Deep Surface Photometry Research Articles

Intrinsic Bar/Ring Misalignment and a Starburst Nuclear Ring in the Peculiar Spiral Galaxy ESO 565-11

view Abstract Citations (35) References (57) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Intrinsic Bar/Ring Misalignment and a Starburst Nuclear Ring in the Peculiar Spiral Galaxy ESO 565-11 Buta, R. ; Purcell, G. B. ; Crocker, D. A. Abstract The southern galaxy ESO 565-11 is a very clear example of a nearly face- on ringed barred spiral where the bar axis and the major axis of the inner ring are significantly misaligned. The object is important because the normal configuration is alignment, based on statistics of apparent bar/ring position angles for large samples of ringed galaxies. In this paper, we verify, using deep CCD surface photometry and Fabry-Perot interferometry, that the bar/ring misalignment of 60^deg^ seen in ESO 565-11 is intrinsic. We show that ESO 565-11 has two important nonaxisymmetric components: the primary bar, and a luminous oval distortion which contains a greater proportion of the total luminosity. The primary bar is of the "ansae" type, showing bright enhancements at the ends. The inner pseudoring is a minor contribution to the total light at the rim of the oval distortion. Thus, ESO 565-11 can also be characterized as a misaligned bar/oval galaxy. There is a very faint outer pseudoring beyond the oval distortion. In the center of the galaxy, a starburst nuclear ring of collosal physical size dominates the morphology. The ring is about 3.5 times the average size of such features and is defined by ten giant and at least three lesser H II regions which contribute 77% of the total Hα luminosity of the galaxy. The position angle of the major axis of the ring changes by 23^deg^ in the direction of rotation from Hα to B to I, and in the latter filter is aligned nearly perpendicular to the bar in projection. The ring is also imbedded in a more extended disk of diffuse Hα emission. The inner pseudoring is defined by much fainter discrete H II regions. Publication: The Astronomical Journal Pub Date: October 1995 DOI: 10.1086/117633 Bibcode: 1995AJ....110.1588B Keywords: GALAXIES: INDIVIDUAL: ESO 565-11; GALAXIES: SPIRAL; GALAXIES: KINEMATICS AND DYNAMICS; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (9) NED (1)

NGC 7217: A Spheroid-dominated, Early-Type Resonance Ring Spiral Galaxy

view Abstract Citations (54) References (81) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS NGC 7217: A Spheroid-dominated, Early-Type Resonance Ring Spiral Galaxy Buta, R. ; van Driel, W. ; Braine, J. ; Combes, F. ; Wakamatsu, K. ; Sofue, Y. ; Tomita, A. Abstract NGC 7217 is a well-known northern spiral galaxy which is characterized by flocculent spiral structure and a series of three optical ringlike zones: a nuclear ring 21" in diameter, a weak inner ring 63" in diameter, and a striking outer ring 2'.6 in diameter. The rings all have nearly the same shape and position angle in projection. The appearance of the galaxy suggests that it may be more axisymmetric than the typical spiral galaxy, since there is little evidence for the presence of a bar, oval, or stellar density wave. This makes the origin of the ring features uncertain. In an effort to understand this kind of ringed galaxy, which is by no means typical, we have obtained multicolor CCD BVRI images, accurate surface photometry, mappings of the CO and H I gas distributions, and rotational velocities from Hα and H I spectral line data. Our deep surface photometry has revealed an important feature of NGC 7217 that was missed in previous studies: The region occupied by the rings of the galaxy is surrounded by an extensive, nearly circular luminous halo. This halo cannot be merely an extension of the disk component because it is much rounder than the inner regions. Instead, we believe the light represents either the outer regions of the bulge or a separate stellar halo component. We are able to successfully model the luminosity profile in terms of an r114 "spheroid" and an exponential disk with a spheroid-to-total disk (including rings) luminosity ratio of 2.3-2.4. This makes NGC 7217 one of the most spheroid-dominated spirals known, and the finding has important implications for the recent discovery by Merrifield and Kuijken of a significant population of counter-rotating stars in the galaxy. Although the spiral structure of NGC 7217 is flocculent in blue light, there is a definite two-armed stellar spiral in the region of the outer ring. This ring includes about 4.4% of the total blue luminosity and is the locus of most of the recent star formation in the galaxy. The ring is also where we find the H I gas to be concentrated. The galaxy is very gas poor (MH I/L0B = 0.024 Msun/Lsun, B for its morphological type. The H I rotational velocities agree well with published and our new Hα-values. Fourier analysis reveals a very weak possible oval distortion in the stellar mass distribution. Using the I-band light distribution to define the potential, we carried out simulations of gas streaming with no self- gravity. A model with a bulge-to-disk mass ratio of 2.4 reproduces the observed optical ring morphology very well. This suggests to us that in spite of the extreme weakness of the observed nonaxisymmetry of this galaxy, this nonaxisymmetry is still sufficient to torque the gas into the usual resonance rings identified in other, more obviously barred galaxies. An additional noteworthy feature that we have identified in a B - I color index map is a symmetric, nuclear dust ring 17" in angular diameter. Other dust lanes are seen mainly on the near side of the galaxy. Publication: The Astrophysical Journal Pub Date: September 1995 DOI: 10.1086/176169 Bibcode: 1995ApJ...450..593B Keywords: GALAXIES: INDIVIDUAL NGC NUMBER: NGC 7217; GALAXIES: KINEMATICS AND DYNAMICS; GALAXIES: PHOTOMETRY; GALAXIES: SPIRAL; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (10) NED (1)

