Nearby Optical Galaxies: Selection of the Sample and Identification of Groups

In this paper we describe the Nearby Optical Galaxy (NOG) sample, which is a complete, distance-limited ($cz\leq$6000 km/s) and magnitude-limited (B$\leq$14) sample of $\sim$7000 optical galaxies. The sample covers 2/3 (8.27 sr) of the sky ($|b|>20^{\circ}$) and appears to have a good completeness in redshift (98%). We select the sample on the basis of homogenized corrected total blue magnitudes in order to minimize systematic effects in galaxy sampling. We identify the groups in this sample by means of both the hierarchical and the percolation {\it friends of friends} methods. The resulting catalogs of loose groups appear to be similar and are among the largest catalogs of groups presently available. Most of the NOG galaxies ($\sim$60%) are found to be members of galaxy pairs ($\sim$580 pairs for a total of $\sim$15% of objects) or groups with at least three members ($\sim$500 groups for a total of $\sim$45% of objects). About 40% of galaxies are left ungrouped (field galaxies). We illustrate the main features of the NOG galaxy distribution. Compared to previous optical and IRAS galaxy samples, the NOG provides a denser sampling of the galaxy distribution in the nearby universe. Given its large sky coverage, the identification of groups, and its high-density sampling, the NOG is suited for the analysis of the galaxy density field of the nearby universe, especially on small scales.Comment: 47 pages including 6 figures. Accepted for publication in Ap

Axillary lymph node dose with tangential whole breast radiation in the prone versus supine position: a dosimetric study

<p>Abstract</p> <p>Background</p> <p>Prone breast positioning reduces skin reaction and heart and lung dose, but may also reduce radiation dose to axillary lymph nodes (ALNs).</p> <p>Methods</p> <p>Women with early stage breast cancer treated with whole breast irradiation (WBI) in the prone position were identified. Patients treated in the supine position were matched for treating physician, laterality, and fractionation. Ipsilateral breast, tumor bed, and Level I, II, and III ALNs were contoured according to the RTOG breast atlas. Clips marking surgically removed sentinel lymph nodes (SLN)s were contoured. Treatment plans developed for each patient were retrospectively analyzed. V90_% and V95_% was calculated for each axillary level. When present, dose to axillary surgical clips was calculated.</p> <p>Results</p> <p>Treatment plans for 46 women (23 prone and 23 supine) were reviewed. The mean V90_% and V95_% of ALN Level I was significantly lower for patients treated in the prone position (21% and 14%, respectively) than in the supine position (50% and 37%, respectively) (<it>p</it> < 0.0001 and <it>p</it> < 0.0001, respectively). Generally, Level II & III ALNs received little dose in either position. Sentinel node biopsy clips were all contained within axillary Level I. The mean V95_% of SLN clips was 47% for patients treated in the supine position and 0% for patients treated in the prone position (<it>p</it> < 0.0001). Mean V90_% to SLN clips was 96% for women treated in the supine position but only 13% for women treated in the prone position.</p> <p>Conclusions</p> <p>Standard tangential breast irradiation in the prone position results in substantially reduced dose to the Level I axilla as compared with treatment in the supine position. For women in whom axillary coverage is indicated such as those with positive sentinel lymph node biopsy who do not undergo completion axillary dissection, treatment in the prone position may be inappropriate.</p