). We here find that all but two galaxies with color profiles show a reddening with increasing radius. UGC 6565 and UGC 7199 have a blue central part when compared to the outer parts. UGC 7047, UGC 7356 and UGC 7298 have flatter color gradients towards their centers. The remaining galaxies show monotonous color profiles.
To summarize, we have presented global photometric parameters for 15 galaxies in the Canes Venatici Cloud I in the B and R bands. Our sample corresponds to approx. one third of all galaxies in the direction of the cloud with heliocentric velocities less than .
T.B. and B.B. thank the Swiss National Science Foundation for financial support. We also thank Bernhard Parodi for taking part in the observing run.
This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration, as well as NASA's Astrophysics Data System Abstract Service.
Copyright The European Southern Observatory (ESO)