We have conducted a V-band CCD surface photometry of 68 disk galaxies to analyze the bulge morphology of nearby spirals. We classify bulges into four types according to their ellipticities and the misalignments between the major axis of the bulge and those of the disk and the bar: spherical, oblate, pseudo triaxial, and triaxial. We found that one third of the bulges are triaxial and they are preponderant in barred galaxies. The presence of the triaxial bulges in a significant fraction of unbarred galaxies as well as in barred galaxies might support the secular evolution hypothesis which postulates that the bar driven mass inflow leads to the formation of triaxial bulges and the destruction of bars when sufficient mass is accumulated in the central regions.
We performed VRI CCD surface photometry of three spiral galaxies of HCG10 in order to understand the effect of interactions in the compact group. The morphology of the largest member NGC 536 seems to be normal but its bulge is thought to be of an oblate spheroid. The central surface brightness of the disk of NGC 536 is much fainter than that of disks of nearby spiral galaxies. The morphologies of NGC 531 and NGG 542 appear to be affected by interactions which lead to a warped disk in NGC 531 and a slightly bent disk in NGC 542. NGC 531 have a boxy bulge and a Freeman Type II disk both of which strongly suggest the presence of a bar in the galaxy. There is a break in the slope of the luminosity profile of NGC 542 which is dominated by the disk component.
We have conducted BV RI CCD surface photometry of three spiral galaxies ESO 598-G009, NGC 1515 and NGC 7456. In order to understand the morphological properties and luminosity distribution characteristics for each galaxy, we derived isophotal map, position angle profile, ellipticity profile, luminosity profile, color profile and color contour map. ESO 598-G009, which has a bright bulge component and a ring, shows a trace of gravitational interaction. NGC 1515 is a spiral galaxy with a bar and dust lane. NGC 7456 shows typical characteristics of a late type spiral galaxy.
We present B VRI CCD surface photometry for the central (6'.35 ×6'.35) regions of the dwarf elliptical galaxies NGC 185 and NGC 205 in the Local Group. Surface brightness profiles of NGC 185 (R<225") and NGC 205 (R<186") show excess components in the central regions. The colors of NGC 185 get bluer inward at R<25", while they remain constant at R ≥ 25". The colors of NGC 205 get bluer inward at 1"<R<50", and remain flat outside. Our photometry, supplemented by the photometry based on the far-ultraviolet and visual images of the HST archive data, shows that there is an inversion of color at the very nucleus region (at about 1"). The implications of the redder color of the core part of the nucleus compared with neighboring regions are discussed. The amount of the excess components in the central regions of these galaxies is estimated to be ≈10 5 L⊙. Distributions of dust clouds in the central regions of the two galaxies are also investigated.
We performed CCD surface photometry in B,V,R and I filters for three southern spiral galaxies:ESO598-G009,NGC1515 and NGC7456. Isophotal map, luminosity profile, ellipticity profile and position angle profile were obtained for these galaxies using SPIRAL package. The results show that one of the galaxies, ESO598-G009 has relatively large bulge component and changes in position angle due to spiral arms. The NGC7456 has very small bulges; and the isophotal map of the NGC1515 shows that it is a typical spiral galaxy with bar.
We perfom a large project for complex study of Blue Compact Galaxies (BCGs) with strong star formation, which includes optical spectroscopy, BVR CCD photometry and HI 21 cm radio survey. The most interesting galaxies are studied also with HST and VLA. In the frame of this project we began the study of Hα morphology of BCGs with 6-m telescope. We present and discuss here the results for the first 6 galaxies. We found the noticeable variety of forms for Hα morphology comparing to broad band images: from very compact HII region in very center of stellar body (Mark 996, possible dwarf post-merger, old galaxy experiencing strong star formation burst), to very extended gas emission encompassing the whole area traced by stars (SBS 0335-052, the most probable young galaxy in formation).
We have started multi-color imaging program of nearby galaxies since last year and present preliminary result here. We selected 12 nearby galaxies classfied from E to Sab type and observed in BVRIJHK' bands. Photomtric parameters such as isophotal diameter, axial ratio, isophotal magnitude were measured and observed colors were compared with theoritical model. We find a standard evolution model agrees well with observed results.
We have developed a new device, Plate-to-CCD Convertor (PCC), to conveniently digitize photographic plates in a relatively short time without losing any plate information (Oh et al. 1995). Using this device we have performed surface photometry of 12 early type galaxies. We determined relative orientations and scales to analyze PCC images. We also determined an ellipticity, position angle of the major axis, and a4 a4 of each galaxy to quantify the distribution of surface brightness. We checked the performance and limitation of this device by comparing the PCC images with those digitized by the ST microdensitometer and those obtained with CCD observations.
We have conducted BVI photographic surface photometry of four spiral galaxies NGC1087, NGC2715, NGC2844 and NGC3593, by making use of the Kiso Schmidt plates. Detailed examination of the morphological properties of the galaxies using isophotal maps and luminosity profiles showed that all the program galaxies have some peculiarities in their luminosity distributions. NGC1087 and NGC2715 have extremely small nuclei with inner rings which contain several bright HII regions. NGC2844 has a very large bulge whose luminosity dominates over the disk luminosity in all the radii. The I-band luminosity profile of NGC3593 shows shallower gradient than B- and V-band profiles. We were able to successfully decompose the luminosity profile into a bulge following de Vaucouleurs γ 1 / 4 − l a w and an exponential disk only for NGC 3953. Other galaxies have more complicated luminosit profiles.
Using the detailed two-dimensional surface photometry of 39 galaxies, the observed profiles are decomposed into spheroid, disk and bar components simultaneously. From the analyses of decomposition parameters, the correlations among the three components are investigated to find the global property of barred galaxies. And the lens and ring components, and spiral arm patterns are also examined with Hubble type and decomposition parameters.
The global morphology and geometric parameters of 39 barred galaxies are investigated, by using isophote map and isodensity tracings obtained from detailed surface photometry with the Kiso V-band plates. The observed results are as follows: i) There is no strong indication that the ratio of bar length to disk size is correlated with Hubble type, except that the largest bars appear in the SBb galaxies. ii) The mean value of axial ratios of bars is 2.0 ± 0.4 and there is a trend that early type galaxies have smaller axial ratios than late type galaxies. iii) About 15% of early type barred galaxies(Sb0-SBb) have triaxial bulges.