DUST AND IONIZED GAS IN ELLIPTICAL GALAXIES

DUST AND IONIZED GAS IN ELLIPTICAL GALAXIES

Stellar populations in edge-on galaxies from deep CCD surface photometry, 1: NGC 5907

We present extremely deep charge coupled device (CCD) surface photometry of the edge-on Sc galaxy NGC 5907. Our data reach reliably to a surface brightness of R=27 mag/sq arcsec, some two magnitudes fainter than any previous work. We obtained this improvement using a 2048X2048 CCD with a wide (approximately 24 min) field, which made it possible to sky subtract directly from the galaxy frame, and by taking many dark sky flatfields. Our analysis of these data, using a full 2D model fitting procedure with a detailed error model, confirm the thin disk parameters of van der Kruit & Searle (1981). In particular, we confirm that the galaxy's disk has a radial cutoff and a constant scale height with radius. We find evidence for a stellar warp in this system, which has the same orientation as the H I warp. Our deep data also confirm that NGC 5907 has no thick disk. This suggests that theories of thick disk formation from star formation in the early stages of disk collapse, or by secular heating mechanisms, are unlikely to be correct, because they would predict that every galaxy would have a thick disk. Thick disk formation from the accretion of satellite galaxies is more likely.

The corona of the giant spiral galaxy NGC 253

view Abstract Citations (23) References (9) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The corona of the giant spiral galaxy NGC 253. Freeman, K. C. ; Carrick, D. W. ; Craft, J. L. Abstract Results are reported for deep photographic surface photometry of the giant spiral galaxy NGC 253, and upper limits are obtained for the total luminosity of its corona. The observational procedures are outlined in detail, and King's (1966) self-consistent spherical models are used to estimate the upper limits. It is shown that the total corona luminosity is unlikely to exceed three billion times that of the sun and that the corona's mass-luminosity ratio will exceed 600 if the corona is typical of those postulated by Ostriker et al. (1974). If it is typical of those proposed by Einasto et al. (1974), the ratio will exceed 5800. Publication: The Astrophysical Journal Pub Date: June 1975 DOI: 10.1086/181820 Bibcode: 1975ApJ...198L..93F Keywords: Astronomical Photometry; Coronas; Galactic Structure; Luminous Intensity; Spiral Galaxies; Astronomical Models; Astronomical Photography; Surface Properties; Astrophysics full text sources ADS | data products NED (1)