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Surface Photometry of Southern Thaisa Storchi Bergmann and Hiriani Griseloa Pastoriza

From a spectroscopic survey of southern galaxies made by one of the authors (Pastoriza), a group of galaxies that showed particularly strong emission x6548-84[NII] lines was selected for further investigation. As an initial approach, surface photographic photometry is being made for these galaxies: blue (B) and visual (V) photographic plates were obtained for NGC4027, 4507, 5643, 6769, 6770 and 6771, with the 1.6 meter telescope of the "Observatório Astrofísico Brasileiro" (Pico dos Dias, Bra- sõpolis, MG, Brazil). For the blue plates, a combination of kodak IIa-0 plate plus GG385 filter was used and for the visual, Ila-D plus G6495. The photometric reductions are being carried out with the PDS microdensitometer and PDP-8 computer of "Observatório Nacional" (Rio de Janeiro, RJ, Brazil) and also with the microdensitometer of "Instituto de Física". Some results for NGC4027 and NGC4507 are presented below. The preliminary results obtained for the magellanic-type barred spiral NGC4027 are: total magnitude in the B system B? = 11.92; total color index (B-V)T = 0.47; total B magnitude corrected for galactic and internal absorption and B° = 11.56; corrected color index (B-V)° = 0.38; adopted distance = 12,5 Mpc t 2.5 Mpc; absolute magnitude

Mo - -18.9; major diameter = 8.5 kpc and minor diameter = 5.4 kpc. The figure shows an isophote map of NGC 4027 obtained from the blue plate. For the regions numbered 1 to 8 (H II regions and nucleus), B-V photographic color indices were obtained which -98-

are, respectively: 0.346, 0.268, 0.321, 0.304, 0.574 (nucleus), 0.261, 0.043, 0.079. The nucleus, as expected, has the reddest B-V, reflecting the presence of older population in the center of the galaxy. An interessant result cones when we compare the B-V values of the HII regions: the regions number 7 and 8, north of the nucleus, are very blue, indicating both the presence there of a very young population or may be just an effect of inclination or rotation of the galaxy, because all the regions south of the nucleus have redder B-V values. This fact is being investigated. For the early type NGC 4507, the preliminary results are: total magnitude in B system By - 13.14; total color index (B-V)-r - 0.81; B magnitude corrected for galactic and internal absorption and redshift B° = 12,61; corrected color

2 index (B-V)° = 0.67; estimated distance (using v = HQd, with

HQ = 100 km/s/Mpc and v = 3540 km/s) = 33.1 Mpc; absolute magnitude Mfi = -20.0; major diameter = 19.2 kpc and minor diameter = 15.2 kpc. Radial B and V brightness profiles, space 10° apart in angle around the galaxy were also obtained for NGC 4027 and NGC 4507. The decomposition of the brightness profiles are now being initiated and will permit the separation of the different components (nucleus, disc and halo) of the galaxies. It will also be possible to verify B-V gradients within each galaxy.

1. de Vaucouleurs, G., de Vaucoulerus, A., Freeman, K.C., MNRAS, 1968, 1_39, 425. 2. Radial velocity from: Martin, W.L., MNRAS, 1976, 175, 641. -99-